-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 HP SECURITY BULLETIN HPSBTU01210 REVISION: 1 SSRT4743, SSRT4884 rev.1 - HP Tru64 UNIX TCP/IP remote Denial of Service (DoS) NOTICE: The information in this Security Bulletin should be acted upon as soon as possible. INITIAL RELEASE: 04 October 2005 POTENTIAL SECURITY IMPACT: Remote Denial of Service (DoS) SOURCE: Hewlett-Packard Company HP Software Security Response Team VULNERABILITY SUMMARY: Several potential security vulnerabilities have been identified in the HP Tru64 UNIX TCP/IP including ICMP, and Initial Sequence Number generation (ISNs). These exploits could result in a remote Denial of Service (DoS) from network throughput reduction for TCP connections, the reset of TCP connections, or TCP spoofing. REFERENCES: CERT CA-2001-09, NISCC Vulnerability Advisory VU#498440 VU#532967, CAN-2004-0790 CAN-2004-0791 CAN-2004-1060 CAN-2001-0328 SUPPORTED SOFTWARE VERSIONS*: ONLY impacted versions are listed. HP Tru64 UNIX 5.1B-3 HP Tru64 UNIX 5.1B-2/PK4 HP Tru64 UNIX 5.1A PK HP Tru64 UNIX 4.0G PK4 HP Tru64 UNIX 4.0F PK8 BACKGROUND: Special Instructions for the Customer The Internet Control Message Protocol (ICMP) (RFC 792) is used in the Internet Architecture to perform fault-isolation and recovery (RFC816), which is the group of actions that hosts and routers take to determine if a network failure has occurred. The industry standard TCP specification (RFC 793) has a vulnerability whereby ICMP packets can be used to perform a variety of attacks such as blind connection reset attacks and blind throughput-reduction attacks. Blind connection reset attacks can be triggered by an attacker sending forged ICMP "Destination Unreachable, host unreachable" packets or ICMP "Destination Unreachable, port unreachable" packets. Blind throughput-reduction attacks can be caused by an attacker sending a forged ICMP type 4 (Source Quench) packet. Path MTU Discovery (RFC 1191) describes a technique for dynamically discovering the MTU (maximum transmission unit) of an arbitrary internet path. This protocol uses ICMP packets from the router to discover the MTU for a TCP connection path. An attacker can reduce the throughput of a TCP connection by sending forged ICMP packets (or their IPv6 counterpart) to the discovering host, causing an incorrect Path MTU setting. HP has addressed these potential vulnerabilities by providing a new kernel tunable in Tru64 UNIX V5.1B and 5.1A, icmp_tcpseqcheck. In Tru64 4.0F and 4.0G, HP has introduced two new kernel tunables, icmp_tcpseqcheck and icmp_rejectcodemask. The icmp_rejectcodemask tunable is already available in Tru64 UNIX V5.1B and 5.1A. icmp_tcpseqcheck The icmp_tcpseqcheck variable mitigates ICMP attacks against TCP by checking that the TCP sequence number contained in the payload of the ICMP error message is within the range of the data already sent but not yet acknowledged. An ICMP error message that does not pass this check is discarded. This behavior protects TCP against spoofed ICMP packets. Set the tunable as follows: icmp_tcpseqcheck=1 (default) Provides a level of protection that reduces the possibility of considering a spoofed ICMP packet as valid to one in two raised to the thirty-second power. icmp_tcpseqcheck=0 Retains existing behavior, i.e., accepts all ICMP packets icmp_rejectcodemask In the Requirements for IP Version 4 Routers (RFC 1812), research suggests that the use of ICMP Source Quench packets is an ineffective (and unfair) antidote for congestion. Thus, HP recommends completely ignoring ICMP Source Quench packets using the icmp_rejectcodemask tunable. The icmp_rejectcodemask is a bitmask that designates the ICMP codes that the system should reject. For example, to reject ICMP Source Quench packets, set the mask bit position for the ICMP_SOURCEQUENCH code 4, which is two to the 4th power = 16 (0x10 hex). The icmp_rejectcodemask tunable can be used to reject any ICMP packet type, or multiple masks can be combined to reject more than one type. Note: The ICMP type codes are defined in "/usr/include/netinet/ip_icmp.h". Set the tunable as follows: icmp_rejectcodemask = 0x10 Rejects ICMP Source Quench packets icmp_rejectcodemask = 0 (default) Retains existing behavior, i.e., accepts all ICMP packets Adjusting the variables The ICMP sequence check variable (icmp_tcpseqcheck) can be adjusted using the sysconfig and sysconfigdb commands: # sysconfig -q inet icmp_tcpseqcheck inet: icmp_tcpseqcheck = 1 # sysconfig -r inet icmp_tcpseqcheck=0 icmp_tcpseqcheck: reconfigured # sysconfig -q inet icmp_tcpseqcheck inet: icmp_tcpseqcheck = 0 # sysconfig -q inet icmp_tcpseqcheck > /tmp/icmp_tcpseqcheck_merge # sysconfigdb -m -f /tmp/icmp_tcpseqcheck_merge inet # sysconfigdb -l inet inet: icmp_tcpseqcheck = 1 Similarly, the icmp_rejectcodemask variable can be adjusted using the sysconfig and sysconfigdb commands: # sysconfig -q inet icmp_rejectcodemask inet: icmp_rejectcodemask = 0 # sysconfig -r inet icmp_rejectcodemask=0x10 icmp_rejectcodemask: reconfigured # sysconfig -q inet icmp_rejectcodemask inet: icmp_rejectcodemask = 16 # sysconfig -q inet icmp_rejectcodemask > /tmp/icmp_rejectcodemask_merge # sysconfigdb -m -f /tmp/icmp_rejectcodemask_merge inet # sysconfigdb -l inet inet: icmp_rejectcodemask = 16 RESOLUTION: Until the corrections are available in a mainstream release patch kit, HP is releasing the following Early Release Patch (ERP) kits publicly for use by any customer. The ERP kits use dupatch to install and will not install over any installed Customer Specific Patches (CSPs) that have file intersections with the ERPs. Contact your service provider for assistance if the ERP installation is blocked by any of your installed CSPs. The fixes contained in the ERP kits are scheduled to be available in the following mainstream patch kits: HP Tru64 Unix 5.1B-4 Early Release Patches The ERPs deliver the following file: /sys/BINARY/inet.mod HP Tru64 UNIX 5.1B-3 ERP Kit Name: T64KIT0026447-V51BB26-ES-20050914 Kit Location: http://www.itrc.hp.com/service/patch/patchDetail.do? patchid=T64KIT0026447-V51BB26-ES-20050914 MD5 checksum: 168639dedac3894e6432957c178e70ba HP Tru64 UNIX 5.1B-2/PK4 ERP Kit Name: T64KIT0026436-V51BB25-ES-20050914 Kit Location: http://www.itrc.hp.com/service/patch/patchDetail.do? patchid=T64KIT0026436-V51BB25-ES-20050914 MD5 checksum: ececa219e125c929d1d33bb5f2824072 HP Tru64 UNIX 5.1A PK6 ERP Kit Name: T64KIT0026446-V51AB24-ES-20050914 Kit Location: http://www.itrc.hp.com/service/patch/patchDetail.do? patchid=T64KIT0026446-V51AB24-ES-20050914 MD5 checksum: 75c1039c63444e530772cc2b7e25cf0a HP Tru64 UNIX 4.0G PK4 ERP Kit Name: T64KIT0025920-V40GB22-ES-20050628 Kit Location: http://www.itrc.hp.com/service/patch/patchDetail.do? patchid=T64KIT0025920-V40GB22-ES-20050628 MD5 checksum: 13849fd555239d75d300d1cb46dc995f HP Tru64 UNIX 4.0F PK8 ERP Kit Name: DUXKIT0025921-V40FB22-ES-20050628 Kit Location: http://www.itrc.hp.com/service/patch/patchDetail.do? patchid=DUXKIT0025921-V40FB22-ES-20050628 MD5 checksum: 743b614d39f185802701b7f2dd14ffa5 MD5 checksums are available from the ITRC patch database main page: http://www.itrc.hp.com/service/patch/mainPage.do - From the patch database main page, click Tru64 UNIX, then click verifying MD5 checksums under useful links. General ITRC Patch Page: http://www.itrc.hp.com/service/patch/mainPage BULLETIN REVISION HISTORY: Revision 0: 15 September 2005 Initial Release Revision 1: 4 October 2005 New ERP kits are available for HP Tru64 Unix V5.1B-3, V5.1B-2/PK4, and V5.1A PK6 SUPPORT: For further information, contact normal HP Services support channel. REPORT: To report a potential security vulnerability with any HP supported product, send Email to: security-alert (at) hp (dot) com. [email concealed] It is strongly recommended that security related information being communicated to HP be encrypted using PGP, especially exploit information. To obtain the security-alert PGP key please send an e-mail message to security-alert (at) hp (dot) com [email concealed] with the Subject of 'get key' (no quotes). SUBSCRIBE: To initiate a subscription to receive future HP Security Bulletins via Email: http://h30046.www3.hp.com/driverAlertProfile.php?regioncode=NA& langcode=USENG&jumpid=in_SC-GEN__driverITRC&topiccode=ITRC On the web page: ITRC security bulletins and patch sign-up Under Step1: your ITRC security bulletins and patches - check ALL categories for which alerts are required and continue. Under Step2: your ITRC operating systems - verify your operating system selections are checked and save. To update an existing subscription: http://h30046.www3.hp.com/subSignIn.php Log in on the web page Subscriber's choice for Business: sign-in. On the Web page: Subscriber's Choice: your profile summary - use Edit Profile to update appropriate sections. To review previously published Security Bulletins visit: http://itrc.hp.com/service/cki/secBullArchive.do * The Software Product Category that this Security Bulletin relates to is represented by the 5th and 6th characters of the Bulletin number: GN = HP General SW, MA = HP Management Agents, MI = Misc. 3rd party SW, MP = HP MPE/iX, NS = HP NonStop Servers, OV = HP OpenVMS, PI = HP Printing & Imaging, ST = HP Storage SW, TL = HP Trusted Linux, TU = HP Tru64 UNIX, UX = HP-UX, VV = HP Virtual Vault System management and security procedures must be reviewed frequently to maintain system integrity. HP is continually reviewing and enhancing the security features of software products to provide customers with current secure solutions. "HP is broadly distributing this Security Bulletin in order to bring to the attention of users of the affected HP products the important security information contained in this Bulletin. HP recommends that all users determine the applicability of this information to their individual situations and take appropriate action. HP does not warrant that this information is necessarily accurate or complete for all user situations and, consequently, HP will not be responsible for any damages resulting from user's use or disregard of the information provided in this Bulletin. To the extent permitted by law, HP disclaims all warranties, either express or implied, including the warranties of merchantability and fitness for a particular purpose, title and non-infringement." (c)Copyright 2005 Hewlett-Packard Development Company, L.P. Hewlett-Packard Company shall not be liable for technical or editorial errors or omissions contained herein. The information provided is provided "as is" without warranty of any kind. To the extent permitted by law, neither HP nor its affiliates, subcontractors or suppliers will be liable for incidental, special or consequential damages including downtime cost; lost profits; damages relating to the procurement of substitute products or services; or damages for loss of data, or software restoration. The information in this document is subject to change without notice. Hewlett-Packard Company and the names of Hewlett-Packard products referenced herein are trademarks of Hewlett-Packard Company in the United States and other countries. Other product and company names mentioned herein may be trademarks of their respective owners. -----BEGIN PGP SIGNATURE----- Version: PGP 8.1 iQA/AwUBQ0O6neAfOvwtKn1ZEQJkKwCg14OzE7FycshYt5p20CuRnJzATOgAoJvf OwYaEJiPWeRj3goiXDZUL/46 =g41n -----END PGP SIGNATURE-----