Kaleidogen Kaleidogen is a little contemplative game (or toy game where, starting from just unicolored disks, you combine abstract circular patterns to breed more interesting patterns. See my FARM 2019 talk for more details, or check out the source repository. BTW, I am looking for help turning it into an Android app!

KaleidogenBot in action

Amazon Lambda Amazon Lambda is the Function as a service offering of Amazon Web Services. The idea is that you don t rent a server, where you have to deal with managing the whole system and that you are paying for constantly, but you just upload the code that responds to outside requests, and AWS takes care of the rest: Starting and stopping instances, providing a secure base system etc. When nobody is using the service, no cost occurs. This sounds ideal for hosting a toy Telegram bot: Most of the time nobody will be using it, and I really don't want to have to baby sit yet another service on my server. On Amazon Lambda, I can probably just forget about it. But Haskell is not one of the officially supported languages on Amazon Lambda. So to run Haskell on Lambda, one has to solve two problems:

• how to invoke the Haskell code on the server, and
• how to build Haskell so that it runs on the Amazon Linux distribution

A Haskell runtime for Lambda For the first we need a custom runtime. While this sounds complicated, it is actually a pretty simple concept: A runtime is an executable called bootstrap that queries the Lambda Runtime Interface for the next request to handle. The Lambda documentation is phrased as if this runtime has to be a dispatcher that calls the separate function s handler. But it could just do all the things directly. I found the Haskell package aws-lambda-haskell-runtime which provides precisely that: A function

runLambda :: (LambdaOptions -> IO (Either String LambdaResult)) -> IO ()

that talks to the Lambda Runtime API and invokes its argument on each message. The package also provides Template Haskell magic to collect handlers of any JSON-able type and generates a dispatcher, like you might expect from other, more dynamic languages. But that was too much magic for me, so I ignored that and just wrote the handler manually:

main :: IO ()
main = runLambda run
  where
   run ::  LambdaOptions -> IO (Either String LambdaResult)
   run opts = do
    result <- handler (decodeObj (eventObject opts)) (decodeObj (contextObject opts))
    either (pure . Left . encodeObj) (pure . Right . LambdaResult . encodeObj) result
data Event = Event
    path :: T.Text
  , body :: Maybe T.Text
    deriving (Generic, FromJSON)
data Response = Response
    statusCode :: Int
  , headers :: Value
  , body :: T.Text
  , isBase64Encoded :: Bool
    deriving (Generic, ToJSON)
handler :: Event -> Context -> IO (Either String Response)
handler Event body, path  context =
 

I expose my Lambda function to the world via Amazon s API Gateway, configured to just proxy the HTTP requests. This means that my code receives a JSON data structure describing the HTTP request (here called Event, listing only the fields I care about), and it will respond with a Response, again as JSON. The handler can then simply pattern-match on the path to decide what to do. For example this code handles URLs like /img/CAFFEEFACE.png, and responds with an image.

handler :: TC -> Event -> Context -> IO (Either String Response)
handler Event body, path  context
      Just bytes <- isImgPath path >>= T.decodeHex = do
        let pngData = genPurePNG bytes
        pure $ Right Response
              statusCode = 200
            , headers = object [ "Content-Type" .= ("image/png" :: String) ]
            , isBase64Encoded = True
            , body = T.decodeUtf8 $ LBS.toStrict $ Base64.encode pngData
             
     
isImgPath :: T.Text -> Maybe T.Text
isImgPath  = T.stripPrefix "/img/" >=> T.stripSuffix ".png"

If this program would grow more, then one should probably use something more structured for routing here; maybe servant, or bridging towards wai apps (amost like wai-lamda, but that still assumes an existing runtime, instead of simply being the runtime). But for my purposes, no extra layers of indirection or abstraction are needed!

Deploying Haskell to Lambda Building Haskell locally and deploying to different machiens is notoriously tricky; you often end up depending on a shared library that is not available on the other platform. The aws-lambda-haskell-runtime package, and similar projects like serverless-haskell, solve this using stack and Docker two technologies that are probably great, but I never warmed up to them. So instead adding layers and complexities, can I solve this instead my making things simpler? If I compiler my bootstrap into a static Linux binary, it should run on any Linux, including Amazon Linux. Unfortunately, building Haskell programs statically is also notoriously tricky. But it is made much simpler by the work of Niklas Hamb chen and others in the context of the Nix package manager, coordinated in the static-haskell-nix project. The promise here is that once you have set up building your project with Nix, then getting a static version is just one flag away. The support is not completely upstreamed into nixpkgs proper yet, but their repository has a nix file that contains a nixpkgs set with their patches:

let pkgs = (import (sources.nixpkgs-static + "/survey/default.nix")  ).pkgs; in

This, plus a fairly standard nix setup to build the package, yields what I was hoping for:

$ nix-build -A kaleidogen
/nix/store/ppwyq4d964ahd6k56wsklh93vzw07ln0-kaleidogen-0.1.0.0
$ file result/bin/kaleidogen-amazon-lambda
result/bin/kaleidogen-amazon-lambda: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), statically linked, stripped
$ ls -sh result/bin/kaleidogen-amazon-lambda
6,7M result/bin/kaleidogen-amazon-lambda

If we put this file, named bootstrap, into a zip file and upload it to Amazon Lambda, then it just works! Creating the zip file is easily scripted using nix:

  function-zip = pkgs.runCommandNoCC "kaleidogen-lambda"  
    buildInputs = [ pkgs.zip ];
    ''
    mkdir -p $out
    cp $ kaleidogen /bin/kaleidogen-amazon-lambda bootstrap
    zip $out/function.zip bootstrap
  '';

So to upload this, I use this one-liner (line-wrapped for your convenience):

nix-build -A function-zip &&
aws lambda update-function-code --function-name kaleidogen \
  --zip-file fileb://result/function.zip

Thanks to how Nix pins all dependencies, I am fairly confident that I can return to this project in 4 months and still be able to build it. Of course, I want continuous integration and deployment. So I build the project with GitHub Actions, using a cachix nix cache to significantly speed up the build, and auto-deploy to Lambda using aws-lambda-deploy; see my workflow file for details.

The Telegram part The above allows me to run basically any stateless service, and a Telegram bot is nothing else: When configured to act as a WebHook, Telegram will send a request with a message to our Lambda function, where we can react on it. The telegram-api package provides bindigs for the Telegram Bot API (although I had to use the repository version, as the version on Hackage has some bitrot). Slightly simplified I can write a handler for an Update:

handleUpdate :: Update -> TelegramClient ()
handleUpdate Update  message = Just m   = do
  let c = ChatId (chat_id (chat m))
  liftIO $ printf "message from %s: %s\n" (maybe "?" user_first_name (from m)) (maybe "" T.unpack (text m))
  if "/start"  T.isPrefixOf  fromMaybe "" (text m)
  then do
    rm <- sendMessageM $ sendMessageRequest c "Hi! I am @KaleidogenBot.  "
    return ()
  else do
    m1 <- sendMessageM $ sendMessageRequest c "One moment "
    withPNGFile  $ \pngFN -> do
      m2 <- uploadPhotoM $ uploadPhotoRequest c
        (FileUpload (Just "image/png") (FileUploadFile pngFN))
      return ()
handleUpdate _ u =
  liftIO $ putStrLn $ "Unhandled message: " ++ show u

and call this from the handler that I wrote above:

     
      path == "/telegram" =
      case eitherDecode (LBS.fromStrict (T.encodeUtf8 (fromMaybe "" body))) of
        Left err ->  
        Right update -> do
          runTelegramClient token manager $ handleUpdate Nothing update
          pure $ Right Response
              statusCode = 200
            , headers = object [ "Content-Type" .= ("text/plain" :: String) ]
            , isBase64Encoded = False
            , body = "Done"
             
     

Note that the Lambda code receives the request as JSON data structure with a body that contains the original HTTP request body. Which, in this case, is itself JSON, so we have to decode that. All that is left to do is to tell Telegram where this code lives:

curl --request POST \
  --url https://api.telegram.org/bot<token>/setWebhook
  --header 'content-type: application/json'
  --data ' "url": "https://api.kaleidogen.nomeata.de/telegram" '

As a little add on, I also created a Telegram game for Kaleidogen. A Telegram game is nothing but a webpage that runs inside Telegram, so it wasn t much work to wrap the Web version of Kaleidogen that way, but the resulting Telegram game (which you can access via https://core.telegram.org/bots/games) still looks pretty neat.

No /dev/dri/renderD128 I am mostly happy with this setup: My game is now available to more people in more ways. I don t have to maintain any infrastructure. When nobody is using this bot no resources are wasted, and the costs of the service are neglectible -- this is unlikely to go beyond the free tier, and even if it would, the cost per generated image is roughly USD 0.000021. There is one slight disappointment, though. What I find most intersting about Kaleidogen from a technical point of view is that when you play it in the browser, the images are not generated by my code. Instead, my code creates a WebGL shader program on the fly, and that program generates the image on your graphics card. I even managed to make the GL rendering code work headlessly, i.e. from a command line program, using EGL and libgbm and a helper written in C. But it needs access to a graphics card via /dev/dri/renderD128. Amazon does not provide that to Lambda code, and neither do the other big Function-as-a-service providers. So I had to swallow my pride and reimplement the rendering in pure Haskell. So if you think the bot is kinda slow, then that s why. Despite properly optimizing the pure implementation (the inner loop does not do allocations and deals only with unboxed Double# values), the GL shader version is still three times as fast. Maybe in a few years GPU access will be so ubiquitous that it s even on Amazon Lambda; then I can easily use that.

Agent forwarding should be enabled with caution. Users with the ability to bypass file permissions on the remote host (for the agent s UNIX-domain socket) can access the local agent through the forwarded connection. An attacker cannot obtain key material from the agent, however they can perform operations on the keys that enable them to authenticate using the identities loaded into the agent. A safer alternative may be to use a jump host (see -J).

• it holds only the private key to connect to the target host, and
• it asks confirmation for each requested signature.

alias assh="ssh-agent ssh -o AddKeysToAgent=confirm -o ForwardAgent=yes"

Request for the agent to use the specified private key

• [DLA 2156-1] e2fsprogs security update for one CVE
• [DLA 2157-1] weechat security update for three CVEs
• [DLA 2160-1] php5 security update for two CVEs
• [DLA 2164-1] gst-plugins-bad0.10 security update for four CVEs
• [DLA 2165-1] apng2gif security update for one CVE

• [DSA 4640-1] graphicsmagick security update in Buster and Strech for 16 CVEs

• ELA-218-1 for e2fsprogs
• ELA-220-1 for php5
• ELA-221-1 for nss

• duktape
• gengetopt and also fixed an FTBFS
• pollen

• ocf-spec-core
• theme-d-gnome

• libctl
• libosmocore
• mpb
• pyicloud
• pywws

Changes in version 0.0.4 (2020-04-03)

• Upgraded to new upstream releases 0.3 and 0.3.1 (Dirk in #9 closing #8)
• Updated example validateJSON to API changes.

Highlights

• Multi-Document Parsing: Read a bundle of JSON documents (ndjson) 2-4x faster than doing it individually. API docs / Design Details
• Simplified API: The API has been completely revamped for ease of use, including a new JSON navigation API and fluent support for error code and exception styles of error handling with a single API. Docs
• Exact Float Parsing: Now simdjson parses floats flawlessly without any performance loss (https://github.com/simdjson/simdjson/pull/558). Blog Post
• Even Faster: The fastest parser got faster! With a shiny new UTF-8 validator and meticulously refactored SIMD core, simdjson 0.3 is 15% faster than before, running at 2.5 GB/s (where 0.2 ran at 2.2 GB/s).

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

podman run --rm -ti -p 8080:8080 \
quay.io/jdowland/opinionated-ikiwiki:latest

Changes in RQuantLib version 0.4.12 (2020-04-01)

• Changes in RQuantLib code:
  • Calls deprecated-in-QuantLib 1.18 were updated (Dirk in #146).

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

• review forks of unity-api, ubuntu-download-manager and unity-app-launch under the names lomiri-api, lomiri-download-manager, lomiri-app-launch.
• request upstream releases of lomiri-api and lomiri-download-manager
• package and upload lomiri-api to Debian unstable (unfortunately still in Debian's NEW queue)
• package and upload lomiri-download-manager to Debian unstable (dito)
• package (and with 'package' I mean Debian policy compliant packaging) lomiri-app-launch (no upload, yet, as there are some strange unit test failures that need more debugging)
• package and upload qtsystems (under the umbrella of the Debian QT/KDE Maintainers' team) to Debian unstable (pending review in Debian's NEW queue)
• package and upload qtfeedback (under the umbrella of the Debian QT/KDE Maintainers' team) to Debian unstable (pending review in Debian's NEW queue)
• package and (upload) [1] qtpim (under the umbrella of the Debian Qt/KDE Maintainers' team) to Debian unstable (pending review in Debian's NEW queue)

• UBports: Packaging of Unity8 Desktop Environment for Debian (part 01)

• [1] Unfortunately, I missed a crucial element of the GPG key update workflow as Debian Developer. My GPG key was about to expire at the end of March 2020. I renewed its expiration date and exported its public key to the public PGP/GPG keyserver. However, for being able to upload packages to Debian, one has to push the public key to Debian's own keyring server. Which I missed. Thus, I won't be able to upload any packages before the end of April myself and will depend on DD colleagues helping out with sponsoring my uploads.

Testing basic WebRTC functionality Before you place a real call, I suggest using the official test page which will test your camera, microphone and network connectivity. Note that this test page makes use of a Google TURN server which is locked to particular HTTP referrers and so you'll need to disable privacy features that might interfere with this:

• Brave: Disable Shields entirely for that page (Simple view) or allow all cookies for that page (Advanced view).

• Firefox: Ensure that http.network.referer.spoofSource is set to false in about:config, which it is by default.
• uMatrix: The "Spoof Referer header" option needs to be turned off for that site.

Checking the type of peer connection you have Once you know that WebRTC is working in your browser, it's time to establish a connection and look at the network configuration that the two peers agreed on. My favorite service at the moment is Whereby (formerly Appear.in), so I'm going to use that to connect from two different computers:

• canada is a laptop behind a regular home router without any port forwarding.
• siberia is a desktop computer in a remote location that is also behind a home router, but in this case its internal IP address (192.168.1.2) is set as the DMZ host.

Chromium For all Chromium-based browsers, such as Brave, Chrome, Edge, Opera and Vivaldi, the debugging page you'll need to open is called chrome://webrtc-internals. Look for RTCIceCandidatePair lines and expand them one at a time until you find the one which says:

• state: succeeded (or state: in-progress)
• nominated: true
• writable: true

Then from the name of that pair (N6cxxnrr_OEpeash in the above example) find the two matching RTCIceCandidate lines (one local-candidate and one remote-candidate) and expand them. In the case of a direct connection, I saw the following on the remote-candidate:

• ip shows the external IP address of siberia
• port shows a random number between 1024 and 65535
• candidateType: srflx

and the following on local-candidate:

• ip shows the external IP address of canada
• port shows a random number between 1024 and 65535
• candidateType: prflx

These candidate types indicate that a STUN server was used to determine the public-facing IP address and port for each computer, but the actual connection between the peers is direct. On the other hand, for a relayed/proxied connection, I saw the following on the remote-candidate side:

• ip shows an IP address belonging to the TURN server
• candidateType: relay

and the same information as before on the local-candidate.

Firefox If you are using Firefox, the debugging page you want to look at is about:webrtc. Expand the top entry under "Session Statistics" and look for the line (should be the first one) which says the following in green:

• ICE State: succeeded
• Nominated: true
• Selected: true

then look in the "Local Candidate" and "Remote Candidate" sections to find the candidate type in brackets.

Firewall ports to open to avoid using a relay In order to get a direct connection to the other WebRTC peer, one of the two computers (in my case, siberia) needs to open all inbound UDP ports since there doesn't appear to be a way to restrict Chromium or Firefox to a smaller port range for incoming WebRTC connections. This isn't great and so I decided to tighten that up in two ways by:

• restricting incoming UDP traffic to the IP range of siberia's ISP, and
• explicitly denying incoming to the UDP ports I know are open on siberia.

To get the IP range, start with the external IP address of the machine (I'll use the IP address of my blog in this example: 66.228.46.55) and pass it to the whois command:

$ whois 66.228.46.55   grep CIDR
CIDR:           66.228.32.0/19

To get the list of open UDP ports on siberia, I sshed into it and ran nmap:

$ sudo nmap -sU localhost
Starting Nmap 7.60 ( https://nmap.org ) at 2020-03-28 15:55 PDT
Nmap scan report for localhost (127.0.0.1)
Host is up (0.000015s latency).
Not shown: 994 closed ports
PORT      STATE         SERVICE
631/udp   open filtered ipp
5060/udp  open filtered sip
5353/udp  open          zeroconf
Nmap done: 1 IP address (1 host up) scanned in 190.25 seconds

I ended up with the following in my /etc/network/iptables.up.rules (ports below 1024 are denied by the default rule and don't need to be included here):

# Deny all known-open high UDP ports before enabling WebRTC for canada
-A INPUT -p udp --dport 5060 -j DROP
-A INPUT -p udp --dport 5353 -j DROP
-A INPUT -s 66.228.32.0/19 -p udp --dport 1024:65535 -j ACCEPT

Changes in RProtoBuf version 0.4.17 (2020-03-xx)

• Condition use of ByteSizeLong() on building with ProtoBuf 3.6.0 or later (Dirk in #71 fixing #70).
• The JSON unit tests are skipped if ProtoBuf 2.* is used (Dirk, also #71).
• The configure script now extracts the version from the DESCRIPTION file ( (Dirk, also #71).

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

  constexpr auto x1 = 2015_y/March/22;
  constexpr auto x2 = March/22/2015;
  constexpr auto x3 = 22_d/March/2015;

  constexpr auto x1 = 2015_y/February/last;
  constexpr auto x2 = February/last/2015;
  constexpr auto x3 = last/February/2015;

Changes in version 0.0.1 (2020-01-17)

• Initial CRAN upload of first version

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

• DebConf fundraising overview page
• Welcome to the fundraising team guide
• DebConf fundraising timeline
• DebConf workflow for onboarding each sponsor
• Migration checklist for a new year of DebConf (wafer system)
• Fundraising best practices and ideas (from outside DebConf)

Do you recall the temple of science, in which the foundations of physics are the bottommost level, and we try to break through to deeper understanding? As I've come to the end of my travels, I worry that the cracks we're seeing in the floor aren't really cracks at all but merely intricate patterns. We're digging in the wrong places.

I went into physics because I don't understand human behavior. I went into physics because math tells it how it is. I liked the cleanliness, the unambiguous machinery, the command math has over nature. Two decades later, what prevents me from understanding physics is that I still don't understand human behavior. "We cannot give exact mathematical rules that define if a theory is attractive or not," says Gian Francesco Giudice. "However, it is surprising how the beauty and elegance of a theory are universally recognized by people from different cultures. When I tell you, 'Look, I have a new paper and my theory is beautiful,' I don't have to tell you the details of my theory; you will get why I'm excited. Right?" I don't get it. That's why I am talking to him. Why should the laws of nature care what I find beautiful? Such a connection between me and the universe seems very mystical, very romantic, very not me. But then Gian doesn't think that nature cares what I find beautiful, but what he finds beautiful.

Changes in RProtoBuf version 0.4.16 (2020-03-19)

• Added support for parsing and printing JSON (Siddhartha Bagaria in #68 closing wishlist #61).
• Switched ByteSize() to ByteSizeLong() to appease clang (Dirk).

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

Changes in version 0.2.7 (2020-03-18)

• Added functions _RcppCCTZ_convertToCivilSecond that converts a time point to the number of seconds since epoch, and _RcppCCTZ_convertToTimePoint that converts a number of seconds since epoch into a time point; these functions are only callable from C level (Leonardo in #34 and #35).
• Added function _RcppCCTZ_getOffset that returns the offset at a speficied time-point for a specified timezone; this function is only callable from C level (Leonardo in #32).

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

Problem statement As part of my work on automating install procedures at Tor, I ended up doing things like:

git clone REPO
./REPO/bootstrap.sh

... something eerily similar to the infamous curl pipe bash method which I often decry. As a short-term workaround, I relied on the SHA-1 checksum of the repository to make sure I have the right code, by running this both on a "trusted" (ie. "local") repository and the remote, then visually comparing the output:

$ git show-ref master
9f9a9d70dd1f1e84dec69a12ebc536c1f05aed1c refs/heads/master

One problem with this approach is that SHA-1 is now considered as flawed as MD5 so it can't be used as an authentication mechanism anymore. It's also fundamentally difficult to compare hashes for humans. The other flaw with comparing local and remote checksums is that we assume we trust the local repository. But how can I trust that repository? I can either:

1. audit all the code present and all the changes done to it after
2. or trust someone else to do so

The first option here is not practical in most cases. In this specific use case, I have audited the source code -- I'm the author, even -- what I need is to transfer that code over to another server. (Note that I am replacing those procedures with Fabric, which makes this use case moot for now as the trust path narrows to "trust the SSH server" which I already had anyways. But it's still important for my fellow Tor developers who worry about trusting the git server, especially now that we're moving to GitLab.) But anyways, in most cases, I do need to trust some other fellow developer I collaborate with. To do this, I would need to trust the entire chain between me and them:

1. the git client
2. the operating system
3. the hardware
4. the network (HTTPS and the CA cartel, specifically)
5. then the hosting provider (and that hardware/software stack)
6. and then backwards all the way back to that other person's computer

I want to shorten that chain as much as possible, make it "peer to peer", so to speak. Concretely, it would eliminate the hosting provider and the network, as attackers.

OpenPGP verification My first reaction is (perhaps perversely) to "use OpenPGP" for this. I figured that if I sign every commit, then I can just check the latest commit and see if the signature is good. The first problem here is that this is surprisingly hard. Let's pick some arbitrary commit I did recently:

commit b3c538898b0ed4e31da27fc9ca22cb55e1de0000
Author: Antoine Beaupr  <anarcat@debian.org>
Date:   Mon Mar 16 14:37:28 2020 -0400
    fix test autoloading
    pytest only looks for file names matching  test  by default. We inline
    tests inside the source code directly, so hijack that.
diff --git a/fabric_tpa/pytest.ini b/fabric_tpa/pytest.ini
new file mode 100644
index 0000000..71004ea
--- /dev/null
+++ b/fabric_tpa/pytest.ini
@@ -0,0 +1,3 @@
+[pytest]
+# we inline tests directly in the source code
+python_files = *.py

That's the output of git log -p in my local repository. I signed that commit, yet git log is not telling me anything special. To check the signature, I need something special: --show-signature, which looks like this:

commit b3c538898b0ed4e31da27fc9ca22cb55e1de0000
gpg: Signature faite le lun 16 mar 2020 14:37:53 EDT
gpg:                avec la clef RSA 7B164204D096723B019635AB3EA1DDDDB261D97B
gpg: Bonne signature de  Antoine Beaupr  <anarcat@orangeseeds.org>  [ultime]
gpg:                 alias  Antoine Beaupr  <anarcat@torproject.org>  [ultime]
gpg:                 alias  Antoine Beaupr  <anarcat@anarc.at>  [ultime]
gpg:                 alias  Antoine Beaupr  <anarcat@koumbit.org>  [ultime]
gpg:                 alias  Antoine Beaupr  <anarcat@debian.org>  [ultime]
Author: Antoine Beaupr  <anarcat@debian.org>
Date:   Mon Mar 16 14:37:28 2020 -0400
    fix test autoloading
    pytest only looks for file names matching  test  by default. We inline
    tests inside the source code directly, so hijack that.

Can you tell if this is a valid signature? If you speak a little french, maybe you can! But even if you would, you are unlikely to see that output on your own computer. What you would see instead is:

commit b3c538898b0ed4e31da27fc9ca22cb55e1de0000
gpg: Signature made Mon Mar 16 14:37:53 2020 EDT
gpg:                using RSA key 7B164204D096723B019635AB3EA1DDDDB261D97B
gpg: Can't check signature: No public key
Author: Antoine Beaupr  <anarcat@debian.org>
Date:   Mon Mar 16 14:37:28 2020 -0400
    fix test autoloading
    pytest only looks for file names matching  test  by default. We inline
    tests inside the source code directly, so hijack that.

Important part: Can't check signature: No public key. No public key. Because of course you would see that. Why would you have my key lying around, unless you're me. Or, to put it another way, why would that server I'm installing from scratch have a copy of my OpenPGP certificate? Because I'm a Debian developer, my key is actually part of the 800 keys in the debian-keyring package, signed by the APT repositories. So I have a trust path. But that won't work for someone who is not a Debian developer. It will also stop working when my key expires in that repository, as it already has on Debian buster (current stable). So I can't assume I have a trust path there either. One could work with a trusted keyring like we do in the Tor and Debian project, and only work inside that project, that said. But I still feel uncomfortable with those commands. Both git log and git show will happily succeed (return code 0 in the shell) even though the signature verification failed on the commits. Same with git pull and git merge, which will happily push your branch ahead even if the remote has unsigned or badly signed commits. To actually verify commits (or tags), you need the git verify-commit (or git verify-tag) command, which seems to do the right thing:

$ LANG=C.UTF-8 git verify-commit b3c538898b0ed4e31da27fc9ca22cb55e1de0000
gpg: Signature made Mon Mar 16 14:37:53 2020 EDT
gpg:                using RSA key 7B164204D096723B019635AB3EA1DDDDB261D97B
gpg: Can't check signature: No public key
[1]$

At least it fails with some error code (1, above). But it's not flexible: I can't use it to verify that a "trusted" developer (say one that is in a trusted keyring) signed a given commit. Also, it is not clear what a failure means. Is a signature by an expired certificate okay? What if the key is signed by some random key in my personal keyring? Why should that be trusted?

Worrying about git and GnuPG In general, I'm worried about git's implementation of OpenPGP signatures. There has been numerous cases of interoperability problems with GnuPG specifically that led to security, like EFAIL or SigSpoof. It would be surprising if such a vulnerability did not exist in git. Even if git did everything "just right" (which I have myself found impossible to do when writing code that talks with GnuPG), what does it actually verify? The commit's SHA-1 checksum? The tree's checksum? The entire archive as a zip file? I would bet it signs the commit's SHA-1 sum, but I just don't know, on the top of my head, and neither do git-commit or git-verify-commit say exactly what is happening. I had an interesting conversation with a fellow Debian developer (dkg) about this and we had to admit those limitations:

<anarcat> i'd like to integrate pgp signing into tor's coding practices more, but so far, my approach has been "sign commits" and the verify step was "TBD" <dkg> that's the main reason i've been reluctant to sign git commits. i haven't heard anyone offer a better subsequent step. if torproject could outline something useful, then i'd be less averse to the practice. i'm also pretty sad that git remains stuck on sha1, esp. given the recent demonstrations. all the fancy strong signatures you can make in git won't matter if the underlying git repo gets changed out from under the signature due to sha1's weakness

In other words, even if git implements the arcane GnuPG dialect just so, and would allow us to setup the trust chain just right, and would give us meaningful and workable error messages, it still would fail because it's still stuck in SHA-1. There is work underway to fix that, but in February 2020, Jonathan Corbet described that work as being in a "relatively unstable state", which is hardly something I would like to trust to verify code. Also, when you clone a fresh new repository, you might get an entirely different repository, with a different root and set of commits. The concept of "validity" of a commit, in itself, is hard to establish in this case, because an hostile server could put you backwards in time, on a different branch, or even on an entirely different repository. Git will warn you about a different repository root with warning: no common commits but that's easy to miss. And complete branch switches, rebases and resets from upstream are hardly more noticeable: only a tiny plus sign (+) instead of a star (*) will tell you that a reset happened, along with a warning (forced update) on the same line. Miss those and your git history can be compromised.

Possible ways forward I don't consider the current implementation of OpenPGP signatures in git to be sufficient. Maybe, eventually, it will mature away from SHA-1 and the interface will be more reasonable, but I don't see that happening in the short term. So what do we do?

git evtag The git-evtag extension is a replacement for git tag -s. It's not designed to sign commits (it only verifies tags) but at least it uses a stronger algorithm (SHA-512) to checksum the tree, and will include everything in that tree, including blobs. If that sounds expensive to you, don't worry too much: it takes about 5 seconds to tag the Linux kernel, according to the author. Unfortunately, that checksum is then signed with GnuPG, in a manner similar to git itself, in that it exposes GnuPG output (which can be confusing) and is likely similarly vulnerable to mis-implementation of the GnuPG dialect as git itself. It also does not allow you to specify a keyring to verify against, so you need to trust GnuPG to make sense of the garbage that lives in your personal keyring (and, trust me, it doesn't). And besides, git-evtag is fundamentally the same as signed git tags: checksum everything and sign with GnuPG. The difference is it uses SHA-512 instead of SHA-1, but that's something git will eventually fix itself anyways.

kernel patch attestations The kernel also faces this problem. Linus Torvalds signs the releases with GnuPG, but patches fly all over mailing list without any form of verification apart from clear-text email. So Konstantin Ryabitsev has proposed a new protocol to sign git patches which uses SHA256 to checksum the patch metadata, commit message and the patch itself, and then sign that with GnuPG. It's unclear to me what this solves, if anything, at all. As dkg argues, it would seem better to add OpenPGP support to git-send-email and teach git tools to recognize that (e.g. git-am) at least if you're going to keep using OpenPGP anyways. And furthermore, it doesn't resolve the problems associated with verifying a full archive either, as it only attests "patches".

jcat Unhappy with the current state of affairs, the author of fwupd (Richard Hughes) wrote his own protocol as well, called jcat, which provides signed "catalog files" similar to the ones provided in Microsoft windows. It consists of a "gzip-compressed JSON catalog files, which can be used to store GPG, PKCS-7 and SHA-256 checksums for each file". So yes, it is yet again another wrapper to GnuPG, probably with all the flaws detailed above, on top of being a niche implementation, disconnected from git.

The Update Framework One more thing dkg correctly identified is:

<dkg> anarcat: even if you could do exactly what you describe, there are still some interesting wrinkles that i think would be problems for you. the big one: "git repo's latest commits" is a loophole big enough to drive a truck through. if your adversary controls that repo, then they get to decide which commits to include in the repo. (since every git repo is a view into the same git repo, just some have more commits than others)

In other words, unless you have a repository that has frequent commits (either because of activity or by a bot generating fake commits), you have to rely on the central server to decide what "the latest version" is. This is the kind of problems that binary package distribution systems like APT and TUF solve correctly. Unfortunately, those don't apply to source code distribution, at least not in git form: TUF only deals with "repositories" and binary packages, and APT only deals with binary packages and source tarballs. That said, there's actually no reason why git could not support the TUF specification. Maybe TUF could be the solution to ensure end-to-end cryptographic integrity of the source code itself. OpenPGP-signed tarballs are nice, and signed git tags can be useful, but from my experience, a lot of OpenPGP (or, more accurately, GnuPG) derived tools are brittle and do not offer clear guarantees, and definitely not to the level that TUF tries to address. This would require changes on the git servers and clients, but I think it would be worth it.

Other Projects

OpenBSD There are other tools trying to do parts of what GnuPG is doing, for example minisign and OpenBSD's signify. But they do not integrate with git at all right now. Although I did find a hack] to use signify with git, it's kind of gross...

Golang Unsurprisingly, this is a problem everyone is trying to solve. Golang is planning on hosting a notary which would leverage a "certificate-transparency-style tamper-proof log" which would be ran by Google (see the spec for details). But that doesn't resolve the "evil server" attack, if we treat Google as an adversary (and we should).

Python Python had OpenPGP going for a while on PyPI, but it's unclear if it ever did anything at all. Now the plan seems to be to use TUF but my hunch is that the complexity of the specification is keeping that from moving ahead.

Docker Docker and the container ecosystem has, in theory, moved to TUF in the form of Notary, "a project that allows anyone to have trust over arbitrary collections of data". In practice however, in my somewhat limited experience, setting up TUF and image verification in Docker is far from trivial.

Android and iOS Even in what is possibly one of the strongest models (at least in terms of user friendliness), mobile phones are surprisingly unclear about those kind of questions. I had to ask if Android had end-to-end authentication and I am still not clear on the answer. I have no idea of what iOS does.

Conclusion One of the core problems with everything here is the common usability aspect of cryptography, and specifically the usability of verification procedures. We have become pretty good at encryption. The harder part (and a requirement for proper encryption) is verification. It seems that problem still remains unsolved, in terms of usability. Even Signal, widely considered to be a success in terms of adoption and usability, doesn't properly solve that problem, as users regularly ignore "The security number has changed" warnings... So, even though they deserve a lot of credit in other areas, it seems unlikely that hardcore C hackers (e.g. git and kernel developers) will be able to resolve that problem without at least a little bit of help. And TUF seems like the state of the art specification around here, it would seem wise to start adopting it in the git community as well. Update: git 2.26 introduced a new gpg.minTrustLevel to "tell various signature verification codepaths the required minimum trust level", presumably to control how Git will treat keys in your keyrings, assuming the "trust database" is valid and up to date. For an interesting narrative of how "normal" (without PGP) git verification can fail, see also A Git Horror Story: Repository Integrity With Signed Commits.

Changes in Rcpp version 1.0.4 (2020-03-13)

• Changes in Rcpp API:
  • Safer Rcpp_list*, Rcpp_lang* and Function.operator() (Romain in #1014, #1015).
  • A number of #nocov markers were added (Dirk in #1036, #1042 and #1044).
  • Finalizer calls clear external pointer first (Kirill M ller and Dirk in #1038).
  • Scalar operations with a rhs matrix no longer change the matrix value (Qiang in #1040 fixing (again) #365).
  • Rcpp::exception and Rcpp::stop are now more thread-safe (Joshua Pritikin in #1043).
• Changes in Rcpp Attributes:
  • The cppFunction helper now deals correctly with mulitple depends arguments (TJ McKinley in #1016 fixing #1017).
  • Invisible return objects are now supported via new option (Kun Ren in #1025 fixing #1024).
  • Unavailable packages referred to in LinkingTo are now reported (Dirk in #1027 fixing #1026).
  • The sourceCpp function can now create a debug DLL on Windows (Dirk in #1037 fixing #1035).
• Changes in Rcpp Documentation:
  • The .github/ directory now has more explicit guidance on contributing, issues, and pull requests (Dirk).
  • The Rcpp Attributes vignette describe the new invisible return object option (Kun Ren in #1025).
  • Vignettes are now included as pre-made pdf files (Dirk in #1029)
  • The Rcpp FAQ has a new entry on the recommended importFrom directive (Dirk in #1031 fixing #1030).
  • The bib file for the vignette was once again updated to current package versions (Dirk).
• Changes in Rcpp Deployment:
  • Added unit test to check if C++ version remains remains aligned with the package number (Dirk in #1022 fixing #1021).
  • The unit test system was switched to tinytest (Dirk in #1028, #1032, #1033).

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

(1) Like when a West-Berliner in a round of 15 East Germans arrogantly talks about the time when the wall came down and tells the story that he could not go shopping between Thursdays and Sundays because the East Germans bought too many products in the supermarkets while this event marked an unimaginable rift in the biographies of 17 million East Germans, 15 of whom are sitting right in front of him. Thirty years after 1989, many of us are finally starting to question this publicly ( links in German language).

(2) Women experience it similary regularly, see Men Explain Things to me, a book by Rebecca Solnit.

(3) By the way, rather than having "recruited the wrong person" conflict may intrinsically arise as part of certain work relationships, simply due to the inter-dependencies of roles or workers, like in a delivery chain.

Just say hi using whatever First off, feel free to use the normal tools you normally use: Signal, Facetime, Skype, Zoom, and Discord can be fine to connect with your folks, and since it doesn't take much to make someone's day please do use those tools to call your close ones and say "hi". People, especially your older folks, will feel alone and maybe scared in those crazy times. Every little bit you can do will help, even if it's just a normal phone call, an impromptu balcony fanfare, a remote workout class, or just a sing-along from your balcony, anything goes. But if those tools don't work well for some reason, or you want to try something new, or someone doesn't have an iPad, or it's too dang cold to go on your balcony, you should know there are other alternatives that you can use.

Jitsi We've been suggesting our folks use a tool called "Jitsi". Jitsi is a free software platform to host audio/video conferences. It has a web app which means anyone with a web browser can join a session. It can also do "screen sharing" if you need to work together on a project. There are many "instances", but here's a subset I know about:

• https://meet.jitsi.org/ - the official one, might overload
• https://meet.mayfirst.org/ - Mayfirst non-profit cooperative, hosted in New York (see also their usage instructions)
• https://meet.greenhost.net/ - Greenhost, hosted in the Netherlands
• https://framatalk.org/ - Framasoft, a popular education network, hosted in France - note that Framasoft is struggling under load as basically everyone in France (including the public education network) seems to think they can all run on their servers all at once, they encourage you to run your own instance instead of using theirs
• another list of instances

You can connect to those with your web browser directly. If your web browser doesn't work, try switching to another (e.g. if Firefox doesn't work, try Chrome and vice-versa). There are also apps for desktop and mobile apps (F-Droid, Google Play, Apple Store) that will work better than just using your browser. Jitsi should scale for small meetings up to a dozen people.

Mumble ... but beyond that, you might have trouble doing a full video-conference with a lot of people anyways. If you need to have a large conference with a lot of people, or if you have bandwidth and reliability problems with Jitsi, you can also try Mumble. Mumble is an audio-only conferencing service, similar to Discord or Teamspeak, but made with free software. It requires users to install an app but there are clients for every platform out there (F-Droid, Google Play, Apple Store). Mumble is harder to setup, but is much more efficient in terms of bandwidth and latency. In other words, it will just scale and sound better. Mumble ships with a list of known servers, but you can also connect to those trusted ones:

• mumble.mayfirst.org - Mayfirst (see also their instructions on how to use it, hosted in New York city
• mumble.riseup.net - Riseup, an autonomous collective, hosted in Seattle (ask me if you need their password) not a public service
• talk.systemli.org - systemli, a left-wing network and technics-collective, hosted in Berlin

Live streaming If for some reason those tools still don't scale, you might have a bigger problem on your hands. If your audience is over 100 people, you will not be able to all join in the same conference together. And besides, maybe you just want to broadcast some news and do not need audio or video feedback from the audience. In this case, you need "live streaming". Here, proprietary services are Twitch, Livestream.com and Youtube. But the community also provides alternatives to those. This is more complicated to setup, but just to get you started, I'll link to:

• https://live.mayfirst.org/ - Mayfirst, based on Icecast and icecream, a web-based client, unfortunately non-free
• https://live.autistici.org/ - Autistici, an autonomous collective, hosted in Italy, based on Nginx and RTMP

For either of those tools, you need an app on your desktop. The Mayfirst instructions use OBS Studio for this, but it might be possible to hotwire VLC to stream video from your computer as well.

Text chat When all else fails, text should go through. Slack, Twitter and Facebook are the best known alternatives here, obviously. I would warn against spending too much time on those, as they can foment harmful rumors and can spread bullshit like a virus on any given day. The situation does not make that any better. But it can be a good way to keep in touch with your loved ones. But if you want to have a large meetings with a crazy number of people, text can actually accomplish wonders. Internet Relay Chat also known as "IRC" (and which oldies might have experienced for a bit as mIRC) is, incredibly, still alive at the venerable age of 30 years old. It is mainly used by free software projects, but can be used by anyone. Here are some networks you can try:

• http://webchat.freenode.net/ - the largest network, Freenode
• https://webchat.oftc.net/ - smaller network, used by the Debian oftc.net/)
• http://irc.indymedia.org/ - a relic of the almost defunct Indymedia network which I help operate

Those are all web interface to the IRC networks, but there are also a plenitude of IRC apps you can install on your desktop if you want the full experience.

Whiteboards and screensharing I decided to add this section later on because it's a frequently mentioned "oh but you forgot..." comment I get from this post.

• Big Blue Button - seems to check all the boxes: free software, VoIP integration, whiteboarding and screen sharing, works from a web browser
• CodiMD: collaborative text editor with UML and diagrams support
• Excalidraw: (collaborative) whiteboard tool that lets you easily sketch diagrams that have a hand-drawn feel

I'll also mention that collaborative editors, in general, like Etherpad are just great for taking minutes because you don't have that single person with the load of writing down what people are saying and is too busy to talk. Google Docs and Nextcloud have similar functionality, of course. Update, public Big Blue Button instances:

• https://bbb.jitsi.rocks/ - also a Jitsi redirector, https://jitsi.rocks/

BBB requires one user to register to start the conference, but once that's done, anyone with the secret URL can join.

Common recommendations Regardless of the tools you pick, audio and video streaming is a technical challenge. A lot of things happen under the hood when you pick up your phone and dial a number, and sometimes using a desktop, it can be difficult to get everything "just right". Some advice:

1. get a good microphone and headset: good audio really makes a difference in how pleasing the experience will be, both for you and your peers. good hardware will reduce echo, feedback and other audio problems. (see also my audio docs)
2. check your audio/video setup before joining the meeting, ideally with another participant on the same platform you will use
3. find a quiet place to meet: even a good microphone will pick up noises from the environment, if you reduce this up front, everything will sound better. if you do live streaming and want high quality recording, considering setting up a smaller room to do recording. (tip: i heard of at least one journalist hiding in a closer full of clothes to make recordings, as it dampens the sound!)
4. mute your microphone when you are not speaking (spacebar in Jitsi, follow the "audio wizard" in Mumble)

If you have questions or need help, feel free to ask! Comment on this blog or just drop me an email (see contact), I'd be happy to answer your questions.

Other ideas Inevitably, when I write a post like this, someone writes something like "I can't believe you did not mention APL!" Here's a list of tools I have not mentioned here, deliberately or because I forgot:

• Nextcloud Talk - needs access to a special server, but can be used for small meetings (less than 5, or so i heard)
• Jabber/XMPP - yes, I know, XMPP can do everything and it's magic. but I've given up a while back, and I don't think setting up audio conferences with multiple enough is easy enough to make the cut here
• Signal - signal is great. i use it every day. it's the primary way I do long distance, international voice calls for free, and the only way I do video-conferencing with family and friends at all. but it's one to one only, and the group (text) chat kind of sucks

Also, all the tools I recommend above are made of free software, which means they can be self-hosted. If things go bad and all those services stop existing, it should be possible for you to run your own instance. Let me know if I forgot anything, but in a friendly way. And stay safe out there. Update: a similar article from the good folks at systemli also recommends Mastodon, Ticker, Wikis and Etherpad. Update 2: same, at SFC, which also mentions Firefox Send and Etherpad (and now I wish I did).

Changes in version 0.0.6 (2020-03-14)

• Accomodate Apt 2.0 code changes by including more header files
• Change is backwards compatible and conditional
• Added configure call using pkg-config and package version comparison (using R) to determine if the define is needed
• Softened unit tests as we cannot assume optional source deb information to be present, so demo code runs but zero results tolerated

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