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.", i);
 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                                 int nchan;
 447                                 len = sizeof(addr);
 448                                 newsock = accept(ch->sock, &addr, &len);
 449                                 if (newsock < 0) {
 450                                         error("accept from auth socket: %.100s", strerror(errno));
 451                                         break;
 452                                 }
 453                                 nchan = channel_allocate(SSH_CHANNEL_OPENING, newsock,
 454                                         xstrdup("accepted auth socket"));
 455                                 packet_start(SSH_SMSG_AGENT_OPEN);
 456                                 packet_put_int(nchan);
 457                                 packet_send();
 458                         }
 459                         break;
 460
 461                 case SSH_CHANNEL_OPEN:
 462                         /*
 463                          * This is an open two-way communication channel. It
 464                          * is not of interest to us at this point what kind
 465                          * of data is being transmitted.
 466                          */
 467
 468                         /*
 469                          * Read available incoming data and append it to
 470                          * buffer; shutdown socket, if read or write failes
 471                          */
 472                         if (FD_ISSET(ch->sock, readset)) {
 473                                 len = read(ch->sock, buf, sizeof(buf));
 474                                 if (len <= 0) {
 475                                         if (compat13) {
 476                                                 buffer_consume(&ch->output, buffer_len(&ch->output));
 477                                                 ch->type = SSH_CHANNEL_INPUT_DRAINING;
 478                                                 debug("Channel %d status set to input draining.", i);
 479                                         } else {
 480                                                 chan_read_failed(ch);
 481                                         }
 482                                         break;
 483                                 }
 484                                 buffer_append(&ch->input, buf, len);
 485                         }
 486                         /* Send buffered output data to the socket. */
 487                         if (FD_ISSET(ch->sock, writeset) && buffer_len(&ch->output) > 0) {
 488                                 len = write(ch->sock, buffer_ptr(&ch->output),
 489                                             buffer_len(&ch->output));
 490                                 if (len <= 0) {
 491                                         if (compat13) {
 492                                                 buffer_consume(&ch->output, buffer_len(&ch->output));
 493                                                 debug("Channel %d status set to input draining.", i);
 494                                                 ch->type = SSH_CHANNEL_INPUT_DRAINING;
 495                                         } else {
 496                                                 chan_write_failed(ch);
 497                                         }
 498                                         break;
 499                                 }
 500                                 buffer_consume(&ch->output, len);
 501                         }
 502                         break;
 503
 504                 case SSH_CHANNEL_OUTPUT_DRAINING:
 505                         if (!compat13)
 506                                 fatal("cannot happen: OUT_DRAIN");
 507                         /* Send buffered output data to the socket. */
 508                         if (FD_ISSET(ch->sock, writeset) && buffer_len(&ch->output) > 0) {
 509                                 len = write(ch->sock, buffer_ptr(&ch->output),
 510                                             buffer_len(&ch->output));
 511                                 if (len <= 0)
 512                                         buffer_consume(&ch->output, buffer_len(&ch->output));
 513                                 else
 514                                         buffer_consume(&ch->output, len);
 515                         }
 516                         break;
 517
 518                 case SSH_CHANNEL_X11_OPEN:
 519                 case SSH_CHANNEL_FREE:
 520                 default:
 521                         continue;
 522                 }
 523         }
 524 }
 525
 526 /* If there is data to send to the connection, send some of it now. */
 527
 528 void
 529 channel_output_poll()
 530 {
 531         int len, i;
 532         Channel *ch;
 533
 534         for (i = 0; i < channels_alloc; i++) {
 535                 ch = &channels[i];
 536                 /* We are only interested in channels that can have buffered incoming data. */
 537                 if (ch->type != SSH_CHANNEL_OPEN &&
 538                     ch->type != SSH_CHANNEL_INPUT_DRAINING)
 539                         continue;
 540
 541                 /* Get the amount of buffered data for this channel. */
 542                 len = buffer_len(&ch->input);
 543                 if (len > 0) {
 544                         /* Send some data for the other side over the secure connection. */
 545                         if (packet_is_interactive()) {
 546                                 if (len > 1024)
 547                                         len = 512;
 548                         } else {
 549                                 /* Keep the packets at reasonable size. */
 550                                 if (len > 16384)
 551                                         len = 16384;
 552                         }
 553                         packet_start(SSH_MSG_CHANNEL_DATA);
 554                         packet_put_int(ch->remote_id);
 555                         packet_put_string(buffer_ptr(&ch->input), len);
 556                         packet_send();
 557                         buffer_consume(&ch->input, len);
 558                 } else if (ch->istate == CHAN_INPUT_WAIT_DRAIN) {
 559                         if (compat13)
 560                                 fatal("cannot happen: istate == INPUT_WAIT_DRAIN for proto 1.3");
 561                         /*
 562                          * input-buffer is empty and read-socket shutdown:
 563                          * tell peer, that we will not send more data: send IEOF
 564                          */
 565                         chan_ibuf_empty(ch);
 566                 }
 567         }
 568 }
 569
 570 /*
 571  * This is called when a packet of type CHANNEL_DATA has just been received.
 572  * The message type has already been consumed, but channel number and data is
 573  * still there.
 574  */
 575
 576 void
 577 channel_input_data(int payload_len)
 578 {
 579         int channel;
 580         char *data;
 581         unsigned int data_len;
 582
 583         /* Get the channel number and verify it. */
 584         channel = packet_get_int();
 585         if (channel < 0 || channel >= channels_alloc ||
 586             channels[channel].type == SSH_CHANNEL_FREE)
 587                 packet_disconnect("Received data for nonexistent channel %d.", channel);
 588
 589         /* Ignore any data for non-open channels (might happen on close) */
 590         if (channels[channel].type != SSH_CHANNEL_OPEN &&
 591             channels[channel].type != SSH_CHANNEL_X11_OPEN)
 592                 return;
 593
 594         /* Get the data. */
 595         data = packet_get_string(&data_len);
 596         packet_integrity_check(payload_len, 4 + 4 + data_len, SSH_MSG_CHANNEL_DATA);
 597         buffer_append(&channels[channel].output, data, data_len);
 598         xfree(data);
 599 }
 600
 601 /*
 602  * Returns true if no channel has too much buffered data, and false if one or
 603  * more channel is overfull.
 604  */
 605
 606 int
 607 channel_not_very_much_buffered_data()
 608 {
 609         unsigned int i;
 610         Channel *ch;
 611
 612         for (i = 0; i < channels_alloc; i++) {
 613                 ch = &channels[i];
 614                 switch (ch->type) {
 615                 case SSH_CHANNEL_X11_LISTENER:
 616                 case SSH_CHANNEL_PORT_LISTENER:
 617                 case SSH_CHANNEL_AUTH_SOCKET:
 618                         continue;
 619                 case SSH_CHANNEL_OPEN:
 620                         if (buffer_len(&ch->input) > packet_get_maxsize())
 621                                 return 0;
 622                         if (buffer_len(&ch->output) > packet_get_maxsize())
 623                                 return 0;
 624                         continue;
 625                 case SSH_CHANNEL_INPUT_DRAINING:
 626                 case SSH_CHANNEL_OUTPUT_DRAINING:
 627                 case SSH_CHANNEL_X11_OPEN:
 628                 case SSH_CHANNEL_FREE:
 629                 default:
 630                         continue;
 631                 }
 632         }
 633         return 1;
 634 }
 635
 636 /* This is called after receiving CHANNEL_CLOSE/IEOF. */
 637
 638 void
 639 channel_input_close()
 640 {
 641         int channel;
 642
 643         /* Get the channel number and verify it. */
 644         channel = packet_get_int();
 645         if (channel < 0 || channel >= channels_alloc ||
 646             channels[channel].type == SSH_CHANNEL_FREE)
 647                 packet_disconnect("Received data for nonexistent channel %d.", channel);
 648
 649         if (!compat13) {
 650                 /* proto version 1.5 overloads CLOSE with IEOF */
 651                 chan_rcvd_ieof(&channels[channel]);
 652                 return;
 653         }
 654
 655         /*
 656          * Send a confirmation that we have closed the channel and no more
 657          * data is coming for it.
 658          */
 659         packet_start(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION);
 660         packet_put_int(channels[channel].remote_id);
 661         packet_send();
 662
 663         /*
 664          * If the channel is in closed state, we have sent a close request,
 665          * and the other side will eventually respond with a confirmation.
 666          * Thus, we cannot free the channel here, because then there would be
 667          * no-one to receive the confirmation.  The channel gets freed when
 668          * the confirmation arrives.
 669          */
 670         if (channels[channel].type != SSH_CHANNEL_CLOSED) {
 671                 /*
 672                  * Not a closed channel - mark it as draining, which will
 673                  * cause it to be freed later.
 674                  */
 675                 buffer_consume(&channels[channel].input,
 676                                buffer_len(&channels[channel].input));
 677                 channels[channel].type = SSH_CHANNEL_OUTPUT_DRAINING;
 678         }
 679 }
 680
 681 /* This is called after receiving CHANNEL_CLOSE_CONFIRMATION/OCLOSE. */
 682
 683 void
 684 channel_input_close_confirmation()
 685 {
 686         int channel;
 687
 688         /* Get the channel number and verify it. */
 689         channel = packet_get_int();
 690         if (channel < 0 || channel >= channels_alloc)
 691                 packet_disconnect("Received close confirmation for out-of-range channel %d.",
 692                                   channel);
 693
 694         if (!compat13) {
 695                 /* proto version 1.5 overloads CLOSE_CONFIRMATION with OCLOSE */
 696                 chan_rcvd_oclose(&channels[channel]);
 697                 return;
 698         }
 699         if (channels[channel].type != SSH_CHANNEL_CLOSED)
 700                 packet_disconnect("Received close confirmation for non-closed channel %d (type %d).",
 701                                   channel, channels[channel].type);
 702
 703         /* Free the channel. */
 704         channel_free(channel);
 705 }
 706
 707 /* This is called after receiving CHANNEL_OPEN_CONFIRMATION. */
 708
 709 void
 710 channel_input_open_confirmation()
 711 {
 712         int channel, remote_channel;
 713
 714         /* Get the channel number and verify it. */
 715         channel = packet_get_int();
 716         if (channel < 0 || channel >= channels_alloc ||
 717             channels[channel].type != SSH_CHANNEL_OPENING)
 718                 packet_disconnect("Received open confirmation for non-opening channel %d.",
 719                                   channel);
 720
 721         /* Get remote side's id for this channel. */
 722         remote_channel = packet_get_int();
 723
 724         /* Record the remote channel number and mark that the channel is now open. */
 725         channels[channel].remote_id = remote_channel;
 726         channels[channel].type = SSH_CHANNEL_OPEN;
 727 }
 728
 729 /* This is called after receiving CHANNEL_OPEN_FAILURE from the other side. */
 730
 731 void
 732 channel_input_open_failure()
 733 {
 734         int channel;
 735
 736         /* Get the channel number and verify it. */
 737         channel = packet_get_int();
 738         if (channel < 0 || channel >= channels_alloc ||
 739             channels[channel].type != SSH_CHANNEL_OPENING)
 740                 packet_disconnect("Received open failure for non-opening channel %d.",
 741                                   channel);
 742
 743         /* Free the channel.  This will also close the socket. */
 744         channel_free(channel);
 745 }
 746
 747 /*
 748  * Stops listening for channels, and removes any unix domain sockets that we
 749  * might have.
 750  */
 751
 752 void
 753 channel_stop_listening()
 754 {
 755         int i;
 756         for (i = 0; i < channels_alloc; i++) {
 757                 switch (channels[i].type) {
 758                 case SSH_CHANNEL_AUTH_SOCKET:
 759                         close(channels[i].sock);
 760                         remove(channels[i].path);
 761                         channel_free(i);
 762                         break;
 763                 case SSH_CHANNEL_PORT_LISTENER:
 764                 case SSH_CHANNEL_X11_LISTENER:
 765                         close(channels[i].sock);
 766                         channel_free(i);
 767                         break;
 768                 default:
 769                         break;
 770                 }
 771         }
 772 }
 773
 774 /*
 775  * Closes the sockets of all channels.  This is used to close extra file
 776  * descriptors after a fork.
 777  */
 778
 779 void
 780 channel_close_all()
 781 {
 782         int i;
 783         for (i = 0; i < channels_alloc; i++) {
 784                 if (channels[i].type != SSH_CHANNEL_FREE)
 785                         close(channels[i].sock);
 786         }
 787 }
 788
 789 /* Returns the maximum file descriptor number used by the channels. */
 790
 791 int
 792 channel_max_fd()
 793 {
 794         return channel_max_fd_value;
 795 }
 796
 797 /* Returns true if any channel is still open. */
 798
 799 int
 800 channel_still_open()
 801 {
 802         unsigned int i;
 803         for (i = 0; i < channels_alloc; i++)
 804                 switch (channels[i].type) {
 805                 case SSH_CHANNEL_FREE:
 806                 case SSH_CHANNEL_X11_LISTENER:
 807                 case SSH_CHANNEL_PORT_LISTENER:
 808                 case SSH_CHANNEL_CLOSED:
 809                 case SSH_CHANNEL_AUTH_SOCKET:
 810                         continue;
 811                 case SSH_CHANNEL_OPENING:
 812                 case SSH_CHANNEL_OPEN:
 813                 case SSH_CHANNEL_X11_OPEN:
 814                         return 1;
 815                 case SSH_CHANNEL_INPUT_DRAINING:
 816                 case SSH_CHANNEL_OUTPUT_DRAINING:
 817                         if (!compat13)
 818                                 fatal("cannot happen: OUT_DRAIN");
 819                         return 1;
 820                 default:
 821                         fatal("channel_still_open: bad channel type %d", channels[i].type);
 822                         /* NOTREACHED */
 823                 }
 824         return 0;
 825 }
 826
 827 /*
 828  * Returns a message describing the currently open forwarded connections,
 829  * suitable for sending to the client.  The message contains crlf pairs for
 830  * newlines.
 831  */
 832
 833 char *
 834 channel_open_message()
 835 {
 836         Buffer buffer;
 837         int i;
 838         char buf[512], *cp;
 839
 840         buffer_init(&buffer);
 841         snprintf(buf, sizeof buf, "The following connections are open:\r\n");
 842         buffer_append(&buffer, buf, strlen(buf));
 843         for (i = 0; i < channels_alloc; i++) {
 844                 Channel *c = &channels[i];
 845                 switch (c->type) {
 846                 case SSH_CHANNEL_FREE:
 847                 case SSH_CHANNEL_X11_LISTENER:
 848                 case SSH_CHANNEL_PORT_LISTENER:
 849                 case SSH_CHANNEL_CLOSED:
 850                 case SSH_CHANNEL_AUTH_SOCKET:
 851                         continue;
 852                 case SSH_CHANNEL_OPENING:
 853                 case SSH_CHANNEL_OPEN:
 854                 case SSH_CHANNEL_X11_OPEN:
 855                 case SSH_CHANNEL_INPUT_DRAINING:
 856                 case SSH_CHANNEL_OUTPUT_DRAINING:
 857                         snprintf(buf, sizeof buf, "  #%d %.300s (t%d r%d i%d o%d)\r\n",
 858                                  c->self, c->remote_name,
 859                                  c->type, c->remote_id, c->istate, c->ostate);
 860                         buffer_append(&buffer, buf, strlen(buf));
 861                         continue;
 862                 default:
 863                         fatal("channel_still_open: bad channel type %d", c->type);
 864                         /* NOTREACHED */
 865                 }
 866         }
 867         buffer_append(&buffer, "\0", 1);
 868         cp = xstrdup(buffer_ptr(&buffer));
 869         buffer_free(&buffer);
 870         return cp;
 871 }
 872
 873 /*
 874  * Initiate forwarding of connections to local port "port" through the secure
 875  * channel to host:port from remote side.
 876  */
 877
 878 void
 879 channel_request_local_forwarding(u_short port, const char *host,
 880                                  u_short host_port, int gateway_ports)
 881 {
 882         int ch, sock, on = 1;
 883         struct sockaddr_in sin;
 884         struct linger linger;
 885
 886         if (strlen(host) > sizeof(channels[0].path) - 1)
 887                 packet_disconnect("Forward host name too long.");
 888
 889         /* Create a port to listen for the host. */
 890         sock = socket(AF_INET, SOCK_STREAM, 0);
 891         if (sock < 0)
 892                 packet_disconnect("socket: %.100s", strerror(errno));
 893
 894         /* Initialize socket address. */
 895         memset(&sin, 0, sizeof(sin));
 896         sin.sin_family = AF_INET;
 897         if (gateway_ports == 1)
 898                 sin.sin_addr.s_addr = htonl(INADDR_ANY);
 899         else
 900                 sin.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
 901         sin.sin_port = htons(port);
 902
 903         /*
 904          * Set socket options.  We would like the socket to disappear as soon
 905          * as it has been closed for whatever reason.
 906          */
 907         setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on));
 908         linger.l_onoff = 1;
 909         linger.l_linger = 5;
 910         setsockopt(sock, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
 911
 912         /* Bind the socket to the address. */
 913         if (bind(sock, (struct sockaddr *) & sin, sizeof(sin)) < 0)
 914                 packet_disconnect("bind: %.100s", strerror(errno));
 915
 916         /* Start listening for connections on the socket. */
 917         if (listen(sock, 5) < 0)
 918                 packet_disconnect("listen: %.100s", strerror(errno));
 919
 920         /* Allocate a channel number for the socket. */
 921         ch = channel_allocate(SSH_CHANNEL_PORT_LISTENER, sock,
 922                               xstrdup("port listener"));
 923         strlcpy(channels[ch].path, host, sizeof(channels[ch].path));
 924         channels[ch].host_port = host_port;
 925         channels[ch].listening_port = port;
 926 }
 927
 928 /*
 929  * Initiate forwarding of connections to port "port" on remote host through
 930  * the secure channel to host:port from local side.
 931  */
 932
 933 void
 934 channel_request_remote_forwarding(u_short port, const char *host,
 935                                   u_short remote_port)
 936 {
 937         int payload_len;
 938         /* Record locally that connection to this host/port is permitted. */
 939         if (num_permitted_opens >= SSH_MAX_FORWARDS_PER_DIRECTION)
 940                 fatal("channel_request_remote_forwarding: too many forwards");
 941
 942         permitted_opens[num_permitted_opens].host = xstrdup(host);
 943         permitted_opens[num_permitted_opens].port = remote_port;
 944         num_permitted_opens++;
 945
 946         /* Send the forward request to the remote side. */
 947         packet_start(SSH_CMSG_PORT_FORWARD_REQUEST);
 948         packet_put_int(port);
 949         packet_put_string(host, strlen(host));
 950         packet_put_int(remote_port);
 951         packet_send();
 952         packet_write_wait();
 953
 954         /*
 955          * Wait for response from the remote side.  It will send a disconnect
 956          * message on failure, and we will never see it here.
 957          */
 958         packet_read_expect(&payload_len, SSH_SMSG_SUCCESS);
 959 }
 960
 961 /*
 962  * This is called after receiving CHANNEL_FORWARDING_REQUEST.  This initates
 963  * listening for the port, and sends back a success reply (or disconnect
 964  * message if there was an error).  This never returns if there was an error.
 965  */
 966
 967 void
 968 channel_input_port_forward_request(int is_root)
 969 {
 970         u_short port, host_port;
 971         char *hostname;
 972
 973         /* Get arguments from the packet. */
 974         port = packet_get_int();
 975         hostname = packet_get_string(NULL);
 976         host_port = packet_get_int();
 977
 978         /*
 979          * Check that an unprivileged user is not trying to forward a
 980          * privileged port.
 981          */
 982         if (port < IPPORT_RESERVED && !is_root)
 983                 packet_disconnect("Requested forwarding of port %d but user is not root.",
 984                                   port);
 985         /*
 986          * Initiate forwarding,
 987          * bind port to localhost only (gateway ports == 0).
 988          */
 989         channel_request_local_forwarding(port, hostname, host_port, 0);
 990
 991         /* Free the argument string. */
 992         xfree(hostname);
 993 }
 994
 995 /*
 996  * This is called after receiving PORT_OPEN message.  This attempts to
 997  * connect to the given host:port, and sends back CHANNEL_OPEN_CONFIRMATION
 998  * or CHANNEL_OPEN_FAILURE.
 999  */
1000
1001 void
1002 channel_input_port_open(int payload_len)
1003 {
1004         int remote_channel, sock, newch, i;
1005         u_short host_port;
1006         struct sockaddr_in sin;
1007         char *host, *originator_string;
1008         struct hostent *hp;
1009         int host_len, originator_len;
1010
1011         /* Get remote channel number. */
1012         remote_channel = packet_get_int();
1013
1014         /* Get host name to connect to. */
1015         host = packet_get_string(&host_len);
1016
1017         /* Get port to connect to. */
1018         host_port = packet_get_int();
1019
1020         /* Get remote originator name. */
1021         if (have_hostname_in_open) {
1022                 originator_string = packet_get_string(&originator_len);
1023                 originator_len += 4;    /* size of packet_int */
1024         } else {
1025                 originator_string = xstrdup("unknown (remote did not supply name)");
1026                 originator_len = 0;     /* no originator supplied */
1027         }
1028
1029         packet_integrity_check(payload_len,
1030                                4 + 4 + host_len + 4 + originator_len,
1031                                SSH_MSG_PORT_OPEN);
1032
1033         /* Check if opening that port is permitted. */
1034         if (!all_opens_permitted) {
1035                 /* Go trough all permitted ports. */
1036                 for (i = 0; i < num_permitted_opens; i++)
1037                         if (permitted_opens[i].port == host_port &&
1038                             strcmp(permitted_opens[i].host, host) == 0)
1039                                 break;
1040
1041                 /* Check if we found the requested port among those permitted. */
1042                 if (i >= num_permitted_opens) {
1043                         /* The port is not permitted. */
1044                         log("Received request to connect to %.100s:%d, but the request was denied.",
1045                             host, host_port);
1046                         packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
1047                         packet_put_int(remote_channel);
1048                         packet_send();
1049                 }
1050         }
1051         memset(&sin, 0, sizeof(sin));
1052         sin.sin_addr.s_addr = inet_addr(host);
1053         if ((sin.sin_addr.s_addr & 0xffffffff) != 0xffffffff) {
1054                 /* It was a valid numeric host address. */
1055                 sin.sin_family = AF_INET;
1056         } else {
1057                 /* Look up the host address from the name servers. */
1058                 hp = gethostbyname(host);
1059                 if (!hp) {
1060                         error("%.100s: unknown host.", host);
1061                         goto fail;
1062                 }
1063                 if (!hp->h_addr_list[0]) {
1064                         error("%.100s: host has no IP address.", host);
1065                         goto fail;
1066                 }
1067                 sin.sin_family = hp->h_addrtype;
1068                 memcpy(&sin.sin_addr, hp->h_addr_list[0],
1069                        sizeof(sin.sin_addr));
1070         }
1071         sin.sin_port = htons(host_port);
1072
1073         /* Create the socket. */
1074         sock = socket(sin.sin_family, SOCK_STREAM, 0);
1075         if (sock < 0) {
1076                 error("socket: %.100s", strerror(errno));
1077                 goto fail;
1078         }
1079         /* Connect to the host/port. */
1080         if (connect(sock, (struct sockaddr *) & sin, sizeof(sin)) < 0) {
1081                 error("connect %.100s:%d: %.100s", host, host_port,
1082                       strerror(errno));
1083                 close(sock);
1084                 goto fail;
1085         }
1086         /* Successful connection. */
1087
1088         /* Allocate a channel for this connection. */
1089         newch = channel_allocate(SSH_CHANNEL_OPEN, sock, originator_string);
1090         channels[newch].remote_id = remote_channel;
1091
1092         /* Send a confirmation to the remote host. */
1093         packet_start(SSH_MSG_CHANNEL_OPEN_CONFIRMATION);
1094         packet_put_int(remote_channel);
1095         packet_put_int(newch);
1096         packet_send();
1097
1098         /* Free the argument string. */
1099         xfree(host);
1100
1101         return;
1102
1103 fail:
1104         /* Free the argument string. */
1105         xfree(host);
1106
1107         /* Send refusal to the remote host. */
1108         packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
1109         packet_put_int(remote_channel);
1110         packet_send();
1111 }
1112
1113 /*
1114  * Creates an internet domain socket for listening for X11 connections.
1115  * Returns a suitable value for the DISPLAY variable, or NULL if an error
1116  * occurs.
1117  */
1118
1119 char *
1120 x11_create_display_inet(int screen_number, int x11_display_offset)
1121 {
1122         int display_number, sock;
1123         u_short port;
1124         struct sockaddr_in sin;
1125         char buf[512];
1126         char hostname[MAXHOSTNAMELEN];
1127
1128         for (display_number = x11_display_offset;
1129              display_number < MAX_DISPLAYS;
1130              display_number++) {
1131                 port = 6000 + display_number;
1132                 memset(&sin, 0, sizeof(sin));
1133                 sin.sin_family = AF_INET;
1134                 sin.sin_addr.s_addr = htonl(INADDR_ANY);
1135                 sin.sin_port = htons(port);
1136
1137                 sock = socket(AF_INET, SOCK_STREAM, 0);
1138                 if (sock < 0) {
1139                         error("socket: %.100s", strerror(errno));
1140                         return NULL;
1141                 }
1142                 if (bind(sock, (struct sockaddr *) & sin, sizeof(sin)) < 0) {
1143                         debug("bind port %d: %.100s", port, strerror(errno));
1144                         shutdown(sock, SHUT_RDWR);
1145                         close(sock);
1146                         continue;
1147                 }
1148                 break;
1149         }
1150         if (display_number >= MAX_DISPLAYS) {
1151                 error("Failed to allocate internet-domain X11 display socket.");
1152                 return NULL;
1153         }
1154         /* Start listening for connections on the socket. */
1155         if (listen(sock, 5) < 0) {
1156                 error("listen: %.100s", strerror(errno));
1157                 shutdown(sock, SHUT_RDWR);
1158                 close(sock);
1159                 return NULL;
1160         }
1161         /* Set up a suitable value for the DISPLAY variable. */
1162
1163         if (gethostname(hostname, sizeof(hostname)) < 0)
1164                 fatal("gethostname: %.100s", strerror(errno));
1165
1166 #ifdef IPADDR_IN_DISPLAY
1167         /*
1168          * HPUX detects the local hostname in the DISPLAY variable and tries
1169          * to set up a shared memory connection to the server, which it
1170          * incorrectly supposes to be local.
1171          *
1172          * The workaround - as used in later $$H and other programs - is
1173          * is to set display to the host's IP address.
1174          */
1175         {
1176                 struct hostent *he;
1177                 struct in_addr my_addr;
1178
1179                 he = gethostbyname(hostname);
1180                 if (he == NULL) {
1181                         error("[X11-broken-fwd-hostname-workaround] Could not get "
1182                                 "IP address for hostname %s.", hostname);
1183
1184                         packet_send_debug("[X11-broken-fwd-hostname-workaround]"
1185                                 "Could not get IP address for hostname %s.", hostname);
1186
1187                         shutdown(sock, SHUT_RDWR);
1188                         close(sock);
1189
1190                         return NULL;
1191                 }
1192
1193                 memcpy(&my_addr, he->h_addr_list[0], sizeof(struct in_addr));
1194
1195                 /* Set DISPLAY to <ip address>:screen.display */
1196                 snprintf(buf, sizeof(buf), "%.50s:%d.%d", inet_ntoa(my_addr),
1197                         display_number, screen_number);
1198         }
1199 #else /* IPADDR_IN_DISPLAY */
1200         /* Just set DISPLAY to hostname:screen.display */
1201         snprintf(buf, sizeof buf, "%.400s:%d.%d", hostname,
1202                 display_number, screen_number);
1203 #endif /* IPADDR_IN_DISPLAY */
1204
1205         /* Allocate a channel for the socket. */
1206         (void) channel_allocate(SSH_CHANNEL_X11_LISTENER, sock,
1207                                 xstrdup("X11 inet listener"));
1208
1209         /* Return a suitable value for the DISPLAY environment variable. */
1210         return xstrdup(buf);
1211 }
1212
1213 #ifndef X_UNIX_PATH
1214 #define X_UNIX_PATH "/tmp/.X11-unix/X"
1215 #endif
1216
1217 static
1218 int
1219 connect_local_xsocket(unsigned int dnr)
1220 {
1221         static const char *const x_sockets[] = {
1222                 X_UNIX_PATH "%u",
1223                 "/var/X/.X11-unix/X" "%u",
1224                 "/usr/spool/sockets/X11/" "%u",
1225                 NULL
1226         };
1227         int sock;
1228         struct sockaddr_un addr;
1229         const char *const * path;
1230
1231         for (path = x_sockets; *path; ++path) {
1232                 sock = socket(AF_UNIX, SOCK_STREAM, 0);
1233                 if (sock < 0)
1234                         error("socket: %.100s", strerror(errno));
1235                 memset(&addr, 0, sizeof(addr));
1236                 addr.sun_family = AF_UNIX;
1237                 snprintf(addr.sun_path, sizeof addr.sun_path, *path, dnr);
1238                 if (connect(sock, (struct sockaddr *) & addr, sizeof(addr)) == 0)
1239                         return sock;
1240                 close(sock);
1241         }
1242         error("connect %.100s: %.100s", addr.sun_path, strerror(errno));
1243         return -1;
1244 }
1245
1246
1247 /*
1248  * This is called when SSH_SMSG_X11_OPEN is received.  The packet contains
1249  * the remote channel number.  We should do whatever we want, and respond
1250  * with either SSH_MSG_OPEN_CONFIRMATION or SSH_MSG_OPEN_FAILURE.
1251  */
1252
1253 void
1254 x11_input_open(int payload_len)
1255 {
1256         int remote_channel, display_number, sock, newch;
1257         const char *display;
1258         struct sockaddr_in sin;
1259         char buf[1024], *cp, *remote_host;
1260         struct hostent *hp;
1261         int remote_len;
1262
1263         /* Get remote channel number. */
1264         remote_channel = packet_get_int();
1265
1266         /* Get remote originator name. */
1267         if (have_hostname_in_open) {
1268                 remote_host = packet_get_string(&remote_len);
1269                 remote_len += 4;
1270         } else {
1271                 remote_host = xstrdup("unknown (remote did not supply name)");
1272                 remote_len = 0;
1273         }
1274
1275         debug("Received X11 open request.");
1276         packet_integrity_check(payload_len, 4 + remote_len, SSH_SMSG_X11_OPEN);
1277
1278         /* Try to open a socket for the local X server. */
1279         display = getenv("DISPLAY");
1280         if (!display) {
1281                 error("DISPLAY not set.");
1282                 goto fail;
1283         }
1284         /*
1285          * Now we decode the value of the DISPLAY variable and make a
1286          * connection to the real X server.
1287          */
1288
1289         /*
1290          * Check if it is a unix domain socket.  Unix domain displays are in
1291          * one of the following formats: unix:d[.s], :d[.s], ::d[.s]
1292          */
1293         if (strncmp(display, "unix:", 5) == 0 ||
1294             display[0] == ':') {
1295                 /* Connect to the unix domain socket. */
1296                 if (sscanf(strrchr(display, ':') + 1, "%d", &display_number) != 1) {
1297                         error("Could not parse display number from DISPLAY: %.100s",
1298                               display);
1299                         goto fail;
1300                 }
1301                 /* Create a socket. */
1302                 sock = connect_local_xsocket(display_number);
1303                 if (sock < 0)
1304                         goto fail;
1305
1306                 /* OK, we now have a connection to the display. */
1307                 goto success;
1308         }
1309         /*
1310          * Connect to an inet socket.  The DISPLAY value is supposedly
1311          * hostname:d[.s], where hostname may also be numeric IP address.
1312          */
1313         strncpy(buf, display, sizeof(buf));
1314         buf[sizeof(buf) - 1] = 0;
1315         cp = strchr(buf, ':');
1316         if (!cp) {
1317                 error("Could not find ':' in DISPLAY: %.100s", display);
1318                 goto fail;
1319         }
1320         *cp = 0;
1321         /* buf now contains the host name.  But first we parse the display number. */
1322         if (sscanf(cp + 1, "%d", &display_number) != 1) {
1323                 error("Could not parse display number from DISPLAY: %.100s",
1324                       display);
1325                 goto fail;
1326         }
1327         /* Try to parse the host name as a numeric IP address. */
1328         memset(&sin, 0, sizeof(sin));
1329         sin.sin_addr.s_addr = inet_addr(buf);
1330         if ((sin.sin_addr.s_addr & 0xffffffff) != 0xffffffff) {
1331                 /* It was a valid numeric host address. */
1332                 sin.sin_family = AF_INET;
1333         } else {
1334                 /* Not a numeric IP address. */
1335                 /* Look up the host address from the name servers. */
1336                 hp = gethostbyname(buf);
1337                 if (!hp) {
1338                         error("%.100s: unknown host.", buf);
1339                         goto fail;
1340                 }
1341                 if (!hp->h_addr_list[0]) {
1342                         error("%.100s: host has no IP address.", buf);
1343                         goto fail;
1344                 }
1345                 sin.sin_family = hp->h_addrtype;
1346                 memcpy(&sin.sin_addr, hp->h_addr_list[0],
1347                        sizeof(sin.sin_addr));
1348         }
1349         /* Set port number. */
1350         sin.sin_port = htons(6000 + display_number);
1351
1352         /* Create a socket. */
1353         sock = socket(sin.sin_family, SOCK_STREAM, 0);
1354         if (sock < 0) {
1355                 error("socket: %.100s", strerror(errno));
1356                 goto fail;
1357         }
1358         /* Connect it to the display. */
1359         if (connect(sock, (struct sockaddr *) & sin, sizeof(sin)) < 0) {
1360                 error("connect %.100s:%d: %.100s", buf, 6000 + display_number,
1361                       strerror(errno));
1362                 close(sock);
1363                 goto fail;
1364         }
1365 success:
1366         /* We have successfully obtained a connection to the real X display. */
1367
1368         /* Allocate a channel for this connection. */
1369         if (x11_saved_proto == NULL)
1370                 newch = channel_allocate(SSH_CHANNEL_OPEN, sock, remote_host);
1371         else
1372                 newch = channel_allocate(SSH_CHANNEL_X11_OPEN, sock, remote_host);
1373         channels[newch].remote_id = remote_channel;
1374
1375         /* Send a confirmation to the remote host. */
1376         packet_start(SSH_MSG_CHANNEL_OPEN_CONFIRMATION);
1377         packet_put_int(remote_channel);
1378         packet_put_int(newch);
1379         packet_send();
1380
1381         return;
1382
1383 fail:
1384         /* Send refusal to the remote host. */
1385         packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
1386         packet_put_int(remote_channel);
1387         packet_send();
1388 }
1389
1390 /*
1391  * Requests forwarding of X11 connections, generates fake authentication
1392  * data, and enables authentication spoofing.
1393  */
1394
1395 void
1396 x11_request_forwarding_with_spoofing(const char *proto, const char *data)
1397 {
1398         unsigned int data_len = (unsigned int) strlen(data) / 2;
1399         unsigned int i, value;
1400         char *new_data;
1401         int screen_number;
1402         const char *cp;
1403         u_int32_t rand = 0;
1404
1405         cp = getenv("DISPLAY");
1406         if (cp)
1407                 cp = strchr(cp, ':');
1408         if (cp)
1409                 cp = strchr(cp, '.');
1410         if (cp)
1411                 screen_number = atoi(cp + 1);
1412         else
1413                 screen_number = 0;
1414
1415         /* Save protocol name. */
1416         x11_saved_proto = xstrdup(proto);
1417
1418         /*
1419          * Extract real authentication data and generate fake data of the
1420          * same length.
1421          */
1422         x11_saved_data = xmalloc(data_len);
1423         x11_fake_data = xmalloc(data_len);
1424         for (i = 0; i < data_len; i++) {
1425                 if (sscanf(data + 2 * i, "%2x", &value) != 1)
1426                         fatal("x11_request_forwarding: bad authentication data: %.100s", data);
1427                 if (i % 4 == 0)
1428                         rand = arc4random();
1429                 x11_saved_data[i] = value;
1430                 x11_fake_data[i] = rand & 0xff;
1431                 rand >>= 8;
1432         }
1433         x11_saved_data_len = data_len;
1434         x11_fake_data_len = data_len;
1435
1436         /* Convert the fake data into hex. */
1437         new_data = xmalloc(2 * data_len + 1);
1438         for (i = 0; i < data_len; i++)
1439                 sprintf(new_data + 2 * i, "%02x", (unsigned char) x11_fake_data[i]);
1440
1441         /* Send the request packet. */
1442         packet_start(SSH_CMSG_X11_REQUEST_FORWARDING);
1443         packet_put_string(proto, strlen(proto));
1444         packet_put_string(new_data, strlen(new_data));
1445         packet_put_int(screen_number);
1446         packet_send();
1447         packet_write_wait();
1448         xfree(new_data);
1449 }
1450
1451 /* Sends a message to the server to request authentication fd forwarding. */
1452
1453 void
1454 auth_request_forwarding()
1455 {
1456         packet_start(SSH_CMSG_AGENT_REQUEST_FORWARDING);
1457         packet_send();
1458         packet_write_wait();
1459 }
1460
1461 /*
1462  * Returns the name of the forwarded authentication socket.  Returns NULL if
1463  * there is no forwarded authentication socket.  The returned value points to
1464  * a static buffer.
1465  */
1466
1467 char *
1468 auth_get_socket_name()
1469 {
1470         return channel_forwarded_auth_socket_name;
1471 }
1472
1473 /* removes the agent forwarding socket */
1474
1475 void
1476 cleanup_socket(void)
1477 {
1478         remove(channel_forwarded_auth_socket_name);
1479         rmdir(channel_forwarded_auth_socket_dir);
1480 }
1481
1482 /*
1483  * This if called to process SSH_CMSG_AGENT_REQUEST_FORWARDING on the server.
1484  * This starts forwarding authentication requests.
1485  */
1486
1487 void
1488 auth_input_request_forwarding(struct passwd * pw)
1489 {
1490         int sock, newch;
1491         struct sockaddr_un sunaddr;
1492
1493         if (auth_get_socket_name() != NULL)
1494                 fatal("Protocol error: authentication forwarding requested twice.");
1495
1496         /* Temporarily drop privileged uid for mkdir/bind. */
1497         temporarily_use_uid(pw->pw_uid);
1498
1499         /* Allocate a buffer for the socket name, and format the name. */
1500         channel_forwarded_auth_socket_name = xmalloc(MAX_SOCKET_NAME);
1501         channel_forwarded_auth_socket_dir = xmalloc(MAX_SOCKET_NAME);
1502         strlcpy(channel_forwarded_auth_socket_dir, "/tmp/ssh-XXXXXXXX", MAX_SOCKET_NAME);
1503
1504         /* Create private directory for socket */
1505         if (mkdtemp(channel_forwarded_auth_socket_dir) == NULL)
1506                 packet_disconnect("mkdtemp: %.100s", strerror(errno));
1507         snprintf(channel_forwarded_auth_socket_name, MAX_SOCKET_NAME, "%s/agent.%d",
1508                  channel_forwarded_auth_socket_dir, (int) getpid());
1509
1510         if (atexit(cleanup_socket) < 0) {
1511                 int saved = errno;
1512                 cleanup_socket();
1513                 packet_disconnect("socket: %.100s", strerror(saved));
1514         }
1515         /* Create the socket. */
1516         sock = socket(AF_UNIX, SOCK_STREAM, 0);
1517         if (sock < 0)
1518                 packet_disconnect("socket: %.100s", strerror(errno));
1519
1520         /* Bind it to the name. */
1521         memset(&sunaddr, 0, sizeof(sunaddr));
1522         sunaddr.sun_family = AF_UNIX;
1523         strncpy(sunaddr.sun_path, channel_forwarded_auth_socket_name,
1524                 sizeof(sunaddr.sun_path));
1525
1526         if (bind(sock, (struct sockaddr *) & sunaddr, sizeof(sunaddr)) < 0)
1527                 packet_disconnect("bind: %.100s", strerror(errno));
1528
1529         /* Restore the privileged uid. */
1530         restore_uid();
1531
1532         /* Start listening on the socket. */
1533         if (listen(sock, 5) < 0)
1534                 packet_disconnect("listen: %.100s", strerror(errno));
1535
1536         /* Allocate a channel for the authentication agent socket. */
1537         newch = channel_allocate(SSH_CHANNEL_AUTH_SOCKET, sock,
1538                                  xstrdup("auth socket"));
1539         strlcpy(channels[newch].path, channel_forwarded_auth_socket_name,
1540             sizeof(channels[newch].path));
1541 }
1542
1543 /* This is called to process an SSH_SMSG_AGENT_OPEN message. */
1544
1545 void
1546 auth_input_open_request()
1547 {
1548         int remch, sock, newch;
1549         char *dummyname;
1550
1551         /* Read the remote channel number from the message. */
1552         remch = packet_get_int();
1553
1554         /*
1555          * Get a connection to the local authentication agent (this may again
1556          * get forwarded).
1557          */
1558         sock = ssh_get_authentication_socket();
1559
1560         /*
1561          * If we could not connect the agent, send an error message back to
1562          * the server. This should never happen unless the agent dies,
1563          * because authentication forwarding is only enabled if we have an
1564          * agent.
1565          */
1566         if (sock < 0) {
1567                 packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
1568                 packet_put_int(remch);
1569                 packet_send();
1570                 return;
1571         }
1572         debug("Forwarding authentication connection.");
1573
1574         /*
1575          * Dummy host name.  This will be freed when the channel is freed; it
1576          * will still be valid in the packet_put_string below since the
1577          * channel cannot yet be freed at that point.
1578          */
1579         dummyname = xstrdup("authentication agent connection");
1580
1581         newch = channel_allocate(SSH_CHANNEL_OPEN, sock, dummyname);
1582         channels[newch].remote_id = remch;
1583
1584         /* Send a confirmation to the remote host. */
1585         packet_start(SSH_MSG_CHANNEL_OPEN_CONFIRMATION);
1586         packet_put_int(remch);
1587         packet_put_int(newch);
1588         packet_send();
1589 }