netdev - Re: [RESEND][PATCH 1/3] PPPoE: improved hashing routine

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20070731090159.GB12071@florz.florz.dyndns.org>
Date:	Tue, 31 Jul 2007 11:01:59 +0200
From:	Florian Zumbiehl <florz@...rz.de>
To:	David Miller <davem@...emloft.net>
Cc:	mostrows@...thlink.net, netdev@...r.kernel.org
Subject: Re: [RESEND][PATCH 1/3] PPPoE: improved hashing routine

Hi,

> > Erm, I'd say this not only produces different results than the old
> > version, but it also produces "wrong" results, in that it ignores quite
> > a bit of the data that's supposed to be hashed. If I didn't overlook
> > something, it only considers addr&0x0f0f0f0f0f00 and sid&0x0f0f, given
> > the right endianness of addr and that PPPOE_HASH_SIZE stays 16.
> 
> You're right, I need to fix the shifts up.  How does this version
> look?
> 
> 	hash ^= (hash >> 4) ^ (hash >> 12) ^ (hash >> 20);
> 	return (head ^ (hash >> 8) ^ (hash >> 24)) &
> 		(PPPOE_HASH_SIZE - 1);

Assuming that it was supposed to read s/head/hash/: Same disclaimers
apply, but I'd say this considers only addr&0xff0fff0f000f and
sid&0x0fff, so, well, yes, it's better, but still not quite what I
think it should be ;-)

> Actually it might be simpler and more efficient to just make
> PPPOE_HASH_SHIFT be 8.

SHIFT? SIZE? BITS?

Florian
-
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html