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-----BEGIN PGP SIGNED MESSAGE----- =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2002.398 -- NetBSD Security Advisory 2002-010 symlink race in pppd 7 August 2002 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: pppd Vendor: NetBSD Operating System: NetBSD-current: source prior to July 31, 2002 NetBSD-1.6 beta NetBSD-1.5.3 NetBSD-1.5.2 NetBSD-1.5.1 NetBSD-1.5 NetBSD-1.4.* BSD Impact: Overwrite Arbitrary Files Access Required: Existing Account Ref: ESB-2002.380 - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- NetBSD Security Advisory 2002-010 ================================= Topic: symlink race in pppd Version: NetBSD-current: source prior to July 31, 2002 NetBSD-1.6 beta: affected NetBSD-1.5.3: affected NetBSD-1.5.2: affected NetBSD-1.5.1: affected NetBSD-1.5: affected NetBSD-1.4.*: affected Severity: Local user may be able to modify permissions on any file Fixed: NetBSD-current: July 31, 2002 NetBSD-1.6 branch: not yet NetBSD-1.5 branch: not yet NetBSD-1.4 branch: not yet Abstract ======== A race condition exists in the pppd program that may be exploited in order to change the permissions of an arbitrary file. A malicious local user may exploit the race condition to acquire write permissions to a critical system file, and leverage the situation to acquire escalated privileges. Technical Details ================= The file specified as the tty device is opened by pppd, and the permissions are recorded. If pppd fails to initialize the tty device in some way (such as a failure of tcgetattr(3)), then pppd will attempt to restore the original permissions by calling chmod(2). The call to chmod(2) is subject to a symlink race, so that the permissions may be `restored' on some other file. Solutions and Workarounds ========================= The following instructions describe how to upgrade your pppd binaries by updating your source tree and rebuilding and installing a new version of pppd. * NetBSD-current: Systems running NetBSD-current dated from before 2002-07-30 should be upgraded to NetBSD-current dated 2002-07-31 or later. The following directories need to be updated from the netbsd-current CVS branch (aka HEAD): usr.sbin/pppd To update from CVS, re-build, and re-install pppd: # cd src # cvs update -d -P usr.sbin/pppd # cd usr.sbin/pppd # make cleandir dependall # make install * NetBSD 1.6 beta: The advisory will be updated to include instructions to remedy this problem for systems running the NetBSD-1.6 branch. * NetBSD 1.5, 1.5.1, 1.5.2, 1.5.3: The advisory will be updated to include instructions to remedy this problem for systems running the NetBSD-1.5 branch. * NetBSD 1.4, 1.4.1, 1.4.2, 1.4.3: The advisory will be updated to include instructions to remedy this problem for systems running the NetBSD-1.4 branch. Thanks To ========= Jun-ichiro itojun Hagino for patches, and preparing the advisory text. Revision History ================ 2002-08-01 Initial release More Information ================ An up-to-date PGP signed copy of this release will be maintained at ftp://ftp.netbsd.org/pub/NetBSD/security/advisories/NetBSD-SA2002-010.txt.asc Information about NetBSD and NetBSD security can be found at http://www.NetBSD.ORG/ and http://www.NetBSD.ORG/Security/. Copyright 2002, The NetBSD Foundation, Inc. All Rights Reserved. $NetBSD: NetBSD-SA2002-010.txt,v 1.7 2002/08/01 17:44:51 wiz Exp $ - -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.6 (NetBSD) Comment: For info see http://www.gnupg.org iQCVAwUBPUk71D5Ru2/4N2IFAQFCLQQAhDzwXJacgTYJWlRGW56aFZuZE/5pyHh+ ccbWNS2ZwlpGEn7ucjlnEgRIN03VL3V4u3+N1HNXC2pb4gdqArP/6KcHMInydYIQ X1BnXCL7xPG8hCrRzy9uorKeL+bgowC+uvPOUErW3y1LfPWhNQTNAjyHVIp5PFxS zGHd/4U+aSI= =otzW - -----END PGP SIGNATURE----- - --------------------------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. This security bulletin is provided as a service to AusCERT's members. 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Previous advisories and external security bulletins can be retrieved from: http://www.auscert.org.au/Information/advisories.html If you believe that your system has been compromised, contact AusCERT or your representative in FIRST (Forum of Incident Response and Security Teams). Internet Email: firstname.lastname@example.org Facsimile: (07) 3365 7031 Telephone: (07) 3365 4417 (International: +61 7 3365 4417) AusCERT personnel answer during Queensland business hours which are GMT+10:00 (AEST). On call after hours for member emergencies only. -----BEGIN PGP SIGNATURE----- Version: 2.6.3i Charset: noconv Comment: ftp://ftp.auscert.org.au/pub/auscert/AUSCERT_PGP.key iQCVAwUBPVEOhCh9+71yA2DNAQEOIAP+Ivd7RPfsYlm8HHRnwwfqVMzfOA1fic/4 jsLLESrj2Y1wgYCqMCAPy+qsdGwjS+rpCB8CkliivcrqUGIv+hFwEHCA/+6yYPs6 PxpvXRk79hCtlFk5Pkygr13kleZ0JlodwZ6ApyN0Xr5GMAxClXN49NqQfXY/s11Y Oy9Z6EgkzLc= =QkHX -----END PGP SIGNATURE-----