backporting security fix of issue 9129 (smtpd module vulnerable to DoS attacks...

backporting security fix of issue 9129 (smtpd module vulnerable to DoS attacks in case of connection bashing)

Lib/smtpd.py

@@ -121,7 +121,15 @@ class SMTPChannel(asynchat.async_chat):
         self.__rcpttos = []
         self.__data = ''
         self.__fqdn = socket.getfqdn()
+        try:
             self.__peer = conn.getpeername()
+        except socket.error as err:
+            # a race condition  may occur if the other end is closing
+            # before we can get the peername
+            self.close()
+            if err.args[0] != errno.ENOTCONN:
+                raise
+            return
         print >> DEBUGSTREAM, 'Peer:', repr(self.__peer)
         self.push('220 %s %s' % (self.__fqdn, __version__))
         self.set_terminator('\r\n')
@@ -291,7 +299,20 @@ class SMTPServer(asyncore.dispatcher):
                 localaddr, remoteaddr)
 
     def handle_accept(self):
+        try:
             conn, addr = self.accept()
+        except TypeError:
+            # sometimes accept() might return None
+            return
+        except socket.error as err:
+            # ECONNABORTED might be thrown
+            if err.args[0] != errno.ECONNABORTED:
+                raise
+            return
+        else:
+            # sometimes addr == None instead of (ip, port)
+            if addr == None:
+                return
         print >> DEBUGSTREAM, 'Incoming connection from %s' % repr(addr)
         channel = SMTPChannel(self, conn, addr)
 

Misc/NEWS

@@ -19,6 +19,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #9129: smtpd.py is vulnerable to DoS attacks deriving from missing
+  error handling when accepting a new connection.
 
 What's New in Python 2.6.6?
 ===========================