.B dn[.<dnstyle>]:<pattern>
.RE
.RS
-.B u[<mech>[<realm>]]:<pattern>
+.B u[.<mech>[/<realm>]]:<pattern>
.RE
.RS
.B group[/objectClass[/attributeType]]:<pattern>
A subset of these rules can be used as third arg in the
.B authz-regexp
statement (see below); significantly, the
-.I URI
+.IR URI ,
+provided it results in exactly one entry,
and the
.I dn.exact:<dn>
forms.
.TP
.B authz-regexp <match> <replace>
Used by the authentication framework to convert simple user names,
-such as provided by SASL subsystem, to an LDAP DN used for
-authorization purposes. Note that the resultant DN need not refer
+such as provided by SASL subsystem, or extracted from certificates
+in case of cert-based SASL EXTERNAL, or provided within the RFC 4370
+"proxied authorization" control, to an LDAP DN used for
+authorization purposes. Note that the resulting DN need not refer
to an existing entry to be considered valid. When an authorization
request is received from the SASL subsystem, the SASL
.BR USERNAME ,