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1 | /* | |
2 | * Author: Tatu Ylonen <ylo@cs.hut.fi> | |
3 | * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland | |
4 | * All rights reserved | |
5 | * Code to connect to a remote host, and to perform the client side of the | |
6 | * login (authentication) dialog. | |
7 | * | |
8 | * As far as I am concerned, the code I have written for this software | |
9 | * can be used freely for any purpose. Any derived versions of this | |
10 | * software must be clearly marked as such, and if the derived work is | |
11 | * incompatible with the protocol description in the RFC file, it must be | |
12 | * called by a name other than "ssh" or "Secure Shell". | |
13 | */ | |
14 | ||
15 | #include "includes.h" | |
16 | RCSID("$OpenBSD: sshconnect.c,v 1.109 2001/06/23 15:12:21 itojun Exp $"); | |
17 | ||
18 | #include <openssl/bn.h> | |
19 | ||
20 | #include "ssh.h" | |
21 | #include "xmalloc.h" | |
22 | #include "rsa.h" | |
23 | #include "buffer.h" | |
24 | #include "packet.h" | |
25 | #include "uidswap.h" | |
26 | #include "compat.h" | |
27 | #include "key.h" | |
28 | #include "sshconnect.h" | |
29 | #include "hostfile.h" | |
30 | #include "log.h" | |
31 | #include "readconf.h" | |
32 | #include "atomicio.h" | |
33 | #include "misc.h" | |
34 | ||
35 | char *client_version_string = NULL; | |
36 | char *server_version_string = NULL; | |
37 | ||
38 | extern Options options; | |
39 | extern char *__progname; | |
40 | ||
41 | /* AF_UNSPEC or AF_INET or AF_INET6 */ | |
42 | extern int IPv4or6; | |
43 | ||
44 | /* | |
45 | * Connect to the given ssh server using a proxy command. | |
46 | */ | |
47 | static int | |
48 | ssh_proxy_connect(const char *host, u_short port, struct passwd *pw, | |
49 | const char *proxy_command) | |
50 | { | |
51 | Buffer command; | |
52 | const char *cp; | |
53 | char *command_string; | |
54 | int pin[2], pout[2]; | |
55 | pid_t pid; | |
56 | char strport[NI_MAXSERV]; | |
57 | ||
58 | /* Convert the port number into a string. */ | |
59 | snprintf(strport, sizeof strport, "%hu", port); | |
60 | ||
61 | /* Build the final command string in the buffer by making the | |
62 | appropriate substitutions to the given proxy command. */ | |
63 | buffer_init(&command); | |
64 | for (cp = proxy_command; *cp; cp++) { | |
65 | if (cp[0] == '%' && cp[1] == '%') { | |
66 | buffer_append(&command, "%", 1); | |
67 | cp++; | |
68 | continue; | |
69 | } | |
70 | if (cp[0] == '%' && cp[1] == 'h') { | |
71 | buffer_append(&command, host, strlen(host)); | |
72 | cp++; | |
73 | continue; | |
74 | } | |
75 | if (cp[0] == '%' && cp[1] == 'p') { | |
76 | buffer_append(&command, strport, strlen(strport)); | |
77 | cp++; | |
78 | continue; | |
79 | } | |
80 | buffer_append(&command, cp, 1); | |
81 | } | |
82 | buffer_append(&command, "\0", 1); | |
83 | ||
84 | /* Get the final command string. */ | |
85 | command_string = buffer_ptr(&command); | |
86 | ||
87 | /* Create pipes for communicating with the proxy. */ | |
88 | if (pipe(pin) < 0 || pipe(pout) < 0) | |
89 | fatal("Could not create pipes to communicate with the proxy: %.100s", | |
90 | strerror(errno)); | |
91 | ||
92 | debug("Executing proxy command: %.500s", command_string); | |
93 | ||
94 | /* Fork and execute the proxy command. */ | |
95 | if ((pid = fork()) == 0) { | |
96 | char *argv[10]; | |
97 | ||
98 | /* Child. Permanently give up superuser privileges. */ | |
99 | permanently_set_uid(pw); | |
100 | ||
101 | /* Redirect stdin and stdout. */ | |
102 | close(pin[1]); | |
103 | if (pin[0] != 0) { | |
104 | if (dup2(pin[0], 0) < 0) | |
105 | perror("dup2 stdin"); | |
106 | close(pin[0]); | |
107 | } | |
108 | close(pout[0]); | |
109 | if (dup2(pout[1], 1) < 0) | |
110 | perror("dup2 stdout"); | |
111 | /* Cannot be 1 because pin allocated two descriptors. */ | |
112 | close(pout[1]); | |
113 | ||
114 | /* Stderr is left as it is so that error messages get | |
115 | printed on the user's terminal. */ | |
116 | argv[0] = _PATH_BSHELL; | |
117 | argv[1] = "-c"; | |
118 | argv[2] = command_string; | |
119 | argv[3] = NULL; | |
120 | ||
121 | /* Execute the proxy command. Note that we gave up any | |
122 | extra privileges above. */ | |
123 | execv(argv[0], argv); | |
124 | perror(argv[0]); | |
125 | exit(1); | |
126 | } | |
127 | /* Parent. */ | |
128 | if (pid < 0) | |
129 | fatal("fork failed: %.100s", strerror(errno)); | |
130 | ||
131 | /* Close child side of the descriptors. */ | |
132 | close(pin[0]); | |
133 | close(pout[1]); | |
134 | ||
135 | /* Free the command name. */ | |
136 | buffer_free(&command); | |
137 | ||
138 | /* Set the connection file descriptors. */ | |
139 | packet_set_connection(pout[0], pin[1]); | |
140 | ||
141 | return 1; | |
142 | } | |
143 | ||
144 | /* | |
145 | * Creates a (possibly privileged) socket for use as the ssh connection. | |
146 | */ | |
147 | static int | |
148 | ssh_create_socket(struct passwd *pw, int privileged, int family) | |
149 | { | |
150 | int sock, gaierr; | |
151 | struct addrinfo hints, *res; | |
152 | ||
153 | /* | |
154 | * If we are running as root and want to connect to a privileged | |
155 | * port, bind our own socket to a privileged port. | |
156 | */ | |
157 | if (privileged) { | |
158 | int p = IPPORT_RESERVED - 1; | |
159 | sock = rresvport_af(&p, family); | |
160 | if (sock < 0) | |
161 | error("rresvport: af=%d %.100s", family, strerror(errno)); | |
162 | else | |
163 | debug("Allocated local port %d.", p); | |
164 | return sock; | |
165 | } | |
166 | /* | |
167 | * Just create an ordinary socket on arbitrary port. We use | |
168 | * the user's uid to create the socket. | |
169 | */ | |
170 | temporarily_use_uid(pw); | |
171 | sock = socket(family, SOCK_STREAM, 0); | |
172 | if (sock < 0) | |
173 | error("socket: %.100s", strerror(errno)); | |
174 | restore_uid(); | |
175 | ||
176 | /* Bind the socket to an alternative local IP address */ | |
177 | if (options.bind_address == NULL) | |
178 | return sock; | |
179 | ||
180 | memset(&hints, 0, sizeof(hints)); | |
181 | hints.ai_family = IPv4or6; | |
182 | hints.ai_socktype = SOCK_STREAM; | |
183 | hints.ai_flags = AI_PASSIVE; | |
184 | gaierr = getaddrinfo(options.bind_address, "0", &hints, &res); | |
185 | if (gaierr) { | |
186 | error("getaddrinfo: %s: %s", options.bind_address, | |
187 | gai_strerror(gaierr)); | |
188 | close(sock); | |
189 | return -1; | |
190 | } | |
191 | if (bind(sock, res->ai_addr, res->ai_addrlen) < 0) { | |
192 | error("bind: %s: %s", options.bind_address, strerror(errno)); | |
193 | close(sock); | |
194 | freeaddrinfo(res); | |
195 | return -1; | |
196 | } | |
197 | freeaddrinfo(res); | |
198 | return sock; | |
199 | } | |
200 | ||
201 | /* | |
202 | * Opens a TCP/IP connection to the remote server on the given host. | |
203 | * The address of the remote host will be returned in hostaddr. | |
204 | * If port is 0, the default port will be used. If anonymous is zero, | |
205 | * a privileged port will be allocated to make the connection. | |
206 | * This requires super-user privileges if anonymous is false. | |
207 | * Connection_attempts specifies the maximum number of tries (one per | |
208 | * second). If proxy_command is non-NULL, it specifies the command (with %h | |
209 | * and %p substituted for host and port, respectively) to use to contact | |
210 | * the daemon. | |
211 | */ | |
212 | int | |
213 | ssh_connect(const char *host, struct sockaddr_storage * hostaddr, | |
214 | u_short port, int connection_attempts, | |
215 | int anonymous, struct passwd *pw, | |
216 | const char *proxy_command) | |
217 | { | |
218 | int gaierr; | |
219 | int on = 1; | |
220 | int sock = -1, attempt; | |
221 | char ntop[NI_MAXHOST], strport[NI_MAXSERV]; | |
222 | struct addrinfo hints, *ai, *aitop; | |
223 | struct linger linger; | |
224 | struct servent *sp; | |
225 | ||
226 | debug("ssh_connect: getuid %u geteuid %u anon %d", | |
227 | (u_int) getuid(), (u_int) geteuid(), anonymous); | |
228 | ||
229 | /* Get default port if port has not been set. */ | |
230 | if (port == 0) { | |
231 | sp = getservbyname(SSH_SERVICE_NAME, "tcp"); | |
232 | if (sp) | |
233 | port = ntohs(sp->s_port); | |
234 | else | |
235 | port = SSH_DEFAULT_PORT; | |
236 | } | |
237 | /* If a proxy command is given, connect using it. */ | |
238 | if (proxy_command != NULL) | |
239 | return ssh_proxy_connect(host, port, pw, proxy_command); | |
240 | ||
241 | /* No proxy command. */ | |
242 | ||
243 | memset(&hints, 0, sizeof(hints)); | |
244 | hints.ai_family = IPv4or6; | |
245 | hints.ai_socktype = SOCK_STREAM; | |
246 | snprintf(strport, sizeof strport, "%d", port); | |
247 | if ((gaierr = getaddrinfo(host, strport, &hints, &aitop)) != 0) | |
248 | fatal("%s: %.100s: %s", __progname, host, | |
249 | gai_strerror(gaierr)); | |
250 | ||
251 | /* | |
252 | * Try to connect several times. On some machines, the first time | |
253 | * will sometimes fail. In general socket code appears to behave | |
254 | * quite magically on many machines. | |
255 | */ | |
256 | for (attempt = 0; attempt < connection_attempts; attempt++) { | |
257 | if (attempt > 0) | |
258 | debug("Trying again..."); | |
259 | ||
260 | /* Loop through addresses for this host, and try each one in | |
261 | sequence until the connection succeeds. */ | |
262 | for (ai = aitop; ai; ai = ai->ai_next) { | |
263 | if (ai->ai_family != AF_INET && ai->ai_family != AF_INET6) | |
264 | continue; | |
265 | if (getnameinfo(ai->ai_addr, ai->ai_addrlen, | |
266 | ntop, sizeof(ntop), strport, sizeof(strport), | |
267 | NI_NUMERICHOST|NI_NUMERICSERV) != 0) { | |
268 | error("ssh_connect: getnameinfo failed"); | |
269 | continue; | |
270 | } | |
271 | debug("Connecting to %.200s [%.100s] port %s.", | |
272 | host, ntop, strport); | |
273 | ||
274 | /* Create a socket for connecting. */ | |
275 | sock = ssh_create_socket(pw, | |
276 | #ifdef HAVE_CYGWIN | |
277 | !anonymous, | |
278 | #else | |
279 | !anonymous && geteuid() == 0, | |
280 | #endif | |
281 | ai->ai_family); | |
282 | if (sock < 0) | |
283 | continue; | |
284 | ||
285 | /* Connect to the host. We use the user's uid in the | |
286 | * hope that it will help with tcp_wrappers showing | |
287 | * the remote uid as root. | |
288 | */ | |
289 | temporarily_use_uid(pw); | |
290 | if (connect(sock, ai->ai_addr, ai->ai_addrlen) >= 0) { | |
291 | /* Successful connection. */ | |
292 | memcpy(hostaddr, ai->ai_addr, ai->ai_addrlen); | |
293 | restore_uid(); | |
294 | break; | |
295 | } else { | |
296 | debug("connect: %.100s", strerror(errno)); | |
297 | restore_uid(); | |
298 | /* | |
299 | * Close the failed socket; there appear to | |
300 | * be some problems when reusing a socket for | |
301 | * which connect() has already returned an | |
302 | * error. | |
303 | */ | |
304 | shutdown(sock, SHUT_RDWR); | |
305 | close(sock); | |
306 | } | |
307 | } | |
308 | if (ai) | |
309 | break; /* Successful connection. */ | |
310 | ||
311 | /* Sleep a moment before retrying. */ | |
312 | sleep(1); | |
313 | } | |
314 | ||
315 | freeaddrinfo(aitop); | |
316 | ||
317 | /* Return failure if we didn't get a successful connection. */ | |
318 | if (attempt >= connection_attempts) | |
319 | return 0; | |
320 | ||
321 | debug("Connection established."); | |
322 | ||
323 | /* | |
324 | * Set socket options. We would like the socket to disappear as soon | |
325 | * as it has been closed for whatever reason. | |
326 | */ | |
327 | /* setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, (void *)&on, sizeof(on)); */ | |
328 | linger.l_onoff = 1; | |
329 | linger.l_linger = 5; | |
330 | setsockopt(sock, SOL_SOCKET, SO_LINGER, (void *)&linger, sizeof(linger)); | |
331 | ||
332 | /* Set keepalives if requested. */ | |
333 | if (options.keepalives && | |
334 | setsockopt(sock, SOL_SOCKET, SO_KEEPALIVE, (void *)&on, | |
335 | sizeof(on)) < 0) | |
336 | error("setsockopt SO_KEEPALIVE: %.100s", strerror(errno)); | |
337 | ||
338 | /* Set the connection. */ | |
339 | packet_set_connection(sock, sock); | |
340 | ||
341 | return 1; | |
342 | } | |
343 | ||
344 | /* | |
345 | * Waits for the server identification string, and sends our own | |
346 | * identification string. | |
347 | */ | |
348 | static void | |
349 | ssh_exchange_identification(void) | |
350 | { | |
351 | char buf[256], remote_version[256]; /* must be same size! */ | |
352 | int remote_major, remote_minor, i, mismatch; | |
353 | int connection_in = packet_get_connection_in(); | |
354 | int connection_out = packet_get_connection_out(); | |
355 | int minor1 = PROTOCOL_MINOR_1; | |
356 | ||
357 | /* Read other side\'s version identification. */ | |
358 | for (;;) { | |
359 | for (i = 0; i < sizeof(buf) - 1; i++) { | |
360 | int len = atomicio(read, connection_in, &buf[i], 1); | |
361 | if (len < 0) | |
362 | fatal("ssh_exchange_identification: read: %.100s", strerror(errno)); | |
363 | if (len != 1) | |
364 | fatal("ssh_exchange_identification: Connection closed by remote host"); | |
365 | if (buf[i] == '\r') { | |
366 | buf[i] = '\n'; | |
367 | buf[i + 1] = 0; | |
368 | continue; /**XXX wait for \n */ | |
369 | } | |
370 | if (buf[i] == '\n') { | |
371 | buf[i + 1] = 0; | |
372 | break; | |
373 | } | |
374 | } | |
375 | buf[sizeof(buf) - 1] = 0; | |
376 | if (strncmp(buf, "SSH-", 4) == 0) | |
377 | break; | |
378 | debug("ssh_exchange_identification: %s", buf); | |
379 | } | |
380 | server_version_string = xstrdup(buf); | |
381 | ||
382 | /* | |
383 | * Check that the versions match. In future this might accept | |
384 | * several versions and set appropriate flags to handle them. | |
385 | */ | |
386 | if (sscanf(server_version_string, "SSH-%d.%d-%[^\n]\n", | |
387 | &remote_major, &remote_minor, remote_version) != 3) | |
388 | fatal("Bad remote protocol version identification: '%.100s'", buf); | |
389 | debug("Remote protocol version %d.%d, remote software version %.100s", | |
390 | remote_major, remote_minor, remote_version); | |
391 | ||
392 | compat_datafellows(remote_version); | |
393 | mismatch = 0; | |
394 | ||
395 | switch(remote_major) { | |
396 | case 1: | |
397 | if (remote_minor == 99 && | |
398 | (options.protocol & SSH_PROTO_2) && | |
399 | !(options.protocol & SSH_PROTO_1_PREFERRED)) { | |
400 | enable_compat20(); | |
401 | break; | |
402 | } | |
403 | if (!(options.protocol & SSH_PROTO_1)) { | |
404 | mismatch = 1; | |
405 | break; | |
406 | } | |
407 | if (remote_minor < 3) { | |
408 | fatal("Remote machine has too old SSH software version."); | |
409 | } else if (remote_minor == 3 || remote_minor == 4) { | |
410 | /* We speak 1.3, too. */ | |
411 | enable_compat13(); | |
412 | minor1 = 3; | |
413 | if (options.forward_agent) { | |
414 | log("Agent forwarding disabled for protocol 1.3"); | |
415 | options.forward_agent = 0; | |
416 | } | |
417 | } | |
418 | break; | |
419 | case 2: | |
420 | if (options.protocol & SSH_PROTO_2) { | |
421 | enable_compat20(); | |
422 | break; | |
423 | } | |
424 | /* FALLTHROUGH */ | |
425 | default: | |
426 | mismatch = 1; | |
427 | break; | |
428 | } | |
429 | if (mismatch) | |
430 | fatal("Protocol major versions differ: %d vs. %d", | |
431 | (options.protocol & SSH_PROTO_2) ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, | |
432 | remote_major); | |
433 | /* Send our own protocol version identification. */ | |
434 | snprintf(buf, sizeof buf, "SSH-%d.%d-%.100s\n", | |
435 | compat20 ? PROTOCOL_MAJOR_2 : PROTOCOL_MAJOR_1, | |
436 | compat20 ? PROTOCOL_MINOR_2 : minor1, | |
437 | SSH_VERSION); | |
438 | if (atomicio(write, connection_out, buf, strlen(buf)) != strlen(buf)) | |
439 | fatal("write: %.100s", strerror(errno)); | |
440 | client_version_string = xstrdup(buf); | |
441 | chop(client_version_string); | |
442 | chop(server_version_string); | |
443 | debug("Local version string %.100s", client_version_string); | |
444 | } | |
445 | ||
446 | /* defaults to 'no' */ | |
447 | static int | |
448 | read_yes_or_no(const char *prompt, int defval) | |
449 | { | |
450 | char buf[1024]; | |
451 | FILE *f; | |
452 | int retval = -1; | |
453 | ||
454 | if (options.batch_mode) | |
455 | return 0; | |
456 | ||
457 | if (isatty(STDIN_FILENO)) | |
458 | f = stdin; | |
459 | else | |
460 | f = fopen(_PATH_TTY, "rw"); | |
461 | ||
462 | if (f == NULL) | |
463 | return 0; | |
464 | ||
465 | fflush(stdout); | |
466 | ||
467 | while (1) { | |
468 | fprintf(stderr, "%s", prompt); | |
469 | if (fgets(buf, sizeof(buf), f) == NULL) { | |
470 | /* | |
471 | * Print a newline (the prompt probably didn\'t have | |
472 | * one). | |
473 | */ | |
474 | fprintf(stderr, "\n"); | |
475 | strlcpy(buf, "no", sizeof buf); | |
476 | } | |
477 | /* Remove newline from response. */ | |
478 | if (strchr(buf, '\n')) | |
479 | *strchr(buf, '\n') = 0; | |
480 | ||
481 | if (buf[0] == 0) | |
482 | retval = defval; | |
483 | if (strcmp(buf, "yes") == 0) | |
484 | retval = 1; | |
485 | else if (strcmp(buf, "no") == 0) | |
486 | retval = 0; | |
487 | else | |
488 | fprintf(stderr, "Please type 'yes' or 'no'.\n"); | |
489 | ||
490 | if (retval != -1) { | |
491 | if (f != stdin) | |
492 | fclose(f); | |
493 | return retval; | |
494 | } | |
495 | } | |
496 | } | |
497 | ||
498 | /* | |
499 | * check whether the supplied host key is valid, return -1 if the key | |
500 | * is not valid. the user_hostfile will not be updated if 'readonly' is true. | |
501 | */ | |
502 | ||
503 | static int | |
504 | check_host_key(char *host, struct sockaddr *hostaddr, Key *host_key, | |
505 | int readonly, const char *user_hostfile, const char *system_hostfile) | |
506 | { | |
507 | Key *file_key; | |
508 | char *type = key_type(host_key); | |
509 | char *ip = NULL; | |
510 | char hostline[1000], *hostp, *fp; | |
511 | HostStatus host_status; | |
512 | HostStatus ip_status; | |
513 | int local = 0, host_ip_differ = 0; | |
514 | int salen; | |
515 | char ntop[NI_MAXHOST]; | |
516 | int host_line, ip_line; | |
517 | const char *host_file = NULL, *ip_file = NULL; | |
518 | ||
519 | /* | |
520 | * Force accepting of the host key for loopback/localhost. The | |
521 | * problem is that if the home directory is NFS-mounted to multiple | |
522 | * machines, localhost will refer to a different machine in each of | |
523 | * them, and the user will get bogus HOST_CHANGED warnings. This | |
524 | * essentially disables host authentication for localhost; however, | |
525 | * this is probably not a real problem. | |
526 | */ | |
527 | /** hostaddr == 0! */ | |
528 | switch (hostaddr->sa_family) { | |
529 | case AF_INET: | |
530 | local = (ntohl(((struct sockaddr_in *)hostaddr)-> | |
531 | sin_addr.s_addr) >> 24) == IN_LOOPBACKNET; | |
532 | salen = sizeof(struct sockaddr_in); | |
533 | break; | |
534 | case AF_INET6: | |
535 | local = IN6_IS_ADDR_LOOPBACK( | |
536 | &(((struct sockaddr_in6 *)hostaddr)->sin6_addr)); | |
537 | salen = sizeof(struct sockaddr_in6); | |
538 | break; | |
539 | default: | |
540 | local = 0; | |
541 | salen = sizeof(struct sockaddr_storage); | |
542 | break; | |
543 | } | |
544 | if (local && options.host_key_alias == NULL) { | |
545 | debug("Forcing accepting of host key for " | |
546 | "loopback/localhost."); | |
547 | return 0; | |
548 | } | |
549 | ||
550 | /* | |
551 | * We don't have the remote ip-address for connections | |
552 | * using a proxy command | |
553 | */ | |
554 | if (options.proxy_command == NULL) { | |
555 | if (getnameinfo(hostaddr, salen, ntop, sizeof(ntop), | |
556 | NULL, 0, NI_NUMERICHOST) != 0) | |
557 | fatal("check_host_key: getnameinfo failed"); | |
558 | ip = xstrdup(ntop); | |
559 | } else { | |
560 | ip = xstrdup("<no hostip for proxy command>"); | |
561 | } | |
562 | /* | |
563 | * Turn off check_host_ip if the connection is to localhost, via proxy | |
564 | * command or if we don't have a hostname to compare with | |
565 | */ | |
566 | if (options.check_host_ip && | |
567 | (local || strcmp(host, ip) == 0 || options.proxy_command != NULL)) | |
568 | options.check_host_ip = 0; | |
569 | ||
570 | /* | |
571 | * Allow the user to record the key under a different name. This is | |
572 | * useful for ssh tunneling over forwarded connections or if you run | |
573 | * multiple sshd's on different ports on the same machine. | |
574 | */ | |
575 | if (options.host_key_alias != NULL) { | |
576 | host = options.host_key_alias; | |
577 | debug("using hostkeyalias: %s", host); | |
578 | } | |
579 | ||
580 | /* | |
581 | * Store the host key from the known host file in here so that we can | |
582 | * compare it with the key for the IP address. | |
583 | */ | |
584 | file_key = key_new(host_key->type); | |
585 | ||
586 | /* | |
587 | * Check if the host key is present in the user\'s list of known | |
588 | * hosts or in the systemwide list. | |
589 | */ | |
590 | host_file = user_hostfile; | |
591 | host_status = check_host_in_hostfile(host_file, host, host_key, | |
592 | file_key, &host_line); | |
593 | if (host_status == HOST_NEW) { | |
594 | host_file = system_hostfile; | |
595 | host_status = check_host_in_hostfile(host_file, host, host_key, | |
596 | file_key, &host_line); | |
597 | } | |
598 | /* | |
599 | * Also perform check for the ip address, skip the check if we are | |
600 | * localhost or the hostname was an ip address to begin with | |
601 | */ | |
602 | if (options.check_host_ip) { | |
603 | Key *ip_key = key_new(host_key->type); | |
604 | ||
605 | ip_file = user_hostfile; | |
606 | ip_status = check_host_in_hostfile(ip_file, ip, host_key, | |
607 | ip_key, &ip_line); | |
608 | if (ip_status == HOST_NEW) { | |
609 | ip_file = system_hostfile; | |
610 | ip_status = check_host_in_hostfile(ip_file, ip, | |
611 | host_key, ip_key, &ip_line); | |
612 | } | |
613 | if (host_status == HOST_CHANGED && | |
614 | (ip_status != HOST_CHANGED || !key_equal(ip_key, file_key))) | |
615 | host_ip_differ = 1; | |
616 | ||
617 | key_free(ip_key); | |
618 | } else | |
619 | ip_status = host_status; | |
620 | ||
621 | key_free(file_key); | |
622 | ||
623 | switch (host_status) { | |
624 | case HOST_OK: | |
625 | /* The host is known and the key matches. */ | |
626 | debug("Host '%.200s' is known and matches the %s host key.", | |
627 | host, type); | |
628 | debug("Found key in %s:%d", host_file, host_line); | |
629 | if (options.check_host_ip && ip_status == HOST_NEW) { | |
630 | if (readonly) | |
631 | log("%s host key for IP address " | |
632 | "'%.128s' not in list of known hosts.", | |
633 | type, ip); | |
634 | else if (!add_host_to_hostfile(user_hostfile, ip, | |
635 | host_key)) | |
636 | log("Failed to add the %s host key for IP " | |
637 | "address '%.128s' to the list of known " | |
638 | "hosts (%.30s).", type, ip, user_hostfile); | |
639 | else | |
640 | log("Warning: Permanently added the %s host " | |
641 | "key for IP address '%.128s' to the list " | |
642 | "of known hosts.", type, ip); | |
643 | } | |
644 | break; | |
645 | case HOST_NEW: | |
646 | if (readonly) | |
647 | goto fail; | |
648 | /* The host is new. */ | |
649 | if (options.strict_host_key_checking == 1) { | |
650 | /* | |
651 | * User has requested strict host key checking. We | |
652 | * will not add the host key automatically. The only | |
653 | * alternative left is to abort. | |
654 | */ | |
655 | error("No %s host key is known for %.200s and you " | |
656 | "have requested strict checking.", type, host); | |
657 | goto fail; | |
658 | } else if (options.strict_host_key_checking == 2) { | |
659 | /* The default */ | |
660 | char prompt[1024]; | |
661 | fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); | |
662 | snprintf(prompt, sizeof(prompt), | |
663 | "The authenticity of host '%.200s (%s)' can't be " | |
664 | "established.\n" | |
665 | "%s key fingerprint is %s.\n" | |
666 | "Are you sure you want to continue connecting " | |
667 | "(yes/no)? ", host, ip, type, fp); | |
668 | xfree(fp); | |
669 | if (!read_yes_or_no(prompt, -1)) { | |
670 | log("Aborted by user!"); | |
671 | goto fail; | |
672 | } | |
673 | } | |
674 | if (options.check_host_ip && ip_status == HOST_NEW) { | |
675 | snprintf(hostline, sizeof(hostline), "%s,%s", host, ip); | |
676 | hostp = hostline; | |
677 | } else | |
678 | hostp = host; | |
679 | ||
680 | /* | |
681 | * If not in strict mode, add the key automatically to the | |
682 | * local known_hosts file. | |
683 | */ | |
684 | if (!add_host_to_hostfile(user_hostfile, hostp, host_key)) | |
685 | log("Failed to add the host to the list of known " | |
686 | "hosts (%.500s).", user_hostfile); | |
687 | else | |
688 | log("Warning: Permanently added '%.200s' (%s) to the " | |
689 | "list of known hosts.", hostp, type); | |
690 | break; | |
691 | case HOST_CHANGED: | |
692 | if (options.check_host_ip && host_ip_differ) { | |
693 | char *msg; | |
694 | if (ip_status == HOST_NEW) | |
695 | msg = "is unknown"; | |
696 | else if (ip_status == HOST_OK) | |
697 | msg = "is unchanged"; | |
698 | else | |
699 | msg = "has a different value"; | |
700 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
701 | error("@ WARNING: POSSIBLE DNS SPOOFING DETECTED! @"); | |
702 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
703 | error("The %s host key for %s has changed,", type, host); | |
704 | error("and the key for the according IP address %s", ip); | |
705 | error("%s. This could either mean that", msg); | |
706 | error("DNS SPOOFING is happening or the IP address for the host"); | |
707 | error("and its host key have changed at the same time."); | |
708 | if (ip_status != HOST_NEW) | |
709 | error("Offending key for IP in %s:%d", ip_file, ip_line); | |
710 | } | |
711 | /* The host key has changed. */ | |
712 | fp = key_fingerprint(host_key, SSH_FP_MD5, SSH_FP_HEX); | |
713 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
714 | error("@ WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! @"); | |
715 | error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); | |
716 | error("IT IS POSSIBLE THAT SOMEONE IS DOING SOMETHING NASTY!"); | |
717 | error("Someone could be eavesdropping on you right now (man-in-the-middle attack)!"); | |
718 | error("It is also possible that the %s host key has just been changed.", type); | |
719 | error("The fingerprint for the %s key sent by the remote host is\n%s.", | |
720 | type, fp); | |
721 | error("Please contact your system administrator."); | |
722 | error("Add correct host key in %.100s to get rid of this message.", | |
723 | user_hostfile); | |
724 | error("Offending key in %s:%d", host_file, host_line); | |
725 | xfree(fp); | |
726 | ||
727 | /* | |
728 | * If strict host key checking is in use, the user will have | |
729 | * to edit the key manually and we can only abort. | |
730 | */ | |
731 | if (options.strict_host_key_checking) { | |
732 | error("%s host key for %.200s has changed and you have " | |
733 | "requested strict checking.", type, host); | |
734 | goto fail; | |
735 | } | |
736 | ||
737 | /* | |
738 | * If strict host key checking has not been requested, allow | |
739 | * the connection but without password authentication or | |
740 | * agent forwarding. | |
741 | */ | |
742 | if (options.password_authentication) { | |
743 | error("Password authentication is disabled to avoid " | |
744 | "man-in-the-middle attacks."); | |
745 | options.password_authentication = 0; | |
746 | } | |
747 | if (options.forward_agent) { | |
748 | error("Agent forwarding is disabled to avoid " | |
749 | "man-in-the-middle attacks."); | |
750 | options.forward_agent = 0; | |
751 | } | |
752 | if (options.forward_x11) { | |
753 | error("X11 forwarding is disabled to avoid " | |
754 | "man-in-the-middle attacks."); | |
755 | options.forward_x11 = 0; | |
756 | } | |
757 | if (options.num_local_forwards > 0 || | |
758 | options.num_remote_forwards > 0) { | |
759 | error("Port forwarding is disabled to avoid " | |
760 | "man-in-the-middle attacks."); | |
761 | options.num_local_forwards = | |
762 | options.num_remote_forwards = 0; | |
763 | } | |
764 | /* | |
765 | * XXX Should permit the user to change to use the new id. | |
766 | * This could be done by converting the host key to an | |
767 | * identifying sentence, tell that the host identifies itself | |
768 | * by that sentence, and ask the user if he/she whishes to | |
769 | * accept the authentication. | |
770 | */ | |
771 | break; | |
772 | } | |
773 | ||
774 | if (options.check_host_ip && host_status != HOST_CHANGED && | |
775 | ip_status == HOST_CHANGED) { | |
776 | log("Warning: the %s host key for '%.200s' " | |
777 | "differs from the key for the IP address '%.128s'", | |
778 | type, host, ip); | |
779 | if (host_status == HOST_OK) | |
780 | log("Matching host key in %s:%d", host_file, host_line); | |
781 | log("Offending key for IP in %s:%d", ip_file, ip_line); | |
782 | if (options.strict_host_key_checking == 1) { | |
783 | error("Exiting, you have requested strict checking."); | |
784 | goto fail; | |
785 | } else if (options.strict_host_key_checking == 2) { | |
786 | if (!read_yes_or_no("Are you sure you want " | |
787 | "to continue connecting (yes/no)? ", -1)) { | |
788 | log("Aborted by user!"); | |
789 | goto fail; | |
790 | } | |
791 | } | |
792 | } | |
793 | ||
794 | xfree(ip); | |
795 | return 0; | |
796 | ||
797 | fail: | |
798 | xfree(ip); | |
799 | return -1; | |
800 | } | |
801 | ||
802 | int | |
803 | verify_host_key(char *host, struct sockaddr *hostaddr, Key *host_key) | |
804 | { | |
805 | struct stat st; | |
806 | ||
807 | /* return ok if the key can be found in an old keyfile */ | |
808 | if (stat(options.system_hostfile2, &st) == 0 || | |
809 | stat(options.user_hostfile2, &st) == 0) { | |
810 | if (check_host_key(host, hostaddr, host_key, /*readonly*/ 1, | |
811 | options.user_hostfile2, options.system_hostfile2) == 0) | |
812 | return 0; | |
813 | } | |
814 | return check_host_key(host, hostaddr, host_key, /*readonly*/ 0, | |
815 | options.user_hostfile, options.system_hostfile); | |
816 | } | |
817 | ||
818 | /* | |
819 | * Starts a dialog with the server, and authenticates the current user on the | |
820 | * server. This does not need any extra privileges. The basic connection | |
821 | * to the server must already have been established before this is called. | |
822 | * If login fails, this function prints an error and never returns. | |
823 | * This function does not require super-user privileges. | |
824 | */ | |
825 | void | |
826 | ssh_login(Key **keys, int nkeys, const char *orighost, | |
827 | struct sockaddr *hostaddr, struct passwd *pw) | |
828 | { | |
829 | char *host, *cp; | |
830 | char *server_user, *local_user; | |
831 | ||
832 | local_user = xstrdup(pw->pw_name); | |
833 | server_user = options.user ? options.user : local_user; | |
834 | ||
835 | /* Convert the user-supplied hostname into all lowercase. */ | |
836 | host = xstrdup(orighost); | |
837 | for (cp = host; *cp; cp++) | |
838 | if (isupper(*cp)) | |
839 | *cp = tolower(*cp); | |
840 | ||
841 | /* Exchange protocol version identification strings with the server. */ | |
842 | ssh_exchange_identification(); | |
843 | ||
844 | /* Put the connection into non-blocking mode. */ | |
845 | packet_set_nonblocking(); | |
846 | ||
847 | /* key exchange */ | |
848 | /* authenticate user */ | |
849 | if (compat20) { | |
850 | ssh_kex2(host, hostaddr); | |
851 | ssh_userauth2(local_user, server_user, host, keys, nkeys); | |
852 | } else { | |
853 | ssh_kex(host, hostaddr); | |
854 | ssh_userauth1(local_user, server_user, host, keys, nkeys); | |
855 | } | |
856 | } | |
857 | ||
858 | void | |
859 | ssh_put_password(char *password) | |
860 | { | |
861 | int size; | |
862 | char *padded; | |
863 | ||
864 | if (datafellows & SSH_BUG_PASSWORDPAD) { | |
865 | packet_put_cstring(password); | |
866 | return; | |
867 | } | |
868 | size = roundup(strlen(password) + 1, 32); | |
869 | padded = xmalloc(size); | |
870 | memset(padded, 0, size); | |
871 | strlcpy(padded, password, size); | |
872 | packet_put_string(padded, size); | |
873 | memset(padded, 0, size); | |
874 | xfree(padded); | |
875 | } |