Bugtraq mailing list archives
Re: qmail starttls patch does not seed the random number generator
From: Brian Hatch <bugtraq () ifokr org>
Date: Wed, 15 Aug 2001 10:56:37 -0500
openssl-0.9.6b does not allow ssl/tls connections when the random number has not been seeded. This is a good idea, and it exposes that the starttls patch for qmail does not seed the random number generator. Here is a small patch that fixes the problem in qmail-remote for systems that support /dev/urandom (the same can be done for qmail-smtpd but I can't test it right now). Not seeding the random number generator is a serious bug and it completely compromises the cryptographic privacy of TLS encrypted emails.
Not seeding the PRNG is a serious error. However OpenSSL should seed from /dev/urandom automatically without even calling RAND_seed: OpenSSL makes sure that the PRNG state is unique for each thread. On systems that provide /dev/urandom, the randomness device is used to seed the PRNG transparently. However, on all other systems, the application is responsible for seeding the PRNG by calling RAND_add(), RAND_egd(3) or RAND_load_file(3). So the question becomes *why* is in not seeding from /dev/urandom on it's own? Also you should make sure to check the return values in your code -- on systems with no /dev/urandom you will seed with 32-64 bytes of non-random data instead, giving the appearance of security where this is none. You may want to check out the RAND_egd() function which can be used to seed from a PRNG daemon. If you want to look at some rather long winded but thougrough PRNG-seeding code, see the initialize_prng function (in ssl.c) in the Stunnel source code. -- Brian Hatch Linux is like wigwam - Systems and no windows, no gates, Security Engineer apache inside. www.hackinglinuxexposed.com Every message PGP signed
Attachment:
_bin
Description:
Current thread:
- qmail starttls patch does not seed the random number generator Felix von Leitner (Aug 15)
- Re: qmail starttls patch does not seed the random number generator Wojciech Purczynski (Aug 15)
- Re: qmail starttls patch does not seed the random number generator Jack Lloyd (Aug 15)
- Re: qmail starttls patch does not seed the random number generator Scott Renfro (Aug 16)
- Re: qmail starttls patch does not seed the random number generator D. J. Bernstein (Aug 19)
- Re: qmail starttls patch does not seed the random number generator Jack Lloyd (Aug 15)
- Re: qmail starttls patch does not seed the random number generator Brian Hatch (Aug 15)
- Re: qmail starttls patch does not seed the random number generator Frederik Vermeulen (Aug 16)
- Re: qmail starttls patch does not seed the random number generator Wojciech Purczynski (Aug 15)