Support configuring TLSv1.3 cipher suites

The ssl_ciphers GUC can only set cipher suites for TLSv1.2, and lower,
connections. For TLSv1.3 connections a different OpenSSL API must be
used.  This adds a new GUC, ssl_tls13_ciphers, which can be used to
configure a colon separated list of cipher suites to support when
performing a TLSv1.3 handshake.

Original patch by Erica Zhang with additional hacking by me.

Author: Erica Zhang <ericazhangy2021@qq.com>
Author: Daniel Gustafsson <daniel@yesql.se>
Reviewed-by: Jacob Champion <jacob.champion@enterprisedb.com>
Reviewed-by: Andres Freund <andres@anarazel.de>
Reviewed-by: Peter Eisentraut <peter@eisentraut.org>
Reviewed-by: Jelte Fennema-Nio <postgres@jeltef.nl>
Discussion: https://postgr.es/m/tencent_063F89FA72CCF2E48A0DF5338841988E9809@qq.com

doc/src/sgml/config.sgml

@@ -1340,6 +1340,28 @@ include_dir 'conf.d'
       </listitem>
      </varlistentry>
 
+     <varlistentry id="guc-ssl-tls13-ciphers" xreflabel="ssl_tls13_ciphers">
+      <term><varname>ssl_tls13_ciphers</varname> (<type>string</type>)
+      <indexterm>
+       <primary><varname>ssl_tls13_ciphers</varname> configuration parameter</primary>
+      </indexterm>
+      </term>
+      <listitem>
+       <para>
+        Specifies a list of cipher suites that are allowed by connections using
+        <acronym>TLS</acronym> version 1.3.  Multiple cipher suites can be
+        specified by using a colon separated list. If left blank, the default
+        set of cipher suites in <productname>OpenSSL</productname> will be used.
+       </para>
+
+       <para>
+        This parameter can only be set in the
+        <filename>postgresql.conf</filename> file or on the server command
+        line.
+       </para>
+      </listitem>
+     </varlistentry>
+
      <varlistentry id="guc-ssl-ciphers" xreflabel="ssl_ciphers">
       <term><varname>ssl_ciphers</varname> (<type>string</type>)
       <indexterm>
@@ -1348,15 +1370,13 @@ include_dir 'conf.d'
       </term>
       <listitem>
        <para>
-        Specifies a list of <acronym>SSL</acronym> cipher suites that are
+        Specifies a list of <acronym>SSL</acronym> ciphers that are allowed by
-        allowed to be used by SSL connections.  See the
+        connections using TLS version 1.2 and lower, see
-        <citerefentry><refentrytitle>ciphers</refentrytitle></citerefentry>
+        <xref linkend="guc-ssl-tls13-ciphers"/> for TLS version 1.3 connections. See
+        the <citerefentry><refentrytitle>ciphers</refentrytitle></citerefentry>
         manual page in the <productname>OpenSSL</productname> package for the
-        syntax of this setting and a list of supported values.  Only
+        syntax of this setting and a list of supported values.  The default value
-        connections using TLS version 1.2 and lower are affected.  There is
+        is <literal>HIGH:MEDIUM:+3DES:!aNULL</literal>.  The default is usually a
-        currently no setting that controls the cipher choices used by TLS
-        version 1.3 connections.  The default value is
-        <literal>HIGH:MEDIUM:+3DES:!aNULL</literal>.  The default is usually a
         reasonable choice unless you have specific security requirements.
        </para>
 

src/backend/libpq/be-secure-openssl.c

@@ -288,15 +288,31 @@ be_tls_init(bool isServerStart)
 	if (!initialize_ecdh(context, isServerStart))
 		goto error;
 
-	/* set up the allowed cipher list */
+	/* set up the allowed cipher list for TLSv1.2 and below */
-	if (SSL_CTX_set_cipher_list(context, SSLCipherSuites) != 1)
+	if (SSL_CTX_set_cipher_list(context, SSLCipherList) != 1)
 	{
 		ereport(isServerStart ? FATAL : LOG,
 				(errcode(ERRCODE_CONFIG_FILE_ERROR),
-				 errmsg("could not set the cipher list (no valid ciphers available)")));
+				 errmsg("could not set the TLSv1.2 cipher list (no valid ciphers available)")));
 		goto error;
 	}
 
+	/*
+	 * Set up the allowed cipher suites for TLSv1.3. If the GUC is an empty
+	 * string we leave the allowed suites to be the OpenSSL default value.
+	 */
+	if (SSLCipherSuites[0])
+	{
+		/* set up the allowed cipher suites */
+		if (SSL_CTX_set_ciphersuites(context, SSLCipherSuites) != 1)
+		{
+			ereport(isServerStart ? FATAL : LOG,
+					(errcode(ERRCODE_CONFIG_FILE_ERROR),
+					 errmsg("could not set the TLSv1.3 cipher suites (no valid ciphers available)")));
+			goto error;
+		}
+	}
+
 	/* Let server choose order */
 	if (SSLPreferServerCiphers)
 		SSL_CTX_set_options(context, SSL_OP_CIPHER_SERVER_PREFERENCE);

src/backend/libpq/be-secure.c

@@ -49,6 +49,7 @@ bool		ssl_loaded_verify_locations = false;
 
 /* GUC variable controlling SSL cipher list */
 char	   *SSLCipherSuites = NULL;
+char	   *SSLCipherList = NULL;
 
 /* GUC variable for default ECHD curve. */
 char	   *SSLECDHCurve;

src/backend/utils/misc/guc_tables.c

@@ -4641,12 +4641,23 @@ struct config_string ConfigureNamesString[] =
 	},
 
 	{
-		{"ssl_ciphers", PGC_SIGHUP, CONN_AUTH_SSL,
+		{"ssl_tls13_ciphers", PGC_SIGHUP, CONN_AUTH_SSL,
-			gettext_noop("Sets the list of allowed SSL ciphers."),
+			gettext_noop("Sets the list of allowed TLSv1.3 cipher suites (leave blank for default)."),
 			NULL,
 			GUC_SUPERUSER_ONLY
 		},
 		&SSLCipherSuites,
+		"",
+		NULL, NULL, NULL
+	},
+
+	{
+		{"ssl_ciphers", PGC_SIGHUP, CONN_AUTH_SSL,
+			gettext_noop("Sets the list of allowed TLSv1.2 (and lower) ciphers."),
+			NULL,
+			GUC_SUPERUSER_ONLY
+		},
+		&SSLCipherList,
 #ifdef USE_OPENSSL
 		"HIGH:MEDIUM:+3DES:!aNULL",
 #else

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

@@ -110,7 +110,8 @@
 #ssl_crl_file = ''
 #ssl_crl_dir = ''
 #ssl_key_file = 'server.key'
-#ssl_ciphers = 'HIGH:MEDIUM:+3DES:!aNULL'	# allowed SSL ciphers
+#ssl_ciphers = 'HIGH:MEDIUM:+3DES:!aNULL'	# allowed TLSv1.2 ciphers
+#ssl_tls13_ciphers = ''	# allowed TLSv1.3 cipher suites, blank for default
 #ssl_prefer_server_ciphers = on
 #ssl_groups = 'prime256v1'
 #ssl_min_protocol_version = 'TLSv1.2'

src/include/libpq/libpq.h

@@ -118,6 +118,7 @@ extern ssize_t secure_open_gssapi(Port *port);
 
 /* GUCs */
 extern PGDLLIMPORT char *SSLCipherSuites;
+extern PGDLLIMPORT char *SSLCipherList;
 extern PGDLLIMPORT char *SSLECDHCurve;
 extern PGDLLIMPORT bool SSLPreferServerCiphers;
 extern PGDLLIMPORT int ssl_min_protocol_version;

src/test/ssl/t/SSL/Server.pm

@@ -300,8 +300,9 @@ sub switch_server_cert
 	ok(unlink($node->data_dir . '/sslconfig.conf'));
 	$node->append_conf('sslconfig.conf', "ssl=on");
 	$node->append_conf('sslconfig.conf', $backend->set_server_cert(\%params));
-	# use lists of ECDH curves for syntax testing
+	# use lists of ECDH curves and cipher suites for syntax testing
 	$node->append_conf('sslconfig.conf', 'ssl_groups=prime256v1:secp521r1');
+	$node->append_conf('sslconfig.conf', 'ssl_tls13_ciphers=TLS_AES_256_GCM_SHA384:TLS_AES_128_GCM_SHA256');
 
 	$node->append_conf('sslconfig.conf',
 		"ssl_passphrase_command='" . $params{passphrase_cmd} . "'")