serverloop.c

   1 /* $OpenBSD: serverloop.c,v 1.191 2017/02/01 02:59:09 dtucker 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 int use_privsep;
  86
  87 static int no_more_sessions = 0; /* Disallow further sessions. */
  88
  89 /*
  90  * This SIGCHLD kludge is used to detect when the child exits.  The server
  91  * will exit after that, as soon as forwarded connections have terminated.
  92  */
  93
  94 static volatile sig_atomic_t child_terminated = 0;      /* The child has terminated. */
  95
  96 /* Cleanup on signals (!use_privsep case only) */
  97 static volatile sig_atomic_t received_sigterm = 0;
  98
  99 /* prototypes */
 100 static void server_init_dispatch(void);
 101
 102 /*
 103  * we write to this pipe if a SIGCHLD is caught in order to avoid
 104  * the race between select() and child_terminated
 105  */
 106 static int notify_pipe[2];
 107 static void
 108 notify_setup(void)
 109 {
 110         if (pipe(notify_pipe) < 0) {
 111                 error("pipe(notify_pipe) failed %s", strerror(errno));
 112         } else if ((fcntl(notify_pipe[0], F_SETFD, FD_CLOEXEC) == -1) ||
 113             (fcntl(notify_pipe[1], F_SETFD, FD_CLOEXEC) == -1)) {
 114                 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno));
 115                 close(notify_pipe[0]);
 116                 close(notify_pipe[1]);
 117         } else {
 118                 set_nonblock(notify_pipe[0]);
 119                 set_nonblock(notify_pipe[1]);
 120                 return;
 121         }
 122         notify_pipe[0] = -1;    /* read end */
 123         notify_pipe[1] = -1;    /* write end */
 124 }
 125 static void
 126 notify_parent(void)
 127 {
 128         if (notify_pipe[1] != -1)
 129                 (void)write(notify_pipe[1], "", 1);
 130 }
 131 static void
 132 notify_prepare(fd_set *readset)
 133 {
 134         if (notify_pipe[0] != -1)
 135                 FD_SET(notify_pipe[0], readset);
 136 }
 137 static void
 138 notify_done(fd_set *readset)
 139 {
 140         char c;
 141
 142         if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset))
 143                 while (read(notify_pipe[0], &c, 1) != -1)
 144                         debug2("notify_done: reading");
 145 }
 146
 147 /*ARGSUSED*/
 148 static void
 149 sigchld_handler(int sig)
 150 {
 151         int save_errno = errno;
 152         child_terminated = 1;
 153 #ifndef _UNICOS
 154         mysignal(SIGCHLD, sigchld_handler);
 155 #endif
 156         notify_parent();
 157         errno = save_errno;
 158 }
 159
 160 /*ARGSUSED*/
 161 static void
 162 sigterm_handler(int sig)
 163 {
 164         received_sigterm = sig;
 165 }
 166
 167 static void
 168 client_alive_check(void)
 169 {
 170         int channel_id;
 171
 172         /* timeout, check to see how many we have had */
 173         if (packet_inc_alive_timeouts() > options.client_alive_count_max) {
 174                 logit("Timeout, client not responding.");
 175                 cleanup_exit(255);
 176         }
 177
 178         /*
 179          * send a bogus global/channel request with "wantreply",
 180          * we should get back a failure
 181          */
 182         if ((channel_id = channel_find_open()) == -1) {
 183                 packet_start(SSH2_MSG_GLOBAL_REQUEST);
 184                 packet_put_cstring("keepalive@openssh.com");
 185                 packet_put_char(1);     /* boolean: want reply */
 186         } else {
 187                 channel_request_start(channel_id, "keepalive@openssh.com", 1);
 188         }
 189         packet_send();
 190 }
 191
 192 /*
 193  * Sleep in select() until we can do something.  This will initialize the
 194  * select masks.  Upon return, the masks will indicate which descriptors
 195  * have data or can accept data.  Optionally, a maximum time can be specified
 196  * for the duration of the wait (0 = infinite).
 197  */
 198 static void
 199 wait_until_can_do_something(int connection_in, int connection_out,
 200     fd_set **readsetp, fd_set **writesetp, int *maxfdp,
 201     u_int *nallocp, u_int64_t max_time_ms)
 202 {
 203         struct timeval tv, *tvp;
 204         int ret;
 205         time_t minwait_secs = 0;
 206         int client_alive_scheduled = 0;
 207
 208         /* Allocate and update select() masks for channel descriptors. */
 209         channel_prepare_select(readsetp, writesetp, maxfdp, nallocp,
 210             &minwait_secs, 0);
 211
 212         /* XXX need proper deadline system for rekey/client alive */
 213         if (minwait_secs != 0)
 214                 max_time_ms = MINIMUM(max_time_ms, (u_int)minwait_secs * 1000);
 215
 216         /*
 217          * if using client_alive, set the max timeout accordingly,
 218          * and indicate that this particular timeout was for client
 219          * alive by setting the client_alive_scheduled flag.
 220          *
 221          * this could be randomized somewhat to make traffic
 222          * analysis more difficult, but we're not doing it yet.
 223          */
 224         if (options.client_alive_interval) {
 225                 uint64_t keepalive_ms =
 226                     (uint64_t)options.client_alive_interval * 1000;
 227
 228                 client_alive_scheduled = 1;
 229                 if (max_time_ms == 0 || max_time_ms > keepalive_ms)
 230                         max_time_ms = keepalive_ms;
 231         }
 232
 233 #if 0
 234         /* wrong: bad condition XXX */
 235         if (channel_not_very_much_buffered_data())
 236 #endif
 237         FD_SET(connection_in, *readsetp);
 238         notify_prepare(*readsetp);
 239
 240         /*
 241          * If we have buffered packet data going to the client, mark that
 242          * descriptor.
 243          */
 244         if (packet_have_data_to_write())
 245                 FD_SET(connection_out, *writesetp);
 246
 247         /*
 248          * If child has terminated and there is enough buffer space to read
 249          * from it, then read as much as is available and exit.
 250          */
 251         if (child_terminated && packet_not_very_much_data_to_write())
 252                 if (max_time_ms == 0 || client_alive_scheduled)
 253                         max_time_ms = 100;
 254
 255         if (max_time_ms == 0)
 256                 tvp = NULL;
 257         else {
 258                 tv.tv_sec = max_time_ms / 1000;
 259                 tv.tv_usec = 1000 * (max_time_ms % 1000);
 260                 tvp = &tv;
 261         }
 262
 263         /* Wait for something to happen, or the timeout to expire. */
 264         ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
 265
 266         if (ret == -1) {
 267                 memset(*readsetp, 0, *nallocp);
 268                 memset(*writesetp, 0, *nallocp);
 269                 if (errno != EINTR)
 270                         error("select: %.100s", strerror(errno));
 271         } else if (ret == 0 && client_alive_scheduled)
 272                 client_alive_check();
 273
 274         notify_done(*readsetp);
 275 }
 276
 277 /*
 278  * Processes input from the client and the program.  Input data is stored
 279  * in buffers and processed later.
 280  */
 281 static int
 282 process_input(fd_set *readset, int connection_in)
 283 {
 284         struct ssh *ssh = active_state; /* XXX */
 285         int len;
 286         char buf[16384];
 287
 288         /* Read and buffer any input data from the client. */
 289         if (FD_ISSET(connection_in, readset)) {
 290                 len = read(connection_in, buf, sizeof(buf));
 291                 if (len == 0) {
 292                         verbose("Connection closed by %.100s port %d",
 293                             ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
 294                         return -1;
 295                 } else if (len < 0) {
 296                         if (errno != EINTR && errno != EAGAIN &&
 297                             errno != EWOULDBLOCK) {
 298                                 verbose("Read error from remote host "
 299                                     "%.100s port %d: %.100s",
 300                                     ssh_remote_ipaddr(ssh),
 301                                     ssh_remote_port(ssh), strerror(errno));
 302                                 cleanup_exit(255);
 303                         }
 304                 } else {
 305                         /* Buffer any received data. */
 306                         packet_process_incoming(buf, len);
 307                 }
 308         }
 309         return 0;
 310 }
 311
 312 /*
 313  * Sends data from internal buffers to client program stdin.
 314  */
 315 static void
 316 process_output(fd_set *writeset, int connection_out)
 317 {
 318         /* Send any buffered packet data to the client. */
 319         if (FD_ISSET(connection_out, writeset))
 320                 packet_write_poll();
 321 }
 322
 323 static void
 324 process_buffered_input_packets(void)
 325 {
 326         dispatch_run(DISPATCH_NONBLOCK, NULL, active_state);
 327 }
 328
 329 static void
 330 collect_children(void)
 331 {
 332         pid_t pid;
 333         sigset_t oset, nset;
 334         int status;
 335
 336         /* block SIGCHLD while we check for dead children */
 337         sigemptyset(&nset);
 338         sigaddset(&nset, SIGCHLD);
 339         sigprocmask(SIG_BLOCK, &nset, &oset);
 340         if (child_terminated) {
 341                 debug("Received SIGCHLD.");
 342                 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
 343                     (pid < 0 && errno == EINTR))
 344                         if (pid > 0)
 345                                 session_close_by_pid(pid, status);
 346                 child_terminated = 0;
 347         }
 348         sigprocmask(SIG_SETMASK, &oset, NULL);
 349 }
 350
 351 void
 352 server_loop2(Authctxt *authctxt)
 353 {
 354         fd_set *readset = NULL, *writeset = NULL;
 355         int max_fd;
 356         u_int nalloc = 0, connection_in, connection_out;
 357         u_int64_t rekey_timeout_ms = 0;
 358
 359         debug("Entering interactive session for SSH2.");
 360
 361         mysignal(SIGCHLD, sigchld_handler);
 362         child_terminated = 0;
 363         connection_in = packet_get_connection_in();
 364         connection_out = packet_get_connection_out();
 365
 366         if (!use_privsep) {
 367                 signal(SIGTERM, sigterm_handler);
 368                 signal(SIGINT, sigterm_handler);
 369                 signal(SIGQUIT, sigterm_handler);
 370         }
 371
 372         notify_setup();
 373
 374         max_fd = MAXIMUM(connection_in, connection_out);
 375         max_fd = MAXIMUM(max_fd, notify_pipe[0]);
 376
 377         server_init_dispatch();
 378
 379         for (;;) {
 380                 process_buffered_input_packets();
 381
 382                 if (!ssh_packet_is_rekeying(active_state) &&
 383                     packet_not_very_much_data_to_write())
 384                         channel_output_poll();
 385                 if (options.rekey_interval > 0 &&
 386                     !ssh_packet_is_rekeying(active_state))
 387                         rekey_timeout_ms = packet_get_rekey_timeout() * 1000;
 388                 else
 389                         rekey_timeout_ms = 0;
 390
 391                 wait_until_can_do_something(connection_in, connection_out,
 392                     &readset, &writeset, &max_fd, &nalloc, rekey_timeout_ms);
 393
 394                 if (received_sigterm) {
 395                         logit("Exiting on signal %d", (int)received_sigterm);
 396                         /* Clean up sessions, utmp, etc. */
 397                         cleanup_exit(255);
 398                 }
 399
 400                 collect_children();
 401                 if (!ssh_packet_is_rekeying(active_state))
 402                         channel_after_select(readset, writeset);
 403                 if (process_input(readset, connection_in) < 0)
 404                         break;
 405                 process_output(writeset, connection_out);
 406         }
 407         collect_children();
 408
 409         free(readset);
 410         free(writeset);
 411
 412         /* free all channels, no more reads and writes */
 413         channel_free_all();
 414
 415         /* free remaining sessions, e.g. remove wtmp entries */
 416         session_destroy_all(NULL);
 417 }
 418
 419 static int
 420 server_input_keep_alive(int type, u_int32_t seq, void *ctxt)
 421 {
 422         debug("Got %d/%u for keepalive", type, seq);
 423         /*
 424          * reset timeout, since we got a sane answer from the client.
 425          * even if this was generated by something other than
 426          * the bogus CHANNEL_REQUEST we send for keepalives.
 427          */
 428         packet_set_alive_timeouts(0);
 429         return 0;
 430 }
 431
 432 static Channel *
 433 server_request_direct_tcpip(int *reason, const char **errmsg)
 434 {
 435         Channel *c = NULL;
 436         char *target, *originator;
 437         u_short target_port, originator_port;
 438
 439         target = packet_get_string(NULL);
 440         target_port = packet_get_int();
 441         originator = packet_get_string(NULL);
 442         originator_port = packet_get_int();
 443         packet_check_eom();
 444
 445         debug("server_request_direct_tcpip: originator %s port %d, target %s "
 446             "port %d", originator, originator_port, target, target_port);
 447
 448         /* XXX fine grained permissions */
 449         if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 &&
 450             !no_port_forwarding_flag && !options.disable_forwarding) {
 451                 c = channel_connect_to_port(target, target_port,
 452                     "direct-tcpip", "direct-tcpip", reason, errmsg);
 453         } else {
 454                 logit("refused local port forward: "
 455                     "originator %s port %d, target %s port %d",
 456                     originator, originator_port, target, target_port);
 457                 if (reason != NULL)
 458                         *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED;
 459         }
 460
 461         free(originator);
 462         free(target);
 463
 464         return c;
 465 }
 466
 467 static Channel *
 468 server_request_direct_streamlocal(void)
 469 {
 470         Channel *c = NULL;
 471         char *target, *originator;
 472         u_short originator_port;
 473         struct passwd *pw = the_authctxt->pw;
 474
 475         if (pw == NULL || !the_authctxt->valid)
 476                 fatal("server_input_global_request: no/invalid user");
 477
 478         target = packet_get_string(NULL);
 479         originator = packet_get_string(NULL);
 480         originator_port = packet_get_int();
 481         packet_check_eom();
 482
 483         debug("server_request_direct_streamlocal: originator %s port %d, target %s",
 484             originator, originator_port, target);
 485
 486         /* XXX fine grained permissions */
 487         if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 &&
 488             !no_port_forwarding_flag && !options.disable_forwarding &&
 489             (pw->pw_uid == 0 || use_privsep)) {
 490                 c = channel_connect_to_path(target,
 491                     "direct-streamlocal@openssh.com", "direct-streamlocal");
 492         } else {
 493                 logit("refused streamlocal port forward: "
 494                     "originator %s port %d, target %s",
 495                     originator, originator_port, target);
 496         }
 497
 498         free(originator);
 499         free(target);
 500
 501         return c;
 502 }
 503
 504 static Channel *
 505 server_request_tun(void)
 506 {
 507         Channel *c = NULL;
 508         int mode, tun;
 509         int sock;
 510
 511         mode = packet_get_int();
 512         switch (mode) {
 513         case SSH_TUNMODE_POINTOPOINT:
 514         case SSH_TUNMODE_ETHERNET:
 515                 break;
 516         default:
 517                 packet_send_debug("Unsupported tunnel device mode.");
 518                 return NULL;
 519         }
 520         if ((options.permit_tun & mode) == 0) {
 521                 packet_send_debug("Server has rejected tunnel device "
 522                     "forwarding");
 523                 return NULL;
 524         }
 525
 526         tun = packet_get_int();
 527         if (forced_tun_device != -1) {
 528                 if (tun != SSH_TUNID_ANY && forced_tun_device != tun)
 529                         goto done;
 530                 tun = forced_tun_device;
 531         }
 532         sock = tun_open(tun, mode);
 533         if (sock < 0)
 534                 goto done;
 535         c = channel_new("tun", SSH_CHANNEL_OPEN, sock, sock, -1,
 536             CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
 537         c->datagram = 1;
 538 #if defined(SSH_TUN_FILTER)
 539         if (mode == SSH_TUNMODE_POINTOPOINT)
 540                 channel_register_filter(c->self, sys_tun_infilter,
 541                     sys_tun_outfilter, NULL, NULL);
 542 #endif
 543
 544  done:
 545         if (c == NULL)
 546                 packet_send_debug("Failed to open the tunnel device.");
 547         return c;
 548 }
 549
 550 static Channel *
 551 server_request_session(void)
 552 {
 553         Channel *c;
 554
 555         debug("input_session_request");
 556         packet_check_eom();
 557
 558         if (no_more_sessions) {
 559                 packet_disconnect("Possible attack: attempt to open a session "
 560                     "after additional sessions disabled");
 561         }
 562
 563         /*
 564          * A server session has no fd to read or write until a
 565          * CHANNEL_REQUEST for a shell is made, so we set the type to
 566          * SSH_CHANNEL_LARVAL.  Additionally, a callback for handling all
 567          * CHANNEL_REQUEST messages is registered.
 568          */
 569         c = channel_new("session", SSH_CHANNEL_LARVAL,
 570             -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
 571             0, "server-session", 1);
 572         if (session_open(the_authctxt, c->self) != 1) {
 573                 debug("session open failed, free channel %d", c->self);
 574                 channel_free(c);
 575                 return NULL;
 576         }
 577         channel_register_cleanup(c->self, session_close_by_channel, 0);
 578         return c;
 579 }
 580
 581 static int
 582 server_input_channel_open(int type, u_int32_t seq, void *ctxt)
 583 {
 584         Channel *c = NULL;
 585         char *ctype;
 586         const char *errmsg = NULL;
 587         int rchan, reason = SSH2_OPEN_CONNECT_FAILED;
 588         u_int rmaxpack, rwindow, len;
 589
 590         ctype = packet_get_string(&len);
 591         rchan = packet_get_int();
 592         rwindow = packet_get_int();
 593         rmaxpack = packet_get_int();
 594
 595         debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
 596             ctype, rchan, rwindow, rmaxpack);
 597
 598         if (strcmp(ctype, "session") == 0) {
 599                 c = server_request_session();
 600         } else if (strcmp(ctype, "direct-tcpip") == 0) {
 601                 c = server_request_direct_tcpip(&reason, &errmsg);
 602         } else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) {
 603                 c = server_request_direct_streamlocal();
 604         } else if (strcmp(ctype, "tun@openssh.com") == 0) {
 605                 c = server_request_tun();
 606         }
 607         if (c != NULL) {
 608                 debug("server_input_channel_open: confirm %s", ctype);
 609                 c->remote_id = rchan;
 610                 c->remote_window = rwindow;
 611                 c->remote_maxpacket = rmaxpack;
 612                 if (c->type != SSH_CHANNEL_CONNECTING) {
 613                         packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
 614                         packet_put_int(c->remote_id);
 615                         packet_put_int(c->self);
 616                         packet_put_int(c->local_window);
 617                         packet_put_int(c->local_maxpacket);
 618                         packet_send();
 619                 }
 620         } else {
 621                 debug("server_input_channel_open: failure %s", ctype);
 622                 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
 623                 packet_put_int(rchan);
 624                 packet_put_int(reason);
 625                 if (!(datafellows & SSH_BUG_OPENFAILURE)) {
 626                         packet_put_cstring(errmsg ? errmsg : "open failed");
 627                         packet_put_cstring("");
 628                 }
 629                 packet_send();
 630         }
 631         free(ctype);
 632         return 0;
 633 }
 634
 635 static int
 636 server_input_hostkeys_prove(struct sshbuf **respp)
 637 {
 638         struct ssh *ssh = active_state; /* XXX */
 639         struct sshbuf *resp = NULL;
 640         struct sshbuf *sigbuf = NULL;
 641         struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL;
 642         int r, ndx, success = 0;
 643         const u_char *blob;
 644         u_char *sig = 0;
 645         size_t blen, slen;
 646
 647         if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL)
 648                 fatal("%s: sshbuf_new", __func__);
 649
 650         while (ssh_packet_remaining(ssh) > 0) {
 651                 sshkey_free(key);
 652                 key = NULL;
 653                 if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 ||
 654                     (r = sshkey_from_blob(blob, blen, &key)) != 0) {
 655                         error("%s: couldn't parse key: %s",
 656                             __func__, ssh_err(r));
 657                         goto out;
 658                 }
 659                 /*
 660                  * Better check that this is actually one of our hostkeys
 661                  * before attempting to sign anything with it.
 662                  */
 663                 if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) {
 664                         error("%s: unknown host %s key",
 665                             __func__, sshkey_type(key));
 666                         goto out;
 667                 }
 668                 /*
 669                  * XXX refactor: make kex->sign just use an index rather
 670                  * than passing in public and private keys
 671                  */
 672                 if ((key_prv = get_hostkey_by_index(ndx)) == NULL &&
 673                     (key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) {
 674                         error("%s: can't retrieve hostkey %d", __func__, ndx);
 675                         goto out;
 676                 }
 677                 sshbuf_reset(sigbuf);
 678                 free(sig);
 679                 sig = NULL;
 680                 if ((r = sshbuf_put_cstring(sigbuf,
 681                     "hostkeys-prove-00@openssh.com")) != 0 ||
 682                     (r = sshbuf_put_string(sigbuf,
 683                     ssh->kex->session_id, ssh->kex->session_id_len)) != 0 ||
 684                     (r = sshkey_puts(key, sigbuf)) != 0 ||
 685                     (r = ssh->kex->sign(key_prv, key_pub, &sig, &slen,
 686                     sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), NULL, 0)) != 0 ||
 687                     (r = sshbuf_put_string(resp, sig, slen)) != 0) {
 688                         error("%s: couldn't prepare signature: %s",
 689                             __func__, ssh_err(r));
 690                         goto out;
 691                 }
 692         }
 693         /* Success */
 694         *respp = resp;
 695         resp = NULL; /* don't free it */
 696         success = 1;
 697  out:
 698         free(sig);
 699         sshbuf_free(resp);
 700         sshbuf_free(sigbuf);
 701         sshkey_free(key);
 702         return success;
 703 }
 704
 705 static int
 706 server_input_global_request(int type, u_int32_t seq, void *ctxt)
 707 {
 708         char *rtype;
 709         int want_reply;
 710         int r, success = 0, allocated_listen_port = 0;
 711         struct sshbuf *resp = NULL;
 712         struct passwd *pw = the_authctxt->pw;
 713
 714         if (pw == NULL || !the_authctxt->valid)
 715                 fatal("server_input_global_request: no/invalid user");
 716
 717         rtype = packet_get_string(NULL);
 718         want_reply = packet_get_char();
 719         debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
 720
 721         /* -R style forwarding */
 722         if (strcmp(rtype, "tcpip-forward") == 0) {
 723                 struct Forward fwd;
 724
 725                 memset(&fwd, 0, sizeof(fwd));
 726                 fwd.listen_host = packet_get_string(NULL);
 727                 fwd.listen_port = (u_short)packet_get_int();
 728                 debug("server_input_global_request: tcpip-forward listen %s port %d",
 729                     fwd.listen_host, fwd.listen_port);
 730
 731                 /* check permissions */
 732                 if ((options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 ||
 733                     no_port_forwarding_flag || options.disable_forwarding ||
 734                     (!want_reply && fwd.listen_port == 0) ||
 735                     (fwd.listen_port != 0 &&
 736                      !bind_permitted(fwd.listen_port, pw->pw_uid))) {
 737                         success = 0;
 738                         packet_send_debug("Server has disabled port forwarding.");
 739                 } else {
 740                         /* Start listening on the port */
 741                         success = channel_setup_remote_fwd_listener(&fwd,
 742                             &allocated_listen_port, &options.fwd_opts);
 743                 }
 744                 free(fwd.listen_host);
 745                 if ((resp = sshbuf_new()) == NULL)
 746                         fatal("%s: sshbuf_new", __func__);
 747                 if (allocated_listen_port != 0 &&
 748                     (r = sshbuf_put_u32(resp, allocated_listen_port)) != 0)
 749                         fatal("%s: sshbuf_put_u32: %s", __func__, ssh_err(r));
 750         } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
 751                 struct Forward fwd;
 752
 753                 memset(&fwd, 0, sizeof(fwd));
 754                 fwd.listen_host = packet_get_string(NULL);
 755                 fwd.listen_port = (u_short)packet_get_int();
 756                 debug("%s: cancel-tcpip-forward addr %s port %d", __func__,
 757                     fwd.listen_host, fwd.listen_port);
 758
 759                 success = channel_cancel_rport_listener(&fwd);
 760                 free(fwd.listen_host);
 761         } else if (strcmp(rtype, "streamlocal-forward@openssh.com") == 0) {
 762                 struct Forward fwd;
 763
 764                 memset(&fwd, 0, sizeof(fwd));
 765                 fwd.listen_path = packet_get_string(NULL);
 766                 debug("server_input_global_request: streamlocal-forward listen path %s",
 767                     fwd.listen_path);
 768
 769                 /* check permissions */
 770                 if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0
 771                     || no_port_forwarding_flag || options.disable_forwarding ||
 772                     (pw->pw_uid != 0 && !use_privsep)) {
 773                         success = 0;
 774                         packet_send_debug("Server has disabled "
 775                             "streamlocal forwarding.");
 776                 } else {
 777                         /* Start listening on the socket */
 778                         success = channel_setup_remote_fwd_listener(
 779                             &fwd, NULL, &options.fwd_opts);
 780                 }
 781                 free(fwd.listen_path);
 782         } else if (strcmp(rtype, "cancel-streamlocal-forward@openssh.com") == 0) {
 783                 struct Forward fwd;
 784
 785                 memset(&fwd, 0, sizeof(fwd));
 786                 fwd.listen_path = packet_get_string(NULL);
 787                 debug("%s: cancel-streamlocal-forward path %s", __func__,
 788                     fwd.listen_path);
 789
 790                 success = channel_cancel_rport_listener(&fwd);
 791                 free(fwd.listen_path);
 792         } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) {
 793                 no_more_sessions = 1;
 794                 success = 1;
 795         } else if (strcmp(rtype, "hostkeys-prove-00@openssh.com") == 0) {
 796                 success = server_input_hostkeys_prove(&resp);
 797         }
 798         if (want_reply) {
 799                 packet_start(success ?
 800                     SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
 801                 if (success && resp != NULL)
 802                         ssh_packet_put_raw(active_state, sshbuf_ptr(resp),
 803                             sshbuf_len(resp));
 804                 packet_send();
 805                 packet_write_wait();
 806         }
 807         free(rtype);
 808         sshbuf_free(resp);
 809         return 0;
 810 }
 811
 812 static int
 813 server_input_channel_req(int type, u_int32_t seq, void *ctxt)
 814 {
 815         Channel *c;
 816         int id, reply, success = 0;
 817         char *rtype;
 818
 819         id = packet_get_int();
 820         rtype = packet_get_string(NULL);
 821         reply = packet_get_char();
 822
 823         debug("server_input_channel_req: channel %d request %s reply %d",
 824             id, rtype, reply);
 825
 826         if ((c = channel_lookup(id)) == NULL)
 827                 packet_disconnect("server_input_channel_req: "
 828                     "unknown channel %d", id);
 829         if (!strcmp(rtype, "eow@openssh.com")) {
 830                 packet_check_eom();
 831                 chan_rcvd_eow(c);
 832         } else if ((c->type == SSH_CHANNEL_LARVAL ||
 833             c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0)
 834                 success = session_input_channel_req(c, rtype);
 835         if (reply && !(c->flags & CHAN_CLOSE_SENT)) {
 836                 packet_start(success ?
 837                     SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
 838                 packet_put_int(c->remote_id);
 839                 packet_send();
 840         }
 841         free(rtype);
 842         return 0;
 843 }
 844
 845 static void
 846 server_init_dispatch(void)
 847 {
 848         debug("server_init_dispatch");
 849         dispatch_init(&dispatch_protocol_error);
 850         dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
 851         dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
 852         dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
 853         dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
 854         dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
 855         dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
 856         dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
 857         dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
 858         dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
 859         dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
 860         /* client_alive */
 861         dispatch_set(SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive);
 862         dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
 863         dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
 864         dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
 865         /* rekeying */
 866         dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
 867 }