Annotation of src/usr.bin/ssh/ssh_api.c, Revision 1.19
1.19 ! djm 1: /* $OpenBSD: ssh_api.c,v 1.18 2019/09/13 04:36:43 dtucker 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 *,
1.19 ! djm 53: const u_char *, u_int, 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,
1.19 ! djm 65: const u_char *data, u_int datalen, const char *alg, const char *sk_provider,
! 66: 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: ssh_packet_close(ssh);
150: /*
151: * we've only created the public keys variants in case we
152: * are a acting as a server.
153: */
154: while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) {
155: TAILQ_REMOVE(&ssh->public_keys, k, next);
156: if (ssh->kex && ssh->kex->server)
157: sshkey_free(k->key);
158: free(k);
159: }
160: while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) {
161: TAILQ_REMOVE(&ssh->private_keys, k, next);
162: free(k);
163: }
164: if (ssh->kex)
165: kex_free(ssh->kex);
166: free(ssh);
167: }
168:
169: void
170: ssh_set_app_data(struct ssh *ssh, void *app_data)
171: {
172: ssh->app_data = app_data;
173: }
174:
175: void *
176: ssh_get_app_data(struct ssh *ssh)
177: {
178: return ssh->app_data;
179: }
180:
181: /* Returns < 0 on error, 0 otherwise */
182: int
183: ssh_add_hostkey(struct ssh *ssh, struct sshkey *key)
184: {
185: struct sshkey *pubkey = NULL;
186: struct key_entry *k = NULL, *k_prv = NULL;
187: int r;
188:
189: if (ssh->kex->server) {
190: if ((r = sshkey_from_private(key, &pubkey)) != 0)
191: return r;
192: if ((k = malloc(sizeof(*k))) == NULL ||
193: (k_prv = malloc(sizeof(*k_prv))) == NULL) {
194: free(k);
195: sshkey_free(pubkey);
196: return SSH_ERR_ALLOC_FAIL;
197: }
198: k_prv->key = key;
199: TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next);
200:
201: /* add the public key, too */
202: k->key = pubkey;
203: TAILQ_INSERT_TAIL(&ssh->public_keys, k, next);
204: r = 0;
205: } else {
206: if ((k = malloc(sizeof(*k))) == NULL)
207: return SSH_ERR_ALLOC_FAIL;
208: k->key = key;
209: TAILQ_INSERT_TAIL(&ssh->public_keys, k, next);
210: r = 0;
211: }
212:
213: return r;
214: }
215:
216: int
217: ssh_set_verify_host_key_callback(struct ssh *ssh,
218: int (*cb)(struct sshkey *, struct ssh *))
219: {
220: if (cb == NULL || ssh->kex == NULL)
221: return SSH_ERR_INVALID_ARGUMENT;
222:
223: ssh->kex->verify_host_key = cb;
224:
225: return 0;
226: }
227:
228: int
229: ssh_input_append(struct ssh *ssh, const u_char *data, size_t len)
230: {
231: return sshbuf_put(ssh_packet_get_input(ssh), data, len);
232: }
233:
234: int
235: ssh_packet_next(struct ssh *ssh, u_char *typep)
236: {
237: int r;
238: u_int32_t seqnr;
239: u_char type;
240:
241: /*
242: * Try to read a packet. Return SSH_MSG_NONE if no packet or not
243: * enough data.
244: */
245: *typep = SSH_MSG_NONE;
1.9 djm 246: if (sshbuf_len(ssh->kex->client_version) == 0 ||
247: sshbuf_len(ssh->kex->server_version) == 0)
1.1 markus 248: return _ssh_exchange_banner(ssh);
249: /*
250: * If we enough data and a dispatch function then
251: * call the function and get the next packet.
252: * Otherwise return the packet type to the caller so it
253: * can decide how to go on.
254: *
255: * We will only call the dispatch function for:
256: * 20-29 Algorithm negotiation
257: * 30-49 Key exchange method specific (numbers can be reused for
258: * different authentication methods)
259: */
260: for (;;) {
261: if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0)
262: return r;
263: if (type > 0 && type < DISPATCH_MAX &&
264: type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX &&
265: ssh->dispatch[type] != NULL) {
266: if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0)
267: return r;
268: } else {
269: *typep = type;
270: return 0;
271: }
272: }
273: }
274:
275: const u_char *
276: ssh_packet_payload(struct ssh *ssh, size_t *lenp)
277: {
278: return sshpkt_ptr(ssh, lenp);
279: }
280:
281: int
282: ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len)
283: {
284: int r;
285:
286: if ((r = sshpkt_start(ssh, type)) != 0 ||
287: (r = sshpkt_put(ssh, data, len)) != 0 ||
288: (r = sshpkt_send(ssh)) != 0)
289: return r;
290: return 0;
291: }
292:
293: const u_char *
294: ssh_output_ptr(struct ssh *ssh, size_t *len)
295: {
296: struct sshbuf *output = ssh_packet_get_output(ssh);
297:
298: *len = sshbuf_len(output);
299: return sshbuf_ptr(output);
300: }
301:
302: int
303: ssh_output_consume(struct ssh *ssh, size_t len)
304: {
305: return sshbuf_consume(ssh_packet_get_output(ssh), len);
306: }
307:
308: int
309: ssh_output_space(struct ssh *ssh, size_t len)
310: {
311: return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len));
312: }
313:
314: int
315: ssh_input_space(struct ssh *ssh, size_t len)
316: {
317: return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len));
318: }
319:
320: /* Read other side's version identification. */
321: int
1.9 djm 322: _ssh_read_banner(struct ssh *ssh, struct sshbuf *banner)
1.1 markus 323: {
1.9 djm 324: struct sshbuf *input = ssh_packet_get_input(ssh);
1.1 markus 325: const char *mismatch = "Protocol mismatch.\r\n";
1.9 djm 326: const u_char *s = sshbuf_ptr(input);
327: u_char c;
1.18 dtucker 328: char *cp = NULL, *remote_version = NULL;
329: int r = 0, remote_major, remote_minor, expect_nl;
1.9 djm 330: size_t n, j;
1.1 markus 331:
332: for (j = n = 0;;) {
1.9 djm 333: sshbuf_reset(banner);
334: expect_nl = 0;
335: for (;;) {
336: if (j >= sshbuf_len(input))
337: return 0; /* insufficient data in input buf */
338: c = s[j++];
339: if (c == '\r') {
340: expect_nl = 1;
341: continue;
1.1 markus 342: }
1.9 djm 343: if (c == '\n')
1.1 markus 344: break;
1.9 djm 345: if (expect_nl)
346: goto bad;
347: if ((r = sshbuf_put_u8(banner, c)) != 0)
348: return r;
349: if (sshbuf_len(banner) > SSH_MAX_BANNER_LEN)
350: goto bad;
1.1 markus 351: }
1.9 djm 352: if (sshbuf_len(banner) >= 4 &&
353: memcmp(sshbuf_ptr(banner), "SSH-", 4) == 0)
1.1 markus 354: break;
1.18 dtucker 355: debug("%s: %.*s", __func__, (int)sshbuf_len(banner),
356: sshbuf_ptr(banner));
1.9 djm 357: /* Accept lines before banner only on client */
358: if (ssh->kex->server || ++n > SSH_MAX_PRE_BANNER_LINES) {
359: bad:
1.1 markus 360: if ((r = sshbuf_put(ssh_packet_get_output(ssh),
361: mismatch, strlen(mismatch))) != 0)
362: return r;
363: return SSH_ERR_NO_PROTOCOL_VERSION;
364: }
365: }
366: if ((r = sshbuf_consume(input, j)) != 0)
367: return r;
368:
1.9 djm 369: /* XXX remote version must be the same size as banner for sscanf */
1.18 dtucker 370: if ((cp = sshbuf_dup_string(banner)) == NULL ||
371: (remote_version = calloc(1, sshbuf_len(banner))) == NULL) {
372: r = SSH_ERR_ALLOC_FAIL;
373: goto out;
374: }
1.9 djm 375:
1.1 markus 376: /*
377: * Check that the versions match. In future this might accept
378: * several versions and set appropriate flags to handle them.
379: */
1.9 djm 380: if (sscanf(cp, "SSH-%d.%d-%[^\n]\n",
1.18 dtucker 381: &remote_major, &remote_minor, remote_version) != 3) {
382: r = SSH_ERR_INVALID_FORMAT;
383: goto out;
384: }
1.1 markus 385: debug("Remote protocol version %d.%d, remote software version %.100s",
386: remote_major, remote_minor, remote_version);
387:
388: ssh->compat = compat_datafellows(remote_version);
389: if (remote_major == 1 && remote_minor == 99) {
390: remote_major = 2;
391: remote_minor = 0;
392: }
393: if (remote_major != 2)
1.18 dtucker 394: r = SSH_ERR_PROTOCOL_MISMATCH;
395:
1.9 djm 396: debug("Remote version string %.100s", cp);
1.18 dtucker 397: out:
1.9 djm 398: free(cp);
1.18 dtucker 399: free(remote_version);
400: return r;
1.1 markus 401: }
402:
403: /* Send our own protocol version identification. */
404: int
1.9 djm 405: _ssh_send_banner(struct ssh *ssh, struct sshbuf *banner)
1.1 markus 406: {
1.9 djm 407: char *cp;
1.1 markus 408: int r;
409:
1.9 djm 410: if ((r = sshbuf_putf(banner, "SSH-2.0-%.100s\r\n", SSH_VERSION)) != 0)
411: return r;
412: if ((r = sshbuf_putb(ssh_packet_get_output(ssh), banner)) != 0)
413: return r;
414: /* Remove trailing \r\n */
415: if ((r = sshbuf_consume_end(banner, 2)) != 0)
1.1 markus 416: return r;
1.9 djm 417: if ((cp = sshbuf_dup_string(banner)) == NULL)
1.1 markus 418: return SSH_ERR_ALLOC_FAIL;
1.9 djm 419: debug("Local version string %.100s", cp);
420: free(cp);
1.1 markus 421: return 0;
422: }
423:
424: int
425: _ssh_exchange_banner(struct ssh *ssh)
426: {
427: struct kex *kex = ssh->kex;
428: int r;
429:
430: /*
431: * if _ssh_read_banner() cannot parse a full version string
432: * it will return NULL and we end up calling it again.
433: */
434:
435: r = 0;
436: if (kex->server) {
1.9 djm 437: if (sshbuf_len(ssh->kex->server_version) == 0)
438: r = _ssh_send_banner(ssh, ssh->kex->server_version);
1.1 markus 439: if (r == 0 &&
1.9 djm 440: sshbuf_len(ssh->kex->server_version) != 0 &&
441: sshbuf_len(ssh->kex->client_version) == 0)
442: r = _ssh_read_banner(ssh, ssh->kex->client_version);
1.1 markus 443: } else {
1.9 djm 444: if (sshbuf_len(ssh->kex->server_version) == 0)
445: r = _ssh_read_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_send_banner(ssh, ssh->kex->client_version);
1.1 markus 450: }
451: if (r != 0)
452: return r;
453: /* start initial kex as soon as we have exchanged the banners */
1.9 djm 454: if (sshbuf_len(ssh->kex->server_version) != 0 &&
455: sshbuf_len(ssh->kex->client_version) != 0) {
1.1 markus 456: if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 ||
457: (r = kex_send_kexinit(ssh)) != 0)
458: return r;
459: }
460: return 0;
461: }
462:
463: struct sshkey *
1.2 djm 464: _ssh_host_public_key(int type, int nid, struct ssh *ssh)
1.1 markus 465: {
466: struct key_entry *k;
467:
468: debug3("%s: need %d", __func__, type);
469: TAILQ_FOREACH(k, &ssh->public_keys, next) {
470: debug3("%s: check %s", __func__, sshkey_type(k->key));
1.2 djm 471: if (k->key->type == type &&
472: (type != KEY_ECDSA || k->key->ecdsa_nid == nid))
1.1 markus 473: return (k->key);
474: }
475: return (NULL);
476: }
477:
478: struct sshkey *
1.2 djm 479: _ssh_host_private_key(int type, int nid, struct ssh *ssh)
1.1 markus 480: {
481: struct key_entry *k;
482:
483: debug3("%s: need %d", __func__, type);
484: TAILQ_FOREACH(k, &ssh->private_keys, next) {
485: debug3("%s: check %s", __func__, sshkey_type(k->key));
1.2 djm 486: if (k->key->type == type &&
487: (type != KEY_ECDSA || k->key->ecdsa_nid == nid))
1.1 markus 488: return (k->key);
489: }
490: return (NULL);
491: }
492:
493: int
494: _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh)
495: {
496: struct key_entry *k;
497:
498: debug3("%s: need %s", __func__, sshkey_type(hostkey));
499: TAILQ_FOREACH(k, &ssh->public_keys, next) {
500: debug3("%s: check %s", __func__, sshkey_type(k->key));
501: if (sshkey_equal_public(hostkey, k->key))
502: return (0); /* ok */
503: }
504: return (-1); /* failed */
505: }
506:
507: /* offer hostkey algorithms in kexinit depending on registered keys */
508: int
509: _ssh_order_hostkeyalgs(struct ssh *ssh)
510: {
511: struct key_entry *k;
512: char *orig, *avail, *oavail = NULL, *alg, *replace = NULL;
513: char **proposal;
514: size_t maxlen;
515: int ktype, r;
516:
517: /* XXX we de-serialize ssh->kex->my, modify it, and change it */
518: if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0)
519: return r;
520: orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS];
521: if ((oavail = avail = strdup(orig)) == NULL) {
522: r = SSH_ERR_ALLOC_FAIL;
523: goto out;
524: }
525: maxlen = strlen(avail) + 1;
526: if ((replace = calloc(1, maxlen)) == NULL) {
527: r = SSH_ERR_ALLOC_FAIL;
528: goto out;
529: }
530: *replace = '\0';
531: while ((alg = strsep(&avail, ",")) && *alg != '\0') {
532: if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC)
533: continue;
534: TAILQ_FOREACH(k, &ssh->public_keys, next) {
535: if (k->key->type == ktype ||
536: (sshkey_is_cert(k->key) && k->key->type ==
537: sshkey_type_plain(ktype))) {
538: if (*replace != '\0')
539: strlcat(replace, ",", maxlen);
540: strlcat(replace, alg, maxlen);
541: break;
542: }
543: }
544: }
545: if (*replace != '\0') {
546: debug2("%s: orig/%d %s", __func__, ssh->kex->server, orig);
547: debug2("%s: replace/%d %s", __func__, ssh->kex->server, replace);
548: free(orig);
549: proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace;
550: replace = NULL; /* owned by proposal */
551: r = kex_prop2buf(ssh->kex->my, proposal);
552: }
553: out:
554: free(oavail);
555: free(replace);
556: kex_prop_free(proposal);
557: return r;
558: }
559:
560: int
1.10 djm 561: _ssh_host_key_sign(struct ssh *ssh, struct sshkey *privkey,
562: struct sshkey *pubkey, u_char **signature, size_t *slen,
563: const u_char *data, size_t dlen, const char *alg)
1.1 markus 564: {
1.10 djm 565: return sshkey_sign(privkey, signature, slen, data, dlen,
1.19 ! djm 566: alg, NULL, ssh->compat);
1.1 markus 567: }
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