From owner-freebsd-security@FreeBSD.ORG Tue Jun 26 11:01:13 2012 Return-Path: Delivered-To: freebsd-security@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [69.147.83.52]) by hub.freebsd.org (Postfix) with ESMTP id 97A64106566B for ; Tue, 26 Jun 2012 11:01:13 +0000 (UTC) (envelope-from des@des.no) Received: from smtp.des.no (smtp.des.no [194.63.250.102]) by mx1.freebsd.org (Postfix) with ESMTP id 54DBA8FC14 for ; Tue, 26 Jun 2012 11:01:13 +0000 (UTC) Received: from ds4.des.no (smtp.des.no [194.63.250.102]) by smtp.des.no (Postfix) with ESMTP id BA8B76E29; Tue, 26 Jun 2012 11:01:12 +0000 (UTC) Received: by ds4.des.no (Postfix, from userid 1001) id 89D838C33; Tue, 26 Jun 2012 13:01:12 +0200 (CEST) From: =?utf-8?Q?Dag-Erling_Sm=C3=B8rgrav?= To: RW References: <86zk7sxvc3.fsf@ds4.des.no> <20120625023104.2a0c7627@gumby.homeunix.com> <86pq8nxtjp.fsf@ds4.des.no> <20120625223807.4dbeb91d@gumby.homeunix.com> Date: Tue, 26 Jun 2012 13:01:12 +0200 In-Reply-To: <20120625223807.4dbeb91d@gumby.homeunix.com> (RW's message of "Mon, 25 Jun 2012 22:38:07 +0100") Message-ID: <86sjdiwd53.fsf@ds4.des.no> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.3 (berkeley-unix) MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Cc: freebsd-security@freebsd.org Subject: Re: Hardware potential to duplicate existing host keys... RSA DSA ECDSA was Add rc.conf variables... X-BeenThere: freebsd-security@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: "Security issues \[members-only posting\]" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 26 Jun 2012 11:01:13 -0000 RW writes: > Dag-Erling Sm=C3=B8rgrav writes: > > [host keys] are used for authentication only. This is crypto 101. > It also generates a shared secret for key exchange, which is pretty > much what I said. No. It is used to *sign* the key exhange, in order to authenticate the server. It is not used to *generate* the key. You need to read up on Diffie Hellman and the SSH transport layer (RFC 4253). The only way to intercept the key is a man-in-the-middle attack (negotiate a KEX with the client, sign it with the stolen host key, and negotiate a KEX with the server, pretending to be the client) > > Having a copy of the host key allows you to do one thing and one thing > > only: impersonate the server. It does not allow you to eavesdrop on > > an already-established connection. > It enables you to eavesdrop on new connections, and eavesdroppers > are often in a position to force reconnection on old ones. No. DES --=20 Dag-Erling Sm=C3=B8rgrav - des@des.no