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                         verbose("bind: %.100s", strerror(errno));
 939                         close(sock);
 940                         continue;
 941                 }
 942                 /* Start listening for connections on the socket. */
 943                 if (listen(sock, 5) < 0) {
 944                         error("listen: %.100s", strerror(errno));
 945                         close(sock);
 946                         continue;
 947                 }
 948                 /* Allocate a channel number for the socket. */
 949                 ch = channel_allocate(SSH_CHANNEL_PORT_LISTENER, sock,
 950                     xstrdup("port listener"));
 951                 strlcpy(channels[ch].path, host, sizeof(channels[ch].path));
 952                 channels[ch].host_port = host_port;
 953                 channels[ch].listening_port = port;
 954                 success = 1;
 955         }
 956         if (success == 0)
 957                 packet_disconnect("cannot listen port: %d", port);
 958         freeaddrinfo(aitop);
 959 }
 960
 961 /*
 962  * Initiate forwarding of connections to port "port" on remote host through
 963  * the secure channel to host:port from local side.
 964  */
 965
 966 void
 967 channel_request_remote_forwarding(u_short port, const char *host,
 968                                   u_short remote_port)
 969 {
 970         int payload_len;
 971         /* Record locally that connection to this host/port is permitted. */
 972         if (num_permitted_opens >= SSH_MAX_FORWARDS_PER_DIRECTION)
 973                 fatal("channel_request_remote_forwarding: too many forwards");
 974
 975         permitted_opens[num_permitted_opens].host = xstrdup(host);
 976         permitted_opens[num_permitted_opens].port = remote_port;
 977         num_permitted_opens++;
 978
 979         /* Send the forward request to the remote side. */
 980         packet_start(SSH_CMSG_PORT_FORWARD_REQUEST);
 981         packet_put_int(port);
 982         packet_put_string(host, strlen(host));
 983         packet_put_int(remote_port);
 984         packet_send();
 985         packet_write_wait();
 986
 987         /*
 988          * Wait for response from the remote side.  It will send a disconnect
 989          * message on failure, and we will never see it here.
 990          */
 991         packet_read_expect(&payload_len, SSH_SMSG_SUCCESS);
 992 }
 993
 994 /*
 995  * This is called after receiving CHANNEL_FORWARDING_REQUEST.  This initates
 996  * listening for the port, and sends back a success reply (or disconnect
 997  * message if there was an error).  This never returns if there was an error.
 998  */
 999
1000 void
1001 channel_input_port_forward_request(int is_root)
1002 {
1003         u_short port, host_port;
1004         char *hostname;
1005
1006         /* Get arguments from the packet. */
1007         port = packet_get_int();
1008         hostname = packet_get_string(NULL);
1009         host_port = packet_get_int();
1010
1011         /*
1012          * Check that an unprivileged user is not trying to forward a
1013          * privileged port.
1014          */
1015         if (port < IPPORT_RESERVED && !is_root)
1016                 packet_disconnect("Requested forwarding of port %d but user is not root.",
1017                                   port);
1018         /*
1019          * Initiate forwarding,
1020          * bind port to localhost only (gateway ports == 0).
1021          */
1022         channel_request_local_forwarding(port, hostname, host_port, 0);
1023
1024         /* Free the argument string. */
1025         xfree(hostname);
1026 }
1027
1028 /*
1029  * This is called after receiving PORT_OPEN message.  This attempts to
1030  * connect to the given host:port, and sends back CHANNEL_OPEN_CONFIRMATION
1031  * or CHANNEL_OPEN_FAILURE.
1032  */
1033
1034 void
1035 channel_input_port_open(int payload_len)
1036 {
1037         int remote_channel, sock = 0, newch, i;
1038         u_short host_port;
1039         char *host, *originator_string;
1040         int host_len, originator_len;
1041         struct addrinfo hints, *ai, *aitop;
1042         char ntop[NI_MAXHOST], strport[NI_MAXSERV];
1043         int gaierr;
1044
1045         /* Get remote channel number. */
1046         remote_channel = packet_get_int();
1047
1048         /* Get host name to connect to. */
1049         host = packet_get_string(&host_len);
1050
1051         /* Get port to connect to. */
1052         host_port = packet_get_int();
1053
1054         /* Get remote originator name. */
1055         if (have_hostname_in_open) {
1056                 originator_string = packet_get_string(&originator_len);
1057                 originator_len += 4;    /* size of packet_int */
1058         } else {
1059                 originator_string = xstrdup("unknown (remote did not supply name)");
1060                 originator_len = 0;     /* no originator supplied */
1061         }
1062
1063         packet_integrity_check(payload_len,
1064                                4 + 4 + host_len + 4 + originator_len,
1065                                SSH_MSG_PORT_OPEN);
1066
1067         /* Check if opening that port is permitted. */
1068         if (!all_opens_permitted) {
1069                 /* Go trough all permitted ports. */
1070                 for (i = 0; i < num_permitted_opens; i++)
1071                         if (permitted_opens[i].port == host_port &&
1072                             strcmp(permitted_opens[i].host, host) == 0)
1073                                 break;
1074
1075                 /* Check if we found the requested port among those permitted. */
1076                 if (i >= num_permitted_opens) {
1077                         /* The port is not permitted. */
1078                         log("Received request to connect to %.100s:%d, but the request was denied.",
1079                             host, host_port);
1080                         packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
1081                         packet_put_int(remote_channel);
1082                         packet_send();
1083                 }
1084         }
1085
1086         memset(&hints, 0, sizeof(hints));
1087         hints.ai_family = IPv4or6;
1088         hints.ai_socktype = SOCK_STREAM;
1089         snprintf(strport, sizeof strport, "%d", host_port);
1090         if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) {
1091                 error("%.100s: unknown host (%s)", host, gai_strerror(gaierr));
1092                 goto fail;
1093         }
1094
1095         for (ai = aitop; ai; ai = ai->ai_next) {
1096                 if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
1097                         continue;
1098                 if (getnameinfo(ai->ai_addr, ai->ai_addrlen, ntop, sizeof(ntop),
1099                     strport, sizeof(strport), NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
1100                         error("channel_input_port_open: getnameinfo failed");
1101                         continue;
1102                 }
1103                 /* Create the socket. */
1104                 sock = socket(ai->ai_family, SOCK_STREAM, 0);
1105                 if (sock < 0) {
1106                         error("socket: %.100s", strerror(errno));
1107                         continue;
1108                 }
1109                 /* Connect to the host/port. */
1110                 if (connect(sock, ai->ai_addr, ai->ai_addrlen) < 0) {
1111                         error("connect %.100s port %s: %.100s", ntop, strport,
1112                             strerror(errno));
1113                         close(sock);
1114                         continue;       /* fail -- try next */
1115                 }
1116                 break; /* success */
1117
1118         }
1119         freeaddrinfo(aitop);
1120
1121         if (!ai) {
1122                 error("connect %.100s port %d: failed.", host, host_port);
1123                 goto fail;
1124         }
1125
1126         /* Successful connection. */
1127
1128         /* Allocate a channel for this connection. */
1129         newch = channel_allocate(SSH_CHANNEL_OPEN, sock, originator_string);
1130         channels[newch].remote_id = remote_channel;
1131
1132         /* Send a confirmation to the remote host. */
1133         packet_start(SSH_MSG_CHANNEL_OPEN_CONFIRMATION);
1134         packet_put_int(remote_channel);
1135         packet_put_int(newch);
1136         packet_send();
1137
1138         /* Free the argument string. */
1139         xfree(host);
1140
1141         return;
1142
1143 fail:
1144         /* Free the argument string. */
1145         xfree(host);
1146
1147         /* Send refusal to the remote host. */
1148         packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
1149         packet_put_int(remote_channel);
1150         packet_send();
1151 }
1152
1153 /*
1154  * Creates an internet domain socket for listening for X11 connections.
1155  * Returns a suitable value for the DISPLAY variable, or NULL if an error
1156  * occurs.
1157  */
1158
1159 #define NUM_SOCKS       10
1160
1161 char *
1162 x11_create_display_inet(int screen_number, int x11_display_offset)
1163 {
1164         int display_number, sock;
1165         u_short port;
1166         struct addrinfo hints, *ai, *aitop;
1167         char strport[NI_MAXSERV];
1168         int gaierr, n, num_socks = 0, socks[NUM_SOCKS];
1169         char display[512];
1170         char hostname[MAXHOSTNAMELEN];
1171
1172         for (display_number = x11_display_offset;
1173              display_number < MAX_DISPLAYS;
1174              display_number++) {
1175                 port = 6000 + display_number;
1176                 memset(&hints, 0, sizeof(hints));
1177                 hints.ai_family = IPv4or6;
1178                 hints.ai_flags = AI_PASSIVE;            /* XXX loopback only ? */
1179                 hints.ai_socktype = SOCK_STREAM;
1180                 snprintf(strport, sizeof strport, "%d", port);
1181                 if ((gaierr = getaddrinfo(NULL, strport, &hints, &aitop)) != 0) {
1182                         error("getaddrinfo: %.100s", gai_strerror(gaierr));
1183                         return NULL;
1184                 }
1185                 for (ai = aitop; ai; ai = ai->ai_next) {
1186                         if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
1187                                 continue;
1188                         sock = socket(ai->ai_family, SOCK_STREAM, 0);
1189                         if (sock < 0) {
1190                                 error("socket: %.100s", strerror(errno));
1191                                 return NULL;
1192                         }
1193                         if (bind(sock, ai->ai_addr, ai->ai_addrlen) < 0) {
1194                                 debug("bind port %d: %.100s", port, strerror(errno));
1195                                 shutdown(sock, SHUT_RDWR);
1196                                 close(sock);
1197                                 for (n = 0; n < num_socks; n++) {
1198                                         shutdown(socks[n], SHUT_RDWR);
1199                                         close(socks[n]);
1200                                 }
1201                                 num_socks = 0;
1202                                 break;
1203                         }
1204                         socks[num_socks++] = sock;
1205                         if (num_socks == NUM_SOCKS)
1206                                 break;
1207                 }
1208                 if (num_socks > 0)
1209                         break;
1210         }
1211         if (display_number >= MAX_DISPLAYS) {
1212                 error("Failed to allocate internet-domain X11 display socket.");
1213                 return NULL;
1214         }
1215         /* Start listening for connections on the socket. */
1216         for (n = 0; n < num_socks; n++) {
1217                 sock = socks[n];
1218                 if (listen(sock, 5) < 0) {
1219                         error("listen: %.100s", strerror(errno));
1220                         shutdown(sock, SHUT_RDWR);
1221                         close(sock);
1222                         return NULL;
1223                 }
1224         }
1225
1226         /* Set up a suitable value for the DISPLAY variable. */
1227
1228         if (gethostname(hostname, sizeof(hostname)) < 0)
1229                 fatal("gethostname: %.100s", strerror(errno));
1230
1231 #ifdef IPADDR_IN_DISPLAY
1232         /*
1233          * HPUX detects the local hostname in the DISPLAY variable and tries
1234          * to set up a shared memory connection to the server, which it
1235          * incorrectly supposes to be local.
1236          *
1237          * The workaround - as used in later $$H and other programs - is
1238          * is to set display to the host's IP address.
1239          */
1240         {
1241                 struct hostent *he;
1242                 struct in_addr my_addr;
1243
1244                 he = gethostbyname(hostname);
1245                 if (he == NULL) {
1246                         error("[X11-broken-fwd-hostname-workaround] Could not get "
1247                                 "IP address for hostname %s.", hostname);
1248
1249                         packet_send_debug("[X11-broken-fwd-hostname-workaround]"
1250                                 "Could not get IP address for hostname %s.", hostname);
1251
1252                         shutdown(sock, SHUT_RDWR);
1253                         close(sock);
1254
1255                         return NULL;
1256                 }
1257
1258                 memcpy(&my_addr, he->h_addr_list[0], sizeof(struct in_addr));
1259
1260                 /* Set DISPLAY to <ip address>:screen.display */
1261                 snprintf(display, sizeof(display), "%.50s:%d.%d", inet_ntoa(my_addr),
1262                         display_number, screen_number);
1263         }
1264 #else /* IPADDR_IN_DISPLAY */
1265         /* Just set DISPLAY to hostname:screen.display */
1266         snprintf(display, sizeof display, "%.400s:%d.%d", hostname,
1267                 display_number, screen_number);
1268 #endif /* IPADDR_IN_DISPLAY */
1269
1270         /* Allocate a channel for each socket. */
1271         for (n = 0; n < num_socks; n++) {
1272                 sock = socks[n];
1273                 (void) channel_allocate(SSH_CHANNEL_X11_LISTENER, sock,
1274                                         xstrdup("X11 inet listener"));
1275         }
1276
1277         /* Return a suitable value for the DISPLAY environment variable. */
1278         return xstrdup(display);
1279 }
1280
1281 #ifndef X_UNIX_PATH
1282 #define X_UNIX_PATH "/tmp/.X11-unix/X"
1283 #endif
1284
1285 static
1286 int
1287 connect_local_xsocket(unsigned int dnr)
1288 {
1289         static const char *const x_sockets[] = {
1290                 X_UNIX_PATH "%u",
1291                 "/var/X/.X11-unix/X" "%u",
1292                 "/usr/spool/sockets/X11/" "%u",
1293                 NULL
1294         };
1295         int sock;
1296         struct sockaddr_un addr;
1297         const char *const * path;
1298
1299         for (path = x_sockets; *path; ++path) {
1300                 sock = socket(AF_UNIX, SOCK_STREAM, 0);
1301                 if (sock < 0)
1302                         error("socket: %.100s", strerror(errno));
1303                 memset(&addr, 0, sizeof(addr));
1304                 addr.sun_family = AF_UNIX;
1305                 snprintf(addr.sun_path, sizeof addr.sun_path, *path, dnr);
1306                 if (connect(sock, (struct sockaddr *) & addr, sizeof(addr)) == 0)
1307                         return sock;
1308                 close(sock);
1309         }
1310         error("connect %.100s: %.100s", addr.sun_path, strerror(errno));
1311         return -1;
1312 }
1313
1314
1315 /*
1316  * This is called when SSH_SMSG_X11_OPEN is received.  The packet contains
1317  * the remote channel number.  We should do whatever we want, and respond
1318  * with either SSH_MSG_OPEN_CONFIRMATION or SSH_MSG_OPEN_FAILURE.
1319  */
1320
1321 void
1322 x11_input_open(int payload_len)
1323 {
1324         int remote_channel, display_number, sock = 0, newch;
1325         const char *display;
1326         char buf[1024], *cp, *remote_host;
1327         int remote_len;
1328         struct addrinfo hints, *ai, *aitop;
1329         char strport[NI_MAXSERV];
1330         int gaierr;
1331
1332         /* Get remote channel number. */
1333         remote_channel = packet_get_int();
1334
1335         /* Get remote originator name. */
1336         if (have_hostname_in_open) {
1337                 remote_host = packet_get_string(&remote_len);
1338                 remote_len += 4;
1339         } else {
1340                 remote_host = xstrdup("unknown (remote did not supply name)");
1341                 remote_len = 0;
1342         }
1343
1344         debug("Received X11 open request.");
1345         packet_integrity_check(payload_len, 4 + remote_len, SSH_SMSG_X11_OPEN);
1346
1347         /* Try to open a socket for the local X server. */
1348         display = getenv("DISPLAY");
1349         if (!display) {
1350                 error("DISPLAY not set.");
1351                 goto fail;
1352         }
1353         /*
1354          * Now we decode the value of the DISPLAY variable and make a
1355          * connection to the real X server.
1356          */
1357
1358         /*
1359          * Check if it is a unix domain socket.  Unix domain displays are in
1360          * one of the following formats: unix:d[.s], :d[.s], ::d[.s]
1361          */
1362         if (strncmp(display, "unix:", 5) == 0 ||
1363             display[0] == ':') {
1364                 /* Connect to the unix domain socket. */
1365                 if (sscanf(strrchr(display, ':') + 1, "%d", &display_number) != 1) {
1366                         error("Could not parse display number from DISPLAY: %.100s",
1367                               display);
1368                         goto fail;
1369                 }
1370                 /* Create a socket. */
1371                 sock = connect_local_xsocket(display_number);
1372                 if (sock < 0)
1373                         goto fail;
1374
1375                 /* OK, we now have a connection to the display. */
1376                 goto success;
1377         }
1378         /*
1379          * Connect to an inet socket.  The DISPLAY value is supposedly
1380          * hostname:d[.s], where hostname may also be numeric IP address.
1381          */
1382         strncpy(buf, display, sizeof(buf));
1383         buf[sizeof(buf) - 1] = 0;
1384         cp = strchr(buf, ':');
1385         if (!cp) {
1386                 error("Could not find ':' in DISPLAY: %.100s", display);
1387                 goto fail;
1388         }
1389         *cp = 0;
1390         /* buf now contains the host name.  But first we parse the display number. */
1391         if (sscanf(cp + 1, "%d", &display_number) != 1) {
1392                 error("Could not parse display number from DISPLAY: %.100s",
1393                       display);
1394                 goto fail;
1395         }
1396
1397         /* Look up the host address */
1398         memset(&hints, 0, sizeof(hints));
1399         hints.ai_family = IPv4or6;
1400         hints.ai_socktype = SOCK_STREAM;
1401         snprintf(strport, sizeof strport, "%d", 6000 + display_number);
1402         if ((gaierr = getaddrinfo(buf, strport, &hints, &aitop)) != 0) {
1403                 error("%.100s: unknown host. (%s)", buf, gai_strerror(gaierr));
1404                 goto fail;
1405         }
1406         for (ai = aitop; ai; ai = ai->ai_next) {
1407                 /* Create a socket. */
1408                 sock = socket(ai->ai_family, SOCK_STREAM, 0);
1409                 if (sock < 0) {
1410                         debug("socket: %.100s", strerror(errno));
1411                 continue;
1412         }
1413         /* Connect it to the display. */
1414         if (connect(sock, ai->ai_addr, ai->ai_addrlen) < 0) {
1415                 debug("connect %.100s port %d: %.100s", buf, 6000 + display_number,
1416                     strerror(errno));
1417                 close(sock);
1418                 continue;
1419         }
1420         /* Success */
1421         break;
1422
1423         } /* (ai = aitop, ai; ai = ai->ai_next) */
1424         freeaddrinfo(aitop);
1425         if (!ai) {
1426                 error("connect %.100s port %d: %.100s", buf, 6000 + display_number,
1427                     strerror(errno));
1428                 goto fail;
1429         }
1430 success:
1431         /* We have successfully obtained a connection to the real X display. */
1432
1433         /* Allocate a channel for this connection. */
1434         if (x11_saved_proto == NULL)
1435                 newch = channel_allocate(SSH_CHANNEL_OPEN, sock, remote_host);
1436         else
1437                 newch = channel_allocate(SSH_CHANNEL_X11_OPEN, sock, remote_host);
1438         channels[newch].remote_id = remote_channel;
1439
1440         /* Send a confirmation to the remote host. */
1441         packet_start(SSH_MSG_CHANNEL_OPEN_CONFIRMATION);
1442         packet_put_int(remote_channel);
1443         packet_put_int(newch);
1444         packet_send();
1445
1446         return;
1447
1448 fail:
1449         /* Send refusal to the remote host. */
1450         packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
1451         packet_put_int(remote_channel);
1452         packet_send();
1453 }
1454
1455 /*
1456  * Requests forwarding of X11 connections, generates fake authentication
1457  * data, and enables authentication spoofing.
1458  */
1459
1460 void
1461 x11_request_forwarding_with_spoofing(const char *proto, const char *data)
1462 {
1463         unsigned int data_len = (unsigned int) strlen(data) / 2;
1464         unsigned int i, value;
1465         char *new_data;
1466         int screen_number;
1467         const char *cp;
1468         u_int32_t rand = 0;
1469
1470         cp = getenv("DISPLAY");
1471         if (cp)
1472                 cp = strchr(cp, ':');
1473         if (cp)
1474                 cp = strchr(cp, '.');
1475         if (cp)
1476                 screen_number = atoi(cp + 1);
1477         else
1478                 screen_number = 0;
1479
1480         /* Save protocol name. */
1481         x11_saved_proto = xstrdup(proto);
1482
1483         /*
1484          * Extract real authentication data and generate fake data of the
1485          * same length.
1486          */
1487         x11_saved_data = xmalloc(data_len);
1488         x11_fake_data = xmalloc(data_len);
1489         for (i = 0; i < data_len; i++) {
1490                 if (sscanf(data + 2 * i, "%2x", &value) != 1)
1491                         fatal("x11_request_forwarding: bad authentication data: %.100s", data);
1492                 if (i % 4 == 0)
1493                         rand = arc4random();
1494                 x11_saved_data[i] = value;
1495                 x11_fake_data[i] = rand & 0xff;
1496                 rand >>= 8;
1497         }
1498         x11_saved_data_len = data_len;
1499         x11_fake_data_len = data_len;
1500
1501         /* Convert the fake data into hex. */
1502         new_data = xmalloc(2 * data_len + 1);
1503         for (i = 0; i < data_len; i++)
1504                 sprintf(new_data + 2 * i, "%02x", (unsigned char) x11_fake_data[i]);
1505
1506         /* Send the request packet. */
1507         packet_start(SSH_CMSG_X11_REQUEST_FORWARDING);
1508         packet_put_string(proto, strlen(proto));
1509         packet_put_string(new_data, strlen(new_data));
1510         packet_put_int(screen_number);
1511         packet_send();
1512         packet_write_wait();
1513         xfree(new_data);
1514 }
1515
1516 /* Sends a message to the server to request authentication fd forwarding. */
1517
1518 void
1519 auth_request_forwarding()
1520 {
1521         packet_start(SSH_CMSG_AGENT_REQUEST_FORWARDING);
1522         packet_send();
1523         packet_write_wait();
1524 }
1525
1526 /*
1527  * Returns the name of the forwarded authentication socket.  Returns NULL if
1528  * there is no forwarded authentication socket.  The returned value points to
1529  * a static buffer.
1530  */
1531
1532 char *
1533 auth_get_socket_name()
1534 {
1535         return channel_forwarded_auth_socket_name;
1536 }
1537
1538 /* removes the agent forwarding socket */
1539
1540 void
1541 cleanup_socket(void)
1542 {
1543         remove(channel_forwarded_auth_socket_name);
1544         rmdir(channel_forwarded_auth_socket_dir);
1545 }
1546
1547 /*
1548  * This if called to process SSH_CMSG_AGENT_REQUEST_FORWARDING on the server.
1549  * This starts forwarding authentication requests.
1550  */
1551
1552 void
1553 auth_input_request_forwarding(struct passwd * pw)
1554 {
1555         int sock, newch;
1556         struct sockaddr_un sunaddr;
1557
1558         if (auth_get_socket_name() != NULL)
1559                 fatal("Protocol error: authentication forwarding requested twice.");
1560
1561         /* Temporarily drop privileged uid for mkdir/bind. */
1562         temporarily_use_uid(pw->pw_uid);
1563
1564         /* Allocate a buffer for the socket name, and format the name. */
1565         channel_forwarded_auth_socket_name = xmalloc(MAX_SOCKET_NAME);
1566         channel_forwarded_auth_socket_dir = xmalloc(MAX_SOCKET_NAME);
1567         strlcpy(channel_forwarded_auth_socket_dir, "/tmp/ssh-XXXXXXXX", MAX_SOCKET_NAME);
1568
1569         /* Create private directory for socket */
1570         if (mkdtemp(channel_forwarded_auth_socket_dir) == NULL)
1571                 packet_disconnect("mkdtemp: %.100s", strerror(errno));
1572         snprintf(channel_forwarded_auth_socket_name, MAX_SOCKET_NAME, "%s/agent.%d",
1573                  channel_forwarded_auth_socket_dir, (int) getpid());
1574
1575         if (atexit(cleanup_socket) < 0) {
1576                 int saved = errno;
1577                 cleanup_socket();
1578                 packet_disconnect("socket: %.100s", strerror(saved));
1579         }
1580         /* Create the socket. */
1581         sock = socket(AF_UNIX, SOCK_STREAM, 0);
1582         if (sock < 0)
1583                 packet_disconnect("socket: %.100s", strerror(errno));
1584
1585         /* Bind it to the name. */
1586         memset(&sunaddr, 0, sizeof(sunaddr));
1587         sunaddr.sun_family = AF_UNIX;
1588         strncpy(sunaddr.sun_path, channel_forwarded_auth_socket_name,
1589                 sizeof(sunaddr.sun_path));
1590
1591         if (bind(sock, (struct sockaddr *) & sunaddr, sizeof(sunaddr)) < 0)
1592                 packet_disconnect("bind: %.100s", strerror(errno));
1593
1594         /* Restore the privileged uid. */
1595         restore_uid();
1596
1597         /* Start listening on the socket. */
1598         if (listen(sock, 5) < 0)
1599                 packet_disconnect("listen: %.100s", strerror(errno));
1600
1601         /* Allocate a channel for the authentication agent socket. */
1602         newch = channel_allocate(SSH_CHANNEL_AUTH_SOCKET, sock,
1603                                  xstrdup("auth socket"));
1604         strlcpy(channels[newch].path, channel_forwarded_auth_socket_name,
1605             sizeof(channels[newch].path));
1606 }
1607
1608 /* This is called to process an SSH_SMSG_AGENT_OPEN message. */
1609
1610 void
1611 auth_input_open_request()
1612 {
1613         int remch, sock, newch;
1614         char *dummyname;
1615
1616         /* Read the remote channel number from the message. */
1617         remch = packet_get_int();
1618
1619         /*
1620          * Get a connection to the local authentication agent (this may again
1621          * get forwarded).
1622          */
1623         sock = ssh_get_authentication_socket();
1624
1625         /*
1626          * If we could not connect the agent, send an error message back to
1627          * the server. This should never happen unless the agent dies,
1628          * because authentication forwarding is only enabled if we have an
1629          * agent.
1630          */
1631         if (sock < 0) {
1632                 packet_start(SSH_MSG_CHANNEL_OPEN_FAILURE);
1633                 packet_put_int(remch);
1634                 packet_send();
1635                 return;
1636         }
1637         debug("Forwarding authentication connection.");
1638
1639         /*
1640          * Dummy host name.  This will be freed when the channel is freed; it
1641          * will still be valid in the packet_put_string below since the
1642          * channel cannot yet be freed at that point.
1643          */
1644         dummyname = xstrdup("authentication agent connection");
1645
1646         newch = channel_allocate(SSH_CHANNEL_OPEN, sock, dummyname);
1647         channels[newch].remote_id = remch;
1648
1649         /* Send a confirmation to the remote host. */
1650         packet_start(SSH_MSG_CHANNEL_OPEN_CONFIRMATION);
1651         packet_put_int(remch);
1652         packet_put_int(newch);
1653         packet_send();
1654 }