1 /* $OpenBSD: authfd.c,v 1.130 2022/04/27 11:08:55 dtucker Exp $ */
3 * Author: Tatu Ylonen <ylo@cs.hut.fi>
4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
6 * Functions for connecting the local authentication agent.
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".
14 * SSH2 implementation,
15 * Copyright (c) 2000 Markus Friedl. All rights reserved.
17 * Redistribution and use in source and binary forms, with or without
18 * modification, are permitted provided that the following conditions
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.
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.
40 #include <sys/types.h>
42 #include <sys/socket.h>
64 #define MAX_AGENT_IDENTITIES 2048 /* Max keys in agent reply */
65 #define MAX_AGENT_REPLY_LEN (256 * 1024) /* Max bytes in agent reply */
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))
73 /* Convert success/failure response from agent to a err.h status */
75 decode_reply(u_char type)
77 if (agent_failed(type))
78 return SSH_ERR_AGENT_FAILURE;
79 else if (type == SSH_AGENT_SUCCESS)
82 return SSH_ERR_INVALID_FORMAT;
86 * Opens an authentication socket at the provided path and stores the file
87 * descriptor in fdp. Returns 0 on success and an error on failure.
90 ssh_get_authentication_socket_path(const char *authsocket, int *fdp)
93 struct sockaddr_un sunaddr;
95 debug3_f("path '%s'", authsocket);
96 memset(&sunaddr, 0, sizeof(sunaddr));
97 sunaddr.sun_family = AF_UNIX;
98 strlcpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path));
100 if ((sock = socket(AF_UNIX, SOCK_STREAM, 0)) == -1)
101 return SSH_ERR_SYSTEM_ERROR;
104 if (fcntl(sock, F_SETFD, FD_CLOEXEC) == -1 ||
105 connect(sock, (struct sockaddr *)&sunaddr, sizeof(sunaddr)) == -1) {
109 return SSH_ERR_SYSTEM_ERROR;
119 * Opens the default authentication socket and stores the file descriptor in
120 * fdp. Returns 0 on success and an error on failure.
123 ssh_get_authentication_socket(int *fdp)
125 const char *authsocket;
130 authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME);
131 if (authsocket == NULL || *authsocket == '\0')
132 return SSH_ERR_AGENT_NOT_PRESENT;
134 return ssh_get_authentication_socket_path(authsocket, fdp);
137 /* Communicate with agent: send request and read reply */
139 ssh_request_reply(int sock, struct sshbuf *request, struct sshbuf *reply)
145 /* Get the length of the message, and format it in the buffer. */
146 len = sshbuf_len(request);
149 /* Send the length and then the packet to the agent. */
150 if (atomicio(vwrite, sock, buf, 4) != 4 ||
151 atomicio(vwrite, sock, sshbuf_mutable_ptr(request),
152 sshbuf_len(request)) != sshbuf_len(request))
153 return SSH_ERR_AGENT_COMMUNICATION;
155 * Wait for response from the agent. First read the length of the
158 if (atomicio(read, sock, buf, 4) != 4)
159 return SSH_ERR_AGENT_COMMUNICATION;
161 /* Extract the length, and check it for sanity. */
163 if (len > MAX_AGENT_REPLY_LEN)
164 return SSH_ERR_INVALID_FORMAT;
166 /* Read the rest of the response in to the buffer. */
172 if (atomicio(read, sock, buf, l) != l)
173 return SSH_ERR_AGENT_COMMUNICATION;
174 if ((r = sshbuf_put(reply, buf, l)) != 0)
181 /* Communicate with agent: sent request, read and decode status reply */
183 ssh_request_reply_decode(int sock, struct sshbuf *request)
185 struct sshbuf *reply;
189 if ((reply = sshbuf_new()) == NULL)
190 return SSH_ERR_ALLOC_FAIL;
191 if ((r = ssh_request_reply(sock, request, reply)) != 0 ||
192 (r = sshbuf_get_u8(reply, &type)) != 0 ||
193 (r = decode_reply(type)) != 0)
203 * Closes the agent socket if it should be closed (depends on how it was
204 * obtained). The argument must have been returned by
205 * ssh_get_authentication_socket().
208 ssh_close_authentication_socket(int sock)
210 if (getenv(SSH_AUTHSOCKET_ENV_NAME))
214 /* Lock/unlock agent */
216 ssh_lock_agent(int sock, int lock, const char *password)
219 u_char type = lock ? SSH_AGENTC_LOCK : SSH_AGENTC_UNLOCK;
222 if ((msg = sshbuf_new()) == NULL)
223 return SSH_ERR_ALLOC_FAIL;
224 if ((r = sshbuf_put_u8(msg, type)) != 0 ||
225 (r = sshbuf_put_cstring(msg, password)) != 0 ||
226 (r = ssh_request_reply_decode(sock, msg)) != 0)
237 deserialise_identity2(struct sshbuf *ids, struct sshkey **keyp, char **commentp)
240 char *comment = NULL;
244 if ((r = sshbuf_get_string_direct(ids, &blob, &blen)) != 0 ||
245 (r = sshbuf_get_cstring(ids, &comment, NULL)) != 0)
247 if ((r = sshkey_from_blob(blob, blen, keyp)) != 0)
249 if (commentp != NULL) {
260 * Fetch list of identities held by the agent.
263 ssh_fetch_identitylist(int sock, struct ssh_identitylist **idlp)
268 struct ssh_identitylist *idl = NULL;
272 * Send a message to the agent requesting for a list of the
273 * identities it can represent.
275 if ((msg = sshbuf_new()) == NULL)
276 return SSH_ERR_ALLOC_FAIL;
277 if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_REQUEST_IDENTITIES)) != 0)
280 if ((r = ssh_request_reply(sock, msg, msg)) != 0)
283 /* Get message type, and verify that we got a proper answer. */
284 if ((r = sshbuf_get_u8(msg, &type)) != 0)
286 if (agent_failed(type)) {
287 r = SSH_ERR_AGENT_FAILURE;
289 } else if (type != SSH2_AGENT_IDENTITIES_ANSWER) {
290 r = SSH_ERR_INVALID_FORMAT;
294 /* Get the number of entries in the response and check it for sanity. */
295 if ((r = sshbuf_get_u32(msg, &num)) != 0)
297 if (num > MAX_AGENT_IDENTITIES) {
298 r = SSH_ERR_INVALID_FORMAT;
302 r = SSH_ERR_AGENT_NO_IDENTITIES;
306 /* Deserialise the response into a list of keys/comments */
307 if ((idl = calloc(1, sizeof(*idl))) == NULL ||
308 (idl->keys = calloc(num, sizeof(*idl->keys))) == NULL ||
309 (idl->comments = calloc(num, sizeof(*idl->comments))) == NULL) {
310 r = SSH_ERR_ALLOC_FAIL;
313 for (i = 0; i < num;) {
314 if ((r = deserialise_identity2(msg, &(idl->keys[i]),
315 &(idl->comments[i]))) != 0) {
316 if (r == SSH_ERR_KEY_TYPE_UNKNOWN) {
317 /* Gracefully skip unknown key types */
332 ssh_free_identitylist(idl);
337 ssh_free_identitylist(struct ssh_identitylist *idl)
343 for (i = 0; i < idl->nkeys; i++) {
344 if (idl->keys != NULL)
345 sshkey_free(idl->keys[i]);
346 if (idl->comments != NULL)
347 free(idl->comments[i]);
355 * Check if the ssh agent has a given key.
356 * Returns 0 if found, or a negative SSH_ERR_* error code on failure.
359 ssh_agent_has_key(int sock, const struct sshkey *key)
361 int r, ret = SSH_ERR_KEY_NOT_FOUND;
363 struct ssh_identitylist *idlist = NULL;
365 if ((r = ssh_fetch_identitylist(sock, &idlist)) != 0) {
369 for (i = 0; i < idlist->nkeys; i++) {
370 if (sshkey_equal_public(idlist->keys[i], key)) {
376 ssh_free_identitylist(idlist);
381 * Sends a challenge (typically from a server via ssh(1)) to the agent,
382 * and waits for a response from the agent.
383 * Returns true (non-zero) if the agent gave the correct answer, zero
388 /* encode signature algorithm in flag bits, so we can keep the msg format */
390 agent_encode_alg(const struct sshkey *key, const char *alg)
392 if (alg != NULL && sshkey_type_plain(key->type) == KEY_RSA) {
393 if (strcmp(alg, "rsa-sha2-256") == 0 ||
394 strcmp(alg, "rsa-sha2-256-cert-v01@openssh.com") == 0)
395 return SSH_AGENT_RSA_SHA2_256;
396 if (strcmp(alg, "rsa-sha2-512") == 0 ||
397 strcmp(alg, "rsa-sha2-512-cert-v01@openssh.com") == 0)
398 return SSH_AGENT_RSA_SHA2_512;
403 /* ask agent to sign data, returns err.h code on error, 0 on success */
405 ssh_agent_sign(int sock, const struct sshkey *key,
406 u_char **sigp, size_t *lenp,
407 const u_char *data, size_t datalen, const char *alg, u_int compat)
410 u_char *sig = NULL, type = 0;
413 int r = SSH_ERR_INTERNAL_ERROR;
418 if (datalen > SSH_KEY_MAX_SIGN_DATA_SIZE)
419 return SSH_ERR_INVALID_ARGUMENT;
420 if ((msg = sshbuf_new()) == NULL)
421 return SSH_ERR_ALLOC_FAIL;
422 flags |= agent_encode_alg(key, alg);
423 if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_SIGN_REQUEST)) != 0 ||
424 (r = sshkey_puts(key, msg)) != 0 ||
425 (r = sshbuf_put_string(msg, data, datalen)) != 0 ||
426 (r = sshbuf_put_u32(msg, flags)) != 0)
428 if ((r = ssh_request_reply(sock, msg, msg)) != 0)
430 if ((r = sshbuf_get_u8(msg, &type)) != 0)
432 if (agent_failed(type)) {
433 r = SSH_ERR_AGENT_FAILURE;
435 } else if (type != SSH2_AGENT_SIGN_RESPONSE) {
436 r = SSH_ERR_INVALID_FORMAT;
439 if ((r = sshbuf_get_string(msg, &sig, &len)) != 0)
441 /* Check what we actually got back from the agent. */
442 if ((r = sshkey_check_sigtype(sig, len, alg)) != 0)
456 /* Encode key for a message to the agent. */
459 encode_dest_constraint_hop(struct sshbuf *m,
460 const struct dest_constraint_hop *dch)
466 if ((b = sshbuf_new()) == NULL)
467 return SSH_ERR_ALLOC_FAIL;
468 if ((r = sshbuf_put_cstring(b, dch->user)) != 0 ||
469 (r = sshbuf_put_cstring(b, dch->hostname)) != 0 ||
470 (r = sshbuf_put_string(b, NULL, 0)) != 0) /* reserved */
472 for (i = 0; i < dch->nkeys; i++) {
473 if ((r = sshkey_puts(dch->keys[i], b)) != 0 ||
474 (r = sshbuf_put_u8(b, dch->key_is_ca[i] != 0)) != 0)
477 if ((r = sshbuf_put_stringb(m, b)) != 0)
487 encode_dest_constraint(struct sshbuf *m, const struct dest_constraint *dc)
492 if ((b = sshbuf_new()) == NULL)
493 return SSH_ERR_ALLOC_FAIL;
494 if ((r = encode_dest_constraint_hop(b, &dc->from) != 0) ||
495 (r = encode_dest_constraint_hop(b, &dc->to) != 0) ||
496 (r = sshbuf_put_string(b, NULL, 0)) != 0) /* reserved */
498 if ((r = sshbuf_put_stringb(m, b)) != 0)
508 encode_constraints(struct sshbuf *m, u_int life, u_int confirm, u_int maxsign,
509 const char *provider, struct dest_constraint **dest_constraints,
510 size_t ndest_constraints)
513 struct sshbuf *b = NULL;
517 if ((r = sshbuf_put_u8(m, SSH_AGENT_CONSTRAIN_LIFETIME)) != 0 ||
518 (r = sshbuf_put_u32(m, life)) != 0)
522 if ((r = sshbuf_put_u8(m, SSH_AGENT_CONSTRAIN_CONFIRM)) != 0)
526 if ((r = sshbuf_put_u8(m, SSH_AGENT_CONSTRAIN_MAXSIGN)) != 0 ||
527 (r = sshbuf_put_u32(m, maxsign)) != 0)
530 if (provider != NULL) {
531 if ((r = sshbuf_put_u8(m,
532 SSH_AGENT_CONSTRAIN_EXTENSION)) != 0 ||
533 (r = sshbuf_put_cstring(m,
534 "sk-provider@openssh.com")) != 0 ||
535 (r = sshbuf_put_cstring(m, provider)) != 0)
538 if (dest_constraints != NULL && ndest_constraints > 0) {
539 if ((b = sshbuf_new()) == NULL) {
540 r = SSH_ERR_ALLOC_FAIL;
543 for (i = 0; i < ndest_constraints; i++) {
544 if ((r = encode_dest_constraint(b,
545 dest_constraints[i])) != 0)
548 if ((r = sshbuf_put_u8(m,
549 SSH_AGENT_CONSTRAIN_EXTENSION)) != 0 ||
550 (r = sshbuf_put_cstring(m,
551 "restrict-destination-v00@openssh.com")) != 0 ||
552 (r = sshbuf_put_stringb(m, b)) != 0)
562 * Adds an identity to the authentication server.
563 * This call is intended only for use by ssh-add(1) and like applications.
566 ssh_add_identity_constrained(int sock, struct sshkey *key,
567 const char *comment, u_int life, u_int confirm, u_int maxsign,
568 const char *provider, struct dest_constraint **dest_constraints,
569 size_t ndest_constraints)
572 int r, constrained = (life || confirm || maxsign ||
573 provider || dest_constraints);
576 if ((msg = sshbuf_new()) == NULL)
577 return SSH_ERR_ALLOC_FAIL;
588 case KEY_ECDSA_SK_CERT:
591 case KEY_ED25519_CERT:
593 case KEY_ED25519_SK_CERT:
597 SSH2_AGENTC_ADD_ID_CONSTRAINED :
598 SSH2_AGENTC_ADD_IDENTITY;
599 if ((r = sshbuf_put_u8(msg, type)) != 0 ||
600 (r = sshkey_private_serialize_maxsign(key, msg, maxsign,
602 (r = sshbuf_put_cstring(msg, comment)) != 0)
606 r = SSH_ERR_INVALID_ARGUMENT;
610 (r = encode_constraints(msg, life, confirm, maxsign,
611 provider, dest_constraints, ndest_constraints)) != 0)
613 if ((r = ssh_request_reply_decode(sock, msg)) != 0)
623 * Removes an identity from the authentication server.
624 * This call is intended only for use by ssh-add(1) and like applications.
627 ssh_remove_identity(int sock, const struct sshkey *key)
634 if ((msg = sshbuf_new()) == NULL)
635 return SSH_ERR_ALLOC_FAIL;
637 if (key->type != KEY_UNSPEC) {
638 if ((r = sshkey_to_blob(key, &blob, &blen)) != 0)
640 if ((r = sshbuf_put_u8(msg,
641 SSH2_AGENTC_REMOVE_IDENTITY)) != 0 ||
642 (r = sshbuf_put_string(msg, blob, blen)) != 0)
645 r = SSH_ERR_INVALID_ARGUMENT;
648 if ((r = ssh_request_reply_decode(sock, msg)) != 0)
654 freezero(blob, blen);
660 * Add/remove an token-based identity from the authentication server.
661 * This call is intended only for use by ssh-add(1) and like applications.
664 ssh_update_card(int sock, int add, const char *reader_id, const char *pin,
665 u_int life, u_int confirm,
666 struct dest_constraint **dest_constraints, size_t ndest_constraints)
669 int r, constrained = (life || confirm);
674 SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED :
675 SSH_AGENTC_ADD_SMARTCARD_KEY;
677 type = SSH_AGENTC_REMOVE_SMARTCARD_KEY;
679 if ((msg = sshbuf_new()) == NULL)
680 return SSH_ERR_ALLOC_FAIL;
681 if ((r = sshbuf_put_u8(msg, type)) != 0 ||
682 (r = sshbuf_put_cstring(msg, reader_id)) != 0 ||
683 (r = sshbuf_put_cstring(msg, pin)) != 0)
686 (r = encode_constraints(msg, life, confirm, 0, NULL,
687 dest_constraints, ndest_constraints)) != 0)
689 if ((r = ssh_request_reply_decode(sock, msg)) != 0)
699 * Removes all identities from the agent.
700 * This call is intended only for use by ssh-add(1) and like applications.
702 * This supports the SSH protocol 1 message to because, when clearing all
703 * keys from an agent, we generally want to clear both protocol v1 and v2
707 ssh_remove_all_identities(int sock, int version)
710 u_char type = (version == 1) ?
711 SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES :
712 SSH2_AGENTC_REMOVE_ALL_IDENTITIES;
715 if ((msg = sshbuf_new()) == NULL)
716 return SSH_ERR_ALLOC_FAIL;
717 if ((r = sshbuf_put_u8(msg, type)) != 0)
719 if ((r = ssh_request_reply_decode(sock, msg)) != 0)
728 /* Binds a session ID to a hostkey via the initial KEX signature. */
730 ssh_agent_bind_hostkey(int sock, const struct sshkey *key,
731 const struct sshbuf *session_id, const struct sshbuf *signature,
737 if (key == NULL || session_id == NULL || signature == NULL)
738 return SSH_ERR_INVALID_ARGUMENT;
739 if ((msg = sshbuf_new()) == NULL)
740 return SSH_ERR_ALLOC_FAIL;
741 if ((r = sshbuf_put_u8(msg, SSH_AGENTC_EXTENSION)) != 0 ||
742 (r = sshbuf_put_cstring(msg, "session-bind@openssh.com")) != 0 ||
743 (r = sshkey_puts(key, msg)) != 0 ||
744 (r = sshbuf_put_stringb(msg, session_id)) != 0 ||
745 (r = sshbuf_put_stringb(msg, signature)) != 0 ||
746 (r = sshbuf_put_u8(msg, forwarding ? 1 : 0)) != 0)
748 if ((r = ssh_request_reply_decode(sock, msg)) != 0)