Date: Thu, 13 Aug 2015 00:20:04 +0200 From: Moritz Jodeit <moritz@...efrostsecurity.de> To: Solar Designer <solar@...nwall.com> Cc: oss-security@...ts.openwall.com Subject: Re: CVE request - OpenSSH 6.9 PAM privilege separation vulnerabilities On 12.08.2015 22:48, Solar Designer wrote: > On Wed, Aug 12, 2015 at 09:50:10PM +0200, Moritz Jodeit wrote: >> The vulnerable code for the two privsep issues was introduced with the merge of the >> FreeBSD PAM code in 2003: >> >> https://github.com/openssh/openssh-portable/commit/4f9f42a9bb6a6aa8f6100d873dc6344f2f9994de >> >> The user impersonation issue was fixed by the following commit: >> >> https://github.com/openssh/openssh-portable/commit/d4697fe9a28dab7255c60433e4dd23cf7fce8a8b >> >> While the use-after-free is fixed by this commit: >> >> https://github.com/openssh/openssh-portable/commit/5e75f5198769056089fb06c4d738ab0e5abc66f7 > > Thank you! > > Are systems with "keyboard interactive" and "challenge-response" > authentication disabled (all of PAMAuthenticationViaKbdInt, > KbdInteractiveAuthentication, and ChallengeResponseAuthentication, as > applicable to a given sshd version, set to no) affected by these issues > as well? The code appears to be specific to this mode, but it isn't > immediately clear whether or not these configuration settings prevent > the vulnerable code from being reached in the privsep monitor even when > the privsep child is compromised. If the settings do not currently > prevent the code from being reached (I hope they do), then this should > be corrected as a hardening measure. As long as UsePAM is enabled in the configuration, all the PAM-related monitor requests can be send to the monitor. This at least allows triggering the use-after-free even if all the settings you mentioned are set to "no". Not sure if a full authentication is possible in this case though. Moritz
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