blob: 0abcf89a0a0732bf7b49d9018d389749453c186c [file] [log] [blame]
Damien Millereba71ba2000-04-29 23:57:08 +10001/*
2 * Copyright (c) 2000 Markus Friedl. All rights reserved.
3 *
4 * Redistribution and use in source and binary forms, with or without
5 * modification, are permitted provided that the following conditions
6 * are met:
7 * 1. Redistributions of source code must retain the above copyright
8 * notice, this list of conditions and the following disclaimer.
9 * 2. Redistributions in binary form must reproduce the above copyright
10 * notice, this list of conditions and the following disclaimer in the
11 * documentation and/or other materials provided with the distribution.
12 * 3. All advertising materials mentioning features or use of this software
13 * must display the following acknowledgement:
14 * This product includes software developed by Markus Friedl.
15 * 4. The name of the author may not be used to endorse or promote products
16 * derived from this software without specific prior written permission.
17 *
18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
19 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
20 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
21 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
23 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
24 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
25 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
27 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
28 */
29
30#include "includes.h"
Damien Millerb1715dc2000-05-30 13:44:51 +100031RCSID("$OpenBSD: sshconnect2.c,v 1.11 2000/05/25 20:45:20 markus Exp $");
Damien Millereba71ba2000-04-29 23:57:08 +100032
33#include <openssl/bn.h>
34#include <openssl/rsa.h>
35#include <openssl/dsa.h>
36#include <openssl/md5.h>
37#include <openssl/dh.h>
38#include <openssl/hmac.h>
39
40#include "ssh.h"
41#include "xmalloc.h"
42#include "rsa.h"
43#include "buffer.h"
44#include "packet.h"
45#include "cipher.h"
46#include "uidswap.h"
47#include "compat.h"
48#include "readconf.h"
49#include "bufaux.h"
50#include "ssh2.h"
51#include "kex.h"
52#include "myproposal.h"
53#include "key.h"
54#include "dsa.h"
55#include "sshconnect.h"
56#include "authfile.h"
57
58/* import */
59extern char *client_version_string;
60extern char *server_version_string;
61extern Options options;
62
63/*
64 * SSH2 key exchange
65 */
66
67unsigned char *session_id2 = NULL;
68int session_id2_len = 0;
69
70void
Damien Millerb1715dc2000-05-30 13:44:51 +100071ssh_kex_dh(Kex *kex, char *host, struct sockaddr *hostaddr,
72 Buffer *client_kexinit, Buffer *server_kexinit)
Damien Millereba71ba2000-04-29 23:57:08 +100073{
Damien Millerb1715dc2000-05-30 13:44:51 +100074 int i;
75 int plen, dlen;
Damien Millereba71ba2000-04-29 23:57:08 +100076 unsigned int klen, kout;
Damien Millereba71ba2000-04-29 23:57:08 +100077 char *signature = NULL;
78 unsigned int slen;
79 char *server_host_key_blob = NULL;
80 Key *server_host_key;
81 unsigned int sbloblen;
82 DH *dh;
83 BIGNUM *dh_server_pub = 0;
84 BIGNUM *shared_secret = 0;
Damien Millereba71ba2000-04-29 23:57:08 +100085 unsigned char *kbuf;
86 unsigned char *hash;
87
Damien Millereba71ba2000-04-29 23:57:08 +100088 debug("Sending SSH2_MSG_KEXDH_INIT.");
Damien Millereba71ba2000-04-29 23:57:08 +100089 /* generate and send 'e', client DH public key */
90 dh = dh_new_group1();
91 packet_start(SSH2_MSG_KEXDH_INIT);
92 packet_put_bignum2(dh->pub_key);
93 packet_send();
94 packet_write_wait();
95
96#ifdef DEBUG_KEXDH
97 fprintf(stderr, "\np= ");
98 bignum_print(dh->p);
99 fprintf(stderr, "\ng= ");
100 bignum_print(dh->g);
101 fprintf(stderr, "\npub= ");
102 bignum_print(dh->pub_key);
103 fprintf(stderr, "\n");
104 DHparams_print_fp(stderr, dh);
105#endif
106
107 debug("Wait SSH2_MSG_KEXDH_REPLY.");
108
Damien Millerb1715dc2000-05-30 13:44:51 +1000109 packet_read_expect(&plen, SSH2_MSG_KEXDH_REPLY);
Damien Millereba71ba2000-04-29 23:57:08 +1000110
111 debug("Got SSH2_MSG_KEXDH_REPLY.");
112
113 /* key, cert */
114 server_host_key_blob = packet_get_string(&sbloblen);
115 server_host_key = dsa_key_from_blob(server_host_key_blob, sbloblen);
116 if (server_host_key == NULL)
117 fatal("cannot decode server_host_key_blob");
118
119 check_host_key(host, hostaddr, server_host_key,
120 options.user_hostfile2, options.system_hostfile2);
121
122 /* DH paramter f, server public DH key */
123 dh_server_pub = BN_new();
124 if (dh_server_pub == NULL)
125 fatal("dh_server_pub == NULL");
126 packet_get_bignum2(dh_server_pub, &dlen);
127
128#ifdef DEBUG_KEXDH
129 fprintf(stderr, "\ndh_server_pub= ");
130 bignum_print(dh_server_pub);
131 fprintf(stderr, "\n");
132 debug("bits %d", BN_num_bits(dh_server_pub));
133#endif
134
135 /* signed H */
136 signature = packet_get_string(&slen);
137 packet_done();
138
139 if (!dh_pub_is_valid(dh, dh_server_pub))
140 packet_disconnect("bad server public DH value");
141
142 klen = DH_size(dh);
143 kbuf = xmalloc(klen);
144 kout = DH_compute_key(kbuf, dh_server_pub, dh);
145#ifdef DEBUG_KEXDH
146 debug("shared secret: len %d/%d", klen, kout);
147 fprintf(stderr, "shared secret == ");
148 for (i = 0; i< kout; i++)
149 fprintf(stderr, "%02x", (kbuf[i])&0xff);
150 fprintf(stderr, "\n");
151#endif
152 shared_secret = BN_new();
153
154 BN_bin2bn(kbuf, kout, shared_secret);
155 memset(kbuf, 0, klen);
156 xfree(kbuf);
157
158 /* calc and verify H */
159 hash = kex_hash(
160 client_version_string,
161 server_version_string,
162 buffer_ptr(client_kexinit), buffer_len(client_kexinit),
163 buffer_ptr(server_kexinit), buffer_len(server_kexinit),
164 server_host_key_blob, sbloblen,
165 dh->pub_key,
166 dh_server_pub,
167 shared_secret
168 );
169 xfree(server_host_key_blob);
Damien Millerb1715dc2000-05-30 13:44:51 +1000170 DH_free(dh);
Damien Millereba71ba2000-04-29 23:57:08 +1000171#ifdef DEBUG_KEXDH
172 fprintf(stderr, "hash == ");
173 for (i = 0; i< 20; i++)
174 fprintf(stderr, "%02x", (hash[i])&0xff);
175 fprintf(stderr, "\n");
176#endif
177 if (dsa_verify(server_host_key, (unsigned char *)signature, slen, hash, 20) != 1)
178 fatal("dsa_verify failed for server_host_key");
179 key_free(server_host_key);
180
181 kex_derive_keys(kex, hash, shared_secret);
182 packet_set_kex(kex);
183
Damien Millereba71ba2000-04-29 23:57:08 +1000184 /* save session id */
185 session_id2_len = 20;
186 session_id2 = xmalloc(session_id2_len);
187 memcpy(session_id2, hash, session_id2_len);
Damien Millerb1715dc2000-05-30 13:44:51 +1000188}
189
190void
191ssh_kex2(char *host, struct sockaddr *hostaddr)
192{
193 int i, plen;
194 Kex *kex;
195 Buffer *client_kexinit, *server_kexinit;
196 char *sprop[PROPOSAL_MAX];
197
198 if (options.ciphers != NULL) {
199 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
200 myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
201 } else if (options.cipher == SSH_CIPHER_3DES) {
202 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
203 myproposal[PROPOSAL_ENC_ALGS_STOC] =
204 (char *) cipher_name(SSH_CIPHER_3DES_CBC);
205 } else if (options.cipher == SSH_CIPHER_BLOWFISH) {
206 myproposal[PROPOSAL_ENC_ALGS_CTOS] =
207 myproposal[PROPOSAL_ENC_ALGS_STOC] =
208 (char *) cipher_name(SSH_CIPHER_BLOWFISH_CBC);
209 }
210 if (options.compression) {
211 myproposal[PROPOSAL_COMP_ALGS_CTOS] = "zlib";
212 myproposal[PROPOSAL_COMP_ALGS_STOC] = "zlib";
213 } else {
214 myproposal[PROPOSAL_COMP_ALGS_CTOS] = "none";
215 myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
216 }
217
218 /* buffers with raw kexinit messages */
219 server_kexinit = xmalloc(sizeof(*server_kexinit));
220 buffer_init(server_kexinit);
221 client_kexinit = kex_init(myproposal);
222
223 /* algorithm negotiation */
224 kex_exchange_kexinit(client_kexinit, server_kexinit, sprop);
225 kex = kex_choose_conf(myproposal, sprop, 0);
226 for (i = 0; i < PROPOSAL_MAX; i++)
227 xfree(sprop[i]);
228
229 /* server authentication and session key agreement */
230 ssh_kex_dh(kex, host, hostaddr, client_kexinit, server_kexinit);
231
232 buffer_free(client_kexinit);
233 buffer_free(server_kexinit);
234 xfree(client_kexinit);
235 xfree(server_kexinit);
Damien Millereba71ba2000-04-29 23:57:08 +1000236
237 debug("Wait SSH2_MSG_NEWKEYS.");
Damien Millerb1715dc2000-05-30 13:44:51 +1000238 packet_read_expect(&plen, SSH2_MSG_NEWKEYS);
Damien Millereba71ba2000-04-29 23:57:08 +1000239 packet_done();
240 debug("GOT SSH2_MSG_NEWKEYS.");
241
242 debug("send SSH2_MSG_NEWKEYS.");
243 packet_start(SSH2_MSG_NEWKEYS);
244 packet_send();
245 packet_write_wait();
246 debug("done: send SSH2_MSG_NEWKEYS.");
247
248#ifdef DEBUG_KEXDH
249 /* send 1st encrypted/maced/compressed message */
250 packet_start(SSH2_MSG_IGNORE);
251 packet_put_cstring("markus");
252 packet_send();
253 packet_write_wait();
254#endif
255 debug("done: KEX2.");
256}
Damien Millerb1715dc2000-05-30 13:44:51 +1000257
Damien Millereba71ba2000-04-29 23:57:08 +1000258/*
259 * Authenticate user
260 */
261int
262ssh2_try_passwd(const char *server_user, const char *host, const char *service)
263{
Damien Millere247cc42000-05-07 12:03:14 +1000264 static int attempt = 0;
Damien Millereba71ba2000-04-29 23:57:08 +1000265 char prompt[80];
266 char *password;
267
Damien Millere247cc42000-05-07 12:03:14 +1000268 if (attempt++ > options.number_of_password_prompts)
269 return 0;
270
Damien Millereba71ba2000-04-29 23:57:08 +1000271 snprintf(prompt, sizeof(prompt), "%.30s@%.40s's password: ",
272 server_user, host);
273 password = read_passphrase(prompt, 0);
274 packet_start(SSH2_MSG_USERAUTH_REQUEST);
275 packet_put_cstring(server_user);
276 packet_put_cstring(service);
277 packet_put_cstring("password");
278 packet_put_char(0);
279 packet_put_cstring(password);
280 memset(password, 0, strlen(password));
281 xfree(password);
282 packet_send();
283 packet_write_wait();
284 return 1;
285}
286
287int
288ssh2_try_pubkey(char *filename,
289 const char *server_user, const char *host, const char *service)
290{
291 Buffer b;
292 Key *k;
293 unsigned char *blob, *signature;
294 int bloblen, slen;
Damien Miller6f83b8e2000-05-02 09:23:45 +1000295 struct stat st;
Damien Millereba71ba2000-04-29 23:57:08 +1000296
Damien Miller6f83b8e2000-05-02 09:23:45 +1000297 if (stat(filename, &st) != 0) {
298 debug("key does not exist: %s", filename);
299 return 0;
300 }
Damien Millereba71ba2000-04-29 23:57:08 +1000301 debug("try pubkey: %s", filename);
302
303 k = key_new(KEY_DSA);
304 if (!load_private_key(filename, "", k, NULL)) {
305 int success = 0;
306 char *passphrase;
307 char prompt[300];
Damien Miller6f83b8e2000-05-02 09:23:45 +1000308 snprintf(prompt, sizeof prompt,
Damien Millereba71ba2000-04-29 23:57:08 +1000309 "Enter passphrase for DSA key '%.100s': ",
Damien Miller6f83b8e2000-05-02 09:23:45 +1000310 filename);
Damien Millereba71ba2000-04-29 23:57:08 +1000311 passphrase = read_passphrase(prompt, 0);
312 success = load_private_key(filename, passphrase, k, NULL);
313 memset(passphrase, 0, strlen(passphrase));
314 xfree(passphrase);
315 if (!success)
316 return 0;
317 }
318 dsa_make_key_blob(k, &blob, &bloblen);
319
320 /* data to be signed */
321 buffer_init(&b);
322 buffer_append(&b, session_id2, session_id2_len);
323 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
324 buffer_put_cstring(&b, server_user);
Damien Miller30c3d422000-05-09 11:02:59 +1000325 buffer_put_cstring(&b,
326 datafellows & SSH_BUG_PUBKEYAUTH ?
327 "ssh-userauth" :
328 service);
Damien Millereba71ba2000-04-29 23:57:08 +1000329 buffer_put_cstring(&b, "publickey");
330 buffer_put_char(&b, 1);
331 buffer_put_cstring(&b, KEX_DSS);
332 buffer_put_string(&b, blob, bloblen);
Damien Millereba71ba2000-04-29 23:57:08 +1000333
334 /* generate signature */
335 dsa_sign(k, &signature, &slen, buffer_ptr(&b), buffer_len(&b));
336 key_free(k);
337#ifdef DEBUG_DSS
338 buffer_dump(&b);
339#endif
Damien Miller30c3d422000-05-09 11:02:59 +1000340 if (datafellows & SSH_BUG_PUBKEYAUTH) {
341 /* e.g. ssh-2.0.13: data-to-be-signed != data-on-the-wire */
342 buffer_clear(&b);
343 buffer_append(&b, session_id2, session_id2_len);
344 buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
345 buffer_put_cstring(&b, server_user);
346 buffer_put_cstring(&b, service);
347 buffer_put_cstring(&b, "publickey");
348 buffer_put_char(&b, 1);
349 buffer_put_cstring(&b, KEX_DSS);
350 buffer_put_string(&b, blob, bloblen);
351 }
352 xfree(blob);
Damien Millereba71ba2000-04-29 23:57:08 +1000353 /* append signature */
354 buffer_put_string(&b, signature, slen);
355 xfree(signature);
356
357 /* skip session id and packet type */
358 if (buffer_len(&b) < session_id2_len + 1)
359 fatal("ssh2_try_pubkey: internal error");
360 buffer_consume(&b, session_id2_len + 1);
361
362 /* put remaining data from buffer into packet */
363 packet_start(SSH2_MSG_USERAUTH_REQUEST);
364 packet_put_raw(buffer_ptr(&b), buffer_len(&b));
365 buffer_free(&b);
366
367 /* send */
368 packet_send();
369 packet_write_wait();
370 return 1;
371}
372
373void
374ssh_userauth2(const char *server_user, char *host)
375{
376 int type;
377 int plen;
378 int sent;
379 unsigned int dlen;
380 int partial;
381 int i = 0;
382 char *auths;
383 char *service = "ssh-connection"; /* service name */
384
385 debug("send SSH2_MSG_SERVICE_REQUEST");
386 packet_start(SSH2_MSG_SERVICE_REQUEST);
387 packet_put_cstring("ssh-userauth");
388 packet_send();
389 packet_write_wait();
390
391 type = packet_read(&plen);
392 if (type != SSH2_MSG_SERVICE_ACCEPT) {
393 fatal("denied SSH2_MSG_SERVICE_ACCEPT: %d", type);
394 }
395 if (packet_remaining() > 0) {
396 char *reply = packet_get_string(&plen);
397 debug("service_accept: %s", reply);
398 xfree(reply);
399 } else {
400 /* payload empty for ssh-2.0.13 ?? */
Damien Miller6d488712000-05-08 13:44:52 +1000401 debug("buggy server: service_accept w/o service");
Damien Millereba71ba2000-04-29 23:57:08 +1000402 }
403 packet_done();
404 debug("got SSH2_MSG_SERVICE_ACCEPT");
405
406 /* INITIAL request for auth */
407 packet_start(SSH2_MSG_USERAUTH_REQUEST);
408 packet_put_cstring(server_user);
409 packet_put_cstring(service);
410 packet_put_cstring("none");
411 packet_send();
412 packet_write_wait();
413
414 for (;;) {
415 sent = 0;
416 type = packet_read(&plen);
417 if (type == SSH2_MSG_USERAUTH_SUCCESS)
418 break;
419 if (type != SSH2_MSG_USERAUTH_FAILURE)
420 fatal("access denied: %d", type);
421 /* SSH2_MSG_USERAUTH_FAILURE means: try again */
422 auths = packet_get_string(&dlen);
423 debug("authentications that can continue: %s", auths);
424 partial = packet_get_char();
425 packet_done();
426 if (partial)
427 debug("partial success");
Damien Millere247cc42000-05-07 12:03:14 +1000428 if (options.dsa_authentication &&
Damien Millereba71ba2000-04-29 23:57:08 +1000429 strstr(auths, "publickey") != NULL) {
430 while (i < options.num_identity_files2) {
431 sent = ssh2_try_pubkey(
432 options.identity_files2[i++],
433 server_user, host, service);
434 if (sent)
435 break;
436 }
437 }
438 if (!sent) {
439 if (options.password_authentication &&
440 !options.batch_mode &&
441 strstr(auths, "password") != NULL) {
442 sent = ssh2_try_passwd(server_user, host, service);
443 }
444 }
445 if (!sent)
446 fatal("Permission denied (%s).", auths);
447 xfree(auths);
448 }
449 packet_done();
450 debug("ssh-userauth2 successfull");
451}