Add conninfo to pg_stat_wal_receiver

Commit b1a9bad9 introduced a stats view to provide insight into the
running WAL receiver, but neglected to include the connection string in
it, as reported by Michaël Paquier.  This commit fixes that omission.
(Any security-sensitive information is not disclosed).

While at it, close the mild security hole that we were exposing the
password in the connection string in shared memory.  This isn't
user-accessible, but it still looks like a good idea to avoid having the
cleartext password in memory.

Author: Michaël Paquier, Álvaro Herrera
Review by: Vik Fearing

Discussion: https://www.postgresql.org/message-id/CAB7nPqStg4M561obo7ryZ5G+fUydG4v1Ajs1xZT1ujtu+woRag@mail.gmail.com

doc/src/sgml/monitoring.sgml

@@ -1302,6 +1302,14 @@ SELECT pid, wait_event_type, wait_event FROM pg_stat_activity WHERE wait_event i
      <entry><type>text</></entry>
      <entry>Replication slot name used by this WAL receiver</entry>
     </row>
+    <row>
+     <entry><structfield>conn_info</></entry>
+     <entry><type>text</></entry>
+     <entry>
+      Connection string used by this WAL receiver,
+      with security-sensitive fields obfuscated.
+     </entry>
+    </row>
    </tbody>
    </tgroup>
   </table>

src/backend/catalog/system_views.sql

@@ -681,7 +681,8 @@ CREATE VIEW pg_stat_wal_receiver AS
             s.last_msg_receipt_time,
             s.latest_end_lsn,
             s.latest_end_time,
-            s.slot_name
+            s.slot_name,
+            s.conn_info
     FROM pg_stat_get_wal_receiver() s
     WHERE s.pid IS NOT NULL;
 

src/backend/replication/libpqwalreceiver/libpqwalreceiver.c

@@ -20,6 +20,7 @@
 #include <sys/time.h>
 
 #include "libpq-fe.h"
+#include "pqexpbuffer.h"
 #include "access/xlog.h"
 #include "miscadmin.h"
 #include "replication/walreceiver.h"
@@ -47,6 +48,7 @@ static char *recvBuf = NULL;
 
 /* Prototypes for interface functions */
 static void libpqrcv_connect(char *conninfo);
+static char *libpqrcv_get_conninfo(void);
 static void libpqrcv_identify_system(TimeLineID *primary_tli);
 static void libpqrcv_readtimelinehistoryfile(TimeLineID tli, char **filename, char **content, int *len);
 static bool libpqrcv_startstreaming(TimeLineID tli, XLogRecPtr startpoint,
@@ -74,6 +76,7 @@ _PG_init(void)
 		walrcv_disconnect != NULL)
 		elog(ERROR, "libpqwalreceiver already loaded");
 	walrcv_connect = libpqrcv_connect;
+	walrcv_get_conninfo = libpqrcv_get_conninfo;
 	walrcv_identify_system = libpqrcv_identify_system;
 	walrcv_readtimelinehistoryfile = libpqrcv_readtimelinehistoryfile;
 	walrcv_startstreaming = libpqrcv_startstreaming;
@@ -117,6 +120,55 @@ libpqrcv_connect(char *conninfo)
 						PQerrorMessage(streamConn))));
 }
 
+/*
+ * Return a user-displayable conninfo string.  Any security-sensitive fields
+ * are obfuscated.
+ */
+static char *
+libpqrcv_get_conninfo(void)
+{
+	PQconninfoOption *conn_opts;
+	PQconninfoOption *conn_opt;
+	PQExpBufferData	buf;
+	char	   *retval;
+
+	Assert(streamConn != NULL);
+
+	initPQExpBuffer(&buf);
+	conn_opts = PQconninfo(streamConn);
+
+	if (conn_opts == NULL)
+		ereport(ERROR,
+				(errmsg("could not parse connection string: %s",
+						_("out of memory"))));
+
+	/* build a clean connection string from pieces */
+	for (conn_opt = conn_opts; conn_opt->keyword != NULL; conn_opt++)
+	{
+		bool	obfuscate;
+
+		/* Skip debug and empty options */
+		if (strchr(conn_opt->dispchar, 'D') ||
+			conn_opt->val == NULL ||
+			conn_opt->val[0] == '\0')
+			continue;
+
+		/* Obfuscate security-sensitive options */
+		obfuscate = strchr(conn_opt->dispchar, '*') != NULL;
+
+		appendPQExpBuffer(&buf, "%s%s=%s",
+						  buf.len == 0 ? "" : " ",
+						  conn_opt->keyword,
+						  obfuscate ? "********" : conn_opt->val);
+	}
+
+	PQconninfoFree(conn_opts);
+
+	retval = PQExpBufferDataBroken(buf) ? NULL : pstrdup(buf.data);
+	termPQExpBuffer(&buf);
+	return retval;
+}
+
 /*
  * Check that primary's system identifier matches ours, and fetch the current
  * timeline ID of the primary.

src/backend/replication/walreceiver.c

@@ -75,6 +75,7 @@ bool		hot_standby_feedback;
 
 /* libpqreceiver hooks to these when loaded */
 walrcv_connect_type walrcv_connect = NULL;
+walrcv_get_conninfo_type walrcv_get_conninfo = NULL;
 walrcv_identify_system_type walrcv_identify_system = NULL;
 walrcv_startstreaming_type walrcv_startstreaming = NULL;
 walrcv_endstreaming_type walrcv_endstreaming = NULL;
@@ -192,6 +193,7 @@ void
 WalReceiverMain(void)
 {
 	char		conninfo[MAXCONNINFO];
+	char	   *tmp_conninfo;
 	char		slotname[NAMEDATALEN];
 	XLogRecPtr	startpoint;
 	TimeLineID	startpointTLI;
@@ -282,7 +284,9 @@ WalReceiverMain(void)
 
 	/* Load the libpq-specific functions */
 	load_file("libpqwalreceiver", false);
-	if (walrcv_connect == NULL || walrcv_startstreaming == NULL ||
+	if (walrcv_connect == NULL ||
+		walrcv_get_conninfo == NULL ||
+		walrcv_startstreaming == NULL ||
 		walrcv_endstreaming == NULL ||
 		walrcv_identify_system == NULL ||
 		walrcv_readtimelinehistoryfile == NULL ||
@@ -304,6 +308,21 @@ WalReceiverMain(void)
 	walrcv_connect(conninfo);
 	DisableWalRcvImmediateExit();
 
+	/*
+	 * Save user-visible connection string.  This clobbers the original
+	 * conninfo, for security.
+	 */
+	tmp_conninfo = walrcv_get_conninfo();
+	SpinLockAcquire(&walrcv->mutex);
+	memset(walrcv->conninfo, 0, MAXCONNINFO);
+	if (tmp_conninfo)
+	{
+		strlcpy((char *) walrcv->conninfo, tmp_conninfo, MAXCONNINFO);
+		pfree(tmp_conninfo);
+	}
+	walrcv->ready_to_display = true;
+	SpinLockRelease(&walrcv->mutex);
+
 	first_stream = true;
 	for (;;)
 	{
@@ -1308,10 +1327,9 @@ WalRcvGetStateString(WalRcvState state)
 Datum
 pg_stat_get_wal_receiver(PG_FUNCTION_ARGS)
 {
-#define PG_STAT_GET_WAL_RECEIVER_COLS	11
 	TupleDesc	tupdesc;
-	Datum		values[PG_STAT_GET_WAL_RECEIVER_COLS];
-	bool		nulls[PG_STAT_GET_WAL_RECEIVER_COLS];
+	Datum	   *values;
+	bool	   *nulls;
 	WalRcvData *walrcv = WalRcv;
 	WalRcvState state;
 	XLogRecPtr	receive_start_lsn;
@@ -1323,41 +1341,33 @@ pg_stat_get_wal_receiver(PG_FUNCTION_ARGS)
 	XLogRecPtr	latest_end_lsn;
 	TimestampTz latest_end_time;
 	char	   *slotname;
+	char	   *conninfo;
 
 	/* No WAL receiver, just return a tuple with NULL values */
 	if (walrcv->pid == 0)
 		PG_RETURN_NULL();
 
-	/* Initialise values and NULL flags arrays */
-	MemSet(values, 0, sizeof(values));
-	MemSet(nulls, 0, sizeof(nulls));
-
-	/* Initialise attributes information in the tuple descriptor */
-	tupdesc = CreateTemplateTupleDesc(PG_STAT_GET_WAL_RECEIVER_COLS, false);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 1, "pid",
-					   INT4OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 2, "status",
-					   TEXTOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 3, "receive_start_lsn",
-					   LSNOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 4, "receive_start_tli",
-					   INT4OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 5, "received_lsn",
-					   LSNOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 6, "received_tli",
-					   INT4OID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 7, "last_msg_send_time",
-					   TIMESTAMPTZOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 8, "last_msg_receipt_time",
-					   TIMESTAMPTZOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 9, "latest_end_lsn",
-					   LSNOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 10, "latest_end_time",
-					   TIMESTAMPTZOID, -1, 0);
-	TupleDescInitEntry(tupdesc, (AttrNumber) 11, "slot_name",
-					   TEXTOID, -1, 0);
-
-	BlessTupleDesc(tupdesc);
+	/*
+	 * Users attempting to read this data mustn't be shown security sensitive
+	 * data, so sleep until everything has been properly obfuscated.
+	 */
+retry:
+	SpinLockAcquire(&walrcv->mutex);
+	if (!walrcv->ready_to_display)
+	{
+		SpinLockRelease(&walrcv->mutex);
+		CHECK_FOR_INTERRUPTS();
+		pg_usleep(1000);
+		goto retry;
+	}
+	SpinLockRelease(&walrcv->mutex);
+
+	/* determine result type */
+	if (get_call_result_type(fcinfo, NULL, &tupdesc) != TYPEFUNC_COMPOSITE)
+		elog(ERROR, "return type must be a row type");
+
+	values = palloc0(sizeof(Datum) * tupdesc->natts);
+	nulls = palloc0(sizeof(bool) * tupdesc->natts);
 
 	/* Take a lock to ensure value consistency */
 	SpinLockAcquire(&walrcv->mutex);
@@ -1371,6 +1381,7 @@ pg_stat_get_wal_receiver(PG_FUNCTION_ARGS)
 	latest_end_lsn = walrcv->latestWalEnd;
 	latest_end_time = walrcv->latestWalEndTime;
 	slotname = pstrdup(walrcv->slotname);
+	conninfo = pstrdup(walrcv->conninfo);
 	SpinLockRelease(&walrcv->mutex);
 
 	/* Fetch values */
@@ -1382,7 +1393,7 @@ pg_stat_get_wal_receiver(PG_FUNCTION_ARGS)
 		 * Only superusers can see details. Other users only get the pid value
 		 * to know whether it is a WAL receiver, but no details.
 		 */
-		MemSet(&nulls[1], true, PG_STAT_GET_WAL_RECEIVER_COLS - 1);
+		MemSet(&nulls[1], true, sizeof(bool) * (tupdesc->natts - 1));
 	}
 	else
 	{
@@ -1418,6 +1429,10 @@ pg_stat_get_wal_receiver(PG_FUNCTION_ARGS)
 			nulls[10] = true;
 		else
 			values[10] = CStringGetTextDatum(slotname);
+		if (*conninfo == '\0')
+			nulls[11] = true;
+		else
+			values[11] = CStringGetTextDatum(conninfo);
 	}
 
 	/* Returns the record as Datum */

src/include/catalog/catversion.h

@@ -53,6 +53,6 @@
  */
 
 /*							yyyymmddN */
-#define CATALOG_VERSION_NO	201606261
+#define CATALOG_VERSION_NO	201606291
 
 #endif

src/include/catalog/pg_proc.h

@@ -2746,7 +2746,7 @@ DATA(insert OID = 3318 (  pg_stat_get_progress_info			  PGNSP PGUID 12 1 100 0 0
 DESCR("statistics: information about progress of backends running maintenance command");
 DATA(insert OID = 3099 (  pg_stat_get_wal_senders	PGNSP PGUID 12 1 10 0 0 f f f f f t s r 0 0 2249 "" "{23,25,3220,3220,3220,3220,23,25}" "{o,o,o,o,o,o,o,o}" "{pid,state,sent_location,write_location,flush_location,replay_location,sync_priority,sync_state}" _null_ _null_ pg_stat_get_wal_senders _null_ _null_ _null_ ));
 DESCR("statistics: information about currently active replication");
-DATA(insert OID = 3317 (  pg_stat_get_wal_receiver	PGNSP PGUID 12 1 0 0 0 f f f f f f s r 0 0 2249 "" "{23,25,3220,23,3220,23,1184,1184,3220,1184,25}" "{o,o,o,o,o,o,o,o,o,o,o}" "{pid,status,receive_start_lsn,receive_start_tli,received_lsn,received_tli,last_msg_send_time,last_msg_receipt_time,latest_end_lsn,latest_end_time,slot_name}" _null_ _null_ pg_stat_get_wal_receiver _null_ _null_ _null_ ));
+DATA(insert OID = 3317 (  pg_stat_get_wal_receiver	PGNSP PGUID 12 1 0 0 0 f f f f f f s r 0 0 2249 "" "{23,25,3220,23,3220,23,1184,1184,3220,1184,25,25}" "{o,o,o,o,o,o,o,o,o,o,o,o}" "{pid,status,receive_start_lsn,receive_start_tli,received_lsn,received_tli,last_msg_send_time,last_msg_receipt_time,latest_end_lsn,latest_end_time,slot_name,conn_info}" _null_ _null_ pg_stat_get_wal_receiver _null_ _null_ _null_ ));
 DESCR("statistics: information about WAL receiver");
 DATA(insert OID = 2026 (  pg_backend_pid				PGNSP PGUID 12 1 0 0 0 f f f f t f s r 0 0 23 "" _null_ _null_ _null_ _null_ _null_ pg_backend_pid _null_ _null_ _null_ ));
 DESCR("statistics: current backend PID");

src/include/replication/walreceiver.h

@@ -100,7 +100,8 @@ typedef struct
 	TimestampTz latestWalEndTime;
 
 	/*
-	 * connection string; is used for walreceiver to connect with the primary.
+	 * connection string; initially set to connect to the primary, and later
+	 * clobbered to hide security-sensitive fields.
 	 */
 	char		conninfo[MAXCONNINFO];
 
@@ -118,6 +119,9 @@ typedef struct
 	 */
 	bool		force_reply;
 
+	/* set true once conninfo is ready to display (obfuscated pwds etc) */
+	bool		ready_to_display;
+
 	/*
 	 * Latch used by startup process to wake up walreceiver after telling it
 	 * where to start streaming (after setting receiveStart and
@@ -133,6 +137,9 @@ extern WalRcvData *WalRcv;
 typedef void (*walrcv_connect_type) (char *conninfo);
 extern PGDLLIMPORT walrcv_connect_type walrcv_connect;
 
+typedef char *(*walrcv_get_conninfo_type) (void);
+extern PGDLLIMPORT walrcv_get_conninfo_type walrcv_get_conninfo;
+
 typedef void (*walrcv_identify_system_type) (TimeLineID *primary_tli);
 extern PGDLLIMPORT walrcv_identify_system_type walrcv_identify_system;