[GT-157] Drop messages from banned dns, and add tests for messages saving to the correct queue

ssm/agents.py

@@ -298,6 +298,10 @@ def run_receiver(protocol, brokers, project, token, cp, log, dn_file):
         dns = get_dns(dn_file, log)
         ssm.set_dns(dns)
 
+        log.info('Fetching banned DNs.')
+        banned_dns = get_banned_dns(log)
+        ssm.set_banned_dns(banned_dns)
+
     except Exception as e:
         log.fatal('Failed to initialise SSM: %s', e)
         log.info(LOG_BREAK)
@@ -379,3 +383,30 @@ def get_dns(dn_file, log):
 
     log.debug('%s DNs found.', len(dns))
     return dns
+
+
+def get_banned_dns(log):
+    """Retrieve the list of banned dns"""
+    banned_dns_list = []
+    try:
+        banned_dns_path = cp.get('auth', 'banned-dns')
+        banned_dns_file = os.path.normpath(os.path.expandvars(banned_dns_path))
+    except ConfigParser.NoOptionError:
+        banned_dns_file = None
+    f = None
+    try:
+        f = open(banned_dns_file, 'r')
+        lines = f.readlines()
+        for line in lines:
+            if line.isspace() or line.strip().startswith('#'):
+                continue
+            elif line.strip().startswith('/'):
+                banned_dns_list.append(line.strip())
+            else:
+                log.warning('DN in banned dns list is not in correct format: %s', line)
+    finally:
+        if f is not None:
+            f.close()
+
+    return banned_dns_list
+

ssm/ssm2.py

@@ -90,6 +90,7 @@ def __init__(self, hosts_and_ports, qpath, cert, key, dest=None, listen=None,
         self._dest = dest
 
         self._valid_dns = []
+        self._banned_dns = []
         self._pidfile = pidfile
 
         # Used to differentiate between STOMP and AMS methods
@@ -189,6 +190,10 @@ def set_dns(self, dn_list):
         """Set the list of DNs which are allowed to sign incoming messages."""
         self._valid_dns = dn_list
 
+    def set_banned_dns(self, banned_dn_list):
+        """Set the list of banned dns, so their messages can be dropped."""
+        self._banned_dns = banned_dn_list
+
     ##########################################################################
     # Methods called by stomppy
     ##########################################################################
@@ -283,8 +288,10 @@ def _handle_msg(self, text):
         Namely:
         - decrypt if necessary
         - verify signature
+        - send an error message if the message wasn't sent from a valid DN
         - Return plain-text message, signer's DN and an error/None.
         """
+
         if text is None or text == '':
             warning = 'Empty text passed to _handle_msg.'
             log.warning(warning)
@@ -307,10 +314,23 @@ def _handle_msg(self, text):
             log.error(error)
             return None, None, error
 
-        if signer not in self._valid_dns:
+        # If the message has been sent from a banned DN,
+        # set a specific error message that can be
+        # checked for later.
+        if signer in self._banned_dns:
+            warning = 'Signer is in the banned DNs list'
+            log.warning(warning)
+            return None, signer, warning
+
+        # Else, if the signer is not in valid DNs list,
+        # but also not a banned dn,
+        # set a specific error message
+        elif signer not in self._valid_dns:
             warning = 'Signer not in valid DNs list: %s' % signer
             log.warning(warning)
             return None, signer, warning
+
+        # Else, the message has been sent from a valid DN
         else:
             log.info('Valid signer: %s', signer)
 
@@ -320,9 +340,15 @@ def _save_msg_to_queue(self, body, empaid):
         """Extract message contents and add to the accept or reject queue."""
         extracted_msg, signer, err_msg = self._handle_msg(body)
         try:
+            # If the warning states the message was sent from a banned DN,
+            # don't send the message to the reject queue.
+            # Instead, drop the message (don't send it to any queue)
+            if err_msg == "Signer is in the banned DNs list":
+                log.info("Message dropped as was sent from a banned dn: %s", signer)
+
             # If the message is empty or the error message is not empty
             # then reject the message.
-            if extracted_msg is None or err_msg is not None:
+            elif extracted_msg is None or err_msg is not None:
                 if signer is None:  # crypto failed
                     signer = 'Not available.'
                 elif extracted_msg is not None: