1 /* $OpenBSD: authfd.c,v 1.133 2023/03/09 21:06:24 jcs 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>
63 #define MAX_AGENT_IDENTITIES 2048 /* Max keys in agent reply */
64 #define MAX_AGENT_REPLY_LEN (256 * 1024) /* Max bytes in agent reply */
66 /* macro to check for "agent failure" message */
67 #define agent_failed(x) \
68 ((x == SSH_AGENT_FAILURE) || \
69 (x == SSH_COM_AGENT2_FAILURE) || \
70 (x == SSH2_AGENT_FAILURE))
72 /* Convert success/failure response from agent to a err.h status */
74 decode_reply(u_char type)
76 if (agent_failed(type))
77 return SSH_ERR_AGENT_FAILURE;
78 else if (type == SSH_AGENT_SUCCESS)
81 return SSH_ERR_INVALID_FORMAT;
85 * Opens an authentication socket at the provided path and stores the file
86 * descriptor in fdp. Returns 0 on success and an error on failure.
89 ssh_get_authentication_socket_path(const char *authsocket, int *fdp)
92 struct sockaddr_un sunaddr;
94 debug3_f("path '%s'", authsocket);
95 memset(&sunaddr, 0, sizeof(sunaddr));
96 sunaddr.sun_family = AF_UNIX;
97 strlcpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path));
99 if ((sock = socket(AF_UNIX, SOCK_STREAM, 0)) == -1)
100 return SSH_ERR_SYSTEM_ERROR;
103 if (fcntl(sock, F_SETFD, FD_CLOEXEC) == -1 ||
104 connect(sock, (struct sockaddr *)&sunaddr, sizeof(sunaddr)) == -1) {
108 return SSH_ERR_SYSTEM_ERROR;
118 * Opens the default authentication socket and stores the file descriptor in
119 * fdp. Returns 0 on success and an error on failure.
122 ssh_get_authentication_socket(int *fdp)
124 const char *authsocket;
129 authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME);
130 if (authsocket == NULL || *authsocket == '\0')
131 return SSH_ERR_AGENT_NOT_PRESENT;
133 return ssh_get_authentication_socket_path(authsocket, fdp);
136 /* Communicate with agent: send request and read reply */
138 ssh_request_reply(int sock, struct sshbuf *request, struct sshbuf *reply)
144 /* Get the length of the message, and format it in the buffer. */
145 len = sshbuf_len(request);
148 /* Send the length and then the packet to the agent. */
149 if (atomicio(vwrite, sock, buf, 4) != 4 ||
150 atomicio(vwrite, sock, sshbuf_mutable_ptr(request),
151 sshbuf_len(request)) != sshbuf_len(request))
152 return SSH_ERR_AGENT_COMMUNICATION;
154 * Wait for response from the agent. First read the length of the
157 if (atomicio(read, sock, buf, 4) != 4)
158 return SSH_ERR_AGENT_COMMUNICATION;
160 /* Extract the length, and check it for sanity. */
162 if (len > MAX_AGENT_REPLY_LEN)
163 return SSH_ERR_INVALID_FORMAT;
165 /* Read the rest of the response in to the buffer. */
171 if (atomicio(read, sock, buf, l) != l)
172 return SSH_ERR_AGENT_COMMUNICATION;
173 if ((r = sshbuf_put(reply, buf, l)) != 0)
180 /* Communicate with agent: sent request, read and decode status reply */
182 ssh_request_reply_decode(int sock, struct sshbuf *request)
184 struct sshbuf *reply;
188 if ((reply = sshbuf_new()) == NULL)
189 return SSH_ERR_ALLOC_FAIL;
190 if ((r = ssh_request_reply(sock, request, reply)) != 0 ||
191 (r = sshbuf_get_u8(reply, &type)) != 0 ||
192 (r = decode_reply(type)) != 0)
202 * Closes the agent socket if it should be closed (depends on how it was
203 * obtained). The argument must have been returned by
204 * ssh_get_authentication_socket().
207 ssh_close_authentication_socket(int sock)
209 if (getenv(SSH_AUTHSOCKET_ENV_NAME))
213 /* Lock/unlock agent */
215 ssh_lock_agent(int sock, int lock, const char *password)
218 u_char type = lock ? SSH_AGENTC_LOCK : SSH_AGENTC_UNLOCK;
221 if ((msg = sshbuf_new()) == NULL)
222 return SSH_ERR_ALLOC_FAIL;
223 if ((r = sshbuf_put_u8(msg, type)) != 0 ||
224 (r = sshbuf_put_cstring(msg, password)) != 0 ||
225 (r = ssh_request_reply_decode(sock, msg)) != 0)
236 deserialise_identity2(struct sshbuf *ids, struct sshkey **keyp, char **commentp)
239 char *comment = NULL;
243 if ((r = sshbuf_get_string_direct(ids, &blob, &blen)) != 0 ||
244 (r = sshbuf_get_cstring(ids, &comment, NULL)) != 0)
246 if ((r = sshkey_from_blob(blob, blen, keyp)) != 0)
248 if (commentp != NULL) {
259 * Fetch list of identities held by the agent.
262 ssh_fetch_identitylist(int sock, struct ssh_identitylist **idlp)
267 struct ssh_identitylist *idl = NULL;
271 * Send a message to the agent requesting for a list of the
272 * identities it can represent.
274 if ((msg = sshbuf_new()) == NULL)
275 return SSH_ERR_ALLOC_FAIL;
276 if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_REQUEST_IDENTITIES)) != 0)
279 if ((r = ssh_request_reply(sock, msg, msg)) != 0)
282 /* Get message type, and verify that we got a proper answer. */
283 if ((r = sshbuf_get_u8(msg, &type)) != 0)
285 if (agent_failed(type)) {
286 r = SSH_ERR_AGENT_FAILURE;
288 } else if (type != SSH2_AGENT_IDENTITIES_ANSWER) {
289 r = SSH_ERR_INVALID_FORMAT;
293 /* Get the number of entries in the response and check it for sanity. */
294 if ((r = sshbuf_get_u32(msg, &num)) != 0)
296 if (num > MAX_AGENT_IDENTITIES) {
297 r = SSH_ERR_INVALID_FORMAT;
301 r = SSH_ERR_AGENT_NO_IDENTITIES;
305 /* Deserialise the response into a list of keys/comments */
306 if ((idl = calloc(1, sizeof(*idl))) == NULL ||
307 (idl->keys = calloc(num, sizeof(*idl->keys))) == NULL ||
308 (idl->comments = calloc(num, sizeof(*idl->comments))) == NULL) {
309 r = SSH_ERR_ALLOC_FAIL;
312 for (i = 0; i < num;) {
313 if ((r = deserialise_identity2(msg, &(idl->keys[i]),
314 &(idl->comments[i]))) != 0) {
315 if (r == SSH_ERR_KEY_TYPE_UNKNOWN) {
316 /* Gracefully skip unknown key types */
331 ssh_free_identitylist(idl);
336 ssh_free_identitylist(struct ssh_identitylist *idl)
342 for (i = 0; i < idl->nkeys; i++) {
343 if (idl->keys != NULL)
344 sshkey_free(idl->keys[i]);
345 if (idl->comments != NULL)
346 free(idl->comments[i]);
354 * Check if the ssh agent has a given key.
355 * Returns 0 if found, or a negative SSH_ERR_* error code on failure.
358 ssh_agent_has_key(int sock, const struct sshkey *key)
360 int r, ret = SSH_ERR_KEY_NOT_FOUND;
362 struct ssh_identitylist *idlist = NULL;
364 if ((r = ssh_fetch_identitylist(sock, &idlist)) != 0) {
368 for (i = 0; i < idlist->nkeys; i++) {
369 if (sshkey_equal_public(idlist->keys[i], key)) {
375 ssh_free_identitylist(idlist);
380 * Sends a challenge (typically from a server via ssh(1)) to the agent,
381 * and waits for a response from the agent.
382 * Returns true (non-zero) if the agent gave the correct answer, zero
387 /* encode signature algorithm in flag bits, so we can keep the msg format */
389 agent_encode_alg(const struct sshkey *key, const char *alg)
391 if (alg != NULL && sshkey_type_plain(key->type) == KEY_RSA) {
392 if (strcmp(alg, "rsa-sha2-256") == 0 ||
393 strcmp(alg, "rsa-sha2-256-cert-v01@openssh.com") == 0)
394 return SSH_AGENT_RSA_SHA2_256;
395 if (strcmp(alg, "rsa-sha2-512") == 0 ||
396 strcmp(alg, "rsa-sha2-512-cert-v01@openssh.com") == 0)
397 return SSH_AGENT_RSA_SHA2_512;
402 /* ask agent to sign data, returns err.h code on error, 0 on success */
404 ssh_agent_sign(int sock, const struct sshkey *key,
405 u_char **sigp, size_t *lenp,
406 const u_char *data, size_t datalen, const char *alg, u_int compat)
409 u_char *sig = NULL, type = 0;
412 int r = SSH_ERR_INTERNAL_ERROR;
417 if (datalen > SSH_KEY_MAX_SIGN_DATA_SIZE)
418 return SSH_ERR_INVALID_ARGUMENT;
419 if ((msg = sshbuf_new()) == NULL)
420 return SSH_ERR_ALLOC_FAIL;
421 flags |= agent_encode_alg(key, alg);
422 if ((r = sshbuf_put_u8(msg, SSH2_AGENTC_SIGN_REQUEST)) != 0 ||
423 (r = sshkey_puts(key, msg)) != 0 ||
424 (r = sshbuf_put_string(msg, data, datalen)) != 0 ||
425 (r = sshbuf_put_u32(msg, flags)) != 0)
427 if ((r = ssh_request_reply(sock, msg, msg)) != 0)
429 if ((r = sshbuf_get_u8(msg, &type)) != 0)
431 if (agent_failed(type)) {
432 r = SSH_ERR_AGENT_FAILURE;
434 } else if (type != SSH2_AGENT_SIGN_RESPONSE) {
435 r = SSH_ERR_INVALID_FORMAT;
438 if ((r = sshbuf_get_string(msg, &sig, &len)) != 0)
440 /* Check what we actually got back from the agent. */
441 if ((r = sshkey_check_sigtype(sig, len, alg)) != 0)
455 /* Encode key for a message to the agent. */
458 encode_dest_constraint_hop(struct sshbuf *m,
459 const struct dest_constraint_hop *dch)
465 if ((b = sshbuf_new()) == NULL)
466 return SSH_ERR_ALLOC_FAIL;
467 if ((r = sshbuf_put_cstring(b, dch->user)) != 0 ||
468 (r = sshbuf_put_cstring(b, dch->hostname)) != 0 ||
469 (r = sshbuf_put_string(b, NULL, 0)) != 0) /* reserved */
471 for (i = 0; i < dch->nkeys; i++) {
472 if ((r = sshkey_puts(dch->keys[i], b)) != 0 ||
473 (r = sshbuf_put_u8(b, dch->key_is_ca[i] != 0)) != 0)
476 if ((r = sshbuf_put_stringb(m, b)) != 0)
486 encode_dest_constraint(struct sshbuf *m, const struct dest_constraint *dc)
491 if ((b = sshbuf_new()) == NULL)
492 return SSH_ERR_ALLOC_FAIL;
493 if ((r = encode_dest_constraint_hop(b, &dc->from)) != 0 ||
494 (r = encode_dest_constraint_hop(b, &dc->to)) != 0 ||
495 (r = sshbuf_put_string(b, NULL, 0)) != 0) /* reserved */
497 if ((r = sshbuf_put_stringb(m, b)) != 0)
507 encode_constraints(struct sshbuf *m, u_int life, u_int confirm, u_int maxsign,
508 const char *provider, struct dest_constraint **dest_constraints,
509 size_t ndest_constraints)
512 struct sshbuf *b = NULL;
516 if ((r = sshbuf_put_u8(m, SSH_AGENT_CONSTRAIN_LIFETIME)) != 0 ||
517 (r = sshbuf_put_u32(m, life)) != 0)
521 if ((r = sshbuf_put_u8(m, SSH_AGENT_CONSTRAIN_CONFIRM)) != 0)
525 if ((r = sshbuf_put_u8(m, SSH_AGENT_CONSTRAIN_MAXSIGN)) != 0 ||
526 (r = sshbuf_put_u32(m, maxsign)) != 0)
529 if (provider != NULL) {
530 if ((r = sshbuf_put_u8(m,
531 SSH_AGENT_CONSTRAIN_EXTENSION)) != 0 ||
532 (r = sshbuf_put_cstring(m,
533 "sk-provider@openssh.com")) != 0 ||
534 (r = sshbuf_put_cstring(m, provider)) != 0)
537 if (dest_constraints != NULL && ndest_constraints > 0) {
538 if ((b = sshbuf_new()) == NULL) {
539 r = SSH_ERR_ALLOC_FAIL;
542 for (i = 0; i < ndest_constraints; i++) {
543 if ((r = encode_dest_constraint(b,
544 dest_constraints[i])) != 0)
547 if ((r = sshbuf_put_u8(m,
548 SSH_AGENT_CONSTRAIN_EXTENSION)) != 0 ||
549 (r = sshbuf_put_cstring(m,
550 "restrict-destination-v00@openssh.com")) != 0 ||
551 (r = sshbuf_put_stringb(m, b)) != 0)
561 * Adds an identity to the authentication server.
562 * This call is intended only for use by ssh-add(1) and like applications.
565 ssh_add_identity_constrained(int sock, struct sshkey *key,
566 const char *comment, u_int life, u_int confirm, u_int maxsign,
567 const char *provider, struct dest_constraint **dest_constraints,
568 size_t ndest_constraints)
571 int r, constrained = (life || confirm || maxsign ||
572 provider || dest_constraints);
575 if ((msg = sshbuf_new()) == NULL)
576 return SSH_ERR_ALLOC_FAIL;
587 case KEY_ECDSA_SK_CERT:
590 case KEY_ED25519_CERT:
592 case KEY_ED25519_SK_CERT:
596 SSH2_AGENTC_ADD_ID_CONSTRAINED :
597 SSH2_AGENTC_ADD_IDENTITY;
598 if ((r = sshbuf_put_u8(msg, type)) != 0 ||
599 (r = sshkey_private_serialize_maxsign(key, msg, maxsign,
601 (r = sshbuf_put_cstring(msg, comment)) != 0)
605 r = SSH_ERR_INVALID_ARGUMENT;
609 (r = encode_constraints(msg, life, confirm, maxsign,
610 provider, dest_constraints, ndest_constraints)) != 0)
612 if ((r = ssh_request_reply_decode(sock, msg)) != 0)
622 * Removes an identity from the authentication server.
623 * This call is intended only for use by ssh-add(1) and like applications.
626 ssh_remove_identity(int sock, const struct sshkey *key)
633 if ((msg = sshbuf_new()) == NULL)
634 return SSH_ERR_ALLOC_FAIL;
636 if (key->type != KEY_UNSPEC) {
637 if ((r = sshkey_to_blob(key, &blob, &blen)) != 0)
639 if ((r = sshbuf_put_u8(msg,
640 SSH2_AGENTC_REMOVE_IDENTITY)) != 0 ||
641 (r = sshbuf_put_string(msg, blob, blen)) != 0)
644 r = SSH_ERR_INVALID_ARGUMENT;
647 if ((r = ssh_request_reply_decode(sock, msg)) != 0)
653 freezero(blob, blen);
659 * Add/remove an token-based identity from the authentication server.
660 * This call is intended only for use by ssh-add(1) and like applications.
663 ssh_update_card(int sock, int add, const char *reader_id, const char *pin,
664 u_int life, u_int confirm,
665 struct dest_constraint **dest_constraints, size_t ndest_constraints)
668 int r, constrained = (life || confirm || dest_constraints);
673 SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED :
674 SSH_AGENTC_ADD_SMARTCARD_KEY;
676 type = SSH_AGENTC_REMOVE_SMARTCARD_KEY;
678 if ((msg = sshbuf_new()) == NULL)
679 return SSH_ERR_ALLOC_FAIL;
680 if ((r = sshbuf_put_u8(msg, type)) != 0 ||
681 (r = sshbuf_put_cstring(msg, reader_id)) != 0 ||
682 (r = sshbuf_put_cstring(msg, pin)) != 0)
685 (r = encode_constraints(msg, life, confirm, 0, NULL,
686 dest_constraints, ndest_constraints)) != 0)
688 if ((r = ssh_request_reply_decode(sock, msg)) != 0)
698 * Removes all identities from the agent.
699 * This call is intended only for use by ssh-add(1) and like applications.
701 * This supports the SSH protocol 1 message to because, when clearing all
702 * keys from an agent, we generally want to clear both protocol v1 and v2
706 ssh_remove_all_identities(int sock, int version)
709 u_char type = (version == 1) ?
710 SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES :
711 SSH2_AGENTC_REMOVE_ALL_IDENTITIES;
714 if ((msg = sshbuf_new()) == NULL)
715 return SSH_ERR_ALLOC_FAIL;
716 if ((r = sshbuf_put_u8(msg, type)) != 0)
718 if ((r = ssh_request_reply_decode(sock, msg)) != 0)
727 /* Binds a session ID to a hostkey via the initial KEX signature. */
729 ssh_agent_bind_hostkey(int sock, const struct sshkey *key,
730 const struct sshbuf *session_id, const struct sshbuf *signature,
736 if (key == NULL || session_id == NULL || signature == NULL)
737 return SSH_ERR_INVALID_ARGUMENT;
738 if ((msg = sshbuf_new()) == NULL)
739 return SSH_ERR_ALLOC_FAIL;
740 if ((r = sshbuf_put_u8(msg, SSH_AGENTC_EXTENSION)) != 0 ||
741 (r = sshbuf_put_cstring(msg, "session-bind@openssh.com")) != 0 ||
742 (r = sshkey_puts(key, msg)) != 0 ||
743 (r = sshbuf_put_stringb(msg, session_id)) != 0 ||
744 (r = sshbuf_put_stringb(msg, signature)) != 0 ||
745 (r = sshbuf_put_u8(msg, forwarding ? 1 : 0)) != 0)
747 if ((r = ssh_request_reply_decode(sock, msg)) != 0)