Annotation of src/usr.bin/ssh/ssh_api.c, Revision 1.21
1.21 ! djm 1: /* $OpenBSD: ssh_api.c,v 1.20 2020/07/01 16:28:31 markus 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;
121: ssh->kex->kex[KEX_KEM_SNTRUP4591761X25519_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;
137: ssh->kex->kex[KEX_KEM_SNTRUP4591761X25519_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;
148:
149: /*
150: * we've only created the public keys variants in case we
151: * are a acting as a server.
152: */
153: while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) {
154: TAILQ_REMOVE(&ssh->public_keys, k, next);
155: if (ssh->kex && ssh->kex->server)
156: sshkey_free(k->key);
157: free(k);
158: }
159: while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) {
160: TAILQ_REMOVE(&ssh->private_keys, k, next);
161: free(k);
162: }
1.20 markus 163: ssh_packet_close(ssh);
1.1 markus 164: free(ssh);
165: }
166:
167: void
168: ssh_set_app_data(struct ssh *ssh, void *app_data)
169: {
170: ssh->app_data = app_data;
171: }
172:
173: void *
174: ssh_get_app_data(struct ssh *ssh)
175: {
176: return ssh->app_data;
177: }
178:
179: /* Returns < 0 on error, 0 otherwise */
180: int
181: ssh_add_hostkey(struct ssh *ssh, struct sshkey *key)
182: {
183: struct sshkey *pubkey = NULL;
184: struct key_entry *k = NULL, *k_prv = NULL;
185: int r;
186:
187: if (ssh->kex->server) {
188: if ((r = sshkey_from_private(key, &pubkey)) != 0)
189: return r;
190: if ((k = malloc(sizeof(*k))) == NULL ||
191: (k_prv = malloc(sizeof(*k_prv))) == NULL) {
192: free(k);
193: sshkey_free(pubkey);
194: return SSH_ERR_ALLOC_FAIL;
195: }
196: k_prv->key = key;
197: TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next);
198:
199: /* add the public key, too */
200: k->key = pubkey;
201: TAILQ_INSERT_TAIL(&ssh->public_keys, k, next);
202: r = 0;
203: } else {
204: if ((k = malloc(sizeof(*k))) == NULL)
205: return SSH_ERR_ALLOC_FAIL;
206: k->key = key;
207: TAILQ_INSERT_TAIL(&ssh->public_keys, k, next);
208: r = 0;
209: }
210:
211: return r;
212: }
213:
214: int
215: ssh_set_verify_host_key_callback(struct ssh *ssh,
216: int (*cb)(struct sshkey *, struct ssh *))
217: {
218: if (cb == NULL || ssh->kex == NULL)
219: return SSH_ERR_INVALID_ARGUMENT;
220:
221: ssh->kex->verify_host_key = cb;
222:
223: return 0;
224: }
225:
226: int
227: ssh_input_append(struct ssh *ssh, const u_char *data, size_t len)
228: {
229: return sshbuf_put(ssh_packet_get_input(ssh), data, len);
230: }
231:
232: int
233: ssh_packet_next(struct ssh *ssh, u_char *typep)
234: {
235: int r;
236: u_int32_t seqnr;
237: u_char type;
238:
239: /*
240: * Try to read a packet. Return SSH_MSG_NONE if no packet or not
241: * enough data.
242: */
243: *typep = SSH_MSG_NONE;
1.9 djm 244: if (sshbuf_len(ssh->kex->client_version) == 0 ||
245: sshbuf_len(ssh->kex->server_version) == 0)
1.1 markus 246: return _ssh_exchange_banner(ssh);
247: /*
248: * If we enough data and a dispatch function then
249: * call the function and get the next packet.
250: * Otherwise return the packet type to the caller so it
251: * can decide how to go on.
252: *
253: * We will only call the dispatch function for:
254: * 20-29 Algorithm negotiation
255: * 30-49 Key exchange method specific (numbers can be reused for
256: * different authentication methods)
257: */
258: for (;;) {
259: if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0)
260: return r;
261: if (type > 0 && type < DISPATCH_MAX &&
262: type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX &&
263: ssh->dispatch[type] != NULL) {
264: if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0)
265: return r;
266: } else {
267: *typep = type;
268: return 0;
269: }
270: }
271: }
272:
273: const u_char *
274: ssh_packet_payload(struct ssh *ssh, size_t *lenp)
275: {
276: return sshpkt_ptr(ssh, lenp);
277: }
278:
279: int
280: ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len)
281: {
282: int r;
283:
284: if ((r = sshpkt_start(ssh, type)) != 0 ||
285: (r = sshpkt_put(ssh, data, len)) != 0 ||
286: (r = sshpkt_send(ssh)) != 0)
287: return r;
288: return 0;
289: }
290:
291: const u_char *
292: ssh_output_ptr(struct ssh *ssh, size_t *len)
293: {
294: struct sshbuf *output = ssh_packet_get_output(ssh);
295:
296: *len = sshbuf_len(output);
297: return sshbuf_ptr(output);
298: }
299:
300: int
301: ssh_output_consume(struct ssh *ssh, size_t len)
302: {
303: return sshbuf_consume(ssh_packet_get_output(ssh), len);
304: }
305:
306: int
307: ssh_output_space(struct ssh *ssh, size_t len)
308: {
309: return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len));
310: }
311:
312: int
313: ssh_input_space(struct ssh *ssh, size_t len)
314: {
315: return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len));
316: }
317:
318: /* Read other side's version identification. */
319: int
1.9 djm 320: _ssh_read_banner(struct ssh *ssh, struct sshbuf *banner)
1.1 markus 321: {
1.9 djm 322: struct sshbuf *input = ssh_packet_get_input(ssh);
1.1 markus 323: const char *mismatch = "Protocol mismatch.\r\n";
1.9 djm 324: const u_char *s = sshbuf_ptr(input);
325: u_char c;
1.18 dtucker 326: char *cp = NULL, *remote_version = NULL;
327: int r = 0, remote_major, remote_minor, expect_nl;
1.9 djm 328: size_t n, j;
1.1 markus 329:
330: for (j = n = 0;;) {
1.9 djm 331: sshbuf_reset(banner);
332: expect_nl = 0;
333: for (;;) {
334: if (j >= sshbuf_len(input))
335: return 0; /* insufficient data in input buf */
336: c = s[j++];
337: if (c == '\r') {
338: expect_nl = 1;
339: continue;
1.1 markus 340: }
1.9 djm 341: if (c == '\n')
1.1 markus 342: break;
1.9 djm 343: if (expect_nl)
344: goto bad;
345: if ((r = sshbuf_put_u8(banner, c)) != 0)
346: return r;
347: if (sshbuf_len(banner) > SSH_MAX_BANNER_LEN)
348: goto bad;
1.1 markus 349: }
1.9 djm 350: if (sshbuf_len(banner) >= 4 &&
351: memcmp(sshbuf_ptr(banner), "SSH-", 4) == 0)
1.1 markus 352: break;
1.18 dtucker 353: debug("%s: %.*s", __func__, (int)sshbuf_len(banner),
354: sshbuf_ptr(banner));
1.9 djm 355: /* Accept lines before banner only on client */
356: if (ssh->kex->server || ++n > SSH_MAX_PRE_BANNER_LINES) {
357: bad:
1.1 markus 358: if ((r = sshbuf_put(ssh_packet_get_output(ssh),
359: mismatch, strlen(mismatch))) != 0)
360: return r;
361: return SSH_ERR_NO_PROTOCOL_VERSION;
362: }
363: }
364: if ((r = sshbuf_consume(input, j)) != 0)
365: return r;
366:
1.9 djm 367: /* XXX remote version must be the same size as banner for sscanf */
1.18 dtucker 368: if ((cp = sshbuf_dup_string(banner)) == NULL ||
369: (remote_version = calloc(1, sshbuf_len(banner))) == NULL) {
370: r = SSH_ERR_ALLOC_FAIL;
371: goto out;
372: }
1.9 djm 373:
1.1 markus 374: /*
375: * Check that the versions match. In future this might accept
376: * several versions and set appropriate flags to handle them.
377: */
1.9 djm 378: if (sscanf(cp, "SSH-%d.%d-%[^\n]\n",
1.18 dtucker 379: &remote_major, &remote_minor, remote_version) != 3) {
380: r = SSH_ERR_INVALID_FORMAT;
381: goto out;
382: }
1.1 markus 383: debug("Remote protocol version %d.%d, remote software version %.100s",
384: remote_major, remote_minor, remote_version);
385:
386: ssh->compat = compat_datafellows(remote_version);
387: if (remote_major == 1 && remote_minor == 99) {
388: remote_major = 2;
389: remote_minor = 0;
390: }
391: if (remote_major != 2)
1.18 dtucker 392: r = SSH_ERR_PROTOCOL_MISMATCH;
393:
1.9 djm 394: debug("Remote version string %.100s", cp);
1.18 dtucker 395: out:
1.9 djm 396: free(cp);
1.18 dtucker 397: free(remote_version);
398: return r;
1.1 markus 399: }
400:
401: /* Send our own protocol version identification. */
402: int
1.9 djm 403: _ssh_send_banner(struct ssh *ssh, struct sshbuf *banner)
1.1 markus 404: {
1.9 djm 405: char *cp;
1.1 markus 406: int r;
407:
1.9 djm 408: if ((r = sshbuf_putf(banner, "SSH-2.0-%.100s\r\n", SSH_VERSION)) != 0)
409: return r;
410: if ((r = sshbuf_putb(ssh_packet_get_output(ssh), banner)) != 0)
411: return r;
412: /* Remove trailing \r\n */
413: if ((r = sshbuf_consume_end(banner, 2)) != 0)
1.1 markus 414: return r;
1.9 djm 415: if ((cp = sshbuf_dup_string(banner)) == NULL)
1.1 markus 416: return SSH_ERR_ALLOC_FAIL;
1.9 djm 417: debug("Local version string %.100s", cp);
418: free(cp);
1.1 markus 419: return 0;
420: }
421:
422: int
423: _ssh_exchange_banner(struct ssh *ssh)
424: {
425: struct kex *kex = ssh->kex;
426: int r;
427:
428: /*
429: * if _ssh_read_banner() cannot parse a full version string
430: * it will return NULL and we end up calling it again.
431: */
432:
433: r = 0;
434: if (kex->server) {
1.9 djm 435: if (sshbuf_len(ssh->kex->server_version) == 0)
436: r = _ssh_send_banner(ssh, ssh->kex->server_version);
1.1 markus 437: if (r == 0 &&
1.9 djm 438: sshbuf_len(ssh->kex->server_version) != 0 &&
439: sshbuf_len(ssh->kex->client_version) == 0)
440: r = _ssh_read_banner(ssh, ssh->kex->client_version);
1.1 markus 441: } else {
1.9 djm 442: if (sshbuf_len(ssh->kex->server_version) == 0)
443: r = _ssh_read_banner(ssh, ssh->kex->server_version);
1.1 markus 444: if (r == 0 &&
1.9 djm 445: sshbuf_len(ssh->kex->server_version) != 0 &&
446: sshbuf_len(ssh->kex->client_version) == 0)
447: r = _ssh_send_banner(ssh, ssh->kex->client_version);
1.1 markus 448: }
449: if (r != 0)
450: return r;
451: /* start initial kex as soon as we have exchanged the banners */
1.9 djm 452: if (sshbuf_len(ssh->kex->server_version) != 0 &&
453: sshbuf_len(ssh->kex->client_version) != 0) {
1.1 markus 454: if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 ||
455: (r = kex_send_kexinit(ssh)) != 0)
456: return r;
457: }
458: return 0;
459: }
460:
461: struct sshkey *
1.2 djm 462: _ssh_host_public_key(int type, int nid, struct ssh *ssh)
1.1 markus 463: {
464: struct key_entry *k;
465:
466: debug3("%s: need %d", __func__, type);
467: TAILQ_FOREACH(k, &ssh->public_keys, next) {
468: debug3("%s: check %s", __func__, sshkey_type(k->key));
1.2 djm 469: if (k->key->type == type &&
470: (type != KEY_ECDSA || k->key->ecdsa_nid == nid))
1.1 markus 471: return (k->key);
472: }
473: return (NULL);
474: }
475:
476: struct sshkey *
1.2 djm 477: _ssh_host_private_key(int type, int nid, struct ssh *ssh)
1.1 markus 478: {
479: struct key_entry *k;
480:
481: debug3("%s: need %d", __func__, type);
482: TAILQ_FOREACH(k, &ssh->private_keys, next) {
483: debug3("%s: check %s", __func__, sshkey_type(k->key));
1.2 djm 484: if (k->key->type == type &&
485: (type != KEY_ECDSA || k->key->ecdsa_nid == nid))
1.1 markus 486: return (k->key);
487: }
488: return (NULL);
489: }
490:
491: int
492: _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh)
493: {
494: struct key_entry *k;
495:
496: debug3("%s: need %s", __func__, sshkey_type(hostkey));
497: TAILQ_FOREACH(k, &ssh->public_keys, next) {
498: debug3("%s: check %s", __func__, sshkey_type(k->key));
499: if (sshkey_equal_public(hostkey, k->key))
500: return (0); /* ok */
501: }
502: return (-1); /* failed */
503: }
504:
505: /* offer hostkey algorithms in kexinit depending on registered keys */
506: int
507: _ssh_order_hostkeyalgs(struct ssh *ssh)
508: {
509: struct key_entry *k;
510: char *orig, *avail, *oavail = NULL, *alg, *replace = NULL;
511: char **proposal;
512: size_t maxlen;
513: int ktype, r;
514:
515: /* XXX we de-serialize ssh->kex->my, modify it, and change it */
516: if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0)
517: return r;
518: orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS];
519: if ((oavail = avail = strdup(orig)) == NULL) {
520: r = SSH_ERR_ALLOC_FAIL;
521: goto out;
522: }
523: maxlen = strlen(avail) + 1;
524: if ((replace = calloc(1, maxlen)) == NULL) {
525: r = SSH_ERR_ALLOC_FAIL;
526: goto out;
527: }
528: *replace = '\0';
529: while ((alg = strsep(&avail, ",")) && *alg != '\0') {
530: if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC)
531: continue;
532: TAILQ_FOREACH(k, &ssh->public_keys, next) {
533: if (k->key->type == ktype ||
534: (sshkey_is_cert(k->key) && k->key->type ==
535: sshkey_type_plain(ktype))) {
536: if (*replace != '\0')
537: strlcat(replace, ",", maxlen);
538: strlcat(replace, alg, maxlen);
539: break;
540: }
541: }
542: }
543: if (*replace != '\0') {
544: debug2("%s: orig/%d %s", __func__, ssh->kex->server, orig);
545: debug2("%s: replace/%d %s", __func__, ssh->kex->server, replace);
546: free(orig);
547: proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace;
548: replace = NULL; /* owned by proposal */
549: r = kex_prop2buf(ssh->kex->my, proposal);
550: }
551: out:
552: free(oavail);
553: free(replace);
554: kex_prop_free(proposal);
555: return r;
556: }
557:
558: int
1.10 djm 559: _ssh_host_key_sign(struct ssh *ssh, struct sshkey *privkey,
560: struct sshkey *pubkey, u_char **signature, size_t *slen,
561: const u_char *data, size_t dlen, const char *alg)
1.1 markus 562: {
1.10 djm 563: return sshkey_sign(privkey, signature, slen, data, dlen,
1.21 ! djm 564: alg, NULL, NULL, ssh->compat);
1.1 markus 565: }
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