Date: Sat, 27 Sep 2014 17:51:10 -0400 From: Rich Felker <dalias@...c.org> To: oss-security@...ts.openwall.com Subject: Re: Re: CVE-2014-6271: remote code execution through bash (3rd vulnerability) On Fri, Sep 26, 2014 at 12:26:05PM -0600, Kurt Seifried wrote: > On 26/09/14 12:12 PM, Rich Felker wrote: > > On Fri, Sep 26, 2014 at 02:06:21PM +0100, Simon McVittie wrote: > >>> Tell everyone to stop using setuid/setgid now and forever? > > > > Yes! > > > >> Minimizing use of setuid/setgid, and making sure the setuid/setgid > >> things are suitably hardened, is a good idea. However, tools for > >> controlled privilege escalation (sudo, pkexec, Apache suexec) rely on > >> setuid in order to work. There's a reason the feature exists at all. > > > > These could all be done by having the process with root privileges > > inherit them from a daemon parent that already has root, rather than > > requiring the kernel to elevate the privileges of a process via the > > setuid bit. This inherently eliminates all attacker control of the > > process's initial state and limits the input/attack surface to the > > communication channel clients have with the daemon (e.g. a single unix > > socket). > > setuid/setgid is not just for root. For example the Postfix server makes > use of various groups and setuid/setgid binaries and directories so that > there are well defined interfaces between Postfix components that run > with different privilege levels. But the same could be achieved, with none of the risks of setuid/setgid, via IPC to a daemon that already has the right user/group. Rich
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