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Date: Fri, 23 Aug 2013 13:40:31 +0200
From: jca+dash@...vbn.org (Jérémie Courrèges-Anglas)
To: Tavis Ormandy <taviso@...gle.com>
Cc: Jilles Tjoelker <jilles@...ck.nl>, Harald van Dijk <harald@...awatt.nl>,
dash@...r.kernel.org, oss-security@...ts.openwall.com
Subject: Re: [PATCH] implement privmode support in dash
Also,
Tavis Ormandy <taviso@...gle.com> writes:
[...]
>> Apart from that, it is better to check the return value from setuid()
>> and similar functions. In particular, some versions of Linux may fail
>> setuid() for [EAGAIN], leaving the process running with the same
>> privileges.
>
> I don't think this is true anymore, but I have no strong objection to
> adding it, so long as it's noted that bash and pdksh do not do this.
Just for reference, from mksh:
[...]
#ifdef SETUID_CAN_FAIL_WITH_EAGAIN
/* we don't need to check for other codes, EPERM won't happen */
#define DO_SETUID(func, argvec) do { \
if ((func argvec) && errno == EAGAIN) \
errorf("%s failed with EAGAIN, probably due to a" \
" too low process limit; aborting", #func); \
} while (/* CONSTCOND */ 0)
#else
#define DO_SETUID(func, argvec) func argvec
#endif
[...]
if (f == FPRIVILEGED && oldval && !newval) {
/* Turning off -p? */
/*XXX this can probably be optimised */
kshegid = kshgid = getgid();
#if HAVE_SETRESUGID
DO_SETUID(setresgid, (kshegid, kshegid, kshegid));
#if HAVE_SETGROUPS
/* setgroups doesn't EAGAIN on Linux */
setgroups(1, &kshegid);
#endif
DO_SETUID(setresuid, (ksheuid, ksheuid, ksheuid));
#else
/* seteuid, setegid, setgid don't EAGAIN on Linux */
ksheuid = kshuid = getuid();
#ifndef MKSH__NO_SETEUGID
seteuid(ksheuid);
#endif
DO_SETUID(setuid, (ksheuid));
#ifndef MKSH__NO_SETEUGID
setegid(kshegid);
#endif
setgid(kshegid);
#endif
} [...]
> Tavis.
--
jca | PGP: 0x06A11494 / 61DB D9A0 00A4 67CF 2A90 8961 6191 8FBF 06A1 1494
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