Annotation of src/usr.bin/ssh/sshd.c, Revision 1.189
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:
18: *
19: * Copyright (c) 2000 Markus Friedl. All rights reserved.
20: *
21: * Redistribution and use in source and binary forms, with or without
22: * modification, are permitted provided that the following conditions
23: * are met:
24: * 1. Redistributions of source code must retain the above copyright
25: * notice, this list of conditions and the following disclaimer.
26: * 2. Redistributions in binary form must reproduce the above copyright
27: * notice, this list of conditions and the following disclaimer in the
28: * documentation and/or other materials provided with the distribution.
29: *
30: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
31: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
32: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
33: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
34: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
35: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
36: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
37: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
38: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
39: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
1.65 deraadt 40: */
1.1 deraadt 41:
42: #include "includes.h"
1.189 ! markus 43: RCSID("$OpenBSD: sshd.c,v 1.188 2001/04/04 09:48:35 markus Exp $");
1.1 deraadt 44:
1.155 markus 45: #include <openssl/dh.h>
46: #include <openssl/bn.h>
47: #include <openssl/hmac.h>
48:
49: #include "ssh.h"
50: #include "ssh1.h"
51: #include "ssh2.h"
1.1 deraadt 52: #include "xmalloc.h"
53: #include "rsa.h"
1.171 djm 54: #include "sshpty.h"
1.1 deraadt 55: #include "packet.h"
56: #include "mpaux.h"
1.155 markus 57: #include "log.h"
1.1 deraadt 58: #include "servconf.h"
59: #include "uidswap.h"
1.33 markus 60: #include "compat.h"
1.96 markus 61: #include "buffer.h"
1.155 markus 62: #include "cipher.h"
1.98 markus 63: #include "kex.h"
1.96 markus 64: #include "key.h"
1.129 provos 65: #include "dh.h"
1.98 markus 66: #include "myproposal.h"
1.108 markus 67: #include "authfile.h"
1.154 markus 68: #include "pathnames.h"
1.155 markus 69: #include "atomicio.h"
70: #include "canohost.h"
71: #include "auth.h"
72: #include "misc.h"
1.186 markus 73: #include "dispatch.h"
1.1 deraadt 74:
75: #ifdef LIBWRAP
76: #include <tcpd.h>
77: #include <syslog.h>
78: int allow_severity = LOG_INFO;
79: int deny_severity = LOG_WARNING;
80: #endif /* LIBWRAP */
81:
82: #ifndef O_NOCTTY
83: #define O_NOCTTY 0
84: #endif
85:
1.138 markus 86: extern char *__progname;
87:
1.1 deraadt 88: /* Server configuration options. */
89: ServerOptions options;
90:
91: /* Name of the server configuration file. */
1.154 markus 92: char *config_file_name = _PATH_SERVER_CONFIG_FILE;
1.1 deraadt 93:
1.105 markus 94: /*
1.75 markus 95: * Flag indicating whether IPv4 or IPv6. This can be set on the command line.
96: * Default value is AF_UNSPEC means both IPv4 and IPv6.
97: */
98: int IPv4or6 = AF_UNSPEC;
99:
1.65 deraadt 100: /*
101: * Debug mode flag. This can be set on the command line. If debug
102: * mode is enabled, extra debugging output will be sent to the system
103: * log, the daemon will not go to background, and will exit after processing
104: * the first connection.
105: */
1.1 deraadt 106: int debug_flag = 0;
107:
108: /* Flag indicating that the daemon is being started from inetd. */
109: int inetd_flag = 0;
110:
1.135 markus 111: /* Flag indicating that sshd should not detach and become a daemon. */
112: int no_daemon_flag = 0;
113:
1.47 markus 114: /* debug goes to stderr unless inetd_flag is set */
115: int log_stderr = 0;
116:
1.1 deraadt 117: /* Saved arguments to main(). */
118: char **saved_argv;
119:
1.66 markus 120: /*
1.75 markus 121: * The sockets that the server is listening; this is used in the SIGHUP
122: * signal handler.
1.66 markus 123: */
1.75 markus 124: #define MAX_LISTEN_SOCKS 16
125: int listen_socks[MAX_LISTEN_SOCKS];
126: int num_listen_socks = 0;
1.1 deraadt 127:
1.66 markus 128: /*
129: * the client's version string, passed by sshd2 in compat mode. if != NULL,
130: * sshd will skip the version-number exchange
131: */
1.61 markus 132: char *client_version_string = NULL;
1.96 markus 133: char *server_version_string = NULL;
1.1 deraadt 134:
1.189 ! markus 135: /* for rekeying XXX fixme */
! 136: Kex *xxx_kex;
! 137:
1.66 markus 138: /*
139: * Any really sensitive data in the application is contained in this
140: * structure. The idea is that this structure could be locked into memory so
141: * that the pages do not get written into swap. However, there are some
142: * problems. The private key contains BIGNUMs, and we do not (in principle)
143: * have access to the internals of them, and locking just the structure is
144: * not very useful. Currently, memory locking is not implemented.
145: */
1.64 markus 146: struct {
1.174 deraadt 147: Key *server_key; /* ephemeral server key */
1.134 markus 148: Key *ssh1_host_key; /* ssh1 host key */
149: Key **host_keys; /* all private host keys */
150: int have_ssh1_key;
151: int have_ssh2_key;
1.169 markus 152: u_char ssh1_cookie[SSH_SESSION_KEY_LENGTH];
1.1 deraadt 153: } sensitive_data;
154:
1.66 markus 155: /*
1.151 markus 156: * Flag indicating whether the RSA server key needs to be regenerated.
157: * Is set in the SIGALRM handler and cleared when the key is regenerated.
1.66 markus 158: */
1.151 markus 159: int key_do_regen = 0;
1.1 deraadt 160:
161: /* This is set to true when SIGHUP is received. */
162: int received_sighup = 0;
163:
1.96 markus 164: /* session identifier, used by RSA-auth */
1.140 markus 165: u_char session_id[16];
1.96 markus 166:
1.108 markus 167: /* same for ssh2 */
1.140 markus 168: u_char *session_id2 = NULL;
1.108 markus 169: int session_id2_len = 0;
170:
1.125 markus 171: /* record remote hostname or ip */
1.140 markus 172: u_int utmp_len = MAXHOSTNAMELEN;
1.125 markus 173:
1.1 deraadt 174: /* Prototypes for various functions defined later in this file. */
1.142 markus 175: void do_ssh1_kex(void);
176: void do_ssh2_kex(void);
1.87 markus 177:
1.129 provos 178: void ssh_dh1_server(Kex *, Buffer *_kexinit, Buffer *);
179: void ssh_dhgex_server(Kex *, Buffer *_kexinit, Buffer *);
180:
1.87 markus 181: /*
1.75 markus 182: * Close all listening sockets
183: */
184: void
185: close_listen_socks(void)
186: {
187: int i;
188: for (i = 0; i < num_listen_socks; i++)
189: close(listen_socks[i]);
190: num_listen_socks = -1;
191: }
192:
193: /*
1.65 deraadt 194: * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
195: * the effect is to reread the configuration file (and to regenerate
196: * the server key).
197: */
1.105 markus 198: void
1.64 markus 199: sighup_handler(int sig)
1.1 deraadt 200: {
1.64 markus 201: received_sighup = 1;
202: signal(SIGHUP, sighup_handler);
1.1 deraadt 203: }
204:
1.65 deraadt 205: /*
206: * Called from the main program after receiving SIGHUP.
207: * Restarts the server.
208: */
1.105 markus 209: void
1.165 itojun 210: sighup_restart(void)
1.1 deraadt 211: {
1.64 markus 212: log("Received SIGHUP; restarting.");
1.75 markus 213: close_listen_socks();
1.64 markus 214: execv(saved_argv[0], saved_argv);
1.138 markus 215: log("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], strerror(errno));
1.64 markus 216: exit(1);
1.1 deraadt 217: }
218:
1.65 deraadt 219: /*
220: * Generic signal handler for terminating signals in the master daemon.
221: * These close the listen socket; not closing it seems to cause "Address
222: * already in use" problems on some machines, which is inconvenient.
223: */
1.105 markus 224: void
1.64 markus 225: sigterm_handler(int sig)
1.1 deraadt 226: {
1.64 markus 227: log("Received signal %d; terminating.", sig);
1.75 markus 228: close_listen_socks();
1.113 markus 229: unlink(options.pid_file);
1.64 markus 230: exit(255);
1.1 deraadt 231: }
232:
1.65 deraadt 233: /*
234: * SIGCHLD handler. This is called whenever a child dies. This will then
235: * reap any zombies left by exited c.
236: */
1.105 markus 237: void
1.64 markus 238: main_sigchld_handler(int sig)
1.1 deraadt 239: {
1.64 markus 240: int save_errno = errno;
241: int status;
1.60 deraadt 242:
1.64 markus 243: while (waitpid(-1, &status, WNOHANG) > 0)
244: ;
1.60 deraadt 245:
1.64 markus 246: signal(SIGCHLD, main_sigchld_handler);
247: errno = save_errno;
1.1 deraadt 248: }
249:
1.65 deraadt 250: /*
251: * Signal handler for the alarm after the login grace period has expired.
252: */
1.105 markus 253: void
1.64 markus 254: grace_alarm_handler(int sig)
1.1 deraadt 255: {
1.64 markus 256: /* Close the connection. */
257: packet_close();
258:
259: /* Log error and exit. */
260: fatal("Timeout before authentication for %s.", get_remote_ipaddr());
1.62 markus 261: }
262:
1.65 deraadt 263: /*
264: * Signal handler for the key regeneration alarm. Note that this
265: * alarm only occurs in the daemon waiting for connections, and it does not
266: * do anything with the private key or random state before forking.
267: * Thus there should be no concurrency control/asynchronous execution
268: * problems.
269: */
1.105 markus 270: void
1.174 deraadt 271: generate_ephemeral_server_key(void)
1.134 markus 272: {
1.169 markus 273: u_int32_t rand = 0;
274: int i;
275:
1.185 djm 276: verbose("Generating %s%d bit RSA key.",
277: sensitive_data.server_key ? "new " : "", options.server_key_bits);
1.134 markus 278: if (sensitive_data.server_key != NULL)
279: key_free(sensitive_data.server_key);
1.185 djm 280: sensitive_data.server_key = key_generate(KEY_RSA1,
281: options.server_key_bits);
282: verbose("RSA key generation complete.");
1.169 markus 283:
284: for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
285: if (i % 4 == 0)
286: rand = arc4random();
287: sensitive_data.ssh1_cookie[i] = rand & 0xff;
288: rand >>= 8;
289: }
1.134 markus 290: arc4random_stir();
291: }
1.147 deraadt 292:
1.134 markus 293: void
1.64 markus 294: key_regeneration_alarm(int sig)
1.1 deraadt 295: {
1.64 markus 296: int save_errno = errno;
1.151 markus 297: signal(SIGALRM, SIG_DFL);
1.64 markus 298: errno = save_errno;
1.151 markus 299: key_do_regen = 1;
1.98 markus 300: }
301:
1.96 markus 302: void
303: sshd_exchange_identification(int sock_in, int sock_out)
304: {
1.102 markus 305: int i, mismatch;
1.96 markus 306: int remote_major, remote_minor;
1.102 markus 307: int major, minor;
1.96 markus 308: char *s;
309: char buf[256]; /* Must not be larger than remote_version. */
310: char remote_version[256]; /* Must be at least as big as buf. */
311:
1.103 markus 312: if ((options.protocol & SSH_PROTO_1) &&
313: (options.protocol & SSH_PROTO_2)) {
1.102 markus 314: major = PROTOCOL_MAJOR_1;
315: minor = 99;
316: } else if (options.protocol & SSH_PROTO_2) {
317: major = PROTOCOL_MAJOR_2;
318: minor = PROTOCOL_MINOR_2;
319: } else {
320: major = PROTOCOL_MAJOR_1;
321: minor = PROTOCOL_MINOR_1;
322: }
323: snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
1.96 markus 324: server_version_string = xstrdup(buf);
325:
326: if (client_version_string == NULL) {
327: /* Send our protocol version identification. */
328: if (atomicio(write, sock_out, server_version_string, strlen(server_version_string))
329: != strlen(server_version_string)) {
330: log("Could not write ident string to %s.", get_remote_ipaddr());
331: fatal_cleanup();
332: }
333:
1.167 markus 334: /* Read other side's version identification. */
335: memset(buf, 0, sizeof(buf));
1.96 markus 336: for (i = 0; i < sizeof(buf) - 1; i++) {
1.119 markus 337: if (atomicio(read, sock_in, &buf[i], 1) != 1) {
1.168 deraadt 338: log("Did not receive identification string from %s.",
339: get_remote_ipaddr());
1.96 markus 340: fatal_cleanup();
341: }
342: if (buf[i] == '\r') {
1.176 deraadt 343: buf[i] = 0;
1.132 markus 344: /* Kludge for F-Secure Macintosh < 1.0.2 */
345: if (i == 12 &&
346: strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
347: break;
1.96 markus 348: continue;
349: }
350: if (buf[i] == '\n') {
1.176 deraadt 351: buf[i] = 0;
1.96 markus 352: break;
353: }
354: }
355: buf[sizeof(buf) - 1] = 0;
356: client_version_string = xstrdup(buf);
357: }
358:
359: /*
360: * Check that the versions match. In future this might accept
361: * several versions and set appropriate flags to handle them.
362: */
363: if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
364: &remote_major, &remote_minor, remote_version) != 3) {
1.105 markus 365: s = "Protocol mismatch.\n";
1.96 markus 366: (void) atomicio(write, sock_out, s, strlen(s));
367: close(sock_in);
368: close(sock_out);
369: log("Bad protocol version identification '%.100s' from %s",
370: client_version_string, get_remote_ipaddr());
371: fatal_cleanup();
372: }
373: debug("Client protocol version %d.%d; client software version %.100s",
374: remote_major, remote_minor, remote_version);
375:
1.98 markus 376: compat_datafellows(remote_version);
1.175 deraadt 377:
378: if (datafellows & SSH_BUG_SCANNER) {
379: log("scanned from %s with %s. Don't panic.",
380: get_remote_ipaddr(), client_version_string);
381: fatal_cleanup();
382: }
1.98 markus 383:
1.102 markus 384: mismatch = 0;
1.96 markus 385: switch(remote_major) {
386: case 1:
1.108 markus 387: if (remote_minor == 99) {
388: if (options.protocol & SSH_PROTO_2)
389: enable_compat20();
390: else
391: mismatch = 1;
392: break;
393: }
1.102 markus 394: if (!(options.protocol & SSH_PROTO_1)) {
395: mismatch = 1;
396: break;
397: }
1.96 markus 398: if (remote_minor < 3) {
1.121 provos 399: packet_disconnect("Your ssh version is too old and "
1.96 markus 400: "is no longer supported. Please install a newer version.");
401: } else if (remote_minor == 3) {
402: /* note that this disables agent-forwarding */
403: enable_compat13();
404: }
1.102 markus 405: break;
1.98 markus 406: case 2:
1.102 markus 407: if (options.protocol & SSH_PROTO_2) {
1.98 markus 408: enable_compat20();
409: break;
410: }
1.99 markus 411: /* FALLTHROUGH */
1.105 markus 412: default:
1.102 markus 413: mismatch = 1;
414: break;
415: }
416: chop(server_version_string);
417: debug("Local version string %.200s", server_version_string);
418:
419: if (mismatch) {
1.96 markus 420: s = "Protocol major versions differ.\n";
421: (void) atomicio(write, sock_out, s, strlen(s));
422: close(sock_in);
423: close(sock_out);
1.102 markus 424: log("Protocol major versions differ for %s: %.200s vs. %.200s",
425: get_remote_ipaddr(),
426: server_version_string, client_version_string);
1.96 markus 427: fatal_cleanup();
428: }
1.108 markus 429: if (compat20)
430: packet_set_ssh2_format();
431: }
432:
433:
1.134 markus 434: /* Destroy the host and server keys. They will no longer be needed. */
1.108 markus 435: void
436: destroy_sensitive_data(void)
437: {
1.134 markus 438: int i;
439:
440: if (sensitive_data.server_key) {
441: key_free(sensitive_data.server_key);
442: sensitive_data.server_key = NULL;
443: }
1.161 stevesk 444: for(i = 0; i < options.num_host_key_files; i++) {
1.134 markus 445: if (sensitive_data.host_keys[i]) {
446: key_free(sensitive_data.host_keys[i]);
447: sensitive_data.host_keys[i] = NULL;
448: }
449: }
450: sensitive_data.ssh1_host_key = NULL;
1.169 markus 451: memset(sensitive_data.ssh1_cookie, 0, SSH_SESSION_KEY_LENGTH);
1.134 markus 452: }
453:
454: char *
455: list_hostkey_types(void)
456: {
457: static char buf[1024];
458: int i;
459: buf[0] = '\0';
460: for(i = 0; i < options.num_host_key_files; i++) {
461: Key *key = sensitive_data.host_keys[i];
462: if (key == NULL)
463: continue;
464: switch(key->type) {
465: case KEY_RSA:
466: case KEY_DSA:
467: strlcat(buf, key_ssh_name(key), sizeof buf);
468: strlcat(buf, ",", sizeof buf);
469: break;
470: }
471: }
472: i = strlen(buf);
473: if (i > 0 && buf[i-1] == ',')
474: buf[i-1] = '\0';
475: debug("list_hostkey_types: %s", buf);
476: return buf;
477: }
478:
479: Key *
480: get_hostkey_by_type(int type)
481: {
482: int i;
483: for(i = 0; i < options.num_host_key_files; i++) {
484: Key *key = sensitive_data.host_keys[i];
485: if (key != NULL && key->type == type)
486: return key;
487: }
488: return NULL;
1.96 markus 489: }
490:
1.124 markus 491: /*
492: * returns 1 if connection should be dropped, 0 otherwise.
493: * dropping starts at connection #max_startups_begin with a probability
494: * of (max_startups_rate/100). the probability increases linearly until
495: * all connections are dropped for startups > max_startups
496: */
497: int
498: drop_connection(int startups)
499: {
500: double p, r;
501:
502: if (startups < options.max_startups_begin)
503: return 0;
504: if (startups >= options.max_startups)
505: return 1;
506: if (options.max_startups_rate == 100)
507: return 1;
508:
509: p = 100 - options.max_startups_rate;
510: p *= startups - options.max_startups_begin;
511: p /= (double) (options.max_startups - options.max_startups_begin);
512: p += options.max_startups_rate;
513: p /= 100.0;
514: r = arc4random() / (double) UINT_MAX;
515:
516: debug("drop_connection: p %g, r %g", p, r);
517: return (r < p) ? 1 : 0;
518: }
519:
1.120 markus 520: int *startup_pipes = NULL; /* options.max_startup sized array of fd ints */
521: int startup_pipe; /* in child */
522:
1.65 deraadt 523: /*
524: * Main program for the daemon.
525: */
1.2 provos 526: int
527: main(int ac, char **av)
1.1 deraadt 528: {
1.64 markus 529: extern char *optarg;
530: extern int optind;
1.120 markus 531: int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1;
1.107 deraadt 532: pid_t pid;
1.75 markus 533: socklen_t fromlen;
534: fd_set *fdset;
535: struct sockaddr_storage from;
1.64 markus 536: const char *remote_ip;
537: int remote_port;
538: FILE *f;
539: struct linger linger;
1.75 markus 540: struct addrinfo *ai;
541: char ntop[NI_MAXHOST], strport[NI_MAXSERV];
542: int listen_sock, maxfd;
1.120 markus 543: int startup_p[2];
544: int startups = 0;
1.179 markus 545: Key *key;
1.151 markus 546: int ret, key_used = 0;
1.64 markus 547:
1.138 markus 548: /* Save argv. */
1.64 markus 549: saved_argv = av;
550:
551: /* Initialize configuration options to their default values. */
552: initialize_server_options(&options);
553:
554: /* Parse command-line arguments. */
1.149 markus 555: while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:dDiqQ46")) != -1) {
1.64 markus 556: switch (opt) {
1.75 markus 557: case '4':
558: IPv4or6 = AF_INET;
559: break;
560: case '6':
561: IPv4or6 = AF_INET6;
562: break;
1.64 markus 563: case 'f':
564: config_file_name = optarg;
565: break;
566: case 'd':
1.127 markus 567: if (0 == debug_flag) {
568: debug_flag = 1;
569: options.log_level = SYSLOG_LEVEL_DEBUG1;
570: } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) {
571: options.log_level++;
572: } else {
573: fprintf(stderr, "Too high debugging level.\n");
574: exit(1);
575: }
1.64 markus 576: break;
1.135 markus 577: case 'D':
578: no_daemon_flag = 1;
579: break;
1.64 markus 580: case 'i':
581: inetd_flag = 1;
582: break;
583: case 'Q':
1.158 markus 584: /* ignored */
1.64 markus 585: break;
586: case 'q':
587: options.log_level = SYSLOG_LEVEL_QUIET;
588: break;
589: case 'b':
590: options.server_key_bits = atoi(optarg);
591: break;
592: case 'p':
1.75 markus 593: options.ports_from_cmdline = 1;
1.127 markus 594: if (options.num_ports >= MAX_PORTS) {
595: fprintf(stderr, "too many ports.\n");
596: exit(1);
597: }
1.75 markus 598: options.ports[options.num_ports++] = atoi(optarg);
1.64 markus 599: break;
600: case 'g':
601: options.login_grace_time = atoi(optarg);
602: break;
603: case 'k':
604: options.key_regeneration_time = atoi(optarg);
605: break;
606: case 'h':
1.134 markus 607: if (options.num_host_key_files >= MAX_HOSTKEYS) {
608: fprintf(stderr, "too many host keys.\n");
609: exit(1);
610: }
611: options.host_key_files[options.num_host_key_files++] = optarg;
1.64 markus 612: break;
613: case 'V':
614: client_version_string = optarg;
615: /* only makes sense with inetd_flag, i.e. no listen() */
616: inetd_flag = 1;
617: break;
1.125 markus 618: case 'u':
619: utmp_len = atoi(optarg);
620: break;
1.64 markus 621: case '?':
622: default:
623: fprintf(stderr, "sshd version %s\n", SSH_VERSION);
1.138 markus 624: fprintf(stderr, "Usage: %s [options]\n", __progname);
1.64 markus 625: fprintf(stderr, "Options:\n");
1.154 markus 626: fprintf(stderr, " -f file Configuration file (default %s)\n", _PATH_SERVER_CONFIG_FILE);
1.127 markus 627: fprintf(stderr, " -d Debugging mode (multiple -d means more debugging)\n");
1.64 markus 628: fprintf(stderr, " -i Started from inetd\n");
1.144 markus 629: fprintf(stderr, " -D Do not fork into daemon mode\n");
1.64 markus 630: fprintf(stderr, " -q Quiet (no logging)\n");
631: fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
632: fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
1.145 markus 633: fprintf(stderr, " -g seconds Grace period for authentication (default: 600)\n");
1.64 markus 634: fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
635: fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
1.154 markus 636: _PATH_HOST_KEY_FILE);
1.125 markus 637: fprintf(stderr, " -u len Maximum hostname length for utmp recording\n");
1.75 markus 638: fprintf(stderr, " -4 Use IPv4 only\n");
639: fprintf(stderr, " -6 Use IPv6 only\n");
1.64 markus 640: exit(1);
641: }
642: }
1.180 markus 643: SSLeay_add_all_algorithms();
1.64 markus 644:
1.75 markus 645: /*
646: * Force logging to stderr until we have loaded the private host
647: * key (unless started from inetd)
648: */
1.138 markus 649: log_init(__progname,
1.152 markus 650: options.log_level == -1 ? SYSLOG_LEVEL_INFO : options.log_level,
1.75 markus 651: options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility,
1.158 markus 652: !inetd_flag);
1.75 markus 653:
1.64 markus 654: /* Read server configuration options from the configuration file. */
655: read_server_config(&options, config_file_name);
656:
657: /* Fill in default values for those options not explicitly set. */
658: fill_default_server_options(&options);
659:
660: /* Check that there are no remaining arguments. */
661: if (optind < ac) {
662: fprintf(stderr, "Extra argument %s.\n", av[optind]);
663: exit(1);
664: }
665:
666: debug("sshd version %.100s", SSH_VERSION);
667:
1.134 markus 668: /* load private host keys */
669: sensitive_data.host_keys = xmalloc(options.num_host_key_files*sizeof(Key*));
1.141 markus 670: for(i = 0; i < options.num_host_key_files; i++)
671: sensitive_data.host_keys[i] = NULL;
1.134 markus 672: sensitive_data.server_key = NULL;
673: sensitive_data.ssh1_host_key = NULL;
674: sensitive_data.have_ssh1_key = 0;
675: sensitive_data.have_ssh2_key = 0;
676:
677: for(i = 0; i < options.num_host_key_files; i++) {
1.179 markus 678: key = key_load_private(options.host_key_files[i], "", NULL);
679: sensitive_data.host_keys[i] = key;
1.134 markus 680: if (key == NULL) {
681: error("Could not load host key: %.200s: %.100s",
682: options.host_key_files[i], strerror(errno));
1.179 markus 683: sensitive_data.host_keys[i] = NULL;
1.134 markus 684: continue;
685: }
686: switch(key->type){
687: case KEY_RSA1:
688: sensitive_data.ssh1_host_key = key;
689: sensitive_data.have_ssh1_key = 1;
690: break;
691: case KEY_RSA:
692: case KEY_DSA:
693: sensitive_data.have_ssh2_key = 1;
694: break;
695: }
1.179 markus 696: debug("private host key: #%d type %d %s", i, key->type,
697: key_type(key));
1.134 markus 698: }
699: if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
700: log("Disabling protocol version 1. Could not load host key");
1.108 markus 701: options.protocol &= ~SSH_PROTO_1;
702: }
1.134 markus 703: if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
704: log("Disabling protocol version 2. Could not load host key");
705: options.protocol &= ~SSH_PROTO_2;
1.108 markus 706: }
1.162 stevesk 707: if (!(options.protocol & (SSH_PROTO_1|SSH_PROTO_2))) {
1.172 millert 708: log("sshd: no hostkeys available -- exiting.");
1.64 markus 709: exit(1);
710: }
711:
1.108 markus 712: /* Check certain values for sanity. */
713: if (options.protocol & SSH_PROTO_1) {
714: if (options.server_key_bits < 512 ||
715: options.server_key_bits > 32768) {
716: fprintf(stderr, "Bad server key size.\n");
717: exit(1);
718: }
719: /*
720: * Check that server and host key lengths differ sufficiently. This
721: * is necessary to make double encryption work with rsaref. Oh, I
722: * hate software patents. I dont know if this can go? Niels
723: */
724: if (options.server_key_bits >
1.134 markus 725: BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - SSH_KEY_BITS_RESERVED &&
1.108 markus 726: options.server_key_bits <
1.134 markus 727: BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1.108 markus 728: options.server_key_bits =
1.134 markus 729: BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED;
1.108 markus 730: debug("Forcing server key to %d bits to make it differ from host key.",
731: options.server_key_bits);
732: }
733: }
734:
735: /* Initialize the log (it is reinitialized below in case we forked). */
1.64 markus 736: if (debug_flag && !inetd_flag)
737: log_stderr = 1;
1.138 markus 738: log_init(__progname, options.log_level, options.log_facility, log_stderr);
1.64 markus 739:
1.108 markus 740: /*
741: * If not in debugging mode, and not started from inetd, disconnect
742: * from the controlling terminal, and fork. The original process
743: * exits.
744: */
1.135 markus 745: if (!(debug_flag || inetd_flag || no_daemon_flag)) {
1.1 deraadt 746: #ifdef TIOCNOTTY
1.64 markus 747: int fd;
1.1 deraadt 748: #endif /* TIOCNOTTY */
1.64 markus 749: if (daemon(0, 0) < 0)
750: fatal("daemon() failed: %.200s", strerror(errno));
751:
752: /* Disconnect from the controlling tty. */
1.1 deraadt 753: #ifdef TIOCNOTTY
1.165 itojun 754: fd = open(_PATH_TTY, O_RDWR | O_NOCTTY);
1.64 markus 755: if (fd >= 0) {
756: (void) ioctl(fd, TIOCNOTTY, NULL);
757: close(fd);
758: }
759: #endif /* TIOCNOTTY */
760: }
761: /* Reinitialize the log (because of the fork above). */
1.138 markus 762: log_init(__progname, options.log_level, options.log_facility, log_stderr);
1.64 markus 763:
764: /* Initialize the random number generator. */
765: arc4random_stir();
766:
767: /* Chdir to the root directory so that the current disk can be
768: unmounted if desired. */
769: chdir("/");
1.178 markus 770:
771: /* ignore SIGPIPE */
772: signal(SIGPIPE, SIG_IGN);
1.64 markus 773:
774: /* Start listening for a socket, unless started from inetd. */
775: if (inetd_flag) {
776: int s1, s2;
777: s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
778: s2 = dup(s1);
779: sock_in = dup(0);
780: sock_out = dup(1);
1.123 djm 781: startup_pipe = -1;
1.108 markus 782: /*
783: * We intentionally do not close the descriptors 0, 1, and 2
784: * as our code for setting the descriptors won\'t work if
785: * ttyfd happens to be one of those.
786: */
1.64 markus 787: debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
1.134 markus 788: if (options.protocol & SSH_PROTO_1)
1.174 deraadt 789: generate_ephemeral_server_key();
1.64 markus 790: } else {
1.75 markus 791: for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
792: if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
793: continue;
794: if (num_listen_socks >= MAX_LISTEN_SOCKS)
795: fatal("Too many listen sockets. "
796: "Enlarge MAX_LISTEN_SOCKS");
797: if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
798: ntop, sizeof(ntop), strport, sizeof(strport),
799: NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
800: error("getnameinfo failed");
801: continue;
802: }
803: /* Create socket for listening. */
804: listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
805: if (listen_sock < 0) {
806: /* kernel may not support ipv6 */
807: verbose("socket: %.100s", strerror(errno));
808: continue;
809: }
810: if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
811: error("listen_sock O_NONBLOCK: %s", strerror(errno));
812: close(listen_sock);
813: continue;
814: }
815: /*
816: * Set socket options. We try to make the port
817: * reusable and have it close as fast as possible
818: * without waiting in unnecessary wait states on
819: * close.
820: */
821: setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
822: (void *) &on, sizeof(on));
823: linger.l_onoff = 1;
824: linger.l_linger = 5;
825: setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
826: (void *) &linger, sizeof(linger));
827:
828: debug("Bind to port %s on %s.", strport, ntop);
829:
830: /* Bind the socket to the desired port. */
831: if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
832: error("Bind to port %s on %s failed: %.200s.",
833: strport, ntop, strerror(errno));
834: close(listen_sock);
835: continue;
836: }
837: listen_socks[num_listen_socks] = listen_sock;
838: num_listen_socks++;
839:
840: /* Start listening on the port. */
841: log("Server listening on %s port %s.", ntop, strport);
842: if (listen(listen_sock, 5) < 0)
843: fatal("listen: %.100s", strerror(errno));
844:
1.64 markus 845: }
1.75 markus 846: freeaddrinfo(options.listen_addrs);
847:
848: if (!num_listen_socks)
849: fatal("Cannot bind any address.");
850:
1.64 markus 851: if (!debug_flag) {
1.66 markus 852: /*
1.136 todd 853: * Record our pid in /var/run/sshd.pid to make it
854: * easier to kill the correct sshd. We don't want to
855: * do this before the bind above because the bind will
1.66 markus 856: * fail if there already is a daemon, and this will
857: * overwrite any old pid in the file.
858: */
1.112 markus 859: f = fopen(options.pid_file, "w");
1.64 markus 860: if (f) {
1.140 markus 861: fprintf(f, "%u\n", (u_int) getpid());
1.64 markus 862: fclose(f);
863: }
864: }
1.151 markus 865: if (options.protocol & SSH_PROTO_1)
1.174 deraadt 866: generate_ephemeral_server_key();
1.64 markus 867:
868: /* Arrange to restart on SIGHUP. The handler needs listen_sock. */
869: signal(SIGHUP, sighup_handler);
1.120 markus 870:
1.64 markus 871: signal(SIGTERM, sigterm_handler);
872: signal(SIGQUIT, sigterm_handler);
873:
874: /* Arrange SIGCHLD to be caught. */
875: signal(SIGCHLD, main_sigchld_handler);
876:
1.75 markus 877: /* setup fd set for listen */
1.120 markus 878: fdset = NULL;
1.75 markus 879: maxfd = 0;
880: for (i = 0; i < num_listen_socks; i++)
881: if (listen_socks[i] > maxfd)
882: maxfd = listen_socks[i];
1.120 markus 883: /* pipes connected to unauthenticated childs */
884: startup_pipes = xmalloc(options.max_startups * sizeof(int));
885: for (i = 0; i < options.max_startups; i++)
886: startup_pipes[i] = -1;
1.75 markus 887:
1.66 markus 888: /*
889: * Stay listening for connections until the system crashes or
890: * the daemon is killed with a signal.
891: */
1.64 markus 892: for (;;) {
893: if (received_sighup)
894: sighup_restart();
1.120 markus 895: if (fdset != NULL)
896: xfree(fdset);
1.148 markus 897: fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask);
1.120 markus 898: fdset = (fd_set *)xmalloc(fdsetsz);
1.75 markus 899: memset(fdset, 0, fdsetsz);
1.120 markus 900:
1.75 markus 901: for (i = 0; i < num_listen_socks; i++)
902: FD_SET(listen_socks[i], fdset);
1.120 markus 903: for (i = 0; i < options.max_startups; i++)
904: if (startup_pipes[i] != -1)
905: FD_SET(startup_pipes[i], fdset);
906:
907: /* Wait in select until there is a connection. */
1.151 markus 908: ret = select(maxfd+1, fdset, NULL, NULL, NULL);
909: if (ret < 0 && errno != EINTR)
910: error("select: %.100s", strerror(errno));
911: if (key_used && key_do_regen) {
1.174 deraadt 912: generate_ephemeral_server_key();
1.151 markus 913: key_used = 0;
914: key_do_regen = 0;
915: }
916: if (ret < 0)
1.75 markus 917: continue;
1.151 markus 918:
1.120 markus 919: for (i = 0; i < options.max_startups; i++)
920: if (startup_pipes[i] != -1 &&
921: FD_ISSET(startup_pipes[i], fdset)) {
922: /*
923: * the read end of the pipe is ready
924: * if the child has closed the pipe
1.143 markus 925: * after successful authentication
1.120 markus 926: * or if the child has died
927: */
928: close(startup_pipes[i]);
929: startup_pipes[i] = -1;
930: startups--;
931: }
1.75 markus 932: for (i = 0; i < num_listen_socks; i++) {
933: if (!FD_ISSET(listen_socks[i], fdset))
1.70 provos 934: continue;
1.120 markus 935: fromlen = sizeof(from);
936: newsock = accept(listen_socks[i], (struct sockaddr *)&from,
937: &fromlen);
938: if (newsock < 0) {
939: if (errno != EINTR && errno != EWOULDBLOCK)
940: error("accept: %.100s", strerror(errno));
941: continue;
942: }
943: if (fcntl(newsock, F_SETFL, 0) < 0) {
944: error("newsock del O_NONBLOCK: %s", strerror(errno));
945: continue;
946: }
1.124 markus 947: if (drop_connection(startups) == 1) {
948: debug("drop connection #%d", startups);
1.120 markus 949: close(newsock);
950: continue;
951: }
952: if (pipe(startup_p) == -1) {
953: close(newsock);
954: continue;
955: }
956:
957: for (j = 0; j < options.max_startups; j++)
958: if (startup_pipes[j] == -1) {
959: startup_pipes[j] = startup_p[0];
960: if (maxfd < startup_p[0])
961: maxfd = startup_p[0];
962: startups++;
963: break;
964: }
1.161 stevesk 965:
1.66 markus 966: /*
1.120 markus 967: * Got connection. Fork a child to handle it, unless
968: * we are in debugging mode.
1.66 markus 969: */
1.120 markus 970: if (debug_flag) {
1.66 markus 971: /*
1.120 markus 972: * In debugging mode. Close the listening
973: * socket, and start processing the
974: * connection without forking.
1.66 markus 975: */
1.120 markus 976: debug("Server will not fork when running in debugging mode.");
1.75 markus 977: close_listen_socks();
1.64 markus 978: sock_in = newsock;
979: sock_out = newsock;
1.122 deraadt 980: startup_pipe = -1;
1.120 markus 981: pid = getpid();
1.64 markus 982: break;
1.120 markus 983: } else {
984: /*
985: * Normal production daemon. Fork, and have
986: * the child process the connection. The
987: * parent continues listening.
988: */
989: if ((pid = fork()) == 0) {
990: /*
991: * Child. Close the listening and max_startup
992: * sockets. Start using the accepted socket.
993: * Reinitialize logging (since our pid has
994: * changed). We break out of the loop to handle
995: * the connection.
996: */
997: startup_pipe = startup_p[1];
998: for (j = 0; j < options.max_startups; j++)
999: if (startup_pipes[j] != -1)
1000: close(startup_pipes[j]);
1001: close_listen_socks();
1002: sock_in = newsock;
1003: sock_out = newsock;
1.138 markus 1004: log_init(__progname, options.log_level, options.log_facility, log_stderr);
1.120 markus 1005: break;
1006: }
1.64 markus 1007: }
1008:
1.120 markus 1009: /* Parent. Stay in the loop. */
1010: if (pid < 0)
1011: error("fork: %.100s", strerror(errno));
1012: else
1013: debug("Forked child %d.", pid);
1014:
1015: close(startup_p[1]);
1.1 deraadt 1016:
1.120 markus 1017: /* Mark that the key has been used (it was "given" to the child). */
1.151 markus 1018: if ((options.protocol & SSH_PROTO_1) &&
1019: key_used == 0) {
1020: /* Schedule server key regeneration alarm. */
1021: signal(SIGALRM, key_regeneration_alarm);
1022: alarm(options.key_regeneration_time);
1023: key_used = 1;
1024: }
1.1 deraadt 1025:
1.120 markus 1026: arc4random_stir();
1.1 deraadt 1027:
1.120 markus 1028: /* Close the new socket (the child is now taking care of it). */
1029: close(newsock);
1030: }
1.75 markus 1031: /* child process check (or debug mode) */
1032: if (num_listen_socks < 0)
1033: break;
1.64 markus 1034: }
1.1 deraadt 1035: }
1036:
1.64 markus 1037: /* This is the child processing a new connection. */
1038:
1.66 markus 1039: /*
1040: * Disable the key regeneration alarm. We will not regenerate the
1041: * key since we are no longer in a position to give it to anyone. We
1042: * will not restart on SIGHUP since it no longer makes sense.
1043: */
1.64 markus 1044: alarm(0);
1045: signal(SIGALRM, SIG_DFL);
1046: signal(SIGHUP, SIG_DFL);
1047: signal(SIGTERM, SIG_DFL);
1048: signal(SIGQUIT, SIG_DFL);
1049: signal(SIGCHLD, SIG_DFL);
1050:
1.66 markus 1051: /*
1052: * Set socket options for the connection. We want the socket to
1053: * close as fast as possible without waiting for anything. If the
1054: * connection is not a socket, these will do nothing.
1055: */
1056: /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
1.64 markus 1057: linger.l_onoff = 1;
1058: linger.l_linger = 5;
1059: setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
1.150 markus 1060:
1061: /* Set keepalives if requested. */
1062: if (options.keepalives &&
1063: setsockopt(sock_in, SOL_SOCKET, SO_KEEPALIVE, (void *)&on,
1064: sizeof(on)) < 0)
1065: error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno));
1.64 markus 1066:
1.66 markus 1067: /*
1068: * Register our connection. This turns encryption off because we do
1069: * not have a key.
1070: */
1.64 markus 1071: packet_set_connection(sock_in, sock_out);
1.1 deraadt 1072:
1.64 markus 1073: remote_port = get_remote_port();
1074: remote_ip = get_remote_ipaddr();
1.52 markus 1075:
1.64 markus 1076: /* Check whether logins are denied from this host. */
1.37 dugsong 1077: #ifdef LIBWRAP
1.75 markus 1078: /* XXX LIBWRAP noes not know about IPv6 */
1.64 markus 1079: {
1080: struct request_info req;
1.37 dugsong 1081:
1.138 markus 1082: request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, NULL);
1.64 markus 1083: fromhost(&req);
1.37 dugsong 1084:
1.64 markus 1085: if (!hosts_access(&req)) {
1.182 markus 1086: refuse(&req);
1.64 markus 1087: close(sock_in);
1088: close(sock_out);
1089: }
1.75 markus 1090: /*XXX IPv6 verbose("Connection from %.500s port %d", eval_client(&req), remote_port); */
1.64 markus 1091: }
1.75 markus 1092: #endif /* LIBWRAP */
1.64 markus 1093: /* Log the connection. */
1094: verbose("Connection from %.500s port %d", remote_ip, remote_port);
1.1 deraadt 1095:
1.66 markus 1096: /*
1097: * We don\'t want to listen forever unless the other side
1098: * successfully authenticates itself. So we set up an alarm which is
1099: * cleared after successful authentication. A limit of zero
1100: * indicates no limit. Note that we don\'t set the alarm in debugging
1101: * mode; it is just annoying to have the server exit just when you
1102: * are about to discover the bug.
1103: */
1.64 markus 1104: signal(SIGALRM, grace_alarm_handler);
1105: if (!debug_flag)
1106: alarm(options.login_grace_time);
1107:
1.96 markus 1108: sshd_exchange_identification(sock_in, sock_out);
1.66 markus 1109: /*
1.137 markus 1110: * Check that the connection comes from a privileged port.
1111: * Rhosts-Authentication only makes sense from priviledged
1.66 markus 1112: * programs. Of course, if the intruder has root access on his local
1113: * machine, he can connect from any port. So do not use these
1114: * authentication methods from machines that you do not trust.
1115: */
1.64 markus 1116: if (remote_port >= IPPORT_RESERVED ||
1117: remote_port < IPPORT_RESERVED / 2) {
1.137 markus 1118: debug("Rhosts Authentication disabled, "
1.133 markus 1119: "originating port not trusted.");
1.64 markus 1120: options.rhosts_authentication = 0;
1121: }
1.76 markus 1122: #ifdef KRB4
1123: if (!packet_connection_is_ipv4() &&
1124: options.kerberos_authentication) {
1125: debug("Kerberos Authentication disabled, only available for IPv4.");
1126: options.kerberos_authentication = 0;
1127: }
1128: #endif /* KRB4 */
1.164 markus 1129: #ifdef AFS
1130: /* If machine has AFS, set process authentication group. */
1131: if (k_hasafs()) {
1132: k_setpag();
1133: k_unlog();
1134: }
1135: #endif /* AFS */
1.76 markus 1136:
1.64 markus 1137: packet_set_nonblocking();
1.1 deraadt 1138:
1.77 markus 1139: /* perform the key exchange */
1140: /* authenticate user and start session */
1.98 markus 1141: if (compat20) {
1142: do_ssh2_kex();
1143: do_authentication2();
1144: } else {
1145: do_ssh1_kex();
1146: do_authentication();
1147: }
1.1 deraadt 1148:
1149: #ifdef KRB4
1.64 markus 1150: /* Cleanup user's ticket cache file. */
1151: if (options.kerberos_ticket_cleanup)
1152: (void) dest_tkt();
1.1 deraadt 1153: #endif /* KRB4 */
1154:
1.64 markus 1155: /* The connection has been terminated. */
1156: verbose("Closing connection to %.100s", remote_ip);
1157: packet_close();
1158: exit(0);
1.1 deraadt 1159: }
1160:
1.65 deraadt 1161: /*
1.77 markus 1162: * SSH1 key exchange
1.65 deraadt 1163: */
1.52 markus 1164: void
1.142 markus 1165: do_ssh1_kex(void)
1.1 deraadt 1166: {
1.64 markus 1167: int i, len;
1.77 markus 1168: int plen, slen;
1.159 markus 1169: int rsafail = 0;
1.64 markus 1170: BIGNUM *session_key_int;
1.140 markus 1171: u_char session_key[SSH_SESSION_KEY_LENGTH];
1172: u_char cookie[8];
1173: u_int cipher_type, auth_mask, protocol_flags;
1.64 markus 1174: u_int32_t rand = 0;
1175:
1.66 markus 1176: /*
1177: * Generate check bytes that the client must send back in the user
1178: * packet in order for it to be accepted; this is used to defy ip
1179: * spoofing attacks. Note that this only works against somebody
1180: * doing IP spoofing from a remote machine; any machine on the local
1181: * network can still see outgoing packets and catch the random
1182: * cookie. This only affects rhosts authentication, and this is one
1183: * of the reasons why it is inherently insecure.
1184: */
1.64 markus 1185: for (i = 0; i < 8; i++) {
1186: if (i % 4 == 0)
1187: rand = arc4random();
1.77 markus 1188: cookie[i] = rand & 0xff;
1.64 markus 1189: rand >>= 8;
1190: }
1191:
1.66 markus 1192: /*
1193: * Send our public key. We include in the packet 64 bits of random
1194: * data that must be matched in the reply in order to prevent IP
1195: * spoofing.
1196: */
1.64 markus 1197: packet_start(SSH_SMSG_PUBLIC_KEY);
1198: for (i = 0; i < 8; i++)
1.77 markus 1199: packet_put_char(cookie[i]);
1.64 markus 1200:
1201: /* Store our public server RSA key. */
1.134 markus 1202: packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
1203: packet_put_bignum(sensitive_data.server_key->rsa->e);
1204: packet_put_bignum(sensitive_data.server_key->rsa->n);
1.64 markus 1205:
1206: /* Store our public host RSA key. */
1.134 markus 1207: packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1208: packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
1209: packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
1.64 markus 1210:
1211: /* Put protocol flags. */
1212: packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1213:
1214: /* Declare which ciphers we support. */
1.131 markus 1215: packet_put_int(cipher_mask_ssh1(0));
1.64 markus 1216:
1217: /* Declare supported authentication types. */
1218: auth_mask = 0;
1219: if (options.rhosts_authentication)
1220: auth_mask |= 1 << SSH_AUTH_RHOSTS;
1221: if (options.rhosts_rsa_authentication)
1222: auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1223: if (options.rsa_authentication)
1224: auth_mask |= 1 << SSH_AUTH_RSA;
1.1 deraadt 1225: #ifdef KRB4
1.64 markus 1226: if (options.kerberos_authentication)
1227: auth_mask |= 1 << SSH_AUTH_KERBEROS;
1.1 deraadt 1228: #endif
1.5 dugsong 1229: #ifdef AFS
1.64 markus 1230: if (options.kerberos_tgt_passing)
1231: auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
1232: if (options.afs_token_passing)
1233: auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
1.1 deraadt 1234: #endif
1.157 markus 1235: if (options.challenge_reponse_authentication == 1)
1.64 markus 1236: auth_mask |= 1 << SSH_AUTH_TIS;
1237: if (options.password_authentication)
1238: auth_mask |= 1 << SSH_AUTH_PASSWORD;
1239: packet_put_int(auth_mask);
1240:
1241: /* Send the packet and wait for it to be sent. */
1242: packet_send();
1243: packet_write_wait();
1244:
1.134 markus 1245: debug("Sent %d bit server key and %d bit host key.",
1246: BN_num_bits(sensitive_data.server_key->rsa->n),
1247: BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1.64 markus 1248:
1249: /* Read clients reply (cipher type and session key). */
1250: packet_read_expect(&plen, SSH_CMSG_SESSION_KEY);
1251:
1.69 markus 1252: /* Get cipher type and check whether we accept this. */
1.64 markus 1253: cipher_type = packet_get_char();
1.69 markus 1254:
1.131 markus 1255: if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
1.69 markus 1256: packet_disconnect("Warning: client selects unsupported cipher.");
1.64 markus 1257:
1258: /* Get check bytes from the packet. These must match those we
1259: sent earlier with the public key packet. */
1260: for (i = 0; i < 8; i++)
1.77 markus 1261: if (cookie[i] != packet_get_char())
1.64 markus 1262: packet_disconnect("IP Spoofing check bytes do not match.");
1263:
1264: debug("Encryption type: %.200s", cipher_name(cipher_type));
1265:
1266: /* Get the encrypted integer. */
1267: session_key_int = BN_new();
1268: packet_get_bignum(session_key_int, &slen);
1269:
1270: protocol_flags = packet_get_int();
1271: packet_set_protocol_flags(protocol_flags);
1272:
1273: packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY);
1274:
1.66 markus 1275: /*
1276: * Decrypt it using our private server key and private host key (key
1277: * with larger modulus first).
1278: */
1.134 markus 1279: if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
1.159 markus 1280: /* Server key has bigger modulus. */
1.134 markus 1281: if (BN_num_bits(sensitive_data.server_key->rsa->n) <
1282: BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1283: fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1284: get_remote_ipaddr(),
1285: BN_num_bits(sensitive_data.server_key->rsa->n),
1286: BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1287: SSH_KEY_BITS_RESERVED);
1.64 markus 1288: }
1.159 markus 1289: if (rsa_private_decrypt(session_key_int, session_key_int,
1290: sensitive_data.server_key->rsa) <= 0)
1291: rsafail++;
1292: if (rsa_private_decrypt(session_key_int, session_key_int,
1293: sensitive_data.ssh1_host_key->rsa) <= 0)
1294: rsafail++;
1.64 markus 1295: } else {
1296: /* Host key has bigger modulus (or they are equal). */
1.134 markus 1297: if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
1298: BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1299: fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
1300: get_remote_ipaddr(),
1301: BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1302: BN_num_bits(sensitive_data.server_key->rsa->n),
1303: SSH_KEY_BITS_RESERVED);
1.64 markus 1304: }
1.159 markus 1305: if (rsa_private_decrypt(session_key_int, session_key_int,
1306: sensitive_data.ssh1_host_key->rsa) < 0)
1307: rsafail++;
1308: if (rsa_private_decrypt(session_key_int, session_key_int,
1309: sensitive_data.server_key->rsa) < 0)
1310: rsafail++;
1.64 markus 1311: }
1.66 markus 1312: /*
1313: * Extract session key from the decrypted integer. The key is in the
1314: * least significant 256 bits of the integer; the first byte of the
1315: * key is in the highest bits.
1316: */
1.159 markus 1317: if (!rsafail) {
1318: BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1319: len = BN_num_bytes(session_key_int);
1320: if (len < 0 || len > sizeof(session_key)) {
1321: error("do_connection: bad session key len from %s: "
1.165 itojun 1322: "session_key_int %d > sizeof(session_key) %lu",
1323: get_remote_ipaddr(), len, (u_long)sizeof(session_key));
1.159 markus 1324: rsafail++;
1325: } else {
1326: memset(session_key, 0, sizeof(session_key));
1327: BN_bn2bin(session_key_int,
1328: session_key + sizeof(session_key) - len);
1.169 markus 1329:
1330: compute_session_id(session_id, cookie,
1331: sensitive_data.ssh1_host_key->rsa->n,
1332: sensitive_data.server_key->rsa->n);
1333: /*
1334: * Xor the first 16 bytes of the session key with the
1335: * session id.
1336: */
1337: for (i = 0; i < 16; i++)
1338: session_key[i] ^= session_id[i];
1.159 markus 1339: }
1340: }
1341: if (rsafail) {
1.169 markus 1342: int bytes = BN_num_bytes(session_key_int);
1343: char *buf = xmalloc(bytes);
1344: MD5_CTX md;
1345:
1.159 markus 1346: log("do_connection: generating a fake encryption key");
1.169 markus 1347: BN_bn2bin(session_key_int, buf);
1348: MD5_Init(&md);
1349: MD5_Update(&md, buf, bytes);
1350: MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1351: MD5_Final(session_key, &md);
1352: MD5_Init(&md);
1353: MD5_Update(&md, session_key, 16);
1354: MD5_Update(&md, buf, bytes);
1355: MD5_Update(&md, sensitive_data.ssh1_cookie, SSH_SESSION_KEY_LENGTH);
1356: MD5_Final(session_key + 16, &md);
1357: memset(buf, 0, bytes);
1358: xfree(buf);
1.170 markus 1359: for (i = 0; i < 16; i++)
1360: session_id[i] = session_key[i] ^ session_key[i + 16];
1.159 markus 1361: }
1.169 markus 1362: /* Destroy the private and public keys. They will no longer be needed. */
1363: destroy_sensitive_data();
1364:
1.77 markus 1365: /* Destroy the decrypted integer. It is no longer needed. */
1366: BN_clear_free(session_key_int);
1.64 markus 1367:
1368: /* Set the session key. From this on all communications will be encrypted. */
1369: packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1370:
1371: /* Destroy our copy of the session key. It is no longer needed. */
1372: memset(session_key, 0, sizeof(session_key));
1373:
1374: debug("Received session key; encryption turned on.");
1375:
1376: /* Send an acknowledgement packet. Note that this packet is sent encrypted. */
1377: packet_start(SSH_SMSG_SUCCESS);
1378: packet_send();
1379: packet_write_wait();
1.98 markus 1380: }
1381:
1382: /*
1383: * SSH2 key exchange: diffie-hellman-group1-sha1
1384: */
1385: void
1.142 markus 1386: do_ssh2_kex(void)
1.98 markus 1387: {
1388: Kex *kex;
1.102 markus 1389:
1390: if (options.ciphers != NULL) {
1.105 markus 1391: myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1.102 markus 1392: myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1.166 markus 1393: }
1.184 stevesk 1394: myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1395: compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_CTOS]);
1396: myproposal[PROPOSAL_ENC_ALGS_STOC] =
1397: compat_cipher_proposal(myproposal[PROPOSAL_ENC_ALGS_STOC]);
1398:
1.166 markus 1399: if (options.macs != NULL) {
1400: myproposal[PROPOSAL_MAC_ALGS_CTOS] =
1401: myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
1.102 markus 1402: }
1.134 markus 1403: myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
1404:
1.189 ! markus 1405: /* start key exchange */
1.188 markus 1406: kex = kex_setup(myproposal);
1.186 markus 1407: kex->server = 1;
1408: kex->client_version_string=client_version_string;
1409: kex->server_version_string=server_version_string;
1410: kex->load_host_key=&get_hostkey_by_type;
1.129 provos 1411:
1.189 ! markus 1412: xxx_kex = kex;
! 1413:
1.186 markus 1414: dispatch_run(DISPATCH_BLOCK, &kex->newkeys, kex);
1.187 markus 1415:
1416: session_id2 = kex->session_id;
1417: session_id2_len = kex->session_id_len;
1.129 provos 1418:
1419: #ifdef DEBUG_KEXDH
1420: /* send 1st encrypted/maced/compressed message */
1421: packet_start(SSH2_MSG_IGNORE);
1422: packet_put_cstring("markus");
1423: packet_send();
1424: packet_write_wait();
1425: #endif
1.186 markus 1426: debug("KEX done");
1.1 deraadt 1427: }
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