libpq: Remove code for SCM credential authentication

Support for SCM credential authentication has been removed in the
backend in 9.1, and libpq has kept some code to handle it for
compatibility.

Commit be4585b, that did the cleanup of the backend code, has done
so because the code was not really portable originally.  And, as there
are likely little chances that this is used these days, this removes the
remaining code from libpq.  An error will now be raised by libpq if
attempting to connect to a server that returns AUTH_REQ_SCM_CREDS,
instead.

References to SCM credential authentication are removed from the
protocol documentation.  This removes some meson and configure checks.

Author: Michael Paquier
Reviewed-by: Tom Lane
Discussion: https://postgr.es/m/ZBLH8a4otfqgd6Kn@paquier.xyz

2 files changed, 0 insertions, 62 deletions

diff --git a/doc/src/sgml/libpq.sgml b/doc/src/sgml/libpq.sgml
index 3706d349ab..9ee5532c07 100644
--- a/doc/src/sgml/libpq.sgml
+++ b/doc/src/sgml/libpq.sgml
@@ -1301,16 +1301,6 @@ postgresql://%2Fvar%2Flib%2Fpostgresql/dbname
          </varlistentry>
 
          <varlistentry>
-          <term><literal>creds</literal></term>
-          <listitem>
-           <para>
-            The server must request SCM credential authentication (deprecated
-            as of <productname>PostgreSQL</productname> 9.1).
-           </para>
-          </listitem>
-         </varlistentry>
-
-         <varlistentry>
           <term><literal>none</literal></term>
           <listitem>
            <para>
diff --git a/doc/src/sgml/protocol.sgml b/doc/src/sgml/protocol.sgml
index 73b7f4432f..8b5e7b1ad7 100644
--- a/doc/src/sgml/protocol.sgml
+++ b/doc/src/sgml/protocol.sgml
@@ -316,24 +316,6 @@
      </varlistentry>
 
      <varlistentry>
-      <term>AuthenticationSCMCredential</term>
-      <listitem>
-       <para>
-        This response is only possible for local Unix-domain connections
-        on platforms that support SCM credential messages.  The frontend
-        must issue an SCM credential message and then send a single data
-        byte.  (The contents of the data byte are uninteresting; it's
-        only used to ensure that the server waits long enough to receive
-        the credential message.)  If the credential is acceptable,
-        the server responds with an
-        AuthenticationOk, otherwise it responds with an ErrorResponse.
-        (This message type is only issued by pre-9.1 servers.  It may
-        eventually be removed from the protocol specification.)
-       </para>
-      </listitem>
-     </varlistentry>
-
-     <varlistentry>
       <term>AuthenticationGSS</term>
       <listitem>
        <para>
@@ -3449,40 +3431,6 @@ psql "dbname=postgres replication=database" -c "IDENTIFY_SYSTEM;"
     </listitem>
    </varlistentry>
 
-   <varlistentry id="protocol-message-formats-AuthenticationSCMCredential">
-    <term>AuthenticationSCMCredential (B)</term>
-    <listitem>
-     <variablelist>
-      <varlistentry>
-       <term>Byte1('R')</term>
-       <listitem>
-        <para>
-         Identifies the message as an authentication request.
-        </para>
-       </listitem>
-      </varlistentry>
-
-      <varlistentry>
-       <term>Int32(8)</term>
-       <listitem>
-        <para>
-         Length of message contents in bytes, including self.
-        </para>
-       </listitem>
-      </varlistentry>
-
-      <varlistentry>
-       <term>Int32(6)</term>
-       <listitem>
-        <para>
-         Specifies that an SCM credentials message is required.
-        </para>
-       </listitem>
-      </varlistentry>
-     </variablelist>
-    </listitem>
-   </varlistentry>
-
    <varlistentry id="protocol-message-formats-AuthenticationGSS">
     <term>AuthenticationGSS (B)</term>
     <listitem>