Annotation of src/usr.bin/ssh/sshconnect2.c, Revision 1.18
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"
1.18 ! deraadt 26: RCSID("$OpenBSD: sshconnect2.c,v 1.17 2000/08/19 21:34:44 markus 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: {
1.11 markus 70: int plen, dlen;
1.1 markus 71: unsigned int klen, kout;
72: char *signature = NULL;
73: unsigned int slen;
74: char *server_host_key_blob = NULL;
75: Key *server_host_key;
76: unsigned int sbloblen;
77: DH *dh;
78: BIGNUM *dh_server_pub = 0;
79: BIGNUM *shared_secret = 0;
80: unsigned char *kbuf;
81: unsigned char *hash;
82:
83: debug("Sending SSH2_MSG_KEXDH_INIT.");
84: /* generate and send 'e', client DH public key */
85: dh = dh_new_group1();
86: packet_start(SSH2_MSG_KEXDH_INIT);
87: packet_put_bignum2(dh->pub_key);
88: packet_send();
89: packet_write_wait();
90:
91: #ifdef DEBUG_KEXDH
92: fprintf(stderr, "\np= ");
93: bignum_print(dh->p);
94: fprintf(stderr, "\ng= ");
95: bignum_print(dh->g);
96: fprintf(stderr, "\npub= ");
97: bignum_print(dh->pub_key);
98: fprintf(stderr, "\n");
99: DHparams_print_fp(stderr, dh);
100: #endif
101:
102: debug("Wait SSH2_MSG_KEXDH_REPLY.");
103:
1.11 markus 104: packet_read_expect(&plen, SSH2_MSG_KEXDH_REPLY);
1.1 markus 105:
106: debug("Got SSH2_MSG_KEXDH_REPLY.");
107:
108: /* key, cert */
109: server_host_key_blob = packet_get_string(&sbloblen);
110: server_host_key = dsa_key_from_blob(server_host_key_blob, sbloblen);
111: if (server_host_key == NULL)
112: fatal("cannot decode server_host_key_blob");
113:
114: check_host_key(host, hostaddr, server_host_key,
115: options.user_hostfile2, options.system_hostfile2);
116:
117: /* DH paramter f, server public DH key */
118: dh_server_pub = BN_new();
119: if (dh_server_pub == NULL)
120: fatal("dh_server_pub == NULL");
121: packet_get_bignum2(dh_server_pub, &dlen);
122:
123: #ifdef DEBUG_KEXDH
124: fprintf(stderr, "\ndh_server_pub= ");
125: bignum_print(dh_server_pub);
126: fprintf(stderr, "\n");
127: debug("bits %d", BN_num_bits(dh_server_pub));
128: #endif
129:
130: /* signed H */
131: signature = packet_get_string(&slen);
132: packet_done();
133:
134: if (!dh_pub_is_valid(dh, dh_server_pub))
135: packet_disconnect("bad server public DH value");
136:
137: klen = DH_size(dh);
138: kbuf = xmalloc(klen);
139: kout = DH_compute_key(kbuf, dh_server_pub, dh);
140: #ifdef DEBUG_KEXDH
141: debug("shared secret: len %d/%d", klen, kout);
142: fprintf(stderr, "shared secret == ");
143: for (i = 0; i< kout; i++)
144: fprintf(stderr, "%02x", (kbuf[i])&0xff);
145: fprintf(stderr, "\n");
146: #endif
147: shared_secret = BN_new();
148:
149: BN_bin2bn(kbuf, kout, shared_secret);
150: memset(kbuf, 0, klen);
151: xfree(kbuf);
152:
153: /* calc and verify H */
154: hash = kex_hash(
155: client_version_string,
156: server_version_string,
157: buffer_ptr(client_kexinit), buffer_len(client_kexinit),
158: buffer_ptr(server_kexinit), buffer_len(server_kexinit),
159: server_host_key_blob, sbloblen,
160: dh->pub_key,
161: dh_server_pub,
162: shared_secret
163: );
1.3 markus 164: xfree(server_host_key_blob);
1.11 markus 165: DH_free(dh);
1.1 markus 166: #ifdef DEBUG_KEXDH
167: fprintf(stderr, "hash == ");
168: for (i = 0; i< 20; i++)
169: fprintf(stderr, "%02x", (hash[i])&0xff);
170: fprintf(stderr, "\n");
171: #endif
172: if (dsa_verify(server_host_key, (unsigned char *)signature, slen, hash, 20) != 1)
173: fatal("dsa_verify failed for server_host_key");
174: key_free(server_host_key);
175:
176: kex_derive_keys(kex, hash, shared_secret);
177: packet_set_kex(kex);
178:
179: /* save session id */
180: session_id2_len = 20;
181: session_id2 = xmalloc(session_id2_len);
182: memcpy(session_id2, hash, session_id2_len);
1.11 markus 183: }
184:
185: void
186: ssh_kex2(char *host, struct sockaddr *hostaddr)
187: {
188: int i, plen;
189: Kex *kex;
190: Buffer *client_kexinit, *server_kexinit;
191: char *sprop[PROPOSAL_MAX];
192:
193: if (options.ciphers != NULL) {
194: myproposal[PROPOSAL_ENC_ALGS_CTOS] =
195: myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
196: } else if (options.cipher == SSH_CIPHER_3DES) {
197: myproposal[PROPOSAL_ENC_ALGS_CTOS] =
198: myproposal[PROPOSAL_ENC_ALGS_STOC] =
199: (char *) cipher_name(SSH_CIPHER_3DES_CBC);
200: } else if (options.cipher == SSH_CIPHER_BLOWFISH) {
201: myproposal[PROPOSAL_ENC_ALGS_CTOS] =
202: myproposal[PROPOSAL_ENC_ALGS_STOC] =
203: (char *) cipher_name(SSH_CIPHER_BLOWFISH_CBC);
204: }
205: if (options.compression) {
206: myproposal[PROPOSAL_COMP_ALGS_CTOS] = "zlib";
207: myproposal[PROPOSAL_COMP_ALGS_STOC] = "zlib";
208: } else {
209: myproposal[PROPOSAL_COMP_ALGS_CTOS] = "none";
210: myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
211: }
212:
213: /* buffers with raw kexinit messages */
214: server_kexinit = xmalloc(sizeof(*server_kexinit));
215: buffer_init(server_kexinit);
216: client_kexinit = kex_init(myproposal);
217:
218: /* algorithm negotiation */
219: kex_exchange_kexinit(client_kexinit, server_kexinit, sprop);
220: kex = kex_choose_conf(myproposal, sprop, 0);
221: for (i = 0; i < PROPOSAL_MAX; i++)
222: xfree(sprop[i]);
223:
224: /* server authentication and session key agreement */
225: ssh_kex_dh(kex, host, hostaddr, client_kexinit, server_kexinit);
226:
227: buffer_free(client_kexinit);
228: buffer_free(server_kexinit);
229: xfree(client_kexinit);
230: xfree(server_kexinit);
1.1 markus 231:
232: debug("Wait SSH2_MSG_NEWKEYS.");
1.11 markus 233: packet_read_expect(&plen, SSH2_MSG_NEWKEYS);
1.1 markus 234: packet_done();
235: debug("GOT SSH2_MSG_NEWKEYS.");
236:
237: debug("send SSH2_MSG_NEWKEYS.");
238: packet_start(SSH2_MSG_NEWKEYS);
239: packet_send();
240: packet_write_wait();
241: debug("done: send SSH2_MSG_NEWKEYS.");
242:
243: #ifdef DEBUG_KEXDH
244: /* send 1st encrypted/maced/compressed message */
245: packet_start(SSH2_MSG_IGNORE);
246: packet_put_cstring("markus");
247: packet_send();
248: packet_write_wait();
249: #endif
250: debug("done: KEX2.");
251: }
1.11 markus 252:
1.1 markus 253: /*
254: * Authenticate user
255: */
256: int
257: ssh2_try_passwd(const char *server_user, const char *host, const char *service)
258: {
1.6 markus 259: static int attempt = 0;
1.1 markus 260: char prompt[80];
261: char *password;
1.6 markus 262:
1.13 todd 263: if (attempt++ >= options.number_of_password_prompts)
1.6 markus 264: return 0;
1.13 todd 265:
266: if(attempt != 1)
267: error("Permission denied, please try again.");
1.1 markus 268:
269: snprintf(prompt, sizeof(prompt), "%.30s@%.40s's password: ",
270: server_user, host);
271: password = read_passphrase(prompt, 0);
272: packet_start(SSH2_MSG_USERAUTH_REQUEST);
273: packet_put_cstring(server_user);
274: packet_put_cstring(service);
275: packet_put_cstring("password");
276: packet_put_char(0);
277: packet_put_cstring(password);
278: memset(password, 0, strlen(password));
279: xfree(password);
280: packet_send();
281: packet_write_wait();
282: return 1;
283: }
284:
1.16 markus 285: typedef int sign_fn(
286: Key *key,
287: unsigned char **sigp, int *lenp,
288: unsigned char *data, int datalen);
289:
1.17 markus 290: int
1.16 markus 291: ssh2_sign_and_send_pubkey(Key *k, sign_fn *do_sign,
1.1 markus 292: const char *server_user, const char *host, const char *service)
293: {
294: Buffer b;
295: unsigned char *blob, *signature;
296: int bloblen, slen;
1.14 markus 297: int skip = 0;
1.17 markus 298: int ret = -1;
1.1 markus 299:
300: dsa_make_key_blob(k, &blob, &bloblen);
301:
302: /* data to be signed */
303: buffer_init(&b);
1.14 markus 304: if (datafellows & SSH_COMPAT_SESSIONID_ENCODING) {
305: buffer_put_string(&b, session_id2, session_id2_len);
306: skip = buffer_len(&b);
307: } else {
308: buffer_append(&b, session_id2, session_id2_len);
309: skip = session_id2_len;
310: }
1.1 markus 311: buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
312: buffer_put_cstring(&b, server_user);
1.10 markus 313: buffer_put_cstring(&b,
314: datafellows & SSH_BUG_PUBKEYAUTH ?
315: "ssh-userauth" :
316: service);
1.1 markus 317: buffer_put_cstring(&b, "publickey");
318: buffer_put_char(&b, 1);
319: buffer_put_cstring(&b, KEX_DSS);
320: buffer_put_string(&b, blob, bloblen);
321:
322: /* generate signature */
1.17 markus 323: ret = do_sign(k, &signature, &slen, buffer_ptr(&b), buffer_len(&b));
324: if (ret == -1) {
325: xfree(blob);
326: buffer_free(&b);
327: return 0;
328: }
1.1 markus 329: #ifdef DEBUG_DSS
330: buffer_dump(&b);
331: #endif
1.10 markus 332: if (datafellows & SSH_BUG_PUBKEYAUTH) {
333: buffer_clear(&b);
334: buffer_append(&b, session_id2, session_id2_len);
335: buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
336: buffer_put_cstring(&b, server_user);
337: buffer_put_cstring(&b, service);
338: buffer_put_cstring(&b, "publickey");
339: buffer_put_char(&b, 1);
340: buffer_put_cstring(&b, KEX_DSS);
341: buffer_put_string(&b, blob, bloblen);
342: }
343: xfree(blob);
1.1 markus 344: /* append signature */
345: buffer_put_string(&b, signature, slen);
346: xfree(signature);
347:
348: /* skip session id and packet type */
1.14 markus 349: if (buffer_len(&b) < skip + 1)
1.1 markus 350: fatal("ssh2_try_pubkey: internal error");
1.14 markus 351: buffer_consume(&b, skip + 1);
1.1 markus 352:
353: /* put remaining data from buffer into packet */
354: packet_start(SSH2_MSG_USERAUTH_REQUEST);
355: packet_put_raw(buffer_ptr(&b), buffer_len(&b));
356: buffer_free(&b);
357:
358: /* send */
359: packet_send();
360: packet_write_wait();
1.17 markus 361:
362: return 1;
1.16 markus 363: }
364:
365: int
366: ssh2_try_pubkey(char *filename,
367: const char *server_user, const char *host, const char *service)
368: {
369: Key *k;
1.17 markus 370: int ret = 0;
1.16 markus 371: struct stat st;
372:
373: if (stat(filename, &st) != 0) {
374: debug("key does not exist: %s", filename);
375: return 0;
376: }
377: debug("try pubkey: %s", filename);
378:
379: k = key_new(KEY_DSA);
380: if (!load_private_key(filename, "", k, NULL)) {
381: int success = 0;
382: char *passphrase;
383: char prompt[300];
384: snprintf(prompt, sizeof prompt,
385: "Enter passphrase for DSA key '%.100s': ",
386: filename);
387: passphrase = read_passphrase(prompt, 0);
388: success = load_private_key(filename, passphrase, k, NULL);
389: memset(passphrase, 0, strlen(passphrase));
390: xfree(passphrase);
391: if (!success) {
392: key_free(k);
393: return 0;
394: }
395: }
1.17 markus 396: ret = ssh2_sign_and_send_pubkey(k, dsa_sign, server_user, host, service);
397: key_free(k);
398: return ret;
399: }
400:
401: int agent_sign(
402: Key *key,
403: unsigned char **sigp, int *lenp,
404: unsigned char *data, int datalen)
405: {
406: int ret = -1;
407: AuthenticationConnection *ac = ssh_get_authentication_connection();
408: if (ac != NULL) {
409: ret = ssh_agent_sign(ac, key, sigp, lenp, data, datalen);
410: ssh_close_authentication_connection(ac);
411: }
412: return ret;
413: }
414:
415: int
416: ssh2_try_agent(AuthenticationConnection *ac,
417: const char *server_user, const char *host, const char *service)
418: {
419: static int called = 0;
420: char *comment;
421: Key *k;
422: int ret;
423:
424: if (called == 0) {
425: k = ssh_get_first_identity(ac, &comment, 2);
426: called ++;
427: } else {
428: k = ssh_get_next_identity(ac, &comment, 2);
429: }
430: if (k == NULL)
431: return 0;
432: debug("trying DSA agent key %s", comment);
433: xfree(comment);
434: ret = ssh2_sign_and_send_pubkey(k, agent_sign, server_user, host, service);
435: key_free(k);
436: return ret;
1.1 markus 437: }
438:
439: void
440: ssh_userauth2(const char *server_user, char *host)
441: {
1.17 markus 442: AuthenticationConnection *ac = ssh_get_authentication_connection();
1.1 markus 443: int type;
444: int plen;
445: int sent;
446: unsigned int dlen;
447: int partial;
448: int i = 0;
449: char *auths;
450: char *service = "ssh-connection"; /* service name */
451:
452: debug("send SSH2_MSG_SERVICE_REQUEST");
453: packet_start(SSH2_MSG_SERVICE_REQUEST);
454: packet_put_cstring("ssh-userauth");
455: packet_send();
456: packet_write_wait();
457:
458: type = packet_read(&plen);
459: if (type != SSH2_MSG_SERVICE_ACCEPT) {
460: fatal("denied SSH2_MSG_SERVICE_ACCEPT: %d", type);
461: }
462: if (packet_remaining() > 0) {
463: char *reply = packet_get_string(&plen);
464: debug("service_accept: %s", reply);
465: xfree(reply);
466: } else {
467: /* payload empty for ssh-2.0.13 ?? */
1.8 markus 468: debug("buggy server: service_accept w/o service");
1.1 markus 469: }
470: packet_done();
471: debug("got SSH2_MSG_SERVICE_ACCEPT");
472:
473: /* INITIAL request for auth */
474: packet_start(SSH2_MSG_USERAUTH_REQUEST);
475: packet_put_cstring(server_user);
476: packet_put_cstring(service);
477: packet_put_cstring("none");
478: packet_send();
479: packet_write_wait();
480:
481: for (;;) {
482: sent = 0;
483: type = packet_read(&plen);
484: if (type == SSH2_MSG_USERAUTH_SUCCESS)
485: break;
486: if (type != SSH2_MSG_USERAUTH_FAILURE)
487: fatal("access denied: %d", type);
488: /* SSH2_MSG_USERAUTH_FAILURE means: try again */
489: auths = packet_get_string(&dlen);
490: debug("authentications that can continue: %s", auths);
491: partial = packet_get_char();
492: packet_done();
493: if (partial)
494: debug("partial success");
1.7 markus 495: if (options.dsa_authentication &&
1.4 markus 496: strstr(auths, "publickey") != NULL) {
1.17 markus 497: if (ac != NULL)
498: sent = ssh2_try_agent(ac,
1.1 markus 499: server_user, host, service);
1.17 markus 500: if (!sent) {
501: while (i < options.num_identity_files2) {
502: sent = ssh2_try_pubkey(
503: options.identity_files2[i++],
504: server_user, host, service);
505: if (sent)
506: break;
507: }
1.1 markus 508: }
509: }
510: if (!sent) {
1.4 markus 511: if (options.password_authentication &&
512: !options.batch_mode &&
513: strstr(auths, "password") != NULL) {
1.1 markus 514: sent = ssh2_try_passwd(server_user, host, service);
515: }
516: }
1.4 markus 517: if (!sent)
518: fatal("Permission denied (%s).", auths);
1.1 markus 519: xfree(auths);
520: }
1.17 markus 521: if (ac != NULL)
522: ssh_close_authentication_connection(ac);
1.1 markus 523: packet_done();
524: debug("ssh-userauth2 successfull");
525: }
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