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Date: Thu, 08 Dec 2011 15:04:20 -0500
From: Jeff Mitchell <>
CC: Kurt Seifried <>
Subject: Re: Disputing CVE-2011-4122

On 12/8/2011 2:47 PM, Kurt Seifried wrote:
> On 12/08/2011 07:11 AM, Jeff Mitchell wrote:
>> On 12/07/2011 11:26 AM, Kurt Seifried wrote:
>>>> One could assume that kcheckpass should do the validation. However, the
>>>> PAM documentation makes no mention of what a service name is supposed to
>>>> look like, and consequently it must be treated as opaque by the
>>>> application code. Therefore all validation must be expected to be done
>>>> by the library, and failure to do so must be seen as a bug in the
>>>> library exclusively.
>>> Can you provide a link to the documentation?
>> Thanks,
>> Jeff
> Looking around I did find:
> =====================
> 15.2.1. PAM Service Files
> Each PAM-aware application or service has a file within the /etc/pam.d/
> directory. Each file within this directory bears the name of the service
> for which it controls access.
> It is up to the PAM-aware program to define its service name and install
> its own PAM configuration file in the /etc/pam.d/ directory. For
> example, the login program defines its service name as login and
> installs the /etc/pam.d/login PAM configuration file.
> =====================
> so to some degree it is defined: the service name must fit legal file
> name constraints, but this means things like length, but on ext4 for
> example this means 256 chars max, and only NULL and "/" are disallowed,
> to say nothing of other file systems like xfs (any bytes except null)
> and Joliet (CDFS, max 64 characters, unicode supported[1])
> So perhaps going for a lowest common denominator of common filesystems
> you'd expect to find /etc/ on (so ext4, xfs, maybe Joliet for cd based
> systems?) as a filter would be appropriate? And poking the PAM people to
> refine the specification a little bit? Thoughts or comments anyone?
> [1]

The documentation you linked to above is for LinuxPAM, not OpenPAM.
They're different systems and the bug only affects OpenPAM.


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