Bug 139477 – net-dialup/ppp setuid() issue (CVE-2006-2194)

• Product: Gentoo Security
• Status: RESOLVED FIXED

[Description Sune Kloppenborg Jeppesen (RETIRED) 2006-07-06 13:30:52 UTC]

Marcus Meissner discovered that the winbind plugin of pppd does not
check the result of the setuid() call. On systems that configure PAM
limits for the maximum number of user processes and enable the winbind
plugin, a local attacker could exploit this to execute the winbind
NTLM authentication helper as root. Depending on the local winbind
configuration, this could potentially lead to privilege escalation.

[Comment 1 Raphael Marichez (Falco) (RETIRED) 2006-07-06 15:06:23 UTC]

--> C because it does not affect the default conf (pam limits + winbind plugin)

--> *1 because there is a possible privilege escalation

i don't understand how CVE can reference ppp 2.4.4 as vulnerable, since from the officiel web site :

"ppp 2.4.3
The latest version of ppp is version 2.4.3, released on 14 November 2004."
http://samba.org/ppp/

--> setting to [upstream] status. Waiting.

[Comment 2 Raphael Marichez (Falco) (RETIRED) 2006-07-06 15:23:34 UTC]

C1 -> major, the policy says.

[Comment 3 Alin Năstac (RETIRED) 2006-07-06 23:31:16 UTC]

I understand that patch available at http://lists.opensuse.org/archive/opensuse-commit/2006-Jun/0117.html fixes this problem. Btw, I find it strange that upstream wasn't informed about it.

Can someone enlighten me how could setuid(getuid()) be exploited? If the effective user is root, it will always succeed, isn't so?

[Comment 4 Wolf Giesen (RETIRED) 2006-07-06 23:34:34 UTC]

No, we had a couple of those lately. It's not guaranteed that you can drop privs. If user's process limit is exceeded, for example, dropping fails. If you don't check the return code, your code will run as root as opposed to the unprivileged user you wanted to change to.

[Comment 5 Wolf Giesen (RETIRED) 2006-07-06 23:37:47 UTC]

BTW, good reading IMHO: http://www.csl.sri.com/users/ddean/papers/usenix02.pdf

[Comment 6 Alin Năstac (RETIRED) 2006-07-07 00:11:48 UTC]

Created attachment 91097 [details, diff]
winbind-drop-privs.patch

Would this patch be OK from the security pov?

[Comment 7 Wolf Giesen (RETIRED) 2006-07-07 00:32:57 UTC]

Looks ok to me. Any different POVs?

[Comment 8 Raphael Marichez (Falco) (RETIRED) 2006-07-07 00:49:14 UTC]

> 
> Would this patch be OK from the security pov?
> 

it's OK for me

[Comment 9 Alin Năstac (RETIRED) 2006-07-07 01:01:27 UTC]

Fixed in ppp-2.4.3-r16 (give it a couple of hours till patches tarball is uploaded on our mirrors from dev.g.o:/space/distfiles-local).

The stable version (2.4.2-r15) isn't affected by this bug since it doesn't have winbind plugin.

[Comment 10 Raphael Marichez (Falco) (RETIRED) 2006-07-07 01:07:41 UTC]

> Fixed in ppp-2.4.3-r16 (give it a couple of hours till patches tarball is
> uploaded on our mirrors from dev.g.o:/space/distfiles-local).

good, thanks

> The stable version (2.4.2-r15) isn't affected by this bug since it doesn't have
> winbind plugin.

there will be no glsa then; closing. Thank you for the fastness, Alin.
As usual, feel free to reopen if needed.