crypto/openssh/serverloop.c

   1 /* $OpenBSD: serverloop.c,v 1.198 2017/09/12 06:35:32 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 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(struct ssh *ssh)
 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(ssh)) == -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(ssh, channel_id,
 188                     "keepalive@openssh.com", 1);
 189         }
 190         packet_send();
 191 }
 192
 193 /*
 194  * Sleep in select() until we can do something.  This will initialize the
 195  * select masks.  Upon return, the masks will indicate which descriptors
 196  * have data or can accept data.  Optionally, a maximum time can be specified
 197  * for the duration of the wait (0 = infinite).
 198  */
 199 static void
 200 wait_until_can_do_something(struct ssh *ssh,
 201     int connection_in, int connection_out,
 202     fd_set **readsetp, fd_set **writesetp, int *maxfdp,
 203     u_int *nallocp, u_int64_t max_time_ms)
 204 {
 205         struct timeval tv, *tvp;
 206         int ret;
 207         time_t minwait_secs = 0;
 208         int client_alive_scheduled = 0;
 209         static time_t last_client_time;
 210
 211         /* Allocate and update select() masks for channel descriptors. */
 212         channel_prepare_select(ssh, readsetp, writesetp, maxfdp,
 213             nallocp, &minwait_secs);
 214
 215         /* XXX need proper deadline system for rekey/client alive */
 216         if (minwait_secs != 0)
 217                 max_time_ms = MINIMUM(max_time_ms, (u_int)minwait_secs * 1000);
 218
 219         /*
 220          * if using client_alive, set the max timeout accordingly,
 221          * and indicate that this particular timeout was for client
 222          * alive by setting the client_alive_scheduled flag.
 223          *
 224          * this could be randomized somewhat to make traffic
 225          * analysis more difficult, but we're not doing it yet.
 226          */
 227         if (options.client_alive_interval) {
 228                 uint64_t keepalive_ms =
 229                     (uint64_t)options.client_alive_interval * 1000;
 230
 231                 client_alive_scheduled = 1;
 232                 if (max_time_ms == 0 || max_time_ms > keepalive_ms)
 233                         max_time_ms = keepalive_ms;
 234         }
 235
 236 #if 0
 237         /* wrong: bad condition XXX */
 238         if (channel_not_very_much_buffered_data())
 239 #endif
 240         FD_SET(connection_in, *readsetp);
 241         notify_prepare(*readsetp);
 242
 243         /*
 244          * If we have buffered packet data going to the client, mark that
 245          * descriptor.
 246          */
 247         if (packet_have_data_to_write())
 248                 FD_SET(connection_out, *writesetp);
 249
 250         /*
 251          * If child has terminated and there is enough buffer space to read
 252          * from it, then read as much as is available and exit.
 253          */
 254         if (child_terminated && packet_not_very_much_data_to_write())
 255                 if (max_time_ms == 0 || client_alive_scheduled)
 256                         max_time_ms = 100;
 257
 258         if (max_time_ms == 0)
 259                 tvp = NULL;
 260         else {
 261                 tv.tv_sec = max_time_ms / 1000;
 262                 tv.tv_usec = 1000 * (max_time_ms % 1000);
 263                 tvp = &tv;
 264         }
 265
 266         /* Wait for something to happen, or the timeout to expire. */
 267         ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp);
 268
 269         if (ret == -1) {
 270                 memset(*readsetp, 0, *nallocp);
 271                 memset(*writesetp, 0, *nallocp);
 272                 if (errno != EINTR)
 273                         error("select: %.100s", strerror(errno));
 274         } else if (client_alive_scheduled) {
 275                 time_t now = monotime();
 276
 277                 if (ret == 0) { /* timeout */
 278                         client_alive_check(ssh);
 279                 } else if (FD_ISSET(connection_in, *readsetp)) {
 280                         last_client_time = now;
 281                 } else if (last_client_time != 0 && last_client_time +
 282                     options.client_alive_interval <= now) {
 283                         client_alive_check(ssh);
 284                         last_client_time = now;
 285                 }
 286         }
 287
 288         notify_done(*readsetp);
 289 }
 290
 291 /*
 292  * Processes input from the client and the program.  Input data is stored
 293  * in buffers and processed later.
 294  */
 295 static int
 296 process_input(struct ssh *ssh, fd_set *readset, int connection_in)
 297 {
 298         int len;
 299         char buf[16384];
 300
 301         /* Read and buffer any input data from the client. */
 302         if (FD_ISSET(connection_in, readset)) {
 303                 len = read(connection_in, buf, sizeof(buf));
 304                 if (len == 0) {
 305                         verbose("Connection closed by %.100s port %d",
 306                             ssh_remote_ipaddr(ssh), ssh_remote_port(ssh));
 307                         return -1;
 308                 } else if (len < 0) {
 309                         if (errno != EINTR && errno != EAGAIN &&
 310                             errno != EWOULDBLOCK) {
 311                                 verbose("Read error from remote host "
 312                                     "%.100s port %d: %.100s",
 313                                     ssh_remote_ipaddr(ssh),
 314                                     ssh_remote_port(ssh), strerror(errno));
 315                                 cleanup_exit(255);
 316                         }
 317                 } else {
 318                         /* Buffer any received data. */
 319                         packet_process_incoming(buf, len);
 320                 }
 321         }
 322         return 0;
 323 }
 324
 325 /*
 326  * Sends data from internal buffers to client program stdin.
 327  */
 328 static void
 329 process_output(fd_set *writeset, int connection_out)
 330 {
 331         /* Send any buffered packet data to the client. */
 332         if (FD_ISSET(connection_out, writeset))
 333                 packet_write_poll();
 334 }
 335
 336 static void
 337 process_buffered_input_packets(struct ssh *ssh)
 338 {
 339         ssh_dispatch_run_fatal(ssh, DISPATCH_NONBLOCK, NULL);
 340 }
 341
 342 static void
 343 collect_children(struct ssh *ssh)
 344 {
 345         pid_t pid;
 346         sigset_t oset, nset;
 347         int status;
 348
 349         /* block SIGCHLD while we check for dead children */
 350         sigemptyset(&nset);
 351         sigaddset(&nset, SIGCHLD);
 352         sigprocmask(SIG_BLOCK, &nset, &oset);
 353         if (child_terminated) {
 354                 debug("Received SIGCHLD.");
 355                 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 ||
 356                     (pid < 0 && errno == EINTR))
 357                         if (pid > 0)
 358                                 session_close_by_pid(ssh, pid, status);
 359                 child_terminated = 0;
 360         }
 361         sigprocmask(SIG_SETMASK, &oset, NULL);
 362 }
 363
 364 void
 365 server_loop2(struct ssh *ssh, Authctxt *authctxt)
 366 {
 367         fd_set *readset = NULL, *writeset = NULL;
 368         int max_fd;
 369         u_int nalloc = 0, connection_in, connection_out;
 370         u_int64_t rekey_timeout_ms = 0;
 371
 372         debug("Entering interactive session for SSH2.");
 373
 374         mysignal(SIGCHLD, sigchld_handler);
 375         child_terminated = 0;
 376         connection_in = packet_get_connection_in();
 377         connection_out = packet_get_connection_out();
 378
 379         if (!use_privsep) {
 380                 signal(SIGTERM, sigterm_handler);
 381                 signal(SIGINT, sigterm_handler);
 382                 signal(SIGQUIT, sigterm_handler);
 383         }
 384
 385         notify_setup();
 386
 387         max_fd = MAXIMUM(connection_in, connection_out);
 388         max_fd = MAXIMUM(max_fd, notify_pipe[0]);
 389
 390         server_init_dispatch();
 391
 392         for (;;) {
 393                 process_buffered_input_packets(ssh);
 394
 395                 if (!ssh_packet_is_rekeying(ssh) &&
 396                     packet_not_very_much_data_to_write())
 397                         channel_output_poll(ssh);
 398                 if (options.rekey_interval > 0 && !ssh_packet_is_rekeying(ssh))
 399                         rekey_timeout_ms = packet_get_rekey_timeout() * 1000;
 400                 else
 401                         rekey_timeout_ms = 0;
 402
 403                 wait_until_can_do_something(ssh, connection_in, connection_out,
 404                     &readset, &writeset, &max_fd, &nalloc, rekey_timeout_ms);
 405
 406                 if (received_sigterm) {
 407                         logit("Exiting on signal %d", (int)received_sigterm);
 408                         /* Clean up sessions, utmp, etc. */
 409                         cleanup_exit(255);
 410                 }
 411
 412                 collect_children(ssh);
 413                 if (!ssh_packet_is_rekeying(ssh))
 414                         channel_after_select(ssh, readset, writeset);
 415                 if (process_input(ssh, readset, connection_in) < 0)
 416                         break;
 417                 process_output(writeset, connection_out);
 418         }
 419         collect_children(ssh);
 420
 421         free(readset);
 422         free(writeset);
 423
 424         /* free all channels, no more reads and writes */
 425         channel_free_all(ssh);
 426
 427         /* free remaining sessions, e.g. remove wtmp entries */
 428         session_destroy_all(ssh, NULL);
 429 }
 430
 431 static int
 432 server_input_keep_alive(int type, u_int32_t seq, struct ssh *ssh)
 433 {
 434         debug("Got %d/%u for keepalive", type, seq);
 435         /*
 436          * reset timeout, since we got a sane answer from the client.
 437          * even if this was generated by something other than
 438          * the bogus CHANNEL_REQUEST we send for keepalives.
 439          */
 440         packet_set_alive_timeouts(0);
 441         return 0;
 442 }
 443
 444 static Channel *
 445 server_request_direct_tcpip(struct ssh *ssh, int *reason, const char **errmsg)
 446 {
 447         Channel *c = NULL;
 448         char *target, *originator;
 449         u_short target_port, originator_port;
 450
 451         target = packet_get_string(NULL);
 452         target_port = packet_get_int();
 453         originator = packet_get_string(NULL);
 454         originator_port = packet_get_int();
 455         packet_check_eom();
 456
 457         debug("server_request_direct_tcpip: originator %s port %d, target %s "
 458             "port %d", originator, originator_port, target, target_port);
 459
 460         /* XXX fine grained permissions */
 461         if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 &&
 462             !no_port_forwarding_flag && !options.disable_forwarding) {
 463                 c = channel_connect_to_port(ssh, target, target_port,
 464                     "direct-tcpip", "direct-tcpip", reason, errmsg);
 465         } else {
 466                 logit("refused local port forward: "
 467                     "originator %s port %d, target %s port %d",
 468                     originator, originator_port, target, target_port);
 469                 if (reason != NULL)
 470                         *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED;
 471         }
 472
 473         free(originator);
 474         free(target);
 475
 476         return c;
 477 }
 478
 479 static Channel *
 480 server_request_direct_streamlocal(struct ssh *ssh)
 481 {
 482         Channel *c = NULL;
 483         char *target, *originator;
 484         u_short originator_port;
 485         struct passwd *pw = the_authctxt->pw;
 486
 487         if (pw == NULL || !the_authctxt->valid)
 488                 fatal("server_input_global_request: no/invalid user");
 489
 490         target = packet_get_string(NULL);
 491         originator = packet_get_string(NULL);
 492         originator_port = packet_get_int();
 493         packet_check_eom();
 494
 495         debug("server_request_direct_streamlocal: originator %s port %d, target %s",
 496             originator, originator_port, target);
 497
 498         /* XXX fine grained permissions */
 499         if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 &&
 500             !no_port_forwarding_flag && !options.disable_forwarding &&
 501             (pw->pw_uid == 0 || use_privsep)) {
 502                 c = channel_connect_to_path(ssh, target,
 503                     "direct-streamlocal@openssh.com", "direct-streamlocal");
 504         } else {
 505                 logit("refused streamlocal port forward: "
 506                     "originator %s port %d, target %s",
 507                     originator, originator_port, target);
 508         }
 509
 510         free(originator);
 511         free(target);
 512
 513         return c;
 514 }
 515
 516 static Channel *
 517 server_request_tun(struct ssh *ssh)
 518 {
 519         Channel *c = NULL;
 520         int mode, tun;
 521         int sock;
 522
 523         mode = packet_get_int();
 524         switch (mode) {
 525         case SSH_TUNMODE_POINTOPOINT:
 526         case SSH_TUNMODE_ETHERNET:
 527                 break;
 528         default:
 529                 packet_send_debug("Unsupported tunnel device mode.");
 530                 return NULL;
 531         }
 532         if ((options.permit_tun & mode) == 0) {
 533                 packet_send_debug("Server has rejected tunnel device "
 534                     "forwarding");
 535                 return NULL;
 536         }
 537
 538         tun = packet_get_int();
 539         if (forced_tun_device != -1) {
 540                 if (tun != SSH_TUNID_ANY && forced_tun_device != tun)
 541                         goto done;
 542                 tun = forced_tun_device;
 543         }
 544         sock = tun_open(tun, mode);
 545         if (sock < 0)
 546                 goto done;
 547         c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1,
 548             CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1);
 549         c->datagram = 1;
 550 #if defined(SSH_TUN_FILTER)
 551         if (mode == SSH_TUNMODE_POINTOPOINT)
 552                 channel_register_filter(ssh, c->self, sys_tun_infilter,
 553                     sys_tun_outfilter, NULL, NULL);
 554 #endif
 555
 556  done:
 557         if (c == NULL)
 558                 packet_send_debug("Failed to open the tunnel device.");
 559         return c;
 560 }
 561
 562 static Channel *
 563 server_request_session(struct ssh *ssh)
 564 {
 565         Channel *c;
 566
 567         debug("input_session_request");
 568         packet_check_eom();
 569
 570         if (no_more_sessions) {
 571                 packet_disconnect("Possible attack: attempt to open a session "
 572                     "after additional sessions disabled");
 573         }
 574
 575         /*
 576          * A server session has no fd to read or write until a
 577          * CHANNEL_REQUEST for a shell is made, so we set the type to
 578          * SSH_CHANNEL_LARVAL.  Additionally, a callback for handling all
 579          * CHANNEL_REQUEST messages is registered.
 580          */
 581         c = channel_new(ssh, "session", SSH_CHANNEL_LARVAL,
 582             -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT,
 583             0, "server-session", 1);
 584         if (session_open(the_authctxt, c->self) != 1) {
 585                 debug("session open failed, free channel %d", c->self);
 586                 channel_free(ssh, c);
 587                 return NULL;
 588         }
 589         channel_register_cleanup(ssh, c->self, session_close_by_channel, 0);
 590         return c;
 591 }
 592
 593 static int
 594 server_input_channel_open(int type, u_int32_t seq, struct ssh *ssh)
 595 {
 596         Channel *c = NULL;
 597         char *ctype;
 598         const char *errmsg = NULL;
 599         int rchan, reason = SSH2_OPEN_CONNECT_FAILED;
 600         u_int rmaxpack, rwindow, len;
 601
 602         ctype = packet_get_string(&len);
 603         rchan = packet_get_int();
 604         rwindow = packet_get_int();
 605         rmaxpack = packet_get_int();
 606
 607         debug("server_input_channel_open: ctype %s rchan %d win %d max %d",
 608             ctype, rchan, rwindow, rmaxpack);
 609
 610         if (strcmp(ctype, "session") == 0) {
 611                 c = server_request_session(ssh);
 612         } else if (strcmp(ctype, "direct-tcpip") == 0) {
 613                 c = server_request_direct_tcpip(ssh, &reason, &errmsg);
 614         } else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) {
 615                 c = server_request_direct_streamlocal(ssh);
 616         } else if (strcmp(ctype, "tun@openssh.com") == 0) {
 617                 c = server_request_tun(ssh);
 618         }
 619         if (c != NULL) {
 620                 debug("server_input_channel_open: confirm %s", ctype);
 621                 c->remote_id = rchan;
 622                 c->have_remote_id = 1;
 623                 c->remote_window = rwindow;
 624                 c->remote_maxpacket = rmaxpack;
 625                 if (c->type != SSH_CHANNEL_CONNECTING) {
 626                         packet_start(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION);
 627                         packet_put_int(c->remote_id);
 628                         packet_put_int(c->self);
 629                         packet_put_int(c->local_window);
 630                         packet_put_int(c->local_maxpacket);
 631                         packet_send();
 632                 }
 633         } else {
 634                 debug("server_input_channel_open: failure %s", ctype);
 635                 packet_start(SSH2_MSG_CHANNEL_OPEN_FAILURE);
 636                 packet_put_int(rchan);
 637                 packet_put_int(reason);
 638                 if (!(datafellows & SSH_BUG_OPENFAILURE)) {
 639                         packet_put_cstring(errmsg ? errmsg : "open failed");
 640                         packet_put_cstring("");
 641                 }
 642                 packet_send();
 643         }
 644         free(ctype);
 645         return 0;
 646 }
 647
 648 static int
 649 server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp)
 650 {
 651         struct sshbuf *resp = NULL;
 652         struct sshbuf *sigbuf = NULL;
 653         struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL;
 654         int r, ndx, success = 0;
 655         const u_char *blob;
 656         u_char *sig = 0;
 657         size_t blen, slen;
 658
 659         if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL)
 660                 fatal("%s: sshbuf_new", __func__);
 661
 662         while (ssh_packet_remaining(ssh) > 0) {
 663                 sshkey_free(key);
 664                 key = NULL;
 665                 if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 ||
 666                     (r = sshkey_from_blob(blob, blen, &key)) != 0) {
 667                         error("%s: couldn't parse key: %s",
 668                             __func__, ssh_err(r));
 669                         goto out;
 670                 }
 671                 /*
 672                  * Better check that this is actually one of our hostkeys
 673                  * before attempting to sign anything with it.
 674                  */
 675                 if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) {
 676                         error("%s: unknown host %s key",
 677                             __func__, sshkey_type(key));
 678                         goto out;
 679                 }
 680                 /*
 681                  * XXX refactor: make kex->sign just use an index rather
 682                  * than passing in public and private keys
 683                  */
 684                 if ((key_prv = get_hostkey_by_index(ndx)) == NULL &&
 685                     (key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) {
 686                         error("%s: can't retrieve hostkey %d", __func__, ndx);
 687                         goto out;
 688                 }
 689                 sshbuf_reset(sigbuf);
 690                 free(sig);
 691                 sig = NULL;
 692                 if ((r = sshbuf_put_cstring(sigbuf,
 693                     "hostkeys-prove-00@openssh.com")) != 0 ||
 694                     (r = sshbuf_put_string(sigbuf,
 695                     ssh->kex->session_id, ssh->kex->session_id_len)) != 0 ||
 696                     (r = sshkey_puts(key, sigbuf)) != 0 ||
 697                     (r = ssh->kex->sign(key_prv, key_pub, &sig, &slen,
 698                     sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), NULL, 0)) != 0 ||
 699                     (r = sshbuf_put_string(resp, sig, slen)) != 0) {
 700                         error("%s: couldn't prepare signature: %s",
 701                             __func__, ssh_err(r));
 702                         goto out;
 703                 }
 704         }
 705         /* Success */
 706         *respp = resp;
 707         resp = NULL; /* don't free it */
 708         success = 1;
 709  out:
 710         free(sig);
 711         sshbuf_free(resp);
 712         sshbuf_free(sigbuf);
 713         sshkey_free(key);
 714         return success;
 715 }
 716
 717 static int
 718 server_input_global_request(int type, u_int32_t seq, struct ssh *ssh)
 719 {
 720         char *rtype;
 721         int want_reply;
 722         int r, success = 0, allocated_listen_port = 0;
 723         struct sshbuf *resp = NULL;
 724         struct passwd *pw = the_authctxt->pw;
 725
 726         if (pw == NULL || !the_authctxt->valid)
 727                 fatal("server_input_global_request: no/invalid user");
 728
 729         rtype = packet_get_string(NULL);
 730         want_reply = packet_get_char();
 731         debug("server_input_global_request: rtype %s want_reply %d", rtype, want_reply);
 732
 733         /* -R style forwarding */
 734         if (strcmp(rtype, "tcpip-forward") == 0) {
 735                 struct Forward fwd;
 736
 737                 memset(&fwd, 0, sizeof(fwd));
 738                 fwd.listen_host = packet_get_string(NULL);
 739                 fwd.listen_port = (u_short)packet_get_int();
 740                 debug("server_input_global_request: tcpip-forward listen %s port %d",
 741                     fwd.listen_host, fwd.listen_port);
 742
 743                 /* check permissions */
 744                 if ((options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 ||
 745                     no_port_forwarding_flag || options.disable_forwarding ||
 746                     (!want_reply && fwd.listen_port == 0) ||
 747                     (fwd.listen_port != 0 &&
 748                      !bind_permitted(fwd.listen_port, pw->pw_uid))) {
 749                         success = 0;
 750                         packet_send_debug("Server has disabled port forwarding.");
 751                 } else {
 752                         /* Start listening on the port */
 753                         success = channel_setup_remote_fwd_listener(ssh, &fwd,
 754                             &allocated_listen_port, &options.fwd_opts);
 755                 }
 756                 free(fwd.listen_host);
 757                 if ((resp = sshbuf_new()) == NULL)
 758                         fatal("%s: sshbuf_new", __func__);
 759                 if (allocated_listen_port != 0 &&
 760                     (r = sshbuf_put_u32(resp, allocated_listen_port)) != 0)
 761                         fatal("%s: sshbuf_put_u32: %s", __func__, ssh_err(r));
 762         } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) {
 763                 struct Forward fwd;
 764
 765                 memset(&fwd, 0, sizeof(fwd));
 766                 fwd.listen_host = packet_get_string(NULL);
 767                 fwd.listen_port = (u_short)packet_get_int();
 768                 debug("%s: cancel-tcpip-forward addr %s port %d", __func__,
 769                     fwd.listen_host, fwd.listen_port);
 770
 771                 success = channel_cancel_rport_listener(ssh, &fwd);
 772                 free(fwd.listen_host);
 773         } else if (strcmp(rtype, "streamlocal-forward@openssh.com") == 0) {
 774                 struct Forward fwd;
 775
 776                 memset(&fwd, 0, sizeof(fwd));
 777                 fwd.listen_path = packet_get_string(NULL);
 778                 debug("server_input_global_request: streamlocal-forward listen path %s",
 779                     fwd.listen_path);
 780
 781                 /* check permissions */
 782                 if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0
 783                     || no_port_forwarding_flag || options.disable_forwarding ||
 784                     (pw->pw_uid != 0 && !use_privsep)) {
 785                         success = 0;
 786                         packet_send_debug("Server has disabled "
 787                             "streamlocal forwarding.");
 788                 } else {
 789                         /* Start listening on the socket */
 790                         success = channel_setup_remote_fwd_listener(ssh,
 791                             &fwd, NULL, &options.fwd_opts);
 792                 }
 793                 free(fwd.listen_path);
 794         } else if (strcmp(rtype, "cancel-streamlocal-forward@openssh.com") == 0) {
 795                 struct Forward fwd;
 796
 797                 memset(&fwd, 0, sizeof(fwd));
 798                 fwd.listen_path = packet_get_string(NULL);
 799                 debug("%s: cancel-streamlocal-forward path %s", __func__,
 800                     fwd.listen_path);
 801
 802                 success = channel_cancel_rport_listener(ssh, &fwd);
 803                 free(fwd.listen_path);
 804         } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) {
 805                 no_more_sessions = 1;
 806                 success = 1;
 807         } else if (strcmp(rtype, "hostkeys-prove-00@openssh.com") == 0) {
 808                 success = server_input_hostkeys_prove(ssh, &resp);
 809         }
 810         if (want_reply) {
 811                 packet_start(success ?
 812                     SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE);
 813                 if (success && resp != NULL)
 814                         ssh_packet_put_raw(ssh, sshbuf_ptr(resp),
 815                             sshbuf_len(resp));
 816                 packet_send();
 817                 packet_write_wait();
 818         }
 819         free(rtype);
 820         sshbuf_free(resp);
 821         return 0;
 822 }
 823
 824 static int
 825 server_input_channel_req(int type, u_int32_t seq, struct ssh *ssh)
 826 {
 827         Channel *c;
 828         int id, reply, success = 0;
 829         char *rtype;
 830
 831         id = packet_get_int();
 832         rtype = packet_get_string(NULL);
 833         reply = packet_get_char();
 834
 835         debug("server_input_channel_req: channel %d request %s reply %d",
 836             id, rtype, reply);
 837
 838         if ((c = channel_lookup(ssh, id)) == NULL)
 839                 packet_disconnect("server_input_channel_req: "
 840                     "unknown channel %d", id);
 841         if (!strcmp(rtype, "eow@openssh.com")) {
 842                 packet_check_eom();
 843                 chan_rcvd_eow(ssh, c);
 844         } else if ((c->type == SSH_CHANNEL_LARVAL ||
 845             c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0)
 846                 success = session_input_channel_req(ssh, c, rtype);
 847         if (reply && !(c->flags & CHAN_CLOSE_SENT)) {
 848                 if (!c->have_remote_id)
 849                         fatal("%s: channel %d: no remote_id",
 850                             __func__, c->self);
 851                 packet_start(success ?
 852                     SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE);
 853                 packet_put_int(c->remote_id);
 854                 packet_send();
 855         }
 856         free(rtype);
 857         return 0;
 858 }
 859
 860 static void
 861 server_init_dispatch(void)
 862 {
 863         debug("server_init_dispatch");
 864         dispatch_init(&dispatch_protocol_error);
 865         dispatch_set(SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose);
 866         dispatch_set(SSH2_MSG_CHANNEL_DATA, &channel_input_data);
 867         dispatch_set(SSH2_MSG_CHANNEL_EOF, &channel_input_ieof);
 868         dispatch_set(SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data);
 869         dispatch_set(SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open);
 870         dispatch_set(SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation);
 871         dispatch_set(SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure);
 872         dispatch_set(SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req);
 873         dispatch_set(SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust);
 874         dispatch_set(SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request);
 875         /* client_alive */
 876         dispatch_set(SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive);
 877         dispatch_set(SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive);
 878         dispatch_set(SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive);
 879         dispatch_set(SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive);
 880         /* rekeying */
 881         dispatch_set(SSH2_MSG_KEXINIT, &kex_input_kexinit);
 882 }