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->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, &rs_ctx->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 mbedtls_ecdsa_restart_ctx *rs_ctx ) 258 { 259 int ret, key_tries, sign_tries; 260 int *p_sign_tries = &sign_tries, *p_key_tries = &key_tries; 261 mbedtls_ecp_point R; 262 mbedtls_mpi k, e, t; 263 mbedtls_mpi *pk = &k, *pr = r; 264 265 /* Fail cleanly on curves such as Curve25519 that can't be used for ECDSA */ 266 if( grp->N.p == NULL ) 267 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA ); 268 269 /* Make sure d is in range 1..n-1 */ 270 if( mbedtls_mpi_cmp_int( d, 1 ) < 0 || mbedtls_mpi_cmp_mpi( d, &grp->N ) >= 0 ) 271 return( MBEDTLS_ERR_ECP_INVALID_KEY ); 272 273 mbedtls_ecp_point_init( &R ); 274 mbedtls_mpi_init( &k ); mbedtls_mpi_init( &e ); mbedtls_mpi_init( &t ); 275 276 ECDSA_RS_ENTER( sig ); 277 278 #if defined(MBEDTLS_ECP_RESTARTABLE) 279 if( rs_ctx != NULL && rs_ctx->sig != NULL ) 280 { 281 /* redirect to our context */ 282 p_sign_tries = &rs_ctx->sig->sign_tries; 283 p_key_tries = &rs_ctx->sig->key_tries; 284 pk = &rs_ctx->sig->k; 285 pr = &rs_ctx->sig->r; 286 287 /* jump to current step */ 288 if( rs_ctx->sig->state == ecdsa_sig_mul ) 289 goto mul; 290 if( rs_ctx->sig->state == ecdsa_sig_modn ) 291 goto modn; 292 } 293 #endif /* MBEDTLS_ECP_RESTARTABLE */ 294 295 *p_sign_tries = 0; 296 do 297 { 298 if( *p_sign_tries++ > 10 ) 299 { 300 ret = MBEDTLS_ERR_ECP_RANDOM_FAILED; 301 goto cleanup; 302 } 303 304 /* 305 * Steps 1-3: generate a suitable ephemeral keypair 306 * and set r = xR mod n 307 */ 308 *p_key_tries = 0; 309 do 310 { 311 if( *p_key_tries++ > 10 ) 312 { 313 ret = MBEDTLS_ERR_ECP_RANDOM_FAILED; 314 goto cleanup; 315 } 316 317 MBEDTLS_MPI_CHK( mbedtls_ecp_gen_privkey( grp, pk, f_rng, p_rng ) ); 318 319 #if defined(MBEDTLS_ECP_RESTARTABLE) 320 if( rs_ctx != NULL && rs_ctx->sig != NULL ) 321 rs_ctx->sig->state = ecdsa_sig_mul; 322 323 mul: 324 #endif 325 MBEDTLS_MPI_CHK( mbedtls_ecp_mul_restartable( grp, &R, pk, &grp->G, 326 f_rng, p_rng, ECDSA_RS_ECP ) ); 327 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( pr, &R.X, &grp->N ) ); 328 } 329 while( mbedtls_mpi_cmp_int( pr, 0 ) == 0 ); 330 331 #if defined(MBEDTLS_ECP_RESTARTABLE) 332 if( rs_ctx != NULL && rs_ctx->sig != NULL ) 333 rs_ctx->sig->state = ecdsa_sig_modn; 334 335 modn: 336 #endif 337 /* 338 * Accounting for everything up to the end of the loop 339 * (step 6, but checking now avoids saving e and t) 340 */ 341 ECDSA_BUDGET( MBEDTLS_ECP_OPS_INV + 4 ); 342 343 /* 344 * Step 5: derive MPI from hashed message 345 */ 346 MBEDTLS_MPI_CHK( derive_mpi( grp, &e, buf, blen ) ); 347 348 /* 349 * Generate a random value to blind inv_mod in next step, 350 * avoiding a potential timing leak. 351 */ 352 MBEDTLS_MPI_CHK( mbedtls_ecp_gen_privkey( grp, &t, f_rng, p_rng ) ); 353 354 /* 355 * Step 6: compute s = (e + r * d) / k = t (e + rd) / (kt) mod n 356 */ 357 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( s, pr, d ) ); 358 MBEDTLS_MPI_CHK( mbedtls_mpi_add_mpi( &e, &e, s ) ); 359 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &e, &e, &t ) ); 360 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( pk, pk, &t ) ); 361 MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( s, pk, &grp->N ) ); 362 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( s, s, &e ) ); 363 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( s, s, &grp->N ) ); 364 } 365 while( mbedtls_mpi_cmp_int( s, 0 ) == 0 ); 366 367 #if defined(MBEDTLS_ECP_RESTARTABLE) 368 if( rs_ctx != NULL && rs_ctx->sig != NULL ) 369 mbedtls_mpi_copy( r, pr ); 370 #endif 371 372 cleanup: 373 mbedtls_ecp_point_free( &R ); 374 mbedtls_mpi_free( &k ); mbedtls_mpi_free( &e ); mbedtls_mpi_free( &t ); 375 376 ECDSA_RS_LEAVE( sig ); 377 378 return( ret ); 379 } 380 381 /* 382 * Compute ECDSA signature of a hashed message 383 */ 384 int mbedtls_ecdsa_sign( mbedtls_ecp_group *grp, mbedtls_mpi *r, mbedtls_mpi *s, 385 const mbedtls_mpi *d, const unsigned char *buf, size_t blen, 386 int (*f_rng)(void *, unsigned char *, size_t), void *p_rng ) 387 { 388 ECDSA_VALIDATE_RET( grp != NULL ); 389 ECDSA_VALIDATE_RET( r != NULL ); 390 ECDSA_VALIDATE_RET( s != NULL ); 391 ECDSA_VALIDATE_RET( d != NULL ); 392 ECDSA_VALIDATE_RET( f_rng != NULL ); 393 ECDSA_VALIDATE_RET( buf != NULL || blen == 0 ); 394 395 return( ecdsa_sign_restartable( grp, r, s, d, buf, blen, 396 f_rng, p_rng, NULL ) ); 397 } 398 #endif /* !MBEDTLS_ECDSA_SIGN_ALT */ 399 400 #if defined(MBEDTLS_ECDSA_DETERMINISTIC) 401 /* 402 * Deterministic signature wrapper 403 */ 404 static int ecdsa_sign_det_restartable( mbedtls_ecp_group *grp, 405 mbedtls_mpi *r, mbedtls_mpi *s, 406 const mbedtls_mpi *d, const unsigned char *buf, size_t blen, 407 mbedtls_md_type_t md_alg, 408 mbedtls_ecdsa_restart_ctx *rs_ctx ) 409 { 410 int ret; 411 mbedtls_hmac_drbg_context rng_ctx; 412 mbedtls_hmac_drbg_context *p_rng = &rng_ctx; 413 unsigned char data[2 * MBEDTLS_ECP_MAX_BYTES]; 414 size_t grp_len = ( grp->nbits + 7 ) / 8; 415 const mbedtls_md_info_t *md_info; 416 mbedtls_mpi h; 417 418 if( ( md_info = mbedtls_md_info_from_type( md_alg ) ) == NULL ) 419 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA ); 420 421 mbedtls_mpi_init( &h ); 422 mbedtls_hmac_drbg_init( &rng_ctx ); 423 424 ECDSA_RS_ENTER( det ); 425 426 #if defined(MBEDTLS_ECP_RESTARTABLE) 427 if( rs_ctx != NULL && rs_ctx->det != NULL ) 428 { 429 /* redirect to our context */ 430 p_rng = &rs_ctx->det->rng_ctx; 431 432 /* jump to current step */ 433 if( rs_ctx->det->state == ecdsa_det_sign ) 434 goto sign; 435 } 436 #endif /* MBEDTLS_ECP_RESTARTABLE */ 437 438 /* Use private key and message hash (reduced) to initialize HMAC_DRBG */ 439 MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( d, data, grp_len ) ); 440 MBEDTLS_MPI_CHK( derive_mpi( grp, &h, buf, blen ) ); 441 MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &h, data + grp_len, grp_len ) ); 442 mbedtls_hmac_drbg_seed_buf( p_rng, md_info, data, 2 * grp_len ); 443 444 #if defined(MBEDTLS_ECP_RESTARTABLE) 445 if( rs_ctx != NULL && rs_ctx->det != NULL ) 446 rs_ctx->det->state = ecdsa_det_sign; 447 448 sign: 449 #endif 450 #if defined(MBEDTLS_ECDSA_SIGN_ALT) 451 ret = mbedtls_ecdsa_sign( grp, r, s, d, buf, blen, 452 mbedtls_hmac_drbg_random, p_rng ); 453 #else 454 ret = ecdsa_sign_restartable( grp, r, s, d, buf, blen, 455 mbedtls_hmac_drbg_random, p_rng, rs_ctx ); 456 #endif /* MBEDTLS_ECDSA_SIGN_ALT */ 457 458 cleanup: 459 mbedtls_hmac_drbg_free( &rng_ctx ); 460 mbedtls_mpi_free( &h ); 461 462 ECDSA_RS_LEAVE( det ); 463 464 return( ret ); 465 } 466 467 /* 468 * Deterministic signature wrapper 469 */ 470 int mbedtls_ecdsa_sign_det( mbedtls_ecp_group *grp, mbedtls_mpi *r, mbedtls_mpi *s, 471 const mbedtls_mpi *d, const unsigned char *buf, size_t blen, 472 mbedtls_md_type_t md_alg ) 473 { 474 ECDSA_VALIDATE_RET( grp != NULL ); 475 ECDSA_VALIDATE_RET( r != NULL ); 476 ECDSA_VALIDATE_RET( s != NULL ); 477 ECDSA_VALIDATE_RET( d != NULL ); 478 ECDSA_VALIDATE_RET( buf != NULL || blen == 0 ); 479 480 return( ecdsa_sign_det_restartable( grp, r, s, d, buf, blen, md_alg, NULL ) ); 481 } 482 #endif /* MBEDTLS_ECDSA_DETERMINISTIC */ 483 484 #if !defined(MBEDTLS_ECDSA_VERIFY_ALT) 485 /* 486 * Verify ECDSA signature of hashed message (SEC1 4.1.4) 487 * Obviously, compared to SEC1 4.1.3, we skip step 2 (hash message) 488 */ 489 static int ecdsa_verify_restartable( mbedtls_ecp_group *grp, 490 const unsigned char *buf, size_t blen, 491 const mbedtls_ecp_point *Q, 492 const mbedtls_mpi *r, const mbedtls_mpi *s, 493 mbedtls_ecdsa_restart_ctx *rs_ctx ) 494 { 495 int ret; 496 mbedtls_mpi e, s_inv, u1, u2; 497 mbedtls_ecp_point R; 498 mbedtls_mpi *pu1 = &u1, *pu2 = &u2; 499 500 mbedtls_ecp_point_init( &R ); 501 mbedtls_mpi_init( &e ); mbedtls_mpi_init( &s_inv ); 502 mbedtls_mpi_init( &u1 ); mbedtls_mpi_init( &u2 ); 503 504 /* Fail cleanly on curves such as Curve25519 that can't be used for ECDSA */ 505 if( grp->N.p == NULL ) 506 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA ); 507 508 ECDSA_RS_ENTER( ver ); 509 510 #if defined(MBEDTLS_ECP_RESTARTABLE) 511 if( rs_ctx != NULL && rs_ctx->ver != NULL ) 512 { 513 /* redirect to our context */ 514 pu1 = &rs_ctx->ver->u1; 515 pu2 = &rs_ctx->ver->u2; 516 517 /* jump to current step */ 518 if( rs_ctx->ver->state == ecdsa_ver_muladd ) 519 goto muladd; 520 } 521 #endif /* MBEDTLS_ECP_RESTARTABLE */ 522 523 /* 524 * Step 1: make sure r and s are in range 1..n-1 525 */ 526 if( mbedtls_mpi_cmp_int( r, 1 ) < 0 || mbedtls_mpi_cmp_mpi( r, &grp->N ) >= 0 || 527 mbedtls_mpi_cmp_int( s, 1 ) < 0 || mbedtls_mpi_cmp_mpi( s, &grp->N ) >= 0 ) 528 { 529 ret = MBEDTLS_ERR_ECP_VERIFY_FAILED; 530 goto cleanup; 531 } 532 533 /* 534 * Step 3: derive MPI from hashed message 535 */ 536 MBEDTLS_MPI_CHK( derive_mpi( grp, &e, buf, blen ) ); 537 538 /* 539 * Step 4: u1 = e / s mod n, u2 = r / s mod n 540 */ 541 ECDSA_BUDGET( MBEDTLS_ECP_OPS_CHK + MBEDTLS_ECP_OPS_INV + 2 ); 542 543 MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( &s_inv, s, &grp->N ) ); 544 545 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( pu1, &e, &s_inv ) ); 546 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( pu1, pu1, &grp->N ) ); 547 548 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( pu2, r, &s_inv ) ); 549 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( pu2, pu2, &grp->N ) ); 550 551 #if defined(MBEDTLS_ECP_RESTARTABLE) 552 if( rs_ctx != NULL && rs_ctx->ver != NULL ) 553 rs_ctx->ver->state = ecdsa_ver_muladd; 554 555 muladd: 556 #endif 557 /* 558 * Step 5: R = u1 G + u2 Q 559 */ 560 MBEDTLS_MPI_CHK( mbedtls_ecp_muladd_restartable( grp, 561 &R, pu1, &grp->G, pu2, Q, ECDSA_RS_ECP ) ); 562 563 if( mbedtls_ecp_is_zero( &R ) ) 564 { 565 ret = MBEDTLS_ERR_ECP_VERIFY_FAILED; 566 goto cleanup; 567 } 568 569 /* 570 * Step 6: convert xR to an integer (no-op) 571 * Step 7: reduce xR mod n (gives v) 572 */ 573 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &R.X, &R.X, &grp->N ) ); 574 575 /* 576 * Step 8: check if v (that is, R.X) is equal to r 577 */ 578 if( mbedtls_mpi_cmp_mpi( &R.X, r ) != 0 ) 579 { 580 ret = MBEDTLS_ERR_ECP_VERIFY_FAILED; 581 goto cleanup; 582 } 583 584 cleanup: 585 mbedtls_ecp_point_free( &R ); 586 mbedtls_mpi_free( &e ); mbedtls_mpi_free( &s_inv ); 587 mbedtls_mpi_free( &u1 ); mbedtls_mpi_free( &u2 ); 588 589 ECDSA_RS_LEAVE( ver ); 590 591 return( ret ); 592 } 593 594 /* 595 * Verify ECDSA signature of hashed message 596 */ 597 int mbedtls_ecdsa_verify( mbedtls_ecp_group *grp, 598 const unsigned char *buf, size_t blen, 599 const mbedtls_ecp_point *Q, 600 const mbedtls_mpi *r, 601 const mbedtls_mpi *s) 602 { 603 ECDSA_VALIDATE_RET( grp != NULL ); 604 ECDSA_VALIDATE_RET( Q != NULL ); 605 ECDSA_VALIDATE_RET( r != NULL ); 606 ECDSA_VALIDATE_RET( s != NULL ); 607 ECDSA_VALIDATE_RET( buf != NULL || blen == 0 ); 608 609 return( ecdsa_verify_restartable( grp, buf, blen, Q, r, s, NULL ) ); 610 } 611 #endif /* !MBEDTLS_ECDSA_VERIFY_ALT */ 612 613 /* 614 * Convert a signature (given by context) to ASN.1 615 */ 616 static int ecdsa_signature_to_asn1( const mbedtls_mpi *r, const mbedtls_mpi *s, 617 unsigned char *sig, size_t *slen ) 618 { 619 int ret; 620 unsigned char buf[MBEDTLS_ECDSA_MAX_LEN]; 621 unsigned char *p = buf + sizeof( buf ); 622 size_t len = 0; 623 624 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &p, buf, s ) ); 625 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &p, buf, r ) ); 626 627 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &p, buf, len ) ); 628 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &p, buf, 629 MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ); 630 631 memcpy( sig, p, len ); 632 *slen = len; 633 634 return( 0 ); 635 } 636 637 /* 638 * Compute and write signature 639 */ 640 int mbedtls_ecdsa_write_signature_restartable( mbedtls_ecdsa_context *ctx, 641 mbedtls_md_type_t md_alg, 642 const unsigned char *hash, size_t hlen, 643 unsigned char *sig, size_t *slen, 644 int (*f_rng)(void *, unsigned char *, size_t), 645 void *p_rng, 646 mbedtls_ecdsa_restart_ctx *rs_ctx ) 647 { 648 int ret; 649 mbedtls_mpi r, s; 650 ECDSA_VALIDATE_RET( ctx != NULL ); 651 ECDSA_VALIDATE_RET( hash != NULL ); 652 ECDSA_VALIDATE_RET( sig != NULL ); 653 ECDSA_VALIDATE_RET( slen != NULL ); 654 655 mbedtls_mpi_init( &r ); 656 mbedtls_mpi_init( &s ); 657 658 #if defined(MBEDTLS_ECDSA_DETERMINISTIC) 659 (void) f_rng; 660 (void) p_rng; 661 662 MBEDTLS_MPI_CHK( ecdsa_sign_det_restartable( &ctx->grp, &r, &s, &ctx->d, 663 hash, hlen, md_alg, rs_ctx ) ); 664 #else 665 (void) md_alg; 666 667 #if defined(MBEDTLS_ECDSA_SIGN_ALT) 668 MBEDTLS_MPI_CHK( mbedtls_ecdsa_sign( &ctx->grp, &r, &s, &ctx->d, 669 hash, hlen, f_rng, p_rng ) ); 670 #else 671 MBEDTLS_MPI_CHK( ecdsa_sign_restartable( &ctx->grp, &r, &s, &ctx->d, 672 hash, hlen, f_rng, p_rng, rs_ctx ) ); 673 #endif /* MBEDTLS_ECDSA_SIGN_ALT */ 674 #endif /* MBEDTLS_ECDSA_DETERMINISTIC */ 675 676 MBEDTLS_MPI_CHK( ecdsa_signature_to_asn1( &r, &s, sig, slen ) ); 677 678 cleanup: 679 mbedtls_mpi_free( &r ); 680 mbedtls_mpi_free( &s ); 681 682 return( ret ); 683 } 684 685 /* 686 * Compute and write signature 687 */ 688 int mbedtls_ecdsa_write_signature( mbedtls_ecdsa_context *ctx, 689 mbedtls_md_type_t md_alg, 690 const unsigned char *hash, size_t hlen, 691 unsigned char *sig, size_t *slen, 692 int (*f_rng)(void *, unsigned char *, size_t), 693 void *p_rng ) 694 { 695 ECDSA_VALIDATE_RET( ctx != NULL ); 696 ECDSA_VALIDATE_RET( hash != NULL ); 697 ECDSA_VALIDATE_RET( sig != NULL ); 698 ECDSA_VALIDATE_RET( slen != NULL ); 699 return( mbedtls_ecdsa_write_signature_restartable( 700 ctx, md_alg, hash, hlen, sig, slen, f_rng, p_rng, NULL ) ); 701 } 702 703 #if !defined(MBEDTLS_DEPRECATED_REMOVED) && \ 704 defined(MBEDTLS_ECDSA_DETERMINISTIC) 705 int mbedtls_ecdsa_write_signature_det( mbedtls_ecdsa_context *ctx, 706 const unsigned char *hash, size_t hlen, 707 unsigned char *sig, size_t *slen, 708 mbedtls_md_type_t md_alg ) 709 { 710 ECDSA_VALIDATE_RET( ctx != NULL ); 711 ECDSA_VALIDATE_RET( hash != NULL ); 712 ECDSA_VALIDATE_RET( sig != NULL ); 713 ECDSA_VALIDATE_RET( slen != NULL ); 714 return( mbedtls_ecdsa_write_signature( ctx, md_alg, hash, hlen, sig, slen, 715 NULL, NULL ) ); 716 } 717 #endif 718 719 /* 720 * Read and check signature 721 */ 722 int mbedtls_ecdsa_read_signature( mbedtls_ecdsa_context *ctx, 723 const unsigned char *hash, size_t hlen, 724 const unsigned char *sig, size_t slen ) 725 { 726 ECDSA_VALIDATE_RET( ctx != NULL ); 727 ECDSA_VALIDATE_RET( hash != NULL ); 728 ECDSA_VALIDATE_RET( sig != NULL ); 729 return( mbedtls_ecdsa_read_signature_restartable( 730 ctx, hash, hlen, sig, slen, NULL ) ); 731 } 732 733 /* 734 * Restartable read and check signature 735 */ 736 int mbedtls_ecdsa_read_signature_restartable( mbedtls_ecdsa_context *ctx, 737 const unsigned char *hash, size_t hlen, 738 const unsigned char *sig, size_t slen, 739 mbedtls_ecdsa_restart_ctx *rs_ctx ) 740 { 741 int ret; 742 unsigned char *p = (unsigned char *) sig; 743 const unsigned char *end = sig + slen; 744 size_t len; 745 mbedtls_mpi r, s; 746 ECDSA_VALIDATE_RET( ctx != NULL ); 747 ECDSA_VALIDATE_RET( hash != NULL ); 748 ECDSA_VALIDATE_RET( sig != NULL ); 749 750 mbedtls_mpi_init( &r ); 751 mbedtls_mpi_init( &s ); 752 753 if( ( ret = mbedtls_asn1_get_tag( &p, end, &len, 754 MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 ) 755 { 756 ret += MBEDTLS_ERR_ECP_BAD_INPUT_DATA; 757 goto cleanup; 758 } 759 760 if( p + len != end ) 761 { 762 ret = MBEDTLS_ERR_ECP_BAD_INPUT_DATA + 763 MBEDTLS_ERR_ASN1_LENGTH_MISMATCH; 764 goto cleanup; 765 } 766 767 if( ( ret = mbedtls_asn1_get_mpi( &p, end, &r ) ) != 0 || 768 ( ret = mbedtls_asn1_get_mpi( &p, end, &s ) ) != 0 ) 769 { 770 ret += MBEDTLS_ERR_ECP_BAD_INPUT_DATA; 771 goto cleanup; 772 } 773 #if defined(MBEDTLS_ECDSA_VERIFY_ALT) 774 if( ( ret = mbedtls_ecdsa_verify( &ctx->grp, hash, hlen, 775 &ctx->Q, &r, &s ) ) != 0 ) 776 goto cleanup; 777 #else 778 if( ( ret = ecdsa_verify_restartable( &ctx->grp, hash, hlen, 779 &ctx->Q, &r, &s, rs_ctx ) ) != 0 ) 780 goto cleanup; 781 #endif /* MBEDTLS_ECDSA_VERIFY_ALT */ 782 783 /* At this point we know that the buffer starts with a valid signature. 784 * Return 0 if the buffer just contains the signature, and a specific 785 * error code if the valid signature is followed by more data. */ 786 if( p != end ) 787 ret = MBEDTLS_ERR_ECP_SIG_LEN_MISMATCH; 788 789 cleanup: 790 mbedtls_mpi_free( &r ); 791 mbedtls_mpi_free( &s ); 792 793 return( ret ); 794 } 795 796 #if !defined(MBEDTLS_ECDSA_GENKEY_ALT) 797 /* 798 * Generate key pair 799 */ 800 int mbedtls_ecdsa_genkey( mbedtls_ecdsa_context *ctx, mbedtls_ecp_group_id gid, 801 int (*f_rng)(void *, unsigned char *, size_t), void *p_rng ) 802 { 803 ECDSA_VALIDATE_RET( ctx != NULL ); 804 ECDSA_VALIDATE_RET( f_rng != NULL ); 805 806 return( mbedtls_ecp_group_load( &ctx->grp, gid ) || 807 mbedtls_ecp_gen_keypair( &ctx->grp, &ctx->d, &ctx->Q, f_rng, p_rng ) ); 808 } 809 #endif /* !MBEDTLS_ECDSA_GENKEY_ALT */ 810 811 /* 812 * Set context from an mbedtls_ecp_keypair 813 */ 814 int mbedtls_ecdsa_from_keypair( mbedtls_ecdsa_context *ctx, const mbedtls_ecp_keypair *key ) 815 { 816 int ret; 817 ECDSA_VALIDATE_RET( ctx != NULL ); 818 ECDSA_VALIDATE_RET( key != NULL ); 819 820 if( ( ret = mbedtls_ecp_group_copy( &ctx->grp, &key->grp ) ) != 0 || 821 ( ret = mbedtls_mpi_copy( &ctx->d, &key->d ) ) != 0 || 822 ( ret = mbedtls_ecp_copy( &ctx->Q, &key->Q ) ) != 0 ) 823 { 824 mbedtls_ecdsa_free( ctx ); 825 } 826 827 return( ret ); 828 } 829 830 /* 831 * Initialize context 832 */ 833 void mbedtls_ecdsa_init( mbedtls_ecdsa_context *ctx ) 834 { 835 ECDSA_VALIDATE( ctx != NULL ); 836 837 mbedtls_ecp_keypair_init( ctx ); 838 } 839 840 /* 841 * Free context 842 */ 843 void mbedtls_ecdsa_free( mbedtls_ecdsa_context *ctx ) 844 { 845 if( ctx == NULL ) 846 return; 847 848 mbedtls_ecp_keypair_free( ctx ); 849 } 850 851 #if defined(MBEDTLS_ECP_RESTARTABLE) 852 /* 853 * Initialize a restart context 854 */ 855 void mbedtls_ecdsa_restart_init( mbedtls_ecdsa_restart_ctx *ctx ) 856 { 857 ECDSA_VALIDATE( ctx != NULL ); 858 859 mbedtls_ecp_restart_init( &ctx->ecp ); 860 861 ctx->ver = NULL; 862 ctx->sig = NULL; 863 #if defined(MBEDTLS_ECDSA_DETERMINISTIC) 864 ctx->det = NULL; 865 #endif 866 } 867 868 /* 869 * Free the components of a restart context 870 */ 871 void mbedtls_ecdsa_restart_free( mbedtls_ecdsa_restart_ctx *ctx ) 872 { 873 if( ctx == NULL ) 874 return; 875 876 mbedtls_ecp_restart_free( &ctx->ecp ); 877 878 ecdsa_restart_ver_free( ctx->ver ); 879 mbedtls_free( ctx->ver ); 880 ctx->ver = NULL; 881 882 ecdsa_restart_sig_free( ctx->sig ); 883 mbedtls_free( ctx->sig ); 884 ctx->sig = NULL; 885 886 #if defined(MBEDTLS_ECDSA_DETERMINISTIC) 887 ecdsa_restart_det_free( ctx->det ); 888 mbedtls_free( ctx->det ); 889 ctx->det = NULL; 890 #endif 891 } 892 #endif /* MBEDTLS_ECP_RESTARTABLE */ 893 894 #endif /* MBEDTLS_ECDSA_C */ 895