Annotation of src/usr.bin/ssh/auth2-jpake.c, Revision 1.3
1.3 ! djm 1: /* $OpenBSD: auth2-jpake.c,v 1.2 2008/11/07 23:34:48 dtucker Exp $ */
1.1 djm 2: /*
3: * Copyright (c) 2008 Damien Miller. All rights reserved.
4: *
5: * Permission to use, copy, modify, and distribute this software for any
6: * purpose with or without fee is hereby granted, provided that the above
7: * copyright notice and this permission notice appear in all copies.
8: *
9: * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
10: * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
11: * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
12: * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
13: * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
14: * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
15: * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
16: */
17:
18: /*
19: * Server side of zero-knowledge password auth using J-PAKE protocol
20: * as described in:
21: *
22: * F. Hao, P. Ryan, "Password Authenticated Key Exchange by Juggling",
23: * 16th Workshop on Security Protocols, Cambridge, April 2008
24: *
25: * http://grouper.ieee.org/groups/1363/Research/contributions/hao-ryan-2008.pdf
26: */
27:
1.2 dtucker 28: #ifdef JPAKE
29:
1.1 djm 30: #include <sys/types.h>
31: #include <sys/param.h>
32:
33: #include <pwd.h>
34: #include <stdio.h>
35: #include <string.h>
36: #include <login_cap.h>
37:
38: #include <openssl/bn.h>
39: #include <openssl/evp.h>
40:
41: #include "xmalloc.h"
42: #include "ssh2.h"
43: #include "key.h"
44: #include "hostfile.h"
45: #include "auth.h"
46: #include "buffer.h"
47: #include "packet.h"
48: #include "dispatch.h"
49: #include "log.h"
50: #include "servconf.h"
51: #include "auth-options.h"
52: #include "canohost.h"
53: #ifdef GSSAPI
54: #include "ssh-gss.h"
55: #endif
56: #include "monitor_wrap.h"
57:
1.3 ! djm 58: #include "schnorr.h"
1.1 djm 59: #include "jpake.h"
60:
61: /*
62: * XXX options->permit_empty_passwd (at the moment, they will be refused
63: * anyway because they will mismatch on fake salt.
64: */
65:
66: /* Dispatch handlers */
67: static void input_userauth_jpake_client_step1(int, u_int32_t, void *);
68: static void input_userauth_jpake_client_step2(int, u_int32_t, void *);
69: static void input_userauth_jpake_client_confirm(int, u_int32_t, void *);
70:
71: static int auth2_jpake_start(Authctxt *);
72:
73: /* import */
74: extern ServerOptions options;
75: extern u_char *session_id2;
76: extern u_int session_id2_len;
77:
78: /*
79: * Attempt J-PAKE authentication.
80: */
81: static int
82: userauth_jpake(Authctxt *authctxt)
83: {
84: int authenticated = 0;
85:
86: packet_check_eom();
87:
88: debug("jpake-01@openssh.com requested");
89:
90: if (authctxt->user != NULL) {
91: if (authctxt->jpake_ctx == NULL)
92: authctxt->jpake_ctx = jpake_new();
93: if (options.zero_knowledge_password_authentication)
94: authenticated = auth2_jpake_start(authctxt);
95: }
96:
97: return authenticated;
98: }
99:
100: Authmethod method_jpake = {
101: "jpake-01@openssh.com",
102: userauth_jpake,
103: &options.zero_knowledge_password_authentication
104: };
105:
106: /* Clear context and callbacks */
107: void
108: auth2_jpake_stop(Authctxt *authctxt)
109: {
110: /* unregister callbacks */
111: dispatch_set(SSH2_MSG_USERAUTH_JPAKE_CLIENT_STEP1, NULL);
112: dispatch_set(SSH2_MSG_USERAUTH_JPAKE_CLIENT_STEP2, NULL);
113: dispatch_set(SSH2_MSG_USERAUTH_JPAKE_CLIENT_CONFIRM, NULL);
114: if (authctxt->jpake_ctx != NULL) {
115: jpake_free(authctxt->jpake_ctx);
116: authctxt->jpake_ctx = NULL;
117: }
118: }
119:
120: /* Returns 1 if 'c' is a valid crypt(3) salt character, 0 otherwise */
121: static int
122: valid_crypt_salt(int c)
123: {
124: if (c >= 'A' && c <= 'Z')
125: return 1;
126: if (c >= 'a' && c <= 'z')
127: return 1;
128: if (c >= '.' && c <= '9')
129: return 1;
130: return 0;
131: }
132:
133: /*
134: * Derive fake salt as H(username || first_private_host_key)
135: * This provides relatively stable fake salts for non-existent
136: * users and avoids the jpake method becoming an account validity
137: * oracle.
138: */
139: static void
140: derive_rawsalt(const char *username, u_char *rawsalt, u_int len)
141: {
142: u_char *digest;
143: u_int digest_len;
144: Buffer b;
145: Key *k;
146:
147: buffer_init(&b);
148: buffer_put_cstring(&b, username);
149: if ((k = get_hostkey_by_index(0)) == NULL ||
150: (k->flags & KEY_FLAG_EXT))
151: fatal("%s: no hostkeys", __func__);
152: switch (k->type) {
153: case KEY_RSA1:
154: case KEY_RSA:
155: if (k->rsa->p == NULL || k->rsa->q == NULL)
156: fatal("%s: RSA key missing p and/or q", __func__);
157: buffer_put_bignum2(&b, k->rsa->p);
158: buffer_put_bignum2(&b, k->rsa->q);
159: break;
160: case KEY_DSA:
161: if (k->dsa->priv_key == NULL)
162: fatal("%s: DSA key missing priv_key", __func__);
163: buffer_put_bignum2(&b, k->dsa->priv_key);
164: break;
165: default:
166: fatal("%s: unknown key type %d", __func__, k->type);
167: }
168: if (hash_buffer(buffer_ptr(&b), buffer_len(&b), EVP_sha256(),
169: &digest, &digest_len) != 0)
170: fatal("%s: hash_buffer", __func__);
171: buffer_free(&b);
172: if (len > digest_len)
173: fatal("%s: not enough bytes for rawsalt (want %u have %u)",
174: __func__, len, digest_len);
175: memcpy(rawsalt, digest, len);
176: bzero(digest, digest_len);
177: xfree(digest);
178: }
179:
180: /* ASCII an integer [0, 64) for inclusion in a password/salt */
181: static char
182: pw_encode64(u_int i64)
183: {
184: const u_char e64[] =
185: "./0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz";
186: return e64[i64 % 64];
187: }
188:
189: /* Generate ASCII salt bytes for user */
190: static char *
191: makesalt(u_int want, const char *user)
192: {
193: u_char rawsalt[32];
194: static char ret[33];
195: u_int i;
196:
197: if (want > sizeof(ret) - 1)
198: fatal("%s: want %u", __func__, want);
199:
200: derive_rawsalt(user, rawsalt, sizeof(rawsalt));
201: bzero(ret, sizeof(ret));
202: for (i = 0; i < want; i++)
203: ret[i] = pw_encode64(rawsalt[i]);
204: bzero(rawsalt, sizeof(rawsalt));
205:
206: return ret;
207: }
208:
209: /*
210: * Select the system's default password hashing scheme and generate
211: * a stable fake salt under it for use by a non-existent account.
212: * Prevents jpake method being used to infer the validity of accounts.
213: */
214: static void
215: fake_salt_and_scheme(Authctxt *authctxt, char **salt, char **scheme)
216: {
217: char *rounds_s, *style;
218: long long rounds;
219: login_cap_t *lc;
220:
221:
222: if ((lc = login_getclass(authctxt->pw->pw_class)) == NULL &&
223: (lc = login_getclass(NULL)) == NULL)
224: fatal("%s: login_getclass failed", __func__);
225: style = login_getcapstr(lc, "localcipher", NULL, NULL);
226: if (style == NULL)
227: style = xstrdup("blowfish,6");
228: login_close(lc);
229:
230: if ((rounds_s = strchr(style, ',')) != NULL)
231: *rounds_s++ = '\0';
232: rounds = strtonum(rounds_s, 1, 1<<31, NULL);
233:
234: if (strcmp(style, "md5") == 0) {
235: xasprintf(salt, "$1$%s$", makesalt(8, authctxt->user));
236: *scheme = xstrdup("md5");
237: } else if (strcmp(style, "old") == 0) {
238: *salt = xstrdup(makesalt(2, authctxt->user));
239: *scheme = xstrdup("crypt");
240: } else if (strcmp(style, "newsalt") == 0) {
241: rounds = MAX(rounds, 7250);
242: rounds = MIN(rounds, (1<<24) - 1);
243: xasprintf(salt, "_%c%c%c%c%s",
244: pw_encode64(rounds), pw_encode64(rounds >> 6),
245: pw_encode64(rounds >> 12), pw_encode64(rounds >> 18),
246: makesalt(4, authctxt->user));
247: *scheme = xstrdup("crypt-extended");
248: } else {
249: /* Default to blowfish */
250: rounds = MAX(rounds, 3);
251: rounds = MIN(rounds, 31);
252: xasprintf(salt, "$2a$%02lld$%s", rounds,
253: makesalt(22, authctxt->user));
254: *scheme = xstrdup("bcrypt");
255: }
256: xfree(style);
257: debug3("%s: fake %s salt for user %s: %s",
258: __func__, *scheme, authctxt->user, *salt);
259: }
260:
261: /*
262: * Fetch password hashing scheme, password salt and derive shared secret
263: * for user. If user does not exist, a fake but stable and user-unique
264: * salt will be returned.
265: */
266: void
267: auth2_jpake_get_pwdata(Authctxt *authctxt, BIGNUM **s,
268: char **hash_scheme, char **salt)
269: {
270: char *cp;
271: u_char *secret;
272: u_int secret_len, salt_len;
273:
274: #ifdef JPAKE_DEBUG
275: debug3("%s: valid %d pw %.5s...", __func__,
276: authctxt->valid, authctxt->pw->pw_passwd);
277: #endif
278:
279: *salt = NULL;
280: *hash_scheme = NULL;
281: if (authctxt->valid) {
282: if (strncmp(authctxt->pw->pw_passwd, "$2$", 3) == 0 &&
283: strlen(authctxt->pw->pw_passwd) > 28) {
284: /*
285: * old-variant bcrypt:
286: * "$2$", 2 digit rounds, "$", 22 bytes salt
287: */
288: salt_len = 3 + 2 + 1 + 22 + 1;
289: *salt = xmalloc(salt_len);
290: strlcpy(*salt, authctxt->pw->pw_passwd, salt_len);
291: *hash_scheme = xstrdup("bcrypt");
292: } else if (strncmp(authctxt->pw->pw_passwd, "$2a$", 4) == 0 &&
293: strlen(authctxt->pw->pw_passwd) > 29) {
294: /*
295: * current-variant bcrypt:
296: * "$2a$", 2 digit rounds, "$", 22 bytes salt
297: */
298: salt_len = 4 + 2 + 1 + 22 + 1;
299: *salt = xmalloc(salt_len);
300: strlcpy(*salt, authctxt->pw->pw_passwd, salt_len);
301: *hash_scheme = xstrdup("bcrypt");
302: } else if (strncmp(authctxt->pw->pw_passwd, "$1$", 3) == 0 &&
303: strlen(authctxt->pw->pw_passwd) > 5) {
304: /*
305: * md5crypt:
306: * "$1$", salt until "$"
307: */
308: cp = strchr(authctxt->pw->pw_passwd + 3, '$');
309: if (cp != NULL) {
310: salt_len = (cp - authctxt->pw->pw_passwd) + 1;
311: *salt = xmalloc(salt_len);
312: strlcpy(*salt, authctxt->pw->pw_passwd,
313: salt_len);
314: *hash_scheme = xstrdup("md5crypt");
315: }
316: } else if (strncmp(authctxt->pw->pw_passwd, "_", 1) == 0 &&
317: strlen(authctxt->pw->pw_passwd) > 9) {
318: /*
319: * BSDI extended crypt:
320: * "_", 4 digits count, 4 chars salt
321: */
322: salt_len = 1 + 4 + 4 + 1;
323: *salt = xmalloc(salt_len);
324: strlcpy(*salt, authctxt->pw->pw_passwd, salt_len);
325: *hash_scheme = xstrdup("crypt-extended");
326: } else if (strlen(authctxt->pw->pw_passwd) == 13 &&
327: valid_crypt_salt(authctxt->pw->pw_passwd[0]) &&
328: valid_crypt_salt(authctxt->pw->pw_passwd[1])) {
329: /*
330: * traditional crypt:
331: * 2 chars salt
332: */
333: salt_len = 2 + 1;
334: *salt = xmalloc(salt_len);
335: strlcpy(*salt, authctxt->pw->pw_passwd, salt_len);
336: *hash_scheme = xstrdup("crypt");
337: }
338: if (*salt == NULL) {
339: debug("%s: unrecognised crypt scheme for user %s",
340: __func__, authctxt->pw->pw_name);
341: }
342: }
343: if (*salt == NULL)
344: fake_salt_and_scheme(authctxt, salt, hash_scheme);
345:
346: if (hash_buffer(authctxt->pw->pw_passwd,
347: strlen(authctxt->pw->pw_passwd), EVP_sha256(),
348: &secret, &secret_len) != 0)
349: fatal("%s: hash_buffer", __func__);
350: if ((*s = BN_bin2bn(secret, secret_len, NULL)) == NULL)
351: fatal("%s: BN_bin2bn (secret)", __func__);
352: #ifdef JPAKE_DEBUG
353: debug3("%s: salt = %s (len %u)", __func__,
354: *salt, (u_int)strlen(*salt));
355: debug3("%s: scheme = %s", __func__, *hash_scheme);
356: JPAKE_DEBUG_BN((*s, "%s: s = ", __func__));
357: #endif
358: bzero(secret, secret_len);
359: xfree(secret);
360: }
361:
362: /*
1.3 ! djm 363: * Begin authentication attempt.
1.1 djm 364: * Note, sets authctxt->postponed while in subprotocol
365: */
366: static int
367: auth2_jpake_start(Authctxt *authctxt)
368: {
369: struct jpake_ctx *pctx = authctxt->jpake_ctx;
370: u_char *x3_proof, *x4_proof;
371: u_int x3_proof_len, x4_proof_len;
372: char *salt, *hash_scheme;
373:
374: debug("%s: start", __func__);
375:
376: PRIVSEP(jpake_step1(pctx->grp,
377: &pctx->server_id, &pctx->server_id_len,
378: &pctx->x3, &pctx->x4, &pctx->g_x3, &pctx->g_x4,
379: &x3_proof, &x3_proof_len,
380: &x4_proof, &x4_proof_len));
381:
382: PRIVSEP(auth2_jpake_get_pwdata(authctxt, &pctx->s,
383: &hash_scheme, &salt));
384:
385: if (!use_privsep)
386: JPAKE_DEBUG_CTX((pctx, "step 1 sending in %s", __func__));
387:
388: packet_start(SSH2_MSG_USERAUTH_JPAKE_SERVER_STEP1);
389: packet_put_cstring(hash_scheme);
390: packet_put_cstring(salt);
391: packet_put_string(pctx->server_id, pctx->server_id_len);
392: packet_put_bignum2(pctx->g_x3);
393: packet_put_bignum2(pctx->g_x4);
394: packet_put_string(x3_proof, x3_proof_len);
395: packet_put_string(x4_proof, x4_proof_len);
396: packet_send();
397: packet_write_wait();
398:
399: bzero(hash_scheme, strlen(hash_scheme));
400: bzero(salt, strlen(salt));
401: xfree(hash_scheme);
402: xfree(salt);
403: bzero(x3_proof, x3_proof_len);
404: bzero(x4_proof, x4_proof_len);
405: xfree(x3_proof);
406: xfree(x4_proof);
407:
408: /* Expect step 1 packet from peer */
409: dispatch_set(SSH2_MSG_USERAUTH_JPAKE_CLIENT_STEP1,
410: input_userauth_jpake_client_step1);
411:
412: authctxt->postponed = 1;
413: return 0;
414: }
415:
416: /* ARGSUSED */
417: static void
418: input_userauth_jpake_client_step1(int type, u_int32_t seq, void *ctxt)
419: {
420: Authctxt *authctxt = ctxt;
421: struct jpake_ctx *pctx = authctxt->jpake_ctx;
422: u_char *x1_proof, *x2_proof, *x4_s_proof;
423: u_int x1_proof_len, x2_proof_len, x4_s_proof_len;
424:
425: /* Disable this message */
426: dispatch_set(SSH2_MSG_USERAUTH_JPAKE_CLIENT_STEP1, NULL);
427:
428: /* Fetch step 1 values */
429: if ((pctx->g_x1 = BN_new()) == NULL ||
430: (pctx->g_x2 = BN_new()) == NULL)
431: fatal("%s: BN_new", __func__);
432: pctx->client_id = packet_get_string(&pctx->client_id_len);
433: packet_get_bignum2(pctx->g_x1);
434: packet_get_bignum2(pctx->g_x2);
435: x1_proof = packet_get_string(&x1_proof_len);
436: x2_proof = packet_get_string(&x2_proof_len);
437: packet_check_eom();
438:
439: if (!use_privsep)
440: JPAKE_DEBUG_CTX((pctx, "step 1 received in %s", __func__));
441:
442: PRIVSEP(jpake_step2(pctx->grp, pctx->s, pctx->g_x3,
443: pctx->g_x1, pctx->g_x2, pctx->x4,
444: pctx->client_id, pctx->client_id_len,
445: pctx->server_id, pctx->server_id_len,
446: x1_proof, x1_proof_len,
447: x2_proof, x2_proof_len,
448: &pctx->b,
449: &x4_s_proof, &x4_s_proof_len));
450:
451: bzero(x1_proof, x1_proof_len);
452: bzero(x2_proof, x2_proof_len);
453: xfree(x1_proof);
454: xfree(x2_proof);
455:
456: if (!use_privsep)
457: JPAKE_DEBUG_CTX((pctx, "step 2 sending in %s", __func__));
458:
459: /* Send values for step 2 */
460: packet_start(SSH2_MSG_USERAUTH_JPAKE_SERVER_STEP2);
461: packet_put_bignum2(pctx->b);
462: packet_put_string(x4_s_proof, x4_s_proof_len);
463: packet_send();
464: packet_write_wait();
465:
466: bzero(x4_s_proof, x4_s_proof_len);
467: xfree(x4_s_proof);
468:
469: /* Expect step 2 packet from peer */
470: dispatch_set(SSH2_MSG_USERAUTH_JPAKE_CLIENT_STEP2,
471: input_userauth_jpake_client_step2);
472: }
473:
474: /* ARGSUSED */
475: static void
476: input_userauth_jpake_client_step2(int type, u_int32_t seq, void *ctxt)
477: {
478: Authctxt *authctxt = ctxt;
479: struct jpake_ctx *pctx = authctxt->jpake_ctx;
480: u_char *x2_s_proof;
481: u_int x2_s_proof_len;
482:
483: /* Disable this message */
484: dispatch_set(SSH2_MSG_USERAUTH_JPAKE_CLIENT_STEP2, NULL);
485:
486: if ((pctx->a = BN_new()) == NULL)
487: fatal("%s: BN_new", __func__);
488:
489: /* Fetch step 2 values */
490: packet_get_bignum2(pctx->a);
491: x2_s_proof = packet_get_string(&x2_s_proof_len);
492: packet_check_eom();
493:
494: if (!use_privsep)
495: JPAKE_DEBUG_CTX((pctx, "step 2 received in %s", __func__));
496:
497: /* Derive shared key and calculate confirmation hash */
498: PRIVSEP(jpake_key_confirm(pctx->grp, pctx->s, pctx->a,
499: pctx->x4, pctx->g_x3, pctx->g_x4, pctx->g_x1, pctx->g_x2,
500: pctx->server_id, pctx->server_id_len,
501: pctx->client_id, pctx->client_id_len,
502: session_id2, session_id2_len,
503: x2_s_proof, x2_s_proof_len,
504: &pctx->k,
505: &pctx->h_k_sid_sessid, &pctx->h_k_sid_sessid_len));
506:
507: bzero(x2_s_proof, x2_s_proof_len);
508: xfree(x2_s_proof);
509:
510: if (!use_privsep)
511: JPAKE_DEBUG_CTX((pctx, "confirm sending in %s", __func__));
512:
513: /* Send key confirmation proof */
514: packet_start(SSH2_MSG_USERAUTH_JPAKE_SERVER_CONFIRM);
515: packet_put_string(pctx->h_k_sid_sessid, pctx->h_k_sid_sessid_len);
516: packet_send();
517: packet_write_wait();
518:
519: /* Expect confirmation from peer */
520: dispatch_set(SSH2_MSG_USERAUTH_JPAKE_CLIENT_CONFIRM,
521: input_userauth_jpake_client_confirm);
522: }
523:
524: /* ARGSUSED */
525: static void
526: input_userauth_jpake_client_confirm(int type, u_int32_t seq, void *ctxt)
527: {
528: Authctxt *authctxt = ctxt;
529: struct jpake_ctx *pctx = authctxt->jpake_ctx;
530: int authenticated = 0;
531:
532: /* Disable this message */
533: dispatch_set(SSH2_MSG_USERAUTH_JPAKE_CLIENT_CONFIRM, NULL);
534:
535: pctx->h_k_cid_sessid = packet_get_string(&pctx->h_k_cid_sessid_len);
536: packet_check_eom();
537:
538: if (!use_privsep)
539: JPAKE_DEBUG_CTX((pctx, "confirm received in %s", __func__));
540:
541: /* Verify expected confirmation hash */
542: if (PRIVSEP(jpake_check_confirm(pctx->k,
543: pctx->client_id, pctx->client_id_len,
544: session_id2, session_id2_len,
545: pctx->h_k_cid_sessid, pctx->h_k_cid_sessid_len)) == 1)
546: authenticated = authctxt->valid ? 1 : 0;
547: else
548: debug("%s: confirmation mismatch", __func__);
549:
550: /* done */
551: authctxt->postponed = 0;
552: jpake_free(authctxt->jpake_ctx);
553: authctxt->jpake_ctx = NULL;
554: userauth_finish(authctxt, authenticated, method_jpake.name);
555: }
556:
557: #endif /* JPAKE */
558:
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