jpake.c revision 197679
1/* $OpenBSD: jpake.c,v 1.2 2009/03/05 07:18:19 djm Exp $ */ 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 * 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" 50#include "schnorr.h" 51 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 64struct modp_group * 65jpake_default_group(void) 66{ 67 return modp_group_from_g_and_safe_p(JPAKE_GROUP_G, JPAKE_GROUP_P); 68} 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 92void 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 192jpake_step1(struct modp_group *grp, 193 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 */ 231 if (schnorr_sign_buf(grp->p, grp->q, grp->g, 232 *priv1, *g_priv1, *id, *id_len, 233 priv1_proof, priv1_proof_len) != 0) 234 fatal("%s: schnorr_sign", __func__); 235 if (schnorr_sign_buf(grp->p, grp->q, grp->g, 236 *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 245jpake_step2(struct modp_group *grp, BIGNUM *s, 246 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__); 262 263 if (schnorr_verify_buf(grp->p, grp->q, grp->g, theirpub1, 264 theirid, theirid_len, theirpub1_proof, theirpub1_proof_len) != 1) 265 fatal("%s: schnorr_verify theirpub1 failed", __func__); 266 if (schnorr_verify_buf(grp->p, grp->q, grp->g, theirpub2, 267 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 */ 307 if (schnorr_sign_buf(grp->p, grp->q, tmp, exponent, *newpub, 308 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 344jpake_key_confirm(struct modp_group *grp, BIGNUM *s, BIGNUM *step2_val, 345 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__)); 378 379 if (schnorr_verify_buf(grp->p, grp->q, tmp, step2_val, 380 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 */ 449 450