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 TLS 1.2

Yulia Vaisman's profile image
Yulia Vaisman posted Mon February 03, 2025 01:53 AM

Hello,

Recently we moved to TLS 1.2 . We use SSLCIPH('ANY') on client CCDT and ANY_TLS12 on SRVCONN in order not to choose a specific cipher . Ibm default is TLS_RSA_WITH_AES_256_GCM_SHA384. We started to get AMQ9288E messages. IBM suggested to move to TLS 1.3 in order to handle it automatically .

But according to this page  

https://www.ibm.com/support/pages/apar/IT46864?myns=swgother&mynp=OCSSYHRD&mync=E&cm_sp=swgother-_-OCSSYHRD-_-E

may be moving to TLS 1.3 is not such good idea. 

I am looking for TLS 1.2  non GCM cipher ( in order to avoid AMQ9288E messages ) . I saw recommendations to use ECDHE_RSA_AES_256_CBC_SHA384 . Any other recommendations? 

Yulia.

Morag Hughson's profile image
Morag Hughson IBM Champion posted Tue February 18, 2025 10:08 PM

Hi Yulia,

AMQ9288E error message is the one telling you that you have transferred the maximum amount of data you can with this algorithm. You get this because, as you note, you have chosen a GCM cipher. You don't have to change the cipher to avoid this message, you can instead make use of secret key reset (as is noted in the error message ACTION section) and in the docs here.

However, if you do want to avoid GCM ciphers and continue to use TLS 1.2, the Enabling CipherSpecs page in IBM Docs shows that you have these options:-

  • TLS_RSA_WITH_AES_128_CBC_SHA2569
  • TLS_RSA_WITH_AES_256_CBC_SHA256
  • ECDHE_ECDSA_AES_128_CBC_SHA256
  • ECDHE_ECDSA_AES_256_CBC_SHA384
  • ECDHE_RSA_AES_128_CBC_SHA256
  • ECDHE_RSA_AES_256_CBC_SHA384

If you decide to go with an ECDHE_ECDSA_* cipherspec then you will likely need to get a different certificate to use (see here) so that probably reduces the list down to the four RSA ones.

Also, remember that the default order that Ciphers are selected is able to be changed (see here).

I don't seem to be able to post another reply so I'll answer here. The best performing CipherSpec is usually the one that gives you the least protection. However, there are also IBM MQ performance reports that can help to answer this question. Check out this one: http://ibm-messaging.github.io/mqperf/MQ_V9.4_Performance_Report_windows.pdf

Cheers,
Morag

Yulia Vaisman's profile image
Yulia Vaisman posted Wed February 19, 2025 02:23 AM

Thanks a lot Morag,

And from perform point of view which one is better ?

Yulia

Francois Brandelik's profile image
Francois Brandelik IBM Champion posted Thu February 20, 2025 08:53 AM

Be aware that NIST says the CBC ciphers are deprecated. You should use a high number (2^28) for key renewal, or use a TLS 1.3 cipher that doesn't use GCM.

see https://www.nist.gov/news-events/news/2023/04/decision-revise-nist-sp-800-38a-recommendation-block-cipher-modes-operation

Hope it helps.