Add new clientcert hba option verify-full

mhagander · mhagander · commit 0516c61b756e · 2019-03-09T12:19:47.000-08:00
This allows a login to require both that the cn of the certificate
matches (like authentication type cert) *and* that another
authentication method (such as password or kerberos) succeeds as well.

The old value of clientcert=1 maps to the new clientcert=verify-ca,
clientcert=0 maps to the new clientcert=no-verify, and the new option
erify-full will add the validation of the CN.

Author: Julian Markwort, Marius Timmer
Reviewed by: Magnus Hagander, Thomas Munro
diff --git a/doc/src/sgml/client-auth.sgml b/doc/src/sgml/client-auth.sgml
@@ -563,10 +563,17 @@ hostnossl  <replaceable>database</replaceable>  <replaceable>user</replaceable>
       <para>
        In addition to the method-specific options listed below, there is one
        method-independent authentication option <literal>clientcert</literal>, which
-       can be specified in any <literal>hostssl</literal> record.  When set
-       to <literal>1</literal>, this option requires the client to present a valid
-       (trusted) SSL certificate, in addition to the other requirements of the
-       authentication method.
+       can be specified in any <literal>hostssl</literal> record.
+       This option can be set to <literal>verify-ca</literal> or
+       <literal>verify-full</literal>. Both options require the client
+       to present a valid (trusted) SSL certificate, while
+       <literal>verify-full</literal> additionally enforces that the
+       <literal>cn</literal> (Common Name) in the certificate matches
+       the username or an applicable mapping.
+       This behavior is similar to the cert authentication method
+       (see <xref linkend="auth-cert"/> ) but enables pairing
+       the verification of client certificates with any authentication
+       method that supports <literal>hostssl</literal> entries.
       </para>
      </listitem>
     </varlistentry>
@@ -1865,11 +1872,11 @@ host ... ldap ldapserver=ldap.example.net ldapbasedn="dc=example, dc=net" ldapse
    <para>
     In a <filename>pg_hba.conf</filename> record specifying certificate
     authentication, the authentication option <literal>clientcert</literal> is
-    assumed to be <literal>1</literal>, and it cannot be turned off since a client
-    certificate is necessary for this method.  What the <literal>cert</literal>
-    method adds to the basic <literal>clientcert</literal> certificate validity test
-    is a check that the <literal>cn</literal> attribute matches the database
-    user name.
+    assumed to be <literal>verify-ca</literal> or <literal>verify-full</literal>,
+    and it cannot be turned off since a client certificate is necessary for this
+    method. What the <literal>cert</literal> method adds to the basic
+    <literal>clientcert</literal> certificate validity test is a check that the
+    <literal>cn</literal> attribute matches the database user name.
    </para>
   </sect1>
 
diff --git a/doc/src/sgml/runtime.sgml b/doc/src/sgml/runtime.sgml
@@ -2316,13 +2316,25 @@ pg_dumpall -p 5432 | psql -d postgres -p 5433
    (<acronym>CA</acronym>s) you trust in a file in the data
    directory, set the parameter <xref linkend="guc-ssl-ca-file"/> in
    <filename>postgresql.conf</filename> to the new file name, and add the
-   authentication option <literal>clientcert=1</literal> to the appropriate
+   authentication option <literal>clientcert=verify-ca</literal> or
+   <literal>clientcert=verify-full</literal> to the appropriate
    <literal>hostssl</literal> line(s) in <filename>pg_hba.conf</filename>.
    A certificate will then be requested from the client during SSL
    connection startup.  (See <xref linkend="libpq-ssl"/> for a description
-   of how to set up certificates on the client.)  The server will
-   verify that the client's certificate is signed by one of the trusted
-   certificate authorities.
+   of how to set up certificates on the client.)
+  </para>
+
+  <para>
+   For a <literal>hostssl</literal> entry with
+   <literal>clientcert=verify-ca</literal>, the server will verify
+   that the client's certificate is signed by one of the trusted
+   certificate authorities. If <literal>clientcert=verify-full</literal>
+   is specified, the server will not only verify the certificate
+   chain, but it will also check whether the username or its mapping
+   matches the <literal>cn</literal> (Common Name) of the provided certificate.
+   Note that certificate chain validation is always ensured when the
+   <literal>cert</literal> authentication method is used
+   (see <xref linkend="auth-cert"/>).
   </para>
 
   <para>
@@ -2341,18 +2353,34 @@ pg_dumpall -p 5432 | psql -d postgres -p 5433
    The <literal>clientcert</literal> authentication option is available for
    all authentication methods, but only in <filename>pg_hba.conf</filename> lines
    specified as <literal>hostssl</literal>.  When <literal>clientcert</literal> is
-   not specified or is set to 0, the server will still verify any presented
-   client certificates against its CA file, if one is configured &mdash; but
-   it will not insist that a client certificate be presented.
+   not specified or is set to <literal>no-verify</literal>, the server will still
+   verify any presented client certificates against its CA file, if one is
+   configured &mdash; but it will not insist that a client certificate be presented.
+  </para>
+
+  <para>
+   There are two approaches to enforce that users provide a certificate during login.
+  </para>
+
+  <para>
+   The first approach makes use of the <literal>cert</literal> authentication
+   method for <literal>hostssl</literal> entries in <filename>pg_hba.conf</filename>,
+   such that the certificate itself is used for authentication while also
+   providing ssl connection security. See <xref linkend="auth-cert"/> for details.
+   (It is not necessary to specify any <literal>clientcert</literal> options
+   explicitly when using the <literal>cert</literal> authentication method.)
+   In this case, the <literal>cn</literal> (Common Name) provided in
+   the certificate is checked against the user name or an applicable mapping.
   </para>
 
   <para>
-   If you are setting up client certificates, you may wish to use
-   the <literal>cert</literal> authentication method, so that the certificates
-   control user authentication as well as providing connection security.
-   See <xref linkend="auth-cert"/> for details.  (It is not necessary to
-   specify <literal>clientcert=1</literal> explicitly when using
-   the <literal>cert</literal> authentication method.)
+   The second approach combines any authentication method for <literal>hostssl</literal>
+   entries with the verification of client certificates by setting the
+   <literal>clientcert</literal> authentication option to <literal>verify-ca</literal>
+   or <literal>verify-full</literal>. The former option only enforces that
+   the certificate is valid, while the latter also ensures that the
+   <literal>cn</literal> (Common Name) in the certificate matches
+   the user name or an applicable mapping.
   </para>
   </sect2>
 
diff --git a/src/backend/libpq/auth.c b/src/backend/libpq/auth.c
@@ -363,7 +363,7 @@ ClientAuthentication(Port *port)
 	 * current connection, so perform any verifications based on the hba
 	 * options field that should be done *before* the authentication here.
 	 */
-	if (port->hba->clientcert)
+	if (port->hba->clientcert != clientCertOff)
 	{
 		/* If we haven't loaded a root certificate store, fail */
 		if (!secure_loaded_verify_locations())
@@ -581,24 +581,32 @@ ClientAuthentication(Port *port)
 			status = CheckLDAPAuth(port);
 #else
 			Assert(false);
-#endif
-			break;
-
-		case uaCert:
-#ifdef USE_SSL
-			status = CheckCertAuth(port);
-#else
-			Assert(false);
 #endif
 			break;
 		case uaRADIUS:
 			status = CheckRADIUSAuth(port);
 			break;
+		case uaCert:
+			/* uaCert will be treated as if clientcert=verify-full (uaTrust) */
 		case uaTrust:
 			status = STATUS_OK;
 			break;
 	}
 
+	if ((status == STATUS_OK && port->hba->clientcert == clientCertFull)
+		|| port->hba->auth_method == uaCert)
+	{
+		/*
+		 * Make sure we only check the certificate if we use the cert method
+		 * or verify-full option.
+		 */
+#ifdef USE_SSL
+		status = CheckCertAuth(port);
+#else
+		Assert(false);
+#endif
+	}
+
 	if (ClientAuthentication_hook)
 		(*ClientAuthentication_hook) (port, status);
 
@@ -2788,6 +2796,8 @@ errdetail_for_ldap(LDAP *ldap)
 static int
 CheckCertAuth(Port *port)
 {
+	int			status_check_usermap = STATUS_ERROR;
+
 	Assert(port->ssl);
 
 	/* Make sure we have received a username in the certificate */
@@ -2800,8 +2810,23 @@ CheckCertAuth(Port *port)
 		return STATUS_ERROR;
 	}
 
-	/* Just pass the certificate CN to the usermap check */
-	return check_usermap(port->hba->usermap, port->user_name, port->peer_cn, false);
+	/* Just pass the certificate cn to the usermap check */
+	status_check_usermap = check_usermap(port->hba->usermap, port->user_name, port->peer_cn, false);
+	if (status_check_usermap != STATUS_OK)
+	{
+		/*
+		 * If clientcert=verify-full was specified and the authentication
+		 * method is other than uaCert, log the reason for rejecting the
+		 * authentication.
+		 */
+		if (port->hba->clientcert == clientCertFull && port->hba->auth_method != uaCert)
+		{
+			ereport(LOG,
+					(errmsg("certificate validation (clientcert=verify-full) failed for user \"%s\": cn mismatch",
+							port->user_name)));
+		}
+	}
+	return status_check_usermap;
 }
 #endif
 
diff --git a/src/backend/libpq/hba.c b/src/backend/libpq/hba.c
@@ -1609,7 +1609,7 @@ parse_hba_line(TokenizedLine *tok_line, int elevel)
 	 */
 	if (parsedline->auth_method == uaCert)
 	{
-		parsedline->clientcert = true;
+		parsedline->clientcert = clientCertCA;
 	}
 
 	return parsedline;
@@ -1675,23 +1675,38 @@ parse_hba_auth_opt(char *name, char *val, HbaLine *hbaline,
 			*err_msg = "clientcert can only be configured for \"hostssl\" rows";
 			return false;
 		}
-		if (strcmp(val, "1") == 0)
+		if (strcmp(val, "1") == 0
+			|| strcmp(val, "verify-ca") == 0)
 		{
-			hbaline->clientcert = true;
+			hbaline->clientcert = clientCertCA;
 		}
-		else
+		else if (strcmp(val, "verify-full") == 0)
+		{
+			hbaline->clientcert = clientCertFull;
+		}
+		else if (strcmp(val, "0") == 0
+				 || strcmp(val, "no-verify") == 0)
 		{
 			if (hbaline->auth_method == uaCert)
 			{
 				ereport(elevel,
 						(errcode(ERRCODE_CONFIG_FILE_ERROR),
-						 errmsg("clientcert can not be set to 0 when using \"cert\" authentication"),
+						 errmsg("clientcert can not be set to \"no-verify\" when using \"cert\" authentication"),
 						 errcontext("line %d of configuration file \"%s\"",
 									line_num, HbaFileName)));
-				*err_msg = "clientcert can not be set to 0 when using \"cert\" authentication";
+				*err_msg = "clientcert can not be set to \"no-verify\" when using \"cert\" authentication";
 				return false;
 			}
-			hbaline->clientcert = false;
+			hbaline->clientcert = clientCertOff;
+		}
+		else
+		{
+			ereport(elevel,
+					(errcode(ERRCODE_CONFIG_FILE_ERROR),
+					 errmsg("invalid value for clientcert: \"%s\"", val),
+					 errcontext("line %d of configuration file \"%s\"",
+								line_num, HbaFileName)));
+			return false;
 		}
 	}
 	else if (strcmp(name, "pamservice") == 0)
@@ -2252,9 +2267,9 @@ gethba_options(HbaLine *hba)
 		options[noptions++] =
 			CStringGetTextDatum(psprintf("map=%s", hba->usermap));
 
-	if (hba->clientcert)
+	if (hba->clientcert != clientCertOff)
 		options[noptions++] =
-			CStringGetTextDatum("clientcert=true");
+			CStringGetTextDatum(psprintf("clientcert=%s", (hba->clientcert == clientCertCA) ? "verify-ca" : "verify-full"));
 
 	if (hba->pamservice)
 		options[noptions++] =
diff --git a/src/include/libpq/hba.h b/src/include/libpq/hba.h
@@ -58,6 +58,13 @@ typedef enum ConnType
 	ctHostNoSSL
 } ConnType;
 
+typedef enum ClientCertMode
+{
+	clientCertOff,
+	clientCertCA,
+	clientCertFull
+} ClientCertMode;
+
 typedef struct HbaLine
 {
 	int			linenumber;
@@ -86,7 +93,7 @@ typedef struct HbaLine
 	int			ldapscope;
 	char	   *ldapprefix;
 	char	   *ldapsuffix;
-	bool		clientcert;
+	ClientCertMode clientcert;
 	char	   *krb_realm;
 	bool		include_realm;
 	bool		compat_realm;
diff --git a/src/test/ssl/t/001_ssltests.pl b/src/test/ssl/t/001_ssltests.pl
@@ -13,7 +13,7 @@
 
 if ($ENV{with_openssl} eq 'yes')
 {
-	plan tests => 71;
+	plan tests => 75;
 }
 else
 {
@@ -378,6 +378,27 @@
 	qr/SSL error/,
 	"certificate authorization fails with revoked client cert");
 
+# Check that connecting with auth-option verify-full in pg_hba:
+# works, iff username matches Common Name
+# fails, iff username doesn't match Common Name.
+$common_connstr =
+"sslrootcert=ssl/root+server_ca.crt sslmode=require dbname=verifydb hostaddr=$SERVERHOSTADDR";
+
+test_connect_ok($common_connstr,
+				"user=ssltestuser sslcert=ssl/client.crt sslkey=ssl/client_tmp.key",
+				"auth_option clientcert=verify-full succeeds with matching username and Common Name");
+
+test_connect_fails($common_connstr,
+				   "user=anotheruser sslcert=ssl/client.crt sslkey=ssl/client_tmp.key",
+				   qr/FATAL/,
+				   "auth_option clientcert=verify-full fails with mismatching username and Common Name");
+
+# Check that connecting with auth-optionverify-ca in pg_hba :
+# works, when username doesn't match Common Name
+test_connect_ok($common_connstr,
+				"user=yetanotheruser sslcert=ssl/client.crt sslkey=ssl/client_tmp.key",
+				"auth_option clientcert=verify-ca succeeds with mismatching username and Common Name");
+
 # intermediate client_ca.crt is provided by client, and isn't in server's ssl_ca_file
 switch_server_cert($node, 'server-cn-only', 'root_ca');
 $common_connstr =
diff --git a/src/test/ssl/t/SSLServer.pm b/src/test/ssl/t/SSLServer.pm
@@ -103,8 +103,10 @@ sub configure_test_server_for_ssl
 	# Create test users and databases
 	$node->psql('postgres', "CREATE USER ssltestuser");
 	$node->psql('postgres', "CREATE USER anotheruser");
+	$node->psql('postgres', "CREATE USER yetanotheruser");
 	$node->psql('postgres', "CREATE DATABASE trustdb");
 	$node->psql('postgres', "CREATE DATABASE certdb");
+	$node->psql('postgres', "CREATE DATABASE verifydb");
 
 	# Update password of each user as needed.
 	if (defined($password))
@@ -183,11 +185,17 @@ sub configure_hba_for_ssl
 	# When connecting to certdb, also check the client certificate.
 	open my $hba, '>', "$pgdata/pg_hba.conf";
 	print $hba
-	  "# TYPE  DATABASE        USER            ADDRESS                 METHOD\n";
+	  "# TYPE  DATABASE        USER            ADDRESS                 METHOD             OPTIONS\n";
 	print $hba
 	  "hostssl trustdb         all             $serverhost/32            $authmethod\n";
 	print $hba
 	  "hostssl trustdb         all             ::1/128                 $authmethod\n";
+	print $hba
+	  "hostssl verifydb        ssltestuser     $serverhost/32          $authmethod        clientcert=verify-full\n";
+	print $hba
+	  "hostssl verifydb        anotheruser     $serverhost/32          $authmethod        clientcert=verify-full\n";
+	print $hba
+	  "hostssl verifydb        yetanotheruser  $serverhost/32          $authmethod        clientcert=verify-ca\n";
 	print $hba
 	  "hostssl certdb          all             $serverhost/32            cert\n";
 	print $hba
