Annotation of src/usr.bin/ssh/sshconnect2.c, Revision 1.12
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"
1.12 ! markus 31: RCSID("$OpenBSD: sshconnect2.c,v 1.11 2000/05/25 20:45:20 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:
267: if (attempt++ > options.number_of_password_prompts)
268: return 0;
1.1 markus 269:
270: snprintf(prompt, sizeof(prompt), "%.30s@%.40s's password: ",
271: server_user, host);
272: password = read_passphrase(prompt, 0);
273: packet_start(SSH2_MSG_USERAUTH_REQUEST);
274: packet_put_cstring(server_user);
275: packet_put_cstring(service);
276: packet_put_cstring("password");
277: packet_put_char(0);
278: packet_put_cstring(password);
279: memset(password, 0, strlen(password));
280: xfree(password);
281: packet_send();
282: packet_write_wait();
283: return 1;
284: }
285:
286: int
287: ssh2_try_pubkey(char *filename,
288: const char *server_user, const char *host, const char *service)
289: {
290: Buffer b;
291: Key *k;
292: unsigned char *blob, *signature;
293: int bloblen, slen;
1.5 markus 294: struct stat st;
1.1 markus 295:
1.5 markus 296: if (stat(filename, &st) != 0) {
297: debug("key does not exist: %s", filename);
298: return 0;
299: }
1.1 markus 300: debug("try pubkey: %s", filename);
301:
302: k = key_new(KEY_DSA);
303: if (!load_private_key(filename, "", k, NULL)) {
304: int success = 0;
305: char *passphrase;
306: char prompt[300];
1.5 markus 307: snprintf(prompt, sizeof prompt,
1.1 markus 308: "Enter passphrase for DSA key '%.100s': ",
1.5 markus 309: filename);
1.1 markus 310: passphrase = read_passphrase(prompt, 0);
311: success = load_private_key(filename, passphrase, k, NULL);
312: memset(passphrase, 0, strlen(passphrase));
313: xfree(passphrase);
314: if (!success)
315: return 0;
316: }
317: dsa_make_key_blob(k, &blob, &bloblen);
318:
319: /* data to be signed */
320: buffer_init(&b);
321: buffer_append(&b, session_id2, session_id2_len);
322: buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
323: buffer_put_cstring(&b, server_user);
1.10 markus 324: buffer_put_cstring(&b,
325: datafellows & SSH_BUG_PUBKEYAUTH ?
326: "ssh-userauth" :
327: service);
1.1 markus 328: buffer_put_cstring(&b, "publickey");
329: buffer_put_char(&b, 1);
330: buffer_put_cstring(&b, KEX_DSS);
331: buffer_put_string(&b, blob, bloblen);
332:
333: /* generate signature */
334: dsa_sign(k, &signature, &slen, buffer_ptr(&b), buffer_len(&b));
335: key_free(k);
336: #ifdef DEBUG_DSS
337: buffer_dump(&b);
338: #endif
1.10 markus 339: if (datafellows & SSH_BUG_PUBKEYAUTH) {
340: /* e.g. ssh-2.0.13: data-to-be-signed != data-on-the-wire */
341: buffer_clear(&b);
342: buffer_append(&b, session_id2, session_id2_len);
343: buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
344: buffer_put_cstring(&b, server_user);
345: buffer_put_cstring(&b, service);
346: buffer_put_cstring(&b, "publickey");
347: buffer_put_char(&b, 1);
348: buffer_put_cstring(&b, KEX_DSS);
349: buffer_put_string(&b, blob, bloblen);
350: }
351: xfree(blob);
1.1 markus 352: /* append signature */
353: buffer_put_string(&b, signature, slen);
354: xfree(signature);
355:
356: /* skip session id and packet type */
357: if (buffer_len(&b) < session_id2_len + 1)
358: fatal("ssh2_try_pubkey: internal error");
359: buffer_consume(&b, session_id2_len + 1);
360:
361: /* put remaining data from buffer into packet */
362: packet_start(SSH2_MSG_USERAUTH_REQUEST);
363: packet_put_raw(buffer_ptr(&b), buffer_len(&b));
364: buffer_free(&b);
365:
366: /* send */
367: packet_send();
368: packet_write_wait();
369: return 1;
370: }
371:
372: void
373: ssh_userauth2(const char *server_user, char *host)
374: {
375: int type;
376: int plen;
377: int sent;
378: unsigned int dlen;
379: int partial;
380: int i = 0;
381: char *auths;
382: char *service = "ssh-connection"; /* service name */
383:
384: debug("send SSH2_MSG_SERVICE_REQUEST");
385: packet_start(SSH2_MSG_SERVICE_REQUEST);
386: packet_put_cstring("ssh-userauth");
387: packet_send();
388: packet_write_wait();
389:
390: type = packet_read(&plen);
391: if (type != SSH2_MSG_SERVICE_ACCEPT) {
392: fatal("denied SSH2_MSG_SERVICE_ACCEPT: %d", type);
393: }
394: if (packet_remaining() > 0) {
395: char *reply = packet_get_string(&plen);
396: debug("service_accept: %s", reply);
397: xfree(reply);
398: } else {
399: /* payload empty for ssh-2.0.13 ?? */
1.8 markus 400: debug("buggy server: service_accept w/o service");
1.1 markus 401: }
402: packet_done();
403: debug("got SSH2_MSG_SERVICE_ACCEPT");
404:
405: /* INITIAL request for auth */
406: packet_start(SSH2_MSG_USERAUTH_REQUEST);
407: packet_put_cstring(server_user);
408: packet_put_cstring(service);
409: packet_put_cstring("none");
410: packet_send();
411: packet_write_wait();
412:
413: for (;;) {
414: sent = 0;
415: type = packet_read(&plen);
416: if (type == SSH2_MSG_USERAUTH_SUCCESS)
417: break;
418: if (type != SSH2_MSG_USERAUTH_FAILURE)
419: fatal("access denied: %d", type);
420: /* SSH2_MSG_USERAUTH_FAILURE means: try again */
421: auths = packet_get_string(&dlen);
422: debug("authentications that can continue: %s", auths);
423: partial = packet_get_char();
424: packet_done();
425: if (partial)
426: debug("partial success");
1.7 markus 427: if (options.dsa_authentication &&
1.4 markus 428: strstr(auths, "publickey") != NULL) {
1.1 markus 429: while (i < options.num_identity_files2) {
430: sent = ssh2_try_pubkey(
431: options.identity_files2[i++],
432: server_user, host, service);
433: if (sent)
434: break;
435: }
436: }
437: if (!sent) {
1.4 markus 438: if (options.password_authentication &&
439: !options.batch_mode &&
440: strstr(auths, "password") != NULL) {
1.1 markus 441: sent = ssh2_try_passwd(server_user, host, service);
442: }
443: }
1.4 markus 444: if (!sent)
445: fatal("Permission denied (%s).", auths);
1.1 markus 446: xfree(auths);
447: }
448: packet_done();
449: debug("ssh-userauth2 successfull");
450: }
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