APT-SECURE(8) | APT | APT-SECURE(8) |
NAME¶
apt-secure - Archive authentication support for APTDESCRIPTION¶
Starting with version 0.6, apt contains code that does signature checking of the Release file for all archives. This ensures that packages in the archive can't be modified by people who have no access to the Release file signing key. If a package comes from a archive without a signature, or with a signature that apt does not have a key for, that package is considered untrusted, and installing it will result in a big warning. apt-get will currently only warn for unsigned archives; future releases might force all sources to be verified before downloading packages from them. The package frontends apt-get(8), aptitude(8) and synaptic(8) support this new authentication feature.TRUSTED ARCHIVES¶
The chain of trust from an apt archive to the end user is made up of several steps. apt-secure is the last step in this chain; trusting an archive does not mean that you trust its packages not to contain malicious code, but means that you trust the archive maintainer. It's the archive maintainer's responsibility to ensure that the archive's integrity is preserved. apt-secure does not review signatures at a package level. If you require tools to do this you should look at debsig-verify and debsign (provided in the debsig-verify and devscripts packages respectively). The chain of trust in Debian starts when a maintainer uploads a new package or a new version of a package to the Debian archive. In order to become effective, this upload needs to be signed by a key contained in the Debian Maintainers keyring (available in the debian-keyring package). Maintainers' keys are signed by other maintainers following pre-established procedures to ensure the identity of the key holder. Once the uploaded package is verified and included in the archive, the maintainer signature is stripped off, and checksums of the package are computed and put in the Packages file. The checksums of all of the Packages files are then computed and put into the Release file. The Release file is then signed by the archive key for this Debian release, and distributed alongside the packages and the Packages files on Debian mirrors. The keys are in the Debian archive keyring available in the debian-archive-keyring package. End users can check the signature of the Release file, extract a checksum of a package from it and compare it with the checksum of the package they downloaded by hand - or rely on APT doing this automatically. Notice that this is distinct from checking signatures on a per package basis. It is designed to prevent two possible attacks:•Network "man in the middle"
attacks. Without signature checking, malicious agents can introduce themselves
into the package download process and provide malicious software either by
controlling a network element (router, switch, etc.) or by redirecting traffic
to a rogue server (through ARP or DNS spoofing attacks).
•Mirror network compromise. Without
signature checking, a malicious agent can compromise a mirror host and modify
the files in it to propagate malicious software to all users downloading
packages from that host.
However, it does not defend against a compromise of the Debian master server
itself (which signs the packages) or against a compromise of the key used to
sign the Release files. In any case, this mechanism can complement a
per-package signature.
USER CONFIGURATION¶
ARCHIVE CONFIGURATION¶
If you want to provide archive signatures in an archive under your maintenance you have to:•Create a toplevel Release file,
if it does not exist already. You can do this by running apt-ftparchive
release (provided in apt-utils).
•Sign it. You can do this by
running gpg --clearsign -o InRelease Release and gpg -abs -o
Release.gpg Release.
•Publish the key fingerprint,
that way your users will know what key they need to import in order to
authenticate the files in the archive.
Whenever the contents of the archive change (new packages are added or removed)
the archive maintainer has to follow the first two steps outlined above.
SEE ALSO¶
BUGS¶
APT bug page[3]. If you wish to report a bug in APT, please see /usr/share/doc/debian/bug-reporting.txt or the reportbug(1) command.AUTHOR¶
APT was written by the APT team <apt@packages.debian.org>.MANPAGE AUTHORS¶
This man-page is based on the work of Javier Fernández-Sanguino Peña, Isaac Jones, Colin Walters, Florian Weimer and Michael Vogt.AUTHORS¶
Jason Gunthorpe APT teamNOTES¶
- 1.
- Debian Security Infrastructure
- 2.
- Strong Distribution HOWTO
- 3.
- APT bug page
09 June 2012 | APT 0.9.7.9 |