Module: Rex::Post::Meterpreter::PacketDispatcher

Included in:
Client
Defined in:
lib/rex/post/meterpreter/packet_dispatcher.rb

Overview

Handles packet transmission, reception, and correlation, and processing

Constant Summary collapse

PACKET_TIMEOUT =

Defualt time, in seconds, to wait for a response after sending a packet

600
PING_TIME =

Number of seconds to wait without getting any packets before we try to send a liveness check. A minute should be generous even on the highest latency networks

See Also:

60

Instance Attribute Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#comm_mutex ⇒ Object

This mutex is used to lock out new commands during an active migration. Unused if this is a passive dispatcher



57
58
59
 
# File 'lib/rex/post/meterpreter/packet_dispatcher.rb', line 57

def comm_mutex
  @comm_mutex
end

#passive_service ⇒ Rex::ServiceManager?

Passive Dispatching

Returns:



64
65
66
 
# File 'lib/rex/post/meterpreter/packet_dispatcher.rb', line 64

def passive_service
  @passive_service
end

#recv_queue ⇒ Array

Returns:

  • (Array) 


70
71
72
 
# File 'lib/rex/post/meterpreter/packet_dispatcher.rb', line 70

def recv_queue
  @recv_queue
end

#send_queue ⇒ Array

Returns:

  • (Array) 


67
68
69
 
# File 'lib/rex/post/meterpreter/packet_dispatcher.rb', line 67

def send_queue
  @send_queue
end

Instance Method Details

#add_response_waiter(request, completion_routine = nil, completion_param = nil) ⇒ Object

Adds a waiter association with the supplied request packet.



442
443
444
445
446
447
448
 
# File 'lib/rex/post/meterpreter/packet_dispatcher.rb', line 442

def add_response_waiter(request, completion_routine = nil, completion_param = nil)
  waiter = PacketResponseWaiter.new(request.rid, completion_routine, completion_param)

  self.waiters << waiter

  return waiter
end

#deregister_inbound_handler(handler) ⇒ Object

Deregisters a previously registered inbound packet handler.



543
544
545
 
# File 'lib/rex/post/meterpreter/packet_dispatcher.rb', line 543

def deregister_inbound_handler(handler)
  @inbound_handlers.delete(handler)
end

#dispatch_inbound_packet(packet) ⇒ Object

Dispatches and processes an inbound packet. If the packet is a response that has an associated waiter, the waiter is notified. Otherwise, the packet is passed onto any registered dispatch handlers until one returns success.



493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
 
# File 'lib/rex/post/meterpreter/packet_dispatcher.rb', line 493

def dispatch_inbound_packet(packet)
  handled = false

  # Update our last reply time
  self.last_checkin = Time.now

  # If the packet is a response, try to notify any potential
  # waiters
  if packet.response?
    if (notify_response_waiter(packet))
      return true
    end
  end

  # Enumerate all of the inbound packet handlers until one handles
  # the packet
  @inbound_handlers.each { |handler|

    handled = nil
    begin

      if packet.response?
        handled = handler.response_handler(self, packet)
      else
        handled = handler.request_handler(self, packet)
      end

    rescue ::Exception => e
      dlog("Exception caught in dispatch_inbound_packet: handler=#{handler} #{e.class} #{e} #{e.backtrace}", 'meterpreter', LEV_1)
      return true
    end

    if (handled)
      break
    end
  }
  return handled
end

#initialize_inbound_handlers ⇒ Object

Initializes the inbound handlers.



483
484
485
 
# File 'lib/rex/post/meterpreter/packet_dispatcher.rb', line 483

def initialize_inbound_handlers
  @inbound_handlers = []
end

#initialize_passive_dispatcher ⇒ Object 



72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
 
# File 'lib/rex/post/meterpreter/packet_dispatcher.rb', line 72

def initialize_passive_dispatcher
  self.send_queue = []
  self.recv_queue = []
  self.waiters    = []
  self.alive      = true

  # Ensure that there is only one leading and trailing slash on the URI
  resource_uri = "/" + self.conn_id.to_s.gsub(/(^\/|\/$)/, '') + "/"

  self.passive_service = self.passive_dispatcher
  self.passive_service.remove_resource(resource_uri)
  self.passive_service.add_resource(resource_uri,
    'Proc'             => Proc.new { |cli, req| on_passive_request(cli, req) },
    'VirtualDirectory' => true
  )
end

#keepalive ⇒ void

This method returns an undefined value.

Send a ping to the server.

Our ‘ping’ is a check for eof on channel id 0. This method has no side effects and always returns an answer (regardless of the existence of chan 0), which is all that’s needed for a liveness check. The answer itself is unimportant and is ignored.



259
260
261
262
263
264
265
266
267
268
269
270
271
272
 
# File 'lib/rex/post/meterpreter/packet_dispatcher.rb', line 259

def keepalive
  if @ping_sent
    if Time.now.to_i - last_checkin.to_i > PING_TIME*2
      dlog("No response to ping, session #{self.sid} is dead", LEV_3)
      self.alive = false
    end
  else
    pkt = Packet.create_request('core_channel_eof')
    pkt.add_tlv(TLV_TYPE_CHANNEL_ID, 0)
    add_response_waiter(pkt, Proc.new { @ping_sent = false })
    send_packet(pkt)
    @ping_sent = true
  end
end

#monitor_socket ⇒ Object

Reception

Monitors the PacketDispatcher’s sock for data in its own thread context and parsers all inbound packets.



283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
 
# File 'lib/rex/post/meterpreter/packet_dispatcher.rb', line 283

def monitor_socket

  # Skip if we are using a passive dispatcher
  return if self.passive_service

  self.comm_mutex = ::Mutex.new

  self.waiters = []

  @pqueue = ::Queue.new
  @ping_sent = false

  # Spawn a thread for receiving packets
  self.receiver_thread = Rex::ThreadFactory.spawn("MeterpreterReceiver", false) do
    while (self.alive)
      begin
        rv = Rex::ThreadSafe.select([ self.sock.fd ], nil, nil, PING_TIME)
        if rv
          packet = receive_packet
          @pqueue << packet if packet
        elsif self.send_keepalives && @pqueue.empty?
          keepalive
        end
      rescue ::Exception => e
        dlog("Exception caught in monitor_socket: #{e.class}: #{e}", 'meterpreter', LEV_1)
        dlog("Call stack: #{e.backtrace.join("\n")}", 'meterpreter', LEV_2)
        self.alive = false
        break
      end
    end
  end

  # Spawn a new thread that monitors the socket
  self.dispatcher_thread = Rex::ThreadFactory.spawn("MeterpreterDispatcher", false) do
    begin
    while (self.alive)
      incomplete = []
      backlog    = []

      backlog << @pqueue.pop
      while(@pqueue.length > 0)
        backlog << @pqueue.pop
      end

      #
      # Prioritize message processing here
      # 1. Close should always be processed at the end
      # 2. Command responses always before channel data
      #

      tmp_command = []
      tmp_channel = []
      tmp_close   = []
      backlog.each do |pkt|
        if(pkt.response?)
          tmp_command << pkt
          next
        end
        if(pkt.method == "core_channel_close")
          tmp_close << pkt
          next
        end
        tmp_channel << pkt
      end

      backlog = []
      backlog.push(*tmp_command)
      backlog.push(*tmp_channel)
      backlog.push(*tmp_close)

      #
      # Process the message queue
      #

      backlog.each do |pkt|

        begin
        if ! dispatch_inbound_packet(pkt)
          # Keep Packets in the receive queue until a handler is registered
          # for them. Packets will live in the receive queue for up to
          # PACKET_TIMEOUT seconds, after which they will be dropped.
          #
          # A common reason why there would not immediately be a handler for
          # a received Packet is in channels, where a connection may
          # open and receive data before anything has asked to read.
          if (::Time.now.to_i - pkt.created_at.to_i < PACKET_TIMEOUT)
            incomplete << pkt
          end
        end

        rescue ::Exception => e
          dlog("Dispatching exception with packet #{pkt}: #{e} #{e.backtrace}", 'meterpreter', LEV_1)
        end
      end

      # If the backlog and incomplete arrays are the same, it means
      # dispatch_inbound_packet wasn't able to handle any of the
      # packets. When that's the case, we can get into a situation
      # where @pqueue is not empty and, since nothing else bounds this
      # loop, we spin CPU trying to handle packets that can't be
      # handled. Sleep here to treat that situation as though the
      # queue is empty.
      if (backlog.length > 0 && backlog.length == incomplete.length)
        ::IO.select(nil, nil, nil, 0.10)
      end

      while incomplete.length > 0
        @pqueue << incomplete.shift
      end

      if(@pqueue.length > 100)
        removed = []
        (1..25).each {
          removed << @pqueue.pop
        }
        dlog("Backlog has grown to over 100 in monitor_socket, dropping older packets: #{removed.map{|x| x.inspect}.join(" - ")}", 'meterpreter', LEV_1)
      end
    end
    rescue ::Exception => e
      dlog("Exception caught in monitor_socket dispatcher: #{e.class} #{e} #{e.backtrace}", 'meterpreter', LEV_1)
    ensure
      self.receiver_thread.kill if self.receiver_thread
    end
  end
end

#monitor_stop ⇒ Object

Stop the monitor



421
422
423
424
425
426
427
428
429
430
431
 
# File 'lib/rex/post/meterpreter/packet_dispatcher.rb', line 421

def monitor_stop
  if(self.receiver_thread)
    self.receiver_thread.kill
    self.receiver_thread = nil
  end

  if(self.dispatcher_thread)
    self.dispatcher_thread.kill
    self.dispatcher_thread = nil
  end
end

#notify_response_waiter(response) ⇒ Object

Notifies a whomever is waiting for a the supplied response, if anyone.



454
455
456
457
458
459
460
461
462
463
464
465
 
# File 'lib/rex/post/meterpreter/packet_dispatcher.rb', line 454

def notify_response_waiter(response)
  handled = false
  self.waiters.each() { |waiter|
    if (waiter.waiting_for?(response))
      waiter.notify(response)
      remove_response_waiter(waiter)
      handled = true
      break
    end
  }
  return handled
end

#on_passive_request(cli, req) ⇒ Object 



110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
 
# File 'lib/rex/post/meterpreter/packet_dispatcher.rb', line 110

def on_passive_request(cli, req)

  begin

  resp = Rex::Proto::Http::Response.new(200, "OK")
  resp['Content-Type'] = 'application/octet-stream'
  resp['Connection']   = 'close'

  self.last_checkin = Time.now

  if req.method == 'GET'
    rpkt = send_queue.shift
    resp.body = rpkt || ''
    begin
      cli.send_response(resp)
    rescue ::Exception => e
      send_queue.unshift(rpkt) if rpkt
      elog("Exception sending a reply to the reader request: #{cli.inspect} #{e.class} #{e} #{e.backtrace}")
    end
  else
    resp.body = ""
    if req.body and req.body.length > 0
      packet = Packet.new(0)
      packet.from_r(req.body)
      dispatch_inbound_packet(packet)
    end
    cli.send_response(resp)
  end

  rescue ::Exception => e
    elog("Exception handling request: #{cli.inspect} #{req.inspect} #{e.class} #{e} #{e.backtrace}")
  end
end

#receive_packet ⇒ Object

Parses data from the dispatcher’s sock and returns a Packet context once a full packet has been received.



414
415
416
 
# File 'lib/rex/post/meterpreter/packet_dispatcher.rb', line 414

def receive_packet
  return parser.recv(self.sock)
end

#register_inbound_handler(handler) ⇒ Object

Registers an inbound packet handler that implements the InboundPacketHandler interface.



536
537
538
 
# File 'lib/rex/post/meterpreter/packet_dispatcher.rb', line 536

def register_inbound_handler(handler)
  @inbound_handlers << handler
end

#remove_response_waiter(waiter) ⇒ Object

Removes a waiter from the list of waiters.



470
471
472
 
# File 'lib/rex/post/meterpreter/packet_dispatcher.rb', line 470

def remove_response_waiter(waiter)
  self.waiters.delete(waiter)
end

#send_packet(packet, completion_routine = nil, completion_param = nil) ⇒ Object

Sends a packet without waiting for a response.



153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
 
# File 'lib/rex/post/meterpreter/packet_dispatcher.rb', line 153

def send_packet(packet, completion_routine = nil, completion_param = nil)
  if (completion_routine)
    add_response_waiter(packet, completion_routine, completion_param)
  end

  bytes = 0
  raw   = packet.to_r
  err   = nil

  # Short-circuit send when using a passive dispatcher
  if self.passive_service
    send_queue.push(raw)
    return raw.size # Lie!
  end

  if (raw)

    self.comm_mutex.synchronize do
      begin
        bytes = self.sock.write(raw)
      rescue ::Exception => e
        err = e
      end
    end


    if bytes.to_i == 0
      # Mark the session itself as dead
      self.alive = false

      # Reraise the error to the top-level caller
      raise err if err
    end
  end

  return bytes
end

#send_packet_wait_response(packet, timeout) ⇒ Object

Transmits a packet and waits for a response.

Parameters:

  • packet (Packet) —

    the request packet to send

  • timeout (Fixnum, nil) —

    number of seconds to wait, or nil to wait forever



223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
 
# File 'lib/rex/post/meterpreter/packet_dispatcher.rb', line 223

def send_packet_wait_response(packet, timeout)
  # First, add the waiter association for the supplied packet
  waiter = add_response_waiter(packet)

  bytes_written = send_packet(packet)

  # Transmit the packet
  if (bytes_written.to_i <= 0)
    # Remove the waiter if we failed to send the packet.
    remove_response_waiter(waiter)
    return nil
  end

  if not timeout
    return nil
  end

  # Wait for the supplied time interval
  response = waiter.wait(timeout)

  # Remove the waiter from the list of waiters in case it wasn't
  # removed. This happens if the waiter timed out above.
  remove_response_waiter(waiter)

  # Return the response packet, if any
  return response
end

#send_request(packet, timeout = self.response_timeout) ⇒ Object

Sends a packet and waits for a timeout for the given time interval.

Parameters:

  • packet (Packet) —

    request to send

  • timeout (Fixnum, nil) (defaults to: self.response_timeout) —

    seconds to wait for response, or nil to ignore the response and return immediately



198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
 
# File 'lib/rex/post/meterpreter/packet_dispatcher.rb', line 198

def send_request(packet, timeout = self.response_timeout)
  response = send_packet_wait_response(packet, timeout)

  if timeout.nil?
    return nil
  elsif response.nil?
    raise TimeoutError.new("Send timed out")
  elsif (response.result != 0)
    einfo = lookup_error(response.result)
    e = RequestError.new(packet.method, einfo, response.result)

    e.set_backtrace(caller)

    raise e
  end

  return response
end

#shutdown_passive_dispatcher ⇒ Object 



89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
 
# File 'lib/rex/post/meterpreter/packet_dispatcher.rb', line 89

def shutdown_passive_dispatcher
  return if not self.passive_service

  # Ensure that there is only one leading and trailing slash on the URI
  resource_uri = "/" + self.conn_id.to_s.gsub(/(^\/|\/$)/, '') + "/"

  self.passive_service.remove_resource(resource_uri)

  # If there are no more resources registered on the service, stop it entirely
  if self.passive_service.resources.empty?
    Rex::ServiceManager.stop_service(self.passive_service)
  end

  self.alive      = false
  self.send_queue = []
  self.recv_queue = []
  self.waiters    = []

  self.passive_service = nil
end