Re: CVE Request -- rpm (X >= 4.10 and X < 3d74c43 commit): Signature checking function returned success on (possibly malicious ) rpm packages

[Panu Matilainen <pmatilai () redhat com>]

On 01/03/2013 07:30 PM, Jan Lieskovsky wrote:
> Hello Kurt, Steve, vendors,
>
>    RPM upstream has corrected the following security issue:
>    [1] https://bugzilla.novell.com/show_bug.cgi?id=796375
>    Relevant upstream patch:
>    [2] http://rpm.org/gitweb?p=rpm.git;a=commitdiff;h=3d74c43
>
> Affected rpm versions include rpm >= 4.10.0 [3] and < than [2] commit.

More precisely, the affected stable versions are 4.10.0 and 4.10.1. Rpm 
4.10.2 (released on Dec 10th 2012) includes a fix already: 
http://rpm.org/wiki/Releases/4.10.2

In addition, rpm 4.11 alpha and beta1 test-releases are affected.

> An attacker could use this flaw to create a syntactically valid rpm
> package, that could bypass the signature check.

To elaborate a bit, it's possible to create a package with an OpenPGP 
signature that's either
a) technically valid but one that rpm doesn't support (eg due to 
"exotic" algorithms used)
b) (intentionally) malformed one

In both cases, rpm issues an error about skipping package/header with 
unverifiable signature but because of the flaw, continues nevertheless, 
effectively bypassing signature checking in the package reading path 
used by eg queries and installation. The explicit signature checking 
path (ie 'rpm -K <package>') is not affected by the flaw.

--
    - Panu -