xref: /freebsd/crypto/openssh/authfd.c (revision a0ee8cc636cd5c2374ec44ca71226564ea0bca95)
1 /* $OpenBSD: authfd.c,v 1.93 2014/04/29 18:01:49 markus Exp $ */
2 /*
3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
4  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
5  *                    All rights reserved
6  * Functions for connecting the local authentication agent.
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  * SSH2 implementation,
15  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
16  *
17  * Redistribution and use in source and binary forms, with or without
18  * modification, are permitted provided that the following conditions
19  * are met:
20  * 1. Redistributions of source code must retain the above copyright
21  *    notice, this list of conditions and the following disclaimer.
22  * 2. Redistributions in binary form must reproduce the above copyright
23  *    notice, this list of conditions and the following disclaimer in the
24  *    documentation and/or other materials provided with the distribution.
25  *
26  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
27  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
28  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
29  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
30  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
31  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
32  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
33  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
34  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
35  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
36  */
37 
38 #include "includes.h"
39 
40 #include <sys/types.h>
41 #include <sys/un.h>
42 #include <sys/socket.h>
43 
44 #include <fcntl.h>
45 #include <stdlib.h>
46 #include <signal.h>
47 #include <stdarg.h>
48 #include <string.h>
49 #include <unistd.h>
50 
51 #include "xmalloc.h"
52 #include "ssh.h"
53 #include "rsa.h"
54 #include "buffer.h"
55 #include "key.h"
56 #include "authfd.h"
57 #include "cipher.h"
58 #include "kex.h"
59 #include "compat.h"
60 #include "log.h"
61 #include "atomicio.h"
62 #include "misc.h"
63 
64 static int agent_present = 0;
65 
66 /* helper */
67 int	decode_reply(int type);
68 
69 /* macro to check for "agent failure" message */
70 #define agent_failed(x) \
71     ((x == SSH_AGENT_FAILURE) || (x == SSH_COM_AGENT2_FAILURE) || \
72     (x == SSH2_AGENT_FAILURE))
73 
74 int
75 ssh_agent_present(void)
76 {
77 	int authfd;
78 
79 	if (agent_present)
80 		return 1;
81 	if ((authfd = ssh_get_authentication_socket()) == -1)
82 		return 0;
83 	else {
84 		ssh_close_authentication_socket(authfd);
85 		return 1;
86 	}
87 }
88 
89 /* Returns the number of the authentication fd, or -1 if there is none. */
90 
91 int
92 ssh_get_authentication_socket(void)
93 {
94 	const char *authsocket;
95 	int sock;
96 	struct sockaddr_un sunaddr;
97 
98 	authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME);
99 	if (!authsocket)
100 		return -1;
101 
102 	memset(&sunaddr, 0, sizeof(sunaddr));
103 	sunaddr.sun_family = AF_UNIX;
104 	strlcpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path));
105 
106 	sock = socket(AF_UNIX, SOCK_STREAM, 0);
107 	if (sock < 0)
108 		return -1;
109 
110 	/* close on exec */
111 	if (fcntl(sock, F_SETFD, FD_CLOEXEC) == -1) {
112 		close(sock);
113 		return -1;
114 	}
115 	if (connect(sock, (struct sockaddr *)&sunaddr, sizeof sunaddr) < 0) {
116 		close(sock);
117 		return -1;
118 	}
119 	agent_present = 1;
120 	return sock;
121 }
122 
123 static int
124 ssh_request_reply(AuthenticationConnection *auth, Buffer *request, Buffer *reply)
125 {
126 	u_int l, len;
127 	char buf[1024];
128 
129 	/* Get the length of the message, and format it in the buffer. */
130 	len = buffer_len(request);
131 	put_u32(buf, len);
132 
133 	/* Send the length and then the packet to the agent. */
134 	if (atomicio(vwrite, auth->fd, buf, 4) != 4 ||
135 	    atomicio(vwrite, auth->fd, buffer_ptr(request),
136 	    buffer_len(request)) != buffer_len(request)) {
137 		error("Error writing to authentication socket.");
138 		return 0;
139 	}
140 	/*
141 	 * Wait for response from the agent.  First read the length of the
142 	 * response packet.
143 	 */
144 	if (atomicio(read, auth->fd, buf, 4) != 4) {
145 	    error("Error reading response length from authentication socket.");
146 	    return 0;
147 	}
148 
149 	/* Extract the length, and check it for sanity. */
150 	len = get_u32(buf);
151 	if (len > 256 * 1024)
152 		fatal("Authentication response too long: %u", len);
153 
154 	/* Read the rest of the response in to the buffer. */
155 	buffer_clear(reply);
156 	while (len > 0) {
157 		l = len;
158 		if (l > sizeof(buf))
159 			l = sizeof(buf);
160 		if (atomicio(read, auth->fd, buf, l) != l) {
161 			error("Error reading response from authentication socket.");
162 			return 0;
163 		}
164 		buffer_append(reply, buf, l);
165 		len -= l;
166 	}
167 	return 1;
168 }
169 
170 /*
171  * Closes the agent socket if it should be closed (depends on how it was
172  * obtained).  The argument must have been returned by
173  * ssh_get_authentication_socket().
174  */
175 
176 void
177 ssh_close_authentication_socket(int sock)
178 {
179 	if (getenv(SSH_AUTHSOCKET_ENV_NAME))
180 		close(sock);
181 }
182 
183 /*
184  * Opens and connects a private socket for communication with the
185  * authentication agent.  Returns the file descriptor (which must be
186  * shut down and closed by the caller when no longer needed).
187  * Returns NULL if an error occurred and the connection could not be
188  * opened.
189  */
190 
191 AuthenticationConnection *
192 ssh_get_authentication_connection(void)
193 {
194 	AuthenticationConnection *auth;
195 	int sock;
196 
197 	sock = ssh_get_authentication_socket();
198 
199 	/*
200 	 * Fail if we couldn't obtain a connection.  This happens if we
201 	 * exited due to a timeout.
202 	 */
203 	if (sock < 0)
204 		return NULL;
205 
206 	auth = xcalloc(1, sizeof(*auth));
207 	auth->fd = sock;
208 	buffer_init(&auth->identities);
209 	auth->howmany = 0;
210 
211 	return auth;
212 }
213 
214 /*
215  * Closes the connection to the authentication agent and frees any associated
216  * memory.
217  */
218 
219 void
220 ssh_close_authentication_connection(AuthenticationConnection *auth)
221 {
222 	buffer_free(&auth->identities);
223 	close(auth->fd);
224 	free(auth);
225 }
226 
227 /* Lock/unlock agent */
228 int
229 ssh_lock_agent(AuthenticationConnection *auth, int lock, const char *password)
230 {
231 	int type;
232 	Buffer msg;
233 
234 	buffer_init(&msg);
235 	buffer_put_char(&msg, lock ? SSH_AGENTC_LOCK : SSH_AGENTC_UNLOCK);
236 	buffer_put_cstring(&msg, password);
237 
238 	if (ssh_request_reply(auth, &msg, &msg) == 0) {
239 		buffer_free(&msg);
240 		return 0;
241 	}
242 	type = buffer_get_char(&msg);
243 	buffer_free(&msg);
244 	return decode_reply(type);
245 }
246 
247 /*
248  * Returns the first authentication identity held by the agent.
249  */
250 
251 int
252 ssh_get_num_identities(AuthenticationConnection *auth, int version)
253 {
254 	int type, code1 = 0, code2 = 0;
255 	Buffer request;
256 
257 	switch (version) {
258 	case 1:
259 		code1 = SSH_AGENTC_REQUEST_RSA_IDENTITIES;
260 		code2 = SSH_AGENT_RSA_IDENTITIES_ANSWER;
261 		break;
262 	case 2:
263 		code1 = SSH2_AGENTC_REQUEST_IDENTITIES;
264 		code2 = SSH2_AGENT_IDENTITIES_ANSWER;
265 		break;
266 	default:
267 		return 0;
268 	}
269 
270 	/*
271 	 * Send a message to the agent requesting for a list of the
272 	 * identities it can represent.
273 	 */
274 	buffer_init(&request);
275 	buffer_put_char(&request, code1);
276 
277 	buffer_clear(&auth->identities);
278 	if (ssh_request_reply(auth, &request, &auth->identities) == 0) {
279 		buffer_free(&request);
280 		return 0;
281 	}
282 	buffer_free(&request);
283 
284 	/* Get message type, and verify that we got a proper answer. */
285 	type = buffer_get_char(&auth->identities);
286 	if (agent_failed(type)) {
287 		return 0;
288 	} else if (type != code2) {
289 		fatal("Bad authentication reply message type: %d", type);
290 	}
291 
292 	/* Get the number of entries in the response and check it for sanity. */
293 	auth->howmany = buffer_get_int(&auth->identities);
294 	if ((u_int)auth->howmany > 1024)
295 		fatal("Too many identities in authentication reply: %d",
296 		    auth->howmany);
297 
298 	return auth->howmany;
299 }
300 
301 Key *
302 ssh_get_first_identity(AuthenticationConnection *auth, char **comment, int version)
303 {
304 	/* get number of identities and return the first entry (if any). */
305 	if (ssh_get_num_identities(auth, version) > 0)
306 		return ssh_get_next_identity(auth, comment, version);
307 	return NULL;
308 }
309 
310 Key *
311 ssh_get_next_identity(AuthenticationConnection *auth, char **comment, int version)
312 {
313 #ifdef WITH_SSH1
314 	int keybits;
315 	u_int bits;
316 #endif
317 	u_char *blob;
318 	u_int blen;
319 	Key *key = NULL;
320 
321 	/* Return failure if no more entries. */
322 	if (auth->howmany <= 0)
323 		return NULL;
324 
325 	/*
326 	 * Get the next entry from the packet.  These will abort with a fatal
327 	 * error if the packet is too short or contains corrupt data.
328 	 */
329 	switch (version) {
330 #ifdef WITH_SSH1
331 	case 1:
332 		key = key_new(KEY_RSA1);
333 		bits = buffer_get_int(&auth->identities);
334 		buffer_get_bignum(&auth->identities, key->rsa->e);
335 		buffer_get_bignum(&auth->identities, key->rsa->n);
336 		*comment = buffer_get_string(&auth->identities, NULL);
337 		keybits = BN_num_bits(key->rsa->n);
338 		if (keybits < 0 || bits != (u_int)keybits)
339 			logit("Warning: identity keysize mismatch: actual %d, announced %u",
340 			    BN_num_bits(key->rsa->n), bits);
341 		break;
342 #endif
343 	case 2:
344 		blob = buffer_get_string(&auth->identities, &blen);
345 		*comment = buffer_get_string(&auth->identities, NULL);
346 		key = key_from_blob(blob, blen);
347 		free(blob);
348 		break;
349 	default:
350 		return NULL;
351 	}
352 	/* Decrement the number of remaining entries. */
353 	auth->howmany--;
354 	return key;
355 }
356 
357 /*
358  * Generates a random challenge, sends it to the agent, and waits for
359  * response from the agent.  Returns true (non-zero) if the agent gave the
360  * correct answer, zero otherwise.  Response type selects the style of
361  * response desired, with 0 corresponding to protocol version 1.0 (no longer
362  * supported) and 1 corresponding to protocol version 1.1.
363  */
364 
365 #ifdef WITH_SSH1
366 int
367 ssh_decrypt_challenge(AuthenticationConnection *auth,
368     Key* key, BIGNUM *challenge,
369     u_char session_id[16],
370     u_int response_type,
371     u_char response[16])
372 {
373 	Buffer buffer;
374 	int success = 0;
375 	int i;
376 	int type;
377 
378 	if (key->type != KEY_RSA1)
379 		return 0;
380 	if (response_type == 0) {
381 		logit("Compatibility with ssh protocol version 1.0 no longer supported.");
382 		return 0;
383 	}
384 	buffer_init(&buffer);
385 	buffer_put_char(&buffer, SSH_AGENTC_RSA_CHALLENGE);
386 	buffer_put_int(&buffer, BN_num_bits(key->rsa->n));
387 	buffer_put_bignum(&buffer, key->rsa->e);
388 	buffer_put_bignum(&buffer, key->rsa->n);
389 	buffer_put_bignum(&buffer, challenge);
390 	buffer_append(&buffer, session_id, 16);
391 	buffer_put_int(&buffer, response_type);
392 
393 	if (ssh_request_reply(auth, &buffer, &buffer) == 0) {
394 		buffer_free(&buffer);
395 		return 0;
396 	}
397 	type = buffer_get_char(&buffer);
398 
399 	if (agent_failed(type)) {
400 		logit("Agent admitted failure to authenticate using the key.");
401 	} else if (type != SSH_AGENT_RSA_RESPONSE) {
402 		fatal("Bad authentication response: %d", type);
403 	} else {
404 		success = 1;
405 		/*
406 		 * Get the response from the packet.  This will abort with a
407 		 * fatal error if the packet is corrupt.
408 		 */
409 		for (i = 0; i < 16; i++)
410 			response[i] = (u_char)buffer_get_char(&buffer);
411 	}
412 	buffer_free(&buffer);
413 	return success;
414 }
415 #endif
416 
417 /* ask agent to sign data, returns -1 on error, 0 on success */
418 int
419 ssh_agent_sign(AuthenticationConnection *auth,
420     Key *key,
421     u_char **sigp, u_int *lenp,
422     u_char *data, u_int datalen)
423 {
424 	extern int datafellows;
425 	Buffer msg;
426 	u_char *blob;
427 	u_int blen;
428 	int type, flags = 0;
429 	int ret = -1;
430 
431 	if (key_to_blob(key, &blob, &blen) == 0)
432 		return -1;
433 
434 	if (datafellows & SSH_BUG_SIGBLOB)
435 		flags = SSH_AGENT_OLD_SIGNATURE;
436 
437 	buffer_init(&msg);
438 	buffer_put_char(&msg, SSH2_AGENTC_SIGN_REQUEST);
439 	buffer_put_string(&msg, blob, blen);
440 	buffer_put_string(&msg, data, datalen);
441 	buffer_put_int(&msg, flags);
442 	free(blob);
443 
444 	if (ssh_request_reply(auth, &msg, &msg) == 0) {
445 		buffer_free(&msg);
446 		return -1;
447 	}
448 	type = buffer_get_char(&msg);
449 	if (agent_failed(type)) {
450 		logit("Agent admitted failure to sign using the key.");
451 	} else if (type != SSH2_AGENT_SIGN_RESPONSE) {
452 		fatal("Bad authentication response: %d", type);
453 	} else {
454 		ret = 0;
455 		*sigp = buffer_get_string(&msg, lenp);
456 	}
457 	buffer_free(&msg);
458 	return ret;
459 }
460 
461 /* Encode key for a message to the agent. */
462 
463 #ifdef WITH_SSH1
464 static void
465 ssh_encode_identity_rsa1(Buffer *b, RSA *key, const char *comment)
466 {
467 	buffer_put_int(b, BN_num_bits(key->n));
468 	buffer_put_bignum(b, key->n);
469 	buffer_put_bignum(b, key->e);
470 	buffer_put_bignum(b, key->d);
471 	/* To keep within the protocol: p < q for ssh. in SSL p > q */
472 	buffer_put_bignum(b, key->iqmp);	/* ssh key->u */
473 	buffer_put_bignum(b, key->q);	/* ssh key->p, SSL key->q */
474 	buffer_put_bignum(b, key->p);	/* ssh key->q, SSL key->p */
475 	buffer_put_cstring(b, comment);
476 }
477 #endif
478 
479 static void
480 ssh_encode_identity_ssh2(Buffer *b, Key *key, const char *comment)
481 {
482 	key_private_serialize(key, b);
483 	buffer_put_cstring(b, comment);
484 }
485 
486 /*
487  * Adds an identity to the authentication server.  This call is not meant to
488  * be used by normal applications.
489  */
490 
491 int
492 ssh_add_identity_constrained(AuthenticationConnection *auth, Key *key,
493     const char *comment, u_int life, u_int confirm)
494 {
495 	Buffer msg;
496 	int type, constrained = (life || confirm);
497 
498 	buffer_init(&msg);
499 
500 	switch (key->type) {
501 #ifdef WITH_SSH1
502 	case KEY_RSA1:
503 		type = constrained ?
504 		    SSH_AGENTC_ADD_RSA_ID_CONSTRAINED :
505 		    SSH_AGENTC_ADD_RSA_IDENTITY;
506 		buffer_put_char(&msg, type);
507 		ssh_encode_identity_rsa1(&msg, key->rsa, comment);
508 		break;
509 #endif
510 #ifdef WITH_OPENSSL
511 	case KEY_RSA:
512 	case KEY_RSA_CERT:
513 	case KEY_RSA_CERT_V00:
514 	case KEY_DSA:
515 	case KEY_DSA_CERT:
516 	case KEY_DSA_CERT_V00:
517 	case KEY_ECDSA:
518 	case KEY_ECDSA_CERT:
519 #endif
520 	case KEY_ED25519:
521 	case KEY_ED25519_CERT:
522 		type = constrained ?
523 		    SSH2_AGENTC_ADD_ID_CONSTRAINED :
524 		    SSH2_AGENTC_ADD_IDENTITY;
525 		buffer_put_char(&msg, type);
526 		ssh_encode_identity_ssh2(&msg, key, comment);
527 		break;
528 	default:
529 		buffer_free(&msg);
530 		return 0;
531 	}
532 	if (constrained) {
533 		if (life != 0) {
534 			buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_LIFETIME);
535 			buffer_put_int(&msg, life);
536 		}
537 		if (confirm != 0)
538 			buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_CONFIRM);
539 	}
540 	if (ssh_request_reply(auth, &msg, &msg) == 0) {
541 		buffer_free(&msg);
542 		return 0;
543 	}
544 	type = buffer_get_char(&msg);
545 	buffer_free(&msg);
546 	return decode_reply(type);
547 }
548 
549 /*
550  * Removes an identity from the authentication server.  This call is not
551  * meant to be used by normal applications.
552  */
553 
554 int
555 ssh_remove_identity(AuthenticationConnection *auth, Key *key)
556 {
557 	Buffer msg;
558 	int type;
559 	u_char *blob;
560 	u_int blen;
561 
562 	buffer_init(&msg);
563 
564 #ifdef WITH_SSH1
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
571 #endif
572 	if (key->type != KEY_UNSPEC) {
573 		key_to_blob(key, &blob, &blen);
574 		buffer_put_char(&msg, SSH2_AGENTC_REMOVE_IDENTITY);
575 		buffer_put_string(&msg, blob, blen);
576 		free(blob);
577 	} else {
578 		buffer_free(&msg);
579 		return 0;
580 	}
581 	if (ssh_request_reply(auth, &msg, &msg) == 0) {
582 		buffer_free(&msg);
583 		return 0;
584 	}
585 	type = buffer_get_char(&msg);
586 	buffer_free(&msg);
587 	return decode_reply(type);
588 }
589 
590 int
591 ssh_update_card(AuthenticationConnection *auth, int add,
592     const char *reader_id, const char *pin, u_int life, u_int confirm)
593 {
594 	Buffer msg;
595 	int type, constrained = (life || confirm);
596 
597 	if (add) {
598 		type = constrained ?
599 		    SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED :
600 		    SSH_AGENTC_ADD_SMARTCARD_KEY;
601 	} else
602 		type = SSH_AGENTC_REMOVE_SMARTCARD_KEY;
603 
604 	buffer_init(&msg);
605 	buffer_put_char(&msg, type);
606 	buffer_put_cstring(&msg, reader_id);
607 	buffer_put_cstring(&msg, pin);
608 
609 	if (constrained) {
610 		if (life != 0) {
611 			buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_LIFETIME);
612 			buffer_put_int(&msg, life);
613 		}
614 		if (confirm != 0)
615 			buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_CONFIRM);
616 	}
617 
618 	if (ssh_request_reply(auth, &msg, &msg) == 0) {
619 		buffer_free(&msg);
620 		return 0;
621 	}
622 	type = buffer_get_char(&msg);
623 	buffer_free(&msg);
624 	return decode_reply(type);
625 }
626 
627 /*
628  * Removes all identities from the agent.  This call is not meant to be used
629  * by normal applications.
630  */
631 
632 int
633 ssh_remove_all_identities(AuthenticationConnection *auth, int version)
634 {
635 	Buffer msg;
636 	int type;
637 	int code = (version==1) ?
638 		SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES :
639 		SSH2_AGENTC_REMOVE_ALL_IDENTITIES;
640 
641 	buffer_init(&msg);
642 	buffer_put_char(&msg, code);
643 
644 	if (ssh_request_reply(auth, &msg, &msg) == 0) {
645 		buffer_free(&msg);
646 		return 0;
647 	}
648 	type = buffer_get_char(&msg);
649 	buffer_free(&msg);
650 	return decode_reply(type);
651 }
652 
653 int
654 decode_reply(int type)
655 {
656 	switch (type) {
657 	case SSH_AGENT_FAILURE:
658 	case SSH_COM_AGENT2_FAILURE:
659 	case SSH2_AGENT_FAILURE:
660 		logit("SSH_AGENT_FAILURE");
661 		return 0;
662 	case SSH_AGENT_SUCCESS:
663 		return 1;
664 	default:
665 		fatal("Bad response from authentication agent: %d", type);
666 	}
667 	/* NOTREACHED */
668 	return 0;
669 }
670