Annotation of src/usr.bin/ssh/sshd.c, Revision 1.29
1.1 deraadt 1: /*
2:
3: sshd.c
4:
5: Author: Tatu Ylonen <ylo@cs.hut.fi>
6:
7: Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
8: All rights reserved
9:
10: Created: Fri Mar 17 17:09:28 1995 ylo
11:
12: This program is the ssh daemon. It listens for connections from clients, and
13: performs authentication, executes use commands or shell, and forwards
14: information to/from the application to the user client over an encrypted
15: connection. This can also handle forwarding of X11, TCP/IP, and authentication
16: agent connections.
17:
18: */
19:
20: #include "includes.h"
1.29 ! deraadt 21: RCSID("$Id: sshd.c,v 1.28 1999/10/11 21:48:29 markus Exp $");
1.1 deraadt 22:
23: #include "xmalloc.h"
24: #include "rsa.h"
25: #include "ssh.h"
26: #include "pty.h"
27: #include "packet.h"
28: #include "buffer.h"
29: #include "cipher.h"
30: #include "mpaux.h"
31: #include "servconf.h"
32: #include "uidswap.h"
33:
34: #ifdef LIBWRAP
35: #include <tcpd.h>
36: #include <syslog.h>
37: #include <sys/syslog.h>
1.25 markus 38: #include <sys/stat.h>
1.1 deraadt 39: int allow_severity = LOG_INFO;
40: int deny_severity = LOG_WARNING;
41: #endif /* LIBWRAP */
42:
43: #ifndef O_NOCTTY
44: #define O_NOCTTY 0
45: #endif
46:
47: #ifdef KRB4
48: char *ticket = NULL;
49: #endif /* KRB4 */
50:
51: /* Local Xauthority file. */
52: char *xauthfile = NULL;
53:
54: /* Server configuration options. */
55: ServerOptions options;
56:
57: /* Name of the server configuration file. */
58: char *config_file_name = SERVER_CONFIG_FILE;
59:
60: /* Debug mode flag. This can be set on the command line. If debug
61: mode is enabled, extra debugging output will be sent to the system
62: log, the daemon will not go to background, and will exit after processing
63: the first connection. */
64: int debug_flag = 0;
65:
66: /* Flag indicating that the daemon is being started from inetd. */
67: int inetd_flag = 0;
68:
69: /* argv[0] without path. */
70: char *av0;
71:
72: /* Saved arguments to main(). */
73: char **saved_argv;
74:
75: /* This is set to the socket that the server is listening; this is used in
76: the SIGHUP signal handler. */
77: int listen_sock;
78:
79: /* Flags set in auth-rsa from authorized_keys flags. These are set in
80: auth-rsa.c. */
81: int no_port_forwarding_flag = 0;
82: int no_agent_forwarding_flag = 0;
83: int no_x11_forwarding_flag = 0;
84: int no_pty_flag = 0;
85: char *forced_command = NULL; /* RSA authentication "command=" option. */
86: struct envstring *custom_environment = NULL;
87: /* RSA authentication "environment=" options. */
88:
89: /* Session id for the current session. */
90: unsigned char session_id[16];
91:
92: /* Any really sensitive data in the application is contained in this structure.
93: The idea is that this structure could be locked into memory so that the
94: pages do not get written into swap. However, there are some problems.
1.2 provos 95: The private key contains BIGNUMs, and we do not (in principle) have
1.1 deraadt 96: access to the internals of them, and locking just the structure is not
97: very useful. Currently, memory locking is not implemented. */
98: struct
99: {
100: /* Private part of server key. */
1.2 provos 101: RSA *private_key;
1.1 deraadt 102:
103: /* Private part of host key. */
1.2 provos 104: RSA *host_key;
1.1 deraadt 105: } sensitive_data;
106:
107: /* Flag indicating whether the current session key has been used. This flag
108: is set whenever the key is used, and cleared when the key is regenerated. */
109: int key_used = 0;
110:
111: /* This is set to true when SIGHUP is received. */
112: int received_sighup = 0;
113:
114: /* Public side of the server key. This value is regenerated regularly with
115: the private key. */
1.2 provos 116: RSA *public_key;
1.1 deraadt 117:
118: /* Prototypes for various functions defined later in this file. */
119: void do_connection(int privileged_port);
120: void do_authentication(char *user, int privileged_port);
121: void do_authenticated(struct passwd *pw);
122: void do_exec_pty(const char *command, int ptyfd, int ttyfd,
123: const char *ttyname, struct passwd *pw, const char *term,
124: const char *display, const char *auth_proto,
125: const char *auth_data);
126: void do_exec_no_pty(const char *command, struct passwd *pw,
127: const char *display, const char *auth_proto,
128: const char *auth_data);
129: void do_child(const char *command, struct passwd *pw, const char *term,
130: const char *display, const char *auth_proto,
131: const char *auth_data, const char *ttyname);
132:
133: /* Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
134: the effect is to reread the configuration file (and to regenerate
135: the server key). */
136:
1.14 deraadt 137: void sighup_handler(int sig)
1.1 deraadt 138: {
139: received_sighup = 1;
140: signal(SIGHUP, sighup_handler);
141: }
142:
143: /* Called from the main program after receiving SIGHUP. Restarts the
144: server. */
145:
146: void sighup_restart()
147: {
148: log("Received SIGHUP; restarting.");
149: close(listen_sock);
150: execv(saved_argv[0], saved_argv);
151: log("RESTART FAILED: av0='%s', error: %s.", av0, strerror(errno));
152: exit(1);
153: }
154:
155: /* Generic signal handler for terminating signals in the master daemon.
156: These close the listen socket; not closing it seems to cause "Address
157: already in use" problems on some machines, which is inconvenient. */
158:
1.14 deraadt 159: void sigterm_handler(int sig)
1.1 deraadt 160: {
161: log("Received signal %d; terminating.", sig);
162: close(listen_sock);
163: exit(255);
164: }
165:
166: /* SIGCHLD handler. This is called whenever a child dies. This will then
167: reap any zombies left by exited c. */
168:
1.14 deraadt 169: void main_sigchld_handler(int sig)
1.1 deraadt 170: {
1.18 deraadt 171: int save_errno = errno;
1.1 deraadt 172: int status;
173: wait(&status);
174: signal(SIGCHLD, main_sigchld_handler);
1.18 deraadt 175: errno = save_errno;
1.1 deraadt 176: }
177:
178: /* Signal handler for the alarm after the login grace period has expired. */
179:
1.14 deraadt 180: void grace_alarm_handler(int sig)
1.1 deraadt 181: {
182: /* Close the connection. */
183: packet_close();
184:
185: /* Log error and exit. */
186: fatal("Timeout before authentication.");
187: }
188:
189: /* Signal handler for the key regeneration alarm. Note that this
190: alarm only occurs in the daemon waiting for connections, and it does not
191: do anything with the private key or random state before forking. Thus there
192: should be no concurrency control/asynchronous execution problems. */
193:
1.14 deraadt 194: void key_regeneration_alarm(int sig)
1.1 deraadt 195: {
1.18 deraadt 196: int save_errno = errno;
197:
1.1 deraadt 198: /* Check if we should generate a new key. */
199: if (key_used)
200: {
201: /* This should really be done in the background. */
202: log("Generating new %d bit RSA key.", options.server_key_bits);
1.2 provos 203:
204: if (sensitive_data.private_key != NULL)
205: RSA_free(sensitive_data.private_key);
206: sensitive_data.private_key = RSA_new();
207:
208: if (public_key != NULL)
209: RSA_free(public_key);
210: public_key = RSA_new();
211:
212: rsa_generate_key(sensitive_data.private_key, public_key,
213: options.server_key_bits);
214: arc4random_stir();
1.1 deraadt 215: key_used = 0;
216: log("RSA key generation complete.");
217: }
218:
219: /* Reschedule the alarm. */
220: signal(SIGALRM, key_regeneration_alarm);
221: alarm(options.key_regeneration_time);
1.18 deraadt 222: errno = save_errno;
1.1 deraadt 223: }
224:
225: /* Main program for the daemon. */
226:
1.2 provos 227: int
228: main(int ac, char **av)
1.1 deraadt 229: {
230: extern char *optarg;
231: extern int optind;
232: int opt, aux, sock_in, sock_out, newsock, i, pid, on = 1;
233: int remote_major, remote_minor;
1.23 deraadt 234: int silentrsa = 0;
1.1 deraadt 235: struct sockaddr_in sin;
236: char buf[100]; /* Must not be larger than remote_version. */
237: char remote_version[100]; /* Must be at least as big as buf. */
238: char *comment;
239: FILE *f;
240: struct linger linger;
241:
242: /* Save argv[0]. */
243: saved_argv = av;
244: if (strchr(av[0], '/'))
245: av0 = strrchr(av[0], '/') + 1;
246: else
247: av0 = av[0];
1.3 deraadt 248:
1.1 deraadt 249: /* Initialize configuration options to their default values. */
250: initialize_server_options(&options);
251:
252: /* Parse command-line arguments. */
1.23 deraadt 253: while ((opt = getopt(ac, av, "f:p:b:k:h:g:diqQ")) != EOF)
1.1 deraadt 254: {
255: switch (opt)
256: {
257: case 'f':
258: config_file_name = optarg;
259: break;
260: case 'd':
261: debug_flag = 1;
262: break;
263: case 'i':
264: inetd_flag = 1;
265: break;
1.23 deraadt 266: case 'Q':
267: silentrsa = 1;
268: break;
1.1 deraadt 269: case 'q':
270: options.quiet_mode = 1;
271: break;
272: case 'b':
273: options.server_key_bits = atoi(optarg);
274: break;
275: case 'p':
276: options.port = atoi(optarg);
277: break;
278: case 'g':
279: options.login_grace_time = atoi(optarg);
280: break;
281: case 'k':
282: options.key_regeneration_time = atoi(optarg);
283: break;
284: case 'h':
285: options.host_key_file = optarg;
286: break;
287: case '?':
288: default:
289: fprintf(stderr, "sshd version %s\n", SSH_VERSION);
290: fprintf(stderr, "Usage: %s [options]\n", av0);
291: fprintf(stderr, "Options:\n");
292: fprintf(stderr, " -f file Configuration file (default %s/sshd_config)\n", ETCDIR);
293: fprintf(stderr, " -d Debugging mode\n");
294: fprintf(stderr, " -i Started from inetd\n");
295: fprintf(stderr, " -q Quiet (no logging)\n");
296: fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
297: fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
298: fprintf(stderr, " -g seconds Grace period for authentication (default: 300)\n");
299: fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
300: fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
301: HOST_KEY_FILE);
302: exit(1);
303: }
304: }
1.23 deraadt 305:
306: /* check if RSA support exists */
307: if (rsa_alive() == 0) {
308: if (silentrsa == 0)
309: printf("sshd: no RSA support in libssl and libcrypto -- exiting. See ssl(8)\n");
310: log("no RSA support in libssl and libcrypto -- exiting. See ssl(8)");
311: exit(1);
312: }
1.1 deraadt 313:
314: /* Read server configuration options from the configuration file. */
315: read_server_config(&options, config_file_name);
316:
317: /* Fill in default values for those options not explicitly set. */
318: fill_default_server_options(&options);
319:
320: /* Check certain values for sanity. */
321: if (options.server_key_bits < 512 ||
322: options.server_key_bits > 32768)
323: {
324: fprintf(stderr, "Bad server key size.\n");
325: exit(1);
326: }
327: if (options.port < 1 || options.port > 65535)
328: {
329: fprintf(stderr, "Bad port number.\n");
330: exit(1);
331: }
332:
333: /* Check that there are no remaining arguments. */
334: if (optind < ac)
335: {
336: fprintf(stderr, "Extra argument %s.\n", av[optind]);
337: exit(1);
338: }
339:
340: /* Initialize the log (it is reinitialized below in case we forked). */
341: log_init(av0, debug_flag && !inetd_flag,
342: debug_flag || options.fascist_logging,
343: options.quiet_mode, options.log_facility);
344:
345: debug("sshd version %.100s", SSH_VERSION);
346:
1.2 provos 347: sensitive_data.host_key = RSA_new();
1.1 deraadt 348: /* Load the host key. It must have empty passphrase. */
349: if (!load_private_key(options.host_key_file, "",
1.2 provos 350: sensitive_data.host_key, &comment))
1.1 deraadt 351: {
352: if (debug_flag)
353: fprintf(stderr, "Could not load host key: %s: %s\n",
354: options.host_key_file, strerror(errno));
355: else
356: {
357: int err = errno;
358: log_init(av0, !inetd_flag, 1, 0, options.log_facility);
359: error("Could not load host key: %.200s: %.100s",
360: options.host_key_file, strerror(err));
361: }
362: exit(1);
363: }
364: xfree(comment);
365:
366: /* If not in debugging mode, and not started from inetd, disconnect from
367: the controlling terminal, and fork. The original process exits. */
368: if (!debug_flag && !inetd_flag)
369: {
370: #ifdef TIOCNOTTY
371: int fd;
372: #endif /* TIOCNOTTY */
373:
374: /* Fork, and have the parent exit. The child becomes the server. */
375: if (fork())
376: exit(0);
377:
378: /* Redirect stdin, stdout, and stderr to /dev/null. */
379: freopen("/dev/null", "r", stdin);
380: freopen("/dev/null", "w", stdout);
381: freopen("/dev/null", "w", stderr);
382:
383: /* Disconnect from the controlling tty. */
384: #ifdef TIOCNOTTY
385: fd = open("/dev/tty", O_RDWR|O_NOCTTY);
386: if (fd >= 0)
387: {
388: (void)ioctl(fd, TIOCNOTTY, NULL);
389: close(fd);
390: }
391: #endif /* TIOCNOTTY */
392: (void)setsid();
393: }
394:
395: /* Reinitialize the log (because of the fork above). */
396: log_init(av0, debug_flag && !inetd_flag,
397: debug_flag || options.fascist_logging,
398: options.quiet_mode, options.log_facility);
399:
400: /* Check that server and host key lengths differ sufficiently. This is
401: necessary to make double encryption work with rsaref. Oh, I hate
1.2 provos 402: software patents. I dont know if this can go? Niels */
1.1 deraadt 403: if (options.server_key_bits >
1.2 provos 404: BN_num_bits(sensitive_data.host_key->n) - SSH_KEY_BITS_RESERVED &&
1.1 deraadt 405: options.server_key_bits <
1.2 provos 406: BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED)
1.1 deraadt 407: {
408: options.server_key_bits =
1.2 provos 409: BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED;
1.1 deraadt 410: debug("Forcing server key to %d bits to make it differ from host key.",
411: options.server_key_bits);
412: }
413:
414: /* Do not display messages to stdout in RSA code. */
415: rsa_set_verbose(0);
416:
417: /* Initialize the random number generator. */
1.2 provos 418: arc4random_stir();
1.1 deraadt 419:
420: /* Chdir to the root directory so that the current disk can be unmounted
421: if desired. */
422: chdir("/");
423:
424: /* Close connection cleanly after attack. */
425: cipher_attack_detected = packet_disconnect;
426:
427: /* Start listening for a socket, unless started from inetd. */
428: if (inetd_flag)
429: {
430: int s1, s2;
431: s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
432: s2 = dup(s1);
433: sock_in = dup(0);
434: sock_out = dup(1);
435: /* We intentionally do not close the descriptors 0, 1, and 2 as our
436: code for setting the descriptors won\'t work if ttyfd happens to
437: be one of those. */
438: debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
439:
1.2 provos 440: public_key = RSA_new();
441: sensitive_data.private_key = RSA_new();
1.1 deraadt 442: /* Generate an rsa key. */
443: log("Generating %d bit RSA key.", options.server_key_bits);
1.2 provos 444: rsa_generate_key(sensitive_data.private_key, public_key,
445: options.server_key_bits);
446: arc4random_stir();
1.1 deraadt 447: log("RSA key generation complete.");
448: }
449: else
450: {
451: /* Create socket for listening. */
452: listen_sock = socket(AF_INET, SOCK_STREAM, 0);
453: if (listen_sock < 0)
454: fatal("socket: %.100s", strerror(errno));
455:
456: /* Set socket options. We try to make the port reusable and have it
457: close as fast as possible without waiting in unnecessary wait states
458: on close. */
459: setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR, (void *)&on,
460: sizeof(on));
461: linger.l_onoff = 1;
462: linger.l_linger = 5;
463: setsockopt(listen_sock, SOL_SOCKET, SO_LINGER, (void *)&linger,
464: sizeof(linger));
465:
466: /* Initialize the socket address. */
467: memset(&sin, 0, sizeof(sin));
468: sin.sin_family = AF_INET;
469: sin.sin_addr = options.listen_addr;
470: sin.sin_port = htons(options.port);
471:
472: /* Bind the socket to the desired port. */
473: if (bind(listen_sock, (struct sockaddr *)&sin, sizeof(sin)) < 0)
474: {
475: error("bind: %.100s", strerror(errno));
1.17 deraadt 476: shutdown(listen_sock, SHUT_RDWR);
1.1 deraadt 477: close(listen_sock);
478: fatal("Bind to port %d failed.", options.port);
479: }
480:
481: if (!debug_flag)
482: {
483: /* Record our pid in /etc/sshd_pid to make it easier to kill the
484: correct sshd. We don\'t want to do this before the bind above
485: because the bind will fail if there already is a daemon, and this
486: will overwrite any old pid in the file. */
487: f = fopen(SSH_DAEMON_PID_FILE, "w");
488: if (f)
489: {
490: fprintf(f, "%u\n", (unsigned int)getpid());
491: fclose(f);
492: }
493: }
494:
495: /* Start listening on the port. */
496: log("Server listening on port %d.", options.port);
497: if (listen(listen_sock, 5) < 0)
498: fatal("listen: %.100s", strerror(errno));
499:
1.2 provos 500: public_key = RSA_new();
501: sensitive_data.private_key = RSA_new();
1.1 deraadt 502: /* Generate an rsa key. */
503: log("Generating %d bit RSA key.", options.server_key_bits);
1.2 provos 504: rsa_generate_key(sensitive_data.private_key, public_key,
1.1 deraadt 505: options.server_key_bits);
1.2 provos 506: arc4random_stir();
1.1 deraadt 507: log("RSA key generation complete.");
508:
509: /* Schedule server key regeneration alarm. */
510: signal(SIGALRM, key_regeneration_alarm);
511: alarm(options.key_regeneration_time);
512:
513: /* Arrange to restart on SIGHUP. The handler needs listen_sock. */
514: signal(SIGHUP, sighup_handler);
515: signal(SIGTERM, sigterm_handler);
516: signal(SIGQUIT, sigterm_handler);
517:
518: /* Arrange SIGCHLD to be caught. */
519: signal(SIGCHLD, main_sigchld_handler);
520:
521: /* Stay listening for connections until the system crashes or the
522: daemon is killed with a signal. */
523: for (;;)
524: {
525: if (received_sighup)
526: sighup_restart();
527: /* Wait in accept until there is a connection. */
528: aux = sizeof(sin);
529: newsock = accept(listen_sock, (struct sockaddr *)&sin, &aux);
530: if (received_sighup)
531: sighup_restart();
532: if (newsock < 0)
533: {
534: if (errno == EINTR)
535: continue;
536: error("accept: %.100s", strerror(errno));
537: continue;
538: }
539:
540: #ifdef LIBWRAP
541: {
542: struct request_info req;
543: request_init(&req, RQ_DAEMON, av0, RQ_FILE, newsock, NULL);
544: fromhost(&req);
545: if (!hosts_access(&req))
546: {
547: error("Connection from %.500s refused by tcp_wrappers.",
548: eval_client(&req));
1.17 deraadt 549: shutdown(newsock, SHUT_RDWR);
1.1 deraadt 550: close(newsock);
551: continue;
552: }
553: /* if from inet: refuse(&req); */
554: log("connect from %.500s", eval_client(&req));
555: }
556: #endif /* LIBWRAP */
557:
558: /* Got connection. Fork a child to handle it, unless we are in
559: debugging mode. */
560: if (debug_flag)
561: {
562: /* In debugging mode. Close the listening socket, and start
563: processing the connection without forking. */
564: debug("Server will not fork when running in debugging mode.");
565: close(listen_sock);
566: sock_in = newsock;
567: sock_out = newsock;
568: pid = getpid();
569: break;
570: }
571: else
572: {
573: /* Normal production daemon. Fork, and have the child process
574: the connection. The parent continues listening. */
575: if ((pid = fork()) == 0)
576: {
577: /* Child. Close the listening socket, and start using
578: the accepted socket. Reinitialize logging (since our
579: pid has changed). We break out of the loop to handle
580: the connection. */
581: close(listen_sock);
582: sock_in = newsock;
583: sock_out = newsock;
584: log_init(av0, debug_flag && !inetd_flag,
585: options.fascist_logging || debug_flag,
586: options.quiet_mode, options.log_facility);
587: break;
588: }
589: }
590:
591: /* Parent. Stay in the loop. */
592: if (pid < 0)
593: error("fork: %.100s", strerror(errno));
594: else
595: debug("Forked child %d.", pid);
596:
597: /* Mark that the key has been used (it was "given" to the child). */
598: key_used = 1;
599:
600: /* Close the new socket (the child is now taking care of it). */
601: close(newsock);
602: }
603: }
604:
605: /* This is the child processing a new connection. */
606:
607: /* Disable the key regeneration alarm. We will not regenerate the key
608: since we are no longer in a position to give it to anyone. We will
609: not restart on SIGHUP since it no longer makes sense. */
610: alarm(0);
611: signal(SIGALRM, SIG_DFL);
612: signal(SIGHUP, SIG_DFL);
613: signal(SIGTERM, SIG_DFL);
614: signal(SIGQUIT, SIG_DFL);
615: signal(SIGCHLD, SIG_DFL);
616:
617: /* Set socket options for the connection. We want the socket to close
618: as fast as possible without waiting for anything. If the connection
619: is not a socket, these will do nothing. */
620: /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
621: linger.l_onoff = 1;
622: linger.l_linger = 5;
623: setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *)&linger, sizeof(linger));
624:
625: /* Register our connection. This turns encryption off because we do not
626: have a key. */
1.2 provos 627: packet_set_connection(sock_in, sock_out);
1.1 deraadt 628:
629: /* Log the connection. */
630: log("Connection from %.100s port %d",
631: get_remote_ipaddr(), get_remote_port());
632:
633: /* Check whether logins are denied from this host. */
634: if (options.num_deny_hosts > 0)
635: {
636: const char *hostname = get_canonical_hostname();
637: const char *ipaddr = get_remote_ipaddr();
638: int i;
639: for (i = 0; i < options.num_deny_hosts; i++)
640: if (match_pattern(hostname, options.deny_hosts[i]) ||
641: match_pattern(ipaddr, options.deny_hosts[i]))
642: {
643: log("Connection from %.200s denied.\n", hostname);
644: hostname = "You are not allowed to connect. Go away!\r\n";
645: write(sock_out, hostname, strlen(hostname));
646: close(sock_in);
647: close(sock_out);
648: exit(0);
649: }
650: }
651:
652: /* We don\'t want to listen forever unless the other side successfully
653: authenticates itself. So we set up an alarm which is cleared after
654: successful authentication. A limit of zero indicates no limit.
655: Note that we don\'t set the alarm in debugging mode; it is just annoying
656: to have the server exit just when you are about to discover the bug. */
657: signal(SIGALRM, grace_alarm_handler);
658: if (!debug_flag)
659: alarm(options.login_grace_time);
660:
661: /* Send our protocol version identification. */
1.6 deraadt 662: snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n",
1.1 deraadt 663: PROTOCOL_MAJOR, PROTOCOL_MINOR, SSH_VERSION);
664: if (write(sock_out, buf, strlen(buf)) != strlen(buf))
665: fatal("Could not write ident string.");
666:
667: /* Read other side\'s version identification. */
668: for (i = 0; i < sizeof(buf) - 1; i++)
669: {
670: if (read(sock_in, &buf[i], 1) != 1)
671: fatal("Did not receive ident string.");
672: if (buf[i] == '\r')
673: {
674: buf[i] = '\n';
675: buf[i + 1] = 0;
676: break;
677: }
678: if (buf[i] == '\n')
679: {
680: /* buf[i] == '\n' */
681: buf[i + 1] = 0;
682: break;
683: }
684: }
685: buf[sizeof(buf) - 1] = 0;
686:
687: /* Check that the versions match. In future this might accept several
688: versions and set appropriate flags to handle them. */
689: if (sscanf(buf, "SSH-%d.%d-%[^\n]\n", &remote_major, &remote_minor,
690: remote_version) != 3)
691: {
692: const char *s = "Protocol mismatch.\n";
693: (void) write(sock_out, s, strlen(s));
694: close(sock_in);
695: close(sock_out);
696: fatal("Bad protocol version identification: %.100s", buf);
697: }
698: debug("Client protocol version %d.%d; client software version %.100s",
699: remote_major, remote_minor, remote_version);
700: if (remote_major != PROTOCOL_MAJOR)
701: {
702: const char *s = "Protocol major versions differ.\n";
703: (void) write(sock_out, s, strlen(s));
704: close(sock_in);
705: close(sock_out);
706: fatal("Protocol major versions differ: %d vs. %d",
707: PROTOCOL_MAJOR, remote_major);
708: }
709:
710: /* Check that the client has sufficiently high software version. */
711: if (remote_major == 1 && remote_minor == 0)
712: packet_disconnect("Your ssh version is too old and is no longer supported. Please install a newer version.");
713:
714: /* Check whether logins are permitted from this host. */
715: if (options.num_allow_hosts > 0)
716: {
717: const char *hostname = get_canonical_hostname();
718: const char *ipaddr = get_remote_ipaddr();
719: int i;
720: for (i = 0; i < options.num_allow_hosts; i++)
721: if (match_pattern(hostname, options.allow_hosts[i]) ||
722: match_pattern(ipaddr, options.allow_hosts[i]))
723: break;
724: if (i >= options.num_allow_hosts)
725: {
726: log("Connection from %.200s not allowed.\n", hostname);
727: packet_disconnect("Sorry, you are not allowed to connect.");
728: /*NOTREACHED*/
729: }
730: }
731:
732: packet_set_nonblocking();
733:
734: /* Handle the connection. We pass as argument whether the connection
735: came from a privileged port. */
1.13 deraadt 736: do_connection(get_remote_port() < IPPORT_RESERVED);
1.1 deraadt 737:
738: #ifdef KRB4
739: /* Cleanup user's ticket cache file. */
740: if (options.kerberos_ticket_cleanup)
741: (void) dest_tkt();
742: #endif /* KRB4 */
743:
744: /* Cleanup user's local Xauthority file. */
745: if (xauthfile) unlink(xauthfile);
746:
747: /* The connection has been terminated. */
748: log("Closing connection to %.100s", inet_ntoa(sin.sin_addr));
749: packet_close();
750: exit(0);
751: }
752:
753: /* Process an incoming connection. Protocol version identifiers have already
754: been exchanged. This sends server key and performs the key exchange.
755: Server and host keys will no longer be needed after this functions. */
756:
757: void do_connection(int privileged_port)
758: {
759: int i;
1.2 provos 760: BIGNUM *session_key_int;
1.1 deraadt 761: unsigned char session_key[SSH_SESSION_KEY_LENGTH];
762: unsigned char check_bytes[8];
763: char *user;
764: unsigned int cipher_type, auth_mask, protocol_flags;
765: int plen, slen;
1.5 dugsong 766: u_int32_t rand = 0;
1.1 deraadt 767:
768: /* Generate check bytes that the client must send back in the user packet
769: in order for it to be accepted; this is used to defy ip spoofing
770: attacks. Note that this only works against somebody doing IP spoofing
771: from a remote machine; any machine on the local network can still see
772: outgoing packets and catch the random cookie. This only affects
773: rhosts authentication, and this is one of the reasons why it is
774: inherently insecure. */
1.2 provos 775: for (i = 0; i < 8; i++) {
776: if (i % 4 == 0)
777: rand = arc4random();
778: check_bytes[i] = rand & 0xff;
779: rand >>= 8;
780: }
1.1 deraadt 781:
782: /* Send our public key. We include in the packet 64 bits of random
783: data that must be matched in the reply in order to prevent IP spoofing. */
784: packet_start(SSH_SMSG_PUBLIC_KEY);
785: for (i = 0; i < 8; i++)
786: packet_put_char(check_bytes[i]);
787:
788: /* Store our public server RSA key. */
1.2 provos 789: packet_put_int(BN_num_bits(public_key->n));
790: packet_put_bignum(public_key->e);
791: packet_put_bignum(public_key->n);
1.1 deraadt 792:
793: /* Store our public host RSA key. */
1.2 provos 794: packet_put_int(BN_num_bits(sensitive_data.host_key->n));
795: packet_put_bignum(sensitive_data.host_key->e);
796: packet_put_bignum(sensitive_data.host_key->n);
1.1 deraadt 797:
798: /* Put protocol flags. */
799: packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
800:
801: /* Declare which ciphers we support. */
802: packet_put_int(cipher_mask());
803:
804: /* Declare supported authentication types. */
805: auth_mask = 0;
806: if (options.rhosts_authentication)
807: auth_mask |= 1 << SSH_AUTH_RHOSTS;
808: if (options.rhosts_rsa_authentication)
809: auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
810: if (options.rsa_authentication)
811: auth_mask |= 1 << SSH_AUTH_RSA;
812: #ifdef KRB4
1.8 dugsong 813: if (options.kerberos_authentication)
1.1 deraadt 814: auth_mask |= 1 << SSH_AUTH_KERBEROS;
815: #endif
1.5 dugsong 816: #ifdef AFS
1.1 deraadt 817: if (options.kerberos_tgt_passing)
818: auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
1.8 dugsong 819: if (options.afs_token_passing)
1.1 deraadt 820: auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
821: #endif
822: if (options.password_authentication)
823: auth_mask |= 1 << SSH_AUTH_PASSWORD;
824: packet_put_int(auth_mask);
825:
826: /* Send the packet and wait for it to be sent. */
827: packet_send();
828: packet_write_wait();
829:
830: debug("Sent %d bit public key and %d bit host key.",
1.2 provos 831: BN_num_bits(public_key->n), BN_num_bits(sensitive_data.host_key->n));
1.1 deraadt 832:
833: /* Read clients reply (cipher type and session key). */
834: packet_read_expect(&plen, SSH_CMSG_SESSION_KEY);
835:
836: /* Get cipher type. */
837: cipher_type = packet_get_char();
838:
839: /* Get check bytes from the packet. These must match those we sent earlier
840: with the public key packet. */
841: for (i = 0; i < 8; i++)
842: if (check_bytes[i] != packet_get_char())
843: packet_disconnect("IP Spoofing check bytes do not match.");
844:
845: debug("Encryption type: %.200s", cipher_name(cipher_type));
846:
847: /* Get the encrypted integer. */
1.2 provos 848: session_key_int = BN_new();
849: packet_get_bignum(session_key_int, &slen);
1.1 deraadt 850:
851: /* Get protocol flags. */
852: protocol_flags = packet_get_int();
853: packet_set_protocol_flags(protocol_flags);
854:
855: packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY);
856:
857: /* Decrypt it using our private server key and private host key (key with
858: larger modulus first). */
1.2 provos 859: if (BN_cmp(sensitive_data.private_key->n, sensitive_data.host_key->n) > 0)
1.1 deraadt 860: {
861: /* Private key has bigger modulus. */
1.2 provos 862: assert(BN_num_bits(sensitive_data.private_key->n) >=
863: BN_num_bits(sensitive_data.host_key->n) + SSH_KEY_BITS_RESERVED);
864: rsa_private_decrypt(session_key_int, session_key_int,
865: sensitive_data.private_key);
866: rsa_private_decrypt(session_key_int, session_key_int,
867: sensitive_data.host_key);
1.1 deraadt 868: }
869: else
870: {
871: /* Host key has bigger modulus (or they are equal). */
1.2 provos 872: assert(BN_num_bits(sensitive_data.host_key->n) >=
873: BN_num_bits(sensitive_data.private_key->n) +
874: SSH_KEY_BITS_RESERVED);
875: rsa_private_decrypt(session_key_int, session_key_int,
876: sensitive_data.host_key);
877: rsa_private_decrypt(session_key_int, session_key_int,
878: sensitive_data.private_key);
1.1 deraadt 879: }
880:
881: /* Compute session id for this session. */
1.2 provos 882: compute_session_id(session_id, check_bytes,
883: BN_num_bits(sensitive_data.host_key->n),
884: sensitive_data.host_key->n,
885: BN_num_bits(sensitive_data.private_key->n),
886: sensitive_data.private_key->n);
1.1 deraadt 887:
888: /* Extract session key from the decrypted integer. The key is in the
889: least significant 256 bits of the integer; the first byte of the
890: key is in the highest bits. */
1.2 provos 891: assert(BN_num_bytes(session_key_int) == sizeof(session_key));
892: BN_bn2bin(session_key_int, session_key);
1.1 deraadt 893:
894: /* Xor the first 16 bytes of the session key with the session id. */
895: for (i = 0; i < 16; i++)
896: session_key[i] ^= session_id[i];
897:
898: /* Destroy the decrypted integer. It is no longer needed. */
1.2 provos 899: BN_clear_free(session_key_int);
1.1 deraadt 900:
901: /* Set the session key. From this on all communications will be
902: encrypted. */
903: packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH,
904: cipher_type, 0);
905:
906: /* Destroy our copy of the session key. It is no longer needed. */
907: memset(session_key, 0, sizeof(session_key));
908:
909: debug("Received session key; encryption turned on.");
910:
911: /* Send an acknowledgement packet. Note that this packet is sent
912: encrypted. */
913: packet_start(SSH_SMSG_SUCCESS);
914: packet_send();
915: packet_write_wait();
916:
917: /* Get the name of the user that we wish to log in as. */
918: packet_read_expect(&plen, SSH_CMSG_USER);
919:
920: /* Get the user name. */
921: {
922: int ulen;
923: user = packet_get_string(&ulen);
924: packet_integrity_check(plen, (4 + ulen), SSH_CMSG_USER);
925: }
926:
927: /* Destroy the private and public keys. They will no longer be needed. */
1.2 provos 928: RSA_free(public_key);
929: RSA_free(sensitive_data.private_key);
930: RSA_free(sensitive_data.host_key);
1.1 deraadt 931:
1.16 deraadt 932: setproctitle("%s", user);
1.1 deraadt 933: /* Do the authentication. */
934: do_authentication(user, privileged_port);
935: }
936:
1.28 markus 937: /* Check if the user is allowed to log in via ssh. If user is listed in
938: DenyUsers or user's primary group is listed in DenyGroups, false will
939: be returned. If AllowUsers isn't empty and user isn't listed there, or
940: if AllowGroups isn't empty and user isn't listed there, false will be
941: returned. Otherwise true is returned.
942: XXX This function should also check if user has a valid shell */
943:
944: static int
945: allowed_user(struct passwd *pw)
946: {
947: struct group *grp;
948: int i;
949:
950: /* Shouldn't be called if pw is NULL, but better safe than sorry... */
951: if (!pw)
952: return 0;
953:
954: /* XXX Should check for valid login shell */
955:
956: /* Return false if user is listed in DenyUsers */
957: if (options.num_deny_users > 0)
958: {
959: if (!pw->pw_name)
960: return 0;
961: for (i = 0; i < options.num_deny_users; i++)
962: if (match_pattern(pw->pw_name, options.deny_users[i]))
963: return 0;
964: }
965:
966: /* Return false if AllowUsers isn't empty and user isn't listed there */
967: if (options.num_allow_users > 0)
968: {
969: if (!pw->pw_name)
970: return 0;
971: for (i = 0; i < options.num_allow_users; i++)
972: if (match_pattern(pw->pw_name, options.allow_users[i]))
973: break;
974: /* i < options.num_allow_users iff we break for loop */
975: if (i >= options.num_allow_users)
976: return 0;
977: }
978:
979: /* Get the primary group name if we need it. Return false if it fails */
980: if (options.num_deny_groups > 0 || options.num_allow_groups > 0 )
981: {
982: grp = getgrgid(pw->pw_gid);
983: if (!grp)
984: return 0;
985:
986: /* Return false if user's group is listed in DenyGroups */
987: if (options.num_deny_groups > 0)
988: {
989: if (!grp->gr_name)
990: return 0;
991: for (i = 0; i < options.num_deny_groups; i++)
992: if (match_pattern(grp->gr_name, options.deny_groups[i]))
993: return 0;
994: }
995:
996: /* Return false if AllowGroups isn't empty and user's group isn't
997: listed there */
998: if (options.num_allow_groups > 0)
999: {
1000: if (!grp->gr_name)
1001: return 0;
1002: for (i = 0; i < options.num_allow_groups; i++)
1003: if (match_pattern(grp->gr_name, options.allow_groups[i]))
1004: break;
1005: /* i < options.num_allow_groups iff we break for loop */
1006: if (i >= options.num_allow_groups)
1007: return 0;
1008: }
1009: }
1010:
1011: /* We found no reason not to let this user try to log on... */
1012: return 1;
1013: }
1014:
1.1 deraadt 1015: /* Performs authentication of an incoming connection. Session key has already
1016: been exchanged and encryption is enabled. User is the user name to log
1017: in as (received from the clinet). Privileged_port is true if the
1018: connection comes from a privileged port (used for .rhosts authentication).*/
1019:
1.24 markus 1020: #define MAX_AUTH_FAILURES 5
1021:
1.2 provos 1022: void
1023: do_authentication(char *user, int privileged_port)
1.1 deraadt 1024: {
1025: int type;
1026: int authenticated = 0;
1.24 markus 1027: int authentication_failures = 0;
1.1 deraadt 1028: char *password;
1029: struct passwd *pw, pwcopy;
1030: char *client_user;
1031: unsigned int client_host_key_bits;
1.2 provos 1032: BIGNUM *client_host_key_e, *client_host_key_n;
1.1 deraadt 1033:
1034: #ifdef AFS
1035: /* If machine has AFS, set process authentication group. */
1036: if (k_hasafs()) {
1037: k_setpag();
1038: k_unlog();
1039: }
1040: #endif /* AFS */
1041:
1042: /* Verify that the user is a valid user. */
1043: pw = getpwnam(user);
1.28 markus 1044: if (!pw || !allowed_user(pw))
1.1 deraadt 1045: {
1.28 markus 1046: /* The user does not exist or access is denied,
1047: but fake indication that authentication is needed. */
1.1 deraadt 1048: packet_start(SSH_SMSG_FAILURE);
1049: packet_send();
1050: packet_write_wait();
1051:
1052: /* Keep reading packets, and always respond with a failure. This is to
1053: avoid disclosing whether such a user really exists. */
1054: for (;;)
1055: {
1056: /* Read a packet. This will not return if the client disconnects. */
1057: int plen;
1.24 markus 1058: int type = packet_read(&plen);
1059: #ifdef SKEY
1060: int passw_len;
1061: char *password, *skeyinfo;
1062: if (options.password_authentication &&
1063: options.skey_authentication == 1 &&
1064: type == SSH_CMSG_AUTH_PASSWORD &&
1065: (password = packet_get_string(&passw_len)) != NULL &&
1066: passw_len == 5 &&
1067: strncasecmp(password, "s/key", 5) == 0 &&
1068: (skeyinfo = skey_fake_keyinfo(user)) != NULL ){
1069: /* Send a fake s/key challenge. */
1070: packet_send_debug(skeyinfo);
1071: }
1072: #endif
1.1 deraadt 1073: /* Send failure. This should be indistinguishable from a failed
1074: authentication. */
1075: packet_start(SSH_SMSG_FAILURE);
1076: packet_send();
1077: packet_write_wait();
1.24 markus 1078: if (++authentication_failures >= MAX_AUTH_FAILURES) {
1079: packet_disconnect("To many authentication failures for %.100s from %.200s",
1080: user, get_canonical_hostname());
1081: }
1.1 deraadt 1082: }
1083: /*NOTREACHED*/
1084: abort();
1085: }
1086:
1087: /* Take a copy of the returned structure. */
1088: memset(&pwcopy, 0, sizeof(pwcopy));
1089: pwcopy.pw_name = xstrdup(pw->pw_name);
1090: pwcopy.pw_passwd = xstrdup(pw->pw_passwd);
1091: pwcopy.pw_uid = pw->pw_uid;
1092: pwcopy.pw_gid = pw->pw_gid;
1093: pwcopy.pw_dir = xstrdup(pw->pw_dir);
1094: pwcopy.pw_shell = xstrdup(pw->pw_shell);
1095: pw = &pwcopy;
1096:
1097: /* If we are not running as root, the user must have the same uid as the
1098: server. */
1099: if (getuid() != 0 && pw->pw_uid != getuid())
1100: packet_disconnect("Cannot change user when server not running as root.");
1101:
1102: debug("Attempting authentication for %.100s.", user);
1103:
1104: /* If the user has no password, accept authentication immediately. */
1105: if (options.password_authentication &&
1106: #ifdef KRB4
1107: options.kerberos_or_local_passwd &&
1108: #endif /* KRB4 */
1.24 markus 1109: auth_password(pw, ""))
1.1 deraadt 1110: {
1111: /* Authentication with empty password succeeded. */
1112: debug("Login for user %.100s accepted without authentication.", user);
1113: /* authentication_type = SSH_AUTH_PASSWORD; */
1114: authenticated = 1;
1115: /* Success packet will be sent after loop below. */
1116: }
1117: else
1118: {
1119: /* Indicate that authentication is needed. */
1120: packet_start(SSH_SMSG_FAILURE);
1121: packet_send();
1122: packet_write_wait();
1123: }
1124:
1125: /* Loop until the user has been authenticated or the connection is closed. */
1126: while (!authenticated)
1127: {
1128: int plen;
1129: /* Get a packet from the client. */
1130: type = packet_read(&plen);
1131:
1132: /* Process the packet. */
1133: switch (type)
1134: {
1135:
1.5 dugsong 1136: #ifdef AFS
1.1 deraadt 1137: case SSH_CMSG_HAVE_KERBEROS_TGT:
1138: if (!options.kerberos_tgt_passing)
1139: {
1.5 dugsong 1140: /* packet_get_all(); */
1.1 deraadt 1141: log("Kerberos tgt passing disabled.");
1142: break;
1143: }
1.5 dugsong 1144: else {
1145: /* Accept Kerberos tgt. */
1.1 deraadt 1146: int dlen;
1.5 dugsong 1147: char *tgt = packet_get_string(&dlen);
1.1 deraadt 1148: packet_integrity_check(plen, 4 + dlen, type);
1.5 dugsong 1149: if (!auth_kerberos_tgt(pw, tgt))
1150: debug("Kerberos tgt REFUSED for %s", user);
1151: xfree(tgt);
1.1 deraadt 1152: }
1153: continue;
1.5 dugsong 1154:
1.1 deraadt 1155: case SSH_CMSG_HAVE_AFS_TOKEN:
1156: if (!options.afs_token_passing || !k_hasafs()) {
1157: /* packet_get_all(); */
1158: log("AFS token passing disabled.");
1159: break;
1160: }
1161: else {
1162: /* Accept AFS token. */
1163: int dlen;
1164: char *token_string = packet_get_string(&dlen);
1165: packet_integrity_check(plen, 4 + dlen, type);
1166: if (!auth_afs_token(user, pw->pw_uid, token_string))
1.5 dugsong 1167: debug("AFS token REFUSED for %s", user);
1.1 deraadt 1168: xfree(token_string);
1169: continue;
1170: }
1171: #endif /* AFS */
1172:
1173: #ifdef KRB4
1174: case SSH_CMSG_AUTH_KERBEROS:
1175: if (!options.kerberos_authentication)
1176: {
1.5 dugsong 1177: /* packet_get_all(); */
1.1 deraadt 1178: log("Kerberos authentication disabled.");
1179: break;
1180: }
1.5 dugsong 1181: else {
1.1 deraadt 1182: /* Try Kerberos v4 authentication. */
1183: KTEXT_ST auth;
1184: char *tkt_user = NULL;
1185: char *kdata = packet_get_string((unsigned int *)&auth.length);
1186: packet_integrity_check(plen, 4 + auth.length, type);
1187:
1.5 dugsong 1188: if (auth.length < MAX_KTXT_LEN)
1189: memcpy(auth.dat, kdata, auth.length);
1.1 deraadt 1190: xfree(kdata);
1.5 dugsong 1191:
1.1 deraadt 1192: if (auth_krb4(user, &auth, &tkt_user)) {
1193: /* Client has successfully authenticated to us. */
1.5 dugsong 1194: log("Kerberos authentication accepted %s for account "
1195: "%s from %s", tkt_user, user, get_canonical_hostname());
1.1 deraadt 1196: /* authentication_type = SSH_AUTH_KERBEROS; */
1197: authenticated = 1;
1198: xfree(tkt_user);
1199: }
1.5 dugsong 1200: else {
1201: log("Kerberos authentication failed for account "
1202: "%s from %s", user, get_canonical_hostname());
1203: }
1.1 deraadt 1204: }
1205: break;
1206: #endif /* KRB4 */
1207:
1208: case SSH_CMSG_AUTH_RHOSTS:
1209: if (!options.rhosts_authentication)
1210: {
1211: log("Rhosts authentication disabled.");
1212: break;
1213: }
1214:
1215: /* Rhosts authentication (also uses /etc/hosts.equiv). */
1216: if (!privileged_port)
1217: {
1218: log("Rhosts authentication not available for connections from unprivileged port.");
1219: break;
1220: }
1221:
1222: /* Get client user name. Note that we just have to trust the client;
1223: this is one reason why rhosts authentication is insecure.
1224: (Another is IP-spoofing on a local network.) */
1225: {
1226: int dlen;
1227: client_user = packet_get_string(&dlen);
1228: packet_integrity_check(plen, 4 + dlen, type);
1229: }
1230:
1231: /* Try to authenticate using /etc/hosts.equiv and .rhosts. */
1232: if (auth_rhosts(pw, client_user, options.ignore_rhosts,
1233: options.strict_modes))
1234: {
1235: /* Authentication accepted. */
1236: log("Rhosts authentication accepted for %.100s, remote %.100s on %.700s.",
1237: user, client_user, get_canonical_hostname());
1238: authenticated = 1;
1239: xfree(client_user);
1240: break;
1241: }
1.4 deraadt 1242: log("Rhosts authentication failed for %.100s, remote %.100s.",
1.1 deraadt 1243: user, client_user);
1244: xfree(client_user);
1245: break;
1246:
1247: case SSH_CMSG_AUTH_RHOSTS_RSA:
1248: if (!options.rhosts_rsa_authentication)
1249: {
1250: log("Rhosts with RSA authentication disabled.");
1251: break;
1252: }
1253:
1254: /* Rhosts authentication (also uses /etc/hosts.equiv) with RSA
1255: host authentication. */
1256: if (!privileged_port)
1257: {
1258: log("Rhosts authentication not available for connections from unprivileged port.");
1259: break;
1260: }
1261:
1262: {
1263: int ulen, elen, nlen;
1264: /* Get client user name. Note that we just have to trust
1265: the client; root on the client machine can claim to be
1266: any user. */
1267: client_user = packet_get_string(&ulen);
1268:
1269: /* Get the client host key. */
1.2 provos 1270: client_host_key_e = BN_new();
1271: client_host_key_n = BN_new();
1.1 deraadt 1272: client_host_key_bits = packet_get_int();
1.2 provos 1273: packet_get_bignum(client_host_key_e, &elen);
1274: packet_get_bignum(client_host_key_n, &nlen);
1.1 deraadt 1275:
1276: packet_integrity_check(plen, (4 + ulen) + 4 + elen + nlen, type);
1277: }
1278:
1279: /* Try to authenticate using /etc/hosts.equiv and .rhosts. */
1.2 provos 1280: if (auth_rhosts_rsa(pw, client_user,
1281: client_host_key_bits, client_host_key_e,
1282: client_host_key_n, options.ignore_rhosts,
1.1 deraadt 1283: options.strict_modes))
1284: {
1285: /* Authentication accepted. */
1286: authenticated = 1;
1287: xfree(client_user);
1.2 provos 1288: BN_clear_free(client_host_key_e);
1289: BN_clear_free(client_host_key_n);
1.1 deraadt 1290: break;
1291: }
1.4 deraadt 1292: log("Rhosts authentication failed for %.100s, remote %.100s.",
1.1 deraadt 1293: user, client_user);
1294: xfree(client_user);
1.2 provos 1295: BN_clear_free(client_host_key_e);
1296: BN_clear_free(client_host_key_n);
1.1 deraadt 1297: break;
1298:
1299: case SSH_CMSG_AUTH_RSA:
1300: if (!options.rsa_authentication)
1301: {
1302: log("RSA authentication disabled.");
1303: break;
1304: }
1305:
1306: /* RSA authentication requested. */
1307: {
1308: int nlen;
1.2 provos 1309: BIGNUM *n;
1310: n = BN_new();
1311: packet_get_bignum(n, &nlen);
1.1 deraadt 1312:
1313: packet_integrity_check(plen, nlen, type);
1314:
1.26 markus 1315: if (auth_rsa(pw, n, options.strict_modes))
1.1 deraadt 1316: {
1317: /* Successful authentication. */
1.2 provos 1318: BN_clear_free(n);
1.1 deraadt 1319: log("RSA authentication for %.100s accepted.", user);
1320: authenticated = 1;
1321: break;
1322: }
1.2 provos 1323: BN_clear_free(n);
1.4 deraadt 1324: log("RSA authentication for %.100s failed.", user);
1.1 deraadt 1325: }
1326: break;
1327:
1328: case SSH_CMSG_AUTH_PASSWORD:
1329: if (!options.password_authentication)
1330: {
1331: log("Password authentication disabled.");
1332: break;
1333: }
1334:
1335: /* Password authentication requested. */
1336: /* Read user password. It is in plain text, but was transmitted
1337: over the encrypted channel so it is not visible to an outside
1338: observer. */
1339: {
1340: int passw_len;
1341: password = packet_get_string(&passw_len);
1342: packet_integrity_check(plen, 4 + passw_len, type);
1343: }
1344:
1345: /* Try authentication with the password. */
1.24 markus 1346: if (auth_password(pw, password))
1.1 deraadt 1347: {
1348: /* Successful authentication. */
1349: /* Clear the password from memory. */
1350: memset(password, 0, strlen(password));
1351: xfree(password);
1352: log("Password authentication for %.100s accepted.", user);
1353: authenticated = 1;
1354: break;
1355: }
1.4 deraadt 1356: log("Password authentication for %.100s failed.", user);
1.1 deraadt 1357: memset(password, 0, strlen(password));
1358: xfree(password);
1359: break;
1360:
1361: default:
1362: /* Any unknown messages will be ignored (and failure returned)
1363: during authentication. */
1364: log("Unknown message during authentication: type %d", type);
1365: break; /* Respond with a failure message. */
1366: }
1367: /* If successfully authenticated, break out of loop. */
1368: if (authenticated)
1369: break;
1370:
1371: /* Send a message indicating that the authentication attempt failed. */
1372: packet_start(SSH_SMSG_FAILURE);
1373: packet_send();
1374: packet_write_wait();
1.24 markus 1375:
1376: if (++authentication_failures >= MAX_AUTH_FAILURES) {
1377: packet_disconnect("To many authentication failures for %.100s from %.200s",
1378: pw->pw_name, get_canonical_hostname());
1379: }
1.1 deraadt 1380: }
1381:
1382: /* Check if the user is logging in as root and root logins are disallowed. */
1383: if (pw->pw_uid == 0 && !options.permit_root_login)
1384: {
1385: if (forced_command)
1386: log("Root login accepted for forced command.", forced_command);
1387: else
1388: packet_disconnect("ROOT LOGIN REFUSED FROM %.200s",
1389: get_canonical_hostname());
1390: }
1391:
1392: /* The user has been authenticated and accepted. */
1393: packet_start(SSH_SMSG_SUCCESS);
1394: packet_send();
1395: packet_write_wait();
1396:
1397: /* Perform session preparation. */
1398: do_authenticated(pw);
1399: }
1400:
1401: /* Prepares for an interactive session. This is called after the user has
1402: been successfully authenticated. During this message exchange, pseudo
1403: terminals are allocated, X11, TCP/IP, and authentication agent forwardings
1404: are requested, etc. */
1405:
1406: void do_authenticated(struct passwd *pw)
1407: {
1408: int type;
1409: int compression_level = 0, enable_compression_after_reply = 0;
1.20 dugsong 1410: int have_pty = 0, ptyfd = -1, ttyfd = -1, xauthfd = -1;
1.1 deraadt 1411: int row, col, xpixel, ypixel, screen;
1412: char ttyname[64];
1413: char *command, *term = NULL, *display = NULL, *proto = NULL, *data = NULL;
1414: struct group *grp;
1415: gid_t tty_gid;
1416: mode_t tty_mode;
1417: int n_bytes;
1418:
1419: /* Cancel the alarm we set to limit the time taken for authentication. */
1420: alarm(0);
1421:
1422: /* Inform the channel mechanism that we are the server side and that
1423: the client may request to connect to any port at all. (The user could
1424: do it anyway, and we wouldn\'t know what is permitted except by the
1425: client telling us, so we can equally well trust the client not to request
1426: anything bogus.) */
1427: channel_permit_all_opens();
1428:
1429: /* We stay in this loop until the client requests to execute a shell or a
1430: command. */
1431: while (1)
1432: {
1433: int plen, dlen;
1434:
1435: /* Get a packet from the client. */
1436: type = packet_read(&plen);
1437:
1438: /* Process the packet. */
1439: switch (type)
1440: {
1441: case SSH_CMSG_REQUEST_COMPRESSION:
1442: packet_integrity_check(plen, 4, type);
1443: compression_level = packet_get_int();
1444: if (compression_level < 1 || compression_level > 9)
1445: {
1446: packet_send_debug("Received illegal compression level %d.",
1447: compression_level);
1448: goto fail;
1449: }
1450: /* Enable compression after we have responded with SUCCESS. */
1451: enable_compression_after_reply = 1;
1452: break;
1453:
1454: case SSH_CMSG_REQUEST_PTY:
1455: if (no_pty_flag)
1456: {
1457: debug("Allocating a pty not permitted for this authentication.");
1458: goto fail;
1459: }
1460: if (have_pty)
1461: packet_disconnect("Protocol error: you already have a pty.");
1462:
1463: debug("Allocating pty.");
1464:
1465: /* Allocate a pty and open it. */
1466: if (!pty_allocate(&ptyfd, &ttyfd, ttyname))
1467: {
1468: error("Failed to allocate pty.");
1469: goto fail;
1470: }
1471:
1472: /* Determine the group to make the owner of the tty. */
1473: grp = getgrnam("tty");
1474: if (grp)
1475: {
1476: tty_gid = grp->gr_gid;
1477: tty_mode = S_IRUSR|S_IWUSR|S_IWGRP;
1478: }
1479: else
1480: {
1481: tty_gid = pw->pw_gid;
1482: tty_mode = S_IRUSR|S_IWUSR|S_IWGRP|S_IWOTH;
1483: }
1484:
1485: /* Change ownership of the tty. */
1486: if (chown(ttyname, pw->pw_uid, tty_gid) < 0)
1487: fatal("chown(%.100s, %d, %d) failed: %.100s",
1488: ttyname, pw->pw_uid, tty_gid, strerror(errno));
1489: if (chmod(ttyname, tty_mode) < 0)
1490: fatal("chmod(%.100s, 0%o) failed: %.100s",
1491: ttyname, tty_mode, strerror(errno));
1492:
1493: /* Get TERM from the packet. Note that the value may be of arbitrary
1494: length. */
1495:
1496: term = packet_get_string(&dlen);
1497: packet_integrity_check(dlen, strlen(term), type);
1498: /* packet_integrity_check(plen, 4 + dlen + 4*4 + n_bytes, type); */
1499: /* Remaining bytes */
1500: n_bytes = plen - (4 + dlen + 4*4);
1501:
1502: if (strcmp(term, "") == 0)
1503: term = NULL;
1504:
1505: /* Get window size from the packet. */
1506: row = packet_get_int();
1507: col = packet_get_int();
1508: xpixel = packet_get_int();
1509: ypixel = packet_get_int();
1510: pty_change_window_size(ptyfd, row, col, xpixel, ypixel);
1511:
1512: /* Get tty modes from the packet. */
1513: tty_parse_modes(ttyfd, &n_bytes);
1514: packet_integrity_check(plen, 4 + dlen + 4*4 + n_bytes, type);
1515:
1516: /* Indicate that we now have a pty. */
1517: have_pty = 1;
1518: break;
1519:
1520: case SSH_CMSG_X11_REQUEST_FORWARDING:
1521: if (!options.x11_forwarding)
1522: {
1523: packet_send_debug("X11 forwarding disabled in server configuration file.");
1524: goto fail;
1525: }
1526: #ifdef XAUTH_PATH
1527: if (no_x11_forwarding_flag)
1528: {
1529: packet_send_debug("X11 forwarding not permitted for this authentication.");
1530: goto fail;
1531: }
1532: debug("Received request for X11 forwarding with auth spoofing.");
1533: if (display)
1534: packet_disconnect("Protocol error: X11 display already set.");
1535: {
1536: int proto_len, data_len;
1537: proto = packet_get_string(&proto_len);
1538: data = packet_get_string(&data_len);
1539: packet_integrity_check(plen, 4+proto_len + 4+data_len + 4, type);
1540: }
1541: if (packet_get_protocol_flags() & SSH_PROTOFLAG_SCREEN_NUMBER)
1542: screen = packet_get_int();
1543: else
1544: screen = 0;
1545: display = x11_create_display_inet(screen);
1546: if (!display)
1547: goto fail;
1548:
1549: /* Setup to always have a local .Xauthority. */
1550: xauthfile = xmalloc(MAXPATHLEN);
1.20 dugsong 1551: snprintf(xauthfile, MAXPATHLEN, "/tmp/XauthXXXXXX");
1552:
1553: if ((xauthfd = mkstemp(xauthfile)) != -1) {
1554: fchown(xauthfd, pw->pw_uid, pw->pw_gid);
1555: close(xauthfd);
1556: }
1557: else {
1558: xfree(xauthfile);
1.21 dugsong 1559: xauthfile = NULL;
1.20 dugsong 1560: }
1.1 deraadt 1561: break;
1562: #else /* XAUTH_PATH */
1563: /* No xauth program; we won't accept forwarding with spoofing. */
1564: packet_send_debug("No xauth program; cannot forward with spoofing.");
1565: goto fail;
1566: #endif /* XAUTH_PATH */
1567:
1568: case SSH_CMSG_AGENT_REQUEST_FORWARDING:
1569: if (no_agent_forwarding_flag)
1570: {
1571: debug("Authentication agent forwarding not permitted for this authentication.");
1572: goto fail;
1573: }
1574: debug("Received authentication agent forwarding request.");
1575: auth_input_request_forwarding(pw);
1576: break;
1577:
1578: case SSH_CMSG_PORT_FORWARD_REQUEST:
1579: if (no_port_forwarding_flag)
1580: {
1581: debug("Port forwarding not permitted for this authentication.");
1582: goto fail;
1583: }
1584: debug("Received TCP/IP port forwarding request.");
1585: channel_input_port_forward_request(pw->pw_uid == 0);
1586: break;
1587:
1588: case SSH_CMSG_EXEC_SHELL:
1589: /* Set interactive/non-interactive mode. */
1590: packet_set_interactive(have_pty || display != NULL,
1591: options.keepalives);
1592:
1593: if (forced_command != NULL)
1594: goto do_forced_command;
1595: debug("Forking shell.");
1596: packet_integrity_check(plen, 0, type);
1597: if (have_pty)
1598: do_exec_pty(NULL, ptyfd, ttyfd, ttyname, pw, term, display, proto,
1599: data);
1600: else
1601: do_exec_no_pty(NULL, pw, display, proto, data);
1602: return;
1603:
1604: case SSH_CMSG_EXEC_CMD:
1605: /* Set interactive/non-interactive mode. */
1606: packet_set_interactive(have_pty || display != NULL,
1607: options.keepalives);
1608:
1609: if (forced_command != NULL)
1610: goto do_forced_command;
1611: /* Get command from the packet. */
1612: {
1613: int dlen;
1614: command = packet_get_string(&dlen);
1615: debug("Executing command '%.500s'", command);
1616: packet_integrity_check(plen, 4 + dlen, type);
1617: }
1618: if (have_pty)
1619: do_exec_pty(command, ptyfd, ttyfd, ttyname, pw, term, display,
1620: proto, data);
1621: else
1622: do_exec_no_pty(command, pw, display, proto, data);
1623: xfree(command);
1624: return;
1625:
1626: default:
1627: /* Any unknown messages in this phase are ignored, and a failure
1628: message is returned. */
1629: log("Unknown packet type received after authentication: %d", type);
1630: goto fail;
1631: }
1632:
1633: /* The request was successfully processed. */
1634: packet_start(SSH_SMSG_SUCCESS);
1635: packet_send();
1636: packet_write_wait();
1637:
1638: /* Enable compression now that we have replied if appropriate. */
1639: if (enable_compression_after_reply)
1640: {
1641: enable_compression_after_reply = 0;
1642: packet_start_compression(compression_level);
1643: }
1644:
1645: continue;
1646:
1647: fail:
1648: /* The request failed. */
1649: packet_start(SSH_SMSG_FAILURE);
1650: packet_send();
1651: packet_write_wait();
1652: continue;
1653:
1654: do_forced_command:
1655: /* There is a forced command specified for this login. Execute it. */
1656: debug("Executing forced command: %.900s", forced_command);
1657: if (have_pty)
1658: do_exec_pty(forced_command, ptyfd, ttyfd, ttyname, pw, term, display,
1659: proto, data);
1660: else
1661: do_exec_no_pty(forced_command, pw, display, proto, data);
1662: return;
1663: }
1664: }
1665:
1666: /* This is called to fork and execute a command when we have no tty. This
1667: will call do_child from the child, and server_loop from the parent after
1668: setting up file descriptors and such. */
1669:
1670: void do_exec_no_pty(const char *command, struct passwd *pw,
1671: const char *display, const char *auth_proto,
1672: const char *auth_data)
1673: {
1674: int pid;
1675:
1676: #ifdef USE_PIPES
1677: int pin[2], pout[2], perr[2];
1678: /* Allocate pipes for communicating with the program. */
1679: if (pipe(pin) < 0 || pipe(pout) < 0 || pipe(perr) < 0)
1680: packet_disconnect("Could not create pipes: %.100s",
1681: strerror(errno));
1682: #else /* USE_PIPES */
1683: int inout[2], err[2];
1684: /* Uses socket pairs to communicate with the program. */
1685: if (socketpair(AF_UNIX, SOCK_STREAM, 0, inout) < 0 ||
1686: socketpair(AF_UNIX, SOCK_STREAM, 0, err) < 0)
1687: packet_disconnect("Could not create socket pairs: %.100s",
1688: strerror(errno));
1689: #endif /* USE_PIPES */
1690:
1.16 deraadt 1691: setproctitle("%s@notty", pw->pw_name);
1692:
1.1 deraadt 1693: /* Fork the child. */
1694: if ((pid = fork()) == 0)
1695: {
1696: /* Child. Reinitialize the log since the pid has changed. */
1697: log_init(av0, debug_flag && !inetd_flag, debug_flag,
1698: options.quiet_mode, options.log_facility);
1699:
1.29 ! deraadt 1700: /* Create a new session and process group since the 4.4BSD setlogin()
! 1701: affects the entire process group. */
! 1702: if (setsid() < 0)
! 1703: error("setsid failed: %.100s", strerror(errno));
! 1704:
1.1 deraadt 1705: #ifdef USE_PIPES
1706: /* Redirect stdin. We close the parent side of the socket pair,
1707: and make the child side the standard input. */
1708: close(pin[1]);
1709: if (dup2(pin[0], 0) < 0)
1710: perror("dup2 stdin");
1711: close(pin[0]);
1712:
1713: /* Redirect stdout. */
1714: close(pout[0]);
1715: if (dup2(pout[1], 1) < 0)
1716: perror("dup2 stdout");
1717: close(pout[1]);
1718:
1719: /* Redirect stderr. */
1720: close(perr[0]);
1721: if (dup2(perr[1], 2) < 0)
1722: perror("dup2 stderr");
1723: close(perr[1]);
1724: #else /* USE_PIPES */
1725: /* Redirect stdin, stdout, and stderr. Stdin and stdout will use the
1726: same socket, as some programs (particularly rdist) seem to depend
1727: on it. */
1728: close(inout[1]);
1729: close(err[1]);
1730: if (dup2(inout[0], 0) < 0) /* stdin */
1731: perror("dup2 stdin");
1732: if (dup2(inout[0], 1) < 0) /* stdout. Note: same socket as stdin. */
1733: perror("dup2 stdout");
1734: if (dup2(err[0], 2) < 0) /* stderr */
1735: perror("dup2 stderr");
1736: #endif /* USE_PIPES */
1737:
1738: /* Do processing for the child (exec command etc). */
1739: do_child(command, pw, NULL, display, auth_proto, auth_data, NULL);
1740: /*NOTREACHED*/
1741: }
1742: if (pid < 0)
1743: packet_disconnect("fork failed: %.100s", strerror(errno));
1744: #ifdef USE_PIPES
1745: /* We are the parent. Close the child sides of the pipes. */
1746: close(pin[0]);
1747: close(pout[1]);
1748: close(perr[1]);
1749:
1750: /* Enter the interactive session. */
1751: server_loop(pid, pin[1], pout[0], perr[0]);
1752: /* server_loop has closed pin[1], pout[1], and perr[1]. */
1753: #else /* USE_PIPES */
1754: /* We are the parent. Close the child sides of the socket pairs. */
1755: close(inout[0]);
1756: close(err[0]);
1757:
1758: /* Enter the interactive session. Note: server_loop must be able to handle
1759: the case that fdin and fdout are the same. */
1760: server_loop(pid, inout[1], inout[1], err[1]);
1761: /* server_loop has closed inout[1] and err[1]. */
1762: #endif /* USE_PIPES */
1763: }
1764:
1765: struct pty_cleanup_context
1766: {
1767: const char *ttyname;
1768: int pid;
1769: };
1770:
1771: /* Function to perform cleanup if we get aborted abnormally (e.g., due to a
1772: dropped connection). */
1773:
1774: void pty_cleanup_proc(void *context)
1775: {
1776: struct pty_cleanup_context *cu = context;
1777:
1778: debug("pty_cleanup_proc called");
1779:
1.5 dugsong 1780: #if defined(KRB4)
1.1 deraadt 1781: /* Destroy user's ticket cache file. */
1782: (void) dest_tkt();
1.5 dugsong 1783: #endif /* KRB4 */
1.1 deraadt 1784:
1785: /* Record that the user has logged out. */
1786: record_logout(cu->pid, cu->ttyname);
1787:
1788: /* Release the pseudo-tty. */
1789: pty_release(cu->ttyname);
1790: }
1791:
1792: /* This is called to fork and execute a command when we have a tty. This
1793: will call do_child from the child, and server_loop from the parent after
1794: setting up file descriptors, controlling tty, updating wtmp, utmp,
1795: lastlog, and other such operations. */
1796:
1797: void do_exec_pty(const char *command, int ptyfd, int ttyfd,
1798: const char *ttyname, struct passwd *pw, const char *term,
1799: const char *display, const char *auth_proto,
1800: const char *auth_data)
1801: {
1802: int pid, fdout;
1803: const char *hostname;
1804: time_t last_login_time;
1805: char buf[100], *time_string;
1806: FILE *f;
1807: char line[256];
1808: struct stat st;
1809: int quiet_login;
1810: struct sockaddr_in from;
1811: int fromlen;
1812: struct pty_cleanup_context cleanup_context;
1813:
1814: /* Get remote host name. */
1815: hostname = get_canonical_hostname();
1816:
1817: /* Get the time when the user last logged in. Buf will be set to contain
1818: the hostname the last login was from. */
1.27 markus 1819: if(!options.use_login) {
1820: last_login_time = get_last_login_time(pw->pw_uid, pw->pw_name,
1821: buf, sizeof(buf));
1822: }
1.16 deraadt 1823:
1824: setproctitle("%s@%s", pw->pw_name, strrchr(ttyname, '/') + 1);
1.1 deraadt 1825:
1826: /* Fork the child. */
1827: if ((pid = fork()) == 0)
1828: {
1829: pid = getpid();
1830:
1831: /* Child. Reinitialize the log because the pid has changed. */
1832: log_init(av0, debug_flag && !inetd_flag, debug_flag, options.quiet_mode,
1833: options.log_facility);
1834:
1835: /* Close the master side of the pseudo tty. */
1836: close(ptyfd);
1837:
1838: /* Make the pseudo tty our controlling tty. */
1839: pty_make_controlling_tty(&ttyfd, ttyname);
1840:
1841: /* Redirect stdin from the pseudo tty. */
1842: if (dup2(ttyfd, fileno(stdin)) < 0)
1843: error("dup2 stdin failed: %.100s", strerror(errno));
1844:
1845: /* Redirect stdout to the pseudo tty. */
1846: if (dup2(ttyfd, fileno(stdout)) < 0)
1847: error("dup2 stdin failed: %.100s", strerror(errno));
1848:
1849: /* Redirect stderr to the pseudo tty. */
1850: if (dup2(ttyfd, fileno(stderr)) < 0)
1851: error("dup2 stdin failed: %.100s", strerror(errno));
1852:
1853: /* Close the extra descriptor for the pseudo tty. */
1854: close(ttyfd);
1855:
1856: /* Get IP address of client. This is needed because we want to record
1857: where the user logged in from. If the connection is not a socket,
1858: let the ip address be 0.0.0.0. */
1859: memset(&from, 0, sizeof(from));
1860: if (packet_get_connection_in() == packet_get_connection_out())
1861: {
1862: fromlen = sizeof(from);
1863: if (getpeername(packet_get_connection_in(),
1864: (struct sockaddr *)&from, &fromlen) < 0)
1865: fatal("getpeername: %.100s", strerror(errno));
1866: }
1867:
1868: /* Record that there was a login on that terminal. */
1869: record_login(pid, ttyname, pw->pw_name, pw->pw_uid, hostname,
1870: &from);
1871:
1872: /* Check if .hushlogin exists. */
1.6 deraadt 1873: snprintf(line, sizeof line, "%.200s/.hushlogin", pw->pw_dir);
1.1 deraadt 1874: quiet_login = stat(line, &st) >= 0;
1875:
1876: /* If the user has logged in before, display the time of last login.
1877: However, don't display anything extra if a command has been
1878: specified (so that ssh can be used to execute commands on a remote
1.27 markus 1879: machine without users knowing they are going to another machine).
1880: Login(1) will do this for us as well, so check if login(1) is used */
1881: if (command == NULL && last_login_time != 0 && !quiet_login &&
1882: !options.use_login)
1.1 deraadt 1883: {
1884: /* Convert the date to a string. */
1885: time_string = ctime(&last_login_time);
1886: /* Remove the trailing newline. */
1887: if (strchr(time_string, '\n'))
1888: *strchr(time_string, '\n') = 0;
1889: /* Display the last login time. Host if displayed if known. */
1890: if (strcmp(buf, "") == 0)
1891: printf("Last login: %s\r\n", time_string);
1892: else
1893: printf("Last login: %s from %s\r\n", time_string, buf);
1894: }
1895:
1896: /* Print /etc/motd unless a command was specified or printing it was
1.27 markus 1897: disabled in server options or login(1) will be used. Note that
1898: some machines appear to print it in /etc/profile or similar. */
1899: if (command == NULL && options.print_motd && !quiet_login &&
1900: !options.use_login)
1.1 deraadt 1901: {
1902: /* Print /etc/motd if it exists. */
1903: f = fopen("/etc/motd", "r");
1904: if (f)
1905: {
1906: while (fgets(line, sizeof(line), f))
1907: fputs(line, stdout);
1908: fclose(f);
1909: }
1910: }
1911:
1912: /* Do common processing for the child, such as execing the command. */
1913: do_child(command, pw, term, display, auth_proto, auth_data, ttyname);
1914: /*NOTREACHED*/
1915: }
1916: if (pid < 0)
1917: packet_disconnect("fork failed: %.100s", strerror(errno));
1918: /* Parent. Close the slave side of the pseudo tty. */
1919: close(ttyfd);
1920:
1921: /* Create another descriptor of the pty master side for use as the standard
1922: input. We could use the original descriptor, but this simplifies code
1923: in server_loop. The descriptor is bidirectional. */
1924: fdout = dup(ptyfd);
1925: if (fdout < 0)
1926: packet_disconnect("dup failed: %.100s", strerror(errno));
1927:
1928: /* Add a cleanup function to clear the utmp entry and record logout time
1929: in case we call fatal() (e.g., the connection gets closed). */
1930: cleanup_context.pid = pid;
1931: cleanup_context.ttyname = ttyname;
1932: fatal_add_cleanup(pty_cleanup_proc, (void *)&cleanup_context);
1933:
1934: /* Enter interactive session. */
1935: server_loop(pid, ptyfd, fdout, -1);
1936: /* server_loop has not closed ptyfd and fdout. */
1937:
1938: /* Cancel the cleanup function. */
1939: fatal_remove_cleanup(pty_cleanup_proc, (void *)&cleanup_context);
1940:
1941: /* Record that the user has logged out. */
1942: record_logout(pid, ttyname);
1943:
1944: /* Release the pseudo-tty. */
1945: pty_release(ttyname);
1946:
1947: /* Close the server side of the socket pairs. We must do this after the
1948: pty cleanup, so that another process doesn't get this pty while we're
1949: still cleaning up. */
1950: close(ptyfd);
1951: close(fdout);
1952: }
1953:
1954: /* Sets the value of the given variable in the environment. If the variable
1955: already exists, its value is overriden. */
1956:
1957: void child_set_env(char ***envp, unsigned int *envsizep, const char *name,
1958: const char *value)
1959: {
1960: unsigned int i, namelen;
1961: char **env;
1962:
1963: /* Find the slot where the value should be stored. If the variable already
1964: exists, we reuse the slot; otherwise we append a new slot at the end
1965: of the array, expanding if necessary. */
1966: env = *envp;
1967: namelen = strlen(name);
1968: for (i = 0; env[i]; i++)
1969: if (strncmp(env[i], name, namelen) == 0 && env[i][namelen] == '=')
1970: break;
1971: if (env[i])
1972: {
1973: /* Name already exists. Reuse the slot. */
1974: xfree(env[i]);
1975: }
1976: else
1977: {
1978: /* New variable. Expand the array if necessary. */
1979: if (i >= (*envsizep) - 1)
1980: {
1981: (*envsizep) += 50;
1982: env = (*envp) = xrealloc(env, (*envsizep) * sizeof(char *));
1983: }
1984:
1985: /* Need to set the NULL pointer at end of array beyond the new
1986: slot. */
1987: env[i + 1] = NULL;
1988: }
1989:
1990: /* Allocate space and format the variable in the appropriate slot. */
1991: env[i] = xmalloc(strlen(name) + 1 + strlen(value) + 1);
1.6 deraadt 1992: snprintf(env[i], strlen(name) + 1 + strlen(value) + 1, "%s=%s", name, value);
1.1 deraadt 1993: }
1994:
1995: /* Reads environment variables from the given file and adds/overrides them
1996: into the environment. If the file does not exist, this does nothing.
1997: Otherwise, it must consist of empty lines, comments (line starts with '#')
1998: and assignments of the form name=value. No other forms are allowed. */
1999:
2000: void read_environment_file(char ***env, unsigned int *envsize,
2001: const char *filename)
2002: {
2003: FILE *f;
2004: char buf[4096];
2005: char *cp, *value;
2006:
2007: /* Open the environment file. */
2008: f = fopen(filename, "r");
2009: if (!f)
2010: return; /* Not found. */
2011:
2012: /* Process each line. */
2013: while (fgets(buf, sizeof(buf), f))
2014: {
2015: /* Skip leading whitespace. */
2016: for (cp = buf; *cp == ' ' || *cp == '\t'; cp++)
2017: ;
2018:
2019: /* Ignore empty and comment lines. */
2020: if (!*cp || *cp == '#' || *cp == '\n')
2021: continue;
2022:
2023: /* Remove newline. */
2024: if (strchr(cp, '\n'))
2025: *strchr(cp, '\n') = '\0';
2026:
2027: /* Find the equals sign. Its lack indicates badly formatted line. */
2028: value = strchr(cp, '=');
2029: if (value == NULL)
2030: {
2031: fprintf(stderr, "Bad line in %.100s: %.200s\n", filename, buf);
2032: continue;
2033: }
2034:
2035: /* Replace the equals sign by nul, and advance value to the value
2036: string. */
2037: *value = '\0';
2038: value++;
2039:
2040: /* Set the value in environment. */
2041: child_set_env(env, envsize, cp, value);
2042: }
2043:
2044: fclose(f);
2045: }
2046:
2047: /* Performs common processing for the child, such as setting up the
2048: environment, closing extra file descriptors, setting the user and group
2049: ids, and executing the command or shell. */
2050:
2051: void do_child(const char *command, struct passwd *pw, const char *term,
2052: const char *display, const char *auth_proto,
2053: const char *auth_data, const char *ttyname)
2054: {
2055: const char *shell, *cp;
2056: char buf[256];
2057: FILE *f;
2058: unsigned int envsize, i;
2059: char **env;
2060: extern char **environ;
2061: struct stat st;
2062: char *argv[10];
2063:
2064: /* Check /etc/nologin. */
2065: f = fopen("/etc/nologin", "r");
2066: if (f)
2067: { /* /etc/nologin exists. Print its contents and exit. */
2068: while (fgets(buf, sizeof(buf), f))
2069: fputs(buf, stderr);
2070: fclose(f);
2071: if (pw->pw_uid != 0)
2072: exit(254);
2073: }
2074:
2075: /* Set login name in the kernel. */
1.29 ! deraadt 2076: if (setlogin(pw->pw_name) < 0)
! 2077: error("setlogin failed: %s", strerror(errno));
1.1 deraadt 2078:
2079: /* Set uid, gid, and groups. */
1.27 markus 2080: /* Login(1) does this as well, and it needs uid 0 for the "-h" switch,
2081: so we let login(1) to this for us. */
2082: if(!options.use_login) {
2083: if (getuid() == 0 || geteuid() == 0)
2084: {
2085: if (setgid(pw->pw_gid) < 0)
2086: {
2087: perror("setgid");
2088: exit(1);
2089: }
2090: /* Initialize the group list. */
2091: if (initgroups(pw->pw_name, pw->pw_gid) < 0)
2092: {
2093: perror("initgroups");
2094: exit(1);
2095: }
2096: endgrent();
2097:
2098: /* Permanently switch to the desired uid. */
2099: permanently_set_uid(pw->pw_uid);
2100: }
2101:
2102: if (getuid() != pw->pw_uid || geteuid() != pw->pw_uid)
2103: fatal("Failed to set uids to %d.", (int)pw->pw_uid);
2104: }
1.1 deraadt 2105:
2106: /* Get the shell from the password data. An empty shell field is legal,
2107: and means /bin/sh. */
1.9 deraadt 2108: shell = (pw->pw_shell[0] == '\0') ? _PATH_BSHELL : pw->pw_shell;
1.1 deraadt 2109:
2110: #ifdef AFS
2111: /* Try to get AFS tokens for the local cell. */
2112: if (k_hasafs()) {
2113: char cell[64];
2114:
2115: if (k_afs_cell_of_file(pw->pw_dir, cell, sizeof(cell)) == 0)
2116: krb_afslog(cell, 0);
2117:
2118: krb_afslog(0, 0);
2119: }
2120: #endif /* AFS */
2121:
2122: /* Initialize the environment. In the first part we allocate space for
2123: all environment variables. */
2124: envsize = 100;
2125: env = xmalloc(envsize * sizeof(char *));
2126: env[0] = NULL;
2127:
1.27 markus 2128: if(!options.use_login) {
2129: /* Set basic environment. */
2130: child_set_env(&env, &envsize, "USER", pw->pw_name);
2131: child_set_env(&env, &envsize, "LOGNAME", pw->pw_name);
2132: child_set_env(&env, &envsize, "HOME", pw->pw_dir);
2133: child_set_env(&env, &envsize, "PATH", _PATH_STDPATH);
2134:
2135: snprintf(buf, sizeof buf, "%.200s/%.50s",
2136: _PATH_MAILDIR, pw->pw_name);
2137: child_set_env(&env, &envsize, "MAIL", buf);
2138:
2139: /* Normal systems set SHELL by default. */
2140: child_set_env(&env, &envsize, "SHELL", shell);
2141: }
1.1 deraadt 2142:
2143: /* Let it inherit timezone if we have one. */
2144: if (getenv("TZ"))
2145: child_set_env(&env, &envsize, "TZ", getenv("TZ"));
2146:
2147: /* Set custom environment options from RSA authentication. */
2148: while (custom_environment)
2149: {
2150: struct envstring *ce = custom_environment;
2151: char *s = ce->s;
2152: int i;
2153: for (i = 0; s[i] != '=' && s[i]; i++)
2154: ;
2155: if (s[i] == '=')
2156: {
2157: s[i] = 0;
2158: child_set_env(&env, &envsize, s, s + i + 1);
2159: }
2160: custom_environment = ce->next;
2161: xfree(ce->s);
2162: xfree(ce);
2163: }
2164:
2165: /* Set SSH_CLIENT. */
1.6 deraadt 2166: snprintf(buf, sizeof buf, "%.50s %d %d",
1.1 deraadt 2167: get_remote_ipaddr(), get_remote_port(), options.port);
2168: child_set_env(&env, &envsize, "SSH_CLIENT", buf);
2169:
2170: /* Set SSH_TTY if we have a pty. */
2171: if (ttyname)
2172: child_set_env(&env, &envsize, "SSH_TTY", ttyname);
2173:
2174: /* Set TERM if we have a pty. */
2175: if (term)
2176: child_set_env(&env, &envsize, "TERM", term);
2177:
2178: /* Set DISPLAY if we have one. */
2179: if (display)
2180: child_set_env(&env, &envsize, "DISPLAY", display);
2181:
1.5 dugsong 2182: #ifdef KRB4
1.1 deraadt 2183: if (ticket)
2184: child_set_env(&env, &envsize, "KRBTKFILE", ticket);
2185: #endif /* KRB4 */
2186:
2187: /* Set XAUTHORITY to always be a local file. */
2188: if (xauthfile)
2189: child_set_env(&env, &envsize, "XAUTHORITY", xauthfile);
2190:
2191: /* Set variable for forwarded authentication connection, if we have one. */
1.19 markus 2192: if (auth_get_socket_name() != NULL)
2193: child_set_env(&env, &envsize, SSH_AUTHSOCKET_ENV_NAME,
2194: auth_get_socket_name());
1.1 deraadt 2195:
2196: /* Read $HOME/.ssh/environment. */
1.27 markus 2197: if(!options.use_login) {
2198: snprintf(buf, sizeof buf, "%.200s/.ssh/environment", pw->pw_dir);
2199: read_environment_file(&env, &envsize, buf);
2200: }
1.1 deraadt 2201:
2202: /* If debugging, dump the environment to stderr. */
2203: if (debug_flag)
2204: {
2205: fprintf(stderr, "Environment:\n");
2206: for (i = 0; env[i]; i++)
2207: fprintf(stderr, " %.200s\n", env[i]);
2208: }
2209:
2210: /* Close the connection descriptors; note that this is the child, and the
2211: server will still have the socket open, and it is important that we
2212: do not shutdown it. Note that the descriptors cannot be closed before
2213: building the environment, as we call get_remote_ipaddr there. */
2214: if (packet_get_connection_in() == packet_get_connection_out())
2215: close(packet_get_connection_in());
2216: else
2217: {
2218: close(packet_get_connection_in());
2219: close(packet_get_connection_out());
2220: }
2221: /* Close all descriptors related to channels. They will still remain
2222: open in the parent. */
2223: channel_close_all();
2224:
2225: /* Close any extra file descriptors. Note that there may still be
2226: descriptors left by system functions. They will be closed later. */
2227: endpwent();
2228: endhostent();
2229:
2230: /* Close any extra open file descriptors so that we don\'t have them
2231: hanging around in clients. Note that we want to do this after
2232: initgroups, because at least on Solaris 2.3 it leaves file descriptors
2233: open. */
2234: for (i = 3; i < 64; i++)
1.22 markus 2235: close(i);
1.1 deraadt 2236:
2237: /* Change current directory to the user\'s home directory. */
2238: if (chdir(pw->pw_dir) < 0)
2239: fprintf(stderr, "Could not chdir to home directory %s: %s\n",
2240: pw->pw_dir, strerror(errno));
2241:
2242: /* Must take new environment into use so that .ssh/rc, /etc/sshrc and
2243: xauth are run in the proper environment. */
2244: environ = env;
2245:
2246: /* Run $HOME/.ssh/rc, /etc/sshrc, or xauth (whichever is found first
2247: in this order). */
1.27 markus 2248: if(!options.use_login) {
2249: if (stat(SSH_USER_RC, &st) >= 0)
1.1 deraadt 2250: {
1.27 markus 2251: if (debug_flag)
2252: fprintf(stderr, "Running /bin/sh %s\n", SSH_USER_RC);
2253:
2254: f = popen("/bin/sh " SSH_USER_RC, "w");
2255: if (f)
2256: {
2257: if (auth_proto != NULL && auth_data != NULL)
2258: fprintf(f, "%s %s\n", auth_proto, auth_data);
2259: pclose(f);
2260: }
2261: else
2262: fprintf(stderr, "Could not run %s\n", SSH_USER_RC);
1.1 deraadt 2263: }
1.27 markus 2264: else
2265: if (stat(SSH_SYSTEM_RC, &st) >= 0)
2266: {
2267: if (debug_flag)
2268: fprintf(stderr, "Running /bin/sh %s\n", SSH_SYSTEM_RC);
2269:
2270: f = popen("/bin/sh " SSH_SYSTEM_RC, "w");
2271: if (f)
2272: {
2273: if (auth_proto != NULL && auth_data != NULL)
2274: fprintf(f, "%s %s\n", auth_proto, auth_data);
2275: pclose(f);
2276: }
2277: else
2278: fprintf(stderr, "Could not run %s\n", SSH_SYSTEM_RC);
2279: }
1.1 deraadt 2280: #ifdef XAUTH_PATH
1.27 markus 2281: else
2282: {
2283: /* Add authority data to .Xauthority if appropriate. */
2284: if (auth_proto != NULL && auth_data != NULL)
2285: {
2286: if (debug_flag)
2287: fprintf(stderr, "Running %.100s add %.100s %.100s %.100s\n",
2288: XAUTH_PATH, display, auth_proto, auth_data);
2289:
2290: f = popen(XAUTH_PATH " -q -", "w");
2291: if (f)
2292: {
2293: fprintf(f, "add %s %s %s\n", display, auth_proto, auth_data);
2294: fclose(f);
2295: }
2296: else
2297: fprintf(stderr, "Could not run %s -q -\n", XAUTH_PATH);
2298: }
2299: }
1.1 deraadt 2300: #endif /* XAUTH_PATH */
2301:
1.27 markus 2302: /* Get the last component of the shell name. */
2303: cp = strrchr(shell, '/');
2304: if (cp)
2305: cp++;
2306: else
2307: cp = shell;
2308: }
1.1 deraadt 2309:
2310: /* If we have no command, execute the shell. In this case, the shell name
2311: to be passed in argv[0] is preceded by '-' to indicate that this is
2312: a login shell. */
2313: if (!command)
2314: {
1.27 markus 2315: if(!options.use_login) {
2316: char buf[256];
1.1 deraadt 2317:
1.27 markus 2318: /* Check for mail if we have a tty and it was enabled in server options. */
2319: if (ttyname && options.check_mail) {
2320: char *mailbox;
2321: struct stat mailstat;
2322: mailbox = getenv("MAIL");
2323: if(mailbox != NULL) {
2324: if(stat(mailbox, &mailstat) != 0 || mailstat.st_size == 0) {
2325: printf("No mail.\n");
2326: } else if(mailstat.st_mtime < mailstat.st_atime) {
2327: printf("You have mail.\n");
2328: } else {
2329: printf("You have new mail.\n");
2330: }
1.25 markus 2331: }
2332: }
1.27 markus 2333: /* Start the shell. Set initial character to '-'. */
2334: buf[0] = '-';
2335: strncpy(buf + 1, cp, sizeof(buf) - 1);
2336: buf[sizeof(buf) - 1] = 0;
2337: /* Execute the shell. */
2338: argv[0] = buf;
2339: argv[1] = NULL;
2340: execve(shell, argv, env);
2341: /* Executing the shell failed. */
2342: perror(shell);
2343: exit(1);
2344:
2345: } else {
2346: /* Launch login(1). */
2347:
2348: execl("/usr/bin/login", "login", "-h", get_remote_ipaddr(), "-p", "-f", "--", pw->pw_name, NULL);
2349:
2350: /* Login couldn't be executed, die. */
2351:
2352: perror("login");
2353: exit(1);
1.25 markus 2354: }
1.1 deraadt 2355: }
2356:
2357: /* Execute the command using the user's shell. This uses the -c option
2358: to execute the command. */
2359: argv[0] = (char *)cp;
2360: argv[1] = "-c";
2361: argv[2] = (char *)command;
2362: argv[3] = NULL;
2363: execve(shell, argv, env);
2364: perror(shell);
2365: exit(1);
2366: }
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