Buffer Management Vulnerability in OpenSSH

[101200] 主题： Buffer Management Vulnerability in OpenSSH

	作者： hace. (hace.)
	标题： Buffer Management Vulnerability in OpenSSH[转载]
	来自： 202.112..
	发贴时间： 2003年09月17日 11:39:29
	长度： 11086字

	发信人：hace.bbs@hace.dhs.org (半边海)，信区：cn.bbs.comp.securi ty 标题：Buffer Management Vulnerability in OpenSSH 发信站：BBS_半边海站转信站：LeafOK!news.zixia.net!news2.happynet.org!hace CERT?Advisory CA-2003-24 Buffer Management Vulnerability in Open SSH Original release date: September 16, 2003 Last revised: -- Source: CERT/CC A complete revision history can be found at the end of this f ile. Systems Affected * Systems running versions of OpenSSH prior to 3.7 * Systems that use or derive code from vulnerable versions of OpenSSH Overview There is a remotely exploitable vulnerability in a general bu ffer management function in versions of OpenSSH prior to 3.7. This may allow a remote attacker to corrupt heap memory which could ca use a denial-of-service condition. It may also be possible for an a ttacker to execute arbitrary code. I. Description A vulnerability exists in the buffer management code of OpenS SH. This vulnerability affects versions prior to 3.7. The error occurs when a buffer is allocated for a large packet. When the buffer is cl eared, an improperly sized chunk of memory is filled with zeros. This l eads to heap corruption, which could cause a denial-of-service condit ion. This vulnerability may also allow an attacker to execute arbitrary code. This vulnerability is described in an advisory from OpenSSH [27]http://www.openssh.com/txt/buffer.adv and in FreeBSD-SA-03:12: [28]ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/advisories/FreeB SD-SA-03 :12.openssh.asc Other systems that use or derive code from OpenSSH may be aff ected. This includes network equipment and embedded systems. We have monitored incident reports that may be related to this vulner ability. Vulnerability Note [29]VU#333628 lists the vendors we contact ed about this vulnerability. The vulnerability note is available from [30]http://www.kb.cert.org/vuls/id/333628 This vulnerability has been assigned the following Common Vulnerabilities and Exposures (CVE) number: [31]http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2003- 0693 II. Impact While the full impact of this vulnerability is unclear, the m ost likely result is heap corruption, which could lead to a denia l of service. If it is possible for an attacker to execute arbitrary code, then they may be able to so with the privileges of the user running the sshd process, typically root. This impact may be limited on system s using the privilege separation (privsep) feature available in OpenS SH. III. Solution Upgrade to OpenSSH version 3.7 This vulnerability is resolved in OpenSSH version 3.7, which is available from the OpenSSH web site at [32]http://www.openssh.com/ Apply a patch from your vendor A patch for this vulnerability is included in the OpenSSH adv isory at [33]http://www.openssh.com/txt/buffer.adv This patch may be manually applied to correct this vulnerabil ity in affected versions of OpenSSH. If your vendor has provided a p atch or upgrade, you may want to apply it rather than using the patch from OpenSSH. Find information about vendor patches in [34]Appendi x A. We will update this document as vendors provide additional infor mation. Use privilege separation to minimize impact System administrators running OpenSSH versions 3.2 or higher may be able to reduce the impact of this vulnerability by enabling t he "UsePrivilegeSeparation" configuration option in th eir sshd configuration file. Typically, this is accomplished by creati ng a privsep user, setting up a restricted (chroot) environment, a nd adding the following line to /etc/ssh/sshd_config: UsePrivilegeSeparation yes This workaround does not prevent this vulnerability from bein g exploited, however due to the privilege separation mechanism, the intruder may be limited to a constrained chroot environment w ith restricted privileges. This workaround will not prevent this vulnerability from creating a denial-of-service condition. No t all operating system vendors have implemented the privilege separ ation code, and on some operating systems it may limit the function ality of OpenSSH. System administrators are encouraged to carefully re view the implications of using the workaround in their environment and use a more comprehensive solution if one is available. The use of p rivilege separation to limit the impact of future vulnerabilities is encouraged. Appendix A. - Vendor Information This appendix contains information provided by vendors for th is advisory. As vendors report new information to the CERT/CC, w e will update this section and note the changes in the revision hist ory. Additional vendors who have not provided direct statements, b ut who have made public statements or informed us of their status ar e listed in [35]VU#333628. If a vendor is not listed below or in [36]V U#333628, we have not received their comments. Bitvise Our software shares no codebase with the OpenSSH implementa tion, therefore we believe that, in our products, this problem do es not exist. Cray, Inc. Cray Inc. supports OpenSSH through its Cray Open Software ( COS) package. Cray is vulnerable to this buffer management error and is in the process of compiling OpenSSH 3.7. The new version wi ll be made available in the next COS release. Debian A fix for the buffer management vulnerability is available for the ssh package at [37]http://www.debian.org/security/2003/dsa- 382 A fix for the ssh-krb5 (ssh with kerberos support) package is available at [38]http://www.debian.org/security/2003/dsa-38 3 Mandrake Software Mandrake Linux is affected and MDKSA-2003:090 will be relea sed today with patched versions of OpenSSH to resolve this issu e. PuTTY PuTTY is not based on the OpenSSH code base, so it should n ot be vulnerable to any OpenSSH-specific attacks. ___________________________________________________________ ______ The CERT/CC thanks Markus Friedl of the OpenSSH project for h is technical assistance in producing this advisory. ___________________________________________________________ ______ Authors: [39]Jason A. Rafail and Art Manion _____________________________________________________________ _________ This document is available from: [40]http://www.cert.org/advisories/CA-2003-24.html _____________________________________________________________ _________ CERT/CC Contact Information Email: [41]cert@cert.org Phone: +1 412-268-7090 (24-hour hotline) Fax: +1 412-268-6989 Postal address: CERT Coordination Center Software Engineering Institute Carnegie Mellon University Pittsburgh PA 15213-3890 U.S.A. CERT/CC personnel answer the hotline 08:00-17:00 EST(GMT-5) / EDT(GMT-4) Monday through Friday; they are on call for emerge ncies during other hours, on U.S. holidays, and on weekends. Using encryption We strongly urge you to encrypt sensitive information sent by email. Our public PGP key is available from [42]http://www.cert.org/CERT_PGP.key If you prefer to use DES, please call the CERT hotline for mo re information. Getting security information CERT publications and other security information are availabl e from our web site [43]http://www.cert.org/ To subscribe to the CERT mailing list for advisories and bull etins, send email to [44]majordomo@cert.org. Please include in the b ody of your message subscribe cert-advisory * "CERT" and "CERT Coordination Center" a re registered in the U.S. Patent and Trademark Office. _____________________________________________________________ _________ NO WARRANTY Any material furnished by Carnegie Mellon University and the Software Engineering Institute is furnished on an "as is" ba sis. Carnegie Mellon University makes no warranties of any kind, either exp ressed or implied as to any matter including, but not limited to, warra nty of fitness for a particular purpose or merchantability, exclusiv ity or results obtained from use of the material. Carnegie Mellon Un iversity does not make any warranty of any kind with respect to freedo m from patent, trademark, or copyright infringement. _____________________________________________________________ _________ [45]Conditions for use, disclaimers, and sponsorship informat ion Copyright 2003 Carnegie Mellon University. Revision History September 16, 2003: Initial release References 1. http://www.cert.org/nav/index.html 2. http://www.cert.org/nav/index_main.html 3. http://www.cert.org/contents/contents.html 4. http://search.cert.org/ 5. http://www.cert.org/contact_cert/ 6. http://www.cert.org/faq/cert_faq.html 7. http://www.cert.org/nav/index_red.html 8. http://www.cert.org/nav/index_green.html 9. http://www.cert.org/nav/index_purple.html 10. http://www.cert.org/nav/index_gold.html 11. http://www.cert.org/advisories 12. http://www.kb.cert.org/vuls/ 13. http://www.cert.org/incident_notes/ 14. http://www.cert.org/current/current_activity.html 15. http://www.cert.org/summaries 16. http://www.cert.org/tech_tips 17. http://www.cert.org/kb/aircert/ 18. http://www.cert.org/jobs 19. http://www.cert.org/stats 20. http://www.kb.cert.org/vuls/html/disclosure 21. http://www.cert.org/kb 22. http://www.cert.org/training 23. http://www.cert.org/training 24. http://www.cert.org/other_sources 25. http://www.cert.org/channels 26. http://www.isalliance.org/ 27. http://www.openssh.com/txt/buffer.adv 28. ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-03: 12.openssh.asc 29. http://www.kb.cert.org/vuls/id/333628 30. http://www.kb.cert.org/vuls/id/333628 31. http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2003-069 3 32. http://www.openssh.com/ 33. http://www.openssh.com/txt/buffer.adv 34. http://www.cert.org/advisories/CA-2003-24.html#vendors 35. http://www.kb.cert.org/vuls/id/333628#systems 36. http://www.kb.cert.org/vuls/id/333628#systems 37. http://www.debian.org/security/2003/dsa-382 38. http://www.debian.org/security/2003/dsa-383 39. mailto:cert@cert.org?subject=CA-2003-24%20Feedback%20VU%23 333628 40. http://www.cert.org/advisories/CA-2003-24.html 41. mailto:cert@cert.org 42. http://www.cert.org/CERT_PGP.key 43. http://www.cert.org/ 44. mailto:majordomo@cert.org 45. http://www.cert.org/legal_stuff.html -- / /__ __ __ __ / / / ) / /__) / / \_/\ \__ \__ ※ 来源:·BBS 半边海站 hace.dhs.org·[FROM: 深海]
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