Add parameter krb_realm used by GSSAPI, SSPI and Kerberos

to validate the realm of the connecting user. By default
it's empty meaning no verification, which is the way
Kerberos authentication has traditionally worked in
PostgreSQL.

6 files changed, 115 insertions, 34 deletions

diff --git a/doc/src/sgml/client-auth.sgml b/doc/src/sgml/client-auth.sgml
index d93568bcfa..fb12e2f69b 100644
--- a/doc/src/sgml/client-auth.sgml
+++ b/doc/src/sgml/client-auth.sgml
@@ -773,10 +773,10 @@ local   db1,db2,@demodbs  all                         md5
    <para>
     Client principals must have their <productname>PostgreSQL</> database user
     name as their first component, for example
-    <literal>pgusername/otherstuff@realm</>. At present the realm of
-    the client is not checked by <productname>PostgreSQL</>; so if you
-    have cross-realm authentication enabled, then any principal in any
-    realm that can communicate with yours will be accepted.
+    <literal>pgusername@realm</>. By default, the realm of the client is
+	not checked by <productname>PostgreSQL</>. If you have cross-realm
+	authentication enabled and need to verify the realm, use the
+	<xref linkend="guc-krb-realm"> parameter.
    </para>
 
    <para>
diff --git a/doc/src/sgml/config.sgml b/doc/src/sgml/config.sgml
index 9acc919532..94dfa6e1f5 100644
--- a/doc/src/sgml/config.sgml
+++ b/doc/src/sgml/config.sgml
@@ -601,6 +601,21 @@ SET ENABLE_SEQSCAN TO OFF;
       </listitem>
      </varlistentry>
 
+	 <varlistentry id="guc-krb-realm" xreflabel="krb_realm">
+	  <term><varname>krb_realm</varname> (<type>string</type>)</term>
+	  <indexterm>
+	   <primary><varname>krb_realm</> configuration parameter</primary>
+	  </indexterm>
+	  <listitem>
+	   <para>
+	    Sets the realm to match Kerberos, GSSAPI and SSPI usernames against.
+		See <xref linkend="kerberos-auth">, <xref linkend="gssapi-auth"> or
+		<xref linkend="sspi-auth"> for details. This parameter can only be
+		set at server start.
+       </para>
+	  </listitem>
+	 </varlistentry>
+
      <varlistentry id="guc-krb-server-keyfile" xreflabel="krb_server_keyfile">
       <term><varname>krb_server_keyfile</varname> (<type>string</type>)</term>
       <indexterm>
diff --git a/src/backend/libpq/auth.c b/src/backend/libpq/auth.c
index 5ae6467940..e87cb3b156 100644
--- a/src/backend/libpq/auth.c
+++ b/src/backend/libpq/auth.c
@@ -42,6 +42,7 @@ char	   *pg_krb_server_keyfile;
 char	   *pg_krb_srvnam;
 bool		pg_krb_caseins_users;
 char	   *pg_krb_server_hostname = NULL;
+char	   *pg_krb_realm = NULL;
 
 #ifdef USE_PAM
 #ifdef HAVE_PAM_PAM_APPL_H
@@ -103,30 +104,6 @@ static int	CheckLDAPAuth(Port *port);
 #endif
 
 /*
- * pg_an_to_ln -- return the local name corresponding to an authentication
- *				  name
- *
- * XXX Assumes that the first aname component is the user name.  This is NOT
- *	   necessarily so, since an aname can actually be something out of your
- *	   worst X.400 nightmare, like
- *		  ORGANIZATION=U. C. Berkeley/NAME=Paul M. [email protected]
- *	   Note that the MIT an_to_ln code does the same thing if you don't
- *	   provide an aname mapping database...it may be a better idea to use
- *	   krb5_an_to_ln, except that it punts if multiple components are found,
- *	   and we can't afford to punt.
- */
-static char *
-pg_an_to_ln(char *aname)
-{
-	char	   *p;
-
-	if ((p = strchr(aname, '/')) || (p = strchr(aname, '@')))
-		*p = '\0';
-	return aname;
-}
-
-
-/*
  * Various krb5 state which is not connection specfic, and a flag to
  * indicate whether we have initialised it yet.
  */
@@ -216,6 +193,7 @@ pg_krb5_recvauth(Port *port)
 	krb5_auth_context auth_context = NULL;
 	krb5_ticket *ticket;
 	char	   *kusername;
+	char	   *cp;
 
 	if (get_role_line(port->user_name) == NULL)
 		return STATUS_ERROR;
@@ -240,8 +218,6 @@ pg_krb5_recvauth(Port *port)
 	 * The "client" structure comes out of the ticket and is therefore
 	 * authenticated.  Use it to check the username obtained from the
 	 * postmaster startup packet.
-	 *
-	 * I have no idea why this is considered necessary.
 	 */
 #if defined(HAVE_KRB5_TICKET_ENC_PART2)
 	retval = krb5_unparse_name(pg_krb5_context,
@@ -263,7 +239,42 @@ pg_krb5_recvauth(Port *port)
 		return STATUS_ERROR;
 	}
 
-	kusername = pg_an_to_ln(kusername);
+	cp = strchr(kusername, '@');
+	if (cp)
+	{
+		*cp = '\0';
+		cp++;
+
+		if (pg_krb_realm != NULL && strlen(pg_krb_realm))
+		{
+			/* Match realm against configured */
+			if (pg_krb_caseins_users)
+				ret = pg_strcasecmp(pg_krb_realm, cp);
+			else
+				ret = strcmp(pg_krb_realm, cp);
+
+			if (ret)
+			{
+				elog(DEBUG2,
+					 "krb5 realm (%s) and configured realm (%s) don't match",
+					 cp, pg_krb_realm);
+
+				krb5_free_ticket(pg_krb5_context, ticket);
+				krb5_auth_con_free(pg_krb5_context, auth_context);
+				return STATUS_ERROR;
+			}
+		}
+	}
+	else if (pg_krb_realm && strlen(pg_krb_realm))
+	{
+		elog(DEBUG2,
+			 "krb5 did not return realm but realm matching was requested");
+
+		krb5_free_ticket(pg_krb5_context, ticket);
+		krb5_auth_con_free(pg_krb5_context, auth_context);
+		return STATUS_ERROR;
+	}
+
 	if (pg_krb_caseins_users)
 		ret = pg_strncasecmp(port->user_name, kusername, SM_DATABASE_USER);
 	else
@@ -509,14 +520,42 @@ pg_GSS_recvauth(Port *port)
 					 maj_stat, min_stat);
 
 	/*
-	 * Compare the part of the username that comes before the @
-	 * sign only (ignore realm). The GSSAPI libraries won't have 
-	 * authenticated the user if he's from an invalid realm.
+	 * Split the username at the realm separator
 	 */
 	if (strchr(gbuf.value, '@'))
 	{
 		char *cp = strchr(gbuf.value, '@');
 		*cp = '\0';
+		cp++;
+
+		if (pg_krb_realm != NULL && strlen(pg_krb_realm))
+		{
+			/*
+			 * Match the realm part of the name first
+			 */
+			if (pg_krb_caseins_users)
+				ret = pg_strcasecmp(pg_krb_realm, cp);
+			else
+				ret = strcmp(pg_krb_realm, cp);
+
+			if (ret)
+			{
+				/* GSS realm does not match */
+				elog(DEBUG2,
+					 "GSSAPI realm (%s) and configured realm (%s) don't match",
+					 cp, pg_krb_realm);
+				gss_release_buffer(&lmin_s, &gbuf);
+				return STATUS_ERROR;
+			}
+		}
+	}
+	else if (pg_krb_realm && strlen(pg_krb_realm))
+	{
+		elog(DEBUG2,
+			 "GSSAPI did not return realm but realm matching was requested");
+
+		gss_release_buffer(&lmin_s, &gbuf);
+		return STATUS_ERROR;
 	}
 
 	if (pg_krb_caseins_users)
@@ -792,6 +831,21 @@ pg_SSPI_recvauth(Port *port)
 
 	free(tokenuser);
 
+	/* 
+	 * Compare realm/domain if requested. In SSPI, always compare case insensitive.
+	 */
+	if (pg_krb_realm && strlen(pg_krb_realm))
+	{
+		if (pg_strcasecmp(pg_krb_realm, domainname))
+		{
+			elog(DEBUG2,
+				 "SSPI domain (%s) and configured domain (%s) don't match",
+				 domainname, pg_krb_realm);
+			
+			return STATUS_ERROR;
+		}
+	}
+
 	/*
 	 * We have the username (without domain/realm) in accountname, compare 
 	 * to the supplied value. In SSPI, always compare case insensitive.
diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
index 35836288b1..25f6022d97 100644
--- a/src/backend/utils/misc/guc.c
+++ b/src/backend/utils/misc/guc.c
@@ -2044,6 +2044,16 @@ static struct config_string ConfigureNamesString[] =
 	},
 
 	{
+		{"krb_realm", PGC_POSTMASTER, CONN_AUTH_SECURITY,
+			gettext_noop("Sets realm to match Kerberos and GSSAPI users against."),
+			NULL,
+			GUC_SUPERUSER_ONLY
+		},
+		&pg_krb_realm,
+		NULL, NULL, NULL
+	},
+
+	{
 		{"krb_server_keyfile", PGC_POSTMASTER, CONN_AUTH_SECURITY,
 			gettext_noop("Sets the location of the Kerberos server key file."),
 			NULL,
diff --git a/src/backend/utils/misc/postgresql.conf.sample b/src/backend/utils/misc/postgresql.conf.sample
index 48023bc4dd..3a94829ced 100644
--- a/src/backend/utils/misc/postgresql.conf.sample
+++ b/src/backend/utils/misc/postgresql.conf.sample
@@ -85,6 +85,7 @@
 #krb_server_hostname = ''		# empty string matches any keytab entry
 					# (change requires restart, kerberos only)
 #krb_caseins_users = off		# (change requires restart)
+#krb_realm = ''           		# (change requires restart)
 
 # - TCP Keepalives -
 # see 'man 7 tcp' for details
diff --git a/src/include/libpq/auth.h b/src/include/libpq/auth.h
index c1c3488aff..389a3513f3 100644
--- a/src/include/libpq/auth.h
+++ b/src/include/libpq/auth.h
@@ -20,6 +20,7 @@ extern char *pg_krb_server_keyfile;
 extern char *pg_krb_srvnam;
 extern bool pg_krb_caseins_users;
 extern char *pg_krb_server_hostname;
+extern char *pg_krb_realm;
 
 extern void ClientAuthentication(Port *port);