Date: Tue, 3 May 2016 16:57:13 +0200 From: Salvatore Bonaccorso <carnil@...ian.org> To: cve-assign@...re.org Cc: oss-security@...ts.openwall.com, Vagrant Cascadian <vagrant@...ian.org> Subject: Re: CVE Request: libpam-sshauth: local root privilege escalation Hi, On Sun, May 01, 2016 at 10:02:15AM -0400, cve-assign@...re.org wrote: > -----BEGIN PGP SIGNED MESSAGE----- > Hash: SHA256 > > > Due to a programming error, libpam-sshauth returned PAM_SUCCESS where > > it should fail with PAM_AUTH_ERR. This was fixed in Debian in the last > > upload to unstable with the attached patch. > > > > https://bazaar.launchpad.net/~ltsp-upstream/ltsp/libpam-sshauth/revision/114 > > We can assign a CVE ID because it appears that something definitely is > wrong from the Debian perspective, either the code itself or > documentation/lack-of-documentation about how the code was supposed to > be used. > > Use CVE-2016-4422. Thanks for assigning the CVE identifier. > > However, we don't completely understand the issue: > > > Introduced with: > > https://bazaar.launchpad.net/~ltsp-upstream/ltsp/libpam-sshauth/revision/93/src/pam_sshauth.c > > Here, the commit message for revision 93 was "Succeed for system > accounts." > > We don't know why introducing the undocumented behavior of "Is it a > system user? Fail" would be better than simply not checking > "pwent->pw_uid < UID_MIN" at all. Also, is there any risk that, with > this libpam-sshauth update, a system's PAM configuration might > suddenly provide no way for root to login via SSH? > > Is it possible that the original motivation for revision 93 was that > the PAM_SUCCESS from pam_sm_authenticate was supposed to be specially > handled elsewhere in the "pwent->pw_uid < UID_MIN" case? > > Although not directly applicable to libpam-sshauth, the examples > section of the > http://www.linux-pam.org/Linux-PAM-html/sag-pam_succeed_if.html man > page shows that a set of rules is sometimes designed with UID_MIN > special cases. It might be right that revision 93 cannot be considred the introducing revision for the problem. By following the example as given in the README. https://sources.debian.net/src/libpam-sshauth/0.3.1-1/README/#L75 $ cat /etc/pam.d/testservice auth required pam_sshauth.so host=127.0.0.1 nostrict # or wherever auth required pam_exec.so expose_authtok /usr/bin/ltsp-session session required pam_exec.so /usr/bin/ltsp-session $ pamtester -v testservice root authenticate open_session close_session pamtester: invoking pam_start(testservice, root, ...) pamtester: performing operation - authenticate Password: <anypassword> pamtester: successfully authenticated pamtester: performing operation - open_session pamtester: successfully opened a session pamtester: performing operation - close_session pamtester: session has successfully been closed. I want though to add the Debian maintainer for libpam-sshauth to more accurately answer the raised questions, Vagrant Cascadian <vagrant@...ian.org>. Regards, Salvatore
Powered by blists - more mailing lists
Please check out the Open Source Software Security Wiki, which is counterpart to this mailing list.
Powered by Openwall GNU/*/Linux - Powered by OpenVZ