1 /*
2 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
3 * All rights reserved
4 *
5 * As far as I am concerned, the code I have written for this software
6 * can be used freely for any purpose. Any derived versions of this
7 * software must be clearly marked as such, and if the derived work is
8 * incompatible with the protocol description in the RFC file, it must be
9 * called by a name other than "ssh" or "Secure Shell".
10 *
11 * SSH2 support by Markus Friedl.
12 * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved.
13 *
14 * Redistribution and use in source and binary forms, with or without
15 * modification, are permitted provided that the following conditions
16 * are met:
17 * 1. Redistributions of source code must retain the above copyright
18 * notice, this list of conditions and the following disclaimer.
19 * 2. Redistributions in binary form must reproduce the above copyright
20 * notice, this list of conditions and the following disclaimer in the
21 * documentation and/or other materials provided with the distribution.
22 *
23 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
24 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
25 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
26 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
27 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
28 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
29 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
30 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
31 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
32 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
33 */
34 /*
35 * Copyright 2010 Sun Microsystems, Inc. All rights reserved.
36 * Use is subject to license terms.
37 */
38
39 #include "includes.h"
40 RCSID("$OpenBSD: session.c,v 1.150 2002/09/16 19:55:33 stevesk Exp $");
41
42 #ifdef HAVE_DEFOPEN
43 #include <deflt.h>
44 #include <ulimit.h>
45 #endif /* HAVE_DEFOPEN */
46
47 #ifdef HAVE_LIBGEN_H
48 #include <libgen.h>
49 #endif
50
51 #include <priv.h>
52
53 #include "ssh.h"
54 #include "ssh1.h"
55 #include "ssh2.h"
56 #include "xmalloc.h"
57 #include "sshpty.h"
58 #include "packet.h"
59 #include "buffer.h"
60 #include "mpaux.h"
61 #include "uidswap.h"
62 #include "compat.h"
63 #include "channels.h"
64 #include "bufaux.h"
65 #include "auth.h"
66 #include "auth-options.h"
67 #include "pathnames.h"
68 #include "log.h"
69 #include "servconf.h"
70 #include "sshlogin.h"
71 #include "serverloop.h"
72 #include "canohost.h"
73 #include "session.h"
74 #include "tildexpand.h"
75 #include "misc.h"
76 #include "sftp.h"
77
78 #ifdef USE_PAM
79 #include <security/pam_appl.h>
80 #endif /* USE_PAM */
81
82 #ifdef GSSAPI
83 #include "ssh-gss.h"
84 #endif
85
86 #ifdef ALTPRIVSEP
87 #include "altprivsep.h"
88 #endif /* ALTPRIVSEP */
89
90 #ifdef HAVE_CYGWIN
91 #include <windows.h>
92 #include <sys/cygwin.h>
93 #define is_winnt (GetVersion() < 0x80000000)
94 #endif
95
96 /* func */
97
98 Session *session_new(void);
99 void session_set_fds(Session *, int, int, int);
100 void session_pty_cleanup(void *);
101 void session_xauthfile_cleanup(void *s);
102 void session_proctitle(Session *);
103 int session_setup_x11fwd(Session *);
104 void do_exec_pty(Session *, const char *);
105 void do_exec_no_pty(Session *, const char *);
106 void do_exec(Session *, const char *);
107 void do_login(Session *, const char *);
108 void do_child(Session *, const char *);
109 void do_motd(void);
110 int check_quietlogin(Session *, const char *);
111
112 static void do_authenticated1(Authctxt *);
113 static void do_authenticated2(Authctxt *);
114
115 static int session_pty_req(Session *);
116 static int session_env_req(Session *s);
117 static void session_free_env(char ***envp);
118 static void safely_chroot(const char *path, uid_t uid);
119 static void drop_privs(uid_t uid);
120
121 #ifdef USE_PAM
122 static void session_do_pam(Session *, int);
123 #endif /* USE_PAM */
124
125 /* import */
126 extern ServerOptions options;
127 extern char *__progname;
128 extern int log_stderr;
129 extern int debug_flag;
130 extern u_int utmp_len;
131 extern void destroy_sensitive_data(void);
132
133 #ifdef GSSAPI
134 extern Gssctxt *xxx_gssctxt;
135 #endif /* GSSAPI */
136
137 /* original command from peer. */
138 const char *original_command = NULL;
139
140 /* data */
141 #define MAX_SESSIONS 10
142 Session sessions[MAX_SESSIONS];
143
144 #define SUBSYSTEM_NONE 0
145 #define SUBSYSTEM_EXT 1
146 #define SUBSYSTEM_INT_SFTP 2
147
148 #ifdef HAVE_LOGIN_CAP
149 login_cap_t *lc;
150 #endif
151
152 /* Name and directory of socket for authentication agent forwarding. */
153 static char *auth_sock_name = NULL;
154 static char *auth_sock_dir = NULL;
155
156 /* removes the agent forwarding socket */
157
158 static void
auth_sock_cleanup_proc(void * _pw)159 auth_sock_cleanup_proc(void *_pw)
160 {
161 struct passwd *pw = _pw;
162
163 if (auth_sock_name != NULL) {
164 temporarily_use_uid(pw);
165 unlink(auth_sock_name);
166 rmdir(auth_sock_dir);
167 auth_sock_name = NULL;
168 restore_uid();
169 }
170 }
171
172 static int
auth_input_request_forwarding(struct passwd * pw)173 auth_input_request_forwarding(struct passwd * pw)
174 {
175 Channel *nc;
176 int sock;
177 struct sockaddr_un sunaddr;
178
179 if (auth_sock_name != NULL) {
180 error("authentication forwarding requested twice.");
181 return 0;
182 }
183
184 /* Temporarily drop privileged uid for mkdir/bind. */
185 temporarily_use_uid(pw);
186
187 /* Allocate a buffer for the socket name, and format the name. */
188 auth_sock_name = xmalloc(MAXPATHLEN);
189 auth_sock_dir = xmalloc(MAXPATHLEN);
190 strlcpy(auth_sock_dir, "/tmp/ssh-XXXXXXXX", MAXPATHLEN);
191
192 /* Create private directory for socket */
193 if (mkdtemp(auth_sock_dir) == NULL) {
194 packet_send_debug("Agent forwarding disabled: "
195 "mkdtemp() failed: %.100s", strerror(errno));
196 restore_uid();
197 xfree(auth_sock_name);
198 xfree(auth_sock_dir);
199 auth_sock_name = NULL;
200 auth_sock_dir = NULL;
201 return 0;
202 }
203 snprintf(auth_sock_name, MAXPATHLEN, "%s/agent.%ld",
204 auth_sock_dir, (long) getpid());
205
206 /* delete agent socket on fatal() */
207 fatal_add_cleanup(auth_sock_cleanup_proc, pw);
208
209 /* Create the socket. */
210 sock = socket(AF_UNIX, SOCK_STREAM, 0);
211 if (sock < 0)
212 packet_disconnect("socket: %.100s", strerror(errno));
213
214 /* Bind it to the name. */
215 memset(&sunaddr, 0, sizeof(sunaddr));
216 sunaddr.sun_family = AF_UNIX;
217 strlcpy(sunaddr.sun_path, auth_sock_name, sizeof(sunaddr.sun_path));
218
219 if (bind(sock, (struct sockaddr *) & sunaddr, sizeof(sunaddr)) < 0)
220 packet_disconnect("bind: %.100s", strerror(errno));
221
222 /* Restore the privileged uid. */
223 restore_uid();
224
225 /* Start listening on the socket. */
226 if (listen(sock, 5) < 0)
227 packet_disconnect("listen: %.100s", strerror(errno));
228
229 /* Allocate a channel for the authentication agent socket. */
230 nc = channel_new("auth socket",
231 SSH_CHANNEL_AUTH_SOCKET, sock, sock, -1,
232 CHAN_X11_WINDOW_DEFAULT, CHAN_X11_PACKET_DEFAULT,
233 0, xstrdup("auth socket"), 1);
234 strlcpy(nc->path, auth_sock_name, sizeof(nc->path));
235 return 1;
236 }
237
238
239 void
do_authenticated(Authctxt * authctxt)240 do_authenticated(Authctxt *authctxt)
241 {
242 /* setup the channel layer */
243 if (!no_port_forwarding_flag && options.allow_tcp_forwarding)
244 channel_permit_all_opens();
245
246 if (compat20)
247 do_authenticated2(authctxt);
248 else
249 do_authenticated1(authctxt);
250
251 /* remove agent socket */
252 if (auth_sock_name != NULL)
253 auth_sock_cleanup_proc(authctxt->pw);
254 #ifdef KRB4
255 if (options.kerberos_ticket_cleanup)
256 krb4_cleanup_proc(authctxt);
257 #endif
258 #ifdef KRB5
259 if (options.kerberos_ticket_cleanup)
260 krb5_cleanup_proc(authctxt);
261 #endif
262 }
263
264 /*
265 * Prepares for an interactive session. This is called after the user has
266 * been successfully authenticated. During this message exchange, pseudo
267 * terminals are allocated, X11, TCP/IP, and authentication agent forwardings
268 * are requested, etc.
269 */
270 static void
do_authenticated1(Authctxt * authctxt)271 do_authenticated1(Authctxt *authctxt)
272 {
273 Session *s;
274 char *command;
275 int success, type, screen_flag;
276 int enable_compression_after_reply = 0;
277 u_int proto_len, data_len, dlen, compression_level = 0;
278
279 s = session_new();
280 s->authctxt = authctxt;
281 s->pw = authctxt->pw;
282
283 /*
284 * We stay in this loop until the client requests to execute a shell
285 * or a command.
286 */
287 for (;;) {
288 success = 0;
289
290 /* Get a packet from the client. */
291 type = packet_read();
292
293 /* Process the packet. */
294 switch (type) {
295 case SSH_CMSG_REQUEST_COMPRESSION:
296 compression_level = packet_get_int();
297 packet_check_eom();
298 if (compression_level < 1 || compression_level > 9) {
299 packet_send_debug("Received illegal compression level %d.",
300 compression_level);
301 break;
302 }
303 if (!options.compression) {
304 debug2("compression disabled");
305 break;
306 }
307 /* Enable compression after we have responded with SUCCESS. */
308 enable_compression_after_reply = 1;
309 success = 1;
310 break;
311
312 case SSH_CMSG_REQUEST_PTY:
313 success = session_pty_req(s);
314 break;
315
316 case SSH_CMSG_X11_REQUEST_FORWARDING:
317 s->auth_proto = packet_get_string(&proto_len);
318 s->auth_data = packet_get_string(&data_len);
319
320 screen_flag = packet_get_protocol_flags() &
321 SSH_PROTOFLAG_SCREEN_NUMBER;
322 debug2("SSH_PROTOFLAG_SCREEN_NUMBER: %d", screen_flag);
323
324 if (packet_remaining() == 4) {
325 if (!screen_flag)
326 debug2("Buggy client: "
327 "X11 screen flag missing");
328 s->screen = packet_get_int();
329 } else {
330 s->screen = 0;
331 }
332 packet_check_eom();
333 success = session_setup_x11fwd(s);
334 if (!success) {
335 xfree(s->auth_proto);
336 xfree(s->auth_data);
337 s->auth_proto = NULL;
338 s->auth_data = NULL;
339 }
340 break;
341
342 case SSH_CMSG_AGENT_REQUEST_FORWARDING:
343 if (no_agent_forwarding_flag || compat13) {
344 debug("Authentication agent forwarding not permitted for this authentication.");
345 break;
346 }
347 debug("Received authentication agent forwarding request.");
348 success = auth_input_request_forwarding(s->pw);
349 break;
350
351 case SSH_CMSG_PORT_FORWARD_REQUEST:
352 if (no_port_forwarding_flag) {
353 debug("Port forwarding not permitted for this authentication.");
354 break;
355 }
356 if (!options.allow_tcp_forwarding) {
357 debug("Port forwarding not permitted.");
358 break;
359 }
360 debug("Received TCP/IP port forwarding request.");
361 channel_input_port_forward_request(s->pw->pw_uid == 0, options.gateway_ports);
362 success = 1;
363 break;
364
365 case SSH_CMSG_MAX_PACKET_SIZE:
366 if (packet_set_maxsize(packet_get_int()) > 0)
367 success = 1;
368 break;
369
370 #if defined(AFS) || defined(KRB5)
371 case SSH_CMSG_HAVE_KERBEROS_TGT:
372 if (!options.kerberos_tgt_passing) {
373 verbose("Kerberos TGT passing disabled.");
374 } else {
375 char *kdata = packet_get_string(&dlen);
376 packet_check_eom();
377
378 /* XXX - 0x41, see creds_to_radix version */
379 if (kdata[0] != 0x41) {
380 #ifdef KRB5
381 krb5_data tgt;
382 tgt.data = kdata;
383 tgt.length = dlen;
384
385 if (auth_krb5_tgt(s->authctxt, &tgt))
386 success = 1;
387 else
388 verbose("Kerberos v5 TGT refused for %.100s", s->authctxt->user);
389 #endif /* KRB5 */
390 } else {
391 #ifdef AFS
392 if (auth_krb4_tgt(s->authctxt, kdata))
393 success = 1;
394 else
395 verbose("Kerberos v4 TGT refused for %.100s", s->authctxt->user);
396 #endif /* AFS */
397 }
398 xfree(kdata);
399 }
400 break;
401 #endif /* AFS || KRB5 */
402
403 #ifdef AFS
404 case SSH_CMSG_HAVE_AFS_TOKEN:
405 if (!options.afs_token_passing || !k_hasafs()) {
406 verbose("AFS token passing disabled.");
407 } else {
408 /* Accept AFS token. */
409 char *token = packet_get_string(&dlen);
410 packet_check_eom();
411
412 if (auth_afs_token(s->authctxt, token))
413 success = 1;
414 else
415 verbose("AFS token refused for %.100s",
416 s->authctxt->user);
417 xfree(token);
418 }
419 break;
420 #endif /* AFS */
421
422 case SSH_CMSG_EXEC_SHELL:
423 case SSH_CMSG_EXEC_CMD:
424 if (type == SSH_CMSG_EXEC_CMD) {
425 command = packet_get_string(&dlen);
426 debug("Exec command '%.500s'", command);
427 do_exec(s, command);
428 xfree(command);
429 } else {
430 do_exec(s, NULL);
431 }
432 packet_check_eom();
433 session_close(s);
434 return;
435
436 default:
437 /*
438 * Any unknown messages in this phase are ignored,
439 * and a failure message is returned.
440 */
441 log("Unknown packet type received after authentication: %d", type);
442 }
443 packet_start(success ? SSH_SMSG_SUCCESS : SSH_SMSG_FAILURE);
444 packet_send();
445 packet_write_wait();
446
447 /* Enable compression now that we have replied if appropriate. */
448 if (enable_compression_after_reply) {
449 enable_compression_after_reply = 0;
450 packet_start_compression(compression_level);
451 }
452 }
453 }
454
455 /*
456 * This is called to fork and execute a command when we have no tty. This
457 * will call do_child from the child, and server_loop from the parent after
458 * setting up file descriptors and such.
459 */
460 void
do_exec_no_pty(Session * s,const char * command)461 do_exec_no_pty(Session *s, const char *command)
462 {
463 pid_t pid;
464
465 int inout[2], err[2];
466 /* Uses socket pairs to communicate with the program. */
467 if (socketpair(AF_UNIX, SOCK_STREAM, 0, inout) < 0 ||
468 socketpair(AF_UNIX, SOCK_STREAM, 0, err) < 0)
469 packet_disconnect("Could not create socket pairs: %.100s",
470 strerror(errno));
471 if (s == NULL)
472 fatal("do_exec_no_pty: no session");
473
474 session_proctitle(s);
475
476 /* Fork the child. */
477 if ((pid = fork()) == 0) {
478 fatal_remove_all_cleanups();
479
480 /* Child. Reinitialize the log since the pid has changed. */
481 log_init(__progname, options.log_level, options.log_facility, log_stderr);
482
483 /*
484 * Create a new session and process group since the 4.4BSD
485 * setlogin() affects the entire process group.
486 */
487 if (setsid() < 0)
488 error("setsid failed: %.100s", strerror(errno));
489
490 /*
491 * Redirect stdin, stdout, and stderr. Stdin and stdout will
492 * use the same socket, as some programs (particularly rdist)
493 * seem to depend on it.
494 */
495 close(inout[1]);
496 close(err[1]);
497 if (dup2(inout[0], 0) < 0) /* stdin */
498 perror("dup2 stdin");
499 if (dup2(inout[0], 1) < 0) /* stdout. Note: same socket as stdin. */
500 perror("dup2 stdout");
501 if (s->is_subsystem) {
502 /*
503 * Redirect the subsystem's stderr to /dev/null. We might send it
504 * over to the other side but changing that might break existing
505 * SSH clients.
506 */
507 close(err[0]);
508 if ((err[0] = open(_PATH_DEVNULL, O_WRONLY)) == -1)
509 fatal("Cannot open /dev/null: %.100s", strerror(errno));
510 }
511 if (dup2(err[0], 2) < 0) /* stderr */
512 perror("dup2 stderr");
513
514 #ifdef _UNICOS
515 cray_init_job(s->pw); /* set up cray jid and tmpdir */
516 #endif
517
518 /* Do processing for the child (exec command etc). */
519 do_child(s, command);
520 /* NOTREACHED */
521 }
522 #ifdef _UNICOS
523 signal(WJSIGNAL, cray_job_termination_handler);
524 #endif /* _UNICOS */
525 #ifdef HAVE_CYGWIN
526 if (is_winnt)
527 cygwin_set_impersonation_token(INVALID_HANDLE_VALUE);
528 #endif
529 if (pid < 0)
530 packet_disconnect("fork failed: %.100s", strerror(errno));
531
532 s->pid = pid;
533 /* Set interactive/non-interactive mode. */
534 packet_set_interactive(s->display != NULL);
535
536 /* We are the parent. Close the child sides of the socket pairs. */
537 close(inout[0]);
538 close(err[0]);
539
540 /*
541 * Enter the interactive session. Note: server_loop must be able to
542 * handle the case that fdin and fdout are the same.
543 */
544 if (compat20) {
545 session_set_fds(s, inout[1], inout[1], s->is_subsystem ? -1 : err[1]);
546 if (s->is_subsystem)
547 close(err[1]);
548 /* Don't close channel before sending exit-status! */
549 channel_set_wait_for_exit(s->chanid, 1);
550 } else {
551 server_loop(pid, inout[1], inout[1], err[1]);
552 /* server_loop has closed inout[1] and err[1]. */
553 }
554 }
555
556 /*
557 * This is called to fork and execute a command when we have a tty. This
558 * will call do_child from the child, and server_loop from the parent after
559 * setting up file descriptors, controlling tty, updating wtmp, utmp,
560 * lastlog, and other such operations.
561 */
562 void
do_exec_pty(Session * s,const char * command)563 do_exec_pty(Session *s, const char *command)
564 {
565 int fdout, ptyfd, ttyfd, ptymaster, pipe_fds[2];
566 pid_t pid;
567
568 if (s == NULL)
569 fatal("do_exec_pty: no session");
570 ptyfd = s->ptyfd;
571 ttyfd = s->ttyfd;
572
573 #ifdef USE_PAM
574 session_do_pam(s, 1); /* pam_open_session() */
575 #endif /* USE_PAM */
576
577 /*
578 * This pipe lets sshd wait for child to exec or exit. This is
579 * particularly important for ALTPRIVSEP because the child is
580 * the one to call the monitor to request a record_login() and
581 * we don't want the child and the parent to compete for the
582 * monitor's attention. But this is generic code and doesn't
583 * hurt to have here even if ALTPRIVSEP is not used.
584 */
585 if (pipe(pipe_fds) != 0)
586 packet_disconnect("pipe failed: %.100s", strerror(errno));
587
588 (void) fcntl(pipe_fds[0], F_SETFD, FD_CLOEXEC);
589 (void) fcntl(pipe_fds[1], F_SETFD, FD_CLOEXEC);
590
591 /* Fork the child. */
592 if ((pid = fork()) == 0) {
593 (void) close(pipe_fds[0]);
594
595 fatal_remove_all_cleanups();
596
597 /* Child. Reinitialize the log because the pid has changed. */
598 log_init(__progname, options.log_level, options.log_facility, log_stderr);
599 /* Close the master side of the pseudo tty. */
600 close(ptyfd);
601
602 /* Make the pseudo tty our controlling tty. */
603 pty_make_controlling_tty(&ttyfd, s->tty);
604
605 /* Redirect stdin/stdout/stderr from the pseudo tty. */
606 if (dup2(ttyfd, 0) < 0)
607 error("dup2 stdin: %s", strerror(errno));
608 if (dup2(ttyfd, 1) < 0)
609 error("dup2 stdout: %s", strerror(errno));
610 if (dup2(ttyfd, 2) < 0)
611 error("dup2 stderr: %s", strerror(errno));
612
613 /* Close the extra descriptor for the pseudo tty. */
614 close(ttyfd);
615
616 /* record login, etc. similar to login(1) */
617 do_login(s, command);
618
619 /*
620 * Close the pipe to the parent so it can re-enter its event
621 * loop and service the ptm; if enough debug messages get
622 * written to the pty before this happens there will be a
623 * deadlock.
624 */
625 close(pipe_fds[1]);
626
627 /*
628 * do_motd() was called originally in do_login(). However,
629 * when the /etc/motd file is large, a deadlock would happen,
630 * because
631 * - The child is blocked at fputs() to pty, when pty buffer
632 * is full.
633 * - The parent can not consume the pty buffer, because it is
634 * still blocked at read(pipe_fds[0]).
635 *
636 * To resolve the deadlock issue, we defer do_motd() after
637 * close(pipe_fds[1]).
638 */
639 do_motd();
640
641 /* Do common processing for the child, such as execing the command. */
642 do_child(s, command);
643 /* NOTREACHED */
644 }
645
646 /* Wait for child to exec() or exit() */
647 (void) close(pipe_fds[1]);
648 (void) read(pipe_fds[0], &pipe_fds[1], sizeof(int));
649
650 #ifdef _UNICOS
651 signal(WJSIGNAL, cray_job_termination_handler);
652 #endif /* _UNICOS */
653 #ifdef HAVE_CYGWIN
654 if (is_winnt)
655 cygwin_set_impersonation_token(INVALID_HANDLE_VALUE);
656 #endif
657 if (pid < 0)
658 packet_disconnect("fork failed: %.100s", strerror(errno));
659 s->pid = pid;
660
661 /* Parent. Close the slave side of the pseudo tty. */
662 close(ttyfd);
663
664 /*
665 * Create another descriptor of the pty master side for use as the
666 * standard input. We could use the original descriptor, but this
667 * simplifies code in server_loop. The descriptor is bidirectional.
668 */
669 fdout = dup(ptyfd);
670 if (fdout < 0)
671 packet_disconnect("dup #1 failed: %.100s", strerror(errno));
672
673 /* we keep a reference to the pty master */
674 ptymaster = dup(ptyfd);
675 if (ptymaster < 0)
676 packet_disconnect("dup #2 failed: %.100s", strerror(errno));
677 s->ptymaster = ptymaster;
678
679 /* Enter interactive session. */
680 packet_set_interactive(1);
681 if (compat20) {
682 session_set_fds(s, ptyfd, fdout, -1);
683 /* Don't close channel before sending exit-status! */
684 channel_set_wait_for_exit(s->chanid, 1);
685 } else {
686 server_loop(pid, ptyfd, fdout, -1);
687 /* server_loop _has_ closed ptyfd and fdout. */
688 }
689 }
690
691 /*
692 * This is called to fork and execute a command. If another command is
693 * to be forced, execute that instead.
694 */
695 void
do_exec(Session * s,const char * command)696 do_exec(Session *s, const char *command)
697 {
698 if (command)
699 s->command = xstrdup(command);
700
701 if (forced_command) {
702 original_command = command;
703 command = forced_command;
704 debug("Forced command '%.900s'", command);
705 }
706
707 if (s->ttyfd != -1)
708 do_exec_pty(s, command);
709 else
710 do_exec_no_pty(s, command);
711
712 original_command = NULL;
713 }
714
715
716 /* administrative, login(1)-like work */
717 void
do_login(Session * s,const char * command)718 do_login(Session *s, const char *command)
719 {
720 char *time_string;
721 #ifndef ALTPRIVSEP
722 struct passwd * pw = s->pw;
723 #endif /* ALTPRIVSEP*/
724 pid_t pid = getpid();
725
726 /* Record that there was a login on that tty from the remote host. */
727 #ifdef ALTPRIVSEP
728 debug3("Recording SSHv2 channel login in utmpx/wtmpx");
729 altprivsep_record_login(pid, s->tty);
730 #endif /* ALTPRIVSEP*/
731
732 if (check_quietlogin(s, command))
733 return;
734
735 #ifdef USE_PAM
736 print_pam_messages();
737 #endif /* USE_PAM */
738 #ifdef WITH_AIXAUTHENTICATE
739 if (aixloginmsg && *aixloginmsg)
740 printf("%s\n", aixloginmsg);
741 #endif /* WITH_AIXAUTHENTICATE */
742
743 #ifndef NO_SSH_LASTLOG
744 if (options.print_lastlog && s->last_login_time != 0) {
745 time_string = ctime(&s->last_login_time);
746 if (strchr(time_string, '\n'))
747 *strchr(time_string, '\n') = 0;
748 if (strcmp(s->hostname, "") == 0)
749 printf("Last login: %s\r\n", time_string);
750 else
751 printf("Last login: %s from %s\r\n", time_string,
752 s->hostname);
753 }
754 #endif /* NO_SSH_LASTLOG */
755
756 }
757
758 /*
759 * Display the message of the day.
760 */
761 void
do_motd(void)762 do_motd(void)
763 {
764 FILE *f;
765 char buf[256];
766
767 if (options.print_motd) {
768 #ifdef HAVE_LOGIN_CAP
769 f = fopen(login_getcapstr(lc, "welcome", "/etc/motd",
770 "/etc/motd"), "r");
771 #else
772 f = fopen("/etc/motd", "r");
773 #endif
774 if (f) {
775 while (fgets(buf, sizeof(buf), f))
776 fputs(buf, stdout);
777 fclose(f);
778 }
779 }
780 }
781
782
783 /*
784 * Check for quiet login, either .hushlogin or command given.
785 */
786 int
check_quietlogin(Session * s,const char * command)787 check_quietlogin(Session *s, const char *command)
788 {
789 char buf[256];
790 struct passwd *pw = s->pw;
791 struct stat st;
792
793 /* Return 1 if .hushlogin exists or a command given. */
794 if (command != NULL)
795 return 1;
796 snprintf(buf, sizeof(buf), "%.200s/.hushlogin", pw->pw_dir);
797 #ifdef HAVE_LOGIN_CAP
798 if (login_getcapbool(lc, "hushlogin", 0) || stat(buf, &st) >= 0)
799 return 1;
800 #else
801 if (stat(buf, &st) >= 0)
802 return 1;
803 #endif
804 return 0;
805 }
806
807 /*
808 * Sets the value of the given variable in the environment. If the variable
809 * already exists, its value is overriden.
810 */
811 void
child_set_env(char *** envp,u_int * envsizep,const char * name,const char * value)812 child_set_env(char ***envp, u_int *envsizep, const char *name,
813 const char *value)
814 {
815 debug3("child_set_env(%s, %s)", name, value);
816 child_set_env_silent(envp, envsizep, name, value);
817 }
818
819
820 void
child_set_env_silent(char *** envp,u_int * envsizep,const char * name,const char * value)821 child_set_env_silent(char ***envp, u_int *envsizep, const char *name,
822 const char *value)
823 {
824 u_int i, namelen;
825 char **env;
826
827 /*
828 * Find the slot where the value should be stored. If the variable
829 * already exists, we reuse the slot; otherwise we append a new slot
830 * at the end of the array, expanding if necessary.
831 */
832 env = *envp;
833 namelen = strlen(name);
834 for (i = 0; env[i]; i++)
835 if (strncmp(env[i], name, namelen) == 0 && env[i][namelen] == '=')
836 break;
837 if (env[i]) {
838 /* Reuse the slot. */
839 xfree(env[i]);
840 } else {
841 /* New variable. Expand if necessary. */
842 if (i >= (*envsizep) - 1) {
843 if (*envsizep >= 1000)
844 fatal("child_set_env: too many env vars,"
845 " skipping: %.100s", name);
846 (*envsizep) += 50;
847 env = (*envp) = xrealloc(env, (*envsizep) * sizeof(char *));
848 }
849 /* Need to set the NULL pointer at end of array beyond the new slot. */
850 env[i + 1] = NULL;
851 }
852
853 /* Allocate space and format the variable in the appropriate slot. */
854 env[i] = xmalloc(strlen(name) + 1 + strlen(value) + 1);
855 snprintf(env[i], strlen(name) + 1 + strlen(value) + 1, "%s=%s", name, value);
856 }
857
858 /*
859 * Reads environment variables from the given file and adds/overrides them
860 * into the environment. If the file does not exist, this does nothing.
861 * Otherwise, it must consist of empty lines, comments (line starts with '#')
862 * and assignments of the form name=value. No other forms are allowed.
863 */
864 static void
read_environment_file(char *** env,u_int * envsize,const char * filename)865 read_environment_file(char ***env, u_int *envsize,
866 const char *filename)
867 {
868 FILE *f;
869 char buf[4096];
870 char *cp, *value;
871 u_int lineno = 0;
872
873 f = fopen(filename, "r");
874 if (!f)
875 return;
876
877 while (fgets(buf, sizeof(buf), f)) {
878 if (++lineno > 1000)
879 fatal("Too many lines in environment file %s", filename);
880 for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
881 ;
882 if (!*cp || *cp == '#' || *cp == '\n')
883 continue;
884 if (strchr(cp, '\n'))
885 *strchr(cp, '\n') = '\0';
886 value = strchr(cp, '=');
887 if (value == NULL) {
888 fprintf(stderr, gettext("Bad line %u in %.100s\n"),
889 lineno, filename);
890 continue;
891 }
892 /*
893 * Replace the equals sign by nul, and advance value to
894 * the value string.
895 */
896 *value = '\0';
897 value++;
898 child_set_env(env, envsize, cp, value);
899 }
900 fclose(f);
901 }
902
copy_environment(char ** source,char *** env,u_int * envsize)903 void copy_environment(char **source, char ***env, u_int *envsize)
904 {
905 char *var_name, *var_val;
906 int i;
907
908 if (source == NULL)
909 return;
910
911 for(i = 0; source[i] != NULL; i++) {
912 var_name = xstrdup(source[i]);
913 if ((var_val = strstr(var_name, "=")) == NULL) {
914 xfree(var_name);
915 continue;
916 }
917 *var_val++ = '\0';
918
919 debug3("Copy environment: %s=%s", var_name, var_val);
920 child_set_env(env, envsize, var_name, var_val);
921
922 xfree(var_name);
923 }
924 }
925
926 #ifdef HAVE_DEFOPEN
927 static
928 void
deflt_do_setup_env(Session * s,const char * shell,char *** env,u_int * envsize)929 deflt_do_setup_env(Session *s, const char *shell, char ***env, u_int *envsize)
930 {
931 int flags;
932 char *ptr;
933 mode_t Umask = 022;
934
935 if (defopen(_PATH_DEFAULT_LOGIN))
936 return;
937
938 /* Ignore case */
939 flags = defcntl(DC_GETFLAGS, 0);
940 TURNOFF(flags, DC_CASE);
941 (void) defcntl(DC_SETFLAGS, flags);
942
943 /* TZ & HZ */
944 if ((ptr = defread("TIMEZONE=")) != NULL)
945 child_set_env(env, envsize, "TZ", ptr);
946 if ((ptr = defread("HZ=")) != NULL)
947 child_set_env(env, envsize, "HZ", ptr);
948
949 /* PATH */
950 if (s->pw->pw_uid != 0 && (ptr = defread("PATH=")) != NULL)
951 child_set_env(env, envsize, "PATH", ptr);
952 if (s->pw->pw_uid == 0 && (ptr = defread("SUPATH=")) != NULL)
953 child_set_env(env, envsize, "PATH", ptr);
954
955 /* SHELL */
956 if ((ptr = defread("ALTSHELL=")) != NULL) {
957 if (strcasecmp("YES", ptr) == 0)
958 child_set_env(env, envsize, "SHELL", shell);
959 else
960 child_set_env(env, envsize, "SHELL", "");
961 }
962
963 /* UMASK */
964 if ((ptr = defread("UMASK=")) != NULL &&
965 sscanf(ptr, "%lo", &Umask) == 1 &&
966 Umask <= (mode_t)0777)
967 (void) umask(Umask);
968 else
969 (void) umask(022);
970
971 /* ULIMIT */
972 if ((ptr = defread("ULIMIT=")) != NULL && atol(ptr) > 0L &&
973 ulimit(UL_SETFSIZE, atol(ptr)) < 0L)
974 error("Could not set ULIMIT to %ld from %s\n", atol(ptr),
975 _PATH_DEFAULT_LOGIN);
976
977 (void) defopen(NULL);
978 }
979 #endif /* HAVE_DEFOPEN */
980
981 static char **
do_setup_env(Session * s,const char * shell)982 do_setup_env(Session *s, const char *shell)
983 {
984 char buf[256];
985 char path_maildir[] = _PATH_MAILDIR;
986 u_int i, envsize, pm_len;
987 char **env;
988 struct passwd *pw = s->pw;
989
990 /* Initialize the environment. */
991 envsize = 100;
992 env = xmalloc(envsize * sizeof(char *));
993 env[0] = NULL;
994
995 #ifdef HAVE_CYGWIN
996 /*
997 * The Windows environment contains some setting which are
998 * important for a running system. They must not be dropped.
999 */
1000 copy_environment(environ, &env, &envsize);
1001 #endif
1002
1003 #ifdef GSSAPI
1004 /* Allow any GSSAPI methods that we've used to alter
1005 * the childs environment as they see fit
1006 */
1007 ssh_gssapi_do_child(xxx_gssctxt, &env,&envsize);
1008 #endif
1009
1010 /* Set basic environment. */
1011 child_set_env(&env, &envsize, "USER", pw->pw_name);
1012 child_set_env(&env, &envsize, "LOGNAME", pw->pw_name);
1013 child_set_env(&env, &envsize, "HOME", pw->pw_dir);
1014 #ifdef HAVE_LOGIN_CAP
1015 if (setusercontext(lc, pw, pw->pw_uid, LOGIN_SETPATH) < 0)
1016 child_set_env(&env, &envsize, "PATH", _PATH_STDPATH);
1017 else
1018 child_set_env(&env, &envsize, "PATH", getenv("PATH"));
1019 #else /* HAVE_LOGIN_CAP */
1020 # ifndef HAVE_CYGWIN
1021 /*
1022 * There's no standard path on Windows. The path contains
1023 * important components pointing to the system directories,
1024 * needed for loading shared libraries. So the path better
1025 * remains intact here.
1026 */
1027 # ifdef SUPERUSER_PATH
1028 child_set_env(&env, &envsize, "PATH",
1029 s->pw->pw_uid == 0 ? SUPERUSER_PATH : _PATH_STDPATH);
1030 # else
1031 child_set_env(&env, &envsize, "PATH", _PATH_STDPATH);
1032 # endif /* SUPERUSER_PATH */
1033 # endif /* HAVE_CYGWIN */
1034 #endif /* HAVE_LOGIN_CAP */
1035
1036 pm_len = strlen(path_maildir);
1037 if (path_maildir[pm_len - 1] == '/' && pm_len > 1)
1038 path_maildir[pm_len - 1] = NULL;
1039 snprintf(buf, sizeof buf, "%.200s/%.50s",
1040 path_maildir, pw->pw_name);
1041 child_set_env(&env, &envsize, "MAIL", buf);
1042
1043 /* Normal systems set SHELL by default. */
1044 child_set_env(&env, &envsize, "SHELL", shell);
1045
1046 #ifdef HAVE_DEFOPEN
1047 deflt_do_setup_env(s, shell, &env, &envsize);
1048 #endif /* HAVE_DEFOPEN */
1049
1050 #define PASS_ENV(x) \
1051 if (getenv(x)) \
1052 child_set_env(&env, &envsize, x, getenv(x));
1053
1054 if (getenv("TZ"))
1055 child_set_env(&env, &envsize, "TZ", getenv("TZ"));
1056
1057 if (s->auth_file != NULL)
1058 child_set_env(&env, &envsize, "XAUTHORITY", s->auth_file);
1059
1060 PASS_ENV("LANG")
1061 PASS_ENV("LC_ALL")
1062 PASS_ENV("LC_CTYPE")
1063 PASS_ENV("LC_COLLATE")
1064 PASS_ENV("LC_TIME")
1065 PASS_ENV("LC_NUMERIC")
1066 PASS_ENV("LC_MONETARY")
1067 PASS_ENV("LC_MESSAGES")
1068
1069 #undef PASS_ENV
1070
1071 if (s->env != NULL)
1072 copy_environment(s->env, &env, &envsize);
1073
1074 /* Set custom environment options from RSA authentication. */
1075 while (custom_environment) {
1076 struct envstring *ce = custom_environment;
1077 char *str = ce->s;
1078
1079 for (i = 0; str[i] != '=' && str[i]; i++)
1080 ;
1081 if (str[i] == '=') {
1082 str[i] = 0;
1083 child_set_env(&env, &envsize, str, str + i + 1);
1084 }
1085 custom_environment = ce->next;
1086 xfree(ce->s);
1087 xfree(ce);
1088 }
1089
1090 /* SSH_CLIENT deprecated */
1091 snprintf(buf, sizeof buf, "%.50s %d %d",
1092 get_remote_ipaddr(), get_remote_port(), get_local_port());
1093 child_set_env(&env, &envsize, "SSH_CLIENT", buf);
1094
1095 snprintf(buf, sizeof buf, "%.50s %d %.50s %d",
1096 get_remote_ipaddr(), get_remote_port(),
1097 get_local_ipaddr(packet_get_connection_in()), get_local_port());
1098 child_set_env(&env, &envsize, "SSH_CONNECTION", buf);
1099
1100 if (s->ttyfd != -1)
1101 child_set_env(&env, &envsize, "SSH_TTY", s->tty);
1102 if (s->term)
1103 child_set_env(&env, &envsize, "TERM", s->term);
1104 if (s->display)
1105 child_set_env(&env, &envsize, "DISPLAY", s->display);
1106 if (original_command)
1107 child_set_env(&env, &envsize, "SSH_ORIGINAL_COMMAND",
1108 original_command);
1109
1110 #ifdef _UNICOS
1111 if (cray_tmpdir[0] != '\0')
1112 child_set_env(&env, &envsize, "TMPDIR", cray_tmpdir);
1113 #endif /* _UNICOS */
1114
1115 #ifdef _AIX
1116 {
1117 char *cp;
1118
1119 if ((cp = getenv("AUTHSTATE")) != NULL)
1120 child_set_env(&env, &envsize, "AUTHSTATE", cp);
1121 if ((cp = getenv("KRB5CCNAME")) != NULL)
1122 child_set_env(&env, &envsize, "KRB5CCNAME", cp);
1123 read_environment_file(&env, &envsize, "/etc/environment");
1124 }
1125 #endif
1126 #ifdef KRB4
1127 if (s->authctxt->krb4_ticket_file)
1128 child_set_env(&env, &envsize, "KRBTKFILE",
1129 s->authctxt->krb4_ticket_file);
1130 #endif
1131 #ifdef KRB5
1132 if (s->authctxt->krb5_ticket_file)
1133 child_set_env(&env, &envsize, "KRB5CCNAME",
1134 s->authctxt->krb5_ticket_file);
1135 #endif
1136 #ifdef USE_PAM
1137 /*
1138 * Pull in any environment variables that may have
1139 * been set by PAM.
1140 */
1141 {
1142 char **p;
1143
1144 p = fetch_pam_environment(s->authctxt);
1145 copy_environment(p, &env, &envsize);
1146 free_pam_environment(p);
1147 }
1148 #endif /* USE_PAM */
1149
1150 if (auth_sock_name != NULL)
1151 child_set_env(&env, &envsize, SSH_AUTHSOCKET_ENV_NAME,
1152 auth_sock_name);
1153
1154 /* read $HOME/.ssh/environment. */
1155 if (options.permit_user_env) {
1156 snprintf(buf, sizeof buf, "%.200s/.ssh/environment",
1157 strcmp(pw->pw_dir, "/") ? pw->pw_dir : "");
1158 read_environment_file(&env, &envsize, buf);
1159 }
1160 if (debug_flag) {
1161 /* dump the environment */
1162 fprintf(stderr, gettext("Environment:\n"));
1163 for (i = 0; env[i]; i++)
1164 fprintf(stderr, " %.200s\n", env[i]);
1165 }
1166 return env;
1167 }
1168
1169 /*
1170 * Run $HOME/.ssh/rc, /etc/ssh/sshrc, or xauth (whichever is found
1171 * first in this order).
1172 */
1173 static void
do_rc_files(Session * s,const char * shell)1174 do_rc_files(Session *s, const char *shell)
1175 {
1176 FILE *f = NULL;
1177 char cmd[1024];
1178 int do_xauth;
1179 struct stat st;
1180
1181 do_xauth =
1182 s->display != NULL && s->auth_proto != NULL && s->auth_data != NULL;
1183
1184 /* ignore _PATH_SSH_USER_RC for subsystems */
1185 if (!s->is_subsystem && (stat(_PATH_SSH_USER_RC, &st) >= 0)) {
1186 snprintf(cmd, sizeof cmd, "%s -c '%s %s'",
1187 shell, _PATH_BSHELL, _PATH_SSH_USER_RC);
1188 if (debug_flag)
1189 fprintf(stderr, "Running %s\n", cmd);
1190 f = popen(cmd, "w");
1191 if (f) {
1192 if (do_xauth)
1193 fprintf(f, "%s %s\n", s->auth_proto,
1194 s->auth_data);
1195 pclose(f);
1196 } else
1197 fprintf(stderr, "Could not run %s\n",
1198 _PATH_SSH_USER_RC);
1199 } else if (stat(_PATH_SSH_SYSTEM_RC, &st) >= 0) {
1200 if (debug_flag)
1201 fprintf(stderr, "Running %s %s\n", _PATH_BSHELL,
1202 _PATH_SSH_SYSTEM_RC);
1203 f = popen(_PATH_BSHELL " " _PATH_SSH_SYSTEM_RC, "w");
1204 if (f) {
1205 if (do_xauth)
1206 fprintf(f, "%s %s\n", s->auth_proto,
1207 s->auth_data);
1208 pclose(f);
1209 } else
1210 fprintf(stderr, "Could not run %s\n",
1211 _PATH_SSH_SYSTEM_RC);
1212 } else if (do_xauth && options.xauth_location != NULL) {
1213 /* Add authority data to .Xauthority if appropriate. */
1214 if (debug_flag) {
1215 fprintf(stderr,
1216 "Running %.500s add "
1217 "%.100s %.100s %.100s\n",
1218 options.xauth_location, s->auth_display,
1219 s->auth_proto, s->auth_data);
1220 }
1221 snprintf(cmd, sizeof cmd, "%s -q -",
1222 options.xauth_location);
1223 f = popen(cmd, "w");
1224 if (f) {
1225 fprintf(f, "add %s %s %s\n",
1226 s->auth_display, s->auth_proto,
1227 s->auth_data);
1228 pclose(f);
1229 } else {
1230 fprintf(stderr, "Could not run %s\n",
1231 cmd);
1232 }
1233 }
1234 }
1235
1236 /* Disallow logins if /etc/nologin exists. This does not apply to root. */
1237 static void
do_nologin(struct passwd * pw)1238 do_nologin(struct passwd *pw)
1239 {
1240 FILE *f = NULL;
1241 char buf[1024];
1242 struct stat sb;
1243
1244 if (pw->pw_uid == 0)
1245 return;
1246
1247 if (stat(_PATH_NOLOGIN, &sb) == -1)
1248 return;
1249
1250 /* /etc/nologin exists. Print its contents if we can and exit. */
1251 log("User %.100s not allowed because %s exists.", pw->pw_name,
1252 _PATH_NOLOGIN);
1253 if ((f = fopen(_PATH_NOLOGIN, "r")) != NULL) {
1254 while (fgets(buf, sizeof(buf), f))
1255 fputs(buf, stderr);
1256 fclose(f);
1257 }
1258 exit(254);
1259 }
1260
1261 /* Chroot into ChrootDirectory if the option is set. */
1262 void
chroot_if_needed(struct passwd * pw)1263 chroot_if_needed(struct passwd *pw)
1264 {
1265 char *chroot_path, *tmp;
1266
1267 if (chroot_requested(options.chroot_directory)) {
1268 tmp = tilde_expand_filename(options.chroot_directory,
1269 pw->pw_uid);
1270 chroot_path = percent_expand(tmp, "h", pw->pw_dir,
1271 "u", pw->pw_name, (char *)NULL);
1272 safely_chroot(chroot_path, pw->pw_uid);
1273 free(tmp);
1274 free(chroot_path);
1275 }
1276 }
1277
1278 /*
1279 * Chroot into a directory after checking it for safety: all path components
1280 * must be root-owned directories with strict permissions.
1281 */
1282 static void
safely_chroot(const char * path,uid_t uid)1283 safely_chroot(const char *path, uid_t uid)
1284 {
1285 const char *cp;
1286 char component[MAXPATHLEN];
1287 struct stat st;
1288
1289 if (*path != '/')
1290 fatal("chroot path does not begin at root");
1291 if (strlen(path) >= sizeof(component))
1292 fatal("chroot path too long");
1293
1294 /*
1295 * Descend the path, checking that each component is a
1296 * root-owned directory with strict permissions.
1297 */
1298 for (cp = path; cp != NULL;) {
1299 if ((cp = strchr(cp, '/')) == NULL)
1300 strlcpy(component, path, sizeof(component));
1301 else {
1302 cp++;
1303 memcpy(component, path, cp - path);
1304 component[cp - path] = '\0';
1305 }
1306
1307 debug3("%s: checking '%s'", __func__, component);
1308
1309 if (stat(component, &st) != 0)
1310 fatal("%s: stat(\"%s\"): %s", __func__,
1311 component, strerror(errno));
1312 if (st.st_uid != 0 || (st.st_mode & 022) != 0)
1313 fatal("bad ownership or modes for chroot "
1314 "directory %s\"%s\"",
1315 cp == NULL ? "" : "component ", component);
1316 if (!S_ISDIR(st.st_mode))
1317 fatal("chroot path %s\"%s\" is not a directory",
1318 cp == NULL ? "" : "component ", component);
1319 }
1320
1321 if (chdir(path) == -1)
1322 fatal("Unable to chdir to chroot path \"%s\": "
1323 "%s", path, strerror(errno));
1324 if (chroot(path) == -1)
1325 fatal("chroot(\"%s\"): %s", path, strerror(errno));
1326 if (chdir("/") == -1)
1327 fatal("%s: chdir(/) after chroot: %s",
1328 __func__, strerror(errno));
1329 verbose("Changed root directory to \"%s\"", path);
1330 }
1331
1332 static void
launch_login(struct passwd * pw,const char * hostname)1333 launch_login(struct passwd *pw, const char *hostname)
1334 {
1335 /* Launch login(1). */
1336
1337 execl(LOGIN_PROGRAM, "login", "-h", hostname,
1338 #ifdef xxxLOGIN_NEEDS_TERM
1339 (s->term ? s->term : "unknown"),
1340 #endif /* LOGIN_NEEDS_TERM */
1341 #ifdef LOGIN_NO_ENDOPT
1342 "-p", "-f", pw->pw_name, (char *)NULL);
1343 #else
1344 "-p", "-f", "--", pw->pw_name, (char *)NULL);
1345 #endif
1346
1347 /* Login couldn't be executed, die. */
1348
1349 perror("login");
1350 exit(1);
1351 }
1352
1353 /*
1354 * Performs common processing for the child, such as setting up the
1355 * environment, closing extra file descriptors, setting the user and group
1356 * ids, and executing the command or shell.
1357 */
1358 #define ARGV_MAX 10
1359 void
do_child(Session * s,const char * command)1360 do_child(Session *s, const char *command)
1361 {
1362 extern char **environ;
1363 char **env;
1364 char *argv[ARGV_MAX];
1365 const char *shell, *shell0;
1366 struct passwd *pw = s->pw;
1367
1368 /* remove hostkey from the child's memory */
1369 destroy_sensitive_data();
1370
1371 do_nologin(pw);
1372 chroot_if_needed(pw);
1373
1374 /*
1375 * Get the shell from the password data. An empty shell field is
1376 * legal, and means /bin/sh.
1377 */
1378 shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell;
1379 #ifdef HAVE_LOGIN_CAP
1380 shell = login_getcapstr(lc, "shell", (char *)shell, (char *)shell);
1381 #endif
1382
1383 env = do_setup_env(s, shell);
1384
1385 /*
1386 * Close the connection descriptors; note that this is the child, and
1387 * the server will still have the socket open, and it is important
1388 * that we do not shutdown it. Note that the descriptors cannot be
1389 * closed before building the environment, as we call
1390 * get_remote_ipaddr there.
1391 */
1392 if (packet_get_connection_in() == packet_get_connection_out())
1393 close(packet_get_connection_in());
1394 else {
1395 close(packet_get_connection_in());
1396 close(packet_get_connection_out());
1397 }
1398 /*
1399 * Close all descriptors related to channels. They will still remain
1400 * open in the parent.
1401 */
1402 /* XXX better use close-on-exec? -markus */
1403 channel_close_all();
1404
1405 /*
1406 * Close any extra file descriptors. Note that there may still be
1407 * descriptors left by system functions. They will be closed later.
1408 */
1409 endpwent();
1410
1411 /*
1412 * Must switch to the new environment variables so that .ssh/rc,
1413 * /etc/ssh/sshrc, and xauth are run in the proper environment.
1414 */
1415 environ = env;
1416
1417 /*
1418 * New environment has been installed. We need to update locale
1419 * so that error messages beyond this point have the proper
1420 * character encoding.
1421 */
1422 (void) setlocale(LC_ALL, "");
1423
1424 /*
1425 * Close any extra open file descriptors so that we don\'t have them
1426 * hanging around in clients. Note that we want to do this after
1427 * initgroups, because at least on Solaris 2.3 it leaves file
1428 * descriptors open.
1429 */
1430 closefrom(STDERR_FILENO + 1);
1431
1432 #ifdef AFS
1433 /* Try to get AFS tokens for the local cell. */
1434 if (k_hasafs()) {
1435 char cell[64];
1436
1437 if (k_afs_cell_of_file(pw->pw_dir, cell, sizeof(cell)) == 0)
1438 krb_afslog(cell, 0);
1439
1440 krb_afslog(0, 0);
1441 }
1442 #endif /* AFS */
1443
1444 /* Change current directory to the user's home directory. */
1445 if (chdir(pw->pw_dir) < 0) {
1446 /* Suppress missing homedir warning for chroot case */
1447 if (!chroot_requested(options.chroot_directory))
1448 fprintf(stderr, "Could not chdir to home "
1449 "directory %s: %s\n", pw->pw_dir,
1450 strerror(errno));
1451 }
1452
1453 do_rc_files(s, shell);
1454
1455 /* restore SIGPIPE for child */
1456 signal(SIGPIPE, SIG_DFL);
1457
1458 if (s->is_subsystem == SUBSYSTEM_INT_SFTP) {
1459 int i;
1460 char *p, *args;
1461 extern int optind, optreset;
1462
1463 /* This will set the E/P sets here, simulating exec(2). */
1464 drop_privs(pw->pw_uid);
1465
1466 setproctitle("%s@internal-sftp-server", s->pw->pw_name);
1467 args = xstrdup(command ? command : "sftp-server");
1468
1469 i = 0;
1470 for ((p = strtok(args, " ")); p != NULL; (p = strtok(NULL, " "))) {
1471 if (i < ARGV_MAX - 1)
1472 argv[i++] = p;
1473 }
1474
1475 argv[i] = NULL;
1476 optind = optreset = 1;
1477 __progname = argv[0];
1478 exit(sftp_server_main(i, argv, s->pw));
1479 }
1480
1481 /* Get the last component of the shell name. */
1482 if ((shell0 = strrchr(shell, '/')) != NULL)
1483 shell0++;
1484 else
1485 shell0 = shell;
1486
1487 /*
1488 * If we have no command, execute the shell. In this case, the shell
1489 * name to be passed in argv[0] is preceded by '-' to indicate that
1490 * this is a login shell.
1491 */
1492 if (!command) {
1493 char argv0[256];
1494
1495 /* Start the shell. Set initial character to '-'. */
1496 argv0[0] = '-';
1497
1498 if (strlcpy(argv0 + 1, shell0, sizeof(argv0) - 1)
1499 >= sizeof(argv0) - 1) {
1500 errno = EINVAL;
1501 perror(shell);
1502 exit(1);
1503 }
1504
1505 /* Execute the shell. */
1506 argv[0] = argv0;
1507 argv[1] = NULL;
1508 execve(shell, argv, env);
1509
1510 /* Executing the shell failed. */
1511 perror(shell);
1512 exit(1);
1513 }
1514 /*
1515 * Execute the command using the user's shell. This uses the -c
1516 * option to execute the command.
1517 */
1518 argv[0] = (char *) shell0;
1519 argv[1] = "-c";
1520 argv[2] = (char *) command;
1521 argv[3] = NULL;
1522 execve(shell, argv, env);
1523 perror(shell);
1524 exit(1);
1525 }
1526
1527 Session *
session_new(void)1528 session_new(void)
1529 {
1530 int i;
1531 static int did_init = 0;
1532 if (!did_init) {
1533 debug("session_new: init");
1534 for (i = 0; i < MAX_SESSIONS; i++) {
1535 sessions[i].used = 0;
1536 }
1537 did_init = 1;
1538 }
1539 for (i = 0; i < MAX_SESSIONS; i++) {
1540 Session *s = &sessions[i];
1541 if (! s->used) {
1542 memset(s, 0, sizeof(*s));
1543 s->chanid = -1;
1544 s->ptyfd = -1;
1545 s->ttyfd = -1;
1546 s->used = 1;
1547 s->self = i;
1548 s->env = NULL;
1549 debug("session_new: session %d", i);
1550 return s;
1551 }
1552 }
1553 return NULL;
1554 }
1555
1556 static void
session_dump(void)1557 session_dump(void)
1558 {
1559 int i;
1560 for (i = 0; i < MAX_SESSIONS; i++) {
1561 Session *s = &sessions[i];
1562 debug("dump: used %d session %d %p channel %d pid %ld",
1563 s->used,
1564 s->self,
1565 s,
1566 s->chanid,
1567 (long)s->pid);
1568 }
1569 }
1570
1571 int
session_open(Authctxt * authctxt,int chanid)1572 session_open(Authctxt *authctxt, int chanid)
1573 {
1574 Session *s = session_new();
1575 debug("session_open: channel %d", chanid);
1576 if (s == NULL) {
1577 error("no more sessions");
1578 return 0;
1579 }
1580 s->authctxt = authctxt;
1581 s->pw = authctxt->pw;
1582 if (s->pw == NULL)
1583 fatal("no user for session %d", s->self);
1584 debug("session_open: session %d: link with channel %d", s->self, chanid);
1585 s->chanid = chanid;
1586 return 1;
1587 }
1588
1589 #ifndef lint
1590 Session *
session_by_tty(char * tty)1591 session_by_tty(char *tty)
1592 {
1593 int i;
1594 for (i = 0; i < MAX_SESSIONS; i++) {
1595 Session *s = &sessions[i];
1596 if (s->used && s->ttyfd != -1 && strcmp(s->tty, tty) == 0) {
1597 debug("session_by_tty: session %d tty %s", i, tty);
1598 return s;
1599 }
1600 }
1601 debug("session_by_tty: unknown tty %.100s", tty);
1602 session_dump();
1603 return NULL;
1604 }
1605 #endif /* lint */
1606
1607 static Session *
session_by_channel(int id)1608 session_by_channel(int id)
1609 {
1610 int i;
1611 for (i = 0; i < MAX_SESSIONS; i++) {
1612 Session *s = &sessions[i];
1613 if (s->used && s->chanid == id) {
1614 debug("session_by_channel: session %d channel %d", i, id);
1615 return s;
1616 }
1617 }
1618 debug("session_by_channel: unknown channel %d", id);
1619 session_dump();
1620 return NULL;
1621 }
1622
1623 static Session *
session_by_pid(pid_t pid)1624 session_by_pid(pid_t pid)
1625 {
1626 int i;
1627 debug("session_by_pid: pid %ld", (long)pid);
1628 for (i = 0; i < MAX_SESSIONS; i++) {
1629 Session *s = &sessions[i];
1630 if (s->used && s->pid == pid)
1631 return s;
1632 }
1633 error("session_by_pid: unknown pid %ld", (long)pid);
1634 session_dump();
1635 return NULL;
1636 }
1637
1638 static int
session_window_change_req(Session * s)1639 session_window_change_req(Session *s)
1640 {
1641 s->col = packet_get_int();
1642 s->row = packet_get_int();
1643 s->xpixel = packet_get_int();
1644 s->ypixel = packet_get_int();
1645 packet_check_eom();
1646 pty_change_window_size(s->ptyfd, s->row, s->col, s->xpixel, s->ypixel);
1647 return 1;
1648 }
1649
1650 static int
session_pty_req(Session * s)1651 session_pty_req(Session *s)
1652 {
1653 u_int len;
1654 int n_bytes;
1655
1656 if (no_pty_flag) {
1657 debug("Allocating a pty not permitted for this authentication.");
1658 return 0;
1659 }
1660 if (s->ttyfd != -1) {
1661 packet_disconnect("Protocol error: you already have a pty.");
1662 return 0;
1663 }
1664 /* Get the time and hostname when the user last logged in. */
1665 if (options.print_lastlog) {
1666 s->hostname[0] = '\0';
1667 s->last_login_time = get_last_login_time(s->pw->pw_uid,
1668 s->pw->pw_name, s->hostname, sizeof(s->hostname));
1669
1670 /*
1671 * PAM may update the last login date.
1672 *
1673 * Ideally PAM would also show the last login date as a
1674 * PAM_TEXT_INFO conversation message, and then we could just
1675 * always force the use of keyboard-interactive just so we can
1676 * pass any such PAM prompts and messages from the account and
1677 * session stacks, but skip pam_authenticate() if other userauth
1678 * has succeeded and the user's password isn't expired.
1679 *
1680 * Unfortunately this depends on support for keyboard-
1681 * interactive in the client, and support for lastlog messages
1682 * in some PAM module.
1683 *
1684 * As it is Solaris updates the lastlog in PAM, but does
1685 * not show the lastlog date in PAM. If and when this state of
1686 * affairs changes this hack can be reconsidered, and, maybe,
1687 * removed.
1688 *
1689 * So we're stuck with a crude hack: get the lastlog
1690 * time before calling pam_open_session() and store it
1691 * in the Authctxt and then use it here once. After
1692 * that, if the client opens any more pty sessions we'll
1693 * show the last lastlog entry since userauth.
1694 */
1695 if (s->authctxt != NULL && s->authctxt->last_login_time > 0) {
1696 s->last_login_time = s->authctxt->last_login_time;
1697 (void) strlcpy(s->hostname,
1698 s->authctxt->last_login_host,
1699 sizeof(s->hostname));
1700 s->authctxt->last_login_time = 0;
1701 s->authctxt->last_login_host[0] = '\0';
1702 }
1703 }
1704
1705 s->term = packet_get_string(&len);
1706
1707 if (compat20) {
1708 s->col = packet_get_int();
1709 s->row = packet_get_int();
1710 } else {
1711 s->row = packet_get_int();
1712 s->col = packet_get_int();
1713 }
1714 s->xpixel = packet_get_int();
1715 s->ypixel = packet_get_int();
1716
1717 if (strcmp(s->term, "") == 0) {
1718 xfree(s->term);
1719 s->term = NULL;
1720 }
1721
1722 /* Allocate a pty and open it. */
1723 debug("Allocating pty.");
1724 if (!pty_allocate(&s->ptyfd, &s->ttyfd, s->tty, sizeof(s->tty))) {
1725 if (s->term)
1726 xfree(s->term);
1727 s->term = NULL;
1728 s->ptyfd = -1;
1729 s->ttyfd = -1;
1730 error("session_pty_req: session %d alloc failed", s->self);
1731 return 0;
1732 }
1733 debug("session_pty_req: session %d alloc %s", s->self, s->tty);
1734
1735 /* for SSH1 the tty modes length is not given */
1736 if (!compat20)
1737 n_bytes = packet_remaining();
1738 tty_parse_modes(s->ttyfd, &n_bytes);
1739
1740 /*
1741 * Add a cleanup function to clear the utmp entry and record logout
1742 * time in case we call fatal() (e.g., the connection gets closed).
1743 */
1744 fatal_add_cleanup(session_pty_cleanup, (void *)s);
1745 pty_setowner(s->pw, s->tty);
1746
1747 /* Set window size from the packet. */
1748 pty_change_window_size(s->ptyfd, s->row, s->col, s->xpixel, s->ypixel);
1749
1750 packet_check_eom();
1751 session_proctitle(s);
1752 return 1;
1753 }
1754
1755 static int
session_subsystem_req(Session * s)1756 session_subsystem_req(Session *s)
1757 {
1758 struct stat st;
1759 u_int len;
1760 int success = 0;
1761 char *prog, *cmd, *subsys = packet_get_string(&len);
1762 u_int i;
1763
1764 packet_check_eom();
1765 log("subsystem request for %.100s", subsys);
1766
1767 for (i = 0; i < options.num_subsystems; i++) {
1768 if (strcmp(subsys, options.subsystem_name[i]) == 0) {
1769 prog = options.subsystem_command[i];
1770 cmd = options.subsystem_args[i];
1771 if (strcmp(INTERNAL_SFTP_NAME, prog) == 0) {
1772 s->is_subsystem = SUBSYSTEM_INT_SFTP;
1773 /*
1774 * We must stat(2) the subsystem before we chroot in
1775 * order to be able to send a proper error message.
1776 */
1777 } else if (chroot_requested(options.chroot_directory)) {
1778 char chdirsub[MAXPATHLEN];
1779
1780 strlcpy(chdirsub, options.chroot_directory,
1781 sizeof (chdirsub));
1782 strlcat(chdirsub, "/", sizeof (chdirsub));
1783 strlcat(chdirsub, prog, sizeof (chdirsub));
1784 if (stat(chdirsub, &st) < 0) {
1785 error("subsystem: cannot stat %s under "
1786 "chroot directory %s: %s", prog,
1787 options.chroot_directory,
1788 strerror(errno));
1789 if (strcmp(subsys, "sftp") == 0)
1790 error("subsystem: please see "
1791 "the Subsystem option in "
1792 "sshd_config(4) for an "
1793 "explanation of '%s'.",
1794 INTERNAL_SFTP_NAME);
1795 break;
1796 }
1797 } else if (stat(prog, &st) < 0) {
1798 error("subsystem: cannot stat %s: %s", prog,
1799 strerror(errno));
1800 break;
1801 } else {
1802 s->is_subsystem = SUBSYSTEM_EXT;
1803 }
1804 debug("subsystem: exec() %s", cmd);
1805 do_exec(s, cmd);
1806 success = 1;
1807 break;
1808 }
1809 }
1810
1811 if (!success)
1812 log("subsystem request for %.100s failed, subsystem not found",
1813 subsys);
1814
1815 xfree(subsys);
1816 return success;
1817 }
1818
1819 /*
1820 * Serve "x11-req" channel request for X11 forwarding for the current session
1821 * channel.
1822 */
1823 static int
session_x11_req(Session * s)1824 session_x11_req(Session *s)
1825 {
1826 int success, fd;
1827 char xauthdir[] = "/tmp/ssh-xauth-XXXXXX";
1828
1829 s->single_connection = packet_get_char();
1830 s->auth_proto = packet_get_string(NULL);
1831 s->auth_data = packet_get_string(NULL);
1832 s->screen = packet_get_int();
1833 packet_check_eom();
1834
1835 success = session_setup_x11fwd(s);
1836 if (!success) {
1837 xfree(s->auth_proto);
1838 xfree(s->auth_data);
1839 s->auth_proto = NULL;
1840 s->auth_data = NULL;
1841 return (success);
1842 }
1843
1844 /*
1845 * Create per session X authority file so that different sessions
1846 * don't contend for one common file. The reason for this is that
1847 * xauth(1) locking doesn't work too well over network filesystems.
1848 *
1849 * If mkdtemp() or open() fails then s->auth_file remains NULL which
1850 * means that we won't set XAUTHORITY variable in child's environment
1851 * and xauth(1) will use the default location for the authority file.
1852 */
1853 if (mkdtemp(xauthdir) != NULL) {
1854 s->auth_file = xmalloc(MAXPATHLEN);
1855 snprintf(s->auth_file, MAXPATHLEN, "%s/xauthfile",
1856 xauthdir);
1857 /*
1858 * we don't want that "creating new authority file" message to
1859 * be printed by xauth(1) so we must create that file
1860 * beforehand.
1861 */
1862 if ((fd = open(s->auth_file, O_CREAT | O_EXCL | O_RDONLY,
1863 S_IRUSR | S_IWUSR)) == -1) {
1864 error("failed to create the temporary X authority "
1865 "file %s: %.100s; will use the default one",
1866 s->auth_file, strerror(errno));
1867 xfree(s->auth_file);
1868 s->auth_file = NULL;
1869 if (rmdir(xauthdir) == -1) {
1870 error("cannot remove xauth directory %s: %.100s",
1871 xauthdir, strerror(errno));
1872 }
1873 } else {
1874 close(fd);
1875 debug("temporary X authority file %s created",
1876 s->auth_file);
1877
1878 /*
1879 * add a cleanup function to remove the temporary
1880 * xauth file in case we call fatal() (e.g., the
1881 * connection gets closed).
1882 */
1883 fatal_add_cleanup(session_xauthfile_cleanup, (void *)s);
1884 }
1885 }
1886 else {
1887 error("failed to create a directory for the temporary X "
1888 "authority file: %.100s; will use the default xauth file",
1889 strerror(errno));
1890 }
1891
1892 return (success);
1893 }
1894
1895 static int
session_shell_req(Session * s)1896 session_shell_req(Session *s)
1897 {
1898 packet_check_eom();
1899 do_exec(s, NULL);
1900 return 1;
1901 }
1902
1903 static int
session_exec_req(Session * s)1904 session_exec_req(Session *s)
1905 {
1906 u_int len;
1907 char *command = packet_get_string(&len);
1908 packet_check_eom();
1909 do_exec(s, command);
1910 xfree(command);
1911 return 1;
1912 }
1913
1914 static int
session_auth_agent_req(Session * s)1915 session_auth_agent_req(Session *s)
1916 {
1917 static int called = 0;
1918 packet_check_eom();
1919 if (no_agent_forwarding_flag) {
1920 debug("session_auth_agent_req: no_agent_forwarding_flag");
1921 return 0;
1922 }
1923 if (called) {
1924 return 0;
1925 } else {
1926 called = 1;
1927 return auth_input_request_forwarding(s->pw);
1928 }
1929 }
1930
1931 static int
session_loc_env_check(char * var,char * val)1932 session_loc_env_check(char *var, char *val)
1933 {
1934 char *current;
1935 int cat, ret;
1936
1937 if (strcmp(var, "LANG") == 0)
1938 cat = LC_ALL;
1939 else if (strcmp(var, "LC_ALL") == 0)
1940 cat = LC_ALL;
1941 else if (strcmp(var, "LC_CTYPE") == 0)
1942 cat = LC_CTYPE;
1943 else if (strcmp(var, "LC_COLLATE") == 0)
1944 cat = LC_COLLATE;
1945 else if (strcmp(var, "LC_TIME") == 0)
1946 cat = LC_TIME;
1947 else if (strcmp(var, "LC_NUMERIC") == 0)
1948 cat = LC_NUMERIC;
1949 else if (strcmp(var, "LC_MONETARY") == 0)
1950 cat = LC_MONETARY;
1951 else if (strcmp(var, "LC_MESSAGES") == 0)
1952 cat = LC_MESSAGES;
1953
1954 current = setlocale(cat, NULL);
1955
1956 ret = (setlocale(cat, val) != NULL);
1957 (void) setlocale(cat, current);
1958 return (ret);
1959 }
1960
1961 static int
session_env_req(Session * s)1962 session_env_req(Session *s)
1963 {
1964 Channel *c;
1965 char *var, *val, *e;
1966 char **p;
1967 size_t len;
1968 int ret = 0;
1969
1970 /* Get var/val from the rest of this packet */
1971 var = packet_get_string(NULL);
1972 val = packet_get_string(NULL);
1973
1974 /*
1975 * We'll need the channel ID for the packet_send_debug messages,
1976 * so get it now.
1977 */
1978 if ((c = channel_lookup(s->chanid)) == NULL)
1979 goto done; /* shouldn't happen! */
1980
1981 debug2("Received request for environment variable %s=%s", var, val);
1982
1983 /* For now allow only LANG and LC_* */
1984 if (strcmp(var, "LANG") != 0 && strncmp(var, "LC_", 3) != 0) {
1985 debug2("Rejecting request for environment variable %s", var);
1986 goto done;
1987 }
1988
1989 if (!session_loc_env_check(var, val)) {
1990 packet_send_debug(gettext("Missing locale support for %s=%s"),
1991 var, val);
1992 goto done;
1993 }
1994
1995 packet_send_debug(gettext("Channel %d set: %s=%s"), c->remote_id,
1996 var, val);
1997
1998 /*
1999 * Always append new environment variables without regard to old
2000 * ones being overriden. The way these are actually added to
2001 * the environment of the session process later settings
2002 * override earlier ones; see copy_environment().
2003 */
2004 if (s->env == NULL) {
2005 char **env;
2006
2007 env = xmalloc(sizeof (char **) * 2);
2008 memset(env, 0, sizeof (char **) * 2);
2009
2010 s->env = env;
2011 p = env;
2012 } else {
2013 for (p = s->env; *p != NULL ; p++);
2014
2015 s->env = xrealloc(s->env, (p - s->env + 2) * sizeof (char **));
2016
2017 for (p = s->env; *p != NULL ; p++);
2018 }
2019
2020 len = snprintf(NULL, 0, "%s=%s", var, val);
2021 e = xmalloc(len + 1);
2022 (void) snprintf(e, len + 1, "%s=%s", var, val);
2023
2024 (*p++) = e;
2025 *p = NULL;
2026
2027 ret = 1;
2028
2029 done:
2030 xfree(var);
2031 xfree(val);
2032
2033 return (ret);
2034 }
2035
2036 static void
session_free_env(char *** envp)2037 session_free_env(char ***envp)
2038 {
2039 char **env, **p;
2040
2041 if (envp == NULL || *envp == NULL)
2042 return;
2043
2044 env = *envp;
2045
2046 *envp = NULL;
2047
2048 for (p = env; *p != NULL; p++)
2049 xfree(*p);
2050
2051 xfree(env);
2052 }
2053
2054 int
session_input_channel_req(Channel * c,const char * rtype)2055 session_input_channel_req(Channel *c, const char *rtype)
2056 {
2057 int success = 0;
2058 Session *s;
2059
2060 if ((s = session_by_channel(c->self)) == NULL) {
2061 log("session_input_channel_req: no session %d req %.100s",
2062 c->self, rtype);
2063 return 0;
2064 }
2065 debug("session_input_channel_req: session %d req %s", s->self, rtype);
2066
2067 /*
2068 * a session is in LARVAL state until a shell, a command
2069 * or a subsystem is executed
2070 */
2071 if (c->type == SSH_CHANNEL_LARVAL) {
2072 if (strcmp(rtype, "shell") == 0) {
2073 success = session_shell_req(s);
2074 } else if (strcmp(rtype, "exec") == 0) {
2075 success = session_exec_req(s);
2076 } else if (strcmp(rtype, "pty-req") == 0) {
2077 success = session_pty_req(s);
2078 } else if (strcmp(rtype, "x11-req") == 0) {
2079 success = session_x11_req(s);
2080 } else if (strcmp(rtype, "auth-agent-req@openssh.com") == 0) {
2081 success = session_auth_agent_req(s);
2082 } else if (strcmp(rtype, "subsystem") == 0) {
2083 success = session_subsystem_req(s);
2084 } else if (strcmp(rtype, "env") == 0) {
2085 success = session_env_req(s);
2086 }
2087 }
2088 if (strcmp(rtype, "window-change") == 0) {
2089 success = session_window_change_req(s);
2090 }
2091 return success;
2092 }
2093
2094 void
session_set_fds(Session * s,int fdin,int fdout,int fderr)2095 session_set_fds(Session *s, int fdin, int fdout, int fderr)
2096 {
2097 if (!compat20)
2098 fatal("session_set_fds: called for proto != 2.0");
2099 /*
2100 * now that have a child and a pipe to the child,
2101 * we can activate our channel and register the fd's
2102 */
2103 if (s->chanid == -1)
2104 fatal("no channel for session %d", s->self);
2105 channel_set_fds(s->chanid,
2106 fdout, fdin, fderr,
2107 fderr == -1 ? CHAN_EXTENDED_IGNORE : CHAN_EXTENDED_READ,
2108 1,
2109 CHAN_SES_WINDOW_DEFAULT);
2110 }
2111
2112 /*
2113 * Function to perform pty cleanup. Also called if we get aborted abnormally
2114 * (e.g., due to a dropped connection).
2115 */
2116 void
session_pty_cleanup2(void * session)2117 session_pty_cleanup2(void *session)
2118 {
2119 Session *s = session;
2120
2121 if (s == NULL) {
2122 error("session_pty_cleanup: no session");
2123 return;
2124 }
2125 if (s->ttyfd == -1)
2126 return;
2127
2128 debug("session_pty_cleanup: session %d release %s", s->self, s->tty);
2129
2130 #ifdef USE_PAM
2131 session_do_pam(s, 0);
2132 #endif /* USE_PAM */
2133
2134 /* Record that the user has logged out. */
2135 if (s->pid != 0) {
2136 debug3("Recording SSHv2 channel logout in utmpx/wtmpx");
2137 #ifdef ALTPRIVSEP
2138 altprivsep_record_logout(s->pid);
2139 #endif /* ALTPRIVSEP */
2140 }
2141
2142 /* Release the pseudo-tty. */
2143 if (getuid() == 0)
2144 pty_release(s->tty);
2145
2146 /*
2147 * Close the server side of the socket pairs. We must do this after
2148 * the pty cleanup, so that another process doesn't get this pty
2149 * while we're still cleaning up.
2150 */
2151 if (close(s->ptymaster) < 0)
2152 error("close(s->ptymaster/%d): %s", s->ptymaster, strerror(errno));
2153
2154 /* unlink pty from session */
2155 s->ttyfd = -1;
2156 }
2157
2158 void
session_pty_cleanup(void * session)2159 session_pty_cleanup(void *session)
2160 {
2161 session_pty_cleanup2(session);
2162 }
2163
2164 /*
2165 * We use a different temporary X authority file per every session so we
2166 * should remove those files when fatal() is called.
2167 */
2168 void
session_xauthfile_cleanup(void * session)2169 session_xauthfile_cleanup(void *session)
2170 {
2171 Session *s = session;
2172
2173 if (s == NULL) {
2174 error("session_xauthfile_cleanup: no session");
2175 return;
2176 }
2177
2178 debug("session_xauthfile_cleanup: session %d removing %s", s->self,
2179 s->auth_file);
2180
2181 if (unlink(s->auth_file) == -1) {
2182 error("session_xauthfile_cleanup: cannot remove xauth file: "
2183 "%.100s", strerror(errno));
2184 return;
2185 }
2186
2187 /* dirname() will modify s->auth_file but that's ok */
2188 if (rmdir(dirname(s->auth_file)) == -1) {
2189 error("session_xauthfile_cleanup: "
2190 "cannot remove xauth directory: %.100s", strerror(errno));
2191 return;
2192 }
2193 }
2194
2195 static char *
sig2name(int sig)2196 sig2name(int sig)
2197 {
2198 #define SSH_SIG(x) if (sig == SIG ## x) return #x
2199 SSH_SIG(ABRT);
2200 SSH_SIG(ALRM);
2201 SSH_SIG(FPE);
2202 SSH_SIG(HUP);
2203 SSH_SIG(ILL);
2204 SSH_SIG(INT);
2205 SSH_SIG(KILL);
2206 SSH_SIG(PIPE);
2207 SSH_SIG(QUIT);
2208 SSH_SIG(SEGV);
2209 SSH_SIG(TERM);
2210 SSH_SIG(USR1);
2211 SSH_SIG(USR2);
2212 #undef SSH_SIG
2213 return "SIG@openssh.com";
2214 }
2215
2216 static void
session_exit_message(Session * s,int status)2217 session_exit_message(Session *s, int status)
2218 {
2219 Channel *c;
2220
2221 if ((c = channel_lookup(s->chanid)) == NULL)
2222 fatal("session_exit_message: session %d: no channel %d",
2223 s->self, s->chanid);
2224 debug("session_exit_message: session %d channel %d pid %ld",
2225 s->self, s->chanid, (long)s->pid);
2226
2227 if (WIFEXITED(status)) {
2228 channel_request_start(s->chanid, "exit-status", 0);
2229 packet_put_int(WEXITSTATUS(status));
2230 packet_send();
2231 } else if (WIFSIGNALED(status)) {
2232 channel_request_start(s->chanid, "exit-signal", 0);
2233 packet_put_cstring(sig2name(WTERMSIG(status)));
2234 #ifdef WCOREDUMP
2235 packet_put_char(WCOREDUMP(status));
2236 #else /* WCOREDUMP */
2237 packet_put_char(0);
2238 #endif /* WCOREDUMP */
2239 packet_put_cstring("");
2240 packet_put_cstring("");
2241 packet_send();
2242 } else {
2243 /* Some weird exit cause. Just exit. */
2244 packet_disconnect("wait returned status %04x.", status);
2245 }
2246
2247 /* Ok to close channel now */
2248 channel_set_wait_for_exit(s->chanid, 0);
2249
2250 /* disconnect channel */
2251 debug("session_exit_message: release channel %d", s->chanid);
2252 channel_cancel_cleanup(s->chanid);
2253 /*
2254 * emulate a write failure with 'chan_write_failed', nobody will be
2255 * interested in data we write.
2256 * Note that we must not call 'chan_read_failed', since there could
2257 * be some more data waiting in the pipe.
2258 */
2259 if (c->ostate != CHAN_OUTPUT_CLOSED)
2260 chan_write_failed(c);
2261 s->chanid = -1;
2262 }
2263
2264 void
session_close(Session * s)2265 session_close(Session *s)
2266 {
2267 debug("session_close: session %d pid %ld", s->self, (long)s->pid);
2268 if (s->ttyfd != -1) {
2269 fatal_remove_cleanup(session_pty_cleanup, (void *)s);
2270 session_pty_cleanup(s);
2271 }
2272 if (s->auth_file != NULL) {
2273 fatal_remove_cleanup(session_xauthfile_cleanup, (void *)s);
2274 session_xauthfile_cleanup(s);
2275 xfree(s->auth_file);
2276 }
2277 if (s->term)
2278 xfree(s->term);
2279 if (s->display)
2280 xfree(s->display);
2281 if (s->auth_display)
2282 xfree(s->auth_display);
2283 if (s->auth_data)
2284 xfree(s->auth_data);
2285 if (s->auth_proto)
2286 xfree(s->auth_proto);
2287 if (s->command)
2288 xfree(s->command);
2289 session_free_env(&s->env);
2290 s->used = 0;
2291 session_proctitle(s);
2292 }
2293
2294 void
session_close_by_pid(pid_t pid,int status)2295 session_close_by_pid(pid_t pid, int status)
2296 {
2297 Session *s = session_by_pid(pid);
2298 if (s == NULL) {
2299 debug("session_close_by_pid: no session for pid %ld",
2300 (long)pid);
2301 return;
2302 }
2303 if (s->chanid != -1)
2304 session_exit_message(s, status);
2305 session_close(s);
2306 }
2307
2308 /*
2309 * This is called when a channel dies before the session 'child' itself dies.
2310 * It can happen for example if we exit from an interactive shell before we
2311 * exit from forwarded X11 applications.
2312 */
2313 void
session_close_by_channel(int id,void * arg)2314 session_close_by_channel(int id, void *arg)
2315 {
2316 Session *s = session_by_channel(id);
2317 if (s == NULL) {
2318 debug("session_close_by_channel: no session for id %d", id);
2319 return;
2320 }
2321 debug("session_close_by_channel: channel %d child %ld",
2322 id, (long)s->pid);
2323 if (s->pid != 0) {
2324 debug("session_close_by_channel: channel %d: has child", id);
2325 /*
2326 * delay detach of session, but release pty, since
2327 * the fd's to the child are already closed
2328 */
2329 if (s->ttyfd != -1) {
2330 fatal_remove_cleanup(session_pty_cleanup, (void *)s);
2331 session_pty_cleanup(s);
2332 }
2333 return;
2334 }
2335 /* detach by removing callback */
2336 channel_cancel_cleanup(s->chanid);
2337 s->chanid = -1;
2338 session_close(s);
2339 }
2340
2341 void
session_destroy_all(void (* closefunc)(Session *))2342 session_destroy_all(void (*closefunc)(Session *))
2343 {
2344 int i;
2345 for (i = 0; i < MAX_SESSIONS; i++) {
2346 Session *s = &sessions[i];
2347 if (s->used) {
2348 if (closefunc != NULL)
2349 closefunc(s);
2350 else
2351 session_close(s);
2352 }
2353 }
2354 }
2355
2356 static char *
session_tty_list(void)2357 session_tty_list(void)
2358 {
2359 static char buf[1024];
2360 int i;
2361 buf[0] = '\0';
2362 for (i = 0; i < MAX_SESSIONS; i++) {
2363 Session *s = &sessions[i];
2364 if (s->used && s->ttyfd != -1) {
2365 if (buf[0] != '\0')
2366 strlcat(buf, ",", sizeof buf);
2367 strlcat(buf, strrchr(s->tty, '/') + 1, sizeof buf);
2368 }
2369 }
2370 if (buf[0] == '\0')
2371 strlcpy(buf, "notty", sizeof buf);
2372 return buf;
2373 }
2374
2375 void
session_proctitle(Session * s)2376 session_proctitle(Session *s)
2377 {
2378 if (s->pw == NULL)
2379 error("no user for session %d", s->self);
2380 else
2381 setproctitle("%s@%s", s->pw->pw_name, session_tty_list());
2382 }
2383
2384 int
session_setup_x11fwd(Session * s)2385 session_setup_x11fwd(Session *s)
2386 {
2387 struct stat st;
2388 char display[512], auth_display[512];
2389 char hostname[MAXHOSTNAMELEN];
2390
2391 if (no_x11_forwarding_flag) {
2392 packet_send_debug("X11 forwarding disabled in user configuration file.");
2393 return 0;
2394 }
2395 if (!options.x11_forwarding) {
2396 debug("X11 forwarding disabled in server configuration file.");
2397 return 0;
2398 }
2399 if (!options.xauth_location ||
2400 (stat(options.xauth_location, &st) == -1)) {
2401 packet_send_debug("No xauth program; cannot forward with spoofing.");
2402 return 0;
2403 }
2404 if (s->display != NULL) {
2405 debug("X11 display already set.");
2406 return 0;
2407 }
2408 if (x11_create_display_inet(options.x11_display_offset,
2409 options.x11_use_localhost, s->single_connection,
2410 &s->display_number) == -1) {
2411 debug("x11_create_display_inet failed.");
2412 return 0;
2413 }
2414
2415 /* Set up a suitable value for the DISPLAY variable. */
2416 if (gethostname(hostname, sizeof(hostname)) < 0)
2417 fatal("gethostname: %.100s", strerror(errno));
2418 /*
2419 * auth_display must be used as the displayname when the
2420 * authorization entry is added with xauth(1). This will be
2421 * different than the DISPLAY string for localhost displays.
2422 */
2423 if (options.x11_use_localhost) {
2424 snprintf(display, sizeof display, "localhost:%u.%u",
2425 s->display_number, s->screen);
2426 snprintf(auth_display, sizeof auth_display, "unix:%u.%u",
2427 s->display_number, s->screen);
2428 s->display = xstrdup(display);
2429 s->auth_display = xstrdup(auth_display);
2430 } else {
2431 #ifdef IPADDR_IN_DISPLAY
2432 struct hostent *he;
2433 struct in_addr my_addr;
2434
2435 he = gethostbyname(hostname);
2436 if (he == NULL) {
2437 error("Can't get IP address for X11 DISPLAY.");
2438 packet_send_debug("Can't get IP address for X11 DISPLAY.");
2439 return 0;
2440 }
2441 memcpy(&my_addr, he->h_addr_list[0], sizeof(struct in_addr));
2442 snprintf(display, sizeof display, "%.50s:%u.%u", inet_ntoa(my_addr),
2443 s->display_number, s->screen);
2444 #else
2445 snprintf(display, sizeof display, "%.400s:%u.%u", hostname,
2446 s->display_number, s->screen);
2447 #endif
2448 s->display = xstrdup(display);
2449 s->auth_display = xstrdup(display);
2450 }
2451
2452 return 1;
2453 }
2454
2455 #ifdef USE_PAM
2456 int session_do_pam_conv(int, struct pam_message **,
2457 struct pam_response **, void *);
2458
2459 static struct pam_conv session_pam_conv = {
2460 session_do_pam_conv,
2461 NULL
2462 };
2463
2464 static void
session_do_pam(Session * s,int do_open)2465 session_do_pam(Session *s, int do_open)
2466 {
2467 int pam_retval;
2468 char *where, *old_tty, *old_tty_copy = NULL;
2469 struct pam_conv old_conv, *old_conv_ptr;
2470
2471 if (!s || !s->authctxt || !s->authctxt->pam || !s->authctxt->pam->h)
2472 return;
2473
2474 /* Save current PAM item values */
2475 where = "getting PAM_CONV";
2476 pam_retval = pam_get_item(s->authctxt->pam->h, PAM_CONV,
2477 (void **) &old_conv_ptr);
2478 if (pam_retval != PAM_SUCCESS)
2479 goto done;
2480 old_conv = *old_conv_ptr;
2481
2482 where = "getting PAM_TTY";
2483 pam_retval = pam_get_item(s->authctxt->pam->h, PAM_TTY,
2484 (void **) &old_tty);
2485 if (pam_retval != PAM_SUCCESS)
2486 goto done;
2487 old_tty_copy = xstrdup(old_tty);
2488
2489 /* Change PAM_TTY and PAM_CONV items */
2490 where = "setting PAM_TTY";
2491 pam_retval = pam_set_item(s->authctxt->pam->h, PAM_TTY, s->tty);
2492 if (pam_retval != PAM_SUCCESS)
2493 goto done;
2494
2495 where = "setting PAM_CONV";
2496 session_pam_conv.appdata_ptr = s;
2497 pam_retval = pam_set_item(s->authctxt->pam->h,
2498 PAM_CONV, &session_pam_conv);
2499 if (pam_retval != PAM_SUCCESS)
2500 goto done;
2501
2502 /* Call pam_open/close_session() */
2503 if (do_open) {
2504 where = "calling pam_open_session()";
2505 pam_retval = pam_open_session(s->authctxt->pam->h, 0);
2506 }
2507 else {
2508 where = "calling pam_close_session()";
2509 pam_retval = pam_close_session(s->authctxt->pam->h, 0);
2510 }
2511
2512 /* Reset PAM_TTY and PAM_CONV items to previous values */
2513 where = "setting PAM_TTY";
2514 pam_retval = pam_set_item(s->authctxt->pam->h, PAM_TTY, old_tty_copy);
2515 if (pam_retval != PAM_SUCCESS)
2516 goto done;
2517
2518 where = "setting PAM_CONV";
2519 pam_retval = pam_set_item(s->authctxt->pam->h, PAM_CONV, &old_conv);
2520 if (pam_retval != PAM_SUCCESS)
2521 goto done;
2522
2523 session_pam_conv.appdata_ptr = NULL;
2524
2525 done:
2526 if (old_tty_copy)
2527 xfree(old_tty_copy);
2528
2529 if (pam_retval == PAM_SUCCESS)
2530 return;
2531
2532 /* fatal()? probably not... */
2533 log("PAM failed[%d] while %s: %s", pam_retval, where,
2534 PAM_STRERROR(s->authctxt->pam->h, pam_retval));
2535 }
2536
2537 int
session_do_pam_conv(int num_prompts,struct pam_message ** prompts,struct pam_response ** resp,void * app_data)2538 session_do_pam_conv(int num_prompts,
2539 struct pam_message **prompts,
2540 struct pam_response **resp,
2541 void *app_data)
2542 {
2543 Session *s = (Session *) app_data;
2544
2545 struct pam_response *reply;
2546 int count;
2547 char *prompt;
2548
2549 if (channel_lookup(s->chanid) == NULL)
2550 return PAM_CONV_ERR;
2551
2552 /* PAM will free this later */
2553 reply = xmalloc(num_prompts * sizeof(*reply));
2554
2555 (void) memset(reply, 0, num_prompts * sizeof(*reply));
2556 for (count = 0; count < num_prompts; count++) {
2557 switch(PAM_MSG_MEMBER(prompts, count, msg_style)) {
2558 case PAM_TEXT_INFO:
2559 /* Write to stdout of channel */
2560 prompt = PAM_MSG_MEMBER(prompts, count, msg);
2561 if (prompt != NULL && s->ttyfd != -1) {
2562 debug2("session_do_pam_conv: text info "
2563 "prompt: %s", prompt);
2564 (void) write(s->ttyfd, prompt, strlen(prompt));
2565 (void) write(s->ttyfd, "\n", 1);
2566 }
2567 reply[count].resp = xstrdup("");
2568 reply[count].resp_retcode = PAM_SUCCESS;
2569 break;
2570 case PAM_ERROR_MSG:
2571 /* Write to stderr of channel */
2572 prompt = PAM_MSG_MEMBER(prompts, count, msg);
2573 if (prompt != NULL && s->ttyfd != -1) {
2574 debug2("session_do_pam_conv: error "
2575 "prompt: %s", prompt);
2576 (void) write(s->ttyfd, prompt, strlen(prompt));
2577 (void) write(s->ttyfd, "\n", 1);
2578 }
2579 reply[count].resp = xstrdup("");
2580 reply[count].resp_retcode = PAM_SUCCESS;
2581 break;
2582 case PAM_PROMPT_ECHO_ON:
2583 case PAM_PROMPT_ECHO_OFF:
2584 /*
2585 * XXX Someday add support for echo on/off prompts
2586 * here on sessions with ttys.
2587 */
2588 default:
2589 xfree(reply);
2590 return PAM_CONV_ERR;
2591 }
2592 }
2593
2594 *resp = reply;
2595
2596 return PAM_SUCCESS;
2597 }
2598 #endif /* USE_PAM */
2599
2600 static void
do_authenticated2(Authctxt * authctxt)2601 do_authenticated2(Authctxt *authctxt)
2602 {
2603 server_loop2(authctxt);
2604 }
2605
2606 /*
2607 * Drop the privileges. We need this for the in-process SFTP server only. For
2608 * the shell and the external subsystem the exec(2) call will do the P = E = I
2609 * assignment itself. Never change the privileges if the connecting user is
2610 * root. See privileges(5) if the terminology used here is not known to you.
2611 */
2612 static void
drop_privs(uid_t uid)2613 drop_privs(uid_t uid)
2614 {
2615 priv_set_t *priv_inherit;
2616
2617 /* If root is connecting we are done. */
2618 if (uid == 0)
2619 return;
2620
2621 if ((priv_inherit = priv_allocset()) == NULL)
2622 fatal("priv_allocset: %s", strerror(errno));
2623 if (getppriv(PRIV_INHERITABLE, priv_inherit) != 0)
2624 fatal("getppriv: %s", strerror(errno));
2625
2626 /*
2627 * This will limit E as well. Note that before this P was a
2628 * superset of I, see permanently_set_uid().
2629 */
2630 if (setppriv(PRIV_SET, PRIV_PERMITTED, priv_inherit) == -1)
2631 fatal("setppriv: %s", strerror(errno));
2632
2633 priv_freeset(priv_inherit);
2634
2635 /*
2636 * By manipulating the P set above we entered a PA mode which we
2637 * do not need to retain in.
2638 */
2639 if (setpflags(PRIV_AWARE, 0) == -1)
2640 fatal("setpflags: %s", strerror(errno));
2641 }
2642