Annotation of src/usr.bin/ssh/ssh_api.c, Revision 1.24
1.24 ! djm 1: /* $OpenBSD: ssh_api.c,v 1.23 2020/12/04 02:29:56 djm Exp $ */
1.1 markus 2: /*
3: * Copyright (c) 2012 Markus Friedl. All rights reserved.
4: *
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.
8: *
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.
16: */
1.16 djm 17:
18: #include <sys/types.h>
19:
20: #include <stdio.h>
21: #include <stdlib.h>
1.1 markus 22:
23: #include "ssh_api.h"
24: #include "compat.h"
25: #include "log.h"
26: #include "authfile.h"
27: #include "sshkey.h"
28: #include "misc.h"
29: #include "ssh2.h"
30: #include "version.h"
31: #include "myproposal.h"
32: #include "ssherr.h"
33: #include "sshbuf.h"
34:
35: #include <string.h>
36:
37: int _ssh_exchange_banner(struct ssh *);
1.9 djm 38: int _ssh_send_banner(struct ssh *, struct sshbuf *);
39: int _ssh_read_banner(struct ssh *, struct sshbuf *);
1.1 markus 40: int _ssh_order_hostkeyalgs(struct ssh *);
41: int _ssh_verify_host_key(struct sshkey *, struct ssh *);
1.2 djm 42: struct sshkey *_ssh_host_public_key(int, int, struct ssh *);
43: struct sshkey *_ssh_host_private_key(int, int, struct ssh *);
1.10 djm 44: int _ssh_host_key_sign(struct ssh *, struct sshkey *, struct sshkey *,
45: u_char **, size_t *, const u_char *, size_t, const char *);
1.1 markus 46:
47: /*
48: * stubs for the server side implementation of kex.
49: * disable privsep so our stubs will never be called.
50: */
51: int use_privsep = 0;
52: int mm_sshkey_sign(struct sshkey *, u_char **, u_int *,
1.21 djm 53: const u_char *, u_int, const char *, const char *, const char *, u_int);
1.17 djm 54:
55: #ifdef WITH_OPENSSL
1.1 markus 56: DH *mm_choose_dh(int, int, int);
1.17 djm 57: #endif
1.1 markus 58:
59: /* Define these two variables here so that they are part of the library */
60: u_char *session_id2 = NULL;
61: u_int session_id2_len = 0;
62:
63: int
64: mm_sshkey_sign(struct sshkey *key, u_char **sigp, u_int *lenp,
1.21 djm 65: const u_char *data, u_int datalen, const char *alg,
66: const char *sk_provider, const char *sk_pin, u_int compat)
1.1 markus 67: {
68: return (-1);
69: }
70:
1.17 djm 71: #ifdef WITH_OPENSSL
1.1 markus 72: DH *
73: mm_choose_dh(int min, int nbits, int max)
74: {
75: return (NULL);
76: }
1.17 djm 77: #endif
1.1 markus 78:
79: /* API */
80:
81: int
82: ssh_init(struct ssh **sshp, int is_server, struct kex_params *kex_params)
83: {
84: char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT };
85: struct ssh *ssh;
86: char **proposal;
87: static int called;
88: int r;
89:
90: if (!called) {
1.17 djm 91: #ifdef WITH_OPENSSL
1.1 markus 92: OpenSSL_add_all_algorithms();
1.17 djm 93: #endif
1.1 markus 94: called = 1;
95: }
96:
1.3 djm 97: if ((ssh = ssh_packet_set_connection(NULL, -1, -1)) == NULL)
98: return SSH_ERR_ALLOC_FAIL;
1.1 markus 99: if (is_server)
100: ssh_packet_set_server(ssh);
101:
102: /* Initialize key exchange */
103: proposal = kex_params ? kex_params->proposal : myproposal;
1.9 djm 104: if ((r = kex_ready(ssh, proposal)) != 0) {
1.1 markus 105: ssh_free(ssh);
106: return r;
107: }
108: ssh->kex->server = is_server;
109: if (is_server) {
110: #ifdef WITH_OPENSSL
1.15 djm 111: ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server;
112: ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server;
113: ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server;
114: ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server;
115: ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server;
1.1 markus 116: ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
117: ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
1.15 djm 118: ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_server;
1.1 markus 119: #endif /* WITH_OPENSSL */
1.15 djm 120: ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_server;
1.24 ! djm 121: ssh->kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_server;
1.1 markus 122: ssh->kex->load_host_public_key=&_ssh_host_public_key;
123: ssh->kex->load_host_private_key=&_ssh_host_private_key;
124: ssh->kex->sign=&_ssh_host_key_sign;
125: } else {
126: #ifdef WITH_OPENSSL
1.15 djm 127: ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_client;
128: ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_client;
129: ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_client;
130: ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_client;
131: ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_client;
1.1 markus 132: ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client;
133: ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client;
1.15 djm 134: ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_client;
1.1 markus 135: #endif /* WITH_OPENSSL */
1.15 djm 136: ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_client;
1.24 ! djm 137: ssh->kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_client;
1.1 markus 138: ssh->kex->verify_host_key =&_ssh_verify_host_key;
139: }
140: *sshp = ssh;
141: return 0;
142: }
143:
144: void
145: ssh_free(struct ssh *ssh)
146: {
147: struct key_entry *k;
1.23 djm 148:
149: if (ssh == NULL)
150: return;
1.1 markus 151:
152: /*
153: * we've only created the public keys variants in case we
154: * are a acting as a server.
155: */
156: while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) {
157: TAILQ_REMOVE(&ssh->public_keys, k, next);
158: if (ssh->kex && ssh->kex->server)
159: sshkey_free(k->key);
160: free(k);
161: }
162: while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) {
163: TAILQ_REMOVE(&ssh->private_keys, k, next);
164: free(k);
165: }
1.20 markus 166: ssh_packet_close(ssh);
1.1 markus 167: free(ssh);
168: }
169:
170: void
171: ssh_set_app_data(struct ssh *ssh, void *app_data)
172: {
173: ssh->app_data = app_data;
174: }
175:
176: void *
177: ssh_get_app_data(struct ssh *ssh)
178: {
179: return ssh->app_data;
180: }
181:
182: /* Returns < 0 on error, 0 otherwise */
183: int
184: ssh_add_hostkey(struct ssh *ssh, struct sshkey *key)
185: {
186: struct sshkey *pubkey = NULL;
187: struct key_entry *k = NULL, *k_prv = NULL;
188: int r;
189:
190: if (ssh->kex->server) {
191: if ((r = sshkey_from_private(key, &pubkey)) != 0)
192: return r;
193: if ((k = malloc(sizeof(*k))) == NULL ||
194: (k_prv = malloc(sizeof(*k_prv))) == NULL) {
195: free(k);
196: sshkey_free(pubkey);
197: return SSH_ERR_ALLOC_FAIL;
198: }
199: k_prv->key = key;
200: TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next);
201:
202: /* add the public key, too */
203: k->key = pubkey;
204: TAILQ_INSERT_TAIL(&ssh->public_keys, k, next);
205: r = 0;
206: } else {
207: if ((k = malloc(sizeof(*k))) == NULL)
208: return SSH_ERR_ALLOC_FAIL;
209: k->key = key;
210: TAILQ_INSERT_TAIL(&ssh->public_keys, k, next);
211: r = 0;
212: }
213:
214: return r;
215: }
216:
217: int
218: ssh_set_verify_host_key_callback(struct ssh *ssh,
219: int (*cb)(struct sshkey *, struct ssh *))
220: {
221: if (cb == NULL || ssh->kex == NULL)
222: return SSH_ERR_INVALID_ARGUMENT;
223:
224: ssh->kex->verify_host_key = cb;
225:
226: return 0;
227: }
228:
229: int
230: ssh_input_append(struct ssh *ssh, const u_char *data, size_t len)
231: {
232: return sshbuf_put(ssh_packet_get_input(ssh), data, len);
233: }
234:
235: int
236: ssh_packet_next(struct ssh *ssh, u_char *typep)
237: {
238: int r;
239: u_int32_t seqnr;
240: u_char type;
241:
242: /*
243: * Try to read a packet. Return SSH_MSG_NONE if no packet or not
244: * enough data.
245: */
246: *typep = SSH_MSG_NONE;
1.9 djm 247: if (sshbuf_len(ssh->kex->client_version) == 0 ||
248: sshbuf_len(ssh->kex->server_version) == 0)
1.1 markus 249: return _ssh_exchange_banner(ssh);
250: /*
251: * If we enough data and a dispatch function then
252: * call the function and get the next packet.
253: * Otherwise return the packet type to the caller so it
254: * can decide how to go on.
255: *
256: * We will only call the dispatch function for:
257: * 20-29 Algorithm negotiation
258: * 30-49 Key exchange method specific (numbers can be reused for
259: * different authentication methods)
260: */
261: for (;;) {
262: if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0)
263: return r;
264: if (type > 0 && type < DISPATCH_MAX &&
265: type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX &&
266: ssh->dispatch[type] != NULL) {
267: if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0)
268: return r;
269: } else {
270: *typep = type;
271: return 0;
272: }
273: }
274: }
275:
276: const u_char *
277: ssh_packet_payload(struct ssh *ssh, size_t *lenp)
278: {
279: return sshpkt_ptr(ssh, lenp);
280: }
281:
282: int
283: ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len)
284: {
285: int r;
286:
287: if ((r = sshpkt_start(ssh, type)) != 0 ||
288: (r = sshpkt_put(ssh, data, len)) != 0 ||
289: (r = sshpkt_send(ssh)) != 0)
290: return r;
291: return 0;
292: }
293:
294: const u_char *
295: ssh_output_ptr(struct ssh *ssh, size_t *len)
296: {
297: struct sshbuf *output = ssh_packet_get_output(ssh);
298:
299: *len = sshbuf_len(output);
300: return sshbuf_ptr(output);
301: }
302:
303: int
304: ssh_output_consume(struct ssh *ssh, size_t len)
305: {
306: return sshbuf_consume(ssh_packet_get_output(ssh), len);
307: }
308:
309: int
310: ssh_output_space(struct ssh *ssh, size_t len)
311: {
312: return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len));
313: }
314:
315: int
316: ssh_input_space(struct ssh *ssh, size_t len)
317: {
318: return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len));
319: }
320:
321: /* Read other side's version identification. */
322: int
1.9 djm 323: _ssh_read_banner(struct ssh *ssh, struct sshbuf *banner)
1.1 markus 324: {
1.9 djm 325: struct sshbuf *input = ssh_packet_get_input(ssh);
1.1 markus 326: const char *mismatch = "Protocol mismatch.\r\n";
1.9 djm 327: const u_char *s = sshbuf_ptr(input);
328: u_char c;
1.18 dtucker 329: char *cp = NULL, *remote_version = NULL;
330: int r = 0, remote_major, remote_minor, expect_nl;
1.9 djm 331: size_t n, j;
1.1 markus 332:
333: for (j = n = 0;;) {
1.9 djm 334: sshbuf_reset(banner);
335: expect_nl = 0;
336: for (;;) {
337: if (j >= sshbuf_len(input))
338: return 0; /* insufficient data in input buf */
339: c = s[j++];
340: if (c == '\r') {
341: expect_nl = 1;
342: continue;
1.1 markus 343: }
1.9 djm 344: if (c == '\n')
1.1 markus 345: break;
1.9 djm 346: if (expect_nl)
347: goto bad;
348: if ((r = sshbuf_put_u8(banner, c)) != 0)
349: return r;
350: if (sshbuf_len(banner) > SSH_MAX_BANNER_LEN)
351: goto bad;
1.1 markus 352: }
1.9 djm 353: if (sshbuf_len(banner) >= 4 &&
354: memcmp(sshbuf_ptr(banner), "SSH-", 4) == 0)
1.1 markus 355: break;
1.22 djm 356: debug_f("%.*s", (int)sshbuf_len(banner),
1.18 dtucker 357: sshbuf_ptr(banner));
1.9 djm 358: /* Accept lines before banner only on client */
359: if (ssh->kex->server || ++n > SSH_MAX_PRE_BANNER_LINES) {
360: bad:
1.1 markus 361: if ((r = sshbuf_put(ssh_packet_get_output(ssh),
362: mismatch, strlen(mismatch))) != 0)
363: return r;
364: return SSH_ERR_NO_PROTOCOL_VERSION;
365: }
366: }
367: if ((r = sshbuf_consume(input, j)) != 0)
368: return r;
369:
1.9 djm 370: /* XXX remote version must be the same size as banner for sscanf */
1.18 dtucker 371: if ((cp = sshbuf_dup_string(banner)) == NULL ||
372: (remote_version = calloc(1, sshbuf_len(banner))) == NULL) {
373: r = SSH_ERR_ALLOC_FAIL;
374: goto out;
375: }
1.9 djm 376:
1.1 markus 377: /*
378: * Check that the versions match. In future this might accept
379: * several versions and set appropriate flags to handle them.
380: */
1.9 djm 381: if (sscanf(cp, "SSH-%d.%d-%[^\n]\n",
1.18 dtucker 382: &remote_major, &remote_minor, remote_version) != 3) {
383: r = SSH_ERR_INVALID_FORMAT;
384: goto out;
385: }
1.1 markus 386: debug("Remote protocol version %d.%d, remote software version %.100s",
387: remote_major, remote_minor, remote_version);
388:
389: ssh->compat = compat_datafellows(remote_version);
390: if (remote_major == 1 && remote_minor == 99) {
391: remote_major = 2;
392: remote_minor = 0;
393: }
394: if (remote_major != 2)
1.18 dtucker 395: r = SSH_ERR_PROTOCOL_MISMATCH;
396:
1.9 djm 397: debug("Remote version string %.100s", cp);
1.18 dtucker 398: out:
1.9 djm 399: free(cp);
1.18 dtucker 400: free(remote_version);
401: return r;
1.1 markus 402: }
403:
404: /* Send our own protocol version identification. */
405: int
1.9 djm 406: _ssh_send_banner(struct ssh *ssh, struct sshbuf *banner)
1.1 markus 407: {
1.9 djm 408: char *cp;
1.1 markus 409: int r;
410:
1.9 djm 411: if ((r = sshbuf_putf(banner, "SSH-2.0-%.100s\r\n", SSH_VERSION)) != 0)
412: return r;
413: if ((r = sshbuf_putb(ssh_packet_get_output(ssh), banner)) != 0)
414: return r;
415: /* Remove trailing \r\n */
416: if ((r = sshbuf_consume_end(banner, 2)) != 0)
1.1 markus 417: return r;
1.9 djm 418: if ((cp = sshbuf_dup_string(banner)) == NULL)
1.1 markus 419: return SSH_ERR_ALLOC_FAIL;
1.9 djm 420: debug("Local version string %.100s", cp);
421: free(cp);
1.1 markus 422: return 0;
423: }
424:
425: int
426: _ssh_exchange_banner(struct ssh *ssh)
427: {
428: struct kex *kex = ssh->kex;
429: int r;
430:
431: /*
432: * if _ssh_read_banner() cannot parse a full version string
433: * it will return NULL and we end up calling it again.
434: */
435:
436: r = 0;
437: if (kex->server) {
1.9 djm 438: if (sshbuf_len(ssh->kex->server_version) == 0)
439: r = _ssh_send_banner(ssh, ssh->kex->server_version);
1.1 markus 440: if (r == 0 &&
1.9 djm 441: sshbuf_len(ssh->kex->server_version) != 0 &&
442: sshbuf_len(ssh->kex->client_version) == 0)
443: r = _ssh_read_banner(ssh, ssh->kex->client_version);
1.1 markus 444: } else {
1.9 djm 445: if (sshbuf_len(ssh->kex->server_version) == 0)
446: r = _ssh_read_banner(ssh, ssh->kex->server_version);
1.1 markus 447: if (r == 0 &&
1.9 djm 448: sshbuf_len(ssh->kex->server_version) != 0 &&
449: sshbuf_len(ssh->kex->client_version) == 0)
450: r = _ssh_send_banner(ssh, ssh->kex->client_version);
1.1 markus 451: }
452: if (r != 0)
453: return r;
454: /* start initial kex as soon as we have exchanged the banners */
1.9 djm 455: if (sshbuf_len(ssh->kex->server_version) != 0 &&
456: sshbuf_len(ssh->kex->client_version) != 0) {
1.1 markus 457: if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 ||
458: (r = kex_send_kexinit(ssh)) != 0)
459: return r;
460: }
461: return 0;
462: }
463:
464: struct sshkey *
1.2 djm 465: _ssh_host_public_key(int type, int nid, struct ssh *ssh)
1.1 markus 466: {
467: struct key_entry *k;
468:
1.22 djm 469: debug3_f("need %d", type);
1.1 markus 470: TAILQ_FOREACH(k, &ssh->public_keys, next) {
1.22 djm 471: debug3_f("check %s", sshkey_type(k->key));
1.2 djm 472: if (k->key->type == type &&
473: (type != KEY_ECDSA || k->key->ecdsa_nid == nid))
1.1 markus 474: return (k->key);
475: }
476: return (NULL);
477: }
478:
479: struct sshkey *
1.2 djm 480: _ssh_host_private_key(int type, int nid, struct ssh *ssh)
1.1 markus 481: {
482: struct key_entry *k;
483:
1.22 djm 484: debug3_f("need %d", type);
1.1 markus 485: TAILQ_FOREACH(k, &ssh->private_keys, next) {
1.22 djm 486: debug3_f("check %s", sshkey_type(k->key));
1.2 djm 487: if (k->key->type == type &&
488: (type != KEY_ECDSA || k->key->ecdsa_nid == nid))
1.1 markus 489: return (k->key);
490: }
491: return (NULL);
492: }
493:
494: int
495: _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh)
496: {
497: struct key_entry *k;
498:
1.22 djm 499: debug3_f("need %s", sshkey_type(hostkey));
1.1 markus 500: TAILQ_FOREACH(k, &ssh->public_keys, next) {
1.22 djm 501: debug3_f("check %s", sshkey_type(k->key));
1.1 markus 502: if (sshkey_equal_public(hostkey, k->key))
503: return (0); /* ok */
504: }
505: return (-1); /* failed */
506: }
507:
508: /* offer hostkey algorithms in kexinit depending on registered keys */
509: int
510: _ssh_order_hostkeyalgs(struct ssh *ssh)
511: {
512: struct key_entry *k;
513: char *orig, *avail, *oavail = NULL, *alg, *replace = NULL;
514: char **proposal;
515: size_t maxlen;
516: int ktype, r;
517:
518: /* XXX we de-serialize ssh->kex->my, modify it, and change it */
519: if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0)
520: return r;
521: orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS];
522: if ((oavail = avail = strdup(orig)) == NULL) {
523: r = SSH_ERR_ALLOC_FAIL;
524: goto out;
525: }
526: maxlen = strlen(avail) + 1;
527: if ((replace = calloc(1, maxlen)) == NULL) {
528: r = SSH_ERR_ALLOC_FAIL;
529: goto out;
530: }
531: *replace = '\0';
532: while ((alg = strsep(&avail, ",")) && *alg != '\0') {
533: if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC)
534: continue;
535: TAILQ_FOREACH(k, &ssh->public_keys, next) {
536: if (k->key->type == ktype ||
537: (sshkey_is_cert(k->key) && k->key->type ==
538: sshkey_type_plain(ktype))) {
539: if (*replace != '\0')
540: strlcat(replace, ",", maxlen);
541: strlcat(replace, alg, maxlen);
542: break;
543: }
544: }
545: }
546: if (*replace != '\0') {
1.22 djm 547: debug2_f("orig/%d %s", ssh->kex->server, orig);
548: debug2_f("replace/%d %s", ssh->kex->server, replace);
1.1 markus 549: free(orig);
550: proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace;
551: replace = NULL; /* owned by proposal */
552: r = kex_prop2buf(ssh->kex->my, proposal);
553: }
554: out:
555: free(oavail);
556: free(replace);
557: kex_prop_free(proposal);
558: return r;
559: }
560:
561: int
1.10 djm 562: _ssh_host_key_sign(struct ssh *ssh, struct sshkey *privkey,
563: struct sshkey *pubkey, u_char **signature, size_t *slen,
564: const u_char *data, size_t dlen, const char *alg)
1.1 markus 565: {
1.10 djm 566: return sshkey_sign(privkey, signature, slen, data, dlen,
1.21 djm 567: alg, NULL, NULL, ssh->compat);
1.1 markus 568: }
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