Reproducible Builds in August 2020

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Welcome to the August 2020 report from the Reproducible Builds project.

In our monthly reports, we summarise the things that we have been up to over the past month. The motivation behind the Reproducible Builds effort is to ensure no flaws have been introduced from the original free software source code to the pre-compiled binaries we install on our systems. If you’re interested in contributing to the project, please visit our main website.




This month, Jennifer Helsby launched a new reproduciblewheels.com website to address the lack of reproducibility of Python wheels.

To quote Jennifer’s accompanying explanatory blog post:

One hiccup we’ve encountered in SecureDrop development is that not all Python wheels can be built reproducibly. We ship multiple (Python) projects in Debian packages, with Python dependencies included in those packages as wheels. In order for our Debian packages to be reproducible, we need that wheel build process to also be reproducible

Parallel to this, transparencylog.com was also launched, a service that verifies the contents of URLs against a publicly recorded cryptographic log. It keeps an append-only log of the cryptographic digests of all URLs it has seen. (GitHub repo)

On 18th September, Bernhard M. Wiedemann will give a presentation in German, titled Wie reproducible builds Software sicherer machen (“How reproducible builds make software more secure”) at the Internet Security Digital Days 2020 conference.


Reproducible builds at DebConf20

There were a number of talks at the recent online-only DebConf20 conference on the topic of reproducible builds.

Holger gave a talk titled “Reproducing Bullseye in practice”, focusing on independently verifying that the binaries distributed from ftp.debian.org are made from their claimed sources. It also served as a general update on the status of reproducible builds within Debian. The video (145 MB) and slides are available.

There were also a number of other talks that involved Reproducible Builds too. For example, the Malayalam language mini-conference had a talk titled എനിയ്ക്കും ഡെബിയനില്‍ വരണം, ഞാന്‍ എന്തു് ചെയ്യണം? (“I want to join Debian, what should I do?”) presented by Praveen Arimbrathodiyil, the Clojure Packaging Team BoF session led by Elana Hashman, as well as Where is Salsa CI right now? that was on the topic of Salsa, the collaborative development server that Debian uses to provide the necessary tools for package maintainers, packaging teams and so on.

Jonathan Bustillos (Jathan) also gave a talk in Spanish titled Un camino verificable desde el origen hasta el binario (“A verifiable path from source to binary”). (Video, 88MB)


Development work

After many years of development work, the compiler for the Rust programming language now generates reproducible binary code. This generated some general discussion on Reddit on the topic of reproducibility in general.

Paul Spooren posted a ‘request for comments’ to OpenWrt’s openwrt-devel mailing list asking for clarification on when to raise the PKG_RELEASE identifier of a package. This is needed in order to successfully perform rebuilds in a reproducible builds context.

In openSUSE, Bernhard M. Wiedemann published his monthly Reproducible Builds status update.

Chris Lamb provided some comments and pointers on an upstream issue regarding the reproducibility of a Snap / SquashFS archive file. []

Debian

Holger Levsen identified that a large number of Debian .buildinfo build certificates have been “tainted” on the official Debian build servers, as these environments have files underneath the /usr/local/sbin directory []. He also filed against bug for debrebuild after spotting that it can fail to download packages from snapshot.debian.org [].

This month, several issues were uncovered (or assisted) due to the efforts of reproducible builds.

For instance, Debian bug #968710 was filed by Simon McVittie, which describes a problem with detached debug symbol files (required to generate a traceback) that is unlikely to have been discovered without reproducible builds. In addition, Jelmer Vernooij called attention that the new Debian Janitor tool is using the property of reproducibility (as well as diffoscope when applying archive-wide changes to Debian:

New merge proposals also include a link to the diffoscope diff between a vanilla build and the build with changes. Unfortunately these can be a bit noisy for packages that are not reproducible yet, due to the difference in build environment between the two builds. []

56 reviews of Debian packages were added, 38 were updated and 24 were removed this month adding to our knowledge about identified issues. Specifically, Chris Lamb added and categorised the nondeterministic_version_generated_by_python_param and the lessc_nondeterministic_keys toolchain issues. [][]

Holger Levsen sponsored Lukas Puehringer’s upload of the python-securesystemslib pacage, which is a dependency of in-toto, a framework to secure the integrity of software supply chains. []

Lastly, Chris Lamb further refined his merge request against the debian-installer component to allow all arguments from sources.list files (such as [check-valid-until=no]) in order that we can test the reproducibility of the installer images on the Reproducible Builds own testing infrastructure and sent a ping to the team that maintains that code.


Upstream patches

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

diffoscope

diffoscope is our in-depth and content-aware diff utility that can not only locate and diagnose reproducibility issues, it provides human-readable diffs of all kinds. In August, Chris Lamb made the following changes to diffoscope, including preparing and uploading versions 155, 156, 157 and 158 to Debian:

  • New features:

    • Support extracting data of PGP signed data. (#214)
    • Try files named .pgp against pgpdump(1) to determine whether they are Pretty Good Privacy (PGP) files. (#211)
    • Support multiple options for all file extension matching. []
  • Bug fixes:

    • Don’t raise an exception when we encounter XML files with <!ENTITY> declarations inside the Document Type Definition (DTD), or when a DTD or entity references an external resource. (#212)
    • pgpdump(1) can successfully parse some binary files, so check that the parsed output contains something sensible before accepting it. []
    • Temporarily drop gnumeric from the Debian build-dependencies as it has been removed from the testing distribution. (#968742)
    • Correctly use fallback_recognises to prevent matching .xsb binary XML files.
    • Correct identify signed PGP files as file(1) returns “data”. (#211)
  • Logging improvements:

    • Emit a message when ppudump version does not match our file header. []
    • Don’t use Python’s repr(object) output in “Calling external command” messages. []
    • Include the filename in the “… not identified by any comparator” message. []
  • Codebase improvements:

    • Bump Python requirement from 3.6 to 3.7. Most distributions are either shipping with Python 3.5 or 3.7, so supporting 3.6 is not only somewhat unnecessary but also cumbersome to test locally. []
    • Drop some unused imports [], drop an unnecessary dictionary comprehensions [] and some unnecessary control flow [].
    • Correct typo of “output” in a comment. []
  • Release process:

    • Move generation of debian/tests/control to an external script. []
    • Add some URLs for the site that will appear on PyPI.org. []
    • Update “author” and “author email” in setup.py for PyPI.org and similar. []
  • Testsuite improvements:

    • Update PPU tests for compatibility with Free Pascal versions 3.2.0 or greater. (#968124)
    • Mark that our identification test for .ppu files requires ppudump version 3.2.0 or higher. []
    • Add an assert_diff helper that loads and compares a fixture output. [][][][]
  • Misc:

In addition, Mattia Rizzolo documented in setup.py that diffoscope works with Python version 3.8 [] and Frazer Clews applied some Pylint suggestions [] and removed some deprecated methods [].

Website

This month, Chris Lamb updated the main Reproducible Builds website and documentation to:

  • Clarify & fix a few entries on the “who” page [][] and ensure that images do not get to large on some viewports [].
  • Clarify use of a pronoun re. Conservancy. []
  • Use “View all our monthly reports” over “View all monthly reports”. []
  • Move a “is a” suffix out of the link target on the SOURCE_DATE_EPOCH age. []

In addition, Javier Jardón added the freedesktop-sdk project [] and Kushal Das added SecureDrop project [] to our projects page. Lastly, Michael Pöhn added internationalisation and translation support with help from Hans-Christoph Steiner [].

Testing framework

The Reproducible Builds project operate a Jenkins-based testing framework to power tests.reproducible-builds.org. This month, Holger Levsen made the following changes:

  • System health checks:

    • Improve explanation how the status and scores are calculated. [][]
    • Update and condense view of detected issues. [][]
    • Query the canonical configuration file to determine whether a job is disabled instead of duplicating/hardcoding this. []
    • Detect several problems when updating the status of reporting-oriented ‘metapackage’ sets. []
    • Detect when diffoscope is not installable  [] and failures in DNS resolution [].
  • Debian:

    • Update the URL to the Debian security team bug tracker’s Git repository. []
    • Reschedule the unstable and bullseye distributions often for the arm64 architecture. []
    • Schedule buster less often for armhf. [][][]
    • Force the build of certain packages in the work-in-progress package rebuilder. [][]
    • Only update the stretch and buster base build images when necessary. []
  • Other distributions:

    • For F-Droid, trigger jobs by commits, not by a timer. []
    • Disable the Archlinux HTML page generation job as it has never worked. []
    • Disable the alternative OpenWrt rebuilder jobs. []
  • Misc;

Many other changes were made too, including:

Finally, build node maintenance was performed by Holger Levsen [], Mattia Rizzolo [][] and Vagrant Cascadian [][][][]


Mailing list

On our mailing list this month, Leo Wandersleb sent a message to the list after he was wondering how to expand his WalletScrutiny.com project (which aims to improve the security of Bitcoin wallets) from Android wallets to also monitor Linux wallets as well:

If you think you know how to spread the word about reproducibility in the context of Bitcoin wallets through WalletScrutiny, your contributions are highly welcome on this PR []

Julien Lepiller posted to the list linking to a blog post by Tavis Ormandy titled You don’t need reproducible builds. Morten Linderud (foxboron) responded with a clear rebuttal that Tavis was only considering the narrow use-case of proprietary vendors and closed-source software. He additionally noted that the criticism that reproducible builds cannot prevent against backdoors being deliberately introduced into the upstream source (“bugdoors”) are decidedly (and deliberately) outside the scope of reproducible builds to begin with.

Chris Lamb included the Reproducible Builds mailing list in a wider discussion regarding a tentative proposal to include .buildinfo files in .deb packages, adding his remarks regarding requiring a custom tool in order to determine whether generated build artifacts are ‘identical’ in a reproducible context. []

Jonathan Bustillos (Jathan) posted a quick email to the list requesting whether there was a list of To do tasks in Reproducible Builds.

Lastly, Chris Lamb responded at length to a query regarding the status of reproducible builds for Debian ISO or installation images. He noted that most of the technical work has been performed but “there are at least four issues until they can be generally advertised as such”. He pointed that the privacy-oriented Tails operation system, which is based directly on Debian, has had reproducible builds for a number of years now. []



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