Date: Mon, 18 May 1998 19:40:41 +0200 (MET DST) From: FreeBSD Security Officer <security-officer@FreeBSD.ORG> To: undisclosed-recipients:; Subject: FreeBSD Security Advisory: FreeBSD-SA-98:03.ttcp REVISED Message-ID: <199805181740.TAA07658@gvr.gvr.org>
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-----BEGIN PGP SIGNED MESSAGE----- WARNING: The patch given in the original advisory had an error. You should apply the patch in this advisory. In order to do so, you should have the original file. If you do no longer have the original, look at ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-98:03/ttcp.orig It contains the original patch. You should then apply it first using patch with the -R option. We're sorry for any inconvenience this may cause. This advisory also contains a valid patch for FreeBSD 2.1.* versions. ============================================================================= FreeBSD-SA-98:03 Security Advisory FreeBSD, Inc. Topic: Problems with TTCP Category: core Module: kernel Announced: 1998-05-14, revised at 1998-05-18 Affects: FreeBSD 2.1.* FreeBSD 2.2.*, FreeBSD-2.2-stable before 1998/05/14 and FreeBSD-3.0-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-2.1-stable as of 1998/05/18 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 2.1.* systems, for 2.1-stable, for 2.2.* systems, for 2.2-stable and for 3.0-current. 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/ncvs/src/sys/netinet/tcp_input.c,v retrieving revision 1.74 retrieving revision 1.77 diff -u -r1.74 -r1.77 --- tcp_input.c 1998/04/24 10:08:57 1.74 +++ tcp_input.c 1998/05/18 17:11:24 1.77 @@ -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_flags & TF_NOPUSH) != 0) && + 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-officer@freebsd.org Security notifications: security-notifications@freebsd.org Security public discussion: freebsd-security@freebsd.org 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: 2.6.3ia Charset: noconv iQCVAwUBNWBwolUuHi5z0oilAQFXGwP9FhHKXkdktCGBQ3cfP4pHBmDHGFPwFL/E zcF05EFSxKR8Fw62b9zQw9vws1FN9L0ZXJjxVAFx7umSYnYqPrxFBgzzLs1Brfbh G4c+br73C9RsN6yyTo6Am7TxBiCFtRfneS91jZQGpNfZcFWx84oy5hhmTLXaaJK7 qIdrquhtTSo= =qxDF -----END PGP SIGNATURE----- This is the moderated mailing list freebsd-announce. The list contains announcements of new FreeBSD capabilities, important events and project milestones. See also the FreeBSD Web pages at http://www.freebsd.org To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-announce" in the body of the message
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