Class: Rex::Proto::TFTP::Server

Inherits:
Object
  • Object
show all
Defined in:
lib/rex/proto/tftp/server.rb

Overview

TFTP Server class

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(port = 69, listen_host = '0.0.0.0', context = {}) ⇒ Server

Returns a new instance of Server.



36
37
38
39
40
41
42
43
44
45
46
47
48
 
# File 'lib/rex/proto/tftp/server.rb', line 36

def initialize(port = 69, listen_host = '0.0.0.0', context = {})
  self.listen_host = listen_host
  self.listen_port = port
  self.context = context
  self.sock = nil
  @shutting_down = false
  @output_dir = nil
  @tftproot = nil

  self.files = []
  self.uploaded = []
  self.transfers = []
end

Instance Attribute Details

#context ⇒ Object

Returns the value of attribute context.



187
188
189
 
# File 'lib/rex/proto/tftp/server.rb', line 187

def context
  @context
end

#files ⇒ Object

Returns the value of attribute files.



188
189
190
 
# File 'lib/rex/proto/tftp/server.rb', line 188

def files
  @files
end

#incoming_file_hook ⇒ Object

Returns the value of attribute incoming_file_hook.



191
192
193
 
# File 'lib/rex/proto/tftp/server.rb', line 191

def incoming_file_hook
  @incoming_file_hook
end

#listen_host ⇒ Object

Returns the value of attribute listen_host.



187
188
189
 
# File 'lib/rex/proto/tftp/server.rb', line 187

def listen_host
  @listen_host
end

#listen_port ⇒ Object

Returns the value of attribute listen_port.



187
188
189
 
# File 'lib/rex/proto/tftp/server.rb', line 187

def listen_port
  @listen_port
end

#sock ⇒ Object

Returns the value of attribute sock.



188
189
190
 
# File 'lib/rex/proto/tftp/server.rb', line 188

def sock
  @sock
end

#thread ⇒ Object

Returns the value of attribute thread.



189
190
191
 
# File 'lib/rex/proto/tftp/server.rb', line 189

def thread
  @thread
end

#transfers ⇒ Object

Returns the value of attribute transfers.



188
189
190
 
# File 'lib/rex/proto/tftp/server.rb', line 188

def transfers
  @transfers
end

#uploaded ⇒ Object

Returns the value of attribute uploaded.



188
189
190
 
# File 'lib/rex/proto/tftp/server.rb', line 188

def uploaded
  @uploaded
end

Class Method Details

.hardcore_alias(port, host, *_rest) ⇒ Object 



28
29
30
 
# File 'lib/rex/proto/tftp/server.rb', line 28

def self.hardcore_alias(port, host, *_rest)
  "#{host}-#{port}"
end

Instance Method Details

#alias ⇒ Object 



32
33
34
 
# File 'lib/rex/proto/tftp/server.rb', line 32

def alias
  @alias || "TFTP Server"
end

#check_retransmission(tr) ⇒ Object (protected) 



221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
 
# File 'lib/rex/proto/tftp/server.rb', line 221

def check_retransmission(tr)
  elapsed = ::Time.now - tr[:last_sent]
  if (elapsed >= tr[:timeout])
    # max retries reached?
    if (tr[:retries] < 3)
      #if (tr[:type] == OpRead)
      #	puts "[-] ack timed out, resending block"
      #else
      #	puts "[-] block timed out, resending ack"
      #end
      tr[:last_sent] = nil
      tr[:retries] += 1
    else
      #puts "[-] maximum tries reached, terminating transfer"
      self.transfers.delete(tr)
    end
  end
end

#deregister_file(fn) ⇒ Object

Remove a previously registered file by name



102
103
104
 
# File 'lib/rex/proto/tftp/server.rb', line 102

def deregister_file(fn)
  self.files.delete_if { |f| f[:name] == fn }
end

#dispatch_request(from, buf) ⇒ Object (protected)

Dispatch a packet that we received



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
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
 
# File 'lib/rex/proto/tftp/server.rb', line 329

def dispatch_request(from, buf)

  op = buf.unpack('n')[0]
  buf.slice!(0,2)

  #XXX: todo - create call backs for status
  #start = "[*] TFTP - %s:%u - %s" % [from[0], from[1], OPCODES[op]]

  case op
  when Constants::OpRead
    # Process RRQ packets
    fn = TFTP::get_string(buf)
    mode = TFTP::get_string(buf).downcase

    #puts "%s %s %s" % [start, fn, mode]

    if (not @shutting_down) and (file = self.find_file(fn))
      if (file[:once] and file[:started])
        send_error(from, Constants::ErrFileNotFound)
      else
        transfer = {
          :type => Constants::OpRead,
          :from => from,
          :file => file,
          :block => 1,
          :blksize => 512,
          :offset => 0,
          :timeout => 3,
          :last_sent => nil,
          :retries => 0
        }

        process_options(from, buf, transfer)

        self.transfers << transfer
      end
    else
      #puts "[-] file not found!"
      send_error(from, Constants::ErrFileNotFound)
    end

  when Constants::OpWrite
    # Process WRQ packets
    fn = TFTP::get_string(buf)
    mode = TFTP::get_string(buf).downcase

    #puts "%s %s %s" % [start, fn, mode]

    if not @shutting_down
      transfer = {
        :type => Constants::OpWrite,
        :from => from,
        :file => { :name => fn, :data => '' },
        :block => 0, # WRQ starts at 0
        :blksize => 512,
        :timeout => 3,
        :last_sent => nil,
        :retries => 0
      }

      process_options(from, buf, transfer)

      self.transfers << transfer
    else
      send_error(from, Constants::ErrIllegalOperation)
    end

  when Constants::OpAck
    # Process ACK packets
    block = buf.unpack('n')[0]

    #puts "%s %d" % [start, block]

    tr = find_transfer(Constants::OpRead, from, block)
    if not tr
      # NOTE: some clients, such as pxelinux, send an ack for block 0.
      # To deal with this, we simply ignore it as we start with block 1.
      return if block == 0

      # If we didn't find it, send an error.
      send_error(from, Constants::ErrUnknownTransferId)
    else
      # acked! send the next block
      tr[:offset] += tr[:blksize]
      next_block(tr)

      # If the transfer is finished, delete it
      if (tr[:offset] > tr[:file][:data].length)
        #puts "[*] Transfer complete"
        self.transfers.delete(tr)

        # if the file is a one-serve, delete it from the files array
        if tr[:file][:once]
          #puts "[*] Removed one-serve file: #{tr[:file][:name]}"
          self.files.delete(tr[:file])
        end
      end
    end

  when Constants::OpData
    # Process Data packets
    block = buf.unpack('n')[0]
    data = buf.slice(2, buf.length)

    #puts "%s %d %d bytes" % [start, block, data.length]

    tr = find_transfer(Constants::OpWrite, from, (block-1))
    if not tr
      # If we didn't find it, send an error.
      send_error(from, Constants::ErrUnknownTransferId)
    else
      tr[:file][:data] << data
      tr[:last_size] = data.length
      next_block(tr)

      # Similar to RRQ transfers, we cannot detect that the
      # transfer finished here. We must do so after transmitting
      # the final ACK.
    end

  else
    # Other packets are unsupported
    #puts start
    send_error(from, Constants::ErrAccessViolation)

  end
end

#find_file(fname) ⇒ Object

Find the hash entry for a file that may be offered



149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
 
# File 'lib/rex/proto/tftp/server.rb', line 149

def find_file(fname)
  # Files served via register_file() take precedence.
  self.files.each do |f|
    if (fname == f[:name])
      return f
    end
  end

  # Now, if we have a tftproot, see if it can serve from it
  if @tftproot
    return find_file_in_root(fname)
  end

  nil
end

#find_file_in_root(fname) ⇒ Object

Find the file in the specified tftp root and add a temporary entry to the files hash.



170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
 
# File 'lib/rex/proto/tftp/server.rb', line 170

def find_file_in_root(fname)
  fn = ::File.expand_path(::File.join(@tftproot, fname))

  # Don't allow directory traversal
  return nil if fn.index(@tftproot) != 0

  return nil if not ::File.file?(fn) or not ::File.readable?(fn)

  # Read the file contents, and register it as being served once
  data = data = ::File.open(fn, "rb") { |fd| fd.read(fd.stat.size) }
  register_file(fname, data)

  # Return the last file in the array
  return self.files[-1]
end

#find_transfer(type, from, block) ⇒ Object (protected) 



195
196
197
198
199
200
201
202
 
# File 'lib/rex/proto/tftp/server.rb', line 195

def find_transfer(type, from, block)
  self.transfers.each do |tr|
    if (tr[:type] == type and tr[:from] == from and tr[:block] == block)
      return tr
    end
  end
  nil
end

#monitor_socket ⇒ Object (protected)

See if there is anything to do.. If so, dispatch it.



244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
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
 
# File 'lib/rex/proto/tftp/server.rb', line 244

def monitor_socket
  while true
    rds = [@sock]
    wds = []
    self.transfers.each do |tr|
      if (not tr[:last_sent])
        wds << @sock
        break
      end
    end
    eds = [@sock]

    r,w,e = ::IO.select(rds,wds,eds,1)

    if (r != nil and r[0] == self.sock)
      buf, addr = self.sock.recvfrom(65535)
      host, port = addr[3], addr[1]
      # Lame compatabilitiy :-/
      from = [host, port]
      dispatch_request(from, buf)
    end

    #
    # Check to see if transfers need maintenance
    #
    self.transfers.each do |tr|
      # We handle RRQ and WRQ separately
      #
      if (tr[:type] == Constants::OpRead)
        # Are we awaiting an ack?
        if (tr[:last_sent])
          check_retransmission(tr)
        elsif (w != nil and w[0] == self.sock)
          # No ack waiting, send next block..
          chunk = tr[:file][:data].slice(tr[:offset], tr[:blksize])
          if (chunk and chunk.length >= 0)
            pkt = [Constants::OpData, tr[:block]].pack('nn')
            pkt << chunk

            send_packet(tr[:from], pkt)
            tr[:last_sent] = ::Time.now

            # If the file is a one-serve, mark it as started
            tr[:file][:started] = true if (tr[:file][:once])
          else
            # No more chunks.. transfer is most likely done.
            # However, we can only delete it once the last chunk has been
            # acked.
          end
        end
      else
        # Are we awaiting data?
        if (tr[:last_sent])
          check_retransmission(tr)
        elsif (w != nil and w[0] == self.sock)
          # Not waiting for data, send an ack..
          #puts "[*] sending ack for block %d" % [tr[:block]]
          pkt = [Constants::OpAck, tr[:block]].pack('nn')

          send_packet(tr[:from], pkt)
          tr[:last_sent] = ::Time.now

          # If we had a 0-511 byte chunk, we're done.
          if (tr[:last_size] and tr[:last_size] < tr[:blksize])
            #puts "[*] Transfer complete, saving output"
            save_output(tr)
            self.transfers.delete(tr)
          end
        end
      end
    end
  end
end

#next_block(tr) ⇒ Object (protected) 



319
320
321
322
323
 
# File 'lib/rex/proto/tftp/server.rb', line 319

def next_block(tr)
  tr[:block] += 1
  tr[:last_sent] = nil
  tr[:retries] = 0
end

#process_options(from, buf, tr) ⇒ Object (protected) 



457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
 
# File 'lib/rex/proto/tftp/server.rb', line 457

def process_options(from, buf, tr)
  found = 0
  to_ack = []
  while buf.length >= 4
    opt = TFTP::get_string(buf)
    break if not opt
    val = TFTP::get_string(buf)
    break if not val

    found += 1

    # Is it one we support?
    opt.downcase!

    case opt
    when "blksize"
      val = val.to_i
      if val > 0
        tr[:blksize] = val
        to_ack << [ opt, val.to_s ]
      end

    when "timeout"
      val = val.to_i
      if val >= 1 and val <= 255
        tr[:timeout] = val
        to_ack << [ opt, val.to_s ]
      end

    when "tsize"
      if tr[:type] == Constants::OpRead
        len = tr[:file][:data].length
      else
        val = val.to_i
        len = val
      end
      to_ack << [ opt, len.to_s ]

    end
  end

  return if to_ack.length < 1

  # if we have anything to ack, do it
  data = [Constants::OpOptAck].pack('n')
  to_ack.each { |el|
    data << el[0] << "\x00" << el[1] << "\x00"
  }

  send_packet(from, data)
end

#register_file(fn, content, once = false) ⇒ Object

Register a filename and content for a client to request



90
91
92
93
94
95
96
 
# File 'lib/rex/proto/tftp/server.rb', line 90

def register_file(fn, content, once = false)
  self.files << {
    :name => fn,
    :data => content,
    :once => once
  }
end

#save_output(tr) ⇒ Object (protected) 



204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
 
# File 'lib/rex/proto/tftp/server.rb', line 204

def save_output(tr)
  self.uploaded << tr[:file]

  return incoming_file_hook.call(tr) if incoming_file_hook

  if @output_dir
    fn = tr[:file][:name].split(File::SEPARATOR)[-1]
    if fn
      fn = ::File.join(@output_dir, Rex::FileUtils.clean_path(fn))
      ::File.open(fn, "wb") { |fd|
        fd.write(tr[:file][:data])
      }
    end
  end
end

#send_error(from, num) ⇒ Object

Send an error packet w/the specified code and string



126
127
128
129
130
131
132
133
134
135
 
# File 'lib/rex/proto/tftp/server.rb', line 126

def send_error(from, num)
  if (num < 1 or num >= Constants::ERRCODES.length)
    # ignore..
    return
  end
  pkt = [Constants::OpError, num].pack('nn')
  pkt << Constants::ERRCODES[num]
  pkt << "\x00"
  send_packet(from, pkt)
end

#send_packet(from, pkt) ⇒ Object

Send a single packet to the specified host



141
142
143
 
# File 'lib/rex/proto/tftp/server.rb', line 141

def send_packet(from, pkt)
  self.sock.sendto(pkt, from[0], from[1])
end

#set_output_dir(outdir) ⇒ Object

Register a directory to write uploaded files to



118
119
120
 
# File 'lib/rex/proto/tftp/server.rb', line 118

def set_output_dir(outdir)
  @output_dir = outdir if ::File.directory?(outdir)
end

#set_tftproot(rootdir) ⇒ Object

Register an entire directory to serve files from



110
111
112
 
# File 'lib/rex/proto/tftp/server.rb', line 110

def set_tftproot(rootdir)
  @tftproot = rootdir if ::File.directory?(rootdir)
end

#start ⇒ Object

Start the TFTP server



54
55
56
57
58
59
60
61
62
63
64
 
# File 'lib/rex/proto/tftp/server.rb', line 54

def start
  self.sock = Rex::Socket::Udp.create(
    'LocalHost' => listen_host,
    'LocalPort' => listen_port,
    'Context'   => context
    )

  self.thread = Rex::ThreadFactory.spawn("TFTPServerMonitor", false) {
    monitor_socket
  }
end

#stop ⇒ Object

Stop the TFTP server



70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
 
# File 'lib/rex/proto/tftp/server.rb', line 70

def stop
  @shutting_down = true

  # Wait a maximum of 30 seconds for all transfers to finish.
  start = ::Time.now
  while (self.transfers.length > 0)
    ::IO.select(nil, nil, nil, 0.5)
    dur = ::Time.now - start
    break if (dur > 30)
  end

  self.files.clear
  self.thread.kill
  self.sock.close rescue nil # might be closed already
end