This file is indexed.

/usr/lib/python2.7/dist-packages/paramiko/channel.py is in python-paramiko 1.10.1-1git1build1.

This file is owned by root:root, with mode 0o644.

The actual contents of the file can be viewed below.

   1
   2
   3
   4
   5
   6
   7
   8
   9
  10
  11
  12
  13
  14
  15
  16
  17
  18
  19
  20
  21
  22
  23
  24
  25
  26
  27
  28
  29
  30
  31
  32
  33
  34
  35
  36
  37
  38
  39
  40
  41
  42
  43
  44
  45
  46
  47
  48
  49
  50
  51
  52
  53
  54
  55
  56
  57
  58
  59
  60
  61
  62
  63
  64
  65
  66
  67
  68
  69
  70
  71
  72
  73
  74
  75
  76
  77
  78
  79
  80
  81
  82
  83
  84
  85
  86
  87
  88
  89
  90
  91
  92
  93
  94
  95
  96
  97
  98
  99
 100
 101
 102
 103
 104
 105
 106
 107
 108
 109
 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
 143
 144
 145
 146
 147
 148
 149
 150
 151
 152
 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
 190
 191
 192
 193
 194
 195
 196
 197
 198
 199
 200
 201
 202
 203
 204
 205
 206
 207
 208
 209
 210
 211
 212
 213
 214
 215
 216
 217
 218
 219
 220
 221
 222
 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
 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
 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
 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
 456
 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
 508
 509
 510
 511
 512
 513
 514
 515
 516
 517
 518
 519
 520
 521
 522
 523
 524
 525
 526
 527
 528
 529
 530
 531
 532
 533
 534
 535
 536
 537
 538
 539
 540
 541
 542
 543
 544
 545
 546
 547
 548
 549
 550
 551
 552
 553
 554
 555
 556
 557
 558
 559
 560
 561
 562
 563
 564
 565
 566
 567
 568
 569
 570
 571
 572
 573
 574
 575
 576
 577
 578
 579
 580
 581
 582
 583
 584
 585
 586
 587
 588
 589
 590
 591
 592
 593
 594
 595
 596
 597
 598
 599
 600
 601
 602
 603
 604
 605
 606
 607
 608
 609
 610
 611
 612
 613
 614
 615
 616
 617
 618
 619
 620
 621
 622
 623
 624
 625
 626
 627
 628
 629
 630
 631
 632
 633
 634
 635
 636
 637
 638
 639
 640
 641
 642
 643
 644
 645
 646
 647
 648
 649
 650
 651
 652
 653
 654
 655
 656
 657
 658
 659
 660
 661
 662
 663
 664
 665
 666
 667
 668
 669
 670
 671
 672
 673
 674
 675
 676
 677
 678
 679
 680
 681
 682
 683
 684
 685
 686
 687
 688
 689
 690
 691
 692
 693
 694
 695
 696
 697
 698
 699
 700
 701
 702
 703
 704
 705
 706
 707
 708
 709
 710
 711
 712
 713
 714
 715
 716
 717
 718
 719
 720
 721
 722
 723
 724
 725
 726
 727
 728
 729
 730
 731
 732
 733
 734
 735
 736
 737
 738
 739
 740
 741
 742
 743
 744
 745
 746
 747
 748
 749
 750
 751
 752
 753
 754
 755
 756
 757
 758
 759
 760
 761
 762
 763
 764
 765
 766
 767
 768
 769
 770
 771
 772
 773
 774
 775
 776
 777
 778
 779
 780
 781
 782
 783
 784
 785
 786
 787
 788
 789
 790
 791
 792
 793
 794
 795
 796
 797
 798
 799
 800
 801
 802
 803
 804
 805
 806
 807
 808
 809
 810
 811
 812
 813
 814
 815
 816
 817
 818
 819
 820
 821
 822
 823
 824
 825
 826
 827
 828
 829
 830
 831
 832
 833
 834
 835
 836
 837
 838
 839
 840
 841
 842
 843
 844
 845
 846
 847
 848
 849
 850
 851
 852
 853
 854
 855
 856
 857
 858
 859
 860
 861
 862
 863
 864
 865
 866
 867
 868
 869
 870
 871
 872
 873
 874
 875
 876
 877
 878
 879
 880
 881
 882
 883
 884
 885
 886
 887
 888
 889
 890
 891
 892
 893
 894
 895
 896
 897
 898
 899
 900
 901
 902
 903
 904
 905
 906
 907
 908
 909
 910
 911
 912
 913
 914
 915
 916
 917
 918
 919
 920
 921
 922
 923
 924
 925
 926
 927
 928
 929
 930
 931
 932
 933
 934
 935
 936
 937
 938
 939
 940
 941
 942
 943
 944
 945
 946
 947
 948
 949
 950
 951
 952
 953
 954
 955
 956
 957
 958
 959
 960
 961
 962
 963
 964
 965
 966
 967
 968
 969
 970
 971
 972
 973
 974
 975
 976
 977
 978
 979
 980
 981
 982
 983
 984
 985
 986
 987
 988
 989
 990
 991
 992
 993
 994
 995
 996
 997
 998
 999
1000
1001
1002
1003
1004
1005
1006
1007
1008
1009
1010
1011
1012
1013
1014
1015
1016
1017
1018
1019
1020
1021
1022
1023
1024
1025
1026
1027
1028
1029
1030
1031
1032
1033
1034
1035
1036
1037
1038
1039
1040
1041
1042
1043
1044
1045
1046
1047
1048
1049
1050
1051
1052
1053
1054
1055
1056
1057
1058
1059
1060
1061
1062
1063
1064
1065
1066
1067
1068
1069
1070
1071
1072
1073
1074
1075
1076
1077
1078
1079
1080
1081
1082
1083
1084
1085
1086
1087
1088
1089
1090
1091
1092
1093
1094
1095
1096
1097
1098
1099
1100
1101
1102
1103
1104
1105
1106
1107
1108
1109
1110
1111
1112
1113
1114
1115
1116
1117
1118
1119
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1171
1172
1173
1174
1175
1176
1177
1178
1179
1180
1181
1182
1183
1184
1185
1186
1187
1188
1189
1190
1191
1192
1193
1194
1195
1196
1197
1198
1199
1200
1201
1202
1203
1204
1205
1206
1207
1208
1209
1210
1211
1212
1213
1214
1215
1216
1217
1218
1219
1220
1221
1222
1223
1224
1225
1226
1227
1228
1229
1230
1231
1232
1233
1234
1235
1236
1237
1238
1239
1240
1241
1242
1243
1244
1245
1246
1247
1248
1249
1250
1251
1252
1253
1254
1255
1256
1257
1258
1259
1260
1261
1262
1263
1264
1265
1266
1267
1268
1269
1270
1271
1272
# Copyright (C) 2003-2007  Robey Pointer <robeypointer@gmail.com>
#
# This file is part of paramiko.
#
# Paramiko is free software; you can redistribute it and/or modify it under the
# terms of the GNU Lesser General Public License as published by the Free
# Software Foundation; either version 2.1 of the License, or (at your option)
# any later version.
#
# Paramiko is distrubuted in the hope that it will be useful, but WITHOUT ANY
# WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
# A PARTICULAR PURPOSE.  See the GNU Lesser General Public License for more
# details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with Paramiko; if not, write to the Free Software Foundation, Inc.,
# 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA.

"""
Abstraction for an SSH2 channel.
"""

import binascii
import sys
import time
import threading
import socket
import os

from paramiko.common import *
from paramiko import util
from paramiko.message import Message
from paramiko.ssh_exception import SSHException
from paramiko.file import BufferedFile
from paramiko.buffered_pipe import BufferedPipe, PipeTimeout
from paramiko import pipe


# lower bound on the max packet size we'll accept from the remote host
MIN_PACKET_SIZE = 1024


class Channel (object):
    """
    A secure tunnel across an SSH L{Transport}.  A Channel is meant to behave
    like a socket, and has an API that should be indistinguishable from the
    python socket API.

    Because SSH2 has a windowing kind of flow control, if you stop reading data
    from a Channel and its buffer fills up, the server will be unable to send
    you any more data until you read some of it.  (This won't affect other
    channels on the same transport -- all channels on a single transport are
    flow-controlled independently.)  Similarly, if the server isn't reading
    data you send, calls to L{send} may block, unless you set a timeout.  This
    is exactly like a normal network socket, so it shouldn't be too surprising.
    """

    def __init__(self, chanid):
        """
        Create a new channel.  The channel is not associated with any
        particular session or L{Transport} until the Transport attaches it.
        Normally you would only call this method from the constructor of a
        subclass of L{Channel}.

        @param chanid: the ID of this channel, as passed by an existing
            L{Transport}.
        @type chanid: int
        """
        self.chanid = chanid
        self.remote_chanid = 0
        self.transport = None
        self.active = False
        self.eof_received = 0
        self.eof_sent = 0
        self.in_buffer = BufferedPipe()
        self.in_stderr_buffer = BufferedPipe()
        self.timeout = None
        self.closed = False
        self.ultra_debug = False
        self.lock = threading.Lock()
        self.out_buffer_cv = threading.Condition(self.lock)
        self.in_window_size = 0
        self.out_window_size = 0
        self.in_max_packet_size = 0
        self.out_max_packet_size = 0
        self.in_window_threshold = 0
        self.in_window_sofar = 0
        self.status_event = threading.Event()
        self._name = str(chanid)
        self.logger = util.get_logger('paramiko.transport')
        self._pipe = None
        self.event = threading.Event()
        self.event_ready = False
        self.combine_stderr = False
        self.exit_status = -1
        self.origin_addr = None
    
    def __del__(self):
        try:
            self.close()
        except:
            pass
        
    def __repr__(self):
        """
        Return a string representation of this object, for debugging.

        @rtype: str
        """
        out = '<paramiko.Channel %d' % self.chanid
        if self.closed:
            out += ' (closed)'
        elif self.active:
            if self.eof_received:
                out += ' (EOF received)'
            if self.eof_sent:
                out += ' (EOF sent)'
            out += ' (open) window=%d' % (self.out_window_size)
            if len(self.in_buffer) > 0:
                out += ' in-buffer=%d' % (len(self.in_buffer),)
        out += ' -> ' + repr(self.transport)
        out += '>'
        return out

    def get_pty(self, term='vt100', width=80, height=24, width_pixels=0,
                height_pixels=0):
        """
        Request a pseudo-terminal from the server.  This is usually used right
        after creating a client channel, to ask the server to provide some
        basic terminal semantics for a shell invoked with L{invoke_shell}.
        It isn't necessary (or desirable) to call this method if you're going
        to exectue a single command with L{exec_command}.

        @param term: the terminal type to emulate (for example, C{'vt100'})
        @type term: str
        @param width: width (in characters) of the terminal screen
        @type width: int
        @param height: height (in characters) of the terminal screen
        @type height: int
        @param width_pixels: width (in pixels) of the terminal screen
        @type width_pixels: int
        @param height_pixels: height (in pixels) of the terminal screen
        @type height_pixels: int
        
        @raise SSHException: if the request was rejected or the channel was
            closed
        """
        if self.closed or self.eof_received or self.eof_sent or not self.active:
            raise SSHException('Channel is not open')
        m = Message()
        m.add_byte(chr(MSG_CHANNEL_REQUEST))
        m.add_int(self.remote_chanid)
        m.add_string('pty-req')
        m.add_boolean(True)
        m.add_string(term)
        m.add_int(width)
        m.add_int(height)
        m.add_int(width_pixels)
        m.add_int(height_pixels)
        m.add_string('')
        self._event_pending()
        self.transport._send_user_message(m)
        self._wait_for_event()

    def invoke_shell(self):
        """
        Request an interactive shell session on this channel.  If the server
        allows it, the channel will then be directly connected to the stdin,
        stdout, and stderr of the shell.
        
        Normally you would call L{get_pty} before this, in which case the
        shell will operate through the pty, and the channel will be connected
        to the stdin and stdout of the pty.
        
        When the shell exits, the channel will be closed and can't be reused.
        You must open a new channel if you wish to open another shell.
        
        @raise SSHException: if the request was rejected or the channel was
            closed
        """
        if self.closed or self.eof_received or self.eof_sent or not self.active:
            raise SSHException('Channel is not open')
        m = Message()
        m.add_byte(chr(MSG_CHANNEL_REQUEST))
        m.add_int(self.remote_chanid)
        m.add_string('shell')
        m.add_boolean(1)
        self._event_pending()
        self.transport._send_user_message(m)
        self._wait_for_event()

    def exec_command(self, command):
        """
        Execute a command on the server.  If the server allows it, the channel
        will then be directly connected to the stdin, stdout, and stderr of
        the command being executed.
        
        When the command finishes executing, the channel will be closed and
        can't be reused.  You must open a new channel if you wish to execute
        another command.

        @param command: a shell command to execute.
        @type command: str

        @raise SSHException: if the request was rejected or the channel was
            closed
        """
        if self.closed or self.eof_received or self.eof_sent or not self.active:
            raise SSHException('Channel is not open')
        m = Message()
        m.add_byte(chr(MSG_CHANNEL_REQUEST))
        m.add_int(self.remote_chanid)
        m.add_string('exec')
        m.add_boolean(True)
        m.add_string(command)
        self._event_pending()
        self.transport._send_user_message(m)
        self._wait_for_event()

    def invoke_subsystem(self, subsystem):
        """
        Request a subsystem on the server (for example, C{sftp}).  If the
        server allows it, the channel will then be directly connected to the
        requested subsystem.
        
        When the subsystem finishes, the channel will be closed and can't be
        reused.

        @param subsystem: name of the subsystem being requested.
        @type subsystem: str

        @raise SSHException: if the request was rejected or the channel was
            closed
        """
        if self.closed or self.eof_received or self.eof_sent or not self.active:
            raise SSHException('Channel is not open')
        m = Message()
        m.add_byte(chr(MSG_CHANNEL_REQUEST))
        m.add_int(self.remote_chanid)
        m.add_string('subsystem')
        m.add_boolean(True)
        m.add_string(subsystem)
        self._event_pending()
        self.transport._send_user_message(m)
        self._wait_for_event()

    def resize_pty(self, width=80, height=24, width_pixels=0, height_pixels=0):
        """
        Resize the pseudo-terminal.  This can be used to change the width and
        height of the terminal emulation created in a previous L{get_pty} call.

        @param width: new width (in characters) of the terminal screen
        @type width: int
        @param height: new height (in characters) of the terminal screen
        @type height: int
        @param width_pixels: new width (in pixels) of the terminal screen
        @type width_pixels: int
        @param height_pixels: new height (in pixels) of the terminal screen
        @type height_pixels: int

        @raise SSHException: if the request was rejected or the channel was
            closed
        """
        if self.closed or self.eof_received or self.eof_sent or not self.active:
            raise SSHException('Channel is not open')
        m = Message()
        m.add_byte(chr(MSG_CHANNEL_REQUEST))
        m.add_int(self.remote_chanid)
        m.add_string('window-change')
        m.add_boolean(False)
        m.add_int(width)
        m.add_int(height)
        m.add_int(width_pixels)
        m.add_int(height_pixels)
        self.transport._send_user_message(m)

    def exit_status_ready(self):
        """
        Return true if the remote process has exited and returned an exit
        status. You may use this to poll the process status if you don't
        want to block in L{recv_exit_status}. Note that the server may not
        return an exit status in some cases (like bad servers).
        
        @return: True if L{recv_exit_status} will return immediately
        @rtype: bool
        @since: 1.7.3
        """
        return self.closed or self.status_event.isSet()
        
    def recv_exit_status(self):
        """
        Return the exit status from the process on the server.  This is
        mostly useful for retrieving the reults of an L{exec_command}.
        If the command hasn't finished yet, this method will wait until
        it does, or until the channel is closed.  If no exit status is
        provided by the server, -1 is returned.
        
        @return: the exit code of the process on the server.
        @rtype: int
        
        @since: 1.2
        """
        self.status_event.wait()
        assert self.status_event.isSet()
        return self.exit_status

    def send_exit_status(self, status):
        """
        Send the exit status of an executed command to the client.  (This
        really only makes sense in server mode.)  Many clients expect to
        get some sort of status code back from an executed command after
        it completes.
        
        @param status: the exit code of the process
        @type status: int
        
        @since: 1.2
        """
        # in many cases, the channel will not still be open here.
        # that's fine.
        m = Message()
        m.add_byte(chr(MSG_CHANNEL_REQUEST))
        m.add_int(self.remote_chanid)
        m.add_string('exit-status')
        m.add_boolean(False)
        m.add_int(status)
        self.transport._send_user_message(m)
    
    def request_x11(self, screen_number=0, auth_protocol=None, auth_cookie=None,
                    single_connection=False, handler=None):
        """
        Request an x11 session on this channel.  If the server allows it,
        further x11 requests can be made from the server to the client,
        when an x11 application is run in a shell session.
        
        From RFC4254::

            It is RECOMMENDED that the 'x11 authentication cookie' that is
            sent be a fake, random cookie, and that the cookie be checked and
            replaced by the real cookie when a connection request is received.
        
        If you omit the auth_cookie, a new secure random 128-bit value will be
        generated, used, and returned.  You will need to use this value to
        verify incoming x11 requests and replace them with the actual local
        x11 cookie (which requires some knoweldge of the x11 protocol).
        
        If a handler is passed in, the handler is called from another thread
        whenever a new x11 connection arrives.  The default handler queues up
        incoming x11 connections, which may be retrieved using
        L{Transport.accept}.  The handler's calling signature is::
        
            handler(channel: Channel, (address: str, port: int))
        
        @param screen_number: the x11 screen number (0, 10, etc)
        @type screen_number: int
        @param auth_protocol: the name of the X11 authentication method used;
            if none is given, C{"MIT-MAGIC-COOKIE-1"} is used
        @type auth_protocol: str
        @param auth_cookie: hexadecimal string containing the x11 auth cookie;
            if none is given, a secure random 128-bit value is generated
        @type auth_cookie: str
        @param single_connection: if True, only a single x11 connection will be
            forwarded (by default, any number of x11 connections can arrive
            over this session)
        @type single_connection: bool
        @param handler: an optional handler to use for incoming X11 connections
        @type handler: function
        @return: the auth_cookie used
        """
        if self.closed or self.eof_received or self.eof_sent or not self.active:
            raise SSHException('Channel is not open')
        if auth_protocol is None:
            auth_protocol = 'MIT-MAGIC-COOKIE-1'
        if auth_cookie is None:
            auth_cookie = binascii.hexlify(self.transport.rng.read(16))

        m = Message()
        m.add_byte(chr(MSG_CHANNEL_REQUEST))
        m.add_int(self.remote_chanid)
        m.add_string('x11-req')
        m.add_boolean(True)
        m.add_boolean(single_connection)
        m.add_string(auth_protocol)
        m.add_string(auth_cookie)
        m.add_int(screen_number)
        self._event_pending()
        self.transport._send_user_message(m)
        self._wait_for_event()
        self.transport._set_x11_handler(handler)
        return auth_cookie

    def request_forward_agent(self, handler):
        """
        Request for a forward SSH Agent on this channel.
        This is only valid for an ssh-agent from openssh !!!

        @param handler: a required handler to use for incoming SSH Agent connections
        @type handler: function

        @return: if we are ok or not (at that time we always return ok)
        @rtype: boolean

        @raise: SSHException in case of channel problem.
        """
        if self.closed or self.eof_received or self.eof_sent or not self.active:
            raise SSHException('Channel is not open')

        m = Message()
        m.add_byte(chr(MSG_CHANNEL_REQUEST))
        m.add_int(self.remote_chanid)
        m.add_string('auth-agent-req@openssh.com')
        m.add_boolean(False)
        self.transport._send_user_message(m)
        self.transport._set_forward_agent_handler(handler)
        return True

    def get_transport(self):
        """
        Return the L{Transport} associated with this channel.

        @return: the L{Transport} that was used to create this channel.
        @rtype: L{Transport}
        """
        return self.transport

    def set_name(self, name):
        """
        Set a name for this channel.  Currently it's only used to set the name
        of the channel in logfile entries.  The name can be fetched with the
        L{get_name} method.

        @param name: new channel name
        @type name: str
        """
        self._name = name

    def get_name(self):
        """
        Get the name of this channel that was previously set by L{set_name}.

        @return: the name of this channel.
        @rtype: str
        """
        return self._name

    def get_id(self):
        """
        Return the ID # for this channel.  The channel ID is unique across
        a L{Transport} and usually a small number.  It's also the number
        passed to L{ServerInterface.check_channel_request} when determining
        whether to accept a channel request in server mode.

        @return: the ID of this channel.
        @rtype: int
        """
        return self.chanid
    
    def set_combine_stderr(self, combine):
        """
        Set whether stderr should be combined into stdout on this channel.
        The default is C{False}, but in some cases it may be convenient to
        have both streams combined.
        
        If this is C{False}, and L{exec_command} is called (or C{invoke_shell}
        with no pty), output to stderr will not show up through the L{recv}
        and L{recv_ready} calls.  You will have to use L{recv_stderr} and
        L{recv_stderr_ready} to get stderr output.
        
        If this is C{True}, data will never show up via L{recv_stderr} or
        L{recv_stderr_ready}.
        
        @param combine: C{True} if stderr output should be combined into
            stdout on this channel.
        @type combine: bool
        @return: previous setting.
        @rtype: bool
        
        @since: 1.1
        """
        data = ''
        self.lock.acquire()
        try:
            old = self.combine_stderr
            self.combine_stderr = combine
            if combine and not old:
                # copy old stderr buffer into primary buffer
                data = self.in_stderr_buffer.empty()
        finally:
            self.lock.release()
        if len(data) > 0:
            self._feed(data)
        return old

    
    ###  socket API


    def settimeout(self, timeout):
        """
        Set a timeout on blocking read/write operations.  The C{timeout}
        argument can be a nonnegative float expressing seconds, or C{None}.  If
        a float is given, subsequent channel read/write operations will raise
        a timeout exception if the timeout period value has elapsed before the
        operation has completed.  Setting a timeout of C{None} disables
        timeouts on socket operations.

        C{chan.settimeout(0.0)} is equivalent to C{chan.setblocking(0)};
        C{chan.settimeout(None)} is equivalent to C{chan.setblocking(1)}.

        @param timeout: seconds to wait for a pending read/write operation
            before raising C{socket.timeout}, or C{None} for no timeout.
        @type timeout: float
        """
        self.timeout = timeout

    def gettimeout(self):
        """
        Returns the timeout in seconds (as a float) associated with socket
        operations, or C{None} if no timeout is set.  This reflects the last
        call to L{setblocking} or L{settimeout}.

        @return: timeout in seconds, or C{None}.
        @rtype: float
        """
        return self.timeout

    def setblocking(self, blocking):
        """
        Set blocking or non-blocking mode of the channel: if C{blocking} is 0,
        the channel is set to non-blocking mode; otherwise it's set to blocking
        mode. Initially all channels are in blocking mode.

        In non-blocking mode, if a L{recv} call doesn't find any data, or if a
        L{send} call can't immediately dispose of the data, an error exception
        is raised. In blocking mode, the calls block until they can proceed. An
        EOF condition is considered "immediate data" for L{recv}, so if the
        channel is closed in the read direction, it will never block.

        C{chan.setblocking(0)} is equivalent to C{chan.settimeout(0)};
        C{chan.setblocking(1)} is equivalent to C{chan.settimeout(None)}.

        @param blocking: 0 to set non-blocking mode; non-0 to set blocking
            mode.
        @type blocking: int
        """
        if blocking:
            self.settimeout(None)
        else:
            self.settimeout(0.0)

    def getpeername(self):
        """
        Return the address of the remote side of this Channel, if possible.
        This is just a wrapper around C{'getpeername'} on the Transport, used
        to provide enough of a socket-like interface to allow asyncore to work.
        (asyncore likes to call C{'getpeername'}.)

        @return: the address if the remote host, if known
        @rtype: tuple(str, int)
        """
        return self.transport.getpeername()

    def close(self):
        """
        Close the channel.  All future read/write operations on the channel
        will fail.  The remote end will receive no more data (after queued data
        is flushed).  Channels are automatically closed when their L{Transport}
        is closed or when they are garbage collected.
        """
        self.lock.acquire()
        try:
            # only close the pipe when the user explicitly closes the channel.
            # otherwise they will get unpleasant surprises.  (and do it before
            # checking self.closed, since the remote host may have already
            # closed the connection.)
            if self._pipe is not None:
                self._pipe.close()
                self._pipe = None

            if not self.active or self.closed:
                return
            msgs = self._close_internal()
        finally:
            self.lock.release()
        for m in msgs:
            if m is not None:
                self.transport._send_user_message(m)

    def recv_ready(self):
        """
        Returns true if data is buffered and ready to be read from this
        channel.  A C{False} result does not mean that the channel has closed;
        it means you may need to wait before more data arrives.
        
        @return: C{True} if a L{recv} call on this channel would immediately
            return at least one byte; C{False} otherwise.
        @rtype: boolean
        """
        return self.in_buffer.read_ready()

    def recv(self, nbytes):
        """
        Receive data from the channel.  The return value is a string
        representing the data received.  The maximum amount of data to be
        received at once is specified by C{nbytes}.  If a string of length zero
        is returned, the channel stream has closed.

        @param nbytes: maximum number of bytes to read.
        @type nbytes: int
        @return: data.
        @rtype: str
        
        @raise socket.timeout: if no data is ready before the timeout set by
            L{settimeout}.
        """
        try:
            out = self.in_buffer.read(nbytes, self.timeout)
        except PipeTimeout, e:
            raise socket.timeout()

        ack = self._check_add_window(len(out))
        # no need to hold the channel lock when sending this
        if ack > 0:
            m = Message()
            m.add_byte(chr(MSG_CHANNEL_WINDOW_ADJUST))
            m.add_int(self.remote_chanid)
            m.add_int(ack)
            self.transport._send_user_message(m)

        return out

    def recv_stderr_ready(self):
        """
        Returns true if data is buffered and ready to be read from this
        channel's stderr stream.  Only channels using L{exec_command} or
        L{invoke_shell} without a pty will ever have data on the stderr
        stream.
        
        @return: C{True} if a L{recv_stderr} call on this channel would
            immediately return at least one byte; C{False} otherwise.
        @rtype: boolean
        
        @since: 1.1
        """
        return self.in_stderr_buffer.read_ready()

    def recv_stderr(self, nbytes):
        """
        Receive data from the channel's stderr stream.  Only channels using
        L{exec_command} or L{invoke_shell} without a pty will ever have data
        on the stderr stream.  The return value is a string representing the
        data received.  The maximum amount of data to be received at once is
        specified by C{nbytes}.  If a string of length zero is returned, the
        channel stream has closed.

        @param nbytes: maximum number of bytes to read.
        @type nbytes: int
        @return: data.
        @rtype: str
        
        @raise socket.timeout: if no data is ready before the timeout set by
            L{settimeout}.
        
        @since: 1.1
        """
        try:
            out = self.in_stderr_buffer.read(nbytes, self.timeout)
        except PipeTimeout, e:
            raise socket.timeout()
            
        ack = self._check_add_window(len(out))
        # no need to hold the channel lock when sending this
        if ack > 0:
            m = Message()
            m.add_byte(chr(MSG_CHANNEL_WINDOW_ADJUST))
            m.add_int(self.remote_chanid)
            m.add_int(ack)
            self.transport._send_user_message(m)

        return out

    def send_ready(self):
        """
        Returns true if data can be written to this channel without blocking.
        This means the channel is either closed (so any write attempt would
        return immediately) or there is at least one byte of space in the 
        outbound buffer. If there is at least one byte of space in the
        outbound buffer, a L{send} call will succeed immediately and return
        the number of bytes actually written.
        
        @return: C{True} if a L{send} call on this channel would immediately
            succeed or fail
        @rtype: boolean
        """
        self.lock.acquire()
        try:
            if self.closed or self.eof_sent:
                return True
            return self.out_window_size > 0
        finally:
            self.lock.release()
    
    def send(self, s):
        """
        Send data to the channel.  Returns the number of bytes sent, or 0 if
        the channel stream is closed.  Applications are responsible for
        checking that all data has been sent: if only some of the data was
        transmitted, the application needs to attempt delivery of the remaining
        data.

        @param s: data to send
        @type s: str
        @return: number of bytes actually sent
        @rtype: int

        @raise socket.timeout: if no data could be sent before the timeout set
            by L{settimeout}.
        """
        size = len(s)
        self.lock.acquire()
        try:
            size = self._wait_for_send_window(size)
            if size == 0:
                # eof or similar
                return 0
            m = Message()
            m.add_byte(chr(MSG_CHANNEL_DATA))
            m.add_int(self.remote_chanid)
            m.add_string(s[:size])
        finally:
            self.lock.release()
        # Note: We release self.lock before calling _send_user_message.
        # Otherwise, we can deadlock during re-keying.
        self.transport._send_user_message(m)
        return size

    def send_stderr(self, s):
        """
        Send data to the channel on the "stderr" stream.  This is normally
        only used by servers to send output from shell commands -- clients
        won't use this.  Returns the number of bytes sent, or 0 if the channel
        stream is closed.  Applications are responsible for checking that all
        data has been sent: if only some of the data was transmitted, the
        application needs to attempt delivery of the remaining data.
        
        @param s: data to send.
        @type s: str
        @return: number of bytes actually sent.
        @rtype: int
        
        @raise socket.timeout: if no data could be sent before the timeout set
            by L{settimeout}.
        
        @since: 1.1
        """
        size = len(s)
        self.lock.acquire()
        try:
            size = self._wait_for_send_window(size)
            if size == 0:
                # eof or similar
                return 0
            m = Message()
            m.add_byte(chr(MSG_CHANNEL_EXTENDED_DATA))
            m.add_int(self.remote_chanid)
            m.add_int(1)
            m.add_string(s[:size])
        finally:
            self.lock.release()
        # Note: We release self.lock before calling _send_user_message.
        # Otherwise, we can deadlock during re-keying.
        self.transport._send_user_message(m)
        return size

    def sendall(self, s):
        """
        Send data to the channel, without allowing partial results.  Unlike
        L{send}, this method continues to send data from the given string until
        either all data has been sent or an error occurs.  Nothing is returned.

        @param s: data to send.
        @type s: str

        @raise socket.timeout: if sending stalled for longer than the timeout
            set by L{settimeout}.
        @raise socket.error: if an error occured before the entire string was
            sent.
        
        @note: If the channel is closed while only part of the data hase been
            sent, there is no way to determine how much data (if any) was sent.
            This is irritating, but identically follows python's API.
        """
        while s:
            if self.closed:
                # this doesn't seem useful, but it is the documented behavior of Socket
                raise socket.error('Socket is closed')
            sent = self.send(s)
            s = s[sent:]
        return None

    def sendall_stderr(self, s):
        """
        Send data to the channel's "stderr" stream, without allowing partial
        results.  Unlike L{send_stderr}, this method continues to send data
        from the given string until all data has been sent or an error occurs.
        Nothing is returned.
        
        @param s: data to send to the client as "stderr" output.
        @type s: str
        
        @raise socket.timeout: if sending stalled for longer than the timeout
            set by L{settimeout}.
        @raise socket.error: if an error occured before the entire string was
            sent.
            
        @since: 1.1
        """
        while s:
            if self.closed:
                raise socket.error('Socket is closed')
            sent = self.send_stderr(s)
            s = s[sent:]
        return None

    def makefile(self, *params):
        """
        Return a file-like object associated with this channel.  The optional
        C{mode} and C{bufsize} arguments are interpreted the same way as by
        the built-in C{file()} function in python.

        @return: object which can be used for python file I/O.
        @rtype: L{ChannelFile}
        """
        return ChannelFile(*([self] + list(params)))

    def makefile_stderr(self, *params):
        """
        Return a file-like object associated with this channel's stderr
        stream.   Only channels using L{exec_command} or L{invoke_shell}
        without a pty will ever have data on the stderr stream.
        
        The optional C{mode} and C{bufsize} arguments are interpreted the
        same way as by the built-in C{file()} function in python.  For a
        client, it only makes sense to open this file for reading.  For a
        server, it only makes sense to open this file for writing.
        
        @return: object which can be used for python file I/O.
        @rtype: L{ChannelFile}

        @since: 1.1
        """
        return ChannelStderrFile(*([self] + list(params)))
        
    def fileno(self):
        """
        Returns an OS-level file descriptor which can be used for polling, but
        but I{not} for reading or writing.  This is primaily to allow python's
        C{select} module to work.

        The first time C{fileno} is called on a channel, a pipe is created to
        simulate real OS-level file descriptor (FD) behavior.  Because of this,
        two OS-level FDs are created, which will use up FDs faster than normal.
        (You won't notice this effect unless you have hundreds of channels
        open at the same time.)

        @return: an OS-level file descriptor
        @rtype: int
        
        @warning: This method causes channel reads to be slightly less
            efficient.
        """
        self.lock.acquire()
        try:
            if self._pipe is not None:
                return self._pipe.fileno()
            # create the pipe and feed in any existing data
            self._pipe = pipe.make_pipe()
            p1, p2 = pipe.make_or_pipe(self._pipe)
            self.in_buffer.set_event(p1)
            self.in_stderr_buffer.set_event(p2)
            return self._pipe.fileno()
        finally:
            self.lock.release()

    def shutdown(self, how):
        """
        Shut down one or both halves of the connection.  If C{how} is 0,
        further receives are disallowed.  If C{how} is 1, further sends
        are disallowed.  If C{how} is 2, further sends and receives are
        disallowed.  This closes the stream in one or both directions.

        @param how: 0 (stop receiving), 1 (stop sending), or 2 (stop
            receiving and sending).
        @type how: int
        """
        if (how == 0) or (how == 2):
            # feign "read" shutdown
            self.eof_received = 1
        if (how == 1) or (how == 2):
            self.lock.acquire()
            try:
                m = self._send_eof()
            finally:
                self.lock.release()
            if m is not None:
                self.transport._send_user_message(m)
    
    def shutdown_read(self):
        """
        Shutdown the receiving side of this socket, closing the stream in
        the incoming direction.  After this call, future reads on this
        channel will fail instantly.  This is a convenience method, equivalent
        to C{shutdown(0)}, for people who don't make it a habit to
        memorize unix constants from the 1970s.
        
        @since: 1.2
        """
        self.shutdown(0)
    
    def shutdown_write(self):
        """
        Shutdown the sending side of this socket, closing the stream in
        the outgoing direction.  After this call, future writes on this
        channel will fail instantly.  This is a convenience method, equivalent
        to C{shutdown(1)}, for people who don't make it a habit to
        memorize unix constants from the 1970s.
        
        @since: 1.2
        """
        self.shutdown(1)


    ###  calls from Transport


    def _set_transport(self, transport):
        self.transport = transport
        self.logger = util.get_logger(self.transport.get_log_channel())

    def _set_window(self, window_size, max_packet_size):
        self.in_window_size = window_size
        self.in_max_packet_size = max_packet_size
        # threshold of bytes we receive before we bother to send a window update
        self.in_window_threshold = window_size // 10
        self.in_window_sofar = 0
        self._log(DEBUG, 'Max packet in: %d bytes' % max_packet_size)
        
    def _set_remote_channel(self, chanid, window_size, max_packet_size):
        self.remote_chanid = chanid
        self.out_window_size = window_size
        self.out_max_packet_size = max(max_packet_size, MIN_PACKET_SIZE)
        self.active = 1
        self._log(DEBUG, 'Max packet out: %d bytes' % max_packet_size)
        
    def _request_success(self, m):
        self._log(DEBUG, 'Sesch channel %d request ok' % self.chanid)
        self.event_ready = True
        self.event.set()
        return

    def _request_failed(self, m):
        self.lock.acquire()
        try:
            msgs = self._close_internal()
        finally:
            self.lock.release()
        for m in msgs:
            if m is not None:
                self.transport._send_user_message(m)

    def _feed(self, m):
        if type(m) is str:
            # passed from _feed_extended
            s = m
        else:
            s = m.get_string()
        self.in_buffer.feed(s)

    def _feed_extended(self, m):
        code = m.get_int()
        s = m.get_string()
        if code != 1:
            self._log(ERROR, 'unknown extended_data type %d; discarding' % code)
            return
        if self.combine_stderr:
            self._feed(s)
        else:
            self.in_stderr_buffer.feed(s)
        
    def _window_adjust(self, m):
        nbytes = m.get_int()
        self.lock.acquire()
        try:
            if self.ultra_debug:
                self._log(DEBUG, 'window up %d' % nbytes)
            self.out_window_size += nbytes
            self.out_buffer_cv.notifyAll()
        finally:
            self.lock.release()

    def _handle_request(self, m):
        key = m.get_string()
        want_reply = m.get_boolean()
        server = self.transport.server_object
        ok = False
        if key == 'exit-status':
            self.exit_status = m.get_int()
            self.status_event.set()
            ok = True
        elif key == 'xon-xoff':
            # ignore
            ok = True
        elif key == 'pty-req':
            term = m.get_string()
            width = m.get_int()
            height = m.get_int()
            pixelwidth = m.get_int()
            pixelheight = m.get_int()
            modes = m.get_string()
            if server is None:
                ok = False
            else:
                ok = server.check_channel_pty_request(self, term, width, height, pixelwidth,
                                                      pixelheight, modes)
        elif key == 'shell':
            if server is None:
                ok = False
            else:
                ok = server.check_channel_shell_request(self)
        elif key == 'exec':
            cmd = m.get_string()
            if server is None:
                ok = False
            else:
                ok = server.check_channel_exec_request(self, cmd)
        elif key == 'subsystem':
            name = m.get_string()
            if server is None:
                ok = False
            else:
                ok = server.check_channel_subsystem_request(self, name)
        elif key == 'window-change':
            width = m.get_int()
            height = m.get_int()
            pixelwidth = m.get_int()
            pixelheight = m.get_int()
            if server is None:
                ok = False
            else:
                ok = server.check_channel_window_change_request(self, width, height, pixelwidth,
                                                                pixelheight)
        elif key == 'x11-req':
            single_connection = m.get_boolean()
            auth_proto = m.get_string()
            auth_cookie = m.get_string()
            screen_number = m.get_int()
            if server is None:
                ok = False
            else:
                ok = server.check_channel_x11_request(self, single_connection,
                                                      auth_proto, auth_cookie, screen_number)
        elif key == 'auth-agent-req@openssh.com':
            if server is None:
                ok = False
            else:
                ok = server.check_channel_forward_agent_request(self)
        else:
            self._log(DEBUG, 'Unhandled channel request "%s"' % key)
            ok = False
        if want_reply:
            m = Message()
            if ok:
                m.add_byte(chr(MSG_CHANNEL_SUCCESS))
            else:
                m.add_byte(chr(MSG_CHANNEL_FAILURE))
            m.add_int(self.remote_chanid)
            self.transport._send_user_message(m)

    def _handle_eof(self, m):
        self.lock.acquire()
        try:
            if not self.eof_received:
                self.eof_received = True
                self.in_buffer.close()
                self.in_stderr_buffer.close()
                if self._pipe is not None:
                    self._pipe.set_forever()
        finally:
            self.lock.release()
        self._log(DEBUG, 'EOF received (%s)', self._name)

    def _handle_close(self, m):
        self.lock.acquire()
        try:
            msgs = self._close_internal()
            self.transport._unlink_channel(self.chanid)
        finally:
            self.lock.release()
        for m in msgs:
            if m is not None:
                self.transport._send_user_message(m)


    ###  internals...


    def _log(self, level, msg, *args):
        self.logger.log(level, "[chan " + self._name + "] " + msg, *args)

    def _event_pending(self):
        self.event.clear()
        self.event_ready = False

    def _wait_for_event(self):
        self.event.wait()
        assert self.event.isSet()
        if self.event_ready:
            return
        e = self.transport.get_exception()
        if e is None:
            e = SSHException('Channel closed.')
        raise e

    def _set_closed(self):
        # you are holding the lock.
        self.closed = True
        self.in_buffer.close()
        self.in_stderr_buffer.close()
        self.out_buffer_cv.notifyAll()
        # Notify any waiters that we are closed
        self.event.set()
        self.status_event.set()
        if self._pipe is not None:
            self._pipe.set_forever()

    def _send_eof(self):
        # you are holding the lock.
        if self.eof_sent:
            return None
        m = Message()
        m.add_byte(chr(MSG_CHANNEL_EOF))
        m.add_int(self.remote_chanid)
        self.eof_sent = True
        self._log(DEBUG, 'EOF sent (%s)', self._name)
        return m

    def _close_internal(self):
        # you are holding the lock.
        if not self.active or self.closed:
            return None, None
        m1 = self._send_eof()
        m2 = Message()
        m2.add_byte(chr(MSG_CHANNEL_CLOSE))
        m2.add_int(self.remote_chanid)
        self._set_closed()
        # can't unlink from the Transport yet -- the remote side may still
        # try to send meta-data (exit-status, etc)
        return m1, m2

    def _unlink(self):
        # server connection could die before we become active: still signal the close!
        if self.closed:
            return
        self.lock.acquire()
        try:
            self._set_closed()
            self.transport._unlink_channel(self.chanid)
        finally:
            self.lock.release()

    def _check_add_window(self, n):
        self.lock.acquire()
        try:
            if self.closed or self.eof_received or not self.active:
                return 0
            if self.ultra_debug:
                self._log(DEBUG, 'addwindow %d' % n)
            self.in_window_sofar += n
            if self.in_window_sofar <= self.in_window_threshold:
                return 0
            if self.ultra_debug:
                self._log(DEBUG, 'addwindow send %d' % self.in_window_sofar)
            out = self.in_window_sofar
            self.in_window_sofar = 0
            return out
        finally:
            self.lock.release()

    def _wait_for_send_window(self, size):
        """
        (You are already holding the lock.)
        Wait for the send window to open up, and allocate up to C{size} bytes
        for transmission.  If no space opens up before the timeout, a timeout
        exception is raised.  Returns the number of bytes available to send
        (may be less than requested).
        """
        # you are already holding the lock
        if self.closed or self.eof_sent:
            return 0
        if self.out_window_size == 0:
            # should we block?
            if self.timeout == 0.0:
                raise socket.timeout()
            # loop here in case we get woken up but a different thread has filled the buffer
            timeout = self.timeout
            while self.out_window_size == 0:
                if self.closed or self.eof_sent:
                    return 0
                then = time.time()
                self.out_buffer_cv.wait(timeout)
                if timeout != None:
                    timeout -= time.time() - then
                    if timeout <= 0.0:
                        raise socket.timeout()
        # we have some window to squeeze into
        if self.closed or self.eof_sent:
            return 0
        if self.out_window_size < size:
            size = self.out_window_size
        if self.out_max_packet_size - 64 < size:
            size = self.out_max_packet_size - 64
        self.out_window_size -= size
        if self.ultra_debug:
            self._log(DEBUG, 'window down to %d' % self.out_window_size)
        return size
        

class ChannelFile (BufferedFile):
    """
    A file-like wrapper around L{Channel}.  A ChannelFile is created by calling
    L{Channel.makefile}.

    @bug: To correctly emulate the file object created from a socket's
        C{makefile} method, a L{Channel} and its C{ChannelFile} should be able
        to be closed or garbage-collected independently.  Currently, closing
        the C{ChannelFile} does nothing but flush the buffer.
    """

    def __init__(self, channel, mode = 'r', bufsize = -1):
        self.channel = channel
        BufferedFile.__init__(self)
        self._set_mode(mode, bufsize)

    def __repr__(self):
        """
        Returns a string representation of this object, for debugging.

        @rtype: str
        """
        return '<paramiko.ChannelFile from ' + repr(self.channel) + '>'

    def _read(self, size):
        return self.channel.recv(size)

    def _write(self, data):
        self.channel.sendall(data)
        return len(data)


class ChannelStderrFile (ChannelFile):
    def __init__(self, channel, mode = 'r', bufsize = -1):
        ChannelFile.__init__(self, channel, mode, bufsize)

    def _read(self, size):
        return self.channel.recv_stderr(size)
    
    def _write(self, data):
        self.channel.sendall_stderr(data)
        return len(data)


# vim: set shiftwidth=4 expandtab :