Annotation of src/usr.bin/ssh/sshd.c, Revision 1.236
1.86 markus 1: /*
1.65 deraadt 2: * Author: Tatu Ylonen <ylo@cs.hut.fi>
3: * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
4: * All rights reserved
1.126 deraadt 5: * This program is the ssh daemon. It listens for connections from clients,
6: * and performs authentication, executes use commands or shell, and forwards
1.65 deraadt 7: * information to/from the application to the user client over an encrypted
1.126 deraadt 8: * connection. This can also handle forwarding of X11, TCP/IP, and
9: * authentication agent connections.
1.98 markus 10: *
1.126 deraadt 11: * As far as I am concerned, the code I have written for this software
12: * can be used freely for any purpose. Any derived versions of this
13: * software must be clearly marked as such, and if the derived work is
14: * incompatible with the protocol description in the RFC file, it must be
15: * called by a name other than "ssh" or "Secure Shell".
16: *
17: * SSH2 implementation:
1.231 provos 18: * Privilege Separation:
1.126 deraadt 19: *
1.231 provos 20: * Copyright (c) 2000, 2001, 2002 Markus Friedl. All rights reserved.
21: * Copyright (c) 2002 Niels Provos. All rights reserved.
1.126 deraadt 22: *
23: * Redistribution and use in source and binary forms, with or without
24: * modification, are permitted provided that the following conditions
25: * are met:
26: * 1. Redistributions of source code must retain the above copyright
27: * notice, this list of conditions and the following disclaimer.
28: * 2. Redistributions in binary form must reproduce the above copyright
29: * notice, this list of conditions and the following disclaimer in the
30: * documentation and/or other materials provided with the distribution.
31: *
32: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
33: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
34: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
35: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
36: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
37: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
38: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
39: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
40: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
41: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1.65 deraadt 42: */
1.1 deraadt 43:
44: #include "includes.h"
1.236 ! stevesk 45: RCSID("$OpenBSD: sshd.c,v 1.235 2002/03/20 19:12:25 stevesk Exp $");
1.1 deraadt 46:
1.155 markus 47: #include <openssl/dh.h>
48: #include <openssl/bn.h>
1.226 markus 49: #include <openssl/md5.h>
1.231 provos 50: #include <openssl/rand.h>
1.155 markus 51:
52: #include "ssh.h"
53: #include "ssh1.h"
54: #include "ssh2.h"
1.1 deraadt 55: #include "xmalloc.h"
56: #include "rsa.h"
1.171 djm 57: #include "sshpty.h"
1.1 deraadt 58: #include "packet.h"
59: #include "mpaux.h"
1.155 markus 60: #include "log.h"
1.1 deraadt 61: #include "servconf.h"
62: #include "uidswap.h"
1.33 markus 63: #include "compat.h"
1.96 markus 64: #include "buffer.h"
1.155 markus 65: #include "cipher.h"
1.98 markus 66: #include "kex.h"
1.96 markus 67: #include "key.h"
1.129 provos 68: #include "dh.h"
1.98 markus 69: #include "myproposal.h"
1.108 markus 70: #include "authfile.h"
1.154 markus 71: #include "pathnames.h"
1.155 markus 72: #include "atomicio.h"
73: #include "canohost.h"
74: #include "auth.h"
75: #include "misc.h"
1.186 markus 76: #include "dispatch.h"
1.206 stevesk 77: #include "channels.h"
1.230 provos 78: #include "session.h"
1.231 provos 79: #include "monitor_mm.h"
80: #include "monitor.h"
81: #include "monitor_wrap.h"
82: #include "monitor_fdpass.h"
1.1 deraadt 83:
84: #ifdef LIBWRAP
85: #include <tcpd.h>
86: #include <syslog.h>
87: int allow_severity = LOG_INFO;
88: int deny_severity = LOG_WARNING;
89: #endif /* LIBWRAP */
90:
91: #ifndef O_NOCTTY
92: #define O_NOCTTY 0
93: #endif
94:
1.138 markus 95: extern char *__progname;
96:
1.1 deraadt 97: /* Server configuration options. */
98: ServerOptions options;
99:
100: /* Name of the server configuration file. */
1.154 markus 101: char *config_file_name = _PATH_SERVER_CONFIG_FILE;
1.1 deraadt 102:
1.105 markus 103: /*
1.75 markus 104: * Flag indicating whether IPv4 or IPv6. This can be set on the command line.
105: * Default value is AF_UNSPEC means both IPv4 and IPv6.
106: */
107: int IPv4or6 = AF_UNSPEC;
108:
1.65 deraadt 109: /*
110: * Debug mode flag. This can be set on the command line. If debug
111: * mode is enabled, extra debugging output will be sent to the system
112: * log, the daemon will not go to background, and will exit after processing
113: * the first connection.
114: */
1.1 deraadt 115: int debug_flag = 0;
116:
1.203 stevesk 117: /* Flag indicating that the daemon should only test the configuration and keys. */
118: int test_flag = 0;
119:
1.1 deraadt 120: /* Flag indicating that the daemon is being started from inetd. */
121: int inetd_flag = 0;
122:
1.135 markus 123: /* Flag indicating that sshd should not detach and become a daemon. */
124: int no_daemon_flag = 0;
125:
1.47 markus 126: /* debug goes to stderr unless inetd_flag is set */
127: int log_stderr = 0;
128:
1.1 deraadt 129: /* Saved arguments to main(). */
130: char **saved_argv;
131:
1.66 markus 132: /*
1.75 markus 133: * The sockets that the server is listening; this is used in the SIGHUP
134: * signal handler.
1.66 markus 135: */
1.75 markus 136: #define MAX_LISTEN_SOCKS 16
137: int listen_socks[MAX_LISTEN_SOCKS];
138: int num_listen_socks = 0;
1.1 deraadt 139:
1.66 markus 140: /*
141: * the client's version string, passed by sshd2 in compat mode. if != NULL,
142: * sshd will skip the version-number exchange
143: */
1.61 markus 144: char *client_version_string = NULL;
1.96 markus 145: char *server_version_string = NULL;
1.1 deraadt 146:
1.189 markus 147: /* for rekeying XXX fixme */
148: Kex *xxx_kex;
149:
1.66 markus 150: /*
151: * Any really sensitive data in the application is contained in this
152: * structure. The idea is that this structure could be locked into memory so
153: * that the pages do not get written into swap. However, there are some
154: * problems. The private key contains BIGNUMs, and we do not (in principle)
155: * have access to the internals of them, and locking just the structure is
156: * not very useful. Currently, memory locking is not implemented.
157: */
1.64 markus 158: struct {
1.174 deraadt 159: Key *server_key; /* ephemeral server key */
1.134 markus 160: Key *ssh1_host_key; /* ssh1 host key */
161: Key **host_keys; /* all private host keys */
162: int have_ssh1_key;
163: int have_ssh2_key;
1.169 markus 164: u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH];
1.1 deraadt 165: } sensitive_data;
166:
1.66 markus 167: /*
1.151 markus 168: * Flag indicating whether the RSA server key needs to be regenerated.
169: * Is set in the SIGALRM handler and cleared when the key is regenerated.
1.66 markus 170: */
1.212 markus 171: static volatile sig_atomic_t key_do_regen = 0;
1.1 deraadt 172:
1.199 markus 173: /* This is set to true when a signal is received. */
1.212 markus 174: static volatile sig_atomic_t received_sighup = 0;
175: static volatile sig_atomic_t received_sigterm = 0;
1.1 deraadt 176:
1.96 markus 177: /* session identifier, used by RSA-auth */
1.140 markus 178: u_char session_id[16];
1.96 markus 179:
1.108 markus 180: /* same for ssh2 */
1.140 markus 181: u_char *session_id2 = NULL;
1.108 markus 182: int session_id2_len = 0;
183:
1.125 markus 184: /* record remote hostname or ip */
1.140 markus 185: u_int utmp_len = MAXHOSTNAMELEN;
1.125 markus 186:
1.211 markus 187: /* options.max_startup sized array of fd ints */
188: int *startup_pipes = NULL;
189: int startup_pipe; /* in child */
190:
1.231 provos 191: /* variables used for privilege separation */
192: extern struct monitor *monitor;
193: extern int use_privsep;
194:
1.1 deraadt 195: /* Prototypes for various functions defined later in this file. */
1.200 itojun 196: void destroy_sensitive_data(void);
1.231 provos 197: void demote_sensitive_data(void);
1.87 markus 198:
1.200 itojun 199: static void do_ssh1_kex(void);
200: static void do_ssh2_kex(void);
1.129 provos 201:
1.87 markus 202: /*
1.75 markus 203: * Close all listening sockets
204: */
1.200 itojun 205: static void
1.75 markus 206: close_listen_socks(void)
207: {
208: int i;
209: for (i = 0; i < num_listen_socks; i++)
210: close(listen_socks[i]);
211: num_listen_socks = -1;
212: }
213:
1.211 markus 214: static void
215: close_startup_pipes(void)
216: {
217: int i;
218: if (startup_pipes)
219: for (i = 0; i < options.max_startups; i++)
220: if (startup_pipes[i] != -1)
221: close(startup_pipes[i]);
222: }
223:
1.75 markus 224: /*
1.65 deraadt 225: * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
226: * the effect is to reread the configuration file (and to regenerate
227: * the server key).
228: */
1.200 itojun 229: static void
1.64 markus 230: sighup_handler(int sig)
1.1 deraadt 231: {
1.210 deraadt 232: int save_errno = errno;
233:
1.64 markus 234: received_sighup = 1;
235: signal(SIGHUP, sighup_handler);
1.210 deraadt 236: errno = save_errno;
1.1 deraadt 237: }
238:
1.65 deraadt 239: /*
240: * Called from the main program after receiving SIGHUP.
241: * Restarts the server.
242: */
1.200 itojun 243: static void
1.165 itojun 244: sighup_restart(void)
1.1 deraadt 245: {
1.64 markus 246: log("Received SIGHUP; restarting.");
1.75 markus 247: close_listen_socks();
1.211 markus 248: close_startup_pipes();
1.64 markus 249: execv(saved_argv[0], saved_argv);
1.138 markus 250: log("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], strerror(errno));
1.64 markus 251: exit(1);
1.1 deraadt 252: }
253:
1.65 deraadt 254: /*
255: * Generic signal handler for terminating signals in the master daemon.
256: */
1.200 itojun 257: static void
1.64 markus 258: sigterm_handler(int sig)
1.1 deraadt 259: {
1.199 markus 260: received_sigterm = sig;
1.1 deraadt 261: }
262:
1.65 deraadt 263: /*
264: * SIGCHLD handler. This is called whenever a child dies. This will then
1.199 markus 265: * reap any zombies left by exited children.
1.65 deraadt 266: */
1.200 itojun 267: static void
1.64 markus 268: main_sigchld_handler(int sig)
1.1 deraadt 269: {
1.64 markus 270: int save_errno = errno;
271: int status;
1.60 deraadt 272:
1.64 markus 273: while (waitpid(-1, &status, WNOHANG) > 0)
274: ;
1.60 deraadt 275:
1.64 markus 276: signal(SIGCHLD, main_sigchld_handler);
277: errno = save_errno;
1.1 deraadt 278: }
279:
1.65 deraadt 280: /*
281: * Signal handler for the alarm after the login grace period has expired.
282: */
1.200 itojun 283: static void
1.64 markus 284: grace_alarm_handler(int sig)
1.1 deraadt 285: {
1.199 markus 286: /* XXX no idea how fix this signal handler */
287:
1.64 markus 288: /* Close the connection. */
289: packet_close();
290:
291: /* Log error and exit. */
292: fatal("Timeout before authentication for %s.", get_remote_ipaddr());
1.62 markus 293: }
294:
1.65 deraadt 295: /*
296: * Signal handler for the key regeneration alarm. Note that this
297: * alarm only occurs in the daemon waiting for connections, and it does not
298: * do anything with the private key or random state before forking.
299: * Thus there should be no concurrency control/asynchronous execution
300: * problems.
301: */
1.200 itojun 302: static void
1.174 deraadt 303: generate_ephemeral_server_key(void)
1.134 markus 304: {
1.169 markus 305: u_int32_t rand = 0;
306: int i;
307:
1.191 markus 308: verbose("Generating %s%d bit RSA key.",
1.185 djm 309: sensitive_data.server_key ? "new " : "", options.server_key_bits);
1.134 markus 310: if (sensitive_data.server_key != NULL)
311: key_free(sensitive_data.server_key);
1.191 markus 312: sensitive_data.server_key = key_generate(KEY_RSA1,
1.185 djm 313: options.server_key_bits);
314: verbose("RSA key generation complete.");
1.169 markus 315:
316: for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
317: if (i % 4 == 0)
318: rand = arc4random();
319: sensitive_data.ssh1_cookie[i] = rand & 0xff;
320: rand >>= 8;
321: }
1.134 markus 322: arc4random_stir();
323: }
1.147 deraadt 324:
1.200 itojun 325: static void
1.64 markus 326: key_regeneration_alarm(int sig)
1.1 deraadt 327: {
1.64 markus 328: int save_errno = errno;
1.151 markus 329: signal(SIGALRM, SIG_DFL);
1.64 markus 330: errno = save_errno;
1.151 markus 331: key_do_regen = 1;
1.98 markus 332: }
333:
1.200 itojun 334: static void
1.96 markus 335: sshd_exchange_identification(int sock_in, int sock_out)
336: {
1.102 markus 337: int i, mismatch;
1.96 markus 338: int remote_major, remote_minor;
1.102 markus 339: int major, minor;
1.96 markus 340: char *s;
341: char buf[256]; /* Must not be larger than remote_version. */
342: char remote_version[256]; /* Must be at least as big as buf. */
343:
1.103 markus 344: if ((options.protocol & SSH_PROTO_1) &&
345: (options.protocol & SSH_PROTO_2)) {
1.102 markus 346: major = PROTOCOL_MAJOR_1;
347: minor = 99;
348: } else if (options.protocol & SSH_PROTO_2) {
349: major = PROTOCOL_MAJOR_2;
350: minor = PROTOCOL_MINOR_2;
351: } else {
352: major = PROTOCOL_MAJOR_1;
353: minor = PROTOCOL_MINOR_1;
354: }
355: snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
1.96 markus 356: server_version_string = xstrdup(buf);
357:
358: if (client_version_string == NULL) {
359: /* Send our protocol version identification. */
360: if (atomicio(write, sock_out, server_version_string, strlen(server_version_string))
361: != strlen(server_version_string)) {
1.208 markus 362: log("Could not write ident string to %s", get_remote_ipaddr());
1.96 markus 363: fatal_cleanup();
364: }
365:
1.167 markus 366: /* Read other side's version identification. */
1.191 markus 367: memset(buf, 0, sizeof(buf));
1.96 markus 368: for (i = 0; i < sizeof(buf) - 1; i++) {
1.119 markus 369: if (atomicio(read, sock_in, &buf[i], 1) != 1) {
1.208 markus 370: log("Did not receive identification string from %s",
1.168 deraadt 371: get_remote_ipaddr());
1.96 markus 372: fatal_cleanup();
373: }
374: if (buf[i] == '\r') {
1.176 deraadt 375: buf[i] = 0;
1.132 markus 376: /* Kludge for F-Secure Macintosh < 1.0.2 */
377: if (i == 12 &&
378: strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
379: break;
1.96 markus 380: continue;
381: }
382: if (buf[i] == '\n') {
1.176 deraadt 383: buf[i] = 0;
1.96 markus 384: break;
385: }
386: }
387: buf[sizeof(buf) - 1] = 0;
388: client_version_string = xstrdup(buf);
389: }
390:
391: /*
392: * Check that the versions match. In future this might accept
393: * several versions and set appropriate flags to handle them.
394: */
395: if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
396: &remote_major, &remote_minor, remote_version) != 3) {
1.105 markus 397: s = "Protocol mismatch.\n";
1.96 markus 398: (void) atomicio(write, sock_out, s, strlen(s));
399: close(sock_in);
400: close(sock_out);
401: log("Bad protocol version identification '%.100s' from %s",
402: client_version_string, get_remote_ipaddr());
403: fatal_cleanup();
404: }
405: debug("Client protocol version %d.%d; client software version %.100s",
1.217 deraadt 406: remote_major, remote_minor, remote_version);
1.96 markus 407:
1.98 markus 408: compat_datafellows(remote_version);
1.175 deraadt 409:
410: if (datafellows & SSH_BUG_SCANNER) {
411: log("scanned from %s with %s. Don't panic.",
412: get_remote_ipaddr(), client_version_string);
413: fatal_cleanup();
414: }
1.98 markus 415:
1.102 markus 416: mismatch = 0;
1.214 deraadt 417: switch (remote_major) {
1.96 markus 418: case 1:
1.108 markus 419: if (remote_minor == 99) {
420: if (options.protocol & SSH_PROTO_2)
421: enable_compat20();
422: else
423: mismatch = 1;
424: break;
425: }
1.102 markus 426: if (!(options.protocol & SSH_PROTO_1)) {
427: mismatch = 1;
428: break;
429: }
1.96 markus 430: if (remote_minor < 3) {
1.121 provos 431: packet_disconnect("Your ssh version is too old and "
1.96 markus 432: "is no longer supported. Please install a newer version.");
433: } else if (remote_minor == 3) {
434: /* note that this disables agent-forwarding */
435: enable_compat13();
436: }
1.102 markus 437: break;
1.98 markus 438: case 2:
1.102 markus 439: if (options.protocol & SSH_PROTO_2) {
1.98 markus 440: enable_compat20();
441: break;
442: }
1.99 markus 443: /* FALLTHROUGH */
1.105 markus 444: default:
1.102 markus 445: mismatch = 1;
446: break;
447: }
448: chop(server_version_string);
449: debug("Local version string %.200s", server_version_string);
450:
451: if (mismatch) {
1.96 markus 452: s = "Protocol major versions differ.\n";
453: (void) atomicio(write, sock_out, s, strlen(s));
454: close(sock_in);
455: close(sock_out);
1.102 markus 456: log("Protocol major versions differ for %s: %.200s vs. %.200s",
457: get_remote_ipaddr(),
458: server_version_string, client_version_string);
1.96 markus 459: fatal_cleanup();
460: }
1.108 markus 461: }
462:
463:
1.134 markus 464: /* Destroy the host and server keys. They will no longer be needed. */
1.108 markus 465: void
466: destroy_sensitive_data(void)
467: {
1.134 markus 468: int i;
469:
470: if (sensitive_data.server_key) {
471: key_free(sensitive_data.server_key);
472: sensitive_data.server_key = NULL;
473: }
1.217 deraadt 474: for (i = 0; i < options.num_host_key_files; i++) {
1.134 markus 475: if (sensitive_data.host_keys[i]) {
476: key_free(sensitive_data.host_keys[i]);
477: sensitive_data.host_keys[i] = NULL;
478: }
479: }
480: sensitive_data.ssh1_host_key = NULL;
1.169 markus 481: memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
1.134 markus 482: }
483:
1.231 provos 484: /* Demote private to public keys for network child */
485: void
486: demote_sensitive_data(void)
487: {
488: Key *tmp;
489: int i;
490:
491: if (sensitive_data.server_key) {
492: tmp = key_demote(sensitive_data.server_key);
493: key_free(sensitive_data.server_key);
494: sensitive_data.server_key = tmp;
495: }
496:
497: for (i = 0; i < options.num_host_key_files; i++) {
498: if (sensitive_data.host_keys[i]) {
499: tmp = key_demote(sensitive_data.host_keys[i]);
500: key_free(sensitive_data.host_keys[i]);
501: sensitive_data.host_keys[i] = tmp;
502: if (tmp->type == KEY_RSA1)
503: sensitive_data.ssh1_host_key = tmp;
504: }
505: }
506:
507: /* We do not clear ssh1_host key and cookie. XXX - Okay Niels? */
508: }
509:
1.233 markus 510: static void
1.231 provos 511: privsep_preauth_child(void)
512: {
513: u_int32_t rand[256];
514: int i;
1.235 stevesk 515: struct passwd *pw;
1.231 provos 516:
517: /* Enable challenge-response authentication for privilege separation */
518: privsep_challenge_enable();
519:
520: for (i = 0; i < 256; i++)
521: rand[i] = arc4random();
522: RAND_seed(rand, sizeof(rand));
523:
524: /* Demote the private keys to public keys. */
525: demote_sensitive_data();
526:
1.235 stevesk 527: if ((pw = getpwnam(SSH_PRIVSEP_USER)) == NULL)
528: fatal("%s: no user", SSH_PRIVSEP_USER);
529: memset(pw->pw_passwd, 0, strlen(pw->pw_passwd));
530: endpwent();
531:
1.231 provos 532: /* Change our root directory*/
1.232 stevesk 533: if (chroot(_PATH_PRIVSEP_CHROOT_DIR) == -1)
534: fatal("chroot(\"%s\"): %s", _PATH_PRIVSEP_CHROOT_DIR,
535: strerror(errno));
1.231 provos 536: if (chdir("/") == -1)
1.236 ! stevesk 537: fatal("chdir(\"/\"): %s", strerror(errno));
1.234 markus 538:
1.231 provos 539: /* Drop our privileges */
1.235 stevesk 540: debug3("privsep user:group %u:%u", (u_int)pw->pw_uid,
541: (u_int)pw->pw_gid);
542: do_setusercontext(pw);
1.231 provos 543: }
544:
1.233 markus 545: static void
1.231 provos 546: privsep_postauth(Authctxt *authctxt, pid_t pid)
547: {
548: extern Authctxt *x_authctxt;
549: int status;
550:
551: /* Wait for the child's exit status */
552: waitpid(pid, &status, 0);
553:
554: /* XXX - Remote port forwarding */
555: x_authctxt = authctxt;
556:
557: if (authctxt->pw->pw_uid == 0 || options.use_login) {
558: /* File descriptor passing is broken or root login */
559: monitor_apply_keystate(monitor);
560: use_privsep = 0;
561: return;
562: }
1.234 markus 563:
1.231 provos 564: /* Authentication complete */
565: alarm(0);
566: if (startup_pipe != -1) {
567: close(startup_pipe);
568: startup_pipe = -1;
569: }
570:
571: /* New socket pair */
572: monitor_reinit(monitor);
573:
574: monitor->m_pid = fork();
575: if (monitor->m_pid == -1)
576: fatal("fork of unprivileged child failed");
577: else if (monitor->m_pid != 0) {
578: debug2("User child is on pid %d", pid);
579: close(monitor->m_recvfd);
580: monitor_child_postauth(monitor);
581:
582: /* NEVERREACHED */
583: exit(0);
584: }
585:
586: close(monitor->m_sendfd);
587:
588: /* Demote the private keys to public keys. */
589: demote_sensitive_data();
590:
591: /* Drop privileges */
592: do_setusercontext(authctxt->pw);
593:
594: /* It is safe now to apply the key state */
595: monitor_apply_keystate(monitor);
596: }
597:
598:
1.200 itojun 599: static char *
1.134 markus 600: list_hostkey_types(void)
601: {
1.223 markus 602: Buffer b;
603: char *p;
1.134 markus 604: int i;
1.223 markus 605:
606: buffer_init(&b);
1.217 deraadt 607: for (i = 0; i < options.num_host_key_files; i++) {
1.134 markus 608: Key *key = sensitive_data.host_keys[i];
609: if (key == NULL)
610: continue;
1.214 deraadt 611: switch (key->type) {
1.134 markus 612: case KEY_RSA:
613: case KEY_DSA:
1.223 markus 614: if (buffer_len(&b) > 0)
615: buffer_append(&b, ",", 1);
616: p = key_ssh_name(key);
617: buffer_append(&b, p, strlen(p));
1.134 markus 618: break;
619: }
620: }
1.223 markus 621: buffer_append(&b, "\0", 1);
622: p = xstrdup(buffer_ptr(&b));
623: buffer_free(&b);
624: debug("list_hostkey_types: %s", p);
625: return p;
1.134 markus 626: }
627:
1.231 provos 628: Key *
1.134 markus 629: get_hostkey_by_type(int type)
630: {
631: int i;
1.217 deraadt 632: for (i = 0; i < options.num_host_key_files; i++) {
1.134 markus 633: Key *key = sensitive_data.host_keys[i];
634: if (key != NULL && key->type == type)
635: return key;
636: }
637: return NULL;
1.96 markus 638: }
639:
1.231 provos 640: Key *
641: get_hostkey_by_index(int ind)
642: {
643: if (ind < 0 || ind >= options.num_host_key_files)
644: return (NULL);
645: return (sensitive_data.host_keys[ind]);
646: }
647:
648: int
649: get_hostkey_index(Key *key)
650: {
651: int i;
652: for (i = 0; i < options.num_host_key_files; i++) {
653: if (key == sensitive_data.host_keys[i])
654: return (i);
655: }
656: return (-1);
657: }
658:
1.124 markus 659: /*
660: * returns 1 if connection should be dropped, 0 otherwise.
661: * dropping starts at connection #max_startups_begin with a probability
662: * of (max_startups_rate/100). the probability increases linearly until
663: * all connections are dropped for startups > max_startups
664: */
1.200 itojun 665: static int
1.124 markus 666: drop_connection(int startups)
667: {
668: double p, r;
669:
670: if (startups < options.max_startups_begin)
671: return 0;
672: if (startups >= options.max_startups)
673: return 1;
674: if (options.max_startups_rate == 100)
675: return 1;
676:
677: p = 100 - options.max_startups_rate;
678: p *= startups - options.max_startups_begin;
679: p /= (double) (options.max_startups - options.max_startups_begin);
680: p += options.max_startups_rate;
681: p /= 100.0;
682: r = arc4random() / (double) UINT_MAX;
683:
684: debug("drop_connection: p %g, r %g", p, r);
685: return (r < p) ? 1 : 0;
686: }
687:
1.215 markus 688: static void
689: usage(void)
690: {
691: fprintf(stderr, "sshd version %s\n", SSH_VERSION);
692: fprintf(stderr, "Usage: %s [options]\n", __progname);
693: fprintf(stderr, "Options:\n");
694: fprintf(stderr, " -f file Configuration file (default %s)\n", _PATH_SERVER_CONFIG_FILE);
695: fprintf(stderr, " -d Debugging mode (multiple -d means more debugging)\n");
696: fprintf(stderr, " -i Started from inetd\n");
697: fprintf(stderr, " -D Do not fork into daemon mode\n");
698: fprintf(stderr, " -t Only test configuration file and keys\n");
699: fprintf(stderr, " -q Quiet (no logging)\n");
700: fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
701: fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
702: fprintf(stderr, " -g seconds Grace period for authentication (default: 600)\n");
703: fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
704: fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
705: _PATH_HOST_KEY_FILE);
706: fprintf(stderr, " -u len Maximum hostname length for utmp recording\n");
707: fprintf(stderr, " -4 Use IPv4 only\n");
708: fprintf(stderr, " -6 Use IPv6 only\n");
709: fprintf(stderr, " -o option Process the option as if it was read from a configuration file.\n");
710: exit(1);
711: }
712:
1.65 deraadt 713: /*
714: * Main program for the daemon.
715: */
1.2 provos 716: int
717: main(int ac, char **av)
1.1 deraadt 718: {
1.64 markus 719: extern char *optarg;
720: extern int optind;
1.120 markus 721: int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1;
1.107 deraadt 722: pid_t pid;
1.75 markus 723: socklen_t fromlen;
724: fd_set *fdset;
725: struct sockaddr_storage from;
1.64 markus 726: const char *remote_ip;
727: int remote_port;
728: FILE *f;
729: struct linger linger;
1.75 markus 730: struct addrinfo *ai;
731: char ntop[NI_MAXHOST], strport[NI_MAXSERV];
732: int listen_sock, maxfd;
1.120 markus 733: int startup_p[2];
734: int startups = 0;
1.230 provos 735: Authctxt *authctxt;
1.179 markus 736: Key *key;
1.151 markus 737: int ret, key_used = 0;
1.64 markus 738:
1.138 markus 739: /* Save argv. */
1.64 markus 740: saved_argv = av;
741:
742: /* Initialize configuration options to their default values. */
743: initialize_server_options(&options);
744:
745: /* Parse command-line arguments. */
1.215 markus 746: while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:o:dDeiqtQ46")) != -1) {
1.64 markus 747: switch (opt) {
1.75 markus 748: case '4':
749: IPv4or6 = AF_INET;
750: break;
751: case '6':
752: IPv4or6 = AF_INET6;
753: break;
1.64 markus 754: case 'f':
755: config_file_name = optarg;
756: break;
757: case 'd':
1.127 markus 758: if (0 == debug_flag) {
759: debug_flag = 1;
760: options.log_level = SYSLOG_LEVEL_DEBUG1;
761: } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) {
762: options.log_level++;
763: } else {
764: fprintf(stderr, "Too high debugging level.\n");
765: exit(1);
766: }
1.64 markus 767: break;
1.135 markus 768: case 'D':
769: no_daemon_flag = 1;
1.192 lebel 770: break;
771: case 'e':
772: log_stderr = 1;
1.135 markus 773: break;
1.64 markus 774: case 'i':
775: inetd_flag = 1;
776: break;
777: case 'Q':
1.158 markus 778: /* ignored */
1.64 markus 779: break;
780: case 'q':
781: options.log_level = SYSLOG_LEVEL_QUIET;
782: break;
783: case 'b':
784: options.server_key_bits = atoi(optarg);
785: break;
786: case 'p':
1.75 markus 787: options.ports_from_cmdline = 1;
1.127 markus 788: if (options.num_ports >= MAX_PORTS) {
789: fprintf(stderr, "too many ports.\n");
790: exit(1);
791: }
1.193 stevesk 792: options.ports[options.num_ports++] = a2port(optarg);
793: if (options.ports[options.num_ports-1] == 0) {
794: fprintf(stderr, "Bad port number.\n");
795: exit(1);
796: }
1.64 markus 797: break;
798: case 'g':
1.197 stevesk 799: if ((options.login_grace_time = convtime(optarg)) == -1) {
800: fprintf(stderr, "Invalid login grace time.\n");
801: exit(1);
802: }
1.64 markus 803: break;
804: case 'k':
1.197 stevesk 805: if ((options.key_regeneration_time = convtime(optarg)) == -1) {
806: fprintf(stderr, "Invalid key regeneration interval.\n");
807: exit(1);
808: }
1.64 markus 809: break;
810: case 'h':
1.134 markus 811: if (options.num_host_key_files >= MAX_HOSTKEYS) {
812: fprintf(stderr, "too many host keys.\n");
813: exit(1);
814: }
815: options.host_key_files[options.num_host_key_files++] = optarg;
1.64 markus 816: break;
817: case 'V':
818: client_version_string = optarg;
819: /* only makes sense with inetd_flag, i.e. no listen() */
820: inetd_flag = 1;
821: break;
1.203 stevesk 822: case 't':
823: test_flag = 1;
824: break;
1.125 markus 825: case 'u':
826: utmp_len = atoi(optarg);
827: break;
1.215 markus 828: case 'o':
1.217 deraadt 829: if (process_server_config_line(&options, optarg,
1.215 markus 830: "command-line", 0) != 0)
1.217 deraadt 831: exit(1);
1.215 markus 832: break;
1.64 markus 833: case '?':
834: default:
1.215 markus 835: usage();
836: break;
1.64 markus 837: }
838: }
1.180 markus 839: SSLeay_add_all_algorithms();
1.205 markus 840: channel_set_af(IPv4or6);
1.64 markus 841:
1.75 markus 842: /*
843: * Force logging to stderr until we have loaded the private host
844: * key (unless started from inetd)
845: */
1.138 markus 846: log_init(__progname,
1.224 markus 847: options.log_level == SYSLOG_LEVEL_NOT_SET ?
848: SYSLOG_LEVEL_INFO : options.log_level,
849: options.log_facility == SYSLOG_FACILITY_NOT_SET ?
850: SYSLOG_FACILITY_AUTH : options.log_facility,
1.158 markus 851: !inetd_flag);
1.75 markus 852:
1.64 markus 853: /* Read server configuration options from the configuration file. */
854: read_server_config(&options, config_file_name);
855:
856: /* Fill in default values for those options not explicitly set. */
857: fill_default_server_options(&options);
858:
859: /* Check that there are no remaining arguments. */
860: if (optind < ac) {
861: fprintf(stderr, "Extra argument %s.\n", av[optind]);
862: exit(1);
863: }
864:
865: debug("sshd version %.100s", SSH_VERSION);
866:
1.134 markus 867: /* load private host keys */
868: sensitive_data.host_keys = xmalloc(options.num_host_key_files*sizeof(Key*));
1.217 deraadt 869: for (i = 0; i < options.num_host_key_files; i++)
1.141 markus 870: sensitive_data.host_keys[i] = NULL;
1.134 markus 871: sensitive_data.server_key = NULL;
872: sensitive_data.ssh1_host_key = NULL;
873: sensitive_data.have_ssh1_key = 0;
874: sensitive_data.have_ssh2_key = 0;
875:
1.217 deraadt 876: for (i = 0; i < options.num_host_key_files; i++) {
1.179 markus 877: key = key_load_private(options.host_key_files[i], "", NULL);
878: sensitive_data.host_keys[i] = key;
1.134 markus 879: if (key == NULL) {
1.195 markus 880: error("Could not load host key: %s",
881: options.host_key_files[i]);
1.179 markus 882: sensitive_data.host_keys[i] = NULL;
1.134 markus 883: continue;
884: }
1.214 deraadt 885: switch (key->type) {
1.134 markus 886: case KEY_RSA1:
887: sensitive_data.ssh1_host_key = key;
888: sensitive_data.have_ssh1_key = 1;
889: break;
890: case KEY_RSA:
891: case KEY_DSA:
892: sensitive_data.have_ssh2_key = 1;
893: break;
894: }
1.179 markus 895: debug("private host key: #%d type %d %s", i, key->type,
896: key_type(key));
1.134 markus 897: }
898: if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
899: log("Disabling protocol version 1. Could not load host key");
1.108 markus 900: options.protocol &= ~SSH_PROTO_1;
901: }
1.134 markus 902: if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
903: log("Disabling protocol version 2. Could not load host key");
904: options.protocol &= ~SSH_PROTO_2;
1.108 markus 905: }
1.162 stevesk 906: if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
1.172 millert 907: log("sshd: no hostkeys available -- exiting.");
1.64 markus 908: exit(1);
909: }
910:
1.108 markus 911: /* Check certain values for sanity. */
912: if (options.protocol & SSH_PROTO_1) {
913: if (options.server_key_bits < 512 ||
914: options.server_key_bits > 32768) {
915: fprintf(stderr, "Bad server key size.\n");
916: exit(1);
917: }
918: /*
919: * Check that server and host key lengths differ sufficiently. This
920: * is necessary to make double encryption work with rsaref. Oh, I
921: * hate software patents. I dont know if this can go? Niels
922: */
923: if (options.server_key_bits >
1.134 markus 924: BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - SSH_KEY_BITS_RESERVED &&
1.108 markus 925: options.server_key_bits <
1.134 markus 926: BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1.108 markus 927: options.server_key_bits =
1.134 markus 928: BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED;
1.108 markus 929: debug("Forcing server key to %d bits to make it differ from host key.",
930: options.server_key_bits);
931: }
932: }
1.203 stevesk 933:
934: /* Configuration looks good, so exit if in test mode. */
935: if (test_flag)
936: exit(0);
1.108 markus 937:
938: /* Initialize the log (it is reinitialized below in case we forked). */
1.64 markus 939: if (debug_flag && !inetd_flag)
940: log_stderr = 1;
1.138 markus 941: log_init(__progname, options.log_level, options.log_facility, log_stderr);
1.64 markus 942:
1.108 markus 943: /*
944: * If not in debugging mode, and not started from inetd, disconnect
945: * from the controlling terminal, and fork. The original process
946: * exits.
947: */
1.135 markus 948: if (!(debug_flag || inetd_flag || no_daemon_flag)) {
1.1 deraadt 949: #ifdef TIOCNOTTY
1.64 markus 950: int fd;
1.1 deraadt 951: #endif /* TIOCNOTTY */
1.64 markus 952: if (daemon(0, 0) < 0)
953: fatal("daemon() failed: %.200s", strerror(errno));
954:
955: /* Disconnect from the controlling tty. */
1.1 deraadt 956: #ifdef TIOCNOTTY
1.165 itojun 957: fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
1.64 markus 958: if (fd >= 0) {
959: (void) ioctl(fd, TIOCNOTTY, NULL);
960: close(fd);
961: }
962: #endif /* TIOCNOTTY */
963: }
964: /* Reinitialize the log (because of the fork above). */
1.138 markus 965: log_init(__progname, options.log_level, options.log_facility, log_stderr);
1.64 markus 966:
967: /* Initialize the random number generator. */
968: arc4random_stir();
969:
970: /* Chdir to the root directory so that the current disk can be
971: unmounted if desired. */
972: chdir("/");
1.217 deraadt 973:
1.178 markus 974: /* ignore SIGPIPE */
975: signal(SIGPIPE, SIG_IGN);
1.64 markus 976:
977: /* Start listening for a socket, unless started from inetd. */
978: if (inetd_flag) {
1.194 markus 979: int s1;
1.64 markus 980: s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
1.194 markus 981: dup(s1);
1.64 markus 982: sock_in = dup(0);
983: sock_out = dup(1);
1.123 djm 984: startup_pipe = -1;
1.108 markus 985: /*
986: * We intentionally do not close the descriptors 0, 1, and 2
987: * as our code for setting the descriptors won\'t work if
988: * ttyfd happens to be one of those.
989: */
1.64 markus 990: debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
1.134 markus 991: if (options.protocol & SSH_PROTO_1)
1.174 deraadt 992: generate_ephemeral_server_key();
1.64 markus 993: } else {
1.75 markus 994: for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
995: if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
996: continue;
997: if (num_listen_socks >= MAX_LISTEN_SOCKS)
998: fatal("Too many listen sockets. "
999: "Enlarge MAX_LISTEN_SOCKS");
1000: if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
1001: ntop, sizeof(ntop), strport, sizeof(strport),
1002: NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
1003: error("getnameinfo failed");
1004: continue;
1005: }
1006: /* Create socket for listening. */
1007: listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
1008: if (listen_sock < 0) {
1009: /* kernel may not support ipv6 */
1010: verbose("socket: %.100s", strerror(errno));
1011: continue;
1012: }
1013: if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
1014: error("listen_sock O_NONBLOCK: %s", strerror(errno));
1015: close(listen_sock);
1016: continue;
1017: }
1018: /*
1019: * Set socket options. We try to make the port
1020: * reusable and have it close as fast as possible
1021: * without waiting in unnecessary wait states on
1022: * close.
1023: */
1024: setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
1.228 stevesk 1025: &on, sizeof(on));
1.75 markus 1026: linger.l_onoff = 1;
1027: linger.l_linger = 5;
1028: setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
1.228 stevesk 1029: &linger, sizeof(linger));
1.75 markus 1030:
1031: debug("Bind to port %s on %s.", strport, ntop);
1032:
1033: /* Bind the socket to the desired port. */
1034: if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
1035: error("Bind to port %s on %s failed: %.200s.",
1036: strport, ntop, strerror(errno));
1037: close(listen_sock);
1038: continue;
1039: }
1040: listen_socks[num_listen_socks] = listen_sock;
1041: num_listen_socks++;
1042:
1043: /* Start listening on the port. */
1044: log("Server listening on %s port %s.", ntop, strport);
1045: if (listen(listen_sock, 5) < 0)
1046: fatal("listen: %.100s", strerror(errno));
1047:
1.64 markus 1048: }
1.75 markus 1049: freeaddrinfo(options.listen_addrs);
1050:
1051: if (!num_listen_socks)
1052: fatal("Cannot bind any address.");
1053:
1.201 markus 1054: if (options.protocol & SSH_PROTO_1)
1055: generate_ephemeral_server_key();
1056:
1057: /*
1058: * Arrange to restart on SIGHUP. The handler needs
1059: * listen_sock.
1060: */
1061: signal(SIGHUP, sighup_handler);
1062:
1063: signal(SIGTERM, sigterm_handler);
1064: signal(SIGQUIT, sigterm_handler);
1065:
1066: /* Arrange SIGCHLD to be caught. */
1067: signal(SIGCHLD, main_sigchld_handler);
1068:
1069: /* Write out the pid file after the sigterm handler is setup */
1.64 markus 1070: if (!debug_flag) {
1.66 markus 1071: /*
1.136 todd 1072: * Record our pid in /var/run/sshd.pid to make it
1073: * easier to kill the correct sshd. We don't want to
1074: * do this before the bind above because the bind will
1.66 markus 1075: * fail if there already is a daemon, and this will
1076: * overwrite any old pid in the file.
1077: */
1.112 markus 1078: f = fopen(options.pid_file, "w");
1.64 markus 1079: if (f) {
1.140 markus 1080: fprintf(f, "%u\n", (u_int) getpid());
1.64 markus 1081: fclose(f);
1082: }
1083: }
1084:
1.75 markus 1085: /* setup fd set for listen */
1.120 markus 1086: fdset = NULL;
1.75 markus 1087: maxfd = 0;
1088: for (i = 0; i < num_listen_socks; i++)
1089: if (listen_socks[i] > maxfd)
1090: maxfd = listen_socks[i];
1.120 markus 1091: /* pipes connected to unauthenticated childs */
1092: startup_pipes = xmalloc(options.max_startups * sizeof(int));
1093: for (i = 0; i < options.max_startups; i++)
1094: startup_pipes[i] = -1;
1.75 markus 1095:
1.66 markus 1096: /*
1097: * Stay listening for connections until the system crashes or
1098: * the daemon is killed with a signal.
1099: */
1.64 markus 1100: for (;;) {
1101: if (received_sighup)
1102: sighup_restart();
1.120 markus 1103: if (fdset != NULL)
1104: xfree(fdset);
1.148 markus 1105: fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask);
1.120 markus 1106: fdset = (fd_set *)xmalloc(fdsetsz);
1.75 markus 1107: memset(fdset, 0, fdsetsz);
1.120 markus 1108:
1.75 markus 1109: for (i = 0; i < num_listen_socks; i++)
1110: FD_SET(listen_socks[i], fdset);
1.120 markus 1111: for (i = 0; i < options.max_startups; i++)
1112: if (startup_pipes[i] != -1)
1113: FD_SET(startup_pipes[i], fdset);
1114:
1115: /* Wait in select until there is a connection. */
1.151 markus 1116: ret = select(maxfd+1, fdset, NULL, NULL, NULL);
1117: if (ret < 0 && errno != EINTR)
1118: error("select: %.100s", strerror(errno));
1.199 markus 1119: if (received_sigterm) {
1120: log("Received signal %d; terminating.",
1.213 itojun 1121: (int) received_sigterm);
1.199 markus 1122: close_listen_socks();
1123: unlink(options.pid_file);
1124: exit(255);
1125: }
1.151 markus 1126: if (key_used && key_do_regen) {
1.174 deraadt 1127: generate_ephemeral_server_key();
1.151 markus 1128: key_used = 0;
1129: key_do_regen = 0;
1130: }
1131: if (ret < 0)
1.75 markus 1132: continue;
1.151 markus 1133:
1.120 markus 1134: for (i = 0; i < options.max_startups; i++)
1135: if (startup_pipes[i] != -1 &&
1136: FD_ISSET(startup_pipes[i], fdset)) {
1137: /*
1138: * the read end of the pipe is ready
1139: * if the child has closed the pipe
1.143 markus 1140: * after successful authentication
1.120 markus 1141: * or if the child has died
1142: */
1143: close(startup_pipes[i]);
1144: startup_pipes[i] = -1;
1145: startups--;
1146: }
1.75 markus 1147: for (i = 0; i < num_listen_socks; i++) {
1148: if (!FD_ISSET(listen_socks[i], fdset))
1.70 provos 1149: continue;
1.120 markus 1150: fromlen = sizeof(from);
1151: newsock = accept(listen_socks[i], (struct sockaddr *)&from,
1152: &fromlen);
1153: if (newsock < 0) {
1154: if (errno != EINTR && errno != EWOULDBLOCK)
1155: error("accept: %.100s", strerror(errno));
1156: continue;
1157: }
1158: if (fcntl(newsock, F_SETFL, 0) < 0) {
1159: error("newsock del O_NONBLOCK: %s", strerror(errno));
1.216 stevesk 1160: close(newsock);
1.120 markus 1161: continue;
1162: }
1.124 markus 1163: if (drop_connection(startups) == 1) {
1164: debug("drop connection #%d", startups);
1.120 markus 1165: close(newsock);
1166: continue;
1167: }
1168: if (pipe(startup_p) == -1) {
1169: close(newsock);
1170: continue;
1171: }
1172:
1173: for (j = 0; j < options.max_startups; j++)
1174: if (startup_pipes[j] == -1) {
1175: startup_pipes[j] = startup_p[0];
1176: if (maxfd < startup_p[0])
1177: maxfd = startup_p[0];
1178: startups++;
1179: break;
1180: }
1.161 stevesk 1181:
1.66 markus 1182: /*
1.120 markus 1183: * Got connection. Fork a child to handle it, unless
1184: * we are in debugging mode.
1.66 markus 1185: */
1.120 markus 1186: if (debug_flag) {
1.66 markus 1187: /*
1.120 markus 1188: * In debugging mode. Close the listening
1189: * socket, and start processing the
1190: * connection without forking.
1.66 markus 1191: */
1.120 markus 1192: debug("Server will not fork when running in debugging mode.");
1.75 markus 1193: close_listen_socks();
1.64 markus 1194: sock_in = newsock;
1195: sock_out = newsock;
1.122 deraadt 1196: startup_pipe = -1;
1.120 markus 1197: pid = getpid();
1.64 markus 1198: break;
1.120 markus 1199: } else {
1200: /*
1201: * Normal production daemon. Fork, and have
1202: * the child process the connection. The
1203: * parent continues listening.
1204: */
1205: if ((pid = fork()) == 0) {
1206: /*
1207: * Child. Close the listening and max_startup
1208: * sockets. Start using the accepted socket.
1209: * Reinitialize logging (since our pid has
1210: * changed). We break out of the loop to handle
1211: * the connection.
1212: */
1213: startup_pipe = startup_p[1];
1.211 markus 1214: close_startup_pipes();
1.120 markus 1215: close_listen_socks();
1216: sock_in = newsock;
1217: sock_out = newsock;
1.138 markus 1218: log_init(__progname, options.log_level, options.log_facility, log_stderr);
1.120 markus 1219: break;
1220: }
1.64 markus 1221: }
1222:
1.120 markus 1223: /* Parent. Stay in the loop. */
1224: if (pid < 0)
1225: error("fork: %.100s", strerror(errno));
1226: else
1227: debug("Forked child %d.", pid);
1228:
1229: close(startup_p[1]);
1.1 deraadt 1230:
1.120 markus 1231: /* Mark that the key has been used (it was "given" to the child). */
1.151 markus 1232: if ((options.protocol & SSH_PROTO_1) &&
1233: key_used == 0) {
1234: /* Schedule server key regeneration alarm. */
1235: signal(SIGALRM, key_regeneration_alarm);
1236: alarm(options.key_regeneration_time);
1237: key_used = 1;
1238: }
1.1 deraadt 1239:
1.120 markus 1240: arc4random_stir();
1.1 deraadt 1241:
1.120 markus 1242: /* Close the new socket (the child is now taking care of it). */
1243: close(newsock);
1244: }
1.75 markus 1245: /* child process check (or debug mode) */
1246: if (num_listen_socks < 0)
1247: break;
1.64 markus 1248: }
1.1 deraadt 1249: }
1250:
1.64 markus 1251: /* This is the child processing a new connection. */
1252:
1.66 markus 1253: /*
1254: * Disable the key regeneration alarm. We will not regenerate the
1255: * key since we are no longer in a position to give it to anyone. We
1256: * will not restart on SIGHUP since it no longer makes sense.
1257: */
1.64 markus 1258: alarm(0);
1259: signal(SIGALRM, SIG_DFL);
1260: signal(SIGHUP, SIG_DFL);
1261: signal(SIGTERM, SIG_DFL);
1262: signal(SIGQUIT, SIG_DFL);
1263: signal(SIGCHLD, SIG_DFL);
1264:
1.66 markus 1265: /*
1266: * Set socket options for the connection. We want the socket to
1267: * close as fast as possible without waiting for anything. If the
1268: * connection is not a socket, these will do nothing.
1269: */
1270: /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
1.64 markus 1271: linger.l_onoff = 1;
1272: linger.l_linger = 5;
1.228 stevesk 1273: setsockopt(sock_in, SOL_SOCKET, SO_LINGER, &linger, sizeof(linger));
1.150 markus 1274:
1275: /* Set keepalives if requested. */
1276: if (options.keepalives &&
1.228 stevesk 1277: setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, &on,
1.150 markus 1278: sizeof(on)) < 0)
1279: error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1.64 markus 1280:
1.66 markus 1281: /*
1282: * Register our connection. This turns encryption off because we do
1283: * not have a key.
1284: */
1.64 markus 1285: packet_set_connection(sock_in, sock_out);
1.1 deraadt 1286:
1.64 markus 1287: remote_port = get_remote_port();
1288: remote_ip = get_remote_ipaddr();
1.52 markus 1289:
1.209 markus 1290: #ifdef LIBWRAP
1.64 markus 1291: /* Check whether logins are denied from this host. */
1292: {
1293: struct request_info req;
1.37 dugsong 1294:
1.204 camield 1295: request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, 0);
1.64 markus 1296: fromhost(&req);
1.37 dugsong 1297:
1.64 markus 1298: if (!hosts_access(&req)) {
1.209 markus 1299: debug("Connection refused by tcp wrapper");
1.182 markus 1300: refuse(&req);
1.209 markus 1301: /* NOTREACHED */
1302: fatal("libwrap refuse returns");
1.64 markus 1303: }
1304: }
1.75 markus 1305: #endif /* LIBWRAP */
1.209 markus 1306:
1.64 markus 1307: /* Log the connection. */
1308: verbose("Connection from %.500s port %d", remote_ip, remote_port);
1.1 deraadt 1309:
1.66 markus 1310: /*
1311: * We don\'t want to listen forever unless the other side
1312: * successfully authenticates itself. So we set up an alarm which is
1313: * cleared after successful authentication. A limit of zero
1314: * indicates no limit. Note that we don\'t set the alarm in debugging
1315: * mode; it is just annoying to have the server exit just when you
1316: * are about to discover the bug.
1317: */
1.64 markus 1318: signal(SIGALRM, grace_alarm_handler);
1319: if (!debug_flag)
1320: alarm(options.login_grace_time);
1321:
1.96 markus 1322: sshd_exchange_identification(sock_in, sock_out);
1.66 markus 1323: /*
1.137 markus 1324: * Check that the connection comes from a privileged port.
1325: * Rhosts-Authentication only makes sense from priviledged
1.66 markus 1326: * programs. Of course, if the intruder has root access on his local
1327: * machine, he can connect from any port. So do not use these
1328: * authentication methods from machines that you do not trust.
1329: */
1.225 markus 1330: if (options.rhosts_authentication &&
1331: (remote_port >= IPPORT_RESERVED ||
1332: remote_port < IPPORT_RESERVED / 2)) {
1.137 markus 1333: debug("Rhosts Authentication disabled, "
1.207 markus 1334: "originating port %d not trusted.", remote_port);
1.64 markus 1335: options.rhosts_authentication = 0;
1336: }
1.202 dugsong 1337: #if defined(KRB4) && !defined(KRB5)
1.76 markus 1338: if (!packet_connection_is_ipv4() &&
1339: options.kerberos_authentication) {
1340: debug("Kerberos Authentication disabled, only available for IPv4.");
1341: options.kerberos_authentication = 0;
1342: }
1.202 dugsong 1343: #endif /* KRB4 && !KRB5 */
1.164 markus 1344: #ifdef AFS
1345: /* If machine has AFS, set process authentication group. */
1346: if (k_hasafs()) {
1347: k_setpag();
1348: k_unlog();
1349: }
1350: #endif /* AFS */
1.76 markus 1351:
1.64 markus 1352: packet_set_nonblocking();
1.1 deraadt 1353:
1.231 provos 1354: if (!use_privsep)
1355: goto skip_privilegeseparation;
1.234 markus 1356:
1.231 provos 1357: /* Set up unprivileged child process to deal with network data */
1358: monitor = monitor_init();
1359: /* Store a pointer to the kex for later rekeying */
1360: monitor->m_pkex = &xxx_kex;
1361:
1362: pid = fork();
1363: if (pid == -1)
1364: fatal("fork of unprivileged child failed");
1365: else if (pid != 0) {
1366: debug2("Network child is on pid %d", pid);
1367:
1368: close(monitor->m_recvfd);
1369: authctxt = monitor_child_preauth(monitor);
1370: close(monitor->m_sendfd);
1371:
1372: /* Sync memory */
1373: monitor_sync(monitor);
1374: goto authenticated;
1375: } else {
1376: close(monitor->m_sendfd);
1377:
1378: /* Demote the child */
1379: if (getuid() == 0 || geteuid() == 0)
1380: privsep_preauth_child();
1381: }
1382:
1383: skip_privilegeseparation:
1384:
1.77 markus 1385: /* perform the key exchange */
1386: /* authenticate user and start session */
1.98 markus 1387: if (compat20) {
1388: do_ssh2_kex();
1.230 provos 1389: authctxt = do_authentication2();
1.98 markus 1390: } else {
1391: do_ssh1_kex();
1.230 provos 1392: authctxt = do_authentication();
1.98 markus 1393: }
1.231 provos 1394: if (use_privsep)
1395: mm_send_keystate(monitor);
1396:
1397: /* If we use privilege separation, the unprivileged child exits */
1398: if (use_privsep)
1399: exit(0);
1400:
1401: authenticated:
1.234 markus 1402: /*
1.231 provos 1403: * In privilege separation, we fork another child and prepare
1404: * file descriptor passing.
1405: */
1406: if (use_privsep) {
1407: privsep_postauth(authctxt, pid);
1408: if (!compat20)
1409: destroy_sensitive_data();
1410: }
1.230 provos 1411:
1412: /* Perform session preparation. */
1413: do_authenticated(authctxt);
1414:
1.64 markus 1415: /* The connection has been terminated. */
1416: verbose("Closing connection to %.100s", remote_ip);
1417: packet_close();
1.231 provos 1418:
1419: if (use_privsep)
1420: mm_terminate();
1421:
1.64 markus 1422: exit(0);
1.1 deraadt 1423: }
1424:
1.65 deraadt 1425: /*
1.229 markus 1426: * Decrypt session_key_int using our private server key and private host key
1427: * (key with larger modulus first).
1428: */
1.231 provos 1429: int
1.229 markus 1430: ssh1_session_key(BIGNUM *session_key_int)
1431: {
1432: int rsafail = 0;
1433:
1434: if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
1435: /* Server key has bigger modulus. */
1436: if (BN_num_bits(sensitive_data.server_key->rsa->n) <
1437: BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1438: fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1439: get_remote_ipaddr(),
1440: BN_num_bits(sensitive_data.server_key->rsa->n),
1441: BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1442: SSH_KEY_BITS_RESERVED);
1443: }
1444: if (rsa_private_decrypt(session_key_int, session_key_int,
1445: sensitive_data.server_key->rsa) <= 0)
1446: rsafail++;
1447: if (rsa_private_decrypt(session_key_int, session_key_int,
1448: sensitive_data.ssh1_host_key->rsa) <= 0)
1449: rsafail++;
1450: } else {
1451: /* Host key has bigger modulus (or they are equal). */
1452: if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
1453: BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1454: fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
1455: get_remote_ipaddr(),
1456: BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1457: BN_num_bits(sensitive_data.server_key->rsa->n),
1458: SSH_KEY_BITS_RESERVED);
1459: }
1460: if (rsa_private_decrypt(session_key_int, session_key_int,
1461: sensitive_data.ssh1_host_key->rsa) < 0)
1462: rsafail++;
1463: if (rsa_private_decrypt(session_key_int, session_key_int,
1464: sensitive_data.server_key->rsa) < 0)
1465: rsafail++;
1466: }
1467: return (rsafail);
1468: }
1469: /*
1.77 markus 1470: * SSH1 key exchange
1.65 deraadt 1471: */
1.200 itojun 1472: static void
1.142 markus 1473: do_ssh1_kex(void)
1.1 deraadt 1474: {
1.64 markus 1475: int i, len;
1.159 markus 1476: int rsafail = 0;
1.64 markus 1477: BIGNUM *session_key_int;
1.140 markus 1478: u_char session_key[SSH_SESSION_KEY_LENGTH];
1479: u_char cookie[8];
1480: u_int cipher_type, auth_mask, protocol_flags;
1.64 markus 1481: u_int32_t rand = 0;
1482:
1.66 markus 1483: /*
1484: * Generate check bytes that the client must send back in the user
1485: * packet in order for it to be accepted; this is used to defy ip
1486: * spoofing attacks. Note that this only works against somebody
1487: * doing IP spoofing from a remote machine; any machine on the local
1488: * network can still see outgoing packets and catch the random
1489: * cookie. This only affects rhosts authentication, and this is one
1490: * of the reasons why it is inherently insecure.
1491: */
1.64 markus 1492: for (i = 0; i < 8; i++) {
1493: if (i % 4 == 0)
1494: rand = arc4random();
1.77 markus 1495: cookie[i] = rand & 0xff;
1.64 markus 1496: rand >>= 8;
1497: }
1498:
1.66 markus 1499: /*
1500: * Send our public key. We include in the packet 64 bits of random
1501: * data that must be matched in the reply in order to prevent IP
1502: * spoofing.
1503: */
1.64 markus 1504: packet_start(SSH_SMSG_PUBLIC_KEY);
1505: for (i = 0; i < 8; i++)
1.77 markus 1506: packet_put_char(cookie[i]);
1.64 markus 1507:
1508: /* Store our public server RSA key. */
1.134 markus 1509: packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
1510: packet_put_bignum(sensitive_data.server_key->rsa->e);
1511: packet_put_bignum(sensitive_data.server_key->rsa->n);
1.64 markus 1512:
1513: /* Store our public host RSA key. */
1.134 markus 1514: packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1515: packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
1516: packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
1.64 markus 1517:
1518: /* Put protocol flags. */
1519: packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1520:
1521: /* Declare which ciphers we support. */
1.131 markus 1522: packet_put_int(cipher_mask_ssh1(0));
1.64 markus 1523:
1524: /* Declare supported authentication types. */
1525: auth_mask = 0;
1526: if (options.rhosts_authentication)
1527: auth_mask |= 1 << SSH_AUTH_RHOSTS;
1528: if (options.rhosts_rsa_authentication)
1529: auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1530: if (options.rsa_authentication)
1531: auth_mask |= 1 << SSH_AUTH_RSA;
1.202 dugsong 1532: #if defined(KRB4) || defined(KRB5)
1.64 markus 1533: if (options.kerberos_authentication)
1534: auth_mask |= 1 << SSH_AUTH_KERBEROS;
1.1 deraadt 1535: #endif
1.202 dugsong 1536: #if defined(AFS) || defined(KRB5)
1.64 markus 1537: if (options.kerberos_tgt_passing)
1538: auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
1.202 dugsong 1539: #endif
1540: #ifdef AFS
1.64 markus 1541: if (options.afs_token_passing)
1542: auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
1.1 deraadt 1543: #endif
1.196 markus 1544: if (options.challenge_response_authentication == 1)
1.64 markus 1545: auth_mask |= 1 << SSH_AUTH_TIS;
1546: if (options.password_authentication)
1547: auth_mask |= 1 << SSH_AUTH_PASSWORD;
1548: packet_put_int(auth_mask);
1549:
1550: /* Send the packet and wait for it to be sent. */
1551: packet_send();
1552: packet_write_wait();
1553:
1.134 markus 1554: debug("Sent %d bit server key and %d bit host key.",
1555: BN_num_bits(sensitive_data.server_key->rsa->n),
1556: BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1.64 markus 1557:
1558: /* Read clients reply (cipher type and session key). */
1.222 markus 1559: packet_read_expect(SSH_CMSG_SESSION_KEY);
1.64 markus 1560:
1.69 markus 1561: /* Get cipher type and check whether we accept this. */
1.64 markus 1562: cipher_type = packet_get_char();
1.69 markus 1563:
1.131 markus 1564: if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
1.69 markus 1565: packet_disconnect("Warning: client selects unsupported cipher.");
1.64 markus 1566:
1567: /* Get check bytes from the packet. These must match those we
1568: sent earlier with the public key packet. */
1569: for (i = 0; i < 8; i++)
1.77 markus 1570: if (cookie[i] != packet_get_char())
1.64 markus 1571: packet_disconnect("IP Spoofing check bytes do not match.");
1572:
1573: debug("Encryption type: %.200s", cipher_name(cipher_type));
1574:
1575: /* Get the encrypted integer. */
1.218 markus 1576: if ((session_key_int = BN_new()) == NULL)
1577: fatal("do_ssh1_kex: BN_new failed");
1.221 markus 1578: packet_get_bignum(session_key_int);
1.64 markus 1579:
1580: protocol_flags = packet_get_int();
1581: packet_set_protocol_flags(protocol_flags);
1.220 markus 1582: packet_check_eom();
1.64 markus 1583:
1.229 markus 1584: /* Decrypt session_key_int using host/server keys */
1.231 provos 1585: rsafail = PRIVSEP(ssh1_session_key(session_key_int));
1586:
1.66 markus 1587: /*
1588: * Extract session key from the decrypted integer. The key is in the
1589: * least significant 256 bits of the integer; the first byte of the
1590: * key is in the highest bits.
1591: */
1.159 markus 1592: if (!rsafail) {
1593: BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1594: len = BN_num_bytes(session_key_int);
1595: if (len < 0 || len > sizeof(session_key)) {
1596: error("do_connection: bad session key len from %s: "
1.165 itojun 1597: "session_key_int %d > sizeof(session_key) %lu",
1598: get_remote_ipaddr(), len, (u_long)sizeof(session_key));
1.159 markus 1599: rsafail++;
1600: } else {
1601: memset(session_key, 0, sizeof(session_key));
1602: BN_bn2bin(session_key_int,
1603: session_key + sizeof(session_key) - len);
1.169 markus 1604:
1605: compute_session_id(session_id, cookie,
1606: sensitive_data.ssh1_host_key->rsa->n,
1607: sensitive_data.server_key->rsa->n);
1608: /*
1609: * Xor the first 16 bytes of the session key with the
1610: * session id.
1611: */
1612: for (i = 0; i < 16; i++)
1613: session_key[i] ^= session_id[i];
1.159 markus 1614: }
1615: }
1616: if (rsafail) {
1.169 markus 1617: int bytes = BN_num_bytes(session_key_int);
1.227 stevesk 1618: u_char *buf = xmalloc(bytes);
1.169 markus 1619: MD5_CTX md;
1620:
1.159 markus 1621: log("do_connection: generating a fake encryption key");
1.169 markus 1622: BN_bn2bin(session_key_int, buf);
1623: MD5_Init(&md);
1624: MD5_Update(&md, buf, bytes);
1625: MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1626: MD5_Final(session_key, &md);
1627: MD5_Init(&md);
1628: MD5_Update(&md, session_key, 16);
1629: MD5_Update(&md, buf, bytes);
1630: MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1631: MD5_Final(session_key + 16, &md);
1632: memset(buf, 0, bytes);
1633: xfree(buf);
1.170 markus 1634: for (i = 0; i < 16; i++)
1635: session_id[i] = session_key[i] ^ session_key[i + 16];
1.159 markus 1636: }
1.231 provos 1637: /* Destroy the private and public keys. No longer. */
1.169 markus 1638: destroy_sensitive_data();
1639:
1.231 provos 1640: if (use_privsep)
1641: mm_ssh1_session_id(session_id);
1642:
1.77 markus 1643: /* Destroy the decrypted integer. It is no longer needed. */
1644: BN_clear_free(session_key_int);
1.64 markus 1645:
1646: /* Set the session key. From this on all communications will be encrypted. */
1647: packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1648:
1649: /* Destroy our copy of the session key. It is no longer needed. */
1650: memset(session_key, 0, sizeof(session_key));
1651:
1652: debug("Received session key; encryption turned on.");
1653:
1654: /* Send an acknowledgement packet. Note that this packet is sent encrypted. */
1655: packet_start(SSH_SMSG_SUCCESS);
1656: packet_send();
1657: packet_write_wait();
1.98 markus 1658: }
1659:
1660: /*
1661: * SSH2 key exchange: diffie-hellman-group1-sha1
1662: */
1.200 itojun 1663: static void
1.142 markus 1664: do_ssh2_kex(void)
1.98 markus 1665: {
1666: Kex *kex;
1.102 markus 1667:
1668: if (options.ciphers != NULL) {
1.105 markus 1669: myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1.102 markus 1670: myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1.166 markus 1671: }
1.184 stevesk 1672: myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1673: compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
1674: myproposal[PROPOSAL_ENC_ALGS_STOC] =
1675: compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
1676:
1.166 markus 1677: if (options.macs != NULL) {
1678: myproposal[PROPOSAL_MAC_ALGS_CTOS] =
1679: myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
1.102 markus 1680: }
1.134 markus 1681: myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
1682:
1.189 markus 1683: /* start key exchange */
1.188 markus 1684: kex = kex_setup(myproposal);
1.186 markus 1685: kex->server = 1;
1686: kex->client_version_string=client_version_string;
1687: kex->server_version_string=server_version_string;
1688: kex->load_host_key=&get_hostkey_by_type;
1.231 provos 1689: kex->host_key_index=&get_hostkey_index;
1.129 provos 1690:
1.189 markus 1691: xxx_kex = kex;
1692:
1.190 markus 1693: dispatch_run(DISPATCH_BLOCK, &kex->done, kex);
1.187 markus 1694:
1695: session_id2 = kex->session_id;
1696: session_id2_len = kex->session_id_len;
1.129 provos 1697:
1698: #ifdef DEBUG_KEXDH
1699: /* send 1st encrypted/maced/compressed message */
1700: packet_start(SSH2_MSG_IGNORE);
1701: packet_put_cstring("markus");
1702: packet_send();
1703: packet_write_wait();
1704: #endif
1.186 markus 1705: debug("KEX done");
1.1 deraadt 1706: }
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