Raise the maximum authentication token (Kerberos ticket) size in GSSAPI

and SSPI athentication methods. While the old 2000 byte limit was more than
enough for Unix Kerberos implementations, tickets issued by Windows Domain
Controllers can be much larger.

Ian Turner

src/backend/libpq/auth.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/libpq/auth.c,v 1.184 2009/08/29 19:26:51 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/libpq/auth.c,v 1.185 2009/10/14 07:27:13 heikki Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -183,6 +183,21 @@ static int	pg_SSPI_recvauth(Port *port);
 #endif
 
 
+/*
+ * Maximum size of GSS and SSPI authentication tokens.
+ *
+ * Kerberos tickets are usually quite small, but the TGTs issued by Windows
+ * domain controllers include an authorization field known as the Privilege
+ * Attribute Certificate (PAC), which contains the user's Windows permissions
+ * (group memberships etc.). The PAC is copied into all tickets obtained on
+ * the basis of this TGT (even those issued by Unix realms which the Windows
+ * realm trusts), and can be several kB in size. The maximum token size
+ * accepted by Windows systems is determined by the MaxAuthToken Windows
+ * registry setting. Microsoft recommends that it is not set higher than
+ * 65535 bytes, so that seems like a reasonable limit for us as well.
+ */
+#define MAX_AUTH_TOKEN_LENGTH	65535
+
 
 /*----------------------------------------------------------------
  * Global authentication functions
@@ -948,7 +963,7 @@ pg_GSS_recvauth(Port *port)
 
 		/* Get the actual GSS token */
 		initStringInfo(&buf);
-		if (pq_getmessage(&buf, 2000))
+		if (pq_getmessage(&buf, MAX_AUTH_TOKEN_LENGTH))
 		{
 			/* EOF - pq_getmessage already logged error */
 			pfree(buf.data);
@@ -1186,7 +1201,7 @@ pg_SSPI_recvauth(Port *port)
 
 		/* Get the actual SSPI token */
 		initStringInfo(&buf);
-		if (pq_getmessage(&buf, 2000))
+		if (pq_getmessage(&buf, MAX_AUTH_TOKEN_LENGTH))
 		{
 			/* EOF - pq_getmessage already logged error */
 			pfree(buf.data);