Installation and Upgrade • Zimbra 10.0.7 FIPS manage ciphers offered?

Hi,
Release 10.0.7.GA.3969.UBUNTU20.64 UBUNTU20_64 FOSS edition.

Our security scanning service is picking up on vulnerable Diffie-Helmann ciphers being available, under TLS 1.2 which could be used for a DoS D(HE)ater attack. We previously used the info from https://blog.zimbra.com/2022/12/update- ... -hellmann/, and https://wiki.zimbra.com/wiki/Cipher_suites but the approach for ssl_ciphers and the DH exclusions is apparently now deprecated under FIPS mode.

In detail, the ciphers the scanner is listing are:

TLS_DHE_RSA_WITH_AES_128_CBC_SHA
TLS_DHE_RSA_WITH_AES_128_CBC_SHA256
TLS_DHE_RSA_WITH_AES_128_CCM
TLS_DHE_RSA_WITH_AES_128_CCM_8
TLS_DHE_RSA_WITH_AES_128_GCM_SHA256
TLS_DHE_RSA_WITH_AES_256_CBC_SHA
TLS_DHE_RSA_WITH_AES_256_CBC_SHA256
TLS_DHE_RSA_WITH_AES_256_CCM
TLS_DHE_RSA_WITH_AES_256_CCM_8
TLS_DHE_RSA_WITH_AES_256_GCM_SHA384

I tried using the original zimbraSSLExcludeCipherSuites command to exclude these, but despite restarting the system, the scanner is still picking up those weak/vulnerable ciphers from our server.

What the server says it has configured:

$ zmprov gcf zimbraSSLExcludeCipherSuites
zimbraSSLExcludeCipherSuites: .*_RC4_.*
zimbraSSLExcludeCipherSuites: TLS_RSA_WITH_CAMELLIA_128_CBC_SHA
zimbraSSLExcludeCipherSuites: TLS_DHE_RSA_WITH_CAMELLIA_128_CBC_SHA
zimbraSSLExcludeCipherSuites: TLS_RSA_WITH_CAMELLIA_256_CBC_SHA
zimbraSSLExcludeCipherSuites: TLS_DHE_RSA_WITH_CAMELLIA_256_CBC_SHA
zimbraSSLExcludeCipherSuites: TLS_DHE_RSA_WITH_AES_128_CBC_SHA
zimbraSSLExcludeCipherSuites: TLS_DHE_RSA_WITH_AES_128_CBC_SHA256
zimbraSSLExcludeCipherSuites: TLS_DHE_RSA_WITH_AES_128_CCM
zimbraSSLExcludeCipherSuites: TLS_DHE_RSA_WITH_AES_128_CCM_8
zimbraSSLExcludeCipherSuites: TLS_DHE_RSA_WITH_AES_128_GCM_SHA256
zimbraSSLExcludeCipherSuites: TLS_DHE_RSA_WITH_AES_256_CBC_SHA
zimbraSSLExcludeCipherSuites: TLS_DHE_RSA_WITH_AES_256_CBC_SHA256
zimbraSSLExcludeCipherSuites: TLS_DHE_RSA_WITH_AES_256_CCM
zimbraSSLExcludeCipherSuites: TLS_DHE_RSA_WITH_AES_256_CCM_8
zimbraSSLExcludeCipherSuites: TLS_DHE_RSA_WITH_AES_256_GCM_SHA384

We have also applied the DH4096 pem as per the guidance in the Cipher_Suites wiki page.

Is there a way to control FIPS mode, to stop it offering these weak ciphers, or others that may be listed in future? (Other than disabling TLS 1.2, though this might become a necessity eventually)
Thanks

Statistics: Posted by Al-MacLean — Fri Apr 19, 2024 10:16 am

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