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smp_86112's avatar
smp_86112
Icon for Cirrostratus rankCirrostratus
Apr 25, 2014

TLS version on serverside of connection

I have a HTTPS virtual server which needs both a client and server ssl profile. The application broke after upgrading from 10.2.4 -> 11.4.1. I took network traces and found that the LTM is using TLS1...
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Ian_124377's avatar
Ian_124377
Icon for Nimbostratus rankNimbostratus
Apr 25, 2014

From my understanding of the articles I have read, the sorting (@SPEED or @STRENGTH) are actually sorting the encryption algorithms, and not the TLS protocol versions. What is supposed to happen in the SSL negotiation:

 

1.) The client sends a ClientHello message specifying the highest TLS protocol version it supports and a list of suggested CipherSuites.

 

2.) The server responds with a ServerHello message, containing the chosen TLS protocol version and the CipherSuite from the choices offered by the client.

 

For some reason the 10.2.4 has the ability to use TLS 1.2, but chooses not use it. And 11.4.1 has the ability to use TLS 1.2, and chooses to use it. I have not found any F5 doc on ordering the TLS protocol versions to use. It seems you can either order the encyption algorithms (RC4,AES,DEC,etc.) -OR- exclude certain TLS protocol versions/encryption algorithms altogether.

 

I think one of the following may be true which would explain this behavior:

 

1.) This may be because the release of 10.2.3 (which first included TLS 1.2) was too new, or not a completed standard, and F5 opted to not default to use it as their highest supported TLS version in the ClientHello's.

 

2.) It is a bug in 10.2.4 that the highest supported TLS version is not selected.

 

One final thing I would mention. The pool member you reference should not fail, if you are sending a ClientHello, and you tell the pool member "Hey, I can use up to TLS 1.2", then the pool member choose TLS 1.0 if that is the highest supported version it can use. But, it sounds to me like your pool member is terminating the connection rather than selecting the lower TLS version. That sounds like a problem with the pool member to me.

 

Articles of interest

 

Note the 11.2.1 through 11.4.1 default NATIVE:!MD5:!EXPORT:!DES:!DHE:!EDH:@SPEED http://support.f5.com/kb/en-us/solutions/public/13000/100/sol13171.htmlTLSv1.2

 

Note the 10.2.x default !SSLv2:ALL:!DH:!ADH:!EDH:!MD5:!EXPORT:!DES:@SPEED http://support.f5.com/kb/en-us/solutions/public/7000/800/sol7815.html

 

http://en.wikipedia.org/wiki/Transport_Layer_SecurityTLS_handshake