Search Results: "beh"

17 November 2021

Raphaël Hertzog: Freexian s report about Debian Long Term Support, October 2021

A Debian LTS logo
Every month we review the work funded by Freexian s Debian LTS offering. Please find the report for October below. Debian project funding We re looking forward to receiving more projects from various Debian teams! Learn more about the rationale behind this initiative in this article. Debian LTS contributors In October 12 contributors were paid to work on Debian LTS, their reports are available below. Evolution of the situation In October we released 34 DLAs.

Also, we would like to remark once again that we are constantly looking for new contributors. Please contact Jeremiah if you are interested! The security tracker currently lists 37 packages with a known CVE and the dla-needed.txt file has 22 packages needing an update. Thanks to our sponsors Sponsors that joined recently are in bold.

13 November 2021

John Goerzen: Managing an External Display on Linux Shouldn t Be This Hard

I first started using Linux and FreeBSD on laptops in the late 1990s. Back then, there were all sorts of hassles and problems, from hangs on suspend to pure failure to boot. I still worry a bit about suspend on unknown hardware, but by and large, the picture of Linux on laptops has dramatically improved over the last years. So much so that now I can complain about what would once have been a minor nit: dealing with external monitors. I have a USB-C dock that provides both power and a Thunderbolt display output over the single cable to the laptop. I think I am similar to most people in wanting the following behavior from the laptop: This sounds so simple. But somehow on Linux we ve split up these things into a dozen tiny bits: Problems I ve Seen My problems don t even begin with laptops, but with my desktop, running XFCE with xmonad and lightdm. My desktop is hooked to a display that has multiple inputs. This scenario (reproducible in both buster and bullseye) causes the display to be unusable until a reboot on the desktop:
  1. Be logged in and using the desktop
  2. Without locking the desktop screen, switch the display input to another device
  3. Keep the display input on another device long enough for the desktop screen to auto-lock
  4. At this point, it is impossible to re-awaken the desktop screen.
I should not here that the problems aren t limited to Debian, but also extend to Ubuntu and various hardware. Lightdm: which greeter? At some point while troubleshooting things after upgrading my laptop to bullseye, I noticed that while both were running lightdm, I had different settings and a different appearance between the two. Upon further investigation, I realized that one hat slick-greeter and lightdm-settings installed, while the other had lightdm-gtk-greeter and lightdm-gtk-greeter-settings installed. Very strange. XFCE: giving up I eventually gave up on making lightdm work. No combination of settings or greeters would make things work reliably when changing screen configurations. I installed xscreensaver. It doesn t hang, but it does sometimes take a few tries before it figures out what device to display on. Worse, since updating from buster to bullseye, XFCE no longer automatically switches audio output when the docking station is plugged in, and there seems to be no easy way to convince Pulseaudio to do this. X-Based Gnome and derivatives sigh. I also tried Gnome, Mate, and Cinnamon, and all of them had various inabilities to configure things to act the way I laid out above. I ve long not been a fan of Gnome s way of hiding things from the user. It now has a Windows-like situation of three distinct settings programs (settings, tweaks, and dconf editor), which overlap in strange ways and interact with systemd in even stranger ways. Gnome 3 make it quite non-intuitive to make app icons from various programs work, and so forth. Trying Wayland I recently decided to set up an older laptop that I hadn t used in awhile. After reading up on Wayland, I decided to try Gnome 3 under Wayland. Both the Debian and Arch wikis note that KDE is buggy on Wayland. Gnome is the only desktop environment that supports it then, unless I want to go with Sway. There s some appeal to Sway to this xmonad user, but I ve read of incompatibilities of Wayland software when Gnome s not available, so I opted to try Gnome. Well, it s better. Not perfect, but better. After finding settings buried in a ton of different Settings and Tweaks boxes, I had it mostly working, except gdm3 would never shut off power to the external display. Eventually I found /etc/gdm3/greeter.dconf-defaults, and aadded:
sleep-inactive-ac-timeout=60
sleep-inactive-ac-type='blank'
sleep-inactive-battery-timeout=120
sleep-inactive-battery-type='suspend'
Of course, these overlap with but are distinct from the same kinds of things in Gnome settings. Sway? Running without Gnome seems like a challenge; Gnome is switching audio output appropriately, for instance. I am looking at some of the Gnome Shell tiling window manager extensions and hope that some of them may work for me.

9 November 2021

Joachim Breitner: How to audit an Internet Computer canister

I was recently called upon by Origyn to audit the source code of some of their Internet Computer canisters ( canisters are services or smart contracts on the Internet Computer), which were written in the Motoko programming language. Both the application model of the Internet Computer as well as Motoko bring with them their own particular pitfalls and possible sources for bugs. So given that I was involved in the creation of both, they reached out to me. In the course of that audit work I collected a list of things to watch out for, and general advice around them. Origyn generously allowed me to share that list here, in the hope that it will be helpful to the wider community.

Inter-canister calls The Internet Computer system provides inter-canister communication that follows the actor model: Inter-canister calls are implemented via two asynchronous messages, one to initiate the call, and one to return the response. Canisters process messages atomically (and roll back upon certain error conditions), but not complete calls. This makes programming with inter-canister calls error-prone. Possible common sources for bugs, vulnerabilities or simply unexpected behavior are:
  • Reading global state before issuing an inter-canister call, and assuming it to still hold when the call comes back.
  • Changing global state before issuing an inter-canister call, changing it again in the response handler, but assuming nothing else changes the state in between (reentrancy).
  • Changing global state before issuing an inter-canister call, and not handling failures correctly, e.g. when the code handling the callback rolls backs.
If you find such pattern in your code, you should analyze if a malicious party can trigger them, and assess the severity that effect These issues apply to all canisters, and are not Motoko-specific.

Rollbacks Even in the absence of inter-canister calls the behavior of rollbacks can be surprising. In particular, rejecting (i.e. throw) does not rollback state changes done before, while trapping (e.g. Debug.trap, assert , out of cycle conditions) does. Therefore, one should check all public update call entry points for unwanted state changes or unwanted rollbacks. In particular, look for methods (or rather, messages, i.e. the code between commit points) where a state change is followed by a throw. This issues apply to all canisters, and are not Motoko-specific, although other CDKs may not turn exceptions into rejects (which don t roll back).

Talking to malicious canisters Talking to untrustworthy canisters can be risky, for the following (likely incomplete) reasons:
  • The other canister can withhold a response. Although the bidirectional messaging paradigm of the Internet Computer was designed to guarantee a response eventually, the other party can busy-loop for as long as they are willing to pay for before responding. Worse, there are ways to deadlock a canister.
  • The other canister can respond with invalidly encoded Candid. This will cause a Motoko-implemented canister to trap in the reply handler, with no easy way to recover. Other CDKs may give you better ways to handle invalid Candid, but even then you will have to worry about Candid cycle bombs that will cause your reply handler to trap.
Many canisters do not even do inter-canister calls, or only call other trustwothy canisters. For the others, the impact of this needs to be carefully assessed.

Canister upgrade: overview For most services it is crucial that canisters can be upgraded reliably. This can be broken down into the following aspects:
  1. Can the canister be upgraded at all?
  2. Will the canister upgrade retain all data?
  3. Can the canister be upgraded promptly?
  4. Is three a recovery plan for when upgrading is not possible?

Canister upgradeability A canister that traps, for whatever reason, in its canister_preupgrade system method is no longer upgradeable. This is a major risk. The canister_preupgrade method of a Motoko canister consists of the developer-written code in any system func preupgrade() block, followed by the system-generated code that serializes the content of any stable var into a binary format, and then copies that to stable memory. Since the Motoko-internal serialization code will first serialize into a scratch space in the main heap, and then copy that to stable memory, canisters with more than 2GB of live data will likely be unupgradeable. But this is unlikely the first limit: The system imposes an instruction limit on upgrading a canister (spanning both canister_preupgrade and canister_postupgrade). This limit is a subnet configuration value, and sepearate (and likely higher) than the normal per-message limit, and not easily determined. If the canister s live data becomes too large to be serialized within this limit, the canister becomes non-upgradeable. This risk cannot be eliminated completely, as long as Motoko and Stable Variables are used. It can be mitigated by appropriate load testing: Install a canister, fill it up with live data, and exercise the upgrade. If this succeeds with a live data set exceeding the expected amount of data by a margin, this risk is probably acceptable. Bonus points for adding functionality that will prevent the canister s live data to increase above a certain size. If this testing is to be done on a local replica, extra care needs to be taken to make sure the local replica actually performs instruction counting and has the same resource limits as the production subnet. An alternative mitigation is to avoid canister_pre_upgrade as much as possible. This means no use of stable var (or restricted to small, fixed-size configuration data). All other data could be
  • mirrored off the canister (possibly off chain), and manually re-hydrated after an upgrade.
  • stored in stable memory manually, during each update call, using the ExperimentalStableMemory API. While this matches what high-assurance Rust canisters (e.g. the Internet Identity) do, This requires manual binary encoding of the data, and is marked experimental, so I cannot recommend this at the moment.
  • not put into a Motoko canister until Motoko has a scalable solution for stable variable (for example keeping them in stable memory permanently, with smart caching in main memory, and thus obliterating the need for pre-upgrade code.)

Data retention on upgrades Obviously, all live data ought to be retained during upgrades. Motoko automatically ensures this for stable var data. But often canisters want to work with their data in a different format (e.g. in objects that are not shared and thus cannot be put in stable vars, such as HashMap or Buffer objects), and thus may follow following idiom:
stable var fooStable =  ;
var foo = fooFromStable(fooStable);
system func preupgrade()   fooStable := fooToStable(foo);  )
system func postupgrade()   fooStable := (empty);  )
In this case, it is important to check that
  • All non-stable global vars, or global lets with mutable values, have a stable companion.
  • The assignments to foo and fooStable are not forgotten.
  • The fooToStable and fooFromStable form bijections.
An example would be HashMaps stored as arrays via Iter.toArray( .entries()) and HashMap.fromIter( .vals()). It is worth pointiong out that a code view will only look at a single version of the code, but cannot check whether code changes will preserve data on upgrade. This can easily go wrong if the names and types of stable variables are changed in incompatible way. The upgrade may fail loudly in this cases, but in bad cases, the upgrade may even succeed, losing data along the way. This risk needs to be mitigated by thorough testing, and possibly backups (see below).

Prompt upgrades Motoko and Rust canisters cannot be safely upgraded when they are still waiting for responses to inter-canister calls (the callback would eventually reach the new instance, and because of infelicities of the IC s System API, could possibly call arbitrary internal functions). Therefore, the canister needs to be stopped before upgrading, and started again. If the inter-canister calls take a long time, this mean that upgrading may take a long time, which may be undesirable. Again, this risk is reduced if all calls are made to trustworthy canisters, and elevated when possibly untrustworthy canisters are called, directly or indirectly.

Backup and recovery Because of the above risk around upgrades it is advisable to have a disaster recovery strategy. This could involve off-chain backups of all relevant data, so that it is possible to reinstall (not upgrade) the canister and re-upload all data. Note that reinstall has the same issue as upgrade described above in prompt upgrades : It ought to be stopped first to be safe. Note that the instruction limit for messages, as well as the message size limit, limit the amount of data returned. If the canister needs to hold more data than that, the backup query method might have to return chunks or deltas, with all the extra complexity that entails, e.g. state changes between downloading chunks. If large data load testing is performed (as Irecommend anyways to test upgradeability), one can test whether the backup query method works within the resource limits.

Time is not strictly monotonic The timestamps for current time that the Internet Computer provides to its canisters is guaranteed to be monotonic, but not strictly monotonic. It can return the same values, even in the same messages, as long as they are processed in the same block. It should therefore not be used to detect happens-before relations. Instead of using and comparing time stamps to check whether Y has been performed after X happened last, introduce an explicit var y_done : Bool state, which is set to False by X and then to True by Y. When things become more complex, it will be easier to model that state via an enumeration with speaking tag names, and update this state machine along the way. Another solution to this problem is to introduce a var v : Nat counter that you bump in every update method, and after each await. Now v is your canister s state counter, and can be used like a timestamp in many ways. While we are talking about time: The system time (typically) changes across an await. So if you do let now = Time.now() and then await, the value in now may no longer be what you want.

Wrapping arithmetic The Nat64 data type, and the other fixed-width numeric types provide opt-in wrapping arithmetic (e.g. +%, fromIntWrap). Unless explicitly required by the current application, this should be avoided, as usually a too large or negatie value is a serious, unrecoverable logic error, and trapping is the best one can do.

Cycle balance drain attacks Because of the IC s canister pays model, all canisters are prone to DoS attacks by draining their cycle balance, and this risk needs to be taken into account. The most elementary mitigation strategy is to monitor the cycle balance of canisters and keep it far from the (configurable) freezing threshold. On the raw IC-level, further mitigation strategies are possible:
  • If all update calls are authenticated, perform this authentication as quickly as possible, possibly before decoding the caller s argument. This way, a cycle drain attack by an unauthenticated attacker is less effective (but still possible).
  • Additionally, implementing the canister_inspect_message system method allows the above checks to be performed before the message even is accepted by the Internet Computer. But it does not defend against inter-canister messages and is therefore not a complete solution.
  • If an attack from an authenticated user (e.g. a stakeholder) is to be expected, the above methods are not effective, and an effective defense might require relatively involved additional program logic (e.g. per-caller statistics) to detect such an attack, and react (e.g. rate-limiting).
  • Such defenses are pointless if there is only a single method where they do not apply (e.g. an unauthenticated user registration method). If the application is inherently attackable this way, it is not worth the bother to raise defenses for other methods.
Related: A justification why the Internet Identity does not use canister_inspect_message) A motoko-implemented canister currently cannot perform most of these defenses: Argument decoding happens unconditionally before any user code that may reject a message based on the caller, and canister_inspect_message is not supported. Furthermore, Candid decoding is not very cycle defensive, and one should assume that it is possible to construct Candid messages that require many instructions to decode, even for simple argument type signatures. The conclusion for the audited canisters is to rely on monitoring to keep the cycle blance up, even during an attack, if the expense can be born, and maybe pray for IC-level DoS protections to kick in.

Large data attacks Another DoS attack vector exists if public methods allow untrustworthy users to send data of unlimited size that is persisted in the canister memory. Because of the translation of async-await code into multiple message handlers, this applies not only to data that is obviously stored in global state, but also local data that is live across an await point. The effectiveness of such attacks is limited by the Internet Computer s message size limit, which is in the order of a few megabytes, but many of those also add up. The problem becomes much worse if a method has an argument type that allows a Candid space bomb: It is possible to encode very large vectors with all values null in Candid, so if any method has an argument of type [Null] or [?t], a small message will expand to a large value in the Motoko heap. Other types to watch out:
  • Nat and Int: This is an unbounded natural number, and thus can be arbitrarily large. The Motoko representation will however not be much larger than the Candid encoding (so this does not qualify as a space bomb).
It is still advisable to check if the number is reasonable in size before storing it or doing an await. For example, when it denotes an index in an array, throw early if it exceeds the size of the array; if it denotes a token amount to transfer, check it against the available balance, if it denotes time, check it against reasonable bounds.
  • Principal: A Principal is effectively a Blob. The Interface specification says that principals are at most 29 bytes in length, but the Motoko Candid decoder does not check that currently (fixed in the next version of Motoko). Until then, a Principal passed as an argument can be large (the principal in msg.caller is system-provided and thus safe). If you cannot wait for the fix to reach you, manually check the size of the princial (via Principal.toBlob) before doing the await.

Shadowing of msg or caller Don t use the same name for the message context of the enclosing actor and the methods of the canister: It is dangerous to write shared(msg) actor, because now msg is in scope across all public methods. As long as these also use public shared(msg) func , and thus shadow the outer msg, it is correct, but it if one accidentially omits or mis-types the msg, no compiler error would occur, but suddenly msg.caller would now be the original controller, likely defeating an important authorization step. Instead, write shared(init_msg) actor or shared( caller = controller ) actor to avoid using msg.

Conclusion If you write a serious canister, whether in Motoko or not, it is worth to go through the code and watch out for these patterns. Or better, have someone else review your code, as it may be hard to spot issues in your own code. Unfortunately, such a list is never complete, and there are surely more ways to screw up your code in addition to all the non-IC-specific ways in which code can be wrong. Still, things get done out there, so best of luck!

6 November 2021

Vincent Bernat: How to rsync files between two remotes?

scp -3 can copy files between two remote hosts through localhost. This comes in handy when the two servers cannot communicate directly or if they are unable to authenticate one to the other.1 Unfortunately, rsync does not support such a feature. Here is a trick to emulate the behavior of scp -3 with SSH tunnels. When syncing with a remote host, rsync invokes ssh to spawn a remote rsync --server process. It interacts with it through its standard input and output. The idea is to recreate the same setup using SSH tunnels and socat, a versatile tool to establish bidirectional data transfers. The first step is to connect to the source server and ask rsync the command-line to spawn the remote rsync --server process. The -e flag overrides the command to use to get a remote shell: instead of ssh, we use echo.
$ ssh web04
$ rsync -e 'sh -c ">&2 echo $@" echo' -aLv /data/. web05:/data/.
web05 rsync --server -vlogDtpre.iLsfxCIvu . /data/.
rsync: connection unexpectedly closed (0 bytes received so far) [sender]
rsync error: error in rsync protocol data stream (code 12) at io.c(228) [sender=3.2.3]
The second step is to connect to the destination server with local port forwarding. When connecting to the local port 5000, the TCP connection is forwarded through SSH to the remote port 5000 and handled by socat. When receiving the connection, socat spawns the rsync --server command we got at the previous step and connects its standard input and output to the incoming TCP socket.
$ ssh -L 127.0.0.1:5000:127.0.0.1:5000 web05
$ socat tcp-listen:5000,reuseaddr exec:"rsync --server -vlogDtpre.iLsfxCIvu . /data/."
The last step is to connect to the source with remote port forwarding. socat is used in place of a regular SSH connection and connects its standard input and output to a TCP socket connected to the remote port 5000. Thanks to the remote port forwarding, SSH forwards the data to the local port 5000. From there, it is relayed back to the destination, as described in the previous step.
$ ssh -R 127.0.0.1:5000:127.0.0.1:5000 web04
$ rsync -e 'sh -c "socat stdio tcp-connect:127.0.0.1:5000"' -aLv /data/. remote:/data/.
sending incremental file list
haproxy.debian.net/
haproxy.debian.net/dists/buster-backports-1.8/Contents-amd64.bz2
haproxy.debian.net/dists/buster-backports-1.8/Contents-i386.bz2
[ ]
media.luffy.cx/videos/2021-frnog34-jerikan/progressive.mp4
sent 921,719,453 bytes  received 26,939 bytes  7,229,383.47 bytes/sec
total size is 7,526,872,300  speedup is 8.17
This little diagram may help understand how everything fits together:
Diagram showing how all processes are connected together: rsync, socat and ssh
How each process is connected together. Arrows labeled stdio are implemented as two pipes connecting the process to the left to the standard input and output of the process to the right. Don't be fooled by the apparent symmetry!
The rsync manual page prohibits the use of --server. Use this hack at your own risk!
The options --server and --sender are used internally by rsync, and should never be typed by a user under normal circumstances. Some awareness of these options may be needed in certain scenarios, such as when setting up a login that can only run an rsync command. For instance, the support directory of the rsync distribution has an example script named rrsync (for restricted rsync) that can be used with a restricted ssh login.

Addendum I was hoping to get something similar with a one-liner. But this does not work!
$ socat \
>  exec:"ssh web04 rsync --server --sender -vlLogDtpre.iLsfxCIvu . /data/." \
>  exec:"ssh web05 rsync --server -vlogDtpre.iLsfxCIvu /data/. /data/." \
over-long vstring received (511 > 255)
over-long vstring received (511 > 255)
rsync error: requested action not supported (code 4) at compat.c(387) [sender=3.2.3]
rsync error: requested action not supported (code 4) at compat.c(387) [Receiver=3.2.3]
socat[878291] E waitpid(): child 878292 exited with status 4
socat[878291] E waitpid(): child 878293 exited with status 4

  1. And SSH agent forwarding is dangerous. Don t use it if you can.

23 October 2021

Antoine Beaupr : The Neo-Colonial Internet

I grew up with the Internet and its ethics and politics have always been important in my life. But I have also been involved at other levels, against police brutality, for Food, Not Bombs, worker autonomy, software freedom, etc. For a long time, that all seemed coherent. But the more I look at the modern Internet -- and the mega-corporations that control it -- and the less confidence I have in my original political analysis of the liberating potential of technology. I have come to believe that most of our technological development is harmful to the large majority of the population of the planet, and of course the rest of the biosphere. And now I feel this is not a new problem. This is because the Internet is a neo-colonial device, and has been from the start. Let me explain.

What is Neo-Colonialism? The term "neo-colonialism" was coined by Kwame Nkrumah, first president of Ghana. In Neo-Colonialism, the Last Stage of Imperialism (1965), he wrote:
In place of colonialism, as the main instrument of imperialism, we have today neo-colonialism ... [which] like colonialism, is an attempt to export the social conflicts of the capitalist countries. ... The result of neo-colonialism is that foreign capital is used for the exploitation rather than for the development of the less developed parts of the world. Investment, under neo-colonialism, increases, rather than decreases, the gap between the rich and the poor countries of the world.
So basically, if colonialism is Europeans bringing genocide, war, and its religion to the Africa, Asia, and the Americas, neo-colonialism is the Americans (note the "n") bringing capitalism to the world. Before we see how this applies to the Internet, we must therefore make a detour into US history. This matters, because anyone would be hard-pressed to decouple neo-colonialism from the empire under which it evolves, and here we can only name the United States of America.

US Declaration of Independence Let's start with the United States declaration of independence (1776). Many Americans may roll their eyes at this, possibly because that declaration is not actually part of the US constitution and therefore may have questionable legal standing. Still, it was obviously a driving philosophical force in the founding of the nation. As its author, Thomas Jefferson, stated:
it was intended to be an expression of the American mind, and to give to that expression the proper tone and spirit called for by the occasion
In that aging document, we find the following pearl:
We hold these truths to be self-evident, that all men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the pursuit of Happiness.
As a founding document, the Declaration still has an impact in the sense that the above quote has been called an:
"immortal declaration", and "perhaps [the] single phrase" of the American Revolutionary period with the greatest "continuing importance." (Wikipedia)
Let's read that "immortal declaration" again: "all men are created equal". "Men", in that context, is limited to a certain number of people, namely "property-owning or tax-paying white males, or about 6% of the population". Back when this was written, women didn't have the right to vote, and slavery was legal. Jefferson himself owned hundreds of slaves. The declaration was aimed at the King and was a list of grievances. A concern of the colonists was that the King:
has excited domestic insurrections amongst us, and has endeavoured to bring on the inhabitants of our frontiers, the merciless Indian Savages whose known rule of warfare, is an undistinguished destruction of all ages, sexes and conditions.
This is a clear mark of the frontier myth which paved the way for the US to exterminate and colonize the territory some now call the United States of America. The declaration of independence is obviously a colonial document, having being written by colonists. None of this is particularly surprising, historically, but I figured it serves as a good reminder of where the Internet is coming from, since it was born in the US.

A Declaration of the Independence of Cyberspace Two hundred and twenty years later, in 1996, John Perry Barlow wrote a declaration of independence of cyberspace. At this point, (almost) everyone has a right to vote (including women), slavery was abolished (although some argue it still exists in the form of the prison system); the US has made tremendous progress. Surely this text will have aged better than the previous declaration it is obviously derived from. Let's see how it reads today and how it maps to how the Internet is actually built now.

Borders of Independence One of the key ideas that Barlow brings up is that "cyberspace does not lie within your borders". In that sense, cyberspace is the final frontier: having failed to colonize the moon, Americans turn inwards, deeper into technology, but still in the frontier ideology. And indeed, Barlow is one of the co-founder of the Electronic Frontier Foundation (the beloved EFF), founded six years prior. But there are other problems with this idea. As Wikipedia quotes:
The declaration has been criticized for internal inconsistencies.[9] The declaration's assertion that 'cyberspace' is a place removed from the physical world has also been challenged by people who point to the fact that the Internet is always linked to its underlying geography.[10]
And indeed, the Internet is definitely a physical object. First controlled and severely restricted by "telcos" like AT&T, it was somewhat "liberated" from that monopoly in 1982 when an anti-trust lawsuit broke up the monopoly, a key historical event that, one could argue, made the Internet possible. (From there on, "backbone" providers could start competing and emerge, and eventually coalesce into new monopolies: Google has a monopoly on search and advertisement, Facebook on communications for a few generations, Amazon on storage and computing, Microsoft on hardware, etc. Even AT&T is now pretty much as consolidated as it was before.) The point is: all those companies have gigantic data centers and intercontinental cables. And those are definitely prioritizing the western world, the heart of the empire. Take for example Google's latest 3,900 mile undersea cable: it does not connect Argentina to South Africa or New Zealand, it connects the US to UK and Spain. Hardly a revolutionary prospect.

Private Internet But back to the Declaration:
Do not think that you can build it, as though it were a public construction project. You cannot. It is an act of nature and it grows itself through our collective actions.
In Barlow's mind, the "public" is bad, and private is good, natural. Or, in other words, a "public construction project" is unnatural. And indeed, the modern "nature" of development is private: most of the Internet is now privately owned and operated. I must admit that, as an anarchist, I loved that sentence when I read it. I was rooting for "us", the underdogs, the revolutionaries. And, in a way, I still do: I am on the board of Koumbit and work for a non-profit that has pivoted towards censorship and surveillance evasion. Yet I cannot help but think that, as a whole, we have failed to establish that independence and put too much trust in private companies. It is obvious in retrospect, but it was not, 30 years ago. Now, the infrastructure of the Internet has zero accountability to traditional political entities supposedly representing the people, or even its users. The situation is actually worse than when the US was founded (e.g. "6% of the population can vote"), because the owners of the tech giants are only a handful of people who can override any decision. There's only one Amazon CEO, he's called Jeff Bezos, and he has total control. (Update: Bezos actually ceded the CEO role to Andy Jassy, AWS and Amazon music founder, while remaining executive chairman. I would argue that, as the founder and the richest man on earth, he still has strong control over Amazon.)

Social Contract Here's another claim of the Declaration:
We are forming our own Social Contract.
I remember the early days, back when "netiquette" was a word, it did feel we had some sort of a contract. Not written in standards of course -- or barely (see RFC1855) -- but as a tacit agreement. How wrong we were. One just needs to look at Facebook to see how problematic that idea is on a global network. Facebook is the quintessential "hacker" ideology put in practice. Mark Zuckerberg explicitly refused to be "arbiter of truth" which implicitly means he will let lies take over its platforms. He also sees Facebook as place where everyone is equal, something that echoes the Declaration:
We are creating a world that all may enter without privilege or prejudice accorded by race, economic power, military force, or station of birth.
(We note, in passing, the omission of gender in that list, also mirroring the infamous "All men are created equal" claim of the US declaration.) As the Wall Street Journal's (WSJ) Facebook files later shown, both of those "contracts" have serious limitations inside Facebook. There are VIPs who systematically bypass moderation systems including fascists and rapists. Drug cartels and human traffickers thrive on the platform. Even when Zuckerberg himself tried to tame the platform -- to get people vaccinated or to make it healthier -- he failed: "vaxxer" conspiracies multiplied and Facebook got angrier. This is because the "social contract" behind Facebook and those large companies is a lie: their concern is profit and that means advertising, "engagement" with the platform, which causes increased anxiety and depression in teens, for example. Facebook's response to this is that they are working really hard on moderation. But the truth is that even that system is severely skewed. The WSJ showed that Facebook has translators for only 50 languages. It's a surprisingly hard to count human languages but estimates range the number of distinct languages between 2500 and 7000. So while 50 languages seems big at first, it's actually a tiny fraction of the human population using Facebook. Taking the first 50 of the Wikipedia list of languages by native speakers we omit languages like Dutch (52), Greek (74), and Hungarian (78), and that's just a few random nations picks from Europe. As an example, Facebook has trouble moderating even a major language like Arabic. It censored content from legitimate Arab news sources when they mentioned the word al-Aqsa because Facebook associates it with the al-Aqsa Martyrs' Brigades when they were talking about the Al-Aqsa Mosque... This bias against Arabs also shows how Facebook reproduces the American colonizer politics. The WSJ also pointed out that Facebook spends only 13% of its moderation efforts outside of the US, even if that represents 90% of its users. Facebook spends three more times moderating on "brand safety", which shows its priority is not the safety of its users, but of the advertisers.

Military Internet Sergey Brin and Larry Page are the Lewis and Clark of our generation. Just like the latter were sent by Jefferson (the same) to declare sovereignty over the entire US west coast, Google declared sovereignty over all human knowledge, with its mission statement "to organize the world's information and make it universally accessible and useful". (It should be noted that Page somewhat questioned that mission but only because it was not ambitious enough, Google having "outgrown" it.) The Lewis and Clark expedition, just like Google, had a scientific pretext, because that is what you do to colonize a world, presumably. Yet both men were military and had to receive scientific training before they left. The Corps of Discovery was made up of a few dozen enlisted men and a dozen civilians, including York an African American slave owned by Clark and sold after the expedition, with his final fate lost in history. And just like Lewis and Clark, Google has a strong military component. For example, Google Earth was not originally built at Google but is the acquisition of a company called Keyhole which had ties with the CIA. Those ties were brought inside Google during the acquisition. Google's increasing investment inside the military-industrial complex eventually led Google to workers organizing a revolt although it is currently unclear to me how much Google is involved in the military apparatus. Other companies, obviously, do not have such reserve, with Microsoft, Amazon, and plenty of others happily bidding on military contracts all the time.

Spreading the Internet I am obviously not the first to identify colonial structures in the Internet. In an article titled The Internet as an Extension of Colonialism, Heather McDonald correctly identifies fundamental problems with the "development" of new "markets" of Internet "consumers", primarily arguing that it creates a digital divide which creates a "lack of agency and individual freedom":
Many African people have gained access to these technologies but not the freedom to develop content such as web pages or social media platforms in their own way. Digital natives have much more power and therefore use this to create their own space with their own norms, shaping their online world according to their own outlook.
But the digital divide is certainly not the worst problem we have to deal with on the Internet today. Going back to the Declaration, we originally believed we were creating an entirely new world:
This governance will arise according to the conditions of our world, not yours. Our world is different.
How I dearly wished that was true. Unfortunately, the Internet is not that different from the offline world. Or, to be more accurate, the values we have embedded in the Internet, particularly of free speech absolutism, sexism, corporatism, and exploitation, are now exploding outside of the Internet, into the "real" world. The Internet was built with free software which, fundamentally, was based on quasi-volunteer labour of an elite force of white men with obviously too much time on their hands (and also: no children). The mythical writing of GCC and Emacs by Richard Stallman is a good example of this, but the entirety of the Internet now seems to be running on random bits and pieces built by hit-and-run programmers working on their copious free time. Whenever any of those fails, it can compromise or bring down entire systems. (Heck, I wrote this article on my day off...) This model of what is fundamentally "cheap labour" is spreading out from the Internet. Delivery workers are being exploited to the bone by apps like Uber -- although it should be noted that workers organise and fight back. Amazon workers are similarly exploited beyond belief, forbidden to take breaks until they pee in bottles, with ambulances nearby to carry out the bodies. During peak of the pandemic, workers were being dangerously exposed to the virus in warehouses. All this while Amazon is basically taking over the entire economy. The Declaration culminates with this prophecy:
We will spread ourselves across the Planet so that no one can arrest our thoughts.
This prediction, which first felt revolutionary, is now chilling.

Colonial Internet The Internet is, if not neo-colonial, plain colonial. The US colonies had cotton fields and slaves, we have disposable cell phones and Foxconn workers. Canada has its cultural genocide, Facebook has his own genocides in Ethiopia, Myanmar, and mob violence in India. Apple is at least implicitly accepting the Uyghur genocide. And just like the slaves of the colony, those atrocities are what makes the empire run. The Declaration actually ends like this, a quote which I have in my fortune cookies file:
We will create a civilization of the Mind in Cyberspace. May it be more humane and fair than the world your governments have made before.
That is still inspiring to me. But if we want to make "cyberspace" more humane, we need to decolonize it. Work on cyberpeace instead of cyberwar. Establish clear code of conduct, discuss ethics, and question your own privileges, biases, and culture. For me the first step in decolonizing my own mind is writing this article. Breaking up tech monopolies might be an important step, but it won't be enough: we have to do a culture shift as well, and that's the hard part.

Appendix: an apology to Barlow I kind of feel bad going through Barlow's declaration like this, point by point. It is somewhat unfair, especially since Barlow passed away a few years ago and cannot mount a response (even humbly assuming that he might read this). But then again, he himself recognized he was a bit too "optimistic" in 2009, saying: "we all get older and smarter":
I'm an optimist. In order to be libertarian, you have to be an optimist. You have to have a benign view of human nature, to believe that human beings left to their own devices are basically good. But I'm not so sure about human institutions, and I think the real point of argument here is whether or not large corporations are human institutions or some other entity we need to be thinking about curtailing. Most libertarians are worried about government but not worried about business. I think we need to be worrying about business in exactly the same way we are worrying about government.
And, in a sense, it was a little naive to expect Barlow to not be a colonist. Barlow is, among many things, a cattle rancher who grew up on a colonial ranch in Wyoming. The ranch was founded in 1907 by his great uncle, 17 years after the state joined the Union, and only a generation or two after the Powder River War (1866-1868) and Black Hills War (1876-1877) during which the US took over lands occupied by Lakota, Cheyenne, Arapaho, and other native American nations, in some of the last major First Nations Wars.

Appendix: further reading There is another article that almost has the same title as this one: Facebook and the New Colonialism. (Interestingly, the <title> tag on the article is actually "Facebook the Colonial Empire" which I also find appropriate.) The article is worth reading in full, but I loved this quote so much that I couldn't resist reproducing it here:
Representations of colonialism have long been present in digital landscapes. ( Even Super Mario Brothers, the video game designer Steven Fox told me last year. You run through the landscape, stomp on everything, and raise your flag at the end. ) But web-based colonialism is not an abstraction. The online forces that shape a new kind of imperialism go beyond Facebook.
It goes on:
Consider, for example, digitization projects that focus primarily on English-language literature. If the web is meant to be humanity s new Library of Alexandria, a living repository for all of humanity s knowledge, this is a problem. So is the fact that the vast majority of Wikipedia pages are about a relatively tiny square of the planet. For instance, 14 percent of the world s population lives in Africa, but less than 3 percent of the world s geotagged Wikipedia articles originate there, according to a 2014 Oxford Internet Institute report.
And they introduce another definition of Neo-colonialism, while warning about abusing the word like I am sort of doing here:
I m loath to toss around words like colonialism but it s hard to ignore the family resemblances and recognizable DNA, to wit, said Deepika Bahri, an English professor at Emory University who focuses on postcolonial studies. In an email, Bahri summed up those similarities in list form:
  1. ride in like the savior
  2. bandy about words like equality, democracy, basic rights
  3. mask the long-term profit motive (see 2 above)
  4. justify the logic of partial dissemination as better than nothing
  5. partner with local elites and vested interests
  6. accuse the critics of ingratitude
In the end, she told me, if it isn t a duck, it shouldn t quack like a duck.
Another good read is the classic Code and other laws of cyberspace (1999, free PDF) which is also critical of Barlow's Declaration. In "Code is law", Lawrence Lessig argues that:
computer code (or "West Coast Code", referring to Silicon Valley) regulates conduct in much the same way that legal code (or "East Coast Code", referring to Washington, D.C.) does (Wikipedia)
And now it feels like the west coast has won over the east coast, or maybe it recolonized it. In any case, Internet now christens emperors.

Arthur Diniz: Dropdown for GitHub workflows input parameters

Dropdown for GitHub workflows input parameters Sometimes when we look at CI/CD tools embedded within git-based software repository manager like GitHub, GitLab or Bitbucket, we ran into a lack of some features. This time me and my DevOps/SRE team were facing a pain of not being able to have the option to create drop-downs within GitHub workflows using input parameters. Although this functionality is already available on other platforms such as Bitbucket, the specific client we were working on stored the code inside GitHub. At first I thought that someone has already solved this problem somehow, but doing an extensive search on the internet I found several angry GitHub users opening requests within the Support Community and even in the stack overflow. comment-1 comment-2 comment-3 comment-5 comment-4 So I decided to create a solution for this, always thinking about simplicity and in a way that makes it easy to get this missing functionality. I started by creating an input array pattern using commas and using a tag (the selector) e.g brackets as the default value marker. Here is an example of what an input string would look like:
name: gh-action-dropdown-list-input
on:
  workflow_dispatch:
    inputs:
      environment:
        description: 'Environment'
        required: true
        default: 'dev,staging,[uat],prod'
Now the final question that would turn out to be the most complicated to deal with. How can I change the GitHub Actions interface to replace the input pattern we created earlier to a dropdown? The simplest answer I thought was to create a chrome and firefox extension that would do all this logic behind the scenes and replace the HTML input element with the selected tag containing the array values and leaving the tag value (selector) always as the default. All code was developed in pure JavaScript, open-source licensed under Apache 2.0 and available at https://github.com/arthurbdiniz/gh-action-dropdown-list-input.

Install extension Once installed, the extension is ready to use and the final result we see is the Actions interface with drop-downs. :) showcase-1 showcase-2

Configuring selectors Go to the top right corner of the browser you are using and click on the extension logo. A screen will popup with tag options. Choose the right tags for you and save it.
This action might require reloading the GitHub workflow tab. config

Have fun using drop-downs inside GitHub. If you liked this project please share this post and if possible star within the repository. Also feel free to connect with me on LinkedIn: https://www.linkedin.com/in/arthurbdiniz

References
  • https://github.community/t/can-workflow-dispatch-input-be-option-list/127338
  • https://stackoverflow.com/questions/69296314/dropdown-for-github-workflows-input-parameters

19 October 2021

Rapha&#235;l Hertzog: Freexian s report about Debian Long Term Support, September 2021

A Debian LTS logo
Like each month, have a look at the work funded by Freexian s Debian LTS offering. Debian project funding Folks from the LTS team, along with members of the Debian Android Tools team and Phil Morrel, have proposed work on the Java build tool, gradle, which is currently blocked due to the need to build with a plugin not available in Debian. The LTS team reviewed the project submission and it has been approved. After approval we ve created a Request for Bids which is active now. You ll hear more about this through official Debian channels, but in the meantime, if you feel you can help with this project, please submit a bid. Thanks! This September, Freexian set aside 2550 EUR to fund Debian projects. We re looking forward to receive more projects from various Debian teams! Learn more about the rationale behind this initiative in this article. Debian LTS contributors In September, 15 contributors have been paid to work on Debian LTS, their reports are available: Evolution of the situation In September we released 30 DLAs. September was also the second month of Jeremiah coordinating LTS contributors. Also, we would like say that we are always looking for new contributors to LTS. Please contact Jeremiah if you are interested! The security tracker currently lists 33 packages with a known CVE and the dla-needed.txt file has 26 packages needing an update. Thanks to our sponsors Sponsors that joined recently are in bold.

17 October 2021

Russ Allbery: pam-krb5 4.11

The primary change in this release of my Kerberos PAM module is support for calling pam_end with PAM_DATA_SILENT. I had not known that the intent of this flag was to signal that only process resources were being cleaned up and external resources should not be (in part because an older version of the man page doesn't make this clear). This flag is used when a proces forks with an open PAM library handle and wants to clean it up in the child process. In previous versions, this would delete the user's ticket cache, which is not the desired behavior. This version correctly leaves the ticket cache alone. The implementation required some improvements to the PAM testing framework to support this case as well. The other significant change in this release is that the build system no longer attempts to guess the correct PAM module installation path and instead documents that to install the module in a Linux system PAM module path, you will probably need to set --libdir explicitly. The logic used to decide between Debian and Red Hat multiarch paths broke in the presence of Debian usrmerge systems and was incredibly fragile even before that, so I've now dropped it completely. You can get the latest version from the pam-krb5 distribution page.

8 October 2021

Neil Williams: Using Salsa with contrib and non-free

OK, I know contrib and non-free aren't popular topics to many but I've had to sort out some simple CI for such contributions and I thought it best to document how to get it working. You will need access to the GitLab Settings for the project in Salsa - or ask someone to add some CI/CD variables on your behalf. (If CI isn't running at all, the settings will need to be modified to enable debian/salsa-ci.yml first, in the same way as packages in main). The default Salsa config (debian/salsa-ci.yml) won't get a passing build for packages in contrib or non-free:
# For more information on what jobs are run see:
# https://salsa.debian.org/salsa-ci-team/pipeline
#
---
include:
  - https://salsa.debian.org/salsa-ci-team/pipeline/raw/master/salsa-ci.yml
  - https://salsa.debian.org/salsa-ci-team/pipeline/raw/master/pipeline-jobs.yml
Variables need to be added. piuparts can use the extra contrib and non-free components directly from these variables.
variables:
   RELEASE: 'unstable'
   SALSA_CI_COMPONENTS: 'main contrib non-free'
Many packages in contrib and non-free only support amd64 - so the i386 build job needs to be removed from the pipeline by extending the variables dictionary:
variables:
   RELEASE: 'unstable'
   SALSA_CI_COMPONENTS: 'main contrib non-free'
   SALSA_CI_DISABLE_BUILD_PACKAGE_I386: 1
The extra step is to add the apt source file variable to the CI/CD settings for the project. The CI/CD settings are at a URL like:
https://salsa.debian.org/<team>/<project>/-/settings/ci_cd
Expand the section on Variables and add a <b>File</b> type variable:
Key: SALSA_CI_EXTRA_REPOSITORY Value: deb https://deb.debian.org/debian/ sid contrib non-free
The pipeline will run at the next push - alternatively, the CI/CD pipelines page has a "Run Pipeline" button. The settings added to the main CI/CD settings will be applied, so there is no need to add a variable at this stage. (This can be used to test the variables themselves but only with manually triggered CI pipelines.) For more information and additional settings (for example disabling or allowing certain jobs to fail), check https://salsa.debian.org/salsa-ci-team/pipeline

6 October 2021

Matthew Palmer: Discovering AWS IAM accounts

Let s say you re someone who happens to discover an AWS account number, and would like to take a stab at guessing what IAM users might be valid in that account. Tricky problem, right? Not with this One Weird Trick! In your own AWS account, create a KMS key and try to reference an ARN representing an IAM user in the other account as the principal. If the policy is accepted by PutKeyPolicy, then that IAM account exists, and if the error says Policy contains a statement with one or more invalid principals then the user doesn t exist. As an example, say you want to guess at IAM users in AWS account 111111111111. Then make sure this statement is in your key policy:
 
  "Sid": "Test existence of user",
  "Effect": "Allow",
  "Principal":  
    "AWS": "arn:aws:iam::111111111111:user/bob"
   ,
  "Action": "kms:DescribeKey",
  "Resource": "*"
 
If that policy is accepted, then the account has an IAM user named bob. Otherwise, the user doesn t exist. Scripting this is left as an exercise for the reader. Sadly, wildcards aren t accepted in the username portion of the ARN, otherwise you could do some funky searching with ...:user/a*, ...:user/b*, etc. You can t have everything; where would you put it all? I did mention this to AWS as an account enumeration risk. They re of the opinion that it s a good thing you can know what users exist in random other AWS accounts. I guess that means this is a technique you can put in your toolbox safe in the knowledge it ll work forever. Given this is intended behaviour, I assume you don t need to use a key policy for this, but that s where I stumbled over it. Also, you can probably use it to enumerate roles and anything else that can be a principal, but since I don t see as much use for that, I didn t bother exploring it. There you are, then. If you ever need to guess at IAM users in another AWS account, now you can!

Reproducible Builds: Reproducible Builds in September 2021

The goal behind reproducible builds is to ensure that no deliberate flaws have been introduced during compilation processes via promising or mandating that identical results are always generated from a given source. This allowing multiple third-parties to come to an agreement on whether a build was compromised or not by a system of distributed consensus. In these reports we outline the most important things that have been happening in the world of reproducible builds in the past month:
First mentioned in our March 2021 report, Martin Heinz published two blog posts on sigstore, a project that endeavours to offer software signing as a public good, [the] software-signing equivalent to Let s Encrypt . The two posts, the first entitled Sigstore: A Solution to Software Supply Chain Security outlines more about the project and justifies its existence:
Software signing is not a new problem, so there must be some solution already, right? Yes, but signing software and maintaining keys is very difficult especially for non-security folks and UX of existing tools such as PGP leave much to be desired. That s why we need something like sigstore - an easy to use software/toolset for signing software artifacts.
The second post (titled Signing Software The Easy Way with Sigstore and Cosign) goes into some technical details of getting started.
There was an interesting thread in the /r/Signal subreddit that started from the observation that Signal s apk doesn t match with the source code:
Some time ago I checked Signal s reproducibility and it failed. I asked others to test in case I did something wrong, but nobody made any reports. Since then I tried to test the Google Play Store version of the apk against one I compiled myself, and that doesn t match either.

BitcoinBinary.org was announced this month, which aims to be a repository of Reproducible Build Proofs for Bitcoin Projects :
Most users are not capable of building from source code themselves, but we can at least get them able enough to check signatures and shasums. When reputable people who can tell everyone they were able to reproduce the project s build, others at least have a secondary source of validation.

Distribution work Fr d ric Pierret announced a new testing service at beta.tests.reproducible-builds.org, showing actual rebuilds of binaries distributed by both the Debian and Qubes distributions. In Debian specifically, however, 51 reviews of Debian packages were added, 31 were updated and 31 were removed this month to our database of classified issues. As part of this, Chris Lamb refreshed a number of notes, including the build_path_in_record_file_generated_by_pybuild_flit_plugin issue. Elsewhere in Debian, Roland Clobus posted his Fourth status update about reproducible live-build ISO images in Jenkins to our mailing list, which mentions (amongst other things) that:
  • All major configurations are still built regularly using live-build and bullseye.
  • All major configurations are reproducible now; Jenkins is green.
    • I ve worked around the issue for the Cinnamon image.
    • The patch was accepted and released within a few hours.
  • My main focus for the last month was on the live-build tool itself.
Related to this, there was continuing discussion on how to embed/encode the build metadata for the Debian live images which were being worked on by Roland Clobus.
Ariadne Conill published another detailed blog post related to various security initiatives within the Alpine Linux distribution. After summarising some conventional security work being done (eg. with sudo and the release of OpenSSH version 3.0), Ariadne included another section on reproducible builds: The main blocker [was] determining what to do about storing the build metadata so that a build environment can be recreated precisely . Finally, Bernhard M. Wiedemann posted his monthly reproducible builds status report.

Community news On our website this month, Bernhard M. Wiedemann fixed some broken links [ ] and Holger Levsen made a number of changes to the Who is Involved? page [ ][ ][ ]. On our mailing list, Magnus Ihse Bursie started a thread with the subject Reproducible builds on Java, which begins as follows:
I m working for Oracle in the Build Group for OpenJDK which is primary responsible for creating a built artifact of the OpenJDK source code. [ ] For the last few years, we have worked on a low-effort, background-style project to make the build of OpenJDK itself building reproducible. We ve come far, but there are still issues I d like to address. [ ]

diffoscope diffoscope is our in-depth and content-aware diff utility. Not only can it locate and diagnose reproducibility issues, it can provide human-readable diffs from many kinds of binary formats. This month, Chris Lamb prepared and uploaded versions 183, 184 and 185 as well as performed significant triaging of merge requests and other issues in addition to making the following changes:
  • New features:
    • Support a newer format version of the R language s .rds files. [ ]
    • Update tests for OCaml 4.12. [ ]
    • Add a missing format_class import. [ ]
  • Bug fixes:
    • Don t call close_archive when garbage collecting Archive instances, unless open_archive definitely returned successfully. This prevents, for example, an AttributeError where PGPContainer s cleanup routines were rightfully assuming that its temporary directory had actually been created. [ ]
    • Fix (and test) the comparison of R language s .rdb files after refactoring temporary directory handling. [ ]
    • Ensure that RPM archives exists in the Debian package description, regardless of whether python3-rpm is installed or not at build time. [ ]
  • Codebase improvements:
    • Use our assert_diff routine in tests/comparators/test_rdata.py. [ ]
    • Move diffoscope.versions to diffoscope.tests.utils.versions. [ ]
    • Reformat a number of modules with Black. [ ][ ]
However, the following changes were also made:
  • Mattia Rizzolo:
    • Fix an autopkgtest caused by the androguard module not being in the (expected) python3-androguard Debian package. [ ]
    • Appease a shellcheck warning in debian/tests/control.sh. [ ]
    • Ignore a warning from h5py in our tests that doesn t concern us. [ ]
    • Drop a trailing .1 from the Standards-Version field as it s required. [ ]
  • Zbigniew J drzejewski-Szmek:
    • Stop using the deprecated distutils.spawn.find_executable utility. [ ][ ][ ][ ][ ]
    • Adjust an LLVM-related test for LLVM version 13. [ ]
    • Update invocations of llvm-objdump. [ ]
    • Adjust a test with a one-byte text file for file version 5.40. [ ]
And, finally, Benjamin Peterson added a --diff-context option to control unified diff context size [ ] and Jean-Romain Garnier fixed the Macho comparator for architectures other than x86-64 [ ].

Upstream patches The Reproducible Builds project detects, dissects and attempts to fix as many currently-unreproducible packages as possible. We endeavour to send all of our patches upstream where appropriate. This month, we wrote a large number of such patches, including:

Testing framework The Reproducible Builds project runs a testing framework at tests.reproducible-builds.org, to check packages and other artifacts for reproducibility. This month, the following changes were made:
  • Holger Levsen:
    • Drop my package rebuilder prototype as it s not useful anymore. [ ]
    • Schedule old packages in Debian bookworm. [ ]
    • Stop scheduling packages for Debian buster. [ ][ ]
    • Don t include PostgreSQL debug output in package lists. [ ]
    • Detect Python library mismatches during build in the node health check. [ ]
    • Update a note on updating the FreeBSD system. [ ]
  • Mattia Rizzolo:
    • Silence a warning from Git. [ ]
    • Update a setting to reflect that Debian bookworm is the new testing. [ ]
    • Upgrade the PostgreSQL database to version 13. [ ]
  • Roland Clobus (Debian live image generation):
    • Workaround non-reproducible config files in the libxml-sax-perl package. [ ]
    • Use the new DNS for the snapshot service. [ ]
  • Vagrant Cascadian:
    • Also note that the armhf architecture also systematically varies by the kernel. [ ]

Contributing If you are interested in contributing to the Reproducible Builds project, please visit our Contribute page on our website. However, you can get in touch with us via:

4 October 2021

Rapha&#235;l Hertzog: Freexian s report about Debian Long Term Support, August 2021

A Debian LTS logo
Like each month, have a look at the work funded by Freexian s Debian LTS offering. Debian project funding In August, we put aside 2460 EUR to fund Debian projects. We received a new project proposal that got approved and there s an associated bid request if you feel like proposing yourself to implement this project. We re looking forward to receive more projects from various Debian teams! Learn more about the rationale behind this initiative in this article. Debian LTS contributors In August, 14 contributors have been paid to work on Debian LTS, their reports are available: Evolution of the situation In August we released 30 DLAs.

This is the first month of Jeremiah coordinating LTS contributors. We would like to thank Holger Levsen for his work on this role up to now.

Also, we would like to remark once again that we are constantly looking for new contributors. Please contact Jeremiah if you are interested! The security tracker currently lists 73 packages with a known CVE and the dla-needed.txt file has 29 packages needing an update. Thanks to our sponsors Sponsors that joined recently are in bold.

22 September 2021

Ian Jackson: Tricky compatibility issue - Rust's io::ErrorKind

This post is about some changes recently made to Rust's ErrorKind, which aims to categorise OS errors in a portable way. Audiences for this post Background and context Error handling principles Handling different errors differently is often important (although, sadly, often neglected). For example, if a program tries to read its default configuration file, and gets a "file not found" error, it can proceed with its default configuration, knowing that the user hasn't provided a specific config. If it gets some other error, it should probably complain and quit, printing the message from the error (and the filename). Otherwise, if the network fileserver is down (say), the program might erroneously run with the default configuration and do something entirely wrong. Rust's portability aims The Rust programming language tries to make it straightforward to write portable code. Portable error handling is always a bit tricky. One of Rust's facilities in this area is std::io::ErrorKind which is an enum which tries to categorise (and, sometimes, enumerate) OS errors. The idea is that a program can check the error kind, and handle the error accordingly. That these ErrorKinds are part of the Rust standard library means that to get this right, you don't need to delve down and get the actual underlying operating system error number, and write separate code for each platform you want to support. You can check whether the error is ErrorKind::NotFound (or whatever). Because ErrorKind is so important in many Rust APIs, some code which isn't really doing an OS call can still have to provide an ErrorKind. For this purpose, Rust provides a special category ErrorKind::Other, which doesn't correspond to any particular OS error. Rust's stability aims and approach Another thing Rust tries to do is keep existing code working. More specifically, Rust tries to:
  1. Avoid making changes which would contradict the previously-published documentation of Rust's language and features.
  2. Tell you if you accidentally rely on properties which are not part of the published documentation.
By and large, this has been very successful. It means that if you write code now, and it compiles and runs cleanly, it is quite likely that it will continue work properly in the future, even as the language and ecosystem evolves. This blog post is about a case where Rust failed to do (2), above, and, sadly, it turned out that several people had accidentally relied on something the Rust project definitely intended to change. Furthermore, it was something which needed to change. And the new (corrected) way of using the API is not so obvious. Rust enums, as relevant to io::ErrorKind (Very briefly:) When you have a value which is an io::ErrorKind, you can compare it with specific values:
    if error.kind() == ErrorKind::NotFound   ...
  
But in Rust it's more usual to write something like this (which you can read like a switch statement):
    match error.kind()  
      ErrorKind::NotFound => use_default_configuration(),
      _ => panic!("could not read config file  :  ", &file, &error),
     
  
Here _ means "anything else". Rust insists that match statements are exhaustive, meaning that each one covers all the possibilities. So if you left out the line with the _, it wouldn't compile. Rust enums can also be marked non_exhaustive, which is a declaration by the API designer that they plan to add more kinds. This has been done for ErrorKind, so the _ is mandatory, even if you write out all the possibilities that exist right now: this ensures that if new ErrorKinds appear, they won't stop your code compiling. Improving the error categorisation The set of error categories stabilised in Rust 1.0 was too small. It missed many important kinds of error. This makes writing error-handling code awkward. In any case, we expect to add new error categories occasionally. I set about trying to improve this by proposing new ErrorKinds. This obviously needed considerable community review, which is why it took about 9 months. The trouble with Other and tests Rust has to assign an ErrorKind to every OS error, even ones it doesn't really know about. Until recently, it mapped all errors it didn't understand to ErrorKind::Other - reusing the category for "not an OS error at all". Serious people who write serious code like to have serious tests. In particular, testing error conditions is really important. For example, you might want to test your program's handling of disk full, to make sure it didn't crash, or corrupt files. You would set up some contraption that would simulate a full disk. And then, in your tests, you might check that the error was correct. But until very recently (still now, in Stable Rust), there was no ErrorKind::StorageFull. You would get ErrorKind::Other. If you were diligent you would dig out the OS error code (and check for ENOSPC on Unix, corresponding Windows errors, etc.). But that's tiresome. The more obvious thing to do is to check that the kind is Other. Obvious but wrong. ErrorKind is non_exhaustive, implying that more error kinds will appears, and, naturally, these would more finely categorise previously-Other OS errors. Unfortunately, the documentation note
Errors that are Other now may move to a different or a new ErrorKind variant in the future.
was only added in May 2020. So the wrongness of the "obvious" approach was, itself, not very obvious. And even with that docs note, there was no compiler warning or anything. The unfortunate result is that there is a body of code out there in the world which might break any time an error that was previously Other becomes properly categorised. Furthermore, there was nothing stopping new people writing new obvious-but-wrong code. Chosen solution: Uncategorized The Rust developers wanted an engineered safeguard against the bug of assuming that a particular error shows up as Other. They chose the following solution: There is now a new ErrorKind::Uncategorized which is now used for all OS errors for which there isn't a more specific categorisation. The fallback translation of unknown errors was changed from Other to Uncategorised. This is de jure justified by the fact that this enum has always been marked non_exhaustive. But in practice because this bug wasn't previously detected, there is such code in the wild. That code now breaks (usually, in the form of failing test cases). Usually when Rust starts to detect a particular programming error, it is reported as a new warning, which doesn't break anything. But that's not possible here, because this is a behavioural change. The new ErrorKind::Uncategorized is marked unstable. This makes it impossible to write code on Stable Rust which insists that an error comes out as Uncategorized. So, one cannot now write code that will break when new ErrorKinds are added. That's the intended effect. The downside is that this does break old code, and, worse, it is not as clear as it should be what the fixed code looks like. Alternatives considered and rejected by the Rust developers Not adding more ErrorKinds This was not tenable. The existing set is already too small, and error categorisation is in any case expected to improve over time. Just adding ErrorKinds as had been done before This would mean occasionally breaking test cases (or, possibly, production code) when an error that was previously Other becomes categorised. The broken code would have been "obvious", but de jure wrong, just as it is now, So this option amounts to expecting this broken code to continue to be written and continuing to break it occasionally. Somehow using Rust's Edition system The Rust language has a system to allow language evolution, where code declares its Edition (2015, 2018, 2021). Code from multiple editions can be combined, so that the ecosystem can upgrade gradually. It's not clear how this could be used for ErrorKind, though. Errors have to be passed between code with different editions. If those different editions had different categorisations, the resulting programs would have incoherent and broken error handling. Also some of the schemes for making this change would mean that new ErrorKinds could only be stabilised about once every 3 years, which is far too slow. How to fix code broken by this change Most main-line error handling code already has a fallback case for unknown errors. Simply replacing any occurrence of Other with _ is right. How to fix thorough tests The tricky problem is tests. Typically, a thorough test case wants to check that the error is "precisely as expected" (as far as the test can tell). Now that unknown errors come out as an unstable Uncategorized variant that's not so easy. If the test is expecting an error that is currently not categorised, you want to write code that says "if the error is any of the recognised kinds, call it a test failure". What does "any of the recognised kinds" mean here ? It doesn't meany any of the kinds recognised by the version of the Rust stdlib that is actually in use. That set might get bigger. When the test is compiled and run later, perhaps years later, the error in this test case might indeed be categorised. What you actually mean is "the error must not be any of the kinds which existed when the test was written". IMO therefore the right solution for such a test case is to cut and paste the current list of stable ErrorKinds into your code. This will seem wrong at first glance, because the list in your code and in Rust can get out of step. But when they do get out of step you want your version, not the stdlib's. So freezing the list at a point in time is precisely right. You probably only want to maintain one copy of this list, so put it somewhere central in your codebase's test support machinery. Periodically, you can update the list deliberately - and fix any resulting test failures. Unfortunately this approach is not suggested by the documentation. In theory you could work all this out yourself from first principles, given even the situation prior to May 2020, but it seems unlikely that many people have done so. In particular, cutting and pasting the list of recognised errors would seem very unnatural. Conclusions This was not an easy problem to solve well. I think Rust has done a plausible job given the various constraints, and the result is technically good. It is a shame that this change to make the error handling stability more correct caused the most trouble for the most careful people who write the most thorough tests. I also think the docs could be improved.
edited shortly after posting, and again 2021-09-22 16:11 UTC, to fix HTML slips


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21 September 2021

Norbert Preining: Plasma 5.23 Anniversary Edition Beta for Debian available for testing

Last week has seen the release of the first beta of Plasma 5.23 Anniversary Edition. Work behind the scenes to get this release as soon as possible into Debian has progressed well. Starting with today, we provide binaries of Plasma 5.23 for Debian stable (bullseye), testing, and unstable, in each case for three architectures: amd64, i386, and aarch64. To test the current beta, please add
deb https://download.opensuse.org/repositories/home:/npreining:/debian-kde:/plasma523/DISTRIBUTION/ ./
to your apt sources (replacing DISTRIBUTION with one of Debian_11 (for Bullseye), Debian_Testing, or Debian_Unstable). For further details see this blog. Warning This is a beta release, and let me recall the warning from the upstream release announcement:
DISCLAIMER: This is beta software and is released for testing purposes. You are advised to NOT use Plasma 25th Anniversary Edition Beta in a production environment or as your daily desktop. If you do install Plasma 25th Anniversary Edition Beta, you must be prepared to encounter (and report to the creators) bugs that may interfere with your day-to-day use of your computer. https://kde.org/announcements/plasma/5/5.22.90/
Enjoy, and please report bugs!

16 September 2021

Chris Lamb: On Colson Whitehead's Harlem Shuffle

Colson Whitehead's latest novel, Harlem Shuffle, was always going to be widely reviewed, if only because his last two books won Pulitzer prizes. Still, after enjoying both The Underground Railroad and The Nickel Boys, I was certainly going to read his next book, regardless of what the critics were saying indeed, it was actually quite agreeable to float above the manufactured energy of the book's launch. Saying that, I was encouraged to listen to an interview with the author by Ezra Klein. Now I had heard Whitehead speak once before when he accepted the Orwell Prize in 2020, and once again he came across as a pretty down-to-earth guy. Or if I were to emulate the detached and cynical tone Whitehead embodied in The Nickel Boys, after winning so many literary prizes in the past few years, he has clearly rehearsed how to respond to the cliched questions authors must be asked in every interview. With the obligatory throat-clearing of 'so, how did you get into writing?', for instance, Whitehead replies with his part of the catechism that 'It seemed like being a writer could be a cool job. You could work from home and not talk to people.' The response is the right combination of cute and self-effacing... and with its slight tone-deafness towards enforced isolation, it was no doubt honed before Covid-19. Harlem Shuffle tells three separate stories about Ray Carney, a furniture salesman and 'fence' for stolen goods in New York in the 1960s. Carney doesn't consider himself a genuine criminal though, and there's a certain logic to his relativistic morality. After all, everyone in New York City is on the take in some way, and if some 'lightly used items' in Carney's shop happened to have had 'previous owners', well, that's not quite his problem. 'Nothing solid in the city but the bedrock,' as one character dryly observes. Yet as Ezra pounces on in his NYT interview mentioned abov, the focus on the Harlem underworld means there are very few women in the book, and Whitehead's circular response ah well, it's a book about the criminals at that time! was a little unsatisfying. Not only did it feel uncharacteristically slippery of someone justly lauded for his unflinching power of observation (after all, it was the author who decided what to write about in the first place), it foreclosed on the opportunity to delve into why the heist and caper genres (from The Killing, The Feather Thief, Ocean's 11, etc.) have historically been a 'male' mode of storytelling. Perhaps knowing this to be the case, the conversation quickly steered towards Ray Carney's wife, Elizabeth, the only woman in the book who could be said possesses some plausible interiority. The following off-hand remark from Whitehead caught my attention:
My wife is convinced that [Elizabeth] knows everything about Carney's criminal life, and is sort of giving him a pass. And I'm not sure if that's true. I have to have to figure out exactly what she knows and when she knows it and how she feels about it.
I was quite taken by this, although not simply due to its effect on the story it self. As in, it immediately conjured up a charming picture of Whitehead's domestic arrangements: not only does Whitehead's wife feel free to disagree with what one of Whitehead's 'own' characters knows or believes, but that Colson has no problem whatsoever sharing that disagreement with the public at large. (It feels somehow natural that Whitehead's wife believes her counterpart knows more than she lets on, whilst Whitehead himself imbues the protagonist's wife with a kind of neo-Victorian innocence.) I'm minded to agree with Whitehead's partner myself, if only due to the passages where Elizabeth is studiously ignoring Carney's otherwise unexplained freak-outs. But all of these meta-thoughts simply underline just how emancipatory the Death of the Author can be. This product of academic literary criticism (the term was coined by Roland Barthes' 1967 essay of the same name) holds that the original author's intentions, ideas or biographical background carry no especial weight in determining how others should interpret their work. It is usually understood as meaning that a writer's own views are no more valid or 'correct' than the views held by someone else. (As an aside, I've found that most readers who encounter this concept for the first time have been reading books in this way since they were young. But the opposite is invariably true with cinephiles, who often have a bizarre obsession with researching or deciphering the 'true' interpretation of a film.) And with all that in mind, can you think of a more wry example of how freeing (and fun) nature of the Death of the Author than an author's own partner dissenting with their (Pulitzer Prize-winning) husband on the position of a lynchpin character?
The 1964 Harlem riot began after James Powell, a 15-year-old African American, was shot and killed by Thomas Gilligan, an NYPD police officer in front of 10s of witnesses. Gilligan was subsequently cleared by a grand jury.
As it turns out, the reviews for Harlem Shuffle have been almost universally positive, and after reading it in the two days after its release, I would certainly agree it is an above-average book. But it didn't quite take hold of me in the way that The Underground Railroad or The Nickel Boys did, especially the later chapters of The Nickel Boys that were set in contemporary New York and could thus make some (admittedly fairly explicit) connections from the 1960s to the present day that kind of connection is not there in Harlem Shuffle, or at least I did not pick up on it during my reading. I can see why one might take exception to that, though. For instance, it is certainly true that the week-long Harlem Riot forms a significant part of the plot, and some events in particular are entirely contingent on the ramifications of this momentous event. But it's difficult to argue the riot's impact are truly integral to the story, so not only is this uprising against police brutality almost regarded as a background event, any contemporary allusion to the murder of George Floyd is subsequently watered down. It's nowhere near the historical rubbernecking of Forrest Gump (1994), of course, but that's not a battle you should ever be fighting. Indeed, whilst a certain smoothness of affect is to be priced into the Whitehead reading experience, my initial overall reaction to Harlem Shuffle was fairly flat, despite all the action and intrigue on the page. The book perhaps belies its origins as a work conceived during quarantine after all, the book is essentially comprised of three loosely connected novellas, almost as if the unreality and mental turbulence of lockdown prevented the author from performing the psychological 'deep work' of producing a novel-length text with his usual depth of craft. A few other elements chimed with this being a 'lockdown novel' as well, particularly the book's preoccupation with the sheer physicality of the city compared to the usual complex interplay between its architecture and its inhabitants. This felt like it had been directly absorbed into the book from the author walking around his deserted city, and thus being able to take in details for the first time:
The doorways were entrances into different cities no, different entrances into one vast, secret city. Ever close, adjacent to all you know, just underneath. If you know where to look.
And I can't fail to mention that you can almost touch Whitehead's sublimated hunger to eat out again as well:
Stickups were chops they cook fast and hot, you re in and out. A stakeout was ribs fire down low, slow, taking your time. [ ] Sometimes when Carney jumped into the Hudson when he was a kid, some of that stuff got into his mouth. The Big Apple Diner served it up and called it coffee.
More seriously, however, the relatively thin personalities of minor characters then reminded me of the simulacrum of Zoom-based relationships, and the essentially unsatisfactory endings to the novellas felt reminiscent of lockdown pseudo-events that simply fizzle out without a bang. One of the stories ties up loose ends with: 'These things were usually enough to terminate a mob war, and they appeared to end the hostilities in this case as well.' They did? Well, okay, I guess.
The corner of 125th Street and Morningside Avenue in 2019, the purported location of Carney's fictional furniture store. Signage plays a prominent role in Harlem Shuffle, possibly due to the author's quarantine walks.
Still, it would be unfair to characterise myself as 'disappointed' with the novel, and none of this piece should be taken as really deep criticism. The book certainly was entertaining enough, and pretty funny in places as well:
Carney didn t have an etiquette book in front of him, but he was sure it was bad manners to sit on a man s safe. [ ] The manager of the laundromat was a scrawny man in a saggy undershirt painted with sweat stains. Launderer, heal thyself.
Yet I can't shake the feeling that every book you write is a book that you don't, and so we might need to hold out a little longer for Whitehead's 'George Floyd novel'. (Although it is for others to say how much of this sentiment is the expectations of a White Reader for The Black Author to ventriloquise the pain of 'their' community.) Some room for personal critique is surely permitted. I dearly missed the junk food energy of the dry and acerbic observations that run through Whitehead's previous work. At one point he had a good line on the model tokenisation that lurks behind 'The First Negro to...' labels, but the callbacks to this idea ceased without any payoff. Similar things happened with the not-so-subtle critiques of the American Dream:
Entrepreneur? Pepper said the last part like manure. That s just a hustler who pays taxes. [ ] One thing I ve learned in my job is that life is cheap, and when things start getting expensive, it gets cheaper still.
Ultimately, though, I think I just wanted more. I wanted a deeper exploration of how the real power in New York is not wielded by individual street hoodlums or even the cops but in the form of real estate, essentially serving as a synecdoche for Capital as a whole. (A recent take of this can be felt in Jed Rothstein's 2021 documentary, WeWork: Or the Making and Breaking of a $47 Billion Unicorn and it is perhaps pertinent to remember that the US President at the time this novel was written was affecting to be a real estate tycoon.). Indeed, just like the concluding scenes of J. J. Connolly's Layer Cake, although you can certainly pull off a cool heist against the Man, power ultimately resides in those who control the means of production... and a homespun furniture salesman on the corner of 125 & Morningside just ain't that. There are some nods to kind of analysis in the conclusion of the final story ('Their heist unwound as if it had never happened, and Van Wyck kept throwing up buildings.'), but, again, I would have simply liked more. And when I attempted then file this book away into the broader media landscape, given the current cultural visibility of 1960s pop culture (e.g. One Night in Miami (2020), Judas and the Black Messiah (2021), Summer of Soul (2021), etc.), Harlem Shuffle also seemed like a missed opportunity to critically analyse our (highly-qualified) longing for the civil rights era. I can certainly understand why we might look fondly on the cultural products from a period when politics was less alienated, when society was less atomised, and when it was still possible to imagine meaningful change, but in this dimension at least, Harlem Shuffle seems to merely contribute to this nostalgic escapism.

7 September 2021

Joachim Breitner: A Candid explainer: Opt is special

This is the third post in a series about the interface description language Candid.

The record extension problem Initially, the upgrade rules of Candid were a straight-forward application of the canonical subtyping rules. This worked and was sound, but it forbid one very commonly requested use case: Extending records in argument position. The subtyping rule for records say that
   record   old_field : nat; new_field : int  
<: record   old_field : nat  
or, in words, that subtypes can have more field than supertypes. This makes intuitive sense: A user of a such a record value that only expects old_field to be there is not bothered if suddenly a new_field appears. But a user who expects new_field to be there is thrown off if it suddenly isn t anymore. Therefore it is ok to extend the records returned by a service with new fields, but not to extend the record in your methods s argument types. But users want to extend their record types over time, also in argument position! In fact, they often want to extend them in both positions. Consider a service with the following interface, where the CUser record appears both in argument and result position:
type CUser = record   login : text; name : text  ;
service C :  
  register_user : (CUser) -> ();
  get_user_data : (text) -> (CUser);
 
It seems quite natural to want to extend the record with a new field (say, the age of the user). But simply changing the definition of CUser to
type CUser = record   login : text; name : text; age : nat  
is not ok, because now register_user requires the age field, but old clients don t provide it. So how can we allow developers to make changes like this (because they really really want that), while keeping the soundness guarantees made by Candid (because we really really want that)? This question has bothered us for over two years, and we even created a meta issue that records the dozen approached we considered, discussed and eventually ditched.

Dynamic subtyping checks in opt I will spare you the history lesson, though, and explain the solution we eventually came up with. In the example above it seems unreasonable to let the developer add a field age of type nat. Since there may be old clients around, the service unavoidably has to deal with records that don t have an age field. If the code expects an age value, what should it do in that case? But one can argue that changing the record type to
type CUser = record   login : text; name : text; age : opt nat  
could work: If the age field is present, use the value. If the field is absent, inject a null value during decoding. In the first-order case, this rather obvious solution would work just fine, and we d be done. But Candid aims to solve the higher order case, and I said things get tricky here, didn t I? Consider another, independent service D with the following interface:
type DUser = record   login : text; name : text  ;
service D :  
  on_user_added : (func (DUser) -> ()) -> ()
 
This service has a method that takes a method reference, presumably with the intention of calling it whenever a new user was added to service D. And because the types line up nicely, we can compose these two services, by once calling D.on_user_added(C.register_user), so that from now on D calls C.register_user( ). These kind of service mesh-ups are central to the vision of the Internet Computer! But what happens if the services now evolve their types in different ways, e.g. towards
type CUser = record   login : text; name : text; age : opt nat  
and
type DUser = record   login : text; name : text; age : opt variant   under_age; adult  
Individually, these are type changes that we want to allow. But now the call from D to C may transmit a value of record ; age = opt variant under_age when C expects a natural number! This is precisely what we want to prevent by introducing types, and it seems we have lost soundness. The best solution we could find is to make the opt type somewhat special, and apply these extra rules when decoding at an expected type of opt t.
  • If this was a record field, and the provided record value doesn t even have a field of that name, don t fail but instead treat this as null. This handles the first-order example above.
  • If there is a value, look at its type (which, in Candid, is part of the message).
    • If it is opt t' and t' <: t, then decode as normal.
    • If it is opt t' but t' <: t does not hold, then treat that as null. This should only happen in these relatively obscure higher-order cases where services evolved differently and incompatibly, and makes sure that the calls that worked before the upgrades will continue to work afterwards. It is not advisable to actually use that rule when changing your service s interface. Tools that assist the developer with an upgrade check should prevent or warn about the use of this rule.
  • Not strictly required here, but since we are making opt special anyways: If its type t' is not of the form opt , pretend it was opt t', and also pretend that the given value was wrapped in opt. This allows services to make record field in arguments that were required in the old version optional in a new version, e.g. as a way to deprecated them. So it is mildly useful, although I can report that it makes the meta-theory and implementation rather complex, in particular together with equirecursion and beasts like type O = opt O. See this discussion for a glimpse of that.
In the above I stress that we look at the type of the provided value, and not just the value. For example, if the sender sends the value opt vec at type opt vec nat, and the recipient expects opt vec bool, then this will decode as null, even though one could argue that the value opt vec could easily be understood at type opt vec bool. We initially had that, but then noticed that this still breaks soundness when there are references inside, and we have to do a full subtyping check in the decoder. This is very unfortunate, because it makes writing a Candid decoder a noticeably harder task that requires complicated graph algorithms with memoization (which I must admit Motoko has not implemented yet), but it s the least bad solution we could find so far.

Isn t that just dynamic typing? You might have noticed that with these rules, t <: opt t' holds for all types t and t'. In other words, every opt is a top type (like reserved), thus all optional types are equivalent. One could argue that we are throwing all of the benefits of static typing over board this way. But it s not quite as bad: It s true that decoding Candid values now involves a dynamic check inserting null values in certain situations, but as long as everyone plays by the rules (i.e. upgrades their services according to the Candid safe upgrade rules, and heeds the warning alluded to above), these certain situations will only happen in the obscurest of cases. It is, by the way, not material to this solution that the special subtyping behavior is applied to the opt type, and a neighboring point in the design space would be a dedicated upgraded t type constructor. That would allow developers to use the canonical opt type with the usual subtyping rules and communicate their intent ( clients should consider this field optional vs. old clients don t know about this field, but new clients should use it ) more cleanly at the expense of having more non-canonical types in the type system. To see why it is convenient if Candid has mostly just the normal types, read the next post, which will describe how Candid can be integrated into a host language.

6 September 2021

Vincent Bernat: Switching to the i3 window manager

I have been using the awesome window manager for 10 years. It is a tiling window manager, configurable and extendable with the Lua language. Using a general-purpose programming language to configure every aspect is a double-edged sword. Due to laziness and the apparent difficulty of adapting my configuration about 3000 lines to newer releases, I was stuck with the 3.4 version, whose last release is from 2013. It was time for a rewrite. Instead, I have switched to the i3 window manager, lured by the possibility to migrate to Wayland and Sway later with minimal pain. Using an embedded interpreter for configuration is not as important to me as it was in the past: it brings both complexity and brittleness.
i3 dual screen setup
Dual screen desktop running i3, Emacs, some terminals, including a Quake console, Firefox, Polybar as the status bar, and Dunst as the notification daemon.
The window manager is only one part of a desktop environment. There are several options for the other components. I am also introducing them in this post.

i3: the window manager i3 aims to be a minimal tiling window manager. Its documentation can be read from top to bottom in less than an hour. i3 organize windows in a tree. Each non-leaf node contains one or several windows and has an orientation and a layout. This information arbitrates the window positions. i3 features three layouts: split, stacking, and tabbed. They are demonstrated in the below screenshot:
Example of layouts
Demonstration of the layouts available in i3. The main container is split horizontally. The first child is split vertically. The second one is tabbed. The last one is stacking.
Tree representation of the previous screenshot
Tree representation of the previous screenshot.
Most of the other tiling window managers, including the awesome window manager, use predefined layouts. They usually feature a large area for the main window and another area divided among the remaining windows. These layouts can be tuned a bit, but you mostly stick to a couple of them. When a new window is added, the behavior is quite predictable. Moreover, you can cycle through the various windows without thinking too much as they are ordered. i3 is more flexible with its ability to build any layout on the fly, it can feel quite overwhelming as you need to visualize the tree in your head. At first, it is not unusual to find yourself with a complex tree with many useless nested containers. Moreover, you have to navigate windows using directions. It takes some time to get used to. I set up a split layout for Emacs and a few terminals, but most of the other workspaces are using a tabbed layout. I don t use the stacking layout. You can find many scripts trying to emulate other tiling window managers but I did try to get my setup pristine of these tentatives and get a chance to familiarize myself. i3 can also save and restore layouts, which is quite a powerful feature. My configuration is quite similar to the default one and has less than 200 lines.

i3 companion: the missing bits i3 philosophy is to keep a minimal core and let the user implements missing features using the IPC protocol:
Do not add further complexity when it can be avoided. We are generally happy with the feature set of i3 and instead focus on fixing bugs and maintaining it for stability. New features will therefore only be considered if the benefit outweighs the additional complexity, and we encourage users to implement features using the IPC whenever possible. Introduction to the i3 window manager
While this is not as powerful as an embedded language, it is enough for many cases. Moreover, as high-level features may be opinionated, delegating them to small, loosely coupled pieces of code keeps them more maintainable. Libraries exist for this purpose in several languages. Users have published many scripts to extend i3: automatic layout and window promotion to mimic the behavior of other tiling window managers, window swallowing to put a new app on top of the terminal launching it, and cycling between windows with Alt+Tab. Instead of maintaining a script for each feature, I have centralized everything into a single Python process, i3-companion using asyncio and the i3ipc-python library. Each feature is self-contained into a function. It implements the following components:
make a workspace exclusive to an application
When a workspace contains Emacs or Firefox, I would like other applications to move to another workspace, except for the terminal which is allowed to intrude into any workspace. The workspace_exclusive() function monitors new windows and moves them if needed to an empty workspace or to one with the same application already running.
implement a Quake console
The quake_console() function implements a drop-down console available from any workspace. It can be toggled with Mod+ . This is implemented as a scratchpad window.
back and forth workspace switching on the same output
With the workspace back_and_forth command, we can ask i3 to switch to the previous workspace. However, this feature is not restricted to the current output. I prefer to have one keybinding to switch to the workspace on the next output and one keybinding to switch to the previous workspace on the same output. This behavior is implemented in the previous_workspace() function by keeping a per-output history of the focused workspaces.
create a new empty workspace or move a window to an empty workspace
To create a new empty workspace or move a window to an empty workspace, you have to locate a free slot and use workspace number 4 or move container to workspace number 4. The new_workspace() function finds a free number and use it as the target workspace.
restart some services on output change
When adding or removing an output, some actions need to be executed: refresh the wallpaper, restart some components unable to adapt their configuration on their own, etc. i3 triggers an event for this purpose. The output_update() function also takes an extra step to coalesce multiple consecutive events and to check if there is a real change with the low-level library xcffib.
I will detail the other features as this post goes on. On the technical side, each function is decorated with the events it should react to:
@on(CommandEvent("previous-workspace"), I3Event.WORKSPACE_FOCUS)
async def previous_workspace(i3, event):
    """Go to previous workspace on the same output."""
The CommandEvent() event class is my way to send a command to the companion, using either i3-msg -t send_tick or binding a key to a nop command. The latter is used to avoid spawning a shell and a i3-msg process just to send a message. The companion listens to binding events and checks if this is a nop command.
bindsym $mod+Tab nop "previous-workspace"
There are other decorators to avoid code duplication: @debounce() to coalesce multiple consecutive calls, @static() to define a static variable, and @retry() to retry a function on failure. The whole script is a bit more than 1000 lines. I think this is worth a read as I am quite happy with the result.

dunst: the notification daemon Unlike the awesome window manager, i3 does not come with a built-in notification system. Dunst is a lightweight notification daemon. I am running a modified version with HiDPI support for X11 and recursive icon lookup. The i3 companion has a helper function, notify(), to send notifications using DBus. container_info() and workspace_info() uses it to display information about the container or the tree for a workspace.
Notification showing i3 tree for a workspace
Notification showing i3 s tree for a workspace

polybar: the status bar i3 bundles i3bar, a versatile status bar, but I have opted for Polybar. A wrapper script runs one instance for each monitor. The first module is the built-in support for i3 workspaces. To not have to remember which application is running in a workspace, the i3 companion renames workspaces to include an icon for each application. This is done in the workspace_rename() function. The icons are from the Font Awesome project. I maintain a mapping between applications and icons. This is a bit cumbersome but it looks great.
i3 workspaces in Polybar
i3 workspaces in Polybar
For CPU, memory, brightness, battery, disk, and audio volume, I am relying on the built-in modules. Polybar s wrapper script generates the list of filesystems to monitor and they get only displayed when available space is low. The battery widget turns red and blinks slowly when running out of power. Check my Polybar configuration for more details.
Various modules for Polybar
Polybar displaying various information: CPU usage, memory usage, screen brightness, battery status, Bluetooth status (with a connected headset), network status (connected to a wireless network and to a VPN), notification status, and speaker volume.
For Bluetooh, network, and notification statuses, I am using Polybar s ipc module: the next version of Polybar can receive an arbitrary text on an IPC socket. The module is defined with a single hook to be executed at the start to restore the latest status.
[module/network]
type = custom/ipc
hook-0 = cat $XDG_RUNTIME_DIR/i3/network.txt 2> /dev/null
initial = 1
It can be updated with polybar-msg action "#network.send.XXXX". In the i3 companion, the @polybar() decorator takes the string returned by a function and pushes the update through the IPC socket. The i3 companion reacts to DBus signals to update the Bluetooth and network icons. The @on() decorator accepts a DBusSignal() object:
@on(
    StartEvent,
    DBusSignal(
        path="/org/bluez",
        interface="org.freedesktop.DBus.Properties",
        member="PropertiesChanged",
        signature="sa sv as",
        onlyif=lambda args: (
            args[0] == "org.bluez.Device1"
            and "Connected" in args[1]
            or args[0] == "org.bluez.Adapter1"
            and "Powered" in args[1]
        ),
    ),
)
@retry(2)
@debounce(0.2)
@polybar("bluetooth")
async def bluetooth_status(i3, event, *args):
    """Update bluetooth status for Polybar."""
The middle of the bar is occupied by the date and a weather forecast. The latest also uses the IPC mechanism, but the source is a Python script triggered by a timer.
Date and weather in Polybar
Current date and weather forecast for the day in Polybar. The data is retrieved with the OpenWeather API.
I don t use the system tray integrated with Polybar. The embedded icons usually look horrible and they all behave differently. A few years back, Gnome has removed the system tray. Most of the problems are fixed by the DBus-based Status Notifier Item protocol also known as Application Indicators or Ayatana Indicators for GNOME. However, Polybar does not support this protocol. In the i3 companion, The implementation of Bluetooth and network icons, including displaying notifications on change, takes about 200 lines. I got to learn a bit about how DBus works and I get exactly the info I want.

picom: the compositor I like having slightly transparent backgrounds for terminals and to reduce the opacity of unfocused windows. This requires a compositor.1 picom is a lightweight compositor. It works well for me, but it may need some tweaking depending on your graphic card.2 Unlike the awesome window manager, i3 does not handle transparency, so the compositor needs to decide by itself the opacity of each window. Check my configuration for details.

systemd: the service manager I use systemd to start i3 and the various services around it. My xsession script only sets some environment variables and lets systemd handles everything else. Have a look at this article from Micha G ral for the rationale. Notably, each component can be easily restarted and their logs are not mangled inside the ~/.xsession-errors file.3 I am using a two-stage setup: i3.service depends on xsession.target to start services before i3:
[Unit]
Description=X session
BindsTo=graphical-session.target
Wants=autorandr.service
Wants=dunst.socket
Wants=inputplug.service
Wants=picom.service
Wants=pulseaudio.socket
Wants=policykit-agent.service
Wants=redshift.service
Wants=spotify-clean.timer
Wants=ssh-agent.service
Wants=xiccd.service
Wants=xsettingsd.service
Wants=xss-lock.service
Then, i3 executes the second stage by invoking the i3-session.target:
[Unit]
Description=i3 session
BindsTo=graphical-session.target
Wants=wallpaper.service
Wants=wallpaper.timer
Wants=polybar-weather.service
Wants=polybar-weather.timer
Wants=polybar.service
Wants=i3-companion.service
Wants=misc-x.service
Have a look on my configuration files for more details.

rofi: the application launcher Rofi is an application launcher. Its appearance can be customized through a CSS-like language and it comes with several themes. Have a look at my configuration for mine.
Rofi as an application launcher
Rofi as an application launcher
It can also act as a generic menu application. I have a script to control a media player and another one to select the wifi network. It is quite a flexible application.
Rofi as a wifi network selector
Rofi to select a wireless network

xss-lock and i3lock: the screen locker i3lock is a simple screen locker. xss-lock invokes it reliably on inactivity or before a system suspend. For inactivity, it uses the XScreenSaver events. The delay is configured using the xset s command. The locker can be invoked immediately with xset s activate. X11 applications know how to prevent the screen saver from running. I have also developed a small dimmer application that is executed 20 seconds before the locker to give me a chance to move the mouse if I am not away.4 Have a look at my configuration script.
Demonstration of xss-lock, xss-dimmer and i3lock with a 4 speedup.

The remaining components
  • autorandr is a tool to detect the connected display, match them against a set of profiles, and configure them with xrandr.
  • inputplug executes a script for each new mouse and keyboard plugged. This is quite useful to load the appropriate the keyboard map. See my configuration.
  • xsettingsd provides settings to X11 applications, not unlike xrdb but it notifies applications for changes. The main use is to configure the Gtk and DPI settings. See my article on HiDPI support on Linux with X11.
  • Redshift adjusts the color temperature of the screen according to the time of day.
  • maim is a utility to take screenshots. I use Prt Scn to trigger a screenshot of a window or a specific area and Mod+Prt Scn to capture the whole desktop to a file. Check the helper script for details.
  • I have a collection of wallpapers I rotate every hour. A script selects them using advanced machine learning algorithms and stitches them together on multi-screen setups. The selected wallpaper is reused by i3lock.

  1. Apart from the eye candy, a compositor also helps to get tear-free video playbacks.
  2. My configuration works with both Haswell (2014) and Whiskey Lake (2018) Intel GPUs. It also works with AMD GPU based on the Polaris chipset (2017).
  3. You cannot manage two different displays this way e.g. :0 and :1. In the first implementation, I did try to parametrize each service with the associated display, but this is useless: there is only one DBus user session and many services rely on it. For example, you cannot run two notification daemons.
  4. I have only discovered later that XSecureLock ships such a dimmer with a similar implementation. But mine has a cool countdown!

5 September 2021

Antoine Beaupr : Automating major Debian upgrades

It's major upgrade time again! The Debian project just published the Debian 11 "bullseye" release, and it's pretty awesome! This makes me realized that I have never written here about my peculiar upgrade process, and figured it was worth bringing that up to a wider audience. My upgrade process also has a notable changes section which includes major version changes (e.g. Inkscape 1.0!), new packages (e.g. podman!) and important behavior changes (e.g. driverless scanning and printing!). I'm particularly interested to hear about any significant change I might have missed. If you know of a cool new package that shipped with bullseye and that I forgot, do let me know! But that's for the cool new stuff. We need to talk about the problems with Debian major upgrades.

Background I have been maintaining detailed upgrade guides, on my wiki, starting with the jessie release, but I have actually written such guides for Koumbit.org as far back as Debian squeeze in 2011 (another worker wrote the older Debian lenny upgrade guide in 2009). Koumbit, since then, has kept maintaining those guides all the way to the latest bullseye upgrade, through 7 major releases! Over the years, those guides evolved from a quick "cheat-sheet" format copied from the release notes into a more or less "scripted" form that I currently use. Each guide has a procedure made of a few steps that can be basically copy-pasted to batch-upgrade a host (or multiple hosts in parallel) as quickly as possible. There is also the predict-os script which allows you to keep track of progress of the upgrades in a Puppet cluster.

Limitations of the official procedure In comparison with my procedure, the official upgrade guide is mostly designed to upgrade a single machine, typically a workstation, with a rather slow and exhaustive process. The PDF version of the upgrade guide is 14 pages long! This, obviously, does not work when you have tens or hundreds of machines to upgrade. Debian upgrades are notorious for being extremely reliable, but we have a lot of packages, and there are always corner cases where the upgrade will just fail because of a bug specific to your environment. Those will only be fixed after some back and forth in the community (and that's assuming users report those bugs, which is not always the case). There's no obvious way to deploy "hot fixes" in this context, at least not without fixing the package and publishing it on an unofficial Debian archive while the official ones catch up. This is slow and difficult. Or some packages require manual labor. Examples of this are the PostgreSQL or Ganeti packages which require you to upgrade your clusters by hand, while the old and new packages live side by side. Debian packages bring you far in the upgrade process, but sometimes not all the way. Which means every Debian install needs to be manually upgraded and inspected when a new release comes out. That's slow and error prone and we can do better.

How to automate major upgrades I have a proposal to automate this. It's been mostly dormant in the Debian wiki, for 5 years now. Fundamentally, this is a hard problem: Debian gets installed in so many different environments, from workstations to physical servers to virtual machines, embedded systems and so on, that it's extremely hard to come up with a "one size fits all" system. The (manual) procedure I'm using is mostly targeting servers, but I'm also using it on workstations. And I'll note that it's specific to my home setup: I have a different procedure at work, although it has a lot of common code. To automate this, I would factor out that common code with hooks where you could easily inject special code like "you need to upgrade ferm first", "you need an extra reboot here", or "this is how you finish the PostgreSQL upgrade". With Debian getting closer to a 2 year release cycle, with the previous release being supported basically only one year after the new stable comes out, I feel more and more strongly that this needs better automation. So I'm thinking that I should write a prototype for this. Ubuntu has do-release-upgrade that is too Ubuntu-specific to be reused. An attempt at collaborating on this has been mostly met with silence from Ubuntu's side as well. I'm thinking that using something like Fabric, Mitogen, or Transilience: anything that will allow me to write simple, portable Python code that can run transparently on a local machine (for single systems upgrades, possibly with a GUI frontend) to remote servers (for large clusters of servers, maybe with canaries and grouping using Cumin). I'll note that Koumbit started experimenting with Puppet Bolt in the bullseye upgrade process, but that feels too site-specific to be useful more broadly.

Trade-offs I am not sure where this stands in the XKCD time trade-off evaluation, because the table doesn't actually cover the time frequency of Debian release (which is basically "biennial") and the amount of time the upgrade would take across a cluster (which varies a lot, but that I estimate to be between one to 6 hours per machine). Assuming I have 80 machines to upgrade, that is 80 to 480 hours (between ~3 to 20 days) of work! It's unclear how much work such an automated system would shave off, however. Assuming things are an order of magnitude faster (say I upgrade 10 machines at a time), I would shave off between 3 and 18 days of work, which implies I might allow myself to spend a minimum of 5 days working on such a project.

The other option: never upgrade Before people mention those: I am aware of containers, Kubernetes, and other deployment mechanisms. Indeed, those may be a long-term solution, we currently can't afford to migrate everything over to containers right now: that is a huge migration and a total paradigm shift. At that point, whatever is left might not even be Debian in the first place. And besides, if you run Kubernetes, you still need to run some OS underneath and upgrade that, so that problem never completely disappears. Still, maybe that's the final answer: never upgrade. For some stateless machines like DNS replicas or load balancers, that might make a lot of sense as there's no or little data to carry to the new host. But this implies a seamless and fast provisioning process, and we don't have that either: at my work, installing a machine takes about as long as upgrading it, and that's after a significant amount of work automating that process, partly writing my own Debian installer with Fabric (!).

What is your process? I'm curious to hear what people think of those ideas. It strikes me as really odd that no one has really tackled that problem yet, considering how many clusters of Debian machines are out there. Surely people are upgrading those, and not following that slow step by step guide, right? I suspect everyone is doing the same thing: we all have our little copy-paste script we batch onto multiple machines, sometimes in parallel. That is what the Debian.org sysadmins are doing as well. There must be a better way. What is yours?

My upgrades so far So far, I have upgraded 2 out of my 3 home machines running buster -- others have been installed directly in bullseye -- with only my main, old, messy server left. Upgrades have been pretty painless so far (see another report, for example), much better than the previous buster upgrade. Obviously, for me personal use, automating this is pointless. Work-side, however, is another story: we have over 80 boxes to upgrade there and that will take a while. The last stretch to buster cycle took about two years to complete, so we might be done by the time the next release (12, "bookworm") is released, but that's actually a full year after "buster" becomes EOL, so it's actually too late... At least I fixed the installers so that new the machines we create all ship with bullseye, so we stopped accumulating new buster hosts...
Thanks to lelutin and pabs for reviewing a draft of this post.

2 September 2021

Eddy Petri&#537;or: Stretch to Buster upgrade issues: "Grub error: symbol grub_is_lockdown not found", missing RTL8111/8168/8411 Ethernet driver and RTL8821CE Wireless adapter on Linux Kernel 5.10 (and 4.19)

I have been Debian Stretch running on my HP Pavilion 14-ce0000nq laptop since buying it back in April 2019, just before my presence at Oxidizeconf where I presented "How to Rust When Standards Are Defined in C".Debian Buster (aka Debian 10) was released about 4 months later and I've been postponing the upgrade as my free time isn't what it used to be. I also tend to wait for the first or even second update of the release to avoid any sharp edges.As this laptop has a Realtek 8821CE wireless card that wasn't officially supported in the Linux kernel, I had to use an out-of-tree hacked driver to have the wireless work on Stretch kernels such as 4.19, it didn't even got along with DKMS, so all compilations and installations of it, I did them manually. More reason to wait for a newer release that would contain a driver inside the official kernel.I was waiting for the inevitable and dreading the wireless issues, but since mid-august Bullseye became stable, turning Stretch into oldoldstable, I decided that I had to do the upgrade, at least to buster.The Grub error and the fix
Everything went quite smooth, except that after the reboot, the laptop failed to boot with this Grub error:

error: symbol grub_is_lockdown not found
I looked for a solution and it seemed everyone was stuck or the solution was unclear.There is even a bug report in Debian about this error, bug #984760.
Adding to the pile of confusion my own confused solution: I tried supergrubdisk2/rescatux, it didn't work for me, it might have been a combination of me using LVM and grub-efi-amd64. I also tried to boot in rescue mode the Buster first DVD (to avoid the need for network), I was able to enter the partition, mount the EFI partition, too, but since I didn't want to mess the setup even more or depend on an external USB stick, I didn't know where should I try to write the Grub EFI config - the root partition is on an NVME storage.When buying the laptop it had FreeDOS installed on it and some HP rescue app, which I did not wipe when installing Debian. I even forgot where or how was the EFI installed on the disk and EFI, even if it should be more reliable and simpler, I never got the hang of it.
In the end, I realized that I could via BIOS actually select manually which EFI executable should be booted into, so I was able to boot with some manual intervention during boot into the regular system.I tried regenerating the grub configuration, installing it and also tried restoring the default proper boot sequence (and I even installed refind in the system during my fumbling), but I think somewhere between grub-efi-amd64 reconfiguration and its reinstallation I managed to do the right thing, as the default boot screen is the Grub one now.Hints for anyone reading this in the hope to fix the same issue, hopefully it will make things better, not worse (see the text below):1) regenerate the grub config:
update-grub2
2) reinstall grub-efi-amd64 and make Debian the default
dpkg-reconfigure -plow grub-efi-amd64
When reinstalling grub-efi-amd64 onto the disk, I think the scariest questions were to these:

Force extra installation to the EFI removable media path?

Some EFI-based systems are buggy and do not handle new bootloaders correctly. If you force an extra installation of GRUB to the EFI removable media path, this should ensure that this system will boot Debian correctly despite such a problem. However, it may remove the ability to boot any other operating systems that also depend on this path. If so, you will need to make sure that GRUB is configured successfully to be able to boot any other OS installations correctly.

and
Update NVRAM variables to automatically boot into Debian?

GRUB can configure your platform's NVRAM variables so that it boots into Debian automatically when powered on. However, you may prefer to disable this behavior and avoid changes to your boot configuration. For example, if your NVRAM variables have been set up such that your system contacts a PXE server on every boot, this would preserve that behavior.

I think the first can be safely answered "No" if you don't plan on booting via a removable USB stick, while the second is the one that does the restoring.The second question is probably safe if you don't use PXE boot or other boot method, at least that's what I understand. But if you do, I suspect by installing refind, by playing with the multiple efi* named packages and tools, you can restore that, or it might be that your BIOS allows that directly.
I just did a walk through of these 2 steps again on my laptop and answered "No" to the removable media question as it leads to errors when the media was not inserted (in my case the internal SD card reader), and "Yes" to making Debian the default.It seems that for me this broke the FreeDOS and HP utilities boot entries from Grub, but I still can boot via the BIOS options and my goal was to have Debian boot correctly by default.
Fixing the missing RTL811/8168/8411 Ethernet card issue
As a side note for people with computers having Realtek RTL8111/8168/8411 Gigabit Ethernet Controller and upgrading to Buster or switching to a newer kernel, please note that you might end up having the unpleasant surprise even your Ethernet card to disappear because the r8169 driver is not loader by default.I had to add it to /etc/modules so is loaded by default:
eddy@aptonia:/ $ cat /etc/modules
# /etc/modules: kernel modules to load at boot time.
#
# This file contains the names of kernel modules that should be loaded
# at boot time, one per line. Lines beginning with "#" are ignored.
r8169

The 5.10 compatible driver for RTL8821CE wireless adapterAfter the upgrade to Buster, the oldstable version of the kernel, 4.19, the hacked version of the driver I've been using on Stretch on 4.9 kernels was no longer compatible - failed to compile due to missing symbols.The fix for me was to switch to the DKMS compatible driver from https://github.com/tomaspinho/rtl8821ce, as this seems to work for both 4.19 and 5.10 kernels (installed from backports).
I installed it via a modification of the manual install method only for the 4.19 and 5.10 kernels, leaving the legacy 4.9 kernels working with the hacked driver. You can do the same if instead of running the provided script, you do its steps manually and you install only for the kernel versions you want, instead of the default to install for all:I looked inside the dkms-install.sh script to do the required steps:Copy the driver, add it to the dkms set of known drivers:
DRV_NAME=rtl8821ce
DRV_VERSION=v5.5.2_34066.20200325

cp -r . /usr/src/$ DRV_NAME -$ DRV_VERSION

dkms add -m $ DRV_NAME -v $ DRV_VERSION
But you just build and install them only for the select kernel versions of your choice:
dkms build -m $ DRV_NAME -v $ DRV_VERSION -k 5.10.0-0.bpo.8-amd64
dkms install -m $ DRV_NAME -v $ DRV_VERSION -k 5.10.0-0.bpo.8-amd64
Or, without the variables:
dkms build rtl8821ce/v5.5.2_34066.20200325 -k 4.19.0-17-amd64
dkms install rtl8821ce/v5.5.2_34066.20200325 -k 4.19.0-17-amd64
dkms status should confirm everything is in place and I think you need to update grub2 again after this.
Please note this driver is no longer maintained and the 5.10 tree should support the RTL8821CE wireless card with the rtw88 driver from the kernel, but for me it did not. I'll probably try this at a later time, or after I upgrade to the current Debian stable, Bullseye.

31 August 2021

Russ Allbery: kstart 4.3

kstart provides the programs k5start and krenew, which are similar to the Kerberos kinit program with some extra support for running programs with separate credentials and running as a daemon. This is the first full release in nearly six years. The major change is new support for the Linux kafs module, which is a native Linux implementation of the AFS protocol that David Howells and others have been working on for years. It has an entirely different way of thinking about tokens and credential isolation built on Linux keyrings rather than the AFS token concept (which sometimes uses keyrings, but in a different way, and sometimes uses other hacks). k5start and krenew, when run with the -t option to get AFS tokens, would fail if AFS was not available. That meant -t would fail with kafs even if the AKLOG environment variable were set properly to aklog-kafs. This release fixes that. The programs also optionally link with libkeyutils and use it when used to run a command to isolate the AFS credentials from the calling process. This is done by creating a new session keyring and linking it to the user keyring before running the aklog program. Thanks to Bill MacAllister, David Howells, and Jeffrey Altman for the help with this feature. I'm not sure that I have it right, so please let me know if it doesn't work for you. Also in this release is a fix from Aasif Versi to use a smarter exit status if k5start or krenew is running another program and that program is killed with a signal. Previously, that would cause k5start or krenew to exit with a status of 0, which was not helpful. Now it exits with a status formed by adding 128 to the signal number, which matches the behavior of bash. Since this is the first release in a while, it also contains some other minor fixes and portability updates. You can get the latest release from the kstart distribution page.

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