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How do I disable some cipher suites in Webserver Protection?

Tony Ayre

After running an SSL check for one of our sites, which is served by our UTM, it turned up that we have 3 weak ciphers being supported by the UTM:

TLS_ECDHE_RSA_WITH_3DES_EDE_CBC_SHA _0xc012_ ECDH secp256r1 _eq. 3072 bits RSA_ FS WEAK 112
TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA _0x16_ DH 2048 bits FS WEAK 112
TLS_RSA_WITH_3DES_EDE_CBC_SHA _0xa_ WEAK 112

How do I disable these ciphers?



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  • +1

    I have chased these issues, and what follows below are from my notes.  The current settings vary with the UTM release.   The new settings are suggestions, which you should be able to tailor to your preference by mimicking the examples.

    HIGH, MEDIUM, and LOW are OpenSSL keywords which correspond to a bundle of ciphers.   Only HIGH ciphers are considered acceptable anymore.

    To test the cipher results for any given keyword combination, you can use this command from the shell

    openssl ciphers keywordlist

    Except that not (like !MD5 ) commands, you need to add an escape from the shell, 

    for example: 

    openssl ciphers HIGH:\!MD5:\!SHA1

    -------------------------------------------------

     

     

    Applies to: WebAdmin, User Portal, Mail Manager, SPX Reply Portal

    cd /var/sec/chroot-httpd/etc/httpd/

    vi httpd.conf
    --- Current -----
    SSLCipherSuite ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:ECDH+AES128:DH+AES:RSA+AES:!ADH:!AECDH:!MD5:!DSS:!3DES
    SSLProtocol +TLSv1.1 +TLSv1.2
    --- New -----
    SSLCipherSuite HIGH:!MD5:!SHA1
    SSLProtocol +TLSv1.2
    -------------

    /etc/init.d/httpd restart

    *** completed **** still have cert issue
    ==================================================================

    Applies to: WAF ReverseProxy

    cd /var/chroot-reverseproxy/usr/apache/conf/

    vi httpd.conf
    --- Current -----
    SSLCipherSuite ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:ECDH+AES128:DH+AES:RSA+AESGCM:RSA+AES:ECDH+3DES:DH+3DES:RSA+3DES:!aNULL:!MD5:!DSS
    SSLProtocol all -SSLv2 -SSLv3
    --- New -----
    SSLCipherSuite HIGH:!MD5:!SHA1
    SSLProtocol +TLSv1.2
    -------------

    /var/mdw/scripts/reverseproxy restart

  • 0 in reply to DouglasFoster

    Excellent, Doug - thanks for holding on to that!

    In newer versions, things are a little different for WAF.  Instead of making those changes in httpd.conf, they must be made in reverseproxy.conf which is now an Include in httpd.conf.

    Before looking at reverseproxy.conf, I set "TLSv1.2" as the 'Minimum TLS version' on the 'Advanced' tab.  Instead of SSLProtocol all -SSLv2 -SSLv3, I found SSLProtocol -all +TLSv1.2, which meant that can be changed in the GUI.  BenediktWehr has suggested allowing a separate TLS setting in each Virtual Server definition;  I could find no place where the SSLCipherSuite could be permanently changed, so there's a risk that such a manual change might be overwritten.

    Since there's an httpd.conf-default in /var/sec/chroot-httpd/etc/httpd/, I assume configuration changes in the GUI might also overwrite any manual changes.

    Let's hope that one of the Sophos folks visits this thread.

    Cheers - Bob

     
    Sophos UTM Community Moderator
    Sophos Certified Architect - UTM
    Sophos Certified Engineer - XG
    Gold Solution Partner since 2005
    MediaSoft, Inc. USA
  • 0 in reply to BAlfson

    Bob is correct. You can limit WAF to use TLS v1.2 only (under Advanced), which will also removes the weak ciphers. 

    We did not want to remove the ciphers from the default list because it may cause compatibility issues with existing customers. If you want to remove these ciphers, setting 'TLS v1.2 only' is the recommended approach. 

    You can also modify reverseproxy.conf on the backend as others have suggested, but the changes will be overwritten by any change in the UI. 

Reply
  • 0 in reply to BAlfson

    Bob is correct. You can limit WAF to use TLS v1.2 only (under Advanced), which will also removes the weak ciphers. 

    We did not want to remove the ciphers from the default list because it may cause compatibility issues with existing customers. If you want to remove these ciphers, setting 'TLS v1.2 only' is the recommended approach. 

    You can also modify reverseproxy.conf on the backend as others have suggested, but the changes will be overwritten by any change in the UI. 

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  • 0 in reply to bobbylam

    To confirm what others have said:

    I set my UTM to TLS1.2 only in the user interface, then restested some of my WAF sites using ssllabs . com.   It had no complaints, and I passed my PCI scan for the WAF resources

  • 0 in reply to DouglasFoster

    Thanks all for your valuable feedback. Its true that in UTM WebAdmin's newer version we can select the "TLS 1.1 or above"  or "TLS1.2 only" under "Advanced" tab . I used  "TLS 1.1 or above" and then used a Penetration Testing tool to verify the WAF functionality, the weak ciphers were still enabled but I need to test it with the other option "TLS 1.2 only" as suggested by  DouglasFoster.

     

    Thanks,

    Asif

  • 0 in reply to AMU-FCO

    Hi,

         If we use "TLS v1.2" option in UTM (Verison 9.5) WebAdmin's  under "Webserver Protection ---> Web Application Firewall ----> Advanced" tab, then weak ciphers are disabled and can be verified  through "/var/chroot-reverseproxy/usr/apache/conf/reverseproxy.conf" file.

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