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