crypto/openssh/serverloop.c

   1 /* $OpenBSD: serverloop.c,v 1.205 2018/03/03 03:15:51 djm Exp $ */
   2 /*
   3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   4  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   5  *                    All rights reserved
   6  * Server main loop for handling the interactive session.
   7  *
   8  * As far as I am concerned, the code I have written for this software
   9  * can be used freely for any purpose.  Any derived versions of this
  10  * software must be clearly marked as such, and if the derived work is
  11  * incompatible with the protocol description in the RFC file, it must be
  12  * called by a name other than "ssh" or "Secure Shell".
  13  *
  14  * SSH2 support by Markus Friedl.
  15  * Copyright (c) 2000, 2001 Markus Friedl.  All rights reserved.
  16  *
  17  * Redistribution and use in source and binary forms, with or without
  18  * modification, are permitted provided that the following conditions
  19  * are met:
  20  * 1. Redistributions of source code must retain the above copyright
  21  *    notice, this list of conditions and the following disclaimer.
  22  * 2. Redistributions in binary form must reproduce the above copyright
  23  *    notice, this list of conditions and the following disclaimer in the
  24  *    documentation and/or other materials provided with the distribution.
  25  *
  26  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  27  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  28  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  29  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  30  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  31  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  32  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  33  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  34  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  35  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  36  */
  37
  38 #include "includes.h"
  39
  40 #include <sys/types.h>
  41 #include <sys/wait.h>
  42 #include <sys/socket.h>
  43 #ifdef HAVE_SYS_TIME_H
  44 # include <sys/time.h>
  45 #endif
  46
  47 #include <netinet/in.h>
  48
  49 #include <errno.h>
  50 #include <fcntl.h>
  51 #include <pwd.h>
  52 #include <signal.h>
  53 #include <string.h>
  54 #include <termios.h>
  55 #include <unistd.h>
  56 #include <stdarg.h>
  57
  58 #include "openbsd-compat/sys-queue.h"
  59 #include "xmalloc.h"
  60 #include "packet.h"
  61 #include "buffer.h"
  62 #include "log.h"
  63 #include "misc.h"
  64 #include "servconf.h"
  65 #include "canohost.h"
  66 #include "sshpty.h"
  67 #include "channels.h"
  68 #include "compat.h"
  69 #include "ssh2.h"
  70 #include "key.h"
  71 #include "cipher.h"
  72 #include "kex.h"
  73 #include "hostfile.h"
  74 #include "auth.h"
  75 #include "session.h"
  76 #include "dispatch.h"
  77 #include "auth-options.h"
  78 #include "serverloop.h"
  79 #include "ssherr.h"
  80
  81 extern ServerOptions options;
  82
  83 /* XXX */
  84 extern Authctxt *the_authctxt;
  85 extern struct sshauthopt *auth_opts;
  86 extern int use_privsep;
  87
  88 static int no_more_sessions = 0; /* Disallow further sessions. */
  89
  90 /*
  91  * This SIGCHLD kludge is used to detect when the child exits.  The server
  92  * will exit after that, as soon as forwarded connections have terminated.
  93  */
  94
  95 static volatile sig_atomic_t child_terminated = 0;      /* The child has terminated. */
  96
  97 /* Cleanup on signals (!use_privsep case only) */
  98 static volatile sig_atomic_t received_sigterm = 0;
  99
 100 /* prototypes */
 101 static void server_init_dispatch(void);
 102
 103 /* requested tunnel forwarding interface(s), shared with session.c */
 104 char *tun_fwd_ifnames = NULL;
 105
 106 /*
 107  * we write to this pipe if a SIGCHLD is caught in order to avoid
 108  * the race between select() and child_terminated
 109  */
 110 static int notify_pipe[2];
 111 static void
 112 notify_setup(void)
 113 {
 114         if (pipe(notify_pipe) < 0) {
 115                 error("pipe(notify_pipe) failed %s", strerror(errno));
 116         } else if ((fcntl(notify_pipe[0], F_SETFD, FD_CLOEXEC) == -1) ||
 117             (fcntl(notify_pipe[1], F_SETFD, FD_CLOEXEC) == -1)) {
 118                 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno));
 119                 close(notify_pipe[0]);
 120                 close(notify_pipe[1]);
 121         } else {
 122                 set_nonblock(notify_pipe[0]);
 123                 set_nonblock(notify_pipe[1]);
 124                 return;
 125         }
 126         notify_pipe[0] = -1;    /* read end */
 127         notify_pipe[1] = -1;    /* write end */
 128 }
 129 static void
 130 notify_parent(void)
 131 {
 132         if (notify_pipe[1] != -1)
 133                 (void)write(notify_pipe[1], "", 1);
 134 }
 135 static void
 136 notify_prepare(fd_set *readset)
 137 {
 138         if (notify_pipe[0] != -1)
 139                 FD_SET(notify_pipe[0], readset);
 140 }
 141 static void
 142 notify_done(fd_set *readset)
 143 {
 144         char c;
 145
 146         if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset))
 147                 while (read(notify_pipe[0], &c, 1) != -1)
 148                         debug2("notify_done: reading");
 149 }
 150
 151 /*ARGSUSED*/
 152 static void
 153 sigchld_handler(int sig)
 154 {
 155         int save_errno = errno;
 156         child_terminated = 1;
 157         notify_parent();
 158         errno = save_errno;
 159 }
 160
 161 /*ARGSUSED*/
 162 static void
 163 sigterm_handler(int sig)
 164 {
 165         received_sigterm = sig;
 166 }
 167
 168 static void
 169 client_alive_check(struct ssh *ssh)
 170 {
 171         int channel_id;
 172         char remote_id[512];
 173
 174         /* timeout, check to see how many we have had */
 175         if (packet_inc_alive_timeouts() > options.client_alive_count_max) {
 176                 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id));
 177                 logit("Timeout, client not responding from %s", remote_id);
 178                 cleanup_exit(255);
 179         }
 180
 181         /*
 182          * send a bogus global/channel request with "wantreply",
 183          * we should get back a failure
 184          */
 185         if ((channel_id = channel_find_open(ssh)) == -1) {
 186                 packet_start(SSH2_MSG_GLOBAL_REQUEST);
 187                 packet_put_cstring("keepalive@openssh.com");
 188                 packet_put_char(1);     /* boolean: want reply */
 189         } else {
 190                 channel_request_start(ssh, channel_id,
 191                     "keepalive@openssh.com", 1);
 192         }
 193         packet_send();
 194 }
 195
 196 /*
 197  * Sleep in select() until we can do something.  This will initialize the
 198  * select masks.  Upon return, the masks will indicate which descriptors
 199  * have data or can accept data.  Optionally, a maximum time can be specified
 200  * for the duration of the wait (0 = infinite).
 201  */
 202 static void
 203 wait_until_can_do_something(struct ssh *ssh,
 204     int connection_in, int connection_out,
 205     fd_set **readsetp, fd_set **writesetp, int *maxfdp,
 206     u_int *nallocp, u_int64_t max_time_ms)
 207 {
 208         struct timeval tv, *tvp;
 209         int ret;
 210         time_t minwait_secs = 0;
 211         int client_alive_scheduled = 0;
 212         static time_t last_client_time;
 213
 214         /* Allocate and update select() masks for channel descriptors. */
 215         channel_prepare_select(ssh, readsetp, writesetp, maxfdp,
 216             nallocp, &minwait_secs);
 217
 218         /* XXX need proper deadline system for rekey/client alive */
 219         if (minwait_secs != 0)
 220                 max_time_ms = MINIMUM(max_time_ms, (u_int)minwait_secs * 1000);
 221
 222         /*
 223          * if using client_alive, set the max timeout accordingly,
 224          * and indicate that this particular timeout was for client
 225          * alive by setting the client_alive_scheduled flag.
 226          *
 227          * this could be randomized somewhat to make traffic
 228          * analysis more difficult, but we're not doing it yet.
 229          */
 230         if (options.client_alive_interval) {
 231                 uint64_t keepalive_ms =
 232                     (uint64_t)options.client_alive_interval * 1000;
 233
 234                 client_alive_scheduled = 1;
 235                 if (max_time_ms == 0 || max_time_ms > keepalive_ms)
 236                         max_time_ms = keepalive_ms;
 237         }
 238
 239 #if 0
 240         /* wrong: bad condition XXX */
 241         if (channel_not_very_much_buffered_data())
 242 #endif
 243         FD_SET(connection_in, *readsetp);
 244         notify_prepare(*readsetp);
 245
 246         /*
 247          * If we have buffered packet data going to the client, mark that
 248          * descriptor.
 249          */
 250         if (packet_have_data_to_write())
 251                 FD_SET(connection_out, *writesetp);
 252
 253         /*
 254          * If child has terminated and there is enough buffer space to read
 255          * from it, then read as much as is available and exit.
 256          */
 257         if (child_terminated && packet_not_very_much_data_to_write())
 258                 if (max_time_ms == 0 || client_alive_scheduled)
 259                         max_time_ms = 100;
 260
 261         if (max_time_ms == 0)
 262                 tvp = NULL;
 263         else {
 264                 tv.tv_sec = max_time_ms / 1000;
 265                 tv.tv_usec = 1000 * (max_time_ms % 1000);
 266                 tvp = &tv;
 267         }
 268
 269         /* Wait for something to happen, or the timeout to expire. */
 270         ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
 271
 272         if (ret == -1) {
 273                 memset(*readsetp, 0, *nallocp);
 274                 memset(*writesetp, 0, *nallocp);
 275                 if (errno != EINTR)
 276                         error("select: %.100s", strerror(errno));
 277         } else if (client_alive_scheduled) {
 278                 time_t now = monotime();
 279
 280                 if (ret == 0) { /* timeout */
 281                         client_alive_check(ssh);
 282                 } else if (FD_ISSET(connection_in, *readsetp)) {
 283                         last_client_time = now;
 284                 } else if (last_client_time != 0 && last_client_time +
 285                     options.client_alive_interval <= now) {
 286                         client_alive_check(ssh);
 287                         last_client_time = now;
 288                 }
 289         }
 290
 291         notify_done(*readsetp);
 292 }
 293
 294 /*
 295  * Processes input from the client and the program.  Input data is stored
 296  * in buffers and processed later.
 297  */
 298 static int
 299 process_input(struct ssh *ssh, fd_set *readset, int connection_in)
 300 {
 301         int len;
 302         char buf[16384];
 303
 304         /* Read and buffer any input data from the client. */
 305         if (FD_ISSET(connection_in, readset)) {
 306                 len = read(connection_in, buf, sizeof(buf));
 307                 if (len == 0) {
 308                         verbose("Connection closed by %.100s port %d",
 309                             ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
 310                         return -1;
 311                 } else if (len < 0) {
 312                         if (errno != EINTR && errno != EAGAIN &&
 313                             errno != EWOULDBLOCK) {
 314                                 verbose("Read error from remote host "
 315                                     "%.100s port %d: %.100s",
 316                                     ssh_remote_ipaddr(ssh),
 317                                     ssh_remote_port(ssh), strerror(errno));
 318                                 cleanup_exit(255);
 319                         }
 320                 } else {
 321                         /* Buffer any received data. */
 322                         packet_process_incoming(buf, len);
 323                 }
 324         }
 325         return 0;
 326 }
 327
 328 /*
 329  * Sends data from internal buffers to client program stdin.
 330  */
 331 static void
 332 process_output(fd_set *writeset, int connection_out)
 333 {
 334         /* Send any buffered packet data to the client. */
 335         if (FD_ISSET(connection_out, writeset))
 336                 packet_write_poll();
 337 }
 338
 339 static void
 340 process_buffered_input_packets(struct ssh *ssh)
 341 {
 342         ssh_dispatch_run_fatal(ssh, DISPATCH_NONBLOCK, NULL);
 343 }
 344
 345 static void
 346 collect_children(struct ssh *ssh)
 347 {
 348         pid_t pid;
 349         sigset_t oset, nset;
 350         int status;
 351
 352         /* block SIGCHLD while we check for dead children */
 353         sigemptyset(&nset);
 354         sigaddset(&nset, SIGCHLD);
 355         sigprocmask(SIG_BLOCK, &nset, &oset);
 356         if (child_terminated) {
 357                 debug("Received SIGCHLD.");
 358                 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
 359                     (pid < 0 && errno == EINTR))
 360                         if (pid > 0)
 361                                 session_close_by_pid(ssh, pid, status);
 362                 child_terminated = 0;
 363         }
 364         sigprocmask(SIG_SETMASK, &oset, NULL);
 365 }
 366
 367 void
 368 server_loop2(struct ssh *ssh, Authctxt *authctxt)
 369 {
 370         fd_set *readset = NULL, *writeset = NULL;
 371         int max_fd;
 372         u_int nalloc = 0, connection_in, connection_out;
 373         u_int64_t rekey_timeout_ms = 0;
 374
 375         debug("Entering interactive session for SSH2.");
 376
 377         signal(SIGCHLD, sigchld_handler);
 378         child_terminated = 0;
 379         connection_in = packet_get_connection_in();
 380         connection_out = packet_get_connection_out();
 381
 382         if (!use_privsep) {
 383                 signal(SIGTERM, sigterm_handler);
 384                 signal(SIGINT, sigterm_handler);
 385                 signal(SIGQUIT, sigterm_handler);
 386         }
 387
 388         notify_setup();
 389
 390         max_fd = MAXIMUM(connection_in, connection_out);
 391         max_fd = MAXIMUM(max_fd, notify_pipe[0]);
 392
 393         server_init_dispatch();
 394
 395         for (;;) {
 396                 process_buffered_input_packets(ssh);
 397
 398                 if (!ssh_packet_is_rekeying(ssh) &&
 399                     packet_not_very_much_data_to_write())
 400                         channel_output_poll(ssh);
 401                 if (options.rekey_interval > 0 && !ssh_packet_is_rekeying(ssh))
 402                         rekey_timeout_ms = packet_get_rekey_timeout() * 1000;
 403                 else
 404                         rekey_timeout_ms = 0;
 405
 406                 wait_until_can_do_something(ssh, connection_in, connection_out,
 407                     &readset, &writeset, &max_fd, &nalloc, rekey_timeout_ms);
 408
 409                 if (received_sigterm) {
 410                         logit("Exiting on signal %d", (int)received_sigterm);
 411                         /* Clean up sessions, utmp, etc. */
 412                         cleanup_exit(255);
 413                 }
 414
 415                 collect_children(ssh);
 416                 if (!ssh_packet_is_rekeying(ssh))
 417                         channel_after_select(ssh, readset, writeset);
 418                 if (process_input(ssh, readset, connection_in) < 0)
 419                         break;
 420                 process_output(writeset, connection_out);
 421         }
 422         collect_children(ssh);
 423
 424         free(readset);
 425         free(writeset);
 426
 427         /* free all channels, no more reads and writes */
 428         channel_free_all(ssh);
 429
 430         /* free remaining sessions, e.g. remove wtmp entries */
 431         session_destroy_all(ssh, NULL);
 432 }
 433
 434 static int
 435 server_input_keep_alive(int type, u_int32_t seq, struct ssh *ssh)
 436 {
 437         debug("Got %d/%u for keepalive", type, seq);
 438         /*
 439          * reset timeout, since we got a sane answer from the client.
 440          * even if this was generated by something other than
 441          * the bogus CHANNEL_REQUEST we send for keepalives.
 442          */
 443         packet_set_alive_timeouts(0);
 444         return 0;
 445 }
 446
 447 static Channel *
 448 server_request_direct_tcpip(struct ssh *ssh, int *reason, const char **errmsg)
 449 {
 450         Channel *c = NULL;
 451         char *target, *originator;
 452         u_short target_port, originator_port;
 453
 454         target = packet_get_string(NULL);
 455         target_port = packet_get_int();
 456         originator = packet_get_string(NULL);
 457         originator_port = packet_get_int();
 458         packet_check_eom();
 459
 460         debug("%s: originator %s port %d, target %s port %d", __func__,
 461             originator, originator_port, target, target_port);
 462
 463         /* XXX fine grained permissions */
 464         if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 &&
 465             auth_opts->permit_port_forwarding_flag &&
 466             !options.disable_forwarding) {
 467                 c = channel_connect_to_port(ssh, target, target_port,
 468                     "direct-tcpip", "direct-tcpip", reason, errmsg);
 469         } else {
 470                 logit("refused local port forward: "
 471                     "originator %s port %d, target %s port %d",
 472                     originator, originator_port, target, target_port);
 473                 if (reason != NULL)
 474                         *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED;
 475         }
 476
 477         free(originator);
 478         free(target);
 479
 480         return c;
 481 }
 482
 483 static Channel *
 484 server_request_direct_streamlocal(struct ssh *ssh)
 485 {
 486         Channel *c = NULL;
 487         char *target, *originator;
 488         u_short originator_port;
 489         struct passwd *pw = the_authctxt->pw;
 490
 491         if (pw == NULL || !the_authctxt->valid)
 492                 fatal("%s: no/invalid user", __func__);
 493
 494         target = packet_get_string(NULL);
 495         originator = packet_get_string(NULL);
 496         originator_port = packet_get_int();
 497         packet_check_eom();
 498
 499         debug("%s: originator %s port %d, target %s", __func__,
 500             originator, originator_port, target);
 501
 502         /* XXX fine grained permissions */
 503         if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 &&
 504             auth_opts->permit_port_forwarding_flag &&
 505             !options.disable_forwarding && (pw->pw_uid == 0 || use_privsep)) {
 506                 c = channel_connect_to_path(ssh, target,
 507                     "direct-streamlocal@openssh.com", "direct-streamlocal");
 508         } else {
 509                 logit("refused streamlocal port forward: "
 510                     "originator %s port %d, target %s",
 511                     originator, originator_port, target);
 512         }
 513
 514         free(originator);
 515         free(target);
 516
 517         return c;
 518 }
 519
 520 static Channel *
 521 server_request_tun(struct ssh *ssh)
 522 {
 523         Channel *c = NULL;
 524         int mode, tun, sock;
 525         char *tmp, *ifname = NULL;
 526
 527         mode = packet_get_int();
 528         switch (mode) {
 529         case SSH_TUNMODE_POINTOPOINT:
 530         case SSH_TUNMODE_ETHERNET:
 531                 break;
 532         default:
 533                 packet_send_debug("Unsupported tunnel device mode.");
 534                 return NULL;
 535         }
 536         if ((options.permit_tun & mode) == 0) {
 537                 packet_send_debug("Server has rejected tunnel device "
 538                     "forwarding");
 539                 return NULL;
 540         }
 541
 542         tun = packet_get_int();
 543         if (auth_opts->force_tun_device != -1) {
 544                 if (tun != SSH_TUNID_ANY && auth_opts->force_tun_device != tun)
 545                         goto done;
 546                 tun = auth_opts->force_tun_device;
 547         }
 548         sock = tun_open(tun, mode, &ifname);
 549         if (sock < 0)
 550                 goto done;
 551         debug("Tunnel forwarding using interface %s", ifname);
 552
 553         c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1,
 554             CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
 555         c->datagram = 1;
 556 #if defined(SSH_TUN_FILTER)
 557         if (mode == SSH_TUNMODE_POINTOPOINT)
 558                 channel_register_filter(ssh, c->self, sys_tun_infilter,
 559                     sys_tun_outfilter, NULL, NULL);
 560 #endif
 561
 562         /*
 563          * Update the list of names exposed to the session
 564          * XXX remove these if the tunnels are closed (won't matter
 565          * much if they are already in the environment though)
 566          */
 567         tmp = tun_fwd_ifnames;
 568         xasprintf(&tun_fwd_ifnames, "%s%s%s",
 569             tun_fwd_ifnames == NULL ? "" : tun_fwd_ifnames,
 570             tun_fwd_ifnames == NULL ? "" : ",",
 571             ifname);
 572         free(tmp);
 573         free(ifname);
 574
 575  done:
 576         if (c == NULL)
 577                 packet_send_debug("Failed to open the tunnel device.");
 578         return c;
 579 }
 580
 581 static Channel *
 582 server_request_session(struct ssh *ssh)
 583 {
 584         Channel *c;
 585
 586         debug("input_session_request");
 587         packet_check_eom();
 588
 589         if (no_more_sessions) {
 590                 packet_disconnect("Possible attack: attempt to open a session "
 591                     "after additional sessions disabled");
 592         }
 593
 594         /*
 595          * A server session has no fd to read or write until a
 596          * CHANNEL_REQUEST for a shell is made, so we set the type to
 597          * SSH_CHANNEL_LARVAL.  Additionally, a callback for handling all
 598          * CHANNEL_REQUEST messages is registered.
 599          */
 600         c = channel_new(ssh, "session", SSH_CHANNEL_LARVAL,
 601             -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
 602             0, "server-session", 1);
 603         if (session_open(the_authctxt, c->self) != 1) {
 604                 debug("session open failed, free channel %d", c->self);
 605                 channel_free(ssh, c);
 606                 return NULL;
 607         }
 608         channel_register_cleanup(ssh, c->self, session_close_by_channel, 0);
 609         return c;
 610 }
 611
 612 static int
 613 server_input_channel_open(int type, u_int32_t seq, struct ssh *ssh)
 614 {
 615         Channel *c = NULL;
 616         char *ctype;
 617         const char *errmsg = NULL;
 618         int rchan, reason = SSH2_OPEN_CONNECT_FAILED;
 619         u_int rmaxpack, rwindow, len;
 620
 621         ctype = packet_get_string(&len);
 622         rchan = packet_get_int();
 623         rwindow = packet_get_int();
 624         rmaxpack = packet_get_int();
 625
 626         debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
 627             ctype, rchan, rwindow, rmaxpack);
 628
 629         if (strcmp(ctype, "session") == 0) {
 630                 c = server_request_session(ssh);
 631         } else if (strcmp(ctype, "direct-tcpip") == 0) {
 632                 c = server_request_direct_tcpip(ssh, &reason, &errmsg);
 633         } else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) {
 634                 c = server_request_direct_streamlocal(ssh);
 635         } else if (strcmp(ctype, "tun@openssh.com") == 0) {
 636                 c = server_request_tun(ssh);
 637         }
 638         if (c != NULL) {
 639                 debug("server_input_channel_open: confirm %s", ctype);
 640                 c->remote_id = rchan;
 641                 c->have_remote_id = 1;
 642                 c->remote_window = rwindow;
 643                 c->remote_maxpacket = rmaxpack;
 644                 if (c->type != SSH_CHANNEL_CONNECTING) {
 645                         packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
 646                         packet_put_int(c->remote_id);
 647                         packet_put_int(c->self);
 648                         packet_put_int(c->local_window);
 649                         packet_put_int(c->local_maxpacket);
 650                         packet_send();
 651                 }
 652         } else {
 653                 debug("server_input_channel_open: failure %s", ctype);
 654                 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
 655                 packet_put_int(rchan);
 656                 packet_put_int(reason);
 657                 packet_put_cstring(errmsg ? errmsg : "open failed");
 658                 packet_put_cstring("");
 659                 packet_send();
 660         }
 661         free(ctype);
 662         return 0;
 663 }
 664
 665 static int
 666 server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp)
 667 {
 668         struct sshbuf *resp = NULL;
 669         struct sshbuf *sigbuf = NULL;
 670         struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL;
 671         int r, ndx, kexsigtype, use_kexsigtype, success = 0;
 672         const u_char *blob;
 673         u_char *sig = 0;
 674         size_t blen, slen;
 675
 676         if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL)
 677                 fatal("%s: sshbuf_new", __func__);
 678
 679         kexsigtype = sshkey_type_plain(
 680             sshkey_type_from_name(ssh->kex->hostkey_alg));
 681         while (ssh_packet_remaining(ssh) > 0) {
 682                 sshkey_free(key);
 683                 key = NULL;
 684                 if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 ||
 685                     (r = sshkey_from_blob(blob, blen, &key)) != 0) {
 686                         error("%s: couldn't parse key: %s",
 687                             __func__, ssh_err(r));
 688                         goto out;
 689                 }
 690                 /*
 691                  * Better check that this is actually one of our hostkeys
 692                  * before attempting to sign anything with it.
 693                  */
 694                 if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) {
 695                         error("%s: unknown host %s key",
 696                             __func__, sshkey_type(key));
 697                         goto out;
 698                 }
 699                 /*
 700                  * XXX refactor: make kex->sign just use an index rather
 701                  * than passing in public and private keys
 702                  */
 703                 if ((key_prv = get_hostkey_by_index(ndx)) == NULL &&
 704                     (key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) {
 705                         error("%s: can't retrieve hostkey %d", __func__, ndx);
 706                         goto out;
 707                 }
 708                 sshbuf_reset(sigbuf);
 709                 free(sig);
 710                 sig = NULL;
 711                 /*
 712                  * For RSA keys, prefer to use the signature type negotiated
 713                  * during KEX to the default (SHA1).
 714                  */
 715                 use_kexsigtype = kexsigtype == KEY_RSA &&
 716                     sshkey_type_plain(key->type) == KEY_RSA;
 717                 if ((r = sshbuf_put_cstring(sigbuf,
 718                     "hostkeys-prove-00@openssh.com")) != 0 ||
 719                     (r = sshbuf_put_string(sigbuf,
 720                     ssh->kex->session_id, ssh->kex->session_id_len)) != 0 ||
 721                     (r = sshkey_puts(key, sigbuf)) != 0 ||
 722                     (r = ssh->kex->sign(key_prv, key_pub, &sig, &slen,
 723                     sshbuf_ptr(sigbuf), sshbuf_len(sigbuf),
 724                     use_kexsigtype ? ssh->kex->hostkey_alg : NULL, 0)) != 0 ||
 725                     (r = sshbuf_put_string(resp, sig, slen)) != 0) {
 726                         error("%s: couldn't prepare signature: %s",
 727                             __func__, ssh_err(r));
 728                         goto out;
 729                 }
 730         }
 731         /* Success */
 732         *respp = resp;
 733         resp = NULL; /* don't free it */
 734         success = 1;
 735  out:
 736         free(sig);
 737         sshbuf_free(resp);
 738         sshbuf_free(sigbuf);
 739         sshkey_free(key);
 740         return success;
 741 }
 742
 743 static int
 744 server_input_global_request(int type, u_int32_t seq, struct ssh *ssh)
 745 {
 746         char *rtype;
 747         int want_reply;
 748         int r, success = 0, allocated_listen_port = 0;
 749         struct sshbuf *resp = NULL;
 750         struct passwd *pw = the_authctxt->pw;
 751
 752         if (pw == NULL || !the_authctxt->valid)
 753                 fatal("server_input_global_request: no/invalid user");
 754
 755         rtype = packet_get_string(NULL);
 756         want_reply = packet_get_char();
 757         debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
 758
 759         /* -R style forwarding */
 760         if (strcmp(rtype, "tcpip-forward") == 0) {
 761                 struct Forward fwd;
 762
 763                 memset(&fwd, 0, sizeof(fwd));
 764                 fwd.listen_host = packet_get_string(NULL);
 765                 fwd.listen_port = (u_short)packet_get_int();
 766                 debug("server_input_global_request: tcpip-forward listen %s port %d",
 767                     fwd.listen_host, fwd.listen_port);
 768
 769                 /* check permissions */
 770                 if ((options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 ||
 771                     !auth_opts->permit_port_forwarding_flag ||
 772                     options.disable_forwarding ||
 773                     (!want_reply && fwd.listen_port == 0) ||
 774                     (fwd.listen_port != 0 &&
 775                      !bind_permitted(fwd.listen_port, pw->pw_uid))) {
 776                         success = 0;
 777                         packet_send_debug("Server has disabled port forwarding.");
 778                 } else {
 779                         /* Start listening on the port */
 780                         success = channel_setup_remote_fwd_listener(ssh, &fwd,
 781                             &allocated_listen_port, &options.fwd_opts);
 782                 }
 783                 free(fwd.listen_host);
 784                 if ((resp = sshbuf_new()) == NULL)
 785                         fatal("%s: sshbuf_new", __func__);
 786                 if (allocated_listen_port != 0 &&
 787                     (r = sshbuf_put_u32(resp, allocated_listen_port)) != 0)
 788                         fatal("%s: sshbuf_put_u32: %s", __func__, ssh_err(r));
 789         } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
 790                 struct Forward fwd;
 791
 792                 memset(&fwd, 0, sizeof(fwd));
 793                 fwd.listen_host = packet_get_string(NULL);
 794                 fwd.listen_port = (u_short)packet_get_int();
 795                 debug("%s: cancel-tcpip-forward addr %s port %d", __func__,
 796                     fwd.listen_host, fwd.listen_port);
 797
 798                 success = channel_cancel_rport_listener(ssh, &fwd);
 799                 free(fwd.listen_host);
 800         } else if (strcmp(rtype, "streamlocal-forward@openssh.com") == 0) {
 801                 struct Forward fwd;
 802
 803                 memset(&fwd, 0, sizeof(fwd));
 804                 fwd.listen_path = packet_get_string(NULL);
 805                 debug("server_input_global_request: streamlocal-forward listen path %s",
 806                     fwd.listen_path);
 807
 808                 /* check permissions */
 809                 if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0
 810                     || !auth_opts->permit_port_forwarding_flag ||
 811                     options.disable_forwarding ||
 812                     (pw->pw_uid != 0 && !use_privsep)) {
 813                         success = 0;
 814                         packet_send_debug("Server has disabled "
 815                             "streamlocal forwarding.");
 816                 } else {
 817                         /* Start listening on the socket */
 818                         success = channel_setup_remote_fwd_listener(ssh,
 819                             &fwd, NULL, &options.fwd_opts);
 820                 }
 821                 free(fwd.listen_path);
 822         } else if (strcmp(rtype, "cancel-streamlocal-forward@openssh.com") == 0) {
 823                 struct Forward fwd;
 824
 825                 memset(&fwd, 0, sizeof(fwd));
 826                 fwd.listen_path = packet_get_string(NULL);
 827                 debug("%s: cancel-streamlocal-forward path %s", __func__,
 828                     fwd.listen_path);
 829
 830                 success = channel_cancel_rport_listener(ssh, &fwd);
 831                 free(fwd.listen_path);
 832         } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) {
 833                 no_more_sessions = 1;
 834                 success = 1;
 835         } else if (strcmp(rtype, "hostkeys-prove-00@openssh.com") == 0) {
 836                 success = server_input_hostkeys_prove(ssh, &resp);
 837         }
 838         if (want_reply) {
 839                 packet_start(success ?
 840                     SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
 841                 if (success && resp != NULL)
 842                         ssh_packet_put_raw(ssh, sshbuf_ptr(resp),
 843                             sshbuf_len(resp));
 844                 packet_send();
 845                 packet_write_wait();
 846         }
 847         free(rtype);
 848         sshbuf_free(resp);
 849         return 0;
 850 }
 851
 852 static int
 853 server_input_channel_req(int type, u_int32_t seq, struct ssh *ssh)
 854 {
 855         Channel *c;
 856         int id, reply, success = 0;
 857         char *rtype;
 858
 859         id = packet_get_int();
 860         rtype = packet_get_string(NULL);
 861         reply = packet_get_char();
 862
 863         debug("server_input_channel_req: channel %d request %s reply %d",
 864             id, rtype, reply);
 865
 866         if ((c = channel_lookup(ssh, id)) == NULL)
 867                 packet_disconnect("server_input_channel_req: "
 868                     "unknown channel %d", id);
 869         if (!strcmp(rtype, "eow@openssh.com")) {
 870                 packet_check_eom();
 871                 chan_rcvd_eow(ssh, c);
 872         } else if ((c->type == SSH_CHANNEL_LARVAL ||
 873             c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0)
 874                 success = session_input_channel_req(ssh, c, rtype);
 875         if (reply && !(c->flags & CHAN_CLOSE_SENT)) {
 876                 if (!c->have_remote_id)
 877                         fatal("%s: channel %d: no remote_id",
 878                             __func__, c->self);
 879                 packet_start(success ?
 880                     SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
 881                 packet_put_int(c->remote_id);
 882                 packet_send();
 883         }
 884         free(rtype);
 885         return 0;
 886 }
 887
 888 static void
 889 server_init_dispatch(void)
 890 {
 891         debug("server_init_dispatch");
 892         dispatch_init(&dispatch_protocol_error);
 893         dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
 894         dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
 895         dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
 896         dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
 897         dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
 898         dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
 899         dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
 900         dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
 901         dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
 902         dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
 903         /* client_alive */
 904         dispatch_set(SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive);
 905         dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
 906         dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
 907         dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
 908         /* rekeying */
 909         dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
 910 }