Added a flag (_send_traceback_header) to the SimpleXMLRPCServer class

that allows sending back exception/stack trace information about
internal server errors (this flag defaults to False to avoid sending
such information unless explicitly enabled).  Added tests to verify
behavior of this new feature (these tests are skipped on win32 because
of problems with WSAEWOULDBLOCK). Renamed HTTPTestCase to
SimpleServerTestCase. [GSoC - Alan McIntyre]

Lib/SimpleXMLRPCServer.py

@@ -105,6 +105,7 @@ def export_add(self, x, y):
 import BaseHTTPServer
 import sys
 import os
+import traceback
 try:
     import fcntl
 except ImportError:
@@ -470,9 +471,16 @@ def do_POST(self):
             response = self.server._marshaled_dispatch(
                     data, getattr(self, '_dispatch', None)
                 )
-        except: # This should only happen if the module is buggy
+        except Exception, e: # This should only happen if the module is buggy
             # internal error, report as HTTP server error
             self.send_response(500)
+
+            # Send information about the exception if requested
+            if hasattr(self.server, '_send_traceback_header') and \
+                    self.server._send_traceback_header:
+                self.send_header("X-exception", str(e))
+                self.send_header("X-traceback", traceback.format_exc())
+
             self.end_headers()
         else:
             # got a valid XML RPC response
@@ -517,6 +525,12 @@ class SimpleXMLRPCServer(SocketServer.TCPServer,
 
     allow_reuse_address = True
 
+    # Warning: this is for debugging purposes only! Never set this to True in
+    # production code, as will be sending out sensitive information (exception
+    # and stack trace details) when exceptions are raised inside
+    # SimpleXMLRPCRequestHandler.do_POST
+    _send_traceback_header = False
+
     def __init__(self, addr, requestHandler=SimpleXMLRPCRequestHandler,
                  logRequests=True, allow_none=False, encoding=None, bind_and_activate=True):
         self.logRequests = logRequests

Lib/test/test_xmlrpc.py

@@ -6,6 +6,7 @@
 import xmlrpclib
 import SimpleXMLRPCServer
 import threading
+import mimetools
 from test import test_support
 
 try:
@@ -298,11 +299,9 @@ def div(self, x, y):
             '''This is the div function'''
             return x // y
 
-
-    serv = SimpleXMLRPCServer.SimpleXMLRPCServer(("localhost", 0),
-                    logRequests=False, bind_and_activate=False)
-
     try:
+        serv = SimpleXMLRPCServer.SimpleXMLRPCServer(("localhost", 0),
+                        logRequests=False, bind_and_activate=False)
         serv.socket.settimeout(3)
         serv.server_bind()
         global PORT
@@ -327,11 +326,15 @@ def div(self, x, y):
         evt.set()
 
 
-class HTTPTestCase(unittest.TestCase):
+class SimpleServerTestCase(unittest.TestCase):
     def setUp(self):
+        # enable traceback reporting
+        SimpleXMLRPCServer.SimpleXMLRPCServer._send_traceback_header = True
+
         self.evt = threading.Event()
-        # start server thread to handle just one request
+        # start server thread to handle requests
-        threading.Thread(target=http_server, args=(self.evt,2)).start()
+        serv_args = (self.evt, 2)
+        threading.Thread(target=http_server, args=serv_args).start()
 
         # wait for port to be assigned to server
         n = 1000
@@ -345,6 +348,9 @@ def tearDown(self):
         # wait on the server thread to terminate
         self.evt.wait()
 
+        # disable traceback reporting
+        SimpleXMLRPCServer.SimpleXMLRPCServer._send_traceback_header = False
+
     def test_simple1(self):
         p = xmlrpclib.ServerProxy('http://localhost:%d' % PORT)
         self.assertEqual(p.pow(6,8), 6**8)
@@ -380,6 +386,82 @@ def test_multicall(self):
         self.assertEqual(div_result, 127//42)
 
 
+# This is a contrived way to make a failure occur on the server side
+# in order to test the _send_traceback_header flag on the server
+class FailingMessageClass(mimetools.Message):
+    def __getitem__(self, key):
+        key = key.lower()
+        if key == 'content-length':
+            return 'I am broken'
+        return mimetools.Message.__getitem__(self, key)
+
+
+class FailingServerTestCase(unittest.TestCase):
+    def setUp(self):
+        self.evt = threading.Event()
+        # start server thread to handle requests
+        serv_args = (self.evt, 2)
+        threading.Thread(target=http_server, args=serv_args).start()
+
+        # wait for port to be assigned to server
+        n = 1000
+        while n > 0 and PORT is None:
+            time.sleep(0.001)
+            n -= 1
+
+        time.sleep(0.5)
+
+    def tearDown(self):
+        # wait on the server thread to terminate
+        self.evt.wait()
+        # reset flag
+        SimpleXMLRPCServer.SimpleXMLRPCServer._send_traceback_header = False
+        # reset message class
+        SimpleXMLRPCServer.SimpleXMLRPCRequestHandler.MessageClass = mimetools.Message
+
+    def test_basic(self):
+        # check that flag is false by default
+        flagval = SimpleXMLRPCServer.SimpleXMLRPCServer._send_traceback_header
+        self.assertEqual(flagval, False)
+
+        # test a call that won't fail just as a smoke test
+        p = xmlrpclib.ServerProxy('http://localhost:%d' % PORT)
+        self.assertEqual(p.pow(6,8), 6**8)
+
+    def test_fail_no_info(self):
+        # use the broken message class
+        SimpleXMLRPCServer.SimpleXMLRPCRequestHandler.MessageClass = FailingMessageClass
+
+        try:
+            p = xmlrpclib.ServerProxy('http://localhost:%d' % PORT)
+            p.pow(6,8)
+        except xmlrpclib.ProtocolError, e:
+            # The two server-side error headers shouldn't be sent back in this case
+            self.assertTrue(e.headers.get("X-exception") is None)
+            self.assertTrue(e.headers.get("X-traceback") is None)
+        else:
+            self.fail('ProtocolError not raised')
+
+    def test_fail_with_info(self):
+        # use the broken message class
+        SimpleXMLRPCServer.SimpleXMLRPCRequestHandler.MessageClass = FailingMessageClass
+
+        # Check that errors in the server send back exception/traceback
+        # info when flag is set
+        SimpleXMLRPCServer.SimpleXMLRPCServer._send_traceback_header = True
+
+        try:
+            p = xmlrpclib.ServerProxy('http://localhost:%d' % PORT)
+            p.pow(6,8)
+        except xmlrpclib.ProtocolError, e:
+            # We should get error info in the response
+            expected_err = "invalid literal for int() with base 10: 'I am broken'"
+            self.assertEqual(e.headers.get("x-exception"), expected_err)
+            self.assertTrue(e.headers.get("x-traceback") is not None)
+        else:
+            self.fail('ProtocolError not raised')
+
+
 def test_main():
     xmlrpc_tests = [XMLRPCTestCase, HelperTestCase, DateTimeTestCase,
          BinaryTestCase, FaultTestCase]
@@ -389,7 +471,8 @@ def test_main():
     # run on Windows. This only happens on the first test to run, but it
     # fails every time and so these tests are skipped on win32 platforms.
     if sys.platform != 'win32':
-        xmlrpc_tests.append(HTTPTestCase)
+        xmlrpc_tests.append(SimpleServerTestCase)
+        xmlrpc_tests.append(FailingServerTestCase)
 
     test_support.run_unittest(*xmlrpc_tests)