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What_Lies_Bene1's avatar
What_Lies_Bene1
Icon for Cirrostratus rankCirrostratus
Oct 27, 2014

Management Interface SSL Ciphers

Hey all,

So, I'm trying to restrict the SSL ciphers used with the management interface (including iControl). To test this, I've used the

[tmsh] modify sys httpd ssl-ciphersuite ...
command with a very weak cipher string. I've restarted httpd and also done a full reboot. In either case;

*When using a browser I'm negotiating a TLS cipher suite *When using iControl I'm negotiating an even stronger suite: TLS_RSA_WITH_AES_256_CBC_SHA

I've two reasons to do this;

1) I want to troubleshoot some iControl issues

2) I want to disable SSLv3 ciphers, if my changes are ignored, I'm worried

Any ideas anyone?

The ciphersuite I've configured is: -ALL:RC4-SHA:RC4-MD5:AES128-SHA:AES256-SHA

TMOS v11.4.1 (VE), build 608.0.

  • NONE:RC4+RSA as recommended in SOL7823 did the trick but doesn't remove my concern that what should be valid cipher suites are ignored despite a using valid string and not getting an error.
  • Kevin_K_51432's avatar
    Kevin_K_51432
    Historic F5 Account

    Greetings, Here's the default apache cipher list:

    DEFAULT:!aNULL:!eNULL:!LOW:!RC4:!MD5:!EXP

    Can you simply append !SSLv3 to the list to disable SSLv3?

    tmsh modify sys httpd ssl-ciphersuite 'DEFAULT:!aNULL:!eNULL:!LOW:!RC4:!MD5:!EXP:!SSLv3'
    tmsh save sys config
    bigstart restart httpd
    

    Looks to have been added to /etc/httpd/conf.d/ssl.conf and SSLv3 no longer negotiates.

    SSLCipherSuite DEFAULT:!aNULL:!eNULL:!LOW:!RC4:!MD5:!EXP:!SSLv3

    Kevin

  • Thanks Kevin. To be blunt I think I've not being paying attention. Its all working fine. Cheers

     

  • JG's avatar
    JG
    Icon for Cumulonimbus rankCumulonimbus

    Is there really a cipher suite called SSLv3 for the httpd? It is the SSLv3 protocol that should be disabled entirely, as the two cipher suites supported by that protocol are both insecure.

     

    Please see related thread Disabling SSLv3 for Configuration Utility.

     

  • Thanks Jie but I don't see any solution in SOL15702 or the article you link to, for versions prior to 11.5?

    Regardless, I'm happy that I can disable SSLv3 by simply specifying

    NONE:
    followed by a small set of TLS only ciphers.

    • JG's avatar
      JG
      Icon for Cumulonimbus rankCumulonimbus
      I see. Did you test to see if SSLv3 is really disabled after removing SSLv3 cipher suite?
    • What_Lies_Bene1's avatar
      What_Lies_Bene1
      Icon for Cirrostratus rankCirrostratus
      See below, restricting the ciphers to TLS1.2 ones indirectly 'disables' SSLv3 (i.e its not disabled but will never be used) without the need to modify the Apache ssl.conf file.
  • Just for the benefit of others, I've implemented just TLS1.2 supported ciphers using this string;

    NONE:DHE-RSA-AES256-SHA:AES256-SHA
    

    OpenSSL reports as follows (ignore the SSLv3 output, it's just an OpenSSL 'thing');

    $ openssl ciphers -v NONE:DHE-RSA-AES256-SHA:AES256-SHA
    DHE-RSA-AES256-SHA      SSLv3 Kx=DH       Au=RSA  Enc=AES(256)  Mac=SHA1
    AES256-SHA              SSLv3 Kx=RSA      Au=RSA  Enc=AES(256)  Mac=SHA1
    

    And here's the output from ssldump proving when I connect that only one of these ciphers is used;

    $ ssldump -ndX
        New TCP connection 1: 10.11.12.13(50592) <-> 192.168.1.1(443)
        1 1  0.0491 (0.0491)  C>S  Handshake
              ClientHello
                Version 3.1 
                resume [32]=
                  13 70 c7 87 b7 5a 78 8d b6 ca fd cc 4d 92 f9 17 
                  d0 61 90 36 5b 1b 69 cd f1 e5 e7 f9 5f 2a 5b e1 
                cipher suites
                Unknown value 0xc02b
                Unknown value 0xc02f
                Unknown value 0x9e
                Unknown value 0xcc14
                Unknown value 0xcc13
                Unknown value 0xc00a
                Unknown value 0xc009
                Unknown value 0xc013
                Unknown value 0xc014
                Unknown value 0xc007
                Unknown value 0xc011
                TLS_DHE_RSA_WITH_AES_128_CBC_SHA
                TLS_DHE_DSS_WITH_AES_128_CBC_SHA
                TLS_DHE_RSA_WITH_AES_256_CBC_SHA
                Unknown value 0x9c
                TLS_RSA_WITH_AES_128_CBC_SHA
                TLS_RSA_WITH_AES_256_CBC_SHA
                TLS_RSA_WITH_3DES_EDE_CBC_SHA
                TLS_RSA_WITH_RC4_128_SHA
                TLS_RSA_WITH_RC4_128_MD5
                compression methods
                          NULL
        1 2  0.0513 (0.0022)  S>C  Handshake
              ServerHello
                Version 3.1 
                session_id[32]=
                  13 70 c7 87 b7 5a 78 8d b6 ca fd cc 4d 92 f9 17 
                  d0 61 90 36 5b 1b 69 cd f1 e5 e7 f9 5f 2a 5b e1 
                cipherSuite         TLS_DHE_RSA_WITH_AES_256_CBC_SHA
                compressionMethod                   NULL
    

    Here's what happens if I try to connect using Firefox configured to use unwanted ciphers;

        1 1  0.0074 (0.0074)  C>S  Handshake
              ClientHello
                Version 3.0 
                cipher suites
                Unknown value 0xff
                SSL_DHE_RSA_WITH_AES_128_CBC_SHA
                SSL_DHE_DSS_WITH_AES_128_CBC_SHA
                Unknown value 0x45
                SSL_DHE_RSA_WITH_CAMELLIA_256_CBC_SHA
                SSL_DHE_DSS_WITH_CAMELLIA_256_CBC_SHA
                SSL_DHE_RSA_WITH_3DES_EDE_CBC_SHA
                SSL_RSA_WITH_AES_128_CBC_SHA
                SSL_DHE_RSA_WITH_AES_128_CBC_SHA256
                SSL_RSA_WITH_3DES_EDE_CBC_SHA
                SSL_RSA_WITH_RC4_128_MD5
                compression methods
                          NULL
        1 2  0.0080 (0.0005)  S>C  Alert
            level           fatal
            value           handshake_failure