Annotation of src/usr.bin/ssh/ssh_api.c, Revision 1.10
1.10 ! djm 1: /* $OpenBSD: ssh_api.c,v 1.9 2018/12/27 03:25:25 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: */
17:
18: #include "ssh_api.h"
19: #include "compat.h"
20: #include "log.h"
21: #include "authfile.h"
22: #include "sshkey.h"
23: #include "misc.h"
24: #include "ssh2.h"
25: #include "version.h"
26: #include "myproposal.h"
27: #include "ssherr.h"
28: #include "sshbuf.h"
29:
30: #include <string.h>
31:
32: int _ssh_exchange_banner(struct ssh *);
1.9 djm 33: int _ssh_send_banner(struct ssh *, struct sshbuf *);
34: int _ssh_read_banner(struct ssh *, struct sshbuf *);
1.1 markus 35: int _ssh_order_hostkeyalgs(struct ssh *);
36: int _ssh_verify_host_key(struct sshkey *, struct ssh *);
1.2 djm 37: struct sshkey *_ssh_host_public_key(int, int, struct ssh *);
38: struct sshkey *_ssh_host_private_key(int, int, struct ssh *);
1.10 ! djm 39: int _ssh_host_key_sign(struct ssh *, struct sshkey *, struct sshkey *,
! 40: u_char **, size_t *, const u_char *, size_t, const char *);
1.1 markus 41:
42: /*
43: * stubs for the server side implementation of kex.
44: * disable privsep so our stubs will never be called.
45: */
46: int use_privsep = 0;
47: int mm_sshkey_sign(struct sshkey *, u_char **, u_int *,
1.5 markus 48: u_char *, u_int, char *, u_int);
1.1 markus 49: DH *mm_choose_dh(int, int, int);
50:
51: /* Define these two variables here so that they are part of the library */
52: u_char *session_id2 = NULL;
53: u_int session_id2_len = 0;
54:
55: int
56: mm_sshkey_sign(struct sshkey *key, u_char **sigp, u_int *lenp,
1.5 markus 57: u_char *data, u_int datalen, char *alg, u_int compat)
1.1 markus 58: {
59: return (-1);
60: }
61:
62: DH *
63: mm_choose_dh(int min, int nbits, int max)
64: {
65: return (NULL);
66: }
67:
68: /* API */
69:
70: int
71: ssh_init(struct ssh **sshp, int is_server, struct kex_params *kex_params)
72: {
73: char *myproposal[PROPOSAL_MAX] = { KEX_CLIENT };
74: struct ssh *ssh;
75: char **proposal;
76: static int called;
77: int r;
78:
79: if (!called) {
80: OpenSSL_add_all_algorithms();
81: called = 1;
82: }
83:
1.3 djm 84: if ((ssh = ssh_packet_set_connection(NULL, -1, -1)) == NULL)
85: return SSH_ERR_ALLOC_FAIL;
1.1 markus 86: if (is_server)
87: ssh_packet_set_server(ssh);
88:
89: /* Initialize key exchange */
90: proposal = kex_params ? kex_params->proposal : myproposal;
1.9 djm 91: if ((r = kex_ready(ssh, proposal)) != 0) {
1.1 markus 92: ssh_free(ssh);
93: return r;
94: }
95: ssh->kex->server = is_server;
96: if (is_server) {
97: #ifdef WITH_OPENSSL
98: ssh->kex->kex[KEX_DH_GRP1_SHA1] = kexdh_server;
99: ssh->kex->kex[KEX_DH_GRP14_SHA1] = kexdh_server;
1.6 djm 100: ssh->kex->kex[KEX_DH_GRP14_SHA256] = kexdh_server;
101: ssh->kex->kex[KEX_DH_GRP16_SHA512] = kexdh_server;
102: ssh->kex->kex[KEX_DH_GRP18_SHA512] = kexdh_server;
1.1 markus 103: ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_server;
104: ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_server;
105: ssh->kex->kex[KEX_ECDH_SHA2] = kexecdh_server;
106: #endif /* WITH_OPENSSL */
107: ssh->kex->kex[KEX_C25519_SHA256] = kexc25519_server;
108: ssh->kex->load_host_public_key=&_ssh_host_public_key;
109: ssh->kex->load_host_private_key=&_ssh_host_private_key;
110: ssh->kex->sign=&_ssh_host_key_sign;
111: } else {
112: #ifdef WITH_OPENSSL
113: ssh->kex->kex[KEX_DH_GRP1_SHA1] = kexdh_client;
114: ssh->kex->kex[KEX_DH_GRP14_SHA1] = kexdh_client;
1.6 djm 115: ssh->kex->kex[KEX_DH_GRP14_SHA256] = kexdh_client;
116: ssh->kex->kex[KEX_DH_GRP16_SHA512] = kexdh_client;
117: ssh->kex->kex[KEX_DH_GRP18_SHA512] = kexdh_client;
1.1 markus 118: ssh->kex->kex[KEX_DH_GEX_SHA1] = kexgex_client;
119: ssh->kex->kex[KEX_DH_GEX_SHA256] = kexgex_client;
120: ssh->kex->kex[KEX_ECDH_SHA2] = kexecdh_client;
121: #endif /* WITH_OPENSSL */
122: ssh->kex->kex[KEX_C25519_SHA256] = kexc25519_client;
123: ssh->kex->verify_host_key =&_ssh_verify_host_key;
124: }
125: *sshp = ssh;
126: return 0;
127: }
128:
129: void
130: ssh_free(struct ssh *ssh)
131: {
132: struct key_entry *k;
133:
134: ssh_packet_close(ssh);
135: /*
136: * we've only created the public keys variants in case we
137: * are a acting as a server.
138: */
139: while ((k = TAILQ_FIRST(&ssh->public_keys)) != NULL) {
140: TAILQ_REMOVE(&ssh->public_keys, k, next);
141: if (ssh->kex && ssh->kex->server)
142: sshkey_free(k->key);
143: free(k);
144: }
145: while ((k = TAILQ_FIRST(&ssh->private_keys)) != NULL) {
146: TAILQ_REMOVE(&ssh->private_keys, k, next);
147: free(k);
148: }
149: if (ssh->kex)
150: kex_free(ssh->kex);
151: free(ssh);
152: }
153:
154: void
155: ssh_set_app_data(struct ssh *ssh, void *app_data)
156: {
157: ssh->app_data = app_data;
158: }
159:
160: void *
161: ssh_get_app_data(struct ssh *ssh)
162: {
163: return ssh->app_data;
164: }
165:
166: /* Returns < 0 on error, 0 otherwise */
167: int
168: ssh_add_hostkey(struct ssh *ssh, struct sshkey *key)
169: {
170: struct sshkey *pubkey = NULL;
171: struct key_entry *k = NULL, *k_prv = NULL;
172: int r;
173:
174: if (ssh->kex->server) {
175: if ((r = sshkey_from_private(key, &pubkey)) != 0)
176: return r;
177: if ((k = malloc(sizeof(*k))) == NULL ||
178: (k_prv = malloc(sizeof(*k_prv))) == NULL) {
179: free(k);
180: sshkey_free(pubkey);
181: return SSH_ERR_ALLOC_FAIL;
182: }
183: k_prv->key = key;
184: TAILQ_INSERT_TAIL(&ssh->private_keys, k_prv, next);
185:
186: /* add the public key, too */
187: k->key = pubkey;
188: TAILQ_INSERT_TAIL(&ssh->public_keys, k, next);
189: r = 0;
190: } else {
191: if ((k = malloc(sizeof(*k))) == NULL)
192: return SSH_ERR_ALLOC_FAIL;
193: k->key = key;
194: TAILQ_INSERT_TAIL(&ssh->public_keys, k, next);
195: r = 0;
196: }
197:
198: return r;
199: }
200:
201: int
202: ssh_set_verify_host_key_callback(struct ssh *ssh,
203: int (*cb)(struct sshkey *, struct ssh *))
204: {
205: if (cb == NULL || ssh->kex == NULL)
206: return SSH_ERR_INVALID_ARGUMENT;
207:
208: ssh->kex->verify_host_key = cb;
209:
210: return 0;
211: }
212:
213: int
214: ssh_input_append(struct ssh *ssh, const u_char *data, size_t len)
215: {
216: return sshbuf_put(ssh_packet_get_input(ssh), data, len);
217: }
218:
219: int
220: ssh_packet_next(struct ssh *ssh, u_char *typep)
221: {
222: int r;
223: u_int32_t seqnr;
224: u_char type;
225:
226: /*
227: * Try to read a packet. Return SSH_MSG_NONE if no packet or not
228: * enough data.
229: */
230: *typep = SSH_MSG_NONE;
1.9 djm 231: if (sshbuf_len(ssh->kex->client_version) == 0 ||
232: sshbuf_len(ssh->kex->server_version) == 0)
1.1 markus 233: return _ssh_exchange_banner(ssh);
234: /*
235: * If we enough data and a dispatch function then
236: * call the function and get the next packet.
237: * Otherwise return the packet type to the caller so it
238: * can decide how to go on.
239: *
240: * We will only call the dispatch function for:
241: * 20-29 Algorithm negotiation
242: * 30-49 Key exchange method specific (numbers can be reused for
243: * different authentication methods)
244: */
245: for (;;) {
246: if ((r = ssh_packet_read_poll2(ssh, &type, &seqnr)) != 0)
247: return r;
248: if (type > 0 && type < DISPATCH_MAX &&
249: type >= SSH2_MSG_KEXINIT && type <= SSH2_MSG_TRANSPORT_MAX &&
250: ssh->dispatch[type] != NULL) {
251: if ((r = (*ssh->dispatch[type])(type, seqnr, ssh)) != 0)
252: return r;
253: } else {
254: *typep = type;
255: return 0;
256: }
257: }
258: }
259:
260: const u_char *
261: ssh_packet_payload(struct ssh *ssh, size_t *lenp)
262: {
263: return sshpkt_ptr(ssh, lenp);
264: }
265:
266: int
267: ssh_packet_put(struct ssh *ssh, int type, const u_char *data, size_t len)
268: {
269: int r;
270:
271: if ((r = sshpkt_start(ssh, type)) != 0 ||
272: (r = sshpkt_put(ssh, data, len)) != 0 ||
273: (r = sshpkt_send(ssh)) != 0)
274: return r;
275: return 0;
276: }
277:
278: const u_char *
279: ssh_output_ptr(struct ssh *ssh, size_t *len)
280: {
281: struct sshbuf *output = ssh_packet_get_output(ssh);
282:
283: *len = sshbuf_len(output);
284: return sshbuf_ptr(output);
285: }
286:
287: int
288: ssh_output_consume(struct ssh *ssh, size_t len)
289: {
290: return sshbuf_consume(ssh_packet_get_output(ssh), len);
291: }
292:
293: int
294: ssh_output_space(struct ssh *ssh, size_t len)
295: {
296: return (0 == sshbuf_check_reserve(ssh_packet_get_output(ssh), len));
297: }
298:
299: int
300: ssh_input_space(struct ssh *ssh, size_t len)
301: {
302: return (0 == sshbuf_check_reserve(ssh_packet_get_input(ssh), len));
303: }
304:
305: /* Read other side's version identification. */
306: int
1.9 djm 307: _ssh_read_banner(struct ssh *ssh, struct sshbuf *banner)
1.1 markus 308: {
1.9 djm 309: struct sshbuf *input = ssh_packet_get_input(ssh);
1.1 markus 310: const char *mismatch = "Protocol mismatch.\r\n";
1.9 djm 311: const u_char *s = sshbuf_ptr(input);
312: u_char c;
313: char *cp, *remote_version;
314: int r, remote_major, remote_minor, expect_nl;
315: size_t n, j;
1.1 markus 316:
317: for (j = n = 0;;) {
1.9 djm 318: sshbuf_reset(banner);
319: expect_nl = 0;
320: for (;;) {
321: if (j >= sshbuf_len(input))
322: return 0; /* insufficient data in input buf */
323: c = s[j++];
324: if (c == '\r') {
325: expect_nl = 1;
326: continue;
1.1 markus 327: }
1.9 djm 328: if (c == '\n')
1.1 markus 329: break;
1.9 djm 330: if (expect_nl)
331: goto bad;
332: if ((r = sshbuf_put_u8(banner, c)) != 0)
333: return r;
334: if (sshbuf_len(banner) > SSH_MAX_BANNER_LEN)
335: goto bad;
1.1 markus 336: }
1.9 djm 337: if (sshbuf_len(banner) >= 4 &&
338: memcmp(sshbuf_ptr(banner), "SSH-", 4) == 0)
1.1 markus 339: break;
1.9 djm 340: if ((cp = sshbuf_dup_string(banner)) == NULL)
341: return SSH_ERR_ALLOC_FAIL;
342: debug("%s: %s", __func__, cp);
343: free(cp);
344: /* Accept lines before banner only on client */
345: if (ssh->kex->server || ++n > SSH_MAX_PRE_BANNER_LINES) {
346: bad:
1.1 markus 347: if ((r = sshbuf_put(ssh_packet_get_output(ssh),
348: mismatch, strlen(mismatch))) != 0)
349: return r;
350: return SSH_ERR_NO_PROTOCOL_VERSION;
351: }
352: }
353: if ((r = sshbuf_consume(input, j)) != 0)
354: return r;
355:
1.9 djm 356: if ((cp = sshbuf_dup_string(banner)) == NULL)
357: return SSH_ERR_ALLOC_FAIL;
358: /* XXX remote version must be the same size as banner for sscanf */
359: if ((remote_version = calloc(1, sshbuf_len(banner))) == NULL)
360: return SSH_ERR_ALLOC_FAIL;
361:
1.1 markus 362: /*
363: * Check that the versions match. In future this might accept
364: * several versions and set appropriate flags to handle them.
365: */
1.9 djm 366: if (sscanf(cp, "SSH-%d.%d-%[^\n]\n",
1.1 markus 367: &remote_major, &remote_minor, remote_version) != 3)
368: return SSH_ERR_INVALID_FORMAT;
369: debug("Remote protocol version %d.%d, remote software version %.100s",
370: remote_major, remote_minor, remote_version);
371:
372: ssh->compat = compat_datafellows(remote_version);
373: if (remote_major == 1 && remote_minor == 99) {
374: remote_major = 2;
375: remote_minor = 0;
376: }
377: if (remote_major != 2)
378: return SSH_ERR_PROTOCOL_MISMATCH;
1.9 djm 379: debug("Remote version string %.100s", cp);
380: free(cp);
1.1 markus 381: return 0;
382: }
383:
384: /* Send our own protocol version identification. */
385: int
1.9 djm 386: _ssh_send_banner(struct ssh *ssh, struct sshbuf *banner)
1.1 markus 387: {
1.9 djm 388: char *cp;
1.1 markus 389: int r;
390:
1.9 djm 391: if ((r = sshbuf_putf(banner, "SSH-2.0-%.100s\r\n", SSH_VERSION)) != 0)
392: return r;
393: if ((r = sshbuf_putb(ssh_packet_get_output(ssh), banner)) != 0)
394: return r;
395: /* Remove trailing \r\n */
396: if ((r = sshbuf_consume_end(banner, 2)) != 0)
1.1 markus 397: return r;
1.9 djm 398: if ((cp = sshbuf_dup_string(banner)) == NULL)
1.1 markus 399: return SSH_ERR_ALLOC_FAIL;
1.9 djm 400: debug("Local version string %.100s", cp);
401: free(cp);
1.1 markus 402: return 0;
403: }
404:
405: int
406: _ssh_exchange_banner(struct ssh *ssh)
407: {
408: struct kex *kex = ssh->kex;
409: int r;
410:
411: /*
412: * if _ssh_read_banner() cannot parse a full version string
413: * it will return NULL and we end up calling it again.
414: */
415:
416: r = 0;
417: if (kex->server) {
1.9 djm 418: if (sshbuf_len(ssh->kex->server_version) == 0)
419: r = _ssh_send_banner(ssh, ssh->kex->server_version);
1.1 markus 420: if (r == 0 &&
1.9 djm 421: sshbuf_len(ssh->kex->server_version) != 0 &&
422: sshbuf_len(ssh->kex->client_version) == 0)
423: r = _ssh_read_banner(ssh, ssh->kex->client_version);
1.1 markus 424: } else {
1.9 djm 425: if (sshbuf_len(ssh->kex->server_version) == 0)
426: r = _ssh_read_banner(ssh, ssh->kex->server_version);
1.1 markus 427: if (r == 0 &&
1.9 djm 428: sshbuf_len(ssh->kex->server_version) != 0 &&
429: sshbuf_len(ssh->kex->client_version) == 0)
430: r = _ssh_send_banner(ssh, ssh->kex->client_version);
1.1 markus 431: }
432: if (r != 0)
433: return r;
434: /* start initial kex as soon as we have exchanged the banners */
1.9 djm 435: if (sshbuf_len(ssh->kex->server_version) != 0 &&
436: sshbuf_len(ssh->kex->client_version) != 0) {
1.1 markus 437: if ((r = _ssh_order_hostkeyalgs(ssh)) != 0 ||
438: (r = kex_send_kexinit(ssh)) != 0)
439: return r;
440: }
441: return 0;
442: }
443:
444: struct sshkey *
1.2 djm 445: _ssh_host_public_key(int type, int nid, struct ssh *ssh)
1.1 markus 446: {
447: struct key_entry *k;
448:
449: debug3("%s: need %d", __func__, type);
450: TAILQ_FOREACH(k, &ssh->public_keys, next) {
451: debug3("%s: check %s", __func__, sshkey_type(k->key));
1.2 djm 452: if (k->key->type == type &&
453: (type != KEY_ECDSA || k->key->ecdsa_nid == nid))
1.1 markus 454: return (k->key);
455: }
456: return (NULL);
457: }
458:
459: struct sshkey *
1.2 djm 460: _ssh_host_private_key(int type, int nid, struct ssh *ssh)
1.1 markus 461: {
462: struct key_entry *k;
463:
464: debug3("%s: need %d", __func__, type);
465: TAILQ_FOREACH(k, &ssh->private_keys, next) {
466: debug3("%s: check %s", __func__, sshkey_type(k->key));
1.2 djm 467: if (k->key->type == type &&
468: (type != KEY_ECDSA || k->key->ecdsa_nid == nid))
1.1 markus 469: return (k->key);
470: }
471: return (NULL);
472: }
473:
474: int
475: _ssh_verify_host_key(struct sshkey *hostkey, struct ssh *ssh)
476: {
477: struct key_entry *k;
478:
479: debug3("%s: need %s", __func__, sshkey_type(hostkey));
480: TAILQ_FOREACH(k, &ssh->public_keys, next) {
481: debug3("%s: check %s", __func__, sshkey_type(k->key));
482: if (sshkey_equal_public(hostkey, k->key))
483: return (0); /* ok */
484: }
485: return (-1); /* failed */
486: }
487:
488: /* offer hostkey algorithms in kexinit depending on registered keys */
489: int
490: _ssh_order_hostkeyalgs(struct ssh *ssh)
491: {
492: struct key_entry *k;
493: char *orig, *avail, *oavail = NULL, *alg, *replace = NULL;
494: char **proposal;
495: size_t maxlen;
496: int ktype, r;
497:
498: /* XXX we de-serialize ssh->kex->my, modify it, and change it */
499: if ((r = kex_buf2prop(ssh->kex->my, NULL, &proposal)) != 0)
500: return r;
501: orig = proposal[PROPOSAL_SERVER_HOST_KEY_ALGS];
502: if ((oavail = avail = strdup(orig)) == NULL) {
503: r = SSH_ERR_ALLOC_FAIL;
504: goto out;
505: }
506: maxlen = strlen(avail) + 1;
507: if ((replace = calloc(1, maxlen)) == NULL) {
508: r = SSH_ERR_ALLOC_FAIL;
509: goto out;
510: }
511: *replace = '\0';
512: while ((alg = strsep(&avail, ",")) && *alg != '\0') {
513: if ((ktype = sshkey_type_from_name(alg)) == KEY_UNSPEC)
514: continue;
515: TAILQ_FOREACH(k, &ssh->public_keys, next) {
516: if (k->key->type == ktype ||
517: (sshkey_is_cert(k->key) && k->key->type ==
518: sshkey_type_plain(ktype))) {
519: if (*replace != '\0')
520: strlcat(replace, ",", maxlen);
521: strlcat(replace, alg, maxlen);
522: break;
523: }
524: }
525: }
526: if (*replace != '\0') {
527: debug2("%s: orig/%d %s", __func__, ssh->kex->server, orig);
528: debug2("%s: replace/%d %s", __func__, ssh->kex->server, replace);
529: free(orig);
530: proposal[PROPOSAL_SERVER_HOST_KEY_ALGS] = replace;
531: replace = NULL; /* owned by proposal */
532: r = kex_prop2buf(ssh->kex->my, proposal);
533: }
534: out:
535: free(oavail);
536: free(replace);
537: kex_prop_free(proposal);
538: return r;
539: }
540:
541: int
1.10 ! djm 542: _ssh_host_key_sign(struct ssh *ssh, struct sshkey *privkey,
! 543: struct sshkey *pubkey, u_char **signature, size_t *slen,
! 544: const u_char *data, size_t dlen, const char *alg)
1.1 markus 545: {
1.10 ! djm 546: return sshkey_sign(privkey, signature, slen, data, dlen,
! 547: alg, ssh->compat);
1.1 markus 548: }
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