Why can't I force a specific cipher with the openssl app with TLS 1.3?

Phil Neumiller pneumiller at directstream.com
Thu Nov 14 22:30:43 UTC 2019

Hi Matt, 

That works fine for 256 as you mentioned.  I trying to speak to a piece of
hardware that has one supported cipher, i.e. TLS_AES_256_GCM_SHA384.  I
tried the naive approach of 

openssl s_server -accept 4433 -tls1_3  -nocert -psk $PSK -sigalgs RSA+SHA384
-ciphersuites TLS_AES_256_GCM_SHA384

And the server starts up as it does with ECDSA+SHA384.  However, 

openssl s_client -tls1_3 -psk $PSK -connect :4433 -sigalgs RSA+SHA384
-ciphersuites TLS_AES_256_GCM_SHA384

Fails with invalid signature algorithm - which from your post I'm
interpreting as I need a session file.  The link you mentioned in your post
only describes the problem from the call back or API perspective and I was
really hoping to get this to work with something like:

openssl s_server -session_file fname ...

But when I follow that link it doesn't describe how to create the file.  I
seem to be misinterpreting something.



Phillip Neumiller
Platform Engineering
Directstream, LLC
Sent from: http://openssl.6102.n7.nabble.com/OpenSSL-User-f3.html

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