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Date: Fri, 1 Oct 2010 16:02:04 -0600
From: Vincent Danen <vdanen@...hat.com>
To: oss-security@...ts.openwall.com
Subject: Re: Minor security flaw with pam_xauth

* [2010-09-28 00:17:29 +0400] Solar Designer wrote:

>On Mon, Sep 27, 2010 at 11:36:13AM -0600, Vincent Danen wrote:
>> * [2010-09-24 20:48:23 +0400] Solar Designer wrote:
>> >pam_env and pam_mail accessing the target user's files as root (and thus
>> >susceptible to attacks by the user) in Linux-PAM below 1.1.2, partially
>> >fixed in 1.1.2 - no CVE ID mentioned yet
>> >
>> >pam_env and pam_mail in Linux-PAM 1.1.2 not switching fsgid (or egid)
>> >and groups when accessing the target user's files (and thus potentially
>> >susceptible to attacks by the user) - CVE-2010-3430
>> >
>> >pam_env and pam_mail in Linux-PAM 1.1.2 not checking whether the
>> >setfsuid() calls succeed (no known impact with current Linux kernels,
>> >but poor practice in general) - CVE-2010-3431
>...
>> These that are partially fixed are fixed in that git commit you noted
>> previously?
>>
>> http://git.altlinux.org/people/ldv/packages/?p=pam.git;a=commitdiff;h=06f882f30092a39a1db867c9744b2ca8d60e4ad6
>>
>> Or are they fixed in different commits?  It looks like they should all
>> be fixed in that commit, but I want to double-check.
>
>No, they are not fully fixed at all.  We're working on a patch (so you
>don't need to).  The commit has the mentioned partial fixes only.

Oh, ok.  Gotchya.

>> Are there patches available to fully fix these issues?  And are there
>> patches for 3430 and 3431 yet?
>
>This is the same question asked different ways.  We have a patch that
>we're reviewing internally.  To be made available soon.

Great, looking forward to seeing them.

>> I'm assuming also that those issues have
>> always existed although you say 'in 1.1.2', but they would affect
>> earlier versions yet, right?
>
>The original pam_env and pam_mail issues, yes.  The partial fixes, no,
>because there were no fixes at all before 1.1.2.

Ok, that makes sense.  I wasn't clear on the "partial fix" part.

>> Thanks for any clarification.  I'm trying to wrap my head around this
>> and the impact of these issues.  They all strike me as relatively minor
>> issues, but it is possible that I am missing or misunderstanding
>> something here.
>
>They're relatively minor because these modules are normally not used.
>However, if the modules are used in a PAM stack on a given install, then
>the original issues reported against pam_env and pam_mail by Sebastian
>become major ones.
>
>Additionally, as mentioned by Sebastian, pam_env's intended behavior is
>a security risk (user-provided env vars may affect some services in ways
>not expected by the sysadmin).  I am not sure how to deal with that.
>Maybe improve the documentation.

I'm not sure either, but I think that improving the documentation would
be a good start -- especially if that is pam_env's intended behaviour.

-- 
Vincent Danen / Red Hat Security Response Team 

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