Date: Tue, 29 Apr 2014 18:18:58 -0400 From: Steve Grubb <sgrubb@...hat.com> To: oss-security@...ts.openwall.com Cc: Solar Designer <solar@...nwall.com> Subject: Re: local privilege escalation due to capng_lock as used in seunshare On Wednesday, April 30, 2014 02:12:22 AM Solar Designer wrote: > On Tue, Apr 29, 2014 at 05:49:04PM -0400, Steve Grubb wrote: > > On Tuesday, April 29, 2014 02:20:47 PM Andy Lutomirski wrote: > > > if (setuid(getuid()) != 0) > > > > > > err(1, "setuid(getuid())"); > > > > If you do not want the saved uid to be available, you need to use > > setresuid. That removes it. I would classify this as a bug in the test > > program. > > Not quite. If the program was amended to use setresuid(), does the bug still exist? -Steve > Per POSIX.1-2001, setuid() "shall set the real user ID, effective user > ID, and the saved set-user-ID of the calling process to uid" if the > process has "appropriate privileges". On traditional Unix systems, > without capabilities, running as root historically does constitute > "appropriate privileges". If we want current systems to support safely > running programs written for traditional Unix (including SUID root > programs), which I think is taken for granted by many of us, we must not > deviate from those semantics in dangerous ways. Any such deviation is a > vulnerability in our current kernel code or configuration. > > Distributions must not ship with settings or programs that allow anyone > other than an administrator to alter the definition of "appropriate > privileges" in a way that, while compliant with this vague wording in > POSIX, introduces a vulnerability for correct programs written for > traditional Unix systems. > > What we have here is a reincarnation of: > > "Sendmail Workaround for Linux Capabilities Bug" > https://www.sendmail.com/sm/open_source/security/security_docs/sendmail.8.10 > .1.LINUX-SECURITY.txt > > albeit in slightly different shape (not entirely in the kernel, but with > a userland "helper"). > > I think that sendmail-exposed vulnerability was in the kernel (not in > sendmail), and I think the vulnerability Andy is reporting is in some > distros (apparently, Red Hat's). > > Of course, it is possible that I have missed something important as I > did not look into this issue closely, but the above is my current > understanding based on Andy's message. > > Alexander
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