Add an overall timeout on the client authentication cycle, so that

a hung client or lost connection can't indefinitely block a postmaster
child (not to mention the possibility of deliberate DoS attacks).
Timeout is controlled by new authentication_timeout GUC variable,
which I set to 60 seconds by default ... does that seem reasonable?

doc/src/sgml/runtime.sgml

 <!--
-$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.82 2001/09/21 03:32:35 tgl Exp $
+$Header: /cvsroot/pgsql/doc/src/sgml/runtime.sgml,v 1.83 2001/09/21 17:06:12 tgl Exp $
 -->
 
 <Chapter Id="runtime">
@@ -1018,6 +1018,20 @@ env PGOPTIONS='-c geqo=off' psql
       </listitem>
      </varlistentry>
 
+     <varlistentry>
+      <term><varname>AUTHENTICATION_TIMEOUT</varname> (<type>integer</type>)</term>
+      <listitem>
+       <para>
+        Maximum time to complete client authentication, in seconds.
+	If a would-be client has not completed the authentication protocol
+	in this much time, the server unceremoniously breaks the connection.
+	This prevents hung clients from occupying a connection indefinitely.
+	This option can only be set at server start or in the
+	<filename>postgresql.conf</filename> file.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry>
       <indexterm>
        <primary>deadlock</primary>

src/backend/libpq/pqsignal.c

@@ -9,7 +9,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/libpq/pqsignal.c,v 1.23 2001/09/08 01:10:20 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/libpq/pqsignal.c,v 1.24 2001/09/21 17:06:12 tgl Exp $
  *
  * NOTES
  *		This shouldn't be in libpq, but the monitor and some other
@@ -53,7 +53,7 @@
  * signals that should never be turned off.
  *
  * AuthBlockSig is the set of signals to block during authentication;
- * it's essentially BlockSig minus SIGTERM and SIGQUIT.
+ * it's essentially BlockSig minus SIGTERM, SIGQUIT, SIGALRM.
  *
  * UnBlockSig is the set of signals to block when we don't want to block
  * signals (is this ever nonzero??)
@@ -109,6 +109,9 @@ pqinitmask(void)
 #ifdef SIGQUIT
 	sigdelset(&AuthBlockSig, SIGQUIT);
 #endif
+#ifdef SIGALRM
+	sigdelset(&AuthBlockSig, SIGALRM);
+#endif
 #else
 	UnBlockSig = 0;
 	BlockSig = sigmask(SIGHUP) | sigmask(SIGQUIT) |
@@ -116,7 +119,7 @@ pqinitmask(void)
 		sigmask(SIGINT) | sigmask(SIGUSR1) |
 		sigmask(SIGUSR2) | sigmask(SIGCHLD) |
 		sigmask(SIGWINCH) | sigmask(SIGFPE);
-	AuthBlockSig = sigmask(SIGHUP) | sigmask(SIGALRM) |
+	AuthBlockSig = sigmask(SIGHUP) |
 		sigmask(SIGINT) | sigmask(SIGUSR1) |
 		sigmask(SIGUSR2) | sigmask(SIGCHLD) |
 		sigmask(SIGWINCH) | sigmask(SIGFPE);

src/backend/postmaster/postmaster.c

@@ -37,7 +37,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/postmaster/postmaster.c,v 1.241 2001/09/08 01:10:20 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/postmaster/postmaster.c,v 1.242 2001/09/21 17:06:12 tgl Exp $
  *
  * NOTES
  *
@@ -190,6 +190,8 @@ bool		NetServer = false;	/* listen on TCP/IP */
 bool		EnableSSL = false;
 bool		SilentMode = false; /* silent mode (-S) */
 
+int			PreAuthDelay = 0;
+int			AuthenticationTimeout = 60;
 int			CheckPointTimeout = 300;
 
 /* Startup/shutdown state */
@@ -1941,16 +1943,38 @@ DoBackend(Port *port)
 	/* Reset MyProcPid to new backend's pid */
 	MyProcPid = getpid();
 
+	/*
+	 * Initialize libpq and enable reporting of elog errors to the client.
+	 * Must do this now because authentication uses libpq to send messages.
+	 */
+	pq_init();					/* initialize libpq to talk to client */
+	whereToSendOutput = Remote;	/* now safe to elog to client */
+
 	/*
 	 * We arrange for a simple exit(0) if we receive SIGTERM or SIGQUIT
 	 * during any client authentication related communication. Otherwise
 	 * the postmaster cannot shutdown the database FAST or IMMED cleanly
-	 * if a buggy client blocks a backend during authentication.
+	 * if a buggy client blocks a backend during authentication.  We also
+	 * will exit(0) after a time delay, so that a broken client can't hog
+	 * a connection indefinitely.
+	 *
+	 * PreAuthDelay is a debugging aid for investigating problems in the
+	 * authentication cycle: it can be set in postgresql.conf to allow
+	 * time to attach to the newly-forked backend with a debugger.
+	 * (See also the -W backend switch, which we allow clients to pass
+	 * through PGOPTIONS, but it is not honored until after authentication.)
 	 */
 	pqsignal(SIGTERM, authdie);
 	pqsignal(SIGQUIT, authdie);
+	pqsignal(SIGALRM, authdie);
 	PG_SETMASK(&AuthBlockSig);
 
+	if (PreAuthDelay > 0)
+		sleep(PreAuthDelay);
+
+	if (! enable_sigalrm_interrupt(AuthenticationTimeout * 1000))
+		elog(FATAL, "DoBackend: Unable to set timer for auth timeout");
+
 	/*
 	 * Receive the startup packet (which might turn out to be a cancel
 	 * request packet); then perform client authentication.
@@ -1963,9 +1987,11 @@ DoBackend(Port *port)
 	ClientAuthentication(MyProcPort); /* might not return, if failure */
 
 	/*
-	 * Done with authentication.  Prevent SIGTERM/SIGQUIT again until
-	 * backend startup is complete.
+	 * Done with authentication.  Disable timeout, and prevent SIGTERM/SIGQUIT
+	 * again until backend startup is complete.
 	 */
+	if (! disable_sigalrm_interrupt())
+		elog(FATAL, "DoBackend: Unable to disable timer for auth timeout");
 	PG_SETMASK(&BlockSig);
 
 	/*

src/backend/storage/lmgr/proc.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/storage/lmgr/proc.c,v 1.107 2001/09/07 00:27:29 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/storage/lmgr/proc.c,v 1.108 2001/09/21 17:06:12 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -327,18 +327,7 @@ LockWaitCancel(void)
 	waitingForLock = false;
 
 	/* Turn off the deadlock timer, if it's still running (see ProcSleep) */
-#ifndef __BEOS__
-	{
-		struct itimerval timeval,
-					dummy;
-
-		MemSet(&timeval, 0, sizeof(struct itimerval));
-		setitimer(ITIMER_REAL, &timeval, &dummy);
-	}
-#else
-	/* BeOS doesn't have setitimer, but has set_alarm */
-	set_alarm(B_INFINITE_TIMEOUT, B_PERIODIC_ALARM);
-#endif	 /* __BEOS__ */
+	disable_sigalrm_interrupt();
 
 	/* Unlink myself from the wait queue, if on it (might not be anymore!) */
 	LockLockTable();
@@ -501,12 +490,6 @@ ProcSleep(LOCKMETHODTABLE *lockMethodTable,
 	bool		early_deadlock = false;
 	PROC	   *proc;
 	int			i;
-#ifndef __BEOS__
-	struct itimerval timeval,
-				dummy;
-#else
-	bigtime_t	time_interval;
-#endif
 
 	/*
 	 * Determine where to add myself in the wait queue.
@@ -629,21 +612,9 @@ ProcSleep(LOCKMETHODTABLE *lockMethodTable,
 	 *
 	 * By delaying the check until we've waited for a bit, we can avoid
 	 * running the rather expensive deadlock-check code in most cases.
-	 *
-	 * Need to zero out struct to set the interval and the microseconds
-	 * fields to 0.
 	 */
-#ifndef __BEOS__
-	MemSet(&timeval, 0, sizeof(struct itimerval));
-	timeval.it_value.tv_sec = DeadlockTimeout / 1000;
-	timeval.it_value.tv_usec = (DeadlockTimeout % 1000) * 1000;
-	if (setitimer(ITIMER_REAL, &timeval, &dummy))
+	if (! enable_sigalrm_interrupt(DeadlockTimeout))
 		elog(FATAL, "ProcSleep: Unable to set timer for process wakeup");
-#else
-	time_interval = DeadlockTimeout * 1000000;	/* usecs */
-	if (set_alarm(time_interval, B_ONE_SHOT_RELATIVE_ALARM) < 0)
-		elog(FATAL, "ProcSleep: Unable to set timer for process wakeup");
-#endif
 
 	/*
 	 * If someone wakes us between SpinRelease and IpcSemaphoreLock,
@@ -664,14 +635,8 @@ ProcSleep(LOCKMETHODTABLE *lockMethodTable,
 	/*
 	 * Disable the timer, if it's still running
 	 */
-#ifndef __BEOS__
-	MemSet(&timeval, 0, sizeof(struct itimerval));
-	if (setitimer(ITIMER_REAL, &timeval, &dummy))
-		elog(FATAL, "ProcSleep: Unable to disable timer for process wakeup");
-#else
-	if (set_alarm(B_INFINITE_TIMEOUT, B_PERIODIC_ALARM) < 0)
+	if (! disable_sigalrm_interrupt())
 		elog(FATAL, "ProcSleep: Unable to disable timer for process wakeup");
-#endif
 
 	/*
 	 * Now there is nothing for LockWaitCancel to do.
@@ -949,6 +914,69 @@ ProcSendSignal(BackendId procId)
 }
 
 
+/*****************************************************************************
+ * SIGALRM interrupt support
+ *
+ * Maybe these should be in pqsignal.c?
+ *****************************************************************************/
+
+/*
+ * Enable the SIGALRM interrupt to fire after the specified delay
+ *
+ * Delay is given in milliseconds.  Caller should be sure a SIGALRM
+ * signal handler is installed before this is called.
+ *
+ * Returns TRUE if okay, FALSE on failure.
+ */
+bool
+enable_sigalrm_interrupt(int delayms)
+{
+#ifndef __BEOS__
+	struct itimerval timeval,
+				dummy;
+
+	MemSet(&timeval, 0, sizeof(struct itimerval));
+	timeval.it_value.tv_sec = delayms / 1000;
+	timeval.it_value.tv_usec = (delayms % 1000) * 1000;
+	if (setitimer(ITIMER_REAL, &timeval, &dummy))
+		return false;
+#else
+	/* BeOS doesn't have setitimer, but has set_alarm */
+	bigtime_t	time_interval;
+
+	time_interval = delayms * 1000;	/* usecs */
+	if (set_alarm(time_interval, B_ONE_SHOT_RELATIVE_ALARM) < 0)
+		return false;
+#endif
+
+	return true;
+}
+
+/*
+ * Disable the SIGALRM interrupt, if it has not yet fired
+ *
+ * Returns TRUE if okay, FALSE on failure.
+ */
+bool
+disable_sigalrm_interrupt(void)
+{
+#ifndef __BEOS__
+	struct itimerval timeval,
+				dummy;
+
+	MemSet(&timeval, 0, sizeof(struct itimerval));
+	if (setitimer(ITIMER_REAL, &timeval, &dummy))
+		return false;
+#else
+	/* BeOS doesn't have setitimer, but has set_alarm */
+	if (set_alarm(B_INFINITE_TIMEOUT, B_PERIODIC_ALARM) < 0)
+		return false;
+#endif
+
+	return true;
+}
+
+
 /*****************************************************************************
  *
  *****************************************************************************/

src/backend/tcop/postgres.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/tcop/postgres.c,v 1.232 2001/09/08 01:10:20 tgl Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/tcop/postgres.c,v 1.233 2001/09/21 17:06:12 tgl Exp $
  *
  * NOTES
  *	  this is the "main" module of the postgres backend and
@@ -967,12 +967,12 @@ die(SIGNAL_ARGS)
 }
 
 /*
- * Shutdown signal from postmaster during client authentication.
+ * Timeout or shutdown signal from postmaster during client authentication.
  * Simply exit(0).
  *
  * XXX: possible future improvement: try to send a message indicating
  * why we are disconnecting.  Problem is to be sure we don't block while
- * doing so nor mess up the authentication message exchange.
+ * doing so, nor mess up the authentication message exchange.
  */
 void
 authdie(SIGNAL_ARGS)
@@ -1168,16 +1168,6 @@ PostgresMain(int argc, char *argv[],
 
 	SetProcessingMode(InitProcessing);
 
-	/*
-	 * If under postmaster, initialize libpq and enable reporting of
-	 * elog errors to the client.
-	 */
-	if (IsUnderPostmaster)
-	{
-		pq_init();				/* initialize libpq at backend startup */
-		whereToSendOutput = Remote;	/* now safe to elog to client */
-	}
-
 	/*
 	 * Set default values for command-line options.
 	 */
@@ -1736,7 +1726,7 @@ PostgresMain(int argc, char *argv[],
 	if (!IsUnderPostmaster)
 	{
 		puts("\nPOSTGRES backend interactive interface ");
-		puts("$Revision: 1.232 $ $Date: 2001/09/08 01:10:20 $\n");
+		puts("$Revision: 1.233 $ $Date: 2001/09/21 17:06:12 $\n");
 	}
 
 	/*

src/backend/utils/misc/guc.c

@@ -4,7 +4,7 @@
  * Support for grand unified configuration scheme, including SET
  * command, configuration file, and command line options.
  *
- * $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.50 2001/09/21 03:32:35 tgl Exp $
+ * $Header: /cvsroot/pgsql/src/backend/utils/misc/guc.c,v 1.51 2001/09/21 17:06:12 tgl Exp $
  *
  * Copyright 2000 by PostgreSQL Global Development Group
  * Written by Peter Eisentraut <peter_e@gmx.net>.
@@ -41,6 +41,8 @@
 
 /* XXX these should be in other modules' header files */
 extern bool Log_connections;
+extern int	PreAuthDelay;
+extern int	AuthenticationTimeout;
 extern int	CheckPointTimeout;
 extern int	CommitDelay;
 extern int	CommitSiblings;
@@ -320,6 +322,12 @@ static struct config_int
 	{"max_locks_per_transaction", PGC_POSTMASTER, &max_locks_per_xact,
 	 64, 10, INT_MAX, NULL, NULL},
 
+	{"authentication_timeout", PGC_SIGHUP, &AuthenticationTimeout,
+	60, 1, 600, NULL, NULL},
+
+	{"pre_auth_delay", PGC_SIGHUP, &PreAuthDelay,
+	0, 0, 60, NULL, NULL},
+
 	{"checkpoint_segments", PGC_SIGHUP, &CheckPointSegments,
 	3, 1, INT_MAX, NULL, NULL},
 

src/backend/utils/misc/postgresql.conf.sample

@@ -176,6 +176,7 @@
 #
 #dynamic_library_path = '$libdir'
 #australian_timezones = false
+#authentication_timeout = 60  # min 1, max 600
 #deadlock_timeout = 1000
 #default_transaction_isolation = 'read committed'
 #max_expr_depth = 10000 # min 10

src/include/storage/proc.h

@@ -7,7 +7,7 @@
  * Portions Copyright (c) 1996-2001, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $Id: proc.h,v 1.46 2001/09/07 00:27:30 tgl Exp $
+ * $Id: proc.h,v 1.47 2001/09/21 17:06:12 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -154,4 +154,7 @@ extern void ProcWaitForSignal(void);
 extern void ProcCancelWaitForSignal(void);
 extern void ProcSendSignal(BackendId procId);
 
+extern bool enable_sigalrm_interrupt(int delayms);
+extern bool disable_sigalrm_interrupt(void);
+
 #endif	 /* PROC_H */