Annotation of src/usr.bin/ssh/ssh_api.c, Revision 1.26
1.26 ! djm 1: /* $OpenBSD: ssh_api.c,v 1.25 2021/01/27 09:26:54 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: int
60: mm_sshkey_sign(struct sshkey *key, u_char **sigp, u_int *lenp,
1.21 djm 61: const u_char *data, u_int datalen, const char *alg,
62: const char *sk_provider, const char *sk_pin, u_int compat)
1.1 markus 63: {
64: return (-1);
65: }
66:
1.17 djm 67: #ifdef WITH_OPENSSL
1.1 markus 68: DH *
69: mm_choose_dh(int min, int nbits, int max)
70: {
71: return (NULL);
72: }
1.17 djm 73: #endif
1.1 markus 74:
75: /* API */
76:
77: int
78: ssh_init(struct ssh **sshp, int is_server, struct kex_params *kex_params)
79: {
80: char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT };
81: struct ssh *ssh;
82: char **proposal;
83: static int called;
84: int r;
85:
86: if (!called) {
1.17 djm 87: #ifdef WITH_OPENSSL
1.1 markus 88: OpenSSL_add_all_algorithms();
1.17 djm 89: #endif
1.1 markus 90: called = 1;
91: }
92:
1.3 djm 93: if ((ssh = ssh_packet_set_connection(NULL, -1, -1)) == NULL)
94: return SSH_ERR_ALLOC_FAIL;
1.1 markus 95: if (is_server)
96: ssh_packet_set_server(ssh);
97:
98: /* Initialize key exchange */
99: proposal = kex_params ? kex_params->proposal : myproposal;
1.9 djm 100: if ((r = kex_ready(ssh, proposal)) != 0) {
1.1 markus 101: ssh_free(ssh);
102: return r;
103: }
104: ssh->kex->server = is_server;
105: if (is_server) {
106: #ifdef WITH_OPENSSL
1.15 djm 107: ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server;
108: ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server;
109: ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server;
110: ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server;
111: ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server;
1.1 markus 112: ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
113: ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
1.15 djm 114: ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_server;
1.1 markus 115: #endif /* WITH_OPENSSL */
1.15 djm 116: ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_server;
1.24 djm 117: ssh->kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_server;
1.1 markus 118: ssh->kex->load_host_public_key=&_ssh_host_public_key;
119: ssh->kex->load_host_private_key=&_ssh_host_private_key;
120: ssh->kex->sign=&_ssh_host_key_sign;
121: } else {
122: #ifdef WITH_OPENSSL
1.15 djm 123: ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_client;
124: ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_client;
125: ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_client;
126: ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_client;
127: ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_client;
1.1 markus 128: ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client;
129: ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client;
1.15 djm 130: ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_client;
1.1 markus 131: #endif /* WITH_OPENSSL */
1.15 djm 132: ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_client;
1.24 djm 133: ssh->kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_client;
1.1 markus 134: ssh->kex->verify_host_key =&_ssh_verify_host_key;
135: }
136: *sshp = ssh;
137: return 0;
138: }
139:
140: void
141: ssh_free(struct ssh *ssh)
142: {
143: struct key_entry *k;
1.23 djm 144:
145: if (ssh == NULL)
146: return;
1.1 markus 147:
148: /*
149: * we've only created the public keys variants in case we
150: * are a acting as a server.
151: */
152: while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) {
153: TAILQ_REMOVE(&ssh->public_keys, k, next);
154: if (ssh->kex && ssh->kex->server)
155: sshkey_free(k->key);
156: free(k);
157: }
158: while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) {
159: TAILQ_REMOVE(&ssh->private_keys, k, next);
160: free(k);
161: }
1.20 markus 162: ssh_packet_close(ssh);
1.1 markus 163: free(ssh);
164: }
165:
166: void
167: ssh_set_app_data(struct ssh *ssh, void *app_data)
168: {
169: ssh->app_data = app_data;
170: }
171:
172: void *
173: ssh_get_app_data(struct ssh *ssh)
174: {
175: return ssh->app_data;
176: }
177:
178: /* Returns < 0 on error, 0 otherwise */
179: int
180: ssh_add_hostkey(struct ssh *ssh, struct sshkey *key)
181: {
182: struct sshkey *pubkey = NULL;
183: struct key_entry *k = NULL, *k_prv = NULL;
184: int r;
185:
186: if (ssh->kex->server) {
187: if ((r = sshkey_from_private(key, &pubkey)) != 0)
188: return r;
189: if ((k = malloc(sizeof(*k))) == NULL ||
190: (k_prv = malloc(sizeof(*k_prv))) == NULL) {
191: free(k);
192: sshkey_free(pubkey);
193: return SSH_ERR_ALLOC_FAIL;
194: }
195: k_prv->key = key;
196: TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next);
197:
198: /* add the public key, too */
199: k->key = pubkey;
200: TAILQ_INSERT_TAIL(&ssh->public_keys, k, next);
201: r = 0;
202: } else {
203: if ((k = malloc(sizeof(*k))) == NULL)
204: return SSH_ERR_ALLOC_FAIL;
205: k->key = key;
206: TAILQ_INSERT_TAIL(&ssh->public_keys, k, next);
207: r = 0;
208: }
209:
210: return r;
211: }
212:
213: int
214: ssh_set_verify_host_key_callback(struct ssh *ssh,
215: int (*cb)(struct sshkey *, struct ssh *))
216: {
217: if (cb == NULL || ssh->kex == NULL)
218: return SSH_ERR_INVALID_ARGUMENT;
219:
220: ssh->kex->verify_host_key = cb;
221:
222: return 0;
223: }
224:
225: int
226: ssh_input_append(struct ssh *ssh, const u_char *data, size_t len)
227: {
228: return sshbuf_put(ssh_packet_get_input(ssh), data, len);
229: }
230:
231: int
232: ssh_packet_next(struct ssh *ssh, u_char *typep)
233: {
234: int r;
235: u_int32_t seqnr;
236: u_char type;
237:
238: /*
239: * Try to read a packet. Return SSH_MSG_NONE if no packet or not
240: * enough data.
241: */
242: *typep = SSH_MSG_NONE;
1.9 djm 243: if (sshbuf_len(ssh->kex->client_version) == 0 ||
244: sshbuf_len(ssh->kex->server_version) == 0)
1.1 markus 245: return _ssh_exchange_banner(ssh);
246: /*
247: * If we enough data and a dispatch function then
248: * call the function and get the next packet.
249: * Otherwise return the packet type to the caller so it
250: * can decide how to go on.
251: *
252: * We will only call the dispatch function for:
253: * 20-29 Algorithm negotiation
254: * 30-49 Key exchange method specific (numbers can be reused for
255: * different authentication methods)
256: */
257: for (;;) {
258: if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0)
259: return r;
260: if (type > 0 && type < DISPATCH_MAX &&
261: type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX &&
262: ssh->dispatch[type] != NULL) {
263: if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0)
264: return r;
265: } else {
266: *typep = type;
267: return 0;
268: }
269: }
270: }
271:
272: const u_char *
273: ssh_packet_payload(struct ssh *ssh, size_t *lenp)
274: {
275: return sshpkt_ptr(ssh, lenp);
276: }
277:
278: int
279: ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len)
280: {
281: int r;
282:
283: if ((r = sshpkt_start(ssh, type)) != 0 ||
284: (r = sshpkt_put(ssh, data, len)) != 0 ||
285: (r = sshpkt_send(ssh)) != 0)
286: return r;
287: return 0;
288: }
289:
290: const u_char *
291: ssh_output_ptr(struct ssh *ssh, size_t *len)
292: {
293: struct sshbuf *output = ssh_packet_get_output(ssh);
294:
295: *len = sshbuf_len(output);
296: return sshbuf_ptr(output);
297: }
298:
299: int
300: ssh_output_consume(struct ssh *ssh, size_t len)
301: {
302: return sshbuf_consume(ssh_packet_get_output(ssh), len);
303: }
304:
305: int
306: ssh_output_space(struct ssh *ssh, size_t len)
307: {
308: return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len));
309: }
310:
311: int
312: ssh_input_space(struct ssh *ssh, size_t len)
313: {
314: return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len));
315: }
316:
317: /* Read other side's version identification. */
318: int
1.9 djm 319: _ssh_read_banner(struct ssh *ssh, struct sshbuf *banner)
1.1 markus 320: {
1.9 djm 321: struct sshbuf *input = ssh_packet_get_input(ssh);
1.1 markus 322: const char *mismatch = "Protocol mismatch.\r\n";
1.9 djm 323: const u_char *s = sshbuf_ptr(input);
324: u_char c;
1.18 dtucker 325: char *cp = NULL, *remote_version = NULL;
326: int r = 0, remote_major, remote_minor, expect_nl;
1.9 djm 327: size_t n, j;
1.1 markus 328:
329: for (j = n = 0;;) {
1.9 djm 330: sshbuf_reset(banner);
331: expect_nl = 0;
332: for (;;) {
333: if (j >= sshbuf_len(input))
334: return 0; /* insufficient data in input buf */
335: c = s[j++];
336: if (c == '\r') {
337: expect_nl = 1;
338: continue;
1.1 markus 339: }
1.9 djm 340: if (c == '\n')
1.1 markus 341: break;
1.9 djm 342: if (expect_nl)
343: goto bad;
344: if ((r = sshbuf_put_u8(banner, c)) != 0)
345: return r;
346: if (sshbuf_len(banner) > SSH_MAX_BANNER_LEN)
347: goto bad;
1.1 markus 348: }
1.9 djm 349: if (sshbuf_len(banner) >= 4 &&
350: memcmp(sshbuf_ptr(banner), "SSH-", 4) == 0)
1.1 markus 351: break;
1.22 djm 352: debug_f("%.*s", (int)sshbuf_len(banner),
1.18 dtucker 353: sshbuf_ptr(banner));
1.9 djm 354: /* Accept lines before banner only on client */
355: if (ssh->kex->server || ++n > SSH_MAX_PRE_BANNER_LINES) {
356: bad:
1.1 markus 357: if ((r = sshbuf_put(ssh_packet_get_output(ssh),
358: mismatch, strlen(mismatch))) != 0)
359: return r;
360: return SSH_ERR_NO_PROTOCOL_VERSION;
361: }
362: }
363: if ((r = sshbuf_consume(input, j)) != 0)
364: return r;
365:
1.9 djm 366: /* XXX remote version must be the same size as banner for sscanf */
1.18 dtucker 367: if ((cp = sshbuf_dup_string(banner)) == NULL ||
368: (remote_version = calloc(1, sshbuf_len(banner))) == NULL) {
369: r = SSH_ERR_ALLOC_FAIL;
370: goto out;
371: }
1.9 djm 372:
1.1 markus 373: /*
374: * Check that the versions match. In future this might accept
375: * several versions and set appropriate flags to handle them.
376: */
1.9 djm 377: if (sscanf(cp, "SSH-%d.%d-%[^\n]\n",
1.18 dtucker 378: &remote_major, &remote_minor, remote_version) != 3) {
379: r = SSH_ERR_INVALID_FORMAT;
380: goto out;
381: }
1.1 markus 382: debug("Remote protocol version %d.%d, remote software version %.100s",
383: remote_major, remote_minor, remote_version);
384:
1.25 djm 385: compat_banner(ssh, remote_version);
1.1 markus 386: if (remote_major == 1 && remote_minor == 99) {
387: remote_major = 2;
388: remote_minor = 0;
389: }
390: if (remote_major != 2)
1.18 dtucker 391: r = SSH_ERR_PROTOCOL_MISMATCH;
392:
1.9 djm 393: debug("Remote version string %.100s", cp);
1.18 dtucker 394: out:
1.9 djm 395: free(cp);
1.18 dtucker 396: free(remote_version);
397: return r;
1.1 markus 398: }
399:
400: /* Send our own protocol version identification. */
401: int
1.9 djm 402: _ssh_send_banner(struct ssh *ssh, struct sshbuf *banner)
1.1 markus 403: {
1.9 djm 404: char *cp;
1.1 markus 405: int r;
406:
1.9 djm 407: if ((r = sshbuf_putf(banner, "SSH-2.0-%.100s\r\n", SSH_VERSION)) != 0)
408: return r;
409: if ((r = sshbuf_putb(ssh_packet_get_output(ssh), banner)) != 0)
410: return r;
411: /* Remove trailing \r\n */
412: if ((r = sshbuf_consume_end(banner, 2)) != 0)
1.1 markus 413: return r;
1.9 djm 414: if ((cp = sshbuf_dup_string(banner)) == NULL)
1.1 markus 415: return SSH_ERR_ALLOC_FAIL;
1.9 djm 416: debug("Local version string %.100s", cp);
417: free(cp);
1.1 markus 418: return 0;
419: }
420:
421: int
422: _ssh_exchange_banner(struct ssh *ssh)
423: {
424: struct kex *kex = ssh->kex;
425: int r;
426:
427: /*
428: * if _ssh_read_banner() cannot parse a full version string
429: * it will return NULL and we end up calling it again.
430: */
431:
432: r = 0;
433: if (kex->server) {
1.9 djm 434: if (sshbuf_len(ssh->kex->server_version) == 0)
435: r = _ssh_send_banner(ssh, ssh->kex->server_version);
1.1 markus 436: if (r == 0 &&
1.9 djm 437: sshbuf_len(ssh->kex->server_version) != 0 &&
438: sshbuf_len(ssh->kex->client_version) == 0)
439: r = _ssh_read_banner(ssh, ssh->kex->client_version);
1.1 markus 440: } else {
1.9 djm 441: if (sshbuf_len(ssh->kex->server_version) == 0)
442: r = _ssh_read_banner(ssh, ssh->kex->server_version);
1.1 markus 443: if (r == 0 &&
1.9 djm 444: sshbuf_len(ssh->kex->server_version) != 0 &&
445: sshbuf_len(ssh->kex->client_version) == 0)
446: r = _ssh_send_banner(ssh, ssh->kex->client_version);
1.1 markus 447: }
448: if (r != 0)
449: return r;
450: /* start initial kex as soon as we have exchanged the banners */
1.9 djm 451: if (sshbuf_len(ssh->kex->server_version) != 0 &&
452: sshbuf_len(ssh->kex->client_version) != 0) {
1.1 markus 453: if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 ||
454: (r = kex_send_kexinit(ssh)) != 0)
455: return r;
456: }
457: return 0;
458: }
459:
460: struct sshkey *
1.2 djm 461: _ssh_host_public_key(int type, int nid, struct ssh *ssh)
1.1 markus 462: {
463: struct key_entry *k;
464:
1.22 djm 465: debug3_f("need %d", type);
1.1 markus 466: TAILQ_FOREACH(k, &ssh->public_keys, next) {
1.22 djm 467: debug3_f("check %s", sshkey_type(k->key));
1.2 djm 468: if (k->key->type == type &&
469: (type != KEY_ECDSA || k->key->ecdsa_nid == nid))
1.1 markus 470: return (k->key);
471: }
472: return (NULL);
473: }
474:
475: struct sshkey *
1.2 djm 476: _ssh_host_private_key(int type, int nid, struct ssh *ssh)
1.1 markus 477: {
478: struct key_entry *k;
479:
1.22 djm 480: debug3_f("need %d", type);
1.1 markus 481: TAILQ_FOREACH(k, &ssh->private_keys, next) {
1.22 djm 482: debug3_f("check %s", sshkey_type(k->key));
1.2 djm 483: if (k->key->type == type &&
484: (type != KEY_ECDSA || k->key->ecdsa_nid == nid))
1.1 markus 485: return (k->key);
486: }
487: return (NULL);
488: }
489:
490: int
491: _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh)
492: {
493: struct key_entry *k;
494:
1.22 djm 495: debug3_f("need %s", sshkey_type(hostkey));
1.1 markus 496: TAILQ_FOREACH(k, &ssh->public_keys, next) {
1.22 djm 497: debug3_f("check %s", sshkey_type(k->key));
1.1 markus 498: if (sshkey_equal_public(hostkey, k->key))
499: return (0); /* ok */
500: }
501: return (-1); /* failed */
502: }
503:
504: /* offer hostkey algorithms in kexinit depending on registered keys */
505: int
506: _ssh_order_hostkeyalgs(struct ssh *ssh)
507: {
508: struct key_entry *k;
509: char *orig, *avail, *oavail = NULL, *alg, *replace = NULL;
510: char **proposal;
511: size_t maxlen;
512: int ktype, r;
513:
514: /* XXX we de-serialize ssh->kex->my, modify it, and change it */
515: if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0)
516: return r;
517: orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS];
518: if ((oavail = avail = strdup(orig)) == NULL) {
519: r = SSH_ERR_ALLOC_FAIL;
520: goto out;
521: }
522: maxlen = strlen(avail) + 1;
523: if ((replace = calloc(1, maxlen)) == NULL) {
524: r = SSH_ERR_ALLOC_FAIL;
525: goto out;
526: }
527: *replace = '\0';
528: while ((alg = strsep(&avail, ",")) && *alg != '\0') {
529: if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC)
530: continue;
531: TAILQ_FOREACH(k, &ssh->public_keys, next) {
532: if (k->key->type == ktype ||
533: (sshkey_is_cert(k->key) && k->key->type ==
534: sshkey_type_plain(ktype))) {
535: if (*replace != '\0')
536: strlcat(replace, ",", maxlen);
537: strlcat(replace, alg, maxlen);
538: break;
539: }
540: }
541: }
542: if (*replace != '\0') {
1.22 djm 543: debug2_f("orig/%d %s", ssh->kex->server, orig);
544: debug2_f("replace/%d %s", ssh->kex->server, replace);
1.1 markus 545: free(orig);
546: proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace;
547: replace = NULL; /* owned by proposal */
548: r = kex_prop2buf(ssh->kex->my, proposal);
549: }
550: out:
551: free(oavail);
552: free(replace);
553: kex_prop_free(proposal);
554: return r;
555: }
556:
557: int
1.10 djm 558: _ssh_host_key_sign(struct ssh *ssh, struct sshkey *privkey,
559: struct sshkey *pubkey, u_char **signature, size_t *slen,
560: const u_char *data, size_t dlen, const char *alg)
1.1 markus 561: {
1.10 djm 562: return sshkey_sign(privkey, signature, slen, data, dlen,
1.21 djm 563: alg, NULL, NULL, ssh->compat);
1.1 markus 564: }
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