Bug ID 551451: SSL cipher selection and HTTP/2 may not be in sync leading to connection errors

Last Modified: Sep 13, 2023

Affected Product(s):
BIG-IP LTM(all modules)

Known Affected Versions:
12.0.0, 12.0.0 HF1, 12.1.0 HF1, 12.0.0 HF2, 12.1.0 HF2, 12.1.1 HF1, 12.1.1 HF2, 12.1.2 HF1, 12.1.2 HF2

Fixed In:
12.1.0, 12.0.0 HF3

Opened: Oct 08, 2015

Severity: 3-Major

Related Article: K31840725

Symptoms

SSL performs cipher selection and ALPN protocol selection independently. It is possible that SSL picks a cipher that is not compatible with HTTP/2. This causes an issue where either the client or the BIGIP will refuse a newly established HTTP/2 connection with error INSUFFICIENT_SECURITY.

Impact

Client or the BIG-IP system refuses a newly established HTTP/2 connection with error INSUFFICIENT_SECURITY.

Conditions

SSL picks a cipher that is not compatible with HTTP/2, but picks HTTP/2 (h2) as the next protocol.

Workaround

Make sure HTTP/2 ciphers always come before non HTTP/2 ciphers. This is not the case with the DEFAULT cipher string. HTTP/2 requires TLS 1.2 (or above) Ephemeral keys (EDH/RSA, ECDHE_ECDSA, ECDHE_RSA, DHE/DSS) GCM (AES-GCM).

Fix Information

In this release, HTTP/2 ciphers always come before non HTTP/2 ciphers, at the top of the list, so they always in sync and do not result in connection errors.

Behavior Change

Guides & references

K10134038: F5 Bug Tracker Filter Names and Tips