channels.c

   1 /*
   2  *
   3  * channels.c
   4  *
   5  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   6  *
   7  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   8  *                    All rights reserved
   9  *
  10  * Created: Fri Mar 24 16:35:24 1995 ylo
  11  *
  12  * This file contains functions for generic socket connection forwarding.
  13  * There is also code for initiating connection forwarding for X11 connections,
  14  * arbitrary tcp/ip connections, and the authentication agent connection.
  15  *
  16  */
  17
  18 #include "includes.h"
  19 RCSID("$Id$");
  20
  21 #include "ssh.h"
  22 #include "packet.h"
  23 #include "xmalloc.h"
  24 #include "buffer.h"
  25 #include "authfd.h"
  26 #include "uidswap.h"
  27 #include "readconf.h"
  28 #include "servconf.h"
  29
  30 #include "channels.h"
  31 #include "nchan.h"
  32 #include "compat.h"
  33
  34 /* Maximum number of fake X11 displays to try. */
  35 #define MAX_DISPLAYS  1000
  36
  37 /* Max len of agent socket */
  38 #define MAX_SOCKET_NAME 100
  39
  40 /*
  41  * Pointer to an array containing all allocated channels.  The array is
  42  * dynamically extended as needed.
  43  */
  44 static Channel *channels = NULL;
  45
  46 /*
  47  * Size of the channel array.  All slots of the array must always be
  48  * initialized (at least the type field); unused slots are marked with type
  49  * SSH_CHANNEL_FREE.
  50  */
  51 static int channels_alloc = 0;
  52
  53 /*
  54  * Maximum file descriptor value used in any of the channels.  This is
  55  * updated in channel_allocate.
  56  */
  57 static int channel_max_fd_value = 0;
  58
  59 /* Name and directory of socket for authentication agent forwarding. */
  60 static char *channel_forwarded_auth_socket_name = NULL;
  61 static char *channel_forwarded_auth_socket_dir = NULL;
  62
  63 /* Saved X11 authentication protocol name. */
  64 char *x11_saved_proto = NULL;
  65
  66 /* Saved X11 authentication data.  This is the real data. */
  67 char *x11_saved_data = NULL;
  68 unsigned int x11_saved_data_len = 0;
  69
  70 /*
  71  * Fake X11 authentication data.  This is what the server will be sending us;
  72  * we should replace any occurrences of this by the real data.
  73  */
  74 char *x11_fake_data = NULL;
  75 unsigned int x11_fake_data_len;
  76
  77 /*
  78  * Data structure for storing which hosts are permitted for forward requests.
  79  * The local sides of any remote forwards are stored in this array to prevent
  80  * a corrupt remote server from accessing arbitrary TCP/IP ports on our local
  81  * network (which might be behind a firewall).
  82  */
  83 typedef struct {
  84         char *host;             /* Host name. */
  85         u_short port;           /* Port number. */
  86 } ForwardPermission;
  87
  88 /* List of all permitted host/port pairs to connect. */
  89 static ForwardPermission permitted_opens[SSH_MAX_FORWARDS_PER_DIRECTION];
  90 /* Number of permitted host/port pairs in the array. */
  91 static int num_permitted_opens = 0;
  92 /*
  93  * If this is true, all opens are permitted.  This is the case on the server
  94  * on which we have to trust the client anyway, and the user could do
  95  * anything after logging in anyway.
  96  */
  97 static int all_opens_permitted = 0;
  98
  99 /* This is set to true if both sides support SSH_PROTOFLAG_HOST_IN_FWD_OPEN. */
 100 static int have_hostname_in_open = 0;
 101
 102 /* Sets specific protocol options. */
 103
 104 void
 105 channel_set_options(int hostname_in_open)
 106 {
 107         have_hostname_in_open = hostname_in_open;
 108 }
 109
 110 /*
 111  * Permits opening to any host/port in SSH_MSG_PORT_OPEN.  This is usually
 112  * called by the server, because the user could connect to any port anyway,
 113  * and the server has no way to know but to trust the client anyway.
 114  */
 115
 116 void
 117 channel_permit_all_opens()
 118 {
 119         all_opens_permitted = 1;
 120 }
 121
 122 /*
 123  * Allocate a new channel object and set its type and socket. This will cause
 124  * remote_name to be freed.
 125  */
 126
 127 int
 128 channel_allocate(int type, int sock, char *remote_name)
 129 {
 130         int i, found;
 131         Channel *c;
 132
 133         /* Update the maximum file descriptor value. */
 134         if (sock > channel_max_fd_value)
 135                 channel_max_fd_value = sock;
 136         /* XXX set close-on-exec -markus */
 137
 138         /* Do initial allocation if this is the first call. */
 139         if (channels_alloc == 0) {
 140                 channels_alloc = 10;
 141                 channels = xmalloc(channels_alloc * sizeof(Channel));
 142                 for (i = 0; i < channels_alloc; i++)
 143                         channels[i].type = SSH_CHANNEL_FREE;
 144                 /*
 145                  * Kludge: arrange a call to channel_stop_listening if we
 146                  * terminate with fatal().
 147                  */
 148                 fatal_add_cleanup((void (*) (void *)) channel_stop_listening, NULL);
 149         }
 150         /* Try to find a free slot where to put the new channel. */
 151         for (found = -1, i = 0; i < channels_alloc; i++)
 152                 if (channels[i].type == SSH_CHANNEL_FREE) {
 153                         /* Found a free slot. */
 154                         found = i;
 155                         break;
 156                 }
 157         if (found == -1) {
 158                 /* There are no free slots.  Take last+1 slot and expand the array.  */
 159                 found = channels_alloc;
 160                 channels_alloc += 10;
 161                 debug("channel: expanding %d", channels_alloc);
 162                 channels = xrealloc(channels, channels_alloc * sizeof(Channel));
 163                 for (i = found; i < channels_alloc; i++)
 164                         channels[i].type = SSH_CHANNEL_FREE;
 165         }
 166         /* Initialize and return new channel number. */
 167         c = &channels[found];
 168         buffer_init(&c->input);
 169         buffer_init(&c->output);
 170         chan_init_iostates(c);
 171         c->self = found;
 172         c->type = type;
 173         c->sock = sock;
 174         c->remote_id = -1;
 175         c->remote_name = remote_name;
 176         debug("channel %d: new [%s]", found, remote_name);
 177         return found;
 178 }
 179
 180 /* Free the channel and close its socket. */
 181
 182 void
 183 channel_free(int channel)
 184 {
 185         if (channel < 0 || channel >= channels_alloc ||
 186             channels[channel].type == SSH_CHANNEL_FREE)
 187                 packet_disconnect("channel free: bad local channel %d", channel);
 188
 189         if (compat13)
 190                 shutdown(channels[channel].sock, SHUT_RDWR);
 191         close(channels[channel].sock);
 192         buffer_free(&channels[channel].input);
 193         buffer_free(&channels[channel].output);
 194         channels[channel].type = SSH_CHANNEL_FREE;
 195         if (channels[channel].remote_name) {
 196                 xfree(channels[channel].remote_name);
 197                 channels[channel].remote_name = NULL;
 198         }
 199 }
 200
 201 /*
 202  * This is called just before select() to add any bits relevant to channels
 203  * in the select bitmasks.
 204  */
 205
 206 void
 207 channel_prepare_select(fd_set * readset, fd_set * writeset)
 208 {
 209         int i;
 210         Channel *ch;
 211         unsigned char *ucp;
 212         unsigned int proto_len, data_len;
 213
 214         for (i = 0; i < channels_alloc; i++) {
 215                 ch = &channels[i];
 216 redo:
 217                 switch (ch->type) {
 218                 case SSH_CHANNEL_X11_LISTENER:
 219                 case SSH_CHANNEL_PORT_LISTENER:
 220                 case SSH_CHANNEL_AUTH_SOCKET:
 221                         FD_SET(ch->sock, readset);
 222                         break;
 223
 224                 case SSH_CHANNEL_OPEN:
 225                         if (compat13) {
 226                                 if (buffer_len(&ch->input) < packet_get_maxsize())
 227                                         FD_SET(ch->sock, readset);
 228                                 if (buffer_len(&ch->output) > 0)
 229                                         FD_SET(ch->sock, writeset);
 230                                 break;
 231                         }
 232                         /* test whether sockets are 'alive' for read/write */
 233                         if (ch->istate == CHAN_INPUT_OPEN)
 234                                 if (buffer_len(&ch->input) < packet_get_maxsize())
 235                                         FD_SET(ch->sock, readset);
 236                         if (ch->ostate == CHAN_OUTPUT_OPEN ||
 237                             ch->ostate == CHAN_OUTPUT_WAIT_DRAIN) {
 238                                 if (buffer_len(&ch->output) > 0) {
 239                                         FD_SET(ch->sock, writeset);
 240                                 } else if (ch->ostate == CHAN_OUTPUT_WAIT_DRAIN) {
 241                                         chan_obuf_empty(ch);
 242                                 }
 243                         }
 244                         break;
 245
 246                 case SSH_CHANNEL_INPUT_DRAINING:
 247                         if (!compat13)
 248                                 fatal("cannot happen: IN_DRAIN");
 249                         if (buffer_len(&ch->input) == 0) {
 250                                 packet_start(SSH_MSG_CHANNEL_CLOSE);
 251                                 packet_put_int(ch->remote_id);
 252                                 packet_send();
 253                                 ch->type = SSH_CHANNEL_CLOSED;
 254                                 debug("Closing channel %d after input drain.", ch->self);
 255                                 break;
 256                         }
 257                         break;
 258
 259                 case SSH_CHANNEL_OUTPUT_DRAINING:
 260                         if (!compat13)
 261                                 fatal("cannot happen: OUT_DRAIN");
 262                         if (buffer_len(&ch->output) == 0) {
 263                                 channel_free(i);
 264                                 break;
 265                         }
 266                         FD_SET(ch->sock, writeset);
 267                         break;
 268
 269                 case SSH_CHANNEL_X11_OPEN:
 270                         /*
 271                          * This is a special state for X11 authentication
 272                          * spoofing.  An opened X11 connection (when
 273                          * authentication spoofing is being done) remains in
 274                          * this state until the first packet has been
 275                          * completely read.  The authentication data in that
 276                          * packet is then substituted by the real data if it
 277                          * matches the fake data, and the channel is put into
 278                          * normal mode.
 279                          */
 280                         /* Check if the fixed size part of the packet is in buffer. */
 281                         if (buffer_len(&ch->output) < 12)
 282                                 break;
 283
 284                         /* Parse the lengths of variable-length fields. */
 285                         ucp = (unsigned char *) buffer_ptr(&ch->output);
 286                         if (ucp[0] == 0x42) {   /* Byte order MSB first. */
 287                                 proto_len = 256 * ucp[6] + ucp[7];
 288                                 data_len = 256 * ucp[8] + ucp[9];
 289                         } else if (ucp[0] == 0x6c) {    /* Byte order LSB first. */
 290                                 proto_len = ucp[6] + 256 * ucp[7];
 291                                 data_len = ucp[8] + 256 * ucp[9];
 292                         } else {
 293                                 debug("Initial X11 packet contains bad byte order byte: 0x%x",
 294                                       ucp[0]);
 295                                 ch->type = SSH_CHANNEL_OPEN;
 296                                 goto reject;
 297                         }
 298
 299                         /* Check if the whole packet is in buffer. */
 300                         if (buffer_len(&ch->output) <
 301                             12 + ((proto_len + 3) & ~3) + ((data_len + 3) & ~3))
 302                                 break;
 303
 304                         /* Check if authentication protocol matches. */
 305                         if (proto_len != strlen(x11_saved_proto) ||
 306                             memcmp(ucp + 12, x11_saved_proto, proto_len) != 0) {
 307                                 debug("X11 connection uses different authentication protocol.");
 308                                 ch->type = SSH_CHANNEL_OPEN;
 309                                 goto reject;
 310                         }
 311                         /* Check if authentication data matches our fake data. */
 312                         if (data_len != x11_fake_data_len ||
 313                             memcmp(ucp + 12 + ((proto_len + 3) & ~3),
 314                                 x11_fake_data, x11_fake_data_len) != 0) {
 315                                 debug("X11 auth data does not match fake data.");
 316                                 ch->type = SSH_CHANNEL_OPEN;
 317                                 goto reject;
 318                         }
 319                         /* Check fake data length */
 320                         if (x11_fake_data_len != x11_saved_data_len) {
 321                                 error("X11 fake_data_len %d != saved_data_len %d",
 322                                   x11_fake_data_len, x11_saved_data_len);
 323                                 ch->type = SSH_CHANNEL_OPEN;
 324                                 goto reject;
 325                         }
 326                         /*
 327                          * Received authentication protocol and data match
 328                          * our fake data. Substitute the fake data with real
 329                          * data.
 330                          */
 331                         memcpy(ucp + 12 + ((proto_len + 3) & ~3),
 332                                x11_saved_data, x11_saved_data_len);
 333
 334                         /* Start normal processing for the channel. */
 335                         ch->type = SSH_CHANNEL_OPEN;
 336                         goto redo;
 337
 338         reject:
 339                         /*
 340                          * We have received an X11 connection that has bad
 341                          * authentication information.
 342                          */
 343                         log("X11 connection rejected because of wrong authentication.\r\n");
 344                         buffer_clear(&ch->input);
 345                         buffer_clear(&ch->output);
 346                         if (compat13) {
 347                                 close(ch->sock);
 348                                 ch->sock = -1;
 349                                 ch->type = SSH_CHANNEL_CLOSED;
 350                                 packet_start(SSH_MSG_CHANNEL_CLOSE);
 351                                 packet_put_int(ch->remote_id);
 352                                 packet_send();
 353                         } else {
 354                                 debug("X11 rejected %d i%d/o%d", ch->self, ch->istate, ch->ostate);
 355                                 chan_read_failed(ch);
 356                                 chan_write_failed(ch);
 357                                 debug("X11 rejected %d i%d/o%d", ch->self, ch->istate, ch->ostate);
 358                         }
 359                         break;
 360
 361                 case SSH_CHANNEL_FREE:
 362                 default:
 363                         continue;
 364                 }
 365         }
 366 }
 367
 368 /*
 369  * After select, perform any appropriate operations for channels which have
 370  * events pending.
 371  */
 372
 373 void
 374 channel_after_select(fd_set * readset, fd_set * writeset)
 375 {
 376         struct sockaddr addr;
 377         int addrlen, newsock, i, newch, len;
 378         Channel *ch;
 379         char buf[16384], *remote_hostname;
 380
 381         /* Loop over all channels... */
 382         for (i = 0; i < channels_alloc; i++) {
 383                 ch = &channels[i];
 384                 switch (ch->type) {
 385                 case SSH_CHANNEL_X11_LISTENER:
 386                         /* This is our fake X11 server socket. */
 387                         if (FD_ISSET(ch->sock, readset)) {
 388                                 debug("X11 connection requested.");
 389                                 addrlen = sizeof(addr);
 390                                 newsock = accept(ch->sock, &addr, &addrlen);
 391                                 if (newsock < 0) {
 392                                         error("accept: %.100s", strerror(errno));
 393                                         break;
 394                                 }
 395                                 remote_hostname = get_remote_hostname(newsock);
 396                                 snprintf(buf, sizeof buf, "X11 connection from %.200s port %d",
 397                                 remote_hostname, get_peer_port(newsock));
 398                                 xfree(remote_hostname);
 399                                 newch = channel_allocate(SSH_CHANNEL_OPENING, newsock,
 400                                                          xstrdup(buf));
 401                                 packet_start(SSH_SMSG_X11_OPEN);
 402                                 packet_put_int(newch);
 403                                 if (have_hostname_in_open)
 404                                         packet_put_string(buf, strlen(buf));
 405                                 packet_send();
 406                         }
 407                         break;
 408
 409                 case SSH_CHANNEL_PORT_LISTENER:
 410                         /*
 411                          * This socket is listening for connections to a
 412                          * forwarded TCP/IP port.
 413                          */
 414                         if (FD_ISSET(ch->sock, readset)) {
 415                                 debug("Connection to port %d forwarding to %.100s:%d requested.",
 416                                       ch->listening_port, ch->path, ch->host_port);
 417                                 addrlen = sizeof(addr);
 418                                 newsock = accept(ch->sock, &addr, &addrlen);
 419                                 if (newsock < 0) {
 420                                         error("accept: %.100s", strerror(errno));
 421                                         break;
 422                                 }
 423                                 remote_hostname = get_remote_hostname(newsock);
 424                                 snprintf(buf, sizeof buf, "listen port %d:%.100s:%d, connect from %.200s:%d",
 425                                          ch->listening_port, ch->path, ch->host_port,
 426                                 remote_hostname, get_peer_port(newsock));
 427                                 xfree(remote_hostname);
 428                                 newch = channel_allocate(SSH_CHANNEL_OPENING, newsock,
 429                                                          xstrdup(buf));
 430                                 packet_start(SSH_MSG_PORT_OPEN);
 431                                 packet_put_int(newch);
 432                                 packet_put_string(ch->path, strlen(ch->path));
 433                                 packet_put_int(ch->host_port);
 434                                 if (have_hostname_in_open)
 435                                         packet_put_string(buf, strlen(buf));
 436                                 packet_send();
 437                         }
 438                         break;
 439
 440                 case SSH_CHANNEL_AUTH_SOCKET:
 441                         /*
 442                          * This is the authentication agent socket listening
 443                          * for connections from clients.
 444                          */
 445                         if (FD_ISSET(ch->sock, readset)) {
 446                                 addrlen = sizeof(addr);
 447                                 newsock = accept(ch->sock, &addr, &addrlen);
 448                                 if (newsock < 0) {
 449                                         error("accept from auth socket: %.100s", strerror(errno));
 450                                         break;
 451                                 }
 452                                 newch = channel_allocate(SSH_CHANNEL_OPENING, newsock,
 453                                         xstrdup("accepted auth socket"));
 454                                 packet_start(SSH_SMSG_AGENT_OPEN);
 455                                 packet_put_int(newch);
 456                                 packet_send();
 457                         }
 458                         break;
 459
 460                 case SSH_CHANNEL_OPEN:
 461                         /*
 462                          * This is an open two-way communication channel. It
 463                          * is not of interest to us at this point what kind
 464                          * of data is being transmitted.
 465                          */
 466
 467                         /*
 468                          * Read available incoming data and append it to
 469                          * buffer; shutdown socket, if read or write failes
 470                          */
 471                         if (FD_ISSET(ch->sock, readset)) {
 472                                 len = read(ch->sock, buf, sizeof(buf));
 473                                 if (len <= 0) {
 474                                         if (compat13) {
 475                                                 buffer_consume(&ch->output, buffer_len(&ch->output));
 476                                                 ch->type = SSH_CHANNEL_INPUT_DRAINING;
 477                                                 debug("Channel %d status set to input draining.", i);
 478                                         } else {
 479                                                 chan_read_failed(ch);
 480                                         }
 481                                         break;
 482                                 }
 483                                 buffer_append(&ch->input, buf, len);
 484                         }
 485                         /* Send buffered output data to the socket. */
 486                         if (FD_ISSET(ch->sock, writeset) && buffer_len(&ch->output) > 0) {
 487                                 len = write(ch->sock, buffer_ptr(&ch->output),
 488                                             buffer_len(&ch->output));
 489                                 if (len <= 0) {
 490                                         if (compat13) {
 491                                                 buffer_consume(&ch->output, buffer_len(&ch->output));
 492                                                 debug("Channel %d status set to input draining.", i);
 493                                                 ch->type = SSH_CHANNEL_INPUT_DRAINING;
 494                                         } else {
 495                                                 chan_write_failed(ch);
 496                                         }
 497                                         break;
 498                                 }
 499                                 buffer_consume(&ch->output, len);
 500                         }
 501                         break;
 502
 503                 case SSH_CHANNEL_OUTPUT_DRAINING:
 504                         if (!compat13)
 505                                 fatal("cannot happen: OUT_DRAIN");
 506                         /* Send buffered output data to the socket. */
 507                         if (FD_ISSET(ch->sock, writeset) && buffer_len(&ch->output) > 0) {
 508                                 len = write(ch->sock, buffer_ptr(&ch->output),
 509                                             buffer_len(&ch->output));
 510                                 if (len <= 0)
 511                                         buffer_consume(&ch->output, buffer_len(&ch->output));
 512                                 else
 513                                         buffer_consume(&ch->output, len);
 514                         }
 515                         break;
 516
 517                 case SSH_CHANNEL_X11_OPEN:
 518                 case SSH_CHANNEL_FREE:
 519                 default:
 520                         continue;
 521                 }
 522         }
 523 }
 524
 525 /* If there is data to send to the connection, send some of it now. */
 526
 527 void
 528 channel_output_poll()
 529 {
 530         int len, i;
 531         Channel *ch;
 532
 533         for (i = 0; i < channels_alloc; i++) {
 534                 ch = &channels[i];
 535                 /* We are only interested in channels that can have buffered incoming data. */
 536                 if (ch->type != SSH_CHANNEL_OPEN &&
 537                     ch->type != SSH_CHANNEL_INPUT_DRAINING)
 538                         continue;
 539
 540                 /* Get the amount of buffered data for this channel. */
 541                 len = buffer_len(&ch->input);
 542                 if (len > 0) {
 543                         /* Send some data for the other side over the secure connection. */
 544                         if (packet_is_interactive()) {
 545                                 if (len > 1024)
 546                                         len = 512;
 547                         } else {
 548                                 /* Keep the packets at reasonable size. */
 549                                 if (len > packet_get_maxsize()/2)
 550                                         len = packet_get_maxsize()/2;
 551                         }
 552                         packet_start(SSH_MSG_CHANNEL_DATA);
 553                         packet_put_int(ch->remote_id);
 554                         packet_put_string(buffer_ptr(&ch->input), len);
 555                         packet_send();
 556                         buffer_consume(&ch->input, len);
 557                 } else if (ch->istate == CHAN_INPUT_WAIT_DRAIN) {
 558                         if (compat13)
 559                                 fatal("cannot happen: istate == INPUT_WAIT_DRAIN for proto 1.3");
 560                         /*
 561                          * input-buffer is empty and read-socket shutdown:
 562                          * tell peer, that we will not send more data: send IEOF
 563                          */
 564                         chan_ibuf_empty(ch);
 565                 }
 566         }
 567 }
 568
 569 /*
 570  * This is called when a packet of type CHANNEL_DATA has just been received.
 571  * The message type has already been consumed, but channel number and data is
 572  * still there.
 573  */
 574
 575 void
 576 channel_input_data(int payload_len)
 577 {
 578         int channel;
 579         char *data;
 580         unsigned int data_len;
 581
 582         /* Get the channel number and verify it. */
 583         channel = packet_get_int();
 584         if (channel < 0 || channel >= channels_alloc ||
 585             channels[channel].type == SSH_CHANNEL_FREE)
 586                 packet_disconnect("Received data for nonexistent channel %d.", channel);
 587
 588         /* Ignore any data for non-open channels (might happen on close) */
 589         if (channels[channel].type != SSH_CHANNEL_OPEN &&
 590             channels[channel].type != SSH_CHANNEL_X11_OPEN)
 591                 return;
 592
 593         /* Get the data. */
 594         data = packet_get_string(&data_len);
 595         packet_integrity_check(payload_len, 4 + 4 + data_len, SSH_MSG_CHANNEL_DATA);
 596         buffer_append(&channels[channel].output, data, data_len);
 597         xfree(data);
 598 }
 599
 600 /*
 601  * Returns true if no channel has too much buffered data, and false if one or
 602  * more channel is overfull.
 603  */
 604
 605 int
 606 channel_not_very_much_buffered_data()
 607 {
 608         unsigned int i;
 609         Channel *ch;
 610
 611         for (i = 0; i < channels_alloc; i++) {
 612                 ch = &channels[i];
 613                 switch (ch->type) {
 614                 case SSH_CHANNEL_X11_LISTENER:
 615                 case SSH_CHANNEL_PORT_LISTENER:
 616                 case SSH_CHANNEL_AUTH_SOCKET:
 617                         continue;
 618                 case SSH_CHANNEL_OPEN:
 619                         if (buffer_len(&ch->input) > packet_get_maxsize())
 620                                 return 0;
 621                         if (buffer_len(&ch->output) > packet_get_maxsize())
 622                                 return 0;
 623                         continue;
 624                 case SSH_CHANNEL_INPUT_DRAINING:
 625                 case SSH_CHANNEL_OUTPUT_DRAINING:
 626                 case SSH_CHANNEL_X11_OPEN:
 627                 case SSH_CHANNEL_FREE:
 628                 default:
 629                         continue;
 630                 }
 631         }
 632         return 1;
 633 }
 634
 635 /* This is called after receiving CHANNEL_CLOSE/IEOF. */
 636
 637 void
 638 channel_input_close()
 639 {
 640         int channel;
 641
 642         /* Get the channel number and verify it. */
 643         channel = packet_get_int();
 644         if (channel < 0 || channel >= channels_alloc ||
 645             channels[channel].type == SSH_CHANNEL_FREE)
 646                 packet_disconnect("Received data for nonexistent channel %d.", channel);
 647
 648         if (!compat13) {
 649                 /* proto version 1.5 overloads CLOSE with IEOF */
 650                 chan_rcvd_ieof(&channels[channel]);
 651                 return;
 652         }
 653
 654         /*
 655          * Send a confirmation that we have closed the channel and no more
 656          * data is coming for it.
 657          */
 658         packet_start(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION);
 659         packet_put_int(channels[channel].remote_id);
 660         packet_send();
 661
 662         /*
 663          * If the channel is in closed state, we have sent a close request,
 664          * and the other side will eventually respond with a confirmation.
 665          * Thus, we cannot free the channel here, because then there would be
 666          * no-one to receive the confirmation.  The channel gets freed when
 667          * the confirmation arrives.
 668          */
 669         if (channels[channel].type != SSH_CHANNEL_CLOSED) {
 670                 /*
 671                  * Not a closed channel - mark it as draining, which will
 672                  * cause it to be freed later.
 673                  */
 674                 buffer_consume(&channels[channel].input,
 675                                buffer_len(&channels[channel].input));
 676                 channels[channel].type = SSH_CHANNEL_OUTPUT_DRAINING;
 677         }
 678 }
 679
 680 /* This is called after receiving CHANNEL_CLOSE_CONFIRMATION/OCLOSE. */
 681
 682 void
 683 channel_input_close_confirmation()
 684 {
 685         int channel;
 686
 687         /* Get the channel number and verify it. */
 688         channel = packet_get_int();
 689         if (channel < 0 || channel >= channels_alloc)
 690                 packet_disconnect("Received close confirmation for out-of-range channel %d.",
 691                                   channel);
 692
 693         if (!compat13) {
 694                 /* proto version 1.5 overloads CLOSE_CONFIRMATION with OCLOSE */
 695                 chan_rcvd_oclose(&channels[channel]);
 696                 return;
 697         }
 698         if (channels[channel].type != SSH_CHANNEL_CLOSED)
 699                 packet_disconnect("Received close confirmation for non-closed channel %d (type %d).",
 700                                   channel, channels[channel].type);
 701
 702         /* Free the channel. */
 703         channel_free(channel);
 704 }
 705
 706 /* This is called after receiving CHANNEL_OPEN_CONFIRMATION. */
 707
 708 void
 709 channel_input_open_confirmation()
 710 {
 711         int channel, remote_channel;
 712
 713         /* Get the channel number and verify it. */
 714         channel = packet_get_int();
 715         if (channel < 0 || channel >= channels_alloc ||
 716             channels[channel].type != SSH_CHANNEL_OPENING)
 717                 packet_disconnect("Received open confirmation for non-opening channel %d.",
 718                                   channel);
 719
 720         /* Get remote side's id for this channel. */
 721         remote_channel = packet_get_int();
 722
 723         /* Record the remote channel number and mark that the channel is now open. */
 724         channels[channel].remote_id = remote_channel;
 725         channels[channel].type = SSH_CHANNEL_OPEN;
 726 }
 727
 728 /* This is called after receiving CHANNEL_OPEN_FAILURE from the other side. */
 729
 730 void
 731 channel_input_open_failure()
 732 {
 733         int channel;
 734
 735         /* Get the channel number and verify it. */
 736         channel = packet_get_int();
 737         if (channel < 0 || channel >= channels_alloc ||
 738             channels[channel].type != SSH_CHANNEL_OPENING)
 739                 packet_disconnect("Received open failure for non-opening channel %d.",
 740                                   channel);
 741
 742         /* Free the channel.  This will also close the socket. */
 743         channel_free(channel);
 744 }
 745
 746 /*
 747  * Stops listening for channels, and removes any unix domain sockets that we
 748  * might have.
 749  */
 750
 751 void
 752 channel_stop_listening()
 753 {
 754         int i;
 755         for (i = 0; i < channels_alloc; i++) {
 756                 switch (channels[i].type) {
 757                 case SSH_CHANNEL_AUTH_SOCKET:
 758                         close(channels[i].sock);
 759                         remove(channels[i].path);
 760                         channel_free(i);
 761                         break;
 762                 case SSH_CHANNEL_PORT_LISTENER:
 763                 case SSH_CHANNEL_X11_LISTENER:
 764                         close(channels[i].sock);
 765                         channel_free(i);
 766                         break;
 767                 default:
 768                         break;
 769                 }
 770         }
 771 }
 772
 773 /*
 774  * Closes the sockets of all channels.  This is used to close extra file
 775  * descriptors after a fork.
 776  */
 777
 778 void
 779 channel_close_all()
 780 {
 781         int i;
 782         for (i = 0; i < channels_alloc; i++) {
 783                 if (channels[i].type != SSH_CHANNEL_FREE)
 784                         close(channels[i].sock);
 785         }
 786 }
 787
 788 /* Returns the maximum file descriptor number used by the channels. */
 789
 790 int
 791 channel_max_fd()
 792 {
 793         return channel_max_fd_value;
 794 }
 795
 796 /* Returns true if any channel is still open. */
 797
 798 int
 799 channel_still_open()
 800 {
 801         unsigned int i;
 802         for (i = 0; i < channels_alloc; i++)
 803                 switch (channels[i].type) {
 804                 case SSH_CHANNEL_FREE:
 805                 case SSH_CHANNEL_X11_LISTENER:
 806                 case SSH_CHANNEL_PORT_LISTENER:
 807                 case SSH_CHANNEL_CLOSED:
 808                 case SSH_CHANNEL_AUTH_SOCKET:
 809                         continue;
 810                 case SSH_CHANNEL_OPENING:
 811                 case SSH_CHANNEL_OPEN:
 812                 case SSH_CHANNEL_X11_OPEN:
 813                         return 1;
 814                 case SSH_CHANNEL_INPUT_DRAINING:
 815                 case SSH_CHANNEL_OUTPUT_DRAINING:
 816                         if (!compat13)
 817                                 fatal("cannot happen: OUT_DRAIN");
 818                         return 1;
 819                 default:
 820                         fatal("channel_still_open: bad channel type %d", channels[i].type);
 821                         /* NOTREACHED */
 822                 }
 823         return 0;
 824 }
 825
 826 /*
 827  * Returns a message describing the currently open forwarded connections,
 828  * suitable for sending to the client.  The message contains crlf pairs for
 829  * newlines.
 830  */
 831
 832 char *
 833 channel_open_message()
 834 {
 835         Buffer buffer;
 836         int i;
 837         char buf[512], *cp;
 838
 839         buffer_init(&buffer);
 840         snprintf(buf, sizeof buf, "The following connections are open:\r\n");
 841         buffer_append(&buffer, buf, strlen(buf));
 842         for (i = 0; i < channels_alloc; i++) {
 843                 Channel *c = &channels[i];
 844                 switch (c->type) {
 845                 case SSH_CHANNEL_FREE:
 846                 case SSH_CHANNEL_X11_LISTENER:
 847                 case SSH_CHANNEL_PORT_LISTENER:
 848                 case SSH_CHANNEL_CLOSED:
 849                 case SSH_CHANNEL_AUTH_SOCKET:
 850                         continue;
 851                 case SSH_CHANNEL_OPENING:
 852                 case SSH_CHANNEL_OPEN:
 853                 case SSH_CHANNEL_X11_OPEN:
 854                 case SSH_CHANNEL_INPUT_DRAINING:
 855                 case SSH_CHANNEL_OUTPUT_DRAINING:
 856                         snprintf(buf, sizeof buf, "  #%d %.300s (t%d r%d i%d o%d)\r\n",
 857                                  c->self, c->remote_name,
 858                                  c->type, c->remote_id, c->istate, c->ostate);
 859                         buffer_append(&buffer, buf, strlen(buf));
 860                         continue;
 861                 default:
 862                         fatal("channel_still_open: bad channel type %d", c->type);
 863                         /* NOTREACHED */
 864                 }
 865         }
 866         buffer_append(&buffer, "\0", 1);
 867         cp = xstrdup(buffer_ptr(&buffer));
 868         buffer_free(&buffer);
 869         return cp;
 870 }
 871
 872 /*
 873  * Initiate forwarding of connections to local port "port" through the secure
 874  * channel to host:port from remote side.
 875  */
 876
 877 void
 878 channel_request_local_forwarding(u_short port, const char *host,
 879                                  u_short host_port, int gateway_ports)
 880 {
 881         int ch, sock, on = 1;
 882         struct sockaddr_in sin;
 883         struct linger linger;
 884
 885         if (strlen(host) > sizeof(channels[0].path) - 1)
 886                 packet_disconnect("Forward host name too long.");
 887
 888         /* Create a port to listen for the host. */
 889         sock = socket(AF_INET, SOCK_STREAM, 0);
 890         if (sock < 0)
 891                 packet_disconnect("socket: %.100s", strerror(errno));
 892
 893         /* Initialize socket address. */
 894         memset(&sin, 0, sizeof(sin));
 895         sin.sin_family = AF_INET;
 896         if (gateway_ports == 1)
 897                 sin.sin_addr.s_addr = htonl(INADDR_ANY);
 898         else
 899                 sin.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
 900         sin.sin_port = htons(port);
 901
 902         /*
 903          * Set socket options.  We would like the socket to disappear as soon
 904          * as it has been closed for whatever reason.
 905          */
 906         setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on));
 907         linger.l_onoff = 1;
 908         linger.l_linger = 5;
 909         setsockopt(sock, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
 910
 911         /* Bind the socket to the address. */
 912         if (bind(sock, (struct sockaddr *) & sin, sizeof(sin)) < 0)
 913                 packet_disconnect("bind: %.100s", strerror(errno));
 914
 915         /* Start listening for connections on the socket. */
 916         if (listen(sock, 5) < 0)
 917                 packet_disconnect("listen: %.100s", strerror(errno));
 918
 919         /* Allocate a channel number for the socket. */
 920         ch = channel_allocate(SSH_CHANNEL_PORT_LISTENER, sock,
 921                               xstrdup("port listener"));
 922         strlcpy(channels[ch].path, host, sizeof(channels[ch].path));
 923         channels[ch].host_port = host_port;
 924         channels[ch].listening_port = port;
 925 }
 926
 927 /*
 928  * Initiate forwarding of connections to port "port" on remote host through
 929  * the secure channel to host:port from local side.
 930  */
 931
 932 void
 933 channel_request_remote_forwarding(u_short port, const char *host,
 934                                   u_short remote_port)
 935 {
 936         int payload_len;
 937         /* Record locally that connection to this host/port is permitted. */
 938         if (num_permitted_opens >= SSH_MAX_FORWARDS_PER_DIRECTION)
 939                 fatal("channel_request_remote_forwarding: too many forwards");
 940
 941         permitted_opens[num_permitted_opens].host = xstrdup(host);
 942         permitted_opens[num_permitted_opens].port = remote_port;
 943         num_permitted_opens++;
 944
 945         /* Send the forward request to the remote side. */
 946         packet_start(SSH_CMSG_PORT_FORWARD_REQUEST);
 947         packet_put_int(port);
 948         packet_put_string(host, strlen(host));
 949         packet_put_int(remote_port);
 950         packet_send();
 951         packet_write_wait();
 952
 953         /*
 954          * Wait for response from the remote side.  It will send a disconnect
 955          * message on failure, and we will never see it here.
 956          */
 957         packet_read_expect(&payload_len, SSH_SMSG_SUCCESS);
 958 }
 959
 960 /*
 961  * This is called after receiving CHANNEL_FORWARDING_REQUEST.  This initates
 962  * listening for the port, and sends back a success reply (or disconnect
 963  * message if there was an error).  This never returns if there was an error.
 964  */
 965
 966 void
 967 channel_input_port_forward_request(int is_root)
 968 {
 969         u_short port, host_port;
 970         char *hostname;
 971
 972         /* Get arguments from the packet. */
 973         port = packet_get_int();
 974         hostname = packet_get_string(NULL);
 975         host_port = packet_get_int();
 976
 977         /*
 978          * Check that an unprivileged user is not trying to forward a
 979          * privileged port.
 980          */
 981         if (port < IPPORT_RESERVED && !is_root)
 982                 packet_disconnect("Requested forwarding of port %d but user is not root.",
 983                                   port);
 984         /*
 985          * Initiate forwarding,
 986          * bind port to localhost only (gateway ports == 0).
 987          */
 988         channel_request_local_forwarding(port, hostname, host_port, 0);
 989
 990         /* Free the argument string. */
 991         xfree(hostname);
 992 }
 993
 994 /*
 995  * This is called after receiving PORT_OPEN message.  This attempts to
 996  * connect to the given host:port, and sends back CHANNEL_OPEN_CONFIRMATION
 997  * or CHANNEL_OPEN_FAILURE.
 998  */
 999
1000 void
1001 channel_input_port_open(int payload_len)
1002 {
1003         int remote_channel, sock, newch, i;
1004         u_short host_port;
1005         struct sockaddr_in sin;
1006         char *host, *originator_string;
1007         struct hostent *hp;
1008         int host_len, originator_len;
1009
1010         /* Get remote channel number. */
1011         remote_channel = packet_get_int();
1012
1013         /* Get host name to connect to. */
1014         host = packet_get_string(&host_len);
1015
1016         /* Get port to connect to. */
1017         host_port = packet_get_int();
1018
1019         /* Get remote originator name. */
1020         if (have_hostname_in_open) {
1021                 originator_string = packet_get_string(&originator_len);
1022                 originator_len += 4;    /* size of packet_int */
1023         } else {
1024                 originator_string = xstrdup("unknown (remote did not supply name)");
1025                 originator_len = 0;     /* no originator supplied */
1026         }
1027
1028         packet_integrity_check(payload_len,
1029                                4 + 4 + host_len + 4 + originator_len,
1030                                SSH_MSG_PORT_OPEN);
1031
1032         /* Check if opening that port is permitted. */
1033         if (!all_opens_permitted) {
1034                 /* Go trough all permitted ports. */
1035                 for (i = 0; i < num_permitted_opens; i++)
1036                         if (permitted_opens[i].port == host_port &&
1037                             strcmp(permitted_opens[i].host, host) == 0)
1038                                 break;
1039
1040                 /* Check if we found the requested port among those permitted. */
1041                 if (i >= num_permitted_opens) {
1042                         /* The port is not permitted. */
1043                         log("Received request to connect to %.100s:%d, but the request was denied.",
1044                             host, host_port);
1045                         packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
1046                         packet_put_int(remote_channel);
1047                         packet_send();
1048                 }
1049         }
1050         memset(&sin, 0, sizeof(sin));
1051         sin.sin_addr.s_addr = inet_addr(host);
1052         if ((sin.sin_addr.s_addr & 0xffffffff) != 0xffffffff) {
1053                 /* It was a valid numeric host address. */
1054                 sin.sin_family = AF_INET;
1055         } else {
1056                 /* Look up the host address from the name servers. */
1057                 hp = gethostbyname(host);
1058                 if (!hp) {
1059                         error("%.100s: unknown host.", host);
1060                         goto fail;
1061                 }
1062                 if (!hp->h_addr_list[0]) {
1063                         error("%.100s: host has no IP address.", host);
1064                         goto fail;
1065                 }
1066                 sin.sin_family = hp->h_addrtype;
1067                 memcpy(&sin.sin_addr, hp->h_addr_list[0],
1068                        sizeof(sin.sin_addr));
1069         }
1070         sin.sin_port = htons(host_port);
1071
1072         /* Create the socket. */
1073         sock = socket(sin.sin_family, SOCK_STREAM, 0);
1074         if (sock < 0) {
1075                 error("socket: %.100s", strerror(errno));
1076                 goto fail;
1077         }
1078         /* Connect to the host/port. */
1079         if (connect(sock, (struct sockaddr *) & sin, sizeof(sin)) < 0) {
1080                 error("connect %.100s:%d: %.100s", host, host_port,
1081                       strerror(errno));
1082                 close(sock);
1083                 goto fail;
1084         }
1085         /* Successful connection. */
1086
1087         /* Allocate a channel for this connection. */
1088         newch = channel_allocate(SSH_CHANNEL_OPEN, sock, originator_string);
1089         channels[newch].remote_id = remote_channel;
1090
1091         /* Send a confirmation to the remote host. */
1092         packet_start(SSH_MSG_CHANNEL_OPEN_CONFIRMATION);
1093         packet_put_int(remote_channel);
1094         packet_put_int(newch);
1095         packet_send();
1096
1097         /* Free the argument string. */
1098         xfree(host);
1099
1100         return;
1101
1102 fail:
1103         /* Free the argument string. */
1104         xfree(host);
1105
1106         /* Send refusal to the remote host. */
1107         packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
1108         packet_put_int(remote_channel);
1109         packet_send();
1110 }
1111
1112 /*
1113  * Creates an internet domain socket for listening for X11 connections.
1114  * Returns a suitable value for the DISPLAY variable, or NULL if an error
1115  * occurs.
1116  */
1117
1118 char *
1119 x11_create_display_inet(int screen_number, int x11_display_offset)
1120 {
1121         int display_number, sock;
1122         u_short port;
1123         struct sockaddr_in sin;
1124         char buf[512];
1125         char hostname[MAXHOSTNAMELEN];
1126
1127         for (display_number = x11_display_offset;
1128              display_number < MAX_DISPLAYS;
1129              display_number++) {
1130                 port = 6000 + display_number;
1131                 memset(&sin, 0, sizeof(sin));
1132                 sin.sin_family = AF_INET;
1133                 sin.sin_addr.s_addr = htonl(INADDR_ANY);
1134                 sin.sin_port = htons(port);
1135
1136                 sock = socket(AF_INET, SOCK_STREAM, 0);
1137                 if (sock < 0) {
1138                         error("socket: %.100s", strerror(errno));
1139                         return NULL;
1140                 }
1141                 if (bind(sock, (struct sockaddr *) & sin, sizeof(sin)) < 0) {
1142                         debug("bind port %d: %.100s", port, strerror(errno));
1143                         shutdown(sock, SHUT_RDWR);
1144                         close(sock);
1145                         continue;
1146                 }
1147                 break;
1148         }
1149         if (display_number >= MAX_DISPLAYS) {
1150                 error("Failed to allocate internet-domain X11 display socket.");
1151                 return NULL;
1152         }
1153         /* Start listening for connections on the socket. */
1154         if (listen(sock, 5) < 0) {
1155                 error("listen: %.100s", strerror(errno));
1156                 shutdown(sock, SHUT_RDWR);
1157                 close(sock);
1158                 return NULL;
1159         }
1160         /* Set up a suitable value for the DISPLAY variable. */
1161
1162         if (gethostname(hostname, sizeof(hostname)) < 0)
1163                 fatal("gethostname: %.100s", strerror(errno));
1164
1165 #ifdef IPADDR_IN_DISPLAY
1166         /*
1167          * HPUX detects the local hostname in the DISPLAY variable and tries
1168          * to set up a shared memory connection to the server, which it
1169          * incorrectly supposes to be local.
1170          *
1171          * The workaround - as used in later $$H and other programs - is
1172          * is to set display to the host's IP address.
1173          */
1174         {
1175                 struct hostent *he;
1176                 struct in_addr my_addr;
1177
1178                 he = gethostbyname(hostname);
1179                 if (he == NULL) {
1180                         error("[X11-broken-fwd-hostname-workaround] Could not get "
1181                                 "IP address for hostname %s.", hostname);
1182
1183                         packet_send_debug("[X11-broken-fwd-hostname-workaround]"
1184                                 "Could not get IP address for hostname %s.", hostname);
1185
1186                         shutdown(sock, SHUT_RDWR);
1187                         close(sock);
1188
1189                         return NULL;
1190                 }
1191
1192                 memcpy(&my_addr, he->h_addr_list[0], sizeof(struct in_addr));
1193
1194                 /* Set DISPLAY to <ip address>:screen.display */
1195                 snprintf(buf, sizeof(buf), "%.50s:%d.%d", inet_ntoa(my_addr),
1196                         display_number, screen_number);
1197         }
1198 #else /* IPADDR_IN_DISPLAY */
1199         /* Just set DISPLAY to hostname:screen.display */
1200         snprintf(buf, sizeof buf, "%.400s:%d.%d", hostname,
1201                 display_number, screen_number);
1202 #endif /* IPADDR_IN_DISPLAY */
1203
1204         /* Allocate a channel for the socket. */
1205         (void) channel_allocate(SSH_CHANNEL_X11_LISTENER, sock,
1206                                 xstrdup("X11 inet listener"));
1207
1208         /* Return a suitable value for the DISPLAY environment variable. */
1209         return xstrdup(buf);
1210 }
1211
1212 #ifndef X_UNIX_PATH
1213 #define X_UNIX_PATH "/tmp/.X11-unix/X"
1214 #endif
1215
1216 static
1217 int
1218 connect_local_xsocket(unsigned int dnr)
1219 {
1220         static const char *const x_sockets[] = {
1221                 X_UNIX_PATH "%u",
1222                 "/var/X/.X11-unix/X" "%u",
1223                 "/usr/spool/sockets/X11/" "%u",
1224                 NULL
1225         };
1226         int sock;
1227         struct sockaddr_un addr;
1228         const char *const * path;
1229
1230         for (path = x_sockets; *path; ++path) {
1231                 sock = socket(AF_UNIX, SOCK_STREAM, 0);
1232                 if (sock < 0)
1233                         error("socket: %.100s", strerror(errno));
1234                 memset(&addr, 0, sizeof(addr));
1235                 addr.sun_family = AF_UNIX;
1236                 snprintf(addr.sun_path, sizeof addr.sun_path, *path, dnr);
1237                 if (connect(sock, (struct sockaddr *) & addr, sizeof(addr)) == 0)
1238                         return sock;
1239                 close(sock);
1240         }
1241         error("connect %.100s: %.100s", addr.sun_path, strerror(errno));
1242         return -1;
1243 }
1244
1245
1246 /*
1247  * This is called when SSH_SMSG_X11_OPEN is received.  The packet contains
1248  * the remote channel number.  We should do whatever we want, and respond
1249  * with either SSH_MSG_OPEN_CONFIRMATION or SSH_MSG_OPEN_FAILURE.
1250  */
1251
1252 void
1253 x11_input_open(int payload_len)
1254 {
1255         int remote_channel, display_number, sock, newch;
1256         const char *display;
1257         struct sockaddr_in sin;
1258         char buf[1024], *cp, *remote_host;
1259         struct hostent *hp;
1260         int remote_len;
1261
1262         /* Get remote channel number. */
1263         remote_channel = packet_get_int();
1264
1265         /* Get remote originator name. */
1266         if (have_hostname_in_open) {
1267                 remote_host = packet_get_string(&remote_len);
1268                 remote_len += 4;
1269         } else {
1270                 remote_host = xstrdup("unknown (remote did not supply name)");
1271                 remote_len = 0;
1272         }
1273
1274         debug("Received X11 open request.");
1275         packet_integrity_check(payload_len, 4 + remote_len, SSH_SMSG_X11_OPEN);
1276
1277         /* Try to open a socket for the local X server. */
1278         display = getenv("DISPLAY");
1279         if (!display) {
1280                 error("DISPLAY not set.");
1281                 goto fail;
1282         }
1283         /*
1284          * Now we decode the value of the DISPLAY variable and make a
1285          * connection to the real X server.
1286          */
1287
1288         /*
1289          * Check if it is a unix domain socket.  Unix domain displays are in
1290          * one of the following formats: unix:d[.s], :d[.s], ::d[.s]
1291          */
1292         if (strncmp(display, "unix:", 5) == 0 ||
1293             display[0] == ':') {
1294                 /* Connect to the unix domain socket. */
1295                 if (sscanf(strrchr(display, ':') + 1, "%d", &display_number) != 1) {
1296                         error("Could not parse display number from DISPLAY: %.100s",
1297                               display);
1298                         goto fail;
1299                 }
1300                 /* Create a socket. */
1301                 sock = connect_local_xsocket(display_number);
1302                 if (sock < 0)
1303                         goto fail;
1304
1305                 /* OK, we now have a connection to the display. */
1306                 goto success;
1307         }
1308         /*
1309          * Connect to an inet socket.  The DISPLAY value is supposedly
1310          * hostname:d[.s], where hostname may also be numeric IP address.
1311          */
1312         strncpy(buf, display, sizeof(buf));
1313         buf[sizeof(buf) - 1] = 0;
1314         cp = strchr(buf, ':');
1315         if (!cp) {
1316                 error("Could not find ':' in DISPLAY: %.100s", display);
1317                 goto fail;
1318         }
1319         *cp = 0;
1320         /* buf now contains the host name.  But first we parse the display number. */
1321         if (sscanf(cp + 1, "%d", &display_number) != 1) {
1322                 error("Could not parse display number from DISPLAY: %.100s",
1323                       display);
1324                 goto fail;
1325         }
1326         /* Try to parse the host name as a numeric IP address. */
1327         memset(&sin, 0, sizeof(sin));
1328         sin.sin_addr.s_addr = inet_addr(buf);
1329         if ((sin.sin_addr.s_addr & 0xffffffff) != 0xffffffff) {
1330                 /* It was a valid numeric host address. */
1331                 sin.sin_family = AF_INET;
1332         } else {
1333                 /* Not a numeric IP address. */
1334                 /* Look up the host address from the name servers. */
1335                 hp = gethostbyname(buf);
1336                 if (!hp) {
1337                         error("%.100s: unknown host.", buf);
1338                         goto fail;
1339                 }
1340                 if (!hp->h_addr_list[0]) {
1341                         error("%.100s: host has no IP address.", buf);
1342                         goto fail;
1343                 }
1344                 sin.sin_family = hp->h_addrtype;
1345                 memcpy(&sin.sin_addr, hp->h_addr_list[0],
1346                        sizeof(sin.sin_addr));
1347         }
1348         /* Set port number. */
1349         sin.sin_port = htons(6000 + display_number);
1350
1351         /* Create a socket. */
1352         sock = socket(sin.sin_family, SOCK_STREAM, 0);
1353         if (sock < 0) {
1354                 error("socket: %.100s", strerror(errno));
1355                 goto fail;
1356         }
1357         /* Connect it to the display. */
1358         if (connect(sock, (struct sockaddr *) & sin, sizeof(sin)) < 0) {
1359                 error("connect %.100s:%d: %.100s", buf, 6000 + display_number,
1360                       strerror(errno));
1361                 close(sock);
1362                 goto fail;
1363         }
1364 success:
1365         /* We have successfully obtained a connection to the real X display. */
1366
1367         /* Allocate a channel for this connection. */
1368         if (x11_saved_proto == NULL)
1369                 newch = channel_allocate(SSH_CHANNEL_OPEN, sock, remote_host);
1370         else
1371                 newch = channel_allocate(SSH_CHANNEL_X11_OPEN, sock, remote_host);
1372         channels[newch].remote_id = remote_channel;
1373
1374         /* Send a confirmation to the remote host. */
1375         packet_start(SSH_MSG_CHANNEL_OPEN_CONFIRMATION);
1376         packet_put_int(remote_channel);
1377         packet_put_int(newch);
1378         packet_send();
1379
1380         return;
1381
1382 fail:
1383         /* Send refusal to the remote host. */
1384         packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
1385         packet_put_int(remote_channel);
1386         packet_send();
1387 }
1388
1389 /*
1390  * Requests forwarding of X11 connections, generates fake authentication
1391  * data, and enables authentication spoofing.
1392  */
1393
1394 void
1395 x11_request_forwarding_with_spoofing(const char *proto, const char *data)
1396 {
1397         unsigned int data_len = (unsigned int) strlen(data) / 2;
1398         unsigned int i, value;
1399         char *new_data;
1400         int screen_number;
1401         const char *cp;
1402         u_int32_t rand = 0;
1403
1404         cp = getenv("DISPLAY");
1405         if (cp)
1406                 cp = strchr(cp, ':');
1407         if (cp)
1408                 cp = strchr(cp, '.');
1409         if (cp)
1410                 screen_number = atoi(cp + 1);
1411         else
1412                 screen_number = 0;
1413
1414         /* Save protocol name. */
1415         x11_saved_proto = xstrdup(proto);
1416
1417         /*
1418          * Extract real authentication data and generate fake data of the
1419          * same length.
1420          */
1421         x11_saved_data = xmalloc(data_len);
1422         x11_fake_data = xmalloc(data_len);
1423         for (i = 0; i < data_len; i++) {
1424                 if (sscanf(data + 2 * i, "%2x", &value) != 1)
1425                         fatal("x11_request_forwarding: bad authentication data: %.100s", data);
1426                 if (i % 4 == 0)
1427                         rand = arc4random();
1428                 x11_saved_data[i] = value;
1429                 x11_fake_data[i] = rand & 0xff;
1430                 rand >>= 8;
1431         }
1432         x11_saved_data_len = data_len;
1433         x11_fake_data_len = data_len;
1434
1435         /* Convert the fake data into hex. */
1436         new_data = xmalloc(2 * data_len + 1);
1437         for (i = 0; i < data_len; i++)
1438                 sprintf(new_data + 2 * i, "%02x", (unsigned char) x11_fake_data[i]);
1439
1440         /* Send the request packet. */
1441         packet_start(SSH_CMSG_X11_REQUEST_FORWARDING);
1442         packet_put_string(proto, strlen(proto));
1443         packet_put_string(new_data, strlen(new_data));
1444         packet_put_int(screen_number);
1445         packet_send();
1446         packet_write_wait();
1447         xfree(new_data);
1448 }
1449
1450 /* Sends a message to the server to request authentication fd forwarding. */
1451
1452 void
1453 auth_request_forwarding()
1454 {
1455         packet_start(SSH_CMSG_AGENT_REQUEST_FORWARDING);
1456         packet_send();
1457         packet_write_wait();
1458 }
1459
1460 /*
1461  * Returns the name of the forwarded authentication socket.  Returns NULL if
1462  * there is no forwarded authentication socket.  The returned value points to
1463  * a static buffer.
1464  */
1465
1466 char *
1467 auth_get_socket_name()
1468 {
1469         return channel_forwarded_auth_socket_name;
1470 }
1471
1472 /* removes the agent forwarding socket */
1473
1474 void
1475 cleanup_socket(void)
1476 {
1477         remove(channel_forwarded_auth_socket_name);
1478         rmdir(channel_forwarded_auth_socket_dir);
1479 }
1480
1481 /*
1482  * This if called to process SSH_CMSG_AGENT_REQUEST_FORWARDING on the server.
1483  * This starts forwarding authentication requests.
1484  */
1485
1486 void
1487 auth_input_request_forwarding(struct passwd * pw)
1488 {
1489         int sock, newch;
1490         struct sockaddr_un sunaddr;
1491
1492         if (auth_get_socket_name() != NULL)
1493                 fatal("Protocol error: authentication forwarding requested twice.");
1494
1495         /* Temporarily drop privileged uid for mkdir/bind. */
1496         temporarily_use_uid(pw->pw_uid);
1497
1498         /* Allocate a buffer for the socket name, and format the name. */
1499         channel_forwarded_auth_socket_name = xmalloc(MAX_SOCKET_NAME);
1500         channel_forwarded_auth_socket_dir = xmalloc(MAX_SOCKET_NAME);
1501         strlcpy(channel_forwarded_auth_socket_dir, "/tmp/ssh-XXXXXXXX", MAX_SOCKET_NAME);
1502
1503         /* Create private directory for socket */
1504         if (mkdtemp(channel_forwarded_auth_socket_dir) == NULL)
1505                 packet_disconnect("mkdtemp: %.100s", strerror(errno));
1506         snprintf(channel_forwarded_auth_socket_name, MAX_SOCKET_NAME, "%s/agent.%d",
1507                  channel_forwarded_auth_socket_dir, (int) getpid());
1508
1509         if (atexit(cleanup_socket) < 0) {
1510                 int saved = errno;
1511                 cleanup_socket();
1512                 packet_disconnect("socket: %.100s", strerror(saved));
1513         }
1514         /* Create the socket. */
1515         sock = socket(AF_UNIX, SOCK_STREAM, 0);
1516         if (sock < 0)
1517                 packet_disconnect("socket: %.100s", strerror(errno));
1518
1519         /* Bind it to the name. */
1520         memset(&sunaddr, 0, sizeof(sunaddr));
1521         sunaddr.sun_family = AF_UNIX;
1522         strncpy(sunaddr.sun_path, channel_forwarded_auth_socket_name,
1523                 sizeof(sunaddr.sun_path));
1524
1525         if (bind(sock, (struct sockaddr *) & sunaddr, sizeof(sunaddr)) < 0)
1526                 packet_disconnect("bind: %.100s", strerror(errno));
1527
1528         /* Restore the privileged uid. */
1529         restore_uid();
1530
1531         /* Start listening on the socket. */
1532         if (listen(sock, 5) < 0)
1533                 packet_disconnect("listen: %.100s", strerror(errno));
1534
1535         /* Allocate a channel for the authentication agent socket. */
1536         newch = channel_allocate(SSH_CHANNEL_AUTH_SOCKET, sock,
1537                                  xstrdup("auth socket"));
1538         strlcpy(channels[newch].path, channel_forwarded_auth_socket_name,
1539             sizeof(channels[newch].path));
1540 }
1541
1542 /* This is called to process an SSH_SMSG_AGENT_OPEN message. */
1543
1544 void
1545 auth_input_open_request()
1546 {
1547         int remch, sock, newch;
1548         char *dummyname;
1549
1550         /* Read the remote channel number from the message. */
1551         remch = packet_get_int();
1552
1553         /*
1554          * Get a connection to the local authentication agent (this may again
1555          * get forwarded).
1556          */
1557         sock = ssh_get_authentication_socket();
1558
1559         /*
1560          * If we could not connect the agent, send an error message back to
1561          * the server. This should never happen unless the agent dies,
1562          * because authentication forwarding is only enabled if we have an
1563          * agent.
1564          */
1565         if (sock < 0) {
1566                 packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
1567                 packet_put_int(remch);
1568                 packet_send();
1569                 return;
1570         }
1571         debug("Forwarding authentication connection.");
1572
1573         /*
1574          * Dummy host name.  This will be freed when the channel is freed; it
1575          * will still be valid in the packet_put_string below since the
1576          * channel cannot yet be freed at that point.
1577          */
1578         dummyname = xstrdup("authentication agent connection");
1579
1580         newch = channel_allocate(SSH_CHANNEL_OPEN, sock, dummyname);
1581         channels[newch].remote_id = remch;
1582
1583         /* Send a confirmation to the remote host. */
1584         packet_start(SSH_MSG_CHANNEL_OPEN_CONFIRMATION);
1585         packet_put_int(remch);
1586         packet_put_int(newch);
1587         packet_send();
1588 }