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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2005.0015 -- Exim security advisory Two Exim vulnerabilities - SPA authentication and IPv6 address parsing 7 January 2005 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: Exim 4.43 and prior Operating System: UNIX variants Linux variants Impact: Execute Arbitrary Code/Commands Increased Privileges Access: Remote/Unauthenticated CVE Names: CAN-2005-0021 CAN-2005-0022 Original Bulletin: http://www.exim.org/mail-archives/exim-announce/2005/msg00000.html - --------------------------BEGIN INCLUDED TEXT-------------------- Two relatively minor (IMHO) security issues in Exim were raised over the Christmas break. The patches below address them for the 4.43 release. The same patches will probably easily retrofit onto quite a number of prior releases. I have also put these fixes into the current source, and made a new snapshot for testing in ftp://ftp.csx.cam.ac.uk/pub/software/email/exim/Testing/exim-snapshot.tar.gz ftp://ftp.csx.cam.ac.uk/pub/software/email/exim/Testing/exim-snapshot.tar.gz.sig In addition to the security patches, this snapshot contains some bug fixes and tidies that were reported by testers of the previous snapshot. Discussion of security issues - ----------------------------- 1. The function host_aton() can overflow a buffer if it is presented with an illegal IPv6 address that has more than 8 components. The input to this function is supposed to be checked; the report said that an unchecked value could be passed via the command line (without specifying which command line option, annoyingly). I found one such case, which was a call do a dnsdb lookup for a PTR record, as part of testing expansions using -be. The first patch below fixes this - as it happens, this change had already been made to the current source. The report stated that Exim was running as "exim" when the problem occurred: with -be, Exim runs as the calling user. Therefore, either the report was wrong, or there is another case that I could not find. However, if there is another case, it will now be covered by the second patch below, which puts a test into the host_aton() function itself. (This should, of course, have been there all the time, as a bit of defensive programming, but hey, I'm only human. :-) 2. The second report described a buffer overflow in the function spa_base64_to_bits(), which is part of the code for SPA authentication. This code originated in the Samba project. The overflow can be exploited only if you are using SPA authentication. The remaining patches below fix this problem by adding a buffer length parameter to the problem function. I have tested that SPA authentication still works, but I don't have the tools to test that an attempt to exploit the overflow is now detected. - -- Philip Hazel University of Cambridge Computing Service, ph10@xxxxxxxxxxxxx Cambridge, England. Phone: +44 1223 334714. - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. The mailing list you are subscribed to is maintained within your organisation, so if you do not wish to continue receiving these bulletins you should contact your local IT manager. If you do not know who that is, please send an email to email@example.com and we will forward your request to the appropriate person. NOTE: Third Party Rights This security bulletin is provided as a service to AusCERT's members. As AusCERT did not write the document quoted above, AusCERT has had no control over its content. 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On call after hours for member emergencies only. =========================================================================== -----BEGIN PGP SIGNATURE----- Comment: http://www.auscert.org.au/render.html?it=1967 iQCVAwUBQd3qJyh9+71yA2DNAQKWWwQAj5yRhzj9KynYXkGNd37ve6+VPENysT/w P1hwejt2UN6rstBd5hy5iINjdSxZVBeNJFKiDmFvvYuXWCb/kzqdFju09a+8Qxr5 oKc+RSjWSpD2hxmtN++ZrVi7viUjdN8X+k1TxBnQfikNjSWDGk6qi1bRvIV1R+2c Oywyg6EAv30= =Kcgz -----END PGP SIGNATURE-----