| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * Key exchange protocol |
| 4 | * |
| 5 | * (c) 2001 Straylight/Edgeware |
| 6 | */ |
| 7 | |
| 8 | /*----- Licensing notice --------------------------------------------------* |
| 9 | * |
| 10 | * This file is part of Trivial IP Encryption (TrIPE). |
| 11 | * |
| 12 | * TrIPE is free software; you can redistribute it and/or modify |
| 13 | * it under the terms of the GNU General Public License as published by |
| 14 | * the Free Software Foundation; either version 2 of the License, or |
| 15 | * (at your option) any later version. |
| 16 | * |
| 17 | * TrIPE is distributed in the hope that it will be useful, |
| 18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 20 | * GNU General Public License for more details. |
| 21 | * |
| 22 | * You should have received a copy of the GNU General Public License |
| 23 | * along with TrIPE; if not, write to the Free Software Foundation, |
| 24 | * Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. |
| 25 | */ |
| 26 | |
| 27 | /*----- Header files ------------------------------------------------------*/ |
| 28 | |
| 29 | #include "tripe.h" |
| 30 | |
| 31 | /*----- Brief protocol overview -------------------------------------------* |
| 32 | * |
| 33 | * Let %$G$% be a cyclic group; let %$g$% be a generator of %$G$%, and let |
| 34 | * %$q$% be the order of %$G$%; for a key %$K$%, let %$E_K(\cdot)$% denote |
| 35 | * application of the symmetric packet protocol to a message; let |
| 36 | * %$H(\cdot)$% be the random oracle. Let $\alpha \inr \{0,\ldots,q - 1\}$% |
| 37 | * be Alice's private key; let %$a = g^\alpha$% be her public key; let %$b$% |
| 38 | * be Bob's public key. |
| 39 | * |
| 40 | * At the beginning of the session, Alice chooses |
| 41 | * |
| 42 | * %$\rho_A \inr \{0, \ldots q - 1\}$% |
| 43 | * |
| 44 | * We also have: |
| 45 | * |
| 46 | * %$r_A = g^{\rho_A}$% Alice's challenge |
| 47 | * %$c_A = H(\cookie{cookie}, r_A)$% Alice's cookie |
| 48 | * %$v_A = \rho_A \xor H(\cookie{expected-reply}, a, r_A, r_B, b^{\rho_A})$% |
| 49 | * Alice's challenge check value |
| 50 | * %$r_B^\alpha = a^{\rho_B}$% Alice's reply |
| 51 | * %$K = r_B^{\rho_A} = r_B^{\rho_A} = g^{\rho_A\rho_B}$% |
| 52 | * Alice and Bob's shared secret key |
| 53 | * %$w_A = H(\cookie{switch-request}, c_A, c_B)$% |
| 54 | * Alice's switch request value |
| 55 | * %$u_A = H(\cookie{switch-confirm}, c_A, c_B)$% |
| 56 | * Alice's switch confirm value |
| 57 | * |
| 58 | * The messages are then: |
| 59 | * |
| 60 | * %$\cookie{kx-pre-challenge}, r_A$% |
| 61 | * Initial greeting. In state @KXS_CHAL@. |
| 62 | * |
| 63 | * %$\cookie{kx-challenge}, r_A, c_B, v_A$% |
| 64 | * Here's a full challenge for you to answer. |
| 65 | * |
| 66 | * %$\cookie{kx-reply}, r_A, c_B, v_A, E_K(r_B^\alpha))$% |
| 67 | * Challenge accpeted: here's the answer. Commit to my challenge. Move |
| 68 | * to @KXS_COMMIT@. |
| 69 | * |
| 70 | * %$\cookie{kx-switch-rq}, c_A, c_B, E_K(r_B^\alpha, w_A))$% |
| 71 | * Reply received: here's my reply. Committed; send data; move to |
| 72 | * @KXS_SWITCH@. |
| 73 | * |
| 74 | * %$\cookie{kx-switch-ok}, E_K(u_A))$% |
| 75 | * Switch received. Committed; send data; move to @KXS_SWITCH@. |
| 76 | */ |
| 77 | |
| 78 | /*----- Static tables -----------------------------------------------------*/ |
| 79 | |
| 80 | static const char *const pkname[] = { |
| 81 | "pre-challenge", "challenge", "reply", "switch-rq", "switch-ok" |
| 82 | }; |
| 83 | |
| 84 | /*----- Various utilities -------------------------------------------------*/ |
| 85 | |
| 86 | /* --- @VALIDP@ --- * |
| 87 | * |
| 88 | * Arguments: @const keyexch *kx@ = key exchange state |
| 89 | * @time_t now@ = current time in seconds |
| 90 | * |
| 91 | * Returns: Whether the challenge in the key-exchange state is still |
| 92 | * valid or should be regenerated. |
| 93 | */ |
| 94 | |
| 95 | #define VALIDP(kx, now) ((now) < (kx)->t_valid) |
| 96 | |
| 97 | /* --- @hashge@ --- * |
| 98 | * |
| 99 | * Arguments: @ghash *h@ = pointer to hash context |
| 100 | * @group *g@ = pointer to group |
| 101 | * @ge *x@ = pointer to group element |
| 102 | * |
| 103 | * Returns: --- |
| 104 | * |
| 105 | * Use: Adds the hash of a group element to the context. Corrupts |
| 106 | * @buf_t@. |
| 107 | */ |
| 108 | |
| 109 | static void hashge(ghash *h, group *g, ge *x) |
| 110 | { |
| 111 | buf b; |
| 112 | |
| 113 | buf_init(&b, buf_t, sizeof(buf_t)); |
| 114 | G_TOBUF(g, &b, x); |
| 115 | assert(BOK(&b)); |
| 116 | GH_HASH(h, BBASE(&b), BLEN(&b)); |
| 117 | } |
| 118 | |
| 119 | /* --- @mpmask@ --- * |
| 120 | * |
| 121 | * Arguments: @buf *b@ = output buffer |
| 122 | * @mp *x@ = the plaintext integer |
| 123 | * @size_t n@ = the expected size of the plaintext |
| 124 | * @gcipher *mgfc@ = mask-generating function to use |
| 125 | * @const octet *k@ = pointer to key material |
| 126 | * @size_t ksz@ = size of the key |
| 127 | * |
| 128 | * Returns: Pointer to the output. |
| 129 | * |
| 130 | * Use: Masks a multiprecision integer: returns %$x \xor H(k)$%, so |
| 131 | * it's a random oracle thing rather than an encryption thing. |
| 132 | */ |
| 133 | |
| 134 | static octet *mpmask(buf *b, mp *x, size_t n, |
| 135 | const gccipher *mgfc, const octet *k, size_t ksz) |
| 136 | { |
| 137 | gcipher *mgf; |
| 138 | octet *p; |
| 139 | |
| 140 | if ((p = buf_get(b, n)) == 0) |
| 141 | return (0); |
| 142 | mgf = GC_INIT(mgfc, k, ksz); |
| 143 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 144 | trace(T_CRYPTO, "crypto: masking index = %s", mpstr(x)); |
| 145 | trace_block(T_CRYPTO, "crypto: masking key", k, ksz); |
| 146 | })) |
| 147 | mp_storeb(x, buf_t, n); |
| 148 | GC_ENCRYPT(mgf, buf_t, p, n); |
| 149 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 150 | trace_block(T_CRYPTO, "crypto: index plaintext", buf_t, n); |
| 151 | trace_block(T_CRYPTO, "crypto: masked ciphertext", p, n); |
| 152 | })) |
| 153 | GC_DESTROY(mgf); |
| 154 | return (p); |
| 155 | } |
| 156 | |
| 157 | /* --- @mpunmask@ --- * |
| 158 | * |
| 159 | * Arguments: @mp *d@ = the output integer |
| 160 | * @const octet *p@ = pointer to the ciphertext |
| 161 | * @size_t n@ = the size of the ciphertext |
| 162 | * @gcipher *mgfc@ = mask-generating function to use |
| 163 | * @const octet *k@ = pointer to key material |
| 164 | * @size_t ksz@ = size of the key |
| 165 | * |
| 166 | * Returns: The decrypted integer, or null. |
| 167 | * |
| 168 | * Use: Unmasks a multiprecision integer. |
| 169 | */ |
| 170 | |
| 171 | static mp *mpunmask(mp *d, const octet *p, size_t n, |
| 172 | const gccipher *mgfc, const octet *k, size_t ksz) |
| 173 | { |
| 174 | gcipher *mgf; |
| 175 | |
| 176 | mgf = GC_INIT(mgfc, k, ksz); |
| 177 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 178 | trace_block(T_CRYPTO, "crypto: unmasking key", k, ksz); |
| 179 | trace_block(T_CRYPTO, "crypto: masked ciphertext", p, n); |
| 180 | })) |
| 181 | GC_DECRYPT(mgf, p, buf_t, n); |
| 182 | d = mp_loadb(d, buf_t, n); |
| 183 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 184 | trace_block(T_CRYPTO, "crypto: index plaintext", buf_t, n); |
| 185 | trace(T_CRYPTO, "crypto: unmasked index = %s", mpstr(d)); |
| 186 | })) |
| 187 | GC_DESTROY(mgf); |
| 188 | return (d); |
| 189 | } |
| 190 | |
| 191 | /* --- @hashcheck@ --- * |
| 192 | * |
| 193 | * Arguments: @keyexch *kx@ = pointer to key-exchange block |
| 194 | * @ge *kpub@ = sender's public key |
| 195 | * @ge *cc@ = receiver's challenge |
| 196 | * @ge *c@ = sender's challenge |
| 197 | * @ge *y@ = reply to sender's challenge |
| 198 | * |
| 199 | * Returns: Pointer to the hash value (in @buf_t@) |
| 200 | * |
| 201 | * Use: Computes the check-value hash, used to mask or unmask |
| 202 | * indices to prove the validity of challenges. This computes |
| 203 | * the masking key used in challenge check values. This is |
| 204 | * really the heart of the whole thing, since it ensures that |
| 205 | * the index can be recovered from the history of hashing |
| 206 | * queries, which gives us (a) a proof that the authentication |
| 207 | * process is zero-knowledge, and (b) a proof that the whole |
| 208 | * key-exchange is deniable. |
| 209 | */ |
| 210 | |
| 211 | static const octet *hashcheck(keyexch *kx, ge *kpub, ge *cc, ge *c, ge *y) |
| 212 | { |
| 213 | ghash *h = GH_INIT(kx->kpriv->algs.h); |
| 214 | group *g = kx->kpriv->g; |
| 215 | |
| 216 | HASH_STRING(h, "tripe-expected-reply"); |
| 217 | hashge(h, g, kpub); |
| 218 | hashge(h, g, cc); |
| 219 | hashge(h, g, c); |
| 220 | hashge(h, g, y); |
| 221 | GH_DONE(h, buf_t); |
| 222 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 223 | trace(T_CRYPTO, "crypto: computing challenge check hash"); |
| 224 | trace(T_CRYPTO, "crypto: public key = %s", gestr(g, kpub)); |
| 225 | trace(T_CRYPTO, "crypto: receiver challenge = %s", gestr(g, cc)); |
| 226 | trace(T_CRYPTO, "crypto: sender challenge = %s", gestr(g, c)); |
| 227 | trace(T_CRYPTO, "crypto: sender reply = %s", gestr(g, y)); |
| 228 | trace_block(T_CRYPTO, "crypto: hash output", buf_t, kx->kpriv->algs.hashsz); |
| 229 | })) |
| 230 | GH_DESTROY(h); |
| 231 | return (buf_t); |
| 232 | } |
| 233 | |
| 234 | /* --- @sendchallenge@ --- * |
| 235 | * |
| 236 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
| 237 | * @buf *b@ = output buffer for challenge |
| 238 | * @ge *c@ = peer's actual challenge |
| 239 | * @const octet *hc@ = peer's challenge cookie |
| 240 | * |
| 241 | * Returns: --- |
| 242 | * |
| 243 | * Use: Writes a full challenge to the message buffer. |
| 244 | */ |
| 245 | |
| 246 | static void sendchallenge(keyexch *kx, buf *b, ge *c, const octet *hc) |
| 247 | { |
| 248 | G_TOBUF(kx->kpriv->g, b, kx->c); |
| 249 | buf_put(b, hc, kx->kpriv->algs.hashsz); |
| 250 | mpmask(b, kx->alpha, kx->kpriv->indexsz, kx->kpriv->algs.mgf, |
| 251 | hashcheck(kx, kx->kpriv->kpub, c, kx->c, kx->rx), |
| 252 | kx->kpriv->algs.hashsz); |
| 253 | } |
| 254 | |
| 255 | /* --- @timer@ --- * |
| 256 | * |
| 257 | * Arguments: @struct timeval *tv@ = the current time |
| 258 | * @void *v@ = pointer to key exchange context |
| 259 | * |
| 260 | * Returns: --- |
| 261 | * |
| 262 | * Use: Acts when the key exchange timer goes off. |
| 263 | */ |
| 264 | |
| 265 | static void timer(struct timeval *tv, void *v) |
| 266 | { |
| 267 | keyexch *kx = v; |
| 268 | kx->f &= ~KXF_TIMER; |
| 269 | T( trace(T_KEYEXCH, "keyexch: timer has popped"); ) |
| 270 | kx_start(kx, 0); |
| 271 | } |
| 272 | |
| 273 | /* --- @settimer@ --- * |
| 274 | * |
| 275 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 276 | * @struct timeval *tv@ = when to set the timer for |
| 277 | * |
| 278 | * Returns: --- |
| 279 | * |
| 280 | * Use: Sets the timer for the next key exchange attempt. |
| 281 | */ |
| 282 | |
| 283 | static void settimer(keyexch *kx, struct timeval *tv) |
| 284 | { |
| 285 | if (kx->f & KXF_TIMER) sel_rmtimer(&kx->t); |
| 286 | sel_addtimer(&sel, &kx->t, tv, timer, kx); |
| 287 | kx->f |= KXF_TIMER; |
| 288 | } |
| 289 | |
| 290 | /* --- @f2tv@ --- * |
| 291 | * |
| 292 | * Arguments: @struct timeval *tv@ = where to write the timeval |
| 293 | * @double t@ = a time as a floating point number |
| 294 | * |
| 295 | * Returns: --- |
| 296 | * |
| 297 | * Use: Converts a floating-point time into a timeval. |
| 298 | */ |
| 299 | |
| 300 | static void f2tv(struct timeval *tv, double t) |
| 301 | { |
| 302 | tv->tv_sec = t; |
| 303 | tv->tv_usec = (t - tv->tv_sec)*MILLION; |
| 304 | } |
| 305 | |
| 306 | /* --- @wobble@ --- * |
| 307 | * |
| 308 | * Arguments: @double t@ = a time interval |
| 309 | * |
| 310 | * Returns: The same time interval, with a random error applied. |
| 311 | */ |
| 312 | |
| 313 | static double wobble(double t) |
| 314 | { |
| 315 | uint32 r = rand_global.ops->word(&rand_global); |
| 316 | double w = (r/F_2P32) - 0.5; |
| 317 | return (t + t*w*T_WOBBLE); |
| 318 | } |
| 319 | |
| 320 | /* --- @rs_time@ --- * |
| 321 | * |
| 322 | * Arguments: @retry *rs@ = current retry state |
| 323 | * @struct timeval *tv@ = where to write the result |
| 324 | * @const struct timeval *now@ = current time, or null |
| 325 | * |
| 326 | * Returns: --- |
| 327 | * |
| 328 | * Use: Computes a time at which to retry sending a key-exchange |
| 329 | * packet. This algorithm is subject to change, but it's |
| 330 | * currently a capped exponential backoff, slightly randomized |
| 331 | * to try to keep clients from hammering a server that's only |
| 332 | * just woken up. |
| 333 | * |
| 334 | * If @now@ is null then the function works out the time for |
| 335 | * itself. |
| 336 | */ |
| 337 | |
| 338 | static void rs_time(retry *rs, struct timeval *tv, const struct timeval *now) |
| 339 | { |
| 340 | double t; |
| 341 | struct timeval rtv; |
| 342 | |
| 343 | if (!rs->t) |
| 344 | t = SEC(2); |
| 345 | else { |
| 346 | t = (rs->t * 5)/4; |
| 347 | if (t > MIN(5)) t = MIN(5); |
| 348 | } |
| 349 | rs->t = t; |
| 350 | |
| 351 | if (!now) { |
| 352 | now = tv; |
| 353 | gettimeofday(tv, 0); |
| 354 | } |
| 355 | f2tv(&rtv, wobble(t)); |
| 356 | TV_ADD(tv, now, &rtv); |
| 357 | } |
| 358 | |
| 359 | /* --- @retry_reset@ --- * |
| 360 | * |
| 361 | * Arguments: @retry *rs@ = retry state |
| 362 | * |
| 363 | * Returns: -- |
| 364 | * |
| 365 | * Use: Resets a retry state to indicate that progress has been |
| 366 | * made. Also useful for initializing the state in the first |
| 367 | * place. |
| 368 | */ |
| 369 | |
| 370 | static void rs_reset(retry *rs) { rs->t = 0; } |
| 371 | |
| 372 | /*----- Challenge management ----------------------------------------------*/ |
| 373 | |
| 374 | /* --- Notes on challenge management --- * |
| 375 | * |
| 376 | * We may get multiple different replies to our key exchange; some will be |
| 377 | * correct, some inserted by attackers. Up until @KX_THRESH@, all challenges |
| 378 | * received will be added to the table and given a full response. After |
| 379 | * @KX_THRESH@ distinct challenges are received, we return only a `cookie': |
| 380 | * our existing challenge, followed by a hash of the sender's challenge. We |
| 381 | * do %%\emph{not}%% give a bare challenge a reply slot at this stage. All |
| 382 | * properly-formed cookies are assigned a table slot: if none is spare, a |
| 383 | * used slot is randomly selected and destroyed. A cookie always receives a |
| 384 | * full reply. |
| 385 | */ |
| 386 | |
| 387 | /* --- @kxc_destroy@ --- * |
| 388 | * |
| 389 | * Arguments: @kxchal *kxc@ = pointer to the challenge block |
| 390 | * |
| 391 | * Returns: --- |
| 392 | * |
| 393 | * Use: Disposes of a challenge block. |
| 394 | */ |
| 395 | |
| 396 | static void kxc_destroy(kxchal *kxc) |
| 397 | { |
| 398 | if (kxc->f & KXF_TIMER) |
| 399 | sel_rmtimer(&kxc->t); |
| 400 | G_DESTROY(kxc->kx->kpriv->g, kxc->c); |
| 401 | G_DESTROY(kxc->kx->kpriv->g, kxc->r); |
| 402 | ks_drop(kxc->ks); |
| 403 | DESTROY(kxc); |
| 404 | } |
| 405 | |
| 406 | /* --- @kxc_stoptimer@ --- * |
| 407 | * |
| 408 | * Arguments: @kxchal *kxc@ = pointer to the challenge block |
| 409 | * |
| 410 | * Returns: --- |
| 411 | * |
| 412 | * Use: Stops the challenge's retry timer from sending messages. |
| 413 | * Useful when the state machine is in the endgame of the |
| 414 | * exchange. |
| 415 | */ |
| 416 | |
| 417 | static void kxc_stoptimer(kxchal *kxc) |
| 418 | { |
| 419 | if (kxc->f & KXF_TIMER) |
| 420 | sel_rmtimer(&kxc->t); |
| 421 | kxc->f &= ~KXF_TIMER; |
| 422 | } |
| 423 | |
| 424 | /* --- @kxc_new@ --- * |
| 425 | * |
| 426 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
| 427 | * |
| 428 | * Returns: A pointer to the challenge block. |
| 429 | * |
| 430 | * Use: Returns a pointer to a new challenge block to fill in. |
| 431 | */ |
| 432 | |
| 433 | static kxchal *kxc_new(keyexch *kx) |
| 434 | { |
| 435 | kxchal *kxc; |
| 436 | unsigned i; |
| 437 | |
| 438 | /* --- If we're over reply threshold, discard one at random --- */ |
| 439 | |
| 440 | if (kx->nr < KX_NCHAL) |
| 441 | i = kx->nr++; |
| 442 | else { |
| 443 | i = rand_global.ops->range(&rand_global, KX_NCHAL); |
| 444 | kxc_destroy(kx->r[i]); |
| 445 | } |
| 446 | |
| 447 | /* --- Fill in the new structure --- */ |
| 448 | |
| 449 | kxc = CREATE(kxchal); |
| 450 | kxc->c = G_CREATE(kx->kpriv->g); |
| 451 | kxc->r = G_CREATE(kx->kpriv->g); |
| 452 | kxc->ks = 0; |
| 453 | kxc->kx = kx; |
| 454 | kxc->f = 0; |
| 455 | kx->r[i] = kxc; |
| 456 | rs_reset(&kxc->rs); |
| 457 | return (kxc); |
| 458 | } |
| 459 | |
| 460 | /* --- @kxc_bychal@ --- * |
| 461 | * |
| 462 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
| 463 | * @ge *c@ = challenge from remote host |
| 464 | * |
| 465 | * Returns: Pointer to the challenge block, or null. |
| 466 | * |
| 467 | * Use: Finds a challenge block, given its challenge. |
| 468 | */ |
| 469 | |
| 470 | static kxchal *kxc_bychal(keyexch *kx, ge *c) |
| 471 | { |
| 472 | unsigned i; |
| 473 | |
| 474 | for (i = 0; i < kx->nr; i++) { |
| 475 | if (G_EQ(kx->kpriv->g, c, kx->r[i]->c)) |
| 476 | return (kx->r[i]); |
| 477 | } |
| 478 | return (0); |
| 479 | } |
| 480 | |
| 481 | /* --- @kxc_byhc@ --- * |
| 482 | * |
| 483 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
| 484 | * @const octet *hc@ = challenge hash from remote host |
| 485 | * |
| 486 | * Returns: Pointer to the challenge block, or null. |
| 487 | * |
| 488 | * Use: Finds a challenge block, given a hash of its challenge. |
| 489 | */ |
| 490 | |
| 491 | static kxchal *kxc_byhc(keyexch *kx, const octet *hc) |
| 492 | { |
| 493 | unsigned i; |
| 494 | |
| 495 | for (i = 0; i < kx->nr; i++) { |
| 496 | if (memcmp(hc, kx->r[i]->hc, kx->kpriv->algs.hashsz) == 0) |
| 497 | return (kx->r[i]); |
| 498 | } |
| 499 | return (0); |
| 500 | } |
| 501 | |
| 502 | /* --- @kxc_answer@ --- * |
| 503 | * |
| 504 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
| 505 | * @kxchal *kxc@ = pointer to challenge block |
| 506 | * |
| 507 | * Returns: --- |
| 508 | * |
| 509 | * Use: Sends a reply to the remote host, according to the data in |
| 510 | * this challenge block. |
| 511 | */ |
| 512 | |
| 513 | static void kxc_answer(keyexch *kx, kxchal *kxc); |
| 514 | |
| 515 | static void kxc_timer(struct timeval *tv, void *v) |
| 516 | { |
| 517 | kxchal *kxc = v; |
| 518 | kxc->f &= ~KXF_TIMER; |
| 519 | kxc_answer(kxc->kx, kxc); |
| 520 | } |
| 521 | |
| 522 | static void kxc_answer(keyexch *kx, kxchal *kxc) |
| 523 | { |
| 524 | stats *st = p_stats(kx->p); |
| 525 | buf *b = p_txstart(kx->p, MSG_KEYEXCH | KX_REPLY); |
| 526 | struct timeval tv; |
| 527 | buf bb; |
| 528 | |
| 529 | /* --- Build the reply packet --- */ |
| 530 | |
| 531 | T( trace(T_KEYEXCH, "keyexch: sending reply to `%s'", p_name(kx->p)); ) |
| 532 | sendchallenge(kx, b, kxc->c, kxc->hc); |
| 533 | buf_init(&bb, buf_i, sizeof(buf_i)); |
| 534 | G_TORAW(kx->kpriv->g, &bb, kxc->r); |
| 535 | buf_flip(&bb); |
| 536 | ks_encrypt(kxc->ks, MSG_KEYEXCH | KX_REPLY, &bb, b); |
| 537 | |
| 538 | /* --- Update the statistics --- */ |
| 539 | |
| 540 | if (BOK(b)) { |
| 541 | st->n_kxout++; |
| 542 | st->sz_kxout += BLEN(b); |
| 543 | p_txend(kx->p); |
| 544 | } |
| 545 | |
| 546 | /* --- Schedule another resend --- */ |
| 547 | |
| 548 | if (kxc->f & KXF_TIMER) |
| 549 | sel_rmtimer(&kxc->t); |
| 550 | gettimeofday(&tv, 0); |
| 551 | rs_time(&kxc->rs, &tv, &tv); |
| 552 | sel_addtimer(&sel, &kxc->t, &tv, kxc_timer, kxc); |
| 553 | kxc->f |= KXF_TIMER; |
| 554 | } |
| 555 | |
| 556 | /*----- Individual message handlers ---------------------------------------*/ |
| 557 | |
| 558 | /* --- @doprechallenge@ --- * |
| 559 | * |
| 560 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
| 561 | * @buf *b@ = buffer containing the packet |
| 562 | * |
| 563 | * Returns: Zero if OK, nonzero of the packet was rejected. |
| 564 | * |
| 565 | * Use: Processes a pre-challenge message. |
| 566 | */ |
| 567 | |
| 568 | static int doprechallenge(keyexch *kx, buf *b) |
| 569 | { |
| 570 | stats *st = p_stats(kx->p); |
| 571 | ge *c = G_CREATE(kx->kpriv->g); |
| 572 | ghash *h; |
| 573 | |
| 574 | /* --- Ensure that we're in a sensible state --- */ |
| 575 | |
| 576 | if (kx->s != KXS_CHAL) { |
| 577 | a_warn("KX", "?PEER", kx->p, "unexpected", "pre-challenge", A_END); |
| 578 | goto bad; |
| 579 | } |
| 580 | |
| 581 | /* --- Unpack the packet --- */ |
| 582 | |
| 583 | if (G_FROMBUF(kx->kpriv->g, b, c) || BLEFT(b)) |
| 584 | goto bad; |
| 585 | |
| 586 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 587 | trace(T_CRYPTO, "crypto: challenge = %s", gestr(kx->kpriv->g, c)); |
| 588 | })) |
| 589 | |
| 590 | /* --- Send out a full challenge by return --- */ |
| 591 | |
| 592 | b = p_txstart(kx->p, MSG_KEYEXCH | KX_CHAL); |
| 593 | h = GH_INIT(kx->kpriv->algs.h); |
| 594 | HASH_STRING(h, "tripe-cookie"); |
| 595 | hashge(h, kx->kpriv->g, c); |
| 596 | sendchallenge(kx, b, c, GH_DONE(h, 0)); |
| 597 | GH_DESTROY(h); |
| 598 | st->n_kxout++; |
| 599 | st->sz_kxout += BLEN(b); |
| 600 | p_txend(kx->p); |
| 601 | |
| 602 | /* --- Done --- */ |
| 603 | |
| 604 | G_DESTROY(kx->kpriv->g, c); |
| 605 | return (0); |
| 606 | |
| 607 | bad: |
| 608 | if (c) G_DESTROY(kx->kpriv->g, c); |
| 609 | return (-1); |
| 610 | } |
| 611 | |
| 612 | /* --- @respond@ --- * |
| 613 | * |
| 614 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
| 615 | * @unsigned msg@ = message code for this packet |
| 616 | * @buf *b@ = buffer containing the packet |
| 617 | * |
| 618 | * Returns: Key-exchange challenge block, or null. |
| 619 | * |
| 620 | * Use: Computes a response for the given challenge, entering it into |
| 621 | * a challenge block and so on. |
| 622 | */ |
| 623 | |
| 624 | static kxchal *respond(keyexch *kx, unsigned msg, buf *b) |
| 625 | { |
| 626 | group *g = kx->kpriv->g; |
| 627 | const algswitch *algs = &kx->kpriv->algs; |
| 628 | size_t ixsz = kx->kpriv->indexsz; |
| 629 | ge *c = G_CREATE(g); |
| 630 | ge *r = G_CREATE(g); |
| 631 | ge *cc = G_CREATE(g); |
| 632 | const octet *hc, *ck; |
| 633 | size_t x, y, z; |
| 634 | mp *cv = 0; |
| 635 | kxchal *kxc; |
| 636 | ghash *h = 0; |
| 637 | buf bb; |
| 638 | int ok; |
| 639 | |
| 640 | /* --- Unpack the packet --- */ |
| 641 | |
| 642 | if (G_FROMBUF(g, b, c) || |
| 643 | (hc = buf_get(b, algs->hashsz)) == 0 || |
| 644 | (ck = buf_get(b, ixsz)) == 0) { |
| 645 | a_warn("KX", "?PEER", kx->p, "invalid", "%s", pkname[msg], A_END); |
| 646 | goto bad; |
| 647 | } |
| 648 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 649 | trace(T_CRYPTO, "crypto: challenge = %s", gestr(g, c)); |
| 650 | trace_block(T_CRYPTO, "crypto: cookie", hc, algs->hashsz); |
| 651 | trace_block(T_CRYPTO, "crypto: check-value", ck, ixsz); |
| 652 | })) |
| 653 | |
| 654 | /* --- Discard a packet with an invalid cookie --- */ |
| 655 | |
| 656 | if (hc && memcmp(hc, kx->hc, algs->hashsz) != 0) { |
| 657 | a_warn("KX", "?PEER", kx->p, "incorrect", "cookie", A_END); |
| 658 | goto bad; |
| 659 | } |
| 660 | |
| 661 | /* --- Recover the check value and verify it --- * |
| 662 | * |
| 663 | * To avoid recomputation on replays, we store a hash of the `right' |
| 664 | * value. The `correct' value is unique, so this is right. |
| 665 | * |
| 666 | * This will also find a challenge block and, if necessary, populate it. |
| 667 | */ |
| 668 | |
| 669 | if ((kxc = kxc_bychal(kx, c)) != 0) { |
| 670 | h = GH_INIT(algs->h); |
| 671 | HASH_STRING(h, "tripe-check-hash"); |
| 672 | GH_HASH(h, ck, ixsz); |
| 673 | ok = !memcmp(kxc->ck, GH_DONE(h, 0), algs->hashsz); |
| 674 | GH_DESTROY(h); |
| 675 | if (!ok) goto badcheck; |
| 676 | } else { |
| 677 | |
| 678 | /* --- Compute the reply, and check the magic --- */ |
| 679 | |
| 680 | G_EXP(g, r, c, kx->kpriv->kpriv); |
| 681 | cv = mpunmask(MP_NEW, ck, ixsz, algs->mgf, |
| 682 | hashcheck(kx, kx->kpub->kpub, kx->c, c, r), |
| 683 | algs->hashsz); |
| 684 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 685 | trace(T_CRYPTO, "crypto: computed reply = %s", gestr(g, r)); |
| 686 | trace(T_CRYPTO, "crypto: recovered log = %s", mpstr(cv)); |
| 687 | })) |
| 688 | if (MP_CMP(cv, >, g->r) || |
| 689 | (G_EXP(g, cc, g->g, cv), |
| 690 | !G_EQ(g, c, cc))) |
| 691 | goto badcheck; |
| 692 | |
| 693 | /* --- Fill in a new challenge block --- */ |
| 694 | |
| 695 | kxc = kxc_new(kx); |
| 696 | G_COPY(g, kxc->c, c); |
| 697 | G_COPY(g, kxc->r, r); |
| 698 | |
| 699 | h = GH_INIT(algs->h); HASH_STRING(h, "tripe-check-hash"); |
| 700 | GH_HASH(h, ck, ixsz); |
| 701 | GH_DONE(h, kxc->ck); GH_DESTROY(h); |
| 702 | |
| 703 | h = GH_INIT(algs->h); HASH_STRING(h, "tripe-cookie"); |
| 704 | hashge(h, g, kxc->c); |
| 705 | GH_DONE(h, kxc->hc); GH_DESTROY(h); |
| 706 | |
| 707 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 708 | trace_block(T_CRYPTO, "crypto: computed cookie", |
| 709 | kxc->hc, algs->hashsz); |
| 710 | })) |
| 711 | |
| 712 | /* --- Work out the shared key --- */ |
| 713 | |
| 714 | G_EXP(g, r, c, kx->alpha); |
| 715 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 716 | trace(T_CRYPTO, "crypto: shared secret = %s", gestr(g, r)); |
| 717 | })) |
| 718 | |
| 719 | /* --- Compute the switch messages --- */ |
| 720 | |
| 721 | h = GH_INIT(algs->h); HASH_STRING(h, "tripe-switch-request"); |
| 722 | hashge(h, g, kx->c); hashge(h, g, kxc->c); |
| 723 | GH_DONE(h, kxc->hswrq_out); GH_DESTROY(h); |
| 724 | h = GH_INIT(algs->h); HASH_STRING(h, "tripe-switch-confirm"); |
| 725 | hashge(h, g, kx->c); hashge(h, g, kxc->c); |
| 726 | GH_DONE(h, kxc->hswok_out); GH_DESTROY(h); |
| 727 | |
| 728 | h = GH_INIT(algs->h); HASH_STRING(h, "tripe-switch-request"); |
| 729 | hashge(h, g, kxc->c); hashge(h, g, kx->c); |
| 730 | GH_DONE(h, kxc->hswrq_in); GH_DESTROY(h); |
| 731 | h = GH_INIT(algs->h); HASH_STRING(h, "tripe-switch-confirm"); |
| 732 | hashge(h, g, kxc->c); hashge(h, g, kx->c); |
| 733 | GH_DONE(h, kxc->hswok_in); GH_DESTROY(h); |
| 734 | |
| 735 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 736 | trace_block(T_CRYPTO, "crypto: outbound switch request", |
| 737 | kxc->hswrq_out, algs->hashsz); |
| 738 | trace_block(T_CRYPTO, "crypto: outbound switch confirm", |
| 739 | kxc->hswok_out, algs->hashsz); |
| 740 | trace_block(T_CRYPTO, "crypto: inbound switch request", |
| 741 | kxc->hswrq_in, algs->hashsz); |
| 742 | trace_block(T_CRYPTO, "crypto: inbound switch confirm", |
| 743 | kxc->hswok_in, algs->hashsz); |
| 744 | })) |
| 745 | |
| 746 | /* --- Create a new symmetric keyset --- */ |
| 747 | |
| 748 | buf_init(&bb, buf_o, sizeof(buf_o)); |
| 749 | G_TOBUF(g, &bb, kx->c); x = BLEN(&bb); |
| 750 | G_TOBUF(g, &bb, kxc->c); y = BLEN(&bb); |
| 751 | G_TOBUF(g, &bb, r); z = BLEN(&bb); |
| 752 | assert(BOK(&bb)); |
| 753 | |
| 754 | kxc->ks = ks_gen(BBASE(&bb), x, y, z, kx->p); |
| 755 | } |
| 756 | |
| 757 | G_DESTROY(g, c); |
| 758 | G_DESTROY(g, cc); |
| 759 | G_DESTROY(g, r); |
| 760 | mp_drop(cv); |
| 761 | return (kxc); |
| 762 | |
| 763 | badcheck: |
| 764 | a_warn("KX", "?PEER", kx->p, "bad-expected-reply-log", A_END); |
| 765 | goto bad; |
| 766 | bad: |
| 767 | G_DESTROY(g, c); |
| 768 | G_DESTROY(g, cc); |
| 769 | G_DESTROY(g, r); |
| 770 | mp_drop(cv); |
| 771 | return (0); |
| 772 | } |
| 773 | |
| 774 | /* --- @dochallenge@ --- * |
| 775 | * |
| 776 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
| 777 | * @unsigned msg@ = message code for the packet |
| 778 | * @buf *b@ = buffer containing the packet |
| 779 | * |
| 780 | * Returns: Zero if OK, nonzero if the packet was rejected. |
| 781 | * |
| 782 | * Use: Processes a packet containing a challenge. |
| 783 | */ |
| 784 | |
| 785 | static int dochallenge(keyexch *kx, buf *b) |
| 786 | { |
| 787 | kxchal *kxc; |
| 788 | |
| 789 | if (kx->s != KXS_CHAL) { |
| 790 | a_warn("KX", "?PEER", kx->p, "unexpected", "challenge", A_END); |
| 791 | goto bad; |
| 792 | } |
| 793 | if ((kxc = respond(kx, KX_CHAL, b)) == 0) |
| 794 | goto bad; |
| 795 | if (BLEFT(b)) { |
| 796 | a_warn("KX", "?PEER", kx->p, "invalid", "challenge", A_END); |
| 797 | goto bad; |
| 798 | } |
| 799 | kxc_answer(kx, kxc); |
| 800 | return (0); |
| 801 | |
| 802 | bad: |
| 803 | return (-1); |
| 804 | } |
| 805 | |
| 806 | /* --- @resend@ --- * |
| 807 | * |
| 808 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 809 | * |
| 810 | * Returns: --- |
| 811 | * |
| 812 | * Use: Sends the next message for a key exchange. |
| 813 | */ |
| 814 | |
| 815 | static void resend(keyexch *kx) |
| 816 | { |
| 817 | kxchal *kxc; |
| 818 | buf bb; |
| 819 | stats *st = p_stats(kx->p); |
| 820 | struct timeval tv; |
| 821 | buf *b; |
| 822 | |
| 823 | switch (kx->s) { |
| 824 | case KXS_CHAL: |
| 825 | T( trace(T_KEYEXCH, "keyexch: sending prechallenge to `%s'", |
| 826 | p_name(kx->p)); ) |
| 827 | b = p_txstart(kx->p, MSG_KEYEXCH | KX_PRECHAL); |
| 828 | G_TOBUF(kx->kpriv->g, b, kx->c); |
| 829 | break; |
| 830 | case KXS_COMMIT: |
| 831 | T( trace(T_KEYEXCH, "keyexch: sending switch request to `%s'", |
| 832 | p_name(kx->p)); ) |
| 833 | kxc = kx->r[0]; |
| 834 | b = p_txstart(kx->p, MSG_KEYEXCH | KX_SWITCH); |
| 835 | buf_put(b, kx->hc, kx->kpriv->algs.hashsz); |
| 836 | buf_put(b, kxc->hc, kx->kpriv->algs.hashsz); |
| 837 | buf_init(&bb, buf_i, sizeof(buf_i)); |
| 838 | G_TORAW(kx->kpriv->g, &bb, kxc->r); |
| 839 | buf_put(&bb, kxc->hswrq_out, kx->kpriv->algs.hashsz); |
| 840 | buf_flip(&bb); |
| 841 | ks_encrypt(kxc->ks, MSG_KEYEXCH | KX_SWITCH, &bb, b); |
| 842 | break; |
| 843 | case KXS_SWITCH: |
| 844 | T( trace(T_KEYEXCH, "keyexch: sending switch confirmation to `%s'", |
| 845 | p_name(kx->p)); ) |
| 846 | kxc = kx->r[0]; |
| 847 | b = p_txstart(kx->p, MSG_KEYEXCH | KX_SWITCHOK); |
| 848 | buf_init(&bb, buf_i, sizeof(buf_i)); |
| 849 | buf_put(&bb, kxc->hswok_out, kx->kpriv->algs.hashsz); |
| 850 | buf_flip(&bb); |
| 851 | ks_encrypt(kxc->ks, MSG_KEYEXCH | KX_SWITCHOK, &bb, b); |
| 852 | break; |
| 853 | default: |
| 854 | abort(); |
| 855 | } |
| 856 | |
| 857 | if (BOK(b)) { |
| 858 | st->n_kxout++; |
| 859 | st->sz_kxout += BLEN(b); |
| 860 | p_txend(kx->p); |
| 861 | } |
| 862 | |
| 863 | if (kx->s < KXS_SWITCH) { |
| 864 | rs_time(&kx->rs, &tv, 0); |
| 865 | settimer(kx, &tv); |
| 866 | } |
| 867 | } |
| 868 | |
| 869 | /* --- @decryptrest@ --- * |
| 870 | * |
| 871 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 872 | * @kxchal *kxc@ = pointer to challenge block |
| 873 | * @unsigned msg@ = type of incoming message |
| 874 | * @buf *b@ = encrypted remainder of the packet |
| 875 | * |
| 876 | * Returns: Zero if OK, nonzero on some kind of error. |
| 877 | * |
| 878 | * Use: Decrypts the remainder of the packet, and points @b@ at the |
| 879 | * recovered plaintext. |
| 880 | */ |
| 881 | |
| 882 | static int decryptrest(keyexch *kx, kxchal *kxc, unsigned msg, buf *b) |
| 883 | { |
| 884 | buf bb; |
| 885 | |
| 886 | buf_init(&bb, buf_o, sizeof(buf_o)); |
| 887 | if (ks_decrypt(kxc->ks, MSG_KEYEXCH | msg, b, &bb)) { |
| 888 | a_warn("KX", "?PEER", kx->p, "decrypt-failed", "%s", pkname[msg], A_END); |
| 889 | return (-1); |
| 890 | } |
| 891 | if (!BOK(&bb)) return (-1); |
| 892 | buf_init(b, BBASE(&bb), BLEN(&bb)); |
| 893 | return (0); |
| 894 | } |
| 895 | |
| 896 | /* --- @checkresponse@ --- * |
| 897 | * |
| 898 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 899 | * @unsigned msg@ = type of incoming message |
| 900 | * @buf *b@ = decrypted remainder of the packet |
| 901 | * |
| 902 | * Returns: Zero if OK, nonzero on some kind of error. |
| 903 | * |
| 904 | * Use: Checks a reply or switch packet, ensuring that its response |
| 905 | * is correct. |
| 906 | */ |
| 907 | |
| 908 | static int checkresponse(keyexch *kx, unsigned msg, buf *b) |
| 909 | { |
| 910 | group *g = kx->kpriv->g; |
| 911 | ge *r = G_CREATE(g); |
| 912 | |
| 913 | if (G_FROMRAW(g, b, r)) { |
| 914 | a_warn("KX", "?PEER", kx->p, "invalid", "%s", pkname[msg], A_END); |
| 915 | goto bad; |
| 916 | } |
| 917 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 918 | trace(T_CRYPTO, "crypto: reply = %s", gestr(g, r)); |
| 919 | })) |
| 920 | if (!G_EQ(g, r, kx->rx)) { |
| 921 | a_warn("KX", "?PEER", kx->p, "incorrect", "response", A_END); |
| 922 | goto bad; |
| 923 | } |
| 924 | |
| 925 | G_DESTROY(g, r); |
| 926 | return (0); |
| 927 | |
| 928 | bad: |
| 929 | G_DESTROY(g, r); |
| 930 | return (-1); |
| 931 | } |
| 932 | |
| 933 | /* --- @commit@ --- * |
| 934 | * |
| 935 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 936 | * @kxchal *kxc@ = pointer to challenge to commit to |
| 937 | * |
| 938 | * Returns: --- |
| 939 | * |
| 940 | * Use: Commits to a particular challenge as being the `right' one, |
| 941 | * since a reply has arrived for it. |
| 942 | */ |
| 943 | |
| 944 | static void commit(keyexch *kx, kxchal *kxc) |
| 945 | { |
| 946 | unsigned i; |
| 947 | |
| 948 | for (i = 0; i < kx->nr; i++) { |
| 949 | if (kx->r[i] != kxc) |
| 950 | kxc_destroy(kx->r[i]); |
| 951 | } |
| 952 | kx->r[0] = kxc; |
| 953 | kx->nr = 1; |
| 954 | kxc_stoptimer(kxc); |
| 955 | ksl_link(kx->ks, kxc->ks); |
| 956 | } |
| 957 | |
| 958 | /* --- @doreply@ --- * |
| 959 | * |
| 960 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 961 | * @buf *b@ = buffer containing packet |
| 962 | * |
| 963 | * Returns: Zero if OK, nonzero if the packet was rejected. |
| 964 | * |
| 965 | * Use: Handles a reply packet. This doesn't handle the various |
| 966 | * switch packets: they're rather too different. |
| 967 | */ |
| 968 | |
| 969 | static int doreply(keyexch *kx, buf *b) |
| 970 | { |
| 971 | kxchal *kxc; |
| 972 | |
| 973 | if (kx->s != KXS_CHAL && kx->s != KXS_COMMIT) { |
| 974 | a_warn("KX", "?PEER", kx->p, "unexpected", "reply", A_END); |
| 975 | goto bad; |
| 976 | } |
| 977 | if ((kxc = respond(kx, KX_REPLY, b)) == 0 || |
| 978 | decryptrest(kx, kxc, KX_REPLY, b) || |
| 979 | checkresponse(kx, KX_REPLY, b)) |
| 980 | goto bad; |
| 981 | if (BLEFT(b)) { |
| 982 | a_warn("KX", "?PEER", kx->p, "invalid", "reply", A_END); |
| 983 | goto bad; |
| 984 | } |
| 985 | if (kx->s == KXS_CHAL) { |
| 986 | commit(kx, kxc); |
| 987 | kx->s = KXS_COMMIT; |
| 988 | } |
| 989 | resend(kx); |
| 990 | return (0); |
| 991 | |
| 992 | bad: |
| 993 | return (-1); |
| 994 | } |
| 995 | |
| 996 | /* --- @kxfinish@ --- * |
| 997 | * |
| 998 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
| 999 | * |
| 1000 | * Returns: --- |
| 1001 | * |
| 1002 | * Use: Sets everything up following a successful key exchange. |
| 1003 | */ |
| 1004 | |
| 1005 | static void kxfinish(keyexch *kx) |
| 1006 | { |
| 1007 | kxchal *kxc = kx->r[0]; |
| 1008 | struct timeval now, tv; |
| 1009 | |
| 1010 | ks_activate(kxc->ks); |
| 1011 | gettimeofday(&now, 0); |
| 1012 | f2tv(&tv, wobble(T_REGEN)); |
| 1013 | TV_ADD(&tv, &now, &tv); |
| 1014 | settimer(kx, &tv); |
| 1015 | kx->s = KXS_SWITCH; |
| 1016 | a_notify("KXDONE", "?PEER", kx->p, A_END); |
| 1017 | p_stats(kx->p)->t_kx = time(0); |
| 1018 | } |
| 1019 | |
| 1020 | /* --- @doswitch@ --- * |
| 1021 | * |
| 1022 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
| 1023 | * @buf *b@ = pointer to buffer containing packet |
| 1024 | * |
| 1025 | * Returns: Zero if OK, nonzero if the packet was rejected. |
| 1026 | * |
| 1027 | * Use: Handles a reply with a switch request bolted onto it. |
| 1028 | */ |
| 1029 | |
| 1030 | static int doswitch(keyexch *kx, buf *b) |
| 1031 | { |
| 1032 | size_t hsz = kx->kpriv->algs.hashsz; |
| 1033 | const octet *hc_in, *hc_out, *hswrq; |
| 1034 | kxchal *kxc; |
| 1035 | |
| 1036 | if ((hc_in = buf_get(b, hsz)) == 0 || |
| 1037 | (hc_out = buf_get(b, hsz)) == 0) { |
| 1038 | a_warn("KX", "?PEER", kx->p, "invalid", "switch-rq", A_END); |
| 1039 | goto bad; |
| 1040 | } |
| 1041 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 1042 | trace_block(T_CRYPTO, "crypto: challenge", hc_in, hsz); |
| 1043 | trace_block(T_CRYPTO, "crypto: cookie", hc_out, hsz); |
| 1044 | })) |
| 1045 | if ((kxc = kxc_byhc(kx, hc_in)) == 0 || |
| 1046 | memcmp(hc_out, kx->hc, hsz) != 0) { |
| 1047 | a_warn("KX", "?PEER", kx->p, "incorrect", "switch-rq", A_END); |
| 1048 | goto bad; |
| 1049 | } |
| 1050 | if (decryptrest(kx, kxc, KX_SWITCH, b) || |
| 1051 | checkresponse(kx, KX_SWITCH, b)) |
| 1052 | goto bad; |
| 1053 | if ((hswrq = buf_get(b, hsz)) == 0 || BLEFT(b)) { |
| 1054 | a_warn("KX", "?PEER", kx->p, "invalid", "switch-rq", A_END); |
| 1055 | goto bad; |
| 1056 | } |
| 1057 | IF_TRACING(T_KEYEXCH, { |
| 1058 | trace_block(T_CRYPTO, "crypto: switch request hash", hswrq, hsz); |
| 1059 | }) |
| 1060 | if (memcmp(hswrq, kxc->hswrq_in, hsz) != 0) { |
| 1061 | a_warn("KX", "?PEER", kx->p, "incorrect", "switch-rq", A_END); |
| 1062 | goto bad; |
| 1063 | } |
| 1064 | if (kx->s == KXS_CHAL) |
| 1065 | commit(kx, kxc); |
| 1066 | if (kx->s < KXS_SWITCH) |
| 1067 | kxfinish(kx); |
| 1068 | resend(kx); |
| 1069 | return (0); |
| 1070 | |
| 1071 | bad: |
| 1072 | return (-1); |
| 1073 | } |
| 1074 | |
| 1075 | /* --- @doswitchok@ --- * |
| 1076 | * |
| 1077 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
| 1078 | * @buf *b@ = pointer to buffer containing packet |
| 1079 | * |
| 1080 | * Returns: Zero if OK, nonzero if the packet was rejected. |
| 1081 | * |
| 1082 | * Use: Handles a reply with a switch request bolted onto it. |
| 1083 | */ |
| 1084 | |
| 1085 | static int doswitchok(keyexch *kx, buf *b) |
| 1086 | { |
| 1087 | size_t hsz = kx->kpriv->algs.hashsz; |
| 1088 | const octet *hswok; |
| 1089 | kxchal *kxc; |
| 1090 | buf bb; |
| 1091 | |
| 1092 | if (kx->s < KXS_COMMIT) { |
| 1093 | a_warn("KX", "?PEER", kx->p, "unexpected", "switch-ok", A_END); |
| 1094 | goto bad; |
| 1095 | } |
| 1096 | kxc = kx->r[0]; |
| 1097 | buf_init(&bb, buf_o, sizeof(buf_o)); |
| 1098 | if (decryptrest(kx, kxc, KX_SWITCHOK, b)) |
| 1099 | goto bad; |
| 1100 | if ((hswok = buf_get(b, hsz)) == 0 || BLEFT(b)) { |
| 1101 | a_warn("KX", "?PEER", kx->p, "invalid", "switch-ok", A_END); |
| 1102 | goto bad; |
| 1103 | } |
| 1104 | IF_TRACING(T_KEYEXCH, { |
| 1105 | trace_block(T_CRYPTO, "crypto: switch confirmation hash", |
| 1106 | hswok, hsz); |
| 1107 | }) |
| 1108 | if (memcmp(hswok, kxc->hswok_in, hsz) != 0) { |
| 1109 | a_warn("KX", "?PEER", kx->p, "incorrect", "switch-ok", A_END); |
| 1110 | goto bad; |
| 1111 | } |
| 1112 | if (kx->s < KXS_SWITCH) |
| 1113 | kxfinish(kx); |
| 1114 | return (0); |
| 1115 | |
| 1116 | bad: |
| 1117 | return (-1); |
| 1118 | } |
| 1119 | |
| 1120 | /*----- Main code ---------------------------------------------------------*/ |
| 1121 | |
| 1122 | /* --- @stop@ --- * |
| 1123 | * |
| 1124 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 1125 | * |
| 1126 | * Returns: --- |
| 1127 | * |
| 1128 | * Use: Stops a key exchange dead in its tracks. Throws away all of |
| 1129 | * the context information. The context is left in an |
| 1130 | * inconsistent state. The only functions which understand this |
| 1131 | * state are @kx_free@ and @kx_init@ (which cause it internally |
| 1132 | * it), and @start@ (which expects it to be the prevailing |
| 1133 | * state). |
| 1134 | */ |
| 1135 | |
| 1136 | static void stop(keyexch *kx) |
| 1137 | { |
| 1138 | unsigned i; |
| 1139 | |
| 1140 | if (kx->f & KXF_DEAD) |
| 1141 | return; |
| 1142 | |
| 1143 | if (kx->f & KXF_TIMER) |
| 1144 | sel_rmtimer(&kx->t); |
| 1145 | for (i = 0; i < kx->nr; i++) |
| 1146 | kxc_destroy(kx->r[i]); |
| 1147 | mp_drop(kx->alpha); |
| 1148 | G_DESTROY(kx->kpriv->g, kx->c); |
| 1149 | G_DESTROY(kx->kpriv->g, kx->rx); |
| 1150 | kx->t_valid = 0; |
| 1151 | kx->f |= KXF_DEAD; |
| 1152 | kx->f &= ~KXF_TIMER; |
| 1153 | } |
| 1154 | |
| 1155 | /* --- @start@ --- * |
| 1156 | * |
| 1157 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 1158 | * @time_t now@ = the current time |
| 1159 | * |
| 1160 | * Returns: --- |
| 1161 | * |
| 1162 | * Use: Starts a new key exchange with the peer. The context must be |
| 1163 | * in the bizarre state left by @stop@ or @kx_init@. |
| 1164 | */ |
| 1165 | |
| 1166 | static void start(keyexch *kx, time_t now) |
| 1167 | { |
| 1168 | algswitch *algs = &kx->kpriv->algs; |
| 1169 | group *g = kx->kpriv->g; |
| 1170 | ghash *h; |
| 1171 | |
| 1172 | assert(kx->f & KXF_DEAD); |
| 1173 | |
| 1174 | kx->f &= ~(KXF_DEAD | KXF_CORK); |
| 1175 | kx->nr = 0; |
| 1176 | kx->alpha = mprand_range(MP_NEW, g->r, &rand_global, 0); |
| 1177 | kx->c = G_CREATE(g); G_EXP(g, kx->c, g->g, kx->alpha); |
| 1178 | kx->rx = G_CREATE(g); G_EXP(g, kx->rx, kx->kpub->kpub, kx->alpha); |
| 1179 | kx->s = KXS_CHAL; |
| 1180 | kx->t_valid = now + T_VALID; |
| 1181 | |
| 1182 | h = GH_INIT(algs->h); |
| 1183 | HASH_STRING(h, "tripe-cookie"); |
| 1184 | hashge(h, g, kx->c); |
| 1185 | GH_DONE(h, kx->hc); |
| 1186 | GH_DESTROY(h); |
| 1187 | |
| 1188 | IF_TRACING(T_KEYEXCH, { |
| 1189 | trace(T_KEYEXCH, "keyexch: creating new challenge"); |
| 1190 | IF_TRACING(T_CRYPTO, { |
| 1191 | trace(T_CRYPTO, "crypto: secret = %s", mpstr(kx->alpha)); |
| 1192 | trace(T_CRYPTO, "crypto: challenge = %s", gestr(g, kx->c)); |
| 1193 | trace(T_CRYPTO, "crypto: expected response = %s", gestr(g, kx->rx)); |
| 1194 | trace_block(T_CRYPTO, "crypto: challenge cookie", |
| 1195 | kx->hc, algs->hashsz); |
| 1196 | }) |
| 1197 | }) |
| 1198 | } |
| 1199 | |
| 1200 | /* --- @checkpub@ --- * |
| 1201 | * |
| 1202 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 1203 | * |
| 1204 | * Returns: Zero if OK, nonzero if the peer's public key has expired. |
| 1205 | * |
| 1206 | * Use: Deactivates the key-exchange until the peer acquires a new |
| 1207 | * public key. |
| 1208 | */ |
| 1209 | |
| 1210 | static int checkpub(keyexch *kx) |
| 1211 | { |
| 1212 | time_t now; |
| 1213 | unsigned f = 0; |
| 1214 | |
| 1215 | if (kx->f & KXF_DEAD) |
| 1216 | return (-1); |
| 1217 | now = time(0); |
| 1218 | if (KEY_EXPIRED(now, kx->kpriv->t_exp)) f |= 1; |
| 1219 | if (KEY_EXPIRED(now, kx->kpub->t_exp)) f |= 2; |
| 1220 | if (f) { |
| 1221 | stop(kx); |
| 1222 | if (f & 1) a_warn("KX", "?PEER", kx->p, "private-key-expired", A_END); |
| 1223 | if (f & 2) a_warn("KX", "?PEER", kx->p, "public-key-expired", A_END); |
| 1224 | kx->f &= ~KXF_PUBKEY; |
| 1225 | return (-1); |
| 1226 | } |
| 1227 | return (0); |
| 1228 | } |
| 1229 | |
| 1230 | /* --- @kx_start@ --- * |
| 1231 | * |
| 1232 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 1233 | * @int forcep@ = nonzero to ignore the quiet timer |
| 1234 | * |
| 1235 | * Returns: --- |
| 1236 | * |
| 1237 | * Use: Stimulates a key exchange. If a key exchage is in progress, |
| 1238 | * a new challenge is sent (unless the quiet timer forbids |
| 1239 | * this); if no exchange is in progress, one is commenced. |
| 1240 | */ |
| 1241 | |
| 1242 | void kx_start(keyexch *kx, int forcep) |
| 1243 | { |
| 1244 | time_t now = time(0); |
| 1245 | |
| 1246 | if (checkpub(kx)) |
| 1247 | return; |
| 1248 | if (forcep || !VALIDP(kx, now)) { |
| 1249 | stop(kx); |
| 1250 | start(kx, now); |
| 1251 | a_notify("KXSTART", "?PEER", kx->p, A_END); |
| 1252 | } |
| 1253 | resend(kx); |
| 1254 | } |
| 1255 | |
| 1256 | /* --- @kx_message@ --- * |
| 1257 | * |
| 1258 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 1259 | * @unsigned msg@ = the message code |
| 1260 | * @buf *b@ = pointer to buffer containing the packet |
| 1261 | * |
| 1262 | * Returns: --- |
| 1263 | * |
| 1264 | * Use: Reads a packet containing key exchange messages and handles |
| 1265 | * it. |
| 1266 | */ |
| 1267 | |
| 1268 | void kx_message(keyexch *kx, unsigned msg, buf *b) |
| 1269 | { |
| 1270 | struct timeval now, tv; |
| 1271 | stats *st = p_stats(kx->p); |
| 1272 | size_t sz = BSZ(b); |
| 1273 | int rc; |
| 1274 | |
| 1275 | gettimeofday(&now, 0); |
| 1276 | rs_reset(&kx->rs); |
| 1277 | if (kx->f & KXF_CORK) { |
| 1278 | start(kx, now.tv_sec); |
| 1279 | rs_time(&kx->rs, &tv, &now); |
| 1280 | settimer(kx, &tv); |
| 1281 | a_notify("KXSTART", A_END); |
| 1282 | } |
| 1283 | |
| 1284 | if (checkpub(kx)) |
| 1285 | return; |
| 1286 | |
| 1287 | if (!VALIDP(kx, now.tv_sec)) { |
| 1288 | stop(kx); |
| 1289 | start(kx, now.tv_sec); |
| 1290 | } |
| 1291 | T( trace(T_KEYEXCH, "keyexch: processing %s packet from `%s'", |
| 1292 | msg < KX_NMSG ? pkname[msg] : "unknown", p_name(kx->p)); ) |
| 1293 | |
| 1294 | switch (msg) { |
| 1295 | case KX_PRECHAL: |
| 1296 | rc = doprechallenge(kx, b); |
| 1297 | break; |
| 1298 | case KX_CHAL: |
| 1299 | rc = dochallenge(kx, b); |
| 1300 | break; |
| 1301 | case KX_REPLY: |
| 1302 | rc = doreply(kx, b); |
| 1303 | break; |
| 1304 | case KX_SWITCH: |
| 1305 | rc = doswitch(kx, b); |
| 1306 | break; |
| 1307 | case KX_SWITCHOK: |
| 1308 | rc = doswitchok(kx, b); |
| 1309 | break; |
| 1310 | default: |
| 1311 | a_warn("KX", "?PEER", kx->p, "unknown-message", "0x%02x", msg, A_END); |
| 1312 | rc = -1; |
| 1313 | break; |
| 1314 | } |
| 1315 | |
| 1316 | if (rc) |
| 1317 | st->n_reject++; |
| 1318 | else { |
| 1319 | st->n_kxin++; |
| 1320 | st->sz_kxin += sz; |
| 1321 | } |
| 1322 | } |
| 1323 | |
| 1324 | /* --- @kx_free@ --- * |
| 1325 | * |
| 1326 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 1327 | * |
| 1328 | * Returns: --- |
| 1329 | * |
| 1330 | * Use: Frees everything in a key exchange context. |
| 1331 | */ |
| 1332 | |
| 1333 | void kx_free(keyexch *kx) |
| 1334 | { |
| 1335 | stop(kx); |
| 1336 | km_unref(kx->kpub); |
| 1337 | km_unref(kx->kpriv); |
| 1338 | } |
| 1339 | |
| 1340 | /* --- @kx_newkeys@ --- * |
| 1341 | * |
| 1342 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 1343 | * |
| 1344 | * Returns: --- |
| 1345 | * |
| 1346 | * Use: Informs the key exchange module that its keys may have |
| 1347 | * changed. If fetching the new keys fails, the peer will be |
| 1348 | * destroyed, we log messages and struggle along with the old |
| 1349 | * keys. |
| 1350 | */ |
| 1351 | |
| 1352 | void kx_newkeys(keyexch *kx) |
| 1353 | { |
| 1354 | kdata *kpriv, *kpub; |
| 1355 | unsigned i; |
| 1356 | int switchp; |
| 1357 | time_t now = time(0); |
| 1358 | |
| 1359 | T( trace(T_KEYEXCH, "keyexch: checking new keys for `%s'", |
| 1360 | p_name(kx->p)); ) |
| 1361 | |
| 1362 | /* --- Find out whether we can use new keys --- * |
| 1363 | * |
| 1364 | * Try each available combination of new and old, public and private, |
| 1365 | * except both old (which is status quo anyway). The selection is encoded |
| 1366 | * in @i@, with bit 0 for the private key and bit 1 for public key; a set |
| 1367 | * bit means to use the old value, and a clear bit means to use the new |
| 1368 | * one. |
| 1369 | * |
| 1370 | * This means that we currently prefer `old private and new public' over |
| 1371 | * `new private and old public'. I'm not sure which way round this should |
| 1372 | * actually be. |
| 1373 | */ |
| 1374 | |
| 1375 | for (i = 0; i < 3; i++) { |
| 1376 | |
| 1377 | /* --- Select the keys we're going to examine --- * |
| 1378 | * |
| 1379 | * If we're meant to have a new key and don't, then skip this |
| 1380 | * combination. |
| 1381 | */ |
| 1382 | |
| 1383 | T( trace(T_KEYEXCH, "keyexch: checking %s private, %s public", |
| 1384 | i & 1 ? "old" : "new", i & 2 ? "old" : "new"); ) |
| 1385 | |
| 1386 | if (i & 1) kpriv = kx->kpriv; |
| 1387 | else if (kx->kpriv->kn->kd != kx->kpriv) kpriv = kx->kpriv->kn->kd; |
| 1388 | else { |
| 1389 | T( trace(T_KEYEXCH, "keyexch: private key unchanged, skipping"); ) |
| 1390 | continue; |
| 1391 | } |
| 1392 | |
| 1393 | if (i & 2) kpub = kx->kpub; |
| 1394 | else if (kx->kpub->kn->kd != kx->kpub) kpub = kx->kpub->kn->kd; |
| 1395 | else { |
| 1396 | T( trace(T_KEYEXCH, "keyexch: public key unchanged, skipping"); ) |
| 1397 | continue; |
| 1398 | } |
| 1399 | |
| 1400 | /* --- Skip if either key is expired --- * |
| 1401 | * |
| 1402 | * We're not going to get far with expired keys, and this simplifies the |
| 1403 | * logic below. |
| 1404 | */ |
| 1405 | |
| 1406 | if (KEY_EXPIRED(now, kx->kpriv->t_exp) || |
| 1407 | KEY_EXPIRED(now, kx->kpub->t_exp)) { |
| 1408 | T( trace(T_KEYEXCH, "keyexch: %s expired, skipping", |
| 1409 | !KEY_EXPIRED(now, kx->kpriv->t_exp) ? "public key" : |
| 1410 | !KEY_EXPIRED(now, kx->kpub->t_exp) ? "private key" : |
| 1411 | "both keys"); ) |
| 1412 | continue; |
| 1413 | } |
| 1414 | |
| 1415 | /* --- If the groups don't match then we can't use this pair --- */ |
| 1416 | |
| 1417 | if (!km_samealgsp(kpriv, kpub)) { |
| 1418 | T( trace(T_KEYEXCH, "keyexch: peer `%s' group mismatch; " |
| 1419 | "%s priv `%s' and %s pub `%s'", p_name(kx->p), |
| 1420 | i & 1 ? "old" : "new", km_tag(kx->kpriv), |
| 1421 | i & 2 ? "old" : "new", km_tag(kx->kpub)); ) |
| 1422 | continue; |
| 1423 | } |
| 1424 | goto newkeys; |
| 1425 | } |
| 1426 | T( trace(T_KEYEXCH, "keyexch: peer `%s' continuing with old keys", |
| 1427 | p_name(kx->p)); ) |
| 1428 | return; |
| 1429 | |
| 1430 | /* --- We've chosen new keys --- * |
| 1431 | * |
| 1432 | * Switch the new ones into place. Neither of the keys we're switching to |
| 1433 | * is expired (we checked that above), so we should just crank everything |
| 1434 | * up. |
| 1435 | * |
| 1436 | * A complication arises: we don't really want to force a new key exchange |
| 1437 | * unless we have to. If the group is unchanged, and we're currently |
| 1438 | * running OK, then we should just let things lie. |
| 1439 | */ |
| 1440 | |
| 1441 | newkeys: |
| 1442 | switchp = ((kx->f & KXF_DEAD) || |
| 1443 | kx->s != KXS_SWITCH || |
| 1444 | !group_samep(kx->kpriv->g, kpriv->g)); |
| 1445 | |
| 1446 | T( trace(T_KEYEXCH, "keyexch: peer `%s' adopting " |
| 1447 | "%s priv `%s' and %s pub `%s'; %sforcing exchange", p_name(kx->p), |
| 1448 | i & 1 ? "old" : "new", km_tag(kx->kpriv), |
| 1449 | i & 2 ? "old" : "new", km_tag(kx->kpub), |
| 1450 | switchp ? "" : "not "); ) |
| 1451 | |
| 1452 | if (switchp) stop(kx); |
| 1453 | km_ref(kpriv); km_unref(kx->kpriv); kx->kpriv = kpriv; |
| 1454 | km_ref(kpub); km_unref(kx->kpub); kx->kpub = kpub; |
| 1455 | kx->f |= KXF_PUBKEY; |
| 1456 | if (switchp) { |
| 1457 | T( trace(T_KEYEXCH, "keyexch: restarting key negotiation with `%s'", |
| 1458 | p_name(kx->p)); ) |
| 1459 | start(kx, time(0)); |
| 1460 | resend(kx); |
| 1461 | } |
| 1462 | } |
| 1463 | |
| 1464 | /* --- @kx_init@ --- * |
| 1465 | * |
| 1466 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 1467 | * @peer *p@ = pointer to peer context |
| 1468 | * @keyset **ks@ = pointer to keyset list |
| 1469 | * @unsigned f@ = various useful flags |
| 1470 | * |
| 1471 | * Returns: Zero if OK, nonzero if it failed. |
| 1472 | * |
| 1473 | * Use: Initializes a key exchange module. The module currently |
| 1474 | * contains no keys, and will attempt to initiate a key |
| 1475 | * exchange. |
| 1476 | */ |
| 1477 | |
| 1478 | int kx_init(keyexch *kx, peer *p, keyset **ks, unsigned f) |
| 1479 | { |
| 1480 | if ((kx->kpriv = km_findpriv(p_privtag(p))) == 0) goto fail_0; |
| 1481 | if ((kx->kpub = km_findpub(p_tag(p))) == 0) goto fail_1; |
| 1482 | if (!group_samep(kx->kpriv->g, kx->kpub->g)) { |
| 1483 | a_warn("KX", "?PEER", kx->p, "group-mismatch", |
| 1484 | "local-private-key", "%s", p_privtag(p), |
| 1485 | "peer-public-key", "%s", p_tag(p), |
| 1486 | A_END); |
| 1487 | goto fail_2; |
| 1488 | } |
| 1489 | |
| 1490 | kx->ks = ks; |
| 1491 | kx->p = p; |
| 1492 | kx->f = KXF_DEAD | KXF_PUBKEY | f; |
| 1493 | rs_reset(&kx->rs); |
| 1494 | if (!(kx->f & KXF_CORK)) { |
| 1495 | start(kx, time(0)); |
| 1496 | resend(kx); |
| 1497 | /* Don't notify here: the ADD message hasn't gone out yet. */ |
| 1498 | } |
| 1499 | return (0); |
| 1500 | |
| 1501 | fail_2: |
| 1502 | km_unref(kx->kpub); |
| 1503 | fail_1: |
| 1504 | km_unref(kx->kpriv); |
| 1505 | fail_0: |
| 1506 | return (-1); |
| 1507 | } |
| 1508 | |
| 1509 | /*----- That's all, folks -------------------------------------------------*/ |