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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 | * 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 1.27 2000/09/07 20:27:49 deraadt Exp $"); | |
39 | ||
40 | #include "ssh.h" | |
41 | #include "rsa.h" | |
42 | #include "buffer.h" | |
43 | #include "bufaux.h" | |
44 | #include "xmalloc.h" | |
45 | #include "getput.h" | |
46 | ||
47 | #include <openssl/rsa.h> | |
48 | #include <openssl/dsa.h> | |
49 | #include <openssl/evp.h> | |
50 | #include "key.h" | |
51 | #include "authfd.h" | |
52 | #include "kex.h" | |
53 | #include "dsa.h" | |
54 | ||
55 | /* helper */ | |
56 | int decode_reply(int type); | |
57 | ||
58 | /* Returns the number of the authentication fd, or -1 if there is none. */ | |
59 | ||
60 | int | |
61 | ssh_get_authentication_socket() | |
62 | { | |
63 | const char *authsocket; | |
64 | int sock, len; | |
65 | struct sockaddr_un sunaddr; | |
66 | ||
67 | authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME); | |
68 | if (!authsocket) | |
69 | return -1; | |
70 | ||
71 | sunaddr.sun_family = AF_UNIX; | |
72 | strlcpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path)); | |
73 | #ifdef HAVE_SUN_LEN_IN_SOCKADDR_UN | |
74 | sunaddr.sun_len = len = SUN_LEN(&sunaddr)+1; | |
75 | #else /* HAVE_SUN_LEN_IN_SOCKADDR_UN */ | |
76 | len = SUN_LEN(&sunaddr)+1; | |
77 | #endif /* HAVE_SUN_LEN_IN_SOCKADDR_UN */ | |
78 | ||
79 | sock = socket(AF_UNIX, SOCK_STREAM, 0); | |
80 | if (sock < 0) | |
81 | return -1; | |
82 | ||
83 | /* close on exec */ | |
84 | if (fcntl(sock, F_SETFD, 1) == -1) { | |
85 | close(sock); | |
86 | return -1; | |
87 | } | |
88 | if (connect(sock, (struct sockaddr *) & sunaddr, len) < 0) { | |
89 | close(sock); | |
90 | return -1; | |
91 | } | |
92 | return sock; | |
93 | } | |
94 | ||
95 | int | |
96 | ssh_request_reply(AuthenticationConnection *auth, Buffer *request, Buffer *reply) | |
97 | { | |
98 | int l, len; | |
99 | char buf[1024]; | |
100 | ||
101 | /* Get the length of the message, and format it in the buffer. */ | |
102 | len = buffer_len(request); | |
103 | PUT_32BIT(buf, len); | |
104 | ||
105 | /* Send the length and then the packet to the agent. */ | |
106 | if (atomicio(write, auth->fd, buf, 4) != 4 || | |
107 | atomicio(write, auth->fd, buffer_ptr(request), | |
108 | buffer_len(request)) != buffer_len(request)) { | |
109 | error("Error writing to authentication socket."); | |
110 | return 0; | |
111 | } | |
112 | /* | |
113 | * Wait for response from the agent. First read the length of the | |
114 | * response packet. | |
115 | */ | |
116 | len = 4; | |
117 | while (len > 0) { | |
118 | l = read(auth->fd, buf + 4 - len, len); | |
119 | if (l <= 0) { | |
120 | error("Error reading response length from authentication socket."); | |
121 | return 0; | |
122 | } | |
123 | len -= l; | |
124 | } | |
125 | ||
126 | /* Extract the length, and check it for sanity. */ | |
127 | len = GET_32BIT(buf); | |
128 | if (len > 256 * 1024) | |
129 | fatal("Authentication response too long: %d", len); | |
130 | ||
131 | /* Read the rest of the response in to the buffer. */ | |
132 | buffer_clear(reply); | |
133 | while (len > 0) { | |
134 | l = len; | |
135 | if (l > sizeof(buf)) | |
136 | l = sizeof(buf); | |
137 | l = read(auth->fd, buf, l); | |
138 | if (l <= 0) { | |
139 | error("Error reading response from authentication socket."); | |
140 | return 0; | |
141 | } | |
142 | buffer_append(reply, (char *) buf, l); | |
143 | len -= l; | |
144 | } | |
145 | return 1; | |
146 | } | |
147 | ||
148 | /* | |
149 | * Closes the agent socket if it should be closed (depends on how it was | |
150 | * obtained). The argument must have been returned by | |
151 | * ssh_get_authentication_socket(). | |
152 | */ | |
153 | ||
154 | void | |
155 | ssh_close_authentication_socket(int sock) | |
156 | { | |
157 | if (getenv(SSH_AUTHSOCKET_ENV_NAME)) | |
158 | close(sock); | |
159 | } | |
160 | ||
161 | /* | |
162 | * Opens and connects a private socket for communication with the | |
163 | * authentication agent. Returns the file descriptor (which must be | |
164 | * shut down and closed by the caller when no longer needed). | |
165 | * Returns NULL if an error occurred and the connection could not be | |
166 | * opened. | |
167 | */ | |
168 | ||
169 | AuthenticationConnection * | |
170 | ssh_get_authentication_connection() | |
171 | { | |
172 | AuthenticationConnection *auth; | |
173 | int sock; | |
174 | ||
175 | sock = ssh_get_authentication_socket(); | |
176 | ||
177 | /* | |
178 | * Fail if we couldn't obtain a connection. This happens if we | |
179 | * exited due to a timeout. | |
180 | */ | |
181 | if (sock < 0) | |
182 | return NULL; | |
183 | ||
184 | auth = xmalloc(sizeof(*auth)); | |
185 | auth->fd = sock; | |
186 | buffer_init(&auth->identities); | |
187 | auth->howmany = 0; | |
188 | ||
189 | return auth; | |
190 | } | |
191 | ||
192 | /* | |
193 | * Closes the connection to the authentication agent and frees any associated | |
194 | * memory. | |
195 | */ | |
196 | ||
197 | void | |
198 | ssh_close_authentication_connection(AuthenticationConnection *auth) | |
199 | { | |
200 | buffer_free(&auth->identities); | |
201 | close(auth->fd); | |
202 | xfree(auth); | |
203 | } | |
204 | ||
205 | /* | |
206 | * Returns the first authentication identity held by the agent. | |
207 | */ | |
208 | ||
209 | Key * | |
210 | ssh_get_first_identity(AuthenticationConnection *auth, char **comment, int version) | |
211 | { | |
212 | int type, code1 = 0, code2 = 0; | |
213 | Buffer request; | |
214 | ||
215 | switch(version){ | |
216 | case 1: | |
217 | code1 = SSH_AGENTC_REQUEST_RSA_IDENTITIES; | |
218 | code2 = SSH_AGENT_RSA_IDENTITIES_ANSWER; | |
219 | break; | |
220 | case 2: | |
221 | code1 = SSH2_AGENTC_REQUEST_IDENTITIES; | |
222 | code2 = SSH2_AGENT_IDENTITIES_ANSWER; | |
223 | break; | |
224 | default: | |
225 | return NULL; | |
226 | } | |
227 | ||
228 | /* | |
229 | * Send a message to the agent requesting for a list of the | |
230 | * identities it can represent. | |
231 | */ | |
232 | buffer_init(&request); | |
233 | buffer_put_char(&request, code1); | |
234 | ||
235 | buffer_clear(&auth->identities); | |
236 | if (ssh_request_reply(auth, &request, &auth->identities) == 0) { | |
237 | buffer_free(&request); | |
238 | return NULL; | |
239 | } | |
240 | buffer_free(&request); | |
241 | ||
242 | /* Get message type, and verify that we got a proper answer. */ | |
243 | type = buffer_get_char(&auth->identities); | |
244 | if (type == SSH_AGENT_FAILURE) { | |
245 | return NULL; | |
246 | } else if (type != code2) { | |
247 | fatal("Bad authentication reply message type: %d", type); | |
248 | } | |
249 | ||
250 | /* Get the number of entries in the response and check it for sanity. */ | |
251 | auth->howmany = buffer_get_int(&auth->identities); | |
252 | if (auth->howmany > 1024) | |
253 | fatal("Too many identities in authentication reply: %d\n", | |
254 | auth->howmany); | |
255 | ||
256 | /* Return the first entry (if any). */ | |
257 | return ssh_get_next_identity(auth, comment, version); | |
258 | } | |
259 | ||
260 | Key * | |
261 | ssh_get_next_identity(AuthenticationConnection *auth, char **comment, int version) | |
262 | { | |
263 | unsigned int bits; | |
264 | unsigned char *blob; | |
265 | unsigned int blen; | |
266 | Key *key = NULL; | |
267 | ||
268 | /* Return failure if no more entries. */ | |
269 | if (auth->howmany <= 0) | |
270 | return NULL; | |
271 | ||
272 | /* | |
273 | * Get the next entry from the packet. These will abort with a fatal | |
274 | * error if the packet is too short or contains corrupt data. | |
275 | */ | |
276 | switch(version){ | |
277 | case 1: | |
278 | key = key_new(KEY_RSA); | |
279 | bits = buffer_get_int(&auth->identities); | |
280 | buffer_get_bignum(&auth->identities, key->rsa->e); | |
281 | buffer_get_bignum(&auth->identities, key->rsa->n); | |
282 | *comment = buffer_get_string(&auth->identities, NULL); | |
283 | if (bits != BN_num_bits(key->rsa->n)) | |
284 | log("Warning: identity keysize mismatch: actual %d, announced %u", | |
285 | BN_num_bits(key->rsa->n), bits); | |
286 | break; | |
287 | case 2: | |
288 | blob = buffer_get_string(&auth->identities, &blen); | |
289 | *comment = buffer_get_string(&auth->identities, NULL); | |
290 | key = dsa_key_from_blob(blob, blen); | |
291 | xfree(blob); | |
292 | break; | |
293 | default: | |
294 | return NULL; | |
295 | break; | |
296 | } | |
297 | /* Decrement the number of remaining entries. */ | |
298 | auth->howmany--; | |
299 | return key; | |
300 | } | |
301 | ||
302 | /* | |
303 | * Generates a random challenge, sends it to the agent, and waits for | |
304 | * response from the agent. Returns true (non-zero) if the agent gave the | |
305 | * correct answer, zero otherwise. Response type selects the style of | |
306 | * response desired, with 0 corresponding to protocol version 1.0 (no longer | |
307 | * supported) and 1 corresponding to protocol version 1.1. | |
308 | */ | |
309 | ||
310 | int | |
311 | ssh_decrypt_challenge(AuthenticationConnection *auth, | |
312 | Key* key, BIGNUM *challenge, | |
313 | unsigned char session_id[16], | |
314 | unsigned int response_type, | |
315 | unsigned char response[16]) | |
316 | { | |
317 | Buffer buffer; | |
318 | int success = 0; | |
319 | int i; | |
320 | int type; | |
321 | ||
322 | if (key->type != KEY_RSA) | |
323 | return 0; | |
324 | if (response_type == 0) { | |
325 | log("Compatibility with ssh protocol version 1.0 no longer supported."); | |
326 | return 0; | |
327 | } | |
328 | buffer_init(&buffer); | |
329 | buffer_put_char(&buffer, SSH_AGENTC_RSA_CHALLENGE); | |
330 | buffer_put_int(&buffer, BN_num_bits(key->rsa->n)); | |
331 | buffer_put_bignum(&buffer, key->rsa->e); | |
332 | buffer_put_bignum(&buffer, key->rsa->n); | |
333 | buffer_put_bignum(&buffer, challenge); | |
334 | buffer_append(&buffer, (char *) session_id, 16); | |
335 | buffer_put_int(&buffer, response_type); | |
336 | ||
337 | if (ssh_request_reply(auth, &buffer, &buffer) == 0) { | |
338 | buffer_free(&buffer); | |
339 | return 0; | |
340 | } | |
341 | type = buffer_get_char(&buffer); | |
342 | ||
343 | if (type == SSH_AGENT_FAILURE) { | |
344 | log("Agent admitted failure to authenticate using the key."); | |
345 | } else if (type != SSH_AGENT_RSA_RESPONSE) { | |
346 | fatal("Bad authentication response: %d", type); | |
347 | } else { | |
348 | success = 1; | |
349 | /* | |
350 | * Get the response from the packet. This will abort with a | |
351 | * fatal error if the packet is corrupt. | |
352 | */ | |
353 | for (i = 0; i < 16; i++) | |
354 | response[i] = buffer_get_char(&buffer); | |
355 | } | |
356 | buffer_free(&buffer); | |
357 | return success; | |
358 | } | |
359 | ||
360 | /* ask agent to sign data, returns -1 on error, 0 on success */ | |
361 | int | |
362 | ssh_agent_sign(AuthenticationConnection *auth, | |
363 | Key *key, | |
364 | unsigned char **sigp, int *lenp, | |
365 | unsigned char *data, int datalen) | |
366 | { | |
367 | Buffer msg; | |
368 | unsigned char *blob; | |
369 | unsigned int blen; | |
370 | int type; | |
371 | int ret = -1; | |
372 | ||
373 | if (dsa_make_key_blob(key, &blob, &blen) == 0) | |
374 | return -1; | |
375 | ||
376 | buffer_init(&msg); | |
377 | buffer_put_char(&msg, SSH2_AGENTC_SIGN_REQUEST); | |
378 | buffer_put_string(&msg, blob, blen); | |
379 | buffer_put_string(&msg, data, datalen); | |
380 | buffer_put_int(&msg, 0); /* flags, unused */ | |
381 | xfree(blob); | |
382 | ||
383 | if (ssh_request_reply(auth, &msg, &msg) == 0) { | |
384 | buffer_free(&msg); | |
385 | return -1; | |
386 | } | |
387 | type = buffer_get_char(&msg); | |
388 | if (type == SSH_AGENT_FAILURE) { | |
389 | log("Agent admitted failure to sign using the key."); | |
390 | } else if (type != SSH2_AGENT_SIGN_RESPONSE) { | |
391 | fatal("Bad authentication response: %d", type); | |
392 | } else { | |
393 | ret = 0; | |
394 | *sigp = buffer_get_string(&msg, lenp); | |
395 | } | |
396 | buffer_free(&msg); | |
397 | return ret; | |
398 | } | |
399 | ||
400 | /* Encode key for a message to the agent. */ | |
401 | ||
402 | void | |
403 | ssh_encode_identity_rsa(Buffer *b, RSA *key, const char *comment) | |
404 | { | |
405 | buffer_clear(b); | |
406 | buffer_put_char(b, SSH_AGENTC_ADD_RSA_IDENTITY); | |
407 | buffer_put_int(b, BN_num_bits(key->n)); | |
408 | buffer_put_bignum(b, key->n); | |
409 | buffer_put_bignum(b, key->e); | |
410 | buffer_put_bignum(b, key->d); | |
411 | /* To keep within the protocol: p < q for ssh. in SSL p > q */ | |
412 | buffer_put_bignum(b, key->iqmp); /* ssh key->u */ | |
413 | buffer_put_bignum(b, key->q); /* ssh key->p, SSL key->q */ | |
414 | buffer_put_bignum(b, key->p); /* ssh key->q, SSL key->p */ | |
415 | buffer_put_string(b, comment, strlen(comment)); | |
416 | } | |
417 | ||
418 | void | |
419 | ssh_encode_identity_dsa(Buffer *b, DSA *key, const char *comment) | |
420 | { | |
421 | buffer_clear(b); | |
422 | buffer_put_char(b, SSH2_AGENTC_ADD_IDENTITY); | |
423 | buffer_put_cstring(b, KEX_DSS); | |
424 | buffer_put_bignum2(b, key->p); | |
425 | buffer_put_bignum2(b, key->q); | |
426 | buffer_put_bignum2(b, key->g); | |
427 | buffer_put_bignum2(b, key->pub_key); | |
428 | buffer_put_bignum2(b, key->priv_key); | |
429 | buffer_put_string(b, comment, strlen(comment)); | |
430 | } | |
431 | ||
432 | /* | |
433 | * Adds an identity to the authentication server. This call is not meant to | |
434 | * be used by normal applications. | |
435 | */ | |
436 | ||
437 | int | |
438 | ssh_add_identity(AuthenticationConnection *auth, Key *key, const char *comment) | |
439 | { | |
440 | Buffer msg; | |
441 | int type; | |
442 | ||
443 | buffer_init(&msg); | |
444 | ||
445 | switch (key->type) { | |
446 | case KEY_RSA: | |
447 | ssh_encode_identity_rsa(&msg, key->rsa, comment); | |
448 | break; | |
449 | case KEY_DSA: | |
450 | ssh_encode_identity_dsa(&msg, key->dsa, comment); | |
451 | break; | |
452 | default: | |
453 | buffer_free(&msg); | |
454 | return 0; | |
455 | break; | |
456 | } | |
457 | if (ssh_request_reply(auth, &msg, &msg) == 0) { | |
458 | buffer_free(&msg); | |
459 | return 0; | |
460 | } | |
461 | type = buffer_get_char(&msg); | |
462 | buffer_free(&msg); | |
463 | return decode_reply(type); | |
464 | } | |
465 | ||
466 | /* | |
467 | * Removes an identity from the authentication server. This call is not | |
468 | * meant to be used by normal applications. | |
469 | */ | |
470 | ||
471 | int | |
472 | ssh_remove_identity(AuthenticationConnection *auth, Key *key) | |
473 | { | |
474 | Buffer msg; | |
475 | int type; | |
476 | unsigned char *blob; | |
477 | unsigned int blen; | |
478 | ||
479 | buffer_init(&msg); | |
480 | ||
481 | if (key->type == KEY_RSA) { | |
482 | buffer_put_char(&msg, SSH_AGENTC_REMOVE_RSA_IDENTITY); | |
483 | buffer_put_int(&msg, BN_num_bits(key->rsa->n)); | |
484 | buffer_put_bignum(&msg, key->rsa->e); | |
485 | buffer_put_bignum(&msg, key->rsa->n); | |
486 | } else if (key->type == KEY_DSA) { | |
487 | dsa_make_key_blob(key, &blob, &blen); | |
488 | buffer_put_char(&msg, SSH2_AGENTC_REMOVE_IDENTITY); | |
489 | buffer_put_string(&msg, blob, blen); | |
490 | xfree(blob); | |
491 | } else { | |
492 | buffer_free(&msg); | |
493 | return 0; | |
494 | } | |
495 | if (ssh_request_reply(auth, &msg, &msg) == 0) { | |
496 | buffer_free(&msg); | |
497 | return 0; | |
498 | } | |
499 | type = buffer_get_char(&msg); | |
500 | buffer_free(&msg); | |
501 | return decode_reply(type); | |
502 | } | |
503 | ||
504 | /* | |
505 | * Removes all identities from the agent. This call is not meant to be used | |
506 | * by normal applications. | |
507 | */ | |
508 | ||
509 | int | |
510 | ssh_remove_all_identities(AuthenticationConnection *auth, int version) | |
511 | { | |
512 | Buffer msg; | |
513 | int type; | |
514 | int code = (version==1) ? | |
515 | SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES : | |
516 | SSH2_AGENTC_REMOVE_ALL_IDENTITIES; | |
517 | ||
518 | buffer_init(&msg); | |
519 | buffer_put_char(&msg, code); | |
520 | ||
521 | if (ssh_request_reply(auth, &msg, &msg) == 0) { | |
522 | buffer_free(&msg); | |
523 | return 0; | |
524 | } | |
525 | type = buffer_get_char(&msg); | |
526 | buffer_free(&msg); | |
527 | return decode_reply(type); | |
528 | } | |
529 | ||
530 | int | |
531 | decode_reply(int type) | |
532 | { | |
533 | switch (type) { | |
534 | case SSH_AGENT_FAILURE: | |
535 | log("SSH_AGENT_FAILURE"); | |
536 | return 0; | |
537 | case SSH_AGENT_SUCCESS: | |
538 | return 1; | |
539 | default: | |
540 | fatal("Bad response from authentication agent: %d", type); | |
541 | } | |
542 | /* NOTREACHED */ | |
543 | return 0; | |
544 | } |