[openssl-users] Limit the number of AES-GCM keys allowed in TLS

Paul Dale paul.dale at oracle.com
Wed Sep 12 22:54:38 UTC 2018

I wasn’t aware of other national standards requiring a similar check.


I made the change in the AES-GCM code because FIPS demands the check be inside the FIPS boundary.  I’d have preferred to make it in the TLS layer, but that mustn’t be inside the FIPS boundary.  My understanding is that TLS catches this case earlier and thus the test can never pass.


I don’t think dropping the check down into the algorithm implementations makes sense.  A more generic mechanism at the EVP would.







Dr Paul Dale | Cryptographer | Network Security & Encryption 

Phone +61 7 3031 7217

Oracle Australia


From: Dmitry Belyavsky [mailto:beldmit at gmail.com] 
Sent: Wednesday, 12 September 2018 7:02 PM
To: openssl-users at openssl.org
Subject: [openssl-users] Limit the number of AES-GCM keys allowed in TLS




The issue https://github.com/openssl/openssl/pull/7129 has introduced a possibility to limit the amount of TLS records processed without key changing as required by FIPS.


We in Russia have limitations with the same semantics applicable to Russian GOST TLS ciphersuites (https://datatracker.ietf.org/doc/draft-smyshlyaev-tls12-gost-suites/) so I think that this mechanism is very useful. 


The current implementation is done at EVP level, and it seems suboptimal because of the following reasons:

- If the AES implementation is provided via engine, not by OpenSSL itself, the limitation can be avoided

- the limitation has been made too generic

- the implementation seems to be AEAD-specific. 


So does not it make sense to provide this limitation at least at the ciphersuite level? It can provide more straightforward way to manage such limitations.

Thank you!



SY, Dmitry Belyavsky
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