Add minimum SSF setting

This adds a new configuration setting to the cn=config entry named
nsslapd-minssf. This can be set to a non-negative integer representing
the minimum key strength required to process operations. The default
setting will be 0.

The SSF for a particular connection will be determined by the key
strength cipher used to protect the connection. If the SSF used for a
connection does not meet the minimum requirement, the operation will be
rejected with an error code of LDAP_UNWILLING_TO_PERFORM (53) along
with a message stating that the minimum SSF was not met. Notable
exceptions to this are operations that attempt to protect a connection.
These operations are:

    * SASL BIND
    * startTLS

These operations will be allowed to occur on a connection with a SSF
less than the minimum. If the results of these operations end up with
a SSF smaller than the minimum, they will be rejected.  Additionally,
we allow UNBIND and ABANDON operations to go through.

I also corrected a few issues with the anonymous access switch code
that I noticed while testing.  We need to allow the startTLS extended
operation to go through when sent by an anonymous user since it is
common to send startTLS prior to a BIND to protect the credentials.
I also noticed that we were using the authtype from the operation
struct to determine is a user was anonymous when we really should
have been using the DN.  This was causing anonymous operations to
get through on SSL/TLS connections.

1 files changed, 20 insertions, 0 deletions

diff --git a/ldap/servers/slapd/extendop.c b/ldap/servers/slapd/extendop.c
index d3e6d5a2..003c2ab8 100644
--- a/ldap/servers/slapd/extendop.c
+++ b/ldap/servers/slapd/extendop.c
@@ -295,6 +295,26 @@ do_extended( Slapi_PBlock *pb )
 		goto free_and_return;
 	}
 
+	if (strcmp(extoid, START_TLS_OID) != 0) {
+		int minssf = config_get_minssf();
+
+		/* If anonymous access is disabled and we haven't
+		 * authenticated yet, only allow startTLS. */
+		if (!config_get_anon_access_switch() && ((pb->pb_op->o_authtype == NULL) ||
+    		        (strcasecmp(pb->pb_op->o_authtype, SLAPD_AUTH_NONE) == 0))) {
+			send_ldap_result( pb, LDAP_INAPPROPRIATE_AUTH, NULL,
+				"Anonymous access is not allowed.", 0, NULL );
+			goto free_and_return;
+		}
+
+		/* If the minssf is not met, only allow startTLS. */
+		if ((pb->pb_conn->c_sasl_ssf < minssf) && (pb->pb_conn->c_ssl_ssf < minssf)) {
+			send_ldap_result( pb, LDAP_UNWILLING_TO_PERFORM, NULL,
+				"Minimum SSF not met.", 0, NULL );
+			goto free_and_return;
+		}
+	}
+
 	/* If a password change is required, only allow the password
 	 * modify extended operation */
 	if (!pb->pb_conn->c_isreplication_session &&