1 /* $OpenBSD: serverloop.c,v 1.228 2021/07/16 09:00:23 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 <limits.h> 53 #include <signal.h> 54 #include <string.h> 55 #include <termios.h> 56 #include <unistd.h> 57 #include <stdarg.h> 58 59 #include "openbsd-compat/sys-queue.h" 60 #include "xmalloc.h" 61 #include "packet.h" 62 #include "sshbuf.h" 63 #include "log.h" 64 #include "misc.h" 65 #include "servconf.h" 66 #include "canohost.h" 67 #include "sshpty.h" 68 #include "channels.h" 69 #include "compat.h" 70 #include "ssh2.h" 71 #include "sshkey.h" 72 #include "cipher.h" 73 #include "kex.h" 74 #include "hostfile.h" 75 #include "auth.h" 76 #include "session.h" 77 #include "dispatch.h" 78 #include "auth-options.h" 79 #include "serverloop.h" 80 #include "ssherr.h" 81 82 extern ServerOptions options; 83 84 /* XXX */ 85 extern Authctxt *the_authctxt; 86 extern struct sshauthopt *auth_opts; 87 extern int use_privsep; 88 89 static int no_more_sessions = 0; /* Disallow further sessions. */ 90 91 static volatile sig_atomic_t child_terminated = 0; /* The child has terminated. */ 92 93 /* Cleanup on signals (!use_privsep case only) */ 94 static volatile sig_atomic_t received_sigterm = 0; 95 96 /* prototypes */ 97 static void server_init_dispatch(struct ssh *); 98 99 /* requested tunnel forwarding interface(s), shared with session.c */ 100 char *tun_fwd_ifnames = NULL; 101 102 /* returns 1 if bind to specified port by specified user is permitted */ 103 static int 104 bind_permitted(int port, uid_t uid) 105 { 106 if (use_privsep) 107 return 1; /* allow system to decide */ 108 if (port < IPPORT_RESERVED && uid != 0) 109 return 0; 110 return 1; 111 } 112 113 /*ARGSUSED*/ 114 static void 115 sigchld_handler(int sig) 116 { 117 child_terminated = 1; 118 } 119 120 /*ARGSUSED*/ 121 static void 122 sigterm_handler(int sig) 123 { 124 received_sigterm = sig; 125 } 126 127 static void 128 client_alive_check(struct ssh *ssh) 129 { 130 char remote_id[512]; 131 int r, channel_id; 132 133 /* timeout, check to see how many we have had */ 134 if (options.client_alive_count_max > 0 && 135 ssh_packet_inc_alive_timeouts(ssh) > 136 options.client_alive_count_max) { 137 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id)); 138 logit("Timeout, client not responding from %s", remote_id); 139 cleanup_exit(255); 140 } 141 142 /* 143 * send a bogus global/channel request with "wantreply", 144 * we should get back a failure 145 */ 146 if ((channel_id = channel_find_open(ssh)) == -1) { 147 if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 || 148 (r = sshpkt_put_cstring(ssh, "keepalive@openssh.com")) 149 != 0 || 150 (r = sshpkt_put_u8(ssh, 1)) != 0) /* boolean: want reply */ 151 fatal_fr(r, "compose"); 152 } else { 153 channel_request_start(ssh, channel_id, 154 "keepalive@openssh.com", 1); 155 } 156 if ((r = sshpkt_send(ssh)) != 0) 157 fatal_fr(r, "send"); 158 } 159 160 /* 161 * Sleep in pselect() until we can do something. This will initialize the 162 * pselect masks. Upon return, the masks will indicate which descriptors 163 * have data or can accept data. Optionally, a maximum time can be specified 164 * for the duration of the wait (0 = infinite). 165 */ 166 static void 167 wait_until_can_do_something(struct ssh *ssh, 168 int connection_in, int connection_out, 169 fd_set **readsetp, fd_set **writesetp, int *maxfdp, 170 u_int *nallocp, u_int64_t max_time_ms, sigset_t *sigsetp) 171 { 172 struct timespec ts, *tsp; 173 int ret; 174 time_t minwait_secs = 0; 175 int client_alive_scheduled = 0; 176 /* time we last heard from the client OR sent a keepalive */ 177 static time_t last_client_time; 178 179 /* Allocate and update pselect() masks for channel descriptors. */ 180 channel_prepare_select(ssh, readsetp, writesetp, maxfdp, 181 nallocp, &minwait_secs); 182 183 /* XXX need proper deadline system for rekey/client alive */ 184 if (minwait_secs != 0) 185 max_time_ms = MINIMUM(max_time_ms, (u_int)minwait_secs * 1000); 186 187 /* 188 * if using client_alive, set the max timeout accordingly, 189 * and indicate that this particular timeout was for client 190 * alive by setting the client_alive_scheduled flag. 191 * 192 * this could be randomized somewhat to make traffic 193 * analysis more difficult, but we're not doing it yet. 194 */ 195 if (options.client_alive_interval) { 196 uint64_t keepalive_ms = 197 (uint64_t)options.client_alive_interval * 1000; 198 199 if (max_time_ms == 0 || max_time_ms > keepalive_ms) { 200 max_time_ms = keepalive_ms; 201 client_alive_scheduled = 1; 202 } 203 if (last_client_time == 0) 204 last_client_time = monotime(); 205 } 206 207 #if 0 208 /* wrong: bad condition XXX */ 209 if (channel_not_very_much_buffered_data()) 210 #endif 211 FD_SET(connection_in, *readsetp); 212 213 /* 214 * If we have buffered packet data going to the client, mark that 215 * descriptor. 216 */ 217 if (ssh_packet_have_data_to_write(ssh)) 218 FD_SET(connection_out, *writesetp); 219 220 /* 221 * If child has terminated and there is enough buffer space to read 222 * from it, then read as much as is available and exit. 223 */ 224 if (child_terminated && ssh_packet_not_very_much_data_to_write(ssh)) 225 if (max_time_ms == 0 || client_alive_scheduled) 226 max_time_ms = 100; 227 228 if (max_time_ms == 0) 229 tsp = NULL; 230 else { 231 ts.tv_sec = max_time_ms / 1000; 232 ts.tv_nsec = 1000000 * (max_time_ms % 1000); 233 tsp = &ts; 234 } 235 236 /* Wait for something to happen, or the timeout to expire. */ 237 ret = pselect((*maxfdp)+1, *readsetp, *writesetp, NULL, tsp, sigsetp); 238 239 if (ret == -1) { 240 memset(*readsetp, 0, *nallocp); 241 memset(*writesetp, 0, *nallocp); 242 if (errno != EINTR) 243 error("pselect: %.100s", strerror(errno)); 244 } else if (client_alive_scheduled) { 245 time_t now = monotime(); 246 247 /* 248 * If the pselect timed out, or returned for some other reason 249 * but we haven't heard from the client in time, send keepalive. 250 */ 251 if (ret == 0 || (last_client_time != 0 && last_client_time + 252 options.client_alive_interval <= now)) { 253 client_alive_check(ssh); 254 last_client_time = now; 255 } else if (FD_ISSET(connection_in, *readsetp)) { 256 last_client_time = now; 257 } 258 } 259 } 260 261 /* 262 * Processes input from the client and the program. Input data is stored 263 * in buffers and processed later. 264 */ 265 static int 266 process_input(struct ssh *ssh, fd_set *readset, int connection_in) 267 { 268 int r, len; 269 char buf[16384]; 270 271 /* Read and buffer any input data from the client. */ 272 if (FD_ISSET(connection_in, readset)) { 273 len = read(connection_in, buf, sizeof(buf)); 274 if (len == 0) { 275 verbose("Connection closed by %.100s port %d", 276 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 277 return -1; 278 } else if (len == -1) { 279 if (errno == EINTR || errno == EAGAIN || 280 errno == EWOULDBLOCK) 281 return 0; 282 verbose("Read error from remote host %s port %d: %s", 283 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), 284 strerror(errno)); 285 cleanup_exit(255); 286 } 287 /* Buffer any received data. */ 288 if ((r = ssh_packet_process_incoming(ssh, buf, len)) != 0) 289 fatal_fr(r, "ssh_packet_process_incoming"); 290 } 291 return 0; 292 } 293 294 /* 295 * Sends data from internal buffers to client program stdin. 296 */ 297 static void 298 process_output(struct ssh *ssh, fd_set *writeset, int connection_out) 299 { 300 int r; 301 302 /* Send any buffered packet data to the client. */ 303 if (FD_ISSET(connection_out, writeset)) { 304 if ((r = ssh_packet_write_poll(ssh)) != 0) { 305 sshpkt_fatal(ssh, r, "%s: ssh_packet_write_poll", 306 __func__); 307 } 308 } 309 } 310 311 static void 312 process_buffered_input_packets(struct ssh *ssh) 313 { 314 ssh_dispatch_run_fatal(ssh, DISPATCH_NONBLOCK, NULL); 315 } 316 317 static void 318 collect_children(struct ssh *ssh) 319 { 320 pid_t pid; 321 int status; 322 323 if (child_terminated) { 324 debug("Received SIGCHLD."); 325 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 326 (pid == -1 && errno == EINTR)) 327 if (pid > 0) 328 session_close_by_pid(ssh, pid, status); 329 child_terminated = 0; 330 } 331 } 332 333 void 334 server_loop2(struct ssh *ssh, Authctxt *authctxt) 335 { 336 fd_set *readset = NULL, *writeset = NULL; 337 int r, max_fd; 338 u_int nalloc = 0, connection_in, connection_out; 339 u_int64_t rekey_timeout_ms = 0; 340 sigset_t bsigset, osigset; 341 342 debug("Entering interactive session for SSH2."); 343 344 if (sigemptyset(&bsigset) == -1 || sigaddset(&bsigset, SIGCHLD) == -1) 345 error_f("bsigset setup: %s", strerror(errno)); 346 ssh_signal(SIGCHLD, sigchld_handler); 347 child_terminated = 0; 348 connection_in = ssh_packet_get_connection_in(ssh); 349 connection_out = ssh_packet_get_connection_out(ssh); 350 351 if (!use_privsep) { 352 ssh_signal(SIGTERM, sigterm_handler); 353 ssh_signal(SIGINT, sigterm_handler); 354 ssh_signal(SIGQUIT, sigterm_handler); 355 } 356 357 max_fd = MAXIMUM(connection_in, connection_out); 358 359 server_init_dispatch(ssh); 360 361 for (;;) { 362 process_buffered_input_packets(ssh); 363 364 if (!ssh_packet_is_rekeying(ssh) && 365 ssh_packet_not_very_much_data_to_write(ssh)) 366 channel_output_poll(ssh); 367 if (options.rekey_interval > 0 && 368 !ssh_packet_is_rekeying(ssh)) { 369 rekey_timeout_ms = ssh_packet_get_rekey_timeout(ssh) * 370 1000; 371 } else { 372 rekey_timeout_ms = 0; 373 } 374 375 /* 376 * Block SIGCHLD while we check for dead children, then pass 377 * the old signal mask through to pselect() so that it'll wake 378 * up immediately if a child exits after we've called waitpid(). 379 */ 380 if (sigprocmask(SIG_BLOCK, &bsigset, &osigset) == -1) 381 error_f("bsigset sigprocmask: %s", strerror(errno)); 382 collect_children(ssh); 383 wait_until_can_do_something(ssh, connection_in, connection_out, 384 &readset, &writeset, &max_fd, &nalloc, rekey_timeout_ms, 385 &osigset); 386 if (sigprocmask(SIG_UNBLOCK, &bsigset, &osigset) == -1) 387 error_f("osigset sigprocmask: %s", strerror(errno)); 388 389 if (received_sigterm) { 390 logit("Exiting on signal %d", (int)received_sigterm); 391 /* Clean up sessions, utmp, etc. */ 392 cleanup_exit(255); 393 } 394 395 if (!ssh_packet_is_rekeying(ssh)) 396 channel_after_select(ssh, readset, writeset); 397 if (process_input(ssh, readset, connection_in) < 0) 398 break; 399 /* A timeout may have triggered rekeying */ 400 if ((r = ssh_packet_check_rekey(ssh)) != 0) 401 fatal_fr(r, "cannot start rekeying"); 402 process_output(ssh, writeset, connection_out); 403 } 404 collect_children(ssh); 405 406 free(readset); 407 free(writeset); 408 409 /* free all channels, no more reads and writes */ 410 channel_free_all(ssh); 411 412 /* free remaining sessions, e.g. remove wtmp entries */ 413 session_destroy_all(ssh, NULL); 414 } 415 416 static int 417 server_input_keep_alive(int type, u_int32_t seq, struct ssh *ssh) 418 { 419 debug("Got %d/%u for keepalive", type, seq); 420 /* 421 * reset timeout, since we got a sane answer from the client. 422 * even if this was generated by something other than 423 * the bogus CHANNEL_REQUEST we send for keepalives. 424 */ 425 ssh_packet_set_alive_timeouts(ssh, 0); 426 return 0; 427 } 428 429 static Channel * 430 server_request_direct_tcpip(struct ssh *ssh, int *reason, const char **errmsg) 431 { 432 Channel *c = NULL; 433 char *target = NULL, *originator = NULL; 434 u_int target_port = 0, originator_port = 0; 435 int r; 436 437 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 438 (r = sshpkt_get_u32(ssh, &target_port)) != 0 || 439 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 440 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 441 (r = sshpkt_get_end(ssh)) != 0) 442 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 443 if (target_port > 0xFFFF) { 444 error_f("invalid target port"); 445 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 446 goto out; 447 } 448 if (originator_port > 0xFFFF) { 449 error_f("invalid originator port"); 450 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 451 goto out; 452 } 453 454 debug_f("originator %s port %u, target %s port %u", 455 originator, originator_port, target, target_port); 456 457 /* XXX fine grained permissions */ 458 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 && 459 auth_opts->permit_port_forwarding_flag && 460 !options.disable_forwarding) { 461 c = channel_connect_to_port(ssh, target, target_port, 462 "direct-tcpip", "direct-tcpip", reason, errmsg); 463 } else { 464 logit("refused local port forward: " 465 "originator %s port %d, target %s port %d", 466 originator, originator_port, target, target_port); 467 if (reason != NULL) 468 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 469 } 470 471 out: 472 free(originator); 473 free(target); 474 return c; 475 } 476 477 static Channel * 478 server_request_direct_streamlocal(struct ssh *ssh) 479 { 480 Channel *c = NULL; 481 char *target = NULL, *originator = NULL; 482 u_int originator_port = 0; 483 struct passwd *pw = the_authctxt->pw; 484 int r; 485 486 if (pw == NULL || !the_authctxt->valid) 487 fatal_f("no/invalid user"); 488 489 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 490 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 491 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 492 (r = sshpkt_get_end(ssh)) != 0) 493 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 494 if (originator_port > 0xFFFF) { 495 error_f("invalid originator port"); 496 goto out; 497 } 498 499 debug_f("originator %s port %d, target %s", 500 originator, originator_port, target); 501 502 /* XXX fine grained permissions */ 503 if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 && 504 auth_opts->permit_port_forwarding_flag && 505 !options.disable_forwarding && (pw->pw_uid == 0 || use_privsep)) { 506 c = channel_connect_to_path(ssh, target, 507 "direct-streamlocal@openssh.com", "direct-streamlocal"); 508 } else { 509 logit("refused streamlocal port forward: " 510 "originator %s port %d, target %s", 511 originator, originator_port, target); 512 } 513 514 out: 515 free(originator); 516 free(target); 517 return c; 518 } 519 520 static Channel * 521 server_request_tun(struct ssh *ssh) 522 { 523 Channel *c = NULL; 524 u_int mode, tun; 525 int r, sock; 526 char *tmp, *ifname = NULL; 527 528 if ((r = sshpkt_get_u32(ssh, &mode)) != 0) 529 sshpkt_fatal(ssh, r, "%s: parse mode", __func__); 530 switch (mode) { 531 case SSH_TUNMODE_POINTOPOINT: 532 case SSH_TUNMODE_ETHERNET: 533 break; 534 default: 535 ssh_packet_send_debug(ssh, "Unsupported tunnel device mode."); 536 return NULL; 537 } 538 if ((options.permit_tun & mode) == 0) { 539 ssh_packet_send_debug(ssh, "Server has rejected tunnel device " 540 "forwarding"); 541 return NULL; 542 } 543 544 if ((r = sshpkt_get_u32(ssh, &tun)) != 0) 545 sshpkt_fatal(ssh, r, "%s: parse device", __func__); 546 if (tun > INT_MAX) { 547 debug_f("invalid tun"); 548 goto done; 549 } 550 if (auth_opts->force_tun_device != -1) { 551 if (tun != SSH_TUNID_ANY && 552 auth_opts->force_tun_device != (int)tun) 553 goto done; 554 tun = auth_opts->force_tun_device; 555 } 556 sock = tun_open(tun, mode, &ifname); 557 if (sock < 0) 558 goto done; 559 debug("Tunnel forwarding using interface %s", ifname); 560 561 c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1, 562 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 563 c->datagram = 1; 564 #if defined(SSH_TUN_FILTER) 565 if (mode == SSH_TUNMODE_POINTOPOINT) 566 channel_register_filter(ssh, c->self, sys_tun_infilter, 567 sys_tun_outfilter, NULL, NULL); 568 #endif 569 570 /* 571 * Update the list of names exposed to the session 572 * XXX remove these if the tunnels are closed (won't matter 573 * much if they are already in the environment though) 574 */ 575 tmp = tun_fwd_ifnames; 576 xasprintf(&tun_fwd_ifnames, "%s%s%s", 577 tun_fwd_ifnames == NULL ? "" : tun_fwd_ifnames, 578 tun_fwd_ifnames == NULL ? "" : ",", 579 ifname); 580 free(tmp); 581 free(ifname); 582 583 done: 584 if (c == NULL) 585 ssh_packet_send_debug(ssh, "Failed to open the tunnel device."); 586 return c; 587 } 588 589 static Channel * 590 server_request_session(struct ssh *ssh) 591 { 592 Channel *c; 593 int r; 594 595 debug("input_session_request"); 596 if ((r = sshpkt_get_end(ssh)) != 0) 597 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 598 599 if (no_more_sessions) { 600 ssh_packet_disconnect(ssh, "Possible attack: attempt to open a " 601 "session after additional sessions disabled"); 602 } 603 604 /* 605 * A server session has no fd to read or write until a 606 * CHANNEL_REQUEST for a shell is made, so we set the type to 607 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all 608 * CHANNEL_REQUEST messages is registered. 609 */ 610 c = channel_new(ssh, "session", SSH_CHANNEL_LARVAL, 611 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT, 612 0, "server-session", 1); 613 if (session_open(the_authctxt, c->self) != 1) { 614 debug("session open failed, free channel %d", c->self); 615 channel_free(ssh, c); 616 return NULL; 617 } 618 channel_register_cleanup(ssh, c->self, session_close_by_channel, 0); 619 return c; 620 } 621 622 static int 623 server_input_channel_open(int type, u_int32_t seq, struct ssh *ssh) 624 { 625 Channel *c = NULL; 626 char *ctype = NULL; 627 const char *errmsg = NULL; 628 int r, reason = SSH2_OPEN_CONNECT_FAILED; 629 u_int rchan = 0, rmaxpack = 0, rwindow = 0; 630 631 if ((r = sshpkt_get_cstring(ssh, &ctype, NULL)) != 0 || 632 (r = sshpkt_get_u32(ssh, &rchan)) != 0 || 633 (r = sshpkt_get_u32(ssh, &rwindow)) != 0 || 634 (r = sshpkt_get_u32(ssh, &rmaxpack)) != 0) 635 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 636 debug_f("ctype %s rchan %u win %u max %u", 637 ctype, rchan, rwindow, rmaxpack); 638 639 if (strcmp(ctype, "session") == 0) { 640 c = server_request_session(ssh); 641 } else if (strcmp(ctype, "direct-tcpip") == 0) { 642 c = server_request_direct_tcpip(ssh, &reason, &errmsg); 643 } else if (strcmp(ctype, "direct-streamlocal@openssh.com") == 0) { 644 c = server_request_direct_streamlocal(ssh); 645 } else if (strcmp(ctype, "tun@openssh.com") == 0) { 646 c = server_request_tun(ssh); 647 } 648 if (c != NULL) { 649 debug_f("confirm %s", ctype); 650 c->remote_id = rchan; 651 c->have_remote_id = 1; 652 c->remote_window = rwindow; 653 c->remote_maxpacket = rmaxpack; 654 if (c->type != SSH_CHANNEL_CONNECTING) { 655 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION)) != 0 || 656 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 657 (r = sshpkt_put_u32(ssh, c->self)) != 0 || 658 (r = sshpkt_put_u32(ssh, c->local_window)) != 0 || 659 (r = sshpkt_put_u32(ssh, c->local_maxpacket)) != 0 || 660 (r = sshpkt_send(ssh)) != 0) { 661 sshpkt_fatal(ssh, r, 662 "%s: send open confirm", __func__); 663 } 664 } 665 } else { 666 debug_f("failure %s", ctype); 667 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE)) != 0 || 668 (r = sshpkt_put_u32(ssh, rchan)) != 0 || 669 (r = sshpkt_put_u32(ssh, reason)) != 0 || 670 (r = sshpkt_put_cstring(ssh, errmsg ? errmsg : "open failed")) != 0 || 671 (r = sshpkt_put_cstring(ssh, "")) != 0 || 672 (r = sshpkt_send(ssh)) != 0) { 673 sshpkt_fatal(ssh, r, 674 "%s: send open failure", __func__); 675 } 676 } 677 free(ctype); 678 return 0; 679 } 680 681 static int 682 server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp) 683 { 684 struct sshbuf *resp = NULL; 685 struct sshbuf *sigbuf = NULL; 686 struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL; 687 int r, ndx, kexsigtype, use_kexsigtype, success = 0; 688 const u_char *blob; 689 u_char *sig = 0; 690 size_t blen, slen; 691 692 if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL) 693 fatal_f("sshbuf_new"); 694 695 kexsigtype = sshkey_type_plain( 696 sshkey_type_from_name(ssh->kex->hostkey_alg)); 697 while (ssh_packet_remaining(ssh) > 0) { 698 sshkey_free(key); 699 key = NULL; 700 if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 || 701 (r = sshkey_from_blob(blob, blen, &key)) != 0) { 702 error_fr(r, "parse key"); 703 goto out; 704 } 705 /* 706 * Better check that this is actually one of our hostkeys 707 * before attempting to sign anything with it. 708 */ 709 if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) { 710 error_f("unknown host %s key", sshkey_type(key)); 711 goto out; 712 } 713 /* 714 * XXX refactor: make kex->sign just use an index rather 715 * than passing in public and private keys 716 */ 717 if ((key_prv = get_hostkey_by_index(ndx)) == NULL && 718 (key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) { 719 error_f("can't retrieve hostkey %d", ndx); 720 goto out; 721 } 722 sshbuf_reset(sigbuf); 723 free(sig); 724 sig = NULL; 725 /* 726 * For RSA keys, prefer to use the signature type negotiated 727 * during KEX to the default (SHA1). 728 */ 729 use_kexsigtype = kexsigtype == KEY_RSA && 730 sshkey_type_plain(key->type) == KEY_RSA; 731 if ((r = sshbuf_put_cstring(sigbuf, 732 "hostkeys-prove-00@openssh.com")) != 0 || 733 (r = sshbuf_put_stringb(sigbuf, 734 ssh->kex->session_id)) != 0 || 735 (r = sshkey_puts(key, sigbuf)) != 0 || 736 (r = ssh->kex->sign(ssh, key_prv, key_pub, &sig, &slen, 737 sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), 738 use_kexsigtype ? ssh->kex->hostkey_alg : NULL)) != 0 || 739 (r = sshbuf_put_string(resp, sig, slen)) != 0) { 740 error_fr(r, "assemble signature"); 741 goto out; 742 } 743 } 744 /* Success */ 745 *respp = resp; 746 resp = NULL; /* don't free it */ 747 success = 1; 748 out: 749 free(sig); 750 sshbuf_free(resp); 751 sshbuf_free(sigbuf); 752 sshkey_free(key); 753 return success; 754 } 755 756 static int 757 server_input_global_request(int type, u_int32_t seq, struct ssh *ssh) 758 { 759 char *rtype = NULL; 760 u_char want_reply = 0; 761 int r, success = 0, allocated_listen_port = 0; 762 u_int port = 0; 763 struct sshbuf *resp = NULL; 764 struct passwd *pw = the_authctxt->pw; 765 struct Forward fwd; 766 767 memset(&fwd, 0, sizeof(fwd)); 768 if (pw == NULL || !the_authctxt->valid) 769 fatal_f("no/invalid user"); 770 771 if ((r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 772 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 773 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 774 debug_f("rtype %s want_reply %d", rtype, want_reply); 775 776 /* -R style forwarding */ 777 if (strcmp(rtype, "tcpip-forward") == 0) { 778 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || 779 (r = sshpkt_get_u32(ssh, &port)) != 0) 780 sshpkt_fatal(ssh, r, "%s: parse tcpip-forward", __func__); 781 debug_f("tcpip-forward listen %s port %u", 782 fwd.listen_host, port); 783 if (port <= INT_MAX) 784 fwd.listen_port = (int)port; 785 /* check permissions */ 786 if (port > INT_MAX || 787 (options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 || 788 !auth_opts->permit_port_forwarding_flag || 789 options.disable_forwarding || 790 (!want_reply && fwd.listen_port == 0) || 791 (fwd.listen_port != 0 && 792 !bind_permitted(fwd.listen_port, pw->pw_uid))) { 793 success = 0; 794 ssh_packet_send_debug(ssh, "Server has disabled port forwarding."); 795 } else { 796 /* Start listening on the port */ 797 success = channel_setup_remote_fwd_listener(ssh, &fwd, 798 &allocated_listen_port, &options.fwd_opts); 799 } 800 if ((resp = sshbuf_new()) == NULL) 801 fatal_f("sshbuf_new"); 802 if (allocated_listen_port != 0 && 803 (r = sshbuf_put_u32(resp, allocated_listen_port)) != 0) 804 fatal_fr(r, "sshbuf_put_u32"); 805 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) { 806 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || 807 (r = sshpkt_get_u32(ssh, &port)) != 0) 808 sshpkt_fatal(ssh, r, "%s: parse cancel-tcpip-forward", __func__); 809 810 debug_f("cancel-tcpip-forward addr %s port %d", 811 fwd.listen_host, port); 812 if (port <= INT_MAX) { 813 fwd.listen_port = (int)port; 814 success = channel_cancel_rport_listener(ssh, &fwd); 815 } 816 } else if (strcmp(rtype, "streamlocal-forward@openssh.com") == 0) { 817 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) 818 sshpkt_fatal(ssh, r, "%s: parse streamlocal-forward@openssh.com", __func__); 819 debug_f("streamlocal-forward listen path %s", 820 fwd.listen_path); 821 822 /* check permissions */ 823 if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0 824 || !auth_opts->permit_port_forwarding_flag || 825 options.disable_forwarding || 826 (pw->pw_uid != 0 && !use_privsep)) { 827 success = 0; 828 ssh_packet_send_debug(ssh, "Server has disabled " 829 "streamlocal forwarding."); 830 } else { 831 /* Start listening on the socket */ 832 success = channel_setup_remote_fwd_listener(ssh, 833 &fwd, NULL, &options.fwd_opts); 834 } 835 } else if (strcmp(rtype, "cancel-streamlocal-forward@openssh.com") == 0) { 836 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) 837 sshpkt_fatal(ssh, r, "%s: parse cancel-streamlocal-forward@openssh.com", __func__); 838 debug_f("cancel-streamlocal-forward path %s", 839 fwd.listen_path); 840 841 success = channel_cancel_rport_listener(ssh, &fwd); 842 } else if (strcmp(rtype, "no-more-sessions@openssh.com") == 0) { 843 no_more_sessions = 1; 844 success = 1; 845 } else if (strcmp(rtype, "hostkeys-prove-00@openssh.com") == 0) { 846 success = server_input_hostkeys_prove(ssh, &resp); 847 } 848 /* XXX sshpkt_get_end() */ 849 if (want_reply) { 850 if ((r = sshpkt_start(ssh, success ? 851 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE)) != 0 || 852 (success && resp != NULL && (r = sshpkt_putb(ssh, resp)) != 0) || 853 (r = sshpkt_send(ssh)) != 0 || 854 (r = ssh_packet_write_wait(ssh)) != 0) 855 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 856 } 857 free(fwd.listen_host); 858 free(fwd.listen_path); 859 free(rtype); 860 sshbuf_free(resp); 861 return 0; 862 } 863 864 static int 865 server_input_channel_req(int type, u_int32_t seq, struct ssh *ssh) 866 { 867 Channel *c; 868 int r, success = 0; 869 char *rtype = NULL; 870 u_char want_reply = 0; 871 u_int id = 0; 872 873 if ((r = sshpkt_get_u32(ssh, &id)) != 0 || 874 (r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 875 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 876 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 877 878 debug("server_input_channel_req: channel %u request %s reply %d", 879 id, rtype, want_reply); 880 881 if (id >= INT_MAX || (c = channel_lookup(ssh, (int)id)) == NULL) { 882 ssh_packet_disconnect(ssh, "%s: unknown channel %d", 883 __func__, id); 884 } 885 if (!strcmp(rtype, "eow@openssh.com")) { 886 if ((r = sshpkt_get_end(ssh)) != 0) 887 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 888 chan_rcvd_eow(ssh, c); 889 } else if ((c->type == SSH_CHANNEL_LARVAL || 890 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0) 891 success = session_input_channel_req(ssh, c, rtype); 892 if (want_reply && !(c->flags & CHAN_CLOSE_SENT)) { 893 if (!c->have_remote_id) 894 fatal_f("channel %d: no remote_id", c->self); 895 if ((r = sshpkt_start(ssh, success ? 896 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE)) != 0 || 897 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 898 (r = sshpkt_send(ssh)) != 0) 899 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 900 } 901 free(rtype); 902 return 0; 903 } 904 905 static void 906 server_init_dispatch(struct ssh *ssh) 907 { 908 debug("server_init_dispatch"); 909 ssh_dispatch_init(ssh, &dispatch_protocol_error); 910 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); 911 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_DATA, &channel_input_data); 912 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); 913 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); 914 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); 915 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 916 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 917 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req); 918 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); 919 ssh_dispatch_set(ssh, SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request); 920 /* client_alive */ 921 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive); 922 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive); 923 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive); 924 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive); 925 /* rekeying */ 926 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit); 927 } 928