res_pjsip: allow TLS verification of wildcard cert-bearing servers

Rightly the use of wildcards in certificates is disallowed in accordance
with RFC5922. However, RFC2818 does make some allowances with regards to
their use when using subject alt names with DNS name types.

As such this patch creates a new setting for TLS transports called
'allow_wildcard_certs', which when it and 'verify_server' are both enabled
allows DNS name types, as well as the common name that start with '*.'
to match as a wildcard.

For instance: *.example.com
will match for: foo.example.com

Partial matching is not allowed, e.g. f*.example.com, foo.*.com, etc...
And the starting wildcard only matches for a single level.

For instance: *.example.com
will NOT match for: foo.bar.example.com

The new setting is disabled by default.

ASTERISK-30072 #close

Change-Id: If0be3fdab2e09c2a66bb54824fca406ebaac3da4

res/res_pjsip.c

@@ -1811,6 +1811,18 @@
 						in-progress calls.</para>
 					</description>
 				</configOption>
+				<configOption name="allow_wildcard_certs" default="false">
+					<synopsis>Allow use of wildcards in certificates (TLS ONLY)</synopsis>
+					<description>
+					  <para>In combination with verify_server, when enabled allow use of wildcards,
+					  i.e. '*.' in certs for common,and subject alt names of type DNS for TLS
+					  transport types. Names must start with the wildcard. Partial wildcards, e.g.
+					  'f*.example.com' and 'foo.*.com' are not allowed. As well, names only match
+					  against a single level meaning '*.example.com' matches 'foo.example.com',
+					  but not 'foo.bar.example.com'.
+					  </para>
+					</description>
+				</configOption>
 				<configOption name="symmetric_transport" default="no">
 					<synopsis>Use the same transport for outgoing requests as incoming ones.</synopsis>
 					<description>