Date: Sat, 22 Mar 2014 19:35:08 +0100 From: Gert Doering Message-ID: <20140322183508.GZ16637@...1296...> References: <1395017376-24554-1-git-send-email-james@...515...> <20140317202910.GM16637@...1296...> <532775DD.4050106@...515...> <1CED409804E2164C8104F9E623B08B90155646D4C1@...1436...> <53281720.2050504@...1147...> <5328463F.7090704@...1114...> <53284DA8.1010709@...1147...> <1CED409804E2164C8104F9E623B08B9016F95AD5DC@...1436...> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="kivFfCkDq2bCCRcA" Content-Disposition: inline In-Reply-To: <1CED409804E2164C8104F9E623B08B9016F95AD5DC@...1436...> Subject: Re: [Openvpn-devel] [PATCH] Set SSL_OP_NO_TICKET flag in SSL context for OpenSSL builds, to disable TLS stateless session resumption. List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Steffan Karger Cc: "openvpn-devel@lists.sourceforge.net" --kivFfCkDq2bCCRcA Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: quoted-printable Content-Disposition: inline Hi, On Tue, Mar 18, 2014 at 05:40:41PM +0100, Steffan Karger wrote: > > So it seems I spoke too soon... sorry for the noise, although I must > > say that I'm still in favour of checking for the existence of an IFDEF > > instead of relying on a particular version... >=20 > Point taken, just checking the OpenSSL version does not suffice. > Still, I'd like to prevent more #ifdef's in the code. We could > check the #ifdef in configure.ac, and refuse to build when it's > not present. Any objections against requiring SSL_OP_NO_TICKET to > be present for OpenVPN 2.4+? We have to drop support for 'ancient > stuff' at some point. If I understood this all right, this feature improves OpenVPN security against yet-unknown attacks using a feature of OpenSSL that we don't use anyway. Right? So in that case, I'm fine with your proposal - do something on configure.ac that will check for SSL_OP_NO_TICKET and complain (with a useful error message :) ) if it's not there. For 2.3, I'd propose to add code to ssl_openssl.h like this: /* SSL_OP_NO_TICKET tells OpenSSL to disable "stateless session resumption", * as this is something we do not want nor need, but could potentially be * used for a future attack. For compatibility reasons, in the 2.3.x=20 * series, we keep building if the OpenSSL version is too old to support * this. 2.4 requires it and will fail configure if not present. */ #ifndef SSL_OP_NO_TICKET # define SSL_OP_NO_TICKET 0 #endif ACK? Is the message correct? gert --=20 USENET is *not* the non-clickable part of WWW! //www.muc.de/~ge= rt/ Gert Doering - Munich, Germany gert@...1296... fax: +49-89-35655025 gert@...1297... --kivFfCkDq2bCCRcA Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.13 (NetBSD) iQCVAwUBUy3X26kuBuNlUUl1AQKBDwP/XvQQJqNq+H+V8kNXVeOYajlBSWltMAlh ajnPJZUqdYZ6X8QFBm6Vn3Jgmjc5Rfe1NxfN6cr51jzKNvUFzqFRiCaQJ9xHNaPI 2J/P6jIELl+z4CzmT2w6s/o5cDzUMvJ4h/rpMd4EiqS/p78Y9wlHV2yFD/3ZJO/7 z+Ao++RqynA= =1WcC -----END PGP SIGNATURE----- --kivFfCkDq2bCCRcA--