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The current up-to-date specification of the .buildinfo file can be found in DebianMan:deb-buildinfo(5) and DebianMan:dpkg-buildinfo(1). The current up-to-date specification of the .buildinfo file can be found in [[DebianMan:5/deb-buildinfo|deb-buildinfo(5)]] and [[DebianMan:1/dpkg-genbuildinfo|dpkg-genbuildinfo(1)]].

Information on the system used during a build will be recorded in a new control file, a “buildinfo” file with suffix .buildinfo.

See also ReproducibleBuilds/BuildinfoInfrastructure for higher-level discussion about how these files are used to further the goal of reproducible builds.

Motivation

The .buildinfo file has several goals which are related to each other:

  • It records information about the system environment used during a particular build -- packages installed (toolchain, etc), system architecture, etc. This can be useful for forensics/debugging.
  • It can also be used to try to recreate (partially or in full) the system environment when trying to reproduce a particular build.

We want a debian user (or derivative) to be able to find and fetch all .buildinfo files that were known to produce a given binary package so that they can try to reproduce the package themselves.

In the future, there may be more uses for .buildinfo files (or for collections of .buildinfo files related to a single binary artifact). For example:

  • A debian user could elect to only install binary packages that have been successfully built by multiple builders
  • A debian derivative could attest to the packages it has deterministically rebuilt
  • A triage process could identify toolchain changes that have an effect on large numbers of binary packages.
  • A cross-building process could demonstrate the correctness of the cross-compiling toolchain by reproducing the exact binary artifacts.

Specification

The current up-to-date specification of the .buildinfo file can be found in deb-buildinfo(5) and dpkg-genbuildinfo(1).

Semantics

A buildinfo file is a record of what a particular builder did to build some binary output.

It contains as much information about the build environment as is reasonable to distribute, and attempts to include all information needed to reproduce that build.

It does NOT imply that everything contained within "should" be necessary to reproduce the build. For example, we are working towards builds that are reproducible independently of the build-path, but we still include Build-Path: as a field. This helps us to detect which packages are reproducible independently of the build-path, versus which ones are not.

File name and encoding

Buildinfo files are UTF-8-encoded textfiles, usually clearsigned with OpenPGP (see below). They should be named ${SOURCE}_${DEBIAN_VERSION}_${STRING}.buildinfo, where:

  • SOURCE is the source package name.

  • DEBIAN_VERSION is the full version of the Debian package without the epoch. This is the same as the Version: field in the corresponding .changes file.

  • STRING is an arbitrary string, unique within all ${SOURCE},${DEBIAN_VERSION} builds. The string has the same restrictions as package names. It's likely that debian buildd's would create this string as ${HOSTNAME}-${TIMESTAMP}, where TIMESTAMP is an ISO-8601-formatted numeric string. Debian developers may choose arbitrary strings here. The only requirement from the archive's perspective is that the STRING be unique for source package version, so that multiple .buildinfo files may exist for a given version of a package.

Field descriptions

Format

Same as in `*.changes`.

Build-Architecture

The Debian machine architecture that was used to perform the build; see dpkg-architecture(1) for a more detailed definition. 1

Source

Same as in `*.changes`. If the source and binary versions differ (e.g. binNMUs), the source version is added between parenthesis.

Binary

Same as in `*.changes`.

Architecture

Same as in `*.changes` except source should not be specified: only concrete architectures, no wildcards or any.

Version

Same as in `*.changes`.

Binary-Only-Changes

Only present for binary only uploads: contains the full extra changelog entries.

Checksums-Sha256

Same format as other control files. Must list the *.dsc file and all files listed in `debian/files`.

Build-Path

(optional) Absolute path of the directory in which the package has been built. See ReproducibleBuilds/History#Giving_up_on_build_paths for a rationale.

Build-Environment

List of all packages forming the build environment, their architecture if different from build architecture, and their version. This includes Essential packages, build-essential, and Build-Depends and Build-Depends-Indep. For each packages, their dependencies should be recursively listed. The format is the same as Built-Using.

Signatures

A signed buildinfo file is an implicit claim by a builder (the signer) that they were the entity that executed the build as recorded in the file. Corollaries to this:

  • You MUST NOT sign other people's buildinfo files, or any other builds that you did not execute yourself. To do so is to make a false claim, and will be treated as an attack against the buildinfo infrastructure.
  • The implicit claim as defined above, is true for all time - one can't "unbuild" something. So, expiry dates do not apply here - it is an error to sign a buildinfo file with an expiry date. (We don't support revocation at this time.)

  • A signed buildinfo file is NOT a claim about e.g.
    • the quality of the binary
    • the belief that the binary contains no security holes.
    • whether the binary belongs to a certain distribution such as Debian

    To make these sorts of claims, please invent your own descriptor format for that. You may wrap the buildinfo file if you wish. Most likely, you will need to add some sort of expiry date on those kinds of signatures, since these sorts of complex claims are not true for all time. (You might find out later that it did in fact contain a security hole, for example.)

To sign the file, wrap the entire file in a cleartext OpenPGP signature.

Example

The following file could be named e.g. fweb_1.62-12+b2_brahms-20120530114812.buildinfo:

-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512

Format: 1.0
Build-Architecture: i386
Source: fweb (1.62-12)
Binary: fweb fweb-doc
Architecture: all i386
Version: 1.62-12+b2
Binary-Only-Changes:
 fweb (1.62-12+b2) sid; urgency=low, binary-only=yes
 .
   * Binary-only non-maintainer upload for amd64; no source changes.
   * Rebuild for multiarch sync
 .
  -- amd64 / i386 Build Daemon (brahms) <buildd_amd64-brahms@buildd.debian.org>  Wed, 30 May 2012 09:48:12 +0200 18:37:51 +0000
Checksums-Sha256:
 9921500c4c6159c0019d4b8b600d2d06eef6b1da056abd2f78e66a9f0c3843b9 879 fweb_1.62-12.dsc
 3a7492c2013fbeebff08bee0514481ec0f56d2c4d138188d1ef85156d08ded00 436982 fweb-doc_1.62-12_all.deb
 a916dbb1c63707eaf52a5cdd10769871d2f621848176dc8f7ab4f0dcd999af85 229990 fweb_1.62-12+b2_i386.deb
Build-Path: /usr/src/debian/fweb-1.62-12+b2
Build-Environment:
 acl (= 2.2.52-1),
 adduser (= 3.113+nmu3),
 base-files (= 7.5),
 base-passwd (= 3.5.33),
 bash (= 4.3-9),
 binutils (= 2.24.51.20140818-1),
 bsdmainutils (= 9.0.5),
 bsdutils (= 1:2.20.1-5.8),
 build-essential (= 11.7),
 bzip2 (= 1.0.6-7),
 coreutils (= 8.21-1.2),
 cpp (= 4:4.9.1-3),
 cpp-4.9 (= 4.9.1-9),
 dash (= 0.5.7-4),
 debconf (= 1.5.53),
 debhelper (= 9.20140817),
 debianutils (= 4.4),
 dh-buildinfo (= 0.11),
 diffutils (= 1:3.3-1),
 dmsetup (= 2:1.02.88-1),
 dpkg (= 1.17.13),
 dpkg-dev (= 1.17.13),
 e2fslibs (= 1.42.11-2),
 e2fsprogs (= 1.42.11-2),
 file (= 1:5.19-1),
 findutils (= 4.4.2-9),
 g++ (= 4:4.9.1-3),
 g++-4.9 (= 4.9.1-9),
 gcc (= 4:4.9.1-3),
 gcc-4.9 (= 4.9.1-9),
 gcc-4.9-base (= 4.9.1-9),
 gettext (= 0.19.2-1),
 gettext-base (= 0.19.2-1),
 grep (= 2.20-2),
 groff-base (= 1.22.2-6),
 gzip (= 1.6-3),
 hostname (= 3.15),
 init (= 1.21),
 initscripts (= 2.88dsf-53.4),
 insserv (= 1.14.0-5),
 intltool-debian (= 0.35.0+20060710.1),
 libacl1 (= 2.2.52-1),
 libasan1 (= 4.9.1-9),
 libasprintf0c2 (= 0.19.2-1),
 libatomic1 (= 4.9.1-9),
 libattr1 (= 1:2.4.47-1),
 libaudit1 (= 1:2.3.7-1),
 libaudit-common (= 1:2.3.7-1),
 libblkid1 (= 2.20.1-5.8),
 libbz2-1.0 (= 1.0.6-7),
 libc6 (= 2.19-10),
 libc6-dev (= 2.19-10),
 libcap2 (= 1:2.24-4),
 libcap2-bin (= 1:2.24-4),
 libc-bin (= 2.19-10),
 libc-dev-bin (= 2.19-10),
 libcilkrts5 (= 4.9.1-9),
 libcloog-isl4 (= 0.18.2-1),
 libcomerr2 (= 1.42.11-2),
 libcroco3 (= 0.6.8-3),
 libcryptsetup4 (= 2:1.6.6-1),
 libdb5.3 (= 5.3.28-6),
 libdbus-1-3 (= 1.8.6-2),
 libdebconfclient0 (= 0.191),
 libdevmapper1.02.1 (= 2:1.02.88-1),
 libdpkg-perl (= 1.17.13),
 libffi6 (= 3.1-2),
 libgcc1 (= 1:4.9.1-9),
 libgcc-4.9-dev (= 4.9.1-9),
 libgcrypt11 (= 1.5.4-2),
 libgcrypt20 (= 1.6.2-2),
 libgdbm3 (= 1.8.3-13),
 libglib2.0-0 (= 2.40.0-4),
 libgmp10 (= 2:6.0.0+dfsg-6),
 libgomp1 (= 4.9.1-9),
 libgpg-error0 (= 1.13-3),
 libintl-perl (= 1.23-1),
 libisl10 (= 0.12.2-2),
 libitm1 (= 4.9.1-9),
 libkmod2 (= 18-1),
 liblzma5 (= 5.1.1alpha+20120614-2),
 libmagic1 (= 1:5.19-1),
 libmount1 (= 2.20.1-5.8),
 libmpc3 (= 1.0.2-1),
 libmpfr4 (= 3.1.2-1),
 libncurses5 (= 5.9+20140712-2),
 libncurses5-dev (= 5.9+20140712-2),
 libncursesw5 (= 5.9+20140712-2),
 libpam0g (= 1.1.8-3.1),
 libpam-modules (= 1.1.8-3.1),
 libpam-modules-bin (= 1.1.8-3.1),
 libpam-runtime (= 1.1.8-3.1),
 libpcre3 (= 1:8.35-3),
 libpipeline1 (= 1.3.0-1),
 libprocps3 (= 1:3.3.9-7),
 libquadmath0 (= 4.9.1-9),
 libselinux1 (= 2.3-1),
 libsemanage1 (= 2.3-1),
 libsemanage-common (= 2.3-1),
 libsepol1 (= 2.3-1),
 libss2 (= 1.42.11-2),
 libstdc++-4.9-dev (= 4.9.1-9),
 libstdc++6 (= 4.9.1-9),
 libsystemd-journal0 (= 208-8),
 libsystemd-login0 (= 208-8),
 libtext-unidecode-perl (= 0.04-2),
 libtimedate-perl (= 2.3000-2),
 libtinfo5 (= 5.9+20140712-2),
 libtinfo-dev (= 5.9+20140712-2),
 libubsan0 (= 4.9.1-9),
 libudev1 (= 208-8),
 libunistring0 (= 0.9.3-5.2),
 libustr-1.0-1 (= 1.0.4-3),
 libuuid1 (= 2.20.1-5.8),
 libwrap0 (= 7.6.q-25),
 libxml2 (= 2.9.1+dfsg1-4),
 libxml-libxml-perl (= 2.0116+dfsg-1+b1),
 libxml-namespacesupport-perl (= 1.11-1),
 libxml-sax-base-perl (= 1.07-1),
 libxml-sax-perl (= 0.99+dfsg-2),
 linux-libc-dev (= 3.14.15-2),
 login (= 1:4.2-2+b1),
 lsb-base (= 4.1+Debian13),
 make (= 4.0-8),
 man-db (= 2.6.7.1-1),
 mawk (= 1.3.3-17),
 mount (= 2.20.1-5.8),
 ncurses-base (= 5.9+20140712-2),
 ncurses-bin (= 5.9+20140712-2),
 passwd (= 1:4.2-2+b1),
 patch (= 2.7.1-6),
 perl (= 5.20.0-4),
 perl-base (= 5.20.0-4),
 perl-modules (= 5.20.0-4),
 po-debconf (= 1.0.16+nmu3),
 procps (= 1:3.3.9-7),
 sed (= 4.2.2-4),
 sensible-utils (= 0.0.9),
 startpar (= 0.59-3),
 systemd (= 208-8),
 systemd-sysv (= 208-8),
 sysvinit-utils (= 2.88dsf-53.4),
 sysv-rc (= 2.88dsf-53.4),
 tar (= 1.27.1-2),
 texinfo (= 5.2.0.dfsg.1-4),
 tzdata (= 2014f-1),
 ucf (= 3.0030),
 udev (= 208-8),
 util-linux (= 2.20.1-5.8),
 xz-utils (= 5.1.1alpha+20120614-2),
 zlib1g (= 1:1.2.8.dfsg-2)
-----BEGIN PGP SIGNATURE-----
Version: GnuPG v2

iQJ8BAEBCgBmBQJWYNoZXxSAAAAAAC4AKGlzc3Vlci1mcHJAbm90YXRpb25zLm9w
Dx1xK9OgUkDt+gwh9WK/QrvV7IOjAg/pl6j7px5u6MNKHWPW0tC9M5123Q2KmaGT
-----END PGP SIGNATURE-----

Possible future extensions

We are not currently including the following things, mostly because it is quite hard to do them right now. But it would be nice to, in the future:

  • order in which the system packages (essential, build-essential, build-deps) were installed.
  • the cryptographic digest of the system packages themselves
  • the digest of the source code of the system packages

Inclusion of *.buildinfo in the archive

See ReproducibleBuilds/BuildinfoInfrastructure

Previous ideas

.changes files looked like a good place to record the environment as they list the checksums of the build products and are signed by either the maintainer or the buildd operator.

But the meaning of *.changes files is pretty clear: they describe a transactional change operation on the archive. They are not saved directly in the archive: they are equivalent of a log entry. The name of *.changes file is also not specified and multiple operations can have the same name.

(See also 719854 for the first attempt which tried using XC- field in debian/control.)

We thought that .buildinfo files would be all the data required to do a rebuild, as opposed to a description of the state of the build system. However, it's likely that we don't know the actual requirements, and it's likely that the description will be more detailed than is necessary in some cases. This means that two different buildinfo files could attest to the same exact binary artifact.

We thought at some point that the .buildinfo could be referenced in the Packages index, but this does not seem necessary, and might be overkill, since only some users may actually have varied systems.

We do not need to specify the ordering of fields?

  1. In particular, in GNU terminology this is the build architecture. In Debian, the GNU target architecture for cross compilers is usually encoded in the package name and thus does not need to be encoded here; and the host architecture is the Debian binary package architecture in the Architecture field and file name. (1)