Annotation of src/usr.bin/ssh/sshconnect2.c, Revision 1.19
1.1 markus 1: /*
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: *
13: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
14: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
15: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
16: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
17: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
18: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
19: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
20: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
21: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
22: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
23: */
24:
25: #include "includes.h"
1.19 ! markus 26: RCSID("$OpenBSD: sshconnect2.c,v 1.18 2000/09/07 20:27:55 deraadt Exp $");
1.1 markus 27:
28: #include <openssl/bn.h>
29: #include <openssl/rsa.h>
30: #include <openssl/dsa.h>
31: #include <openssl/md5.h>
32: #include <openssl/dh.h>
33: #include <openssl/hmac.h>
34:
35: #include "ssh.h"
36: #include "xmalloc.h"
37: #include "rsa.h"
38: #include "buffer.h"
39: #include "packet.h"
40: #include "cipher.h"
41: #include "uidswap.h"
42: #include "compat.h"
43: #include "readconf.h"
44: #include "bufaux.h"
45: #include "ssh2.h"
46: #include "kex.h"
47: #include "myproposal.h"
48: #include "key.h"
49: #include "dsa.h"
50: #include "sshconnect.h"
51: #include "authfile.h"
1.17 markus 52: #include "authfd.h"
1.1 markus 53:
54: /* import */
55: extern char *client_version_string;
56: extern char *server_version_string;
57: extern Options options;
58:
59: /*
60: * SSH2 key exchange
61: */
62:
63: unsigned char *session_id2 = NULL;
64: int session_id2_len = 0;
65:
66: void
1.11 markus 67: ssh_kex_dh(Kex *kex, char *host, struct sockaddr *hostaddr,
68: Buffer *client_kexinit, Buffer *server_kexinit)
1.1 markus 69: {
1.19 ! markus 70: #ifdef DEBUG_KEXDH
! 71: int i;
! 72: #endif
1.11 markus 73: int plen, dlen;
1.1 markus 74: unsigned int klen, kout;
75: char *signature = NULL;
76: unsigned int slen;
77: char *server_host_key_blob = NULL;
78: Key *server_host_key;
79: unsigned int sbloblen;
80: DH *dh;
81: BIGNUM *dh_server_pub = 0;
82: BIGNUM *shared_secret = 0;
83: unsigned char *kbuf;
84: unsigned char *hash;
85:
86: debug("Sending SSH2_MSG_KEXDH_INIT.");
87: /* generate and send 'e', client DH public key */
88: dh = dh_new_group1();
89: packet_start(SSH2_MSG_KEXDH_INIT);
90: packet_put_bignum2(dh->pub_key);
91: packet_send();
92: packet_write_wait();
93:
94: #ifdef DEBUG_KEXDH
95: fprintf(stderr, "\np= ");
1.19 ! markus 96: BN_print_fp(stderr, dh->p);
1.1 markus 97: fprintf(stderr, "\ng= ");
1.19 ! markus 98: BN_print_fp(stderr, dh->g);
1.1 markus 99: fprintf(stderr, "\npub= ");
1.19 ! markus 100: BN_print_fp(stderr, dh->pub_key);
1.1 markus 101: fprintf(stderr, "\n");
102: DHparams_print_fp(stderr, dh);
103: #endif
104:
105: debug("Wait SSH2_MSG_KEXDH_REPLY.");
106:
1.11 markus 107: packet_read_expect(&plen, SSH2_MSG_KEXDH_REPLY);
1.1 markus 108:
109: debug("Got SSH2_MSG_KEXDH_REPLY.");
110:
111: /* key, cert */
112: server_host_key_blob = packet_get_string(&sbloblen);
113: server_host_key = dsa_key_from_blob(server_host_key_blob, sbloblen);
114: if (server_host_key == NULL)
115: fatal("cannot decode server_host_key_blob");
116:
117: check_host_key(host, hostaddr, server_host_key,
118: options.user_hostfile2, options.system_hostfile2);
119:
120: /* DH paramter f, server public DH key */
121: dh_server_pub = BN_new();
122: if (dh_server_pub == NULL)
123: fatal("dh_server_pub == NULL");
124: packet_get_bignum2(dh_server_pub, &dlen);
125:
126: #ifdef DEBUG_KEXDH
127: fprintf(stderr, "\ndh_server_pub= ");
1.19 ! markus 128: BN_print_fp(stderr, dh_server_pub);
1.1 markus 129: fprintf(stderr, "\n");
130: debug("bits %d", BN_num_bits(dh_server_pub));
131: #endif
132:
133: /* signed H */
134: signature = packet_get_string(&slen);
135: packet_done();
136:
137: if (!dh_pub_is_valid(dh, dh_server_pub))
138: packet_disconnect("bad server public DH value");
139:
140: klen = DH_size(dh);
141: kbuf = xmalloc(klen);
142: kout = DH_compute_key(kbuf, dh_server_pub, dh);
143: #ifdef DEBUG_KEXDH
144: debug("shared secret: len %d/%d", klen, kout);
145: fprintf(stderr, "shared secret == ");
146: for (i = 0; i< kout; i++)
147: fprintf(stderr, "%02x", (kbuf[i])&0xff);
148: fprintf(stderr, "\n");
149: #endif
150: shared_secret = BN_new();
151:
152: BN_bin2bn(kbuf, kout, shared_secret);
153: memset(kbuf, 0, klen);
154: xfree(kbuf);
155:
156: /* calc and verify H */
157: hash = kex_hash(
158: client_version_string,
159: server_version_string,
160: buffer_ptr(client_kexinit), buffer_len(client_kexinit),
161: buffer_ptr(server_kexinit), buffer_len(server_kexinit),
162: server_host_key_blob, sbloblen,
163: dh->pub_key,
164: dh_server_pub,
165: shared_secret
166: );
1.3 markus 167: xfree(server_host_key_blob);
1.11 markus 168: DH_free(dh);
1.1 markus 169: #ifdef DEBUG_KEXDH
170: fprintf(stderr, "hash == ");
171: for (i = 0; i< 20; i++)
172: fprintf(stderr, "%02x", (hash[i])&0xff);
173: fprintf(stderr, "\n");
174: #endif
175: if (dsa_verify(server_host_key, (unsigned char *)signature, slen, hash, 20) != 1)
176: fatal("dsa_verify failed for server_host_key");
177: key_free(server_host_key);
178:
179: kex_derive_keys(kex, hash, shared_secret);
180: packet_set_kex(kex);
181:
182: /* save session id */
183: session_id2_len = 20;
184: session_id2 = xmalloc(session_id2_len);
185: memcpy(session_id2, hash, session_id2_len);
1.11 markus 186: }
187:
188: void
189: ssh_kex2(char *host, struct sockaddr *hostaddr)
190: {
191: int i, plen;
192: Kex *kex;
193: Buffer *client_kexinit, *server_kexinit;
194: char *sprop[PROPOSAL_MAX];
195:
196: if (options.ciphers != NULL) {
197: myproposal[PROPOSAL_ENC_ALGS_CTOS] =
198: myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
199: } else if (options.cipher == SSH_CIPHER_3DES) {
200: myproposal[PROPOSAL_ENC_ALGS_CTOS] =
201: myproposal[PROPOSAL_ENC_ALGS_STOC] =
202: (char *) cipher_name(SSH_CIPHER_3DES_CBC);
203: } else if (options.cipher == SSH_CIPHER_BLOWFISH) {
204: myproposal[PROPOSAL_ENC_ALGS_CTOS] =
205: myproposal[PROPOSAL_ENC_ALGS_STOC] =
206: (char *) cipher_name(SSH_CIPHER_BLOWFISH_CBC);
207: }
208: if (options.compression) {
209: myproposal[PROPOSAL_COMP_ALGS_CTOS] = "zlib";
210: myproposal[PROPOSAL_COMP_ALGS_STOC] = "zlib";
211: } else {
212: myproposal[PROPOSAL_COMP_ALGS_CTOS] = "none";
213: myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
214: }
215:
216: /* buffers with raw kexinit messages */
217: server_kexinit = xmalloc(sizeof(*server_kexinit));
218: buffer_init(server_kexinit);
219: client_kexinit = kex_init(myproposal);
220:
221: /* algorithm negotiation */
222: kex_exchange_kexinit(client_kexinit, server_kexinit, sprop);
223: kex = kex_choose_conf(myproposal, sprop, 0);
224: for (i = 0; i < PROPOSAL_MAX; i++)
225: xfree(sprop[i]);
226:
227: /* server authentication and session key agreement */
228: ssh_kex_dh(kex, host, hostaddr, client_kexinit, server_kexinit);
229:
230: buffer_free(client_kexinit);
231: buffer_free(server_kexinit);
232: xfree(client_kexinit);
233: xfree(server_kexinit);
1.1 markus 234:
235: debug("Wait SSH2_MSG_NEWKEYS.");
1.11 markus 236: packet_read_expect(&plen, SSH2_MSG_NEWKEYS);
1.1 markus 237: packet_done();
238: debug("GOT SSH2_MSG_NEWKEYS.");
239:
240: debug("send SSH2_MSG_NEWKEYS.");
241: packet_start(SSH2_MSG_NEWKEYS);
242: packet_send();
243: packet_write_wait();
244: debug("done: send SSH2_MSG_NEWKEYS.");
245:
246: #ifdef DEBUG_KEXDH
247: /* send 1st encrypted/maced/compressed message */
248: packet_start(SSH2_MSG_IGNORE);
249: packet_put_cstring("markus");
250: packet_send();
251: packet_write_wait();
252: #endif
253: debug("done: KEX2.");
254: }
1.11 markus 255:
1.1 markus 256: /*
257: * Authenticate user
258: */
259: int
260: ssh2_try_passwd(const char *server_user, const char *host, const char *service)
261: {
1.6 markus 262: static int attempt = 0;
1.1 markus 263: char prompt[80];
264: char *password;
1.6 markus 265:
1.13 todd 266: if (attempt++ >= options.number_of_password_prompts)
1.6 markus 267: return 0;
1.13 todd 268:
269: if(attempt != 1)
270: error("Permission denied, please try again.");
1.1 markus 271:
272: snprintf(prompt, sizeof(prompt), "%.30s@%.40s's password: ",
273: server_user, host);
274: password = read_passphrase(prompt, 0);
275: packet_start(SSH2_MSG_USERAUTH_REQUEST);
276: packet_put_cstring(server_user);
277: packet_put_cstring(service);
278: packet_put_cstring("password");
279: packet_put_char(0);
280: packet_put_cstring(password);
281: memset(password, 0, strlen(password));
282: xfree(password);
283: packet_send();
284: packet_write_wait();
285: return 1;
286: }
287:
1.16 markus 288: typedef int sign_fn(
289: Key *key,
290: unsigned char **sigp, int *lenp,
291: unsigned char *data, int datalen);
292:
1.17 markus 293: int
1.16 markus 294: ssh2_sign_and_send_pubkey(Key *k, sign_fn *do_sign,
1.1 markus 295: const char *server_user, const char *host, const char *service)
296: {
297: Buffer b;
298: unsigned char *blob, *signature;
299: int bloblen, slen;
1.14 markus 300: int skip = 0;
1.17 markus 301: int ret = -1;
1.1 markus 302:
303: dsa_make_key_blob(k, &blob, &bloblen);
304:
305: /* data to be signed */
306: buffer_init(&b);
1.14 markus 307: if (datafellows & SSH_COMPAT_SESSIONID_ENCODING) {
308: buffer_put_string(&b, session_id2, session_id2_len);
309: skip = buffer_len(&b);
310: } else {
311: buffer_append(&b, session_id2, session_id2_len);
312: skip = session_id2_len;
313: }
1.1 markus 314: buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
315: buffer_put_cstring(&b, server_user);
1.10 markus 316: buffer_put_cstring(&b,
317: datafellows & SSH_BUG_PUBKEYAUTH ?
318: "ssh-userauth" :
319: service);
1.1 markus 320: buffer_put_cstring(&b, "publickey");
321: buffer_put_char(&b, 1);
322: buffer_put_cstring(&b, KEX_DSS);
323: buffer_put_string(&b, blob, bloblen);
324:
325: /* generate signature */
1.17 markus 326: ret = do_sign(k, &signature, &slen, buffer_ptr(&b), buffer_len(&b));
327: if (ret == -1) {
328: xfree(blob);
329: buffer_free(&b);
330: return 0;
331: }
1.1 markus 332: #ifdef DEBUG_DSS
333: buffer_dump(&b);
334: #endif
1.10 markus 335: if (datafellows & SSH_BUG_PUBKEYAUTH) {
336: buffer_clear(&b);
337: buffer_append(&b, session_id2, session_id2_len);
338: buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
339: buffer_put_cstring(&b, server_user);
340: buffer_put_cstring(&b, service);
341: buffer_put_cstring(&b, "publickey");
342: buffer_put_char(&b, 1);
343: buffer_put_cstring(&b, KEX_DSS);
344: buffer_put_string(&b, blob, bloblen);
345: }
346: xfree(blob);
1.1 markus 347: /* append signature */
348: buffer_put_string(&b, signature, slen);
349: xfree(signature);
350:
351: /* skip session id and packet type */
1.14 markus 352: if (buffer_len(&b) < skip + 1)
1.1 markus 353: fatal("ssh2_try_pubkey: internal error");
1.14 markus 354: buffer_consume(&b, skip + 1);
1.1 markus 355:
356: /* put remaining data from buffer into packet */
357: packet_start(SSH2_MSG_USERAUTH_REQUEST);
358: packet_put_raw(buffer_ptr(&b), buffer_len(&b));
359: buffer_free(&b);
360:
361: /* send */
362: packet_send();
363: packet_write_wait();
1.17 markus 364:
365: return 1;
1.16 markus 366: }
367:
368: int
369: ssh2_try_pubkey(char *filename,
370: const char *server_user, const char *host, const char *service)
371: {
372: Key *k;
1.17 markus 373: int ret = 0;
1.16 markus 374: struct stat st;
375:
376: if (stat(filename, &st) != 0) {
377: debug("key does not exist: %s", filename);
378: return 0;
379: }
380: debug("try pubkey: %s", filename);
381:
382: k = key_new(KEY_DSA);
383: if (!load_private_key(filename, "", k, NULL)) {
384: int success = 0;
385: char *passphrase;
386: char prompt[300];
387: snprintf(prompt, sizeof prompt,
388: "Enter passphrase for DSA key '%.100s': ",
389: filename);
390: passphrase = read_passphrase(prompt, 0);
391: success = load_private_key(filename, passphrase, k, NULL);
392: memset(passphrase, 0, strlen(passphrase));
393: xfree(passphrase);
394: if (!success) {
395: key_free(k);
396: return 0;
397: }
398: }
1.17 markus 399: ret = ssh2_sign_and_send_pubkey(k, dsa_sign, server_user, host, service);
400: key_free(k);
401: return ret;
402: }
403:
404: int agent_sign(
405: Key *key,
406: unsigned char **sigp, int *lenp,
407: unsigned char *data, int datalen)
408: {
409: int ret = -1;
410: AuthenticationConnection *ac = ssh_get_authentication_connection();
411: if (ac != NULL) {
412: ret = ssh_agent_sign(ac, key, sigp, lenp, data, datalen);
413: ssh_close_authentication_connection(ac);
414: }
415: return ret;
416: }
417:
418: int
419: ssh2_try_agent(AuthenticationConnection *ac,
420: const char *server_user, const char *host, const char *service)
421: {
422: static int called = 0;
423: char *comment;
424: Key *k;
425: int ret;
426:
427: if (called == 0) {
428: k = ssh_get_first_identity(ac, &comment, 2);
429: called ++;
430: } else {
431: k = ssh_get_next_identity(ac, &comment, 2);
432: }
433: if (k == NULL)
434: return 0;
435: debug("trying DSA agent key %s", comment);
436: xfree(comment);
437: ret = ssh2_sign_and_send_pubkey(k, agent_sign, server_user, host, service);
438: key_free(k);
439: return ret;
1.1 markus 440: }
441:
442: void
443: ssh_userauth2(const char *server_user, char *host)
444: {
1.17 markus 445: AuthenticationConnection *ac = ssh_get_authentication_connection();
1.1 markus 446: int type;
447: int plen;
448: int sent;
449: unsigned int dlen;
450: int partial;
451: int i = 0;
452: char *auths;
453: char *service = "ssh-connection"; /* service name */
454:
455: debug("send SSH2_MSG_SERVICE_REQUEST");
456: packet_start(SSH2_MSG_SERVICE_REQUEST);
457: packet_put_cstring("ssh-userauth");
458: packet_send();
459: packet_write_wait();
460:
461: type = packet_read(&plen);
462: if (type != SSH2_MSG_SERVICE_ACCEPT) {
463: fatal("denied SSH2_MSG_SERVICE_ACCEPT: %d", type);
464: }
465: if (packet_remaining() > 0) {
466: char *reply = packet_get_string(&plen);
467: debug("service_accept: %s", reply);
468: xfree(reply);
469: } else {
470: /* payload empty for ssh-2.0.13 ?? */
1.8 markus 471: debug("buggy server: service_accept w/o service");
1.1 markus 472: }
473: packet_done();
474: debug("got SSH2_MSG_SERVICE_ACCEPT");
475:
476: /* INITIAL request for auth */
477: packet_start(SSH2_MSG_USERAUTH_REQUEST);
478: packet_put_cstring(server_user);
479: packet_put_cstring(service);
480: packet_put_cstring("none");
481: packet_send();
482: packet_write_wait();
483:
484: for (;;) {
485: sent = 0;
486: type = packet_read(&plen);
487: if (type == SSH2_MSG_USERAUTH_SUCCESS)
488: break;
489: if (type != SSH2_MSG_USERAUTH_FAILURE)
490: fatal("access denied: %d", type);
491: /* SSH2_MSG_USERAUTH_FAILURE means: try again */
492: auths = packet_get_string(&dlen);
493: debug("authentications that can continue: %s", auths);
494: partial = packet_get_char();
495: packet_done();
496: if (partial)
497: debug("partial success");
1.7 markus 498: if (options.dsa_authentication &&
1.4 markus 499: strstr(auths, "publickey") != NULL) {
1.17 markus 500: if (ac != NULL)
501: sent = ssh2_try_agent(ac,
1.1 markus 502: server_user, host, service);
1.17 markus 503: if (!sent) {
504: while (i < options.num_identity_files2) {
505: sent = ssh2_try_pubkey(
506: options.identity_files2[i++],
507: server_user, host, service);
508: if (sent)
509: break;
510: }
1.1 markus 511: }
512: }
513: if (!sent) {
1.4 markus 514: if (options.password_authentication &&
515: !options.batch_mode &&
516: strstr(auths, "password") != NULL) {
1.1 markus 517: sent = ssh2_try_passwd(server_user, host, service);
518: }
519: }
1.4 markus 520: if (!sent)
521: fatal("Permission denied (%s).", auths);
1.1 markus 522: xfree(auths);
523: }
1.17 markus 524: if (ac != NULL)
525: ssh_close_authentication_connection(ac);
1.1 markus 526: packet_done();
527: debug("ssh-userauth2 successfull");
528: }
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