Re: PATCH: tcp rfc 2385 security/bugfix for sparc64

[David Miller <davem@davemloft.net>]

From: "Peter Lieven" <pl@dlh.net>
Date: Fri, 28 Sep 2007 22:42:25 +0200 (CEST)

> TCP MD5 signatures on sparc64 (big-endian) completely fail on current
> kernel releases in interoperability with Cisco/Foundry or other
> little-endian linux systems.
> 
> The root cause is a cast in the return statement of tcp_v4_md5_do_lookup,
> where a tcp4_md5sig_key is casted onto tcp_md5sig_key without proper
> conversion. On little-endian systems the upper 8 bits are cut of which
> yields the expected behaviour. However, on big-endian systems (like
> sparc64) only the most significant 8 bits are preserved. Since
> TCP_MD5SIG_MAXKEYLEN is 80, this always yields 0.
> 
> In the calculation of the md5 signature afterwards the key is therefore
> not appended to the tcp segment which could result in a security problem
> since only the presence of a md5 signature is checked, and the key itself
> doesn't matter.

Thanks for finding this bug.

> --- linux.old/include/net/tcp.h 2007-09-28 21:43:26.000000000 +0200 +++
> linux/include/net/tcp.h     2007-09-28 21:45:35.000000000 +0200 @@ -1055,6
> +1055,7 @@ static inline void clear_all_retrans_hin

I'll have to apply this patch by hand because your email client
completely corrupted the patch.

> Signed-off-by: Peter Lieven <pl@dlh.net>
> Signed-off-by: Matthias M. Dellweg <2500@gmx.de>

Thanks again.