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Brian_Thompson
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Sep 04, 2013

Need clarification on SSL Ciphers found in SSL Dump

I am trying to determine which corresponding SSL Ciphers in the SSL Profiles that F5 provides address the cipher suite detected by SSLDump as "TLS_RSA _WITH_3DES_EDE_CBC_SHA"

 

Any assistance with its TLS version, SSL version, bit length, strength, etc- would be greatly appreciated.

 

5 Replies

  • It appears to be 168bit SSLV3 only, if this is incorrect- please correct me. If it's correct, please mark this solved by submitter.

     

  • A cipher suite won't provide the TLS/SSL version. For the rest, it breaks down like so;

     

    key exchange/agreement : RSA

     

    bulk cipher : 3DES_EDE_CBC - 168bit key size (112 effective)

     

    message authentication : SHA (1) - 128bit key size

     

    Strength-wise I think it's still strong (it's a matter or personal and mathamatical opinion I guess) but AES is obviously now preferred over 3DES. SHA is still fine as far as I know.

     

    I'm sure Kevin will be along to correct me ;-)

     

  • Okay, that is helpful info. What is the corresponding cipher name in the F5 SSL Profile to enable this and this only? That's the real question I'm attempting to find an answer to

     

  • DES-CBC3-SHA I believe. As this is a 'native' cipher, it will also be full hardware accelerated which is lucky!

     

  • I'd first direct your attention to Jason Rahm's excellent article on cipher suites:

    SSL Profiles Part 4: Cipher Suites

    You can actually see what the ciphers are from the command line using the following command:

    tmm --ciphersuites 'filter'
    

    where 'filter' is what you're looking for. Steve is absolutely correct that the cipher suite itself doesn't include TLS or SSL, as that's the protocol. So to narrow down the SSL cipher to just "TLS_RSA _WITH_3DES_EDE_CBC_SHA", first do this to see what that would look like:

        tmm --clientciphers '!SSLv3:!DTLSv1:DES-CBC3-SHA:@STRENGTH'
        ID SUITE                          BITS  PROT  METHOD CIPHER MAC    KEYX
        0:  10 DES-CBC3-SHA                    192  TLS1  Native DES    SHA    RSA
        1:  10 DES-CBC3-SHA                    192  TLS1.1  Native DES    SHA    RSA
        2:  10 DES-CBC3-SHA                    192  TLS1.2  Native DES    SHA    RSA
    

    I think this is what you're looking for, so then use that filter in your client SSL profile and test:

    !SSLv3:!DTLSv1:DES-CBC3-SHA:@STRENGTH