| 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 | /*----- Tunable parameters ------------------------------------------------*/ |
| 79 | |
| 80 | #define T_VALID MIN(2) /* Challenge validity period */ |
| 81 | #define T_RETRY SEC(10) /* Challenge retransmit interval */ |
| 82 | |
| 83 | #define VALIDP(kx, now) ((now) < (kx)->t_valid) |
| 84 | |
| 85 | /*----- Static tables -----------------------------------------------------*/ |
| 86 | |
| 87 | static const char *const pkname[] = { |
| 88 | "pre-challenge", "cookie", "challenge", |
| 89 | "reply", "switch-rq", "switch-ok" |
| 90 | }; |
| 91 | |
| 92 | /*----- Various utilities -------------------------------------------------*/ |
| 93 | |
| 94 | /* --- @hashge@ --- * |
| 95 | * |
| 96 | * Arguments: @ghash *h@ = pointer to hash context |
| 97 | * @ge *x@ = pointer to group element |
| 98 | * |
| 99 | * Returns: --- |
| 100 | * |
| 101 | * Use: Adds the hash of a group element to the context. Corrupts |
| 102 | * @buf_t@. |
| 103 | */ |
| 104 | |
| 105 | static void hashge(ghash *h, ge *x) |
| 106 | { |
| 107 | buf b; |
| 108 | buf_init(&b, buf_t, sizeof(buf_t)); |
| 109 | G_TOBUF(gg, &b, x); |
| 110 | assert(BOK(&b)); |
| 111 | GH_HASH(h, BBASE(&b), BLEN(&b)); |
| 112 | } |
| 113 | |
| 114 | /* --- @mpmask@ --- * |
| 115 | * |
| 116 | * Arguments: @buf *b@ = output buffer |
| 117 | * @mp *x@ = the plaintext integer |
| 118 | * @size_t n@ = the expected size of the plaintext |
| 119 | * @const octet *k@ = pointer to key material |
| 120 | * @size_t ksz@ = size of the key |
| 121 | * |
| 122 | * Returns: Pointer to the output. |
| 123 | * |
| 124 | * Use: Masks a multiprecision integer: returns %$x \xor H(k)$%, so |
| 125 | * it's a random oracle thing rather than an encryption thing. |
| 126 | */ |
| 127 | |
| 128 | static octet *mpmask(buf *b, mp *x, size_t n, const octet *k, size_t ksz) |
| 129 | { |
| 130 | gcipher *mgf; |
| 131 | octet *p; |
| 132 | |
| 133 | if ((p = buf_get(b, n)) == 0) |
| 134 | return (0); |
| 135 | mgf = GC_INIT(algs.mgf, k, ksz); |
| 136 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 137 | trace(T_CRYPTO, "masking index = %s", mpstr(x)); |
| 138 | trace_block(T_CRYPTO, "masking key", k, ksz); |
| 139 | })) |
| 140 | mp_storeb(x, buf_t, n); |
| 141 | GC_ENCRYPT(mgf, buf_t, p, n); |
| 142 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 143 | trace_block(T_CRYPTO, "index plaintext", buf_t, n); |
| 144 | trace_block(T_CRYPTO, "masked ciphertext", p, n); |
| 145 | })) |
| 146 | GC_DESTROY(mgf); |
| 147 | return (p); |
| 148 | } |
| 149 | |
| 150 | /* --- @mpunmask@ --- * |
| 151 | * |
| 152 | * Arguments: @mp *d@ = the output integer |
| 153 | * @const octet *p@ = pointer to the ciphertext |
| 154 | * @size_t n@ = the size of the ciphertext |
| 155 | * @const octet *k@ = pointer to key material |
| 156 | * @size_t ksz@ = size of the key |
| 157 | * |
| 158 | * Returns: The decrypted integer, or null. |
| 159 | * |
| 160 | * Use: Unmasks a multiprecision integer. |
| 161 | */ |
| 162 | |
| 163 | static mp *mpunmask(mp *d, const octet *p, size_t n, |
| 164 | const octet *k, size_t ksz) |
| 165 | { |
| 166 | gcipher *mgf; |
| 167 | |
| 168 | mgf = GC_INIT(algs.mgf, k, ksz); |
| 169 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 170 | trace_block(T_CRYPTO, "unmasking key", k, ksz); |
| 171 | trace_block(T_CRYPTO, "masked ciphertext", p, n); |
| 172 | })) |
| 173 | GC_DECRYPT(mgf, p, buf_t, n); |
| 174 | d = mp_loadb(d, buf_t, n); |
| 175 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 176 | trace_block(T_CRYPTO, "index plaintext", buf_t, n); |
| 177 | trace(T_CRYPTO, "unmasked index = %s", mpstr(d)); |
| 178 | })) |
| 179 | GC_DESTROY(mgf); |
| 180 | return (d); |
| 181 | } |
| 182 | |
| 183 | /* --- @hashcheck@ --- * |
| 184 | * |
| 185 | * Arguments: @ge *kpub@ = sender's public key |
| 186 | * @ge *cc@ = receiver's challenge |
| 187 | * @ge *c@ = sender's challenge |
| 188 | * @ge *y@ = reply to sender's challenge |
| 189 | * |
| 190 | * Returns: Pointer to the hash value (in @buf_t@) |
| 191 | * |
| 192 | * Use: Computes the check-value hash, used to mask or unmask |
| 193 | * indices to prove the validity of challenges. This computes |
| 194 | * the masking key used in challenge check values. This is |
| 195 | * really the heart of the whole thing, since it ensures that |
| 196 | * the index can be recovered from the history of hashing |
| 197 | * queries, which gives us (a) a proof that the authentication |
| 198 | * process is zero-knowledge, and (b) a proof that the whole |
| 199 | * key-exchange is deniable. |
| 200 | */ |
| 201 | |
| 202 | static const octet *hashcheck(ge *kpub, ge *cc, ge *c, ge *y) |
| 203 | { |
| 204 | ghash *h = GH_INIT(algs.h); |
| 205 | |
| 206 | HASH_STRING(h, "tripe-expected-reply"); |
| 207 | hashge(h, kpub); |
| 208 | hashge(h, cc); |
| 209 | hashge(h, c); |
| 210 | hashge(h, y); |
| 211 | GH_DONE(h, buf_t); |
| 212 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 213 | trace(T_CRYPTO, "computing challenge check hash"); |
| 214 | trace(T_CRYPTO, "public key = %s", gestr(gg, kpub)); |
| 215 | trace(T_CRYPTO, "receiver challenge = %s", gestr(gg, cc)); |
| 216 | trace(T_CRYPTO, "sender challenge = %s", gestr(gg, c)); |
| 217 | trace(T_CRYPTO, "sender reply = %s", gestr(gg, y)); |
| 218 | trace_block(T_CRYPTO, "hash output", buf_t, algs.hashsz); |
| 219 | })) |
| 220 | GH_DESTROY(h); |
| 221 | return (buf_t); |
| 222 | } |
| 223 | |
| 224 | /* --- @sendchallenge@ --- * |
| 225 | * |
| 226 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
| 227 | * @buf *b@ = output buffer for challenge |
| 228 | * @ge *c@ = peer's actual challenge |
| 229 | * @const octet *hc@ = peer's challenge cookie |
| 230 | * |
| 231 | * Returns: --- |
| 232 | * |
| 233 | * Use: Writes a full challenge to the message buffer. |
| 234 | */ |
| 235 | |
| 236 | static void sendchallenge(keyexch *kx, buf *b, ge *c, const octet *hc) |
| 237 | { |
| 238 | G_TOBUF(gg, b, kx->c); |
| 239 | buf_put(b, hc, algs.hashsz); |
| 240 | mpmask(b, kx->alpha, indexsz, |
| 241 | hashcheck(kpub, c, kx->c, kx->rx), algs.hashsz); |
| 242 | } |
| 243 | |
| 244 | /* --- @timer@ --- * |
| 245 | * |
| 246 | * Arguments: @struct timeval *tv@ = the current time |
| 247 | * @void *v@ = pointer to key exchange context |
| 248 | * |
| 249 | * Returns: --- |
| 250 | * |
| 251 | * Use: Acts when the key exchange timer goes off. |
| 252 | */ |
| 253 | |
| 254 | static void timer(struct timeval *tv, void *v) |
| 255 | { |
| 256 | keyexch *kx = v; |
| 257 | kx->f &= ~KXF_TIMER; |
| 258 | T( trace(T_KEYEXCH, "keyexch: timer has popped"); ) |
| 259 | kx_start(kx, 0); |
| 260 | } |
| 261 | |
| 262 | /* --- @settimer@ --- * |
| 263 | * |
| 264 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 265 | * @time_t t@ = when to set the timer for |
| 266 | * |
| 267 | * Returns: --- |
| 268 | * |
| 269 | * Use: Sets the timer for the next key exchange attempt. |
| 270 | */ |
| 271 | |
| 272 | static void settimer(keyexch *kx, time_t t) |
| 273 | { |
| 274 | struct timeval tv; |
| 275 | if (kx->f & KXF_TIMER) |
| 276 | sel_rmtimer(&kx->t); |
| 277 | tv.tv_sec = t; |
| 278 | tv.tv_usec = 0; |
| 279 | sel_addtimer(&sel, &kx->t, &tv, timer, kx); |
| 280 | kx->f |= KXF_TIMER; |
| 281 | } |
| 282 | |
| 283 | /*----- Challenge management ----------------------------------------------*/ |
| 284 | |
| 285 | /* --- Notes on challenge management --- * |
| 286 | * |
| 287 | * We may get multiple different replies to our key exchange; some will be |
| 288 | * correct, some inserted by attackers. Up until @KX_THRESH@, all challenges |
| 289 | * received will be added to the table and given a full response. After |
| 290 | * @KX_THRESH@ distinct challenges are received, we return only a `cookie': |
| 291 | * our existing challenge, followed by a hash of the sender's challenge. We |
| 292 | * do %%\emph{not}%% give a bare challenge a reply slot at this stage. All |
| 293 | * properly-formed cookies are assigned a table slot: if none is spare, a |
| 294 | * used slot is randomly selected and destroyed. A cookie always receives a |
| 295 | * full reply. |
| 296 | */ |
| 297 | |
| 298 | /* --- @kxc_destroy@ --- * |
| 299 | * |
| 300 | * Arguments: @kxchal *kxc@ = pointer to the challenge block |
| 301 | * |
| 302 | * Returns: --- |
| 303 | * |
| 304 | * Use: Disposes of a challenge block. |
| 305 | */ |
| 306 | |
| 307 | static void kxc_destroy(kxchal *kxc) |
| 308 | { |
| 309 | if (kxc->f & KXF_TIMER) |
| 310 | sel_rmtimer(&kxc->t); |
| 311 | G_DESTROY(gg, kxc->c); |
| 312 | G_DESTROY(gg, kxc->r); |
| 313 | ks_drop(kxc->ks); |
| 314 | DESTROY(kxc); |
| 315 | } |
| 316 | |
| 317 | /* --- @kxc_stoptimer@ --- * |
| 318 | * |
| 319 | * Arguments: @kxchal *kxc@ = pointer to the challenge block |
| 320 | * |
| 321 | * Returns: --- |
| 322 | * |
| 323 | * Use: Stops the challenge's retry timer from sending messages. |
| 324 | * Useful when the state machine is in the endgame of the |
| 325 | * exchange. |
| 326 | */ |
| 327 | |
| 328 | static void kxc_stoptimer(kxchal *kxc) |
| 329 | { |
| 330 | if (kxc->f & KXF_TIMER) |
| 331 | sel_rmtimer(&kxc->t); |
| 332 | kxc->f &= ~KXF_TIMER; |
| 333 | } |
| 334 | |
| 335 | /* --- @kxc_new@ --- * |
| 336 | * |
| 337 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
| 338 | * |
| 339 | * Returns: A pointer to the challenge block. |
| 340 | * |
| 341 | * Use: Returns a pointer to a new challenge block to fill in. |
| 342 | */ |
| 343 | |
| 344 | static kxchal *kxc_new(keyexch *kx) |
| 345 | { |
| 346 | kxchal *kxc; |
| 347 | unsigned i; |
| 348 | |
| 349 | /* --- If we're over reply threshold, discard one at random --- */ |
| 350 | |
| 351 | if (kx->nr < KX_NCHAL) |
| 352 | i = kx->nr++; |
| 353 | else { |
| 354 | i = rand_global.ops->range(&rand_global, KX_NCHAL); |
| 355 | kxc_destroy(kx->r[i]); |
| 356 | } |
| 357 | |
| 358 | /* --- Fill in the new structure --- */ |
| 359 | |
| 360 | kxc = CREATE(kxchal); |
| 361 | kxc->c = G_CREATE(gg); |
| 362 | kxc->r = G_CREATE(gg); |
| 363 | kxc->ks = 0; |
| 364 | kxc->kx = kx; |
| 365 | kxc->f = 0; |
| 366 | kx->r[i] = kxc; |
| 367 | return (kxc); |
| 368 | } |
| 369 | |
| 370 | /* --- @kxc_bychal@ --- * |
| 371 | * |
| 372 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
| 373 | * @ge *c@ = challenge from remote host |
| 374 | * |
| 375 | * Returns: Pointer to the challenge block, or null. |
| 376 | * |
| 377 | * Use: Finds a challenge block, given its challenge. |
| 378 | */ |
| 379 | |
| 380 | static kxchal *kxc_bychal(keyexch *kx, ge *c) |
| 381 | { |
| 382 | unsigned i; |
| 383 | |
| 384 | for (i = 0; i < kx->nr; i++) { |
| 385 | if (G_EQ(gg, c, kx->r[i]->c)) |
| 386 | return (kx->r[i]); |
| 387 | } |
| 388 | return (0); |
| 389 | } |
| 390 | |
| 391 | /* --- @kxc_byhc@ --- * |
| 392 | * |
| 393 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
| 394 | * @const octet *hc@ = challenge hash from remote host |
| 395 | * |
| 396 | * Returns: Pointer to the challenge block, or null. |
| 397 | * |
| 398 | * Use: Finds a challenge block, given a hash of its challenge. |
| 399 | */ |
| 400 | |
| 401 | static kxchal *kxc_byhc(keyexch *kx, const octet *hc) |
| 402 | { |
| 403 | unsigned i; |
| 404 | |
| 405 | for (i = 0; i < kx->nr; i++) { |
| 406 | if (memcmp(hc, kx->r[i]->hc, algs.hashsz) == 0) |
| 407 | return (kx->r[i]); |
| 408 | } |
| 409 | return (0); |
| 410 | } |
| 411 | |
| 412 | /* --- @kxc_answer@ --- * |
| 413 | * |
| 414 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
| 415 | * @kxchal *kxc@ = pointer to challenge block |
| 416 | * |
| 417 | * Returns: --- |
| 418 | * |
| 419 | * Use: Sends a reply to the remote host, according to the data in |
| 420 | * this challenge block. |
| 421 | */ |
| 422 | |
| 423 | static void kxc_answer(keyexch *kx, kxchal *kxc); |
| 424 | |
| 425 | static void kxc_timer(struct timeval *tv, void *v) |
| 426 | { |
| 427 | kxchal *kxc = v; |
| 428 | kxc->f &= ~KXF_TIMER; |
| 429 | kxc_answer(kxc->kx, kxc); |
| 430 | } |
| 431 | |
| 432 | static void kxc_answer(keyexch *kx, kxchal *kxc) |
| 433 | { |
| 434 | stats *st = p_stats(kx->p); |
| 435 | buf *b = p_txstart(kx->p, MSG_KEYEXCH | KX_REPLY); |
| 436 | struct timeval tv; |
| 437 | buf bb; |
| 438 | |
| 439 | /* --- Build the reply packet --- */ |
| 440 | |
| 441 | T( trace(T_KEYEXCH, "keyexch: sending reply to `%s'", p_name(kx->p)); ) |
| 442 | sendchallenge(kx, b, kxc->c, kxc->hc); |
| 443 | buf_init(&bb, buf_i, sizeof(buf_i)); |
| 444 | G_TORAW(gg, &bb, kxc->r); |
| 445 | buf_flip(&bb); |
| 446 | ks_encrypt(kxc->ks, MSG_KEYEXCH | KX_REPLY, &bb, b); |
| 447 | |
| 448 | /* --- Update the statistics --- */ |
| 449 | |
| 450 | if (BOK(b)) { |
| 451 | st->n_kxout++; |
| 452 | st->sz_kxout += BLEN(b); |
| 453 | p_txend(kx->p); |
| 454 | } |
| 455 | |
| 456 | /* --- Schedule another resend --- */ |
| 457 | |
| 458 | if (kxc->f & KXF_TIMER) |
| 459 | sel_rmtimer(&kxc->t); |
| 460 | gettimeofday(&tv, 0); |
| 461 | tv.tv_sec += T_RETRY; |
| 462 | sel_addtimer(&sel, &kxc->t, &tv, kxc_timer, kxc); |
| 463 | kxc->f |= KXF_TIMER; |
| 464 | } |
| 465 | |
| 466 | /*----- Individual message handlers ---------------------------------------*/ |
| 467 | |
| 468 | /* --- @doprechallenge@ --- * |
| 469 | * |
| 470 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
| 471 | * @buf *b@ = buffer containing the packet |
| 472 | * |
| 473 | * Returns: Zero if OK, nonzero of the packet was rejected. |
| 474 | * |
| 475 | * Use: Processes a pre-challenge message. |
| 476 | */ |
| 477 | |
| 478 | static int doprechallenge(keyexch *kx, buf *b) |
| 479 | { |
| 480 | stats *st = p_stats(kx->p); |
| 481 | ge *c = G_CREATE(gg); |
| 482 | ghash *h; |
| 483 | |
| 484 | /* --- Ensure that we're in a sensible state --- */ |
| 485 | |
| 486 | if (kx->s != KXS_CHAL) { |
| 487 | a_warn("KX", "?PEER", kx->p, "unexpected", "pre-challenge", A_END); |
| 488 | goto bad; |
| 489 | } |
| 490 | |
| 491 | /* --- Unpack the packet --- */ |
| 492 | |
| 493 | if (G_FROMBUF(gg, b, c) || BLEFT(b)) |
| 494 | goto bad; |
| 495 | |
| 496 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 497 | trace(T_CRYPTO, "crypto: challenge = %s", gestr(gg, c)); |
| 498 | })) |
| 499 | |
| 500 | /* --- Send out a full challenge by return --- */ |
| 501 | |
| 502 | b = p_txstart(kx->p, MSG_KEYEXCH | KX_CHAL); |
| 503 | h = GH_INIT(algs.h); |
| 504 | HASH_STRING(h, "tripe-cookie"); |
| 505 | hashge(h, c); |
| 506 | sendchallenge(kx, b, c, GH_DONE(h, 0)); |
| 507 | GH_DESTROY(h); |
| 508 | st->n_kxout++; |
| 509 | st->sz_kxout += BLEN(b); |
| 510 | p_txend(kx->p); |
| 511 | |
| 512 | /* --- Done --- */ |
| 513 | |
| 514 | G_DESTROY(gg, c); |
| 515 | return (0); |
| 516 | |
| 517 | bad: |
| 518 | if (c) G_DESTROY(gg, c); |
| 519 | return (-1); |
| 520 | } |
| 521 | |
| 522 | /* --- @respond@ --- * |
| 523 | * |
| 524 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
| 525 | * @unsigned msg@ = message code for this packet |
| 526 | * @buf *b@ = buffer containing the packet |
| 527 | * |
| 528 | * Returns: Key-exchange challenge block, or null. |
| 529 | * |
| 530 | * Use: Computes a response for the given challenge, entering it into |
| 531 | * a challenge block and so on. |
| 532 | */ |
| 533 | |
| 534 | static kxchal *respond(keyexch *kx, unsigned msg, buf *b) |
| 535 | { |
| 536 | ge *c = G_CREATE(gg); |
| 537 | ge *r = G_CREATE(gg); |
| 538 | ge *cc = G_CREATE(gg); |
| 539 | const octet *hc, *ck; |
| 540 | size_t x, y, z; |
| 541 | mp *cv = 0; |
| 542 | kxchal *kxc; |
| 543 | ghash *h = 0; |
| 544 | buf bb; |
| 545 | int ok; |
| 546 | |
| 547 | /* --- Unpack the packet --- */ |
| 548 | |
| 549 | if (G_FROMBUF(gg, b, c) || |
| 550 | (hc = buf_get(b, algs.hashsz)) == 0 || |
| 551 | (ck = buf_get(b, indexsz)) == 0) { |
| 552 | a_warn("KX", "?PEER", kx->p, "invalid", "%s", pkname[msg], A_END); |
| 553 | goto bad; |
| 554 | } |
| 555 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 556 | trace(T_CRYPTO, "crypto: challenge = %s", gestr(gg, c)); |
| 557 | trace_block(T_CRYPTO, "crypto: cookie", hc, algs.hashsz); |
| 558 | trace_block(T_CRYPTO, "crypto: check-value", ck, indexsz); |
| 559 | })) |
| 560 | |
| 561 | /* --- Discard a packet with an invalid cookie --- */ |
| 562 | |
| 563 | if (hc && memcmp(hc, kx->hc, algs.hashsz) != 0) { |
| 564 | a_warn("KX", "?PEER", kx->p, "incorrect", "cookie", A_END); |
| 565 | goto bad; |
| 566 | } |
| 567 | |
| 568 | /* --- Recover the check value and verify it --- * |
| 569 | * |
| 570 | * To avoid recomputation on replays, we store a hash of the `right' |
| 571 | * value. The `correct' value is unique, so this is right. |
| 572 | * |
| 573 | * This will also find a challenge block and, if necessary, populate it. |
| 574 | */ |
| 575 | |
| 576 | if ((kxc = kxc_bychal(kx, c)) != 0) { |
| 577 | h = GH_INIT(algs.h); |
| 578 | HASH_STRING(h, "tripe-check-hash"); |
| 579 | GH_HASH(h, ck, indexsz); |
| 580 | ok = !memcmp(kxc->ck, GH_DONE(h, 0), algs.hashsz); |
| 581 | GH_DESTROY(h); |
| 582 | if (!ok) goto badcheck; |
| 583 | } else { |
| 584 | |
| 585 | /* --- Compute the reply, and check the magic --- */ |
| 586 | |
| 587 | G_EXP(gg, r, c, kpriv); |
| 588 | cv = mpunmask(MP_NEW, ck, indexsz, |
| 589 | hashcheck(kx->kpub, kx->c, c, r), algs.hashsz); |
| 590 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 591 | trace(T_CRYPTO, "crypto: computed reply = %s", gestr(gg, r)); |
| 592 | trace(T_CRYPTO, "crypto: recovered log = %s", mpstr(cv)); |
| 593 | })) |
| 594 | if (MP_CMP(cv, >, gg->r) || |
| 595 | (G_EXP(gg, cc, gg->g, cv), !G_EQ(gg, c, cc))) |
| 596 | goto badcheck; |
| 597 | |
| 598 | /* --- Fill in a new challenge block --- */ |
| 599 | |
| 600 | kxc = kxc_new(kx); |
| 601 | G_COPY(gg, kxc->c, c); |
| 602 | G_COPY(gg, kxc->r, r); |
| 603 | |
| 604 | h = GH_INIT(algs.h); |
| 605 | HASH_STRING(h, "tripe-check-hash"); |
| 606 | GH_HASH(h, ck, indexsz); |
| 607 | GH_DONE(h, kxc->hc); |
| 608 | GH_DESTROY(h); |
| 609 | |
| 610 | h = GH_INIT(algs.h); |
| 611 | HASH_STRING(h, "tripe-cookie"); |
| 612 | hashge(h, kxc->c); |
| 613 | GH_DONE(h, kxc->hc); |
| 614 | GH_DESTROY(h); |
| 615 | |
| 616 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 617 | trace_block(T_CRYPTO, "crypto: computed cookie", kxc->hc, algs.hashsz); |
| 618 | })) |
| 619 | |
| 620 | /* --- Work out the shared key --- */ |
| 621 | |
| 622 | G_EXP(gg, r, c, kx->alpha); |
| 623 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 624 | trace(T_CRYPTO, "crypto: shared secret = %s", gestr(gg, r)); |
| 625 | })) |
| 626 | |
| 627 | /* --- Compute the switch messages --- */ |
| 628 | |
| 629 | h = GH_INIT(algs.h); HASH_STRING(h, "tripe-switch-request"); |
| 630 | hashge(h, kx->c); hashge(h, kxc->c); |
| 631 | GH_DONE(h, kxc->hswrq_out); GH_DESTROY(h); |
| 632 | h = GH_INIT(algs.h); HASH_STRING(h, "tripe-switch-confirm"); |
| 633 | hashge(h, kx->c); hashge(h, kxc->c); |
| 634 | GH_DONE(h, kxc->hswok_out); GH_DESTROY(h); |
| 635 | |
| 636 | h = GH_INIT(algs.h); HASH_STRING(h, "tripe-switch-request"); |
| 637 | hashge(h, kxc->c); hashge(h, kx->c); |
| 638 | GH_DONE(h, kxc->hswrq_in); GH_DESTROY(h); |
| 639 | h = GH_INIT(algs.h); HASH_STRING(h, "tripe-switch-confirm"); |
| 640 | hashge(h, kxc->c); hashge(h, kx->c); |
| 641 | GH_DONE(h, kxc->hswok_in); GH_DESTROY(h); |
| 642 | |
| 643 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 644 | trace_block(T_CRYPTO, "crypto: outbound switch request", |
| 645 | kxc->hswrq_out, algs.hashsz); |
| 646 | trace_block(T_CRYPTO, "crypto: outbound switch confirm", |
| 647 | kxc->hswok_out, algs.hashsz); |
| 648 | trace_block(T_CRYPTO, "crypto: inbound switch request", |
| 649 | kxc->hswrq_in, algs.hashsz); |
| 650 | trace_block(T_CRYPTO, "crypto: inbound switch confirm", |
| 651 | kxc->hswok_in, algs.hashsz); |
| 652 | })) |
| 653 | |
| 654 | /* --- Create a new symmetric keyset --- */ |
| 655 | |
| 656 | buf_init(&bb, buf_o, sizeof(buf_o)); |
| 657 | G_TOBUF(gg, &bb, kx->c); x = BLEN(&bb); |
| 658 | G_TOBUF(gg, &bb, kxc->c); y = BLEN(&bb); |
| 659 | G_TOBUF(gg, &bb, r); z = BLEN(&bb); |
| 660 | assert(BOK(&bb)); |
| 661 | |
| 662 | kxc->ks = ks_gen(BBASE(&bb), x, y, z, kx->p); |
| 663 | } |
| 664 | |
| 665 | G_DESTROY(gg, c); |
| 666 | G_DESTROY(gg, cc); |
| 667 | G_DESTROY(gg, r); |
| 668 | mp_drop(cv); |
| 669 | return (kxc); |
| 670 | |
| 671 | badcheck: |
| 672 | a_warn("KX", "?PEER", kx->p, "bad-expected-reply-log", A_END); |
| 673 | goto bad; |
| 674 | bad: |
| 675 | G_DESTROY(gg, c); |
| 676 | G_DESTROY(gg, cc); |
| 677 | G_DESTROY(gg, r); |
| 678 | mp_drop(cv); |
| 679 | return (0); |
| 680 | } |
| 681 | |
| 682 | /* --- @dochallenge@ --- * |
| 683 | * |
| 684 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
| 685 | * @unsigned msg@ = message code for the packet |
| 686 | * @buf *b@ = buffer containing the packet |
| 687 | * |
| 688 | * Returns: Zero if OK, nonzero if the packet was rejected. |
| 689 | * |
| 690 | * Use: Processes a packet containing a challenge. |
| 691 | */ |
| 692 | |
| 693 | static int dochallenge(keyexch *kx, buf *b) |
| 694 | { |
| 695 | kxchal *kxc; |
| 696 | |
| 697 | if (kx->s != KXS_CHAL) { |
| 698 | a_warn("KX", "?PEER", kx->p, "unexpected", "challenge", A_END); |
| 699 | goto bad; |
| 700 | } |
| 701 | if ((kxc = respond(kx, KX_CHAL, b)) == 0) |
| 702 | goto bad; |
| 703 | if (BLEFT(b)) { |
| 704 | a_warn("KX", "?PEER", kx->p, "invalid", "challenge", A_END); |
| 705 | goto bad; |
| 706 | } |
| 707 | kxc_answer(kx, kxc); |
| 708 | return (0); |
| 709 | |
| 710 | bad: |
| 711 | return (-1); |
| 712 | } |
| 713 | |
| 714 | /* --- @resend@ --- * |
| 715 | * |
| 716 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 717 | * |
| 718 | * Returns: --- |
| 719 | * |
| 720 | * Use: Sends the next message for a key exchange. |
| 721 | */ |
| 722 | |
| 723 | static void resend(keyexch *kx) |
| 724 | { |
| 725 | kxchal *kxc; |
| 726 | buf bb; |
| 727 | stats *st = p_stats(kx->p); |
| 728 | buf *b; |
| 729 | |
| 730 | switch (kx->s) { |
| 731 | case KXS_CHAL: |
| 732 | T( trace(T_KEYEXCH, "keyexch: sending prechallenge to `%s'", |
| 733 | p_name(kx->p)); ) |
| 734 | b = p_txstart(kx->p, MSG_KEYEXCH | KX_PRECHAL); |
| 735 | G_TOBUF(gg, b, kx->c); |
| 736 | break; |
| 737 | case KXS_COMMIT: |
| 738 | T( trace(T_KEYEXCH, "keyexch: sending switch request to `%s'", |
| 739 | p_name(kx->p)); ) |
| 740 | kxc = kx->r[0]; |
| 741 | b = p_txstart(kx->p, MSG_KEYEXCH | KX_SWITCH); |
| 742 | buf_put(b, kx->hc, algs.hashsz); |
| 743 | buf_put(b, kxc->hc, algs.hashsz); |
| 744 | buf_init(&bb, buf_i, sizeof(buf_i)); |
| 745 | G_TORAW(gg, &bb, kxc->r); |
| 746 | buf_put(&bb, kxc->hswrq_out, algs.hashsz); |
| 747 | buf_flip(&bb); |
| 748 | ks_encrypt(kxc->ks, MSG_KEYEXCH | KX_SWITCH, &bb, b); |
| 749 | break; |
| 750 | case KXS_SWITCH: |
| 751 | T( trace(T_KEYEXCH, "keyexch: sending switch confirmation to `%s'", |
| 752 | p_name(kx->p)); ) |
| 753 | kxc = kx->r[0]; |
| 754 | b = p_txstart(kx->p, MSG_KEYEXCH | KX_SWITCHOK); |
| 755 | buf_init(&bb, buf_i, sizeof(buf_i)); |
| 756 | buf_put(&bb, kxc->hswok_out, algs.hashsz); |
| 757 | buf_flip(&bb); |
| 758 | ks_encrypt(kxc->ks, MSG_KEYEXCH | KX_SWITCHOK, &bb, b); |
| 759 | break; |
| 760 | default: |
| 761 | abort(); |
| 762 | } |
| 763 | |
| 764 | if (BOK(b)) { |
| 765 | st->n_kxout++; |
| 766 | st->sz_kxout += BLEN(b); |
| 767 | p_txend(kx->p); |
| 768 | } |
| 769 | |
| 770 | if (kx->s < KXS_SWITCH) |
| 771 | settimer(kx, time(0) + T_RETRY); |
| 772 | } |
| 773 | |
| 774 | /* --- @decryptrest@ --- * |
| 775 | * |
| 776 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 777 | * @kxchal *kxc@ = pointer to challenge block |
| 778 | * @unsigned msg@ = type of incoming message |
| 779 | * @buf *b@ = encrypted remainder of the packet |
| 780 | * |
| 781 | * Returns: Zero if OK, nonzero on some kind of error. |
| 782 | * |
| 783 | * Use: Decrypts the remainder of the packet, and points @b@ at the |
| 784 | * recovered plaintext. |
| 785 | */ |
| 786 | |
| 787 | static int decryptrest(keyexch *kx, kxchal *kxc, unsigned msg, buf *b) |
| 788 | { |
| 789 | buf bb; |
| 790 | |
| 791 | buf_init(&bb, buf_o, sizeof(buf_o)); |
| 792 | if (ks_decrypt(kxc->ks, MSG_KEYEXCH | msg, b, &bb)) { |
| 793 | a_warn("KX", "?PEER", kx->p, "decrypt-failed", "%s", pkname[msg], A_END); |
| 794 | return (-1); |
| 795 | } |
| 796 | buf_init(b, BBASE(&bb), BLEN(&bb)); |
| 797 | return (0); |
| 798 | } |
| 799 | |
| 800 | /* --- @checkresponse@ --- * |
| 801 | * |
| 802 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 803 | * @unsigned msg@ = type of incoming message |
| 804 | * @buf *b@ = decrypted remainder of the packet |
| 805 | * |
| 806 | * Returns: Zero if OK, nonzero on some kind of error. |
| 807 | * |
| 808 | * Use: Checks a reply or switch packet, ensuring that its response |
| 809 | * is correct. |
| 810 | */ |
| 811 | |
| 812 | static int checkresponse(keyexch *kx, unsigned msg, buf *b) |
| 813 | { |
| 814 | ge *r = G_CREATE(gg); |
| 815 | |
| 816 | if (G_FROMRAW(gg, b, r)) { |
| 817 | a_warn("KX", "?PEER", kx->p, "invalid", "%s", pkname[msg], A_END); |
| 818 | goto bad; |
| 819 | } |
| 820 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 821 | trace(T_CRYPTO, "crypto: reply = %s", gestr(gg, r)); |
| 822 | })) |
| 823 | if (!G_EQ(gg, r, kx->rx)) { |
| 824 | a_warn("KX", "?PEER", kx->p, "incorrect", "response", A_END); |
| 825 | goto bad; |
| 826 | } |
| 827 | |
| 828 | G_DESTROY(gg, r); |
| 829 | return (0); |
| 830 | |
| 831 | bad: |
| 832 | G_DESTROY(gg, r); |
| 833 | return (-1); |
| 834 | } |
| 835 | |
| 836 | /* --- @commit@ --- * |
| 837 | * |
| 838 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 839 | * @kxchal *kxc@ = pointer to challenge to commit to |
| 840 | * |
| 841 | * Returns: --- |
| 842 | * |
| 843 | * Use: Commits to a particular challenge as being the `right' one, |
| 844 | * since a reply has arrived for it. |
| 845 | */ |
| 846 | |
| 847 | static void commit(keyexch *kx, kxchal *kxc) |
| 848 | { |
| 849 | unsigned i; |
| 850 | |
| 851 | for (i = 0; i < kx->nr; i++) { |
| 852 | if (kx->r[i] != kxc) |
| 853 | kxc_destroy(kx->r[i]); |
| 854 | } |
| 855 | kx->r[0] = kxc; |
| 856 | kx->nr = 1; |
| 857 | kxc_stoptimer(kxc); |
| 858 | ksl_link(kx->ks, kxc->ks); |
| 859 | } |
| 860 | |
| 861 | /* --- @doreply@ --- * |
| 862 | * |
| 863 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 864 | * @buf *b@ = buffer containing packet |
| 865 | * |
| 866 | * Returns: Zero if OK, nonzero if the packet was rejected. |
| 867 | * |
| 868 | * Use: Handles a reply packet. This doesn't handle the various |
| 869 | * switch packets: they're rather too different. |
| 870 | */ |
| 871 | |
| 872 | static int doreply(keyexch *kx, buf *b) |
| 873 | { |
| 874 | kxchal *kxc; |
| 875 | |
| 876 | if (kx->s != KXS_CHAL && kx->s != KXS_COMMIT) { |
| 877 | a_warn("KX", "?PEER", kx->p, "unexpected", "reply", A_END); |
| 878 | goto bad; |
| 879 | } |
| 880 | if ((kxc = respond(kx, KX_REPLY, b)) == 0 || |
| 881 | decryptrest(kx, kxc, KX_REPLY, b) || |
| 882 | checkresponse(kx, KX_REPLY, b)) |
| 883 | goto bad; |
| 884 | if (BLEFT(b)) { |
| 885 | a_warn("KX", "?PEER", kx->p, "invalid", "reply", A_END); |
| 886 | goto bad; |
| 887 | } |
| 888 | if (kx->s == KXS_CHAL) { |
| 889 | commit(kx, kxc); |
| 890 | kx->s = KXS_COMMIT; |
| 891 | } |
| 892 | resend(kx); |
| 893 | return (0); |
| 894 | |
| 895 | bad: |
| 896 | return (-1); |
| 897 | } |
| 898 | |
| 899 | /* --- @kxfinish@ --- * |
| 900 | * |
| 901 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
| 902 | * |
| 903 | * Returns: --- |
| 904 | * |
| 905 | * Use: Sets everything up following a successful key exchange. |
| 906 | */ |
| 907 | |
| 908 | static void kxfinish(keyexch *kx) |
| 909 | { |
| 910 | kxchal *kxc = kx->r[0]; |
| 911 | ks_activate(kxc->ks); |
| 912 | settimer(kx, ks_tregen(kxc->ks)); |
| 913 | kx->s = KXS_SWITCH; |
| 914 | a_notify("KXDONE", "?PEER", kx->p, A_END); |
| 915 | p_stats(kx->p)->t_kx = time(0); |
| 916 | } |
| 917 | |
| 918 | /* --- @doswitch@ --- * |
| 919 | * |
| 920 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
| 921 | * @buf *b@ = pointer to buffer containing packet |
| 922 | * |
| 923 | * Returns: Zero if OK, nonzero if the packet was rejected. |
| 924 | * |
| 925 | * Use: Handles a reply with a switch request bolted onto it. |
| 926 | */ |
| 927 | |
| 928 | static int doswitch(keyexch *kx, buf *b) |
| 929 | { |
| 930 | const octet *hc_in, *hc_out, *hswrq; |
| 931 | kxchal *kxc; |
| 932 | |
| 933 | if ((hc_in = buf_get(b, algs.hashsz)) == 0 || |
| 934 | (hc_out = buf_get(b, algs.hashsz)) == 0) { |
| 935 | a_warn("KX", "?PEER", kx->p, "invalid", "switch-rq", A_END); |
| 936 | goto bad; |
| 937 | } |
| 938 | IF_TRACING(T_KEYEXCH, IF_TRACING(T_CRYPTO, { |
| 939 | trace_block(T_CRYPTO, "crypto: challenge", hc_in, algs.hashsz); |
| 940 | trace_block(T_CRYPTO, "crypto: cookie", hc_out, algs.hashsz); |
| 941 | })) |
| 942 | if ((kxc = kxc_byhc(kx, hc_in)) == 0 || |
| 943 | memcmp(hc_out, kx->hc, algs.hashsz) != 0) { |
| 944 | a_warn("KX", "?PEER", kx->p, "incorrect", "switch-rq", A_END); |
| 945 | goto bad; |
| 946 | } |
| 947 | if (decryptrest(kx, kxc, KX_SWITCH, b) || |
| 948 | checkresponse(kx, KX_SWITCH, b)) |
| 949 | goto bad; |
| 950 | if ((hswrq = buf_get(b, algs.hashsz)) == 0 || BLEFT(b)) { |
| 951 | a_warn("KX", "?PEER", kx->p, "invalid", "switch-rq", A_END); |
| 952 | goto bad; |
| 953 | } |
| 954 | IF_TRACING(T_KEYEXCH, { |
| 955 | trace_block(T_CRYPTO, "crypto: switch request hash", hswrq, algs.hashsz); |
| 956 | }) |
| 957 | if (memcmp(hswrq, kxc->hswrq_in, algs.hashsz) != 0) { |
| 958 | a_warn("KX", "?PEER", kx->p, "incorrect", "switch-rq", A_END); |
| 959 | goto bad; |
| 960 | } |
| 961 | if (kx->s == KXS_CHAL) |
| 962 | commit(kx, kxc); |
| 963 | if (kx->s < KXS_SWITCH) |
| 964 | kxfinish(kx); |
| 965 | resend(kx); |
| 966 | return (0); |
| 967 | |
| 968 | bad: |
| 969 | return (-1); |
| 970 | } |
| 971 | |
| 972 | /* --- @doswitchok@ --- * |
| 973 | * |
| 974 | * Arguments: @keyexch *kx@ = pointer to key exchange block |
| 975 | * @buf *b@ = pointer to buffer containing packet |
| 976 | * |
| 977 | * Returns: Zero if OK, nonzero if the packet was rejected. |
| 978 | * |
| 979 | * Use: Handles a reply with a switch request bolted onto it. |
| 980 | */ |
| 981 | |
| 982 | static int doswitchok(keyexch *kx, buf *b) |
| 983 | { |
| 984 | const octet *hswok; |
| 985 | kxchal *kxc; |
| 986 | buf bb; |
| 987 | |
| 988 | if (kx->s < KXS_COMMIT) { |
| 989 | a_warn("KX", "?PEER", kx->p, "unexpected", "switch-ok", A_END); |
| 990 | goto bad; |
| 991 | } |
| 992 | kxc = kx->r[0]; |
| 993 | buf_init(&bb, buf_o, sizeof(buf_o)); |
| 994 | if (decryptrest(kx, kxc, KX_SWITCHOK, b)) |
| 995 | goto bad; |
| 996 | if ((hswok = buf_get(b, algs.hashsz)) == 0 || BLEFT(b)) { |
| 997 | a_warn("KX", "?PEER", kx->p, "invalid", "switch-ok", A_END); |
| 998 | goto bad; |
| 999 | } |
| 1000 | IF_TRACING(T_KEYEXCH, { |
| 1001 | trace_block(T_CRYPTO, "crypto: switch confirmation hash", |
| 1002 | hswok, algs.hashsz); |
| 1003 | }) |
| 1004 | if (memcmp(hswok, kxc->hswok_in, algs.hashsz) != 0) { |
| 1005 | a_warn("KX", "?PEER", kx->p, "incorrect", "switch-ok", A_END); |
| 1006 | goto bad; |
| 1007 | } |
| 1008 | if (kx->s < KXS_SWITCH) |
| 1009 | kxfinish(kx); |
| 1010 | return (0); |
| 1011 | |
| 1012 | bad: |
| 1013 | return (-1); |
| 1014 | } |
| 1015 | |
| 1016 | /*----- Main code ---------------------------------------------------------*/ |
| 1017 | |
| 1018 | /* --- @stop@ --- * |
| 1019 | * |
| 1020 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 1021 | * |
| 1022 | * Returns: --- |
| 1023 | * |
| 1024 | * Use: Stops a key exchange dead in its tracks. Throws away all of |
| 1025 | * the context information. The context is left in an |
| 1026 | * inconsistent state. The only functions which understand this |
| 1027 | * state are @kx_free@ and @kx_init@ (which cause it internally |
| 1028 | * it), and @start@ (which expects it to be the prevailing |
| 1029 | * state). |
| 1030 | */ |
| 1031 | |
| 1032 | static void stop(keyexch *kx) |
| 1033 | { |
| 1034 | unsigned i; |
| 1035 | |
| 1036 | if (kx->f & KXF_DEAD) |
| 1037 | return; |
| 1038 | |
| 1039 | if (kx->f & KXF_TIMER) |
| 1040 | sel_rmtimer(&kx->t); |
| 1041 | for (i = 0; i < kx->nr; i++) |
| 1042 | kxc_destroy(kx->r[i]); |
| 1043 | mp_drop(kx->alpha); |
| 1044 | G_DESTROY(gg, kx->c); |
| 1045 | G_DESTROY(gg, kx->rx); |
| 1046 | kx->t_valid = 0; |
| 1047 | kx->f |= KXF_DEAD; |
| 1048 | kx->f &= ~KXF_TIMER; |
| 1049 | } |
| 1050 | |
| 1051 | /* --- @start@ --- * |
| 1052 | * |
| 1053 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 1054 | * @time_t now@ = the current time |
| 1055 | * |
| 1056 | * Returns: --- |
| 1057 | * |
| 1058 | * Use: Starts a new key exchange with the peer. The context must be |
| 1059 | * in the bizarre state left by @stop@ or @kx_init@. |
| 1060 | */ |
| 1061 | |
| 1062 | static void start(keyexch *kx, time_t now) |
| 1063 | { |
| 1064 | ghash *h; |
| 1065 | |
| 1066 | assert(kx->f & KXF_DEAD); |
| 1067 | |
| 1068 | kx->f &= ~(KXF_DEAD | KXF_CORK); |
| 1069 | kx->nr = 0; |
| 1070 | kx->alpha = mprand_range(MP_NEW, gg->r, &rand_global, 0); |
| 1071 | kx->c = G_CREATE(gg); G_EXP(gg, kx->c, gg->g, kx->alpha); |
| 1072 | kx->rx = G_CREATE(gg); G_EXP(gg, kx->rx, kx->kpub, kx->alpha); |
| 1073 | kx->s = KXS_CHAL; |
| 1074 | kx->t_valid = now + T_VALID; |
| 1075 | |
| 1076 | h = GH_INIT(algs.h); |
| 1077 | HASH_STRING(h, "tripe-cookie"); |
| 1078 | hashge(h, kx->c); |
| 1079 | GH_DONE(h, kx->hc); |
| 1080 | GH_DESTROY(h); |
| 1081 | |
| 1082 | IF_TRACING(T_KEYEXCH, { |
| 1083 | trace(T_KEYEXCH, "keyexch: creating new challenge"); |
| 1084 | IF_TRACING(T_CRYPTO, { |
| 1085 | trace(T_CRYPTO, "crypto: secret = %s", mpstr(kx->alpha)); |
| 1086 | trace(T_CRYPTO, "crypto: challenge = %s", gestr(gg, kx->c)); |
| 1087 | trace(T_CRYPTO, "crypto: expected response = %s", gestr(gg, kx->rx)); |
| 1088 | trace_block(T_CRYPTO, "crypto: challenge cookie", kx->hc, algs.hashsz); |
| 1089 | }) |
| 1090 | }) |
| 1091 | } |
| 1092 | |
| 1093 | /* --- @checkpub@ --- * |
| 1094 | * |
| 1095 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 1096 | * |
| 1097 | * Returns: Zero if OK, nonzero if the peer's public key has expired. |
| 1098 | * |
| 1099 | * Use: Deactivates the key-exchange until the peer acquires a new |
| 1100 | * public key. |
| 1101 | */ |
| 1102 | |
| 1103 | static int checkpub(keyexch *kx) |
| 1104 | { |
| 1105 | time_t now; |
| 1106 | if (kx->f & KXF_DEAD) |
| 1107 | return (-1); |
| 1108 | now = time(0); |
| 1109 | if (KEY_EXPIRED(now, kx->texp_kpub)) { |
| 1110 | stop(kx); |
| 1111 | a_warn("KX", "?PEER", kx->p, "public-key-expired", A_END); |
| 1112 | G_COPY(gg, kx->kpub, gg->i); |
| 1113 | kx->f &= ~KXF_PUBKEY; |
| 1114 | return (-1); |
| 1115 | } |
| 1116 | return (0); |
| 1117 | } |
| 1118 | |
| 1119 | /* --- @kx_start@ --- * |
| 1120 | * |
| 1121 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 1122 | * @int forcep@ = nonzero to ignore the quiet timer |
| 1123 | * |
| 1124 | * Returns: --- |
| 1125 | * |
| 1126 | * Use: Stimulates a key exchange. If a key exchage is in progress, |
| 1127 | * a new challenge is sent (unless the quiet timer forbids |
| 1128 | * this); if no exchange is in progress, one is commenced. |
| 1129 | */ |
| 1130 | |
| 1131 | void kx_start(keyexch *kx, int forcep) |
| 1132 | { |
| 1133 | time_t now = time(0); |
| 1134 | |
| 1135 | if (checkpub(kx)) |
| 1136 | return; |
| 1137 | if (forcep || !VALIDP(kx, now)) { |
| 1138 | stop(kx); |
| 1139 | start(kx, now); |
| 1140 | a_notify("KXSTART", "?PEER", kx->p, A_END); |
| 1141 | } |
| 1142 | resend(kx); |
| 1143 | } |
| 1144 | |
| 1145 | /* --- @kx_message@ --- * |
| 1146 | * |
| 1147 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 1148 | * @unsigned msg@ = the message code |
| 1149 | * @buf *b@ = pointer to buffer containing the packet |
| 1150 | * |
| 1151 | * Returns: --- |
| 1152 | * |
| 1153 | * Use: Reads a packet containing key exchange messages and handles |
| 1154 | * it. |
| 1155 | */ |
| 1156 | |
| 1157 | void kx_message(keyexch *kx, unsigned msg, buf *b) |
| 1158 | { |
| 1159 | time_t now = time(0); |
| 1160 | stats *st = p_stats(kx->p); |
| 1161 | size_t sz = BSZ(b); |
| 1162 | int rc; |
| 1163 | |
| 1164 | if (kx->f & KXF_CORK) { |
| 1165 | start(kx, now); |
| 1166 | settimer(kx, now + T_RETRY); |
| 1167 | a_notify("KXSTART", A_END); |
| 1168 | } |
| 1169 | |
| 1170 | if (checkpub(kx)) |
| 1171 | return; |
| 1172 | |
| 1173 | if (!VALIDP(kx, now)) { |
| 1174 | stop(kx); |
| 1175 | start(kx, now); |
| 1176 | } |
| 1177 | T( trace(T_KEYEXCH, "keyexch: processing %s packet from `%s'", |
| 1178 | msg < KX_NMSG ? pkname[msg] : "unknown", p_name(kx->p)); ) |
| 1179 | |
| 1180 | switch (msg) { |
| 1181 | case KX_PRECHAL: |
| 1182 | rc = doprechallenge(kx, b); |
| 1183 | break; |
| 1184 | case KX_CHAL: |
| 1185 | rc = dochallenge(kx, b); |
| 1186 | break; |
| 1187 | case KX_REPLY: |
| 1188 | rc = doreply(kx, b); |
| 1189 | break; |
| 1190 | case KX_SWITCH: |
| 1191 | rc = doswitch(kx, b); |
| 1192 | break; |
| 1193 | case KX_SWITCHOK: |
| 1194 | rc = doswitchok(kx, b); |
| 1195 | break; |
| 1196 | default: |
| 1197 | a_warn("KX", "?PEER", kx->p, "unknown-message", "0x%02x", msg, A_END); |
| 1198 | rc = -1; |
| 1199 | break; |
| 1200 | } |
| 1201 | |
| 1202 | if (rc) |
| 1203 | st->n_reject++; |
| 1204 | else { |
| 1205 | st->n_kxin++; |
| 1206 | st->sz_kxin += sz; |
| 1207 | } |
| 1208 | } |
| 1209 | |
| 1210 | /* --- @kx_free@ --- * |
| 1211 | * |
| 1212 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 1213 | * |
| 1214 | * Returns: --- |
| 1215 | * |
| 1216 | * Use: Frees everything in a key exchange context. |
| 1217 | */ |
| 1218 | |
| 1219 | void kx_free(keyexch *kx) |
| 1220 | { |
| 1221 | stop(kx); |
| 1222 | G_DESTROY(gg, kx->kpub); |
| 1223 | } |
| 1224 | |
| 1225 | /* --- @kx_newkeys@ --- * |
| 1226 | * |
| 1227 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 1228 | * |
| 1229 | * Returns: --- |
| 1230 | * |
| 1231 | * Use: Informs the key exchange module that its keys may have |
| 1232 | * changed. If fetching the new keys fails, the peer will be |
| 1233 | * destroyed, we log messages and struggle along with the old |
| 1234 | * keys. |
| 1235 | */ |
| 1236 | |
| 1237 | void kx_newkeys(keyexch *kx) |
| 1238 | { |
| 1239 | if (km_getpubkey(p_name(kx->p), kx->kpub, &kx->texp_kpub)) |
| 1240 | return; |
| 1241 | kx->f |= KXF_PUBKEY; |
| 1242 | if ((kx->f & KXF_DEAD) || kx->s != KXS_SWITCH) { |
| 1243 | T( trace(T_KEYEXCH, "keyexch: restarting key negotiation with `%s'", |
| 1244 | p_name(kx->p)); ) |
| 1245 | stop(kx); |
| 1246 | start(kx, time(0)); |
| 1247 | resend(kx); |
| 1248 | } |
| 1249 | } |
| 1250 | |
| 1251 | /* --- @kx_init@ --- * |
| 1252 | * |
| 1253 | * Arguments: @keyexch *kx@ = pointer to key exchange context |
| 1254 | * @peer *p@ = pointer to peer context |
| 1255 | * @keyset **ks@ = pointer to keyset list |
| 1256 | * @unsigned f@ = various useful flags |
| 1257 | * |
| 1258 | * Returns: Zero if OK, nonzero if it failed. |
| 1259 | * |
| 1260 | * Use: Initializes a key exchange module. The module currently |
| 1261 | * contains no keys, and will attempt to initiate a key |
| 1262 | * exchange. |
| 1263 | */ |
| 1264 | |
| 1265 | int kx_init(keyexch *kx, peer *p, keyset **ks, unsigned f) |
| 1266 | { |
| 1267 | kx->ks = ks; |
| 1268 | kx->p = p; |
| 1269 | kx->kpub = G_CREATE(gg); |
| 1270 | if (km_getpubkey(p_name(p), kx->kpub, &kx->texp_kpub)) { |
| 1271 | G_DESTROY(gg, kx->kpub); |
| 1272 | return (-1); |
| 1273 | } |
| 1274 | kx->f = KXF_DEAD | KXF_PUBKEY | f; |
| 1275 | if (!(kx->f & KXF_CORK)) { |
| 1276 | start(kx, time(0)); |
| 1277 | resend(kx); |
| 1278 | /* Don't notify here: the ADD message hasn't gone out yet. */ |
| 1279 | } |
| 1280 | return (0); |
| 1281 | } |
| 1282 | |
| 1283 | /*----- That's all, folks -------------------------------------------------*/ |