HowTo: Getting an awesome Qualys SSL-Labs rating... (Feb 2017 Update)

Hi Folks,

I've posted in August 2016 a Client SSL Profile configuration to achive a top notch Qualys SSL-Labs rating.

HowTo: Getting an awesome Qualys SSL-Labs rating...

https://devcentral.f5.com/questions/howto-getting-an-awesome-qualys-ssl-labs-rating-48120

In the meantime the Qualys SSL-Labs has decided to put very soon a penalty on those web sites, which are still supporting DES / IDEA algorythms via TLS1.2 (aka. every block cipher with a block size of less or equal 64-bit) .

Penalty for using 3DES with TLS 1.2 (C)

In late August, security researchers demonstrated an attack against ciphers that use 64-bit encryption blocks. The attack has been called Sweet32. The attack is not practical because it requires a very large amount of traffic, but it’s a good reminder that older and weaker ciphers need be retired as a matter of routine. In TLS, that means avoiding 3DES (EDIT 27 Jan: and other ciphers that use 64-bit blocks, for example IDEA). Now, for sites that need to support an old user base completely retiring 3DES might not be possible (hint: Windows XP), but there’s no reason to use this cipher with modern browsers. To that end, we’ll be modifying our grading criteria to penalise sites that negotiate 3DES with TLS 1.2. Such sites will have their scores capped at C. We are aware that most servers don’t allow per-protocol cipher suite configuration, but that shouldn’t be a problem in this case. Sites that negotiate strong cipher suites with modern clients will not be affected if they support 3DES, provided they keep it at the end of their ordered list of suites." -Quallys SSL Labs (see Link)

The result of the announced rating changes is currently just a little warning message which states that the grade will be caped to C very soon:

To maintain your awesome A / A+ grade in the future, you have to change your supported cipher suites once again, so that every DES based algorythm gets either completely removed (this may have a compatibility impact) or at least gets placed at the very buttom of the Cipher Suite list.

Previous Chipher-List (for v11 and v12):

!SSLv2:!EXPORT:!DHE+AES-GCM:!DHE+AES:!DHE+3DES:ECDHE+AES-GCM:ECDHE+AES:RSA+AES-GCM:RSA+AES:ECDHE+3DES:RSA+3DES:-MD5:-SSLv3:-RC4:@STRENGTH

Updated Chipher-List (for v11 and v12):

!SSLv2:!EXPORT:!DHE+AES-GCM:!DHE+AES:!DHE+3DES:ECDHE+AES-GCM:ECDHE+AES:RSA+AES-GCM:RSA+AES:ECDHE+3DES:RSA+3DES:-MD5:-SSLv3:-RC4

After applying the updated Chipher-List, you'll receive a clean A or even A+ (depending on HSTS configurations) rating again, while still supporting those Windows XP/IE8 or other legacy clients:

Cheers, Kai

Additional search tags for the lovely Google bot:

Preventing Logjam Attack

Preventing Sweet32 Attack

Default SSL Profile is a little bit insecure

TLS_DHE_RSA_WITH_AES_128_GCM_SHA256 (0x9e) DH 1024 bits FS WEAK 128 TLS_DHE_RSA_WITH_AES_256_CBC_SHA256 (0x6b) DH 1024 bits FS WEAK 256 TLS_DHE_RSA_WITH_AES_256_CBC_SHA (0x39) DH 1024 bits FS WEAK 256 TLS_DHE_RSA_WITH_AES_128_CBC_SHA256 (0x67) DH 1024 bits FS WEAK 128 TLS_DHE_RSA_WITH_AES_128_CBC_SHA (0x33) DH 1024 bits FS WEAK 128 TLS_DHE_RSA_WITH_3DES_EDE_CBC_SHA (0x16) DH 1024 bits FS WEAK 112