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-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 =========================================================================== AUSCERT External Security Bulletin Redistribution ESB-2019.1309.2 K8072:Obtaining uptime information from TCP timestamps 12 August 2019 =========================================================================== AusCERT Security Bulletin Summary --------------------------------- Product: F5 BIG-IP Products Publisher: F5 Networks Operating System: Network Appliance Impact/Access: Access Confidential Data -- Remote/Unauthenticated Resolution: Patch/Upgrade Original Bulletin: https://support.f5.com/csp/article/K8072 Revision History: August 12 2019: Vendor added more versions April 16 2019: Initial Release - --------------------------BEGIN INCLUDED TEXT-------------------- 8072:Obtaining uptime information from TCP timestamps Security Advisory Original Publication Date: 19 Jul, 2011 Latest Publication Date: 09 Aug, 2019 Security Advisory Description Note: Versions that are not listed in this article have not been evaluated for vulnerability to this security advisory. For information about the F5 security policy regarding evaluating older and unsupported versions of F5 products, refer to K4602: Overview of the F5 security vulnerability response policy. F5 products and versions that have been evaluated for this Security Advisory +-----------------------+-------------------------------+---------------------+ |Product |Versions known to be vulnerable|Fixes introduced in^1| +-----------------------+-------------------------------+---------------------+ | |9.x | | | |10.x |14.0.0 | |BIG-IP LTM |11.x |13.1.3 | | |12.0.0 - 12.1.4 |12.1.4.1 | | |13.0.0 - 13.1.1 | | +-----------------------+-------------------------------+---------------------+ | |11.x |14.0.0 | |BIG-IP AAM |12.0.0 - 12.1.4 |13.1.3 | | |13.0.0 - 13.1.1 |12.1.4.1 | +-----------------------+-------------------------------+---------------------+ | |11.x |14.0.0 | |BIG-IP AFM |12.0.0 - 12.1.4 |13.1.3 | | |13.0.0 - 13.1.1 |12.1.4.1 | +-----------------------+-------------------------------+---------------------+ | |11.x |14.0.0 | |BIG-IP Analytics |12.0.0 - 12.1.4 |13.1.3 | | |13.0.0 - 13.1.1 |12.1.4.1 | +-----------------------+-------------------------------+---------------------+ | |10.x |14.0.0 | |BIG-IP APM |11.x |13.1.3 | | |12.0.0 - 12.1.4 |12.1.4.1 | | |13.0.0 - 13.1.1 | | +-----------------------+-------------------------------+---------------------+ | |9.x | | | |10.x |14.0.0 | |BIG-IP ASM |11.x |13.1.3 | | |12.0.0 - 12.1.4 |12.1.4.1 | | |13.0.0 - 13.1.1 | | +-----------------------+-------------------------------+---------------------+ | |12.0.0 - 12.1.4 |14.0.0 | |BIG-IP DNS |13.0.0 - 13.1.1 |13.1.3 | | | |12.1.4.1 | +-----------------------+-------------------------------+---------------------+ |BIG-IP Edge Gateway |10.x |None | | |11.x | | +-----------------------+-------------------------------+---------------------+ | |9.x | | |BIG-IP GTM |10.x |None | | |11.x | | +-----------------------+-------------------------------+---------------------+ | |9.x | | | |12.0.0 - 12.1.4 |14.0.0 | |BIG-IP Link Controller |11.x |13.1.3 | | |12.x |12.1.4.1 | | |13.0.0 - 13.1.1 | | +-----------------------+-------------------------------+---------------------+ | |11.x |14.0.0 | |BIG-IP PEM |12.0.0 - 12.1.4 |13.1.3 | | |13.0.0 - 13.1.1 |12.1.4.1 | +-----------------------+-------------------------------+---------------------+ | |9.x | | |BIG-IP PSM |10.x |None | | |11.x | | +-----------------------+-------------------------------+---------------------+ | |9.x | | |BIG-IP WebAccelerator |10.x |None | | |11.x | | +-----------------------+-------------------------------+---------------------+ |BIG-IP WAN Optimization|10.x |None | | |11.x | | +-----------------------+-------------------------------+---------------------+ | |1.x | | |Enterprise Manager |2.x |None | | |3.x | | +-----------------------+-------------------------------+---------------------+ | |2.x | | | |3.x | | |ARX |4.x |None | | |5.x | | | |6.x | | +-----------------------+-------------------------------+---------------------+ ^1 The BIG-IP system is not affected when the BigDB key tm.tcpsendrandomtimestamp is set to enabled. The key is disabled by default. A number of publicly-available networking and security utilities (for example, nmap, hping, and some commercial tools) can perform network scans using a TCP timestamp option, which can be used to calculate the uptime (time since boot) of a system. Timestamps are a TCP option used by a TCP/IP networking stack to implement two algorithms: the Round-Trip Time Measurement (RTTM) algorithm and the Protection Against Wrapped Sequence Numbers (PAWS) algorithm. Both algorithms are defined in RFC 1323, and are widely implemented by most modern operating systems' TCP/ IP stacks, including F5 products. Because the values in the timestamp are tied to the passage of time as tracked by the system clock, capturing two or more TCP packets allows interpolation back to the time at which the system started. Uptime information, when combined with other system fingerprinting techniques, may sufficiently identify a system to an attacker as a potentially worthwhile target for an attack. Note: The issue of using uptime information to select a subsequent attack should not to be confused with any attack against the timestamp mechanism directly. Eliminating the use of TCP timestamps is not desirable because a performance penalty would occur without RTTM. More importantly, PAWS can protect against both the loss of data when TCP sequence numbers wrap, but also against denial-of-service attacks, which attempt to shut down an existing TCP connection. Without PAWS, the attacker needs only the IP addresses and port numbers of the connection endpoints to reset the connection. F5 believes that the probability of system uptime information being used as the basis of a subsequent, successful attack is low. Additionally, denying an attacker access to uptime information would be a significant deterrent only if other operating system information could be hidden from fingerprinting techniques, which is not possible. F5 Product Development assigned ID 273104 to this issue. Security Advisory Status BIG-IP system Beginning in BIG-IP 12.1.4.1 for the 12.1.x branch only and beginning in BIG-IP 14.0.0, you can configure each TCP connection handled by the Traffic Management Microkernel (TMM) to start with a random timestamp to eliminate this information disclosure vulnerability. The behavior is controlled with the BigDB key tm.tcpsendrandomtimestamp, which is set to disabled by default. Security Advisory Recommended Actions BIG-IP system Viewing the tm.tcpsendrandomtimestamp BigDB key setting Impact of procedure: Performing the following procedure should not have a negative impact on your system. 1. Log in to the TMOS Shell (tmsh) by typing the following command: tmsh 2. To list the current setting, type the following command: list /sys db tm.tcpsendrandomtimestamp Changing the default tm.tcpsendrandomtimestamp BigDB key setting Enabling this setting should prevent OS fingerprinting tools from obtaining uptime information from the BIG-IP system by way of a TMM interface. To enable the random timestamp setting, perform the following procedure. Impact of procedure: Performing the following procedure should not have a negative impact on your system. 1. Log in to the TMOS Shell (tmsh) by typing the following command: tmsh 2. To change the BigDB key default value, use following command syntax: modify /sys db tm.tcpsendrandomtimestamp value enable Supplemental Information None - --------------------------END INCLUDED TEXT-------------------- You have received this e-mail bulletin as a result of your organisation's registration with AusCERT. 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