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 newsock, i, newch, len;
 378         socklen_t addrlen;
 379         Channel *ch;
 380         char buf[16384], *remote_hostname;
 381
 382         /* Loop over all channels... */
 383         for (i = 0; i < channels_alloc; i++) {
 384                 ch = &channels[i];
 385                 switch (ch->type) {
 386                 case SSH_CHANNEL_X11_LISTENER:
 387                         /* This is our fake X11 server socket. */
 388                         if (FD_ISSET(ch->sock, readset)) {
 389                                 debug("X11 connection requested.");
 390                                 addrlen = sizeof(addr);
 391                                 newsock = accept(ch->sock, &addr, &addrlen);
 392                                 if (newsock < 0) {
 393                                         error("accept: %.100s", strerror(errno));
 394                                         break;
 395                                 }
 396                                 remote_hostname = get_remote_hostname(newsock);
 397                                 snprintf(buf, sizeof buf, "X11 connection from %.200s port %d",
 398                                 remote_hostname, get_peer_port(newsock));
 399                                 xfree(remote_hostname);
 400                                 newch = channel_allocate(SSH_CHANNEL_OPENING, newsock,
 401                                                          xstrdup(buf));
 402                                 packet_start(SSH_SMSG_X11_OPEN);
 403                                 packet_put_int(newch);
 404                                 if (have_hostname_in_open)
 405                                         packet_put_string(buf, strlen(buf));
 406                                 packet_send();
 407                         }
 408                         break;
 409
 410                 case SSH_CHANNEL_PORT_LISTENER:
 411                         /*
 412                          * This socket is listening for connections to a
 413                          * forwarded TCP/IP port.
 414                          */
 415                         if (FD_ISSET(ch->sock, readset)) {
 416                                 debug("Connection to port %d forwarding to %.100s port %d requested.",
 417                                       ch->listening_port, ch->path, ch->host_port);
 418                                 addrlen = sizeof(addr);
 419                                 newsock = accept(ch->sock, &addr, &addrlen);
 420                                 if (newsock < 0) {
 421                                         error("accept: %.100s", strerror(errno));
 422                                         break;
 423                                 }
 424                                 remote_hostname = get_remote_hostname(newsock);
 425                                 snprintf(buf, sizeof buf, "listen port %d for %.100s port %d, connect from %.200s port %d",
 426                                          ch->listening_port, ch->path, ch->host_port,
 427                                 remote_hostname, get_peer_port(newsock));
 428                                 xfree(remote_hostname);
 429                                 newch = channel_allocate(SSH_CHANNEL_OPENING, newsock,
 430                                                          xstrdup(buf));
 431                                 packet_start(SSH_MSG_PORT_OPEN);
 432                                 packet_put_int(newch);
 433                                 packet_put_string(ch->path, strlen(ch->path));
 434                                 packet_put_int(ch->host_port);
 435                                 if (have_hostname_in_open)
 436                                         packet_put_string(buf, strlen(buf));
 437                                 packet_send();
 438                         }
 439                         break;
 440
 441                 case SSH_CHANNEL_AUTH_SOCKET:
 442                         /*
 443                          * This is the authentication agent socket listening
 444                          * for connections from clients.
 445                          */
 446                         if (FD_ISSET(ch->sock, readset)) {
 447                                 addrlen = sizeof(addr);
 448                                 newsock = accept(ch->sock, &addr, &addrlen);
 449                                 if (newsock < 0) {
 450                                         error("accept from auth socket: %.100s", strerror(errno));
 451                                         break;
 452                                 }
 453                                 newch = channel_allocate(SSH_CHANNEL_OPENING, newsock,
 454                                         xstrdup("accepted auth socket"));
 455                                 packet_start(SSH_SMSG_AGENT_OPEN);
 456                                 packet_put_int(newch);
 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
 537                 /* We are only interested in channels that can have buffered incoming data. */
 538                 if (compat13) {
 539                         if (ch->type != SSH_CHANNEL_OPEN &&
 540                             ch->type != SSH_CHANNEL_INPUT_DRAINING)
 541                                 continue;
 542                 } else {
 543                         if (ch->type != SSH_CHANNEL_OPEN)
 544                                 continue;
 545                         if (ch->istate != CHAN_INPUT_OPEN &&
 546                             ch->istate != CHAN_INPUT_WAIT_DRAIN)
 547                                 continue;
 548                 }
 549
 550                 /* Get the amount of buffered data for this channel. */
 551                 len = buffer_len(&ch->input);
 552                 if (len > 0) {
 553                         /* Send some data for the other side over the secure connection. */
 554                         if (packet_is_interactive()) {
 555                                 if (len > 1024)
 556                                         len = 512;
 557                         } else {
 558                                 /* Keep the packets at reasonable size. */
 559                                 if (len > packet_get_maxsize()/2)
 560                                         len = packet_get_maxsize()/2;
 561                         }
 562                         packet_start(SSH_MSG_CHANNEL_DATA);
 563                         packet_put_int(ch->remote_id);
 564                         packet_put_string(buffer_ptr(&ch->input), len);
 565                         packet_send();
 566                         buffer_consume(&ch->input, len);
 567                 } else if (ch->istate == CHAN_INPUT_WAIT_DRAIN) {
 568                         if (compat13)
 569                                 fatal("cannot happen: istate == INPUT_WAIT_DRAIN for proto 1.3");
 570                         /*
 571                          * input-buffer is empty and read-socket shutdown:
 572                          * tell peer, that we will not send more data: send IEOF
 573                          */
 574                         chan_ibuf_empty(ch);
 575                 }
 576         }
 577 }
 578
 579 /*
 580  * This is called when a packet of type CHANNEL_DATA has just been received.
 581  * The message type has already been consumed, but channel number and data is
 582  * still there.
 583  */
 584
 585 void
 586 channel_input_data(int payload_len)
 587 {
 588         int id;
 589         char *data;
 590         unsigned int data_len;
 591         Channel *ch;
 592
 593         /* Get the channel number and verify it. */
 594         id = packet_get_int();
 595         if (id < 0 || id >= channels_alloc)
 596                 packet_disconnect("Received data for nonexistent channel %d.", id);
 597         ch = &channels[id];
 598
 599         if (ch->type == SSH_CHANNEL_FREE)
 600                 packet_disconnect("Received data for free channel %d.", ch->self);
 601
 602         /* Ignore any data for non-open channels (might happen on close) */
 603         if (ch->type != SSH_CHANNEL_OPEN &&
 604             ch->type != SSH_CHANNEL_X11_OPEN)
 605                 return;
 606
 607         /* same for protocol 1.5 if output end is no longer open */
 608         if (!compat13 && ch->ostate != CHAN_OUTPUT_OPEN)
 609                 return;
 610
 611         /* Get the data. */
 612         data = packet_get_string(&data_len);
 613         packet_integrity_check(payload_len, 4 + 4 + data_len, SSH_MSG_CHANNEL_DATA);
 614         buffer_append(&ch->output, data, data_len);
 615         xfree(data);
 616 }
 617
 618 /*
 619  * Returns true if no channel has too much buffered data, and false if one or
 620  * more channel is overfull.
 621  */
 622
 623 int
 624 channel_not_very_much_buffered_data()
 625 {
 626         unsigned int i;
 627         Channel *ch;
 628
 629         for (i = 0; i < channels_alloc; i++) {
 630                 ch = &channels[i];
 631                 if (ch->type == SSH_CHANNEL_OPEN) {
 632                         if (buffer_len(&ch->input) > packet_get_maxsize())
 633                                 return 0;
 634                         if (buffer_len(&ch->output) > packet_get_maxsize())
 635                                 return 0;
 636                 }
 637         }
 638         return 1;
 639 }
 640
 641 /* This is called after receiving CHANNEL_CLOSE/IEOF. */
 642
 643 void
 644 channel_input_close()
 645 {
 646         int channel;
 647
 648         /* Get the channel number and verify it. */
 649         channel = packet_get_int();
 650         if (channel < 0 || channel >= channels_alloc ||
 651             channels[channel].type == SSH_CHANNEL_FREE)
 652                 packet_disconnect("Received data for nonexistent channel %d.", channel);
 653
 654         if (!compat13) {
 655                 /* proto version 1.5 overloads CLOSE with IEOF */
 656                 chan_rcvd_ieof(&channels[channel]);
 657                 return;
 658         }
 659
 660         /*
 661          * Send a confirmation that we have closed the channel and no more
 662          * data is coming for it.
 663          */
 664         packet_start(SSH_MSG_CHANNEL_CLOSE_CONFIRMATION);
 665         packet_put_int(channels[channel].remote_id);
 666         packet_send();
 667
 668         /*
 669          * If the channel is in closed state, we have sent a close request,
 670          * and the other side will eventually respond with a confirmation.
 671          * Thus, we cannot free the channel here, because then there would be
 672          * no-one to receive the confirmation.  The channel gets freed when
 673          * the confirmation arrives.
 674          */
 675         if (channels[channel].type != SSH_CHANNEL_CLOSED) {
 676                 /*
 677                  * Not a closed channel - mark it as draining, which will
 678                  * cause it to be freed later.
 679                  */
 680                 buffer_consume(&channels[channel].input,
 681                                buffer_len(&channels[channel].input));
 682                 channels[channel].type = SSH_CHANNEL_OUTPUT_DRAINING;
 683         }
 684 }
 685
 686 /* This is called after receiving CHANNEL_CLOSE_CONFIRMATION/OCLOSE. */
 687
 688 void
 689 channel_input_close_confirmation()
 690 {
 691         int channel;
 692
 693         /* Get the channel number and verify it. */
 694         channel = packet_get_int();
 695         if (channel < 0 || channel >= channels_alloc)
 696                 packet_disconnect("Received close confirmation for out-of-range channel %d.",
 697                                   channel);
 698
 699         if (!compat13) {
 700                 /* proto version 1.5 overloads CLOSE_CONFIRMATION with OCLOSE */
 701                 chan_rcvd_oclose(&channels[channel]);
 702                 return;
 703         }
 704         if (channels[channel].type != SSH_CHANNEL_CLOSED)
 705                 packet_disconnect("Received close confirmation for non-closed channel %d (type %d).",
 706                                   channel, channels[channel].type);
 707
 708         /* Free the channel. */
 709         channel_free(channel);
 710 }
 711
 712 /* This is called after receiving CHANNEL_OPEN_CONFIRMATION. */
 713
 714 void
 715 channel_input_open_confirmation()
 716 {
 717         int channel, remote_channel;
 718
 719         /* Get the channel number and verify it. */
 720         channel = packet_get_int();
 721         if (channel < 0 || channel >= channels_alloc ||
 722             channels[channel].type != SSH_CHANNEL_OPENING)
 723                 packet_disconnect("Received open confirmation for non-opening channel %d.",
 724                                   channel);
 725
 726         /* Get remote side's id for this channel. */
 727         remote_channel = packet_get_int();
 728
 729         /* Record the remote channel number and mark that the channel is now open. */
 730         channels[channel].remote_id = remote_channel;
 731         channels[channel].type = SSH_CHANNEL_OPEN;
 732 }
 733
 734 /* This is called after receiving CHANNEL_OPEN_FAILURE from the other side. */
 735
 736 void
 737 channel_input_open_failure()
 738 {
 739         int channel;
 740
 741         /* Get the channel number and verify it. */
 742         channel = packet_get_int();
 743         if (channel < 0 || channel >= channels_alloc ||
 744             channels[channel].type != SSH_CHANNEL_OPENING)
 745                 packet_disconnect("Received open failure for non-opening channel %d.",
 746                                   channel);
 747
 748         /* Free the channel.  This will also close the socket. */
 749         channel_free(channel);
 750 }
 751
 752 /*
 753  * Stops listening for channels, and removes any unix domain sockets that we
 754  * might have.
 755  */
 756
 757 void
 758 channel_stop_listening()
 759 {
 760         int i;
 761         for (i = 0; i < channels_alloc; i++) {
 762                 switch (channels[i].type) {
 763                 case SSH_CHANNEL_AUTH_SOCKET:
 764                         close(channels[i].sock);
 765                         remove(channels[i].path);
 766                         channel_free(i);
 767                         break;
 768                 case SSH_CHANNEL_PORT_LISTENER:
 769                 case SSH_CHANNEL_X11_LISTENER:
 770                         close(channels[i].sock);
 771                         channel_free(i);
 772                         break;
 773                 default:
 774                         break;
 775                 }
 776         }
 777 }
 778
 779 /*
 780  * Closes the sockets of all channels.  This is used to close extra file
 781  * descriptors after a fork.
 782  */
 783
 784 void
 785 channel_close_all()
 786 {
 787         int i;
 788         for (i = 0; i < channels_alloc; i++) {
 789                 if (channels[i].type != SSH_CHANNEL_FREE)
 790                         close(channels[i].sock);
 791         }
 792 }
 793
 794 /* Returns the maximum file descriptor number used by the channels. */
 795
 796 int
 797 channel_max_fd()
 798 {
 799         return channel_max_fd_value;
 800 }
 801
 802 /* Returns true if any channel is still open. */
 803
 804 int
 805 channel_still_open()
 806 {
 807         unsigned int i;
 808         for (i = 0; i < channels_alloc; i++)
 809                 switch (channels[i].type) {
 810                 case SSH_CHANNEL_FREE:
 811                 case SSH_CHANNEL_X11_LISTENER:
 812                 case SSH_CHANNEL_PORT_LISTENER:
 813                 case SSH_CHANNEL_CLOSED:
 814                 case SSH_CHANNEL_AUTH_SOCKET:
 815                         continue;
 816                 case SSH_CHANNEL_OPENING:
 817                 case SSH_CHANNEL_OPEN:
 818                 case SSH_CHANNEL_X11_OPEN:
 819                         return 1;
 820                 case SSH_CHANNEL_INPUT_DRAINING:
 821                 case SSH_CHANNEL_OUTPUT_DRAINING:
 822                         if (!compat13)
 823                                 fatal("cannot happen: OUT_DRAIN");
 824                         return 1;
 825                 default:
 826                         fatal("channel_still_open: bad channel type %d", channels[i].type);
 827                         /* NOTREACHED */
 828                 }
 829         return 0;
 830 }
 831
 832 /*
 833  * Returns a message describing the currently open forwarded connections,
 834  * suitable for sending to the client.  The message contains crlf pairs for
 835  * newlines.
 836  */
 837
 838 char *
 839 channel_open_message()
 840 {
 841         Buffer buffer;
 842         int i;
 843         char buf[512], *cp;
 844
 845         buffer_init(&buffer);
 846         snprintf(buf, sizeof buf, "The following connections are open:\r\n");
 847         buffer_append(&buffer, buf, strlen(buf));
 848         for (i = 0; i < channels_alloc; i++) {
 849                 Channel *c = &channels[i];
 850                 switch (c->type) {
 851                 case SSH_CHANNEL_FREE:
 852                 case SSH_CHANNEL_X11_LISTENER:
 853                 case SSH_CHANNEL_PORT_LISTENER:
 854                 case SSH_CHANNEL_CLOSED:
 855                 case SSH_CHANNEL_AUTH_SOCKET:
 856                         continue;
 857                 case SSH_CHANNEL_OPENING:
 858                 case SSH_CHANNEL_OPEN:
 859                 case SSH_CHANNEL_X11_OPEN:
 860                 case SSH_CHANNEL_INPUT_DRAINING:
 861                 case SSH_CHANNEL_OUTPUT_DRAINING:
 862                         snprintf(buf, sizeof buf, "  #%d %.300s (t%d r%d i%d/%d o%d/%d)\r\n",
 863                             c->self, c->remote_name,
 864                             c->type, c->remote_id,
 865                             c->istate, buffer_len(&c->input),
 866                             c->ostate, buffer_len(&c->output));
 867                         buffer_append(&buffer, buf, strlen(buf));
 868                         continue;
 869                 default:
 870                         fatal("channel_still_open: bad channel type %d", c->type);
 871                         /* NOTREACHED */
 872                 }
 873         }
 874         buffer_append(&buffer, "\0", 1);
 875         cp = xstrdup(buffer_ptr(&buffer));
 876         buffer_free(&buffer);
 877         return cp;
 878 }
 879
 880 /*
 881  * Initiate forwarding of connections to local port "port" through the secure
 882  * channel to host:port from remote side.
 883  */
 884
 885 void
 886 channel_request_local_forwarding(u_short port, const char *host,
 887                                  u_short host_port, int gateway_ports)
 888 {
 889         int success, ch, sock, on = 1;
 890         struct addrinfo hints, *ai, *aitop;
 891         char ntop[NI_MAXHOST], strport[NI_MAXSERV];
 892         struct linger linger;
 893
 894         if (strlen(host) > sizeof(channels[0].path) - 1)
 895                 packet_disconnect("Forward host name too long.");
 896
 897         /*
 898          * getaddrinfo returns a loopback address if the hostname is
 899          * set to NULL and hints.ai_flags is not AI_PASSIVE
 900          */
 901         memset(&hints, 0, sizeof(hints));
 902         hints.ai_family = IPv4or6;
 903         hints.ai_flags = gateway_ports ? AI_PASSIVE : 0;
 904         hints.ai_socktype = SOCK_STREAM;
 905         snprintf(strport, sizeof strport, "%d", port);
 906         if (getaddrinfo(NULL, strport, &hints, &aitop) != 0)
 907                 packet_disconnect("getaddrinfo: fatal error");
 908
 909         success = 0;
 910         for (ai = aitop; ai; ai = ai->ai_next) {
 911                 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
 912                         continue;
 913                 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop, sizeof(ntop),
 914                     strport, sizeof(strport), NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
 915                         error("channel_request_local_forwarding: getnameinfo failed");
 916                         continue;
 917                 }
 918                 /* Create a port to listen for the host. */
 919                 sock = socket(ai->ai_family, SOCK_STREAM, 0);
 920                 if (sock < 0) {
 921                         /* this is no error since kernel may not support ipv6 */
 922                         verbose("socket: %.100s", strerror(errno));
 923                         continue;
 924                 }
 925                 /*
 926                  * Set socket options.  We would like the socket to disappear
 927                  * as soon as it has been closed for whatever reason.
 928                  */
 929                 setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on));
 930                 linger.l_onoff = 1;
 931                 linger.l_linger = 5;
 932                 setsockopt(sock, SOL_SOCKET, SO_LINGER, (void *)&linger, sizeof(linger));
 933                 debug("Local forwarding listening on %s port %s.", ntop, strport);
 934
 935                 /* Bind the socket to the address. */
 936                 if (bind(sock, ai->ai_addr, ai->ai_addrlen) < 0) {
 937                         /* address can be in use ipv6 address is already bound */
 938                         if (!ai->ai_next)
 939                                 error("bind: %.100s", strerror(errno));
 940                         else
 941                                 verbose("bind: %.100s", strerror(errno));
 942
 943                         close(sock);
 944                         continue;
 945                 }
 946                 /* Start listening for connections on the socket. */
 947                 if (listen(sock, 5) < 0) {
 948                         error("listen: %.100s", strerror(errno));
 949                         close(sock);
 950                         continue;
 951                 }
 952                 /* Allocate a channel number for the socket. */
 953                 ch = channel_allocate(SSH_CHANNEL_PORT_LISTENER, sock,
 954                     xstrdup("port listener"));
 955                 strlcpy(channels[ch].path, host, sizeof(channels[ch].path));
 956                 channels[ch].host_port = host_port;
 957                 channels[ch].listening_port = port;
 958                 success = 1;
 959         }
 960         if (success == 0)
 961                 packet_disconnect("cannot listen port: %d", port);
 962         freeaddrinfo(aitop);
 963 }
 964
 965 /*
 966  * Initiate forwarding of connections to port "port" on remote host through
 967  * the secure channel to host:port from local side.
 968  */
 969
 970 void
 971 channel_request_remote_forwarding(u_short port, const char *host,
 972                                   u_short remote_port)
 973 {
 974         int payload_len;
 975         /* Record locally that connection to this host/port is permitted. */
 976         if (num_permitted_opens >= SSH_MAX_FORWARDS_PER_DIRECTION)
 977                 fatal("channel_request_remote_forwarding: too many forwards");
 978
 979         permitted_opens[num_permitted_opens].host = xstrdup(host);
 980         permitted_opens[num_permitted_opens].port = remote_port;
 981         num_permitted_opens++;
 982
 983         /* Send the forward request to the remote side. */
 984         packet_start(SSH_CMSG_PORT_FORWARD_REQUEST);
 985         packet_put_int(port);
 986         packet_put_string(host, strlen(host));
 987         packet_put_int(remote_port);
 988         packet_send();
 989         packet_write_wait();
 990
 991         /*
 992          * Wait for response from the remote side.  It will send a disconnect
 993          * message on failure, and we will never see it here.
 994          */
 995         packet_read_expect(&payload_len, SSH_SMSG_SUCCESS);
 996 }
 997
 998 /*
 999  * This is called after receiving CHANNEL_FORWARDING_REQUEST.  This initates
1000  * listening for the port, and sends back a success reply (or disconnect
1001  * message if there was an error).  This never returns if there was an error.
1002  */
1003
1004 void
1005 channel_input_port_forward_request(int is_root)
1006 {
1007         u_short port, host_port;
1008         char *hostname;
1009
1010         /* Get arguments from the packet. */
1011         port = packet_get_int();
1012         hostname = packet_get_string(NULL);
1013         host_port = packet_get_int();
1014
1015         /*
1016          * Check that an unprivileged user is not trying to forward a
1017          * privileged port.
1018          */
1019         if (port < IPPORT_RESERVED && !is_root)
1020                 packet_disconnect("Requested forwarding of port %d but user is not root.",
1021                                   port);
1022         /*
1023          * Initiate forwarding,
1024          * bind port to localhost only (gateway ports == 0).
1025          */
1026         channel_request_local_forwarding(port, hostname, host_port, 0);
1027
1028         /* Free the argument string. */
1029         xfree(hostname);
1030 }
1031
1032 /*
1033  * This is called after receiving PORT_OPEN message.  This attempts to
1034  * connect to the given host:port, and sends back CHANNEL_OPEN_CONFIRMATION
1035  * or CHANNEL_OPEN_FAILURE.
1036  */
1037
1038 void
1039 channel_input_port_open(int payload_len)
1040 {
1041         int remote_channel, sock = 0, newch, i;
1042         u_short host_port;
1043         char *host, *originator_string;
1044         int host_len, originator_len;
1045         struct addrinfo hints, *ai, *aitop;
1046         char ntop[NI_MAXHOST], strport[NI_MAXSERV];
1047         int gaierr;
1048
1049         /* Get remote channel number. */
1050         remote_channel = packet_get_int();
1051
1052         /* Get host name to connect to. */
1053         host = packet_get_string(&host_len);
1054
1055         /* Get port to connect to. */
1056         host_port = packet_get_int();
1057
1058         /* Get remote originator name. */
1059         if (have_hostname_in_open) {
1060                 originator_string = packet_get_string(&originator_len);
1061                 originator_len += 4;    /* size of packet_int */
1062         } else {
1063                 originator_string = xstrdup("unknown (remote did not supply name)");
1064                 originator_len = 0;     /* no originator supplied */
1065         }
1066
1067         packet_integrity_check(payload_len,
1068                                4 + 4 + host_len + 4 + originator_len,
1069                                SSH_MSG_PORT_OPEN);
1070
1071         /* Check if opening that port is permitted. */
1072         if (!all_opens_permitted) {
1073                 /* Go trough all permitted ports. */
1074                 for (i = 0; i < num_permitted_opens; i++)
1075                         if (permitted_opens[i].port == host_port &&
1076                             strcmp(permitted_opens[i].host, host) == 0)
1077                                 break;
1078
1079                 /* Check if we found the requested port among those permitted. */
1080                 if (i >= num_permitted_opens) {
1081                         /* The port is not permitted. */
1082                         log("Received request to connect to %.100s:%d, but the request was denied.",
1083                             host, host_port);
1084                         packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
1085                         packet_put_int(remote_channel);
1086                         packet_send();
1087                 }
1088         }
1089
1090         memset(&hints, 0, sizeof(hints));
1091         hints.ai_family = IPv4or6;
1092         hints.ai_socktype = SOCK_STREAM;
1093         snprintf(strport, sizeof strport, "%d", host_port);
1094         if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) {
1095                 error("%.100s: unknown host (%s)", host, gai_strerror(gaierr));
1096                 goto fail;
1097         }
1098
1099         for (ai = aitop; ai; ai = ai->ai_next) {
1100                 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
1101                         continue;
1102                 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop, sizeof(ntop),
1103                     strport, sizeof(strport), NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
1104                         error("channel_input_port_open: getnameinfo failed");
1105                         continue;
1106                 }
1107                 /* Create the socket. */
1108                 sock = socket(ai->ai_family, SOCK_STREAM, 0);
1109                 if (sock < 0) {
1110                         error("socket: %.100s", strerror(errno));
1111                         continue;
1112                 }
1113                 /* Connect to the host/port. */
1114                 if (connect(sock, ai->ai_addr, ai->ai_addrlen) < 0) {
1115                         error("connect %.100s port %s: %.100s", ntop, strport,
1116                             strerror(errno));
1117                         close(sock);
1118                         continue;       /* fail -- try next */
1119                 }
1120                 break; /* success */
1121
1122         }
1123         freeaddrinfo(aitop);
1124
1125         if (!ai) {
1126                 error("connect %.100s port %d: failed.", host, host_port);
1127                 goto fail;
1128         }
1129
1130         /* Successful connection. */
1131
1132         /* Allocate a channel for this connection. */
1133         newch = channel_allocate(SSH_CHANNEL_OPEN, sock, originator_string);
1134         channels[newch].remote_id = remote_channel;
1135
1136         /* Send a confirmation to the remote host. */
1137         packet_start(SSH_MSG_CHANNEL_OPEN_CONFIRMATION);
1138         packet_put_int(remote_channel);
1139         packet_put_int(newch);
1140         packet_send();
1141
1142         /* Free the argument string. */
1143         xfree(host);
1144
1145         return;
1146
1147 fail:
1148         /* Free the argument string. */
1149         xfree(host);
1150
1151         /* Send refusal to the remote host. */
1152         packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
1153         packet_put_int(remote_channel);
1154         packet_send();
1155 }
1156
1157 /*
1158  * Creates an internet domain socket for listening for X11 connections.
1159  * Returns a suitable value for the DISPLAY variable, or NULL if an error
1160  * occurs.
1161  */
1162
1163 #define NUM_SOCKS       10
1164
1165 char *
1166 x11_create_display_inet(int screen_number, int x11_display_offset)
1167 {
1168         int display_number, sock;
1169         u_short port;
1170         struct addrinfo hints, *ai, *aitop;
1171         char strport[NI_MAXSERV];
1172         int gaierr, n, num_socks = 0, socks[NUM_SOCKS];
1173         char display[512];
1174         char hostname[MAXHOSTNAMELEN];
1175
1176         for (display_number = x11_display_offset;
1177              display_number < MAX_DISPLAYS;
1178              display_number++) {
1179                 port = 6000 + display_number;
1180                 memset(&hints, 0, sizeof(hints));
1181                 hints.ai_family = IPv4or6;
1182                 hints.ai_flags = AI_PASSIVE;            /* XXX loopback only ? */
1183                 hints.ai_socktype = SOCK_STREAM;
1184                 snprintf(strport, sizeof strport, "%d", port);
1185                 if ((gaierr = getaddrinfo(NULL, strport, &hints, &aitop)) != 0) {
1186                         error("getaddrinfo: %.100s", gai_strerror(gaierr));
1187                         return NULL;
1188                 }
1189                 for (ai = aitop; ai; ai = ai->ai_next) {
1190                         if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
1191                                 continue;
1192                         sock = socket(ai->ai_family, SOCK_STREAM, 0);
1193                         if (sock < 0) {
1194                                 if (errno != EINVAL) {
1195                                         error("socket: %.100s", strerror(errno));
1196                                         return NULL;
1197                                 } else {
1198                                         debug("Socket family %d not supported [X11 disp create]", ai->ai_family);
1199                                         continue;
1200                                 }
1201                         }
1202                         if (bind(sock, ai->ai_addr, ai->ai_addrlen) < 0) {
1203                                 debug("bind port %d: %.100s", port, strerror(errno));
1204                                 shutdown(sock, SHUT_RDWR);
1205                                 close(sock);
1206
1207                                 if (ai->ai_next)
1208                                         continue;
1209
1210                                 for (n = 0; n < num_socks; n++) {
1211                                         shutdown(socks[n], SHUT_RDWR);
1212                                         close(socks[n]);
1213                                 }
1214                                 num_socks = 0;
1215                                 break;
1216                         }
1217                         socks[num_socks++] = sock;
1218 #ifndef DONT_TRY_OTHER_AF
1219                         if (num_socks == NUM_SOCKS)
1220                                 break;
1221 #else
1222                         break;
1223 #endif
1224                 }
1225                 if (num_socks > 0)
1226                         break;
1227         }
1228         if (display_number >= MAX_DISPLAYS) {
1229                 error("Failed to allocate internet-domain X11 display socket.");
1230                 return NULL;
1231         }
1232         /* Start listening for connections on the socket. */
1233         for (n = 0; n < num_socks; n++) {
1234                 sock = socks[n];
1235                 if (listen(sock, 5) < 0) {
1236                         error("listen: %.100s", strerror(errno));
1237                         shutdown(sock, SHUT_RDWR);
1238                         close(sock);
1239                         return NULL;
1240                 }
1241         }
1242
1243         /* Set up a suitable value for the DISPLAY variable. */
1244
1245         if (gethostname(hostname, sizeof(hostname)) < 0)
1246                 fatal("gethostname: %.100s", strerror(errno));
1247
1248 #ifdef IPADDR_IN_DISPLAY
1249         /*
1250          * HPUX detects the local hostname in the DISPLAY variable and tries
1251          * to set up a shared memory connection to the server, which it
1252          * incorrectly supposes to be local.
1253          *
1254          * The workaround - as used in later $$H and other programs - is
1255          * is to set display to the host's IP address.
1256          */
1257         {
1258                 struct hostent *he;
1259                 struct in_addr my_addr;
1260
1261                 he = gethostbyname(hostname);
1262                 if (he == NULL) {
1263                         error("[X11-broken-fwd-hostname-workaround] Could not get "
1264                                 "IP address for hostname %s.", hostname);
1265
1266                         packet_send_debug("[X11-broken-fwd-hostname-workaround]"
1267                                 "Could not get IP address for hostname %s.", hostname);
1268
1269                         shutdown(sock, SHUT_RDWR);
1270                         close(sock);
1271
1272                         return NULL;
1273                 }
1274
1275                 memcpy(&my_addr, he->h_addr_list[0], sizeof(struct in_addr));
1276
1277                 /* Set DISPLAY to <ip address>:screen.display */
1278                 snprintf(display, sizeof(display), "%.50s:%d.%d", inet_ntoa(my_addr),
1279                         display_number, screen_number);
1280         }
1281 #else /* IPADDR_IN_DISPLAY */
1282         /* Just set DISPLAY to hostname:screen.display */
1283         snprintf(display, sizeof display, "%.400s:%d.%d", hostname,
1284                 display_number, screen_number);
1285 #endif /* IPADDR_IN_DISPLAY */
1286
1287         /* Allocate a channel for each socket. */
1288         for (n = 0; n < num_socks; n++) {
1289                 sock = socks[n];
1290                 (void) channel_allocate(SSH_CHANNEL_X11_LISTENER, sock,
1291                                         xstrdup("X11 inet listener"));
1292         }
1293
1294         /* Return a suitable value for the DISPLAY environment variable. */
1295         return xstrdup(display);
1296 }
1297
1298 #ifndef X_UNIX_PATH
1299 #define X_UNIX_PATH "/tmp/.X11-unix/X"
1300 #endif
1301
1302 static
1303 int
1304 connect_local_xsocket(unsigned int dnr)
1305 {
1306         static const char *const x_sockets[] = {
1307                 X_UNIX_PATH "%u",
1308                 "/var/X/.X11-unix/X" "%u",
1309                 "/usr/spool/sockets/X11/" "%u",
1310                 NULL
1311         };
1312         int sock;
1313         struct sockaddr_un addr;
1314         const char *const * path;
1315
1316         for (path = x_sockets; *path; ++path) {
1317                 sock = socket(AF_UNIX, SOCK_STREAM, 0);
1318                 if (sock < 0)
1319                         error("socket: %.100s", strerror(errno));
1320                 memset(&addr, 0, sizeof(addr));
1321                 addr.sun_family = AF_UNIX;
1322                 snprintf(addr.sun_path, sizeof addr.sun_path, *path, dnr);
1323                 if (connect(sock, (struct sockaddr *) & addr, sizeof(addr)) == 0)
1324                         return sock;
1325                 close(sock);
1326         }
1327         error("connect %.100s: %.100s", addr.sun_path, strerror(errno));
1328         return -1;
1329 }
1330
1331
1332 /*
1333  * This is called when SSH_SMSG_X11_OPEN is received.  The packet contains
1334  * the remote channel number.  We should do whatever we want, and respond
1335  * with either SSH_MSG_OPEN_CONFIRMATION or SSH_MSG_OPEN_FAILURE.
1336  */
1337
1338 void
1339 x11_input_open(int payload_len)
1340 {
1341         int remote_channel, display_number, sock = 0, newch;
1342         const char *display;
1343         char buf[1024], *cp, *remote_host;
1344         int remote_len;
1345         struct addrinfo hints, *ai, *aitop;
1346         char strport[NI_MAXSERV];
1347         int gaierr;
1348
1349         /* Get remote channel number. */
1350         remote_channel = packet_get_int();
1351
1352         /* Get remote originator name. */
1353         if (have_hostname_in_open) {
1354                 remote_host = packet_get_string(&remote_len);
1355                 remote_len += 4;
1356         } else {
1357                 remote_host = xstrdup("unknown (remote did not supply name)");
1358                 remote_len = 0;
1359         }
1360
1361         debug("Received X11 open request.");
1362         packet_integrity_check(payload_len, 4 + remote_len, SSH_SMSG_X11_OPEN);
1363
1364         /* Try to open a socket for the local X server. */
1365         display = getenv("DISPLAY");
1366         if (!display) {
1367                 error("DISPLAY not set.");
1368                 goto fail;
1369         }
1370         /*
1371          * Now we decode the value of the DISPLAY variable and make a
1372          * connection to the real X server.
1373          */
1374
1375         /*
1376          * Check if it is a unix domain socket.  Unix domain displays are in
1377          * one of the following formats: unix:d[.s], :d[.s], ::d[.s]
1378          */
1379         if (strncmp(display, "unix:", 5) == 0 ||
1380             display[0] == ':') {
1381                 /* Connect to the unix domain socket. */
1382                 if (sscanf(strrchr(display, ':') + 1, "%d", &display_number) != 1) {
1383                         error("Could not parse display number from DISPLAY: %.100s",
1384                               display);
1385                         goto fail;
1386                 }
1387                 /* Create a socket. */
1388                 sock = connect_local_xsocket(display_number);
1389                 if (sock < 0)
1390                         goto fail;
1391
1392                 /* OK, we now have a connection to the display. */
1393                 goto success;
1394         }
1395         /*
1396          * Connect to an inet socket.  The DISPLAY value is supposedly
1397          * hostname:d[.s], where hostname may also be numeric IP address.
1398          */
1399         strncpy(buf, display, sizeof(buf));
1400         buf[sizeof(buf) - 1] = 0;
1401         cp = strchr(buf, ':');
1402         if (!cp) {
1403                 error("Could not find ':' in DISPLAY: %.100s", display);
1404                 goto fail;
1405         }
1406         *cp = 0;
1407         /* buf now contains the host name.  But first we parse the display number. */
1408         if (sscanf(cp + 1, "%d", &display_number) != 1) {
1409                 error("Could not parse display number from DISPLAY: %.100s",
1410                       display);
1411                 goto fail;
1412         }
1413
1414         /* Look up the host address */
1415         memset(&hints, 0, sizeof(hints));
1416         hints.ai_family = IPv4or6;
1417         hints.ai_socktype = SOCK_STREAM;
1418         snprintf(strport, sizeof strport, "%d", 6000 + display_number);
1419         if ((gaierr = getaddrinfo(buf, strport, &hints, &aitop)) != 0) {
1420                 error("%.100s: unknown host. (%s)", buf, gai_strerror(gaierr));
1421                 goto fail;
1422         }
1423         for (ai = aitop; ai; ai = ai->ai_next) {
1424                 /* Create a socket. */
1425                 sock = socket(ai->ai_family, SOCK_STREAM, 0);
1426                 if (sock < 0) {
1427                         debug("socket: %.100s", strerror(errno));
1428                 continue;
1429         }
1430         /* Connect it to the display. */
1431         if (connect(sock, ai->ai_addr, ai->ai_addrlen) < 0) {
1432                 debug("connect %.100s port %d: %.100s", buf, 6000 + display_number,
1433                     strerror(errno));
1434                 close(sock);
1435                 continue;
1436         }
1437         /* Success */
1438         break;
1439
1440         } /* (ai = aitop, ai; ai = ai->ai_next) */
1441         freeaddrinfo(aitop);
1442         if (!ai) {
1443                 error("connect %.100s port %d: %.100s", buf, 6000 + display_number,
1444                     strerror(errno));
1445                 goto fail;
1446         }
1447 success:
1448         /* We have successfully obtained a connection to the real X display. */
1449
1450         /* Allocate a channel for this connection. */
1451         if (x11_saved_proto == NULL)
1452                 newch = channel_allocate(SSH_CHANNEL_OPEN, sock, remote_host);
1453         else
1454                 newch = channel_allocate(SSH_CHANNEL_X11_OPEN, sock, remote_host);
1455         channels[newch].remote_id = remote_channel;
1456
1457         /* Send a confirmation to the remote host. */
1458         packet_start(SSH_MSG_CHANNEL_OPEN_CONFIRMATION);
1459         packet_put_int(remote_channel);
1460         packet_put_int(newch);
1461         packet_send();
1462
1463         return;
1464
1465 fail:
1466         /* Send refusal to the remote host. */
1467         packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
1468         packet_put_int(remote_channel);
1469         packet_send();
1470 }
1471
1472 /*
1473  * Requests forwarding of X11 connections, generates fake authentication
1474  * data, and enables authentication spoofing.
1475  */
1476
1477 void
1478 x11_request_forwarding_with_spoofing(const char *proto, const char *data)
1479 {
1480         unsigned int data_len = (unsigned int) strlen(data) / 2;
1481         unsigned int i, value;
1482         char *new_data;
1483         int screen_number;
1484         const char *cp;
1485         u_int32_t rand = 0;
1486
1487         cp = getenv("DISPLAY");
1488         if (cp)
1489                 cp = strchr(cp, ':');
1490         if (cp)
1491                 cp = strchr(cp, '.');
1492         if (cp)
1493                 screen_number = atoi(cp + 1);
1494         else
1495                 screen_number = 0;
1496
1497         /* Save protocol name. */
1498         x11_saved_proto = xstrdup(proto);
1499
1500         /*
1501          * Extract real authentication data and generate fake data of the
1502          * same length.
1503          */
1504         x11_saved_data = xmalloc(data_len);
1505         x11_fake_data = xmalloc(data_len);
1506         for (i = 0; i < data_len; i++) {
1507                 if (sscanf(data + 2 * i, "%2x", &value) != 1)
1508                         fatal("x11_request_forwarding: bad authentication data: %.100s", data);
1509                 if (i % 4 == 0)
1510                         rand = arc4random();
1511                 x11_saved_data[i] = value;
1512                 x11_fake_data[i] = rand & 0xff;
1513                 rand >>= 8;
1514         }
1515         x11_saved_data_len = data_len;
1516         x11_fake_data_len = data_len;
1517
1518         /* Convert the fake data into hex. */
1519         new_data = xmalloc(2 * data_len + 1);
1520         for (i = 0; i < data_len; i++)
1521                 sprintf(new_data + 2 * i, "%02x", (unsigned char) x11_fake_data[i]);
1522
1523         /* Send the request packet. */
1524         packet_start(SSH_CMSG_X11_REQUEST_FORWARDING);
1525         packet_put_string(proto, strlen(proto));
1526         packet_put_string(new_data, strlen(new_data));
1527         packet_put_int(screen_number);
1528         packet_send();
1529         packet_write_wait();
1530         xfree(new_data);
1531 }
1532
1533 /* Sends a message to the server to request authentication fd forwarding. */
1534
1535 void
1536 auth_request_forwarding()
1537 {
1538         packet_start(SSH_CMSG_AGENT_REQUEST_FORWARDING);
1539         packet_send();
1540         packet_write_wait();
1541 }
1542
1543 /*
1544  * Returns the name of the forwarded authentication socket.  Returns NULL if
1545  * there is no forwarded authentication socket.  The returned value points to
1546  * a static buffer.
1547  */
1548
1549 char *
1550 auth_get_socket_name()
1551 {
1552         return channel_forwarded_auth_socket_name;
1553 }
1554
1555 /* removes the agent forwarding socket */
1556
1557 void
1558 cleanup_socket(void)
1559 {
1560         remove(channel_forwarded_auth_socket_name);
1561         rmdir(channel_forwarded_auth_socket_dir);
1562 }
1563
1564 /*
1565  * This if called to process SSH_CMSG_AGENT_REQUEST_FORWARDING on the server.
1566  * This starts forwarding authentication requests.
1567  */
1568
1569 void
1570 auth_input_request_forwarding(struct passwd * pw)
1571 {
1572         int sock, newch;
1573         struct sockaddr_un sunaddr;
1574
1575         if (auth_get_socket_name() != NULL)
1576                 fatal("Protocol error: authentication forwarding requested twice.");
1577
1578         /* Temporarily drop privileged uid for mkdir/bind. */
1579         temporarily_use_uid(pw->pw_uid);
1580
1581         /* Allocate a buffer for the socket name, and format the name. */
1582         channel_forwarded_auth_socket_name = xmalloc(MAX_SOCKET_NAME);
1583         channel_forwarded_auth_socket_dir = xmalloc(MAX_SOCKET_NAME);
1584         strlcpy(channel_forwarded_auth_socket_dir, "/tmp/ssh-XXXXXXXX", MAX_SOCKET_NAME);
1585
1586         /* Create private directory for socket */
1587         if (mkdtemp(channel_forwarded_auth_socket_dir) == NULL)
1588                 packet_disconnect("mkdtemp: %.100s", strerror(errno));
1589         snprintf(channel_forwarded_auth_socket_name, MAX_SOCKET_NAME, "%s/agent.%d",
1590                  channel_forwarded_auth_socket_dir, (int) getpid());
1591
1592         if (atexit(cleanup_socket) < 0) {
1593                 int saved = errno;
1594                 cleanup_socket();
1595                 packet_disconnect("socket: %.100s", strerror(saved));
1596         }
1597         /* Create the socket. */
1598         sock = socket(AF_UNIX, SOCK_STREAM, 0);
1599         if (sock < 0)
1600                 packet_disconnect("socket: %.100s", strerror(errno));
1601
1602         /* Bind it to the name. */
1603         memset(&sunaddr, 0, sizeof(sunaddr));
1604         sunaddr.sun_family = AF_UNIX;
1605         strncpy(sunaddr.sun_path, channel_forwarded_auth_socket_name,
1606                 sizeof(sunaddr.sun_path));
1607
1608         if (bind(sock, (struct sockaddr *) & sunaddr, sizeof(sunaddr)) < 0)
1609                 packet_disconnect("bind: %.100s", strerror(errno));
1610
1611         /* Restore the privileged uid. */
1612         restore_uid();
1613
1614         /* Start listening on the socket. */
1615         if (listen(sock, 5) < 0)
1616                 packet_disconnect("listen: %.100s", strerror(errno));
1617
1618         /* Allocate a channel for the authentication agent socket. */
1619         newch = channel_allocate(SSH_CHANNEL_AUTH_SOCKET, sock,
1620                                  xstrdup("auth socket"));
1621         strlcpy(channels[newch].path, channel_forwarded_auth_socket_name,
1622             sizeof(channels[newch].path));
1623 }
1624
1625 /* This is called to process an SSH_SMSG_AGENT_OPEN message. */
1626
1627 void
1628 auth_input_open_request()
1629 {
1630         int remch, sock, newch;
1631         char *dummyname;
1632
1633         /* Read the remote channel number from the message. */
1634         remch = packet_get_int();
1635
1636         /*
1637          * Get a connection to the local authentication agent (this may again
1638          * get forwarded).
1639          */
1640         sock = ssh_get_authentication_socket();
1641
1642         /*
1643          * If we could not connect the agent, send an error message back to
1644          * the server. This should never happen unless the agent dies,
1645          * because authentication forwarding is only enabled if we have an
1646          * agent.
1647          */
1648         if (sock < 0) {
1649                 packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
1650                 packet_put_int(remch);
1651                 packet_send();
1652                 return;
1653         }
1654         debug("Forwarding authentication connection.");
1655
1656         /*
1657          * Dummy host name.  This will be freed when the channel is freed; it
1658          * will still be valid in the packet_put_string below since the
1659          * channel cannot yet be freed at that point.
1660          */
1661         dummyname = xstrdup("authentication agent connection");
1662
1663         newch = channel_allocate(SSH_CHANNEL_OPEN, sock, dummyname);
1664         channels[newch].remote_id = remch;
1665
1666         /* Send a confirmation to the remote host. */
1667         packet_start(SSH_MSG_CHANNEL_OPEN_CONFIRMATION);
1668         packet_put_int(remch);
1669         packet_put_int(newch);
1670         packet_send();
1671 }