linux-kernel - Re: [PATCH] Audit: fix handling of 'strings' with NULL characters

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Message-Id: <20080911170920.e88e7bc5.akpm@linux-foundation.org>
Date:	Thu, 11 Sep 2008 17:09:20 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Eric Paris <eparis@...hat.com>
Cc:	linux-audit@...hat.com, linux-kernel@...r.kernel.org,
	viro@...iv.linux.org.uk, jdennis@...hat.com, mitr@...hat.com,
	sgrubb@...hat.com
Subject: Re: [PATCH] Audit: fix handling of 'strings' with NULL characters

On Thu, 11 Sep 2008 17:48:39 -0400
Eric Paris <eparis@...hat.com> wrote:

> currently audit_log_n_untrustedstring() uses
> audit_string_contains_control() to check if the 'string' has any control
> characters.  If the 'string' has an embedded NULL
> audit_string_contains_control() will return that the data has no control
> characters and will then pass the string to audit_log_n_string with the
> total length, not the length up to the first NULL.  audit_log_n_string
> does a memcpy of the entire length and so the actual audit record
> emitted may then contain a NULL and then whatever random memory is after
> the NULL.
> 
> Since we want to log the entire octet stream (if we can't trust the data
> to be a string we can't trust that a NULL isn't actually a part of it)
> we should just consider NULL as a control character.  If the caller is
> certain they want to stop at the first NULL they should be using
> audit_log_untrustedstring.
> 
> Signed-off-by: Eric Paris <eparis@...hat.com>
> 
> ---
> 
> Miloslav, this is also going to take care of nulls in the TTY_AUDIT_USER
> message from userspace.  Is it going to be common to have control
> characters on that code path as well?  Do you want to change
> audit_receive_msg() to also use the hex encoding directly instead of the
> _n_untrustedstring interface?

OK, I am now officially confused about the relationship between this
patch, Miloslav's two patches and 2.6.27/2.6.26/2.6.25.

Think I'll go into hiding for a while - please wake us up when it's all
sorted out.

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