---------- Forwarded message ---------- Date: Thu, 14 May 1998 21:58:14 +0200 (MET DST) From: FreeBSD Security Officer <security-officerat_private> To: undisclosed-recipients:;@FreeBSD.ORG Subject: FreeBSD Security Advisory: FreeBSD-SA-98:03.ttcp -----BEGIN PGP SIGNED MESSAGE----- ============================================================================= FreeBSD-SA-98:03 Security Advisory FreeBSD, Inc. Topic: Problems with TTCP Category: core Module: kernel Announced: 1998-05-14 Affects: FreeBSD 2.1.* FreeBSD 2.2.*, FreeBSD-stable before 1998/05/14 and FreeBSD-current before 1998/05/05 suffer from this problem. Corrected: FreeBSD-3.0-current as of 1998/05/14 FreeBSD-2.2-stable as of 1998/05/05 FreeBSD only: No. Any other system incorporating TTCP extentions may be affected. Patches: ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-98:03/ I. Background RFC 1644 provides an extension to TCP called TCP Extensions for Transactions, or shortly T/TCP. It provides a way of bypassing the standard three-way handshake found in TCP, thus speeding up transactions. T/TCP has been incorporated in FreeBSD since FreeBSD 2.0.5. II. Problem Description An accelerated open is initiated by a client by sending a new TCP option, called CC, to the server. The kernel keeps a special cache for each host it communicated with, among others containing the value of the last CC option used by the client. A new accelerated open is allowed when the CC sent is larger than the one in the per-host cache. Thus one can spoof complete connections. III. Impact The hole can be used to obtain unauthorized acces to the system by spoofing connections to the r*-services. This can only be done in the case where an .rhost file and/or a host.equiv file is used as the sole method of authentication. IV. Workaround Disable all r-* services. Note that setting the kernel variable net.inet.tcp.rfc1644 to 0 does not solve the problem. This variable controls whether the system will initiate rfc1644 based connections and does not affect the ability to receive such connections. V. Solution Apply the following patch, rebuild your kernel, install it and reboot your system. the patch is valid for 2.2.* as well as 2.2-stable and 3.0-current systems. The patch below can be found on ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-98:03/ Index: tcp_input.c =================================================================== RCS file: /home/cvsup/freebsd/CVS/src/sys/netinet/tcp_input.c,v retrieving revision 1.74 retrieving revision 1.75 diff -u -r1.74 -r1.75 --- tcp_input.c 1998/04/24 10:08:57 1.74 +++ tcp_input.c 1998/05/04 17:59:52 1.75 @@ -680,7 +680,9 @@ * - otherwise do a normal 3-way handshake. */ if ((to.to_flag & TOF_CC) != 0) { - if (taop->tao_cc != 0 && CC_GT(to.to_cc, taop->tao_cc)) { + if (tp->t_state & TF_NOPUSH && + taop->tao_cc != 0 && CC_GT(to.to_cc, taop->tao_cc)) { + taop->tao_cc = to.to_cc; tp->t_state = TCPS_ESTABLISHED; ============================================================================= FreeBSD, Inc. Web Site: http://www.freebsd.org/ Confidential contacts: security-officerat_private Security notifications: security-notificationsat_private Security public discussion: freebsd-securityat_private PGP Key: ftp://ftp.freebsd.org/pub/FreeBSD/CERT/public_key.asc Notice: Any patches in this document may not apply cleanly due to modifications caused by digital signature or mailer software. Please reference the URL listed at the top of this document for original copies of all patches if necessary. ========================================================================= -----BEGIN PGP SIGNATURE----- Version: 2.6.2 iQCVAwUBNVtEuVUuHi5z0oilAQGIqQP9FTHxJWljLSFskaF34/GvPBfCuxiJdxPo LLPG3GF2NsUFYSwuj5PnM61n6ByX9Ryoq/FO5kXr6nF6gOt3H+1YbgCUmWfpx5aN GFRdanUzuVJ7ipusehwmgULMXknaDJksV+j7VyaYfa0VheYwbMXKkzdG03/0kioz 2Scwf+BJ8CI= =F0vQ -----END PGP SIGNATURE----- To Unsubscribe: send mail to majordomoat_private with "unsubscribe security" in the body of the message
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