blob: 130661069fbd66dc09df934e38f7308d785a7124 [file] [log] [blame]
Damien Millercee85232009-03-06 00:58:22 +11001/* $OpenBSD: jpake.c,v 1.2 2009/03/05 07:18:19 djm Exp $ */
Damien Miller01ed2272008-11-05 16:20:46 +11002/*
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 * Shared components 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
28#include "includes.h"
29
30#include <sys/types.h>
31
32#include <stdio.h>
33#include <string.h>
34#include <stdarg.h>
35
36#include <openssl/bn.h>
37#include <openssl/evp.h>
38
39#include "xmalloc.h"
40#include "ssh2.h"
41#include "key.h"
42#include "hostfile.h"
43#include "auth.h"
44#include "buffer.h"
45#include "packet.h"
46#include "dispatch.h"
47#include "log.h"
48
49#include "jpake.h"
Damien Millercee85232009-03-06 00:58:22 +110050#include "schnorr.h"
Damien Miller01ed2272008-11-05 16:20:46 +110051
52#ifdef JPAKE
53
54/* RFC3526 group 5, 1536 bits */
55#define JPAKE_GROUP_G "2"
56#define JPAKE_GROUP_P \
57 "FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD129024E088A67CC74" \
58 "020BBEA63B139B22514A08798E3404DDEF9519B3CD3A431B302B0A6DF25F1437" \
59 "4FE1356D6D51C245E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7ED" \
60 "EE386BFB5A899FA5AE9F24117C4B1FE649286651ECE45B3DC2007CB8A163BF05" \
61 "98DA48361C55D39A69163FA8FD24CF5F83655D23DCA3AD961C62F356208552BB" \
62 "9ED529077096966D670C354E4ABC9804F1746C08CA237327FFFFFFFFFFFFFFFF"
63
Damien Millercee85232009-03-06 00:58:22 +110064struct modp_group *
Damien Miller01ed2272008-11-05 16:20:46 +110065jpake_default_group(void)
66{
Damien Millercee85232009-03-06 00:58:22 +110067 return modp_group_from_g_and_safe_p(JPAKE_GROUP_G, JPAKE_GROUP_P);
Damien Miller01ed2272008-11-05 16:20:46 +110068}
69
70struct jpake_ctx *
71jpake_new(void)
72{
73 struct jpake_ctx *ret;
74
75 ret = xcalloc(1, sizeof(*ret));
76
77 ret->grp = jpake_default_group();
78
79 ret->s = ret->k = NULL;
80 ret->x1 = ret->x2 = ret->x3 = ret->x4 = NULL;
81 ret->g_x1 = ret->g_x2 = ret->g_x3 = ret->g_x4 = NULL;
82 ret->a = ret->b = NULL;
83
84 ret->client_id = ret->server_id = NULL;
85 ret->h_k_cid_sessid = ret->h_k_sid_sessid = NULL;
86
87 debug3("%s: alloc %p", __func__, ret);
88
89 return ret;
90}
91
Damien Miller01ed2272008-11-05 16:20:46 +110092void
93jpake_free(struct jpake_ctx *pctx)
94{
95 debug3("%s: free %p", __func__, pctx);
96
97#define JPAKE_BN_CLEAR_FREE(v) \
98 do { \
99 if ((v) != NULL) { \
100 BN_clear_free(v); \
101 (v) = NULL; \
102 } \
103 } while (0)
104#define JPAKE_BUF_CLEAR_FREE(v, l) \
105 do { \
106 if ((v) != NULL) { \
107 bzero((v), (l)); \
108 xfree(v); \
109 (v) = NULL; \
110 (l) = 0; \
111 } \
112 } while (0)
113
114 JPAKE_BN_CLEAR_FREE(pctx->s);
115 JPAKE_BN_CLEAR_FREE(pctx->k);
116 JPAKE_BN_CLEAR_FREE(pctx->x1);
117 JPAKE_BN_CLEAR_FREE(pctx->x2);
118 JPAKE_BN_CLEAR_FREE(pctx->x3);
119 JPAKE_BN_CLEAR_FREE(pctx->x4);
120 JPAKE_BN_CLEAR_FREE(pctx->g_x1);
121 JPAKE_BN_CLEAR_FREE(pctx->g_x2);
122 JPAKE_BN_CLEAR_FREE(pctx->g_x3);
123 JPAKE_BN_CLEAR_FREE(pctx->g_x4);
124 JPAKE_BN_CLEAR_FREE(pctx->a);
125 JPAKE_BN_CLEAR_FREE(pctx->b);
126
127 JPAKE_BUF_CLEAR_FREE(pctx->client_id, pctx->client_id_len);
128 JPAKE_BUF_CLEAR_FREE(pctx->server_id, pctx->server_id_len);
129 JPAKE_BUF_CLEAR_FREE(pctx->h_k_cid_sessid, pctx->h_k_cid_sessid_len);
130 JPAKE_BUF_CLEAR_FREE(pctx->h_k_sid_sessid, pctx->h_k_sid_sessid_len);
131
132#undef JPAKE_BN_CLEAR_FREE
133#undef JPAKE_BUF_CLEAR_FREE
134
135 bzero(pctx, sizeof(pctx));
136 xfree(pctx);
137}
138
139/* dump entire jpake_ctx. NB. includes private values! */
140void
141jpake_dump(struct jpake_ctx *pctx, const char *fmt, ...)
142{
143 char *out;
144 va_list args;
145
146 out = NULL;
147 va_start(args, fmt);
148 vasprintf(&out, fmt, args);
149 va_end(args);
150 if (out == NULL)
151 fatal("%s: vasprintf failed", __func__);
152
153 debug3("%s: %s (ctx at %p)", __func__, out, pctx);
154 if (pctx == NULL) {
155 free(out);
156 return;
157 }
158
159#define JPAKE_DUMP_BN(a) do { \
160 if ((a) != NULL) \
161 JPAKE_DEBUG_BN(((a), "%s = ", #a)); \
162 } while (0)
163#define JPAKE_DUMP_BUF(a, b) do { \
164 if ((a) != NULL) \
165 JPAKE_DEBUG_BUF((a, b, "%s", #a)); \
166 } while (0)
167
168 JPAKE_DUMP_BN(pctx->s);
169 JPAKE_DUMP_BN(pctx->k);
170 JPAKE_DUMP_BN(pctx->x1);
171 JPAKE_DUMP_BN(pctx->x2);
172 JPAKE_DUMP_BN(pctx->x3);
173 JPAKE_DUMP_BN(pctx->x4);
174 JPAKE_DUMP_BN(pctx->g_x1);
175 JPAKE_DUMP_BN(pctx->g_x2);
176 JPAKE_DUMP_BN(pctx->g_x3);
177 JPAKE_DUMP_BN(pctx->g_x4);
178 JPAKE_DUMP_BN(pctx->a);
179 JPAKE_DUMP_BN(pctx->b);
180
181 JPAKE_DUMP_BUF(pctx->client_id, pctx->client_id_len);
182 JPAKE_DUMP_BUF(pctx->server_id, pctx->server_id_len);
183 JPAKE_DUMP_BUF(pctx->h_k_cid_sessid, pctx->h_k_cid_sessid_len);
184 JPAKE_DUMP_BUF(pctx->h_k_sid_sessid, pctx->h_k_sid_sessid_len);
185
186 debug3("%s: %s done", __func__, out);
187 free(out);
188}
189
190/* Shared parts of step 1 exchange calculation */
191void
Damien Millercee85232009-03-06 00:58:22 +1100192jpake_step1(struct modp_group *grp,
Damien Miller01ed2272008-11-05 16:20:46 +1100193 u_char **id, u_int *id_len,
194 BIGNUM **priv1, BIGNUM **priv2, BIGNUM **g_priv1, BIGNUM **g_priv2,
195 u_char **priv1_proof, u_int *priv1_proof_len,
196 u_char **priv2_proof, u_int *priv2_proof_len)
197{
198 BN_CTX *bn_ctx;
199
200 if ((bn_ctx = BN_CTX_new()) == NULL)
201 fatal("%s: BN_CTX_new", __func__);
202
203 /* Random nonce to prevent replay */
204 *id = xmalloc(KZP_ID_LEN);
205 *id_len = KZP_ID_LEN;
206 arc4random_buf(*id, *id_len);
207
208 /*
209 * x1/x3 is a random element of Zq
210 * x2/x4 is a random element of Z*q
211 * We also exclude [1] from x1/x3 candidates and [0, 1] from
212 * x2/x4 candiates to avoid possible degeneracy (i.e. g^0, g^1).
213 */
214 if ((*priv1 = bn_rand_range_gt_one(grp->q)) == NULL ||
215 (*priv2 = bn_rand_range_gt_one(grp->q)) == NULL)
216 fatal("%s: bn_rand_range_gt_one", __func__);
217
218 /*
219 * client: g_x1 = g^x1 mod p / server: g_x3 = g^x3 mod p
220 * client: g_x2 = g^x2 mod p / server: g_x4 = g^x4 mod p
221 */
222 if ((*g_priv1 = BN_new()) == NULL ||
223 (*g_priv2 = BN_new()) == NULL)
224 fatal("%s: BN_new", __func__);
225 if (BN_mod_exp(*g_priv1, grp->g, *priv1, grp->p, bn_ctx) == -1)
226 fatal("%s: BN_mod_exp", __func__);
227 if (BN_mod_exp(*g_priv2, grp->g, *priv2, grp->p, bn_ctx) == -1)
228 fatal("%s: BN_mod_exp", __func__);
229
230 /* Generate proofs for holding x1/x3 and x2/x4 */
Damien Millercee85232009-03-06 00:58:22 +1100231 if (schnorr_sign_buf(grp->p, grp->q, grp->g,
Damien Miller01ed2272008-11-05 16:20:46 +1100232 *priv1, *g_priv1, *id, *id_len,
233 priv1_proof, priv1_proof_len) != 0)
234 fatal("%s: schnorr_sign", __func__);
Damien Millercee85232009-03-06 00:58:22 +1100235 if (schnorr_sign_buf(grp->p, grp->q, grp->g,
Damien Miller01ed2272008-11-05 16:20:46 +1100236 *priv2, *g_priv2, *id, *id_len,
237 priv2_proof, priv2_proof_len) != 0)
238 fatal("%s: schnorr_sign", __func__);
239
240 BN_CTX_free(bn_ctx);
241}
242
243/* Shared parts of step 2 exchange calculation */
244void
Damien Millercee85232009-03-06 00:58:22 +1100245jpake_step2(struct modp_group *grp, BIGNUM *s,
Damien Miller01ed2272008-11-05 16:20:46 +1100246 BIGNUM *mypub1, BIGNUM *theirpub1, BIGNUM *theirpub2, BIGNUM *mypriv2,
247 const u_char *theirid, u_int theirid_len,
248 const u_char *myid, u_int myid_len,
249 const u_char *theirpub1_proof, u_int theirpub1_proof_len,
250 const u_char *theirpub2_proof, u_int theirpub2_proof_len,
251 BIGNUM **newpub,
252 u_char **newpub_exponent_proof, u_int *newpub_exponent_proof_len)
253{
254 BN_CTX *bn_ctx;
255 BIGNUM *tmp, *exponent;
256
257 /* Validate peer's step 1 values */
258 if (BN_cmp(theirpub1, BN_value_one()) <= 0)
259 fatal("%s: theirpub1 <= 1", __func__);
260 if (BN_cmp(theirpub2, BN_value_one()) <= 0)
261 fatal("%s: theirpub2 <= 1", __func__);
262
Damien Millercee85232009-03-06 00:58:22 +1100263 if (schnorr_verify_buf(grp->p, grp->q, grp->g, theirpub1,
Damien Miller01ed2272008-11-05 16:20:46 +1100264 theirid, theirid_len, theirpub1_proof, theirpub1_proof_len) != 1)
265 fatal("%s: schnorr_verify theirpub1 failed", __func__);
Damien Millercee85232009-03-06 00:58:22 +1100266 if (schnorr_verify_buf(grp->p, grp->q, grp->g, theirpub2,
Damien Miller01ed2272008-11-05 16:20:46 +1100267 theirid, theirid_len, theirpub2_proof, theirpub2_proof_len) != 1)
268 fatal("%s: schnorr_verify theirpub2 failed", __func__);
269
270 if ((bn_ctx = BN_CTX_new()) == NULL)
271 fatal("%s: BN_CTX_new", __func__);
272
273 if ((*newpub = BN_new()) == NULL ||
274 (tmp = BN_new()) == NULL ||
275 (exponent = BN_new()) == NULL)
276 fatal("%s: BN_new", __func__);
277
278 /*
279 * client: exponent = x2 * s mod p
280 * server: exponent = x4 * s mod p
281 */
282 if (BN_mod_mul(exponent, mypriv2, s, grp->q, bn_ctx) != 1)
283 fatal("%s: BN_mod_mul (exponent = mypriv2 * s mod p)",
284 __func__);
285
286 /*
287 * client: tmp = g^(x1 + x3 + x4) mod p
288 * server: tmp = g^(x1 + x2 + x3) mod p
289 */
290 if (BN_mod_mul(tmp, mypub1, theirpub1, grp->p, bn_ctx) != 1)
291 fatal("%s: BN_mod_mul (tmp = mypub1 * theirpub1 mod p)",
292 __func__);
293 if (BN_mod_mul(tmp, tmp, theirpub2, grp->p, bn_ctx) != 1)
294 fatal("%s: BN_mod_mul (tmp = tmp * theirpub2 mod p)", __func__);
295
296 /*
297 * client: a = tmp^exponent = g^((x1+x3+x4) * x2 * s) mod p
298 * server: b = tmp^exponent = g^((x1+x2+x3) * x4 * s) mod p
299 */
300 if (BN_mod_exp(*newpub, tmp, exponent, grp->p, bn_ctx) != 1)
301 fatal("%s: BN_mod_mul (newpub = tmp^exponent mod p)", __func__);
302
303 JPAKE_DEBUG_BN((tmp, "%s: tmp = ", __func__));
304 JPAKE_DEBUG_BN((exponent, "%s: exponent = ", __func__));
305
306 /* Note the generator here is 'tmp', not g */
Damien Millercee85232009-03-06 00:58:22 +1100307 if (schnorr_sign_buf(grp->p, grp->q, tmp, exponent, *newpub,
Damien Miller01ed2272008-11-05 16:20:46 +1100308 myid, myid_len,
309 newpub_exponent_proof, newpub_exponent_proof_len) != 0)
310 fatal("%s: schnorr_sign newpub", __func__);
311
312 BN_clear_free(tmp); /* XXX stash for later use? */
313 BN_clear_free(exponent); /* XXX stash for later use? (yes, in conf) */
314
315 BN_CTX_free(bn_ctx);
316}
317
318/* Confirmation hash calculation */
319void
320jpake_confirm_hash(const BIGNUM *k,
321 const u_char *endpoint_id, u_int endpoint_id_len,
322 const u_char *sess_id, u_int sess_id_len,
323 u_char **confirm_hash, u_int *confirm_hash_len)
324{
325 Buffer b;
326
327 /*
328 * Calculate confirmation proof:
329 * client: H(k || client_id || session_id)
330 * server: H(k || server_id || session_id)
331 */
332 buffer_init(&b);
333 buffer_put_bignum2(&b, k);
334 buffer_put_string(&b, endpoint_id, endpoint_id_len);
335 buffer_put_string(&b, sess_id, sess_id_len);
336 if (hash_buffer(buffer_ptr(&b), buffer_len(&b), EVP_sha256(),
337 confirm_hash, confirm_hash_len) != 0)
338 fatal("%s: hash_buffer", __func__);
339 buffer_free(&b);
340}
341
342/* Shared parts of key derivation and confirmation calculation */
343void
Damien Millercee85232009-03-06 00:58:22 +1100344jpake_key_confirm(struct modp_group *grp, BIGNUM *s, BIGNUM *step2_val,
Damien Miller01ed2272008-11-05 16:20:46 +1100345 BIGNUM *mypriv2, BIGNUM *mypub1, BIGNUM *mypub2,
346 BIGNUM *theirpub1, BIGNUM *theirpub2,
347 const u_char *my_id, u_int my_id_len,
348 const u_char *their_id, u_int their_id_len,
349 const u_char *sess_id, u_int sess_id_len,
350 const u_char *theirpriv2_s_proof, u_int theirpriv2_s_proof_len,
351 BIGNUM **k,
352 u_char **confirm_hash, u_int *confirm_hash_len)
353{
354 BN_CTX *bn_ctx;
355 BIGNUM *tmp;
356
357 if ((bn_ctx = BN_CTX_new()) == NULL)
358 fatal("%s: BN_CTX_new", __func__);
359 if ((tmp = BN_new()) == NULL ||
360 (*k = BN_new()) == NULL)
361 fatal("%s: BN_new", __func__);
362
363 /* Validate step 2 values */
364 if (BN_cmp(step2_val, BN_value_one()) <= 0)
365 fatal("%s: step2_val <= 1", __func__);
366
367 /*
368 * theirpriv2_s_proof is calculated with a different generator:
369 * tmp = g^(mypriv1+mypriv2+theirpub1) = g^mypub1*g^mypub2*g^theirpub1
370 * Calculate it here so we can check the signature.
371 */
372 if (BN_mod_mul(tmp, mypub1, mypub2, grp->p, bn_ctx) != 1)
373 fatal("%s: BN_mod_mul (tmp = mypub1 * mypub2 mod p)", __func__);
374 if (BN_mod_mul(tmp, tmp, theirpub1, grp->p, bn_ctx) != 1)
375 fatal("%s: BN_mod_mul (tmp = tmp * theirpub1 mod p)", __func__);
376
377 JPAKE_DEBUG_BN((tmp, "%s: tmp = ", __func__));
378
Damien Millercee85232009-03-06 00:58:22 +1100379 if (schnorr_verify_buf(grp->p, grp->q, tmp, step2_val,
Damien Miller01ed2272008-11-05 16:20:46 +1100380 their_id, their_id_len,
381 theirpriv2_s_proof, theirpriv2_s_proof_len) != 1)
382 fatal("%s: schnorr_verify theirpriv2_s_proof failed", __func__);
383
384 /*
385 * Derive shared key:
386 * client: k = (b / g^(x2*x4*s))^x2 = g^((x1+x3)*x2*x4*s)
387 * server: k = (a / g^(x2*x4*s))^x4 = g^((x1+x3)*x2*x4*s)
388 *
389 * Computed as:
390 * client: k = (g_x4^(q - (x2 * s)) * b)^x2 mod p
391 * server: k = (g_x2^(q - (x4 * s)) * b)^x4 mod p
392 */
393 if (BN_mul(tmp, mypriv2, s, bn_ctx) != 1)
394 fatal("%s: BN_mul (tmp = mypriv2 * s)", __func__);
395 if (BN_mod_sub(tmp, grp->q, tmp, grp->q, bn_ctx) != 1)
396 fatal("%s: BN_mod_sub (tmp = q - tmp mod q)", __func__);
397 if (BN_mod_exp(tmp, theirpub2, tmp, grp->p, bn_ctx) != 1)
398 fatal("%s: BN_mod_exp (tmp = theirpub2^tmp) mod p", __func__);
399 if (BN_mod_mul(tmp, tmp, step2_val, grp->p, bn_ctx) != 1)
400 fatal("%s: BN_mod_mul (tmp = tmp * step2_val) mod p", __func__);
401 if (BN_mod_exp(*k, tmp, mypriv2, grp->p, bn_ctx) != 1)
402 fatal("%s: BN_mod_exp (k = tmp^mypriv2) mod p", __func__);
403
404 BN_CTX_free(bn_ctx);
405 BN_clear_free(tmp);
406
407 jpake_confirm_hash(*k, my_id, my_id_len, sess_id, sess_id_len,
408 confirm_hash, confirm_hash_len);
409}
410
411/*
412 * Calculate and check confirmation hash from peer. Returns 1 on success
413 * 0 on failure/mismatch.
414 */
415int
416jpake_check_confirm(const BIGNUM *k,
417 const u_char *peer_id, u_int peer_id_len,
418 const u_char *sess_id, u_int sess_id_len,
419 const u_char *peer_confirm_hash, u_int peer_confirm_hash_len)
420{
421 u_char *expected_confirm_hash;
422 u_int expected_confirm_hash_len;
423 int success = 0;
424
425 /* Calculate and verify expected confirmation hash */
426 jpake_confirm_hash(k, peer_id, peer_id_len, sess_id, sess_id_len,
427 &expected_confirm_hash, &expected_confirm_hash_len);
428
429 JPAKE_DEBUG_BUF((expected_confirm_hash, expected_confirm_hash_len,
430 "%s: expected confirm hash", __func__));
431 JPAKE_DEBUG_BUF((peer_confirm_hash, peer_confirm_hash_len,
432 "%s: received confirm hash", __func__));
433
434 if (peer_confirm_hash_len != expected_confirm_hash_len)
435 error("%s: confirmation length mismatch (my %u them %u)",
436 __func__, expected_confirm_hash_len, peer_confirm_hash_len);
437 else if (memcmp(peer_confirm_hash, expected_confirm_hash,
438 expected_confirm_hash_len) == 0)
439 success = 1;
440 bzero(expected_confirm_hash, expected_confirm_hash_len);
441 xfree(expected_confirm_hash);
442 debug3("%s: success = %d", __func__, success);
443 return success;
444}
445
446/* XXX main() function with tests */
447
448#endif /* JPAKE */
449