Annotation of src/usr.bin/ssh/ssh_api.c, Revision 1.28
1.28 ! djm 1: /* $OpenBSD: ssh_api.c,v 1.27 2021/04/03 06:18:41 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: {
1.27 djm 80: char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT };
1.28 ! djm 81: char *populated[PROPOSAL_MAX];
1.1 markus 82: struct ssh *ssh;
83: char **proposal;
84: static int called;
85: int r;
86:
87: if (!called) {
1.17 djm 88: #ifdef WITH_OPENSSL
1.1 markus 89: OpenSSL_add_all_algorithms();
1.17 djm 90: #endif
1.1 markus 91: called = 1;
92: }
93:
1.3 djm 94: if ((ssh = ssh_packet_set_connection(NULL, -1, -1)) == NULL)
95: return SSH_ERR_ALLOC_FAIL;
1.1 markus 96: if (is_server)
97: ssh_packet_set_server(ssh);
98:
99: /* Initialize key exchange */
100: proposal = kex_params ? kex_params->proposal : myproposal;
1.28 ! djm 101: kex_proposal_populate_entries(ssh, populated,
! 102: proposal[PROPOSAL_KEX_ALGS],
! 103: proposal[PROPOSAL_ENC_ALGS_CTOS],
! 104: proposal[PROPOSAL_MAC_ALGS_CTOS],
! 105: proposal[PROPOSAL_COMP_ALGS_CTOS],
! 106: proposal[PROPOSAL_SERVER_HOST_KEY_ALGS]);
! 107: r = kex_ready(ssh, populated);
! 108: kex_proposal_free_entries(populated);
! 109: if (r != 0) {
1.1 markus 110: ssh_free(ssh);
111: return r;
112: }
1.28 ! djm 113:
1.1 markus 114: ssh->kex->server = is_server;
115: if (is_server) {
116: #ifdef WITH_OPENSSL
1.15 djm 117: ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_server;
118: ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_server;
119: ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_server;
120: ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_server;
121: ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_server;
1.1 markus 122: ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
123: ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
1.15 djm 124: ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_server;
1.1 markus 125: #endif /* WITH_OPENSSL */
1.15 djm 126: ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_server;
1.24 djm 127: ssh->kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_server;
1.1 markus 128: ssh->kex->load_host_public_key=&_ssh_host_public_key;
129: ssh->kex->load_host_private_key=&_ssh_host_private_key;
130: ssh->kex->sign=&_ssh_host_key_sign;
131: } else {
132: #ifdef WITH_OPENSSL
1.15 djm 133: ssh->kex->kex[KEX_DH_GRP1_SHA1] = kex_gen_client;
134: ssh->kex->kex[KEX_DH_GRP14_SHA1] = kex_gen_client;
135: ssh->kex->kex[KEX_DH_GRP14_SHA256] = kex_gen_client;
136: ssh->kex->kex[KEX_DH_GRP16_SHA512] = kex_gen_client;
137: ssh->kex->kex[KEX_DH_GRP18_SHA512] = kex_gen_client;
1.1 markus 138: ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client;
139: ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client;
1.15 djm 140: ssh->kex->kex[KEX_ECDH_SHA2] = kex_gen_client;
1.1 markus 141: #endif /* WITH_OPENSSL */
1.15 djm 142: ssh->kex->kex[KEX_C25519_SHA256] = kex_gen_client;
1.24 djm 143: ssh->kex->kex[KEX_KEM_SNTRUP761X25519_SHA512] = kex_gen_client;
1.1 markus 144: ssh->kex->verify_host_key =&_ssh_verify_host_key;
145: }
146: *sshp = ssh;
147: return 0;
148: }
149:
150: void
151: ssh_free(struct ssh *ssh)
152: {
153: struct key_entry *k;
1.23 djm 154:
155: if (ssh == NULL)
156: return;
1.1 markus 157:
158: /*
159: * we've only created the public keys variants in case we
160: * are a acting as a server.
161: */
162: while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) {
163: TAILQ_REMOVE(&ssh->public_keys, k, next);
164: if (ssh->kex && ssh->kex->server)
165: sshkey_free(k->key);
166: free(k);
167: }
168: while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) {
169: TAILQ_REMOVE(&ssh->private_keys, k, next);
170: free(k);
171: }
1.20 markus 172: ssh_packet_close(ssh);
1.1 markus 173: free(ssh);
174: }
175:
176: void
177: ssh_set_app_data(struct ssh *ssh, void *app_data)
178: {
179: ssh->app_data = app_data;
180: }
181:
182: void *
183: ssh_get_app_data(struct ssh *ssh)
184: {
185: return ssh->app_data;
186: }
187:
188: /* Returns < 0 on error, 0 otherwise */
189: int
190: ssh_add_hostkey(struct ssh *ssh, struct sshkey *key)
191: {
192: struct sshkey *pubkey = NULL;
193: struct key_entry *k = NULL, *k_prv = NULL;
194: int r;
195:
196: if (ssh->kex->server) {
197: if ((r = sshkey_from_private(key, &pubkey)) != 0)
198: return r;
199: if ((k = malloc(sizeof(*k))) == NULL ||
200: (k_prv = malloc(sizeof(*k_prv))) == NULL) {
201: free(k);
202: sshkey_free(pubkey);
203: return SSH_ERR_ALLOC_FAIL;
204: }
205: k_prv->key = key;
206: TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next);
207:
208: /* add the public key, too */
209: k->key = pubkey;
210: TAILQ_INSERT_TAIL(&ssh->public_keys, k, next);
211: r = 0;
212: } else {
213: if ((k = malloc(sizeof(*k))) == NULL)
214: return SSH_ERR_ALLOC_FAIL;
215: k->key = key;
216: TAILQ_INSERT_TAIL(&ssh->public_keys, k, next);
217: r = 0;
218: }
219:
220: return r;
221: }
222:
223: int
224: ssh_set_verify_host_key_callback(struct ssh *ssh,
225: int (*cb)(struct sshkey *, struct ssh *))
226: {
227: if (cb == NULL || ssh->kex == NULL)
228: return SSH_ERR_INVALID_ARGUMENT;
229:
230: ssh->kex->verify_host_key = cb;
231:
232: return 0;
233: }
234:
235: int
236: ssh_input_append(struct ssh *ssh, const u_char *data, size_t len)
237: {
238: return sshbuf_put(ssh_packet_get_input(ssh), data, len);
239: }
240:
241: int
242: ssh_packet_next(struct ssh *ssh, u_char *typep)
243: {
244: int r;
245: u_int32_t seqnr;
246: u_char type;
247:
248: /*
249: * Try to read a packet. Return SSH_MSG_NONE if no packet or not
250: * enough data.
251: */
252: *typep = SSH_MSG_NONE;
1.9 djm 253: if (sshbuf_len(ssh->kex->client_version) == 0 ||
254: sshbuf_len(ssh->kex->server_version) == 0)
1.1 markus 255: return _ssh_exchange_banner(ssh);
256: /*
257: * If we enough data and a dispatch function then
258: * call the function and get the next packet.
259: * Otherwise return the packet type to the caller so it
260: * can decide how to go on.
261: *
262: * We will only call the dispatch function for:
263: * 20-29 Algorithm negotiation
264: * 30-49 Key exchange method specific (numbers can be reused for
265: * different authentication methods)
266: */
267: for (;;) {
268: if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0)
269: return r;
270: if (type > 0 && type < DISPATCH_MAX &&
271: type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX &&
272: ssh->dispatch[type] != NULL) {
273: if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0)
274: return r;
275: } else {
276: *typep = type;
277: return 0;
278: }
279: }
280: }
281:
282: const u_char *
283: ssh_packet_payload(struct ssh *ssh, size_t *lenp)
284: {
285: return sshpkt_ptr(ssh, lenp);
286: }
287:
288: int
289: ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len)
290: {
291: int r;
292:
293: if ((r = sshpkt_start(ssh, type)) != 0 ||
294: (r = sshpkt_put(ssh, data, len)) != 0 ||
295: (r = sshpkt_send(ssh)) != 0)
296: return r;
297: return 0;
298: }
299:
300: const u_char *
301: ssh_output_ptr(struct ssh *ssh, size_t *len)
302: {
303: struct sshbuf *output = ssh_packet_get_output(ssh);
304:
305: *len = sshbuf_len(output);
306: return sshbuf_ptr(output);
307: }
308:
309: int
310: ssh_output_consume(struct ssh *ssh, size_t len)
311: {
312: return sshbuf_consume(ssh_packet_get_output(ssh), len);
313: }
314:
315: int
316: ssh_output_space(struct ssh *ssh, size_t len)
317: {
318: return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len));
319: }
320:
321: int
322: ssh_input_space(struct ssh *ssh, size_t len)
323: {
324: return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len));
325: }
326:
327: /* Read other side's version identification. */
328: int
1.9 djm 329: _ssh_read_banner(struct ssh *ssh, struct sshbuf *banner)
1.1 markus 330: {
1.9 djm 331: struct sshbuf *input = ssh_packet_get_input(ssh);
1.1 markus 332: const char *mismatch = "Protocol mismatch.\r\n";
1.9 djm 333: const u_char *s = sshbuf_ptr(input);
334: u_char c;
1.18 dtucker 335: char *cp = NULL, *remote_version = NULL;
336: int r = 0, remote_major, remote_minor, expect_nl;
1.9 djm 337: size_t n, j;
1.1 markus 338:
339: for (j = n = 0;;) {
1.9 djm 340: sshbuf_reset(banner);
341: expect_nl = 0;
342: for (;;) {
343: if (j >= sshbuf_len(input))
344: return 0; /* insufficient data in input buf */
345: c = s[j++];
346: if (c == '\r') {
347: expect_nl = 1;
348: continue;
1.1 markus 349: }
1.9 djm 350: if (c == '\n')
1.1 markus 351: break;
1.9 djm 352: if (expect_nl)
353: goto bad;
354: if ((r = sshbuf_put_u8(banner, c)) != 0)
355: return r;
356: if (sshbuf_len(banner) > SSH_MAX_BANNER_LEN)
357: goto bad;
1.1 markus 358: }
1.9 djm 359: if (sshbuf_len(banner) >= 4 &&
360: memcmp(sshbuf_ptr(banner), "SSH-", 4) == 0)
1.1 markus 361: break;
1.22 djm 362: debug_f("%.*s", (int)sshbuf_len(banner),
1.18 dtucker 363: sshbuf_ptr(banner));
1.9 djm 364: /* Accept lines before banner only on client */
365: if (ssh->kex->server || ++n > SSH_MAX_PRE_BANNER_LINES) {
366: bad:
1.1 markus 367: if ((r = sshbuf_put(ssh_packet_get_output(ssh),
1.27 djm 368: mismatch, strlen(mismatch))) != 0)
1.1 markus 369: return r;
370: return SSH_ERR_NO_PROTOCOL_VERSION;
371: }
372: }
373: if ((r = sshbuf_consume(input, j)) != 0)
374: return r;
375:
1.9 djm 376: /* XXX remote version must be the same size as banner for sscanf */
1.18 dtucker 377: if ((cp = sshbuf_dup_string(banner)) == NULL ||
378: (remote_version = calloc(1, sshbuf_len(banner))) == NULL) {
379: r = SSH_ERR_ALLOC_FAIL;
380: goto out;
381: }
1.9 djm 382:
1.1 markus 383: /*
384: * Check that the versions match. In future this might accept
385: * several versions and set appropriate flags to handle them.
386: */
1.9 djm 387: if (sscanf(cp, "SSH-%d.%d-%[^\n]\n",
1.18 dtucker 388: &remote_major, &remote_minor, remote_version) != 3) {
389: r = SSH_ERR_INVALID_FORMAT;
390: goto out;
391: }
1.1 markus 392: debug("Remote protocol version %d.%d, remote software version %.100s",
393: remote_major, remote_minor, remote_version);
394:
1.25 djm 395: compat_banner(ssh, remote_version);
1.1 markus 396: if (remote_major == 1 && remote_minor == 99) {
397: remote_major = 2;
398: remote_minor = 0;
399: }
400: if (remote_major != 2)
1.18 dtucker 401: r = SSH_ERR_PROTOCOL_MISMATCH;
402:
1.9 djm 403: debug("Remote version string %.100s", cp);
1.18 dtucker 404: out:
1.9 djm 405: free(cp);
1.18 dtucker 406: free(remote_version);
407: return r;
1.1 markus 408: }
409:
410: /* Send our own protocol version identification. */
411: int
1.9 djm 412: _ssh_send_banner(struct ssh *ssh, struct sshbuf *banner)
1.1 markus 413: {
1.9 djm 414: char *cp;
1.1 markus 415: int r;
416:
1.9 djm 417: if ((r = sshbuf_putf(banner, "SSH-2.0-%.100s\r\n", SSH_VERSION)) != 0)
418: return r;
419: if ((r = sshbuf_putb(ssh_packet_get_output(ssh), banner)) != 0)
420: return r;
421: /* Remove trailing \r\n */
422: if ((r = sshbuf_consume_end(banner, 2)) != 0)
1.1 markus 423: return r;
1.9 djm 424: if ((cp = sshbuf_dup_string(banner)) == NULL)
1.1 markus 425: return SSH_ERR_ALLOC_FAIL;
1.9 djm 426: debug("Local version string %.100s", cp);
427: free(cp);
1.1 markus 428: return 0;
429: }
430:
431: int
432: _ssh_exchange_banner(struct ssh *ssh)
433: {
434: struct kex *kex = ssh->kex;
435: int r;
436:
437: /*
438: * if _ssh_read_banner() cannot parse a full version string
439: * it will return NULL and we end up calling it again.
440: */
441:
442: r = 0;
443: if (kex->server) {
1.9 djm 444: if (sshbuf_len(ssh->kex->server_version) == 0)
445: r = _ssh_send_banner(ssh, ssh->kex->server_version);
1.1 markus 446: if (r == 0 &&
1.9 djm 447: sshbuf_len(ssh->kex->server_version) != 0 &&
448: sshbuf_len(ssh->kex->client_version) == 0)
449: r = _ssh_read_banner(ssh, ssh->kex->client_version);
1.1 markus 450: } else {
1.9 djm 451: if (sshbuf_len(ssh->kex->server_version) == 0)
452: r = _ssh_read_banner(ssh, ssh->kex->server_version);
1.1 markus 453: if (r == 0 &&
1.9 djm 454: sshbuf_len(ssh->kex->server_version) != 0 &&
455: sshbuf_len(ssh->kex->client_version) == 0)
456: r = _ssh_send_banner(ssh, ssh->kex->client_version);
1.1 markus 457: }
458: if (r != 0)
459: return r;
460: /* start initial kex as soon as we have exchanged the banners */
1.9 djm 461: if (sshbuf_len(ssh->kex->server_version) != 0 &&
462: sshbuf_len(ssh->kex->client_version) != 0) {
1.1 markus 463: if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 ||
464: (r = kex_send_kexinit(ssh)) != 0)
465: return r;
466: }
467: return 0;
468: }
469:
470: struct sshkey *
1.2 djm 471: _ssh_host_public_key(int type, int nid, struct ssh *ssh)
1.1 markus 472: {
473: struct key_entry *k;
474:
1.22 djm 475: debug3_f("need %d", type);
1.1 markus 476: TAILQ_FOREACH(k, &ssh->public_keys, next) {
1.22 djm 477: debug3_f("check %s", sshkey_type(k->key));
1.2 djm 478: if (k->key->type == type &&
479: (type != KEY_ECDSA || k->key->ecdsa_nid == nid))
1.1 markus 480: return (k->key);
481: }
482: return (NULL);
483: }
484:
485: struct sshkey *
1.2 djm 486: _ssh_host_private_key(int type, int nid, struct ssh *ssh)
1.1 markus 487: {
488: struct key_entry *k;
489:
1.22 djm 490: debug3_f("need %d", type);
1.1 markus 491: TAILQ_FOREACH(k, &ssh->private_keys, next) {
1.22 djm 492: debug3_f("check %s", sshkey_type(k->key));
1.2 djm 493: if (k->key->type == type &&
494: (type != KEY_ECDSA || k->key->ecdsa_nid == nid))
1.1 markus 495: return (k->key);
496: }
497: return (NULL);
498: }
499:
500: int
501: _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh)
502: {
503: struct key_entry *k;
504:
1.22 djm 505: debug3_f("need %s", sshkey_type(hostkey));
1.1 markus 506: TAILQ_FOREACH(k, &ssh->public_keys, next) {
1.22 djm 507: debug3_f("check %s", sshkey_type(k->key));
1.1 markus 508: if (sshkey_equal_public(hostkey, k->key))
509: return (0); /* ok */
510: }
511: return (-1); /* failed */
512: }
513:
514: /* offer hostkey algorithms in kexinit depending on registered keys */
515: int
516: _ssh_order_hostkeyalgs(struct ssh *ssh)
517: {
518: struct key_entry *k;
519: char *orig, *avail, *oavail = NULL, *alg, *replace = NULL;
520: char **proposal;
521: size_t maxlen;
522: int ktype, r;
523:
524: /* XXX we de-serialize ssh->kex->my, modify it, and change it */
525: if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0)
526: return r;
527: orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS];
528: if ((oavail = avail = strdup(orig)) == NULL) {
529: r = SSH_ERR_ALLOC_FAIL;
530: goto out;
531: }
532: maxlen = strlen(avail) + 1;
533: if ((replace = calloc(1, maxlen)) == NULL) {
534: r = SSH_ERR_ALLOC_FAIL;
535: goto out;
536: }
537: *replace = '\0';
538: while ((alg = strsep(&avail, ",")) && *alg != '\0') {
539: if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC)
540: continue;
541: TAILQ_FOREACH(k, &ssh->public_keys, next) {
542: if (k->key->type == ktype ||
543: (sshkey_is_cert(k->key) && k->key->type ==
544: sshkey_type_plain(ktype))) {
545: if (*replace != '\0')
546: strlcat(replace, ",", maxlen);
547: strlcat(replace, alg, maxlen);
548: break;
549: }
550: }
551: }
552: if (*replace != '\0') {
1.22 djm 553: debug2_f("orig/%d %s", ssh->kex->server, orig);
554: debug2_f("replace/%d %s", ssh->kex->server, replace);
1.1 markus 555: free(orig);
556: proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace;
557: replace = NULL; /* owned by proposal */
558: r = kex_prop2buf(ssh->kex->my, proposal);
559: }
560: out:
561: free(oavail);
562: free(replace);
563: kex_prop_free(proposal);
564: return r;
565: }
566:
567: int
1.10 djm 568: _ssh_host_key_sign(struct ssh *ssh, struct sshkey *privkey,
569: struct sshkey *pubkey, u_char **signature, size_t *slen,
570: const u_char *data, size_t dlen, const char *alg)
1.1 markus 571: {
1.10 djm 572: return sshkey_sign(privkey, signature, slen, data, dlen,
1.21 djm 573: alg, NULL, NULL, ssh->compat);
1.1 markus 574: }
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