The original patch to disallow non-passworded connections to non-superusers

failed to cover all the ways in which a connection can be initiated in dblink.
Plug the remaining holes.  Also, disallow transient connections in functions
for which that feature makes no sense (because they are only sensible as
part of a sequence of operations on the same connection).  Joe Conway

Security: CVE-2007-6601

contrib/dblink/dblink.c

@@ -8,7 +8,7 @@
  * Darko Prenosil <Darko.Prenosil@finteh.hr>
  * Shridhar Daithankar <shridhar_daithankar@persistent.co.in>
  *
- * $PostgreSQL: pgsql/contrib/dblink/dblink.c,v 1.60.2.1 2007/07/09 01:32:30 joe Exp $
+ * $PostgreSQL: pgsql/contrib/dblink/dblink.c,v 1.60.2.2 2008/01/03 21:28:18 tgl Exp $
  * Copyright (c) 2001-2006, PostgreSQL Global Development Group
  * ALL RIGHTS RESERVED;
  *
@@ -91,6 +91,7 @@ static HeapTuple get_tuple_of_interest(Oid relid, int2vector *pkattnums, int16 p
 static Oid	get_relid_from_relname(text *relname_text);
 static char *generate_relation_name(Oid relid);
 static char *connstr_strip_password(const char *connstr);
+static void dblink_security_check(PGconn *conn, remoteConn *rconn, const char *connstr);
 
 /* Global */
 static remoteConn *pconn = NULL;
@@ -177,6 +178,7 @@ typedef struct remoteConnHashEnt
 			else \
 			{ \
 				connstr = conname_or_str; \
+				dblink_security_check(conn, rconn, connstr); \
 				conn = PQconnectdb(connstr); \
 				if (PQstatus(conn) == CONNECTION_BAD) \
 				{ \
@@ -191,6 +193,16 @@ typedef struct remoteConnHashEnt
 			} \
 	} while (0)
 
+#define DBLINK_GET_NAMED_CONN \
+	do { \
+			char *conname = GET_STR(PG_GETARG_TEXT_P(0)); \
+			rconn = getConnectionByName(conname); \
+			if(rconn) \
+				conn = rconn->conn; \
+			else \
+				DBLINK_CONN_NOT_AVAIL; \
+	} while (0)
+
 #define DBLINK_INIT \
 	do { \
 			if (!pconn) \
@@ -231,27 +243,8 @@ dblink_connect(PG_FUNCTION_ARGS)
 	if (connname)
 		rconn = (remoteConn *) palloc(sizeof(remoteConn));
 
-	/* for non-superusers, check that server requires a password */
+	/* check password used if not superuser */
-	if (!superuser())
+	dblink_security_check(conn, rconn, connstr);
-	{
-		/* this attempt must fail */
-		conn = PQconnectdb(connstr_strip_password(connstr));
-
-		if (PQstatus(conn) == CONNECTION_OK)
-		{
-			PQfinish(conn);
-			if (rconn)
-				pfree(rconn);
-
-			ereport(ERROR,
-					(errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
-					 errmsg("password is required"),
-					 errdetail("Non-superuser cannot connect if the server does not request a password."),
-					 errhint("Target server's authentication method must be changed.")));
-		}
-		else
-			PQfinish(conn);
-	}
 	conn = PQconnectdb(connstr);
 
 	MemoryContextSwitchTo(oldcontext);
@@ -1053,17 +1046,11 @@ PG_FUNCTION_INFO_V1(dblink_is_busy);
 Datum
 dblink_is_busy(PG_FUNCTION_ARGS)
 {
-	char	   *msg;
 	PGconn	   *conn = NULL;
-	char	   *conname = NULL;
-	char	   *connstr = NULL;
 	remoteConn *rconn = NULL;
-	bool		freeconn = false;
 
 	DBLINK_INIT;
-	DBLINK_GET_CONN;
+	DBLINK_GET_NAMED_CONN;
-	if (!conn)
-		DBLINK_CONN_NOT_AVAIL;
 
 	PQconsumeInput(conn);
 	PG_RETURN_INT32(PQisBusy(conn));
@@ -1084,26 +1071,20 @@ PG_FUNCTION_INFO_V1(dblink_cancel_query);
 Datum
 dblink_cancel_query(PG_FUNCTION_ARGS)
 {
-	char	   *msg;
 	int			res = 0;
 	PGconn	   *conn = NULL;
-	char	   *conname = NULL;
-	char	   *connstr = NULL;
 	remoteConn *rconn = NULL;
-	bool		freeconn = false;
 	PGcancel   *cancel;
 	char		errbuf[256];
 
 	DBLINK_INIT;
-	DBLINK_GET_CONN;
+	DBLINK_GET_NAMED_CONN;
-	if (!conn)
-		DBLINK_CONN_NOT_AVAIL;
 	cancel = PQgetCancel(conn);
 
 	res = PQcancel(cancel, errbuf, 256);
 	PQfreeCancel(cancel);
 
-	if (res == 0)
+	if (res == 1)
 		PG_RETURN_TEXT_P(GET_TEXT("OK"));
 	else
 		PG_RETURN_TEXT_P(GET_TEXT(errbuf));
@@ -1126,18 +1107,13 @@ dblink_error_message(PG_FUNCTION_ARGS)
 {
 	char	   *msg;
 	PGconn	   *conn = NULL;
-	char	   *conname = NULL;
-	char	   *connstr = NULL;
 	remoteConn *rconn = NULL;
-	bool		freeconn = false;
 
 	DBLINK_INIT;
-	DBLINK_GET_CONN;
+	DBLINK_GET_NAMED_CONN;
-	if (!conn)
-		DBLINK_CONN_NOT_AVAIL;
 
 	msg = PQerrorMessage(conn);
-	if (!msg)
+	if (msg == NULL || msg[0] == '\0')
 		PG_RETURN_TEXT_P(GET_TEXT("OK"));
 	else
 		PG_RETURN_TEXT_P(GET_TEXT(msg));
@@ -2428,3 +2404,28 @@ connstr_strip_password(const char *connstr)
 
 	return result.data;
 }
+
+static void
+dblink_security_check(PGconn *conn, remoteConn *rconn, const char *connstr)
+{
+	if (!superuser())
+	{
+		/* this attempt must fail */
+		conn = PQconnectdb(connstr_strip_password(connstr));
+
+		if (PQstatus(conn) == CONNECTION_OK)
+		{
+			PQfinish(conn);
+			if (rconn)
+				pfree(rconn);
+
+			ereport(ERROR,
+					(errcode(ERRCODE_S_R_E_PROHIBITED_SQL_STATEMENT_ATTEMPTED),
+					 errmsg("password is required"),
+					 errdetail("Non-superuser cannot connect if the server does not request a password."),
+					 errhint("Target server's authentication method must be changed.")));
+		}
+		else
+			PQfinish(conn);
+	}
+}

contrib/dblink/expected/dblink.out

@@ -722,6 +722,12 @@ SELECT dblink_get_connections();
  {dtest1,dtest2,dtest3}
 (1 row)
 
+SELECT dblink_is_busy('dtest1');
+ dblink_is_busy 
+----------------
+              0
+(1 row)
+
 SELECT dblink_disconnect('dtest1');
  dblink_disconnect 
 -------------------
@@ -756,3 +762,34 @@ SELECT * from result;
  10 | k  | {a10,b10,c10}
 (11 rows)
 
+SELECT dblink_connect('dtest1', 'dbname=contrib_regression');
+ dblink_connect 
+----------------
+ OK
+(1 row)
+
+SELECT * from 
+ dblink_send_query('dtest1', 'select * from foo where f1 < 3') as t1;
+ t1 
+----
+  1
+(1 row)
+
+SELECT dblink_cancel_query('dtest1');
+ dblink_cancel_query 
+---------------------
+ OK
+(1 row)
+
+SELECT dblink_error_message('dtest1');
+ dblink_error_message 
+----------------------
+ OK
+(1 row)
+
+SELECT dblink_disconnect('dtest1');
+ dblink_disconnect 
+-------------------
+ OK
+(1 row)
+

contrib/dblink/sql/dblink.sql

@@ -342,9 +342,18 @@ UNION
 ORDER by f1;
 
 SELECT dblink_get_connections();
+SELECT dblink_is_busy('dtest1');
 
 SELECT dblink_disconnect('dtest1');
 SELECT dblink_disconnect('dtest2');
 SELECT dblink_disconnect('dtest3');
+
 SELECT * from result;
 
+SELECT dblink_connect('dtest1', 'dbname=contrib_regression');
+SELECT * from 
+ dblink_send_query('dtest1', 'select * from foo where f1 < 3') as t1;
+
+SELECT dblink_cancel_query('dtest1');
+SELECT dblink_error_message('dtest1');
+SELECT dblink_disconnect('dtest1');