Annotation of src/usr.bin/ssh/sshd.c, Revision 1.149
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"
1.149 ! markus 43: RCSID("$OpenBSD: sshd.c,v 1.148 2001/01/11 22:14:20 markus Exp $");
1.1 deraadt 44:
45: #include "xmalloc.h"
46: #include "rsa.h"
47: #include "ssh.h"
48: #include "pty.h"
49: #include "packet.h"
50: #include "mpaux.h"
51: #include "servconf.h"
52: #include "uidswap.h"
1.33 markus 53: #include "compat.h"
1.96 markus 54: #include "buffer.h"
55:
1.98 markus 56: #include "ssh2.h"
1.104 markus 57: #include <openssl/dh.h>
58: #include <openssl/bn.h>
59: #include <openssl/hmac.h>
1.98 markus 60: #include "kex.h"
1.104 markus 61: #include <openssl/dsa.h>
62: #include <openssl/rsa.h>
1.96 markus 63: #include "key.h"
1.129 provos 64: #include "dh.h"
1.96 markus 65:
66: #include "auth.h"
1.98 markus 67: #include "myproposal.h"
1.108 markus 68: #include "authfile.h"
1.1 deraadt 69:
70: #ifdef LIBWRAP
71: #include <tcpd.h>
72: #include <syslog.h>
73: int allow_severity = LOG_INFO;
74: int deny_severity = LOG_WARNING;
75: #endif /* LIBWRAP */
76:
77: #ifndef O_NOCTTY
78: #define O_NOCTTY 0
79: #endif
80:
1.138 markus 81: extern char *__progname;
82:
1.1 deraadt 83: /* Server configuration options. */
84: ServerOptions options;
85:
86: /* Name of the server configuration file. */
87: char *config_file_name = SERVER_CONFIG_FILE;
88:
1.105 markus 89: /*
1.75 markus 90: * Flag indicating whether IPv4 or IPv6. This can be set on the command line.
91: * Default value is AF_UNSPEC means both IPv4 and IPv6.
92: */
93: int IPv4or6 = AF_UNSPEC;
94:
1.65 deraadt 95: /*
96: * Debug mode flag. This can be set on the command line. If debug
97: * mode is enabled, extra debugging output will be sent to the system
98: * log, the daemon will not go to background, and will exit after processing
99: * the first connection.
100: */
1.1 deraadt 101: int debug_flag = 0;
102:
103: /* Flag indicating that the daemon is being started from inetd. */
104: int inetd_flag = 0;
105:
1.135 markus 106: /* Flag indicating that sshd should not detach and become a daemon. */
107: int no_daemon_flag = 0;
108:
1.47 markus 109: /* debug goes to stderr unless inetd_flag is set */
110: int log_stderr = 0;
111:
1.1 deraadt 112: /* Saved arguments to main(). */
113: char **saved_argv;
114:
1.66 markus 115: /*
1.75 markus 116: * The sockets that the server is listening; this is used in the SIGHUP
117: * signal handler.
1.66 markus 118: */
1.75 markus 119: #define MAX_LISTEN_SOCKS 16
120: int listen_socks[MAX_LISTEN_SOCKS];
121: int num_listen_socks = 0;
1.1 deraadt 122:
1.66 markus 123: /*
124: * the client's version string, passed by sshd2 in compat mode. if != NULL,
125: * sshd will skip the version-number exchange
126: */
1.61 markus 127: char *client_version_string = NULL;
1.96 markus 128: char *server_version_string = NULL;
1.1 deraadt 129:
1.66 markus 130: /*
131: * Any really sensitive data in the application is contained in this
132: * structure. The idea is that this structure could be locked into memory so
133: * that the pages do not get written into swap. However, there are some
134: * problems. The private key contains BIGNUMs, and we do not (in principle)
135: * have access to the internals of them, and locking just the structure is
136: * not very useful. Currently, memory locking is not implemented.
137: */
1.64 markus 138: struct {
1.134 markus 139: Key *server_key; /* empheral server key */
140: Key *ssh1_host_key; /* ssh1 host key */
141: Key **host_keys; /* all private host keys */
142: int have_ssh1_key;
143: int have_ssh2_key;
1.1 deraadt 144: } sensitive_data;
145:
1.66 markus 146: /*
147: * Flag indicating whether the current session key has been used. This flag
148: * is set whenever the key is used, and cleared when the key is regenerated.
149: */
1.1 deraadt 150: int key_used = 0;
151:
152: /* This is set to true when SIGHUP is received. */
153: int received_sighup = 0;
154:
1.96 markus 155: /* session identifier, used by RSA-auth */
1.140 markus 156: u_char session_id[16];
1.96 markus 157:
1.108 markus 158: /* same for ssh2 */
1.140 markus 159: u_char *session_id2 = NULL;
1.108 markus 160: int session_id2_len = 0;
161:
1.125 markus 162: /* record remote hostname or ip */
1.140 markus 163: u_int utmp_len = MAXHOSTNAMELEN;
1.125 markus 164:
1.1 deraadt 165: /* Prototypes for various functions defined later in this file. */
1.142 markus 166: void do_ssh1_kex(void);
167: void do_ssh2_kex(void);
1.87 markus 168:
1.129 provos 169: void ssh_dh1_server(Kex *, Buffer *_kexinit, Buffer *);
170: void ssh_dhgex_server(Kex *, Buffer *_kexinit, Buffer *);
171:
1.87 markus 172: /*
1.75 markus 173: * Close all listening sockets
174: */
175: void
176: close_listen_socks(void)
177: {
178: int i;
179: for (i = 0; i < num_listen_socks; i++)
180: close(listen_socks[i]);
181: num_listen_socks = -1;
182: }
183:
184: /*
1.65 deraadt 185: * Signal handler for SIGHUP. Sshd execs itself when it receives SIGHUP;
186: * the effect is to reread the configuration file (and to regenerate
187: * the server key).
188: */
1.105 markus 189: void
1.64 markus 190: sighup_handler(int sig)
1.1 deraadt 191: {
1.64 markus 192: received_sighup = 1;
193: signal(SIGHUP, sighup_handler);
1.1 deraadt 194: }
195:
1.65 deraadt 196: /*
197: * Called from the main program after receiving SIGHUP.
198: * Restarts the server.
199: */
1.105 markus 200: void
1.64 markus 201: sighup_restart()
1.1 deraadt 202: {
1.64 markus 203: log("Received SIGHUP; restarting.");
1.75 markus 204: close_listen_socks();
1.64 markus 205: execv(saved_argv[0], saved_argv);
1.138 markus 206: log("RESTART FAILED: av[0]='%.100s', error: %.100s.", saved_argv[0], strerror(errno));
1.64 markus 207: exit(1);
1.1 deraadt 208: }
209:
1.65 deraadt 210: /*
211: * Generic signal handler for terminating signals in the master daemon.
212: * These close the listen socket; not closing it seems to cause "Address
213: * already in use" problems on some machines, which is inconvenient.
214: */
1.105 markus 215: void
1.64 markus 216: sigterm_handler(int sig)
1.1 deraadt 217: {
1.64 markus 218: log("Received signal %d; terminating.", sig);
1.75 markus 219: close_listen_socks();
1.113 markus 220: unlink(options.pid_file);
1.64 markus 221: exit(255);
1.1 deraadt 222: }
223:
1.65 deraadt 224: /*
225: * SIGCHLD handler. This is called whenever a child dies. This will then
226: * reap any zombies left by exited c.
227: */
1.105 markus 228: void
1.64 markus 229: main_sigchld_handler(int sig)
1.1 deraadt 230: {
1.64 markus 231: int save_errno = errno;
232: int status;
1.60 deraadt 233:
1.64 markus 234: while (waitpid(-1, &status, WNOHANG) > 0)
235: ;
1.60 deraadt 236:
1.64 markus 237: signal(SIGCHLD, main_sigchld_handler);
238: errno = save_errno;
1.1 deraadt 239: }
240:
1.65 deraadt 241: /*
242: * Signal handler for the alarm after the login grace period has expired.
243: */
1.105 markus 244: void
1.64 markus 245: grace_alarm_handler(int sig)
1.1 deraadt 246: {
1.64 markus 247: /* Close the connection. */
248: packet_close();
249:
250: /* Log error and exit. */
251: fatal("Timeout before authentication for %s.", get_remote_ipaddr());
1.62 markus 252: }
253:
1.65 deraadt 254: /*
255: * Signal handler for the key regeneration alarm. Note that this
256: * alarm only occurs in the daemon waiting for connections, and it does not
257: * do anything with the private key or random state before forking.
258: * Thus there should be no concurrency control/asynchronous execution
259: * problems.
1.147 deraadt 260: * XXX calling log() is not safe from races.
1.65 deraadt 261: */
1.105 markus 262: void
1.134 markus 263: generate_empheral_server_key(void)
264: {
265: log("Generating %s%d bit RSA key.", sensitive_data.server_key ? "new " : "",
266: options.server_key_bits);
267: if (sensitive_data.server_key != NULL)
268: key_free(sensitive_data.server_key);
269: sensitive_data.server_key = key_generate(KEY_RSA1, options.server_key_bits);
270: arc4random_stir();
271: log("RSA key generation complete.");
272: }
1.147 deraadt 273:
1.134 markus 274: void
1.64 markus 275: key_regeneration_alarm(int sig)
1.1 deraadt 276: {
1.64 markus 277: int save_errno = errno;
1.18 deraadt 278:
1.64 markus 279: /* Check if we should generate a new key. */
280: if (key_used) {
281: /* This should really be done in the background. */
1.134 markus 282: generate_empheral_server_key();
1.64 markus 283: key_used = 0;
284: }
285: /* Reschedule the alarm. */
286: signal(SIGALRM, key_regeneration_alarm);
287: alarm(options.key_regeneration_time);
288: errno = save_errno;
1.98 markus 289: }
290:
1.96 markus 291: void
292: sshd_exchange_identification(int sock_in, int sock_out)
293: {
1.102 markus 294: int i, mismatch;
1.96 markus 295: int remote_major, remote_minor;
1.102 markus 296: int major, minor;
1.96 markus 297: char *s;
298: char buf[256]; /* Must not be larger than remote_version. */
299: char remote_version[256]; /* Must be at least as big as buf. */
300:
1.103 markus 301: if ((options.protocol & SSH_PROTO_1) &&
302: (options.protocol & SSH_PROTO_2)) {
1.102 markus 303: major = PROTOCOL_MAJOR_1;
304: minor = 99;
305: } else if (options.protocol & SSH_PROTO_2) {
306: major = PROTOCOL_MAJOR_2;
307: minor = PROTOCOL_MINOR_2;
308: } else {
309: major = PROTOCOL_MAJOR_1;
310: minor = PROTOCOL_MINOR_1;
311: }
312: snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", major, minor, SSH_VERSION);
1.96 markus 313: server_version_string = xstrdup(buf);
314:
315: if (client_version_string == NULL) {
316: /* Send our protocol version identification. */
317: if (atomicio(write, sock_out, server_version_string, strlen(server_version_string))
318: != strlen(server_version_string)) {
319: log("Could not write ident string to %s.", get_remote_ipaddr());
320: fatal_cleanup();
321: }
322:
323: /* Read other side\'s version identification. */
324: for (i = 0; i < sizeof(buf) - 1; i++) {
1.119 markus 325: if (atomicio(read, sock_in, &buf[i], 1) != 1) {
1.96 markus 326: log("Did not receive ident string from %s.", get_remote_ipaddr());
327: fatal_cleanup();
328: }
329: if (buf[i] == '\r') {
330: buf[i] = '\n';
331: buf[i + 1] = 0;
1.132 markus 332: /* Kludge for F-Secure Macintosh < 1.0.2 */
333: if (i == 12 &&
334: strncmp(buf, "SSH-1.5-W1.0", 12) == 0)
335: break;
1.96 markus 336: continue;
337: }
338: if (buf[i] == '\n') {
339: /* buf[i] == '\n' */
340: buf[i + 1] = 0;
341: break;
342: }
343: }
344: buf[sizeof(buf) - 1] = 0;
345: client_version_string = xstrdup(buf);
346: }
347:
348: /*
349: * Check that the versions match. In future this might accept
350: * several versions and set appropriate flags to handle them.
351: */
352: if (sscanf(client_version_string, "SSH-%d.%d-%[^\n]\n",
353: &remote_major, &remote_minor, remote_version) != 3) {
1.105 markus 354: s = "Protocol mismatch.\n";
1.96 markus 355: (void) atomicio(write, sock_out, s, strlen(s));
356: close(sock_in);
357: close(sock_out);
358: log("Bad protocol version identification '%.100s' from %s",
359: client_version_string, get_remote_ipaddr());
360: fatal_cleanup();
361: }
362: debug("Client protocol version %d.%d; client software version %.100s",
363: remote_major, remote_minor, remote_version);
364:
1.98 markus 365: compat_datafellows(remote_version);
366:
1.102 markus 367: mismatch = 0;
1.96 markus 368: switch(remote_major) {
369: case 1:
1.108 markus 370: if (remote_minor == 99) {
371: if (options.protocol & SSH_PROTO_2)
372: enable_compat20();
373: else
374: mismatch = 1;
375: break;
376: }
1.102 markus 377: if (!(options.protocol & SSH_PROTO_1)) {
378: mismatch = 1;
379: break;
380: }
1.96 markus 381: if (remote_minor < 3) {
1.121 provos 382: packet_disconnect("Your ssh version is too old and "
1.96 markus 383: "is no longer supported. Please install a newer version.");
384: } else if (remote_minor == 3) {
385: /* note that this disables agent-forwarding */
386: enable_compat13();
387: }
1.102 markus 388: break;
1.98 markus 389: case 2:
1.102 markus 390: if (options.protocol & SSH_PROTO_2) {
1.98 markus 391: enable_compat20();
392: break;
393: }
1.99 markus 394: /* FALLTHROUGH */
1.105 markus 395: default:
1.102 markus 396: mismatch = 1;
397: break;
398: }
399: chop(server_version_string);
400: chop(client_version_string);
401: debug("Local version string %.200s", server_version_string);
402:
403: if (mismatch) {
1.96 markus 404: s = "Protocol major versions differ.\n";
405: (void) atomicio(write, sock_out, s, strlen(s));
406: close(sock_in);
407: close(sock_out);
1.102 markus 408: log("Protocol major versions differ for %s: %.200s vs. %.200s",
409: get_remote_ipaddr(),
410: server_version_string, client_version_string);
1.96 markus 411: fatal_cleanup();
412: }
1.108 markus 413: if (compat20)
414: packet_set_ssh2_format();
415: }
416:
417:
1.134 markus 418: /* Destroy the host and server keys. They will no longer be needed. */
1.108 markus 419: void
420: destroy_sensitive_data(void)
421: {
1.134 markus 422: int i;
423:
424: if (sensitive_data.server_key) {
425: key_free(sensitive_data.server_key);
426: sensitive_data.server_key = NULL;
427: }
428: for(i = 0; i < options.num_host_key_files; i++) {
429: if (sensitive_data.host_keys[i]) {
430: key_free(sensitive_data.host_keys[i]);
431: sensitive_data.host_keys[i] = NULL;
432: }
433: }
434: sensitive_data.ssh1_host_key = NULL;
435: }
436: Key *
437: load_private_key_autodetect(const char *filename)
438: {
439: struct stat st;
440: int type;
441: Key *public, *private;
442:
443: if (stat(filename, &st) < 0) {
444: perror(filename);
445: return NULL;
446: }
447: /*
448: * try to load the public key. right now this only works for RSA1,
449: * since SSH2 keys are fully encrypted
450: */
451: type = KEY_RSA1;
452: public = key_new(type);
453: if (!load_public_key(filename, public, NULL)) {
454: /* ok, so we will assume this is 'some' key */
455: type = KEY_UNSPEC;
456: }
457: key_free(public);
458:
459: /* Ok, try key with empty passphrase */
460: private = key_new(type);
461: if (load_private_key(filename, "", private, NULL)) {
462: debug("load_private_key_autodetect: type %d %s",
463: private->type, key_type(private));
464: return private;
465: }
466: key_free(private);
467: return NULL;
468: }
469:
470: char *
471: list_hostkey_types(void)
472: {
473: static char buf[1024];
474: int i;
475: buf[0] = '\0';
476: for(i = 0; i < options.num_host_key_files; i++) {
477: Key *key = sensitive_data.host_keys[i];
478: if (key == NULL)
479: continue;
480: switch(key->type) {
481: case KEY_RSA:
482: case KEY_DSA:
483: strlcat(buf, key_ssh_name(key), sizeof buf);
484: strlcat(buf, ",", sizeof buf);
485: break;
486: }
487: }
488: i = strlen(buf);
489: if (i > 0 && buf[i-1] == ',')
490: buf[i-1] = '\0';
491: debug("list_hostkey_types: %s", buf);
492: return buf;
493: }
494:
495: Key *
496: get_hostkey_by_type(int type)
497: {
498: int i;
499: for(i = 0; i < options.num_host_key_files; i++) {
500: Key *key = sensitive_data.host_keys[i];
501: if (key != NULL && key->type == type)
502: return key;
503: }
504: return NULL;
1.96 markus 505: }
506:
1.124 markus 507: /*
508: * returns 1 if connection should be dropped, 0 otherwise.
509: * dropping starts at connection #max_startups_begin with a probability
510: * of (max_startups_rate/100). the probability increases linearly until
511: * all connections are dropped for startups > max_startups
512: */
513: int
514: drop_connection(int startups)
515: {
516: double p, r;
517:
518: if (startups < options.max_startups_begin)
519: return 0;
520: if (startups >= options.max_startups)
521: return 1;
522: if (options.max_startups_rate == 100)
523: return 1;
524:
525: p = 100 - options.max_startups_rate;
526: p *= startups - options.max_startups_begin;
527: p /= (double) (options.max_startups - options.max_startups_begin);
528: p += options.max_startups_rate;
529: p /= 100.0;
530: r = arc4random() / (double) UINT_MAX;
531:
532: debug("drop_connection: p %g, r %g", p, r);
533: return (r < p) ? 1 : 0;
534: }
535:
1.120 markus 536: int *startup_pipes = NULL; /* options.max_startup sized array of fd ints */
537: int startup_pipe; /* in child */
538:
1.65 deraadt 539: /*
540: * Main program for the daemon.
541: */
1.2 provos 542: int
543: main(int ac, char **av)
1.1 deraadt 544: {
1.64 markus 545: extern char *optarg;
546: extern int optind;
1.120 markus 547: int opt, sock_in = 0, sock_out = 0, newsock, j, i, fdsetsz, on = 1;
1.107 deraadt 548: pid_t pid;
1.75 markus 549: socklen_t fromlen;
1.110 markus 550: int silent = 0;
1.75 markus 551: fd_set *fdset;
552: struct sockaddr_storage from;
1.64 markus 553: const char *remote_ip;
554: int remote_port;
555: FILE *f;
556: struct linger linger;
1.75 markus 557: struct addrinfo *ai;
558: char ntop[NI_MAXHOST], strport[NI_MAXSERV];
559: int listen_sock, maxfd;
1.120 markus 560: int startup_p[2];
561: int startups = 0;
1.64 markus 562:
1.138 markus 563: /* Save argv. */
1.64 markus 564: saved_argv = av;
565:
566: /* Initialize configuration options to their default values. */
567: initialize_server_options(&options);
568:
569: /* Parse command-line arguments. */
1.149 ! markus 570: while ((opt = getopt(ac, av, "f:p:b:k:h:g:V:u:dDiqQ46")) != -1) {
1.64 markus 571: switch (opt) {
1.75 markus 572: case '4':
573: IPv4or6 = AF_INET;
574: break;
575: case '6':
576: IPv4or6 = AF_INET6;
577: break;
1.64 markus 578: case 'f':
579: config_file_name = optarg;
580: break;
581: case 'd':
1.127 markus 582: if (0 == debug_flag) {
583: debug_flag = 1;
584: options.log_level = SYSLOG_LEVEL_DEBUG1;
585: } else if (options.log_level < SYSLOG_LEVEL_DEBUG3) {
586: options.log_level++;
587: } else {
588: fprintf(stderr, "Too high debugging level.\n");
589: exit(1);
590: }
1.64 markus 591: break;
1.135 markus 592: case 'D':
593: no_daemon_flag = 1;
594: break;
1.64 markus 595: case 'i':
596: inetd_flag = 1;
597: break;
598: case 'Q':
1.110 markus 599: silent = 1;
1.64 markus 600: break;
601: case 'q':
602: options.log_level = SYSLOG_LEVEL_QUIET;
603: break;
604: case 'b':
605: options.server_key_bits = atoi(optarg);
606: break;
607: case 'p':
1.75 markus 608: options.ports_from_cmdline = 1;
1.127 markus 609: if (options.num_ports >= MAX_PORTS) {
610: fprintf(stderr, "too many ports.\n");
611: exit(1);
612: }
1.75 markus 613: options.ports[options.num_ports++] = atoi(optarg);
1.64 markus 614: break;
615: case 'g':
616: options.login_grace_time = atoi(optarg);
617: break;
618: case 'k':
619: options.key_regeneration_time = atoi(optarg);
620: break;
621: case 'h':
1.134 markus 622: if (options.num_host_key_files >= MAX_HOSTKEYS) {
623: fprintf(stderr, "too many host keys.\n");
624: exit(1);
625: }
626: options.host_key_files[options.num_host_key_files++] = optarg;
1.64 markus 627: break;
628: case 'V':
629: client_version_string = optarg;
630: /* only makes sense with inetd_flag, i.e. no listen() */
631: inetd_flag = 1;
632: break;
1.125 markus 633: case 'u':
634: utmp_len = atoi(optarg);
635: break;
1.64 markus 636: case '?':
637: default:
638: fprintf(stderr, "sshd version %s\n", SSH_VERSION);
1.138 markus 639: fprintf(stderr, "Usage: %s [options]\n", __progname);
1.64 markus 640: fprintf(stderr, "Options:\n");
1.66 markus 641: fprintf(stderr, " -f file Configuration file (default %s)\n", SERVER_CONFIG_FILE);
1.127 markus 642: fprintf(stderr, " -d Debugging mode (multiple -d means more debugging)\n");
1.64 markus 643: fprintf(stderr, " -i Started from inetd\n");
1.144 markus 644: fprintf(stderr, " -D Do not fork into daemon mode\n");
1.64 markus 645: fprintf(stderr, " -q Quiet (no logging)\n");
646: fprintf(stderr, " -p port Listen on the specified port (default: 22)\n");
647: fprintf(stderr, " -k seconds Regenerate server key every this many seconds (default: 3600)\n");
1.145 markus 648: fprintf(stderr, " -g seconds Grace period for authentication (default: 600)\n");
1.64 markus 649: fprintf(stderr, " -b bits Size of server RSA key (default: 768 bits)\n");
650: fprintf(stderr, " -h file File from which to read host key (default: %s)\n",
1.75 markus 651: HOST_KEY_FILE);
1.125 markus 652: fprintf(stderr, " -u len Maximum hostname length for utmp recording\n");
1.75 markus 653: fprintf(stderr, " -4 Use IPv4 only\n");
654: fprintf(stderr, " -6 Use IPv6 only\n");
1.64 markus 655: exit(1);
656: }
657: }
658:
1.75 markus 659: /*
660: * Force logging to stderr until we have loaded the private host
661: * key (unless started from inetd)
662: */
1.138 markus 663: log_init(__progname,
1.146 markus 664: options.log_level == -1 ? SYSLOG_LEVEL_NOTICE : options.log_level,
1.75 markus 665: options.log_facility == -1 ? SYSLOG_FACILITY_AUTH : options.log_facility,
1.110 markus 666: !silent && !inetd_flag);
1.75 markus 667:
1.64 markus 668: /* Read server configuration options from the configuration file. */
669: read_server_config(&options, config_file_name);
670:
671: /* Fill in default values for those options not explicitly set. */
672: fill_default_server_options(&options);
673:
674: /* Check that there are no remaining arguments. */
675: if (optind < ac) {
676: fprintf(stderr, "Extra argument %s.\n", av[optind]);
677: exit(1);
678: }
679:
680: debug("sshd version %.100s", SSH_VERSION);
681:
1.134 markus 682: /* load private host keys */
683: sensitive_data.host_keys = xmalloc(options.num_host_key_files*sizeof(Key*));
1.141 markus 684: for(i = 0; i < options.num_host_key_files; i++)
685: sensitive_data.host_keys[i] = NULL;
1.134 markus 686: sensitive_data.server_key = NULL;
687: sensitive_data.ssh1_host_key = NULL;
688: sensitive_data.have_ssh1_key = 0;
689: sensitive_data.have_ssh2_key = 0;
690:
691: for(i = 0; i < options.num_host_key_files; i++) {
692: Key *key = load_private_key_autodetect(options.host_key_files[i]);
693: if (key == NULL) {
694: error("Could not load host key: %.200s: %.100s",
695: options.host_key_files[i], strerror(errno));
696: continue;
697: }
698: switch(key->type){
699: case KEY_RSA1:
700: sensitive_data.ssh1_host_key = key;
701: sensitive_data.have_ssh1_key = 1;
702: break;
703: case KEY_RSA:
704: case KEY_DSA:
705: sensitive_data.have_ssh2_key = 1;
706: break;
707: }
708: sensitive_data.host_keys[i] = key;
709: }
710: if ((options.protocol & SSH_PROTO_1) && !sensitive_data.have_ssh1_key) {
711: log("Disabling protocol version 1. Could not load host key");
1.108 markus 712: options.protocol &= ~SSH_PROTO_1;
713: }
1.134 markus 714: if ((options.protocol & SSH_PROTO_2) && !sensitive_data.have_ssh2_key) {
715: log("Disabling protocol version 2. Could not load host key");
716: options.protocol &= ~SSH_PROTO_2;
1.108 markus 717: }
718: if (! options.protocol & (SSH_PROTO_1|SSH_PROTO_2)) {
1.110 markus 719: if (silent == 0)
720: fprintf(stderr, "sshd: no hostkeys available -- exiting.\n");
1.108 markus 721: log("sshd: no hostkeys available -- exiting.\n");
1.64 markus 722: exit(1);
723: }
724:
1.108 markus 725: /* Check certain values for sanity. */
726: if (options.protocol & SSH_PROTO_1) {
727: if (options.server_key_bits < 512 ||
728: options.server_key_bits > 32768) {
729: fprintf(stderr, "Bad server key size.\n");
730: exit(1);
731: }
732: /*
733: * Check that server and host key lengths differ sufficiently. This
734: * is necessary to make double encryption work with rsaref. Oh, I
735: * hate software patents. I dont know if this can go? Niels
736: */
737: if (options.server_key_bits >
1.134 markus 738: BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) - SSH_KEY_BITS_RESERVED &&
1.108 markus 739: options.server_key_bits <
1.134 markus 740: BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1.108 markus 741: options.server_key_bits =
1.134 markus 742: BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED;
1.108 markus 743: debug("Forcing server key to %d bits to make it differ from host key.",
744: options.server_key_bits);
745: }
746: }
747:
748: /* Initialize the log (it is reinitialized below in case we forked). */
1.64 markus 749: if (debug_flag && !inetd_flag)
750: log_stderr = 1;
1.138 markus 751: log_init(__progname, options.log_level, options.log_facility, log_stderr);
1.64 markus 752:
1.108 markus 753: /*
754: * If not in debugging mode, and not started from inetd, disconnect
755: * from the controlling terminal, and fork. The original process
756: * exits.
757: */
1.135 markus 758: if (!(debug_flag || inetd_flag || no_daemon_flag)) {
1.1 deraadt 759: #ifdef TIOCNOTTY
1.64 markus 760: int fd;
1.1 deraadt 761: #endif /* TIOCNOTTY */
1.64 markus 762: if (daemon(0, 0) < 0)
763: fatal("daemon() failed: %.200s", strerror(errno));
764:
765: /* Disconnect from the controlling tty. */
1.1 deraadt 766: #ifdef TIOCNOTTY
1.64 markus 767: fd = open("/dev/tty", O_RDWR | O_NOCTTY);
768: if (fd >= 0) {
769: (void) ioctl(fd, TIOCNOTTY, NULL);
770: close(fd);
771: }
772: #endif /* TIOCNOTTY */
773: }
774: /* Reinitialize the log (because of the fork above). */
1.138 markus 775: log_init(__progname, options.log_level, options.log_facility, log_stderr);
1.64 markus 776:
777: /* Initialize the random number generator. */
778: arc4random_stir();
779:
780: /* Chdir to the root directory so that the current disk can be
781: unmounted if desired. */
782: chdir("/");
783:
784: /* Start listening for a socket, unless started from inetd. */
785: if (inetd_flag) {
786: int s1, s2;
787: s1 = dup(0); /* Make sure descriptors 0, 1, and 2 are in use. */
788: s2 = dup(s1);
789: sock_in = dup(0);
790: sock_out = dup(1);
1.123 djm 791: startup_pipe = -1;
1.108 markus 792: /*
793: * We intentionally do not close the descriptors 0, 1, and 2
794: * as our code for setting the descriptors won\'t work if
795: * ttyfd happens to be one of those.
796: */
1.64 markus 797: debug("inetd sockets after dupping: %d, %d", sock_in, sock_out);
1.134 markus 798: if (options.protocol & SSH_PROTO_1)
799: generate_empheral_server_key();
1.64 markus 800: } else {
1.75 markus 801: for (ai = options.listen_addrs; ai; ai = ai->ai_next) {
802: if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6)
803: continue;
804: if (num_listen_socks >= MAX_LISTEN_SOCKS)
805: fatal("Too many listen sockets. "
806: "Enlarge MAX_LISTEN_SOCKS");
807: if (getnameinfo(ai->ai_addr, ai->ai_addrlen,
808: ntop, sizeof(ntop), strport, sizeof(strport),
809: NI_NUMERICHOST|NI_NUMERICSERV) != 0) {
810: error("getnameinfo failed");
811: continue;
812: }
813: /* Create socket for listening. */
814: listen_sock = socket(ai->ai_family, SOCK_STREAM, 0);
815: if (listen_sock < 0) {
816: /* kernel may not support ipv6 */
817: verbose("socket: %.100s", strerror(errno));
818: continue;
819: }
820: if (fcntl(listen_sock, F_SETFL, O_NONBLOCK) < 0) {
821: error("listen_sock O_NONBLOCK: %s", strerror(errno));
822: close(listen_sock);
823: continue;
824: }
825: /*
826: * Set socket options. We try to make the port
827: * reusable and have it close as fast as possible
828: * without waiting in unnecessary wait states on
829: * close.
830: */
831: setsockopt(listen_sock, SOL_SOCKET, SO_REUSEADDR,
832: (void *) &on, sizeof(on));
833: linger.l_onoff = 1;
834: linger.l_linger = 5;
835: setsockopt(listen_sock, SOL_SOCKET, SO_LINGER,
836: (void *) &linger, sizeof(linger));
837:
838: debug("Bind to port %s on %s.", strport, ntop);
839:
840: /* Bind the socket to the desired port. */
841: if (bind(listen_sock, ai->ai_addr, ai->ai_addrlen) < 0) {
842: error("Bind to port %s on %s failed: %.200s.",
843: strport, ntop, strerror(errno));
844: close(listen_sock);
845: continue;
846: }
847: listen_socks[num_listen_socks] = listen_sock;
848: num_listen_socks++;
849:
850: /* Start listening on the port. */
851: log("Server listening on %s port %s.", ntop, strport);
852: if (listen(listen_sock, 5) < 0)
853: fatal("listen: %.100s", strerror(errno));
854:
1.64 markus 855: }
1.75 markus 856: freeaddrinfo(options.listen_addrs);
857:
858: if (!num_listen_socks)
859: fatal("Cannot bind any address.");
860:
1.64 markus 861: if (!debug_flag) {
1.66 markus 862: /*
1.136 todd 863: * Record our pid in /var/run/sshd.pid to make it
864: * easier to kill the correct sshd. We don't want to
865: * do this before the bind above because the bind will
1.66 markus 866: * fail if there already is a daemon, and this will
867: * overwrite any old pid in the file.
868: */
1.112 markus 869: f = fopen(options.pid_file, "w");
1.64 markus 870: if (f) {
1.140 markus 871: fprintf(f, "%u\n", (u_int) getpid());
1.64 markus 872: fclose(f);
873: }
874: }
1.108 markus 875: if (options.protocol & SSH_PROTO_1) {
1.134 markus 876: generate_empheral_server_key();
1.64 markus 877:
1.108 markus 878: /* Schedule server key regeneration alarm. */
879: signal(SIGALRM, key_regeneration_alarm);
880: alarm(options.key_regeneration_time);
881: }
1.64 markus 882:
883: /* Arrange to restart on SIGHUP. The handler needs listen_sock. */
884: signal(SIGHUP, sighup_handler);
1.120 markus 885:
1.64 markus 886: signal(SIGTERM, sigterm_handler);
887: signal(SIGQUIT, sigterm_handler);
888:
889: /* Arrange SIGCHLD to be caught. */
890: signal(SIGCHLD, main_sigchld_handler);
891:
1.75 markus 892: /* setup fd set for listen */
1.120 markus 893: fdset = NULL;
1.75 markus 894: maxfd = 0;
895: for (i = 0; i < num_listen_socks; i++)
896: if (listen_socks[i] > maxfd)
897: maxfd = listen_socks[i];
1.120 markus 898: /* pipes connected to unauthenticated childs */
899: startup_pipes = xmalloc(options.max_startups * sizeof(int));
900: for (i = 0; i < options.max_startups; i++)
901: startup_pipes[i] = -1;
1.75 markus 902:
1.66 markus 903: /*
904: * Stay listening for connections until the system crashes or
905: * the daemon is killed with a signal.
906: */
1.64 markus 907: for (;;) {
908: if (received_sighup)
909: sighup_restart();
1.120 markus 910: if (fdset != NULL)
911: xfree(fdset);
1.148 markus 912: fdsetsz = howmany(maxfd+1, NFDBITS) * sizeof(fd_mask);
1.120 markus 913: fdset = (fd_set *)xmalloc(fdsetsz);
1.75 markus 914: memset(fdset, 0, fdsetsz);
1.120 markus 915:
1.75 markus 916: for (i = 0; i < num_listen_socks; i++)
917: FD_SET(listen_socks[i], fdset);
1.120 markus 918: for (i = 0; i < options.max_startups; i++)
919: if (startup_pipes[i] != -1)
920: FD_SET(startup_pipes[i], fdset);
921:
922: /* Wait in select until there is a connection. */
1.148 markus 923: if (select(maxfd+1, fdset, NULL, NULL, NULL) < 0) {
1.75 markus 924: if (errno != EINTR)
925: error("select: %.100s", strerror(errno));
926: continue;
927: }
1.120 markus 928: for (i = 0; i < options.max_startups; i++)
929: if (startup_pipes[i] != -1 &&
930: FD_ISSET(startup_pipes[i], fdset)) {
931: /*
932: * the read end of the pipe is ready
933: * if the child has closed the pipe
1.143 markus 934: * after successful authentication
1.120 markus 935: * or if the child has died
936: */
937: close(startup_pipes[i]);
938: startup_pipes[i] = -1;
939: startups--;
940: }
1.75 markus 941: for (i = 0; i < num_listen_socks; i++) {
942: if (!FD_ISSET(listen_socks[i], fdset))
1.70 provos 943: continue;
1.120 markus 944: fromlen = sizeof(from);
945: newsock = accept(listen_socks[i], (struct sockaddr *)&from,
946: &fromlen);
947: if (newsock < 0) {
948: if (errno != EINTR && errno != EWOULDBLOCK)
949: error("accept: %.100s", strerror(errno));
950: continue;
951: }
952: if (fcntl(newsock, F_SETFL, 0) < 0) {
953: error("newsock del O_NONBLOCK: %s", strerror(errno));
954: continue;
955: }
1.124 markus 956: if (drop_connection(startups) == 1) {
957: debug("drop connection #%d", startups);
1.120 markus 958: close(newsock);
959: continue;
960: }
961: if (pipe(startup_p) == -1) {
962: close(newsock);
963: continue;
964: }
965:
966: for (j = 0; j < options.max_startups; j++)
967: if (startup_pipes[j] == -1) {
968: startup_pipes[j] = startup_p[0];
969: if (maxfd < startup_p[0])
970: maxfd = startup_p[0];
971: startups++;
972: break;
973: }
974:
1.66 markus 975: /*
1.120 markus 976: * Got connection. Fork a child to handle it, unless
977: * we are in debugging mode.
1.66 markus 978: */
1.120 markus 979: if (debug_flag) {
1.66 markus 980: /*
1.120 markus 981: * In debugging mode. Close the listening
982: * socket, and start processing the
983: * connection without forking.
1.66 markus 984: */
1.120 markus 985: debug("Server will not fork when running in debugging mode.");
1.75 markus 986: close_listen_socks();
1.64 markus 987: sock_in = newsock;
988: sock_out = newsock;
1.122 deraadt 989: startup_pipe = -1;
1.120 markus 990: pid = getpid();
1.64 markus 991: break;
1.120 markus 992: } else {
993: /*
994: * Normal production daemon. Fork, and have
995: * the child process the connection. The
996: * parent continues listening.
997: */
998: if ((pid = fork()) == 0) {
999: /*
1000: * Child. Close the listening and max_startup
1001: * sockets. Start using the accepted socket.
1002: * Reinitialize logging (since our pid has
1003: * changed). We break out of the loop to handle
1004: * the connection.
1005: */
1006: startup_pipe = startup_p[1];
1007: for (j = 0; j < options.max_startups; j++)
1008: if (startup_pipes[j] != -1)
1009: close(startup_pipes[j]);
1010: close_listen_socks();
1011: sock_in = newsock;
1012: sock_out = newsock;
1.138 markus 1013: log_init(__progname, options.log_level, options.log_facility, log_stderr);
1.120 markus 1014: break;
1015: }
1.64 markus 1016: }
1017:
1.120 markus 1018: /* Parent. Stay in the loop. */
1019: if (pid < 0)
1020: error("fork: %.100s", strerror(errno));
1021: else
1022: debug("Forked child %d.", pid);
1023:
1024: close(startup_p[1]);
1.1 deraadt 1025:
1.120 markus 1026: /* Mark that the key has been used (it was "given" to the child). */
1027: key_used = 1;
1.1 deraadt 1028:
1.120 markus 1029: arc4random_stir();
1.1 deraadt 1030:
1.120 markus 1031: /* Close the new socket (the child is now taking care of it). */
1032: close(newsock);
1033: }
1.75 markus 1034: /* child process check (or debug mode) */
1035: if (num_listen_socks < 0)
1036: break;
1.64 markus 1037: }
1.1 deraadt 1038: }
1039:
1.64 markus 1040: /* This is the child processing a new connection. */
1041:
1.66 markus 1042: /*
1043: * Disable the key regeneration alarm. We will not regenerate the
1044: * key since we are no longer in a position to give it to anyone. We
1045: * will not restart on SIGHUP since it no longer makes sense.
1046: */
1.64 markus 1047: alarm(0);
1048: signal(SIGALRM, SIG_DFL);
1049: signal(SIGHUP, SIG_DFL);
1050: signal(SIGTERM, SIG_DFL);
1051: signal(SIGQUIT, SIG_DFL);
1052: signal(SIGCHLD, SIG_DFL);
1053:
1.66 markus 1054: /*
1055: * Set socket options for the connection. We want the socket to
1056: * close as fast as possible without waiting for anything. If the
1057: * connection is not a socket, these will do nothing.
1058: */
1059: /* setsockopt(sock_in, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */
1.64 markus 1060: linger.l_onoff = 1;
1061: linger.l_linger = 5;
1062: setsockopt(sock_in, SOL_SOCKET, SO_LINGER, (void *) &linger, sizeof(linger));
1063:
1.66 markus 1064: /*
1065: * Register our connection. This turns encryption off because we do
1066: * not have a key.
1067: */
1.64 markus 1068: packet_set_connection(sock_in, sock_out);
1.1 deraadt 1069:
1.64 markus 1070: remote_port = get_remote_port();
1071: remote_ip = get_remote_ipaddr();
1.52 markus 1072:
1.64 markus 1073: /* Check whether logins are denied from this host. */
1.37 dugsong 1074: #ifdef LIBWRAP
1.75 markus 1075: /* XXX LIBWRAP noes not know about IPv6 */
1.64 markus 1076: {
1077: struct request_info req;
1.37 dugsong 1078:
1.138 markus 1079: request_init(&req, RQ_DAEMON, __progname, RQ_FILE, sock_in, NULL);
1.64 markus 1080: fromhost(&req);
1.37 dugsong 1081:
1.64 markus 1082: if (!hosts_access(&req)) {
1083: close(sock_in);
1084: close(sock_out);
1085: refuse(&req);
1086: }
1.75 markus 1087: /*XXX IPv6 verbose("Connection from %.500s port %d", eval_client(&req), remote_port); */
1.64 markus 1088: }
1.75 markus 1089: #endif /* LIBWRAP */
1.64 markus 1090: /* Log the connection. */
1091: verbose("Connection from %.500s port %d", remote_ip, remote_port);
1.1 deraadt 1092:
1.66 markus 1093: /*
1094: * We don\'t want to listen forever unless the other side
1095: * successfully authenticates itself. So we set up an alarm which is
1096: * cleared after successful authentication. A limit of zero
1097: * indicates no limit. Note that we don\'t set the alarm in debugging
1098: * mode; it is just annoying to have the server exit just when you
1099: * are about to discover the bug.
1100: */
1.64 markus 1101: signal(SIGALRM, grace_alarm_handler);
1102: if (!debug_flag)
1103: alarm(options.login_grace_time);
1104:
1.96 markus 1105: sshd_exchange_identification(sock_in, sock_out);
1.66 markus 1106: /*
1.137 markus 1107: * Check that the connection comes from a privileged port.
1108: * Rhosts-Authentication only makes sense from priviledged
1.66 markus 1109: * programs. Of course, if the intruder has root access on his local
1110: * machine, he can connect from any port. So do not use these
1111: * authentication methods from machines that you do not trust.
1112: */
1.64 markus 1113: if (remote_port >= IPPORT_RESERVED ||
1114: remote_port < IPPORT_RESERVED / 2) {
1.137 markus 1115: debug("Rhosts Authentication disabled, "
1.133 markus 1116: "originating port not trusted.");
1.64 markus 1117: options.rhosts_authentication = 0;
1118: }
1.76 markus 1119: #ifdef KRB4
1120: if (!packet_connection_is_ipv4() &&
1121: options.kerberos_authentication) {
1122: debug("Kerberos Authentication disabled, only available for IPv4.");
1123: options.kerberos_authentication = 0;
1124: }
1125: #endif /* KRB4 */
1126:
1.64 markus 1127: packet_set_nonblocking();
1.1 deraadt 1128:
1.77 markus 1129: /* perform the key exchange */
1130: /* authenticate user and start session */
1.98 markus 1131: if (compat20) {
1132: do_ssh2_kex();
1133: do_authentication2();
1134: } else {
1135: do_ssh1_kex();
1136: do_authentication();
1137: }
1.1 deraadt 1138:
1139: #ifdef KRB4
1.64 markus 1140: /* Cleanup user's ticket cache file. */
1141: if (options.kerberos_ticket_cleanup)
1142: (void) dest_tkt();
1.1 deraadt 1143: #endif /* KRB4 */
1144:
1.64 markus 1145: /* The connection has been terminated. */
1146: verbose("Closing connection to %.100s", remote_ip);
1147: packet_close();
1148: exit(0);
1.1 deraadt 1149: }
1150:
1.65 deraadt 1151: /*
1.77 markus 1152: * SSH1 key exchange
1.65 deraadt 1153: */
1.52 markus 1154: void
1.142 markus 1155: do_ssh1_kex(void)
1.1 deraadt 1156: {
1.64 markus 1157: int i, len;
1.77 markus 1158: int plen, slen;
1.64 markus 1159: BIGNUM *session_key_int;
1.140 markus 1160: u_char session_key[SSH_SESSION_KEY_LENGTH];
1161: u_char cookie[8];
1162: u_int cipher_type, auth_mask, protocol_flags;
1.64 markus 1163: u_int32_t rand = 0;
1164:
1.66 markus 1165: /*
1166: * Generate check bytes that the client must send back in the user
1167: * packet in order for it to be accepted; this is used to defy ip
1168: * spoofing attacks. Note that this only works against somebody
1169: * doing IP spoofing from a remote machine; any machine on the local
1170: * network can still see outgoing packets and catch the random
1171: * cookie. This only affects rhosts authentication, and this is one
1172: * of the reasons why it is inherently insecure.
1173: */
1.64 markus 1174: for (i = 0; i < 8; i++) {
1175: if (i % 4 == 0)
1176: rand = arc4random();
1.77 markus 1177: cookie[i] = rand & 0xff;
1.64 markus 1178: rand >>= 8;
1179: }
1180:
1.66 markus 1181: /*
1182: * Send our public key. We include in the packet 64 bits of random
1183: * data that must be matched in the reply in order to prevent IP
1184: * spoofing.
1185: */
1.64 markus 1186: packet_start(SSH_SMSG_PUBLIC_KEY);
1187: for (i = 0; i < 8; i++)
1.77 markus 1188: packet_put_char(cookie[i]);
1.64 markus 1189:
1190: /* Store our public server RSA key. */
1.134 markus 1191: packet_put_int(BN_num_bits(sensitive_data.server_key->rsa->n));
1192: packet_put_bignum(sensitive_data.server_key->rsa->e);
1193: packet_put_bignum(sensitive_data.server_key->rsa->n);
1.64 markus 1194:
1195: /* Store our public host RSA key. */
1.134 markus 1196: packet_put_int(BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1197: packet_put_bignum(sensitive_data.ssh1_host_key->rsa->e);
1198: packet_put_bignum(sensitive_data.ssh1_host_key->rsa->n);
1.64 markus 1199:
1200: /* Put protocol flags. */
1201: packet_put_int(SSH_PROTOFLAG_HOST_IN_FWD_OPEN);
1202:
1203: /* Declare which ciphers we support. */
1.131 markus 1204: packet_put_int(cipher_mask_ssh1(0));
1.64 markus 1205:
1206: /* Declare supported authentication types. */
1207: auth_mask = 0;
1208: if (options.rhosts_authentication)
1209: auth_mask |= 1 << SSH_AUTH_RHOSTS;
1210: if (options.rhosts_rsa_authentication)
1211: auth_mask |= 1 << SSH_AUTH_RHOSTS_RSA;
1212: if (options.rsa_authentication)
1213: auth_mask |= 1 << SSH_AUTH_RSA;
1.1 deraadt 1214: #ifdef KRB4
1.64 markus 1215: if (options.kerberos_authentication)
1216: auth_mask |= 1 << SSH_AUTH_KERBEROS;
1.1 deraadt 1217: #endif
1.5 dugsong 1218: #ifdef AFS
1.64 markus 1219: if (options.kerberos_tgt_passing)
1220: auth_mask |= 1 << SSH_PASS_KERBEROS_TGT;
1221: if (options.afs_token_passing)
1222: auth_mask |= 1 << SSH_PASS_AFS_TOKEN;
1.1 deraadt 1223: #endif
1.63 markus 1224: #ifdef SKEY
1.64 markus 1225: if (options.skey_authentication == 1)
1226: auth_mask |= 1 << SSH_AUTH_TIS;
1.63 markus 1227: #endif
1.64 markus 1228: if (options.password_authentication)
1229: auth_mask |= 1 << SSH_AUTH_PASSWORD;
1230: packet_put_int(auth_mask);
1231:
1232: /* Send the packet and wait for it to be sent. */
1233: packet_send();
1234: packet_write_wait();
1235:
1.134 markus 1236: debug("Sent %d bit server key and %d bit host key.",
1237: BN_num_bits(sensitive_data.server_key->rsa->n),
1238: BN_num_bits(sensitive_data.ssh1_host_key->rsa->n));
1.64 markus 1239:
1240: /* Read clients reply (cipher type and session key). */
1241: packet_read_expect(&plen, SSH_CMSG_SESSION_KEY);
1242:
1.69 markus 1243: /* Get cipher type and check whether we accept this. */
1.64 markus 1244: cipher_type = packet_get_char();
1.69 markus 1245:
1.131 markus 1246: if (!(cipher_mask_ssh1(0) & (1 << cipher_type)))
1.69 markus 1247: packet_disconnect("Warning: client selects unsupported cipher.");
1.64 markus 1248:
1249: /* Get check bytes from the packet. These must match those we
1250: sent earlier with the public key packet. */
1251: for (i = 0; i < 8; i++)
1.77 markus 1252: if (cookie[i] != packet_get_char())
1.64 markus 1253: packet_disconnect("IP Spoofing check bytes do not match.");
1254:
1255: debug("Encryption type: %.200s", cipher_name(cipher_type));
1256:
1257: /* Get the encrypted integer. */
1258: session_key_int = BN_new();
1259: packet_get_bignum(session_key_int, &slen);
1260:
1261: protocol_flags = packet_get_int();
1262: packet_set_protocol_flags(protocol_flags);
1263:
1264: packet_integrity_check(plen, 1 + 8 + slen + 4, SSH_CMSG_SESSION_KEY);
1265:
1.66 markus 1266: /*
1267: * Decrypt it using our private server key and private host key (key
1268: * with larger modulus first).
1269: */
1.134 markus 1270: if (BN_cmp(sensitive_data.server_key->rsa->n, sensitive_data.ssh1_host_key->rsa->n) > 0) {
1.64 markus 1271: /* Private key has bigger modulus. */
1.134 markus 1272: if (BN_num_bits(sensitive_data.server_key->rsa->n) <
1273: BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1274: fatal("do_connection: %s: server_key %d < host_key %d + SSH_KEY_BITS_RESERVED %d",
1275: get_remote_ipaddr(),
1276: BN_num_bits(sensitive_data.server_key->rsa->n),
1277: BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1278: SSH_KEY_BITS_RESERVED);
1.64 markus 1279: }
1280: rsa_private_decrypt(session_key_int, session_key_int,
1.134 markus 1281: sensitive_data.server_key->rsa);
1.64 markus 1282: rsa_private_decrypt(session_key_int, session_key_int,
1.134 markus 1283: sensitive_data.ssh1_host_key->rsa);
1.64 markus 1284: } else {
1285: /* Host key has bigger modulus (or they are equal). */
1.134 markus 1286: if (BN_num_bits(sensitive_data.ssh1_host_key->rsa->n) <
1287: BN_num_bits(sensitive_data.server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
1288: fatal("do_connection: %s: host_key %d < server_key %d + SSH_KEY_BITS_RESERVED %d",
1289: get_remote_ipaddr(),
1290: BN_num_bits(sensitive_data.ssh1_host_key->rsa->n),
1291: BN_num_bits(sensitive_data.server_key->rsa->n),
1292: SSH_KEY_BITS_RESERVED);
1.64 markus 1293: }
1294: rsa_private_decrypt(session_key_int, session_key_int,
1.134 markus 1295: sensitive_data.ssh1_host_key->rsa);
1.64 markus 1296: rsa_private_decrypt(session_key_int, session_key_int,
1.134 markus 1297: sensitive_data.server_key->rsa);
1.64 markus 1298: }
1299:
1.77 markus 1300: compute_session_id(session_id, cookie,
1.134 markus 1301: sensitive_data.ssh1_host_key->rsa->n,
1302: sensitive_data.server_key->rsa->n);
1.64 markus 1303:
1.77 markus 1304: /* Destroy the private and public keys. They will no longer be needed. */
1.108 markus 1305: destroy_sensitive_data();
1.77 markus 1306:
1.66 markus 1307: /*
1308: * Extract session key from the decrypted integer. The key is in the
1309: * least significant 256 bits of the integer; the first byte of the
1310: * key is in the highest bits.
1311: */
1.64 markus 1312: BN_mask_bits(session_key_int, sizeof(session_key) * 8);
1313: len = BN_num_bytes(session_key_int);
1314: if (len < 0 || len > sizeof(session_key))
1315: fatal("do_connection: bad len from %s: session_key_int %d > sizeof(session_key) %d",
1.134 markus 1316: get_remote_ipaddr(),
1317: len, sizeof(session_key));
1.64 markus 1318: memset(session_key, 0, sizeof(session_key));
1319: BN_bn2bin(session_key_int, session_key + sizeof(session_key) - len);
1320:
1.77 markus 1321: /* Destroy the decrypted integer. It is no longer needed. */
1322: BN_clear_free(session_key_int);
1323:
1.64 markus 1324: /* Xor the first 16 bytes of the session key with the session id. */
1325: for (i = 0; i < 16; i++)
1326: session_key[i] ^= session_id[i];
1327:
1328: /* Set the session key. From this on all communications will be encrypted. */
1329: packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, cipher_type);
1330:
1331: /* Destroy our copy of the session key. It is no longer needed. */
1332: memset(session_key, 0, sizeof(session_key));
1333:
1334: debug("Received session key; encryption turned on.");
1335:
1336: /* Send an acknowledgement packet. Note that this packet is sent encrypted. */
1337: packet_start(SSH_SMSG_SUCCESS);
1338: packet_send();
1339: packet_write_wait();
1.98 markus 1340: }
1341:
1342: /*
1343: * SSH2 key exchange: diffie-hellman-group1-sha1
1344: */
1345: void
1.142 markus 1346: do_ssh2_kex(void)
1.98 markus 1347: {
1348: Buffer *server_kexinit;
1349: Buffer *client_kexinit;
1.129 provos 1350: int payload_len;
1.98 markus 1351: int i;
1352: Kex *kex;
1353: char *cprop[PROPOSAL_MAX];
1354:
1355: /* KEXINIT */
1.102 markus 1356:
1357: if (options.ciphers != NULL) {
1.105 markus 1358: myproposal[PROPOSAL_ENC_ALGS_CTOS] =
1.102 markus 1359: myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
1360: }
1.134 markus 1361: myproposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = list_hostkey_types();
1362:
1.118 markus 1363: server_kexinit = kex_init(myproposal);
1.98 markus 1364: client_kexinit = xmalloc(sizeof(*client_kexinit));
1365: buffer_init(client_kexinit);
1366:
1.118 markus 1367: /* algorithm negotiation */
1368: kex_exchange_kexinit(server_kexinit, client_kexinit, cprop);
1369: kex = kex_choose_conf(cprop, myproposal, 1);
1370: for (i = 0; i < PROPOSAL_MAX; i++)
1371: xfree(cprop[i]);
1.98 markus 1372:
1.129 provos 1373: switch (kex->kex_type) {
1374: case DH_GRP1_SHA1:
1375: ssh_dh1_server(kex, client_kexinit, server_kexinit);
1376: break;
1377: case DH_GEX_SHA1:
1378: ssh_dhgex_server(kex, client_kexinit, server_kexinit);
1379: break;
1380: default:
1381: fatal("Unsupported key exchange %d", kex->kex_type);
1382: }
1383:
1384: debug("send SSH2_MSG_NEWKEYS.");
1385: packet_start(SSH2_MSG_NEWKEYS);
1386: packet_send();
1387: packet_write_wait();
1388: debug("done: send SSH2_MSG_NEWKEYS.");
1389:
1390: debug("Wait SSH2_MSG_NEWKEYS.");
1391: packet_read_expect(&payload_len, SSH2_MSG_NEWKEYS);
1392: debug("GOT SSH2_MSG_NEWKEYS.");
1393:
1394: #ifdef DEBUG_KEXDH
1395: /* send 1st encrypted/maced/compressed message */
1396: packet_start(SSH2_MSG_IGNORE);
1397: packet_put_cstring("markus");
1398: packet_send();
1399: packet_write_wait();
1400: #endif
1401:
1402: debug("done: KEX2.");
1403: }
1404:
1405: /*
1406: * SSH2 key exchange
1407: */
1408:
1409: /* diffie-hellman-group1-sha1 */
1410:
1411: void
1412: ssh_dh1_server(Kex *kex, Buffer *client_kexinit, Buffer *server_kexinit)
1413: {
1.130 markus 1414: #ifdef DEBUG_KEXDH
1415: int i;
1416: #endif
1.129 provos 1417: int payload_len, dlen;
1418: int slen;
1.140 markus 1419: u_char *signature = NULL;
1420: u_char *server_host_key_blob = NULL;
1421: u_int sbloblen;
1422: u_int klen, kout;
1423: u_char *kbuf;
1424: u_char *hash;
1.129 provos 1425: BIGNUM *shared_secret = 0;
1426: DH *dh;
1427: BIGNUM *dh_client_pub = 0;
1.134 markus 1428: Key *hostkey;
1429:
1430: hostkey = get_hostkey_by_type(kex->hostkey_type);
1431: if (hostkey == NULL)
1432: fatal("Unsupported hostkey type %d", kex->hostkey_type);
1.129 provos 1433:
1.98 markus 1434: /* KEXDH */
1.139 provos 1435: /* generate DH key */
1436: dh = dh_new_group1(); /* XXX depends on 'kex' */
1437: dh_gen_key(dh);
1438:
1.98 markus 1439: debug("Wait SSH2_MSG_KEXDH_INIT.");
1440: packet_read_expect(&payload_len, SSH2_MSG_KEXDH_INIT);
1441:
1442: /* key, cert */
1443: dh_client_pub = BN_new();
1444: if (dh_client_pub == NULL)
1445: fatal("dh_client_pub == NULL");
1446: packet_get_bignum2(dh_client_pub, &dlen);
1447:
1448: #ifdef DEBUG_KEXDH
1449: fprintf(stderr, "\ndh_client_pub= ");
1.128 markus 1450: BN_print_fp(stderr, dh_client_pub);
1.98 markus 1451: fprintf(stderr, "\n");
1452: debug("bits %d", BN_num_bits(dh_client_pub));
1453: #endif
1454:
1455: #ifdef DEBUG_KEXDH
1456: fprintf(stderr, "\np= ");
1.128 markus 1457: BN_print_fp(stderr, dh->p);
1.98 markus 1458: fprintf(stderr, "\ng= ");
1.128 markus 1459: bn_print(dh->g);
1.98 markus 1460: fprintf(stderr, "\npub= ");
1.128 markus 1461: BN_print_fp(stderr, dh->pub_key);
1.98 markus 1462: fprintf(stderr, "\n");
1.128 markus 1463: DHparams_print_fp(stderr, dh);
1.98 markus 1464: #endif
1.101 markus 1465: if (!dh_pub_is_valid(dh, dh_client_pub))
1466: packet_disconnect("bad client public DH value");
1.98 markus 1467:
1468: klen = DH_size(dh);
1469: kbuf = xmalloc(klen);
1470: kout = DH_compute_key(kbuf, dh_client_pub, dh);
1471:
1472: #ifdef DEBUG_KEXDH
1473: debug("shared secret: len %d/%d", klen, kout);
1474: fprintf(stderr, "shared secret == ");
1475: for (i = 0; i< kout; i++)
1476: fprintf(stderr, "%02x", (kbuf[i])&0xff);
1477: fprintf(stderr, "\n");
1478: #endif
1479: shared_secret = BN_new();
1480:
1481: BN_bin2bn(kbuf, kout, shared_secret);
1482: memset(kbuf, 0, klen);
1483: xfree(kbuf);
1484:
1.111 markus 1485: /* XXX precompute? */
1.134 markus 1486: key_to_blob(hostkey, &server_host_key_blob, &sbloblen);
1.98 markus 1487:
1488: /* calc H */ /* XXX depends on 'kex' */
1489: hash = kex_hash(
1490: client_version_string,
1491: server_version_string,
1492: buffer_ptr(client_kexinit), buffer_len(client_kexinit),
1493: buffer_ptr(server_kexinit), buffer_len(server_kexinit),
1494: (char *)server_host_key_blob, sbloblen,
1495: dh_client_pub,
1496: dh->pub_key,
1497: shared_secret
1498: );
1499: buffer_free(client_kexinit);
1500: buffer_free(server_kexinit);
1501: xfree(client_kexinit);
1502: xfree(server_kexinit);
1503: #ifdef DEBUG_KEXDH
1.105 markus 1504: fprintf(stderr, "hash == ");
1505: for (i = 0; i< 20; i++)
1506: fprintf(stderr, "%02x", (hash[i])&0xff);
1507: fprintf(stderr, "\n");
1.98 markus 1508: #endif
1.108 markus 1509: /* save session id := H */
1510: /* XXX hashlen depends on KEX */
1511: session_id2_len = 20;
1512: session_id2 = xmalloc(session_id2_len);
1513: memcpy(session_id2, hash, session_id2_len);
1514:
1.98 markus 1515: /* sign H */
1.108 markus 1516: /* XXX hashlen depends on KEX */
1.134 markus 1517: key_sign(hostkey, &signature, &slen, hash, 20);
1.108 markus 1518:
1519: destroy_sensitive_data();
1.98 markus 1520:
1521: /* send server hostkey, DH pubkey 'f' and singed H */
1522: packet_start(SSH2_MSG_KEXDH_REPLY);
1523: packet_put_string((char *)server_host_key_blob, sbloblen);
1.114 markus 1524: packet_put_bignum2(dh->pub_key); /* f */
1.98 markus 1525: packet_put_string((char *)signature, slen);
1526: packet_send();
1.106 markus 1527: xfree(signature);
1.111 markus 1528: xfree(server_host_key_blob);
1.98 markus 1529: packet_write_wait();
1530:
1531: kex_derive_keys(kex, hash, shared_secret);
1532: packet_set_kex(kex);
1533:
1534: /* have keys, free DH */
1535: DH_free(dh);
1.129 provos 1536: }
1537:
1538: /* diffie-hellman-group-exchange-sha1 */
1.98 markus 1539:
1.129 provos 1540: void
1541: ssh_dhgex_server(Kex *kex, Buffer *client_kexinit, Buffer *server_kexinit)
1542: {
1.130 markus 1543: #ifdef DEBUG_KEXDH
1544: int i;
1545: #endif
1.129 provos 1546: int payload_len, dlen;
1547: int slen, nbits;
1.140 markus 1548: u_char *signature = NULL;
1549: u_char *server_host_key_blob = NULL;
1550: u_int sbloblen;
1551: u_int klen, kout;
1552: u_char *kbuf;
1553: u_char *hash;
1.129 provos 1554: BIGNUM *shared_secret = 0;
1555: DH *dh;
1556: BIGNUM *dh_client_pub = 0;
1.134 markus 1557: Key *hostkey;
1558:
1559: hostkey = get_hostkey_by_type(kex->hostkey_type);
1560: if (hostkey == NULL)
1561: fatal("Unsupported hostkey type %d", kex->hostkey_type);
1.129 provos 1562:
1563: /* KEXDHGEX */
1564: debug("Wait SSH2_MSG_KEX_DH_GEX_REQUEST.");
1565: packet_read_expect(&payload_len, SSH2_MSG_KEX_DH_GEX_REQUEST);
1566: nbits = packet_get_int();
1567: dh = choose_dh(nbits);
1568:
1569: debug("Sending SSH2_MSG_KEX_DH_GEX_GROUP.");
1570: packet_start(SSH2_MSG_KEX_DH_GEX_GROUP);
1571: packet_put_bignum2(dh->p);
1572: packet_put_bignum2(dh->g);
1.98 markus 1573: packet_send();
1574: packet_write_wait();
1.139 provos 1575:
1576: /* Compute our exchange value in parallel with the client */
1577:
1578: dh_gen_key(dh);
1.98 markus 1579:
1.129 provos 1580: debug("Wait SSH2_MSG_KEX_DH_GEX_INIT.");
1581: packet_read_expect(&payload_len, SSH2_MSG_KEX_DH_GEX_INIT);
1582:
1583: /* key, cert */
1584: dh_client_pub = BN_new();
1585: if (dh_client_pub == NULL)
1586: fatal("dh_client_pub == NULL");
1587: packet_get_bignum2(dh_client_pub, &dlen);
1588:
1589: #ifdef DEBUG_KEXDH
1590: fprintf(stderr, "\ndh_client_pub= ");
1591: BN_print_fp(stderr, dh_client_pub);
1592: fprintf(stderr, "\n");
1593: debug("bits %d", BN_num_bits(dh_client_pub));
1594: #endif
1595:
1596: #ifdef DEBUG_KEXDH
1597: fprintf(stderr, "\np= ");
1598: BN_print_fp(stderr, dh->p);
1599: fprintf(stderr, "\ng= ");
1600: bn_print(dh->g);
1601: fprintf(stderr, "\npub= ");
1602: BN_print_fp(stderr, dh->pub_key);
1603: fprintf(stderr, "\n");
1604: DHparams_print_fp(stderr, dh);
1605: #endif
1606: if (!dh_pub_is_valid(dh, dh_client_pub))
1607: packet_disconnect("bad client public DH value");
1608:
1609: klen = DH_size(dh);
1610: kbuf = xmalloc(klen);
1611: kout = DH_compute_key(kbuf, dh_client_pub, dh);
1612:
1613: #ifdef DEBUG_KEXDH
1614: debug("shared secret: len %d/%d", klen, kout);
1615: fprintf(stderr, "shared secret == ");
1616: for (i = 0; i< kout; i++)
1617: fprintf(stderr, "%02x", (kbuf[i])&0xff);
1618: fprintf(stderr, "\n");
1619: #endif
1620: shared_secret = BN_new();
1621:
1622: BN_bin2bn(kbuf, kout, shared_secret);
1623: memset(kbuf, 0, klen);
1624: xfree(kbuf);
1625:
1626: /* XXX precompute? */
1.134 markus 1627: key_to_blob(hostkey, &server_host_key_blob, &sbloblen);
1.98 markus 1628:
1.129 provos 1629: /* calc H */ /* XXX depends on 'kex' */
1630: hash = kex_hash_gex(
1631: client_version_string,
1632: server_version_string,
1633: buffer_ptr(client_kexinit), buffer_len(client_kexinit),
1634: buffer_ptr(server_kexinit), buffer_len(server_kexinit),
1635: (char *)server_host_key_blob, sbloblen,
1636: nbits, dh->p, dh->g,
1637: dh_client_pub,
1638: dh->pub_key,
1639: shared_secret
1640: );
1641: buffer_free(client_kexinit);
1642: buffer_free(server_kexinit);
1643: xfree(client_kexinit);
1644: xfree(server_kexinit);
1.100 markus 1645: #ifdef DEBUG_KEXDH
1.129 provos 1646: fprintf(stderr, "hash == ");
1647: for (i = 0; i< 20; i++)
1648: fprintf(stderr, "%02x", (hash[i])&0xff);
1649: fprintf(stderr, "\n");
1650: #endif
1651: /* save session id := H */
1652: /* XXX hashlen depends on KEX */
1653: session_id2_len = 20;
1654: session_id2 = xmalloc(session_id2_len);
1655: memcpy(session_id2, hash, session_id2_len);
1656:
1657: /* sign H */
1658: /* XXX hashlen depends on KEX */
1.134 markus 1659: key_sign(hostkey, &signature, &slen, hash, 20);
1.129 provos 1660:
1661: destroy_sensitive_data();
1662:
1663: /* send server hostkey, DH pubkey 'f' and singed H */
1664: packet_start(SSH2_MSG_KEX_DH_GEX_REPLY);
1665: packet_put_string((char *)server_host_key_blob, sbloblen);
1666: packet_put_bignum2(dh->pub_key); /* f */
1667: packet_put_string((char *)signature, slen);
1.98 markus 1668: packet_send();
1.129 provos 1669: xfree(signature);
1670: xfree(server_host_key_blob);
1.98 markus 1671: packet_write_wait();
1.129 provos 1672:
1673: kex_derive_keys(kex, hash, shared_secret);
1674: packet_set_kex(kex);
1675:
1676: /* have keys, free DH */
1677: DH_free(dh);
1.1 deraadt 1678: }
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