crypto/openssh/serverloop.c

   1 /* $OpenBSD: serverloop.c,v 1.209 2018/07/27 05:13:02 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 "sshbuf.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 "sshkey.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 /* returns 1 if bind to specified port by specified user is permitted */
 107 static int
 108 bind_permitted(int port, uid_t uid)
 109 {
 110         if (use_privsep)
 111                 return 1; /* allow system to decide */
 112         if (port < IPPORT_RESERVED && uid != 0)
 113                 return 0;
 114         return 1;
 115 }
 116
 117 /*
 118  * we write to this pipe if a SIGCHLD is caught in order to avoid
 119  * the race between select() and child_terminated
 120  */
 121 static int notify_pipe[2];
 122 static void
 123 notify_setup(void)
 124 {
 125         if (pipe(notify_pipe) < 0) {
 126                 error("pipe(notify_pipe) failed %s", strerror(errno));
 127         } else if ((fcntl(notify_pipe[0], F_SETFD, FD_CLOEXEC) == -1) ||
 128             (fcntl(notify_pipe[1], F_SETFD, FD_CLOEXEC) == -1)) {
 129                 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno));
 130                 close(notify_pipe[0]);
 131                 close(notify_pipe[1]);
 132         } else {
 133                 set_nonblock(notify_pipe[0]);
 134                 set_nonblock(notify_pipe[1]);
 135                 return;
 136         }
 137         notify_pipe[0] = -1;    /* read end */
 138         notify_pipe[1] = -1;    /* write end */
 139 }
 140 static void
 141 notify_parent(void)
 142 {
 143         if (notify_pipe[1] != -1)
 144                 (void)write(notify_pipe[1], "", 1);
 145 }
 146 static void
 147 notify_prepare(fd_set *readset)
 148 {
 149         if (notify_pipe[0] != -1)
 150                 FD_SET(notify_pipe[0], readset);
 151 }
 152 static void
 153 notify_done(fd_set *readset)
 154 {
 155         char c;
 156
 157         if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset))
 158                 while (read(notify_pipe[0], &c, 1) != -1)
 159                         debug2("%s: reading", __func__);
 160 }
 161
 162 /*ARGSUSED*/
 163 static void
 164 sigchld_handler(int sig)
 165 {
 166         int save_errno = errno;
 167         child_terminated = 1;
 168         notify_parent();
 169         errno = save_errno;
 170 }
 171
 172 /*ARGSUSED*/
 173 static void
 174 sigterm_handler(int sig)
 175 {
 176         received_sigterm = sig;
 177 }
 178
 179 static void
 180 client_alive_check(struct ssh *ssh)
 181 {
 182         int channel_id;
 183         char remote_id[512];
 184
 185         /* timeout, check to see how many we have had */
 186         if (packet_inc_alive_timeouts() > options.client_alive_count_max) {
 187                 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id));
 188                 logit("Timeout, client not responding from %s", remote_id);
 189                 cleanup_exit(255);
 190         }
 191
 192         /*
 193          * send a bogus global/channel request with "wantreply",
 194          * we should get back a failure
 195          */
 196         if ((channel_id = channel_find_open(ssh)) == -1) {
 197                 packet_start(SSH2_MSG_GLOBAL_REQUEST);
 198                 packet_put_cstring("keepalive@openssh.com");
 199                 packet_put_char(1);     /* boolean: want reply */
 200         } else {
 201                 channel_request_start(ssh, channel_id,
 202                     "keepalive@openssh.com", 1);
 203         }
 204         packet_send();
 205 }
 206
 207 /*
 208  * Sleep in select() until we can do something.  This will initialize the
 209  * select masks.  Upon return, the masks will indicate which descriptors
 210  * have data or can accept data.  Optionally, a maximum time can be specified
 211  * for the duration of the wait (0 = infinite).
 212  */
 213 static void
 214 wait_until_can_do_something(struct ssh *ssh,
 215     int connection_in, int connection_out,
 216     fd_set **readsetp, fd_set **writesetp, int *maxfdp,
 217     u_int *nallocp, u_int64_t max_time_ms)
 218 {
 219         struct timeval tv, *tvp;
 220         int ret;
 221         time_t minwait_secs = 0;
 222         int client_alive_scheduled = 0;
 223         static time_t last_client_time;
 224
 225         /* Allocate and update select() masks for channel descriptors. */
 226         channel_prepare_select(ssh, readsetp, writesetp, maxfdp,
 227             nallocp, &minwait_secs);
 228
 229         /* XXX need proper deadline system for rekey/client alive */
 230         if (minwait_secs != 0)
 231                 max_time_ms = MINIMUM(max_time_ms, (u_int)minwait_secs * 1000);
 232
 233         /*
 234          * if using client_alive, set the max timeout accordingly,
 235          * and indicate that this particular timeout was for client
 236          * alive by setting the client_alive_scheduled flag.
 237          *
 238          * this could be randomized somewhat to make traffic
 239          * analysis more difficult, but we're not doing it yet.
 240          */
 241         if (options.client_alive_interval) {
 242                 uint64_t keepalive_ms =
 243                     (uint64_t)options.client_alive_interval * 1000;
 244
 245                 client_alive_scheduled = 1;
 246                 if (max_time_ms == 0 || max_time_ms > keepalive_ms)
 247                         max_time_ms = keepalive_ms;
 248         }
 249
 250 #if 0
 251         /* wrong: bad condition XXX */
 252         if (channel_not_very_much_buffered_data())
 253 #endif
 254         FD_SET(connection_in, *readsetp);
 255         notify_prepare(*readsetp);
 256
 257         /*
 258          * If we have buffered packet data going to the client, mark that
 259          * descriptor.
 260          */
 261         if (packet_have_data_to_write())
 262                 FD_SET(connection_out, *writesetp);
 263
 264         /*
 265          * If child has terminated and there is enough buffer space to read
 266          * from it, then read as much as is available and exit.
 267          */
 268         if (child_terminated && packet_not_very_much_data_to_write())
 269                 if (max_time_ms == 0 || client_alive_scheduled)
 270                         max_time_ms = 100;
 271
 272         if (max_time_ms == 0)
 273                 tvp = NULL;
 274         else {
 275                 tv.tv_sec = max_time_ms / 1000;
 276                 tv.tv_usec = 1000 * (max_time_ms % 1000);
 277                 tvp = &tv;
 278         }
 279
 280         /* Wait for something to happen, or the timeout to expire. */
 281         ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
 282
 283         if (ret == -1) {
 284                 memset(*readsetp, 0, *nallocp);
 285                 memset(*writesetp, 0, *nallocp);
 286                 if (errno != EINTR)
 287                         error("select: %.100s", strerror(errno));
 288         } else if (client_alive_scheduled) {
 289                 time_t now = monotime();
 290
 291                 if (ret == 0) { /* timeout */
 292                         client_alive_check(ssh);
 293                 } else if (FD_ISSET(connection_in, *readsetp)) {
 294                         last_client_time = now;
 295                 } else if (last_client_time != 0 && last_client_time +
 296                     options.client_alive_interval <= now) {
 297                         client_alive_check(ssh);
 298                         last_client_time = now;
 299                 }
 300         }
 301
 302         notify_done(*readsetp);
 303 }
 304
 305 /*
 306  * Processes input from the client and the program.  Input data is stored
 307  * in buffers and processed later.
 308  */
 309 static int
 310 process_input(struct ssh *ssh, fd_set *readset, int connection_in)
 311 {
 312         int len;
 313         char buf[16384];
 314
 315         /* Read and buffer any input data from the client. */
 316         if (FD_ISSET(connection_in, readset)) {
 317                 len = read(connection_in, buf, sizeof(buf));
 318                 if (len == 0) {
 319                         verbose("Connection closed by %.100s port %d",
 320                             ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
 321                         return -1;
 322                 } else if (len < 0) {
 323                         if (errno != EINTR && errno != EAGAIN &&
 324                             errno != EWOULDBLOCK) {
 325                                 verbose("Read error from remote host "
 326                                     "%.100s port %d: %.100s",
 327                                     ssh_remote_ipaddr(ssh),
 328                                     ssh_remote_port(ssh), strerror(errno));
 329                                 cleanup_exit(255);
 330                         }
 331                 } else {
 332                         /* Buffer any received data. */
 333                         packet_process_incoming(buf, len);
 334                 }
 335         }
 336         return 0;
 337 }
 338
 339 /*
 340  * Sends data from internal buffers to client program stdin.
 341  */
 342 static void
 343 process_output(fd_set *writeset, int connection_out)
 344 {
 345         /* Send any buffered packet data to the client. */
 346         if (FD_ISSET(connection_out, writeset))
 347                 packet_write_poll();
 348 }
 349
 350 static void
 351 process_buffered_input_packets(struct ssh *ssh)
 352 {
 353         ssh_dispatch_run_fatal(ssh, DISPATCH_NONBLOCK, NULL);
 354 }
 355
 356 static void
 357 collect_children(struct ssh *ssh)
 358 {
 359         pid_t pid;
 360         sigset_t oset, nset;
 361         int status;
 362
 363         /* block SIGCHLD while we check for dead children */
 364         sigemptyset(&nset);
 365         sigaddset(&nset, SIGCHLD);
 366         sigprocmask(SIG_BLOCK, &nset, &oset);
 367         if (child_terminated) {
 368                 debug("Received SIGCHLD.");
 369                 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
 370                     (pid < 0 && errno == EINTR))
 371                         if (pid > 0)
 372                                 session_close_by_pid(ssh, pid, status);
 373                 child_terminated = 0;
 374         }
 375         sigprocmask(SIG_SETMASK, &oset, NULL);
 376 }
 377
 378 void
 379 server_loop2(struct ssh *ssh, Authctxt *authctxt)
 380 {
 381         fd_set *readset = NULL, *writeset = NULL;
 382         int max_fd;
 383         u_int nalloc = 0, connection_in, connection_out;
 384         u_int64_t rekey_timeout_ms = 0;
 385
 386         debug("Entering interactive session for SSH2.");
 387
 388         signal(SIGCHLD, sigchld_handler);
 389         child_terminated = 0;
 390         connection_in = packet_get_connection_in();
 391         connection_out = packet_get_connection_out();
 392
 393         if (!use_privsep) {
 394                 signal(SIGTERM, sigterm_handler);
 395                 signal(SIGINT, sigterm_handler);
 396                 signal(SIGQUIT, sigterm_handler);
 397         }
 398
 399         notify_setup();
 400
 401         max_fd = MAXIMUM(connection_in, connection_out);
 402         max_fd = MAXIMUM(max_fd, notify_pipe[0]);
 403
 404         server_init_dispatch();
 405
 406         for (;;) {
 407                 process_buffered_input_packets(ssh);
 408
 409                 if (!ssh_packet_is_rekeying(ssh) &&
 410                     packet_not_very_much_data_to_write())
 411                         channel_output_poll(ssh);
 412                 if (options.rekey_interval > 0 && !ssh_packet_is_rekeying(ssh))
 413                         rekey_timeout_ms = packet_get_rekey_timeout() * 1000;
 414                 else
 415                         rekey_timeout_ms = 0;
 416
 417                 wait_until_can_do_something(ssh, connection_in, connection_out,
 418                     &readset, &writeset, &max_fd, &nalloc, rekey_timeout_ms);
 419
 420                 if (received_sigterm) {
 421                         logit("Exiting on signal %d", (int)received_sigterm);
 422                         /* Clean up sessions, utmp, etc. */
 423                         cleanup_exit(255);
 424                 }
 425
 426                 collect_children(ssh);
 427                 if (!ssh_packet_is_rekeying(ssh))
 428                         channel_after_select(ssh, readset, writeset);
 429                 if (process_input(ssh, readset, connection_in) < 0)
 430                         break;
 431                 process_output(writeset, connection_out);
 432         }
 433         collect_children(ssh);
 434
 435         free(readset);
 436         free(writeset);
 437
 438         /* free all channels, no more reads and writes */
 439         channel_free_all(ssh);
 440
 441         /* free remaining sessions, e.g. remove wtmp entries */
 442         session_destroy_all(ssh, NULL);
 443 }
 444
 445 static int
 446 server_input_keep_alive(int type, u_int32_t seq, struct ssh *ssh)
 447 {
 448         debug("Got %d/%u for keepalive", type, seq);
 449         /*
 450          * reset timeout, since we got a sane answer from the client.
 451          * even if this was generated by something other than
 452          * the bogus CHANNEL_REQUEST we send for keepalives.
 453          */
 454         packet_set_alive_timeouts(0);
 455         return 0;
 456 }
 457
 458 static Channel *
 459 server_request_direct_tcpip(struct ssh *ssh, int *reason, const char **errmsg)
 460 {
 461         Channel *c = NULL;
 462         char *target, *originator;
 463         u_short target_port, originator_port;
 464
 465         target = packet_get_string(NULL);
 466         target_port = packet_get_int();
 467         originator = packet_get_string(NULL);
 468         originator_port = packet_get_int();
 469         packet_check_eom();
 470
 471         debug("%s: originator %s port %d, target %s port %d", __func__,
 472             originator, originator_port, target, target_port);
 473
 474         /* XXX fine grained permissions */
 475         if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 &&
 476             auth_opts->permit_port_forwarding_flag &&
 477             !options.disable_forwarding) {
 478                 c = channel_connect_to_port(ssh, target, target_port,
 479                     "direct-tcpip", "direct-tcpip", reason, errmsg);
 480         } else {
 481                 logit("refused local port forward: "
 482                     "originator %s port %d, target %s port %d",
 483                     originator, originator_port, target, target_port);
 484                 if (reason != NULL)
 485                         *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED;
 486         }
 487
 488         free(originator);
 489         free(target);
 490
 491         return c;
 492 }
 493
 494 static Channel *
 495 server_request_direct_streamlocal(struct ssh *ssh)
 496 {
 497         Channel *c = NULL;
 498         char *target, *originator;
 499         u_short originator_port;
 500         struct passwd *pw = the_authctxt->pw;
 501
 502         if (pw == NULL || !the_authctxt->valid)
 503                 fatal("%s: no/invalid user", __func__);
 504
 505         target = packet_get_string(NULL);
 506         originator = packet_get_string(NULL);
 507         originator_port = packet_get_int();
 508         packet_check_eom();
 509
 510         debug("%s: originator %s port %d, target %s", __func__,
 511             originator, originator_port, target);
 512
 513         /* XXX fine grained permissions */
 514         if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 &&
 515             auth_opts->permit_port_forwarding_flag &&
 516             !options.disable_forwarding && (pw->pw_uid == 0 || use_privsep)) {
 517                 c = channel_connect_to_path(ssh, target,
 518                     "direct-streamlocal@openssh.com", "direct-streamlocal");
 519         } else {
 520                 logit("refused streamlocal port forward: "
 521                     "originator %s port %d, target %s",
 522                     originator, originator_port, target);
 523         }
 524
 525         free(originator);
 526         free(target);
 527
 528         return c;
 529 }
 530
 531 static Channel *
 532 server_request_tun(struct ssh *ssh)
 533 {
 534         Channel *c = NULL;
 535         int mode, tun, sock;
 536         char *tmp, *ifname = NULL;
 537
 538         mode = packet_get_int();
 539         switch (mode) {
 540         case SSH_TUNMODE_POINTOPOINT:
 541         case SSH_TUNMODE_ETHERNET:
 542                 break;
 543         default:
 544                 packet_send_debug("Unsupported tunnel device mode.");
 545                 return NULL;
 546         }
 547         if ((options.permit_tun & mode) == 0) {
 548                 packet_send_debug("Server has rejected tunnel device "
 549                     "forwarding");
 550                 return NULL;
 551         }
 552
 553         tun = packet_get_int();
 554         if (auth_opts->force_tun_device != -1) {
 555                 if (tun != SSH_TUNID_ANY && auth_opts->force_tun_device != tun)
 556                         goto done;
 557                 tun = auth_opts->force_tun_device;
 558         }
 559         sock = tun_open(tun, mode, &ifname);
 560         if (sock < 0)
 561                 goto done;
 562         debug("Tunnel forwarding using interface %s", ifname);
 563
 564         c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1,
 565             CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
 566         c->datagram = 1;
 567 #if defined(SSH_TUN_FILTER)
 568         if (mode == SSH_TUNMODE_POINTOPOINT)
 569                 channel_register_filter(ssh, c->self, sys_tun_infilter,
 570                     sys_tun_outfilter, NULL, NULL);
 571 #endif
 572
 573         /*
 574          * Update the list of names exposed to the session
 575          * XXX remove these if the tunnels are closed (won't matter
 576          * much if they are already in the environment though)
 577          */
 578         tmp = tun_fwd_ifnames;
 579         xasprintf(&tun_fwd_ifnames, "%s%s%s",
 580             tun_fwd_ifnames == NULL ? "" : tun_fwd_ifnames,
 581             tun_fwd_ifnames == NULL ? "" : ",",
 582             ifname);
 583         free(tmp);
 584         free(ifname);
 585
 586  done:
 587         if (c == NULL)
 588                 packet_send_debug("Failed to open the tunnel device.");
 589         return c;
 590 }
 591
 592 static Channel *
 593 server_request_session(struct ssh *ssh)
 594 {
 595         Channel *c;
 596
 597         debug("input_session_request");
 598         packet_check_eom();
 599
 600         if (no_more_sessions) {
 601                 packet_disconnect("Possible attack: attempt to open a session "
 602                     "after additional sessions disabled");
 603         }
 604
 605         /*
 606          * A server session has no fd to read or write until a
 607          * CHANNEL_REQUEST for a shell is made, so we set the type to
 608          * SSH_CHANNEL_LARVAL.  Additionally, a callback for handling all
 609          * CHANNEL_REQUEST messages is registered.
 610          */
 611         c = channel_new(ssh, "session", SSH_CHANNEL_LARVAL,
 612             -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
 613             0, "server-session", 1);
 614         if (session_open(the_authctxt, c->self) != 1) {
 615                 debug("session open failed, free channel %d", c->self);
 616                 channel_free(ssh, c);
 617                 return NULL;
 618         }
 619         channel_register_cleanup(ssh, c->self, session_close_by_channel, 0);
 620         return c;
 621 }
 622
 623 static int
 624 server_input_channel_open(int type, u_int32_t seq, struct ssh *ssh)
 625 {
 626         Channel *c = NULL;
 627         char *ctype;
 628         const char *errmsg = NULL;
 629         int rchan, reason = SSH2_OPEN_CONNECT_FAILED;
 630         u_int rmaxpack, rwindow, len;
 631
 632         ctype = packet_get_string(&len);
 633         rchan = packet_get_int();
 634         rwindow = packet_get_int();
 635         rmaxpack = packet_get_int();
 636
 637         debug("%s: ctype %s rchan %d win %d max %d", __func__,
 638             ctype, rchan, rwindow, rmaxpack);
 639
 640         if (strcmp(ctype, "session") == 0) {
 641                 c = server_request_session(ssh);
 642         } else if (strcmp(ctype, "direct-tcpip") == 0) {
 643                 c = server_request_direct_tcpip(ssh, &reason, &errmsg);
 644         } else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) {
 645                 c = server_request_direct_streamlocal(ssh);
 646         } else if (strcmp(ctype, "tun@openssh.com") == 0) {
 647                 c = server_request_tun(ssh);
 648         }
 649         if (c != NULL) {
 650                 debug("%s: confirm %s", __func__, ctype);
 651                 c->remote_id = rchan;
 652                 c->have_remote_id = 1;
 653                 c->remote_window = rwindow;
 654                 c->remote_maxpacket = rmaxpack;
 655                 if (c->type != SSH_CHANNEL_CONNECTING) {
 656                         packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
 657                         packet_put_int(c->remote_id);
 658                         packet_put_int(c->self);
 659                         packet_put_int(c->local_window);
 660                         packet_put_int(c->local_maxpacket);
 661                         packet_send();
 662                 }
 663         } else {
 664                 debug("%s: failure %s", __func__, ctype);
 665                 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
 666                 packet_put_int(rchan);
 667                 packet_put_int(reason);
 668                 packet_put_cstring(errmsg ? errmsg : "open failed");
 669                 packet_put_cstring("");
 670                 packet_send();
 671         }
 672         free(ctype);
 673         return 0;
 674 }
 675
 676 static int
 677 server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp)
 678 {
 679         struct sshbuf *resp = NULL;
 680         struct sshbuf *sigbuf = NULL;
 681         struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL;
 682         int r, ndx, kexsigtype, use_kexsigtype, success = 0;
 683         const u_char *blob;
 684         u_char *sig = 0;
 685         size_t blen, slen;
 686
 687         if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL)
 688                 fatal("%s: sshbuf_new", __func__);
 689
 690         kexsigtype = sshkey_type_plain(
 691             sshkey_type_from_name(ssh->kex->hostkey_alg));
 692         while (ssh_packet_remaining(ssh) > 0) {
 693                 sshkey_free(key);
 694                 key = NULL;
 695                 if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 ||
 696                     (r = sshkey_from_blob(blob, blen, &key)) != 0) {
 697                         error("%s: couldn't parse key: %s",
 698                             __func__, ssh_err(r));
 699                         goto out;
 700                 }
 701                 /*
 702                  * Better check that this is actually one of our hostkeys
 703                  * before attempting to sign anything with it.
 704                  */
 705                 if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) {
 706                         error("%s: unknown host %s key",
 707                             __func__, sshkey_type(key));
 708                         goto out;
 709                 }
 710                 /*
 711                  * XXX refactor: make kex->sign just use an index rather
 712                  * than passing in public and private keys
 713                  */
 714                 if ((key_prv = get_hostkey_by_index(ndx)) == NULL &&
 715                     (key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) {
 716                         error("%s: can't retrieve hostkey %d", __func__, ndx);
 717                         goto out;
 718                 }
 719                 sshbuf_reset(sigbuf);
 720                 free(sig);
 721                 sig = NULL;
 722                 /*
 723                  * For RSA keys, prefer to use the signature type negotiated
 724                  * during KEX to the default (SHA1).
 725                  */
 726                 use_kexsigtype = kexsigtype == KEY_RSA &&
 727                     sshkey_type_plain(key->type) == KEY_RSA;
 728                 if ((r = sshbuf_put_cstring(sigbuf,
 729                     "hostkeys-prove-00@openssh.com")) != 0 ||
 730                     (r = sshbuf_put_string(sigbuf,
 731                     ssh->kex->session_id, ssh->kex->session_id_len)) != 0 ||
 732                     (r = sshkey_puts(key, sigbuf)) != 0 ||
 733                     (r = ssh->kex->sign(key_prv, key_pub, &sig, &slen,
 734                     sshbuf_ptr(sigbuf), sshbuf_len(sigbuf),
 735                     use_kexsigtype ? ssh->kex->hostkey_alg : NULL, 0)) != 0 ||
 736                     (r = sshbuf_put_string(resp, sig, slen)) != 0) {
 737                         error("%s: couldn't prepare signature: %s",
 738                             __func__, ssh_err(r));
 739                         goto out;
 740                 }
 741         }
 742         /* Success */
 743         *respp = resp;
 744         resp = NULL; /* don't free it */
 745         success = 1;
 746  out:
 747         free(sig);
 748         sshbuf_free(resp);
 749         sshbuf_free(sigbuf);
 750         sshkey_free(key);
 751         return success;
 752 }
 753
 754 static int
 755 server_input_global_request(int type, u_int32_t seq, struct ssh *ssh)
 756 {
 757         char *rtype;
 758         int want_reply;
 759         int r, success = 0, allocated_listen_port = 0;
 760         struct sshbuf *resp = NULL;
 761         struct passwd *pw = the_authctxt->pw;
 762
 763         if (pw == NULL || !the_authctxt->valid)
 764                 fatal("%s: no/invalid user", __func__);
 765
 766         rtype = packet_get_string(NULL);
 767         want_reply = packet_get_char();
 768         debug("%s: rtype %s want_reply %d", __func__, rtype, want_reply);
 769
 770         /* -R style forwarding */
 771         if (strcmp(rtype, "tcpip-forward") == 0) {
 772                 struct Forward fwd;
 773
 774                 memset(&fwd, 0, sizeof(fwd));
 775                 fwd.listen_host = packet_get_string(NULL);
 776                 fwd.listen_port = (u_short)packet_get_int();
 777                 debug("%s: tcpip-forward listen %s port %d", __func__,
 778                     fwd.listen_host, fwd.listen_port);
 779
 780                 /* check permissions */
 781                 if ((options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 ||
 782                     !auth_opts->permit_port_forwarding_flag ||
 783                     options.disable_forwarding ||
 784                     (!want_reply && fwd.listen_port == 0) ||
 785                     (fwd.listen_port != 0 &&
 786                      !bind_permitted(fwd.listen_port, pw->pw_uid))) {
 787                         success = 0;
 788                         packet_send_debug("Server has disabled port forwarding.");
 789                 } else {
 790                         /* Start listening on the port */
 791                         success = channel_setup_remote_fwd_listener(ssh, &fwd,
 792                             &allocated_listen_port, &options.fwd_opts);
 793                 }
 794                 free(fwd.listen_host);
 795                 if ((resp = sshbuf_new()) == NULL)
 796                         fatal("%s: sshbuf_new", __func__);
 797                 if (allocated_listen_port != 0 &&
 798                     (r = sshbuf_put_u32(resp, allocated_listen_port)) != 0)
 799                         fatal("%s: sshbuf_put_u32: %s", __func__, ssh_err(r));
 800         } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
 801                 struct Forward fwd;
 802
 803                 memset(&fwd, 0, sizeof(fwd));
 804                 fwd.listen_host = packet_get_string(NULL);
 805                 fwd.listen_port = (u_short)packet_get_int();
 806                 debug("%s: cancel-tcpip-forward addr %s port %d", __func__,
 807                     fwd.listen_host, fwd.listen_port);
 808
 809                 success = channel_cancel_rport_listener(ssh, &fwd);
 810                 free(fwd.listen_host);
 811         } else if (strcmp(rtype, "streamlocal-forward@openssh.com") == 0) {
 812                 struct Forward fwd;
 813
 814                 memset(&fwd, 0, sizeof(fwd));
 815                 fwd.listen_path = packet_get_string(NULL);
 816                 debug("%s: streamlocal-forward listen path %s", __func__,
 817                     fwd.listen_path);
 818
 819                 /* check permissions */
 820                 if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0
 821                     || !auth_opts->permit_port_forwarding_flag ||
 822                     options.disable_forwarding ||
 823                     (pw->pw_uid != 0 && !use_privsep)) {
 824                         success = 0;
 825                         packet_send_debug("Server has disabled "
 826                             "streamlocal forwarding.");
 827                 } else {
 828                         /* Start listening on the socket */
 829                         success = channel_setup_remote_fwd_listener(ssh,
 830                             &fwd, NULL, &options.fwd_opts);
 831                 }
 832                 free(fwd.listen_path);
 833         } else if (strcmp(rtype, "cancel-streamlocal-forward@openssh.com") == 0) {
 834                 struct Forward fwd;
 835
 836                 memset(&fwd, 0, sizeof(fwd));
 837                 fwd.listen_path = packet_get_string(NULL);
 838                 debug("%s: cancel-streamlocal-forward path %s", __func__,
 839                     fwd.listen_path);
 840
 841                 success = channel_cancel_rport_listener(ssh, &fwd);
 842                 free(fwd.listen_path);
 843         } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) {
 844                 no_more_sessions = 1;
 845                 success = 1;
 846         } else if (strcmp(rtype, "hostkeys-prove-00@openssh.com") == 0) {
 847                 success = server_input_hostkeys_prove(ssh, &resp);
 848         }
 849         if (want_reply) {
 850                 packet_start(success ?
 851                     SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
 852                 if (success && resp != NULL)
 853                         ssh_packet_put_raw(ssh, sshbuf_ptr(resp),
 854                             sshbuf_len(resp));
 855                 packet_send();
 856                 packet_write_wait();
 857         }
 858         free(rtype);
 859         sshbuf_free(resp);
 860         return 0;
 861 }
 862
 863 static int
 864 server_input_channel_req(int type, u_int32_t seq, struct ssh *ssh)
 865 {
 866         Channel *c;
 867         int id, reply, success = 0;
 868         char *rtype;
 869
 870         id = packet_get_int();
 871         rtype = packet_get_string(NULL);
 872         reply = packet_get_char();
 873
 874         debug("server_input_channel_req: channel %d request %s reply %d",
 875             id, rtype, reply);
 876
 877         if ((c = channel_lookup(ssh, id)) == NULL)
 878                 packet_disconnect("server_input_channel_req: "
 879                     "unknown channel %d", id);
 880         if (!strcmp(rtype, "eow@openssh.com")) {
 881                 packet_check_eom();
 882                 chan_rcvd_eow(ssh, c);
 883         } else if ((c->type == SSH_CHANNEL_LARVAL ||
 884             c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0)
 885                 success = session_input_channel_req(ssh, c, rtype);
 886         if (reply && !(c->flags & CHAN_CLOSE_SENT)) {
 887                 if (!c->have_remote_id)
 888                         fatal("%s: channel %d: no remote_id",
 889                             __func__, c->self);
 890                 packet_start(success ?
 891                     SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
 892                 packet_put_int(c->remote_id);
 893                 packet_send();
 894         }
 895         free(rtype);
 896         return 0;
 897 }
 898
 899 static void
 900 server_init_dispatch(void)
 901 {
 902         debug("server_init_dispatch");
 903         dispatch_init(&dispatch_protocol_error);
 904         dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
 905         dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
 906         dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
 907         dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
 908         dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
 909         dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
 910         dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
 911         dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
 912         dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
 913         dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
 914         /* client_alive */
 915         dispatch_set(SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive);
 916         dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
 917         dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
 918         dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
 919         /* rekeying */
 920         dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
 921 }