bugtraq - Re: Flaw in commonly used bash random seed method

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]

Date: Tue, 4 Apr 2006 09:21:40 +0100
From: Dave English <dave.english@...s.net>
To: bugtraq@...urityfocus.com
Subject: Re: Flaw in commonly used bash random seed method

In message 
<a260a2190604031256g23cf3645s348f829530982b38@...l.gmail.com>, Matthijs 
<thotter@...il.com> writes

>By the way, if the random function can only generate numbers between 0
>and 32767, won't 2 bytes be enough then? The algorithm will perform a
>modulo calculation anyway, so 4 bytes won't really add anything. Of
>course, it is much better then only one byte.

That will depend on whether the state stored between calls to the PRNG 
is only 15-bits, or something larger.

If more state is stored than is enumerated in the result, then the 
generator should have more points on its sequence than 32768 .  In that 
case then, seeding with more than 15 bits would be worthwhile.

I have not looked at Bash myself, to see what it actually does
-- 
Dave English                      Senior Software & Systems Engineer
                              Internet Platform Development, Thus plc

Download attachment "signature.asc" of type "application/pgp-signature" (179 bytes)