[gnutls-help] Priority strings, changing available ciphers

[Sander Smeenk]

Quoting Alexander Sosedkin (asosedkin at redhat.com):

> > According to 'sslyze', this results in these ciphers on my MX:
> > >From this list i want to disable these ciphers:
> Have you checked that it actually lets you connect with these?

Yes. The 'sslyze' tool tries every possible combination and reports what
worked.

> > Am i right to note that GnuTLS does not allow for such intricate
> > configuration of available ciphers?
> It does not, and neither do most of the other TLS libraries.

OpenSSL allows you to specify an exact list of ciphers that should be
in- or excluded and is able to in- or exclude groups of ciphers based
on 'RSA' or 'SHA1' too.

> E.g., your intent looks like a `:-RSA:-SHA1` to me at a cursory glance,
> so are you sure you need ciphersuite-grained control for your usecase?
>
> Email is one curious case historically utilizing opportunistic encryption,
> has the internet finally moved past the times of unencrypted SMTP
> and into TLS algorithm tightening? =)

This is all sparked by the National Cyber Security Centre of the
Netherlands publishing what TLS versions- and ciphers are considered
insufficient, or should be phased out. And a tool called 'internet.nl'
that tests compliance.
So now i am tasked with making my servers score 100%

Regards,
-Sndr.
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