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-----BEGIN PGP SIGNED MESSAGE----- =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2000.325 -- FreeBSD-SA-00:63 getnameinfo function allows remote denial of service 2 November 2000 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: getnameinfo Vendor: FreeBSD Operating System: FreeBSD BSD Impact: Denial of Service Access Required: Remote - --------------------------BEGIN INCLUDED TEXT-------------------- - -----BEGIN PGP SIGNED MESSAGE----- ============================================================================= FreeBSD-SA-00:63 Security Advisory FreeBSD, Inc. Topic: getnameinfo function allows remote denial of service Category: core Module: libc Announced: 2000-11-01 Credits: Pavel Kankovsky <peak@argo.troja.mff.cuni.cz> Affects: FreeBSD 4.x (all releases prior to 4.2), 4.1.1-STABLE prior to the correction date. Corrected: 2000/09/25 (FreeBSD 4.1.1-STABLE) FreeBSD only: NO I. Background The getnameinfo() function is part of the protocol-independent resolver library from the KAME project. II. Problem Description An off-by-one error exists in the processing of DNS hostnames which allows a long DNS hostname to crash the getnameinfo() function when an address resolution of the hostname is performed (e.g. in response to a connection to a service which makes use of getnameinfo()). Under the following conditions, this bug can be used as a denial of service attack against vulnerable services: * The attacker must control their DNS server. * The service must be run as a persistent daemon (i.e. running "standalone", not spawned as-needed from a supervisor process such as inetd) * The daemon must perform the getnameinfo() call on the remote hostname prior to forking a child process to handle the connection (otherwise it is just the child process which dies, and the parent remains running). * The daemon is not automatically restarted by a "watchdog" process. All released versions of FreeBSD 4.x prior to the correction date including 4.0, 4.1, and 4.1.1 are vulnerable to this problem, but it was fixed in the 4.1.1-STABLE branch prior to the release of FreeBSD 4.2-RELEASE. The FreeBSD 3.x branch is unaffected since it does not include the KAME code. Note that this vulnerability is not believed to pose a vulnerability for any servers included in the FreeBSD base system. It is only a potential problem for certain third party servers fulfilling the above conditions (none of which are currently known). Therefore the impact on the vast majority of FreeBSD systems is expected to be nonexistent. III. Impact Remote users may be able to cause a very small class of network servers to terminate abnormally, causing a denial of service condition. IV. Workaround None practical. V. Solution One of the following: 1) Upgrade your vulnerable FreeBSD 4.x system to 4.1.1-STABLE after the correction date. 2) Apply the patch below and recompile the relevant files: Either save this advisory to a file, or download the patch and detached PGP signature from the following locations, and verify the signature using your PGP utility. ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-00:63/getnameinfo.patch ftp://ftp.freebsd.org/pub/FreeBSD/CERT/patches/SA-00:63/getnameinfo.patch.asc Execute the following commands as root: # cd /usr/src/lib/libc # patch -p < /path/to/patch_or_advisory # make depend && make all install Patch for vulnerable systems: --- net/getnameinfo.c 2000/07/05 05:09:17 1.5 +++ net/getnameinfo.c 2000/09/25 23:04:36 1.6 @@ -154,12 +153,12 @@ (flags & NI_DGRAM) ? "udp" : "tcp"); } if (sp) { - if (strlen(sp->s_name) > servlen) + if (strlen(sp->s_name) + 1 > servlen) return ENI_MEMORY; strcpy(serv, sp->s_name); } else { snprintf(numserv, sizeof(numserv), "%d", ntohs(port)); - if (strlen(numserv) > servlen) + if (strlen(numserv) + 1 > servlen) return ENI_MEMORY; strcpy(serv, numserv); } @@ -253,7 +252,7 @@ *p = ''; } #endif - if (strlen(hp->h_name) > hostlen) { + if (strlen(hp->h_name) + 1 > hostlen) { freehostent(hp); return ENI_MEMORY; } - -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.0.4 (FreeBSD) Comment: For info see http://www.gnupg.org iQCVAwUBOgCgVlUuHi5z0oilAQGqfwP/SYLG0yD0uR4wdPHy5S9eXH4HqtNrVpF7 NlN3iMjHrzIDqeFSYoRTbMEhrbTTGMWYIEadadW9zjlnHfGNRniYx2oOhm+0tqsI C3wlqsGAo2GXsXfr1hOpcVc1GqLhsK3oLgz9RRMoMlRWJ+K0bHHLwKlB9uEoxPJ2 X/WHJ//RQXI= =YFwv - -----END PGP SIGNATURE----- - --------------------------END INCLUDED TEXT-------------------- 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. The decision to use any or all of this information is the responsibility of each user or organisation, and should be done so in accordance with site policies and procedures. NOTE: This is only the original release of the security bulletin. It may not be updated when updates to the original are made. If downloading at a later date, it is recommended that the bulletin is retrieved directly from the original authors to ensure that the information is still current. Contact information for the authors of the original document is included in the Security Bulletin above. If you have any questions or need further information, please contact them directly. 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: auscert@auscert.org.au 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 emergencies. -----BEGIN PGP SIGNATURE----- Version: 2.6.3i Charset: noconv Comment: ftp://ftp.auscert.org.au/pub/auscert/AUSCERT_PGP.key iQCVAwUBOlSNJih9+71yA2DNAQFGJQP8DgoZb/LLJRoWgWLZRsawuAGeLt4bXoKd vcz3FODboHNonCGTFVOuV2ZC/Yuzal+yWSvLB2xQSbKTl0LGPQlNAkJJhjaBXa1b KlDzP1hWYvg2LRYlvOdIH/7PSIOnsJVE3m6baMZCDRxUpTLgiDmYVXJlDNZV9ljl eBNILWLITRc= =Ir/L -----END PGP SIGNATURE-----