Search Results: "ina"

23 September 2022

Gunnar Wolf: 6237415

Years ago, it was customary that some of us stated publicly the way we think in time of Debian General Resolutions (GRs). And even if we didn t, vote lists were open (except when voting for people, i.e. when electing a DPL), so if interested we could understand what our different peers thought. This is the first vote, though, where a Debian vote is protected under voting secrecy. I think it is sad we chose that path, as I liken a GR vote more with a voting process within a general assembly of a cooperative than with a countrywide voting one; I feel that understanding who is behind each posture helps us better understand the project as a whole. But anyway, I m digressing Even though I remained quiet during much of the discussion period (I was preparing and attending a conference), I am very much interested in this vote I am the maintainer for the Raspberry Pi firmware, and am a seconder for two of them. Many people know me for being quite inflexible in my interpretation of what should be considered Free Software, and I m proud of it. But still, I believer it to be fundamental for Debian to be able to run on the hardware most users have. So My vote was as follows:
[6] Choice 1: Only one installer, including non-free firmware
[2] Choice 2: Recommend installer containing non-free firmware
[3] Choice 3: Allow presenting non-free installers alongside the free one
[7] Choice 4: Installer with non-free software is not part of Debian
[4] Choice 5: Change SC for non-free firmware in installer, one installer
[1] Choice 6: Change SC for non-free firmware in installer, keep both installers
[5] Choice 7: None Of The Above
For people reading this not into Debian s voting processes: Debian uses the cloneproof Schwatz sequential dropping Condorcet method, which means we don t only choose our favorite option (which could lead to suboptimal strategic voting outcomes), but we rank all the options according to our preferences. To read this vote, we should first locate position of None of the above , which for my ballot is #5. Let me reorder the ballot according to my preferences:
[1] Choice 6: Change SC for non-free firmware in installer, keep both installers
[2] Choice 2: Recommend installer containing non-free firmware
[3] Choice 3: Allow presenting non-free installers alongside the free one
[4] Choice 5: Change SC for non-free firmware in installer, one installer
[5] Choice 7: None Of The Above
[6] Choice 1: Only one installer, including non-free firmware
[7] Choice 4: Installer with non-free software is not part of Debian
This is, I don t agree either with Steve McIntyre s original proposal, Choice 1 (even though I seconded it, this means, I think it s very important to have this vote, and as a first proposal, it s better than the status quo maybe it s contradictory that I prefer it to the status quo, but ranked it below NotA. Well, more on that when I present Choice 5). My least favorite option is Choice 4, presented by Simon Josefsson, which represents the status quo: I don t want Debian not to have at all an installer that cannot be run on most modern hardware with reasonably good user experience (i.e. network support or the ability to boot at all!) Slightly above my acceptability threshold, I ranked Choice 5, presented by Russ Allbery. Debian s voting and its constitution rub each other in interesting ways, so the Project Secretary has to run the votes as they are presented but he has interpreted Choice 1 to be incompatible with the Social Contract (as there would no longer be a DFSG-free installer available), and if it wins, it could lead him to having to declare the vote invalid. I don t want that to happen, and that s why I ranked Choice 1 below None of the above. Other than that, Choice 6 (proposed by Holger Levsen), Choice 2 (proposed by me) and Choice 3 (proposed by Bart Martens) are very much similar; the main difference is that Choice 6 includes a modification to the Social Contract expressing that:
The Debian official media may include firmware that is otherwise not
part of the Debian system to enable use of Debian with hardware that
requires such firmware.
I believe choices 2 and 3 to be mostly the same, being Choice 2 more verbose in explaining the reasoning than Choice 3. Oh! And there are always some more bits to the discussion For example, given they hold modifications to the Social Contract, both Choice 5 and Choice 6 need a 3:1 supermajority to be valid. So, lets wait until the beginning of October to get the results, and to implement the changes they will (or not?) allow. If you are a Debian Project Member, please vote!

22 September 2022

Jonathan Dowland: Nine Inch Nails, Cornwall, June

In June I travelled to see Nine Inch Nails perform two nights at the Eden Project in Cornwall. It'd been eight years since I last saw them live and when they announced the Eden shows, I thought it might be the only chance I'd get to see them for a long time. I committed, and sods law, a week or so later they announced a handful of single-night UK club shows. On the other hand, on previous tours where they'd typically book two club nights in each city, I've attended one night and always felt I should have done both, so this time I was making that happen. Newquay
approach by air approach by air
Towan Beach (I think) Towan Beach (I think)
For personal reasons it's been a difficult year so it was nice to treat myself to a mini holiday. I stayed in Newquay, a seaside town with many similarities to the North East coast, as well as many differences. It's much bigger, and although we have a thriving surfing community in Tynemouth, Newquay have it on another level. They also have a lot more tourism, which is a double-edged sword: in Newquay, besides surfing, there was not a lot to do. There's a lot of tourist tat shops, and bars and cafes (som very nice ones), but no book shops, no record shops, very few of the quaint, unique boutique places we enjoy up here and possibly take for granted. If you want tie-dyed t-shirts though, you're sorted. Nine Inch Nails have a long-established, independently fan-run forum called Echoing The Sound. There is now also an official Discord server. I asked on both whether anyone was around in Newquay and wanted to meet up: not many people were! But I did meet a new friend, James, for a quiet drink. He was due to share a taxi with Sarah, who was flying in but her flight was delayed and she had to figure out another route. Eden Project
the Eden Project the Eden Project
The Eden Project, the venue itself, is a fascinating place. I didn't realise until I'd planned most of my time there that the gig tickets granted you free entry into the Project on the day of the gig as well as the day after. It was quite tricky to get from Newquay to the Eden project, I would have been better off staying in St Austell itself perhaps, so I didn't take advantage of this, but I did have a couple of hours total to explore a little bit at the venue before the gig on each night. Friday 17th (sunny) Once I got to the venue I managed to meet up with several names from ETS and the Discord: James, Sarah (who managed to re-arrange flights), Pete and his wife (sorry I missed your name), Via Tenebrosa (she of crab hat fame), Dave (DaveDiablo), Elliot and his sister and finally James (sheapdean), someone who I've been talking to online for over a decade and finally met in person (and who taped both shows). I also tried to meet up with a friend from the Debian UK community (hi Lief) but I couldn't find him! Support for Friday was Nitzer Ebb, who I wasn't familiar with before. There were two men on stage, one operating instruments, the other singing. It was a tough time to warm up the crowd, the venue was still very empty and it was very bright and sunny, but I enjoyed what I was hearing. They're definitely on my list. I later learned that the band's regular singer (Doug McCarthy) was unable to make it, and so the guy I was watching (Bon Harris) was standing in for full vocal duties. This made the performance (and their subsequent one at Hellfest the week after) all the more impressive.
pic of the band
Via (with crab hat), Sarah, me (behind). pic by kraw Via (with crab hat), Sarah, me (behind). pic by kraw
(Day) and night one, Thursday, was very hot and sunny and the band seemed a little uncomfortable exposed on stage with little cover. Trent commented as such at least once. The setlist was eclectic: and I finally heard some of my white whale songs. Highlights for me were The Perfect Drug, which was unplayed from 1997-2018 and has now become a staple, and the second ever performance of Everything, the first being a few days earlier. Also notable was three cuts in a row from the last LP, Bad Witch, Heresy and Love Is Not Enough. Saturday 18th (rain)
with Elliot, before with Elliot, before
Day/night 2, Friday, was rainy all day. Support was Yves Tumor, who were an interesting clash of styles: a Prince/Bowie-esque inspired lead clashing with a rock-out lead guitarist styling himself similarly to Brian May. I managed to find Sarah, Elliot (new gig best-buddy), Via and James (sheapdean) again. Pete was at this gig too, but opted to take a more relaxed position than the rail this time. I also spent a lot of time talking to a Canadian guy on a press pass (both nights) that I'm ashamed to have forgotten his name. The dank weather had Nine Inch Nails in their element. I think night one had the more interesting setlist, but night two had the best performance, hands down. Highlights for me were mostly a string of heavier songs (in rough order of scarcity, from common to rarely played): wish, burn, letting you, reptile, every day is exactly the same, the line begins to blur, and finally, happiness in slavery, the first UK performance since 1994. This was a crushing set. A girl in front of me was really suffering with the cold and rain after waiting at the venue all day to get a position on the rail. I thought she was going to pass out. A roadie with NIN noticed, and came over and gave her his jacket. He said if she waited to the end of the show and returned his jacket he'd give her a setlist, and true to his word, he did. This was a really nice thing to happen and really gave the impression that the folks who work on these shows are caring people.
Yep I was this close Yep I was this close
A fuckin' rainbow! Photo by "Lazereth of Nazereth"
Afterwards Afterwards
Night two did have some gentler songs and moments to remember: a re-arranged Sanctified (which ended a nineteen-year hiatus in 2013) And All That Could Have Been (recorded 2002, first played 2018), La Mer, during which the rain broke and we were presented with a beautiful pink-hued rainbow. They then segued into Less Than, providing the comic moment of the night when Trent noticed the rainbow mid-song; now a meme that will go down in NIN fan history. Wrap-up This was a blow-out, once in a lifetime trip to go and see a band who are at the top of their career in terms of performance. One problem I've had with NIN gigs in the past is suffering gig flashback to them when I go to other (inferior) gigs afterwards, and I'm pretty sure I will have this problem again. Doing both nights was worth it, the two experiences were very different and each had its own unique moments. The venue was incredible, and Cornwall is (modulo tourist trap stuff) beautiful.

20 September 2022

Simon Josefsson: Privilege separation of GSS-API credentials for Apache

To protect web resources with Kerberos you may use Apache HTTPD with mod_auth_gssapi however, all web scripts (e.g., PHP) run under Apache will have access to the Kerberos long-term symmetric secret credential (keytab). If someone can get it, they can impersonate your server, which is bad. The gssproxy project makes it possible to introduce privilege separation to reduce the attack surface. There is a tutorial for RPM-based distributions (Fedora, RHEL, AlmaLinux, etc), but I wanted to get this to work on a DPKG-based distribution (Debian, Ubuntu, Trisquel, PureOS, etc) and found it worthwhile to document the process. I m using Ubuntu 22.04 below, but have tested it on Debian 11 as well. I have adopted the gssproxy package in Debian, and testing this setup is part of the scripted autopkgtest/debci regression testing. First install the required packages:
root@foo:~# apt-get update
root@foo:~# apt-get install -y apache2 libapache2-mod-auth-gssapi gssproxy curl
This should give you a working and running web server. Verify it is operational under the proper hostname, I ll use in this writeup.
root@foo:~# curl --head
HTTP/1.1 200 OK
The next step is to create a keytab containing the Kerberos V5 secrets for your host, the exact steps depends on your environment (usually kadmin ktadd or ipa-getkeytab), but use the string HTTP/ and then confirm using something like the following.
root@foo:~# ls -la /etc/gssproxy/httpd.keytab
-rw------- 1 root root 176 Sep 18 06:44 /etc/gssproxy/httpd.keytab
root@foo:~# klist -k /etc/gssproxy/httpd.keytab -e
Keytab name: FILE:/etc/gssproxy/httpd.keytab
KVNO Principal
---- --------------------------------------------------------------------------
   2 HTTP/ (aes256-cts-hmac-sha1-96) 
   2 HTTP/ (aes128-cts-hmac-sha1-96) 
The file should be owned by root and not be in the default /etc/krb5.keytab location, so Apache s libapache2-mod-auth-gssapi will have to use gssproxy to use it.

Then configure gssproxy to find the credential and use it with Apache.
root@foo:~# cat<<EOF > /etc/gssproxy/80-httpd.conf
mechs = krb5
cred_store = keytab:/etc/gssproxy/httpd.keytab
cred_store = ccache:/var/lib/gssproxy/clients/krb5cc_%U
euid = www-data
process = /usr/sbin/apache2
For debugging, it may be useful to enable more gssproxy logging:
root@foo:~# cat<<EOF > /etc/gssproxy/gssproxy.conf
debug_level = 1
Restart gssproxy so it finds the new configuration, and monitor syslog as follows:
root@foo:~# tail -F /var/log/syslog &
root@foo:~# systemctl restart gssproxy
You should see something like this in the log file:
Sep 18 07:03:15 foo gssproxy[4076]: [2022/09/18 05:03:15]: Exiting after receiving a signal
Sep 18 07:03:15 foo systemd[1]: Stopping GSSAPI Proxy Daemon
Sep 18 07:03:15 foo systemd[1]: gssproxy.service: Deactivated successfully.
Sep 18 07:03:15 foo systemd[1]: Stopped GSSAPI Proxy Daemon.
Sep 18 07:03:15 foo gssproxy[4092]: [2022/09/18 05:03:15]: Debug Enabled (level: 1)
Sep 18 07:03:15 foo systemd[1]: Starting GSSAPI Proxy Daemon
Sep 18 07:03:15 foo gssproxy[4093]: [2022/09/18 05:03:15]: Kernel doesn't support GSS-Proxy (can't open /proc/net/rpc/use-gss-proxy: 2 (No such file or directory))
Sep 18 07:03:15 foo gssproxy[4093]: [2022/09/18 05:03:15]: Problem with kernel communication! NFS server will not work
Sep 18 07:03:15 foo systemd[1]: Started GSSAPI Proxy Daemon.
Sep 18 07:03:15 foo gssproxy[4093]: [2022/09/18 05:03:15]: Initialization complete.
The NFS-related errors is due to a default gssproxy configuration file, it is harmless and if you don t use NFS with GSS-API you can silence it like this:
root@foo:~# rm /etc/gssproxy/24-nfs-server.conf
root@foo:~# systemctl try-reload-or-restart gssproxy
The log should now indicate that it loaded the keytab:
Sep 18 07:18:59 foo systemd[1]: Reloading GSSAPI Proxy Daemon 
Sep 18 07:18:59 foo gssproxy[4182]: [2022/09/18 05:18:59]: Received SIGHUP; re-reading config.
Sep 18 07:18:59 foo gssproxy[4182]: [2022/09/18 05:18:59]: Service: HTTP, Keytab: /etc/gssproxy/httpd.keytab, Enctype: 18
Sep 18 07:18:59 foo gssproxy[4182]: [2022/09/18 05:18:59]: New config loaded successfully.
Sep 18 07:18:59 foo systemd[1]: Reloaded GSSAPI Proxy Daemon.
To instruct Apache or actually, the MIT Kerberos V5 GSS-API library used by mod_auth_gssap loaded by Apache to use gssproxy instead of using /etc/krb5.keytab as usual, Apache needs to be started in an environment that has GSS_USE_PROXY=1 set. The background is covered by the gssproxy-mech(8) man page and explained by the gssproxy README.

When systemd is used the following can be used to set the environment variable, note the final command to reload systemd.
root@foo:~# mkdir -p /etc/systemd/system/apache2.service.d
root@foo:~# cat<<EOF > /etc/systemd/system/apache2.service.d/gssproxy.conf
root@foo:~# systemctl daemon-reload
The next step is to configure a GSS-API protected Apache resource:
root@foo:~# cat<<EOF > /etc/apache2/conf-available/private.conf
<Location /private>
  AuthType GSSAPI
  AuthName "GSSAPI Login"
  Require valid-user
Enable the configuration and restart Apache the suggested use of reload is not sufficient, because then it won t be restarted with the newly introduced GSS_USE_PROXY variable. This just applies to the first time, after the first restart you may use reload again.
root@foo:~# a2enconf private
Enabling conf private.
To activate the new configuration, you need to run:
systemctl reload apache2
root@foo:~# systemctl restart apache2
When you have debug messages enabled, the log may look like this:
Sep 18 07:32:23 foo systemd[1]: Stopping The Apache HTTP Server 
Sep 18 07:32:23 foo gssproxy[4182]: [2022/09/18 05:32:23]: Client [2022/09/18 05:32:23]: (/usr/sbin/apache2) [2022/09/18 05:32:23]: connected (fd = 10)[2022/09/18 05:32:23]: (pid = 4651) (uid = 0) (gid = 0)[2022/09/18 05:32:23]:
Sep 18 07:32:23 foo gssproxy[4182]: message repeated 4 times: [ [2022/09/18 05:32:23]: Client [2022/09/18 05:32:23]: (/usr/sbin/apache2) [2022/09/18 05:32:23]: connected (fd = 10)[2022/09/18 05:32:23]: (pid = 4651) (uid = 0) (gid = 0)[2022/09/18 05:32:23]:]
Sep 18 07:32:23 foo systemd[1]: apache2.service: Deactivated successfully.
Sep 18 07:32:23 foo systemd[1]: Stopped The Apache HTTP Server.
Sep 18 07:32:23 foo systemd[1]: Starting The Apache HTTP Server
Sep 18 07:32:23 foo gssproxy[4182]: [2022/09/18 05:32:23]: Client [2022/09/18 05:32:23]: (/usr/sbin/apache2) [2022/09/18 05:32:23]: connected (fd = 10)[2022/09/18 05:32:23]: (pid = 4657) (uid = 0) (gid = 0)[2022/09/18 05:32:23]:
root@foo:~# Sep 18 07:32:23 foo gssproxy[4182]: message repeated 8 times: [ [2022/09/18 05:32:23]: Client [2022/09/18 05:32:23]: (/usr/sbin/apache2) [2022/09/18 05:32:23]: connected (fd = 10)[2022/09/18 05:32:23]: (pid = 4657) (uid = 0) (gid = 0)[2022/09/18 05:32:23]:]
Sep 18 07:32:23 foo systemd[1]: Started The Apache HTTP Server.
Finally, set up a dummy test page on the server:
root@foo:~# echo OK > /var/www/html/private
To verify that the server is working properly you may acquire tickets locally and then use curl to retrieve the GSS-API protected resource. The "--negotiate" enables SPNEGO and "--user :" asks curl to use username from the environment.
root@foo:~# klist
Ticket cache: FILE:/tmp/krb5cc_0
Default principal: jas@GSSPROXY.EXAMPLE.ORG
Valid starting Expires Service principal
09/18/22 07:40:37 09/19/22 07:40:37 krbtgt/GSSPROXY.EXAMPLE.ORG@GSSPROXY.EXAMPLE.ORG
root@foo:~# curl --negotiate --user :
The log should contain something like this:
Sep 18 07:56:00 foo gssproxy[4872]: [2022/09/18 05:56:00]: Client [2022/09/18 05:56:00]: (/usr/sbin/apache2) [2022/09/18 05:56:00]: connected (fd = 10)[2022/09/18 05:56:00]: (pid = 5042) (uid = 33) (gid = 33)[2022/09/18 05:56:00]:
Sep 18 07:56:00 foo gssproxy[4872]: [CID 10][2022/09/18 05:56:00]: gp_rpc_execute: executing 6 (GSSX_ACQUIRE_CRED) for service "HTTP", euid: 33,socket: (null)
Sep 18 07:56:00 foo gssproxy[4872]: [CID 10][2022/09/18 05:56:00]: gp_rpc_execute: executing 6 (GSSX_ACQUIRE_CRED) for service "HTTP", euid: 33,socket: (null)
Sep 18 07:56:00 foo gssproxy[4872]: [CID 10][2022/09/18 05:56:00]: gp_rpc_execute: executing 1 (GSSX_INDICATE_MECHS) for service "HTTP", euid: 33,socket: (null)
Sep 18 07:56:00 foo gssproxy[4872]: [CID 10][2022/09/18 05:56:00]: gp_rpc_execute: executing 6 (GSSX_ACQUIRE_CRED) for service "HTTP", euid: 33,socket: (null)
Sep 18 07:56:00 foo gssproxy[4872]: [CID 10][2022/09/18 05:56:00]: gp_rpc_execute: executing 9 (GSSX_ACCEPT_SEC_CONTEXT) for service "HTTP", euid: 33,socket: (null)
The Apache log will look like this, notice the authenticated username shown. - jas@GSSPROXY.EXAMPLE.ORG [18/Sep/2022:07:56:00 +0200] "GET /private HTTP/1.1" 200 481 "-" "curl/7.81.0"
Congratulations, and happy hacking!

Matthew Garrett: Handling WebAuthn over remote SSH connections

Being able to SSH into remote machines and do work there is great. Using hardware security tokens for 2FA is also great. But trying to use them both at the same time doesn't work super well, because if you hit a WebAuthn request on the remote machine it doesn't matter how much you mash your token - it's not going to work.

But could it?

The SSH agent protocol abstracts key management out of SSH itself and into a separate process. When you run "ssh-add .ssh/id_rsa", that key is being loaded into the SSH agent. When SSH wants to use that key to authenticate to a remote system, it asks the SSH agent to perform the cryptographic signatures on its behalf. SSH also supports forwarding the SSH agent protocol over SSH itself, so if you SSH into a remote system then remote clients can also access your keys - this allows you to bounce through one remote system into another without having to copy your keys to those remote systems.

More recently, SSH gained the ability to store SSH keys on hardware tokens such as Yubikeys. If configured appropriately, this means that even if you forward your agent to a remote site, that site can't do anything with your keys unless you physically touch the token. But out of the box, this is only useful for SSH keys - you can't do anything else with this support.

Well, that's what I thought, at least. And then I looked at the code and realised that SSH is communicating with the security tokens using the same library that a browser would, except it ensures that any signature request starts with the string "ssh:" (which a genuine WebAuthn request never will). This constraint can actually be disabled by passing -O no-restrict-websafe to ssh-agent, except that was broken until this weekend. But let's assume there's a glorious future where that patch gets backported everywhere, and see what we can do with it.

First we need to load the key into the security token. For this I ended up hacking up the Go SSH agent support. Annoyingly it doesn't seem to be possible to make calls to the agent without going via one of the exported methods here, so I don't think this logic can be implemented without modifying the agent module itself. But this is basically as simple as adding another key message type that looks something like:
type ecdsaSkKeyMsg struct  
       Type        string  sshtype:"17 25" 
       Curve       string
       PubKeyBytes []byte
       RpId        string
       Flags       uint8
       KeyHandle   []byte
       Reserved    []byte
       Comments    string
       Constraints []byte  ssh:"rest" 
Where Type is ssh.KeyAlgoSKECDSA256, Curve is "nistp256", RpId is the identity of the relying party (eg, ""), Flags is 0x1 if you want the user to have to touch the key, KeyHandle is the hardware token's representation of the key (basically an opaque blob that's sufficient for the token to regenerate the keypair - this is generally stored by the remote site and handed back to you when it wants you to authenticate). The other fields can be ignored, other than PubKeyBytes, which is supposed to be the public half of the keypair.

This causes an obvious problem. We have an opaque blob that represents a keypair. We don't have the public key. And OpenSSH verifies that PubKeyByes is a legitimate ecdsa public key before it'll load the key. Fortunately it only verifies that it's a legitimate ecdsa public key, and does nothing to verify that it's related to the private key in any way. So, just generate a new ECDSA key (ecdsa.GenerateKey(elliptic.P256(), rand.Reader)) and marshal it ( elliptic.Marshal(ecKey.Curve, ecKey.X, ecKey.Y)) and we're good. Pass that struct to ssh.Marshal() and then make an agent call.

Now you can use the standard agent interfaces to trigger a signature event. You want to pass the raw challenge (not the hash of the challenge!) - the SSH code will do the hashing itself. If you're using agent forwarding this will be forwarded from the remote system to your local one, and your security token should start blinking - touch it and you'll get back an ssh.Signature blob. ssh.Unmarshal() the Blob member to a struct like
type ecSig struct  
        R *big.Int
        S *big.Int
and then ssh.Unmarshal the Rest member to
type authData struct  
        Flags    uint8
        SigCount uint32
The signature needs to be converted back to a DER-encoded ASN.1 structure (eg,
var b cryptobyte.Builder
b.AddASN1(asn1.SEQUENCE, func(b *cryptobyte.Builder)  
signatureDER, _ := b.Bytes()
, and then you need to construct the Authenticator Data structure. For this, take the RpId used earlier and generate the sha256. Append the one byte Flags variable, and then convert SigCount to big endian and append those 4 bytes. You should now have a 37 byte structure. This needs to be CBOR encoded (I used and just called cbor.Marshal(data, cbor.EncOptions )).

Now base64 encode the sha256 of the challenge data, the DER-encoded signature and the CBOR-encoded authenticator data and you've got everything you need to provide to the remote site to satisfy the challenge.

There are alternative approaches - you can use USB/IP to forward the hardware token directly to the remote system. But that means you can't use it locally, so it's less than ideal. Or you could implement a proxy that communicates with the key locally and have that tunneled through to the remote host, but at that point you're just reinventing ssh-agent.

And you should bear in mind that the default behaviour of blocking this sort of request is for a good reason! If someone is able to compromise a remote system that you're SSHed into, they can potentially trick you into hitting the key to sign a request they've made on behalf of an arbitrary site. Obviously they could do the same without any of this if they've compromised your local system, but there is some additional risk to this. It would be nice to have sensible MAC policies that default-denied access to the SSH agent socket and only allowed trustworthy binaries to do so, or maybe have some sort of reasonable flatpak-style portal to gate access. For my threat model I think it's a worthwhile security tradeoff, but you should evaluate that carefully yourself.

Anyway. Now to figure out whether there's a reasonable way to get browsers to work with this.

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19 September 2022

Antoine Beaupr : Looking at Wayland terminal emulators

Back in 2018, I made a two part series about terminal emulators that was actually pretty painful to write. So I'm not going to retry this here, not at all. Especially since I'm not submitting this to the excellent LWN editors so I can get away with not being very good at writing. Phew. Still, it seems my future self will thank me for collecting my thoughts on the terminal emulators I have found out about since I wrote that article. Back then, Wayland was not quite at the level where it is now, being the default in Fedora (2016), Debian (2019), RedHat (2019), and Ubuntu (2021). Also, a bunch of folks thought they would solve everything by using OpenGL for rendering. Let's see how things stack up.

Recap In the previous article, I touched on those projects:
Terminal Changes since review
Alacritty releases! scrollback, better latency, URL launcher, clipboard support, still not in Debian, but close
GNOME Terminal not much? couldn't find a changelog
Konsole outdated changelog, color, image previews, clickable files, multi-input, SSH plugin, sixel images
mlterm long changelog but: supports console mode (like GNU screen?!), Wayland support through libvte, sixel graphics, zmodem, mosh (!)
pterm changes: Wayland support
st unparseable changelog, suggests scroll(1) or scrollback.patch for scrollback now
Terminator moved to GitHub, Python 3 support, not being dead
urxvt no significant changes, a single release, still in CVS!
Xfce Terminal hard to parse changelog, presumably some improvements to paste safety?
xterm notoriously hard to parse changelog, improvements to paste safety (disallowedPasteControls), fonts, clipboard improvements?
After writing those articles, bizarrely, I was still using rxvt even though it did not come up as shiny as I would have liked. The colors problems were especially irritating. I briefly played around with Konsole and xterm, and eventually switched to XTerm as my default x-terminal-emulator "alternative" in my Debian system, while writing this. I quickly noticed why I had stopped using it: clickable links are a huge limitation. I ended up adding keybindings to open URLs in a command. There's another keybinding to dump the history into a command. Neither are as satisfactory as just clicking a damn link.

Requirements Figuring out my requirements is actually a pretty hard thing to do. In my last reviews, I just tried a bunch of stuff and collected everything, but a lot of things (like tab support) I don't actually care about. So here's a set of things I actually do care about:
  • latency
  • resource usage
  • proper clipboard support, that is:
    • mouse selection and middle button uses PRIMARY
    • control-shift-c and control-shift-v for CLIPBOARD
  • true color support
  • no known security issues
  • active project
  • paste protection
  • clickable URLs
  • scrollback
  • font resize
  • non-destructive text-wrapping (ie. resizing a window doesn't drop scrollback history)
  • proper unicode support (at least latin-1, ideally "everything")
  • good emoji support (at least showing them, ideally "nicely"), which involves font fallback
Latency is particularly something I wonder about in Wayland. Kitty seem to have been pretty dilligent at doing latency tests, claiming 35ms with a hardware-based latency tester and 7ms with typometer, but it's unclear how those would come up in Wayland because, as far as I know, typometer does not support Wayland.

Candidates Those are the projects I am considering.
  • darktile - GPU rendering, Unicode support, themable, ligatures (optional), Sixel, window transparency, clickable URLs, true color support, not in Debian
  • foot - Wayland only, daemon-mode, sixel images, scrollback search, true color, font resize, URLs not clickable, but keyboard-driven selection, proper clipboard support, in Debian
  • havoc - minimal, scrollback, configurable keybindings, not in Debian
  • sakura - libvte, Wayland support, tabs, no menu bar, original libvte gangster, dynamic font size, probably supports Wayland, in Debian
  • termonad - Haskell? in Debian
  • wez - Rust, Wayland, multiplexer, ligatures, scrollback search, clipboard support, bracketed paste, panes, tabs, serial port support, Sixel, Kitty, iTerm graphics, built-in SSH client (!?), not in Debian
  • XTerm - status quo, no Wayland port obviously
  • zutty: OpenGL rendering, true color, clipboard support, small codebase, no Wayland support, crashes on bremner's, in Debian

Candidates not considered

Alacritty I would really, really like to use Alacritty, but it's still not packaged in Debian, and they haven't fully addressed the latency issues although, to be fair, maybe it's just an impossible task. Once it's packaged in Debian, maybe I'll reconsider.

Kitty Kitty is a "fast, feature-rich, GPU based", with ligatures, emojis, hyperlinks, pluggable, scriptable, tabs, layouts, history, file transfer over SSH, its own graphics system, and probably much more I'm forgetting. It's packaged in Debian. So I immediately got two people commenting (on IRC) that they use Kitty and are pretty happy with it. I've been hesitant in directly talking about Kitty publicly, but since it's likely there will be a pile-up of similar comments, I'll just say why it's not the first in my list, even if it might, considering it's packaged in Debian and otherwise checks all the boxes. I don't trust the Kitty code. Kitty was written by the same author as Calibre, which has a horrible security history and generally really messy source code. I have tried to do LTS work on Calibre, and have mostly given up on the idea of making that program secure in any way. See calibre for the details on that. Now it's possible Kitty is different: it's quite likely the author has gotten some experience writing (and maintaining for so long!) Calibre over the years. But I would be more optimistic if the author's reaction to the security issues were more open and proactive. I've also seen the same reaction play out on Kitty's side of things. As anyone who worked on writing or playing with non-XTerm terminal emulators, it's quite a struggle to make something (bug-for-bug) compatible with everything out there. And Kitty is in that uncomfortable place right now where it diverges from the canon and needs its own entry in the ncurses database. I don't remember the specifics, but the author also managed to get into fights with those people as well, which I don't feel is reassuring for the project going forward. If security and compatibility wasn't such big of a deal for me, I wouldn't mind so much, but I'll need a lot of convincing before I consider Kitty more seriously at this point.

Next steps It seems like Arch Linux defaults to foot in Sway, and I keep seeing it everywhere, so it is probably my next thing to try, if/when I switch to Wayland. One major problem with foot is that it's yet another terminfo entry. They did make it into ncurses (patch 2021-07-31) but only after Debian bullseye stable was released. So expect some weird compatibility issues when connecting to any other system that is older or the same as stable (!). One question mark with all Wayland terminals, and Foot in particular, is how much latency they introduce in the rendering pipeline. The foot performance and benchmarks look excellent, but do not include latency benchmarks.

No conclusion So I guess that's all I've got so far, I may try alacritty if it hits Debian, or foot if I switch to Wayland, but for now I'm hacking in xterm still. Happy to hear ideas in the comments. Stay tuned for more happy days.

17 September 2022

Russ Allbery: Effective altruism and the control trap

William MacAskill has been on a book tour for What We Owe to the Future, which has put effective altruism back in the news. That plus the decision by GiveWell to remove GiveDirectly from their top charity list got me thinking about charity again. I think effective altruism, by embracing long-termism, is falling into an ethical trap, and I'm going to start heavily discounting their recommendations for donations. Background Some background first for people who have no idea what I'm talking about. Effective altruism is the idea that we should hold charities accountable for effectiveness. It's not sufficient to have an appealing mission. A charity should demonstrate that the money they spend accomplishes the goals they claimed it would. There is a lot of debate around defining "effective," but as a basic principle, this is sound. Mainstream charity evaluators such as Charity Navigator measure overhead and (arguable) waste, but they don't ask whether the on-the-ground work of the charity has a positive effect proportional to the resources it's expending. This is a good question to ask. GiveWell is a charity research organization that directs money for donors based on effective altruism principles. It's one of the central organizations in effective altruism. GiveDirectly is a charity that directly transfers money from donors to poor people. It doesn't attempt to build infrastructure, buy specific things, or fund programs. It identifies poor people and gives them cash with no strings attached. Long-termism is part of the debate over what "effectiveness" means. It says we should value impact on future generations more highly than we tend to do. (In other words, we should have a much smaller future discount rate.) A sloppy but intuitive expression of long-termism is that (hopefully) there will be far more humans living in the future than are living today, and therefore a "greatest good for the greatest number" moral philosophy argues that we should invest significant resources into making the long-term future brighter. This has obvious appeal to those of us who are concerned about the long-term impacts of climate change, for example. There is a lot of overlap between the communities of effective altruism, long-termism, and "rationalism." One way this becomes apparent is that all three communities have a tendency to obsess over the risks of sentient AI taking over the world. I'm going to come back to that. Psychology of control GiveWell, early on, discovered that GiveDirectly was measurably more effective than most charities. Giving money directly to poor people without telling them how to spend it produced more benefits for those people and their surrounding society than nearly all international aid charities. GiveDirectly then became the baseline for GiveWell's evaluations, and GiveWell started looking for ways to be more effective than that. There is some logic to thinking more effectiveness is possible. Some problems are poorly addressed by markets and too large for individual spending. Health care infrastructure is an obvious example. That said, there's also a psychological reason to look for other charities. Part of the appeal of charity is picking a cause that supports your values (whether that be raw effectiveness or something else). Your opinions and expertise are valued alongside your money. In some cases, this may be objectively true. But in all cases, it's more flattering to the ego than giving poor people cash. At that point, the argument was over how to address immediate and objectively measurable human problems. The innovation of effective altruism is to tie charitable giving to a research feedback cycle. You measure the world, see if it is improving, and adjust your funding accordingly. Impact is measured by its effects on actual people. Effective altruism was somewhat suspicious of talking directly to individuals and preferred "objective" statistical measures, but the point was to remain in contact with physical reality. Enter long-termism: what if you could get more value for your money by addressing problems that would affect vast numbers of future people, instead of the smaller number of people who happen to be alive today? Rather than looking at the merits of that argument, look at its psychology. Real people are messy. They do things you don't approve of. They have opinions that don't fit your models. They're hard to "objectively" measure. But people who haven't been born yet are much tidier. They're comfortably theoretical; instead of having to go to a strange place with unfamiliar food and languages to talk to people who aren't like you, you can think hard about future trends in the comfort of your home. You control how your theoretical future people are defined, so the results of your analysis will align with your philosophical and ideological beliefs. Problems affecting future humans are still extrapolations of problems visible today in the world, though. They're constrained by observations of real human societies, despite the layer of projection and extrapolation. We can do better: what if the most serious problem facing humanity is the possible future development of rogue AI? Here's a problem that no one can observe or measure because it's never happened. It is purely theoretical, and thus under the control of the smart philosopher or rich western donor. We don't know if a rogue AI is possible, what it would be like, how one might arise, or what we could do about it, but we can convince ourselves that all those things can be calculated with some probability bar through the power of pure logic. Now we have escaped the uncomfortable psychological tension of effective altruism and returned to the familiar world in which the rich donor can define both the problem and the solution. Effectiveness is once again what we say it is. William MacAskill, one of the originators of effective altruism, now constantly talks about the threat of rogue AI. In a way, it's quite sad. Where to give money? The mindset of long-termism is bad for the human brain. It whispers to you that you're smarter than other people, that you know what's really important, and that you should retain control of more resources because you'll spend them more wisely than others. It's the opposite of intellectual humility. A government funding agency should take some risks on theoretical solutions to real problems, and maybe a few on theoretical solutions to theoretical problems (although an order of magnitude less). I don't think this is a useful way for an individual donor to think. So, if I think effective altruism is abandoning the one good idea it had and turning back into psychological support for the egos of philosophers and rich donors, where does this leave my charitable donations? To their credit, GiveWell so far seems uninterested in shifting from concrete to theoretical problems. However, they believe they can do better by picking projects than giving people money, and they're committing to that by dropping GiveDirectly (while still praising them). They may be right. But I'm increasingly suspicious of the level of control donors want to retain. It's too easy to trick oneself into thinking you know better than the people directly affected. I have two goals when I donate money. One is to make the world a better, kinder place. The other is to redistribute wealth. I have more of something than I need, and it should go to someone who does need it. The net effect should be to make the world fairer and more equal. The first goal argues for effective altruism principles: where can I give money to have the most impact on making the world better? The second goal argues for giving across an inequality gradient. I should find the people who are struggling the most and transfer as many resources to them as I can. This is Peter Singer's classic argument for giving money to the global poor. I think one can sometimes do better than transferring money, but doing so requires a deep understanding of the infrastructure and economies of scale that are being used as leverage. The more distant one is from a society, the more dubious I think one should be of one's ability to evaluate that, and the more wary one should be of retaining any control over how resources are used. Therefore, I'm pulling my recurring donation to GiveWell. Half of it is going to go to GiveDirectly, because I think it is an effective way of redistributing wealth while giving up control. The other half is going to my local foodbank, because they have a straightforward analysis of how they can take advantage of economy of scale, and because I have more tools available (such as local news) to understand what problem they're solving and if they're doing so effectively. I don't know that those are the best choices. There are a lot of good ones. But I do feel strongly that the best charity comes from embracing the idea that I do not have special wisdom, other people know more about what they need than I do, and deploying my ego and logic from the comfort of my home is not helpful. Find someone who needs something you have an excess of. Give it to them. Treat them as equals. Don't retain control. You won't go far wrong.

Shirish Agarwal: Books and Indian Tourism

Fiction A few days ago somebody asked me and I think it is an often requested to perhaps all fiction readers as to why we like fiction? First of all, reading in itself is told as food for the soul. Because, whenever you write or read anything you don t just read it, you also visualize it. And that visualization is and would be far greater than any attempt in cinema as there are no budget constraints and it takes no more than a minute to visualize a scenario if the writer is any good. You just close your eyes and in a moment you are transported to a different world. This is also what is known as world building . Something fantasy writers are especially gifted in. Also, with the whole parallel Universes being a reality, it is just so much fertile land for imagination that I just cannot believe that it hasn t been worked to death to date. And you do need a lot of patience to make a world, to make characters, to make characters a bit eccentric one way or the other. And you have to know to put into a three, five, or whatever number of acts you want to put in. And then, of course, they have readers like us who dream and add more color to the story than the author did. As we take his, her, or their story and weave countless stories depending on where we are, where we are and who we are. What people need to understand is that not just readers want escapism but writers too want to escape from the human condition. And they find solace in whatever they write. The well-known example of J.R.R. Tolkien is always there. How he must have felt each day coming after war, to somehow find the strength and just dream away, transport himself to a world of hobbits, elves, and other mysterious beings. It surely must have taken a lot of pain from him that otherwise, he would have felt. There are many others. What also does happen now and then, is authors believe in their own intelligence so much, that they commit crimes, but that s par for the course.

Dean Koontz, Odd Apocalypse Currently, I am reading the above title. It is perhaps one of the first horror title books that I have read which has so much fun. The hero has a great sense of wit, humor, and sarcasm that you can cut butter with it. Now if you got that, this is par for the wordplay happening every second paragraph and I m just 100 pages in of the 500-page Novel. Now, while I haven t read the whole book and I m just speculating, what if at the end we realize that the hero all along was or is the villain. Sadly, we don t have many such twisted stories and that too is perhaps because most people used to have black and white rather than grey characters. From all my reading, and even watching web series and whatnot, it is only the Europeans who seem to have a taste for exploring grey characters and giving twists at the end that people cannot anticipate. Even their heroes or heroines are grey characters. and they can really take you for a ride. It is also perhaps how we humans are, neither black nor white but more greyish. Having grey characters also frees the author quite a bit as she doesn t have to use so-called tropes and just led the characters to lead themselves.

Indian Book publishing Industry I do know Bengali stories do have a lot of grey characters, but sadly most of the good works are still in Bengali and not widely published compared to say European or American authors. While there is huge potential in the Indian publishing market for English books and there is also hunger, getting good and cheap publishers is the issue. Just recently SAGE publishing division shut down and this does not augur well for the Indian market. In the past few years, I and other readers have seen some very good publishing houses quit India for one reason or the other. GST has also made the sector more expensive. The only thing that works now and has been for some time is the seconds and thirds market. For e.g. I just bought today about 15-20 books @INR 125/- a kind of belated present for the self. That would be what, at the most 2 USD or 2 Euros per book. I bet even a burger costs more than that, but again India being a price-sensitive market, at these prices the seconds book sells. And these are all my favorite authors, Lee Child, Tom Clancy, Dean Koontz, and so on and so forth. I also saw a lot of fantasy books but they would have to wait for another day.

Tourism in India for Debconf 23 I had shared a while back that I would write a bit about tourism as Debconf or Annual Debian Conference will happen in India next year around this time. I was supposed to write it in the FAQ but couldn t find a place or a corner where I could write it. There are actually two things that people need to be aware of. The one thing that people need to be very aware of is food poisoning or Delhi Belly. This is a far too common sight that I have witnessed especially with westerners when they come to visit India. I am somewhat shocked that it hasn t been shared in the FAQ but then perhaps we cannot cover all the bases therein. I did find this interesting article and would recommend the suggestions given in it wholeheartedly. I would suggest people coming to India to buy and have purifying water tablets with them if they decide to stay back and explore India. Now the problem with tourism is, that one can have as much tourism as one wants. One of the unique ways I found some westerners having the time of their life is buying an Indian Rickshaw or Tuk-Tuk and traveling with it. A few years ago, when I was more adventourous-spirited I was able to meet a few of them. There is also the Race with Rickshaws that happens in Rajasthan and you get to see about 10 odd cities in and around Rajasthan state and get to see the vibrancy in the North. If somebody really wants to explore India, then I would suggest getting down to Goa, specifically, South Goa, meeting with the hippie crowd, and getting one of the hippie guidebooks to India. Most people forget that the Hippies came to India in the 1960s and many of them just never left. Tap water in Pune is ok, have seen and experienced the same in Himachal, Garwhal, and Uttarakhand, although it has been a few years since I have been to those places. North-East is a place I have yet to venture into. India does have a lot of beauty but most people are not clean-conscious so if you go to common tourist destinations, you will find a lot of garbage. Most cities in India do give you an option of homestays and some even offer food, so if you are on a budget as well as wanna experience life with an Indian family, that could be something you could look into. So you can see and share about India with different eyes. There is casteism, racism, and all that. Generally speaking, you would see it wielded a lot more in your face in North India than in South India where it is there but far more subtle. About food, what has been shared in the India BOF. Have to say, it doesn t even scratch the surface. If you stay with an Indian family, there is probably a much better chance of exploring the variety of food that India has to offer. From the western perspective, we tend to overcook stuff and make food with Masalas but that s the way most people like it. People who have had hot sauces or whatnot would probably find India much easier to adjust to as tastes might be similar to some extent. If you want to socialize with young people, while discos are an option, also is a good place. You can share your passions and many people have taken to it with gusto. We also have been hosting Comiccons in India, but I haven t had the opportunity to attend them so far. India has a rich oral culture reach going back a few thousand years, but many of those who are practicing those reside more in villages rather than in cities. And while there have been attempts in the past to record them, most of those have come to naught as money runs out as there is no commercial viability to such projects, but that probably is for another day. In the end, what I have shared is barely a drop in the ocean that is India. Come, have fun, explore, enjoy and invigorate yourself and others

James Valleroy: How I avoid sysadmin work

The server running this blog is a RockPro64 sitting in my living room. Besides WordPress (the blogging software), I run various other services on it: Most of these are for my personal use, and a few of them have pages for public viewing (linked at the top of this page). Despite running a server, I don t really consider myself to be a system administrator (or sysadmin for short). I generally try to avoid doing system administration work as much as possible. I think this is due to a number of reasons: These reasons might be surprising to some, but they also suggest that an alternative approach: So my approach is this: if I want to run an additional service, enhance an existing one, or fix a bug, I don t do those changes directly on my server. Instead, I will make (or suggest, or request) the change somewhere upstream of my server: So basically my system administration task turns into a software development task instead. And (in my opinion) there are much better tools available for this: source control systems such as git, test suites and Continuous Integration (CI) pipelines, and code review processes. These make it easier to keep track of and understand the changes, and reduce the possibility of making a catastrophic mistake. Besides this, there is one other major advantage to working upstream: the work is not just benefiting the server running in my home, but many others. Anyone who is using the same software or packages will also get the improvements or bug fixes. And likewise, I get to benefit from the work done by many other contributors. Some final notes about this approach:

Jonathan Dowland: Prusa Mini

In June I caved and bought a Prusa Mini 3D printer for home. I bought it just before an announced price hike. I went for a Prusa because of their reputation for "just working", and the Mini mostly as its the cheapest, although, the print area (7" ) is large enough for most of the things I am likely to print.
Prusa Mini in its setting
To get started, at the same time I bought some Prusament recycled PLA to print with which, unfortunately, I've been a little disappointed with. I was attracted to the idea of buying a recycled material and Prusa make a lot about the quality of their filaments. The description was pretty clear that the colour would be somewhat random and vary throughout the spool, but I didn't mind that, and I planned to use it for mainly functional prints where the precise colour didn't matter. The colour examples from the product page were mostly off-white grey with some tint, typically green. There are not a lot of reviews of the recycled PLA that comment on the colour of their spools, but in a couple of youtube videos (1, 2) the spools have looked a grey-ish silver, sometimes with a greenish tint, pretty similar to the product page. The colour I got is quite unlike those: it's a dull brown, with little flecks of glitter, presumably originally from recycling something like Galaxy Black. That's totally within "spec", of course, but it's a bit boring.
Brown recycled Prusament PLA on the right Brown recycled Prusament PLA on the right
In terms of quality, sadly I've ended up with had at least one tangle in the spool wind so far. There's at least two reviews on their own product page from people who have had similar difficulties. Edit: I realised after I wrote this post that I hadn't actually written much about the printer. That's because I'm still in the early days of using it. In short I'd say it's a very high quality machine, very pleasant to use. Since I also went on a tangent about the recycled Prusament, the tone of the whole post was more negative than I intended. Watch this space for some more positive Prusa news soon!

Jonathan Dowland: Introducing Red Hat UBI9 OpenJDK runtime images

A few weeks ago we shipped the first RHEL UBI9-based OpenJDK container images. Universal Base Image (UBI) is an initiative where you can obtain, share and build upon official Red Hat container images without needing a Red Hat subscription. They're exactly the same base images that Red Hat products are built upon, composed entirely of Open Source software. Your precise rights are covered in the EULA. Nowadays we offer two flavours of images, the original style (now termed builder images) and leaner runtime images, which have a subset of the JDK, and no build tools like Maven, etc. We provide JDK11 and JDK17 for UBI9:
podman pull
podman pull
podman pull
podman pull
In comparison to the UBI8 images, we have done a lot of housecleaning. If you are curious as to exactly what we've changed, you can read the list of commits in this pull request. Perhaps most notable is a change in the way we tune the JVM's memory. In our existing images up to now, partially for legacy reasons, the container start up scripts interrogate the cgroups (v1) virtual filesystems to establish any memory limits imposed on the running container. From that, they calculated a percentage of the memory limit as an absolute value, and then ask the JVM to limit its heap to that calculated sum via the -Xmx flag. This dates back to a time when the JVM was not container aware. It now is, so for the UBI9 images we instead ask the JVM directly for the percentage we want using -XX:MaxRAMPercentage. We've also changed the default percentage from 50% to 80%, to better utilise the memory assigned to Java containers. One big advantage of this is the JVM is cgroups (v2) aware, and the legacy start up scripts we wrote are not. But another is reducing the amount of code we run in the start up scripts, easing maintenance and simplifying the containers as much as possible. Please give them a go, and let me (or us) know what you think!

15 September 2022

Jonathan Dowland: things I'd like to 3D print, revisited

Back in November I wrote up a list of 25 things I would 3D print. Let's revisit the list and see how things have developed. Stuff I won't print
  • Some kind of 45 leaning prong to dry bottles and flasks on
  • A tea tray and coasters
  • Small tins to keep loose-leaf tea in
It was pointed out to me that you can't safely print things to store food in with most materials, as their porous/layered nature facilitates the growth of bacteria. So, I'll rule out those items.
A vinyl record.
The size of the grooves in a vinyl record are smaller than conventional FDM printers can achieve. Things I've printed
a replacement prop arm/foot for my computer keyboard
Someone has modelled the exact part I need, and it worked great:
replacement toy bolt replacement toy bolt
replacement bits for an Early Learning Centre Build It Deluxe Set
I was amazed to find that someone has already modelled one of these, too, and it worked beautifully:
Little kids trinkets. Pacman ghosts
The Pacman ghost family so far The Pacman ghost family so far
So far, I've tried to print useful, functional things, but on a few occasions I've printed a little Pacman ghost when testing printer calibration or similar. I've mostly used these models:
  • Lego storage/sorters
  • DIY bits-and-bobs sorter/storage (nuts and bolts etc)
I learned about a Slicer setting sometimes called "Vase mode" and found this interesting system of modular drawers that are designed to be printed in Vase mode, so I gave them a go: I printed one and four drawers for it and gave it to my daughter. It might be used for sorting Lego, or possibly as a chest-of-drawers for a dolls house.
A free-standing inclined vinyl record display stand
A bracket to install a Gotek drive in my Amiga 500 Summary From my original list of 25 things to print, I've done 7 of them and determined 4 are not viable. The things in this list I've printed have been off-the-shelf models that other people have constructed. The things I haven't printed are designs I will do myself, which is one reason I haven't printed them yet: building your own designs is the hard part!

Joachim Breitner: rec-def: Dominators case study

More ICFP-inspired experiments using the rec-def library: In Norman Ramsey s very nice talk about his Functional Pearl Beyond Relooper: Recursive Translation of Unstructured Control Flow to Structured Control Flow , he had the following slide showing the equation for the dominators of a node in a graph:
Norman Ramsey shows a formula Norman Ramsey shows a formula
He said it s ICFP and I wanted to say the dominance relation has a beautiful set of equations you can read all these algorithms how to compute this, but the concept is simple . This made me wonder: If the concept is simple and this formula is beautiful shouldn t this be sufficient for the Haskell programmer to obtain the dominator relation, without reading all those algorithms? Before we start, we have to clarify the formula a bit: If a node is an entry node (no predecessors) then the big intersection is over the empty set, and that is not a well-defined concept. For these nodes, we need that big intersection to return the empty set, as entry nodes are not dominated by any other node. (Let s assume that the entry nodes are exactly those with no predecessors.) Let s try, first using plain Haskell data structures. We begin by implementing this big intersection operator on Data.Set, and also a function to find the predecessors of a node in a graph: Now we can write down the formula that Norman gave, quite elegantly: Does this work? It seems it does: But not surprising if you have read my previous blog posts it falls over once we have recursion: So let us reimplement it with Data.Recursive.Set. The hope is that we can simply replace the operations, and that now it can suddenly handle cyclic graphs as well. Let s see: It does! Well, it does return a result but it looks strange. Clearly node 3 and 4 are also dominated by 1, but the result does not reflect that. But the result is a solution to Norman s equation. Was the equation wrong? No, but we failed to notice that the desired solution is the largest, not the smallest. And Data.Recursive.Set calculates, as documented, the least fixed point. What now? Until the library has code for RDualSet a, we can work around this by using the dual formula to calculate the non-dominators. To do this, we
  • use union instead of intersection
  • delete instead of insert,
  • S.empty, use the set of all nodes (which requires some extra plumbing)
  • subtract the result from the set of all nodes to get the dominators
and thus the code turns into:
And with this, now we do get the correct result:
ghci> domintors3 [(1,2),(1,3),(2,4),(3,4),(4,3)]
fromList [(1,[1]),(2,[1,2]),(3,[1,3]),(4,[1,4])]
We worked a little bit on how to express the beautiful formula to Haskell, but at no point did we have to think about how to solve it. To me, this is the essence of declarative programming.

13 September 2022

Alberto Garc a: Adding software to the Steam Deck with systemd-sysext

Yakuake on SteamOS Introduction: an immutable OS The Steam Deck runs SteamOS, a single-user operating system based on Arch Linux. Although derived from a standard package-based distro, the OS in the Steam Deck is immutable and system updates replace the contents of the root filesystem atomically instead of using the package manager. An immutable OS makes the system more stable and its updates less error-prone, but users cannot install additional packages to add more software. This is not a problem for most users since they are only going to run Steam and its games (which are stored in the home partition). Nevertheless, the OS also has a desktop mode which provides a standard Linux desktop experience, and here it makes sense to be able to install more software. How to do that though? It is possible for the user to become root, make the root filesytem read-write and install additional software there, but any changes will be gone after the next OS update. Modifying the rootfs can also be dangerous if the user is not careful. Ways to add additional software The simplest and safest way to install additional software is with Flatpak, and that s the method recommended in the Steam Deck Desktop FAQ. Flatpak is already installed and integrated in the system via the Discover app so I won t go into more details here. However, while Flatpak works great for desktop applications not every piece of software is currently available, and Flatpak is also not designed for other types of programs like system services or command-line tools. Fortunately there are several ways to add software to the Steam Deck without touching the root filesystem, each one with different pros and cons. I will probably talk about some of them in the future, but in this post I m going to focus on one that is already available in the system: systemd-sysext. About systemd-sysext This is a tool included in recent versions of systemd and it is designed to add additional files (in the form of system extensions) to an otherwise immutable root filesystem. Each one of these extensions contains a set of files. When extensions are enabled (aka merged ) those files will appear on the root filesystem using overlayfs. From then on the user can open and run them normally as if they had been installed with a package manager. Merged extensions are seamlessly integrated with the rest of the OS. Since extensions are just collections of files they can be used to add new applications but also other things like system services, development tools, language packs, etc. Creating an extension: yakuake I m using yakuake as an example for this tutorial since the extension is very easy to create, it is an application that some users are demanding and is not easy to distribute with Flatpak. So let s create a yakuake extension. Here are the steps: 1) Create a directory and unpack the files there:
$ mkdir yakuake
$ wget
$ tar -C yakuake -xaf yakuake-*.tar.zst usr
2) Create a file called extension-release.NAME under usr/lib/extension-release.d with the fields ID and VERSION_ID taken from the Steam Deck s /etc/os-release file.
$ mkdir -p yakuake/usr/lib/extension-release.d/
$ echo ID=steamos > yakuake/usr/lib/extension-release.d/extension-release.yakuake
$ echo VERSION_ID=3.3.1 >> yakuake/usr/lib/extension-release.d/extension-release.yakuake
3) Create an image file with the contents of the extension:
$ mksquashfs yakuake yakuake.raw
That s it! The extension is ready. A couple of important things: image files must have the .raw suffix and, despite the name, they can contain any filesystem that the OS can mount. In this example I used SquashFS but other alternatives like EroFS or ext4 are equally valid. NOTE: systemd-sysext can also use extensions from plain directories (i.e skipping the mksquashfs part). Unfortunately we cannot use them in our case because overlayfs does not work with the casefold feature that is enabled on the Steam Deck. Using the extension Once the extension is created you simply need to copy it to a place where systemd-systext can find it. There are several places where they can be installed (see the manual for a list) but due to the Deck s partition layout and the potentially large size of some extensions it probably makes more sense to store them in the home partition and create a link from one of the supported locations (/var/lib/extensions in this example):
(deck@steamdeck ~)$ mkdir extensions
(deck@steamdeck ~)$ scp user@host:/path/to/yakuake.raw extensions/
(deck@steamdeck ~)$ sudo ln -s $PWD/extensions /var/lib/extensions
Once the extension is installed in that directory you only need to enable and start systemd-sysext:
(deck@steamdeck ~)$ sudo systemctl enable systemd-sysext
(deck@steamdeck ~)$ sudo systemctl start systemd-sysext
After this, if everything went fine you should be able to see (and run) /usr/bin/yakuake. The files should remain there from now on, also if you reboot the device. You can see what extensions are enabled with this command:
$ systemd-sysext status
/opt      none       -
/usr      yakuake    Tue 2022-09-13 18:21:53 CEST
If you add or remove extensions from the directory then a simple systemd-sysext refresh is enough to apply the changes. Unfortunately, and unlike distro packages, extensions don t have any kind of post-installation hooks or triggers, so in the case of Yakuake you probably won t see an entry in the KDE application menu immediately after enabling the extension. You can solve that by running kbuildsycoca5 once from the command line. Limitations and caveats Using systemd extensions is generally very easy but there are some things that you need to take into account:
  1. Using extensions is easy (you put them in the directory and voil !). However, creating extensions is not necessarily always easy. To begin with, any libraries, files, etc., that your extensions may need should be either present in the root filesystem or provided by the extension itself. You may need to combine files from different sources or packages into a single extension, or compile them yourself.
  2. In particular, if the extension contains binaries they should probably come from the Steam Deck repository or they should be built to work with those packages. If you need to build your own binaries then having a SteamOS virtual machine can be handy. There you can install all development files and also test that everything works as expected. One could also create a Steam Deck SDK extension with all the necessary files to develop directly on the Deck
  3. Extensions are not distribution packages, they don t have dependency information and therefore they should be self-contained. They also lack triggers and other features available in packages. For desktop applications I still recommend using a system like Flatpak when possible.
  4. Extensions are tied to a particular version of the OS and, as explained above, the ID and VERSION_ID of each extension must match the values from /etc/os-release. If the fields don t match then the extension will be ignored. This is to be expected because there s no guarantee that a particular extension is going to work with a different version of the OS. This can happen after a system update. In the best case one simply needs to update the extension s VERSION_ID, but in some cases it might be necessary to create the extension again with different/updated files.
  5. Extensions only install files in /usr and /opt. Any other file in the image will be ignored. This can be a problem if a particular piece of software needs files in other directories.
  6. When extensions are enabled the /usr and /opt directories become read-only because they are now part of an overlayfs. They will remain read-only even if you run steamos-readonly disable !!. If you really want to make the rootfs read-write you need to disable the extensions (systemd-sysext unmerge) first.
  7. Unlike Flatpak or Podman (including toolbox / distrobox), this is (by design) not meant to isolate the contents of the extension from the rest of the system, so you should be careful with what you re installing. On the other hand, this lack of isolation makes systemd-sysext better suited to some use cases than those container-based systems.
Conclusion systemd extensions are an easy way to add software (or data files) to the immutable OS of the Steam Deck in a way that is seamlessly integrated with the rest of the system. Creating them can be more or less easy depending on the case, but using them is extremely simple. Extensions are not packages, and systemd-sysext is not a package manager or a general-purpose tool to solve all problems, but if you are aware of its limitations it can be a practical tool. It is also possible to share extensions with other users, but here the usual warning against installing binaries from untrusted sources applies. Use with caution, and enjoy!

12 September 2022

Petter Reinholdtsen: Time to translate the Bullseye edition of the Debian Administrator's Handbook

(The picture is of the previous edition.) Almost two years after the previous Norwegian Bokm l translation of the "The Debian Administrator's Handbook" was published, a new edition is finally being prepared. The english text is updated, and it is time to start working on the translations. Around 37 percent of the strings have been updated, one way or another, and the translations starting from a complete Debian Buster edition now need to bring their translation up from 63% to 100%. The complete book is licensed using a Creative Commons license, and has been published in several languages over the years. The translations are done by volunteers to bring Linux in their native tongue. The last time I checked, it complete text was available in English, Norwegian Bokm l, German, Indonesian, Brazil Portuguese and Spanish. In addition, work has been started for Arabic (Morocco), Catalan, Chinese (Simplified), Chinese (Traditional), Croatian, Czech, Danish, Dutch, French, Greek, Italian, Japanese, Korean, Persian, Polish, Romanian, Russian, Swedish, Turkish and Vietnamese. The translation is conducted on the hosted weblate project page. Prospective translators are recommeded to subscribe to the translators mailing list and should also check out the instructions for contributors. I am one of the Norwegian Bokm l translators of this book, and we have just started. Your contribution is most welcome. As usual, if you use Bitcoin and want to show your support of my activities, please send Bitcoin donations to my address 15oWEoG9dUPovwmUL9KWAnYRtNJEkP1u1b.

11 September 2022

Dirk Eddelbuettel: RcppArmadillo on CRAN: Bugfix and Deprecation

armadillo image Armadillo is a powerful and expressive C++ template library for linear algebra and scientific computing. It aims towards a good balance between speed and ease of use, has a syntax deliberately close to Matlab, and is useful for algorithm development directly in C++, or quick conversion of research code into production environments. RcppArmadillo integrates this library with the R environment and language and is widely used by (currently) 1016 packages other packages on CRAN, downloaded 26.2 million times (per the partial logs from the cloud mirrors of CRAN), and the CSDA paper (preprint / vignette) by Conrad and myself has been cited 493 times according to Google Scholar. This new release (made yesterday) brings three changes. First, it updates the release to the upstream 11.2.4 bugfix release made days ago by Conrad. Second, it contains support for the deprecation transition we are managing in issue #391. In short, the (convenient but non-standard) initialization via use of << has been deprecated upstream. Until all packages are updated, we override this in the RcppArmadillo but aim to become compliant . Out of the over 1000 packages, a mere 25 need small adjustments. I reached out email and PRs, and the response has been great. Eight packages are already updated on CRAN, and several others have already in integrated or merged the change. Lastly, Conrad pointed out that the fastLm() example and application can be written more concisely by using arma::dot(). The full set of changes (since the last CRAN release follows.

Changes in RcppArmadillo version (2022-09-09)
  • Upgraded to Armadillo release 11.2.4 (Classic Roast)
    • fix handling of std::move() involving matrices constructed with auxiliary memory
  • In the fastLm() examples, use arma::dot() to compute to the inner product (as proposed by Conrad), plus small edits
  • Support optional #define named RCPPARMADILLO_FORCE_DEPRECATE to suppress use of ARMA_IGNORE_DEPRECATED_MARKER permitting use and development under deprecation

Courtesy of my CRANberries, there is a diffstat report relative to previous release. More detailed information is on the RcppArmadillo page. Questions, comments etc should go to the rcpp-devel mailing list off the R-Forge page. If you like this or other open-source work I do, you can sponsor me at GitHub.

This post by Dirk Eddelbuettel originated on his Thinking inside the box blog. Please report excessive re-aggregation in third-party for-profit settings.

Shirish Agarwal: Politics, accessibility, books

Politics I have been reading books, both fiction and non-fiction for a long long time. My first book was a comic most probably when I was down with Malaria when I was a kid. I must be around 4-5 years old. Over the years, books have given me great joy and I continue to find nuggets of useful information, both in fiction as well as non-fiction books. So here s to sharing something and how that can lead you to a rabbit hole. This entry would be a bit NSFW as far as language is concerned. NYPD Red 5 by James Patterson First of all, have no clue as to why James Patterson s popularity has been falling. He used to be right there with Lee Child and others, but not so much now. While I try to be mysterious about books, I would give a bit of heads-up so people know what to expect. This is probably more towards the Adult crowd as there is a bit of sex as well as quite a few grey characters. The NYPD Red is a sort of elite police task force that basically is for celebrities. In the book series, they do a lot of ass-kissing (figuratively more than literally). Now the reason I have always liked fiction is that however wild the assumption or presumption is, it does have somewhere a grain of truth. And each and every time I read a book or two, that gets cemented. One of the statements in the book told something about how 9/11 took a lot of police personnel out of the game. First, there were a number of policemen who were patrolling the Two Towers, so they perished literally during the explosion. Then there were policemen who were given the cases to close the cases (bring the cases to conclusion). When you are investigating your own brethren or even civilians who perished 9/11 they must have experienced emotional trauma and no outlet. Mental health even in cops is the same and given similar help as you and me (i.e. next to none.) But both of these were my assumptions. The only statement that was in the book was they lost a lot of bench strength. Even NYFD (New York Fire Department). This led me to me to With Crime At Record Lows, Should NYC Have Fewer Cops? This is more right-wing sentiment and in fact, there have been calls to defund the police. This led me to and one specific graph. Unfortunately, this tells the story from 2010-2022 but not before. I was looking for data from around 1999 to 2005 because that will tell whether or not it happened. Then I remembered reading in newspapers the year or two later how 9/11 had led NYC to recession. I looked up online and for sure NY was booming before 9/11. One can argue that NYC could come down and that is pretty much possible, everything that goes up comes down, it s a law of nature but it would have been steady rather than abrupt. And once you are in recession, the first thing to go is personnel. So people both from NYPD and NYFD were let go, even though they were needed the most then. As you can see, a single statement in a book can take you to places & time literally. Edit: Addition 11th September There were quite a few people who also died from New York Port Authority and they also lost quite a number of people directly and indirectly and did a lot of patrolling of the water bodies near NYC. Later on, even in their department, there were a lot of early retirements.

Kosovo A couple of days back I had a look at the Debconf 2023 BOF that was done in Kosovo. One of the interesting things that happened during the BOF is when a woman participant chimed in and asks India to recognize Kosovo. Immediately it triggered me and I opened the Kosovo Wikipedia page to get some understanding of the topic. Reading up on it, came to know Russia didn t agree and doesn t recognize Kosovo. Mr. Modi likes Putin and India imports a lot of its oil from Russia. Unrelatedly, but still useful, we rejected to join IPEF. Earlier, we had rejected China s BRI. India has never been as vulnerable as she is now. Our foreign balance has reached record lows. Now India has been importing quite a bit of Russian crude and has been buying arms and ammunition from them. We are also scheduled to buy a couple of warships and submarines etc. We even took arms and ammunition from them on lease. So we can t afford that they are displeased with India. Even though Russia has more than friendly relations with both China and Pakistan. At the same time, the U.S. is back to aiding Pakistan which the mainstream media in India refuses to even cover. And to top all of this, we have the Chip 4 Alliance but that needs its own article, truth be told but we will do with a paragraph  Edit Addition 11th September Seems Kosovo isn t unique in that situation, there are 3-4 states like that. A brief look at worldpopulationreview tells you there are many more.

Chip 4 Alliance For almost a decade I have been screaming about this on my blog as well as everywhere that chip fabrication is a national security thing. And for years, most people deny it. And now we have chip 4 alliance. Now to understand this, you have to understand that China for almost a decade, somewhere around 2014 or so came up with something called the big fund . Now one can argue one way or the other how successful the fund has been, but it has, without doubt, created ripples so strong that the U.S., Taiwan, Japan, and probably South Korea will join and try to stem the tide. Interestingly, in this grouping, South Korea is the weakest in the statements and what they have been saying. Within the group itself, there is a lot of tension and China would use that and there are a number of unresolved issues between the three countries that both China & Russia would exploit. For e.g. the Comfort women between South Korea and Japan. Or the 1985 Accord Agreement between Japan and the U.S. Now people need to understand this, this is not just about China but also about us. If China has 5-6x times India s GDP and their research budget is at the very least 100x times what India spends, how do you think we will be self-reliant? Whom are we fooling? Are we not tired of fooling ourselves  In diplomacy, countries use leverage. Sadly, we let go of some of our most experienced negotiators in 2014 and since then have been singing in the wind

Accessibility, Jitsi, IRC, Element-Desktop The Wikipedia page on Accessibility says the following Accessibility is the design of products, devices, services, vehicles, or environments so as to be usable by people with disabilities. The concept of accessible design and practice of accessible development ensures both direct access (i.e. unassisted) and indirect access meaning compatibility with a person s assistive technology. Now IRC or Internet Relay Chat has been accessible for a long time. I know of even blind people who have been able to navigate IRC quite effortlessly as there has been a lot of work done to make sure all the joints speak to each other so people with one or more disabilities still can use, and contribute without an issue. It does help that IRC and many clients have been there since the 1970s so most of them have had more than enough time to get all the bugs fixed and both text-to-speech and speech-to-text work brilliantly on IRC. Newer software like Jitsi or for that matter Telegram is lacking those features. A few days ago, discovered on Telegram I was shared that Samsung Voice input is also able to do the same. The Samsung Voice Input works wonder as it translates voice to text, I have not yet tried the text-to-speech but perhaps somebody can and they can share whatever the results can be one way or the other. I have tried element-desktop both on the desktop as well as mobile phone and it has been disappointing, to say the least. On the desktop, it is unruly and freezes once in a while, and is buggy. The mobile version is a little better but that s not saying a lot. I prefer the desktop version as I can use the full-size keyboard. The bug I reported has been there since its Riot days. I had put up a bug report even then. All in all, yesterday was disappointing

Russ Allbery: Review: Hogfather

Review: Hogfather, by Terry Pratchett
Series: Discworld #20
Publisher: Harper
Copyright: 1996
Printing: February 2014
ISBN: 0-06-227628-X
Format: Mass market
Pages: 402
Hogfather is the 20th Discworld novel and not a very good place to start. I recommend at least reading Soul Music first for a proper introduction to Susan, and you may want to start with Mort. When we last saw Susan, she was a student at the Quirm College for Young Ladies. Now she's a governess for two adorable youngsters, a job that includes telling them stories and dealing quite capably with monsters in the cellar. (She uses a poker.) It also includes answering questions like whether the Hogfather really exists or whether the presents just come from your parents.
"Look at it this way, then," she said, and took a deep mental breath. "Wherever people are obtuse and absurd... and wherever they have, by even the most generous standards, the attention span of a small chicken in a hurricane and the investigative ability of a one-legged cockroach... and wherever people are inanely credulous, pathetically attached to the certainties of the nursery and, in general, have as much grasp of the physical universe as an oyster has of mountaineering... yes, Twyla: there is a Hogfather.
Meanwhile, the Auditors, last seen meddling with Death in Reaper Man, approach the Assassin's Guild in Ankh-Morpork to hire the assassination of the Hogfather. This rather unusual assignment falls to Mister Teatime, an orphan who was taken in by the guild at an early age and trained to be an assassin. Teatime is a little unnerving, mostly because he enjoys being an assassin. Rather a lot. Hogfather has two major things to recommend it: it's a Death novel, and it features Susan, who is one of my favorite Discworld characters. It also has two major strikes against it, at least for me. The first is relatively minor but, for me, the most irritating. A bit of the way into the story, Pratchett introduces the Oh God of Hangovers fair, that's a good pun and then decides that's a good excuse for nausea and vomiting jokes. A lot of nausea and vomiting jokes. Look. I know a lot of people don't mind this. But I beg authors (and, even more so, filmmakers and cartoonists) to consider whether a joke that some of your audience might like is worth making other parts of your audience feel physically ill while trying to enjoy your work. It's not at all a pleasant experience, and while I handle it better in written form, it still knocks me out of the story and makes me want to skip over scenes with the obnoxious character who won't shut up about it. Thankfully this does stop by the end of the book, but there are several segments in the middle that were rather unpleasant. The second is that Pratchett tries to convince the reader of the mythical importance of the Santa Claus myth (for which Hogfather is an obvious stand-in, if with a Discworld twist), an effort for which I am a highly unsympathetic audience. I'm with Susan above, with an extra helping of deep dislike for telling children who trust you something that's literally untrue. Pratchett does try: he has Death makes a memorable and frequently-quoted point near the end of the book (transcribed below) that I don't entirely agree with but still respect. But still, the book is very invested in convincing Susan that people believing mythology is critically important to humanity, and I have so many problems with the literalness of "believing" and the use of trusting children for this purpose by adults who know better. There are few topics that bring out my grumpiness more than Santa Claus. Grumbling aside, though, I did enjoy this book anyway. Susan is always a delight, and I could read about her adventures as a governess for as long as Pratchett wanted to write them. Death is filling in for the Hogfather for most of the book, which is hilarious because he's far too good at it, in his painfully earnest and literal way, to be entirely safe. I was less fond of Albert's supporting role (who I am increasingly coming to dislike as a character), but the entire scene of Death as a mall Santa is brilliant. And Teatime is an effective, creepy villain, something that the Discworld series doesn't always deliver. The powers arrayed on Discworld are so strong that it can be hard to design a villain who effectively challenges them, but Teatime has a sociopathic Professor Moriarty energy with added creepiness that fills that role in this book satisfyingly. As is typical for Pratchett (at least for me), the plot was serviceable but not the highlight. Pratchett plays in some interesting ways with a child's view of the world, the Unseen University bumbles around as a side plot, and it comes together at the end in a way that makes sense, but the journey is the fun of the story. The conclusion felt a bit gratuitous, there mostly to wrap up the story than something that followed naturally from the previous plot. But it does feature one of the most quoted bits in Discworld:
Here's the thing, though: Susan is right. They're not the same sort of thing at all, and Pratchett doesn't present an argument that they are. Death's response is great, but it's also a non sequitur: it is true and correct but has nothing to do with Susan's argument. Justice is not a lie in the sense that Santa Claus is a lie: justice is something that humans can create, just like humans can create gift-giving or a tradition of imaginative story-telling. But this is not at all the same thing as encouraging children to believe in the literal existence of a fat man in red who comes down chimneys to deliver gifts by magic. And Death isn't even correct in Discworld! If one pays careful attention to the story, the consequences he's thinks would follow from the Auditors' attempt on the Hogfather not only don't happen, the exact opposite happens. This is the point of the Unseen University subplot, and it's also what happened in Reaper Man. The Auditors may be trying to kill mythology, but what the books show is that the real danger comes from the backlash. The force they're meddling with is far more powerful and persistent than they are. Death appears to be, by the stated events of the story, completely incorrect in his analysis of Discworld's metaphysics. Maybe Pratchett knows this? He did write a story that contradicts Death's analysis if one reads it carefully. But if so, this is not obvious from the text, or from Susan's reaction to Death's speech, which makes the metaphysics weirdly unsatisfying. So, overall, a mixed bag. Most of the book is very fun, but the metaphysics heavily rest on a pet peeve of mine, and I really could have done without the loving descriptions of the effects of hangovers. This is one of the more famous Discworld novels for the above quote, and on its own this is deserved (it's a great quote), but I think the logic is muddled and the story itself contradicts the implications. A rather odd reading experience. Followed by Jingo in publication order, and Thief of Time thematically. Rating: 7 out of 10

Andrew Cater: 202209110020 - Debian release day(s) - Cambridge - post 4

RattusRattus, Isy, smcv have all just left after a very long day. Steve is finishing up the final stages. The mayhem has quietened, the network cables are coiled, pretty much everything is tidied away. A new experience for two of us - I just hope it hasn't put them off too much.The IRC channels are quiet and we can put this one to bed after a good day's work well done.

10 September 2022

Joachim Breitner: rec-def: Behind the scenes

A week ago I wrote about the rec-def Haskell library, which allows you to write more recursive definitions, such as in this small example:
let s1 = RS.insert 23 s2
    s2 = RS.insert 42 s1
in RS.get s1
This will not loop (as it would if you d just used Data.Set), but rather correctly return the set S.fromList [23,42]. See the previous blog post for more examples and discussion of the user-facing side of this. For quick reference, these are the types of the functions involved here: The type of s1 and s2 above is not Set Int, but rather RSet Int, and in this post I ll explain how RSet works internally.

Propagators, in general The conceptual model behind an recursive equation like above is
  • There are a multiple cells that can hold values of an underlying type (here Set)
  • These cells have relations that explain how the values in the cells should relate to each other
  • After registering all the relations, some form of solving happens.
  • If the solving succeeds, we can read off the values from the cells, and they should satisfy the registered relation.
This is sometimes called a propagator network, and is a quite general model that can support different kind of relations (e.g. equalities, inequalities, functions), there can be various solving strategies (iterative fixed-points, algebraic solution, unification, etc.) and information can flow on along the edges (and hyper-edges) possibly in multiple directions. For our purposes, we only care about propagator networks where all relations are functional, so they have a single output cell that is declared to be a function of multiple (possibly zero) input cells, without affecting these input cells. Furthermore, every cell is the output of exactly one such relation.

IO-infested propagator interfaces This suggests that an implementation of such a propagator network could provide an interface with the following three operations:
  • Functions to declare cells
  • Functions to declare relations
  • Functions to read values off cells
This is clearly an imperative interface, so we ll see monads, and we ll simply use IO. So concretely for our small example above, we might expect
There is no need for an explicit solve function: solving can happen when declareInsert or getCell is called as a User I do not care about that. You might be curious about the implementation of newCell, declareInsert and getCell, but I have to disappoint you: This is not the topic of this article. Instead, I want to discuss how to turn this IO-infested interface into the pure interface seen above?

Pure, but too strict Obviously, we have to get rid of the IO somehow, and have to use unsafePerformIO :: IO a -> a somehow. This dangerous function creates a pure-looking value that, when used the first time, will run the IO-action and turn into that action s result. So maybe we can simply write the following: Indeed, the types line up, but if we try to use that code, nothing will happen. Our insert is too strict to be used recursively: It requires the value of c2 (as it is passed to declareInsert, which we assume to be strict in its arguments) before it can return c1, so the recursive example at the top of this post will not make any progress.

Pure, lazy, but forgetful To work around this, maybe it suffices if we do not run declareInsert right away, but just remember that we have to do it eventually? So let s introduce a new data type for RSet a that contains not just the cell (Cell a), but also an action that we still have to run before getting a value: This is better: insert is now lazy in its arguments (for this it is crucial to pattern-match on RSet only inside the todo code, not in the pattern of insert!) This means that our recursive code above does not get stuck right away.

Pure, lazy, but runs in circles But it is still pretty bad: Note that we do not run get s2 in the example above, so that cell s todo, which would declareInsert 42, will never run. This cannot work! We have to (eventually) run the declaration code from all involved cells before we can use getCell! We can try to run the todo action of all the dependencies as part of a cell s todo action: Now we certainly won t forget to run the second cell s todo action, so that is good. But that cell s todo action will run the first cell s todo action, and that again the second cell s, and so on.

Pure, lazy, terminating, but not thread safe This is silly: We only need (and should!) run that code once! So let s keep track of whether we ran it already: Ah, much better: It works! Our call to get c1 will trigger the first cell s todo action, which will mark it as done before calling the second cell s todo action. When that now invokes the first cell s todo action, it is already marked done and we break the cycle, and by the time we reach getCell, all relations have been correctly registered. In a single-threaded world, this would be all good and fine, but we have to worry about multiple threads running get concurrently, on the same or on different cells. In fact, because we use unsafePerformIO, we have to worry about this even when the program is not using threads. And the above code has problems. Imagine a second call to get c1 while the first one has already marked it as done, but has not finished processing all the dependencies yet: It will call getCell before all relations are registered, which is bad.

Recursive do-once IO actions Making this thread-safe seems to be possible, but would clutter both the code and this blog post. So let s hide that problem behind a nice and clean interface. Maybe there will be a separate blog post about its implementation (let me know if you are curious), or you can inspect the code in System.IO.RecThunk module yourself). The interface is simply
data Thunk
thunk :: IO [Thunk] -> IO Thunk
force :: Thunk -> IO ()
and the idea is that thunk act will defer the action act until the thunk is passed to force for the first time, and force will not return until the action has been performed (possibly waiting if another thread is doing that at the moment), and also until the actions of all the thunks returned by act have performed, recursively, without running into cycles. We can use this in our definition of RSet and get to the final, working solution: This snippet captures the essential ideas behind rec-def:
  • Use laziness to allow recursive definition to describe the propagator graph naturally
  • Use a form of explicit thunk to register the propagator graph relations at the right time (not too early/strict, not too late)

And that s all? The actual implementation in rec-def has a few more moving parts. In particular, it tries to support different value types (not just sets), possibly with different implementations, and even mixing them (e.g. in member :: Ord a => a -> RSet a -> RBool), so the generic code is in Data.Propagator.Purify, and supports various propagators underneath. The type RSet is then just a newtype around that, defined in Data.Recursive.Internal to maintain the safety of the abstraction, I went back and forth on a few variants of the design here, including one where there was a generic R type constructor (R (Set a), R Bool etc.), but then monomorphic interface seems simpler.

Does it really work? The big remaining question is certainly: Is this really safe and pure? Does it still behave like Haskell? The answer to these questions certainly depends on the underlying propagator implementation. But it also depends on what we actually mean by safe and pure ? For example, do we expect the Static Argument Transformation be semantics preserving? Or is it allowed to turn undefined values into defined ones (as it does here)? I am unsure myself yet, so I ll defer this discussion to a separate blog post, after I hopefully had good discussions about this here at ICFP 2022 in Ljubljana. If you are around and want to discuss, please hit me up!

9 September 2022

Reproducible Builds: Reproducible Builds in August 2022

Welcome to the August 2022 report from the Reproducible Builds project! In these reports we outline the most important things that we have been up to over the past month. As a quick recap, whilst anyone may inspect the source code of free software for malicious flaws, almost all software is distributed to end users as pre-compiled binaries. The motivation behind the reproducible builds effort is to ensure no flaws have been introduced during this compilation process by promising identical results are always generated from a given source, thus allowing multiple third-parties to come to a consensus on whether a build was compromised. As ever, if you are interested in contributing to the project, please visit our Contribute page on our website.

Community news As announced last month, registration is currently open for our in-person summit this year which is due to be held between November 1st November 3rd. The event will take place in Venice (Italy). Very soon we intend to pick a venue reachable via the train station and an international airport. However, the precise venue will depend on the number of attendees. Please see the announcement email for information about how to register.
The US National Security Agency (NSA), Cybersecurity and Infrastructure Security Agency (CISA) and the Office of the Director of National Intelligence (ODNI) have released a document called Securing the Software Supply Chain: Recommended Practices Guide for Developers (PDF) as part of their Enduring Security Framework (ESF) work. The document expressly recommends having reproducible builds as part of advanced recommended mitigations, along with hermetic builds. Page 31 (page 35 in the PDF) says:
Reproducible builds provide additional protection and validation against attempts to compromise build systems. They ensure the binary products of each build system match: i.e., they are built from the same source, regardless of variable metadata such as the order of input files, timestamps, locales, and paths. Reproducible builds are those where re-running the build steps with identical input artifacts results in bit-for-bit identical output. Builds that cannot meet this must provide a justification why the build cannot be made reproducible.
The full press release is available online.
On our mailing list this month, Marc Prud hommeaux posted a feature request for diffoscope which additionally outlines a project called The App Fair, an autonomous distribution network of free and open-source macOS and iOS applications, where validated apps are then signed and submitted for publication .
Author/blogger Cory Doctorow posted published a provocative blog post this month titled Your computer is tormented by a wicked god . Touching on Ken Thompson s famous talk, Reflections on Trusting Trust , the early goals of Secure Computing and UEFI firmware interfaces:
This is the core of a two-decade-old debate among security people, and it s one that the benevolent God faction has consistently had the upper hand in. They re the curated computing advocates who insist that preventing you from choosing an alternative app store or side-loading a program is for your own good because if it s possible for you to override the manufacturer s wishes, then malicious software may impersonate you to do so, or you might be tricked into doing so. [..] This benevolent dictatorship model only works so long as the dictator is both perfectly benevolent and perfectly competent. We know the dictators aren t always benevolent. [ ] But even if you trust a dictator s benevolence, you can t trust in their perfection. Everyone makes mistakes. Benevolent dictator computing works well, but fails badly. Designing a computer that intentionally can t be fully controlled by its owner is a nightmare, because that is a computer that, once compromised, can attack its owner with impunity.

Lastly, Chengyu HAN updated the Reproducible Builds website to correct an incorrect Git command. [ ]

Debian In Debian this month, the essential and required package sets became 100% reproducible in Debian bookworm on the amd64 and arm64 architectures. These two subsets of the full Debian archive refer to Debian package priority levels as described in the 2.5 Priorities section of the Debian Policy there is no canonical minimal installation package set in Debian due to its diverse methods of installation. As it happens, these package sets are not reproducible on the i386 architecture because the ncurses package on that architecture is not yet reproducible, and the sed package currently fails to build from source on armhf too. The full list of reproducible packages within these package sets can be viewed within our QA system, such as on the page of required packages in amd64 and the list of essential packages on arm64, both for Debian bullseye.
It recently has become very easy to install reproducible Debian Docker containers using podman on Debian bullseye:
$ sudo apt install podman
$ podman run --rm -it debian:bullseye bash
The (pre-built) image used is itself built using debuerrotype, as explained on This page also details how to build the image yourself and what checksums are expected if you do so.
Related to this, it has also become straightforward to reproducibly bootstrap Debian using mmdebstrap, a replacement for the usual debootstrap tool to create Debian root filesystems:
$ SOURCE_DATE_EPOCH=$(date --utc --date=2022-08-29 +%s) mmdebstrap unstable > unstable.tar
This works for (at least) Debian unstable, bullseye and bookworm, and is tested automatically by a number of QA jobs set up by Holger Levsen (unstable, bookworm and bullseye)
Work has also taken place to ensure that the canonical debootstrap and cdebootstrap tools are also capable of bootstrapping Debian reproducibly, although it currently requires a few extra steps:
  1. Clamping the modification time of files that are newer than $SOURCE_DATE_EPOCH to be not greater than SOURCE_DATE_EPOCH.
  2. Deleting a few files. For debootstrap, this requires the deletion of /etc/machine-id, /var/cache/ldconfig/aux-cache, /var/log/dpkg.log, /var/log/alternatives.log and /var/log/bootstrap.log, and for cdebootstrap we also need to delete the /var/log/apt/history.log and /var/log/apt/term.log files as well.
This process works at least for unstable, bullseye and bookworm and is now being tested automatically by a number of QA jobs setup by Holger Levsen [ ][ ][ ][ ][ ][ ]. As part of this work, Holger filed two bugs to request a better initialisation of the /etc/machine-id file in both debootstrap [ ] and cdebootstrap [ ].
Elsewhere in Debian, 131 reviews of Debian packages were added, 20 were updated and 27 were removed this month, adding to our extensive knowledge about identified issues. Chris Lamb added a number of issue types, including: randomness_in_browserify_output [ ], haskell_abi_hash_differences [ ], nondeterministic_ids_in_html_output_generated_by_python_sphinx_panels [ ]. Lastly, Mattia Rizzolo removed the deterministic flag from the captures_kernel_variant flag [ ].

Other distributions Vagrant Cascadian posted an update of the status of Reproducible Builds in GNU Guix, writing that:
Ignoring the pesky unknown packages, it is more like ~93% reproducible and ~7% unreproducible... that feels a bit better to me! These numbers wander around over time, mostly due to packages moving back into an "unknown" state while the build farms catch up with each other... although the above numbers seem to have been pretty consistent over the last few days.
The post itself contains a lot more details, including a brief discussion of tooling. Elsewhere in GNU Guix, however, Vagrant updated a number of packages such as itpp [ ], perl-class-methodmaker [ ], libnet [ ], directfb [ ] and mm-common [ ], as well as updated the version of reprotest to 0.7.21 [ ]. In openSUSE, Bernhard M. Wiedemann published his usual openSUSE monthly report.

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 220 and 221 to Debian, as well as made the following changes:
  • Update to reflect changes to xxd and the vim-common package. [ ]
  • Depend on the dedicated xxd package now, not the vim-common package. [ ]
  • Don t crash if we can open a PDF file using the PyPDF library, but cannot subsequently parse the annotations within. [ ]
In addition, Vagrant Cascadian updated diffoscope in GNU Guix, first to to version 220 [ ] and later to 221 [ ].

Community news The Reproducible Builds project aims to fix as many currently-unreproducible packages as possible as well as to send all of our patches upstream wherever appropriate. This month we created a number of patches, including:

Testing framework The Reproducible Builds project runs a significant testing framework at, to check packages and other artifacts for reproducibility. This month, Holger Levsen made the following changes:
  • Debian-related changes:
    • Temporarily add Debian unstable deb-src lines to enable test builds a Non-maintainer Upload (NMU) campaign targeting 708 sources without .buildinfo files found in Debian unstable, including 475 in bookworm. [ ][ ]
    • Correctly deal with the Debian Edu packages not being installable. [ ]
    • Finally, stop scheduling stretch. [ ]
    • Make sure all Ubuntu nodes have the linux-image-generic kernel package installed. [ ]
  • Health checks & view:
    • Detect SSH login problems. [ ]
    • Only report the first uninstallable package set. [ ]
    • Show new bootstrap jobs. [ ] and debian-live jobs. [ ] in the job health view.
    • Fix regular expression to detect various zombie jobs. [ ]
  • New jobs:
    • Add a new job to test reproducibility of mmdebstrap bootstrapping tool. [ ][ ][ ][ ]
    • Run our new mmdebstrap job remotely [ ][ ]
    • Improve the output of the mmdebstrap job. [ ][ ][ ]
    • Adjust the mmdebstrap script to additionally support debootstrap as well. [ ][ ][ ]
    • Work around mmdebstrap and debootstrap keeping logfiles within their artifacts. [ ][ ][ ]
    • Add support for testing cdebootstrap too and add such a job for unstable. [ ][ ][ ]
    • Use a reproducible value for SOURCE_DATE_EPOCH for all our new bootstrap jobs. [ ]
  • Misc changes:
    • Send the create_meta_pkg_sets notification to #debian-reproducible-changes instead of #debian-reproducible. [ ]
In addition, Roland Clobus re-enabled the tests for live-build images [ ] and added a feature where the build would retry instead of give up when the archive was synced whilst building an ISO [ ], and Vagrant Cascadian added logging to report the current target of the /bin/sh symlink [ ].

Contact As ever, 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: