1 /* $OpenBSD: serverloop.c,v 1.224 2020/10/18 11:32:02 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 <sys/types.h> 39 #include <sys/wait.h> 40 #include <sys/socket.h> 41 #include <sys/time.h> 42 #include <sys/queue.h> 43 44 #include <netinet/in.h> 45 46 #include <errno.h> 47 #include <fcntl.h> 48 #include <pwd.h> 49 #include <limits.h> 50 #include <signal.h> 51 #include <string.h> 52 #include <termios.h> 53 #include <unistd.h> 54 #include <stdarg.h> 55 56 #include "xmalloc.h" 57 #include "packet.h" 58 #include "sshbuf.h" 59 #include "log.h" 60 #include "misc.h" 61 #include "servconf.h" 62 #include "canohost.h" 63 #include "sshpty.h" 64 #include "channels.h" 65 #include "compat.h" 66 #include "ssh2.h" 67 #include "sshkey.h" 68 #include "cipher.h" 69 #include "kex.h" 70 #include "hostfile.h" 71 #include "auth.h" 72 #include "session.h" 73 #include "dispatch.h" 74 #include "auth-options.h" 75 #include "serverloop.h" 76 #include "ssherr.h" 77 78 extern ServerOptions options; 79 80 /* XXX */ 81 extern Authctxt *the_authctxt; 82 extern struct sshauthopt *auth_opts; 83 extern int use_privsep; 84 85 static int no_more_sessions = 0; /* Disallow further sessions. */ 86 87 /* 88 * This SIGCHLD kludge is used to detect when the child exits. The server 89 * will exit after that, as soon as forwarded connections have terminated. 90 */ 91 92 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */ 93 94 /* Cleanup on signals (!use_privsep case only) */ 95 static volatile sig_atomic_t received_sigterm = 0; 96 97 /* prototypes */ 98 static void server_init_dispatch(struct ssh *); 99 100 /* requested tunnel forwarding interface(s), shared with session.c */ 101 char *tun_fwd_ifnames = NULL; 102 103 /* returns 1 if bind to specified port by specified user is permitted */ 104 static int 105 bind_permitted(int port, uid_t uid) 106 { 107 if (use_privsep) 108 return 1; /* allow system to decide */ 109 if (port < IPPORT_RESERVED && uid != 0) 110 return 0; 111 return 1; 112 } 113 114 /* 115 * we write to this pipe if a SIGCHLD is caught in order to avoid 116 * the race between select() and child_terminated 117 */ 118 static int notify_pipe[2]; 119 static void 120 notify_setup(void) 121 { 122 if (pipe(notify_pipe) == -1) { 123 error("pipe(notify_pipe) failed %s", strerror(errno)); 124 } else if ((fcntl(notify_pipe[0], F_SETFD, FD_CLOEXEC) == -1) || 125 (fcntl(notify_pipe[1], F_SETFD, FD_CLOEXEC) == -1)) { 126 error("fcntl(notify_pipe, F_SETFD) failed %s", strerror(errno)); 127 close(notify_pipe[0]); 128 close(notify_pipe[1]); 129 } else { 130 set_nonblock(notify_pipe[0]); 131 set_nonblock(notify_pipe[1]); 132 return; 133 } 134 notify_pipe[0] = -1; /* read end */ 135 notify_pipe[1] = -1; /* write end */ 136 } 137 static void 138 notify_parent(void) 139 { 140 if (notify_pipe[1] != -1) 141 (void)write(notify_pipe[1], "", 1); 142 } 143 static void 144 notify_prepare(fd_set *readset) 145 { 146 if (notify_pipe[0] != -1) 147 FD_SET(notify_pipe[0], readset); 148 } 149 static void 150 notify_done(fd_set *readset) 151 { 152 char c; 153 154 if (notify_pipe[0] != -1 && FD_ISSET(notify_pipe[0], readset)) 155 while (read(notify_pipe[0], &c, 1) != -1) 156 debug2_f("reading"); 157 } 158 159 /*ARGSUSED*/ 160 static void 161 sigchld_handler(int sig) 162 { 163 int save_errno = errno; 164 child_terminated = 1; 165 notify_parent(); 166 errno = save_errno; 167 } 168 169 /*ARGSUSED*/ 170 static void 171 sigterm_handler(int sig) 172 { 173 received_sigterm = sig; 174 } 175 176 static void 177 client_alive_check(struct ssh *ssh) 178 { 179 char remote_id[512]; 180 int r, channel_id; 181 182 /* timeout, check to see how many we have had */ 183 if (options.client_alive_count_max > 0 && 184 ssh_packet_inc_alive_timeouts(ssh) > 185 options.client_alive_count_max) { 186 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id)); 187 logit("Timeout, client not responding from %s", remote_id); 188 cleanup_exit(255); 189 } 190 191 /* 192 * send a bogus global/channel request with "wantreply", 193 * we should get back a failure 194 */ 195 if ((channel_id = channel_find_open(ssh)) == -1) { 196 if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 || 197 (r = sshpkt_put_cstring(ssh, "keepalive@openssh.com")) 198 != 0 || 199 (r = sshpkt_put_u8(ssh, 1)) != 0) /* boolean: want reply */ 200 fatal_fr(r, "compose"); 201 } else { 202 channel_request_start(ssh, channel_id, 203 "keepalive@openssh.com", 1); 204 } 205 if ((r = sshpkt_send(ssh)) != 0) 206 fatal_fr(r, "send"); 207 } 208 209 /* 210 * Sleep in select() until we can do something. This will initialize the 211 * select masks. Upon return, the masks will indicate which descriptors 212 * have data or can accept data. Optionally, a maximum time can be specified 213 * for the duration of the wait (0 = infinite). 214 */ 215 static void 216 wait_until_can_do_something(struct ssh *ssh, 217 int connection_in, int connection_out, 218 fd_set **readsetp, fd_set **writesetp, int *maxfdp, 219 u_int *nallocp, u_int64_t max_time_ms) 220 { 221 struct timeval tv, *tvp; 222 int ret; 223 time_t minwait_secs = 0; 224 int client_alive_scheduled = 0; 225 /* time we last heard from the client OR sent a keepalive */ 226 static time_t last_client_time; 227 228 /* Allocate and update select() masks for channel descriptors. */ 229 channel_prepare_select(ssh, readsetp, writesetp, maxfdp, 230 nallocp, &minwait_secs); 231 232 /* XXX need proper deadline system for rekey/client alive */ 233 if (minwait_secs != 0) 234 max_time_ms = MINIMUM(max_time_ms, (u_int)minwait_secs * 1000); 235 236 /* 237 * if using client_alive, set the max timeout accordingly, 238 * and indicate that this particular timeout was for client 239 * alive by setting the client_alive_scheduled flag. 240 * 241 * this could be randomized somewhat to make traffic 242 * analysis more difficult, but we're not doing it yet. 243 */ 244 if (options.client_alive_interval) { 245 uint64_t keepalive_ms = 246 (uint64_t)options.client_alive_interval * 1000; 247 248 if (max_time_ms == 0 || max_time_ms > keepalive_ms) { 249 max_time_ms = keepalive_ms; 250 client_alive_scheduled = 1; 251 } 252 if (last_client_time == 0) 253 last_client_time = monotime(); 254 } 255 256 #if 0 257 /* wrong: bad condition XXX */ 258 if (channel_not_very_much_buffered_data()) 259 #endif 260 FD_SET(connection_in, *readsetp); 261 notify_prepare(*readsetp); 262 263 /* 264 * If we have buffered packet data going to the client, mark that 265 * descriptor. 266 */ 267 if (ssh_packet_have_data_to_write(ssh)) 268 FD_SET(connection_out, *writesetp); 269 270 /* 271 * If child has terminated and there is enough buffer space to read 272 * from it, then read as much as is available and exit. 273 */ 274 if (child_terminated && ssh_packet_not_very_much_data_to_write(ssh)) 275 if (max_time_ms == 0 || client_alive_scheduled) 276 max_time_ms = 100; 277 278 if (max_time_ms == 0) 279 tvp = NULL; 280 else { 281 tv.tv_sec = max_time_ms / 1000; 282 tv.tv_usec = 1000 * (max_time_ms % 1000); 283 tvp = &tv; 284 } 285 286 /* Wait for something to happen, or the timeout to expire. */ 287 ret = select((*maxfdp)+1, *readsetp, *writesetp, NULL, tvp); 288 289 if (ret == -1) { 290 memset(*readsetp, 0, *nallocp); 291 memset(*writesetp, 0, *nallocp); 292 if (errno != EINTR) 293 error("select: %.100s", strerror(errno)); 294 } else if (client_alive_scheduled) { 295 time_t now = monotime(); 296 297 /* 298 * If the select timed out, or returned for some other reason 299 * but we haven't heard from the client in time, send keepalive. 300 */ 301 if (ret == 0 || (last_client_time != 0 && last_client_time + 302 options.client_alive_interval <= now)) { 303 client_alive_check(ssh); 304 last_client_time = now; 305 } else if (FD_ISSET(connection_in, *readsetp)) { 306 last_client_time = now; 307 } 308 } 309 310 notify_done(*readsetp); 311 } 312 313 /* 314 * Processes input from the client and the program. Input data is stored 315 * in buffers and processed later. 316 */ 317 static int 318 process_input(struct ssh *ssh, fd_set *readset, int connection_in) 319 { 320 int r, len; 321 char buf[16384]; 322 323 /* Read and buffer any input data from the client. */ 324 if (FD_ISSET(connection_in, readset)) { 325 len = read(connection_in, buf, sizeof(buf)); 326 if (len == 0) { 327 verbose("Connection closed by %.100s port %d", 328 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 329 return -1; 330 } else if (len == -1) { 331 if (errno == EINTR || errno == EAGAIN) 332 return 0; 333 verbose("Read error from remote host %s port %d: %s", 334 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), 335 strerror(errno)); 336 cleanup_exit(255); 337 } 338 /* Buffer any received data. */ 339 if ((r = ssh_packet_process_incoming(ssh, buf, len)) != 0) 340 fatal_fr(r, "ssh_packet_process_incoming"); 341 } 342 return 0; 343 } 344 345 /* 346 * Sends data from internal buffers to client program stdin. 347 */ 348 static void 349 process_output(struct ssh *ssh, fd_set *writeset, int connection_out) 350 { 351 int r; 352 353 /* Send any buffered packet data to the client. */ 354 if (FD_ISSET(connection_out, writeset)) { 355 if ((r = ssh_packet_write_poll(ssh)) != 0) { 356 sshpkt_fatal(ssh, r, "%s: ssh_packet_write_poll", 357 __func__); 358 } 359 } 360 } 361 362 static void 363 process_buffered_input_packets(struct ssh *ssh) 364 { 365 ssh_dispatch_run_fatal(ssh, DISPATCH_NONBLOCK, NULL); 366 } 367 368 static void 369 collect_children(struct ssh *ssh) 370 { 371 pid_t pid; 372 sigset_t oset, nset; 373 int status; 374 375 /* block SIGCHLD while we check for dead children */ 376 sigemptyset(&nset); 377 sigaddset(&nset, SIGCHLD); 378 sigprocmask(SIG_BLOCK, &nset, &oset); 379 if (child_terminated) { 380 debug("Received SIGCHLD."); 381 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 382 (pid == -1 && errno == EINTR)) 383 if (pid > 0) 384 session_close_by_pid(ssh, pid, status); 385 child_terminated = 0; 386 } 387 sigprocmask(SIG_SETMASK, &oset, NULL); 388 } 389 390 void 391 server_loop2(struct ssh *ssh, Authctxt *authctxt) 392 { 393 fd_set *readset = NULL, *writeset = NULL; 394 int max_fd; 395 u_int nalloc = 0, connection_in, connection_out; 396 u_int64_t rekey_timeout_ms = 0; 397 398 debug("Entering interactive session for SSH2."); 399 400 ssh_signal(SIGCHLD, sigchld_handler); 401 child_terminated = 0; 402 connection_in = ssh_packet_get_connection_in(ssh); 403 connection_out = ssh_packet_get_connection_out(ssh); 404 405 if (!use_privsep) { 406 ssh_signal(SIGTERM, sigterm_handler); 407 ssh_signal(SIGINT, sigterm_handler); 408 ssh_signal(SIGQUIT, sigterm_handler); 409 } 410 411 notify_setup(); 412 413 max_fd = MAXIMUM(connection_in, connection_out); 414 max_fd = MAXIMUM(max_fd, notify_pipe[0]); 415 416 server_init_dispatch(ssh); 417 418 for (;;) { 419 process_buffered_input_packets(ssh); 420 421 if (!ssh_packet_is_rekeying(ssh) && 422 ssh_packet_not_very_much_data_to_write(ssh)) 423 channel_output_poll(ssh); 424 if (options.rekey_interval > 0 && 425 !ssh_packet_is_rekeying(ssh)) { 426 rekey_timeout_ms = ssh_packet_get_rekey_timeout(ssh) * 427 1000; 428 } else { 429 rekey_timeout_ms = 0; 430 } 431 432 wait_until_can_do_something(ssh, connection_in, connection_out, 433 &readset, &writeset, &max_fd, &nalloc, rekey_timeout_ms); 434 435 if (received_sigterm) { 436 logit("Exiting on signal %d", (int)received_sigterm); 437 /* Clean up sessions, utmp, etc. */ 438 cleanup_exit(255); 439 } 440 441 collect_children(ssh); 442 if (!ssh_packet_is_rekeying(ssh)) 443 channel_after_select(ssh, readset, writeset); 444 if (process_input(ssh, readset, connection_in) < 0) 445 break; 446 process_output(ssh, writeset, connection_out); 447 } 448 collect_children(ssh); 449 450 free(readset); 451 free(writeset); 452 453 /* free all channels, no more reads and writes */ 454 channel_free_all(ssh); 455 456 /* free remaining sessions, e.g. remove wtmp entries */ 457 session_destroy_all(ssh, NULL); 458 } 459 460 static int 461 server_input_keep_alive(int type, u_int32_t seq, struct ssh *ssh) 462 { 463 debug("Got %d/%u for keepalive", type, seq); 464 /* 465 * reset timeout, since we got a sane answer from the client. 466 * even if this was generated by something other than 467 * the bogus CHANNEL_REQUEST we send for keepalives. 468 */ 469 ssh_packet_set_alive_timeouts(ssh, 0); 470 return 0; 471 } 472 473 static Channel * 474 server_request_direct_tcpip(struct ssh *ssh, int *reason, const char **errmsg) 475 { 476 Channel *c = NULL; 477 char *target = NULL, *originator = NULL; 478 u_int target_port = 0, originator_port = 0; 479 int r; 480 481 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 482 (r = sshpkt_get_u32(ssh, &target_port)) != 0 || 483 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 484 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 485 (r = sshpkt_get_end(ssh)) != 0) 486 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 487 if (target_port > 0xFFFF) { 488 error_f("invalid target port"); 489 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 490 goto out; 491 } 492 if (originator_port > 0xFFFF) { 493 error_f("invalid originator port"); 494 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 495 goto out; 496 } 497 498 debug_f("originator %s port %u, target %s port %u", 499 originator, originator_port, target, target_port); 500 501 /* XXX fine grained permissions */ 502 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 && 503 auth_opts->permit_port_forwarding_flag && 504 !options.disable_forwarding) { 505 c = channel_connect_to_port(ssh, target, target_port, 506 "direct-tcpip", "direct-tcpip", reason, errmsg); 507 } else { 508 logit("refused local port forward: " 509 "originator %s port %d, target %s port %d", 510 originator, originator_port, target, target_port); 511 if (reason != NULL) 512 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 513 } 514 515 out: 516 free(originator); 517 free(target); 518 return c; 519 } 520 521 static Channel * 522 server_request_direct_streamlocal(struct ssh *ssh) 523 { 524 Channel *c = NULL; 525 char *target = NULL, *originator = NULL; 526 u_int originator_port = 0; 527 struct passwd *pw = the_authctxt->pw; 528 int r; 529 530 if (pw == NULL || !the_authctxt->valid) 531 fatal_f("no/invalid user"); 532 533 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 534 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 535 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 536 (r = sshpkt_get_end(ssh)) != 0) 537 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 538 if (originator_port > 0xFFFF) { 539 error_f("invalid originator port"); 540 goto out; 541 } 542 543 debug_f("originator %s port %d, target %s", 544 originator, originator_port, target); 545 546 /* XXX fine grained permissions */ 547 if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 && 548 auth_opts->permit_port_forwarding_flag && 549 !options.disable_forwarding && (pw->pw_uid == 0 || use_privsep)) { 550 c = channel_connect_to_path(ssh, target, 551 "direct-streamlocal@openssh.com", "direct-streamlocal"); 552 } else { 553 logit("refused streamlocal port forward: " 554 "originator %s port %d, target %s", 555 originator, originator_port, target); 556 } 557 558 out: 559 free(originator); 560 free(target); 561 return c; 562 } 563 564 static Channel * 565 server_request_tun(struct ssh *ssh) 566 { 567 Channel *c = NULL; 568 u_int mode, tun; 569 int r, sock; 570 char *tmp, *ifname = NULL; 571 572 if ((r = sshpkt_get_u32(ssh, &mode)) != 0) 573 sshpkt_fatal(ssh, r, "%s: parse mode", __func__); 574 switch (mode) { 575 case SSH_TUNMODE_POINTOPOINT: 576 case SSH_TUNMODE_ETHERNET: 577 break; 578 default: 579 ssh_packet_send_debug(ssh, "Unsupported tunnel device mode."); 580 return NULL; 581 } 582 if ((options.permit_tun & mode) == 0) { 583 ssh_packet_send_debug(ssh, "Server has rejected tunnel device " 584 "forwarding"); 585 return NULL; 586 } 587 588 if ((r = sshpkt_get_u32(ssh, &tun)) != 0) 589 sshpkt_fatal(ssh, r, "%s: parse device", __func__); 590 if (tun > INT_MAX) { 591 debug_f("invalid tun"); 592 goto done; 593 } 594 if (auth_opts->force_tun_device != -1) { 595 if (tun != SSH_TUNID_ANY && 596 auth_opts->force_tun_device != (int)tun) 597 goto done; 598 tun = auth_opts->force_tun_device; 599 } 600 sock = tun_open(tun, mode, &ifname); 601 if (sock < 0) 602 goto done; 603 debug("Tunnel forwarding using interface %s", ifname); 604 605 c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1, 606 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 607 c->datagram = 1; 608 609 /* 610 * Update the list of names exposed to the session 611 * XXX remove these if the tunnels are closed (won't matter 612 * much if they are already in the environment though) 613 */ 614 tmp = tun_fwd_ifnames; 615 xasprintf(&tun_fwd_ifnames, "%s%s%s", 616 tun_fwd_ifnames == NULL ? "" : tun_fwd_ifnames, 617 tun_fwd_ifnames == NULL ? "" : ",", 618 ifname); 619 free(tmp); 620 free(ifname); 621 622 done: 623 if (c == NULL) 624 ssh_packet_send_debug(ssh, "Failed to open the tunnel device."); 625 return c; 626 } 627 628 static Channel * 629 server_request_session(struct ssh *ssh) 630 { 631 Channel *c; 632 int r; 633 634 debug("input_session_request"); 635 if ((r = sshpkt_get_end(ssh)) != 0) 636 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 637 638 if (no_more_sessions) { 639 ssh_packet_disconnect(ssh, "Possible attack: attempt to open a " 640 "session after additional sessions disabled"); 641 } 642 643 /* 644 * A server session has no fd to read or write until a 645 * CHANNEL_REQUEST for a shell is made, so we set the type to 646 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all 647 * CHANNEL_REQUEST messages is registered. 648 */ 649 c = channel_new(ssh, "session", SSH_CHANNEL_LARVAL, 650 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT, 651 0, "server-session", 1); 652 if (session_open(the_authctxt, c->self) != 1) { 653 debug("session open failed, free channel %d", c->self); 654 channel_free(ssh, c); 655 return NULL; 656 } 657 channel_register_cleanup(ssh, c->self, session_close_by_channel, 0); 658 return c; 659 } 660 661 static int 662 server_input_channel_open(int type, u_int32_t seq, struct ssh *ssh) 663 { 664 Channel *c = NULL; 665 char *ctype = NULL; 666 const char *errmsg = NULL; 667 int r, reason = SSH2_OPEN_CONNECT_FAILED; 668 u_int rchan = 0, rmaxpack = 0, rwindow = 0; 669 670 if ((r = sshpkt_get_cstring(ssh, &ctype, NULL)) != 0 || 671 (r = sshpkt_get_u32(ssh, &rchan)) != 0 || 672 (r = sshpkt_get_u32(ssh, &rwindow)) != 0 || 673 (r = sshpkt_get_u32(ssh, &rmaxpack)) != 0) 674 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 675 debug_f("ctype %s rchan %u win %u max %u", 676 ctype, rchan, rwindow, rmaxpack); 677 678 if (strcmp(ctype, "session") == 0) { 679 c = server_request_session(ssh); 680 } else if (strcmp(ctype, "direct-tcpip") == 0) { 681 c = server_request_direct_tcpip(ssh, &reason, &errmsg); 682 } else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) { 683 c = server_request_direct_streamlocal(ssh); 684 } else if (strcmp(ctype, "tun@openssh.com") == 0) { 685 c = server_request_tun(ssh); 686 } 687 if (c != NULL) { 688 debug_f("confirm %s", ctype); 689 c->remote_id = rchan; 690 c->have_remote_id = 1; 691 c->remote_window = rwindow; 692 c->remote_maxpacket = rmaxpack; 693 if (c->type != SSH_CHANNEL_CONNECTING) { 694 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION)) != 0 || 695 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 696 (r = sshpkt_put_u32(ssh, c->self)) != 0 || 697 (r = sshpkt_put_u32(ssh, c->local_window)) != 0 || 698 (r = sshpkt_put_u32(ssh, c->local_maxpacket)) != 0 || 699 (r = sshpkt_send(ssh)) != 0) { 700 sshpkt_fatal(ssh, r, 701 "%s: send open confirm", __func__); 702 } 703 } 704 } else { 705 debug_f("failure %s", ctype); 706 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE)) != 0 || 707 (r = sshpkt_put_u32(ssh, rchan)) != 0 || 708 (r = sshpkt_put_u32(ssh, reason)) != 0 || 709 (r = sshpkt_put_cstring(ssh, errmsg ? errmsg : "open failed")) != 0 || 710 (r = sshpkt_put_cstring(ssh, "")) != 0 || 711 (r = sshpkt_send(ssh)) != 0) { 712 sshpkt_fatal(ssh, r, 713 "%s: send open failure", __func__); 714 } 715 } 716 free(ctype); 717 return 0; 718 } 719 720 static int 721 server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp) 722 { 723 struct sshbuf *resp = NULL; 724 struct sshbuf *sigbuf = NULL; 725 struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL; 726 int r, ndx, kexsigtype, use_kexsigtype, success = 0; 727 const u_char *blob; 728 u_char *sig = 0; 729 size_t blen, slen; 730 731 if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL) 732 fatal_f("sshbuf_new"); 733 734 kexsigtype = sshkey_type_plain( 735 sshkey_type_from_name(ssh->kex->hostkey_alg)); 736 while (ssh_packet_remaining(ssh) > 0) { 737 sshkey_free(key); 738 key = NULL; 739 if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 || 740 (r = sshkey_from_blob(blob, blen, &key)) != 0) { 741 error_fr(r, "parse key"); 742 goto out; 743 } 744 /* 745 * Better check that this is actually one of our hostkeys 746 * before attempting to sign anything with it. 747 */ 748 if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) { 749 error_f("unknown host %s key", sshkey_type(key)); 750 goto out; 751 } 752 /* 753 * XXX refactor: make kex->sign just use an index rather 754 * than passing in public and private keys 755 */ 756 if ((key_prv = get_hostkey_by_index(ndx)) == NULL && 757 (key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) { 758 error_f("can't retrieve hostkey %d", ndx); 759 goto out; 760 } 761 sshbuf_reset(sigbuf); 762 free(sig); 763 sig = NULL; 764 /* 765 * For RSA keys, prefer to use the signature type negotiated 766 * during KEX to the default (SHA1). 767 */ 768 use_kexsigtype = kexsigtype == KEY_RSA && 769 sshkey_type_plain(key->type) == KEY_RSA; 770 if ((r = sshbuf_put_cstring(sigbuf, 771 "hostkeys-prove-00@openssh.com")) != 0 || 772 (r = sshbuf_put_string(sigbuf, 773 ssh->kex->session_id, ssh->kex->session_id_len)) != 0 || 774 (r = sshkey_puts(key, sigbuf)) != 0 || 775 (r = ssh->kex->sign(ssh, key_prv, key_pub, &sig, &slen, 776 sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), 777 use_kexsigtype ? ssh->kex->hostkey_alg : NULL)) != 0 || 778 (r = sshbuf_put_string(resp, sig, slen)) != 0) { 779 error_fr(r, "assemble signature"); 780 goto out; 781 } 782 } 783 /* Success */ 784 *respp = resp; 785 resp = NULL; /* don't free it */ 786 success = 1; 787 out: 788 free(sig); 789 sshbuf_free(resp); 790 sshbuf_free(sigbuf); 791 sshkey_free(key); 792 return success; 793 } 794 795 static int 796 server_input_global_request(int type, u_int32_t seq, struct ssh *ssh) 797 { 798 char *rtype = NULL; 799 u_char want_reply = 0; 800 int r, success = 0, allocated_listen_port = 0; 801 u_int port = 0; 802 struct sshbuf *resp = NULL; 803 struct passwd *pw = the_authctxt->pw; 804 struct Forward fwd; 805 806 memset(&fwd, 0, sizeof(fwd)); 807 if (pw == NULL || !the_authctxt->valid) 808 fatal_f("no/invalid user"); 809 810 if ((r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 811 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 812 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 813 debug_f("rtype %s want_reply %d", rtype, want_reply); 814 815 /* -R style forwarding */ 816 if (strcmp(rtype, "tcpip-forward") == 0) { 817 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || 818 (r = sshpkt_get_u32(ssh, &port)) != 0) 819 sshpkt_fatal(ssh, r, "%s: parse tcpip-forward", __func__); 820 debug_f("tcpip-forward listen %s port %u", 821 fwd.listen_host, port); 822 if (port <= INT_MAX) 823 fwd.listen_port = (int)port; 824 /* check permissions */ 825 if (port > INT_MAX || 826 (options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 || 827 !auth_opts->permit_port_forwarding_flag || 828 options.disable_forwarding || 829 (!want_reply && fwd.listen_port == 0) || 830 (fwd.listen_port != 0 && 831 !bind_permitted(fwd.listen_port, pw->pw_uid))) { 832 success = 0; 833 ssh_packet_send_debug(ssh, "Server has disabled port forwarding."); 834 } else { 835 /* Start listening on the port */ 836 success = channel_setup_remote_fwd_listener(ssh, &fwd, 837 &allocated_listen_port, &options.fwd_opts); 838 } 839 if ((resp = sshbuf_new()) == NULL) 840 fatal_f("sshbuf_new"); 841 if (allocated_listen_port != 0 && 842 (r = sshbuf_put_u32(resp, allocated_listen_port)) != 0) 843 fatal_fr(r, "sshbuf_put_u32"); 844 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) { 845 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || 846 (r = sshpkt_get_u32(ssh, &port)) != 0) 847 sshpkt_fatal(ssh, r, "%s: parse cancel-tcpip-forward", __func__); 848 849 debug_f("cancel-tcpip-forward addr %s port %d", 850 fwd.listen_host, port); 851 if (port <= INT_MAX) { 852 fwd.listen_port = (int)port; 853 success = channel_cancel_rport_listener(ssh, &fwd); 854 } 855 } else if (strcmp(rtype, "streamlocal-forward@openssh.com") == 0) { 856 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) 857 sshpkt_fatal(ssh, r, "%s: parse streamlocal-forward@openssh.com", __func__); 858 debug_f("streamlocal-forward listen path %s", 859 fwd.listen_path); 860 861 /* check permissions */ 862 if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0 863 || !auth_opts->permit_port_forwarding_flag || 864 options.disable_forwarding || 865 (pw->pw_uid != 0 && !use_privsep)) { 866 success = 0; 867 ssh_packet_send_debug(ssh, "Server has disabled " 868 "streamlocal forwarding."); 869 } else { 870 /* Start listening on the socket */ 871 success = channel_setup_remote_fwd_listener(ssh, 872 &fwd, NULL, &options.fwd_opts); 873 } 874 } else if (strcmp(rtype, "cancel-streamlocal-forward@openssh.com") == 0) { 875 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) 876 sshpkt_fatal(ssh, r, "%s: parse cancel-streamlocal-forward@openssh.com", __func__); 877 debug_f("cancel-streamlocal-forward path %s", 878 fwd.listen_path); 879 880 success = channel_cancel_rport_listener(ssh, &fwd); 881 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) { 882 no_more_sessions = 1; 883 success = 1; 884 } else if (strcmp(rtype, "hostkeys-prove-00@openssh.com") == 0) { 885 success = server_input_hostkeys_prove(ssh, &resp); 886 } 887 /* XXX sshpkt_get_end() */ 888 if (want_reply) { 889 if ((r = sshpkt_start(ssh, success ? 890 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE)) != 0 || 891 (success && resp != NULL && (r = sshpkt_putb(ssh, resp)) != 0) || 892 (r = sshpkt_send(ssh)) != 0 || 893 (r = ssh_packet_write_wait(ssh)) != 0) 894 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 895 } 896 free(fwd.listen_host); 897 free(fwd.listen_path); 898 free(rtype); 899 sshbuf_free(resp); 900 return 0; 901 } 902 903 static int 904 server_input_channel_req(int type, u_int32_t seq, struct ssh *ssh) 905 { 906 Channel *c; 907 int r, success = 0; 908 char *rtype = NULL; 909 u_char want_reply = 0; 910 u_int id = 0; 911 912 if ((r = sshpkt_get_u32(ssh, &id)) != 0 || 913 (r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 914 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 915 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 916 917 debug("server_input_channel_req: channel %u request %s reply %d", 918 id, rtype, want_reply); 919 920 if (id >= INT_MAX || (c = channel_lookup(ssh, (int)id)) == NULL) { 921 ssh_packet_disconnect(ssh, "%s: unknown channel %d", 922 __func__, id); 923 } 924 if (!strcmp(rtype, "eow@openssh.com")) { 925 if ((r = sshpkt_get_end(ssh)) != 0) 926 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 927 chan_rcvd_eow(ssh, c); 928 } else if ((c->type == SSH_CHANNEL_LARVAL || 929 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0) 930 success = session_input_channel_req(ssh, c, rtype); 931 if (want_reply && !(c->flags & CHAN_CLOSE_SENT)) { 932 if (!c->have_remote_id) 933 fatal_f("channel %d: no remote_id", c->self); 934 if ((r = sshpkt_start(ssh, success ? 935 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE)) != 0 || 936 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 937 (r = sshpkt_send(ssh)) != 0) 938 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 939 } 940 free(rtype); 941 return 0; 942 } 943 944 static void 945 server_init_dispatch(struct ssh *ssh) 946 { 947 debug("server_init_dispatch"); 948 ssh_dispatch_init(ssh, &dispatch_protocol_error); 949 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); 950 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_DATA, &channel_input_data); 951 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); 952 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); 953 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); 954 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 955 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 956 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req); 957 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); 958 ssh_dispatch_set(ssh, SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request); 959 /* client_alive */ 960 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive); 961 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive); 962 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive); 963 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive); 964 /* rekeying */ 965 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit); 966 } 967