1 /* $OpenBSD: authfd.c,v 1.111 2018/07/09 21:59:10 markus Exp $ */
2 /*
3 * Author: Tatu Ylonen <[email protected]>
4 * Copyright (c) 1995 Tatu Ylonen <[email protected]>, 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 #include <errno.h>
51
52 #include "xmalloc.h"
53 #include "ssh.h"
54 #include "sshbuf.h"
55 #include "sshkey.h"
56 #include "authfd.h"
57 #include "cipher.h"
58 #include "compat.h"
59 #include "log.h"
60 #include "atomicio.h"
61 #include "misc.h"
62 #include "ssherr.h"
63
64 #define MAX_AGENT_IDENTITIES 2048 /* Max keys in agent reply */
65 #define MAX_AGENT_REPLY_LEN (256 * 1024) /* Max bytes in agent reply */
66
67 /* macro to check for "agent failure" message */
68 #define agent_failed(x) \
69 ((x == SSH_AGENT_FAILURE) || \
70 (x == SSH_COM_AGENT2_FAILURE) || \
71 (x == SSH2_AGENT_FAILURE))
72
73 /* Convert success/failure response from agent to a err.h status */
74 static int
decode_reply(u_char type)75 decode_reply(u_char type)
76 {
77 if (agent_failed(type))
78 return SSH_ERR_AGENT_FAILURE;
79 else if (type == SSH_AGENT_SUCCESS)
80 return 0;
81 else
82 return SSH_ERR_INVALID_FORMAT;
83 }
84
85 /* Returns the number of the authentication fd, or -1 if there is none. */
86 int
ssh_get_authentication_socket(int * fdp)87 ssh_get_authentication_socket(int *fdp)
88 {
89 const char *authsocket;
90 int sock, oerrno;
91 struct sockaddr_un sunaddr;
92
93 if (fdp != NULL)
94 *fdp = -1;
95
96 authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME);
97 if (!authsocket)
98 return SSH_ERR_AGENT_NOT_PRESENT;
99
100 memset(&sunaddr, 0, sizeof(sunaddr));
101 sunaddr.sun_family = AF_UNIX;
102 strlcpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path));
103
104 if ((sock = socket(AF_UNIX, SOCK_STREAM, 0)) < 0)
105 return SSH_ERR_SYSTEM_ERROR;
106
107 /* close on exec */
108 if (fcntl(sock, F_SETFD, FD_CLOEXEC) == -1 ||
109 connect(sock, (struct sockaddr *)&sunaddr, sizeof(sunaddr)) < 0) {
110 oerrno = errno;
111 close(sock);
112 errno = oerrno;
113 return SSH_ERR_SYSTEM_ERROR;
114 }
115 if (fdp != NULL)
116 *fdp = sock;
117 else
118 close(sock);
119 return 0;
120 }
121
122 /* Communicate with agent: send request and read reply */
123 static int
ssh_request_reply(int sock,struct sshbuf * request,struct sshbuf * reply)124 ssh_request_reply(int sock, struct sshbuf *request, struct sshbuf *reply)
125 {
126 int r;
127 size_t l, len;
128 char buf[1024];
129
130 /* Get the length of the message, and format it in the buffer. */
131 len = sshbuf_len(request);
132 POKE_U32(buf, len);
133
134 /* Send the length and then the packet to the agent. */
135 if (atomicio(vwrite, sock, buf, 4) != 4 ||
136 atomicio(vwrite, sock, sshbuf_mutable_ptr(request),
137 sshbuf_len(request)) != sshbuf_len(request))
138 return SSH_ERR_AGENT_COMMUNICATION;
139 /*
140 * Wait for response from the agent. First read the length of the
141 * response packet.
142 */
143 if (atomicio(read, sock, buf, 4) != 4)
144 return SSH_ERR_AGENT_COMMUNICATION;
145
146 /* Extract the length, and check it for sanity. */
147 len = PEEK_U32(buf);
148 if (len > MAX_AGENT_REPLY_LEN)
149 return SSH_ERR_INVALID_FORMAT;
150
151 /* Read the rest of the response in to the buffer. */
152 sshbuf_reset(reply);
153 while (len > 0) {
154 l = len;
155 if (l > sizeof(buf))
156 l = sizeof(buf);
157 if (atomicio(read, sock, buf, l) != l)
158 return SSH_ERR_AGENT_COMMUNICATION;
159 if ((r = sshbuf_put(reply, buf, l)) != 0)
160 return r;
161 len -= l;
162 }
163 return 0;
164 }
165
166 /*
167 * Closes the agent socket if it should be closed (depends on how it was
168 * obtained). The argument must have been returned by
169 * ssh_get_authentication_socket().
170 */
171 void
ssh_close_authentication_socket(int sock)172 ssh_close_authentication_socket(int sock)
173 {
174 if (getenv(SSH_AUTHSOCKET_ENV_NAME))
175 close(sock);
176 }
177
178 /* Lock/unlock agent */
179 int
ssh_lock_agent(int sock,int lock,const char * password)180 ssh_lock_agent(int sock, int lock, const char *password)
181 {
182 int r;
183 u_char type = lock ? SSH_AGENTC_LOCK : SSH_AGENTC_UNLOCK;
184 struct sshbuf *msg;
185
186 if ((msg = sshbuf_new()) == NULL)
187 return SSH_ERR_ALLOC_FAIL;
188 if ((r = sshbuf_put_u8(msg, type)) != 0 ||
189 (r = sshbuf_put_cstring(msg, password)) != 0)
190 goto out;
191 if ((r = ssh_request_reply(sock, msg, msg)) != 0)
192 goto out;
193 if ((r = sshbuf_get_u8(msg, &type)) != 0)
194 goto out;
195 r = decode_reply(type);
196 out:
197 sshbuf_free(msg);
198 return r;
199 }
200
201
202 static int
deserialise_identity2(struct sshbuf * ids,struct sshkey ** keyp,char ** commentp)203 deserialise_identity2(struct sshbuf *ids, struct sshkey **keyp, char **commentp)
204 {
205 int r;
206 char *comment = NULL;
207 const u_char *blob;
208 size_t blen;
209
210 if ((r = sshbuf_get_string_direct(ids, &blob, &blen)) != 0 ||
211 (r = sshbuf_get_cstring(ids, &comment, NULL)) != 0)
212 goto out;
213 if ((r = sshkey_from_blob(blob, blen, keyp)) != 0)
214 goto out;
215 if (commentp != NULL) {
216 *commentp = comment;
217 comment = NULL;
218 }
219 r = 0;
220 out:
221 free(comment);
222 return r;
223 }
224
225 /*
226 * Fetch list of identities held by the agent.
227 */
228 int
ssh_fetch_identitylist(int sock,struct ssh_identitylist ** idlp)229 ssh_fetch_identitylist(int sock, struct ssh_identitylist **idlp)
230 {
231 u_char type;
232 u_int32_t num, i;
233 struct sshbuf *msg;
234 struct ssh_identitylist *idl = NULL;
235 int r;
236
237 /*
238 * Send a message to the agent requesting for a list of the
239 * identities it can represent.
240 */
241 if ((msg = sshbuf_new()) == NULL)
242 return SSH_ERR_ALLOC_FAIL;
243 if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_REQUEST_IDENTITIES)) != 0)
244 goto out;
245
246 if ((r = ssh_request_reply(sock, msg, msg)) != 0)
247 goto out;
248
249 /* Get message type, and verify that we got a proper answer. */
250 if ((r = sshbuf_get_u8(msg, &type)) != 0)
251 goto out;
252 if (agent_failed(type)) {
253 r = SSH_ERR_AGENT_FAILURE;
254 goto out;
255 } else if (type != SSH2_AGENT_IDENTITIES_ANSWER) {
256 r = SSH_ERR_INVALID_FORMAT;
257 goto out;
258 }
259
260 /* Get the number of entries in the response and check it for sanity. */
261 if ((r = sshbuf_get_u32(msg, &num)) != 0)
262 goto out;
263 if (num > MAX_AGENT_IDENTITIES) {
264 r = SSH_ERR_INVALID_FORMAT;
265 goto out;
266 }
267 if (num == 0) {
268 r = SSH_ERR_AGENT_NO_IDENTITIES;
269 goto out;
270 }
271
272 /* Deserialise the response into a list of keys/comments */
273 if ((idl = calloc(1, sizeof(*idl))) == NULL ||
274 (idl->keys = calloc(num, sizeof(*idl->keys))) == NULL ||
275 (idl->comments = calloc(num, sizeof(*idl->comments))) == NULL) {
276 r = SSH_ERR_ALLOC_FAIL;
277 goto out;
278 }
279 for (i = 0; i < num;) {
280 if ((r = deserialise_identity2(msg, &(idl->keys[i]),
281 &(idl->comments[i]))) != 0) {
282 if (r == SSH_ERR_KEY_TYPE_UNKNOWN) {
283 /* Gracefully skip unknown key types */
284 num--;
285 continue;
286 } else
287 goto out;
288 }
289 i++;
290 }
291 idl->nkeys = num;
292 *idlp = idl;
293 idl = NULL;
294 r = 0;
295 out:
296 sshbuf_free(msg);
297 if (idl != NULL)
298 ssh_free_identitylist(idl);
299 return r;
300 }
301
302 void
ssh_free_identitylist(struct ssh_identitylist * idl)303 ssh_free_identitylist(struct ssh_identitylist *idl)
304 {
305 size_t i;
306
307 if (idl == NULL)
308 return;
309 for (i = 0; i < idl->nkeys; i++) {
310 if (idl->keys != NULL)
311 sshkey_free(idl->keys[i]);
312 if (idl->comments != NULL)
313 free(idl->comments[i]);
314 }
315 free(idl);
316 }
317
318 /*
319 * Sends a challenge (typically from a server via ssh(1)) to the agent,
320 * and waits for a response from the agent.
321 * Returns true (non-zero) if the agent gave the correct answer, zero
322 * otherwise.
323 */
324
325
326 /* encode signature algorithm in flag bits, so we can keep the msg format */
327 static u_int
agent_encode_alg(const struct sshkey * key,const char * alg)328 agent_encode_alg(const struct sshkey *key, const char *alg)
329 {
330 if (alg != NULL && key->type == KEY_RSA) {
331 if (strcmp(alg, "rsa-sha2-256") == 0)
332 return SSH_AGENT_RSA_SHA2_256;
333 else if (strcmp(alg, "rsa-sha2-512") == 0)
334 return SSH_AGENT_RSA_SHA2_512;
335 }
336 return 0;
337 }
338
339 /* ask agent to sign data, returns err.h code on error, 0 on success */
340 int
ssh_agent_sign(int sock,const struct sshkey * key,u_char ** sigp,size_t * lenp,const u_char * data,size_t datalen,const char * alg,u_int compat)341 ssh_agent_sign(int sock, const struct sshkey *key,
342 u_char **sigp, size_t *lenp,
343 const u_char *data, size_t datalen, const char *alg, u_int compat)
344 {
345 struct sshbuf *msg;
346 u_char *sig = NULL, type = 0;
347 size_t len = 0;
348 u_int flags = 0;
349 int r = SSH_ERR_INTERNAL_ERROR;
350
351 *sigp = NULL;
352 *lenp = 0;
353
354 if (datalen > SSH_KEY_MAX_SIGN_DATA_SIZE)
355 return SSH_ERR_INVALID_ARGUMENT;
356 if ((msg = sshbuf_new()) == NULL)
357 return SSH_ERR_ALLOC_FAIL;
358 flags |= agent_encode_alg(key, alg);
359 if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_SIGN_REQUEST)) != 0 ||
360 (r = sshkey_puts(key, msg)) != 0 ||
361 (r = sshbuf_put_string(msg, data, datalen)) != 0 ||
362 (r = sshbuf_put_u32(msg, flags)) != 0)
363 goto out;
364 if ((r = ssh_request_reply(sock, msg, msg)) != 0)
365 goto out;
366 if ((r = sshbuf_get_u8(msg, &type)) != 0)
367 goto out;
368 if (agent_failed(type)) {
369 r = SSH_ERR_AGENT_FAILURE;
370 goto out;
371 } else if (type != SSH2_AGENT_SIGN_RESPONSE) {
372 r = SSH_ERR_INVALID_FORMAT;
373 goto out;
374 }
375 if ((r = sshbuf_get_string(msg, &sig, &len)) != 0)
376 goto out;
377 /* Check what we actually got back from the agent. */
378 if ((r = sshkey_check_sigtype(sig, len, alg)) != 0)
379 goto out;
380 /* success */
381 *sigp = sig;
382 *lenp = len;
383 sig = NULL;
384 len = 0;
385 r = 0;
386 out:
387 freezero(sig, len);
388 sshbuf_free(msg);
389 return r;
390 }
391
392 /* Encode key for a message to the agent. */
393
394
395 static int
encode_constraints(struct sshbuf * m,u_int life,u_int confirm,u_int maxsign)396 encode_constraints(struct sshbuf *m, u_int life, u_int confirm, u_int maxsign)
397 {
398 int r;
399
400 if (life != 0) {
401 if ((r = sshbuf_put_u8(m, SSH_AGENT_CONSTRAIN_LIFETIME)) != 0 ||
402 (r = sshbuf_put_u32(m, life)) != 0)
403 goto out;
404 }
405 if (confirm != 0) {
406 if ((r = sshbuf_put_u8(m, SSH_AGENT_CONSTRAIN_CONFIRM)) != 0)
407 goto out;
408 }
409 if (maxsign != 0) {
410 if ((r = sshbuf_put_u8(m, SSH_AGENT_CONSTRAIN_MAXSIGN)) != 0 ||
411 (r = sshbuf_put_u32(m, maxsign)) != 0)
412 goto out;
413 }
414 r = 0;
415 out:
416 return r;
417 }
418
419 /*
420 * Adds an identity to the authentication server.
421 * This call is intended only for use by ssh-add(1) and like applications.
422 */
423 int
ssh_add_identity_constrained(int sock,const struct sshkey * key,const char * comment,u_int life,u_int confirm,u_int maxsign)424 ssh_add_identity_constrained(int sock, const struct sshkey *key,
425 const char *comment, u_int life, u_int confirm, u_int maxsign)
426 {
427 struct sshbuf *msg;
428 int r, constrained = (life || confirm || maxsign);
429 u_char type;
430
431 if ((msg = sshbuf_new()) == NULL)
432 return SSH_ERR_ALLOC_FAIL;
433
434 switch (key->type) {
435 #ifdef WITH_OPENSSL
436 case KEY_RSA:
437 case KEY_RSA_CERT:
438 case KEY_DSA:
439 case KEY_DSA_CERT:
440 case KEY_ECDSA:
441 case KEY_ECDSA_CERT:
442 #endif
443 case KEY_ED25519:
444 case KEY_ED25519_CERT:
445 case KEY_XMSS:
446 case KEY_XMSS_CERT:
447 type = constrained ?
448 SSH2_AGENTC_ADD_ID_CONSTRAINED :
449 SSH2_AGENTC_ADD_IDENTITY;
450 if ((r = sshbuf_put_u8(msg, type)) != 0 ||
451 (r = sshkey_private_serialize_maxsign(key, msg, maxsign,
452 NULL)) != 0 ||
453 (r = sshbuf_put_cstring(msg, comment)) != 0)
454 goto out;
455 break;
456 default:
457 r = SSH_ERR_INVALID_ARGUMENT;
458 goto out;
459 }
460 if (constrained &&
461 (r = encode_constraints(msg, life, confirm, maxsign)) != 0)
462 goto out;
463 if ((r = ssh_request_reply(sock, msg, msg)) != 0)
464 goto out;
465 if ((r = sshbuf_get_u8(msg, &type)) != 0)
466 goto out;
467 r = decode_reply(type);
468 out:
469 sshbuf_free(msg);
470 return r;
471 }
472
473 /*
474 * Removes an identity from the authentication server.
475 * This call is intended only for use by ssh-add(1) and like applications.
476 */
477 int
ssh_remove_identity(int sock,struct sshkey * key)478 ssh_remove_identity(int sock, struct sshkey *key)
479 {
480 struct sshbuf *msg;
481 int r;
482 u_char type, *blob = NULL;
483 size_t blen;
484
485 if ((msg = sshbuf_new()) == NULL)
486 return SSH_ERR_ALLOC_FAIL;
487
488 if (key->type != KEY_UNSPEC) {
489 if ((r = sshkey_to_blob(key, &blob, &blen)) != 0)
490 goto out;
491 if ((r = sshbuf_put_u8(msg,
492 SSH2_AGENTC_REMOVE_IDENTITY)) != 0 ||
493 (r = sshbuf_put_string(msg, blob, blen)) != 0)
494 goto out;
495 } else {
496 r = SSH_ERR_INVALID_ARGUMENT;
497 goto out;
498 }
499 if ((r = ssh_request_reply(sock, msg, msg)) != 0)
500 goto out;
501 if ((r = sshbuf_get_u8(msg, &type)) != 0)
502 goto out;
503 r = decode_reply(type);
504 out:
505 if (blob != NULL) {
506 explicit_bzero(blob, blen);
507 free(blob);
508 }
509 sshbuf_free(msg);
510 return r;
511 }
512
513 /*
514 * Add/remove an token-based identity from the authentication server.
515 * This call is intended only for use by ssh-add(1) and like applications.
516 */
517 int
ssh_update_card(int sock,int add,const char * reader_id,const char * pin,u_int life,u_int confirm)518 ssh_update_card(int sock, int add, const char *reader_id, const char *pin,
519 u_int life, u_int confirm)
520 {
521 struct sshbuf *msg;
522 int r, constrained = (life || confirm);
523 u_char type;
524
525 if (add) {
526 type = constrained ?
527 SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED :
528 SSH_AGENTC_ADD_SMARTCARD_KEY;
529 } else
530 type = SSH_AGENTC_REMOVE_SMARTCARD_KEY;
531
532 if ((msg = sshbuf_new()) == NULL)
533 return SSH_ERR_ALLOC_FAIL;
534 if ((r = sshbuf_put_u8(msg, type)) != 0 ||
535 (r = sshbuf_put_cstring(msg, reader_id)) != 0 ||
536 (r = sshbuf_put_cstring(msg, pin)) != 0)
537 goto out;
538 if (constrained &&
539 (r = encode_constraints(msg, life, confirm, 0)) != 0)
540 goto out;
541 if ((r = ssh_request_reply(sock, msg, msg)) != 0)
542 goto out;
543 if ((r = sshbuf_get_u8(msg, &type)) != 0)
544 goto out;
545 r = decode_reply(type);
546 out:
547 sshbuf_free(msg);
548 return r;
549 }
550
551 /*
552 * Removes all identities from the agent.
553 * This call is intended only for use by ssh-add(1) and like applications.
554 *
555 * This supports the SSH protocol 1 message to because, when clearing all
556 * keys from an agent, we generally want to clear both protocol v1 and v2
557 * keys.
558 */
559 int
ssh_remove_all_identities(int sock,int version)560 ssh_remove_all_identities(int sock, int version)
561 {
562 struct sshbuf *msg;
563 u_char type = (version == 1) ?
564 SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES :
565 SSH2_AGENTC_REMOVE_ALL_IDENTITIES;
566 int r;
567
568 if ((msg = sshbuf_new()) == NULL)
569 return SSH_ERR_ALLOC_FAIL;
570 if ((r = sshbuf_put_u8(msg, type)) != 0)
571 goto out;
572 if ((r = ssh_request_reply(sock, msg, msg)) != 0)
573 goto out;
574 if ((r = sshbuf_get_u8(msg, &type)) != 0)
575 goto out;
576 r = decode_reply(type);
577 out:
578 sshbuf_free(msg);
579 return r;
580 }
581