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Date: Sat, 12 Jul 2014 13:00:08 -0400
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: Status towards next release (1.1.4)
On Sat, Jul 12, 2014 at 06:29:44PM +0200, u-igbb@...ey.se wrote:
> > Runtime configuration of the path is a big problem for many usage
> > cases, possibly even if it's blocked for suid. The recent glibc
> > CVE-2014-0475 has me concerned and wanting to avoid any dubious
> > practices with how locales are searched out. This is potentially a
>
> I understand your concern about security but disallowing something at
> the library level just to prevent a certain possible mode of failure of
> a third party's flawed security model? This feels almost like designing
> flats without windows [no pun] to prevent children from falling out.
>
> > much bigger issue than timezones, because for timezones, invalid data
> > probably results in compromises no worse than a crash or information
> > leak. With locales, invalid data can result in full code execution
> > (via injection of %n into format strings, and possibly other ways).
>
> Allowing a user to set environment variables is giving her freedom to
> control her applications iow a policy question. The low level library has
> no proper knowledge to make policy decisions.
>
> Again, I feel you assume more responsibility for musl than is due.
I partly agree with you here, and that's why I've raised a question on
oss-security as to whether CVE-2014-0475 was even a valid
vulnerability rather than just an ordinary non-security bug.
However, format string vulnerabilities are also a sufficiently serious
issue that extra precautions need to be taken to avoid introducing
them in situations where it might be at all non-obvious that they
could arise. This is why (see my other email in the thread spun off
this one) I'm working on a design that avoids the format string issue
entirely.
I think we'll be able to work something out where locale path is
configurable locally (per-process), or at least where absolute paths
are allowed. Of course in suid processes both need to be forbidden;
until we can be sure of what's safe, it might be necessary just to
forbid all non-builtin locales for suid (libc.secure) programs.
Rich
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