Add support for using SSL client certificates to authenticate to the

database (only for SSL connections, obviously).

doc/src/sgml/client-auth.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/client-auth.sgml,v 1.111 2008/11/18 13:10:20 petere Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/client-auth.sgml,v 1.112 2008/11/20 11:48:26 mha Exp $ -->
 
 <chapter id="client-authentication">
  <title>Client Authentication</title>
@@ -387,6 +387,16 @@ hostnossl  <replaceable>database</replaceable>  <replaceable>user</replaceable>
         </listitem>
        </varlistentry>
 
+       <varlistentry>
+        <term><literal>cert</></term>
+        <listitem>
+         <para>
+          Authenticate using SSL client certificates. See
+          <xref linkend="auth-cert"> for details.
+         </para>
+        </listitem>
+       </varlistentry>
+
        <varlistentry>
         <term><literal>pam</></term>
         <listitem>
@@ -1114,6 +1124,25 @@ ldapserver=ldap.example.net prefix="cn=" suffix="dc=example, dc=net"
 
   </sect2>
 
+  <sect2 id="auth-cert">
+   <title>Certificate authentication</title>
+
+   <indexterm zone="auth-cert">
+    <primary>Certificate</primary>
+   </indexterm>
+
+   <para>
+    This authentication method uses SSL client certificates to perform
+    authentication. It is therefore only available for SSL connections.
+    When using this authentication method, the server will require that
+    the client provide a certificate. No password prompt will be sent
+    to the client. The <literal>cn</literal> attribute of the certificate
+    will be matched with the username the user is trying to log in as,
+    and if they match the login will be allowed. Username mapping can be
+    used if the usernames don't match.
+   </para>
+  </sect2>
+
   <sect2 id="auth-pam">
    <title>PAM authentication</title>
 

doc/src/sgml/runtime.sgml

-<!-- $PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.421 2008/11/20 09:29:35 mha Exp $ -->
+<!-- $PostgreSQL: pgsql/doc/src/sgml/runtime.sgml,v 1.422 2008/11/20 11:48:26 mha Exp $ -->
 
 <chapter Id="runtime">
  <title>Operating System Environment</title>
@@ -1674,11 +1674,9 @@ $ <userinput>kill -INT `head -1 /usr/local/pgsql/data/postmaster.pid`</userinput
   </para>
 
   <para>
-   <productname>PostgreSQL</> currently does not support authentication
-   using client certificates, since it cannot differentiate between
-   different users. As long as the user holds any certificate issued
-   by a trusted CA it will be accepted, regardless of what account the
-   user is trying to connect with.
+   You can use the authentication method <literal>cert</> to use the
+   client certificate for authenticating users. See
+   <xref linkend="auth-cert"> for details.
   </para>
   </sect2>
 

src/backend/libpq/auth.c

@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/libpq/auth.c,v 1.172 2008/11/20 09:29:36 mha Exp $
+ *	  $PostgreSQL: pgsql/src/backend/libpq/auth.c,v 1.173 2008/11/20 11:48:26 mha Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -113,6 +113,14 @@ ULONG(*__ldap_start_tls_sA) (
 static int	CheckLDAPAuth(Port *port);
 #endif /* USE_LDAP */
 
+/*----------------------------------------------------------------
+ * Cert authentication
+ *----------------------------------------------------------------
+ */
+#ifdef USE_SSL
+static int	CheckCertAuth(Port *port);
+#endif
+
 
 /*----------------------------------------------------------------
  * Kerberos and GSSAPI GUCs
@@ -431,6 +439,14 @@ ClientAuthentication(Port *port)
 #endif
 			break;
 
+		case uaCert:
+#ifdef USE_SSL
+			status = CheckCertAuth(port);
+#else
+			Assert(false);
+#endif
+			break;
+
 		case uaTrust:
 			status = STATUS_OK;
 			break;
@@ -2120,3 +2136,28 @@ CheckLDAPAuth(Port *port)
 }
 #endif   /* USE_LDAP */
 
+
+/*----------------------------------------------------------------
+ * SSL client certificate authentication
+ *----------------------------------------------------------------
+ */
+#ifdef USE_SSL
+static int
+CheckCertAuth(Port *port)
+{
+	Assert(port->ssl);
+
+	/* Make sure we have received a username in the certificate */
+	if (port->peer_cn == NULL ||
+		strlen(port->peer_cn) <= 0)
+	{
+		ereport(LOG,
+				(errmsg("Certificate login failed for user \"%s\": client certificate contains no username",
+						port->user_name)));
+		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);
+}
+#endif

src/backend/libpq/hba.c

@@ -10,7 +10,7 @@
  *
  *
  * IDENTIFICATION
- *	  $PostgreSQL: pgsql/src/backend/libpq/hba.c,v 1.173 2008/11/20 09:29:36 mha Exp $
+ *	  $PostgreSQL: pgsql/src/backend/libpq/hba.c,v 1.174 2008/11/20 11:48:26 mha Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -858,6 +858,12 @@ parse_hba_line(List *line, int line_num, HbaLine *parsedline)
 		parsedline->auth_method = uaLDAP;
 #else
 		unsupauth = "ldap";
+#endif
+	else if (strcmp(token, "cert") == 0)
+#ifdef USE_SSL
+		parsedline->auth_method = uaCert;
+#else
+		unsupauth = "cert";
 #endif
 	else
 	{
@@ -893,6 +899,17 @@ parse_hba_line(List *line, int line_num, HbaLine *parsedline)
 		return false;
 	}
 
+	if (parsedline->conntype != ctHostSSL &&
+		parsedline->auth_method == uaCert)
+	{
+		ereport(LOG,
+				(errcode(ERRCODE_CONFIG_FILE_ERROR),
+				 errmsg("cert authentication is only supported on hostssl connections"),
+				 errcontext("line %d of configuration file \"%s\"",
+							line_num, HbaFileName)));
+		return false;
+	}
+
 	/* Parse remaining arguments */
 	while ((line_item = lnext(line_item)) != NULL)
 	{
@@ -923,8 +940,9 @@ parse_hba_line(List *line, int line_num, HbaLine *parsedline)
 				if (parsedline->auth_method != uaIdent &&
 					parsedline->auth_method != uaKrb5 &&
 					parsedline->auth_method != uaGSS &&
-					parsedline->auth_method != uaSSPI)
-					INVALID_AUTH_OPTION("map", "ident, krb5, gssapi and sspi");
+					parsedline->auth_method != uaSSPI &&
+					parsedline->auth_method != uaCert)
+					INVALID_AUTH_OPTION("map", "ident, krb5, gssapi, sspi and cert");
 				parsedline->usermap = pstrdup(c);
 			}
 			else if (strcmp(token, "clientcert") == 0)
@@ -957,8 +975,19 @@ parse_hba_line(List *line, int line_num, HbaLine *parsedline)
 					parsedline->clientcert = true;
 				}
 				else
+				{
+					if (parsedline->auth_method == uaCert)
+					{
+						ereport(LOG,
+								(errcode(ERRCODE_CONFIG_FILE_ERROR),
+								 errmsg("clientcert can not be set to 0 when using \"cert\" authentication"),
+								 errcontext("line %d of configuration file \"%s\"",
+											line_num, HbaFileName)));
+						return false;
+					}
 					parsedline->clientcert = false;
 				}
+			}
 			else if (strcmp(token, "pamservice") == 0)
 			{
 				REQUIRE_AUTH_OPTION(uaPAM, "pamservice", "pam");
@@ -1022,6 +1051,14 @@ parse_hba_line(List *line, int line_num, HbaLine *parsedline)
 		MANDATORY_AUTH_ARG(parsedline->ldapserver, "ldapserver", "ldap");
 	}
 
+	/*
+	 * Enforce any parameters implied by other settings.
+	 */
+	if (parsedline->auth_method == uaCert)
+	{
+		parsedline->clientcert = true;
+	}
+	
 	return true;
 }
 

src/backend/libpq/pg_hba.conf.sample

@@ -35,7 +35,7 @@
 # an IP address and netmask in separate columns to specify the set of hosts.
 #
 # METHOD can be "trust", "reject", "md5", "crypt", "password", "gss", "sspi",
-# "krb5", "ident", "pam" or "ldap".  Note that "password" sends passwords
+# "krb5", "ident", "pam", "ldap" or "cert". Note that "password" sends passwords
 # in clear text; "md5" is preferred since it sends encrypted passwords.
 #
 # OPTIONS are a set of options for the authentication in the format

src/include/libpq/hba.h

@@ -4,7 +4,7 @@
  *	  Interface to hba.c
  *
  *
- * $PostgreSQL: pgsql/src/include/libpq/hba.h,v 1.52 2008/11/20 09:29:36 mha Exp $
+ * $PostgreSQL: pgsql/src/include/libpq/hba.h,v 1.53 2008/11/20 11:48:26 mha Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -26,7 +26,8 @@ typedef enum UserAuth
 	uaGSS,
 	uaSSPI,
 	uaPAM,
-	uaLDAP
+	uaLDAP,
+	uaCert
 } UserAuth;
 
 typedef enum ConnType