From owner-freebsd-security Fri Jan 7 12:53:22 2000 Delivered-To: freebsd-security@freebsd.org Received: from bg.sics.se (bg.sics.se [193.10.66.124]) by hub.freebsd.org (Postfix) with ESMTP id 96F6914DE1; Fri, 7 Jan 2000 12:53:18 -0800 (PST) (envelope-from bg@bg.sics.se) Received: (from bg@localhost) by bg.sics.se (8.9.3/8.9.3) id VAA05066; Fri, 7 Jan 2000 21:53:10 +0100 (CET) (envelope-from bg) To: Dag-Erling Smorgrav , Brian Fundakowski Feldman Cc: Markus Friedl , security@FreeBSD.ORG Subject: Re: OpenSSH protocol 1.6 proposal References: From: Bjoern Groenvall Date: 07 Jan 2000 21:53:09 +0100 In-Reply-To: Dag-Erling Smorgrav's message of 06 Jan 2000 14:50:39 +0100 Message-ID: Lines: 39 X-Mailer: Red Gnus v0.52/Emacs 19.34 Sender: owner-freebsd-security@FreeBSD.ORG Precedence: bulk X-Loop: FreeBSD.org Dag-Erling Smorgrav writes: > Brian Fundakowski Feldman writes: > > I've been thinking what the best way to make OpenSSH more secure would be, > > and now it seems to be a change in the protocol. What change? Well, > > SSH version 1.5 and below (all versions so far) have been vulnerable to > > attacks based upon properties of the highly insecure CRC32 hash used. > > Which part of "ssh 1.2.25 fixes the problem" did you not understand? Markus Friedl writes: > 1.2.25 et al do not fix the problem, they just make > attacks a little bit harder. Also remember that the SSH_3DES scheme resists the attack described by Futoranski et.al. The attack is effective against IDEA_CFB, DES_CBC or in general any block cipher that uses CBC or CFB. Currently there is no known attack that is effective when the somewhat weird feedback mode of SSH_3DES is used. So if you are looking for a temporary solution to the SSHv1 problem, disable all ciphers but SSH_3DES. Unlike the attack detector in 1.2.25++, this solution will always resist the Futoranski attack. This does not imply that the SSH_3DES mode is secure, only that there currently has been no published method of attack. In the long run we still need a new packet format. Cheers, Björn -- _ _ ,_______________. Bjorn Gronvall (Björn Grönvall) /_______________/| Swedish Institute of Computer Science | || PO Box 1263, S-164 29 Kista, Sweden | Schroedingers || Email: bg@sics.se, Phone +46 -8 633 15 25 | Cat |/ Cellular +46 -70 768 06 35, Fax +46 -8 751 72 30 `---------------' To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-security" in the body of the message