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19 """
20 L{ServerInterface} is an interface to override for server support.
21 """
22
23 import threading
24 from ssh.common import *
25 from ssh import util
26
27
29 """
30 A query (set of prompts) for a user during interactive authentication.
31 """
32
33 - def __init__(self, name='', instructions='', *prompts):
34 """
35 Create a new interactive query to send to the client. The name and
36 instructions are optional, but are generally displayed to the end
37 user. A list of prompts may be included, or they may be added via
38 the L{add_prompt} method.
39
40 @param name: name of this query
41 @type name: str
42 @param instructions: user instructions (usually short) about this query
43 @type instructions: str
44 @param prompts: one or more authentication prompts
45 @type prompts: str
46 """
47 self.name = name
48 self.instructions = instructions
49 self.prompts = []
50 for x in prompts:
51 if (type(x) is str) or (type(x) is unicode):
52 self.add_prompt(x)
53 else:
54 self.add_prompt(x[0], x[1])
55
57 """
58 Add a prompt to this query. The prompt should be a (reasonably short)
59 string. Multiple prompts can be added to the same query.
60
61 @param prompt: the user prompt
62 @type prompt: str
63 @param echo: C{True} (default) if the user's response should be echoed;
64 C{False} if not (for a password or similar)
65 @type echo: bool
66 """
67 self.prompts.append((prompt, echo))
68
69
71 """
72 This class defines an interface for controlling the behavior of ssh
73 in server mode.
74
75 Methods on this class are called from ssh's primary thread, so you
76 shouldn't do too much work in them. (Certainly nothing that blocks or
77 sleeps.)
78 """
79
81 """
82 Determine if a channel request of a given type will be granted, and
83 return C{OPEN_SUCCEEDED} or an error code. This method is
84 called in server mode when the client requests a channel, after
85 authentication is complete.
86
87 If you allow channel requests (and an ssh server that didn't would be
88 useless), you should also override some of the channel request methods
89 below, which are used to determine which services will be allowed on
90 a given channel:
91 - L{check_channel_pty_request}
92 - L{check_channel_shell_request}
93 - L{check_channel_subsystem_request}
94 - L{check_channel_window_change_request}
95 - L{check_channel_x11_request}
96 - L{check_channel_forward_agent_request}
97
98 The C{chanid} parameter is a small number that uniquely identifies the
99 channel within a L{Transport}. A L{Channel} object is not created
100 unless this method returns C{OPEN_SUCCEEDED} -- once a
101 L{Channel} object is created, you can call L{Channel.get_id} to
102 retrieve the channel ID.
103
104 The return value should either be C{OPEN_SUCCEEDED} (or
105 C{0}) to allow the channel request, or one of the following error
106 codes to reject it:
107 - C{OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED}
108 - C{OPEN_FAILED_CONNECT_FAILED}
109 - C{OPEN_FAILED_UNKNOWN_CHANNEL_TYPE}
110 - C{OPEN_FAILED_RESOURCE_SHORTAGE}
111
112 The default implementation always returns
113 C{OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED}.
114
115 @param kind: the kind of channel the client would like to open
116 (usually C{"session"}).
117 @type kind: str
118 @param chanid: ID of the channel
119 @type chanid: int
120 @return: a success or failure code (listed above)
121 @rtype: int
122 """
123 return OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED
124
126 """
127 Return a list of authentication methods supported by the server.
128 This list is sent to clients attempting to authenticate, to inform them
129 of authentication methods that might be successful.
130
131 The "list" is actually a string of comma-separated names of types of
132 authentication. Possible values are C{"password"}, C{"publickey"},
133 and C{"none"}.
134
135 The default implementation always returns C{"password"}.
136
137 @param username: the username requesting authentication.
138 @type username: str
139 @return: a comma-separated list of authentication types
140 @rtype: str
141 """
142 return 'password'
143
145 """
146 Determine if a client may open channels with no (further)
147 authentication.
148
149 Return L{AUTH_FAILED} if the client must authenticate, or
150 L{AUTH_SUCCESSFUL} if it's okay for the client to not
151 authenticate.
152
153 The default implementation always returns L{AUTH_FAILED}.
154
155 @param username: the username of the client.
156 @type username: str
157 @return: L{AUTH_FAILED} if the authentication fails;
158 L{AUTH_SUCCESSFUL} if it succeeds.
159 @rtype: int
160 """
161 return AUTH_FAILED
162
164 """
165 Determine if a given username and password supplied by the client is
166 acceptable for use in authentication.
167
168 Return L{AUTH_FAILED} if the password is not accepted,
169 L{AUTH_SUCCESSFUL} if the password is accepted and completes
170 the authentication, or L{AUTH_PARTIALLY_SUCCESSFUL} if your
171 authentication is stateful, and this key is accepted for
172 authentication, but more authentication is required. (In this latter
173 case, L{get_allowed_auths} will be called to report to the client what
174 options it has for continuing the authentication.)
175
176 The default implementation always returns L{AUTH_FAILED}.
177
178 @param username: the username of the authenticating client.
179 @type username: str
180 @param password: the password given by the client.
181 @type password: str
182 @return: L{AUTH_FAILED} if the authentication fails;
183 L{AUTH_SUCCESSFUL} if it succeeds;
184 L{AUTH_PARTIALLY_SUCCESSFUL} if the password auth is
185 successful, but authentication must continue.
186 @rtype: int
187 """
188 return AUTH_FAILED
189
191 """
192 Determine if a given key supplied by the client is acceptable for use
193 in authentication. You should override this method in server mode to
194 check the username and key and decide if you would accept a signature
195 made using this key.
196
197 Return L{AUTH_FAILED} if the key is not accepted,
198 L{AUTH_SUCCESSFUL} if the key is accepted and completes the
199 authentication, or L{AUTH_PARTIALLY_SUCCESSFUL} if your
200 authentication is stateful, and this password is accepted for
201 authentication, but more authentication is required. (In this latter
202 case, L{get_allowed_auths} will be called to report to the client what
203 options it has for continuing the authentication.)
204
205 Note that you don't have to actually verify any key signtature here.
206 If you're willing to accept the key, ssh will do the work of
207 verifying the client's signature.
208
209 The default implementation always returns L{AUTH_FAILED}.
210
211 @param username: the username of the authenticating client
212 @type username: str
213 @param key: the key object provided by the client
214 @type key: L{PKey <pkey.PKey>}
215 @return: L{AUTH_FAILED} if the client can't authenticate
216 with this key; L{AUTH_SUCCESSFUL} if it can;
217 L{AUTH_PARTIALLY_SUCCESSFUL} if it can authenticate with
218 this key but must continue with authentication
219 @rtype: int
220 """
221 return AUTH_FAILED
222
224 """
225 Begin an interactive authentication challenge, if supported. You
226 should override this method in server mode if you want to support the
227 C{"keyboard-interactive"} auth type, which requires you to send a
228 series of questions for the client to answer.
229
230 Return L{AUTH_FAILED} if this auth method isn't supported. Otherwise,
231 you should return an L{InteractiveQuery} object containing the prompts
232 and instructions for the user. The response will be sent via a call
233 to L{check_auth_interactive_response}.
234
235 The default implementation always returns L{AUTH_FAILED}.
236
237 @param username: the username of the authenticating client
238 @type username: str
239 @param submethods: a comma-separated list of methods preferred by the
240 client (usually empty)
241 @type submethods: str
242 @return: L{AUTH_FAILED} if this auth method isn't supported; otherwise
243 an object containing queries for the user
244 @rtype: int or L{InteractiveQuery}
245 """
246 return AUTH_FAILED
247
249 """
250 Continue or finish an interactive authentication challenge, if
251 supported. You should override this method in server mode if you want
252 to support the C{"keyboard-interactive"} auth type.
253
254 Return L{AUTH_FAILED} if the responses are not accepted,
255 L{AUTH_SUCCESSFUL} if the responses are accepted and complete
256 the authentication, or L{AUTH_PARTIALLY_SUCCESSFUL} if your
257 authentication is stateful, and this set of responses is accepted for
258 authentication, but more authentication is required. (In this latter
259 case, L{get_allowed_auths} will be called to report to the client what
260 options it has for continuing the authentication.)
261
262 If you wish to continue interactive authentication with more questions,
263 you may return an L{InteractiveQuery} object, which should cause the
264 client to respond with more answers, calling this method again. This
265 cycle can continue indefinitely.
266
267 The default implementation always returns L{AUTH_FAILED}.
268
269 @param responses: list of responses from the client
270 @type responses: list(str)
271 @return: L{AUTH_FAILED} if the authentication fails;
272 L{AUTH_SUCCESSFUL} if it succeeds;
273 L{AUTH_PARTIALLY_SUCCESSFUL} if the interactive auth is
274 successful, but authentication must continue; otherwise an object
275 containing queries for the user
276 @rtype: int or L{InteractiveQuery}
277 """
278 return AUTH_FAILED
279
281 """
282 Handle a request for port forwarding. The client is asking that
283 connections to the given address and port be forwarded back across
284 this ssh connection. An address of C{"0.0.0.0"} indicates a global
285 address (any address associated with this server) and a port of C{0}
286 indicates that no specific port is requested (usually the OS will pick
287 a port).
288
289 The default implementation always returns C{False}, rejecting the
290 port forwarding request. If the request is accepted, you should return
291 the port opened for listening.
292
293 @param address: the requested address
294 @type address: str
295 @param port: the requested port
296 @type port: int
297 @return: the port number that was opened for listening, or C{False} to
298 reject
299 @rtype: int
300 """
301 return False
302
304 """
305 The client would like to cancel a previous port-forwarding request.
306 If the given address and port is being forwarded across this ssh
307 connection, the port should be closed.
308
309 @param address: the forwarded address
310 @type address: str
311 @param port: the forwarded port
312 @type port: int
313 """
314 pass
315
317 """
318 Handle a global request of the given C{kind}. This method is called
319 in server mode and client mode, whenever the remote host makes a global
320 request. If there are any arguments to the request, they will be in
321 C{msg}.
322
323 There aren't any useful global requests defined, aside from port
324 forwarding, so usually this type of request is an extension to the
325 protocol.
326
327 If the request was successful and you would like to return contextual
328 data to the remote host, return a tuple. Items in the tuple will be
329 sent back with the successful result. (Note that the items in the
330 tuple can only be strings, ints, longs, or bools.)
331
332 The default implementation always returns C{False}, indicating that it
333 does not support any global requests.
334
335 @note: Port forwarding requests are handled separately, in
336 L{check_port_forward_request}.
337
338 @param kind: the kind of global request being made.
339 @type kind: str
340 @param msg: any extra arguments to the request.
341 @type msg: L{Message}
342 @return: C{True} or a tuple of data if the request was granted;
343 C{False} otherwise.
344 @rtype: bool
345 """
346 return False
347
348
349
350
351
354 """
355 Determine if a pseudo-terminal of the given dimensions (usually
356 requested for shell access) can be provided on the given channel.
357
358 The default implementation always returns C{False}.
359
360 @param channel: the L{Channel} the pty request arrived on.
361 @type channel: L{Channel}
362 @param term: type of terminal requested (for example, C{"vt100"}).
363 @type term: str
364 @param width: width of screen in characters.
365 @type width: int
366 @param height: height of screen in characters.
367 @type height: int
368 @param pixelwidth: width of screen in pixels, if known (may be C{0} if
369 unknown).
370 @type pixelwidth: int
371 @param pixelheight: height of screen in pixels, if known (may be C{0}
372 if unknown).
373 @type pixelheight: int
374 @return: C{True} if the psuedo-terminal has been allocated; C{False}
375 otherwise.
376 @rtype: bool
377 """
378 return False
379
381 """
382 Determine if a shell will be provided to the client on the given
383 channel. If this method returns C{True}, the channel should be
384 connected to the stdin/stdout of a shell (or something that acts like
385 a shell).
386
387 The default implementation always returns C{False}.
388
389 @param channel: the L{Channel} the request arrived on.
390 @type channel: L{Channel}
391 @return: C{True} if this channel is now hooked up to a shell; C{False}
392 if a shell can't or won't be provided.
393 @rtype: bool
394 """
395 return False
396
398 """
399 Determine if a shell command will be executed for the client. If this
400 method returns C{True}, the channel should be connected to the stdin,
401 stdout, and stderr of the shell command.
402
403 The default implementation always returns C{False}.
404
405 @param channel: the L{Channel} the request arrived on.
406 @type channel: L{Channel}
407 @param command: the command to execute.
408 @type command: str
409 @return: C{True} if this channel is now hooked up to the stdin,
410 stdout, and stderr of the executing command; C{False} if the
411 command will not be executed.
412 @rtype: bool
413
414 @since: 1.1
415 """
416 return False
417
419 """
420 Determine if a requested subsystem will be provided to the client on
421 the given channel. If this method returns C{True}, all future I/O
422 through this channel will be assumed to be connected to the requested
423 subsystem. An example of a subsystem is C{sftp}.
424
425 The default implementation checks for a subsystem handler assigned via
426 L{Transport.set_subsystem_handler}.
427 If one has been set, the handler is invoked and this method returns
428 C{True}. Otherwise it returns C{False}.
429
430 @note: Because the default implementation uses the L{Transport} to
431 identify valid subsystems, you probably won't need to override this
432 method.
433
434 @param channel: the L{Channel} the pty request arrived on.
435 @type channel: L{Channel}
436 @param name: name of the requested subsystem.
437 @type name: str
438 @return: C{True} if this channel is now hooked up to the requested
439 subsystem; C{False} if that subsystem can't or won't be provided.
440 @rtype: bool
441 """
442 handler_class, larg, kwarg = channel.get_transport()._get_subsystem_handler(name)
443 if handler_class is None:
444 return False
445 handler = handler_class(channel, name, self, *larg, **kwarg)
446 handler.start()
447 return True
448
450 """
451 Determine if the pseudo-terminal on the given channel can be resized.
452 This only makes sense if a pty was previously allocated on it.
453
454 The default implementation always returns C{False}.
455
456 @param channel: the L{Channel} the pty request arrived on.
457 @type channel: L{Channel}
458 @param width: width of screen in characters.
459 @type width: int
460 @param height: height of screen in characters.
461 @type height: int
462 @param pixelwidth: width of screen in pixels, if known (may be C{0} if
463 unknown).
464 @type pixelwidth: int
465 @param pixelheight: height of screen in pixels, if known (may be C{0}
466 if unknown).
467 @type pixelheight: int
468 @return: C{True} if the terminal was resized; C{False} if not.
469 @rtype: bool
470 """
471 return False
472
474 """
475 Determine if the client will be provided with an X11 session. If this
476 method returns C{True}, X11 applications should be routed through new
477 SSH channels, using L{Transport.open_x11_channel}.
478
479 The default implementation always returns C{False}.
480
481 @param channel: the L{Channel} the X11 request arrived on
482 @type channel: L{Channel}
483 @param single_connection: C{True} if only a single X11 channel should
484 be opened
485 @type single_connection: bool
486 @param auth_protocol: the protocol used for X11 authentication
487 @type auth_protocol: str
488 @param auth_cookie: the cookie used to authenticate to X11
489 @type auth_cookie: str
490 @param screen_number: the number of the X11 screen to connect to
491 @type screen_number: int
492 @return: C{True} if the X11 session was opened; C{False} if not
493 @rtype: bool
494 """
495 return False
496
498 """
499 Determine if the client will be provided with an forward agent session.
500 If this method returns C{True}, the server will allow SSH Agent
501 forwarding.
502
503 The default implementation always returns C{False}.
504
505 @param channel: the L{Channel} the request arrived on
506 @type channel: L{Channel}
507 @return: C{True} if the AgentForward was loaded; C{False} if not
508 @rtype: bool
509 """
510 return False
511
513 """
514 Determine if a local port forwarding channel will be granted, and
515 return C{OPEN_SUCCEEDED} or an error code. This method is
516 called in server mode when the client requests a channel, after
517 authentication is complete.
518
519 The C{chanid} parameter is a small number that uniquely identifies the
520 channel within a L{Transport}. A L{Channel} object is not created
521 unless this method returns C{OPEN_SUCCEEDED} -- once a
522 L{Channel} object is created, you can call L{Channel.get_id} to
523 retrieve the channel ID.
524
525 The origin and destination parameters are (ip_address, port) tuples
526 that correspond to both ends of the TCP connection in the forwarding
527 tunnel.
528
529 The return value should either be C{OPEN_SUCCEEDED} (or
530 C{0}) to allow the channel request, or one of the following error
531 codes to reject it:
532 - C{OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED}
533 - C{OPEN_FAILED_CONNECT_FAILED}
534 - C{OPEN_FAILED_UNKNOWN_CHANNEL_TYPE}
535 - C{OPEN_FAILED_RESOURCE_SHORTAGE}
536
537 The default implementation always returns
538 C{OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED}.
539
540 @param chanid: ID of the channel
541 @type chanid: int
542 @param origin: 2-tuple containing the IP address and port of the
543 originator (client side)
544 @type origin: tuple
545 @param destination: 2-tuple containing the IP address and port of the
546 destination (server side)
547 @type destination: tuple
548 @return: a success or failure code (listed above)
549 @rtype: int
550 """
551 return OPEN_FAILED_ADMINISTRATIVELY_PROHIBITED
552
553
555 """
556 Handler for a subsytem in server mode. If you create a subclass of this
557 class and pass it to
558 L{Transport.set_subsystem_handler},
559 an object of this
560 class will be created for each request for this subsystem. Each new object
561 will be executed within its own new thread by calling L{start_subsystem}.
562 When that method completes, the channel is closed.
563
564 For example, if you made a subclass C{MP3Handler} and registered it as the
565 handler for subsystem C{"mp3"}, then whenever a client has successfully
566 authenticated and requests subsytem C{"mp3"}, an object of class
567 C{MP3Handler} will be created, and L{start_subsystem} will be called on
568 it from a new thread.
569 """
570 - def __init__(self, channel, name, server):
571 """
572 Create a new handler for a channel. This is used by L{ServerInterface}
573 to start up a new handler when a channel requests this subsystem. You
574 don't need to override this method, but if you do, be sure to pass the
575 C{channel} and C{name} parameters through to the original C{__init__}
576 method here.
577
578 @param channel: the channel associated with this subsystem request.
579 @type channel: L{Channel}
580 @param name: name of the requested subsystem.
581 @type name: str
582 @param server: the server object for the session that started this
583 subsystem
584 @type server: L{ServerInterface}
585 """
586 threading.Thread.__init__(self, target=self._run)
587 self.__channel = channel
588 self.__transport = channel.get_transport()
589 self.__name = name
590 self.__server = server
591
593 """
594 Return the L{ServerInterface} object associated with this channel and
595 subsystem.
596
597 @rtype: L{ServerInterface}
598 """
599 return self.__server
600
602 try:
603 self.__transport._log(DEBUG, 'Starting handler for subsystem %s' % self.__name)
604 self.start_subsystem(self.__name, self.__transport, self.__channel)
605 except Exception, e:
606 self.__transport._log(ERROR, 'Exception in subsystem handler for "%s": %s' %
607 (self.__name, str(e)))
608 self.__transport._log(ERROR, util.tb_strings())
609 try:
610 self.finish_subsystem()
611 except:
612 pass
613
615 """
616 Process an ssh subsystem in server mode. This method is called on a
617 new object (and in a new thread) for each subsystem request. It is
618 assumed that all subsystem logic will take place here, and when the
619 subsystem is finished, this method will return. After this method
620 returns, the channel is closed.
621
622 The combination of C{transport} and C{channel} are unique; this handler
623 corresponds to exactly one L{Channel} on one L{Transport}.
624
625 @note: It is the responsibility of this method to exit if the
626 underlying L{Transport} is closed. This can be done by checking
627 L{Transport.is_active} or noticing an EOF
628 on the L{Channel}. If this method loops forever without checking
629 for this case, your python interpreter may refuse to exit because
630 this thread will still be running.
631
632 @param name: name of the requested subsystem.
633 @type name: str
634 @param transport: the server-mode L{Transport}.
635 @type transport: L{Transport}
636 @param channel: the channel associated with this subsystem request.
637 @type channel: L{Channel}
638 """
639 pass
640
642 """
643 Perform any cleanup at the end of a subsystem. The default
644 implementation just closes the channel.
645
646 @since: 1.1
647 """
648 self.__channel.close()
649