ESB-2019.1309 - [Appliance] F5 BIG-IP Products: Access confidential data - Remote/unauthenticated 2019-04-16

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             AUSCERT External Security Bulletin Redistribution

                               ESB-2019.1309
          K8072:Obtaining uptime information from TCP timestamps
                               16 April 2019

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        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

- --------------------------BEGIN INCLUDED TEXT--------------------

K8072:Obtaining uptime information from TCP timestamps

Security Advisory

Original Publication Date: 01 Nov, 2007

Latest   Publication Date: 16 Apr, 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                           |12.1.4.1             |
|                       |12.0.0 - 12.1.4                |                     |
|                       |13.x                           |                     |
+-----------------------+-------------------------------+---------------------+
|                       |11.x                           |14.0.0               |
|BIG-IP AAM             |12.0.0 - 12.1.4                |12.1.4.1             |
|                       |13.x                           |                     |
+-----------------------+-------------------------------+---------------------+
|                       |11.x                           |14.0.0               |
|BIG-IP AFM             |12.0.0 - 12.1.4                |12.1.4.1             |
|                       |13.x                           |                     |
+-----------------------+-------------------------------+---------------------+
|                       |11.x                           |14.0.0               |
|BIG-IP Analytics       |12.0.0 - 12.1.4                |12.1.4.1             |
|                       |13.x                           |                     |
+-----------------------+-------------------------------+---------------------+
|                       |10.x                           |                     |
|BIG-IP APM             |11.x                           |14.0.0               |
|                       |12.0.0 - 12.1.4                |12.1.4.1             |
|                       |13.x                           |                     |
+-----------------------+-------------------------------+---------------------+
|                       |9.x                            |                     |
|                       |10.x                           |14.0.0               |
|BIG-IP ASM             |11.x                           |12.1.4.1             |
|                       |12.0.0 - 12.1.4                |                     |
|                       |13.x                           |                     |
+-----------------------+-------------------------------+---------------------+
|BIG-IP DNS             |12.0.0 - 12.1.4                |14.0.0               |
|                       |13.x                           |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                           |12.1.4.1             |
|                       |12.x                           |                     |
|                       |13.x                           |                     |
+-----------------------+-------------------------------+---------------------+
|                       |11.x                           |14.0.0               |
|BIG-IP PEM             |12.0.0 - 12.1.4                |12.1.4.1             |
|                       |13.x                           |                     |
+-----------------------+-------------------------------+---------------------+
|                       |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

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