1 /* $OpenBSD: ssh_api.c,v 1.15 2019/01/21 10:38:54 djm Exp $ */
3 * Copyright (c) 2012 Markus Friedl. All rights reserved.
5 * Permission to use, copy, modify, and distribute this software for any
6 * purpose with or without fee is hereby granted, provided that the above
7 * copyright notice and this permission notice appear in all copies.
9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
28 #include "myproposal.h"
32 #include "openbsd-compat/openssl-compat.h"
36 int _ssh_exchange_banner(struct ssh *);
37 int _ssh_send_banner(struct ssh *, struct sshbuf *);
38 int _ssh_read_banner(struct ssh *, struct sshbuf *);
39 int _ssh_order_hostkeyalgs(struct ssh *);
40 int _ssh_verify_host_key(struct sshkey *, struct ssh *);
41 struct sshkey *_ssh_host_public_key(int, int, struct ssh *);
42 struct sshkey *_ssh_host_private_key(int, int, struct ssh *);
43 int _ssh_host_key_sign(struct ssh *, struct sshkey *, struct sshkey *,
44 u_char **, size_t *, const u_char *, size_t, const char *);
47 * stubs for the server side implementation of kex.
48 * disable privsep so our stubs will never be called.
51 int mm_sshkey_sign(struct sshkey *, u_char **, u_int *,
52 u_char *, u_int, char *, u_int);
53 DH *mm_choose_dh(int, int, int);
55 /* Define these two variables here so that they are part of the library */
56 u_char *session_id2 = NULL;
57 u_int session_id2_len = 0;
60 mm_sshkey_sign(struct sshkey *key, u_char **sigp, u_int *lenp,
61 u_char *data, u_int datalen, char *alg, u_int compat)
67 mm_choose_dh(int min, int nbits, int max)
75 ssh_init(struct ssh **sshp, int is_server, struct kex_params *kex_params)
77 char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT };
88 if ((ssh = ssh_packet_set_connection(NULL, -1, -1)) == NULL)
89 return SSH_ERR_ALLOC_FAIL;
91 ssh_packet_set_server(ssh);
93 /* Initialize key exchange */
94 proposal = kex_params ? kex_params->proposal : myproposal;
95 if ((r = kex_ready(ssh, proposal)) != 0) {
99 ssh->kex->server = is_server;
102 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server;
103 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server;
104 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server;
105 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server;
106 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server;
107 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
108 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
109 # ifdef OPENSSL_HAS_ECC
110 ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_server;
112 #endif /* WITH_OPENSSL */
113 ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_server;
114 ssh->kex->kex[KEX_KEM_SNTRUP4591761X25519_SHA512] = kex_gen_server;
115 ssh->kex->load_host_public_key=&_ssh_host_public_key;
116 ssh->kex->load_host_private_key=&_ssh_host_private_key;
117 ssh->kex->sign=&_ssh_host_key_sign;
120 ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_client;
121 ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_client;
122 ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_client;
123 ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_client;
124 ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_client;
125 ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client;
126 ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client;
127 # ifdef OPENSSL_HAS_ECC
128 ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_client;
130 #endif /* WITH_OPENSSL */
131 ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_client;
132 ssh->kex->kex[KEX_KEM_SNTRUP4591761X25519_SHA512] = kex_gen_client;
133 ssh->kex->verify_host_key =&_ssh_verify_host_key;
140 ssh_free(struct ssh *ssh)
144 ssh_packet_close(ssh);
146 * we've only created the public keys variants in case we
147 * are a acting as a server.
149 while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) {
150 TAILQ_REMOVE(&ssh->public_keys, k, next);
151 if (ssh->kex && ssh->kex->server)
155 while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) {
156 TAILQ_REMOVE(&ssh->private_keys, k, next);
165 ssh_set_app_data(struct ssh *ssh, void *app_data)
167 ssh->app_data = app_data;
171 ssh_get_app_data(struct ssh *ssh)
173 return ssh->app_data;
176 /* Returns < 0 on error, 0 otherwise */
178 ssh_add_hostkey(struct ssh *ssh, struct sshkey *key)
180 struct sshkey *pubkey = NULL;
181 struct key_entry *k = NULL, *k_prv = NULL;
184 if (ssh->kex->server) {
185 if ((r = sshkey_from_private(key, &pubkey)) != 0)
187 if ((k = malloc(sizeof(*k))) == NULL ||
188 (k_prv = malloc(sizeof(*k_prv))) == NULL) {
191 return SSH_ERR_ALLOC_FAIL;
194 TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next);
196 /* add the public key, too */
198 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next);
201 if ((k = malloc(sizeof(*k))) == NULL)
202 return SSH_ERR_ALLOC_FAIL;
204 TAILQ_INSERT_TAIL(&ssh->public_keys, k, next);
212 ssh_set_verify_host_key_callback(struct ssh *ssh,
213 int (*cb)(struct sshkey *, struct ssh *))
215 if (cb == NULL || ssh->kex == NULL)
216 return SSH_ERR_INVALID_ARGUMENT;
218 ssh->kex->verify_host_key = cb;
224 ssh_input_append(struct ssh *ssh, const u_char *data, size_t len)
226 return sshbuf_put(ssh_packet_get_input(ssh), data, len);
230 ssh_packet_next(struct ssh *ssh, u_char *typep)
237 * Try to read a packet. Return SSH_MSG_NONE if no packet or not
240 *typep = SSH_MSG_NONE;
241 if (sshbuf_len(ssh->kex->client_version) == 0 ||
242 sshbuf_len(ssh->kex->server_version) == 0)
243 return _ssh_exchange_banner(ssh);
245 * If we enough data and a dispatch function then
246 * call the function and get the next packet.
247 * Otherwise return the packet type to the caller so it
248 * can decide how to go on.
250 * We will only call the dispatch function for:
251 * 20-29 Algorithm negotiation
252 * 30-49 Key exchange method specific (numbers can be reused for
253 * different authentication methods)
256 if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0)
258 if (type > 0 && type < DISPATCH_MAX &&
259 type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX &&
260 ssh->dispatch[type] != NULL) {
261 if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0)
271 ssh_packet_payload(struct ssh *ssh, size_t *lenp)
273 return sshpkt_ptr(ssh, lenp);
277 ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len)
281 if ((r = sshpkt_start(ssh, type)) != 0 ||
282 (r = sshpkt_put(ssh, data, len)) != 0 ||
283 (r = sshpkt_send(ssh)) != 0)
289 ssh_output_ptr(struct ssh *ssh, size_t *len)
291 struct sshbuf *output = ssh_packet_get_output(ssh);
293 *len = sshbuf_len(output);
294 return sshbuf_ptr(output);
298 ssh_output_consume(struct ssh *ssh, size_t len)
300 return sshbuf_consume(ssh_packet_get_output(ssh), len);
304 ssh_output_space(struct ssh *ssh, size_t len)
306 return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len));
310 ssh_input_space(struct ssh *ssh, size_t len)
312 return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len));
315 /* Read other side's version identification. */
317 _ssh_read_banner(struct ssh *ssh, struct sshbuf *banner)
319 struct sshbuf *input = ssh_packet_get_input(ssh);
320 const char *mismatch = "Protocol mismatch.\r\n";
321 const u_char *s = sshbuf_ptr(input);
323 char *cp, *remote_version;
324 int r, remote_major, remote_minor, expect_nl;
328 sshbuf_reset(banner);
331 if (j >= sshbuf_len(input))
332 return 0; /* insufficient data in input buf */
342 if ((r = sshbuf_put_u8(banner, c)) != 0)
344 if (sshbuf_len(banner) > SSH_MAX_BANNER_LEN)
347 if (sshbuf_len(banner) >= 4 &&
348 memcmp(sshbuf_ptr(banner), "SSH-", 4) == 0)
350 if ((cp = sshbuf_dup_string(banner)) == NULL)
351 return SSH_ERR_ALLOC_FAIL;
352 debug("%s: %s", __func__, cp);
354 /* Accept lines before banner only on client */
355 if (ssh->kex->server || ++n > SSH_MAX_PRE_BANNER_LINES) {
357 if ((r = sshbuf_put(ssh_packet_get_output(ssh),
358 mismatch, strlen(mismatch))) != 0)
360 return SSH_ERR_NO_PROTOCOL_VERSION;
363 if ((r = sshbuf_consume(input, j)) != 0)
366 if ((cp = sshbuf_dup_string(banner)) == NULL)
367 return SSH_ERR_ALLOC_FAIL;
368 /* XXX remote version must be the same size as banner for sscanf */
369 if ((remote_version = calloc(1, sshbuf_len(banner))) == NULL)
370 return SSH_ERR_ALLOC_FAIL;
373 * Check that the versions match. In future this might accept
374 * several versions and set appropriate flags to handle them.
376 if (sscanf(cp, "SSH-%d.%d-%[^\n]\n",
377 &remote_major, &remote_minor, remote_version) != 3)
378 return SSH_ERR_INVALID_FORMAT;
379 debug("Remote protocol version %d.%d, remote software version %.100s",
380 remote_major, remote_minor, remote_version);
382 ssh->compat = compat_datafellows(remote_version);
383 if (remote_major == 1 && remote_minor == 99) {
387 if (remote_major != 2)
388 return SSH_ERR_PROTOCOL_MISMATCH;
389 debug("Remote version string %.100s", cp);
394 /* Send our own protocol version identification. */
396 _ssh_send_banner(struct ssh *ssh, struct sshbuf *banner)
401 if ((r = sshbuf_putf(banner, "SSH-2.0-%.100s\r\n", SSH_VERSION)) != 0)
403 if ((r = sshbuf_putb(ssh_packet_get_output(ssh), banner)) != 0)
405 /* Remove trailing \r\n */
406 if ((r = sshbuf_consume_end(banner, 2)) != 0)
408 if ((cp = sshbuf_dup_string(banner)) == NULL)
409 return SSH_ERR_ALLOC_FAIL;
410 debug("Local version string %.100s", cp);
416 _ssh_exchange_banner(struct ssh *ssh)
418 struct kex *kex = ssh->kex;
422 * if _ssh_read_banner() cannot parse a full version string
423 * it will return NULL and we end up calling it again.
428 if (sshbuf_len(ssh->kex->server_version) == 0)
429 r = _ssh_send_banner(ssh, ssh->kex->server_version);
431 sshbuf_len(ssh->kex->server_version) != 0 &&
432 sshbuf_len(ssh->kex->client_version) == 0)
433 r = _ssh_read_banner(ssh, ssh->kex->client_version);
435 if (sshbuf_len(ssh->kex->server_version) == 0)
436 r = _ssh_read_banner(ssh, ssh->kex->server_version);
438 sshbuf_len(ssh->kex->server_version) != 0 &&
439 sshbuf_len(ssh->kex->client_version) == 0)
440 r = _ssh_send_banner(ssh, ssh->kex->client_version);
444 /* start initial kex as soon as we have exchanged the banners */
445 if (sshbuf_len(ssh->kex->server_version) != 0 &&
446 sshbuf_len(ssh->kex->client_version) != 0) {
447 if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 ||
448 (r = kex_send_kexinit(ssh)) != 0)
455 _ssh_host_public_key(int type, int nid, struct ssh *ssh)
459 debug3("%s: need %d", __func__, type);
460 TAILQ_FOREACH(k, &ssh->public_keys, next) {
461 debug3("%s: check %s", __func__, sshkey_type(k->key));
462 if (k->key->type == type &&
463 (type != KEY_ECDSA || k->key->ecdsa_nid == nid))
470 _ssh_host_private_key(int type, int nid, struct ssh *ssh)
474 debug3("%s: need %d", __func__, type);
475 TAILQ_FOREACH(k, &ssh->private_keys, next) {
476 debug3("%s: check %s", __func__, sshkey_type(k->key));
477 if (k->key->type == type &&
478 (type != KEY_ECDSA || k->key->ecdsa_nid == nid))
485 _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh)
489 debug3("%s: need %s", __func__, sshkey_type(hostkey));
490 TAILQ_FOREACH(k, &ssh->public_keys, next) {
491 debug3("%s: check %s", __func__, sshkey_type(k->key));
492 if (sshkey_equal_public(hostkey, k->key))
495 return (-1); /* failed */
498 /* offer hostkey algorithms in kexinit depending on registered keys */
500 _ssh_order_hostkeyalgs(struct ssh *ssh)
503 char *orig, *avail, *oavail = NULL, *alg, *replace = NULL;
508 /* XXX we de-serialize ssh->kex->my, modify it, and change it */
509 if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0)
511 orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS];
512 if ((oavail = avail = strdup(orig)) == NULL) {
513 r = SSH_ERR_ALLOC_FAIL;
516 maxlen = strlen(avail) + 1;
517 if ((replace = calloc(1, maxlen)) == NULL) {
518 r = SSH_ERR_ALLOC_FAIL;
522 while ((alg = strsep(&avail, ",")) && *alg != '\0') {
523 if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC)
525 TAILQ_FOREACH(k, &ssh->public_keys, next) {
526 if (k->key->type == ktype ||
527 (sshkey_is_cert(k->key) && k->key->type ==
528 sshkey_type_plain(ktype))) {
529 if (*replace != '\0')
530 strlcat(replace, ",", maxlen);
531 strlcat(replace, alg, maxlen);
536 if (*replace != '\0') {
537 debug2("%s: orig/%d %s", __func__, ssh->kex->server, orig);
538 debug2("%s: replace/%d %s", __func__, ssh->kex->server, replace);
540 proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace;
541 replace = NULL; /* owned by proposal */
542 r = kex_prop2buf(ssh->kex->my, proposal);
547 kex_prop_free(proposal);
552 _ssh_host_key_sign(struct ssh *ssh, struct sshkey *privkey,
553 struct sshkey *pubkey, u_char **signature, size_t *slen,
554 const u_char *data, size_t dlen, const char *alg)
556 return sshkey_sign(privkey, signature, slen, data, dlen,