Full Disclosure mailing list archives
Re: Working exploit for Debian generated SSH Keys
From: "Garrett M. Groff" <groffg () gmgdesign com>
Date: Tue, 20 May 2008 08:49:58 -0400
-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 Yep, agreed. - - G Salut, Garrett, On Mon, 19 May 2008 13:51:29 -0400, Garrett M. Groff wrote:
Generating pseudo-random numbers isn't hard given a good API, but writing that API is non-trivial (assuming you want high entropy/low predictability). And, apparently, screwing up that API is also very easy.
Generating real pseudo-random streams is a hard problem which is way more than what people can handle. Usually, PRNGs are composed of various periodic elements which, in the end, all combined produce a repeating stream of pseudo-random numbers. OpenSSL uses a modified MAC for this as a state machine and extracts some state bits as random stream on every access. We're not debating the PRNG itself here but the _seed_. OpenSSL supports various ways to influence the state of the PRNG at various stages by XORing in new material; however, Debian chose to only support pre-seeding with uninitialized memory and the Process ID. With the elimination of the uninitialized memory as seed, the seed for the MAC was entirely comprised by the PID. So we're not debating a weakness in the PRNG here at all, which is a _very_ delicate subject. Tonnerre - -- SyGroup GmbH Tonnerre Lombard Solutions Systematiques Tel:+41 61 333 80 33 Güterstrasse 86 Fax:+41 61 383 14 67 4053 Basel Web:www.sygroup.ch tonnerre.lombard () sygroup ch -----BEGIN PGP SIGNATURE----- Version: PGP Desktop 9.6.2 (Build 2014) - not licensed for commercial use: www.pgp.com wj8DBQFIMsjuSGIRT5oVahwRAlLrAJ9O7/osiw1tbwq7tjWPV0jjn/53dQCgwjik IZ7FHvEZJsdKXiRkRvE5uN4= =/qAR -----END PGP SIGNATURE----- _______________________________________________ Full-Disclosure - We believe in it. Charter: http://lists.grok.org.uk/full-disclosure-charter.html Hosted and sponsored by Secunia - http://secunia.com/
Current thread:
- Re: Working exploit for Debian generated SSH Keys, (continued)
- Re: Working exploit for Debian generated SSH Keys bob harley (May 18)
- Re: Working exploit for Debian generated SSH Keys Fredrick Diggle (May 18)
- Re: Working exploit for Debian generated SSH Keys reepex (May 18)
- Re: Working exploit for Debian generated SSH Keys Ronald van der Westen (May 19)
- Re: Working exploit for Debian generated SSH Keys nicolas vigier (May 19)
- Re: Working exploit for Debian generated SSH Keys Skratz0r (May 19)
- Re: Working exploit for Debian generated SSH Keys Garrett M. Groff (May 19)
- Re: Working exploit for Debian generated SSH Keys Tonnerre Lombard (May 20)
- Re: Working exploit for Debian generated SSH Keys Michael Holstein (May 20)
- Re: Working exploit for Debian generated SSH Keys Tonnerre Lombard (May 23)
- Re: Working exploit for Debian generated SSH Keys Garrett M. Groff (May 20)
- Re: Working exploit for Debian generated SSH Keys Valdis . Kletnieks (May 20)
- Re: Working exploit for Debian generated SSH Keys bob harley (May 18)