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Message-ID: <HVOfwapPoUpExeEC6pUVJFD81vMaCFIGaNo0Uodnx5Sk40Z5SD2JmPGp-IWcmnvIX1Qswb0Kif33n0bqakSLFndsMqYgjY4lTVIRwN_MSfw=@protonmail.com>
Date: Tue, 21 Apr 2020 16:27:08 +0000
From: "jellicent@...tonmail.com" <jellicent@...tonmail.com>
To: "oss-security@...ts.openwall.com" <oss-security@...ts.openwall.com>
Subject: Pacman package manager - taking untrusted input

The Pacman package manager, used by Arch Linux and its 10+ derivatives,
introduces a critical security flaw in its current state.

When downloading a package, Pacman checks two files: the database file
and the package itself. According to their wiki[1], the package files
are PGP-signed by the developers. The database, however, is not signed.
This means that Pacman, running as root, is both downloading and parsing
untrusted input from the Internet. Should there be any relevant bug in
Pacman, this would lead to root code execution on every Arch/Arch-based
machine using the package repositories.

Some scenarios in which this could happen:

* One or more of the mirrors (not run by Arch devs) is compromised and
   the malicious database file is picked up by a small set of users or
   project committers

* The main fan-out server (rsync.archlinux.org) is compromised and the
   malicious database file is propagated to all mirrors worldwide

* A new mirror, run by a malicious actor, is submitted for approval to
   be included in the official mirror list

* A man-in-the-middle attack is launched on any number of plain HTTP
   mirrors, replacing the database file with a malicious one in transit

The code supports database signatures, so the real issue is the distro
infrastructure.

[1] https://wiki.archlinux.org/index.php/Pacman/Package_signing

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