Bug ID 531979: SSL version in the record layer of ClientHello is not set to be the lowest supported version.

Last Modified: Feb 13, 2019

Bug Tracker

Affected Product:  See more info
BIG-IP All(all modules)

Known Affected Versions:
11.4.0, 11.4.1, 11.5.0, 11.5.1, 11.5.1 HF1, 11.5.1 HF10, 11.5.1 HF11, 11.5.1 HF2, 11.5.1 HF3, 11.5.1 HF4, 11.5.1 HF5, 11.5.1 HF6, 11.5.1 HF7, 11.5.1 HF8, 11.5.1 HF9, 11.5.2, 11.5.2 HF1, 11.5.3, 11.5.3 HF1, 11.5.3 HF2, 11.5.4, 11.5.4 HF1, 11.6.0, 11.6.0 HF1, 11.6.0 HF2, 11.6.0 HF3, 11.6.0 HF4, 11.6.0 HF5, 11.6.0 HF6, 11.6.0 HF7, 11.6.0 HF8, 11.6.1, 12.0.0, 12.0.0 HF1, 12.0.0 HF2, 12.0.0 HF3, 12.0.0 HF4, 12.1.0

Fixed In:
13.0.0, 12.1.0 HF1, 11.6.1 HF1, 11.5.4 HF2

Opened: Jul 07, 2015
Severity: 3-Major
Related AskF5 Article:
K32114303

Symptoms

In the ClientHello message, the system is now setting the SSL version in the record layer to be the same as version value of ClientHello message, which is the highest SSL version now supported. Although RFC 5246 appendix E.1 does not give specific advice on how to set the TLS versions, the de facto standard used by all major browsers and TLS stacks is to set the ClientHello as follows: SSL Record: Content Type: Handshake (22) Version: $LOWEST_VERSION Handshake Record: Handshake Type: Client Hello (1) Version: $HIGHEST_VERSION The BIG-IP system implementation tells the SSL peer that the system supports only SSL versions from the $HIGHEST_VERSION through the $HIGHEST_VERSION instead of from the $LOWEST_VERSION through the $HIGHEST_VERSION, which effectively limits the range of SSL versions the system can negotiate with the SSL peer.

Impact

SSL handshake fails.

Conditions

This issue occurs when the highest SSL version that the BIG-IP system supports does not fall into the range that an SSL peer supports. For example, with SSL peer support configured for TLS1.0 or TLS1.1, if the BIG-IP system sets the highest SSL version to be TLS1.2, then there will be no version that the SSL peer thinks they have in common, and SSL handshake fails.

Workaround

There is no workaround for this issue.

Fix Information

The SSL version in the record layer of ClientHello is now set to be the lowest supported version, which eliminates that issue that occurred when the highest SSL version that the BIG-IP system supports did not fall into the range that an SSL peer supports.

Behavior Change