1 // SPDX-License-Identifier: Apache-2.0 2 /* 3 * Elliptic curve DSA 4 * 5 * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved 6 * 7 * Licensed under the Apache License, Version 2.0 (the "License"); you may 8 * not use this file except in compliance with the License. 9 * You may obtain a copy of the License at 10 * 11 * http://www.apache.org/licenses/LICENSE-2.0 12 * 13 * Unless required by applicable law or agreed to in writing, software 14 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 15 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 16 * See the License for the specific language governing permissions and 17 * limitations under the License. 18 * 19 * This file is part of mbed TLS (https://tls.mbed.org) 20 */ 21 22 /* 23 * References: 24 * 25 * SEC1 http://www.secg.org/index.php?action=secg,docs_secg 26 */ 27 28 #if !defined(MBEDTLS_CONFIG_FILE) 29 #include "mbedtls/config.h" 30 #else 31 #include MBEDTLS_CONFIG_FILE 32 #endif 33 34 #if defined(MBEDTLS_ECDSA_C) 35 36 #include "mbedtls/ecdsa.h" 37 #include "mbedtls/asn1write.h" 38 39 #include <string.h> 40 41 #if defined(MBEDTLS_ECDSA_DETERMINISTIC) 42 #include "mbedtls/hmac_drbg.h" 43 #endif 44 45 #if defined(MBEDTLS_PLATFORM_C) 46 #include "mbedtls/platform.h" 47 #else 48 #include <stdlib.h> 49 #define mbedtls_calloc calloc 50 #define mbedtls_free free 51 #endif 52 53 #include "mbedtls/platform_util.h" 54 55 /* Parameter validation macros based on platform_util.h */ 56 #define ECDSA_VALIDATE_RET( cond ) \ 57 MBEDTLS_INTERNAL_VALIDATE_RET( cond, MBEDTLS_ERR_ECP_BAD_INPUT_DATA ) 58 #define ECDSA_VALIDATE( cond ) \ 59 MBEDTLS_INTERNAL_VALIDATE( cond ) 60 61 #if defined(MBEDTLS_ECP_RESTARTABLE) 62 63 /* 64 * Sub-context for ecdsa_verify() 65 */ 66 struct mbedtls_ecdsa_restart_ver 67 { 68 mbedtls_mpi u1, u2; /* intermediate values */ 69 enum { /* what to do next? */ 70 ecdsa_ver_init = 0, /* getting started */ 71 ecdsa_ver_muladd, /* muladd step */ 72 } state; 73 }; 74 75 /* 76 * Init verify restart sub-context 77 */ 78 static void ecdsa_restart_ver_init( mbedtls_ecdsa_restart_ver_ctx *ctx ) 79 { 80 mbedtls_mpi_init( &ctx->u1 ); 81 mbedtls_mpi_init( &ctx->u2 ); 82 ctx->state = ecdsa_ver_init; 83 } 84 85 /* 86 * Free the components of a verify restart sub-context 87 */ 88 static void ecdsa_restart_ver_free( mbedtls_ecdsa_restart_ver_ctx *ctx ) 89 { 90 if( ctx == NULL ) 91 return; 92 93 mbedtls_mpi_free( &ctx->u1 ); 94 mbedtls_mpi_free( &ctx->u2 ); 95 96 ecdsa_restart_ver_init( ctx ); 97 } 98 99 /* 100 * Sub-context for ecdsa_sign() 101 */ 102 struct mbedtls_ecdsa_restart_sig 103 { 104 int sign_tries; 105 int key_tries; 106 mbedtls_mpi k; /* per-signature random */ 107 mbedtls_mpi r; /* r value */ 108 enum { /* what to do next? */ 109 ecdsa_sig_init = 0, /* getting started */ 110 ecdsa_sig_mul, /* doing ecp_mul() */ 111 ecdsa_sig_modn, /* mod N computations */ 112 } state; 113 }; 114 115 /* 116 * Init verify sign sub-context 117 */ 118 static void ecdsa_restart_sig_init( mbedtls_ecdsa_restart_sig_ctx *ctx ) 119 { 120 ctx->sign_tries = 0; 121 ctx->key_tries = 0; 122 mbedtls_mpi_init( &ctx->k ); 123 mbedtls_mpi_init( &ctx->r ); 124 ctx->state = ecdsa_sig_init; 125 } 126 127 /* 128 * Free the components of a sign restart sub-context 129 */ 130 static void ecdsa_restart_sig_free( mbedtls_ecdsa_restart_sig_ctx *ctx ) 131 { 132 if( ctx == NULL ) 133 return; 134 135 mbedtls_mpi_free( &ctx->k ); 136 mbedtls_mpi_free( &ctx->r ); 137 } 138 139 #if defined(MBEDTLS_ECDSA_DETERMINISTIC) 140 /* 141 * Sub-context for ecdsa_sign_det() 142 */ 143 struct mbedtls_ecdsa_restart_det 144 { 145 mbedtls_hmac_drbg_context rng_ctx; /* DRBG state */ 146 enum { /* what to do next? */ 147 ecdsa_det_init = 0, /* getting started */ 148 ecdsa_det_sign, /* make signature */ 149 } state; 150 }; 151 152 /* 153 * Init verify sign_det sub-context 154 */ 155 static void ecdsa_restart_det_init( mbedtls_ecdsa_restart_det_ctx *ctx ) 156 { 157 mbedtls_hmac_drbg_init( &ctx->rng_ctx ); 158 ctx->state = ecdsa_det_init; 159 } 160 161 /* 162 * Free the components of a sign_det restart sub-context 163 */ 164 static void ecdsa_restart_det_free( mbedtls_ecdsa_restart_det_ctx *ctx ) 165 { 166 if( ctx == NULL ) 167 return; 168 169 mbedtls_hmac_drbg_free( &ctx->rng_ctx ); 170 171 ecdsa_restart_det_init( ctx ); 172 } 173 #endif /* MBEDTLS_ECDSA_DETERMINISTIC */ 174 175 #define ECDSA_RS_ECP ( rs_ctx == NULL ? NULL : &rs_ctx->ecp ) 176 177 /* Utility macro for checking and updating ops budget */ 178 #define ECDSA_BUDGET( ops ) \ 179 MBEDTLS_MPI_CHK( mbedtls_ecp_check_budget( grp, ECDSA_RS_ECP, ops ) ); 180 181 /* Call this when entering a function that needs its own sub-context */ 182 #define ECDSA_RS_ENTER( SUB ) do { \ 183 /* reset ops count for this call if top-level */ \ 184 if( rs_ctx != NULL && rs_ctx->ecp.depth++ == 0 ) \ 185 rs_ctx->ecp.ops_done = 0; \ 186 \ 187 /* set up our own sub-context if needed */ \ 188 if( mbedtls_ecp_restart_is_enabled() && \ 189 rs_ctx != NULL && rs_ctx->SUB == NULL ) \ 190 { \ 191 rs_ctx->SUB = mbedtls_calloc( 1, sizeof( *rs_ctx->SUB ) ); \ 192 if( rs_ctx->SUB == NULL ) \ 193 return( MBEDTLS_ERR_ECP_ALLOC_FAILED ); \ 194 \ 195 ecdsa_restart_## SUB ##_init( rs_ctx->SUB ); \ 196 } \ 197 } while( 0 ) 198 199 /* Call this when leaving a function that needs its own sub-context */ 200 #define ECDSA_RS_LEAVE( SUB ) do { \ 201 /* clear our sub-context when not in progress (done or error) */ \ 202 if( rs_ctx != NULL && rs_ctx->SUB != NULL && \ 203 ret != MBEDTLS_ERR_ECP_IN_PROGRESS ) \ 204 { \ 205 ecdsa_restart_## SUB ##_free( rs_ctx->SUB ); \ 206 mbedtls_free( rs_ctx->SUB ); \ 207 rs_ctx->SUB = NULL; \ 208 } \ 209 \ 210 if( rs_ctx != NULL ) \ 211 rs_ctx->ecp.depth--; \ 212 } while( 0 ) 213 214 #else /* MBEDTLS_ECP_RESTARTABLE */ 215 216 #define ECDSA_RS_ECP NULL 217 218 #define ECDSA_BUDGET( ops ) /* no-op; for compatibility */ 219 220 #define ECDSA_RS_ENTER( SUB ) (void) rs_ctx 221 #define ECDSA_RS_LEAVE( SUB ) (void) rs_ctx 222 223 #endif /* MBEDTLS_ECP_RESTARTABLE */ 224 225 /* 226 * Derive a suitable integer for group grp from a buffer of length len 227 * SEC1 4.1.3 step 5 aka SEC1 4.1.4 step 3 228 */ 229 static int derive_mpi( const mbedtls_ecp_group *grp, mbedtls_mpi *x, 230 const unsigned char *buf, size_t blen ) 231 { 232 int ret; 233 size_t n_size = ( grp->nbits + 7 ) / 8; 234 size_t use_size = blen > n_size ? n_size : blen; 235 236 MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( x, buf, use_size ) ); 237 if( use_size * 8 > grp->nbits ) 238 MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( x, use_size * 8 - grp->nbits ) ); 239 240 /* While at it, reduce modulo N */ 241 if( mbedtls_mpi_cmp_mpi( x, &grp->N ) >= 0 ) 242 MBEDTLS_MPI_CHK( mbedtls_mpi_sub_mpi( x, x, &grp->N ) ); 243 244 cleanup: 245 return( ret ); 246 } 247 248 #if !defined(MBEDTLS_ECDSA_SIGN_ALT) 249 /* 250 * Compute ECDSA signature of a hashed message (SEC1 4.1.3) 251 * Obviously, compared to SEC1 4.1.3, we skip step 4 (hash message) 252 */ 253 static int ecdsa_sign_restartable( mbedtls_ecp_group *grp, 254 mbedtls_mpi *r, mbedtls_mpi *s, 255 const mbedtls_mpi *d, const unsigned char *buf, size_t blen, 256 int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, 257 int (*f_rng_blind)(void *, unsigned char *, size_t), 258 void *p_rng_blind, 259 mbedtls_ecdsa_restart_ctx *rs_ctx ) 260 { 261 int ret, key_tries, sign_tries; 262 int *p_sign_tries = &sign_tries, *p_key_tries = &key_tries; 263 mbedtls_ecp_point R; 264 mbedtls_mpi k, e, t; 265 mbedtls_mpi *pk = &k, *pr = r; 266 267 /* Fail cleanly on curves such as Curve25519 that can't be used for ECDSA */ 268 if( grp->N.p == NULL ) 269 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA ); 270 271 /* Make sure d is in range 1..n-1 */ 272 if( mbedtls_mpi_cmp_int( d, 1 ) < 0 || mbedtls_mpi_cmp_mpi( d, &grp->N ) >= 0 ) 273 return( MBEDTLS_ERR_ECP_INVALID_KEY ); 274 275 mbedtls_ecp_point_init( &R ); 276 mbedtls_mpi_init( &k ); mbedtls_mpi_init( &e ); mbedtls_mpi_init( &t ); 277 278 ECDSA_RS_ENTER( sig ); 279 280 #if defined(MBEDTLS_ECP_RESTARTABLE) 281 if( rs_ctx != NULL && rs_ctx->sig != NULL ) 282 { 283 /* redirect to our context */ 284 p_sign_tries = &rs_ctx->sig->sign_tries; 285 p_key_tries = &rs_ctx->sig->key_tries; 286 pk = &rs_ctx->sig->k; 287 pr = &rs_ctx->sig->r; 288 289 /* jump to current step */ 290 if( rs_ctx->sig->state == ecdsa_sig_mul ) 291 goto mul; 292 if( rs_ctx->sig->state == ecdsa_sig_modn ) 293 goto modn; 294 } 295 #endif /* MBEDTLS_ECP_RESTARTABLE */ 296 297 *p_sign_tries = 0; 298 do 299 { 300 if( (*p_sign_tries)++ > 10 ) 301 { 302 ret = MBEDTLS_ERR_ECP_RANDOM_FAILED; 303 goto cleanup; 304 } 305 306 /* 307 * Steps 1-3: generate a suitable ephemeral keypair 308 * and set r = xR mod n 309 */ 310 *p_key_tries = 0; 311 do 312 { 313 if( (*p_key_tries)++ > 10 ) 314 { 315 ret = MBEDTLS_ERR_ECP_RANDOM_FAILED; 316 goto cleanup; 317 } 318 319 MBEDTLS_MPI_CHK( mbedtls_ecp_gen_privkey( grp, pk, f_rng, p_rng ) ); 320 321 #if defined(MBEDTLS_ECP_RESTARTABLE) 322 if( rs_ctx != NULL && rs_ctx->sig != NULL ) 323 rs_ctx->sig->state = ecdsa_sig_mul; 324 325 mul: 326 #endif 327 MBEDTLS_MPI_CHK( mbedtls_ecp_mul_restartable( grp, &R, pk, &grp->G, 328 f_rng_blind, 329 p_rng_blind, 330 ECDSA_RS_ECP ) ); 331 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( pr, &R.X, &grp->N ) ); 332 } 333 while( mbedtls_mpi_cmp_int( pr, 0 ) == 0 ); 334 335 #if defined(MBEDTLS_ECP_RESTARTABLE) 336 if( rs_ctx != NULL && rs_ctx->sig != NULL ) 337 rs_ctx->sig->state = ecdsa_sig_modn; 338 339 modn: 340 #endif 341 /* 342 * Accounting for everything up to the end of the loop 343 * (step 6, but checking now avoids saving e and t) 344 */ 345 ECDSA_BUDGET( MBEDTLS_ECP_OPS_INV + 4 ); 346 347 /* 348 * Step 5: derive MPI from hashed message 349 */ 350 MBEDTLS_MPI_CHK( derive_mpi( grp, &e, buf, blen ) ); 351 352 /* 353 * Generate a random value to blind inv_mod in next step, 354 * avoiding a potential timing leak. 355 */ 356 MBEDTLS_MPI_CHK( mbedtls_ecp_gen_privkey( grp, &t, f_rng_blind, 357 p_rng_blind ) ); 358 359 /* 360 * Step 6: compute s = (e + r * d) / k = t (e + rd) / (kt) mod n 361 */ 362 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( s, pr, d ) ); 363 MBEDTLS_MPI_CHK( mbedtls_mpi_add_mpi( &e, &e, s ) ); 364 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &e, &e, &t ) ); 365 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( pk, pk, &t ) ); 366 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( pk, pk, &grp->N ) ); 367 MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( s, pk, &grp->N ) ); 368 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( s, s, &e ) ); 369 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( s, s, &grp->N ) ); 370 } 371 while( mbedtls_mpi_cmp_int( s, 0 ) == 0 ); 372 373 #if defined(MBEDTLS_ECP_RESTARTABLE) 374 if( rs_ctx != NULL && rs_ctx->sig != NULL ) 375 mbedtls_mpi_copy( r, pr ); 376 #endif 377 378 cleanup: 379 mbedtls_ecp_point_free( &R ); 380 mbedtls_mpi_free( &k ); mbedtls_mpi_free( &e ); mbedtls_mpi_free( &t ); 381 382 ECDSA_RS_LEAVE( sig ); 383 384 return( ret ); 385 } 386 387 /* 388 * Compute ECDSA signature of a hashed message 389 */ 390 int mbedtls_ecdsa_sign( mbedtls_ecp_group *grp, mbedtls_mpi *r, mbedtls_mpi *s, 391 const mbedtls_mpi *d, const unsigned char *buf, size_t blen, 392 int (*f_rng)(void *, unsigned char *, size_t), void *p_rng ) 393 { 394 ECDSA_VALIDATE_RET( grp != NULL ); 395 ECDSA_VALIDATE_RET( r != NULL ); 396 ECDSA_VALIDATE_RET( s != NULL ); 397 ECDSA_VALIDATE_RET( d != NULL ); 398 ECDSA_VALIDATE_RET( f_rng != NULL ); 399 ECDSA_VALIDATE_RET( buf != NULL || blen == 0 ); 400 401 /* Use the same RNG for both blinding and ephemeral key generation */ 402 return( ecdsa_sign_restartable( grp, r, s, d, buf, blen, 403 f_rng, p_rng, f_rng, p_rng, NULL ) ); 404 } 405 #endif /* !MBEDTLS_ECDSA_SIGN_ALT */ 406 407 #if defined(MBEDTLS_ECDSA_DETERMINISTIC) 408 /* 409 * Deterministic signature wrapper 410 */ 411 static int ecdsa_sign_det_restartable( mbedtls_ecp_group *grp, 412 mbedtls_mpi *r, mbedtls_mpi *s, 413 const mbedtls_mpi *d, const unsigned char *buf, size_t blen, 414 mbedtls_md_type_t md_alg, 415 int (*f_rng_blind)(void *, unsigned char *, size_t), 416 void *p_rng_blind, 417 mbedtls_ecdsa_restart_ctx *rs_ctx ) 418 { 419 int ret; 420 mbedtls_hmac_drbg_context rng_ctx; 421 mbedtls_hmac_drbg_context *p_rng = &rng_ctx; 422 unsigned char data[2 * MBEDTLS_ECP_MAX_BYTES]; 423 size_t grp_len = ( grp->nbits + 7 ) / 8; 424 const mbedtls_md_info_t *md_info; 425 mbedtls_mpi h; 426 427 if( ( md_info = mbedtls_md_info_from_type( md_alg ) ) == NULL ) 428 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA ); 429 430 mbedtls_mpi_init( &h ); 431 mbedtls_hmac_drbg_init( &rng_ctx ); 432 433 ECDSA_RS_ENTER( det ); 434 435 #if defined(MBEDTLS_ECP_RESTARTABLE) 436 if( rs_ctx != NULL && rs_ctx->det != NULL ) 437 { 438 /* redirect to our context */ 439 p_rng = &rs_ctx->det->rng_ctx; 440 441 /* jump to current step */ 442 if( rs_ctx->det->state == ecdsa_det_sign ) 443 goto sign; 444 } 445 #endif /* MBEDTLS_ECP_RESTARTABLE */ 446 447 /* Use private key and message hash (reduced) to initialize HMAC_DRBG */ 448 MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( d, data, grp_len ) ); 449 MBEDTLS_MPI_CHK( derive_mpi( grp, &h, buf, blen ) ); 450 MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &h, data + grp_len, grp_len ) ); 451 mbedtls_hmac_drbg_seed_buf( p_rng, md_info, data, 2 * grp_len ); 452 453 #if defined(MBEDTLS_ECP_RESTARTABLE) 454 if( rs_ctx != NULL && rs_ctx->det != NULL ) 455 rs_ctx->det->state = ecdsa_det_sign; 456 457 sign: 458 #endif 459 #if defined(MBEDTLS_ECDSA_SIGN_ALT) 460 ret = mbedtls_ecdsa_sign( grp, r, s, d, buf, blen, 461 mbedtls_hmac_drbg_random, p_rng ); 462 #else 463 if( f_rng_blind != NULL ) 464 ret = ecdsa_sign_restartable( grp, r, s, d, buf, blen, 465 mbedtls_hmac_drbg_random, p_rng, 466 f_rng_blind, p_rng_blind, rs_ctx ); 467 else 468 { 469 mbedtls_hmac_drbg_context *p_rng_blind_det; 470 471 #if !defined(MBEDTLS_ECP_RESTARTABLE) 472 /* 473 * To avoid reusing rng_ctx and risking incorrect behavior we seed a 474 * second HMAC-DRBG with the same seed. We also apply a label to avoid 475 * reusing the bits of the ephemeral key for blinding and eliminate the 476 * risk that they leak this way. 477 */ 478 const char* blind_label = "BLINDING CONTEXT"; 479 mbedtls_hmac_drbg_context rng_ctx_blind; 480 481 mbedtls_hmac_drbg_init( &rng_ctx_blind ); 482 p_rng_blind_det = &rng_ctx_blind; 483 484 mbedtls_hmac_drbg_seed_buf( p_rng_blind_det, md_info, 485 data, 2 * grp_len ); 486 ret = mbedtls_hmac_drbg_update_ret( p_rng_blind_det, 487 (const unsigned char*) blind_label, 488 strlen( blind_label ) ); 489 if( ret != 0 ) 490 { 491 mbedtls_hmac_drbg_free( &rng_ctx_blind ); 492 goto cleanup; 493 } 494 #else 495 /* 496 * In the case of restartable computations we would either need to store 497 * the second RNG in the restart context too or set it up at every 498 * restart. The first option would penalize the correct application of 499 * the function and the second would defeat the purpose of the 500 * restartable feature. 501 * 502 * Therefore in this case we reuse the original RNG. This comes with the 503 * price that the resulting signature might not be a valid deterministic 504 * ECDSA signature with a very low probability (same magnitude as 505 * successfully guessing the private key). However even then it is still 506 * a valid ECDSA signature. 507 */ 508 p_rng_blind_det = p_rng; 509 #endif /* MBEDTLS_ECP_RESTARTABLE */ 510 511 /* 512 * Since the output of the RNGs is always the same for the same key and 513 * message, this limits the efficiency of blinding and leaks information 514 * through side channels. After mbedtls_ecdsa_sign_det() is removed NULL 515 * won't be a valid value for f_rng_blind anymore. Therefore it should 516 * be checked by the caller and this branch and check can be removed. 517 */ 518 ret = ecdsa_sign_restartable( grp, r, s, d, buf, blen, 519 mbedtls_hmac_drbg_random, p_rng, 520 mbedtls_hmac_drbg_random, p_rng_blind_det, 521 rs_ctx ); 522 523 #if !defined(MBEDTLS_ECP_RESTARTABLE) 524 mbedtls_hmac_drbg_free( &rng_ctx_blind ); 525 #endif 526 } 527 #endif /* MBEDTLS_ECDSA_SIGN_ALT */ 528 529 cleanup: 530 mbedtls_hmac_drbg_free( &rng_ctx ); 531 mbedtls_mpi_free( &h ); 532 533 ECDSA_RS_LEAVE( det ); 534 535 return( ret ); 536 } 537 538 /* 539 * Deterministic signature wrappers 540 */ 541 int mbedtls_ecdsa_sign_det( mbedtls_ecp_group *grp, mbedtls_mpi *r, 542 mbedtls_mpi *s, const mbedtls_mpi *d, 543 const unsigned char *buf, size_t blen, 544 mbedtls_md_type_t md_alg ) 545 { 546 ECDSA_VALIDATE_RET( grp != NULL ); 547 ECDSA_VALIDATE_RET( r != NULL ); 548 ECDSA_VALIDATE_RET( s != NULL ); 549 ECDSA_VALIDATE_RET( d != NULL ); 550 ECDSA_VALIDATE_RET( buf != NULL || blen == 0 ); 551 552 return( ecdsa_sign_det_restartable( grp, r, s, d, buf, blen, md_alg, 553 NULL, NULL, NULL ) ); 554 } 555 556 int mbedtls_ecdsa_sign_det_ext( mbedtls_ecp_group *grp, mbedtls_mpi *r, 557 mbedtls_mpi *s, const mbedtls_mpi *d, 558 const unsigned char *buf, size_t blen, 559 mbedtls_md_type_t md_alg, 560 int (*f_rng_blind)(void *, unsigned char *, 561 size_t), 562 void *p_rng_blind ) 563 { 564 ECDSA_VALIDATE_RET( grp != NULL ); 565 ECDSA_VALIDATE_RET( r != NULL ); 566 ECDSA_VALIDATE_RET( s != NULL ); 567 ECDSA_VALIDATE_RET( d != NULL ); 568 ECDSA_VALIDATE_RET( buf != NULL || blen == 0 ); 569 ECDSA_VALIDATE_RET( f_rng_blind != NULL ); 570 571 return( ecdsa_sign_det_restartable( grp, r, s, d, buf, blen, md_alg, 572 f_rng_blind, p_rng_blind, NULL ) ); 573 } 574 #endif /* MBEDTLS_ECDSA_DETERMINISTIC */ 575 576 #if !defined(MBEDTLS_ECDSA_VERIFY_ALT) 577 /* 578 * Verify ECDSA signature of hashed message (SEC1 4.1.4) 579 * Obviously, compared to SEC1 4.1.3, we skip step 2 (hash message) 580 */ 581 static int ecdsa_verify_restartable( mbedtls_ecp_group *grp, 582 const unsigned char *buf, size_t blen, 583 const mbedtls_ecp_point *Q, 584 const mbedtls_mpi *r, const mbedtls_mpi *s, 585 mbedtls_ecdsa_restart_ctx *rs_ctx ) 586 { 587 int ret; 588 mbedtls_mpi e, s_inv, u1, u2; 589 mbedtls_ecp_point R; 590 mbedtls_mpi *pu1 = &u1, *pu2 = &u2; 591 592 mbedtls_ecp_point_init( &R ); 593 mbedtls_mpi_init( &e ); mbedtls_mpi_init( &s_inv ); 594 mbedtls_mpi_init( &u1 ); mbedtls_mpi_init( &u2 ); 595 596 /* Fail cleanly on curves such as Curve25519 that can't be used for ECDSA */ 597 if( grp->N.p == NULL ) 598 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA ); 599 600 ECDSA_RS_ENTER( ver ); 601 602 #if defined(MBEDTLS_ECP_RESTARTABLE) 603 if( rs_ctx != NULL && rs_ctx->ver != NULL ) 604 { 605 /* redirect to our context */ 606 pu1 = &rs_ctx->ver->u1; 607 pu2 = &rs_ctx->ver->u2; 608 609 /* jump to current step */ 610 if( rs_ctx->ver->state == ecdsa_ver_muladd ) 611 goto muladd; 612 } 613 #endif /* MBEDTLS_ECP_RESTARTABLE */ 614 615 /* 616 * Step 1: make sure r and s are in range 1..n-1 617 */ 618 if( mbedtls_mpi_cmp_int( r, 1 ) < 0 || mbedtls_mpi_cmp_mpi( r, &grp->N ) >= 0 || 619 mbedtls_mpi_cmp_int( s, 1 ) < 0 || mbedtls_mpi_cmp_mpi( s, &grp->N ) >= 0 ) 620 { 621 ret = MBEDTLS_ERR_ECP_VERIFY_FAILED; 622 goto cleanup; 623 } 624 625 /* 626 * Step 3: derive MPI from hashed message 627 */ 628 MBEDTLS_MPI_CHK( derive_mpi( grp, &e, buf, blen ) ); 629 630 /* 631 * Step 4: u1 = e / s mod n, u2 = r / s mod n 632 */ 633 ECDSA_BUDGET( MBEDTLS_ECP_OPS_CHK + MBEDTLS_ECP_OPS_INV + 2 ); 634 635 MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( &s_inv, s, &grp->N ) ); 636 637 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( pu1, &e, &s_inv ) ); 638 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( pu1, pu1, &grp->N ) ); 639 640 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( pu2, r, &s_inv ) ); 641 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( pu2, pu2, &grp->N ) ); 642 643 #if defined(MBEDTLS_ECP_RESTARTABLE) 644 if( rs_ctx != NULL && rs_ctx->ver != NULL ) 645 rs_ctx->ver->state = ecdsa_ver_muladd; 646 647 muladd: 648 #endif 649 /* 650 * Step 5: R = u1 G + u2 Q 651 */ 652 MBEDTLS_MPI_CHK( mbedtls_ecp_muladd_restartable( grp, 653 &R, pu1, &grp->G, pu2, Q, ECDSA_RS_ECP ) ); 654 655 if( mbedtls_ecp_is_zero( &R ) ) 656 { 657 ret = MBEDTLS_ERR_ECP_VERIFY_FAILED; 658 goto cleanup; 659 } 660 661 /* 662 * Step 6: convert xR to an integer (no-op) 663 * Step 7: reduce xR mod n (gives v) 664 */ 665 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &R.X, &R.X, &grp->N ) ); 666 667 /* 668 * Step 8: check if v (that is, R.X) is equal to r 669 */ 670 if( mbedtls_mpi_cmp_mpi( &R.X, r ) != 0 ) 671 { 672 ret = MBEDTLS_ERR_ECP_VERIFY_FAILED; 673 goto cleanup; 674 } 675 676 cleanup: 677 mbedtls_ecp_point_free( &R ); 678 mbedtls_mpi_free( &e ); mbedtls_mpi_free( &s_inv ); 679 mbedtls_mpi_free( &u1 ); mbedtls_mpi_free( &u2 ); 680 681 ECDSA_RS_LEAVE( ver ); 682 683 return( ret ); 684 } 685 686 /* 687 * Verify ECDSA signature of hashed message 688 */ 689 int mbedtls_ecdsa_verify( mbedtls_ecp_group *grp, 690 const unsigned char *buf, size_t blen, 691 const mbedtls_ecp_point *Q, 692 const mbedtls_mpi *r, 693 const mbedtls_mpi *s) 694 { 695 ECDSA_VALIDATE_RET( grp != NULL ); 696 ECDSA_VALIDATE_RET( Q != NULL ); 697 ECDSA_VALIDATE_RET( r != NULL ); 698 ECDSA_VALIDATE_RET( s != NULL ); 699 ECDSA_VALIDATE_RET( buf != NULL || blen == 0 ); 700 701 return( ecdsa_verify_restartable( grp, buf, blen, Q, r, s, NULL ) ); 702 } 703 #endif /* !MBEDTLS_ECDSA_VERIFY_ALT */ 704 705 /* 706 * Convert a signature (given by context) to ASN.1 707 */ 708 static int ecdsa_signature_to_asn1( const mbedtls_mpi *r, const mbedtls_mpi *s, 709 unsigned char *sig, size_t *slen ) 710 { 711 int ret; 712 unsigned char buf[MBEDTLS_ECDSA_MAX_LEN]; 713 unsigned char *p = buf + sizeof( buf ); 714 size_t len = 0; 715 716 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &p, buf, s ) ); 717 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &p, buf, r ) ); 718 719 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &p, buf, len ) ); 720 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &p, buf, 721 MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ); 722 723 memcpy( sig, p, len ); 724 *slen = len; 725 726 return( 0 ); 727 } 728 729 /* 730 * Compute and write signature 731 */ 732 int mbedtls_ecdsa_write_signature_restartable( mbedtls_ecdsa_context *ctx, 733 mbedtls_md_type_t md_alg, 734 const unsigned char *hash, size_t hlen, 735 unsigned char *sig, size_t *slen, 736 int (*f_rng)(void *, unsigned char *, size_t), 737 void *p_rng, 738 mbedtls_ecdsa_restart_ctx *rs_ctx ) 739 { 740 int ret; 741 mbedtls_mpi r, s; 742 ECDSA_VALIDATE_RET( ctx != NULL ); 743 ECDSA_VALIDATE_RET( hash != NULL ); 744 ECDSA_VALIDATE_RET( sig != NULL ); 745 ECDSA_VALIDATE_RET( slen != NULL ); 746 747 mbedtls_mpi_init( &r ); 748 mbedtls_mpi_init( &s ); 749 750 #if defined(MBEDTLS_ECDSA_DETERMINISTIC) 751 MBEDTLS_MPI_CHK( ecdsa_sign_det_restartable( &ctx->grp, &r, &s, &ctx->d, 752 hash, hlen, md_alg, f_rng, 753 p_rng, rs_ctx ) ); 754 #else 755 (void) md_alg; 756 757 #if defined(MBEDTLS_ECDSA_SIGN_ALT) 758 MBEDTLS_MPI_CHK( mbedtls_ecdsa_sign( &ctx->grp, &r, &s, &ctx->d, 759 hash, hlen, f_rng, p_rng ) ); 760 #else 761 /* Use the same RNG for both blinding and ephemeral key generation */ 762 MBEDTLS_MPI_CHK( ecdsa_sign_restartable( &ctx->grp, &r, &s, &ctx->d, 763 hash, hlen, f_rng, p_rng, f_rng, 764 p_rng, rs_ctx ) ); 765 #endif /* MBEDTLS_ECDSA_SIGN_ALT */ 766 #endif /* MBEDTLS_ECDSA_DETERMINISTIC */ 767 768 MBEDTLS_MPI_CHK( ecdsa_signature_to_asn1( &r, &s, sig, slen ) ); 769 770 cleanup: 771 mbedtls_mpi_free( &r ); 772 mbedtls_mpi_free( &s ); 773 774 return( ret ); 775 } 776 777 /* 778 * Compute and write signature 779 */ 780 int mbedtls_ecdsa_write_signature( mbedtls_ecdsa_context *ctx, 781 mbedtls_md_type_t md_alg, 782 const unsigned char *hash, size_t hlen, 783 unsigned char *sig, size_t *slen, 784 int (*f_rng)(void *, unsigned char *, size_t), 785 void *p_rng ) 786 { 787 ECDSA_VALIDATE_RET( ctx != NULL ); 788 ECDSA_VALIDATE_RET( hash != NULL ); 789 ECDSA_VALIDATE_RET( sig != NULL ); 790 ECDSA_VALIDATE_RET( slen != NULL ); 791 return( mbedtls_ecdsa_write_signature_restartable( 792 ctx, md_alg, hash, hlen, sig, slen, f_rng, p_rng, NULL ) ); 793 } 794 795 #if !defined(MBEDTLS_DEPRECATED_REMOVED) && \ 796 defined(MBEDTLS_ECDSA_DETERMINISTIC) 797 int mbedtls_ecdsa_write_signature_det( mbedtls_ecdsa_context *ctx, 798 const unsigned char *hash, size_t hlen, 799 unsigned char *sig, size_t *slen, 800 mbedtls_md_type_t md_alg ) 801 { 802 ECDSA_VALIDATE_RET( ctx != NULL ); 803 ECDSA_VALIDATE_RET( hash != NULL ); 804 ECDSA_VALIDATE_RET( sig != NULL ); 805 ECDSA_VALIDATE_RET( slen != NULL ); 806 return( mbedtls_ecdsa_write_signature( ctx, md_alg, hash, hlen, sig, slen, 807 NULL, NULL ) ); 808 } 809 #endif 810 811 /* 812 * Read and check signature 813 */ 814 int mbedtls_ecdsa_read_signature( mbedtls_ecdsa_context *ctx, 815 const unsigned char *hash, size_t hlen, 816 const unsigned char *sig, size_t slen ) 817 { 818 ECDSA_VALIDATE_RET( ctx != NULL ); 819 ECDSA_VALIDATE_RET( hash != NULL ); 820 ECDSA_VALIDATE_RET( sig != NULL ); 821 return( mbedtls_ecdsa_read_signature_restartable( 822 ctx, hash, hlen, sig, slen, NULL ) ); 823 } 824 825 /* 826 * Restartable read and check signature 827 */ 828 int mbedtls_ecdsa_read_signature_restartable( mbedtls_ecdsa_context *ctx, 829 const unsigned char *hash, size_t hlen, 830 const unsigned char *sig, size_t slen, 831 mbedtls_ecdsa_restart_ctx *rs_ctx ) 832 { 833 int ret; 834 unsigned char *p = (unsigned char *) sig; 835 const unsigned char *end = sig + slen; 836 size_t len; 837 mbedtls_mpi r, s; 838 ECDSA_VALIDATE_RET( ctx != NULL ); 839 ECDSA_VALIDATE_RET( hash != NULL ); 840 ECDSA_VALIDATE_RET( sig != NULL ); 841 842 mbedtls_mpi_init( &r ); 843 mbedtls_mpi_init( &s ); 844 845 if( ( ret = mbedtls_asn1_get_tag( &p, end, &len, 846 MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 ) 847 { 848 ret += MBEDTLS_ERR_ECP_BAD_INPUT_DATA; 849 goto cleanup; 850 } 851 852 if( p + len != end ) 853 { 854 ret = MBEDTLS_ERR_ECP_BAD_INPUT_DATA + 855 MBEDTLS_ERR_ASN1_LENGTH_MISMATCH; 856 goto cleanup; 857 } 858 859 if( ( ret = mbedtls_asn1_get_mpi( &p, end, &r ) ) != 0 || 860 ( ret = mbedtls_asn1_get_mpi( &p, end, &s ) ) != 0 ) 861 { 862 ret += MBEDTLS_ERR_ECP_BAD_INPUT_DATA; 863 goto cleanup; 864 } 865 #if defined(MBEDTLS_ECDSA_VERIFY_ALT) 866 if( ( ret = mbedtls_ecdsa_verify( &ctx->grp, hash, hlen, 867 &ctx->Q, &r, &s ) ) != 0 ) 868 goto cleanup; 869 #else 870 if( ( ret = ecdsa_verify_restartable( &ctx->grp, hash, hlen, 871 &ctx->Q, &r, &s, rs_ctx ) ) != 0 ) 872 goto cleanup; 873 #endif /* MBEDTLS_ECDSA_VERIFY_ALT */ 874 875 /* At this point we know that the buffer starts with a valid signature. 876 * Return 0 if the buffer just contains the signature, and a specific 877 * error code if the valid signature is followed by more data. */ 878 if( p != end ) 879 ret = MBEDTLS_ERR_ECP_SIG_LEN_MISMATCH; 880 881 cleanup: 882 mbedtls_mpi_free( &r ); 883 mbedtls_mpi_free( &s ); 884 885 return( ret ); 886 } 887 888 #if !defined(MBEDTLS_ECDSA_GENKEY_ALT) 889 /* 890 * Generate key pair 891 */ 892 int mbedtls_ecdsa_genkey( mbedtls_ecdsa_context *ctx, mbedtls_ecp_group_id gid, 893 int (*f_rng)(void *, unsigned char *, size_t), void *p_rng ) 894 { 895 int ret = 0; 896 ECDSA_VALIDATE_RET( ctx != NULL ); 897 ECDSA_VALIDATE_RET( f_rng != NULL ); 898 899 ret = mbedtls_ecp_group_load( &ctx->grp, gid ); 900 if( ret != 0 ) 901 return( ret ); 902 903 return( mbedtls_ecp_gen_keypair( &ctx->grp, &ctx->d, 904 &ctx->Q, f_rng, p_rng ) ); 905 } 906 #endif /* !MBEDTLS_ECDSA_GENKEY_ALT */ 907 908 /* 909 * Set context from an mbedtls_ecp_keypair 910 */ 911 int mbedtls_ecdsa_from_keypair( mbedtls_ecdsa_context *ctx, const mbedtls_ecp_keypair *key ) 912 { 913 int ret; 914 ECDSA_VALIDATE_RET( ctx != NULL ); 915 ECDSA_VALIDATE_RET( key != NULL ); 916 917 if( ( ret = mbedtls_ecp_group_copy( &ctx->grp, &key->grp ) ) != 0 || 918 ( ret = mbedtls_mpi_copy( &ctx->d, &key->d ) ) != 0 || 919 ( ret = mbedtls_ecp_copy( &ctx->Q, &key->Q ) ) != 0 ) 920 { 921 mbedtls_ecdsa_free( ctx ); 922 } 923 924 return( ret ); 925 } 926 927 /* 928 * Initialize context 929 */ 930 void mbedtls_ecdsa_init( mbedtls_ecdsa_context *ctx ) 931 { 932 ECDSA_VALIDATE( ctx != NULL ); 933 934 mbedtls_ecp_keypair_init( ctx ); 935 } 936 937 /* 938 * Free context 939 */ 940 void mbedtls_ecdsa_free( mbedtls_ecdsa_context *ctx ) 941 { 942 if( ctx == NULL ) 943 return; 944 945 mbedtls_ecp_keypair_free( ctx ); 946 } 947 948 #if defined(MBEDTLS_ECP_RESTARTABLE) 949 /* 950 * Initialize a restart context 951 */ 952 void mbedtls_ecdsa_restart_init( mbedtls_ecdsa_restart_ctx *ctx ) 953 { 954 ECDSA_VALIDATE( ctx != NULL ); 955 956 mbedtls_ecp_restart_init( &ctx->ecp ); 957 958 ctx->ver = NULL; 959 ctx->sig = NULL; 960 #if defined(MBEDTLS_ECDSA_DETERMINISTIC) 961 ctx->det = NULL; 962 #endif 963 } 964 965 /* 966 * Free the components of a restart context 967 */ 968 void mbedtls_ecdsa_restart_free( mbedtls_ecdsa_restart_ctx *ctx ) 969 { 970 if( ctx == NULL ) 971 return; 972 973 mbedtls_ecp_restart_free( &ctx->ecp ); 974 975 ecdsa_restart_ver_free( ctx->ver ); 976 mbedtls_free( ctx->ver ); 977 ctx->ver = NULL; 978 979 ecdsa_restart_sig_free( ctx->sig ); 980 mbedtls_free( ctx->sig ); 981 ctx->sig = NULL; 982 983 #if defined(MBEDTLS_ECDSA_DETERMINISTIC) 984 ecdsa_restart_det_free( ctx->det ); 985 mbedtls_free( ctx->det ); 986 ctx->det = NULL; 987 #endif 988 } 989 #endif /* MBEDTLS_ECP_RESTARTABLE */ 990 991 #endif /* MBEDTLS_ECDSA_C */ 992