Bug 1231981 - Part 1: Very basic test TURN server for running in CI. r=ahal,drno
authorByron Campen [:bwc] <docfaraday@gmail.com>
Tue, 26 Apr 2016 09:29:03 -0500
changeset 295555 74ad7376f37fbdbb3f5515970181548dbf1dfa2a
parent 295554 2e2c516bd64f8669e22660afbc76f273d6508266
child 295556 aea71aa8552ad2764c420ad05b1051b1258ccdaa
push id19015
push usercbook@mozilla.com
push dateMon, 02 May 2016 09:39:23 +0000
treeherderfx-team@2080375bc69d [default view] [failures only]
perfherder[talos] [build metrics] [platform microbench] (compared to previous push)
reviewersahal, drno
bugs1231981
milestone49.0a1
Bug 1231981 - Part 1: Very basic test TURN server for running in CI. r=ahal,drno MozReview-Commit-ID: 96vhyPCs99p
testing/tools/iceserver/iceserver.py
new file mode 100644
--- /dev/null
+++ b/testing/tools/iceserver/iceserver.py
@@ -0,0 +1,759 @@
+# vim: set ts=4 et sw=4 tw=80
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+import ipaddr
+import socket
+import hmac
+import hashlib
+import passlib.utils # for saslprep
+import copy
+import random
+import operator
+import platform
+import time
+from string import Template
+from twisted.internet import reactor, protocol
+from twisted.internet.task import LoopingCall
+from twisted.internet.address import IPv4Address
+
+MAGIC_COOKIE = 0x2112A442
+
+REQUEST = 0
+INDICATION = 1
+SUCCESS_RESPONSE = 2
+ERROR_RESPONSE = 3
+
+BINDING = 0x001
+ALLOCATE = 0x003
+REFRESH = 0x004
+SEND = 0x006
+DATA_MSG = 0x007
+CREATE_PERMISSION = 0x008
+CHANNEL_BIND = 0x009
+
+IPV4 = 1
+IPV6 = 2
+
+MAPPED_ADDRESS = 0x0001
+USERNAME = 0x0006
+MESSAGE_INTEGRITY = 0x0008
+ERROR_CODE = 0x0009
+UNKNOWN_ATTRIBUTES = 0x000A
+LIFETIME = 0x000D
+DATA_ATTR = 0x0013
+XOR_PEER_ADDRESS = 0x0012
+REALM = 0x0014
+NONCE = 0x0015
+XOR_RELAYED_ADDRESS = 0x0016
+REQUESTED_TRANSPORT = 0x0019
+DONT_FRAGMENT = 0x001A
+XOR_MAPPED_ADDRESS = 0x0020
+SOFTWARE = 0x8022
+ALTERNATE_SERVER = 0x8023
+FINGERPRINT = 0x8028
+
+def unpack_uint(bytes_buf):
+    result = 0
+    for byte in bytes_buf:
+        result = (result << 8) + byte
+    return result
+
+def pack_uint(value, width):
+    if value < 0:
+        raise ValueError("Invalid value: {}".format(value))
+    buf = bytearray([0]*width)
+    for i in range(0, width):
+        buf[i] = (value >> (8*(width - i - 1))) & 0xFF
+
+    return buf
+
+def unpack(bytes_buf, format_array):
+    results = ()
+    for width in format_array:
+        results = results + (unpack_uint(bytes_buf[0:width]),)
+        bytes_buf = bytes_buf[width:]
+    return results
+
+def pack(values, format_array):
+    if len(values) != len(format_array):
+        raise ValueError()
+    buf = bytearray()
+    for i in range(0, len(values)):
+        buf.extend(pack_uint(values[i], format_array[i]))
+    return buf
+
+def bitwise_pack(source, dest, start_bit, num_bits):
+    if num_bits <= 0 or num_bits > start_bit + 1:
+        raise ValueError("Invalid num_bits: {}, start_bit = {}"
+                         .format(num_bits, start_bit))
+    last_bit = start_bit - num_bits + 1
+    source = source >> last_bit
+    dest = dest << num_bits
+    mask = (1 << num_bits) - 1
+    dest += source & mask
+    return dest
+
+
+class StunAttribute(object):
+    """
+    Represents a STUN attribute in a raw format, according to the following:
+
+     0                   1                   2                   3
+     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+    |   StunAttribute.attr_type     |  Length (derived as needed)   |
+    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+    |           StunAttribute.data (variable length)             ....
+    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+    """
+
+    __attr_header_fmt = [2,2]
+    __attr_header_size = reduce(operator.add, __attr_header_fmt)
+
+    def __init__(self, attr_type=0, buf=bytearray()):
+        self.attr_type = attr_type
+        self.data = buf
+
+    def build(self):
+        buf = pack((self.attr_type, len(self.data)), self.__attr_header_fmt)
+        buf.extend(self.data)
+        # add padding if necessary
+        if len(buf) % 4:
+            buf.extend([0]*(4 - (len(buf) % 4)))
+        return buf
+
+    def parse(self, buf):
+        if self.__attr_header_size  > len(buf):
+            raise Exception('truncated at attribute: incomplete header')
+
+        self.attr_type, length = unpack(buf, self.__attr_header_fmt)
+        length += self.__attr_header_size
+
+        if length > len(buf):
+            raise Exception('truncated at attribute: incomplete contents')
+
+        self.data = buf[self.__attr_header_size:length]
+
+        # verify padding
+        while length % 4:
+            if buf[length]:
+                raise ValueError("Non-zero padding")
+            length += 1
+
+        return length
+
+
+class StunMessage(object):
+    """
+    Represents a STUN message. Contains a method, msg_class, cookie,
+    transaction_id, and attributes (as an array of StunAttribute).
+
+    Has various functions for getting/adding attributes.
+    """
+
+    def __init__(self):
+        self.method = 0
+        self.msg_class = 0
+        self.cookie = MAGIC_COOKIE
+        self.transaction_id = 0
+        self.attributes = []
+
+#      0                   1                   2                   3
+#      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+#     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+#     |0 0|M M M M M|C|M M M|C|M M M M|         Message Length        |
+#     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+#     |                         Magic Cookie                          |
+#     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+#     |                                                               |
+#     |                     Transaction ID (96 bits)                  |
+#     |                                                               |
+#     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+    __header_fmt = [2, 2, 4, 12]
+    __header_size = reduce(operator.add, __header_fmt)
+
+    # Returns how many bytes were parsed if buf was large enough, or how many
+    # bytes we would have needed if not. Throws if buf is malformed.
+    def parse(self, buf):
+        min_buf_size = self.__header_size
+        if len(buf) < min_buf_size:
+            return min_buf_size
+
+        message_type, length, cookie, self.transaction_id = unpack(
+                buf, self.__header_fmt)
+        min_buf_size += length
+        if len(buf) < min_buf_size:
+            return min_buf_size
+
+        # Avert your eyes...
+        self.method = bitwise_pack(message_type, 0, 13, 5)
+        self.msg_class = bitwise_pack(message_type, 0, 8, 1)
+        self.method = bitwise_pack(message_type, self.method, 7, 3)
+        self.msg_class = bitwise_pack(message_type, self.msg_class, 4, 1)
+        self.method = bitwise_pack(message_type, self.method, 3, 4)
+
+        if cookie != self.cookie:
+            raise Exception('Invalid cookie: {}'.format(cookie))
+
+        buf = buf[self.__header_size:min_buf_size]
+        while len(buf):
+            attr = StunAttribute()
+            length = attr.parse(buf)
+            buf = buf[length:]
+            self.attributes.append(attr)
+
+        return min_buf_size
+
+    # stop_after_attr_type is useful for calculating MESSAGE-DIGEST
+    def build(self, stop_after_attr_type=0):
+        attrs = bytearray()
+        for attr in self.attributes:
+            attrs.extend(attr.build())
+            if attr.attr_type == stop_after_attr_type:
+                break
+
+        message_type = bitwise_pack(self.method, 0, 11, 5)
+        message_type = bitwise_pack(self.msg_class, message_type, 1, 1)
+        message_type = bitwise_pack(self.method, message_type, 6, 3)
+        message_type = bitwise_pack(self.msg_class, message_type, 0, 1)
+        message_type = bitwise_pack(self.method, message_type, 3, 4)
+
+        message = pack((message_type,
+                        len(attrs),
+                        self.cookie,
+                        self.transaction_id), self.__header_fmt)
+        message.extend(attrs)
+
+        return message
+
+    def add_error_code(self, code, phrase=None):
+#      0                   1                   2                   3
+#      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+#     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+#     |           Reserved, should be 0         |Class|     Number    |
+#     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+#     |      Reason Phrase (variable)                                ..
+#     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+        error_code_fmt = [3, 1]
+        error_code = pack((code // 100, code % 100), error_code_fmt)
+        if phrase != None:
+            error_code.extend(bytearray(phrase))
+        self.attributes.append(StunAttribute(ERROR_CODE, error_code))
+
+#     0                   1                   2                   3
+#     0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+#    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+#    |x x x x x x x x|    Family     |         X-Port                |
+#    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+#    |                X-Address (Variable)
+#    +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+    __xor_v4addr_fmt = [1, 1, 2, 4]
+    __xor_v6addr_fmt = [1, 1, 2, 16]
+    __xor_v4addr_size = reduce(operator.add, __xor_v4addr_fmt)
+    __xor_v6addr_size = reduce(operator.add, __xor_v6addr_fmt)
+
+    def get_xaddr(self, ip_addr, version):
+        if version == IPV4:
+            return self.cookie ^ ip_addr
+        elif version == IPV6:
+            return ((self.cookie << 96) + self.transaction_id) ^ ip_addr
+        else:
+            raise ValueError("Invalid family: {}".format(family))
+
+    def get_xport(self, port):
+        return (self.cookie >> 16) ^ port
+
+    def add_xor_address(self, addr_port, attr_type):
+        ip_address = ipaddr.IPAddress(addr_port.host)
+        xport = self.get_xport(addr_port.port)
+
+        if ip_address.version == 4:
+            xaddr = self.get_xaddr(int(ip_address), IPV4)
+            xor_address = pack((0, IPV4, xport, xaddr), self.__xor_v4addr_fmt)
+        elif ip_address.version == 6:
+            xaddr = self.get_xaddr(int(ip_address), IPV6)
+            xor_address = pack((0, IPV6, xport, xaddr), self.__xor_v6addr_fmt)
+        else:
+            raise ValueError("Invalid ip version: {}"
+                             .format(ip_address.version))
+
+        self.attributes.append(StunAttribute(attr_type, xor_address))
+
+    def add_data(self, buf):
+        self.attributes.append(StunAttribute(DATA_ATTR, buf))
+
+    def find(self, attr_type):
+        for attr in self.attributes:
+            if attr.attr_type == attr_type:
+                return attr
+        return None
+
+    def get_xor_address(self, attr_type):
+        addr_attr = self.find(attr_type)
+        if not addr_attr:
+            return None
+
+        padding, family, xport, xaddr = unpack(addr_attr.data,
+                                               self.__xor_v4addr_fmt)
+        addr_ctor = IPv4Address
+        if family == IPV6:
+            from twisted.internet.address import IPv6Address
+            padding, family, xport, xaddr = unpack(addr_attr.data,
+                                                   self.__xor_v6addr_fmt)
+            addr_ctor = IPv6Address
+        elif family != IPV4:
+            raise ValueError("Invalid family: {}".format(family))
+
+        return addr_ctor('UDP',
+                         str(ipaddr.IPAddress(self.get_xaddr(xaddr, family))),
+                         self.get_xport(xport))
+
+    def add_nonce(self, nonce):
+        self.attributes.append(StunAttribute(NONCE, bytearray(nonce)))
+
+    def add_realm(self, realm):
+        self.attributes.append(StunAttribute(REALM, bytearray(realm)))
+
+    def calculate_message_digest(self, username, realm, password):
+        digest_buf = self.build(MESSAGE_INTEGRITY)
+        # Trim off the MESSAGE-INTEGRITY attr
+        digest_buf = digest_buf[:len(digest_buf) - 24]
+        password = passlib.utils.saslprep(unicode(password))
+        key_string = "{}:{}:{}".format(username, realm, password)
+        md5 = hashlib.md5()
+        md5.update(key_string)
+        key = md5.digest()
+        return bytearray(hmac.new(key, digest_buf, hashlib.sha1).digest())
+
+    def add_lifetime(self, lifetime):
+        self.attributes.append(StunAttribute(LIFETIME, pack_uint(lifetime, 4)))
+
+    def get_lifetime(self):
+        lifetime_attr = self.find(LIFETIME)
+        if not lifetime_attr:
+            return None
+        return unpack_uint(lifetime_attr.data[0:4])
+
+    def get_username(self):
+        username = self.find(USERNAME)
+        if not username:
+            return None
+        return str(username.data)
+
+    def add_message_integrity(self, username, realm, password):
+        dummy_value = bytearray([0]*20)
+        self.attributes.append(StunAttribute(MESSAGE_INTEGRITY, dummy_value))
+        digest = self.calculate_message_digest(username, realm, password)
+        self.find(MESSAGE_INTEGRITY).data = digest
+
+
+class Allocation(protocol.DatagramProtocol):
+    """
+    Comprises the socket for a TURN allocation, a back-reference to the
+    transport we will forward received traffic on, the allocator's address and
+    username, the set of permissions for the allocation, and the allocation's
+    expiry.
+    """
+
+    def __init__(self, other_transport_handler, allocator_address, username):
+        self.permissions = set() # str, int tuples
+        # Handler to use when sending stuff that arrives on the allocation
+        self.other_transport_handler = other_transport_handler
+        self.allocator_address = allocator_address
+        self.username = username
+        self.expiry = time.time()
+        self.port = reactor.listenUDP(0, self, interface=v4_address)
+
+    def datagramReceived(self, data, (host, port)):
+        if not host in self.permissions:
+            print("Dropping packet from {}:{}, no permission on allocation {}"
+                  .format(host, port, self.transport.getHost()))
+            return
+
+        data_indication = StunMessage()
+        data_indication.method = DATA_MSG
+        data_indication.msg_class = INDICATION
+        data_indication.transaction_id = random.getrandbits(96)
+
+        # Only handles UDP allocations. Doubtful that we need more than this.
+        data_indication.add_xor_address(IPv4Address('UDP', host, port),
+                                        XOR_PEER_ADDRESS)
+        data_indication.add_data(data)
+
+        self.other_transport_handler.write(data_indication.build(),
+                                           self.allocator_address)
+
+    def close(self):
+        self.port.stopListening()
+        self.port = None
+
+
+class StunHandler(object):
+    """
+    Frames and handles STUN messages. This is the core logic of the TURN
+    server, along with Allocation.
+    """
+
+    def __init__(self, transport_handler):
+        self.client_address = None
+        self.data = str()
+        self.transport_handler = transport_handler
+
+    def data_received(self, data, address):
+        self.data += bytearray(data)
+        while True:
+            stun_message = StunMessage()
+            parsed_len = stun_message.parse(self.data)
+            if parsed_len > len(self.data):
+                break
+            self.data = self.data[parsed_len:]
+
+            response = self.handle_stun(stun_message, address)
+            if response:
+                self.transport_handler.write(response, address)
+
+    def handle_stun(self, stun_message, address):
+        self.client_address = address
+        if stun_message.msg_class == INDICATION:
+            if stun_message.method == SEND:
+                self.handle_send_indication(stun_message)
+            else:
+                print("Dropping unknown indication method: {}"
+                      .format(stun_message.method))
+            return None
+
+        if stun_message.msg_class != REQUEST:
+            print("Dropping STUN response, method: {}"
+                  .format(stun_message.method))
+            return None
+
+        if stun_message.method == BINDING:
+            return self.make_success_response(stun_message).build()
+        elif stun_message.method == ALLOCATE:
+            return self.handle_allocation(stun_message).build()
+        elif stun_message.method == REFRESH:
+            return self.handle_refresh(stun_message).build()
+        elif stun_message.method == CREATE_PERMISSION:
+            return self.handle_permission(stun_message).build()
+        else:
+            return self.make_error_response(
+                    stun_message,
+                    400,
+                    ("Unsupported STUN request, method: {}"
+                     .format(stun_message.method))).build()
+
+    def get_allocation_tuple(self):
+        return (self.client_address.host,
+                self.client_address.port,
+                self.transport_handler.transport.getHost().type,
+                self.transport_handler.transport.getHost().host,
+                self.transport_handler.transport.getHost().port)
+
+    def handle_allocation(self, request):
+        allocate_response = self.check_long_term_auth(request)
+        if allocate_response.msg_class == SUCCESS_RESPONSE:
+            if self.get_allocation_tuple() in allocations:
+                return self.make_error_response(
+                        request,
+                        437,
+                        ("Duplicate allocation request for tuple {}"
+                         .format(self.get_allocation_tuple())))
+
+            allocation = Allocation(self.transport_handler,
+                                    self.client_address,
+                                    request.get_username())
+
+            allocate_response.add_xor_address(allocation.transport.getHost(),
+                                              XOR_RELAYED_ADDRESS)
+
+            lifetime = request.get_lifetime()
+            if lifetime == None:
+                return self.make_error_response(
+                        request,
+                        400,
+                        "Missing lifetime attribute in allocation request")
+
+            lifetime = min(lifetime, 3600)
+            allocate_response.add_lifetime(lifetime)
+            allocation.expiry = time.time() + lifetime
+
+            allocate_response.add_message_integrity(turn_user,
+                                                    turn_realm,
+                                                    turn_pass)
+            allocations[self.get_allocation_tuple()] = allocation
+        return allocate_response
+
+    def handle_refresh(self, request):
+        refresh_response = self.check_long_term_auth(request)
+        if refresh_response.msg_class == SUCCESS_RESPONSE:
+            try:
+                allocation = allocations[self.get_allocation_tuple()]
+            except KeyError:
+                return self.make_error_response(
+                        request,
+                        437,
+                        ("Refresh request for non-existing allocation, tuple {}"
+                         .format(self.get_allocation_tuple())))
+
+            if allocation.username != request.get_username():
+                return self.make_error_response(
+                        request,
+                        441,
+                        ("Refresh request with wrong user, exp {}, got {}"
+                         .format(allocation.username, request.get_username())))
+
+            lifetime = request.get_lifetime()
+            if lifetime == None:
+                return self.make_error_response(
+                        request,
+                        400,
+                        "Missing lifetime attribute in allocation request")
+
+            lifetime = min(lifetime, 3600)
+            refresh_response.add_lifetime(lifetime)
+            allocation.expiry = time.time() + lifetime
+
+            refresh_response.add_message_integrity(turn_user,
+                                                   turn_realm,
+                                                   turn_pass)
+        return refresh_response
+
+    def handle_permission(self, request):
+        permission_response = self.check_long_term_auth(request)
+        if permission_response.msg_class == SUCCESS_RESPONSE:
+            try:
+                allocation = allocations[self.get_allocation_tuple()]
+            except KeyError:
+                return self.make_error_response(
+                        request,
+                        437,
+                        ("No such allocation for permission request, tuple {}"
+                         .format(self.get_allocation_tuple())))
+
+            if allocation.username != request.get_username():
+                return self.make_error_response(
+                        request,
+                        441,
+                        ("Permission request with wrong user, exp {}, got {}"
+                         .format(allocation.username, request.get_username())))
+
+            # TODO: Handle multiple XOR-PEER-ADDRESS
+            peer_address = request.get_xor_address(XOR_PEER_ADDRESS)
+            if not peer_address:
+                return self.make_error_response(
+                        request,
+                        400,
+                        "Missing XOR-PEER-ADDRESS on permission request")
+
+            permission_response.add_message_integrity(turn_user,
+                                                      turn_realm,
+                                                      turn_pass)
+            allocation.permissions.add(peer_address.host)
+
+        return permission_response
+
+    def handle_send_indication(self, indication):
+        try:
+            allocation = allocations[self.get_allocation_tuple()]
+        except KeyError:
+            print("Dropping send indication; no allocation for tuple {}"
+                  .format(self.get_allocation_tuple()))
+            return
+
+        peer_address = indication.get_xor_address(XOR_PEER_ADDRESS)
+        if not peer_address:
+            print("Dropping send indication, missing XOR-PEER-ADDRESS")
+            return
+
+        data_attr = indication.find(DATA_ATTR)
+        if not data_attr:
+            print("Dropping send indication, missing DATA")
+            return
+
+        if indication.find(DONT_FRAGMENT):
+            print("Dropping send indication, DONT-FRAGMENT set")
+            return
+
+        if not peer_address.host in allocation.permissions:
+            print("Dropping send indication, no permission for {} on tuple {}"
+                  .format(peer_address.host, self.get_allocation_tuple()))
+            return
+
+        allocation.transport.write(data_attr.data,
+                                   (peer_address.host, peer_address.port))
+
+    def make_success_response(self, request):
+        response = copy.deepcopy(request)
+        response.attributes = []
+        response.add_xor_address(self.client_address, XOR_MAPPED_ADDRESS)
+        response.msg_class = SUCCESS_RESPONSE
+        return response
+
+    def make_error_response(self, request, code, reason=None):
+        if reason:
+            print("{}: rejecting with {}".format(reason, code))
+        response = copy.deepcopy(request)
+        response.attributes = []
+        response.add_error_code(code, reason)
+        response.msg_class = ERROR_RESPONSE
+        return response
+
+    def make_challenge_response(self, request, reason=None):
+        response = self.make_error_response(request, 401, reason)
+        # 65 means the hex encoding will need padding half the time
+        response.add_nonce("{:x}".format(random.getrandbits(65)))
+        response.add_realm(turn_realm)
+        return response
+
+    def check_long_term_auth(self, request):
+        message_integrity = request.find(MESSAGE_INTEGRITY)
+        if not message_integrity:
+            return self.make_challenge_response(request)
+
+        username = request.find(USERNAME)
+        realm = request.find(REALM)
+        nonce = request.find(NONCE)
+        if not username or not realm or not nonce:
+            return self.make_error_response(
+                    request,
+                    400,
+                    "Missing either USERNAME, NONCE, or REALM")
+
+        if str(username.data) != turn_user:
+            return self.make_challenge_response(
+                    request,
+                    "Wrong user {}, exp {}".format(username.data, turn_user))
+
+        expected_message_digest = request.calculate_message_digest(turn_user,
+                                                                  turn_realm,
+                                                                  turn_pass)
+        if message_integrity.data != expected_message_digest:
+            return self.make_challenge_response(request,
+                                                "Incorrect message disgest")
+
+        return self.make_success_response(request)
+
+
+class UdpStunHandler(protocol.DatagramProtocol):
+    """
+    Represents a UDP listen port for TURN.
+    """
+
+    def datagramReceived(self, data, address):
+        stun_handler = StunHandler(self)
+        stun_handler.data_received(data,
+                                   IPv4Address('UDP', address[0], address[1]))
+
+    def write(self, data, address):
+        self.transport.write(str(data), (address.host, address.port))
+
+
+class TcpStunHandlerFactory(protocol.Factory):
+    """
+    Represents a TCP listen port for TURN.
+    """
+
+    def buildProtocol(self, addr):
+        return TcpStunHandler(addr)
+
+
+class TcpStunHandler(protocol.Protocol):
+    """
+    Represents a connected TCP port for TURN.
+    """
+
+    def __init__(self, addr):
+        self.address = addr
+        self.stun_handler = None
+
+    def dataReceived(self, data):
+        # This needs to persist, since it handles framing
+        if not self.stun_handler:
+            self.stun_handler = StunHandler(self)
+        self.stun_handler.data_received(data, self.address)
+
+    def connectionLost(self, reason):
+        print("Lost connection from {}".format(self.address))
+        # Destroy allocations that this connection made
+        for key, allocation in allocations.items():
+            if allocation.other_transport_handler == self:
+                print("Closing allocation due to dropped connection: {}"
+                      .format(key))
+                del allocations[key]
+                allocation.close()
+
+    def write(self, data, address):
+        self.transport.write(str(data))
+
+def get_default_route(family):
+    dummy_socket = socket.socket(family, socket.SOCK_DGRAM)
+    if family is socket.AF_INET:
+        dummy_socket.connect(("8.8.8.8", 53))
+    else:
+        dummy_socket.connect(("2001:4860:4860::8888", 53))
+
+    default_route = dummy_socket.getsockname()[0]
+    dummy_socket.close()
+    return default_route
+
+turn_user="foo"
+turn_pass="bar"
+turn_realm="mozilla.invalid"
+allocations = {}
+v4_address = get_default_route(socket.AF_INET)
+try:
+    v6_address = get_default_route(socket.AF_INET6)
+except:
+    v6_address = ""
+
+def prune_allocations():
+    now = time.time()
+    for key, allocation in allocations.items():
+        if allocation.expiry < now:
+            print("Allocation expired: {}".format(key))
+            del allocations[key]
+            allocation.close()
+
+if __name__ == "__main__":
+    random.seed()
+
+    if platform.system() is "Windows":
+      # Windows is finicky about allowing real interfaces to talk to loopback.
+      interface_4 = v4_address
+      interface_6 = v6_address
+      hostname = socket.gethostname()
+    else:
+      # Our linux builders do not have a hostname that resolves to the real
+      # interface.
+      interface_4 = "127.0.0.1"
+      interface_6 = "::1"
+      hostname = "localhost"
+
+    reactor.listenUDP(3478, UdpStunHandler(), interface=interface_4)
+    reactor.listenTCP(3478, TcpStunHandlerFactory(), interface=interface_4)
+
+    try:
+        reactor.listenUDP(3478, UdpStunHandler(), interface=interface_6)
+        reactor.listenTCP(3478, TcpStunHandlerFactory(), interface=interface_6)
+    except:
+        pass
+
+    allocation_pruner = LoopingCall(prune_allocations)
+    allocation_pruner.start(1)
+
+    template = Template(
+'[\
+{"url":"stun:$hostname"}, \
+{"url":"stun:$hostname?transport=tcp"}, \
+{"username":"$user","credential":"$pwd","url":"turn:$hostname"}, \
+{"username":"$user","credential":"$pwd","url":"turn:$hostname?transport=tcp"}]'
+)
+
+    print(template.substitute(user=turn_user,
+                              pwd=turn_pass,
+                              hostname=hostname))
+
+    reactor.run()
+