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Message-ID: <5424320B.7000107@oracle.com>
Date: Thu, 25 Sep 2014 16:17:31 +0100
From: John Haxby <john.haxby@...cle.com>
To: oss-security@...ts.openwall.com
CC: chet.ramey@...e.edu
Subject: Re: CVE-2014-6271: remote code execution through bash
On 25/09/14 04:01, Chet Ramey wrote:
> On 9/24/14, 9:30 PM, Solar Designer wrote:
>
>>>>>> The bash patch seems incomplete to me, function parsing is still
>>>>>> brittle. e.g. $ env X='() { (a)=>\' sh -c "echo date"; cat echo
There seems to be a wider issue even when we have well-formed functions
coming in, for example,
env rm='() { echo will not; }' bash -c 'rm core'
Well, that's OK, I thought, I'll just start my scripts with
PATH=...
unalias -a
unset -f $(typeset -F)
or something like that. But what if
env unset='() { :; }' bash ...
unset does nothing now.
command unset -f $(typeset -F)
countered with
command='() { eval "$@"; }'
At some stage scripts are going to break, especially if they're relying
on command, but this whole exercise leaves me feeling uneasy. ssh and
sudo both restrict environment variables, but I just tried this:
$ xxx='() { echo hello; }' su
Password:
# xxx
hello
Of course, su isn't affected, but if I drop one of these in for an
overly-trusting admin who runs su on my terminal ...
My feeling is that if you're going to import functions from the
environment then you should do that explicitly either through a switch
(--import?) or a builtin that can import all or selected functions. Or
both.
I worry that simply fixing CVE-2014-6271 and CVE-2014-7129 is just
setting the scene for the next parser problem.
jch
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