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Date: Mon, 29 Sep 2014 19:50:52 -0400
From: Chet Ramey <>
To: Eric Blake <>, Tavis Ormandy <>,
        Florian Weimer <>
CC:, Michal Zalewski <>,
        Solar Designer <>,
Subject: Re: CVE-2014-6271: remote code execution through bash

On 9/27/14, 10:15 PM, Eric Blake wrote:

> Are you 100% sure that posixly_correct is correctly initialized at this
> point in parsing the incoming environment variables, regardless of
> whether you invoked '/bin/sh', 'bash -o posix', or 'POSIXLY_CORRECT=1
> bash'?  

For POSIXLY_CORRECT: yes.  Very early on in main() the shell looks for
POSIXLY_CORRECT and POSIX_PEDANTIC in the environment and sets
posixly_correct to 1 if either one is found.

For bash -o posix: yes.  Options (including long options like --posix)
are parsed well before the environment is read.

For /bin/sh: no.  As documented, the shell enters posix mode after it
reads the startup files.

``The lyf so short, the craft so long to lerne.'' - Chaucer
		 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU

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