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Re: The restricted shell can be easily circumvented.


From: Pierre Gaston
Subject: Re: The restricted shell can be easily circumvented.
Date: Sat, 4 Apr 2015 17:23:21 +0300



On Sat, Apr 4, 2015 at 8:22 AM, David Bonner <address@hidden> wrote:
Bash Bug Report

Configuration Information [Automatically generated, do not change]:
Machine: x86_64
OS: linux-gnu
Compiler: gcc
Compilation CFLAGS:  -DPROGRAM='bash' -DCONF_HOSTTYPE='x86_64' -DCONF_OSTYPE='linux-gnu' -DCONF_MACHTYPE='x86_64-pc-linux-gnu' -DCONF_VENDOR='p$
uname output: Linux LFS-BUILD 3.16.0-23-generic #31-Ubuntu SMP Tue Oct 21 17:56:17 UTC 2014 x86_64 x86_64 x86_64 GNU/Linux
Machine Type: x86_64-pc-linux-gnu

Bash Version: 4.3
Patch Level: 30
Release Status: release

Description:
        The restricted shell opened by calling rbash or bash with the -r or --restricted option can be easily circumvented with the
        command 'chroot / bash' making the restricted shell useless because anyone can get out of it with this command.

Repeat-By:
        1:Open a restricted shell
        2:Test with 'cd ..'
        3:Use 'chroot / bash'
        4:Test that you are no longer restricted with 'chroot / bash'


This has already been discussed in the mailing list, you should be able to find previous discussions about this and the fact that bash -r is not an all inclusive solution (eg https://lists.gnu.org/archive/html/bug-bash/2012-01/msg00048.html ) .

However your example is not a very convincing one, you cannot use "cd" with a restricted shell, so it's not clear what you are really using and it is obvious that many commands will allow to not be restricted if they are made available.
 


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