oss-sec mailing list archives
Re: Healing the bash fork
From: Florian Weimer <fweimer () redhat com>
Date: Wed, 01 Oct 2014 16:27:46 +0200
On 10/01/2014 03:32 PM, Tomas Hoger wrote:
On Tue, 30 Sep 2014 19:19:55 -0400 (EDT) David A. Wheeler wrote:* Approach 1: Florian Weimer's approach. Bash functions to be exported have a prefix ("BASH_FUNC_") and suffix added. Then, ONLY environment variables with that prefix and suffix are interpreted specially. This approach is used by Red Hat, CentOS, Debian, Ubuntu, and Cygwin (at least), and was later accepted into bash upstream. The original approach used "()" as the suffix; bash upstream took this but switched to the "%%" suffix instead, which is a nice improvement (since "%" is not a shell metacharacter this is less likely to trigger OTHER problems). I know Cygwin is using the bash upstream '%%' suffix.The following indicates there is other prefix and suffix used, that makes these incompatibility issues worse: http://support.apple.com/kb/HT6495 The names of all environment variables that introduce function definitions are required to have a prefix "__BASH_FUNC<" and suffix ">()" to prevent unintended function passing via HTTP headers.
I initially dismissed this as a presentation artifact in the web page, but it's true, there are additional <> characters in the mangled name. I wonder what breaks as a result. At least () and %% are somewhat benign in their effect if they are used unquoted in the relevant places (error, not accidental file creation).
(To be absolute clear, I do not see any security issues with Apple's choice of mangling.)
-- Florian Weimer / Red Hat Product Security
Current thread:
- Re: Healing the bash fork, (continued)
- Re: Healing the bash fork Michal Zalewski (Sep 30)
- Re: Healing the bash fork Stuart D. Gathman (Oct 01)
- Re: Healing the bash fork Hanno Böck (Oct 01)
- Re: Healing the bash fork Jason Cooper (Oct 01)
- Re: Healing the bash fork Greg KH (Oct 01)
- Re: Healing the bash fork Jason Cooper (Oct 01)
- Re: Healing the bash fork Greg KH (Oct 01)
- Re: Healing the bash fork Loganaden Velvindron (Oct 01)
- Re: Healing the bash fork Colin Mahns (Oct 01)
- Re: Healing the bash fork Jason Cooper (Oct 01)
- Re: Healing the bash fork Michal Zalewski (Sep 30)
- Re: Healing the bash fork Florian Weimer (Oct 01)
- Re: Healing the bash fork David A. Wheeler (Oct 02)
- Re: Healing the bash fork David A. Wheeler (Oct 06)