Add configuration parameter ssl_renegotiation_limit to control

how often we do SSL session key renegotiation. Can be set to
0 to disable renegotiation completely, which is required if
a broken SSL library is used (broken patches to CVE-2009-3555
a known cause) or when using a client library that can't do
renegotiation.

Author: mhagander

doc/src/sgml/config.sgml

@@ -1,4 +1,4 @@
-<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.252 2010/02/17 04:19:37 tgl Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/config.sgml,v 1.253 2010/02/25 13:26:15 mha Exp $ -->
 
 <chapter Id="runtime-config">
   <title>Server Configuration</title>
@@ -606,6 +606,32 @@ SET ENABLE_SEQSCAN TO OFF;
       </listitem>
      </varlistentry>
 
+     <varlistentry id="guc-ssl-renegotiation-limit" xreflabel="ssl_renegotiation_limit">
+      <term><varname>ssl_renegotiation_limit</varname> (<type>int</type>)</term>
+      <indexterm>
+       <primary><varname>ssl_renegotiation_limit</> configuration parameter</primary>
+      </indexterm>
+      <listitem>
+       <para>
+        Specifies how much data can flow over an <acronym>SSL</> encrypted connection
+        before renegotiation of the session will take place. Renegotiation of the
+        session decreases the chance of doing cryptanalysis when large amounts of data
+        are sent, but it also carries a large performance penalty. The sum of
+        sent and received traffic is used to check the limit. If the parameter is
+        set to 0, renegotiation is disabled. The default is <literal>512MB</>.
+       </para>
+       <note>
+        <para>
+         SSL libraries from before November 2009 are insecure when using SSL
+         renegotiation, due to a vulnerability in the SSL protocol. As a stop-gap fix
+         for this vulnerability, some vendors also shipped SSL libraries incapable
+         of doing renegotiation. If any of these libraries are in use on the client
+         or server, SSL renegotiation should be disabled.
+        </para>
+       </note>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="guc-ssl-ciphers" xreflabel="ssl_ciphers">
       <term><varname>ssl_ciphers</varname> (<type>string</type>)</term>
       <indexterm>

src/backend/libpq/be-secure.c

@@ -11,7 +11,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/libpq/be-secure.c,v 1.97 2010/02/18 11:13:45 heikki Exp $
+ *	  $PostgreSQL: pgsql/src/backend/libpq/be-secure.c,v 1.98 2010/02/25 13:26:15 mha Exp $
  *
  *	  Since the server static private key ($DataDir/server.key)
  *	  will normally be stored unencrypted so that the database
@@ -93,13 +93,14 @@ static void close_SSL(Port *);
 static const char *SSLerrmessage(void);
 #endif
 
-#ifdef USE_SSL
 /*
  *	How much data can be sent across a secure connection
  *	(total in both directions) before we require renegotiation.
+ *	Set to 0 to disable renegotiation completely.
  */
-#define RENEGOTIATION_LIMIT (512 * 1024 * 1024)
+int ssl_renegotiation_limit;
 
+#ifdef USE_SSL
 static SSL_CTX *SSL_context = NULL;
 static bool ssl_loaded_verify_locations = false;
 
@@ -320,7 +321,7 @@ secure_write(Port *port, void *ptr, size_t len)
 	{
 		int			err;
 
-		if (port->count > RENEGOTIATION_LIMIT)
+		if (ssl_renegotiation_limit && port->count > ssl_renegotiation_limit * 1024L)
 		{
 			SSL_set_session_id_context(port->ssl, (void *) &SSL_context,
 									   sizeof(SSL_context));

src/backend/utils/misc/guc.c

@@ -10,7 +10,7 @@
  * Written by Peter Eisentraut <peter_e@gmx.net>.
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.541 2010/02/17 04:19:40 tgl Exp $
+ *	  $PostgreSQL: pgsql/src/backend/utils/misc/guc.c,v 1.542 2010/02/25 13:26:15 mha Exp $
  *
  *--------------------------------------------------------------------
  */
@@ -117,6 +117,7 @@ extern char *temp_tablespaces;
 extern bool synchronize_seqscans;
 extern bool fullPageWrites;
 extern int	vacuum_defer_cleanup_age;
+extern int	ssl_renegotiation_limit;
 
 int	trace_recovery_messages = LOG;
 
@@ -1968,6 +1969,16 @@ static struct config_int ConfigureNamesInt[] =
 		0, 0, INT_MAX, assign_tcp_keepalives_interval, show_tcp_keepalives_interval
 	},
 
+	{
+		{"ssl_renegotiation_limit", PGC_USERSET, CONN_AUTH_SECURITY,
+			gettext_noop("Set the amount of traffic to send and receive before renegotiating the encryption keys."),
+			NULL,
+			GUC_UNIT_KB,
+		},
+		&ssl_renegotiation_limit,
+		512 * 1024, 0, MAX_KILOBYTES, NULL, NULL
+	},
+
 	{
 		{"tcp_keepalives_count", PGC_USERSET, CLIENT_CONN_OTHER,
 			gettext_noop("Maximum number of TCP keepalive retransmits."),

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

@@ -80,6 +80,7 @@
 #ssl = off				# (change requires restart)
 #ssl_ciphers = 'ALL:!ADH:!LOW:!EXP:!MD5:@STRENGTH'	# allowed SSL ciphers
 					# (change requires restart)
+#ssl_renegotiation_limit = 512MB	# amount of data between renegotiations
 #password_encryption = on
 #db_user_namespace = off