1 /* $NetBSD: serverloop.c,v 1.40 2026/04/08 18:58:41 christos Exp $ */ 2 /* $OpenBSD: serverloop.c,v 1.246 2026/03/03 09:57:25 dtucker Exp $ */ 3 4 /* 5 * Author: Tatu Ylonen <ylo (at) cs.hut.fi> 6 * Copyright (c) 1995 Tatu Ylonen <ylo (at) cs.hut.fi>, Espoo, Finland 7 * All rights reserved 8 * Server main loop for handling the interactive session. 9 * 10 * As far as I am concerned, the code I have written for this software 11 * can be used freely for any purpose. Any derived versions of this 12 * software must be clearly marked as such, and if the derived work is 13 * incompatible with the protocol description in the RFC file, it must be 14 * called by a name other than "ssh" or "Secure Shell". 15 * 16 * SSH2 support by Markus Friedl. 17 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. 18 * 19 * Redistribution and use in source and binary forms, with or without 20 * modification, are permitted provided that the following conditions 21 * are met: 22 * 1. Redistributions of source code must retain the above copyright 23 * notice, this list of conditions and the following disclaimer. 24 * 2. Redistributions in binary form must reproduce the above copyright 25 * notice, this list of conditions and the following disclaimer in the 26 * documentation and/or other materials provided with the distribution. 27 * 28 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 29 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 30 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 31 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 32 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 33 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 34 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 35 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 36 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 37 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 38 */ 39 40 #include "includes.h" 41 __RCSID("$NetBSD: serverloop.c,v 1.40 2026/04/08 18:58:41 christos Exp $"); 42 43 #include <sys/param.h> /* MIN MAX */ 44 #include <sys/types.h> 45 #include <sys/wait.h> 46 #include <sys/socket.h> 47 #include <sys/time.h> 48 #include <sys/queue.h> 49 50 #include <netinet/in.h> 51 52 #include <errno.h> 53 #include <fcntl.h> 54 #include <pwd.h> 55 #include <limits.h> 56 #include <poll.h> 57 #include <signal.h> 58 #include <string.h> 59 #include <termios.h> 60 #include <unistd.h> 61 #include <stdarg.h> 62 63 #include "xmalloc.h" 64 #include "packet.h" 65 #include "sshbuf.h" 66 #include "log.h" 67 #include "misc.h" 68 #include "servconf.h" 69 #include "canohost.h" 70 #include "sshpty.h" 71 #include "channels.h" 72 #include "ssh2.h" 73 #include "sshkey.h" 74 #include "cipher.h" 75 #include "kex.h" 76 #include "hostfile.h" 77 #include "auth.h" 78 #include "session.h" 79 #include "dispatch.h" 80 #include "auth-options.h" 81 #include "serverloop.h" 82 #include "ssherr.h" 83 84 static u_long stdin_bytes = 0; /* Number of bytes written to stdin. */ 85 static u_long fdout_bytes = 0; /* Number of stdout bytes read from program. */ 86 87 extern ServerOptions options; 88 89 /* XXX */ 90 extern Authctxt *the_authctxt; 91 extern struct sshauthopt *auth_opts; 92 93 static int no_more_sessions = 0; /* Disallow further sessions. */ 94 95 static volatile sig_atomic_t child_terminated = 0; /* set on SIGCHLD */ 96 static volatile sig_atomic_t siginfo_received = 0; 97 98 /* prototypes */ 99 static void server_init_dispatch(struct ssh *); 100 101 /* requested tunnel forwarding interface(s), shared with session.c */ 102 char *tun_fwd_ifnames = NULL; 103 104 /* 105 * Returns current time in seconds from Jan 1, 1970 with the maximum 106 * available resolution. 107 */ 108 109 static double 110 get_current_time(void) 111 { 112 struct timeval tv; 113 gettimeofday(&tv, NULL); 114 return (double) tv.tv_sec + (double) tv.tv_usec / 1000000.0; 115 } 116 117 static void 118 sigchld_handler(int sig) 119 { 120 child_terminated = 1; 121 } 122 123 static void 124 siginfo_handler(int sig) 125 { 126 siginfo_received = 1; 127 } 128 129 static void 130 client_alive_check(struct ssh *ssh) 131 { 132 char remote_id[512]; 133 int r, channel_id; 134 135 /* timeout, check to see how many we have had */ 136 if (options.client_alive_count_max > 0 && 137 ssh_packet_inc_alive_timeouts(ssh) > 138 options.client_alive_count_max) { 139 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id)); 140 logit("Timeout, client not responding from %s", remote_id); 141 cleanup_exit(255); 142 } 143 144 /* 145 * send a bogus global/channel request with "wantreply", 146 * we should get back a failure 147 */ 148 if ((channel_id = channel_find_open(ssh)) == -1) { 149 if ((r = sshpkt_start(ssh, SSH2_MSG_GLOBAL_REQUEST)) != 0 || 150 (r = sshpkt_put_cstring(ssh, "keepalive (at) openssh.com")) 151 != 0 || 152 (r = sshpkt_put_u8(ssh, 1)) != 0) /* boolean: want reply */ 153 fatal_fr(r, "compose"); 154 } else { 155 channel_request_start(ssh, channel_id, 156 "keepalive (at) openssh.com", 1); 157 } 158 if ((r = sshpkt_send(ssh)) != 0) 159 fatal_fr(r, "send"); 160 } 161 162 /* 163 * Sleep in ppoll() until we can do something. 164 * Optionally, a maximum time can be specified for the duration of 165 * the wait (0 = infinite). 166 */ 167 static void 168 wait_until_can_do_something(struct ssh *ssh, 169 int connection_in, int connection_out, struct pollfd **pfdp, 170 u_int *npfd_allocp, u_int *npfd_activep, sigset_t *sigsetp, 171 int *conn_in_readyp, int *conn_out_readyp) 172 { 173 struct timespec timeout; 174 char remote_id[512]; 175 int ret; 176 int client_alive_scheduled = 0; 177 u_int p; 178 time_t now; 179 static time_t last_client_time, unused_connection_expiry; 180 181 *conn_in_readyp = *conn_out_readyp = 0; 182 183 /* Prepare channel poll. First two pollfd entries are reserved */ 184 ptimeout_init(&timeout); 185 channel_prepare_poll(ssh, pfdp, npfd_allocp, npfd_activep, 2, &timeout); 186 now = monotime(); 187 if (*npfd_activep < 2) 188 fatal_f("bad npfd %u", *npfd_activep); /* shouldn't happen */ 189 if (options.rekey_interval > 0 && !ssh_packet_is_rekeying(ssh)) { 190 ptimeout_deadline_sec(&timeout, 191 ssh_packet_get_rekey_timeout(ssh)); 192 } 193 194 /* 195 * If no channels are open and UnusedConnectionTimeout is set, then 196 * start the clock to terminate the connection. 197 */ 198 if (options.unused_connection_timeout != 0) { 199 if (channel_still_open(ssh)) 200 unused_connection_expiry = 0; 201 else if (unused_connection_expiry == 0) { 202 unused_connection_expiry = now + 203 options.unused_connection_timeout; 204 } 205 } 206 if (unused_connection_expiry != 0) 207 ptimeout_deadline_monotime(&timeout, unused_connection_expiry); 208 209 /* 210 * if using client_alive, set the max timeout accordingly, 211 * and indicate that this particular timeout was for client 212 * alive by setting the client_alive_scheduled flag. 213 * 214 * this could be randomized somewhat to make traffic 215 * analysis more difficult, but we're not doing it yet. 216 */ 217 if (options.client_alive_interval) { 218 /* Time we last heard from the client OR sent a keepalive */ 219 if (last_client_time == 0) 220 last_client_time = now; 221 ptimeout_deadline_sec(&timeout, options.client_alive_interval); 222 /* XXX ? deadline_monotime(last_client_time + alive_interval) */ 223 client_alive_scheduled = 1; 224 } 225 226 #if 0 227 /* wrong: bad condition XXX */ 228 if (channel_not_very_much_buffered_data()) 229 #endif 230 /* Monitor client connection on reserved pollfd entries */ 231 (*pfdp)[0].fd = connection_in; 232 (*pfdp)[0].events = POLLIN; 233 (*pfdp)[1].fd = connection_out; 234 (*pfdp)[1].events = ssh_packet_have_data_to_write(ssh) ? POLLOUT : 0; 235 236 /* 237 * If child has terminated and there is enough buffer space to read 238 * from it, then read as much as is available and exit. 239 */ 240 if (child_terminated && ssh_packet_not_very_much_data_to_write(ssh)) 241 ptimeout_deadline_ms(&timeout, 100); 242 243 /* Wait for something to happen, or the timeout to expire. */ 244 ret = ppoll(*pfdp, *npfd_activep, ptimeout_get_tsp(&timeout), sigsetp); 245 246 if (ret == -1) { 247 for (p = 0; p < *npfd_activep; p++) 248 (*pfdp)[p].revents = 0; 249 if (errno != EINTR) 250 fatal_f("ppoll: %.100s", strerror(errno)); 251 return; 252 } 253 254 *conn_in_readyp = (*pfdp)[0].revents != 0; 255 *conn_out_readyp = (*pfdp)[1].revents != 0; 256 257 now = monotime(); /* need to reset after ppoll() */ 258 /* ClientAliveInterval probing */ 259 if (client_alive_scheduled) { 260 if (ret == 0 && 261 now >= last_client_time + options.client_alive_interval) { 262 /* ppoll timed out and we're due to probe */ 263 client_alive_check(ssh); 264 last_client_time = now; 265 } else if (ret != 0 && *conn_in_readyp) { 266 /* Data from peer; reset probe timer. */ 267 last_client_time = now; 268 } 269 } 270 271 /* UnusedConnectionTimeout handling */ 272 if (unused_connection_expiry != 0 && 273 now > unused_connection_expiry && !channel_still_open(ssh)) { 274 sshpkt_fmt_connection_id(ssh, remote_id, sizeof(remote_id)); 275 logit("terminating inactive connection from %s", remote_id); 276 cleanup_exit(255); 277 } 278 } 279 280 /* 281 * Processes input from the client and the program. Input data is stored 282 * in buffers and processed later. 283 */ 284 static int 285 process_input(struct ssh *ssh, int connection_in) 286 { 287 int r; 288 289 if ((r = ssh_packet_process_read(ssh, connection_in)) == 0) 290 return 0; /* success */ 291 if (r == SSH_ERR_SYSTEM_ERROR) { 292 if (errno == EAGAIN || errno == EINTR) 293 return 0; 294 if (errno == EPIPE) { 295 logit("Connection closed by %.100s port %d", 296 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh)); 297 return -1; 298 } 299 logit("Read error from remote host %s port %d: %s", 300 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), 301 strerror(errno)); 302 cleanup_exit(255); 303 } 304 return -1; 305 } 306 307 /* 308 * Sends data from internal buffers to client program stdin. 309 */ 310 static void 311 process_output(struct ssh *ssh, int connection_out) 312 { 313 int r; 314 static int interactive = -1; 315 316 /* Send any buffered packet data to the client. */ 317 if (interactive != !channel_has_bulk(ssh)) { 318 interactive = !channel_has_bulk(ssh); 319 debug2_f("session QoS is now %s", interactive ? 320 "interactive" : "non-interactive"); 321 ssh_packet_set_interactive(ssh, interactive); 322 } 323 if ((r = ssh_packet_write_poll(ssh)) < 0) { 324 sshpkt_fatal(ssh, r, "%s: ssh_packet_write_poll", 325 __func__); 326 } 327 } 328 329 static void 330 process_buffered_input_packets(struct ssh *ssh) 331 { 332 ssh_dispatch_run_fatal(ssh, DISPATCH_NONBLOCK, NULL); 333 } 334 335 static void 336 collect_children(struct ssh *ssh) 337 { 338 pid_t pid; 339 int status; 340 341 if (child_terminated) { 342 debug("Received SIGCHLD."); 343 while ((pid = waitpid(-1, &status, WNOHANG)) > 0 || 344 (pid == -1 && errno == EINTR)) 345 if (pid > 0) 346 session_close_by_pid(ssh, pid, status); 347 child_terminated = 0; 348 } 349 } 350 351 void 352 server_loop2(struct ssh *ssh, Authctxt *authctxt) 353 { 354 struct pollfd *pfd = NULL; 355 u_int npfd_alloc = 0, npfd_active = 0; 356 int r, conn_in_ready, conn_out_ready; 357 u_int connection_in, connection_out; 358 double start_time, total_time; 359 sigset_t bsigset, osigset; 360 361 debug("Entering interactive session for SSH2."); 362 start_time = get_current_time(); 363 364 if (sigemptyset(&bsigset) == -1 || 365 sigaddset(&bsigset, SIGCHLD) == -1 || 366 sigaddset(&bsigset, SIGINFO) == -1) 367 error_f("bsigset setup: %s", strerror(errno)); 368 ssh_signal(SIGCHLD, sigchld_handler); 369 ssh_signal(SIGINFO, siginfo_handler); 370 child_terminated = 0; 371 connection_in = ssh_packet_get_connection_in(ssh); 372 connection_out = ssh_packet_get_connection_out(ssh); 373 374 server_init_dispatch(ssh); 375 376 for (;;) { 377 process_buffered_input_packets(ssh); 378 379 if (!ssh_packet_is_rekeying(ssh) && 380 ssh_packet_not_very_much_data_to_write(ssh)) 381 channel_output_poll(ssh); 382 383 /* 384 * Block SIGCHLD while we check for dead children, then pass 385 * the old signal mask through to ppoll() so that it'll wake 386 * up immediately if a child exits after we've called waitpid(). 387 */ 388 if (sigprocmask(SIG_BLOCK, &bsigset, &osigset) == -1) 389 error_f("bsigset sigprocmask: %s", strerror(errno)); 390 collect_children(ssh); 391 if (siginfo_received) { 392 siginfo_received = 0; 393 channel_report_open(ssh, SYSLOG_LEVEL_INFO); 394 } 395 wait_until_can_do_something(ssh, connection_in, connection_out, 396 &pfd, &npfd_alloc, &npfd_active, &osigset, 397 &conn_in_ready, &conn_out_ready); 398 if (sigprocmask(SIG_SETMASK, &osigset, NULL) == -1) 399 error_f("osigset sigprocmask: %s", strerror(errno)); 400 401 channel_after_poll(ssh, pfd, npfd_active); 402 if (conn_in_ready && 403 process_input(ssh, connection_in) < 0) 404 break; 405 /* A timeout may have triggered rekeying */ 406 if ((r = ssh_packet_check_rekey(ssh)) != 0) 407 fatal_fr(r, "cannot start rekeying"); 408 if (conn_out_ready) 409 process_output(ssh, connection_out); 410 } 411 collect_children(ssh); 412 free(pfd); 413 414 /* free all channels, no more reads and writes */ 415 channel_free_all(ssh); 416 417 /* free remaining sessions, e.g. remove wtmp entries */ 418 session_destroy_all(ssh, NULL); 419 total_time = get_current_time() - start_time; 420 logit("SSH: Server;LType: Throughput;Remote: %s-%d;IN: %lu;OUT: %lu;Duration: %.1f;tPut_in: %.1f;tPut_out: %.1f", 421 ssh_remote_ipaddr(ssh), ssh_remote_port(ssh), 422 stdin_bytes, fdout_bytes, total_time, stdin_bytes / total_time, 423 fdout_bytes / total_time); 424 } 425 426 static int 427 server_input_keep_alive(int type, uint32_t seq, struct ssh *ssh) 428 { 429 debug("Got %d/%u for keepalive", type, seq); 430 /* 431 * reset timeout, since we got a sane answer from the client. 432 * even if this was generated by something other than 433 * the bogus CHANNEL_REQUEST we send for keepalives. 434 */ 435 ssh_packet_set_alive_timeouts(ssh, 0); 436 return 0; 437 } 438 439 static Channel * 440 server_request_direct_tcpip(struct ssh *ssh, int *reason, const char **errmsg) 441 { 442 Channel *c = NULL; 443 char *target = NULL, *originator = NULL; 444 u_int target_port = 0, originator_port = 0; 445 int r; 446 447 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 448 (r = sshpkt_get_u32(ssh, &target_port)) != 0 || 449 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 450 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 451 (r = sshpkt_get_end(ssh)) != 0) 452 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 453 if (target_port > 0xFFFF) { 454 error_f("invalid target port"); 455 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 456 goto out; 457 } 458 if (originator_port > 0xFFFF) { 459 error_f("invalid originator port"); 460 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 461 goto out; 462 } 463 464 debug_f("originator %s port %u, target %s port %u", 465 originator, originator_port, target, target_port); 466 467 /* XXX fine grained permissions */ 468 if ((options.allow_tcp_forwarding & FORWARD_LOCAL) != 0 && 469 auth_opts->permit_port_forwarding_flag && 470 !options.disable_forwarding) { 471 c = channel_connect_to_port(ssh, target, target_port, 472 "direct-tcpip", "direct-tcpip", reason, errmsg); 473 } else { 474 logit("refused local port forward: " 475 "originator %s port %d, target %s port %d", 476 originator, originator_port, target, target_port); 477 if (reason != NULL) 478 *reason = SSH2_OPEN_ADMINISTRATIVELY_PROHIBITED; 479 } 480 481 out: 482 free(originator); 483 free(target); 484 return c; 485 } 486 487 static Channel * 488 server_request_direct_streamlocal(struct ssh *ssh) 489 { 490 Channel *c = NULL; 491 char *target = NULL, *originator = NULL; 492 u_int originator_port = 0; 493 struct passwd *pw = the_authctxt->pw; 494 int r; 495 496 if (pw == NULL || !the_authctxt->valid) 497 fatal_f("no/invalid user"); 498 499 if ((r = sshpkt_get_cstring(ssh, &target, NULL)) != 0 || 500 (r = sshpkt_get_cstring(ssh, &originator, NULL)) != 0 || 501 (r = sshpkt_get_u32(ssh, &originator_port)) != 0 || 502 (r = sshpkt_get_end(ssh)) != 0) 503 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 504 if (originator_port > 0xFFFF) { 505 error_f("invalid originator port"); 506 goto out; 507 } 508 509 debug_f("originator %s port %d, target %s", 510 originator, originator_port, target); 511 512 /* XXX fine grained permissions */ 513 if ((options.allow_streamlocal_forwarding & FORWARD_LOCAL) != 0 && 514 auth_opts->permit_port_forwarding_flag && 515 !options.disable_forwarding) { 516 c = channel_connect_to_path(ssh, target, 517 "direct-streamlocal (at) openssh.com", "direct-streamlocal"); 518 } else { 519 logit("refused streamlocal port forward: " 520 "originator %s port %d, target %s", 521 originator, originator_port, target); 522 } 523 524 out: 525 free(originator); 526 free(target); 527 return c; 528 } 529 530 static Channel * 531 server_request_tun(struct ssh *ssh) 532 { 533 Channel *c = NULL; 534 u_int mode, tun; 535 int r, sock; 536 char *tmp, *ifname = NULL; 537 538 if ((r = sshpkt_get_u32(ssh, &mode)) != 0) 539 sshpkt_fatal(ssh, r, "%s: parse mode", __func__); 540 switch (mode) { 541 case SSH_TUNMODE_POINTOPOINT: 542 case SSH_TUNMODE_ETHERNET: 543 break; 544 default: 545 ssh_packet_send_debug(ssh, "Unsupported tunnel device mode."); 546 return NULL; 547 } 548 if ((options.permit_tun & mode) == 0) { 549 ssh_packet_send_debug(ssh, "Server has rejected tunnel device " 550 "forwarding"); 551 return NULL; 552 } 553 554 if ((r = sshpkt_get_u32(ssh, &tun)) != 0) 555 sshpkt_fatal(ssh, r, "%s: parse device", __func__); 556 if (tun > INT_MAX) { 557 debug_f("invalid tun"); 558 goto done; 559 } 560 if (auth_opts->force_tun_device != -1) { 561 if (tun != SSH_TUNID_ANY && 562 auth_opts->force_tun_device != (int)tun) 563 goto done; 564 tun = auth_opts->force_tun_device; 565 } 566 sock = tun_open(tun, mode, &ifname); 567 if (sock < 0) 568 goto done; 569 debug("Tunnel forwarding using interface %s", ifname); 570 571 if (options.hpn_disabled) 572 c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1, 573 CHAN_TCP_WINDOW_DEFAULT, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 574 else 575 c = channel_new(ssh, "tun", SSH_CHANNEL_OPEN, sock, sock, -1, 576 options.hpn_buffer_size, CHAN_TCP_PACKET_DEFAULT, 0, "tun", 1); 577 c->datagram = 1; 578 579 /* 580 * Update the list of names exposed to the session 581 * XXX remove these if the tunnels are closed (won't matter 582 * much if they are already in the environment though) 583 */ 584 tmp = tun_fwd_ifnames; 585 xasprintf(&tun_fwd_ifnames, "%s%s%s", 586 tun_fwd_ifnames == NULL ? "" : tun_fwd_ifnames, 587 tun_fwd_ifnames == NULL ? "" : ",", 588 ifname); 589 free(tmp); 590 free(ifname); 591 592 done: 593 if (c == NULL) 594 ssh_packet_send_debug(ssh, "Failed to open the tunnel device."); 595 return c; 596 } 597 598 static Channel * 599 server_request_session(struct ssh *ssh) 600 { 601 Channel *c; 602 int r; 603 604 debug("input_session_request"); 605 if ((r = sshpkt_get_end(ssh)) != 0) 606 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 607 608 if (no_more_sessions) { 609 ssh_packet_disconnect(ssh, "Possible attack: attempt to open a " 610 "session after additional sessions disabled"); 611 } 612 613 /* 614 * A server session has no fd to read or write until a 615 * CHANNEL_REQUEST for a shell is made, so we set the type to 616 * SSH_CHANNEL_LARVAL. Additionally, a callback for handling all 617 * CHANNEL_REQUEST messages is registered. 618 */ 619 c = channel_new(ssh, "session", SSH_CHANNEL_LARVAL, 620 -1, -1, -1, /*window size*/0, CHAN_SES_PACKET_DEFAULT, 621 0, "server-session", 1); 622 if ((options.tcp_rcv_buf_poll > 0) && (!options.hpn_disabled)) 623 c->dynamic_window = 1; 624 if (session_open(the_authctxt, c->self) != 1) { 625 debug("session open failed, free channel %d", c->self); 626 channel_free(ssh, c); 627 return NULL; 628 } 629 channel_register_cleanup(ssh, c->self, session_close_by_channel, 0); 630 return c; 631 } 632 633 static int 634 server_input_channel_open(int type, uint32_t seq, struct ssh *ssh) 635 { 636 Channel *c = NULL; 637 char *ctype = NULL; 638 const char *errmsg = NULL; 639 int r, reason = SSH2_OPEN_CONNECT_FAILED; 640 u_int rchan = 0, rmaxpack = 0, rwindow = 0; 641 642 if ((r = sshpkt_get_cstring(ssh, &ctype, NULL)) != 0 || 643 (r = sshpkt_get_u32(ssh, &rchan)) != 0 || 644 (r = sshpkt_get_u32(ssh, &rwindow)) != 0 || 645 (r = sshpkt_get_u32(ssh, &rmaxpack)) != 0) 646 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 647 debug_f("ctype %s rchan %u win %u max %u", 648 ctype, rchan, rwindow, rmaxpack); 649 650 if (strcmp(ctype, "session") == 0) { 651 c = server_request_session(ssh); 652 } else if (strcmp(ctype, "direct-tcpip") == 0) { 653 c = server_request_direct_tcpip(ssh, &reason, &errmsg); 654 } else if (strcmp(ctype, "direct-streamlocal (at) openssh.com") == 0) { 655 c = server_request_direct_streamlocal(ssh); 656 } else if (strcmp(ctype, "tun (at) openssh.com") == 0) { 657 c = server_request_tun(ssh); 658 } 659 if (c != NULL) { 660 debug_f("confirm %s", ctype); 661 c->remote_id = rchan; 662 c->have_remote_id = 1; 663 c->remote_window = rwindow; 664 c->remote_maxpacket = rmaxpack; 665 if (c->type != SSH_CHANNEL_CONNECTING) { 666 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION)) != 0 || 667 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 668 (r = sshpkt_put_u32(ssh, c->self)) != 0 || 669 (r = sshpkt_put_u32(ssh, c->local_window)) != 0 || 670 (r = sshpkt_put_u32(ssh, c->local_maxpacket)) != 0 || 671 (r = sshpkt_send(ssh)) != 0) { 672 sshpkt_fatal(ssh, r, 673 "%s: send open confirm", __func__); 674 } 675 } 676 } else { 677 debug_f("failure %s", ctype); 678 if ((r = sshpkt_start(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE)) != 0 || 679 (r = sshpkt_put_u32(ssh, rchan)) != 0 || 680 (r = sshpkt_put_u32(ssh, reason)) != 0 || 681 (r = sshpkt_put_cstring(ssh, errmsg ? errmsg : "open failed")) != 0 || 682 (r = sshpkt_put_cstring(ssh, "")) != 0 || 683 (r = sshpkt_send(ssh)) != 0) { 684 sshpkt_fatal(ssh, r, 685 "%s: send open failure", __func__); 686 } 687 } 688 free(ctype); 689 return 0; 690 } 691 692 static int 693 server_input_hostkeys_prove(struct ssh *ssh, struct sshbuf **respp) 694 { 695 struct sshbuf *resp = NULL; 696 struct sshbuf *sigbuf = NULL; 697 struct sshkey *key = NULL, *key_pub = NULL, *key_prv = NULL; 698 int r, ndx, success = 0; 699 const u_char *blob; 700 const char *sigalg, *kex_rsa_sigalg = NULL; 701 u_char *sig = NULL; 702 size_t blen, slen; 703 704 if ((resp = sshbuf_new()) == NULL || (sigbuf = sshbuf_new()) == NULL) 705 fatal_f("sshbuf_new"); 706 if (sshkey_type_plain(sshkey_type_from_name( 707 ssh->kex->hostkey_alg)) == KEY_RSA) 708 kex_rsa_sigalg = ssh->kex->hostkey_alg; 709 while (ssh_packet_remaining(ssh) > 0) { 710 sshkey_free(key); 711 key = NULL; 712 if ((r = sshpkt_get_string_direct(ssh, &blob, &blen)) != 0 || 713 (r = sshkey_from_blob(blob, blen, &key)) != 0) { 714 error_fr(r, "parse key"); 715 goto out; 716 } 717 /* 718 * Better check that this is actually one of our hostkeys 719 * before attempting to sign anything with it. 720 */ 721 if ((ndx = ssh->kex->host_key_index(key, 1, ssh)) == -1) { 722 error_f("unknown host %s key", sshkey_type(key)); 723 goto out; 724 } 725 /* 726 * XXX refactor: make kex->sign just use an index rather 727 * than passing in public and private keys 728 */ 729 if ((key_prv = get_hostkey_by_index(ndx)) == NULL && 730 (key_pub = get_hostkey_public_by_index(ndx, ssh)) == NULL) { 731 error_f("can't retrieve hostkey %d", ndx); 732 goto out; 733 } 734 sshbuf_reset(sigbuf); 735 free(sig); 736 sig = NULL; 737 /* 738 * For RSA keys, prefer to use the signature type negotiated 739 * during KEX to the default (SHA1). 740 */ 741 sigalg = sshkey_ssh_name(key); 742 if (sshkey_type_plain(key->type) == KEY_RSA) { 743 if (kex_rsa_sigalg != NULL) 744 sigalg = kex_rsa_sigalg; 745 else if (ssh->kex->flags & KEX_RSA_SHA2_512_SUPPORTED) 746 sigalg = "rsa-sha2-512"; 747 else if (ssh->kex->flags & KEX_RSA_SHA2_256_SUPPORTED) 748 sigalg = "rsa-sha2-256"; 749 } 750 751 debug3_f("sign %s key (index %d) using sigalg %s", 752 sshkey_type(key), ndx, sigalg == NULL ? "default" : sigalg); 753 if ((r = sshbuf_put_cstring(sigbuf, 754 "hostkeys-prove-00 (at) openssh.com")) != 0 || 755 (r = sshbuf_put_stringb(sigbuf, 756 ssh->kex->session_id)) != 0 || 757 (r = sshkey_puts(key, sigbuf)) != 0 || 758 (r = ssh->kex->sign(ssh, key_prv, key_pub, &sig, &slen, 759 sshbuf_ptr(sigbuf), sshbuf_len(sigbuf), sigalg)) != 0 || 760 (r = sshbuf_put_string(resp, sig, slen)) != 0) { 761 error_fr(r, "assemble signature"); 762 goto out; 763 } 764 } 765 /* Success */ 766 *respp = resp; 767 resp = NULL; /* don't free it */ 768 success = 1; 769 out: 770 free(sig); 771 sshbuf_free(resp); 772 sshbuf_free(sigbuf); 773 sshkey_free(key); 774 return success; 775 } 776 777 static int 778 server_input_global_request(int type, uint32_t seq, struct ssh *ssh) 779 { 780 char *rtype = NULL; 781 u_char want_reply = 0; 782 int r, success = 0, allocated_listen_port = 0; 783 u_int port = 0; 784 struct sshbuf *resp = NULL; 785 struct passwd *pw = the_authctxt->pw; 786 struct Forward fwd; 787 788 memset(&fwd, 0, sizeof(fwd)); 789 if (pw == NULL || !the_authctxt->valid) 790 fatal_f("no/invalid user"); 791 792 if ((r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 793 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 794 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 795 debug_f("rtype %s want_reply %d", rtype, want_reply); 796 797 /* -R style forwarding */ 798 if (strcmp(rtype, "tcpip-forward") == 0) { 799 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || 800 (r = sshpkt_get_u32(ssh, &port)) != 0) 801 sshpkt_fatal(ssh, r, "%s: parse tcpip-forward", __func__); 802 debug_f("tcpip-forward listen %s port %u", 803 fwd.listen_host, port); 804 if (port <= INT_MAX) 805 fwd.listen_port = (int)port; 806 /* check permissions */ 807 if (port > INT_MAX || 808 (options.allow_tcp_forwarding & FORWARD_REMOTE) == 0 || 809 !auth_opts->permit_port_forwarding_flag || 810 options.disable_forwarding || 811 (!want_reply && fwd.listen_port == 0)) { 812 success = 0; 813 ssh_packet_send_debug(ssh, "Server has disabled port forwarding."); 814 } else { 815 /* Start listening on the port */ 816 success = channel_setup_remote_fwd_listener(ssh, &fwd, 817 &allocated_listen_port, &options.fwd_opts); 818 } 819 if ((resp = sshbuf_new()) == NULL) 820 fatal_f("sshbuf_new"); 821 if (allocated_listen_port != 0 && 822 (r = sshbuf_put_u32(resp, allocated_listen_port)) != 0) 823 fatal_fr(r, "sshbuf_put_u32"); 824 } else if (strcmp(rtype, "cancel-tcpip-forward") == 0) { 825 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_host, NULL)) != 0 || 826 (r = sshpkt_get_u32(ssh, &port)) != 0) 827 sshpkt_fatal(ssh, r, "%s: parse cancel-tcpip-forward", __func__); 828 829 debug_f("cancel-tcpip-forward addr %s port %d", 830 fwd.listen_host, port); 831 if (port <= INT_MAX) { 832 fwd.listen_port = (int)port; 833 success = channel_cancel_rport_listener(ssh, &fwd); 834 } 835 } else if (strcmp(rtype, "streamlocal-forward (at) openssh.com") == 0) { 836 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) 837 sshpkt_fatal(ssh, r, "%s: parse streamlocal-forward (at) openssh.com", __func__); 838 debug_f("streamlocal-forward listen path %s", 839 fwd.listen_path); 840 841 /* check permissions */ 842 if ((options.allow_streamlocal_forwarding & FORWARD_REMOTE) == 0 843 || !auth_opts->permit_port_forwarding_flag || 844 options.disable_forwarding) { 845 success = 0; 846 ssh_packet_send_debug(ssh, "Server has disabled " 847 "streamlocal forwarding."); 848 } else { 849 /* Start listening on the socket */ 850 success = channel_setup_remote_fwd_listener(ssh, 851 &fwd, NULL, &options.fwd_opts); 852 } 853 } else if (strcmp(rtype, "cancel-streamlocal-forward (at) openssh.com") == 0) { 854 if ((r = sshpkt_get_cstring(ssh, &fwd.listen_path, NULL)) != 0) 855 sshpkt_fatal(ssh, r, "%s: parse cancel-streamlocal-forward (at) openssh.com", __func__); 856 debug_f("cancel-streamlocal-forward path %s", 857 fwd.listen_path); 858 859 success = channel_cancel_rport_listener(ssh, &fwd); 860 } else if (strcmp(rtype, "no-more-sessions (at) openssh.com") == 0) { 861 no_more_sessions = 1; 862 success = 1; 863 } else if (strcmp(rtype, "hostkeys-prove-00 (at) openssh.com") == 0) { 864 success = server_input_hostkeys_prove(ssh, &resp); 865 } 866 /* XXX sshpkt_get_end() */ 867 if (want_reply) { 868 if ((r = sshpkt_start(ssh, success ? 869 SSH2_MSG_REQUEST_SUCCESS : SSH2_MSG_REQUEST_FAILURE)) != 0 || 870 (success && resp != NULL && (r = sshpkt_putb(ssh, resp)) != 0) || 871 (r = sshpkt_send(ssh)) != 0 || 872 (r = ssh_packet_write_wait(ssh)) < 0) 873 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 874 } 875 free(fwd.listen_host); 876 free(fwd.listen_path); 877 free(rtype); 878 sshbuf_free(resp); 879 return 0; 880 } 881 882 static int 883 server_input_channel_req(int type, uint32_t seq, struct ssh *ssh) 884 { 885 Channel *c; 886 int r, success = 0; 887 char *rtype = NULL; 888 u_char want_reply = 0; 889 u_int id = 0; 890 891 if ((r = sshpkt_get_u32(ssh, &id)) != 0 || 892 (r = sshpkt_get_cstring(ssh, &rtype, NULL)) != 0 || 893 (r = sshpkt_get_u8(ssh, &want_reply)) != 0) 894 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 895 896 debug("server_input_channel_req: channel %u request %s reply %d", 897 id, rtype, want_reply); 898 899 if (id >= INT_MAX || (c = channel_lookup(ssh, (int)id)) == NULL) { 900 ssh_packet_disconnect(ssh, "%s: unknown channel %d", 901 __func__, id); 902 } 903 if (!strcmp(rtype, "eow (at) openssh.com")) { 904 if ((r = sshpkt_get_end(ssh)) != 0) 905 sshpkt_fatal(ssh, r, "%s: parse packet", __func__); 906 chan_rcvd_eow(ssh, c); 907 } else if ((c->type == SSH_CHANNEL_LARVAL || 908 c->type == SSH_CHANNEL_OPEN) && strcmp(c->ctype, "session") == 0) 909 success = session_input_channel_req(ssh, c, rtype); 910 if (want_reply && !(c->flags & CHAN_CLOSE_SENT)) { 911 if (!c->have_remote_id) 912 fatal_f("channel %d: no remote_id", c->self); 913 if ((r = sshpkt_start(ssh, success ? 914 SSH2_MSG_CHANNEL_SUCCESS : SSH2_MSG_CHANNEL_FAILURE)) != 0 || 915 (r = sshpkt_put_u32(ssh, c->remote_id)) != 0 || 916 (r = sshpkt_send(ssh)) != 0) 917 sshpkt_fatal(ssh, r, "%s: send reply", __func__); 918 } 919 free(rtype); 920 return 0; 921 } 922 923 static void 924 server_init_dispatch(struct ssh *ssh) 925 { 926 debug("server_init_dispatch"); 927 ssh_dispatch_init(ssh, &dispatch_protocol_error); 928 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_CLOSE, &channel_input_oclose); 929 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_DATA, &channel_input_data); 930 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EOF, &channel_input_ieof); 931 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_EXTENDED_DATA, &channel_input_extended_data); 932 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN, &server_input_channel_open); 933 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_CONFIRMATION, &channel_input_open_confirmation); 934 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_OPEN_FAILURE, &channel_input_open_failure); 935 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_REQUEST, &server_input_channel_req); 936 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_WINDOW_ADJUST, &channel_input_window_adjust); 937 ssh_dispatch_set(ssh, SSH2_MSG_GLOBAL_REQUEST, &server_input_global_request); 938 /* client_alive */ 939 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_SUCCESS, &server_input_keep_alive); 940 ssh_dispatch_set(ssh, SSH2_MSG_CHANNEL_FAILURE, &server_input_keep_alive); 941 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_SUCCESS, &server_input_keep_alive); 942 ssh_dispatch_set(ssh, SSH2_MSG_REQUEST_FAILURE, &server_input_keep_alive); 943 /* rekeying */ 944 ssh_dispatch_set(ssh, SSH2_MSG_KEXINIT, &kex_input_kexinit); 945 } 946
Indexes created Wed Jul 29 00:25:28 UTC 2026