DHE ciphers do not present a security risk if the key is big enough but
they are slow and mostly obsoleted by ECDHE. This patch removes any
default DH parameters. This will effectively disable all DHE ciphers
unless a global ssl-dh-param-file is defined, or
tune.ssl.default-dh-param is set, or a frontend has DH parameters
included in its PEM certificate. In this latter case, only the frontends
that have DH parameters will have DHE ciphers enabled.
Adding explicitely a DHE ciphers in a "bind" line will not be enough to
actually enable DHE. We would still need to know which DH parameters to
use so one of the three conditions described above must be met.
This request was described in GitHub issue #1604.
This new test checks that the DH-related mechanism works, be it through
specific DH parameters included in a bind line's certificate or by using
the ssl-dh-param-file or tune.ssl.default-dh-param global options.
William Lallemand
Andrew Hopkins
Remi Tricot-Le Breton