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 * Functions for connecting the local authentication agent.
6 *
7 * As far as I am concerned, the code I have written for this software
8 * can be used freely for any purpose. Any derived versions of this
9 * software must be clearly marked as such, and if the derived work is
10 * incompatible with the protocol description in the RFC file, it must be
11 * called by a name other than "ssh" or "Secure Shell".
12 *
13 * SSH2 implementation,
14 * Copyright (c) 2000 Markus Friedl. All rights reserved.
15 *
16 * Redistribution and use in source and binary forms, with or without
17 * modification, are permitted provided that the following conditions
18 * are met:
19 * 1. Redistributions of source code must retain the above copyright
20 * notice, this list of conditions and the following disclaimer.
21 * 2. Redistributions in binary form must reproduce the above copyright
22 * notice, this list of conditions and the following disclaimer in the
23 * documentation and/or other materials provided with the distribution.
24 *
25 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
26 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
27 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
28 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
29 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
30 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
31 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
32 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
33 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
34 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
35 */
36
37 #include "includes.h"
38 RCSID("$OpenBSD: authfd.c,v 1.57 2002/09/11 18:27:26 stevesk Exp $");
39
40 #include <openssl/opensslconf.h>
41 #include <openssl/evp.h>
42
43 #include "ssh.h"
44 #include "rsa.h"
45 #include "buffer.h"
46 #include "bufaux.h"
47 #include "xmalloc.h"
48 #include "getput.h"
49 #include "key.h"
50 #include "authfd.h"
51 #include "cipher.h"
52 #include "kex.h"
53 #include "compat.h"
54 #include "log.h"
55 #include "atomicio.h"
56
57 static int agent_present = 0;
58
59 /* helper */
60 int decode_reply(int type);
61
62 /* macro to check for "agent failure" message */
63 #define agent_failed(x) \
64 ((x == SSH_AGENT_FAILURE) || (x == SSH_COM_AGENT2_FAILURE) || \
65 (x == SSH2_AGENT_FAILURE))
66
67 int
68 ssh_agent_present(void)
69 {
70 int authfd;
71
72 if (agent_present)
73 return 1;
74 if ((authfd = ssh_get_authentication_socket()) == -1)
75 return 0;
76 else {
77 ssh_close_authentication_socket(authfd);
78 return 1;
79 }
80 }
81
82 /* Returns the number of the authentication fd, or -1 if there is none. */
83
84 int
85 ssh_get_authentication_socket(void)
86 {
87 const char *authsocket;
88 int sock;
89 struct sockaddr_un sunaddr;
90
91 authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME);
92 if (!authsocket)
93 return -1;
94
95 sunaddr.sun_family = AF_UNIX;
96 strlcpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path));
97
98 sock = socket(AF_UNIX, SOCK_STREAM, 0);
99 if (sock < 0)
100 return -1;
101
102 /* close on exec */
103 if (fcntl(sock, F_SETFD, FD_CLOEXEC) == -1) {
104 close(sock);
105 return -1;
106 }
107 if (connect(sock, (struct sockaddr *) &sunaddr, sizeof sunaddr) < 0) {
108 close(sock);
109 return -1;
110 }
111 agent_present = 1;
112 return sock;
113 }
114
115 static int
116 ssh_request_reply(AuthenticationConnection *auth, Buffer *request, Buffer *reply)
117 {
118 int l, len;
119 char buf[1024];
120
121 /* Get the length of the message, and format it in the buffer. */
122 len = buffer_len(request);
123 PUT_32BIT(buf, len);
124
125 /* Send the length and then the packet to the agent. */
126 if (atomicio(write, auth->fd, buf, 4) != 4 ||
127 atomicio(write, auth->fd, buffer_ptr(request),
128 buffer_len(request)) != buffer_len(request)) {
129 error("Error writing to authentication socket.");
130 return 0;
131 }
132 /*
133 * Wait for response from the agent. First read the length of the
134 * response packet.
135 */
136 len = 4;
137 while (len > 0) {
138 l = read(auth->fd, buf + 4 - len, len);
139 if (l == -1 && (errno == EAGAIN || errno == EINTR))
140 continue;
141 if (l <= 0) {
142 error("Error reading response length from authentication socket.");
143 return 0;
144 }
145 len -= l;
146 }
147
148 /* Extract the length, and check it for sanity. */
149 len = GET_32BIT(buf);
150 if (len > 256 * 1024)
151 fatal("Authentication response too long: %d", len);
152
153 /* Read the rest of the response in to the buffer. */
154 buffer_clear(reply);
155 while (len > 0) {
156 l = len;
157 if (l > sizeof(buf))
158 l = sizeof(buf);
159 l = read(auth->fd, buf, l);
160 if (l == -1 && (errno == EAGAIN || errno == EINTR))
161 continue;
162 if (l <= 0) {
163 error("Error reading response from authentication socket.");
164 return 0;
165 }
166 buffer_append(reply, buf, l);
167 len -= l;
168 }
169 return 1;
170 }
171
172 /*
173 * Closes the agent socket if it should be closed (depends on how it was
174 * obtained). The argument must have been returned by
175 * ssh_get_authentication_socket().
176 */
177
178 void
179 ssh_close_authentication_socket(int sock)
180 {
181 if (getenv(SSH_AUTHSOCKET_ENV_NAME))
182 close(sock);
183 }
184
185 /*
186 * Opens and connects a private socket for communication with the
187 * authentication agent. Returns the file descriptor (which must be
188 * shut down and closed by the caller when no longer needed).
189 * Returns NULL if an error occurred and the connection could not be
190 * opened.
191 */
192
193 AuthenticationConnection *
194 ssh_get_authentication_connection(void)
195 {
196 AuthenticationConnection *auth;
197 int sock;
198
199 sock = ssh_get_authentication_socket();
200
201 /*
202 * Fail if we couldn't obtain a connection. This happens if we
203 * exited due to a timeout.
204 */
205 if (sock < 0)
206 return NULL;
207
208 auth = xmalloc(sizeof(*auth));
209 auth->fd = sock;
210 buffer_init(&auth->identities);
211 auth->howmany = 0;
212
213 return auth;
214 }
215
216 /*
217 * Closes the connection to the authentication agent and frees any associated
218 * memory.
219 */
220
221 void
222 ssh_close_authentication_connection(AuthenticationConnection *auth)
223 {
224 buffer_free(&auth->identities);
225 close(auth->fd);
226 xfree(auth);
227 }
228
229 /* Lock/unlock agent */
230 int
231 ssh_lock_agent(AuthenticationConnection *auth, int lock, const char *password)
232 {
233 int type;
234 Buffer msg;
235
236 buffer_init(&msg);
237 buffer_put_char(&msg, lock ? SSH_AGENTC_LOCK : SSH_AGENTC_UNLOCK);
238 buffer_put_cstring(&msg, password);
239
240 if (ssh_request_reply(auth, &msg, &msg) == 0) {
241 buffer_free(&msg);
242 return 0;
243 }
244 type = buffer_get_char(&msg);
245 buffer_free(&msg);
246 return decode_reply(type);
247 }
248
249 /*
250 * Returns the first authentication identity held by the agent.
251 */
252
253 int
254 ssh_get_num_identities(AuthenticationConnection *auth, int version)
255 {
256 int type, code1 = 0, code2 = 0;
257 Buffer request;
258
259 switch (version) {
260 case 1:
261 code1 = SSH_AGENTC_REQUEST_RSA_IDENTITIES;
262 code2 = SSH_AGENT_RSA_IDENTITIES_ANSWER;
263 break;
264 case 2:
265 code1 = SSH2_AGENTC_REQUEST_IDENTITIES;
266 code2 = SSH2_AGENT_IDENTITIES_ANSWER;
267 break;
268 default:
269 return 0;
270 }
271
272 /*
273 * Send a message to the agent requesting for a list of the
274 * identities it can represent.
275 */
276 buffer_init(&request);
277 buffer_put_char(&request, code1);
278
279 buffer_clear(&auth->identities);
280 if (ssh_request_reply(auth, &request, &auth->identities) == 0) {
281 buffer_free(&request);
282 return 0;
283 }
284 buffer_free(&request);
285
286 /* Get message type, and verify that we got a proper answer. */
287 type = buffer_get_char(&auth->identities);
288 if (agent_failed(type)) {
289 return 0;
290 } else if (type != code2) {
291 fatal("Bad authentication reply message type: %d", type);
292 }
293
294 /* Get the number of entries in the response and check it for sanity. */
295 auth->howmany = buffer_get_int(&auth->identities);
296 if (auth->howmany > 1024)
297 fatal("Too many identities in authentication reply: %d",
298 auth->howmany);
299
300 return auth->howmany;
301 }
302
303 Key *
304 ssh_get_first_identity(AuthenticationConnection *auth, char **comment, int version)
305 {
306 /* get number of identities and return the first entry (if any). */
307 if (ssh_get_num_identities(auth, version) > 0)
308 return ssh_get_next_identity(auth, comment, version);
309 return NULL;
310 }
311
312 Key *
313 ssh_get_next_identity(AuthenticationConnection *auth, char **comment, int version)
314 {
315 u_int bits;
316 u_char *blob;
317 u_int blen;
318 Key *key = NULL;
319
320 /* Return failure if no more entries. */
321 if (auth->howmany <= 0)
322 return NULL;
323
324 /*
325 * Get the next entry from the packet. These will abort with a fatal
326 * error if the packet is too short or contains corrupt data.
327 */
328 switch (version) {
329 case 1:
330 key = key_new(KEY_RSA1);
331 bits = buffer_get_int(&auth->identities);
332 buffer_get_bignum(&auth->identities, key->rsa->e);
333 buffer_get_bignum(&auth->identities, key->rsa->n);
334 *comment = buffer_get_string(&auth->identities, NULL);
335 if (bits != BN_num_bits(key->rsa->n))
336 log("Warning: identity keysize mismatch: actual %d, announced %u",
337 BN_num_bits(key->rsa->n), bits);
338 break;
339 case 2:
340 blob = buffer_get_string(&auth->identities, &blen);
341 *comment = buffer_get_string(&auth->identities, NULL);
342 key = key_from_blob(blob, blen);
343 xfree(blob);
344 break;
345 default:
346 return NULL;
347 break;
348 }
349 /* Decrement the number of remaining entries. */
350 auth->howmany--;
351 return key;
352 }
353
354 /*
355 * Generates a random challenge, sends it to the agent, and waits for
356 * response from the agent. Returns true (non-zero) if the agent gave the
357 * correct answer, zero otherwise. Response type selects the style of
358 * response desired, with 0 corresponding to protocol version 1.0 (no longer
359 * supported) and 1 corresponding to protocol version 1.1.
360 */
361
362 int
363 ssh_decrypt_challenge(AuthenticationConnection *auth,
364 Key* key, BIGNUM *challenge,
365 u_char session_id[16],
366 u_int response_type,
367 u_char response[16])
368 {
369 Buffer buffer;
370 int success = 0;
371 int i;
372 int type;
373
374 if (key->type != KEY_RSA1)
375 return 0;
376 if (response_type == 0) {
377 log("Compatibility with ssh protocol version 1.0 no longer supported.");
378 return 0;
379 }
380 buffer_init(&buffer);
381 buffer_put_char(&buffer, SSH_AGENTC_RSA_CHALLENGE);
382 buffer_put_int(&buffer, BN_num_bits(key->rsa->n));
383 buffer_put_bignum(&buffer, key->rsa->e);
384 buffer_put_bignum(&buffer, key->rsa->n);
385 buffer_put_bignum(&buffer, challenge);
386 buffer_append(&buffer, session_id, 16);
387 buffer_put_int(&buffer, response_type);
388
389 if (ssh_request_reply(auth, &buffer, &buffer) == 0) {
390 buffer_free(&buffer);
391 return 0;
392 }
393 type = buffer_get_char(&buffer);
394
395 if (agent_failed(type)) {
396 log("Agent admitted failure to authenticate using the key.");
397 } else if (type != SSH_AGENT_RSA_RESPONSE) {
398 fatal("Bad authentication response: %d", type);
399 } else {
400 success = 1;
401 /*
402 * Get the response from the packet. This will abort with a
403 * fatal error if the packet is corrupt.
404 */
405 for (i = 0; i < 16; i++)
406 response[i] = buffer_get_char(&buffer);
407 }
408 buffer_free(&buffer);
409 return success;
410 }
411
412 /* ask agent to sign data, returns -1 on error, 0 on success */
413 int
414 ssh_agent_sign(AuthenticationConnection *auth,
415 Key *key,
416 u_char **sigp, u_int *lenp,
417 u_char *data, u_int datalen)
418 {
419 Buffer msg;
420 u_char *blob;
421 u_int blen;
422 int type, flags = 0;
423 int ret = -1;
424
425 if (key_to_blob(key, &blob, &blen) == 0)
426 return -1;
427
428 if (datafellows & SSH_BUG_SIGBLOB)
429 flags = SSH_AGENT_OLD_SIGNATURE;
430
431 buffer_init(&msg);
432 buffer_put_char(&msg, SSH2_AGENTC_SIGN_REQUEST);
433 buffer_put_string(&msg, blob, blen);
434 buffer_put_string(&msg, data, datalen);
435 buffer_put_int(&msg, flags);
436 xfree(blob);
437
438 if (ssh_request_reply(auth, &msg, &msg) == 0) {
439 buffer_free(&msg);
440 return -1;
441 }
442 type = buffer_get_char(&msg);
443 if (agent_failed(type)) {
444 log("Agent admitted failure to sign using the key.");
445 } else if (type != SSH2_AGENT_SIGN_RESPONSE) {
446 fatal("Bad authentication response: %d", type);
447 } else {
448 ret = 0;
449 *sigp = buffer_get_string(&msg, lenp);
450 }
451 buffer_free(&msg);
452 return ret;
453 }
454
455 /* Encode key for a message to the agent. */
456
457 static void
458 ssh_encode_identity_rsa1(Buffer *b, RSA *key, const char *comment)
459 {
460 buffer_put_int(b, BN_num_bits(key->n));
461 buffer_put_bignum(b, key->n);
462 buffer_put_bignum(b, key->e);
463 buffer_put_bignum(b, key->d);
464 /* To keep within the protocol: p < q for ssh. in SSL p > q */
465 buffer_put_bignum(b, key->iqmp); /* ssh key->u */
466 buffer_put_bignum(b, key->q); /* ssh key->p, SSL key->q */
467 buffer_put_bignum(b, key->p); /* ssh key->q, SSL key->p */
468 buffer_put_cstring(b, comment);
469 }
470
471 static void
472 ssh_encode_identity_ssh2(Buffer *b, Key *key, const char *comment)
473 {
474 buffer_put_cstring(b, key_ssh_name(key));
475 switch (key->type) {
476 case KEY_RSA:
477 buffer_put_bignum2(b, key->rsa->n);
478 buffer_put_bignum2(b, key->rsa->e);
479 buffer_put_bignum2(b, key->rsa->d);
480 buffer_put_bignum2(b, key->rsa->iqmp);
481 buffer_put_bignum2(b, key->rsa->p);
482 buffer_put_bignum2(b, key->rsa->q);
483 break;
484 case KEY_DSA:
485 buffer_put_bignum2(b, key->dsa->p);
486 buffer_put_bignum2(b, key->dsa->q);
487 buffer_put_bignum2(b, key->dsa->g);
488 buffer_put_bignum2(b, key->dsa->pub_key);
489 buffer_put_bignum2(b, key->dsa->priv_key);
490 break;
491 }
492 buffer_put_cstring(b, comment);
493 }
494
495 /*
496 * Adds an identity to the authentication server. This call is not meant to
497 * be used by normal applications.
498 */
499
500 int
501 ssh_add_identity_constrained(AuthenticationConnection *auth, Key *key,
502 const char *comment, u_int life)
503 {
504 Buffer msg;
505 int type, constrained = (life != 0);
506
507 buffer_init(&msg);
508
509 switch (key->type) {
510 case KEY_RSA1:
511 type = constrained ?
512 SSH_AGENTC_ADD_RSA_ID_CONSTRAINED :
513 SSH_AGENTC_ADD_RSA_IDENTITY;
514 buffer_put_char(&msg, type);
515 ssh_encode_identity_rsa1(&msg, key->rsa, comment);
516 break;
517 case KEY_RSA:
518 case KEY_DSA:
519 type = constrained ?
520 SSH2_AGENTC_ADD_ID_CONSTRAINED :
521 SSH2_AGENTC_ADD_IDENTITY;
522 buffer_put_char(&msg, type);
523 ssh_encode_identity_ssh2(&msg, key, comment);
524 break;
525 default:
526 buffer_free(&msg);
527 return 0;
528 break;
529 }
530 if (constrained) {
531 if (life != 0) {
532 buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_LIFETIME);
533 buffer_put_int(&msg, life);
534 }
535 }
536 if (ssh_request_reply(auth, &msg, &msg) == 0) {
537 buffer_free(&msg);
538 return 0;
539 }
540 type = buffer_get_char(&msg);
541 buffer_free(&msg);
542 return decode_reply(type);
543 }
544
545 int
546 ssh_add_identity(AuthenticationConnection *auth, Key *key, const char *comment)
547 {
548 return ssh_add_identity_constrained(auth, key, comment, 0);
549 }
550
551 /*
552 * Removes an identity from the authentication server. This call is not
553 * meant to be used by normal applications.
554 */
555
556 int
557 ssh_remove_identity(AuthenticationConnection *auth, Key *key)
558 {
559 Buffer msg;
560 int type;
561 u_char *blob;
562 u_int blen;
563
564 buffer_init(&msg);
565
566 if (key->type == KEY_RSA1) {
567 buffer_put_char(&msg, SSH_AGENTC_REMOVE_RSA_IDENTITY);
568 buffer_put_int(&msg, BN_num_bits(key->rsa->n));
569 buffer_put_bignum(&msg, key->rsa->e);
570 buffer_put_bignum(&msg, key->rsa->n);
571 } else if (key->type == KEY_DSA || key->type == KEY_RSA) {
572 key_to_blob(key, &blob, &blen);
573 buffer_put_char(&msg, SSH2_AGENTC_REMOVE_IDENTITY);
574 buffer_put_string(&msg, blob, blen);
575 xfree(blob);
576 } else {
577 buffer_free(&msg);
578 return 0;
579 }
580 if (ssh_request_reply(auth, &msg, &msg) == 0) {
581 buffer_free(&msg);
582 return 0;
583 }
584 type = buffer_get_char(&msg);
585 buffer_free(&msg);
586 return decode_reply(type);
587 }
588
589
590 /*
591 * Removes all identities from the agent. This call is not meant to be used
592 * by normal applications.
593 */
594
595 int
596 ssh_remove_all_identities(AuthenticationConnection *auth, int version)
597 {
598 Buffer msg;
599 int type;
600 int code = (version==1) ?
601 SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES :
602 SSH2_AGENTC_REMOVE_ALL_IDENTITIES;
603
604 buffer_init(&msg);
605 buffer_put_char(&msg, code);
606
607 if (ssh_request_reply(auth, &msg, &msg) == 0) {
608 buffer_free(&msg);
609 return 0;
610 }
611 type = buffer_get_char(&msg);
612 buffer_free(&msg);
613 return decode_reply(type);
614 }
615
616 int
617 decode_reply(int type)
618 {
619 switch (type) {
620 case SSH_AGENT_FAILURE:
621 case SSH_COM_AGENT2_FAILURE:
622 case SSH2_AGENT_FAILURE:
623 log("SSH_AGENT_FAILURE");
624 return 0;
625 case SSH_AGENT_SUCCESS:
626 return 1;
627 default:
628 fatal("Bad response from authentication agent: %d", type);
629 }
630 /* NOTREACHED */
631 return 0;
632 }