Re: Minor security flaw with pam_xauth

[Solar Designer <solar () openwall com>]

On Mon, Sep 27, 2010 at 11:44:03AM -0600, Vincent Danen wrote:
> > * [2010-09-24 20:48:23 +0400] Solar Designer wrote:
> > > pam_xauth missing return value checks from setuid() and similar calls,
> > > fixed in Linux-PAM 1.1.2 - CVE-2010-3316
> > >
> > > 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
...
> Oh, hang on.  Re-read some older messages again trying to grok this and
> it looks like these checks were introduced in 1.1.2, so they would _not_
> affect earlier versions if I'm understanding correctly.

Older versions were "fully vulnerable".  1.1.2 is "partially vulnerable".

> So only 3316 and the second issue without a CVE name affect pre-1.1.2.

Yes, in a sense.

> So what about previous versions that _don't_ have privilege switching in
> pam_env and pam_mail?  Would that require yet another CVE or would the
> addition of privilege switching be considered an enhancement, not a
> security fix?

I think it should be considered a security fix.  Moreover, of these four
issues (if we keep the separation above), the currently-CVE-less is the
most serious one.

Alexander