diff options
| -rw-r--r-- | paramiko/auth_handler.py | 36 | ||||
| -rw-r--r-- | sites/www/changelog.rst | 12 | ||||
| -rw-r--r-- | tests/test_transport.py | 51 |
3 files changed, 94 insertions, 5 deletions
diff --git a/paramiko/auth_handler.py b/paramiko/auth_handler.py index 9a5fd0f6..ef1220cc 100644 --- a/paramiko/auth_handler.py +++ b/paramiko/auth_handler.py @@ -676,17 +676,39 @@ class AuthHandler(object): self.auth_event.set() return - _handler_table = { + # TODO: do the same to the other tables, in Transport. + # TODO 3.0: MAY make sense to make these tables into actual + # classes/instances that can be fed a mode bool or whatever. Or, + # alternately (both?) make the message types small classes or enums that + # embed this info within themselves (which could also then tidy up the + # current 'integer -> human readable short string' stuff in common.py). + # TODO: if we do that, also expose 'em publicly. + + # Messages which should be handled _by_ servers (sent by clients) + _server_handler_table = { MSG_SERVICE_REQUEST: _parse_service_request, - MSG_SERVICE_ACCEPT: _parse_service_accept, MSG_USERAUTH_REQUEST: _parse_userauth_request, + MSG_USERAUTH_INFO_RESPONSE: _parse_userauth_info_response, + } + + # Messages which should be handled _by_ clients (sent by servers) + _client_handler_table = { + MSG_SERVICE_ACCEPT: _parse_service_accept, MSG_USERAUTH_SUCCESS: _parse_userauth_success, MSG_USERAUTH_FAILURE: _parse_userauth_failure, MSG_USERAUTH_BANNER: _parse_userauth_banner, MSG_USERAUTH_INFO_REQUEST: _parse_userauth_info_request, - MSG_USERAUTH_INFO_RESPONSE: _parse_userauth_info_response, } + # NOTE: prior to the fix for #1283, this was a static dict instead of a + # property. Should be backwards compatible in most/all cases. + @property + def _handler_table(self): + if self.transport.server_mode: + return self._server_handler_table + else: + return self._client_handler_table + class GssapiWithMicAuthHandler(object): """A specialized Auth handler for gssapi-with-mic @@ -782,9 +804,15 @@ class GssapiWithMicAuthHandler(object): self._restore_delegate_auth_handler() return self._delegate._parse_userauth_request(m) - _handler_table = { + __handler_table = { MSG_SERVICE_REQUEST: _parse_service_request, MSG_USERAUTH_REQUEST: _parse_userauth_request, MSG_USERAUTH_GSSAPI_TOKEN: _parse_userauth_gssapi_token, MSG_USERAUTH_GSSAPI_MIC: _parse_userauth_gssapi_mic, } + + @property + def _handler_table(self): + # TODO: determine if we can cut this up like we did for the primary + # AuthHandler class. + return self.__handler_table diff --git a/sites/www/changelog.rst b/sites/www/changelog.rst index 207bfe59..d6845e8e 100644 --- a/sites/www/changelog.rst +++ b/sites/www/changelog.rst @@ -7,6 +7,18 @@ Changelog This behavior probably didn't cause any outright errors, but it doesn't seem to conform to the RFCs and could cause (non-infinite) feedback loops in some scenarios (usually those involving Paramiko on both ends). +- :bug:`1283 (1.17+)` Fix exploit (CVE pending) in Paramiko's server mode + (**not** client mode) where hostile clients could trick the server into + thinking they were authenticated without actually submitting valid + authentication. + + Specifically, steps have been taken to start separating client and server + related message types in the message handling tables within ``Transport`` and + ``AuthHandler``; this work is not complete but enough has been performed to + close off this particular exploit (which was the only obvious such exploit + for this particular channel). + + Thanks to Daniel Hoffman for the detailed report. - :support:`1292 backported` Backport changes from :issue:`979` (added in Paramiko 2.3) to Paramiko 2.0-2.2, using duck-typing to preserve backwards compatibility. This allows these older versions to use newer Cryptography diff --git a/tests/test_transport.py b/tests/test_transport.py index 3ea2cb26..2b8ee3bc 100644 --- a/tests/test_transport.py +++ b/tests/test_transport.py @@ -42,6 +42,7 @@ from paramiko import ( ChannelException, Packetizer, Channel, + AuthHandler, ) from paramiko import AUTH_FAILED, AUTH_SUCCESSFUL from paramiko import OPEN_SUCCEEDED, OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED @@ -54,8 +55,11 @@ from paramiko.common import ( MAX_WINDOW_SIZE, DEFAULT_WINDOW_SIZE, DEFAULT_MAX_PACKET_SIZE, + MSG_NAMES, + MSG_UNIMPLEMENTED, + MSG_USERAUTH_SUCCESS, ) -from paramiko.py3compat import bytes +from paramiko.py3compat import bytes, byte_chr from paramiko.message import Message from .util import needs_builtin, _support, slow @@ -1052,3 +1056,48 @@ class TransportTest(unittest.TestCase): def test_client_does_not_respond_to_MSG_UNIMPLEMENTED(self): self._send_unimplemented(server_is_sender=True) + + def _send_client_message(self, message_type): + self.setup_test_server(connect_kwargs={}) + self.ts._send_message = Mock() + # NOTE: this isn't 100% realistic (most of these message types would + # have actual other fields in 'em) but it suffices to test the level of + # message dispatch we're interested in here. + msg = Message() + # TODO: really not liking the whole cMSG_XXX vs MSG_XXX duality right + # now, esp since the former is almost always just byte_chr(the + # latter)...but since that's the case... + msg.add_byte(byte_chr(message_type)) + self.tc._send_message(msg) + # No good way to actually wait for server action (see above tests re: + # MSG_UNIMPLEMENTED). Grump. + time.sleep(0.1) + + def _expect_unimplemented(self): + # Ensure MSG_UNIMPLEMENTED was sent (implies it hit end of loop instead + # of truly handling the given message). + # NOTE: When bug present, this will actually be the first thing that + # fails (since in many cases actual message handling doesn't involve + # sending a message back right away). + assert self.ts._send_message.call_count == 1 + reply = self.ts._send_message.call_args[0][0] + reply.rewind() # Because it's pre-send, not post-receive + assert reply.get_byte() == cMSG_UNIMPLEMENTED + + def test_server_transports_reject_client_message_types(self): + # TODO: handle Transport's own tables too, not just its inner auth + # handler's table. See TODOs in auth_handler.py + for message_type in AuthHandler._client_handler_table: + self._send_client_message(message_type) + self._expect_unimplemented() + # Reset for rest of loop + self.tearDown() + self.setUp() + + def test_server_rejects_client_MSG_USERAUTH_SUCCESS(self): + self._send_client_message(MSG_USERAUTH_SUCCESS) + # Sanity checks + assert not self.ts.authenticated + assert not self.ts.auth_handler.authenticated + # Real fix's behavior + self._expect_unimplemented() |