TLSv1 on CentOS-8

[Viktor Dukhovni]

On Tue, Apr 21, 2020 at 04:06:04PM +0100, Junaid Mukhtar wrote:

> I have managed to block the RC4 and enable tlsv1 as per our requirements.
> 
> We have a requirement to match cipher list on the internal server to match
> the native browser cipher list as shown by the
> https://clienttest.ssllabs.com:8443/ssltest/viewMyClient.html

That requirement is likely ill-considered and unwise.  You end up
freezing in a stale list that was somebody's idea of best practice at a
point in time, often for a specific use-case that may not be yours, and
sometimes without understanding what they're doing.

> I have tried setting up different combinations on the CipherString but none
> helped. Do you have any suggestions as to how to do achieve this?

Instead, configure a broadly interoperable list of ciphers that are
known to be safe enough.  The 'DEFAULT' list is a good starting point,
and you can subtract a few types of ciphers from that as needed.

On my FreeBSD 12 system, which has OpenSSL 1.1.1, I get:

    $ openssl ciphers -v -s -tls1_2 DEFAULT
    ECDHE-ECDSA-AES256-GCM-SHA384 TLSv1.2 Kx=ECDH     Au=ECDSA Enc=AESGCM(256) Mac=AEAD
    ECDHE-RSA-AES256-GCM-SHA384 TLSv1.2 Kx=ECDH     Au=RSA  Enc=AESGCM(256) Mac=AEAD
    DHE-RSA-AES256-GCM-SHA384 TLSv1.2 Kx=DH       Au=RSA  Enc=AESGCM(256) Mac=AEAD
    ECDHE-ECDSA-CHACHA20-POLY1305 TLSv1.2 Kx=ECDH     Au=ECDSA Enc=CHACHA20/POLY1305(256) Mac=AEAD
    ECDHE-RSA-CHACHA20-POLY1305 TLSv1.2 Kx=ECDH     Au=RSA  Enc=CHACHA20/POLY1305(256) Mac=AEAD
    DHE-RSA-CHACHA20-POLY1305 TLSv1.2 Kx=DH       Au=RSA  Enc=CHACHA20/POLY1305(256) Mac=AEAD
    ECDHE-ECDSA-AES128-GCM-SHA256 TLSv1.2 Kx=ECDH     Au=ECDSA Enc=AESGCM(128) Mac=AEAD
    ECDHE-RSA-AES128-GCM-SHA256 TLSv1.2 Kx=ECDH     Au=RSA  Enc=AESGCM(128) Mac=AEAD
    DHE-RSA-AES128-GCM-SHA256 TLSv1.2 Kx=DH       Au=RSA  Enc=AESGCM(128) Mac=AEAD
    ECDHE-ECDSA-AES256-SHA384 TLSv1.2 Kx=ECDH     Au=ECDSA Enc=AES(256)  Mac=SHA384
    ECDHE-RSA-AES256-SHA384 TLSv1.2 Kx=ECDH     Au=RSA  Enc=AES(256)  Mac=SHA384
    DHE-RSA-AES256-SHA256   TLSv1.2 Kx=DH       Au=RSA  Enc=AES(256)  Mac=SHA256
    ECDHE-ECDSA-AES128-SHA256 TLSv1.2 Kx=ECDH     Au=ECDSA Enc=AES(128)  Mac=SHA256
    ECDHE-RSA-AES128-SHA256 TLSv1.2 Kx=ECDH     Au=RSA  Enc=AES(128)  Mac=SHA256
    DHE-RSA-AES128-SHA256   TLSv1.2 Kx=DH       Au=RSA  Enc=AES(128)  Mac=SHA256
    ECDHE-ECDSA-AES256-SHA  TLSv1 Kx=ECDH     Au=ECDSA Enc=AES(256)  Mac=SHA1
    ECDHE-RSA-AES256-SHA    TLSv1 Kx=ECDH     Au=RSA  Enc=AES(256)  Mac=SHA1
    DHE-RSA-AES256-SHA      SSLv3 Kx=DH       Au=RSA  Enc=AES(256)  Mac=SHA1
    ECDHE-ECDSA-AES128-SHA  TLSv1 Kx=ECDH     Au=ECDSA Enc=AES(128)  Mac=SHA1
    ECDHE-RSA-AES128-SHA    TLSv1 Kx=ECDH     Au=RSA  Enc=AES(128)  Mac=SHA1
    DHE-RSA-AES128-SHA      SSLv3 Kx=DH       Au=RSA  Enc=AES(128)  Mac=SHA1
    AES256-GCM-SHA384       TLSv1.2 Kx=RSA      Au=RSA  Enc=AESGCM(256) Mac=AEAD
    AES128-GCM-SHA256       TLSv1.2 Kx=RSA      Au=RSA  Enc=AESGCM(128) Mac=AEAD
    AES256-SHA256           TLSv1.2 Kx=RSA      Au=RSA  Enc=AES(256)  Mac=SHA256
    AES128-SHA256           TLSv1.2 Kx=RSA      Au=RSA  Enc=AES(128)  Mac=SHA256
    AES256-SHA              SSLv3 Kx=RSA      Au=RSA  Enc=AES(256)  Mac=SHA1
    AES128-SHA              SSLv3 Kx=RSA      Au=RSA  Enc=AES(128)  Mac=SHA1

from which you could perhaps remove the kRSA ciphers, if insisting on
forward-secrecy does not break some important-enough pool of clients.

    DEFAULT:!kRSA

Otherwise, I don't see anything on that list I'd be inclined to remove.

For a more advance "performance-optimized" list where AES128 is
preferred over CHACHA20 and AES256, you could go with:

    AES128:CHACHA20:AES256:-ALL:ALL:!COMPLEMENTOFDEFAULT:!kRSA

The idea is to resist the temptation to explicitly order a specific list
of individual ciphers, and instead take the DEFAULT list, and lightly
prune it and/or rearrange it to optimize for some particular features.

-- 
    Viktor.