If built with EXPERIMENTAL_CERTNAMES defined, code is
included to do so for server certificates, and a new smtp transport option
-"tls_verify_cert_hostnames" supported which takes a list of
-names for which the additional checks must be made.
+"tls_verify_cert_hostnames" supported which takes a hostlist
+which must match the target host for the additional checks must be made.
The option currently defaults to empty, but this may change in
the future. "*" is probably a suitable value.
Whether certificate verification is done at all, and the result of
it failing, is stll under the control of "tls_verify_hosts" nad
"tls_try_verify_hosts".
+The name being checked is that for the host, generally
+the result of an MX lookup.
+
Both Subject and Subject-Alternate-Name certificate fields
are supported, as are wildcard certificates (limited to
a single wildcard being the initial component of a 3-or-more
The equivalent check on the server for client certificates is not
implemented. At least one major email provider is using a client
certificate which fails this check. They do not retry either without
-hte client certificate or in clear.
+the client certificate or in clear.
It is possible to duplicate the effect of this checking by
creative use of Events.
A TLSA lookup will be done if either of the above options match
and the host-lookup succeded using dnssec.
-If the TLSA lookup succeeds, a TLS connection will be required
-for the host.
+If a TLSA lookup is done and succeeds, a DANE-verified TLS connection
+will be required for the host.
(TODO: specify when fallback happens vs. when the host is not used)
-If dane is in use the following transport options are ignored:
+If DANE is requested and useable (see above) the following transport
+options are ignored:
hosts_require_tls
tls_verify_hosts
tls_try_verify_hosts
tls_crl
tls_verify_cert_hostnames
+If DANE is not usable, whether requested or not, and CA-anchored
+verification evaluation is wanted, the above variables should be set
+appropriately.
+
Currently dnssec_request_domains must be active (need to think about that)
and dnssec_require_domains is ignored.