Annotation of src/usr.bin/ssh/sshconnect2.c, Revision 1.16
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: * 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"
1.15 markus 31: RCSID("$OpenBSD: sshconnect2.c,v 1.14 2000/06/19 00:50:11 markus Exp $");
1.1 markus 32:
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 */
59: extern char *client_version_string;
60: extern char *server_version_string;
61: extern Options options;
62:
63: /*
64: * SSH2 key exchange
65: */
66:
67: unsigned char *session_id2 = NULL;
68: int session_id2_len = 0;
69:
70: void
1.11 markus 71: ssh_kex_dh(Kex *kex, char *host, struct sockaddr *hostaddr,
72: Buffer *client_kexinit, Buffer *server_kexinit)
1.1 markus 73: {
1.11 markus 74: int plen, dlen;
1.1 markus 75: unsigned int klen, kout;
76: char *signature = NULL;
77: unsigned int slen;
78: char *server_host_key_blob = NULL;
79: Key *server_host_key;
80: unsigned int sbloblen;
81: DH *dh;
82: BIGNUM *dh_server_pub = 0;
83: BIGNUM *shared_secret = 0;
84: unsigned char *kbuf;
85: unsigned char *hash;
86:
87: debug("Sending SSH2_MSG_KEXDH_INIT.");
88: /* generate and send 'e', client DH public key */
89: dh = dh_new_group1();
90: packet_start(SSH2_MSG_KEXDH_INIT);
91: packet_put_bignum2(dh->pub_key);
92: packet_send();
93: packet_write_wait();
94:
95: #ifdef DEBUG_KEXDH
96: fprintf(stderr, "\np= ");
97: bignum_print(dh->p);
98: fprintf(stderr, "\ng= ");
99: bignum_print(dh->g);
100: fprintf(stderr, "\npub= ");
101: bignum_print(dh->pub_key);
102: fprintf(stderr, "\n");
103: DHparams_print_fp(stderr, dh);
104: #endif
105:
106: debug("Wait SSH2_MSG_KEXDH_REPLY.");
107:
1.11 markus 108: packet_read_expect(&plen, SSH2_MSG_KEXDH_REPLY);
1.1 markus 109:
110: debug("Got SSH2_MSG_KEXDH_REPLY.");
111:
112: /* key, cert */
113: server_host_key_blob = packet_get_string(&sbloblen);
114: server_host_key = dsa_key_from_blob(server_host_key_blob, sbloblen);
115: if (server_host_key == NULL)
116: fatal("cannot decode server_host_key_blob");
117:
118: check_host_key(host, hostaddr, server_host_key,
119: options.user_hostfile2, options.system_hostfile2);
120:
121: /* DH paramter f, server public DH key */
122: dh_server_pub = BN_new();
123: if (dh_server_pub == NULL)
124: fatal("dh_server_pub == NULL");
125: packet_get_bignum2(dh_server_pub, &dlen);
126:
127: #ifdef DEBUG_KEXDH
128: fprintf(stderr, "\ndh_server_pub= ");
129: bignum_print(dh_server_pub);
130: fprintf(stderr, "\n");
131: debug("bits %d", BN_num_bits(dh_server_pub));
132: #endif
133:
134: /* signed H */
135: signature = packet_get_string(&slen);
136: packet_done();
137:
138: if (!dh_pub_is_valid(dh, dh_server_pub))
139: packet_disconnect("bad server public DH value");
140:
141: klen = DH_size(dh);
142: kbuf = xmalloc(klen);
143: kout = DH_compute_key(kbuf, dh_server_pub, dh);
144: #ifdef DEBUG_KEXDH
145: debug("shared secret: len %d/%d", klen, kout);
146: fprintf(stderr, "shared secret == ");
147: for (i = 0; i< kout; i++)
148: fprintf(stderr, "%02x", (kbuf[i])&0xff);
149: fprintf(stderr, "\n");
150: #endif
151: shared_secret = BN_new();
152:
153: BN_bin2bn(kbuf, kout, shared_secret);
154: memset(kbuf, 0, klen);
155: xfree(kbuf);
156:
157: /* calc and verify H */
158: hash = kex_hash(
159: client_version_string,
160: server_version_string,
161: buffer_ptr(client_kexinit), buffer_len(client_kexinit),
162: buffer_ptr(server_kexinit), buffer_len(server_kexinit),
163: server_host_key_blob, sbloblen,
164: dh->pub_key,
165: dh_server_pub,
166: shared_secret
167: );
1.3 markus 168: xfree(server_host_key_blob);
1.11 markus 169: DH_free(dh);
1.1 markus 170: #ifdef DEBUG_KEXDH
171: fprintf(stderr, "hash == ");
172: for (i = 0; i< 20; i++)
173: fprintf(stderr, "%02x", (hash[i])&0xff);
174: fprintf(stderr, "\n");
175: #endif
176: if (dsa_verify(server_host_key, (unsigned char *)signature, slen, hash, 20) != 1)
177: fatal("dsa_verify failed for server_host_key");
178: key_free(server_host_key);
179:
180: kex_derive_keys(kex, hash, shared_secret);
181: packet_set_kex(kex);
182:
183: /* save session id */
184: session_id2_len = 20;
185: session_id2 = xmalloc(session_id2_len);
186: memcpy(session_id2, hash, session_id2_len);
1.11 markus 187: }
188:
189: void
190: ssh_kex2(char *host, struct sockaddr *hostaddr)
191: {
192: int i, plen;
193: Kex *kex;
194: Buffer *client_kexinit, *server_kexinit;
195: char *sprop[PROPOSAL_MAX];
196:
197: if (options.ciphers != NULL) {
198: myproposal[PROPOSAL_ENC_ALGS_CTOS] =
199: myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
200: } else if (options.cipher == SSH_CIPHER_3DES) {
201: myproposal[PROPOSAL_ENC_ALGS_CTOS] =
202: myproposal[PROPOSAL_ENC_ALGS_STOC] =
203: (char *) cipher_name(SSH_CIPHER_3DES_CBC);
204: } else if (options.cipher == SSH_CIPHER_BLOWFISH) {
205: myproposal[PROPOSAL_ENC_ALGS_CTOS] =
206: myproposal[PROPOSAL_ENC_ALGS_STOC] =
207: (char *) cipher_name(SSH_CIPHER_BLOWFISH_CBC);
208: }
209: if (options.compression) {
210: myproposal[PROPOSAL_COMP_ALGS_CTOS] = "zlib";
211: myproposal[PROPOSAL_COMP_ALGS_STOC] = "zlib";
212: } else {
213: myproposal[PROPOSAL_COMP_ALGS_CTOS] = "none";
214: myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
215: }
216:
217: /* buffers with raw kexinit messages */
218: server_kexinit = xmalloc(sizeof(*server_kexinit));
219: buffer_init(server_kexinit);
220: client_kexinit = kex_init(myproposal);
221:
222: /* algorithm negotiation */
223: kex_exchange_kexinit(client_kexinit, server_kexinit, sprop);
224: kex = kex_choose_conf(myproposal, sprop, 0);
225: for (i = 0; i < PROPOSAL_MAX; i++)
226: xfree(sprop[i]);
227:
228: /* server authentication and session key agreement */
229: ssh_kex_dh(kex, host, hostaddr, client_kexinit, server_kexinit);
230:
231: buffer_free(client_kexinit);
232: buffer_free(server_kexinit);
233: xfree(client_kexinit);
234: xfree(server_kexinit);
1.1 markus 235:
236: debug("Wait SSH2_MSG_NEWKEYS.");
1.11 markus 237: packet_read_expect(&plen, SSH2_MSG_NEWKEYS);
1.1 markus 238: packet_done();
239: debug("GOT SSH2_MSG_NEWKEYS.");
240:
241: debug("send SSH2_MSG_NEWKEYS.");
242: packet_start(SSH2_MSG_NEWKEYS);
243: packet_send();
244: packet_write_wait();
245: debug("done: send SSH2_MSG_NEWKEYS.");
246:
247: #ifdef DEBUG_KEXDH
248: /* send 1st encrypted/maced/compressed message */
249: packet_start(SSH2_MSG_IGNORE);
250: packet_put_cstring("markus");
251: packet_send();
252: packet_write_wait();
253: #endif
254: debug("done: KEX2.");
255: }
1.11 markus 256:
1.1 markus 257: /*
258: * Authenticate user
259: */
260: int
261: ssh2_try_passwd(const char *server_user, const char *host, const char *service)
262: {
1.6 markus 263: static int attempt = 0;
1.1 markus 264: char prompt[80];
265: char *password;
1.6 markus 266:
1.13 todd 267: if (attempt++ >= options.number_of_password_prompts)
1.6 markus 268: return 0;
1.13 todd 269:
270: if(attempt != 1)
271: error("Permission denied, please try again.");
1.1 markus 272:
273: snprintf(prompt, sizeof(prompt), "%.30s@%.40s's password: ",
274: server_user, host);
275: password = read_passphrase(prompt, 0);
276: packet_start(SSH2_MSG_USERAUTH_REQUEST);
277: packet_put_cstring(server_user);
278: packet_put_cstring(service);
279: packet_put_cstring("password");
280: packet_put_char(0);
281: packet_put_cstring(password);
282: memset(password, 0, strlen(password));
283: xfree(password);
284: packet_send();
285: packet_write_wait();
286: return 1;
287: }
288:
1.16 ! markus 289: typedef int sign_fn(
! 290: Key *key,
! 291: unsigned char **sigp, int *lenp,
! 292: unsigned char *data, int datalen);
! 293:
! 294: void
! 295: ssh2_sign_and_send_pubkey(Key *k, sign_fn *do_sign,
1.1 markus 296: const char *server_user, const char *host, const char *service)
297: {
298: Buffer b;
299: unsigned char *blob, *signature;
300: int bloblen, slen;
1.14 markus 301: int skip = 0;
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 */
1.16 ! markus 326: do_sign(k, &signature, &slen, buffer_ptr(&b), buffer_len(&b));
! 327: key_free(k); /* XXX */
1.1 markus 328: #ifdef DEBUG_DSS
329: buffer_dump(&b);
330: #endif
1.10 markus 331: if (datafellows & SSH_BUG_PUBKEYAUTH) {
332: buffer_clear(&b);
333: buffer_append(&b, session_id2, session_id2_len);
334: buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
335: buffer_put_cstring(&b, server_user);
336: buffer_put_cstring(&b, service);
337: buffer_put_cstring(&b, "publickey");
338: buffer_put_char(&b, 1);
339: buffer_put_cstring(&b, KEX_DSS);
340: buffer_put_string(&b, blob, bloblen);
341: }
342: xfree(blob);
1.1 markus 343: /* append signature */
344: buffer_put_string(&b, signature, slen);
345: xfree(signature);
346:
347: /* skip session id and packet type */
1.14 markus 348: if (buffer_len(&b) < skip + 1)
1.1 markus 349: fatal("ssh2_try_pubkey: internal error");
1.14 markus 350: buffer_consume(&b, skip + 1);
1.1 markus 351:
352: /* put remaining data from buffer into packet */
353: packet_start(SSH2_MSG_USERAUTH_REQUEST);
354: packet_put_raw(buffer_ptr(&b), buffer_len(&b));
355: buffer_free(&b);
356:
357: /* send */
358: packet_send();
359: packet_write_wait();
1.16 ! markus 360: }
! 361:
! 362: int
! 363: ssh2_try_pubkey(char *filename,
! 364: const char *server_user, const char *host, const char *service)
! 365: {
! 366: Key *k;
! 367: struct stat st;
! 368:
! 369: if (stat(filename, &st) != 0) {
! 370: debug("key does not exist: %s", filename);
! 371: return 0;
! 372: }
! 373: debug("try pubkey: %s", filename);
! 374:
! 375: k = key_new(KEY_DSA);
! 376: if (!load_private_key(filename, "", k, NULL)) {
! 377: int success = 0;
! 378: char *passphrase;
! 379: char prompt[300];
! 380: snprintf(prompt, sizeof prompt,
! 381: "Enter passphrase for DSA key '%.100s': ",
! 382: filename);
! 383: passphrase = read_passphrase(prompt, 0);
! 384: success = load_private_key(filename, passphrase, k, NULL);
! 385: memset(passphrase, 0, strlen(passphrase));
! 386: xfree(passphrase);
! 387: if (!success) {
! 388: key_free(k);
! 389: return 0;
! 390: }
! 391: }
! 392: ssh2_sign_and_send_pubkey(k, dsa_sign, server_user, host, service);
1.1 markus 393: return 1;
394: }
395:
396: void
397: ssh_userauth2(const char *server_user, char *host)
398: {
399: int type;
400: int plen;
401: int sent;
402: unsigned int dlen;
403: int partial;
404: int i = 0;
405: char *auths;
406: char *service = "ssh-connection"; /* service name */
407:
408: debug("send SSH2_MSG_SERVICE_REQUEST");
409: packet_start(SSH2_MSG_SERVICE_REQUEST);
410: packet_put_cstring("ssh-userauth");
411: packet_send();
412: packet_write_wait();
413:
414: type = packet_read(&plen);
415: if (type != SSH2_MSG_SERVICE_ACCEPT) {
416: fatal("denied SSH2_MSG_SERVICE_ACCEPT: %d", type);
417: }
418: if (packet_remaining() > 0) {
419: char *reply = packet_get_string(&plen);
420: debug("service_accept: %s", reply);
421: xfree(reply);
422: } else {
423: /* payload empty for ssh-2.0.13 ?? */
1.8 markus 424: debug("buggy server: service_accept w/o service");
1.1 markus 425: }
426: packet_done();
427: debug("got SSH2_MSG_SERVICE_ACCEPT");
428:
429: /* INITIAL request for auth */
430: packet_start(SSH2_MSG_USERAUTH_REQUEST);
431: packet_put_cstring(server_user);
432: packet_put_cstring(service);
433: packet_put_cstring("none");
434: packet_send();
435: packet_write_wait();
436:
437: for (;;) {
438: sent = 0;
439: type = packet_read(&plen);
440: if (type == SSH2_MSG_USERAUTH_SUCCESS)
441: break;
442: if (type != SSH2_MSG_USERAUTH_FAILURE)
443: fatal("access denied: %d", type);
444: /* SSH2_MSG_USERAUTH_FAILURE means: try again */
445: auths = packet_get_string(&dlen);
446: debug("authentications that can continue: %s", auths);
447: partial = packet_get_char();
448: packet_done();
449: if (partial)
450: debug("partial success");
1.7 markus 451: if (options.dsa_authentication &&
1.4 markus 452: strstr(auths, "publickey") != NULL) {
1.1 markus 453: while (i < options.num_identity_files2) {
454: sent = ssh2_try_pubkey(
455: options.identity_files2[i++],
456: server_user, host, service);
457: if (sent)
458: break;
459: }
460: }
461: if (!sent) {
1.4 markus 462: if (options.password_authentication &&
463: !options.batch_mode &&
464: strstr(auths, "password") != NULL) {
1.1 markus 465: sent = ssh2_try_passwd(server_user, host, service);
466: }
467: }
1.4 markus 468: if (!sent)
469: fatal("Permission denied (%s).", auths);
1.1 markus 470: xfree(auths);
471: }
472: packet_done();
473: debug("ssh-userauth2 successfull");
474: }
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