Search Results: "cts"

30 April 2023

Matthew Palmer: dev-dependencies and Rust's unused_crate_dependencies lint

I m in the process of getting super-strict about the code quality of cretrit, the comparison-revealing encryption library that underlies the queryable encryption of the Enquo project. While I m going to write a whole big thing about Rust linting in the future, I bumped across a rather gnarly problem that I thought was worth sharing separately. The problem, in short, is that the unused_crate_dependencies lint interacts badly with crates that are only needed for benchmarking, such as (in my case) criterion. Rust has a whole bucketload of lints that can help your codebase adhere to certain standards, by warning (or exploding) if the problem is detected. The unused_crate_dependencies lint, as the name suggests, gets snippy when there s a crate listed in your Cargo.toml that doesn t appear to be used anywhere. All well and good so far. However, while Rust has the ability to specify crates needed for running the testsuite (the [dev-dependencies] section of Cargo.toml) separately from crates needed for actually using this thing ([dependencies]), it doesn t have a way to specify crates needed for running the benchmarks . That is a problem when you re using something like criterion for benchmarking, because it doesn t get refered to at all in your project code it only gets used in the benchmarks. When building your codebase for running the test suite, the compiler sees that you ve specified criterion as one of your testsuite dependencies , but it never gets used in your testsuite. This causes the unused_crate_dependencies lint to lose its tiny mind, and make your build look ugly (or fail). Thankfully, the solution is very simple, once you know the trick (this could be the unofficial theme song of the entire Rust ecosystem). You need to refer to the criterion crate somewhere in the code that gets built during the testsuite. The lint tells you most of what you need to do (like most things Rust, it tries hard to be helpful), but since it s a development dependency, you need a little extra secret sauce. All you need to do is add these two lines to the bottom of your src/lib.rs (or src/main.rs for a binary crate):
#[cfg(test)]
use criterion as _;
For the less Rust-literate, this means when the build-time configuration flag test is set, import the criterion crate, but don t, like, allow it to actually be referred to . This is enough to make the lint believe that the dependency is being used, and making it only happen when the test build-time config flag is set avoids the ugliness of it trying to refer to the crate during regular builds (which would fail, because criterion is only a dev-dependency). Simple? Yes. Did it take me a lot of skull-sweat to figure out? You betcha. That s why I m writing it down even if everyone else already knows this, at least future Matt will find this post next time he trips over this problem.

29 April 2023

Simon Josefsson: How To Trust A Machine

Let s reflect on some of my recent work that started with understanding Trisquel GNU/Linux, improving transparency into apt-archives, working on reproducible builds of Trisquel, strengthening verification of apt-archives with Sigstore, and finally thinking about security device threat models. A theme in all this is improving methods to have trust in machines, or generally any external entity. While I believe that everything starts by trusting something, usually something familiar and well-known, we need to deal with misuse of that trust that leads to failure to deliver what is desired and expected from the trusted entity. How can an entity behave to invite trust? Let s argue for some properties that can be quantitatively measured, with a focus on computer software and hardware: Essentially, this boils down to: Trust, Verify and Hold Accountable. To put this dogma in perspective, it helps to understand that this approach may be harmful to human relationships (which could explain the social awkwardness of hackers), but it remains useful as a method to improve the design of computer systems, and a useful method to evaluate safety of computer systems. When a system fails some of the criteria above, we know we have more work to do to improve it. How far have we come on this journey? Through earlier efforts, we are in a fairly good situation. Richard Stallman through GNU/FSF made us aware of the importance of free software, the Reproducible/Bootstrappable build projects made us aware of the importance of verifiability, and Certificate Transparency highlighted the need for accountable signature logs leading to efforts like Sigstore for software. None of these efforts would have seen the light of day unless people wrote free software and packaged them into distributions that we can use, and built hardware that we can run it on. While there certainly exists more work to be done on the software side, with the recent amazing full-source build of Guix based on a 357-byte hand-written seed, I believe that we are closing that loop on the software engineering side. So what remains? Some inspiration for further work: Onwards and upwards, happy hacking! Update 2023-05-03: Added the Liberating property regarding free software, instead of having it be part of the Verifiability and Transparency .

28 April 2023

Shirish Agarwal: John Grisham s books, Evolution removed from textbooks

Gray Mountain John Grisham I have been perusing John Grisham s books, some read and some re-read again. Almost all of the books that Mr. Grisham wrote are relevant even today. The Gray Mountain talks about how mountain top removal was done in Applachia, the U.S. (South). In fact NASA made a summary which either was borrowed from this book or the author borrowed from NASA, either could be true although seems it might be the former. And this is when GOI just made a new Forest Conservation Bill 2023 which does the opposite. There are many examples of the same, the latest from my own city as an e.g. Vetal Tekdi is and was a haven for people animals, birds all kinds of ecosystem and is a vital lung of the city, one of the few remaining green spaces in the city but BJP wants to commercialize it as it has been doing for everything, I haven t been to the Himalayas since 4-5 years back as I hear the rape of the land daily. Even after Joshimath tragedy, if people are not opening the eyes what can I do  The more I say, the more depressed I will become so will leave it for now. In many ways the destruction seems similar to the destruction that happened in Brazil under Jair Bolsonaro. So as can be seen from what I have shared this book was mostly about environment and punitive damages and also how punitive damages have been ceiling in America (South). This was done via lobbying by the coal groups and apparently destroyed people s lives, communities, even whole villages. It also shared how most people called black lung and how those claims had been denied by Coal Companies all the time. And there are hardly any unions. While the book itself is a fiction piece, there is a large amount of truth in it. And that is one of the reasons people write a fiction book. You could write about reality using fictional names and nobody can sue you while you set the reality as it is. In many ways, it is a tell-all.

The Testament John Grisham One of the things I have loved about John Grisham is he understands human condition. In this book it starts with an eccentric billionaire who makes a will which leaves all his property to an illegitimate child who coincidentally also lives in Brazil, she is a missionary. The whole book is about human failings as well as about finding the heir. I am not going to give much detail as the book itself is fun.

The Appeal John Grisham In this, we are introduced to a company that does a chemical spill for decades and how that leads to lobbying and funding Judicial elections. It does go into quite a bit of length how private money coming from Big business does all kind of shady things to get their person elected to the Supreme Court. Sadly, this seems to happen all the time, for e.g. two weeks ago. This piece from the Atlantic also says the same. Again, won t tell as there is a bit of irony at the end of the book.

The Rainmaker John Grisham This in short is about how Insurance Companies stiff people. It s a wonderful story that has all people in grey including our hero. An engaging book that sorta tells how the Insurance Industry plays the game. In India, the companies are safe as they ask for continuance for years together and their object is to delay the hearings till the grandchildren are not alive unlike in the U.S. or UK. It also does tell how more lawyers are there then required. Both of which are the same in my country.

The Litigators John Grisham This one is about Product Liability, both medicines as well as toys for young kids. What I do find funny a bit is how the law in States allows people to file cases but doesn t protect people while in EU they try their best that if there is any controversy behind any medicine or product, they will simply ban it. Huge difference between the two cultures.

Evolution no longer part of Indian Education A few days ago, NCERT (one of the major bodies) that looks into Indian Education due to BJP influence has removed Darwin s Theory of Evolution. You can t even debate because the people do not understand adaptability. So the only conclusion is that Man suddenly appeared out of nowhere. If that is so, then we are the true aliens. They discard the notion that we and Chimpanzees are similar. Then they also have to discard this finding that genetically we are 96% similar.

27 April 2023

Jonathan McDowell: Repurposing my C.H.I.P.

Way back at DebConf16 Gunnar managed to arrange for a number of Next Thing Co. C.H.I.P. boards to be distributed to those who were interested. I was lucky enough to be amongst those who received one, but I have to confess after some initial experimentation it ended up sitting in its box unused. The reasons for that were varied; partly about not being quite sure what best to do with it, partly due to a number of limitations it had, partly because NTC sadly went insolvent and there was less momentum around the hardware. I ve always meant to go back to it, poking it every now and then but never completing a project. I m finally almost there, and I figure I should write some of it up. TL;DR: My C.H.I.P. is currently running a mainline Linux 6.3 kernel with only a few DTS patches, an upstream u-boot v2022.1 with a couple of minor patches and an unmodified Debian bullseye armhf userspace.

Storage The main issue with the C.H.I.P. is that it uses MLC NAND, in particular mine has an 8MB H27QCG8T2E5R. That ended up unsupported in Linux, with the UBIFS folk disallowing operation on MLC devices. There s been subsequent work to enable an SLC emulation mode which makes the device more reliable at the cost of losing capacity by pairing up writes/reads in cells (AFAICT). Some of this hit for the H27UCG8T2ETR in 5.16 kernels, but I definitely did some experimentation with 5.17 without having much success. I should maybe go back and try again, but I ended up going a different route. It turned out that BytePorter had documented how to add a microSD slot to the NTC C.H.I.P., using just a microSD to full SD card adapter. Every microSD card I buy seems to come with one of these, so I had plenty lying around to test with. I started with ensuring the kernel could see it ok (by modifying the device tree), but once that was all confirmed I went further and built a more modern u-boot that talked to the SD card, and defaulted to booting off it. That meant no more relying on the internal NAND at all! I do see some flakiness with the SD card, which is possibly down to the dodgy way it s hooked up (I should probably do a basic PCB layout with JLCPCB instead). That s mostly been mitigated by forcing it into 1-bit mode instead of 4-bit mode (I tried lowering the frequency too, but that didn t make a difference). The problem manifests as:
sunxi-mmc 1c11000.mmc: data error, sending stop command
and then all storage access freezing (existing logins still work, if the program you re trying to run is in cache). I can t find a conclusive software solution to this; I m pretty sure it s the hardware, but I don t understand why the recovery doesn t generally work.

Random power offs After I had storage working I d see random hangs or power offs. It wasn t quite clear what was going on. So I started trying to work out how to find out the CPU temperature, in case it was overheating. It turns out the temperature sensor on the R8 is part of the touchscreen driver, and I d taken my usual approach of turning off all the drivers I didn t think I d need. Enabling it (CONFIG_TOUCHSCREEN_SUN4I) gave temperature readings and seemed to help somewhat with stability, though not completely. Next I ended up looking at the AXP209 PMIC. There were various scripts still installed (I d started out with the NTC Debian install and slowly upgraded it to bullseye while stripping away the obvious pieces I didn t need) and a start-up script called enable-no-limit. This turned out to not be running (some sort of expectation of i2c-dev being loaded and another failing check), but looking at the script and the data sheet revealed the issue. The AXP209 can cope with 3 power sources; an external DC source, a Li-battery, and finally a USB port. I was powering my board via the USB port, using a charger rated for 2A. It turns out that the AXP209 defaults to limiting USB current to 900mA, and that with wifi active and the CPU busy the C.H.I.P. can rise above that. At which point the AXP shuts everything down. Armed with that info I was able to understand what the power scripts were doing and which bit I needed - i2cset -f -y 0 0x34 0x30 0x03 to set no limit and disable the auto-power off. Additionally I also discovered that the AXP209 had a built in temperature sensor as well, so I added support for that via iio-hwmon.

WiFi WiFi on the C.H.I.P. is provided by an RTL8723BS SDIO attached device. It s terrible (and not just here, I had an x86 based device with one where it also sucked). Thankfully there s a driver in staging in the kernel these days, but I ve still found it can fall out with my house setup, end up connecting to a further away AP which then results in lots of retries, dropped frames and CPU consumption. Nailing it to the AP on the other side of the wall from where it is helps. I haven t done any serious testing with the Bluetooth other than checking it s detected and can scan ok.

Patches I patched u-boot v2022.01 (which shows you how long ago I was trying this out) with the following to enable boot from external SD:
u-boot C.H.I.P. external SD patch
diff --git a/arch/arm/dts/sun5i-r8-chip.dts b/arch/arm/dts/sun5i-r8-chip.dts
index 879a4b0f3b..1cb3a754d6 100644
--- a/arch/arm/dts/sun5i-r8-chip.dts
+++ b/arch/arm/dts/sun5i-r8-chip.dts
@@ -84,6 +84,13 @@
 		reset-gpios = <&pio 2 19 GPIO_ACTIVE_LOW>; /* PC19 */
 	 ;
 
+	mmc2_pins_e: mmc2@0  
+		pins = "PE4", "PE5", "PE6", "PE7", "PE8", "PE9";
+		function = "mmc2";
+		drive-strength = <30>;
+		bias-pull-up;
+	 ;
+
 	onewire  
 		compatible = "w1-gpio";
 		gpios = <&pio 3 2 GPIO_ACTIVE_HIGH>; /* PD2 */
@@ -175,6 +182,16 @@
 	status = "okay";
  ;
 
+&mmc2  
+	pinctrl-names = "default";
+	pinctrl-0 = <&mmc2_pins_e>;
+	vmmc-supply = <&reg_vcc3v3>;
+	vqmmc-supply = <&reg_vcc3v3>;
+	bus-width = <4>;
+	broken-cd;
+	status = "okay";
+ ;
+
 &ohci0  
 	status = "okay";
  ;
diff --git a/arch/arm/include/asm/arch-sunxi/gpio.h b/arch/arm/include/asm/arch-sunxi/gpio.h
index f3ab1aea0e..c0dfd85a6c 100644
--- a/arch/arm/include/asm/arch-sunxi/gpio.h
+++ b/arch/arm/include/asm/arch-sunxi/gpio.h
@@ -167,6 +167,7 @@ enum sunxi_gpio_number  
 
 #define SUN8I_GPE_TWI2		3
 #define SUN50I_GPE_TWI2		3
+#define SUNXI_GPE_SDC2		4
 
 #define SUNXI_GPF_SDC0		2
 #define SUNXI_GPF_UART0		4
diff --git a/board/sunxi/board.c b/board/sunxi/board.c
index fdbcd40269..f538cb7e20 100644
--- a/board/sunxi/board.c
+++ b/board/sunxi/board.c
@@ -433,9 +433,9 @@ static void mmc_pinmux_setup(int sdc)
 			sunxi_gpio_set_drv(pin, 2);
 		 
 #elif defined(CONFIG_MACH_SUN5I)
-		/* SDC2: PC6-PC15 */
-		for (pin = SUNXI_GPC(6); pin <= SUNXI_GPC(15); pin++)  
-			sunxi_gpio_set_cfgpin(pin, SUNXI_GPC_SDC2);
+		/* SDC2: PE4-PE9 */
+		for (pin = SUNXI_GPE(4); pin <= SUNXI_GPE(9); pin++)  
+			sunxi_gpio_set_cfgpin(pin, SUNXI_GPE_SDC2);
 			sunxi_gpio_set_pull(pin, SUNXI_GPIO_PULL_UP);
 			sunxi_gpio_set_drv(pin, 2);
 		 

I ve sent some patches for the kernel device tree upstream - there s an outstanding issue with the Bluetooth wake GPIO causing the serial port not to probe(!) that I need to resolve before sending a v2, but what s there works for me. The only remaining piece is patch to enable the external SD for Linux; I don t think it s appropriate to send upstream but it s fairly basic. This limits the bus to 1 bit rather than the 4 bits it s capable of, as mentioned above.
Linux C.H.I.P. external SD DTS patch diff diff --git a/arch/arm/boot/dts/sun5i-r8-chip.dts b/arch/arm/boot/dts/sun5i-r8-chip.dts index fd37bd1f3920..2b5aa4952620 100644 --- a/arch/arm/boot/dts/sun5i-r8-chip.dts +++ b/arch/arm/boot/dts/sun5i-r8-chip.dts @@ -163,6 +163,17 @@ &mmc0 status = "okay"; ; +&mmc2 + pinctrl-names = "default"; + pinctrl-0 = <&mmc2_4bit_pe_pins>; + vmmc-supply = <&reg_vcc3v3>; + vqmmc-supply = <&reg_vcc3v3>; + bus-width = <1>; + non-removable; + disable-wp; + status = "okay"; + ; + &ohci0 status = "okay"; ;

As for what I m doing with it, I think that ll have to be a separate post.

Simon Josefsson: A Security Device Threat Model: The Substitution Attack

I d like to describe and discuss a threat model for computational devices. This is generic but we will narrow it down to security-related devices. For example, portable hardware dongles used for OpenPGP/OpenSSH keys, FIDO/U2F, OATH HOTP/TOTP, PIV, payment cards, wallets etc and more permanently attached devices like a Hardware Security Module (HSM), a TPM-chip, or the hybrid variant of a mostly permanently-inserted but removable hardware security dongles. Our context is cryptographic hardware engineering, and the purpose of the threat model is to serve as as a thought experiment for how to build and design security devices that offer better protection. The threat model is related to the Evil maid attack. Our focus is to improve security for the end-user rather than the traditional focus to improve security for the organization that provides the token to the end-user, or to improve security for the site that the end-user is authenticating to. This is a critical but often under-appreciated distinction, and leads to surprising recommendations related to onboard key generation, randomness etc below.

The Substitution Attack
An attacker is able to substitute any component of the device (hardware or software) at any time for any period of time.
Your takeaway should be that devices should be designed to mitigate harmful consequences if any component of the device (hardware or software) is substituted for a malicious component for some period of time, at any time, during the lifespan of that component. Some designs protect better against this attack than other designs, and the threat model can be used to understand which designs are really bad, and which are less so.

Terminology The threat model involves at least one device that is well-behaving and one that is not, and we call these Good Device and Bad Device respectively. The bad device may be the same physical device as the good key, but with some minor software modification or a minor component replaced, but could also be a completely separate physical device. We don t care about that distinction, we just care if a particular device has a malicious component in it or not. I ll use terms like security device , device , hardware key , security co-processor etc interchangeably. From an engineering point of view, malicious here includes unintentional behavior such as software or hardware bugs. It is not possible to differentiate an intentionally malicious device from a well-designed device with a critical bug. Don t attribute to malice what can be adequately explained by stupidity, but don t na vely attribute to stupidity what may be deniable malicious.

What is some period of time ? Some period of time can be any length of time: seconds, minutes, days, weeks, etc. It may also occur at any time: During manufacturing, during transportation to the user, after first usage by the user, or after a couple of months usage by the user. Note that we intentionally consider time-of-manufacturing as a vulnerable phase. Even further, the substitution may occur multiple times. So the Good Key may be replaced with a Bad Key by the attacker for one day, then returned, and later this repeats a month later.

What is harmful consequences ? Since a security key has a fairly well-confined scope and purpose, we can get a fairly good exhaustive list of things that could go wrong. Harmful consequences include:
  • Attacker learns any secret keys stored on a Good Key.
  • Attacker causes user to trust a public generated by a Bad Key.
  • Attacker is able to sign something using a Good Key.
  • Attacker learns the PIN code used to unlock a Good Key.
  • Attacker learns data that is decrypted by a Good Key.

Thin vs Deep solutions One approach to mitigate many issues arising from device substitution is to have the host (or remote site) require that the device prove that it is the intended unique device before it continues to talk to it. This require an authentication/authorization protocol, which usually involves unique device identity and out-of-band trust anchors. Such trust anchors is often problematic, since a common use-case for security device is to connect it to a host that has never seen the device before. A weaker approach is to have the device prove that it merely belongs to a class of genuine devices from a trusted manufacturer, usually by providing a signature generated by a device-specific private key signed by the device manufacturer. This is weaker since then the user cannot differentiate two different good devices. In both cases, the host (or remote site) would stop talking to the device if it cannot prove that it is the intended key, or at least belongs to a class of known trusted genuine devices. Upon scrutiny, this solution is still vulnerable to a substitution attack, just earlier in the manufacturing chain: how can the process that injects the per-device or per-class identities/secrets know that it is putting them into a good key rather than a malicious device? Consider also the consequences if the cryptographic keys that guarantee that a device is genuine leaks. The model of the thin solution is similar to the old approach to network firewalls: have a filtering firewall that only lets through intended traffic, and then run completely insecure protocols internally such as telnet. The networking world has evolved, and now we have defense in depth: even within strongly firewall ed networks, it is prudent to run for example SSH with publickey-based user authentication even on locally physical trusted networks. This approach requires more thought and adds complexity, since each level has to provide some security checking. I m arguing we need similar defense-in-depth for security devices. Security key designs cannot simply dodge this problem by assuming it is working in a friendly environment where component substitution never occur.

Example: Device authentication using PIN codes To see how this threat model can be applied to reason about security key designs, let s consider a common design. Many security keys uses PIN codes to unlock private key operations, for example on OpenPGP cards that lacks built-in PIN-entry functionality. The software on the computer just sends a PIN code to the device, and the device allows private-key operations if the PIN code was correct. Let s apply the substitution threat model to this design: the attacker replaces the intended good key with a malicious device that saves a copy of the PIN code presented to it, and then gives out error messages. Once the user has entered the PIN code and gotten an error message, presumably temporarily giving up and doing other things, the attacker replaces the device back again. The attacker has learnt the PIN code, and can later use this to perform private-key operations on the good device. This means a good design involves not sending PIN codes in clear, but use a stronger authentication protocol that allows the card to know that the PIN was correct without learning the PIN. This is implemented optionally for many OpenPGP cards today as the key-derivation-function extension. That should be mandatory, and users should not use setups that sends device authentication in the clear, and ultimately security devices should not even include support for that. Compare how I build Gnuk on my PGP card with the kdf_do=required option.

Example: Onboard non-predictable key-generation Many devices offer both onboard key-generation, for example OpenPGP cards that generate a Ed25519 key internally on the devices, or externally where the device imports an externally generated cryptographic key. Let s apply the subsitution threat model to this design: the user wishes to generate a key and trust the public key that came out of that process. The attacker substitutes the device for a malicious device during key-generation, imports the private key into a good device and gives that back to the user. Most of the time except during key generation the user uses a good device but still the attacker succeeded in having the user trust a public key which the attacker knows the private key for. The substitution may be a software modification, and the method to leak the private key to the attacker may be out-of-band signalling. This means a good design never generates key on-board, but imports them from a user-controllable environment. That approach should be mandatory, and users should not use setups that generates private keys on-board, and ultimately security devices should not even include support for that.

Example: Non-predictable randomness-generation Many devices claims to generate random data, often with elaborate design documents explaining how good the randomness is. Let s apply the substitution threat model to this design: the attacker replaces the intended good key with a malicious design that generates (for the attacker) predictable randomness. The user will never be able to detect the difference since the random output is, well, random, and typically not distinguishable from weak randomness. The user cannot know if any cryptographic keys generated by a generator was faulty or not. This means a good design never generates non-predictable randomness on the device. That approach should be mandatory, and users should not use setups that generates non-predictable randomness on the device, and ideally devices should not have this functionality.

Case-Study: Tillitis I have warmed up a bit for this. Tillitis is a new security device with interesting properties, and core to its operation is the Compound Device Identifier (CDI), essentially your Ed25519 private key (used for SSH etc) is derived from the CDI that is computed like this:
cdi = blake2s(UDS, blake2s(device_app), USS)
Let s apply the substitution threat model to this design: Consider someone replacing the Tillitis key with a malicious key during postal delivery of the key to the user, and the replacement device is identical with the real Tillitis key but implements the following key derivation function:
cdi = weakprng(UDS , weakprng(device_app), USS)
Where weakprng is a compromised algorithm that is predictable for the attacker, but still appears random. Everything will work correctly, but the attacker will be able to learn the secrets used by the user, and the user will typically not be able to tell the difference since the CDI is secret and the Ed25519 public key is not self-verifiable.

Conclusion Remember that it is impossible to fully protect against this attack, that s why it is merely a thought experiment, intended to be used during design of these devices. Consider an attacker that never gives you access to a good key and as a user you only ever use a malicious device. There is no way to have good security in this situation. This is not hypothetical, many well-funded organizations do what they can to derive people from having access to trustworthy security devices. Philosophically it does not seem possible to tell if these organizations have succeeded 100% already and there are only bad security devices around where further resistance is futile, but to end on an optimistic note let s assume that there is a non-negligible chance that they haven t succeeded. In these situations, this threat model becomes useful to improve the situation by identifying less good designs, and that s why the design mantra of mitigate harmful consequences is crucial as a takeaway from this. Let s improve the design of security devices that further the security of its users!

Arturo Borrero Gonz lez: Kubecon and CloudNativeCon 2023 Europe summary

Post logo This post serves as a report from my attendance to Kubecon and CloudNativeCon 2023 Europe that took place in Amsterdam in April 2023. It was my second time physically attending this conference, the first one was in Austin, Texas (USA) in 2017. I also attended once in a virtual fashion. The content here is mostly generated for the sake of my own recollection and learnings, and is written from the notes I took during the event. The very first session was the opening keynote, which reunited the whole crowd to bootstrap the event and share the excitement about the days ahead. Some astonishing numbers were announced: there were more than 10.000 people attending, and apparently it could confidently be said that it was the largest open source technology conference taking place in Europe in recent times. It was also communicated that the next couple iteration of the event will be run in China in September 2023 and Paris in March 2024. More numbers, the CNCF was hosting about 159 projects, involving 1300 maintainers and about 200.000 contributors. The cloud-native community is ever-increasing, and there seems to be a strong trend in the industry for cloud-native technology adoption and all-things related to PaaS and IaaS. The event program had different tracks, and in each one there was an interesting mix of low-level and higher level talks for a variety of audience. On many occasions I found that reading the talk title alone was not enough to know in advance if a talk was a 101 kind of thing or for experienced engineers. But unlike in previous editions, I didn t have the feeling that the purpose of the conference was to try selling me anything. Obviously, speakers would make sure to mention, or highlight in a subtle way, the involvement of a given company in a given solution or piece of the ecosystem. But it was non-invasive and fair enough for me. On a different note, I found the breakout rooms to be often small. I think there were only a couple of rooms that could accommodate more than 500 people, which is a fairly small allowance for 10k attendees. I realized with frustration that the more interesting talks were immediately fully booked, with people waiting in line some 45 minutes before the session time. Because of this, I missed a few important sessions that I ll hopefully watch online later. Finally, on a more technical side, I ve learned many things, that instead of grouping by session I ll group by topic, given how some subjects were mentioned in several talks. On gitops and CI/CD pipelines Most of the mentions went to FluxCD and ArgoCD. At that point there were no doubts that gitops was a mature approach and both flux and argoCD could do an excellent job. ArgoCD seemed a bit more over-engineered to be a more general purpose CD pipeline, and flux felt a bit more tailored for simpler gitops setups. I discovered that both have nice web user interfaces that I wasn t previously familiar with. However, in two different talks I got the impression that the initial setup of them was simple, but migrating your current workflow to gitops could result in a bumpy ride. This is, the challenge is not deploying flux/argo itself, but moving everything into a state that both humans and flux/argo can understand. I also saw some curious mentions to the config drifts that can happen in some cases, even if the goal of gitops is precisely for that to never happen. Such mentions were usually accompanied by some hints on how to operate the situation by hand. Worth mentioning, I missed any practical information about one of the key pieces to this whole gitops story: building container images. Most of the showcased scenarios were using pre-built container images, so in that sense they were simple. Building and pushing to an image registry is one of the two key points we would need to solve in Toolforge Kubernetes if adopting gitops. In general, even if gitops were already in our radar for Toolforge Kubernetes, I think it climbed a few steps in my priority list after the conference. Another learning was this site: https://opengitops.dev/. Group On etcd, performance and resource management I attended a talk focused on etcd performance tuning that was very encouraging. They were basically talking about the exact same problems we have had in Toolforge Kubernetes, like api-server and etcd failure modes, and how sensitive etcd is to disk latency, IO pressure and network throughput. Even though Toolforge Kubernetes scale is small compared to other Kubernetes deployments out there, I found it very interesting to see other s approaches to the same set of challenges. I learned how most Kubernetes components and apps can overload the api-server. Because even the api-server talks to itself. Simple things like kubectl may have a completely different impact on the API depending on usage, for example when listing the whole list of objects (very expensive) vs a single object. The conclusion was to try avoiding hitting the api-server with LIST calls, and use ResourceVersion which avoids full-dumps from etcd (which, by the way, is the default when using bare kubectl get calls). I already knew some of this, and for example the jobs-framework-emailer was already making use of this ResourceVersion functionality. There have been a lot of improvements in the performance side of Kubernetes in recent times, or more specifically, in how resources are managed and used by the system. I saw a review of resource management from the perspective of the container runtime and kubelet, and plans to support fancy things like topology-aware scheduling decisions and dynamic resource claims (changing the pod resource claims without re-defining/re-starting the pods). On cluster management, bootstrapping and multi-tenancy I attended a couple of talks that mentioned kubeadm, and one in particular was from the maintainers themselves. This was of interest to me because as of today we use it for Toolforge. They shared all the latest developments and improvements, and the plans and roadmap for the future, with a special mention to something they called kubeadm operator , apparently capable of auto-upgrading the cluster, auto-renewing certificates and such. I also saw a comparison between the different cluster bootstrappers, which to me confirmed that kubeadm was the best, from the point of view of being a well established and well-known workflow, plus having a very active contributor base. The kubeadm developers invited the audience to submit feature requests, so I did. The different talks confirmed that the basic unit for multi-tenancy in kubernetes is the namespace. Any serious multi-tenant usage should leverage this. There were some ongoing conversations, in official sessions and in the hallway, about the right tool to implement K8s-whitin-K8s, and vcluster was mentioned enough times for me to be convinced it was the right candidate. This was despite of my impression that multiclusters / multicloud are regarded as hard topics in the general community. I definitely would like to play with it sometime down the road. On networking I attended a couple of basic sessions that served really well to understand how Kubernetes instrumented the network to achieve its goal. The conference program had sessions to cover topics ranging from network debugging recommendations, CNI implementations, to IPv6 support. Also, one of the keynote sessions had a reference to how kube-proxy is not able to perform NAT for SIP connections, which is interesting because I believe Netfilter Conntrack could do it if properly configured. One of the conclusions on the CNI front was that Calico has a massive community adoption (in Netfilter mode), which is reassuring, especially considering it is the one we use for Toolforge Kubernetes. Slide On jobs I attended a couple of talks that were related to HPC/grid-like usages of Kubernetes. I was truly impressed by some folks out there who were using Kubernetes Jobs on massive scales, such as to train machine learning models and other fancy AI projects. It is acknowledged in the community that the early implementation of things like Jobs and CronJobs had some limitations that are now gone, or at least greatly improved. Some new functionalities have been added as well. Indexed Jobs, for example, enables each Job to have a number (index) and process a chunk of a larger batch of data based on that index. It would allow for full grid-like features like sequential (or again, indexed) processing, coordination between Job and more graceful Job restarts. My first reaction was: Is that something we would like to enable in Toolforge Jobs Framework? On policy and security A surprisingly good amount of sessions covered interesting topics related to policy and security. It was nice to learn two realities:
  1. kubernetes is capable of doing pretty much anything security-wise and create greatly secured environments.
  2. it does not by default. The defaults are not security-strict on purpose.
It kind of made sense to me: Kubernetes was used for a wide range of use cases, and developers didn t know beforehand to which particular setup they should accommodate the default security levels. One session in particular covered the most basic security features that should be enabled for any Kubernetes system that would get exposed to random end users. In my opinion, the Toolforge Kubernetes setup was already doing a good job in that regard. To my joy, some sessions referred to the Pod Security Admission mechanism, which is one of the key security features we re about to adopt (when migrating away from Pod Security Policy). I also learned a bit more about Secret resources, their current implementation and how to leverage a combo of CSI and RBAC for a more secure usage of external secrets. Finally, one of the major takeaways from the conference was learning about kyverno and kubeaudit. I was previously aware of the OPA Gatekeeper. From the several demos I saw, it was to me that kyverno should help us make Toolforge Kubernetes more sustainable by replacing all of our custom admission controllers with it. I already opened a ticket to track this idea, which I ll be proposing to my team soon. Final notes In general, I believe I learned many things, and perhaps even more importantly I re-learned some stuff I had forgotten because of lack of daily exposure. I m really happy that the cloud native way of thinking was reinforced in me, which I still need because most of my muscle memory to approach systems architecture and engineering is from the old pre-cloud days. List of sessions I attended on the first day: List of sessions I attended on the second day: List of sessions I attended on third day: The videos have been published on Youtube.

25 April 2023

B lint R czey: Improve build time of Rust, Java and Intel Fortran projects with Firebuild s new release!

Rust is a hugely popular compiled programming language and accelerating it was an important goal for Firebuild for some time. Firebuild s v0.8.0 release finally added Rust support in addition to numerous other improvements including support for Doxygen, Intel s Fortran compiler and restored javac and javadoc acceleration.

Firebuild s Rust + Cargo support Firebuild treats programs as black boxes intercepting C standard library calls and system calls. It shortcuts the program invocations that predictably generate the same outputs because the program itself is known to be deterministic and all inputs are known in advance. Rust s compiler, rustc is deterministic in itself and simple rustc invocations were already accelerated, but parallel builds driven by Cargo needed a few enhancements in Firebuild.

Cargo s jobserver Cargo uses the Rust variant of the GNU Make s jobserver to control the parallelism in a build. The jobserver creates a file descriptor from which descendant processes can read tokens and are allowed to run one extra thread or parallel process per token received. After the extra threads or processes are finished the tokens must be returned by writing to the other file descriptor the jobserver created. The jobserver s file descriptors are shared with the descendant processes via environment variables:
# rustc's environment variables
...
CARGO_MAKEFLAGS="-j --jobserver-fds=4,5 --jobserver-auth=4,5"
...
Since getting tokens from the jobserver involves reading them as nondeterministic bytes from an inherited file descriptor this is clearly an operation that would depend on input not known in advance. Firebuild needs to make an exception and ignore jobserver usage related reads and writes since they are not meant to change the build results. However, there are programs not caring at all about jobservers and their file descriptors. They happily close the inherited file descriptors and open new ones with the same id, to use them for entirely different purposes. One such program is the widely used ./configure script, thus the case is far from being theoretical. To stay on the safe side firebuild ignores jobserver fd usage only in programs which are known to use the jobserver properly. The list of the programs is now configurable in /etc/firebuild.conf and since rustc is on the list by default parallel Rust builds are accelerated out of the box!

Writable dependency dir The other issue that prevented highly accelerated Rust builds was rustc s -L dependency=<dir> parameter. This directory is populated in a not fully deterministic order in parallel builds. Firebuild on the other hand hashes directory listings of open()-ed directories treating them as inputs assuming that the directory content will influence the intercepted programs outputs. As rustc programs started in parallel scanned the dependency directory in different states depending on what other Rust compilations finished already Firebuild had to store the full directory content as an input for each rustc cache entry resulting low hit rate when rustc was started again with otherwise identical inputs. The solution here is ignoring rustc scanning the dependency directory, because the dependencies actually used are still treated as input and are checked when shortcutting rustc. With that implemented in firebuild, too, librsvg s build that uses Rust and Cargo can be accelerated by more than 90%, even on a system having 12 cores/24 threads!:
Firebuild accelerating librsvg s Rust + Cargo build from 38s to 2.8s on a Ryzen 5900X (12C/24T) system

On the way to accelerate anything Firebuild s latest release incorporated more than 100 changes just from the last two months. They unlocked acceleration of Rust builds with Cargo, fixed Firebuild to work with the latest Java update that slightly changed its behavior, started accelerating Intel s Fortran compiler in addition to accelerating gfortran that was already supported and included many smaller changes improving the acceleration of other compilers and tools. If your favorite toolchain is not mentioned, there is still a good chance that it is already supported. Give Firebuild a try and tell us about your experience! Update 1: Comparison to sccache came up in the reddit topic about Firebuild s Rust acceleration , thus by popular demand this is how sccache performs on the same project:
Firebuild 0.8.0 vs. sccache 0.4.2 accelerating librsvg s Rust + Cargo build
All builds took place on the same Ryzen 5900X system with 12 cores / 24 threads in LXC containers limited to using 1-12 virtual CPUs. A warm-up build took place before the vanilla (without any instrumentation) build to download and compile the dependency crates to measure only the project s build time. A git clean command cleared all the build artifacts from the project directory before each build and ./autogen.sh was run to measure only clean rebuilds (without autotools). See test configuration in the Firebuild performance test repository for more details and easy reproduction. Firebuild had lower overhead than sccache (2.83% vs. 6.10% on 1 CPU and 7.71% vs. 22.05% on 12 CPUs) and made the accelerated build finish much faster (2.26% vs. 19.41% of vanilla build s time on 1 CPU and 7.5% vs. 27.4% of vanilla build s time on 12 CPUs).

20 April 2023

Simon Josefsson: Sigstore for Apt Archives: apt-cosign

As suggested in my initial announcement of apt-sigstore my plan was to look into stronger uses of Sigstore than rekor, and I m now happy to announce that the apt-cosign plugin has been added to apt-sigstore and the operational project debdistcanary is publishing cosign-statements about the InRelease file published by the following distributions: Trisquel GNU/Linux, PureOS, Gnuinos, Ubuntu, Debian and Devuan. Summarizing the commands that you need to run as root to experience the great new world:
# run everything as root: su / sudo -i / doas -s
apt-get install -y apt gpg bsdutils wget
wget -nv -O/usr/local/bin/apt-verify-gpgv https://gitlab.com/debdistutils/apt-verify/-/raw/main/apt-verify-gpgv
chmod +x /usr/local/bin/apt-verify-gpgv
mkdir -p /etc/apt/verify.d
ln -s /usr/bin/gpgv /etc/apt/verify.d
echo 'APT::Key::gpgvcommand "apt-verify-gpgv";' > /etc/apt/apt.conf.d/75verify
wget -O/usr/local/bin/cosign https://github.com/sigstore/cosign/releases/download/v2.0.1/cosign-linux-amd64
echo 924754b2e62f25683e3e74f90aa5e166944a0f0cf75b4196ee76cb2f487dd980  /usr/local/bin/cosign   sha256sum -c
chmod +x /usr/local/bin/cosign
wget -nv -O/etc/apt/verify.d/apt-cosign https://gitlab.com/debdistutils/apt-sigstore/-/raw/main/apt-cosign
chmod +x /etc/apt/verify.d/apt-cosign
mkdir -p /etc/apt/trusted.cosign.d
dist=$(lsb_release --short --id   tr A-Z a-z)
wget -O/etc/apt/trusted.cosign.d/cosign-public-key-$dist.txt "https://gitlab.com/debdistutils/debdistcanary/-/raw/main/cosign/cosign-public-key-$dist.txt"
echo "Cosign::Base-URL \"https://gitlab.com/debdistutils/canary/$dist/-/raw/main/cosign\";" > /etc/apt/apt.conf.d/77cosign
Then run your usual apt-get update and look in the syslog to debug things. This is the kind of work that gets done while waiting for the build machines to attempt to reproducibly build PureOS. Unfortunately, the results is that a meager 16% of the 765 added/modifed packages are reproducible by me. There is some infrastructure work to be done to improve things: we should use sbuild for example. The build infrastructure should produce signed statements for each package it builds: One statement saying that it attempted to reproducible build a particular binary package (thus generated some build logs and diffoscope-output for auditing), and one statements saying that it actually was able to reproduce a package. Verifying such claims during apt-get install or possibly dpkg -i is a logical next step. There is some code cleanups and release work to be done now. Which distribution will be the first apt-based distribution that includes native support for Sigstore? Let s see. Sigstore is not the only relevant transparency log around, and I ve been trying to learn a bit about Sigsum to be able to support it as well. The more improved confidence about system security, the merrier!

19 April 2023

Ian Jackson: The Rust Foundation's bad draft trademark policy

tl;dr The Rust Foundation s proposed new trademark policy is far too restrictive, and will cause (more) drama unless it is substantially revised. Process Rust is a trademark owned by the Foundation. The Rust Foundation still seems to be finding its feet. Evidently, one of the items on its backlog was to update the trademark policy. Apparently they have been working on this for some time, in an informal working group. In August, there was a survey. (I saw it in This Week In Rust, the community-curated newsletter where most important stuff appears, and responded.) I don t think the results of this survey have been published anywhere. Last week (12th April) the Foundation published an official Inside Rust blog post linking to a draft. They included a link to a feedback survey, closing on the 17th of April i.e., it was open for 5 days. This is far too short a period for formal feedback on such a draft. Especially given that this process has apparently already been generating significant controversy within parts of the Rust community. Substance Overall, this policy is poor. It is far too restrictive. It is likely to lead to (further) controversy and argument, including conflicts with Rust s downstreams. It does not serve the needs of the Rust community. In particular, the Rust community does not need the trademark to: The community does need the trademark to: It might be useful to use the trademark to strengthen licensing or CoC compliance. For example, good faith redistributions of a modified Rust, as Rust , would be Free Software, even though the copyright licence permits proprietary derivatives; so use of the Rust trademark should probably require use of a Free licence. There should be a series of blanket permissions to use the word Rust in for example: Currently there aren t. For example the current Debian practice of calling Rust libraries rust-<name-of-crate> is probably in violation. There are a number of more detailed problems with the wording. Values The policy has all the hallmarks of excessive influence from traditional trademark lawyers and not enough influence from the Free Software community. I would like to remind the Free Software activists on the inside of this process that the lawyers are there to serve you and the community. The values embodied in trademark law often conflict with the values of the Free Software community. The Rust Project should adopt a trademark policy which follows the community s values - even if that might weaken our ability to sue evildoers. Next steps The Foundation should take a step back and pause the process. Then, the Foundation should restart the process from a much earlier stage, with much wider publicity. Each stage should be widely advertised to the whole community, with opportunities for feedback. This should include publishing the results of the August 2022 survey. The Foundation should publish a sketch of the legal advice they have received, publicly say what the plausible options are and what their consequences might be (for the community, for downstreams, and for the Foundation s enforcement ability). (Some of this will no doubt repeat the work that has been done in the informal trademark working group. That work wasn t widely enough advertised.) Echoes of a dispute from 2006 Mozilla made a very similar mistake with Firefox in 2006. The official policy stated that no-one was allowed to distribute Firefox with any patches, unless those patches had been pre-approved by Mozilla. Debian is committed to Software Freedom. This must includes the freedom to modify the software as one sees fit, even if the original authors don t agree. Now, overly-restrictive trademark policies are hardly new. Debian often takes the practical view that usually the upstream with such a policy doesn t really mean it. But Mozilla decided they did mean it. They contacted Debian asking for Debian to get their patches approved. Since that wasn t acceptable to Debian, they stopped using the word Firefox . For a decade, Debian s Firefox browser was called Iceweasel . We don t want something similar happening to Rust .

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18 April 2023

Shirish Agarwal: Philips LCD Monitor 22 , 1984, Reaper Man, The Firm.

PHILIPS PHL 221S8L Those who have been reading this blog for a long time would perhaps know that I had bought a Viewsonic 19 almost 12 years ago. The Monitor was functioning well till last week. I had thought to change it to a 24 monitor almost 3-4 years ago when 24 LCD Monitors were going for around 4k/- or thereabouts. But the monitor kept on functioning and I didn t have space (nor do) to have a dual-monitor setup. It just didn t make sense. Apart from higher electricity charges it would have also have made more demands on my old system which somehow is still functioning even after all those years. Then last week, it started to dim and after couple of days completely conked out. I had wanted to buy a new monitor in front of mum so she could watch movies or whatever but this was not to be. Sp I had to buy an LCD Monitor as Government raised taxes enormously after pandemic. Same/similar monitor that used to cost INR 4k/- today costed me almost INR 7k/- almost double the price. Hooking it to Debian I got the following

$ sudo hwinfo --monitor grep Model Model: "PHILIPS PHL 221S8L" FWIW hwinfo is the latest version

~$ sudo hwinfo --version21.82
I did see couple of movies before starting to write this blog post. Not an exceptional monitor but better than before. I had option from three brands, Dell (most expensive), Philips (middle) and & LG (lowest in prices). Interestingly, Viewsonic disappeared from the market about 5 years back and made a comeback just couple of years ago. Even Philips which had exited the PC Monitor almost a decade back re-entered the market. Apart from the branding, it doesn t make much of a difference as almost all the products including the above monitors are produced in China. I did remember her a lot while buying the monitor as I m sure she would have enjoyed it far more than me but that was not to be

1984 During last week when I didn t have the monitor I re-read 1984. To be completely honest, I had read the above book when I was in the 20 s and I had no context. The protagonist seemed like a whiner and for the life of me I couldn t understand why he didn t try to escape. Re-reading after almost 2 decades and a bit more I shat a number of times because now the context is pretty near and pretty real. I can see why the Republicans in the U.S. banned it. I also realized why the protagnist didn t attempt to run away because wherever he would run away it would be the same thing. It probably is one of the most depressing books I have ever read. To willfully accept what is false after all that torture. What was also interesting to me is to find that George Orwell was also a soldier just like Tolkien was. Both took part and wrote such different stories. While Mr. Tolkien writes and shares the pendulum between hope and despair, Mr. Orwell is decidedly dark. Not grey but dark. I am not sure if I would like to read Animal Farm anytime soon.

The Reaper Man Terry Pratchett It is by sheer coincidence or perhaps I needed something to fill me up when I got The Reaper Man from Terry Pratchett. It was practically like a breath of fresh air. And I love Mr. Pratchett for the inclusivity he brings in. We think about skin color, and what not and here Mr. Pratchett writes about an undead gentleman who s extremely polite as he was a wizard. I won t talk more as I don t really want to spoil the surprise but rest assured everybody is gonna love it. I also read Long Utopia but this is for those who believe and think of multiverses long before it became a buzzword that it is today.

The Firm John Grisham Now I don t know what I should write about this book as there aren t many John Grisham books where a rookie wins against more than one party opposite him. I wouldn t go much into depth but simply say it was worth a read. I am currently reading Gray Mountain. It very much shows how the coal Industry is corrupt and what all it does. It also brings to mind the amount of mining that is done in which Iron is the mostly sought after and done. Now if we are mining 94% Iron then wouldn t it make sense to ask to have a circular economy around Iron but we don t even hear a word about it. Even with all the imagined projections of lithium mining, it would hardly be 10% . I could go on but will finish for now, till later.

Matt Brown: co2mon.nz: Ventilation monitoring as a service

Previously, I explained why ventilation monitoring is important, and the opportunity I see to help accelerate deployment of high quality ventilation monitoring for small businesses and organisations. In this post, I m going to discuss my plans to tackle that opportunity:

My journey to ventilation monitoring I started looking into ventilation monitoring in detail last year when I wanted to ensure that the classrooms of our local primary school were well ventilated during the Omicron outbreak. That research revealed that the existing products on offer were challenging to deploy in a school environment from a cost perspective while also not providing perfect functionality. I built and deployed a set of monitors to our local school, along with a corresponding set of software and web services that provide management of the monitors and visibility into the collected data and trends. The benefit of the monitoring is evident - CO2 concentration drops immediately after a notification occurs, indicating the intended action of increasing ventilation is taking place. Initially this occurred more frequently, but over time low concentrations of CO2, indicating good ventilation levels, are regularly achieved across the school day thanks to simple changes in routine being established, such as leaving windows cracked open. As the benefits of the project to the school became clear, my ambition and vision for ventilation monitoring grew from wanting to see my children learn in a safe and effective environment to desiring safe and effective learning, working, living and social spaces for everyone.

co2mon.nz: Ventilation monitoring as a service prototype co2mon.nz is the service that I have launched to explore this opportunity. Based on the same hardware and software that I used for the school deployment I am selling both a physical CO2 monitor and an ongoing subscription service for the management and monitoring. Together, the monitor and software provide an effective and affordable path to understanding indoor air quality and ventilation status that anyone can use.

CO2 monitor The CO2 monitor hardware and firmware are based on Oliver Seiler s design using a Sensirion SCD40 module for CO2 measurement and providing immediate in-room feedback via an on-monitor screen as well as a red/orange/green traffic light . In addition to the immediate feedback provided by the monitor itself, a WiFi connection can be configured allowing every measurement to be reported back to the supporting monitoring and management service. At the current prototype stage, I am building all the hardware, 3D printing the plastic cases and assembling the circuit board from purchased components through a production line in my home workshop. The monitor is powered via a standard USB cable and wall adaptor for simplicity. The first batch of monitors I built have been operating smoothly for nearly a year now. Further refinement and development of the design is required but already I am impressed with the potential this combination of easily accessible components provides to enable widespread adoption and deployment of ventilation monitoring.

Monitoring and management service The web service provides a historical record of CO2 levels from each monitor through a set of graphs and other dashboards and allows for this data to be shared or published. This is useful both for providing visibility into ventilation status to those not directly present in the space (e.g. across an entire school) and to allow insights into trends and patterns in ventilation to be observed and acted upon. When I began the project I approached the software side as an opportunity to explore the real-world equivalents of many of the internal tools and components that I was used to using within Google. That s been a fun process, even though it means I ve invested far more time on the software than the current number of customers or business state can really justify. Communication with the monitors occurs via MQTT into a custom Go service responsible for maintaining the fleet and exposing the measurement data to Prometheus which acts as the storage layer. A second service (based on the Buffalo web framework) is responsible for serving the web interface containing the dashboards and configuration options. Alongside these core components another small Golang service manages a private X509 certificate authority to provide monitor identity and encryption of the measurement data and an automated pipeline of scripts and triggers takes care of firmware provisioning, sensor calibration and burn-in/failure testing when building batches of monitors. While simple, the design is easy to manage and could scale to support many, many more monitors without significant effort. I m hosting the infrastructure on AWS, which I ve found pleasant and easy to use, and while not a typical choice, I m very pleased with the performance and flexibility that Prometheus offers as a data storage layer.

Areas of development The prototype has been effective in proving the feasibility of offering ventilation monitoring as a service, but to evolve the prototype into an actual business is going to require further effort in the following areas:

Finding product market fit I m confident that what co2mon.nz is offering could provide a useful and needed service for many small business owners and numerous others, but the question of whether it s sufficiently compelling that a sizeable group of customers see enough value that they re willing to regularly pay for it and therefore sustain a business providing the service is not yet proven. While initial feedback on the idea has been positive, much of it has been from family and friends and I ve spent more time building the software (which has been fun and educational) than I have talking to actual potential customers and understanding their needs and wants. This is a classic trap that technical founders fall into, and I m guilty despite my best intentions it s comfortable and easy for me to work on the parts where I have existing experience and neglect putting time into the customer-facing sales, marketing and research which are more uncomfortable, new and challenging!

Scaling monitor production Scaling from the current prototype batches I have built to even modest levels (e.g. hundreds) of sales will require outsourcing. There are several potential New Zealand and overseas providers I can work with which look very promising, but will require iteration of the hardware design (e.g. to remove through-hole components which add complexity and expense to the PCB assembly process). The lead times I ve been quoted for working with these outsourced providers are in the order of 1-2 months per batch, and on top of this there are a number of other risks in terms of component availability and regulatory compliance that may add additional delays or time to resolve, particularly as my experience leans towards the software rather than the hardware. It seems counter-intuitive to worry about how to scale to meet demand that doesn t yet provably exist, but given the potentially long lead times involved in establishing outsourced production I think it s worth taking some risk in starting this journey early.

Next steps My aim now is to intentionally change my focus from the software to learning about the market and finding the right product to offer via two channels:
  1. Via online marketing, to reach a wide range of potential customers and allow rapid iteration and testing of a variety of product/service combinations, including referral options for existing customers.
  2. In-person with small businesses in my local area to seek out direct feedback and thoughts on the general issue of ventilation monitoring and the specific service I m offering.
One concrete possibility I m keen to test via both channels is a simple monthly price for the combined service, rather than purchasing a monitor and separate software subscription. This has the potential to be both simpler to market and explain to customers, while also opening the possibility of short-term rental or evaluation to customers who are not willing to make a long-term investment or commitment. In parallel to the customer-focused discovery work, but as an explicit lower priority, I ll order an initial small batch of outsourced monitors to begin gaining experience with that process accepting the risk that the time and cost may turn out to be wasted if the product is wrong or not a good match for customers needs.

Matthew Palmer: Rutie and Magnus, Two Good Ways to Build Ruby Extensions in Rust

I wrote the Ruby bindings for the Enquo Project, my attempt to bring queryable encryption to all databases, using the Rutie library. Recently, I ve rewritten the bindings to use Magnus instead, and I thought I d put down my thoughts about the whole situation.

The Story So Far The Enquo Project core cryptography is all written in Rust, as seems to be the vogue these days. Rust is fast, safe, and easily interoperable with most of the rest of the modern software development ecosystem, making it a good choice as a language to implement the cryptographic primitives that Enquo needs, like Order-Revealing Encryption. Of course, since not everyone writes their applications in Rust, we need to provide the functionality of the Enquo client in the languages that people do use, such as Ruby, Python, and so on. Since re-writing all that cryptographic code in a myriad of languages would be tedious and error-prone, we instead provide bindings to the core Rust code. These are just thin shims of code that translate the data types and function calls between Rust and the target language.
Shim in a Can Wrong sort of shim, but canned language bindings would be handy
As I m most familiar with Ruby and its development ecosystem (particularly Ruby on Rails), it was natural that I d make Ruby bindings for Enquo as my first target. Rummaging around, it seemed that Rutie was a good library to use, so off I went.

What are Rutie and Magnus, Anyway? Both libraries share the same goal: provide the ability to write some Rust code, run that through a compiler, and produce something that can be loaded by the Ruby interpreter and used just like any other Ruby class. They re both fairly high level interfaces, trying to abstract away much of the gory details, and do a lot of the common heavy lifting that can make writing bindings fiddly and annoying. Things like mapping data types (like strings and integers) between Rust data types and the closest equivalents in Ruby. This mapping never goes perfectly smoothly. For example, Ruby integers don t have a fixed range of values they can represent you can store a huge number like 2256 more-or-less as easily as you can the number 12. But Rust, being a lower-level language, only has a set of integer types that have fixed boundaries, like the u32 type, which can only store integers between zero and about four billion (232 - 1, to be precise). There s also lots of little things that need to be just right, also, like translating the different memory management approaches of the languages, and dealing with a myriad of fiddly little issues like passing arguments and return values in and out of method calls, helpers for defining classes and methods (and pointing to the correct Rust functions), and so on.
A mass of tangled pipes and valves This is what I imagine it looks like inside these libraries
(Herv Cozanet / Wikimedia Commons, CC-BY-SA)
All in all, these libraries are fairly significant pieces of work, and I m mighty glad that someone else has taken on the job of building (and maintaining!) them.

So Why the Change? Good question. It s important to say at the outset that there s nothing particularly wrong with Rutie. I found using Rutie to be very straightforward, and the Ruby bindings came together very quickly and easily. If someone chose to use Rutie for their project, I m sure they d have a good experience. What made me take the time to rewrite using Magnus was a set of a few tiny things, which together gave me enough of a shove to do the work. Firstly, I d had a hiccup with Rutie s support of newer versions of Ruby, particularly 3.2 (PR). Also, I d hit a couple of segfault issues, which were ultimately caused by Ruby garbage-collecting data out from underneath me. These were ultimately my fault, of course, but Rutie wasn t helping me out in avoiding the problems in the first place. Finally, while Rutie helped translate data types, there was still a bit of boilerplate and ugliness that needed to be included. This wasn t a showstopper, but I m appreciating the extra smoothness that Magnus provides here. As an example, here s what s required in Rutie to get native Rust data types from Ruby method parameters (and the self reference to the current object):
fn enquo_field_decrypt_text(ciphertext_obj: RString, context_obj: RString) -> RString  
    let ciphertext = ciphertext_obj.to_str_unchecked();
    let context = context_obj.to_vec_u8_unchecked();
    let field = rbself.get_data(&*FIELD_WRAPPER);
    // etc etc etc
The equivalent in Magnus is just the function signature:
fn decrypt_text(&self, ciphertext: String, context: String) -> Result<String, magnus::Error>  
You can also see there that Magnus signals an exception via the Result return value, while Rutie s approach to raising an exception involves poking the Ruby VM directly, which always struck me as a bit ugly. There are several other minor things in Magnus (like its cleaner approach to wrapping structs so they can be stored in Ruby objects) that I m appreciating, too. Never discount the power of ergonomics for making a happy developer.

The End Result I spent a bit over half of last weekend doing the rewrite maybe ten hours of so. Since Magnus did more type checking and data validation, and its approach to error handling was smoother, I took the opportunity to rewrite a bunch of Ruby wrapper code I d written (which just existed to check things like ranges of values and string encodings) into Rust, as well. To make sure that the conversion was accurate, I added a heap more unit tests to the bindings. I also took the opportunity to restructure the codebase to split the code for the different Ruby classes into separate files, which I hadn t done initially as the code had originally accreted, rather than being purposefully written. All up, though, my rewrite ended up removing over 60 lines (excluding the extra specs I added):
$ git diff --stat -- lib ext/enquo/src
 ruby/ext/enquo/src/field.rs         342 ++++++++++++++++++++++++++++++++++++++
 ruby/ext/enquo/src/lib.rs           338 ++++---------------------------------
 ruby/ext/enquo/src/root.rs           39 +++++
 ruby/ext/enquo/src/root_key.rs       67 ++++++++
 ruby/lib/enquo.rb                     6 +-
 ruby/lib/enquo/field.rb             173 -------------------
 ruby/lib/enquo/root.rb               28 ----
 ruby/lib/enquo/root_key.rb            1 -
 ruby/lib/enquo/root_key/static.rb    27 ---
 9 files changed, 479 insertions(+), 542 deletions(-)
Considering that I was translating from a higher level language into a lower level one, the removal of so much code is quite remarkable. Magnus was able to automagically replace rather a lot of raise ArgumentError if something.isnt_right code in those .rb files. So, in conclusion, if you, too, are building Ruby extensions in Rust, while Rutie is a solid choice (and you probably should stick with it if you re already using it), I highly recommend giving Magnus a look for your next extension.

17 April 2023

Simon Josefsson: More on Differential Reproducible Builds: Devuan is 46% reproducible!

Building on my work to rebuild Trisquel GNU/Linux 11.0 aramo, it felt simple to generalize the tooling to any two apt-repository pairs and I ve created debdistreproduce as a template-project for doing this through the infrastructure of GitLab CI/CD and meanwhile even set up my own gitlab-runner on spare hardware. I ve brought over reproduce/trisquel to using debdistreproduce as well, and archived the old reproduce-trisquel project. After fixing some quirks, building Devuan GNU+Linux 4.0 Chimaera was fairly quick since they do not modify that many packages, and I m now able to reproduce 46% of the packages that Devuan Chimaera add/modify on amd64. I have more work in progress here (hint: reproduce/pureos), but PureOS is considerably larger than both Trisquel and Devuan together. I m not sure how interested Devuan or PureOS are in reproducible builds though. Reflecting on this work made me realize that while the natural thing to do here was to differentiate two different apt-based distributions, I have realized the same way I did for debdistdiff that it would also be interesting to compare, say, Debian bookworm from Debian unstable, especially now that they should be fairly close together. My tooling should support that too. However, to really provide any benefit from the more complete existing reproducible testing of Debian, some further benefit from doing that would be useful and I can t articulate one right now. One ultimate goal with my effort is to improve trust in apt-repositories, and combining transparency-style protection a la apt-sigstore with third-party validated reproducible builds may indeed be one such use-case that would benefit the wider community of apt-repositories. Imagine having your system not install any package unless it can verify it against a third-party reproducible build organization that commits their results in a tamper-proof transparency ledger. But I m now on repeat here, so will stop.

16 April 2023

Iustin Pop: Quick note: nftables and TCP MSS clamping

Another short note to myself, and whomever cares/searches later for nft or nftables, tcp mss clamping. Somewhat surprising, many/most of the instructions found by Google are still related to iptables. I guess people stopped writing blog posts by the time nftables became widely used? The only official documentation I can find is in the official wiki, but it doesn t list/explain exactly how does this work/in which conditions. I think this results in posts like this one that suggest additionally limiting the packets it acts on using a size limiter, in order to prevent changing small packets. Looking at the code that actually implements this, in net/netfilter/xt_TCPMSS.c (and not in the lower case-named file, which is about matching, TIL), in the function tcpmss_mangle_packet, first there is this comment:
/* Never increase MSS, even when setting it, as
 * doing so results in problems for hosts that rely
 * on MSS being set correctly.
 */
So at least the intent is that this always does the right thing (only decrease). Second, the code does correctly look at both directions of the packet when using auto-clamping (set rt mtu rather than set 1452), in the if branch for XT_TCPMSS_CLAMP_PMTU. This means, it s safer to use auto-clamping, rather than manually set the value. And finally, there is handling of some corner cases as well (syn packet with data, syn packet without the MSS option - unlikely for modern stacks - in which case it defaults to minimal values). All in all, it seems to me that it should always be correct to simply do what the wiki recommends, setting this for all packets traversing the host:
nft add rule ip filter forward tcp flags syn tcp option maxseg size set rt mtu
Of course, if you d rather not do it always, but only for external interfaces, make sure you set it in both directions:
nft add rule ip filter forward iifname ppp0 tcp flags syn tcp option maxseg size set rt mtu
nft add rule ip filter forward oifname ppp0 tcp flags syn tcp option maxseg size set rt mtu
And that should be it. Well, use iifgroup/oifgroup for better rules .

15 April 2023

Simon Josefsson: Sigstore protects Apt archives: apt-verify & apt-sigstore

Do you want your apt-get update to only ever use files whose hash checksum have been recorded in the globally immutable tamper-resistance ledger rekor provided by the Sigstore project? Well I thought you d never ask, but now you can, thanks to my new projects apt-verify and apt-sigstore. I have not done proper stable releases yet, so this is work in progress. To try it out, adapt to the modern era of running random stuff from the Internet as root, and run the following commands. Use a container or virtual machine if you have trust issues.
apt-get install -y apt gpg bsdutils wget
wget -nv -O/usr/local/bin/rekor-cli 'https://github.com/sigstore/rekor/releases/download/v1.1.0/rekor-cli-linux-amd64'
echo afde22f01d9b6f091a7829a6f5d759d185dc0a8f3fd21de22c6ae9463352cf7d  /usr/local/bin/rekor-cli   sha256sum -c
chmod +x /usr/local/bin/rekor-cli
wget -nv -O/usr/local/bin/apt-verify-gpgv https://gitlab.com/debdistutils/apt-verify/-/raw/main/apt-verify-gpgv
chmod +x /usr/local/bin/apt-verify-gpgv
mkdir -p /etc/apt/verify.d
ln -s /usr/bin/gpgv /etc/apt/verify.d
echo 'APT::Key::gpgvcommand "apt-verify-gpgv";' > /etc/apt/apt.conf.d/75verify
wget -nv -O/etc/apt/verify.d/apt-rekor https://gitlab.com/debdistutils/apt-sigstore/-/raw/main/apt-rekor
chmod +x /etc/apt/verify.d/apt-rekor
apt-get update
less /var/log/syslog
If the stars are aligned (and the puppet projects of debdistget and debdistcanary have ran their GitLab CI/CD pipeline recently enough) you will see a successful output from apt-get update and your syslog will contain debug logs showing the entries from the rekor log for the release index files that you downloaded. See sample outputs in the README. If you get tired of it, disabling is easy:
chmod -x /etc/apt/verify.d/apt-rekor
Our project currently supports Trisquel GNU/Linux 10 (nabia) & 11 (aramo), PureOS 10 (byzantium), Gnuinos chimaera, Ubuntu 20.04 (focal) & 22.04 (jammy), Debian 10 (buster) & 11 (bullseye), and Devuan GNU+Linux 4.0 (chimaera). Others can be supported to, please open an issue about it, although my focus is on FSDG-compliant distributions and their upstreams. This is a continuation of my previous work on apt-canary. I have realized that it was better to separate out the generic part of apt-canary into my new project apt-verify that offers a plugin-based method, and then rewrote apt-canary to be one such plugin. Then apt-sigstore s apt-rekor was my second plugin for apt-verify. Due to the design of things, and some current limitations, Ubuntu is the least stable since they push out new signed InRelease files frequently (mostly due to their use of Phased-Update-Percentage) and debdistget and debdistcanary CI/CD runs have a hard time keeping up. If you have insight on how to improve this, please comment me in the issue tracking the race condition. There are limitations of what additional safety a rekor-based solution actually provides, but I expect that to improve as I get a cosign-based approach up and running. Currently apt-rekor mostly make targeted attacks less deniable. With a cosign-based approach, we could design things such that your machine only downloads updates when they have been publicly archived in an immutable fashion, or submitted for validation by a third-party such as my reproducible build setup for Trisquel GNU/Linux aramo. What do you think? Happy Hacking!

14 April 2023

Russ Allbery: Review: Babel

Review: Babel, by R.F. Kuang
Publisher: Harper Voyage
Copyright: August 2022
ISBN: 0-06-302144-7
Format: Kindle
Pages: 544
Babel, or the Necessity of Violence: An Arcane History of the Oxford Translators' Revolution, to give it its full title, is a standalone dark academia fantasy set in the 1830s and 1840s, primarily in Oxford, England. The first book of R.F. Kuang's previous trilogy, The Poppy War, was nominated for multiple awards and won the Compton Crook Award for best first novel. Babel is her fourth book. Robin Swift, although that was not his name at the time, was born and raised in Canton and educated by an inexplicable English tutor his family could not have afforded. After his entire family dies of cholera, he is plucked from China by a British professor and offered a life in England as his ward. What follows is a paradise of books, a hell of relentless and demanding instruction, and an unpredictably abusive emotional environment, all aiming him towards admission to Oxford University. Robin will join University College and the Royal Institute of Translation. The politics of this imperial Britain are almost precisely the same as in our history, but one of the engines is profoundly different. This world has magic. If words from two different languages are engraved on a metal bar (silver is best), the meaning and nuance lost in translation becomes magical power. With a careful choice of translation pairs, and sometimes additional help from other related words and techniques, the silver bar becomes a persistent spell. Britain's industrial revolution is in overdrive thanks to the country's vast stores of silver and the applied translation prowess of Babel. This means Babel is also the only part of very racist Oxford that accepts non-white students and women. They need translators (barely) more than they care about maintaining social hierarchy; translation pairs only work when the translator is fluent in both languages. The magic is also stronger when meanings are more distinct, which is creating serious worries about classical and European languages. Those are still the bulk of Babel's work, but increased trade and communication within Europe is eroding the meaning distinctions and thus the amount of magical power. More remote languages, such as Chinese and Urdu, are full of untapped promise that Britain's colonial empire wants to capture. Professor Lowell, Robin's dubious benefactor, is a specialist in Chinese languages; Robin is a potential tool for his plans. As Robin discovers shortly after arriving in Oxford, he is not the first of Lowell's tools. His predecessor turned against Babel and is trying to break its chokehold on translation magic. He wants Robin to help. This is one of those books that is hard to review because it does some things exceptionally well and other things that did not work for me. It's not obvious if the latter are flaws in the book or a mismatch between book and reader (or, frankly, flaws in the reader). I'll try to explain as best I can so that you can draw your own conclusions. First, this is one of the all-time great magical system hooks. The way words are tapped for power is fully fleshed out and exceptionally well-done. Kuang is a professional translator, which shows in the attention to detail on translation pairs. I think this is the best-constructed and explained word-based magic system I've read in fantasy. Many word-based systems treat magic as its own separate language that is weirdly universal. Here, Kuang does the exact opposite, and the result is immensely satisfying. A fantasy reader may expect exploration of this magic system to be the primary point of the book, however, and this is not the case. It is an important part of the book, and its implications are essential to the plot resolution, but this is not the type of fantasy novel where the plot is driven by character exploration of the magic system. The magic system exists, the characters use it, and we do get some crunchy details, but the heart of the book is elsewhere. If you were expecting the typical relationship of a fantasy novel to its magic system, you may get a bit wrong-footed. Similarly, this is historical fantasy, but it is the type of historical fantasy where the existence of magic causes no significant differences. For some people, this is a pet peeve; personally, I don't mind that choice in the abstract, but some of the specifics bugged me. The villains of this book assert that any country could have done what Britain did in developing translation magic, and thus their hoarding of it is not immoral. They are obviously partly lying (this is a classic justification for imperialism), but it's not clear from the book how they are lying. Technologies (and magic here works like a technology) tend to concentrate power when they require significant capital investment, and tend to dilute power when they are portable and easy to teach. Translation magic feels like the latter, but its effect in the book is clearly the former, and I was never sure why. England is not an obvious choice to be a translation superpower. Yes, it's a colonial empire, but India, southeast Asia, and most certainly Africa (the continent largely not appearing in this book) are home to considerably more languages from more wildly disparate families than western Europe. Translation is not a peculiarly European idea, and this magic system does not seem hard to stumble across. It's not clear why England, and Oxford in particular, is so dramatically far ahead. There is some sign that Babel is keeping the mechanics of translation magic secret, but that secret has leaked, seems easy to develop independently, and is simple enough that a new student can perform basic magic with a few hours of instruction. This does not feel like the kind of power that would be easy to concentrate, let alone to the extreme extent required by the last quarter of this book. The demand for silver as a base material for translation magic provides a justification for mercantilism that avoids the confusing complexities of currency economics in our actual history, so fine, I guess, but it was a bit disappointing for this great of an idea for a magic system to have this small of an impact on politics. I'll come to the actual thrust of this book in a moment, but first something else Babel does exceptionally well: dark academia. The remainder of Robin's cohort at Oxford is Remy, a dark-skinned Muslim from Calcutta; Victoire, a Haitian woman raised in France; and Letty, the daughter of a British admiral. All of them are non-white except Letty, and Letty and Victoire additionally have to deal with the blatant sexism of the time. (For example, they have to live several miles from Oxford because women living near the college would be a "distraction.") The interpersonal dynamics between the four are exceptionally well done. Kuang captures the dislocation of going away to college, the unsettled life upheaval that makes it both easy and vital to form suddenly tight friendships, and the way that the immense pressure from classes and exams leaves one so devoid of spare emotional capacity that those friendships become both unbreakable and badly strained. Robin and Remy almost immediately become inseparable in that type of college friendship in which profound trust and constant companionship happen first and learning about the other person happens afterwards. It's tricky to talk about this without spoilers, but one of the things Kuang sets up with this friend group is a pointed look at intersectionality. Babel has gotten a lot of positive review buzz, and I think this is one of the reasons why. Kuang does not pass over or make excuses for characters in a place where many other books do. This mostly worked for me, but with a substantial caveat that I think you may want to be aware of before you dive into this book. Babel is set in the 1830s, but it is very much about the politics of 2022. That does not necessarily mean that the politics are off for the 1830s; I haven't done the research to know, and it's possible I'm seeing the Tiffany problem (Jo Walton's observation that Tiffany is a historical 12th century women's name, but an author can't use it as a medieval name because readers think it sounds too modern). But I found it hard to shake the feeling that the characters make sense of their world using modern analytical frameworks of imperialism, racism, sexism, and intersectional feminism, although without using modern terminology, and characters from the 1830s would react somewhat differently. This is a valid authorial choice; all books are written for the readers of the time when they're published. But as with magical systems that don't change history, it's a pet peeve for some readers. If that's you, be aware that's the feel I got from it. The true center of this book is not the magic system or the history. It's advertised directly in the title the necessity of violence although it's not until well into the book before the reader knows what that means. This is a book about revolution, what revolution means, what decisions you have to make along the way, how the personal affects the political, and the inadequacy of reform politics. It is hard, uncomfortable, and not gentle on its characters. The last quarter of this book was exceptional, and I understand why it's getting so much attention. Kuang directly confronts the desire for someone else to do the necessary work, the hope that surely the people with power will see reason, and the feeling of despair when there are no good plans and every reason to wait and do nothing when atrocities are about to happen. If you are familiar with radical politics, these aren't new questions, but this is not the sort of thing that normally shows up in fantasy. It does not surprise me that Babel struck a nerve with readers a generation or two younger than me. It captures that heady feeling on the cusp of adulthood when everything is in flux and one is assembling an independent politics for the first time. Once I neared the end of the book, I could not put it down. The ending is brutal, but I think it was the right ending for this book. There are two things, though, that I did not like about the political arc. The first is that Victoire is a much more interesting character than Robin, but is sidelined for most of the book. The difference of perspectives between her and Robin is the heart of what makes the end of this book so good, and I wish that had started 300 pages earlier. Or, even better, I wish Victoire has been the protagonist; I liked Robin, but he's a very predictable character for most of the book. Victoire is not; even the conflicts she had earlier in the book, when she didn't get much attention in the story, felt more dynamic and more thoughtful than Robin's mix of guilt and anxiety. The second is that I wish Kuang had shown more of Robin's intellectual evolution. All of the pieces of why he makes the decisions that he does are present in this book, and Kuang shows his emotional state (sometimes in agonizing detail) at each step, but the sense-making, the development of theory and ideology beneath the actions, is hinted at but not shown. This is a stylistic choice with no one right answer, but it felt odd because so much of the rest of the plot is obvious and telegraphed. If the reader shares Robin's perspective, I think it's easy to fill in the gaps, but it felt odd to read Robin giving clearly thought-out political analyses at the end of the book without seeing the hashing-out and argument with friends required to develop those analyses. I felt like I had to do a lot of heavy lifting as the reader, work that I wish had been done directly by the book. My final note about this book is that I found much of it extremely predictable. I think that's part of why reviewers describe it as accessible and easy to read; accessibility and predictability can be two sides of the same coin. Kuang did not intend for this book to be subtle, and I think that's part of the appeal. But very few of Robin's actions for the first three-quarters of the book surprised me, and that's not always the reading experience I want. The end of the book is different, and I therefore found it much more gripping, but it takes a while to get there. Babel is, for better or worse, the type of fantasy where the politics, economics, and magic system exist primarily to justify the plot the author wanted. I don't think the societal position of the Institute of Translation that makes the ending possible is that believable given the nature of the technology in question and the politics of the time, and if you are inclined to dig into the specifics of the world-building, I think you will find it frustrating. Where it succeeds brilliantly is in capturing the social dynamics of hothouse academic cohorts, and in making a sharp and unfortunately timely argument about the role of violence in political change, in a way that the traditionally conservative setting of fantasy rarely does. I can't say Babel blew me away, but I can see why others liked it so much. If I had to guess, I'd say that the closer one is in age to the characters in the book and to that moment of political identity construction, the more it's likely to appeal. Rating: 7 out of 10

John Goerzen: Easily Accessing All Your Stuff with a Zero-Trust Mesh VPN

Probably everyone is familiar with a regular VPN. The traditional use case is to connect to a corporate or home network from a remote location, and access services as if you were there. But these days, the notion of corporate network and home network are less based around physical location. For instance, a company may have no particular office at all, may have a number of offices plus a number of people working remotely, and so forth. A home network might have, say, a PVR and file server, while highly portable devices such as laptops, tablets, and phones may want to talk to each other regardless of location. For instance, a family member might be traveling with a laptop, another at a coffee shop, and those two devices might want to communicate, in addition to talking to the devices at home. And, in both scenarios, there might be questions about giving limited access to friends. Perhaps you d like to give a friend access to part of your file server, or as a company, you might have contractors working on a limited project. Pretty soon you wind up with a mess of VPNs, forwarded ports, and tricks to make it all work. With the increasing prevalence of CGNAT, a lot of times you can t even open a port to the public Internet. Each application or device probably has its own gateway just to make it visible on the Internet, some of which you pay for. Then you add on the question of: should you really trust your LAN anyhow? With possibilities of guests using it, rogue access points, etc., the answer is probably no . We can move the responsibility for dealing with NAT, fluctuating IPs, encryption, and authentication, from the application layer further down into the network stack. We then arrive at a much simpler picture for all. So this page is fundamentally about making the network work, simply and effectively.

How do we make the Internet work in these scenarios? We re going to combine three concepts:
  1. A VPN, providing fully encrypted and authenticated communication and stable IPs
  2. Mesh Networking, in which devices automatically discover optimal paths to reach each other
  3. Zero-trust networking, in which we do not need to trust anything about the underlying LAN, because all our traffic uses the secure systems in points 1 and 2.
By combining these concepts, we arrive at some nice results:
  • You can ssh hostname, where hostname is one of your machines (server, laptop, whatever), and as long as hostname is up, you can reach it, wherever it is, wherever you are.
    • Combined with mosh, these sessions will be durable even across moving to other host networks.
    • You could just as well use telnet, because the underlying network should be secure.
  • You don t have to mess with encryption keys, certs, etc., for every internal-only service. Since IPs are now trustworthy, that s all you need. hosts.allow could make a comeback!
  • You have a way of transiting out of extremely restrictive networks. Every tool discussed here has a way of falling back on routing things via a broker (relay) on TCP port 443 if all else fails.
There might sometimes be tradeoffs. For instance:
  • On LANs faster than 1Gbps, performance may degrade due to encryption and encapsulation overhead. However, these tools should let hosts discover the locality of each other and not send traffic over the Internet if the devices are local.
  • With some of these tools, hosts local to each other (on the same LAN) may be unable to find each other if they can t reach the control plane over the Internet (Internet is down or provider is down)
Some other features that some of the tools provide include:
  • Easy sharing of limited access with friends/guests
  • Taking care of everything you need, including SSL certs, for exposing a certain on-net service to the public Internet
  • Optional routing of your outbound Internet traffic via an exit node on your network. Useful, for instance, if your local network is blocking tons of stuff.
Let s dive in.

Types of Mesh VPNs I ll go over several types of meshes in this article:
  1. Fully decentralized with automatic hop routing This model has no special central control plane. Nodes discover each other in various ways, and establish routes to each other. These routes can be direct connections over the Internet, or via other nodes. This approach offers the greatest resilience. Examples I ll cover include Yggdrasil and tinc.
  2. Automatic peer-to-peer with centralized control In this model, nodes, by default, communicate by establishing direct links between them. A regular node never carries traffic on behalf of other nodes. Special-purpose relays are used to handle cases in which NAT traversal is impossible. This approach tends to offer simple setup. Examples I ll cover include Tailscale, Zerotier, Nebula, and Netmaker.
  3. Roll your own and hybrid approaches This is a grab bag of other ideas; for instance, running Yggdrasil over Tailscale.

Terminology For the sake of consistency, I m going to use common language to discuss things that have different terms in different ecosystems:
  • Every tool discussed here has a way of dealing with NAT traversal. It may assist with establishing direct connections (eg, STUN), and if that fails, it may simply relay traffic between nodes. I ll call such a relay a broker . This may or may not be the same system that is a control plane for a tool.
  • All of these systems operate over lower layers that are unencrypted. Those lower layers may be a LAN (wired or wireless, which may or may not have Internet access), or the public Internet (IPv4 and/or IPv6). I m going to call the unencrypted lower layer, whatever it is, the clearnet .

Evaluation Criteria Here are the things I want to see from a solution:
  • Secure, with all communications end-to-end encrypted and authenticated, and prevention of traffic from untrusted devices.
  • Flexible, adapting to changes in network topology quickly and automatically.
  • Resilient, without single points of failure, and with devices local to each other able to communicate even if cut off from the Internet or other parts of the network.
  • Private, minimizing leakage of information or metadata about me and my systems
  • Able to traverse CGNAT without having to use a broker whenever possible
  • A lesser requirement for me, but still a nice to have, is the ability to include others via something like Internet publishing or inviting guests.
  • Fully or nearly fully Open Source
  • Free or very cheap for personal use
  • Wide operating system support, including headless Linux on x86_64 and ARM.

Fully Decentralized VPNs with Automatic Hop Routing Two systems fit this description: Yggdrasil and Tinc. Let s dive in.

Yggdrasil I ll start with Yggdrasil because I ve written so much about it already. It featured in prior posts such as:

Yggdrasil can be a private mesh VPN, or something more Yggdrasil can be a private mesh VPN, just like the other tools covered here. It s unique, however, in that a key goal of the project is to also make it useful as a planet-scale global mesh network. As such, Yggdrasil is a testbed of new ideas in distributed routing designed to scale up to massive sizes and all sorts of connection conditions. As of 2023-04-10, the main global Yggdrasil mesh has over 5000 nodes in it. You can choose whether or not to participate. Every node in a Yggdrasil mesh has a public/private keypair. Each node then has an IPv6 address (in a private address space) derived from its public key. Using these IPv6 addresses, you can communicate right away. Yggdrasil differs from most of the other tools here in that it does not necessarily seek to establish a direct link on the clearnet between, say, host A and host G for them to communicate. It will prefer such a direct link if it exists, but it is perfectly happy if it doesn t. The reason is that every Yggdrasil node is also a router in the Yggdrasil mesh. Let s sit with that concept for a moment. Consider:
  • If you have a bunch of machines on your LAN, but only one of them can peer over the clearnet, that s fine; all the other machines will discover this route to the world and use it when necessary.
  • All you need to run a broker is just a regular node with a public IP address. If you are participating in the global mesh, you can use one (or more) of the free public peers for this purpose.
  • It is not necessary for every node to know about the clearnet IP address of every other node (improving privacy). In fact, it s not even necessary for every node to know about the existence of all the other nodes, so long as it can find a route to a given node when it s asked to.
  • Yggdrasil can find one or more routes between nodes, and it can use this knowledge of multiple routes to aggressively optimize for varying network conditions, including combinations of, say, downloads and low-latency ssh sessions.
Behind the scenes, Yggdrasil calculates optimal routes between nodes as necessary, using a mesh-wide DHT for initial contact and then deriving more optimal paths. (You can also read more details about the routing algorithm.) One final way that Yggdrasil is different from most of the other tools is that there is no separate control server. No node is special , in charge, the sole keeper of metadata, or anything like that. The entire system is completely distributed and auto-assembling.

Meeting neighbors There are two ways that Yggdrasil knows about peers:
  • By broadcast discovery on the local LAN
  • By listening on a specific port (or being told to connect to a specific host/port)
Sometimes this might lead to multiple ways to connect to a node; Yggdrasil prefers the connection auto-discovered by broadcast first, then the lowest-latency of the defined path. In other words, when your laptops are in the same room as each other on your local LAN, your packets will flow directly between them without traversing the Internet.

Unique uses Yggdrasil is uniquely suited to network-challenged situations. As an example, in a post-disaster situation, Internet access may be unavailable or flaky, yet there may be many local devices perhaps ones that had never known of each other before that could share information. Yggdrasil meets this situation perfectly. The combination of broadcast auto-detection, distributed routing, and so forth, basically means that if there is any physical path between two nodes, Yggdrasil will find and enable it. Ad-hoc wifi is rarely used because it is a real pain. Yggdrasil actually makes it useful! Its broadcast discovery doesn t require any IP address provisioned on the interface at all (it just uses the IPv6 link-local address), so you don t need to figure out a DHCP server or some such. And, Yggdrasil will tend to perform routing along the contours of the RF path. So you could have a laptop in the middle of a long distance relaying communications from people farther out, because it could see both. Or even a chain of such things.

Yggdrasil: Security and Privacy Yggdrasil s mesh is aggressively greedy. It will peer with any node it can find (unless told otherwise) and will find a route to anywhere it can. There are two main ways to make sure you keep unauthorized traffic out: by restricting who can talk to your mesh, and by firewalling the Yggdrasil interface. Both can be used, and they can be used simultaneously. I ll discuss firewalling more at the end of this article. Basically, you ll almost certainly want to do this if you participate in the public mesh, because doing so is akin to having a globally-routable public IP address direct to your device. If you want to restrict who can talk to your mesh, you just disable the broadcast feature on all your nodes (empty MulticastInterfaces section in the config), and avoid telling any of your nodes to connect to a public peer. You can set a list of authorized public keys that can connect to your nodes listening interfaces, which you ll probably want to do. You will probably want to either open up some inbound ports (if you can) or set up a node with a known clearnet IP on a place like a $5/mo VPS to help with NAT traversal (again, setting AllowedPublicKeys as appropriate). Yggdrasil doesn t allow filtering multicast clients by public key, only by network interface, so that s why we disable broadcast discovery. You can easily enough teach Yggdrasil about static internal LAN IPs of your nodes and have things work that way. (Or, set up an internal gateway node or two, that the clients just connect to when they re local). But fundamentally, you need to put a bit more thought into this with Yggdrasil than with the other tools here, which are closed-only. Compared to some of the other tools here, Yggdrasil is better about information leakage; nodes only know details, such as clearnet IPs, of directly-connected peers. You can obtain the list of directly-connected peers of any known node in the mesh but that list is the public keys of the directly-connected peers, not the clearnet IPs. Some of the other tools contain a limited integrated firewall of sorts (with limited ACLs and such). Yggdrasil does not, but is fully compatible with on-host firewalls. I recommend these anyway even with many other tools.

Yggdrasil: Connectivity and NAT traversal Compared to the other tools, Yggdrasil is an interesting mix. It provides a fully functional mesh and facilitates connectivity in situations in which no other tool can. Yet its NAT traversal, while it exists and does work, results in using a broker under some of the more challenging CGNAT situations more often than some of the other tools, which can impede performance. Yggdrasil s underlying protocol is TCP-based. Before you run away screaming that it must be slow and unreliable like OpenVPN over TCP it s not, and it is even surprisingly good around bufferbloat. I ve found its performance to be on par with the other tools here, and it works as well as I d expect even on flaky 4G links. Overall, the NAT traversal story is mixed. On the one hand, you can run a node that listens on port 443 and Yggdrasil can even make it speak TLS (even though that s unnecessary from a security standpoint), so you can likely get out of most restrictive firewalls you will ever encounter. If you join the public mesh, know that plenty of public peers do listen on port 443 (and other well-known ports like 53, plus random high-numbered ones). If you connect your system to multiple public peers, there is a chance though a very small one that some public transit traffic might be routed via it. In practice, public peers hopefully are already peered with each other, preventing this from happening (you can verify this with yggdrasilctl debug_remotegetpeers key=ABC...). I have never experienced a problem with this. Also, since latency is a factor in routing for Yggdrasil, it is highly unlikely that random connections we use are going to be competitive with datacenter peers.

Yggdrasil: Sharing with friends If you re open to participating in the public mesh, this is one of the easiest things of all. Have your friend install Yggdrasil, point them to a public peer, give them your Yggdrasil IP, and that s it. (Well, presumably you also open up your firewall you did follow my advice to set one up, right?) If your friend is visiting at your location, they can just hop on your wifi, install Yggdrasil, and it will automatically discover a route to you. Yggdrasil even has a zero-config mode for ephemeral nodes such as certain Docker containers. Yggdrasil doesn t directly support publishing to the clearnet, but it is certainly possible to proxy (or even NAT) to/from the clearnet, and people do.

Yggdrasil: DNS There is no particular extra DNS in Yggdrasil. You can, of course, run a DNS server within Yggdrasil, just as you can anywhere else. Personally I just add relevant hosts to /etc/hosts and leave it at that, but it s up to you.

Yggdrasil: Source code, pricing, and portability Yggdrasil is fully open source (LGPLv3 plus additional permissions in an exception) and highly portable. It is written in Go, and has prebuilt binaries for all major platforms (including a Debian package which I made). There is no charge for anything with Yggdrasil. Listed public peers are free and run by volunteers. You can run your own peers if you like; they can be public and unlisted, public and listed (just submit a PR to get it listed), or private (accepting connections only from certain nodes keys). A peer in this case is just a node with a known clearnet IP address. Yggdrasil encourages use in other projects. For instance, NNCP integrates a Yggdrasil node for easy communication with other NNCP nodes.

Yggdrasil conclusions Yggdrasil is tops in reliability (having no single point of failure) and flexibility. It will maintain opportunistic connections between peers even if the Internet is down. The unique added feature of being able to be part of a global mesh is a nice one. The tradeoffs include being more prone to need to use a broker in restrictive CGNAT environments. Some other tools have clients that override the OS DNS resolver to also provide resolution of hostnames of member nodes; Yggdrasil doesn t, though you can certainly run your own DNS infrastructure over Yggdrasil (or, for that matter, let public DNS servers provide Yggdrasil answers if you wish). There is also a need to pay more attention to firewalling or maintaining separation from the public mesh. However, as I explain below, many other options have potential impacts if the control plane, or your account for it, are compromised, meaning you ought to firewall those, too. Still, it may be a more immediate concern with Yggdrasil. Although Yggdrasil is listed as experimental, I have been using it for over a year and have found it to be rock-solid. They did change how mesh IPs were calculated when moving from 0.3 to 0.4, causing a global renumbering, so just be aware that this is a possibility while it is experimental.

tinc tinc is the oldest tool on this list; version 1.0 came out in 2003! You can think of tinc as something akin to an older Yggdrasil without the public option. I will be discussing tinc 1.0.36, the latest stable version, which came out in 2019. The development branch, 1.1, has been going since 2011 and had its latest release in 2021. The last commit to the Github repo was in June 2022. Tinc is the only tool here to support both tun and tap style interfaces. I go into the difference more in the Zerotier review below. Tinc actually provides a better tap implementation than Zerotier, with various sane options for broadcasts, but I still think the call for an Ethernet, as opposed to IP, VPN is small. To configure tinc, you generate a per-host configuration and then distribute it to every tinc node. It contains a host s public key. Therefore, adding a host to the mesh means distributing its key everywhere; de-authorizing it means removing its key everywhere. This makes it rather unwieldy. tinc can do LAN broadcast discovery and mesh routing, but generally speaking you must manually teach it where to connect initially. Somewhat confusingly, the examples all mention listing a public address for a node. This doesn t make sense for a laptop, and I suspect you d just omit it. I think that address is used for something akin to a Yggdrasil peer with a clearnet IP. Unlike all of the other tools described here, tinc has no tool to inspect the running state of the mesh. Some of the properties of tinc made it clear I was unlikely to adopt it, so this review wasn t as thorough as that of Yggdrasil.

tinc: Security and Privacy As mentioned above, every host in the tinc mesh is authenticated based on its public key. However, to be more precise, this key is validated only at the point it connects to its next hop peer. (To be sure, this is also the same as how the list of allowed pubkeys works in Yggdrasil.) Since IPs in tinc are not derived from their key, and any host can assign itself whatever mesh IP it likes, this implies that a compromised host could impersonate another. It is unclear whether packets are end-to-end encrypted when using a tinc node as a router. The fact that they can be routed at the kernel level by the tun interface implies that they may not be.

tinc: Connectivity and NAT traversal I was unable to find much information about NAT traversal in tinc, other than that it does support it. tinc can run over UDP or TCP and auto-detects which to use, preferring UDP.

tinc: Sharing with friends tinc has no special support for this, and the difficulty of configuration makes it unlikely you d do this with tinc.

tinc: Source code, pricing, and portability tinc is fully open source (GPLv2). It is written in C and generally portable. It supports some very old operating systems. Mobile support is iffy. tinc does not seem to be very actively maintained.

tinc conclusions I haven t mentioned performance in my other reviews (see the section at the end of this post). But, it is so poor as to only run about 300Mbps on my 2.5Gbps network. That s 1/3 the speed of Yggdrasil or Tailscale. Combine that with the unwieldiness of adding hosts and some uncertainties in security, and I m not going to be using tinc.

Automatic Peer-to-Peer Mesh VPNs with centralized control These tend to be the options that are frequently discussed. Let s talk about the options.

Tailscale Tailscale is a popular choice in this type of VPN. To use Tailscale, you first sign up on tailscale.com. Then, you install the tailscale client on each machine. On first run, it prints a URL for you to click on to authorize the client to your mesh ( tailnet ). Tailscale assigns a mesh IP to each system. The Tailscale client lets the Tailscale control plane gather IP information about each node, including all detectable public and private clearnet IPs. When you attempt to contact a node via Tailscale, the client will fetch the known contact information from the control plane and attempt to establish a link. If it can contact over the local LAN, it will (it doesn t have broadcast autodetection like Yggdrasil; the information must come from the control plane). Otherwise, it will try various NAT traversal options. If all else fails, it will use a broker to relay traffic; Tailscale calls a broker a DERP relay server. Unlike Yggdrasil, a Tailscale node never relays traffic for another; all connections are either direct P2P or via a broker. Tailscale, like several others, is based around Wireguard; though wireguard-go rather than the in-kernel Wireguard. Tailscale has a number of somewhat unique features in this space:
  • Funnel, which lets you expose ports on your system to the public Internet via the VPN.
  • Exit nodes, which automate the process of routing your public Internet traffic over some other node in the network. This is possible with every tool mentioned here, but Tailscale makes switching it on or off a couple of quick commands away.
  • Node sharing, which lets you share a subset of your network with guests
  • A fantastic set of documentation, easily the best of the bunch.
Funnel, in particular, is interesting. With a couple of tailscale serve -style commands, you can expose a directory tree (or a development webserver) to the world. Tailscale gives you a public hostname, obtains a cert for it, and proxies inbound traffic to you. This is subject to some unspecified bandwidth limits, and you can only choose from three public ports, so it s not really a production solution but as a quick and easy way to demonstrate something cool to a friend, it s a neat feature.

Tailscale: Security and Privacy With Tailscale, as with the other tools in this category, one of the main threats to consider is the control plane. What are the consequences of a compromise of Tailscale s control plane, or of the credentials you use to access it? Let s begin with the credentials used to access it. Tailscale operates no identity system itself, instead relying on third parties. For individuals, this means Google, Github, or Microsoft accounts; Okta and other SAML and similar identity providers are also supported, but this runs into complexity and expense that most individuals aren t wanting to take on. Unfortunately, all three of those types of accounts often have saved auth tokens in a browser. Personally I would rather have a separate, very secure, login. If a person does compromise your account or the Tailscale servers themselves, they can t directly eavesdrop on your traffic because it is end-to-end encrypted. However, assuming an attacker obtains access to your account, they could:
  • Tamper with your Tailscale ACLs, permitting new actions
  • Add new nodes to the network
  • Forcibly remove nodes from the network
  • Enable or disable optional features
Of note is that they cannot just commandeer an existing IP. I would say the riskiest possibility here is that could add new nodes to the mesh. Because they could also tamper with your ACLs, they could then proceed to attempt to access all your internal services. They could even turn on service collection and have Tailscale tell them what and where all the services are. Therefore, as with other tools, I recommend a local firewall on each machine with Tailscale. More on that below. Tailscale has a new alpha feature called tailnet lock which helps with this problem. It requires existing nodes in the mesh to sign a request for a new node to join. Although this doesn t address ACL tampering and some of the other things, it does represent a significant help with the most significant concern. However, tailnet lock is in alpha, only available on the Enterprise plan, and has a waitlist, so I have been unable to test it. Any Tailscale node can request the IP addresses belonging to any other Tailscale node. The Tailscale control plane captures, and exposes to you, this information about every node in your network: the OS hostname, IP addresses and port numbers, operating system, creation date, last seen timestamp, and NAT traversal parameters. You can optionally enable service data capture as well, which sends data about open ports on each node to the control plane. Tailscale likes to highlight their key expiry and rotation feature. By default, all keys expire after 180 days, and traffic to and from the expired node will be interrupted until they are renewed (basically, you re-login with your provider and do a renew operation). Unfortunately, the only mention I can see of warning of impeding expiration is in the Windows client, and even there you need to edit a registry key to get the warning more than the default 24 hours in advance. In short, it seems likely to cut off communications when it s most important. You can disable key expiry on a per-node basis in the admin console web interface, and I mostly do, due to not wanting to lose connectivity at an inopportune time.

Tailscale: Connectivity and NAT traversal When thinking about reliability, the primary consideration here is being able to reach the Tailscale control plane. While it is possible in limited circumstances to reach nodes without the Tailscale control plane, it is a fairly brittle setup and notably will not survive a client restart. So if you use Tailscale to reach other nodes on your LAN, that won t work unless your Internet is up and the control plane is reachable. Assuming your Internet is up and Tailscale s infrastructure is up, there is little to be concerned with. Your own comfort level with cloud providers and your Internet should guide you here. Tailscale wrote a fantastic article about NAT traversal and they, predictably, do very well with it. Tailscale prefers UDP but falls back to TCP if needed. Broker (DERP) servers step in as a last resort, and Tailscale clients automatically select the best ones. I m not aware of anything that is more successful with NAT traversal than Tailscale. This maximizes the situations in which a direct P2P connection can be used without a broker. I have found Tailscale to be a bit slow to notice changes in network topography compared to Yggdrasil, and sometimes needs a kick in the form of restarting the client process to re-establish communications after a network change. However, it s possible (maybe even probable) that if I d waited a bit longer, it would have sorted this all out.

Tailscale: Sharing with friends I touched on the funnel feature earlier. The sharing feature lets you give an invite to an outsider. By default, a person accepting a share can make only outgoing connections to the network they re invited to, and cannot receive incoming connections from that network this makes sense. When sharing an exit node, you get a checkbox that lets you share access to the exit node as well. Of course, the person accepting the share needs to install the Tailnet client. The combination of funnel and sharing make Tailscale the best for ad-hoc sharing.

Tailscale: DNS Tailscale s DNS is called MagicDNS. It runs as a layer atop your standard DNS taking over /etc/resolv.conf on Linux and provides resolution of mesh hostnames and some other features. This is a concept that is pretty slick. It also is a bit flaky on Linux; dueling programs want to write to /etc/resolv.conf. I can t really say this is entirely Tailscale s fault; they document the problem and some workarounds. I would love to be able to add custom records to this service; for instance, to override the public IP for a service to use the in-mesh IP. Unfortunately, that s not yet possible. However, MagicDNS can query existing nameservers for certain domains in a split DNS setup.

Tailscale: Source code, pricing, and portability Tailscale is almost fully open source and the client is highly portable. The client is open source (BSD 3-clause) on open source platforms, and closed source on closed source platforms. The DERP servers are open source. The coordination server is closed source, although there is an open source coordination server called Headscale (also BSD 3-clause) made available with Tailscale s blessing and informal support. It supports most, but not all, features in the Tailscale coordination server. Tailscale s pricing (which does not apply when using Headscale) provides a free plan for 1 user with up to 20 devices. A Personal Pro plan expands that to 100 devices for $48 per year - not a bad deal at $4/mo. A Community on Github plan also exists, and then there are more business-oriented plans as well. See the pricing page for details. As a small note, I appreciated Tailscale s install script. It properly added Tailscale s apt key in a way that it can only be used to authenticate the Tailscale repo, rather than as a systemwide authenticator. This is a nice touch and speaks well of their developers.

Tailscale conclusions Tailscale is tops in sharing and has a broad feature set and excellent documentation. Like other solutions with a centralized control plane, device communications can stop working if the control plane is unreachable, and the threat model of the control plane should be carefully considered.

Zerotier Zerotier is a close competitor to Tailscale, and is similar to it in a lot of ways. So rather than duplicate all of the Tailscale information here, I m mainly going to describe how it differs from Tailscale. The primary difference between the two is that Zerotier emulates an Ethernet network via a Linux tap interface, while Tailscale emulates a TCP/IP network via a Linux tun interface. However, Zerotier has a number of things that make it be a somewhat imperfect Ethernet emulator. For one, it has a problem with broadcast amplification; the machine sending the broadcast sends it to all the other nodes that should receive it (up to a set maximum). I wouldn t want to have a lot of programs broadcasting on a slow link. While in theory this could let you run Netware or DECNet across Zerotier, I m not really convinced there s much call for that these days, and Zerotier is clearly IP-focused as it allocates IP addresses and such anyhow. Zerotier provides special support for emulated ARP (IPv4) and NDP (IPv6). While you could theoretically run Zerotier as a bridge, this eliminates the zero trust principle, and Tailscale supports subnet routers, which provide much of the same feature set anyhow. A somewhat obscure feature, but possibly useful, is Zerotier s built-in support for multipath WAN for the public interface. This actually lets you do a somewhat basic kind of channel bonding for WAN.

Zerotier: Security and Privacy The picture here is similar to Tailscale, with the difference that you can create a Zerotier-local account rather than relying on cloud authentication. I was unable to find as much detail about Zerotier as I could about Tailscale - notably I couldn t find anything about how sticky an IP address is. However, the configuration screen lets me delete a node and assign additional arbitrary IPs within a subnet to other nodes, so I think the assumption here is that if your Zerotier account (or the Zerotier control plane) is compromised, an attacker could remove a legit device, add a malicious one, and assign the previous IP of the legit device to the malicious one. I m not sure how to mitigate against that risk, as firewalling specific IPs is ineffective if an attacker can simply take them over. Zerotier also lacks anything akin to Tailnet Lock. For this reason, I didn t proceed much further in my Zerotier evaluation.

Zerotier: Connectivity and NAT traversal Like Tailscale, Zerotier has NAT traversal with STUN. However, it looks like it s more limited than Tailscale s, and in particular is incompatible with double NAT that is often seen these days. Zerotier operates brokers ( root servers ) that can do relaying, including TCP relaying. So you should be able to connect even from hostile networks, but you are less likely to form a P2P connection than with Tailscale.

Zerotier: Sharing with friends I was unable to find any special features relating to this in the Zerotier documentation. Therefore, it would be at the same level as Yggdrasil: possible, maybe even not too difficult, but without any specific help.

Zerotier: DNS Unlike Tailscale, Zerotier does not support automatically adding DNS entries for your hosts. Therefore, your options are approximately the same as Yggdrasil, though with the added option of pushing configuration pointing to your own non-Zerotier DNS servers to the client.

Zerotier: Source code, pricing, and portability The client ZeroTier One is available on Github under a custom business source license which prevents you from using it in certain settings. This license would preclude it being included in Debian. Their library, libzt, is available under the same license. The pricing page mentions a community edition for self hosting, but the documentation is sparse and it was difficult to understand what its feature set really is. The free plan lets you have 1 user with up to 25 devices. Paid plans are also available.

Zerotier conclusions Frankly I don t see much reason to use Zerotier. The virtual Ethernet model seems to be a weird hybrid that doesn t bring much value. I m concerned about the implications of a compromise of a user account or the control plane, and it lacks a lot of Tailscale features (MagicDNS and sharing). The only thing it may offer in particular is multipath WAN, but that s esoteric enough and also solvable at other layers that it doesn t seem all that compelling to me. Add to that the strange license and, to me anyhow, I don t see much reason to bother with it.

Netmaker Netmaker is one of the projects that is making noise these days. Netmaker is the only one here that is a wrapper around in-kernel Wireguard, which can make a performance difference when talking to peers on a 1Gbps or faster link. Also, unlike other tools, it has an ingress gateway feature that lets people that don t have the Netmaker client, but do have Wireguard, participate in the VPN. I believe I also saw a reference somewhere to nodes as routers as with Yggdrasil, but I m failing to dig it up now. The project is in a bit of an early state; you can sign up for an upcoming closed beta with a SaaS host, but really you are generally pointed to self-hosting using the code in the github repo. There are community and enterprise editions, but it s not clear how to actually choose. The server has a bunch of components: binary, CoreDNS, database, and web server. It also requires elevated privileges on the host, in addition to a container engine. Contrast that to the single binary that some others provide. It looks like releases are frequent, but sometimes break things, and have a somewhat more laborious upgrade processes than most. I don t want to spend a lot of time managing my mesh. So because of the heavy needs of the server, the upgrades being labor-intensive, it taking over iptables and such on the server, I didn t proceed with a more in-depth evaluation of Netmaker. It has a lot of promise, but for me, it doesn t seem to be in a state that will meet my needs yet.

Nebula Nebula is an interesting mesh project that originated within Slack, seems to still be primarily sponsored by Slack, but is also being developed by Defined Networking (though their product looks early right now). Unlike the other tools in this section, Nebula doesn t have a web interface at all. Defined Networking looks likely to provide something of a SaaS service, but for now, you will need to run a broker ( lighthouse ) yourself; perhaps on a $5/mo VPS. Due to the poor firewall traversal properties, I didn t do a full evaluation of Nebula, but it still has a very interesting design.

Nebula: Security and Privacy Since Nebula lacks a traditional control plane, the root of trust in Nebula is a CA (certificate authority). The documentation gives this example of setting it up:
./nebula-cert sign -name "lighthouse1" -ip "192.168.100.1/24"
./nebula-cert sign -name "laptop" -ip "192.168.100.2/24" -groups "laptop,home,ssh"
./nebula-cert sign -name "server1" -ip "192.168.100.9/24" -groups "servers"
./nebula-cert sign -name "host3" -ip "192.168.100.10/24"
So the cert contains your IP, hostname, and group allocation. Each host in the mesh gets your CA certificate, and the per-host cert and key generated from each of these steps. This leads to a really nice security model. Your CA is the gatekeeper to what is trusted in your mesh. You can even have it airgapped or something to make it exceptionally difficult to breach the perimeter. Nebula contains an integrated firewall. Because the ability to keep out unwanted nodes is so strong, I would say this may be the one mesh VPN you might consider using without bothering with an additional on-host firewall. You can define static mappings from a Nebula mesh IP to a clearnet IP. I haven t found information on this, but theoretically if NAT traversal isn t required, these static mappings may allow Nebula nodes to reach each other even if Internet is down. I don t know if this is truly the case, however.

Nebula: Connectivity and NAT traversal This is a weak point of Nebula. Nebula sends all traffic over a single UDP port; there is no provision for using TCP. This is an issue at certain hotel and other public networks which open only TCP egress ports 80 and 443. I couldn t find a lot of detail on what Nebula s NAT traversal is capable of, but according to a certain Github issue, this has been a sore spot for years and isn t as capable as Tailscale. You can designate nodes in Nebula as brokers (relays). The concept is the same as Yggdrasil, but it s less versatile. You have to manually designate what relay to use. It s unclear to me what happens if different nodes designate different relays. Keep in mind that this always happens over a UDP port.

Nebula: Sharing with friends There is no particular support here.

Nebula: DNS Nebula has experimental DNS support. In contrast with Tailscale, which has an internal DNS server on every node, Nebula only runs a DNS server on a lighthouse. This means that it can t forward requests to a DNS server that s upstream for your laptop s particular current location. Actually, Nebula s DNS server doesn t forward at all. It also doesn t resolve its own name. The Nebula documentation makes reference to using multiple lighthouses, which you may want to do for DNS redundancy or performance, but it s unclear to me if this would make each lighthouse form a complete picture of the network.

Nebula: Source code, pricing, and portability Nebula is fully open source (MIT). It consists of a single Go binary and configuration. It is fairly portable.

Nebula conclusions I am attracted to Nebula s unique security model. I would probably be more seriously considering it if not for the lack of support for TCP and poor general NAT traversal properties. Its datacenter connectivity heritage does show through.

Roll your own and hybrid Here is a grab bag of ideas:

Running Yggdrasil over Tailscale One possibility would be to use Tailscale for its superior NAT traversal, then allow Yggdrasil to run over it. (You will need a firewall to prevent Tailscale from trying to run over Yggdrasil at the same time!) This creates a closed network with all the benefits of Yggdrasil, yet getting the NAT traversal from Tailscale. Drawbacks might be the overhead of the double encryption and double encapsulation. A good Yggdrasil peer may wind up being faster than this anyhow.

Public VPN provider for NAT traversal A public VPN provider such as Mullvad will often offer incoming port forwarding and nodes in many cities. This could be an attractive way to solve a bunch of NAT traversal problems: just use one of those services to get you an incoming port, and run whatever you like over that. Be aware that a number of public VPN clients have a kill switch to prevent any traffic from egressing without using the VPN; see, for instance, Mullvad s. You ll need to disable this if you are running a mesh atop it.

Other

Combining with local firewalls For most of these tools, I recommend using a local firewal in conjunction with them. I have been using firehol and find it to be quite nice. This means you don t have to trust the mesh, the control plane, or whatever. The catch is that you do need your mesh VPN to provide strong association between IP address and node. Most, but not all, do.

Performance I tested some of these for performance using iperf3 on a 2.5Gbps LAN. Here are the results. All speeds are in Mbps.
Tool iperf3 (default) iperf3 -P 10 iperf3 -R
Direct (no VPN) 2406 2406 2764
Wireguard (kernel) 1515 1566 2027
Yggdrasil 892 1126 1105
Tailscale 950 1034 1085
Tinc 296 300 277
You can see that Wireguard was significantly faster than the other options. Tailscale and Yggdrasil were roughly comparable, and Tinc was terrible.

IP collisions When you are communicating over a network such as these, you need to trust that the IP address you are communicating with belongs to the system you think it does. This protects against two malicious actor scenarios:
  1. Someone compromises one machine on your mesh and reconfigures it to impersonate a more important one
  2. Someone connects an unauthorized system to the mesh, taking over a trusted IP, and uses the privileges of the trusted IP to access resources
To summarize the state of play as highlighted in the reviews above:
  • Yggdrasil derives IPv6 addresses from a public key
  • tinc allows any node to set any IP
  • Tailscale IPs aren t user-assignable, but the assignment algorithm is unknown
  • Zerotier allows any IP to be allocated to any node at the control plane
  • I don t know what Netmaker does
  • Nebula IPs are baked into the cert and signed by the CA, but I haven t verified the enforcement algorithm
So this discussion really only applies to Yggdrasil and Tailscale. tinc and Zerotier lack detailed IP security, while Nebula expects IP allocations to be handled outside of the tool and baked into the certs (therefore enforcing rigidity at that level). So the question for Yggdrasil and Tailscale is: how easy is it to commandeer a trusted IP? Yggdrasil has a brief discussion of this. In short, Yggdrasil offers you both a dedicated IP and a rarely-used /64 prefix which you can delegate to other machines on your LAN. Obviously by taking the dedicated IP, a lot more bits are available for the hash of the node s public key, making collisions technically impractical, if not outright impossible. However, if you use the /64 prefix, a collision may be more possible. Yggdrasil s hashing algorithm includes some optimizations to make this more difficult. Yggdrasil includes a genkeys tool that uses more CPU cycles to generate keys that are maximally difficult to collide with. Tailscale doesn t document their IP assignment algorithm, but I think it is safe to say that the larger subnet you use, the better. If you try to use a /24 for your mesh, it is certainly conceivable that an attacker could remove your trusted node, then just manually add the 240 or so machines it would take to get that IP reassigned. It might be a good idea to use a purely IPv6 mesh with Tailscale to minimize this problem as well. So, I think the risk is low in the default configurations of both Yggdrasil and Tailscale (certainly lower than with tinc or Zerotier). You can drive the risk even lower with both.

Final thoughts For my own purposes, I suspect I will remain with Yggdrasil in some fashion. Maybe I will just take the small performance hit that using a relay node implies. Or perhaps I will get clever and use an incoming VPN port forward or go over Tailscale. Tailscale was the other option that seemed most interesting. However, living in a region with Internet that goes down more often than I d like, I would like to just be able to send as much traffic over a mesh as possible, trusting that if the LAN is up, the mesh is up. I have one thing that really benefits from performance in excess of Yggdrasil or Tailscale: NFS. That s between two machines that never leave my LAN, so I will probably just set up a direct Wireguard link between them. Heck of a lot easier than trying to do Kerberos! Finally, I wrote this intending to be useful. I dealt with a lot of complexity and under-documentation, so it s possible I got something wrong somewhere. Please let me know if you find any errors.
This blog post is a copy of a page on my website. That page may be periodically updated.

13 April 2023

Russ Allbery: Review: Once Upon a Tome

Review: Once Upon a Tome, by Oliver Darkshire
Publisher: W.W. Norton & Company
Copyright: 2022
Printing: 2023
ISBN: 1-324-09208-4
Format: Kindle
Pages: 243
The full title page of this book, in delightful 19th century style, is:
Once Upon a Tome: The Misadventures of a Rare Bookseller, wherein the theory of the profession is partially explained, with a variety of insufficient examples, by Oliver Darkshire. Interspersed with several diverting FOOTNOTES of a comical nature, ably ILLUSTRATED by Rohan Eason, PUBLISHED by W.W. Norton, and humbly proposed to the consideration of the public in this YEAR 2023
That may already be enough to give you a feel for this book. Oliver Darkshire works for Sotheran's Rare Books and Prints in London, most notably running their highly entertaining Twitter account. This is his first book. If you have been hanging out in the right corners of Twitter, you have probably been anticipating the release of this book, and may already have your own copy. If you have not (and to be honest it's increasingly dubious whether there are right corners of Twitter left), you're in for a treat. Darkshire has made Sotheran's a minor Twitter phenomenon due to tweets like this:
CUSTOMER: oh thank heavens I have been searching for a rare book expert with the knowledge to solve my complex problem ME (extremely and unhelpfully specialized): ok well the words are usually on the inside and I can see that's true here, so that's a good start I find I know lots of things until anyone asks me about it or there is a question to answer, at which point I know nothing, I am a void, a tragic bucket of ignorance
My hope was that Once Upon a Tome would be the same thing at book length, and I am delighted to report that's exactly what it is. By the time I finished reading the story of Darkshire's early training, I knew I was going to savor every word.
The hardest part, though, lies in recording precisely in what ways a book has survived the ravages of time. An entire lexicon of book-related terminology has evolved over hundreds of years for exactly this purpose terminology that means absolutely nothing to the average observer. It's traditional to adopt this baroque language when describing your books, for two reasons. The first is that the specific language of the book trade allows you to be exceedingly accurate and precise without using hundreds of words, and the second is that the elegance of it serves to dull the blow a little. Most rare books come with some minor defects, but that doesn't mean one has to be rude about it.
You will learn something about rare book selling in this book, and more about Darkshire's colleagues, but primarily this is a book-length attempt to convey the slightly uncanny experience of working in a rare bookstore in an entertaining way. Also, to be fully accurate, it is an attempt shift the bookstore sideways in the reader's mind into a fantasy world that mostly but not entirely parallels ours; as the introduction mentions, this is not a strictly accurate day-by-day account of life at the store, and stories have been altered and conflated in the telling. Rare bookselling is a retail job but a rather strange one, with its own conventions and unusual customers. Darkshire memorably divides rare book collectors into Smaugs and Draculas: Smaugs assemble vast lairs of precious items, Draculas have one very specific interest, and one's success at selling a book depends on identifying which type of customer one is dealing with. Like all good writing about retail jobs, half of the fun is descriptions of the customers.
The Suited Gentlemen turn up annually, smartly dressed in matching suits and asking to see any material we have on Ayn Rand. Faces usually obscured by large dark glasses, they move without making a sound, and only travel in pairs. Sometimes they will bark out a laugh at nothing in particular, as if mimicking what they think humans do.
There are more facets than the typical retail job, though, since the suppliers of the rare book trade (book runners, estate sales, and collectors who have been sternly instructed by spouses to trim down their collections) are as odd and varied as the buyers. This sort of book rests entirely on the sense of humor of the author, and I thought Darkshire's approach was perfect. He has the knack of poking fun at himself as much as he pokes fun at anyone around him. This book conveys an air of perpetual bafflement at stumbling into a job that suits him as well as this one does, praise of the skills of his coworkers, and gently self-deprecating descriptions of his own efforts. Combine that with well-honed sentences, a flair for brief and memorable description, and an accurate sense of how long a story should last, and one couldn't ask for more from this style of book.
The book rest where the bible would be held (leaving arms free for gesticulation) was carved into the shape of a huge wooden eagle. I m given to understand this is the kind of eloquent and confusing metaphor one expects in a place of worship, as the talons of the divine descend from above in a flurry of wings and death, but it seemed to alarm people to come face to face with the beaked fury of God as they entered the bookshop.
I've barely scratched the surface of great quotes from this book. If you like rare books, bookstores, or even just well-told absurd stories of working a retail job, read this. It reminds me of True Porn Clerk Stories, except with much less off-putting subject matter and even better writing. (Interestingly to me, it also shares with those stories, albeit for different reasons, a more complicated balance of power between the retail worker and the customer than the typical retail establishment.) My one wish is that I would have enjoyed more specific detail about the rare books themselves, since Darkshire only rarely describes successful retail transactions. But that's only a minor quibble. This was a pure delight from cover to cover and exactly what I was hoping for when I preordered it. Highly recommended. Rating: 9 out of 10

12 April 2023

Andrej Shadura: Connecting lights to a Swytch e-bike kit

Last year I purchased an e-bike upgrade kit for my mother in law. We decided to install it on a bicycle she originally bought back in the 80s, which I fixed and refurbished a couple of years ago and used until September 2022 when I bought myself a Dutch Cortina U4. When I used this bicycle, I installed a lightweight Shutter Precision dynamo hub and compatible lights, XLC at the front, B chel at the back. Unfortunately, since Swytch is a front wheel with a built-in electric motor, these lights don t have a dynamo to connect to anymore, and Swytch doesn t have a dedicated connector for lights. I tried asking the manufacturer for more documentation or schematics, but they refused to do so. Luckily, a Canadian member of the Pedelecs forum managed to reverse-engineer the Swytch connector pinouts, which gave me an idea on how to proceed. Unfortunately, that meant that I had to replace both lights, and by trial and error I found specific models that worked. Before the Axa lights, I also tried B chel s Tivoli e-bike light, but it didn t work because the voltage was too low:
B chel Tivoli light that didn t workB chel Tivoli light that didn t work
Once I knew what to do, the rest was super easy So, here we go:
  1. Get a 3-pin (yellow) male connector with a cable, e.g. off AliExpress. Only two wires will be used, the white one is +4.2V (4-point-2, not 42!), the black one is earth. This will go into the throttle port. If you actually have a throttle, you need some sort of Y-splitter, but I don t, so this was not an issue for me. (However, I bought both sides (M and F), just to be sure.)
    Cable for the throttle portCable for the throttle port
  2. Purchase an Axa 606 E6-48 front light. The 606 comes in two versions, for dynamos and e-bikes, use the one for e-bikes; despite being officially rated as 6 48V, these lights work quite well off 4.2V too.
    Axa 606 E6-48 lightAxa 606 E6-48 light
  3. Purchase an Axa Spark Steady rear light. This light works with both AC and DC (just like the 606, the official rating is 6 48V), and works off 4.2V without an issue.
    Axa Spark lightAxa Spark light
  4. Wire lights up. I used tiny wire terminals to join the wires, but I m sure there are better options too. Insulate them well, make sure the red wire from the throttle connector is insulated too. I used a bunch of shrink tubes and black insulation tape. Since the voltage is not wildly different from what the dynamo hub produced (although AC, not DC), I was able to reuse the cable I had already routed to the rear carrier.
  5. Lights go on automatically as soon as you touch the power button on the battery pack, and stay on until the battery pack is switched off completely. I was considering adding a handlebar switch, but since I lost the only one I had, I had to do without.
Front lightFront light
Rear lightRear light
The side effect of using the Axa Spark at the rear is that it has a capacitor inside and keeps going for a couple more minutes after the battery pack is off I haven t decided whether that s a benefit or a drawback

Freexian Collaborators: Debian Contributions: Debian Developer Survey Results, DebConf updates, and more! (by Utkarsh Gupta)

Contributing to Debian is part of Freexian s mission. This article covers the latest achievements of Freexian and their collaborators. All of this is made possible by organizations subscribing to our Long Term Support contracts and consulting services.

Results of the Debian Developer Survey, by Roberto C. S nchez In 2022, Freexian polled Debian Developers about the usage of money in Debian. More than 200 Debian Developers graciously participated, providing useful and constructive answers. Roberto and Utkarsh have worked on reviewing this feedback and summarizing it in a report recently published and announced to the project.

DebConf 23 Website, by Stefano Rivera In preparation for DebConf 23, Stefano did some work on the DebConf website s registration system. To support an expected large number of local registration requests, and a limited venue size, Stefano added a review system for registration requests. There was also some infrastructure work for the website framework. We use the same framework for miniconfs and DebConf, but without the full registration system. Since last DebConf, we have migrated from a pure-JS toolchain for the static assets, to django-compressor, to be friendlier to contributors and have a simpler dependency setup. This required some updates in the full-DebConf registration system that hadn t been noticed yet in miniDebConfs. Finally, with Utkarsh, we started to wind up the DebConf 22 travel bursary reimbursement process.

Debian Reimbursements Web App Progress, by Stefano Rivera In a project funded by Freexian s Project Funding initiative, Stefano made some more progress on the Debian Reimbursements Web App. The first rough implementation core request lifecycle is almost complete. Receipts can be collected and itemized, and the request can be submitted for a reimbursement request.

Debian Printing, by Thorsten Alteholz Due to the upcoming release, only bug fixing uploads are allowed in this part of the release cycle and Thorsten did uploads of three Debian Printing packages. The upload of hplip was rather straightforward and five bugs could be closed. cups-filters suddenly started to FTBFS and thus got an RC bug. It failed due to a compile error in a header file of some dependency. Luckily the maintainer of that dependency knew that his package now needed c++17, so the fix was to just remove an old compile flag that forced the compiler to use c++0x. This flag was once progressive but nowadays it is more of a hindrance than a help. The third package upload was for cups, which got some translation updates. Unfortunately this was the most tricky one as some translations did not appear in the binary packages. After debugging for some time, it turned out that the handling of links did not work properly. Now the version in Bookworm will be the cups version with the most translated man pages ever.

Miscellaneous contributions
  • Stefano Rivera updated a few Python modules in the Debian Python Team, to the latest upstream versions.
  • Stefano Rivera reviewed the current patch series applied to Python 3.12, as an Arch package maintainer had noticed that we dropped a patch by mistake, and reinstated it.
  • Anton Gladky prepared an upload of newer version (9.2.6) of vtk library and uploaded it into the experimental due to a freeze. VTK is the visualization kit - a library used mostly for scientific and engineering applications to visualize complex objects. Transition of dependent packages is planned on after-release phase.
  • Helmut Grohne, in the continual effort to improve Debian s cross-build support, provided 22 cross-build patches to packages in the archive.

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