Marco Zecchini / Mbed OS Example_RTOS

Rtos API example

mbed-os/features/mbedtls/src/ecdsa.c@0:9fca2b23d0ba, 2019-02-23 (annotated)

Committer:
marcozecchini
Date:
Sat Feb 23 12:13:36 2019 +0000
Revision:
0:9fca2b23d0ba
final commit

Who changed what in which revision?

UserRevisionLine numberNew contents of line
marcozecchini 0:9fca2b23d0ba 1 /*
marcozecchini 0:9fca2b23d0ba 2 * Elliptic curve DSA
marcozecchini 0:9fca2b23d0ba 3 *
marcozecchini 0:9fca2b23d0ba 4 * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
marcozecchini 0:9fca2b23d0ba 5 * SPDX-License-Identifier: Apache-2.0
marcozecchini 0:9fca2b23d0ba 6 *
marcozecchini 0:9fca2b23d0ba 7 * Licensed under the Apache License, Version 2.0 (the "License"); you may
marcozecchini 0:9fca2b23d0ba 8 * not use this file except in compliance with the License.
marcozecchini 0:9fca2b23d0ba 9 * You may obtain a copy of the License at
marcozecchini 0:9fca2b23d0ba 10 *
marcozecchini 0:9fca2b23d0ba 11 * http://www.apache.org/licenses/LICENSE-2.0
marcozecchini 0:9fca2b23d0ba 12 *
marcozecchini 0:9fca2b23d0ba 13 * Unless required by applicable law or agreed to in writing, software
marcozecchini 0:9fca2b23d0ba 14 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
marcozecchini 0:9fca2b23d0ba 15 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
marcozecchini 0:9fca2b23d0ba 16 * See the License for the specific language governing permissions and
marcozecchini 0:9fca2b23d0ba 17 * limitations under the License.
marcozecchini 0:9fca2b23d0ba 18 *
marcozecchini 0:9fca2b23d0ba 19 * This file is part of mbed TLS (https://tls.mbed.org)
marcozecchini 0:9fca2b23d0ba 20 */
marcozecchini 0:9fca2b23d0ba 21
marcozecchini 0:9fca2b23d0ba 22 /*
marcozecchini 0:9fca2b23d0ba 23 * References:
marcozecchini 0:9fca2b23d0ba 24 *
marcozecchini 0:9fca2b23d0ba 25 * SEC1 http://www.secg.org/index.php?action=secg,docs_secg
marcozecchini 0:9fca2b23d0ba 26 */
marcozecchini 0:9fca2b23d0ba 27
marcozecchini 0:9fca2b23d0ba 28 #if !defined(MBEDTLS_CONFIG_FILE)
marcozecchini 0:9fca2b23d0ba 29 #include "mbedtls/config.h"
marcozecchini 0:9fca2b23d0ba 30 #else
marcozecchini 0:9fca2b23d0ba 31 #include MBEDTLS_CONFIG_FILE
marcozecchini 0:9fca2b23d0ba 32 #endif
marcozecchini 0:9fca2b23d0ba 33
marcozecchini 0:9fca2b23d0ba 34 #if defined(MBEDTLS_ECDSA_C)
marcozecchini 0:9fca2b23d0ba 35
marcozecchini 0:9fca2b23d0ba 36 #include "mbedtls/ecdsa.h"
marcozecchini 0:9fca2b23d0ba 37 #include "mbedtls/asn1write.h"
marcozecchini 0:9fca2b23d0ba 38
marcozecchini 0:9fca2b23d0ba 39 #include <string.h>
marcozecchini 0:9fca2b23d0ba 40
marcozecchini 0:9fca2b23d0ba 41 #if defined(MBEDTLS_ECDSA_DETERMINISTIC)
marcozecchini 0:9fca2b23d0ba 42 #include "mbedtls/hmac_drbg.h"
marcozecchini 0:9fca2b23d0ba 43 #endif
marcozecchini 0:9fca2b23d0ba 44
marcozecchini 0:9fca2b23d0ba 45 /*
marcozecchini 0:9fca2b23d0ba 46 * Derive a suitable integer for group grp from a buffer of length len
marcozecchini 0:9fca2b23d0ba 47 * SEC1 4.1.3 step 5 aka SEC1 4.1.4 step 3
marcozecchini 0:9fca2b23d0ba 48 */
marcozecchini 0:9fca2b23d0ba 49 static int derive_mpi( const mbedtls_ecp_group *grp, mbedtls_mpi *x,
marcozecchini 0:9fca2b23d0ba 50 const unsigned char *buf, size_t blen )
marcozecchini 0:9fca2b23d0ba 51 {
marcozecchini 0:9fca2b23d0ba 52 int ret;
marcozecchini 0:9fca2b23d0ba 53 size_t n_size = ( grp->nbits + 7 ) / 8;
marcozecchini 0:9fca2b23d0ba 54 size_t use_size = blen > n_size ? n_size : blen;
marcozecchini 0:9fca2b23d0ba 55
marcozecchini 0:9fca2b23d0ba 56 MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( x, buf, use_size ) );
marcozecchini 0:9fca2b23d0ba 57 if( use_size * 8 > grp->nbits )
marcozecchini 0:9fca2b23d0ba 58 MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( x, use_size * 8 - grp->nbits ) );
marcozecchini 0:9fca2b23d0ba 59
marcozecchini 0:9fca2b23d0ba 60 /* While at it, reduce modulo N */
marcozecchini 0:9fca2b23d0ba 61 if( mbedtls_mpi_cmp_mpi( x, &grp->N ) >= 0 )
marcozecchini 0:9fca2b23d0ba 62 MBEDTLS_MPI_CHK( mbedtls_mpi_sub_mpi( x, x, &grp->N ) );
marcozecchini 0:9fca2b23d0ba 63
marcozecchini 0:9fca2b23d0ba 64 cleanup:
marcozecchini 0:9fca2b23d0ba 65 return( ret );
marcozecchini 0:9fca2b23d0ba 66 }
marcozecchini 0:9fca2b23d0ba 67
marcozecchini 0:9fca2b23d0ba 68 /*
marcozecchini 0:9fca2b23d0ba 69 * Compute ECDSA signature of a hashed message (SEC1 4.1.3)
marcozecchini 0:9fca2b23d0ba 70 * Obviously, compared to SEC1 4.1.3, we skip step 4 (hash message)
marcozecchini 0:9fca2b23d0ba 71 */
marcozecchini 0:9fca2b23d0ba 72 int mbedtls_ecdsa_sign( mbedtls_ecp_group *grp, mbedtls_mpi *r, mbedtls_mpi *s,
marcozecchini 0:9fca2b23d0ba 73 const mbedtls_mpi *d, const unsigned char *buf, size_t blen,
marcozecchini 0:9fca2b23d0ba 74 int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
marcozecchini 0:9fca2b23d0ba 75 {
marcozecchini 0:9fca2b23d0ba 76 int ret, key_tries, sign_tries, blind_tries;
marcozecchini 0:9fca2b23d0ba 77 mbedtls_ecp_point R;
marcozecchini 0:9fca2b23d0ba 78 mbedtls_mpi k, e, t;
marcozecchini 0:9fca2b23d0ba 79
marcozecchini 0:9fca2b23d0ba 80 /* Fail cleanly on curves such as Curve25519 that can't be used for ECDSA */
marcozecchini 0:9fca2b23d0ba 81 if( grp->N.p == NULL )
marcozecchini 0:9fca2b23d0ba 82 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
marcozecchini 0:9fca2b23d0ba 83
marcozecchini 0:9fca2b23d0ba 84 mbedtls_ecp_point_init( &R );
marcozecchini 0:9fca2b23d0ba 85 mbedtls_mpi_init( &k ); mbedtls_mpi_init( &e ); mbedtls_mpi_init( &t );
marcozecchini 0:9fca2b23d0ba 86
marcozecchini 0:9fca2b23d0ba 87 sign_tries = 0;
marcozecchini 0:9fca2b23d0ba 88 do
marcozecchini 0:9fca2b23d0ba 89 {
marcozecchini 0:9fca2b23d0ba 90 /*
marcozecchini 0:9fca2b23d0ba 91 * Steps 1-3: generate a suitable ephemeral keypair
marcozecchini 0:9fca2b23d0ba 92 * and set r = xR mod n
marcozecchini 0:9fca2b23d0ba 93 */
marcozecchini 0:9fca2b23d0ba 94 key_tries = 0;
marcozecchini 0:9fca2b23d0ba 95 do
marcozecchini 0:9fca2b23d0ba 96 {
marcozecchini 0:9fca2b23d0ba 97 MBEDTLS_MPI_CHK( mbedtls_ecp_gen_keypair( grp, &k, &R, f_rng, p_rng ) );
marcozecchini 0:9fca2b23d0ba 98 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( r, &R.X, &grp->N ) );
marcozecchini 0:9fca2b23d0ba 99
marcozecchini 0:9fca2b23d0ba 100 if( key_tries++ > 10 )
marcozecchini 0:9fca2b23d0ba 101 {
marcozecchini 0:9fca2b23d0ba 102 ret = MBEDTLS_ERR_ECP_RANDOM_FAILED;
marcozecchini 0:9fca2b23d0ba 103 goto cleanup;
marcozecchini 0:9fca2b23d0ba 104 }
marcozecchini 0:9fca2b23d0ba 105 }
marcozecchini 0:9fca2b23d0ba 106 while( mbedtls_mpi_cmp_int( r, 0 ) == 0 );
marcozecchini 0:9fca2b23d0ba 107
marcozecchini 0:9fca2b23d0ba 108 /*
marcozecchini 0:9fca2b23d0ba 109 * Step 5: derive MPI from hashed message
marcozecchini 0:9fca2b23d0ba 110 */
marcozecchini 0:9fca2b23d0ba 111 MBEDTLS_MPI_CHK( derive_mpi( grp, &e, buf, blen ) );
marcozecchini 0:9fca2b23d0ba 112
marcozecchini 0:9fca2b23d0ba 113 /*
marcozecchini 0:9fca2b23d0ba 114 * Generate a random value to blind inv_mod in next step,
marcozecchini 0:9fca2b23d0ba 115 * avoiding a potential timing leak.
marcozecchini 0:9fca2b23d0ba 116 */
marcozecchini 0:9fca2b23d0ba 117 blind_tries = 0;
marcozecchini 0:9fca2b23d0ba 118 do
marcozecchini 0:9fca2b23d0ba 119 {
marcozecchini 0:9fca2b23d0ba 120 size_t n_size = ( grp->nbits + 7 ) / 8;
marcozecchini 0:9fca2b23d0ba 121 MBEDTLS_MPI_CHK( mbedtls_mpi_fill_random( &t, n_size, f_rng, p_rng ) );
marcozecchini 0:9fca2b23d0ba 122 MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( &t, 8 * n_size - grp->nbits ) );
marcozecchini 0:9fca2b23d0ba 123
marcozecchini 0:9fca2b23d0ba 124 /* See mbedtls_ecp_gen_keypair() */
marcozecchini 0:9fca2b23d0ba 125 if( ++blind_tries > 30 )
marcozecchini 0:9fca2b23d0ba 126 return( MBEDTLS_ERR_ECP_RANDOM_FAILED );
marcozecchini 0:9fca2b23d0ba 127 }
marcozecchini 0:9fca2b23d0ba 128 while( mbedtls_mpi_cmp_int( &t, 1 ) < 0 ||
marcozecchini 0:9fca2b23d0ba 129 mbedtls_mpi_cmp_mpi( &t, &grp->N ) >= 0 );
marcozecchini 0:9fca2b23d0ba 130
marcozecchini 0:9fca2b23d0ba 131 /*
marcozecchini 0:9fca2b23d0ba 132 * Step 6: compute s = (e + r * d) / k = t (e + rd) / (kt) mod n
marcozecchini 0:9fca2b23d0ba 133 */
marcozecchini 0:9fca2b23d0ba 134 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( s, r, d ) );
marcozecchini 0:9fca2b23d0ba 135 MBEDTLS_MPI_CHK( mbedtls_mpi_add_mpi( &e, &e, s ) );
marcozecchini 0:9fca2b23d0ba 136 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &e, &e, &t ) );
marcozecchini 0:9fca2b23d0ba 137 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &k, &k, &t ) );
marcozecchini 0:9fca2b23d0ba 138 MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( s, &k, &grp->N ) );
marcozecchini 0:9fca2b23d0ba 139 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( s, s, &e ) );
marcozecchini 0:9fca2b23d0ba 140 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( s, s, &grp->N ) );
marcozecchini 0:9fca2b23d0ba 141
marcozecchini 0:9fca2b23d0ba 142 if( sign_tries++ > 10 )
marcozecchini 0:9fca2b23d0ba 143 {
marcozecchini 0:9fca2b23d0ba 144 ret = MBEDTLS_ERR_ECP_RANDOM_FAILED;
marcozecchini 0:9fca2b23d0ba 145 goto cleanup;
marcozecchini 0:9fca2b23d0ba 146 }
marcozecchini 0:9fca2b23d0ba 147 }
marcozecchini 0:9fca2b23d0ba 148 while( mbedtls_mpi_cmp_int( s, 0 ) == 0 );
marcozecchini 0:9fca2b23d0ba 149
marcozecchini 0:9fca2b23d0ba 150 cleanup:
marcozecchini 0:9fca2b23d0ba 151 mbedtls_ecp_point_free( &R );
marcozecchini 0:9fca2b23d0ba 152 mbedtls_mpi_free( &k ); mbedtls_mpi_free( &e ); mbedtls_mpi_free( &t );
marcozecchini 0:9fca2b23d0ba 153
marcozecchini 0:9fca2b23d0ba 154 return( ret );
marcozecchini 0:9fca2b23d0ba 155 }
marcozecchini 0:9fca2b23d0ba 156
marcozecchini 0:9fca2b23d0ba 157 #if defined(MBEDTLS_ECDSA_DETERMINISTIC)
marcozecchini 0:9fca2b23d0ba 158 /*
marcozecchini 0:9fca2b23d0ba 159 * Deterministic signature wrapper
marcozecchini 0:9fca2b23d0ba 160 */
marcozecchini 0:9fca2b23d0ba 161 int mbedtls_ecdsa_sign_det( mbedtls_ecp_group *grp, mbedtls_mpi *r, mbedtls_mpi *s,
marcozecchini 0:9fca2b23d0ba 162 const mbedtls_mpi *d, const unsigned char *buf, size_t blen,
marcozecchini 0:9fca2b23d0ba 163 mbedtls_md_type_t md_alg )
marcozecchini 0:9fca2b23d0ba 164 {
marcozecchini 0:9fca2b23d0ba 165 int ret;
marcozecchini 0:9fca2b23d0ba 166 mbedtls_hmac_drbg_context rng_ctx;
marcozecchini 0:9fca2b23d0ba 167 unsigned char data[2 * MBEDTLS_ECP_MAX_BYTES];
marcozecchini 0:9fca2b23d0ba 168 size_t grp_len = ( grp->nbits + 7 ) / 8;
marcozecchini 0:9fca2b23d0ba 169 const mbedtls_md_info_t *md_info;
marcozecchini 0:9fca2b23d0ba 170 mbedtls_mpi h;
marcozecchini 0:9fca2b23d0ba 171
marcozecchini 0:9fca2b23d0ba 172 if( ( md_info = mbedtls_md_info_from_type( md_alg ) ) == NULL )
marcozecchini 0:9fca2b23d0ba 173 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
marcozecchini 0:9fca2b23d0ba 174
marcozecchini 0:9fca2b23d0ba 175 mbedtls_mpi_init( &h );
marcozecchini 0:9fca2b23d0ba 176 mbedtls_hmac_drbg_init( &rng_ctx );
marcozecchini 0:9fca2b23d0ba 177
marcozecchini 0:9fca2b23d0ba 178 /* Use private key and message hash (reduced) to initialize HMAC_DRBG */
marcozecchini 0:9fca2b23d0ba 179 MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( d, data, grp_len ) );
marcozecchini 0:9fca2b23d0ba 180 MBEDTLS_MPI_CHK( derive_mpi( grp, &h, buf, blen ) );
marcozecchini 0:9fca2b23d0ba 181 MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &h, data + grp_len, grp_len ) );
marcozecchini 0:9fca2b23d0ba 182 mbedtls_hmac_drbg_seed_buf( &rng_ctx, md_info, data, 2 * grp_len );
marcozecchini 0:9fca2b23d0ba 183
marcozecchini 0:9fca2b23d0ba 184 ret = mbedtls_ecdsa_sign( grp, r, s, d, buf, blen,
marcozecchini 0:9fca2b23d0ba 185 mbedtls_hmac_drbg_random, &rng_ctx );
marcozecchini 0:9fca2b23d0ba 186
marcozecchini 0:9fca2b23d0ba 187 cleanup:
marcozecchini 0:9fca2b23d0ba 188 mbedtls_hmac_drbg_free( &rng_ctx );
marcozecchini 0:9fca2b23d0ba 189 mbedtls_mpi_free( &h );
marcozecchini 0:9fca2b23d0ba 190
marcozecchini 0:9fca2b23d0ba 191 return( ret );
marcozecchini 0:9fca2b23d0ba 192 }
marcozecchini 0:9fca2b23d0ba 193 #endif /* MBEDTLS_ECDSA_DETERMINISTIC */
marcozecchini 0:9fca2b23d0ba 194
marcozecchini 0:9fca2b23d0ba 195 /*
marcozecchini 0:9fca2b23d0ba 196 * Verify ECDSA signature of hashed message (SEC1 4.1.4)
marcozecchini 0:9fca2b23d0ba 197 * Obviously, compared to SEC1 4.1.3, we skip step 2 (hash message)
marcozecchini 0:9fca2b23d0ba 198 */
marcozecchini 0:9fca2b23d0ba 199 int mbedtls_ecdsa_verify( mbedtls_ecp_group *grp,
marcozecchini 0:9fca2b23d0ba 200 const unsigned char *buf, size_t blen,
marcozecchini 0:9fca2b23d0ba 201 const mbedtls_ecp_point *Q, const mbedtls_mpi *r, const mbedtls_mpi *s)
marcozecchini 0:9fca2b23d0ba 202 {
marcozecchini 0:9fca2b23d0ba 203 int ret;
marcozecchini 0:9fca2b23d0ba 204 mbedtls_mpi e, s_inv, u1, u2;
marcozecchini 0:9fca2b23d0ba 205 mbedtls_ecp_point R;
marcozecchini 0:9fca2b23d0ba 206
marcozecchini 0:9fca2b23d0ba 207 mbedtls_ecp_point_init( &R );
marcozecchini 0:9fca2b23d0ba 208 mbedtls_mpi_init( &e ); mbedtls_mpi_init( &s_inv ); mbedtls_mpi_init( &u1 ); mbedtls_mpi_init( &u2 );
marcozecchini 0:9fca2b23d0ba 209
marcozecchini 0:9fca2b23d0ba 210 /* Fail cleanly on curves such as Curve25519 that can't be used for ECDSA */
marcozecchini 0:9fca2b23d0ba 211 if( grp->N.p == NULL )
marcozecchini 0:9fca2b23d0ba 212 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
marcozecchini 0:9fca2b23d0ba 213
marcozecchini 0:9fca2b23d0ba 214 /*
marcozecchini 0:9fca2b23d0ba 215 * Step 1: make sure r and s are in range 1..n-1
marcozecchini 0:9fca2b23d0ba 216 */
marcozecchini 0:9fca2b23d0ba 217 if( mbedtls_mpi_cmp_int( r, 1 ) < 0 || mbedtls_mpi_cmp_mpi( r, &grp->N ) >= 0 ||
marcozecchini 0:9fca2b23d0ba 218 mbedtls_mpi_cmp_int( s, 1 ) < 0 || mbedtls_mpi_cmp_mpi( s, &grp->N ) >= 0 )
marcozecchini 0:9fca2b23d0ba 219 {
marcozecchini 0:9fca2b23d0ba 220 ret = MBEDTLS_ERR_ECP_VERIFY_FAILED;
marcozecchini 0:9fca2b23d0ba 221 goto cleanup;
marcozecchini 0:9fca2b23d0ba 222 }
marcozecchini 0:9fca2b23d0ba 223
marcozecchini 0:9fca2b23d0ba 224 /*
marcozecchini 0:9fca2b23d0ba 225 * Additional precaution: make sure Q is valid
marcozecchini 0:9fca2b23d0ba 226 */
marcozecchini 0:9fca2b23d0ba 227 MBEDTLS_MPI_CHK( mbedtls_ecp_check_pubkey( grp, Q ) );
marcozecchini 0:9fca2b23d0ba 228
marcozecchini 0:9fca2b23d0ba 229 /*
marcozecchini 0:9fca2b23d0ba 230 * Step 3: derive MPI from hashed message
marcozecchini 0:9fca2b23d0ba 231 */
marcozecchini 0:9fca2b23d0ba 232 MBEDTLS_MPI_CHK( derive_mpi( grp, &e, buf, blen ) );
marcozecchini 0:9fca2b23d0ba 233
marcozecchini 0:9fca2b23d0ba 234 /*
marcozecchini 0:9fca2b23d0ba 235 * Step 4: u1 = e / s mod n, u2 = r / s mod n
marcozecchini 0:9fca2b23d0ba 236 */
marcozecchini 0:9fca2b23d0ba 237 MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( &s_inv, s, &grp->N ) );
marcozecchini 0:9fca2b23d0ba 238
marcozecchini 0:9fca2b23d0ba 239 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &u1, &e, &s_inv ) );
marcozecchini 0:9fca2b23d0ba 240 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &u1, &u1, &grp->N ) );
marcozecchini 0:9fca2b23d0ba 241
marcozecchini 0:9fca2b23d0ba 242 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &u2, r, &s_inv ) );
marcozecchini 0:9fca2b23d0ba 243 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &u2, &u2, &grp->N ) );
marcozecchini 0:9fca2b23d0ba 244
marcozecchini 0:9fca2b23d0ba 245 /*
marcozecchini 0:9fca2b23d0ba 246 * Step 5: R = u1 G + u2 Q
marcozecchini 0:9fca2b23d0ba 247 *
marcozecchini 0:9fca2b23d0ba 248 * Since we're not using any secret data, no need to pass a RNG to
marcozecchini 0:9fca2b23d0ba 249 * mbedtls_ecp_mul() for countermesures.
marcozecchini 0:9fca2b23d0ba 250 */
marcozecchini 0:9fca2b23d0ba 251 MBEDTLS_MPI_CHK( mbedtls_ecp_muladd( grp, &R, &u1, &grp->G, &u2, Q ) );
marcozecchini 0:9fca2b23d0ba 252
marcozecchini 0:9fca2b23d0ba 253 if( mbedtls_ecp_is_zero( &R ) )
marcozecchini 0:9fca2b23d0ba 254 {
marcozecchini 0:9fca2b23d0ba 255 ret = MBEDTLS_ERR_ECP_VERIFY_FAILED;
marcozecchini 0:9fca2b23d0ba 256 goto cleanup;
marcozecchini 0:9fca2b23d0ba 257 }
marcozecchini 0:9fca2b23d0ba 258
marcozecchini 0:9fca2b23d0ba 259 /*
marcozecchini 0:9fca2b23d0ba 260 * Step 6: convert xR to an integer (no-op)
marcozecchini 0:9fca2b23d0ba 261 * Step 7: reduce xR mod n (gives v)
marcozecchini 0:9fca2b23d0ba 262 */
marcozecchini 0:9fca2b23d0ba 263 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &R.X, &R.X, &grp->N ) );
marcozecchini 0:9fca2b23d0ba 264
marcozecchini 0:9fca2b23d0ba 265 /*
marcozecchini 0:9fca2b23d0ba 266 * Step 8: check if v (that is, R.X) is equal to r
marcozecchini 0:9fca2b23d0ba 267 */
marcozecchini 0:9fca2b23d0ba 268 if( mbedtls_mpi_cmp_mpi( &R.X, r ) != 0 )
marcozecchini 0:9fca2b23d0ba 269 {
marcozecchini 0:9fca2b23d0ba 270 ret = MBEDTLS_ERR_ECP_VERIFY_FAILED;
marcozecchini 0:9fca2b23d0ba 271 goto cleanup;
marcozecchini 0:9fca2b23d0ba 272 }
marcozecchini 0:9fca2b23d0ba 273
marcozecchini 0:9fca2b23d0ba 274 cleanup:
marcozecchini 0:9fca2b23d0ba 275 mbedtls_ecp_point_free( &R );
marcozecchini 0:9fca2b23d0ba 276 mbedtls_mpi_free( &e ); mbedtls_mpi_free( &s_inv ); mbedtls_mpi_free( &u1 ); mbedtls_mpi_free( &u2 );
marcozecchini 0:9fca2b23d0ba 277
marcozecchini 0:9fca2b23d0ba 278 return( ret );
marcozecchini 0:9fca2b23d0ba 279 }
marcozecchini 0:9fca2b23d0ba 280
marcozecchini 0:9fca2b23d0ba 281 /*
marcozecchini 0:9fca2b23d0ba 282 * Convert a signature (given by context) to ASN.1
marcozecchini 0:9fca2b23d0ba 283 */
marcozecchini 0:9fca2b23d0ba 284 static int ecdsa_signature_to_asn1( const mbedtls_mpi *r, const mbedtls_mpi *s,
marcozecchini 0:9fca2b23d0ba 285 unsigned char *sig, size_t *slen )
marcozecchini 0:9fca2b23d0ba 286 {
marcozecchini 0:9fca2b23d0ba 287 int ret;
marcozecchini 0:9fca2b23d0ba 288 unsigned char buf[MBEDTLS_ECDSA_MAX_LEN];
marcozecchini 0:9fca2b23d0ba 289 unsigned char *p = buf + sizeof( buf );
marcozecchini 0:9fca2b23d0ba 290 size_t len = 0;
marcozecchini 0:9fca2b23d0ba 291
marcozecchini 0:9fca2b23d0ba 292 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &p, buf, s ) );
marcozecchini 0:9fca2b23d0ba 293 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &p, buf, r ) );
marcozecchini 0:9fca2b23d0ba 294
marcozecchini 0:9fca2b23d0ba 295 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &p, buf, len ) );
marcozecchini 0:9fca2b23d0ba 296 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &p, buf,
marcozecchini 0:9fca2b23d0ba 297 MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) );
marcozecchini 0:9fca2b23d0ba 298
marcozecchini 0:9fca2b23d0ba 299 memcpy( sig, p, len );
marcozecchini 0:9fca2b23d0ba 300 *slen = len;
marcozecchini 0:9fca2b23d0ba 301
marcozecchini 0:9fca2b23d0ba 302 return( 0 );
marcozecchini 0:9fca2b23d0ba 303 }
marcozecchini 0:9fca2b23d0ba 304
marcozecchini 0:9fca2b23d0ba 305 /*
marcozecchini 0:9fca2b23d0ba 306 * Compute and write signature
marcozecchini 0:9fca2b23d0ba 307 */
marcozecchini 0:9fca2b23d0ba 308 int mbedtls_ecdsa_write_signature( mbedtls_ecdsa_context *ctx, mbedtls_md_type_t md_alg,
marcozecchini 0:9fca2b23d0ba 309 const unsigned char *hash, size_t hlen,
marcozecchini 0:9fca2b23d0ba 310 unsigned char *sig, size_t *slen,
marcozecchini 0:9fca2b23d0ba 311 int (*f_rng)(void *, unsigned char *, size_t),
marcozecchini 0:9fca2b23d0ba 312 void *p_rng )
marcozecchini 0:9fca2b23d0ba 313 {
marcozecchini 0:9fca2b23d0ba 314 int ret;
marcozecchini 0:9fca2b23d0ba 315 mbedtls_mpi r, s;
marcozecchini 0:9fca2b23d0ba 316
marcozecchini 0:9fca2b23d0ba 317 mbedtls_mpi_init( &r );
marcozecchini 0:9fca2b23d0ba 318 mbedtls_mpi_init( &s );
marcozecchini 0:9fca2b23d0ba 319
marcozecchini 0:9fca2b23d0ba 320 #if defined(MBEDTLS_ECDSA_DETERMINISTIC)
marcozecchini 0:9fca2b23d0ba 321 (void) f_rng;
marcozecchini 0:9fca2b23d0ba 322 (void) p_rng;
marcozecchini 0:9fca2b23d0ba 323
marcozecchini 0:9fca2b23d0ba 324 MBEDTLS_MPI_CHK( mbedtls_ecdsa_sign_det( &ctx->grp, &r, &s, &ctx->d,
marcozecchini 0:9fca2b23d0ba 325 hash, hlen, md_alg ) );
marcozecchini 0:9fca2b23d0ba 326 #else
marcozecchini 0:9fca2b23d0ba 327 (void) md_alg;
marcozecchini 0:9fca2b23d0ba 328
marcozecchini 0:9fca2b23d0ba 329 MBEDTLS_MPI_CHK( mbedtls_ecdsa_sign( &ctx->grp, &r, &s, &ctx->d,
marcozecchini 0:9fca2b23d0ba 330 hash, hlen, f_rng, p_rng ) );
marcozecchini 0:9fca2b23d0ba 331 #endif
marcozecchini 0:9fca2b23d0ba 332
marcozecchini 0:9fca2b23d0ba 333 MBEDTLS_MPI_CHK( ecdsa_signature_to_asn1( &r, &s, sig, slen ) );
marcozecchini 0:9fca2b23d0ba 334
marcozecchini 0:9fca2b23d0ba 335 cleanup:
marcozecchini 0:9fca2b23d0ba 336 mbedtls_mpi_free( &r );
marcozecchini 0:9fca2b23d0ba 337 mbedtls_mpi_free( &s );
marcozecchini 0:9fca2b23d0ba 338
marcozecchini 0:9fca2b23d0ba 339 return( ret );
marcozecchini 0:9fca2b23d0ba 340 }
marcozecchini 0:9fca2b23d0ba 341
marcozecchini 0:9fca2b23d0ba 342 #if ! defined(MBEDTLS_DEPRECATED_REMOVED) && \
marcozecchini 0:9fca2b23d0ba 343 defined(MBEDTLS_ECDSA_DETERMINISTIC)
marcozecchini 0:9fca2b23d0ba 344 int mbedtls_ecdsa_write_signature_det( mbedtls_ecdsa_context *ctx,
marcozecchini 0:9fca2b23d0ba 345 const unsigned char *hash, size_t hlen,
marcozecchini 0:9fca2b23d0ba 346 unsigned char *sig, size_t *slen,
marcozecchini 0:9fca2b23d0ba 347 mbedtls_md_type_t md_alg )
marcozecchini 0:9fca2b23d0ba 348 {
marcozecchini 0:9fca2b23d0ba 349 return( mbedtls_ecdsa_write_signature( ctx, md_alg, hash, hlen, sig, slen,
marcozecchini 0:9fca2b23d0ba 350 NULL, NULL ) );
marcozecchini 0:9fca2b23d0ba 351 }
marcozecchini 0:9fca2b23d0ba 352 #endif
marcozecchini 0:9fca2b23d0ba 353
marcozecchini 0:9fca2b23d0ba 354 /*
marcozecchini 0:9fca2b23d0ba 355 * Read and check signature
marcozecchini 0:9fca2b23d0ba 356 */
marcozecchini 0:9fca2b23d0ba 357 int mbedtls_ecdsa_read_signature( mbedtls_ecdsa_context *ctx,
marcozecchini 0:9fca2b23d0ba 358 const unsigned char *hash, size_t hlen,
marcozecchini 0:9fca2b23d0ba 359 const unsigned char *sig, size_t slen )
marcozecchini 0:9fca2b23d0ba 360 {
marcozecchini 0:9fca2b23d0ba 361 int ret;
marcozecchini 0:9fca2b23d0ba 362 unsigned char *p = (unsigned char *) sig;
marcozecchini 0:9fca2b23d0ba 363 const unsigned char *end = sig + slen;
marcozecchini 0:9fca2b23d0ba 364 size_t len;
marcozecchini 0:9fca2b23d0ba 365 mbedtls_mpi r, s;
marcozecchini 0:9fca2b23d0ba 366
marcozecchini 0:9fca2b23d0ba 367 mbedtls_mpi_init( &r );
marcozecchini 0:9fca2b23d0ba 368 mbedtls_mpi_init( &s );
marcozecchini 0:9fca2b23d0ba 369
marcozecchini 0:9fca2b23d0ba 370 if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
marcozecchini 0:9fca2b23d0ba 371 MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 )
marcozecchini 0:9fca2b23d0ba 372 {
marcozecchini 0:9fca2b23d0ba 373 ret += MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
marcozecchini 0:9fca2b23d0ba 374 goto cleanup;
marcozecchini 0:9fca2b23d0ba 375 }
marcozecchini 0:9fca2b23d0ba 376
marcozecchini 0:9fca2b23d0ba 377 if( p + len != end )
marcozecchini 0:9fca2b23d0ba 378 {
marcozecchini 0:9fca2b23d0ba 379 ret = MBEDTLS_ERR_ECP_BAD_INPUT_DATA +
marcozecchini 0:9fca2b23d0ba 380 MBEDTLS_ERR_ASN1_LENGTH_MISMATCH;
marcozecchini 0:9fca2b23d0ba 381 goto cleanup;
marcozecchini 0:9fca2b23d0ba 382 }
marcozecchini 0:9fca2b23d0ba 383
marcozecchini 0:9fca2b23d0ba 384 if( ( ret = mbedtls_asn1_get_mpi( &p, end, &r ) ) != 0 ||
marcozecchini 0:9fca2b23d0ba 385 ( ret = mbedtls_asn1_get_mpi( &p, end, &s ) ) != 0 )
marcozecchini 0:9fca2b23d0ba 386 {
marcozecchini 0:9fca2b23d0ba 387 ret += MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
marcozecchini 0:9fca2b23d0ba 388 goto cleanup;
marcozecchini 0:9fca2b23d0ba 389 }
marcozecchini 0:9fca2b23d0ba 390
marcozecchini 0:9fca2b23d0ba 391 if( ( ret = mbedtls_ecdsa_verify( &ctx->grp, hash, hlen,
marcozecchini 0:9fca2b23d0ba 392 &ctx->Q, &r, &s ) ) != 0 )
marcozecchini 0:9fca2b23d0ba 393 goto cleanup;
marcozecchini 0:9fca2b23d0ba 394
marcozecchini 0:9fca2b23d0ba 395 if( p != end )
marcozecchini 0:9fca2b23d0ba 396 ret = MBEDTLS_ERR_ECP_SIG_LEN_MISMATCH;
marcozecchini 0:9fca2b23d0ba 397
marcozecchini 0:9fca2b23d0ba 398 cleanup:
marcozecchini 0:9fca2b23d0ba 399 mbedtls_mpi_free( &r );
marcozecchini 0:9fca2b23d0ba 400 mbedtls_mpi_free( &s );
marcozecchini 0:9fca2b23d0ba 401
marcozecchini 0:9fca2b23d0ba 402 return( ret );
marcozecchini 0:9fca2b23d0ba 403 }
marcozecchini 0:9fca2b23d0ba 404
marcozecchini 0:9fca2b23d0ba 405 /*
marcozecchini 0:9fca2b23d0ba 406 * Generate key pair
marcozecchini 0:9fca2b23d0ba 407 */
marcozecchini 0:9fca2b23d0ba 408 int mbedtls_ecdsa_genkey( mbedtls_ecdsa_context *ctx, mbedtls_ecp_group_id gid,
marcozecchini 0:9fca2b23d0ba 409 int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
marcozecchini 0:9fca2b23d0ba 410 {
marcozecchini 0:9fca2b23d0ba 411 return( mbedtls_ecp_group_load( &ctx->grp, gid ) ||
marcozecchini 0:9fca2b23d0ba 412 mbedtls_ecp_gen_keypair( &ctx->grp, &ctx->d, &ctx->Q, f_rng, p_rng ) );
marcozecchini 0:9fca2b23d0ba 413 }
marcozecchini 0:9fca2b23d0ba 414
marcozecchini 0:9fca2b23d0ba 415 /*
marcozecchini 0:9fca2b23d0ba 416 * Set context from an mbedtls_ecp_keypair
marcozecchini 0:9fca2b23d0ba 417 */
marcozecchini 0:9fca2b23d0ba 418 int mbedtls_ecdsa_from_keypair( mbedtls_ecdsa_context *ctx, const mbedtls_ecp_keypair *key )
marcozecchini 0:9fca2b23d0ba 419 {
marcozecchini 0:9fca2b23d0ba 420 int ret;
marcozecchini 0:9fca2b23d0ba 421
marcozecchini 0:9fca2b23d0ba 422 if( ( ret = mbedtls_ecp_group_copy( &ctx->grp, &key->grp ) ) != 0 ||
marcozecchini 0:9fca2b23d0ba 423 ( ret = mbedtls_mpi_copy( &ctx->d, &key->d ) ) != 0 ||
marcozecchini 0:9fca2b23d0ba 424 ( ret = mbedtls_ecp_copy( &ctx->Q, &key->Q ) ) != 0 )
marcozecchini 0:9fca2b23d0ba 425 {
marcozecchini 0:9fca2b23d0ba 426 mbedtls_ecdsa_free( ctx );
marcozecchini 0:9fca2b23d0ba 427 }
marcozecchini 0:9fca2b23d0ba 428
marcozecchini 0:9fca2b23d0ba 429 return( ret );
marcozecchini 0:9fca2b23d0ba 430 }
marcozecchini 0:9fca2b23d0ba 431
marcozecchini 0:9fca2b23d0ba 432 /*
marcozecchini 0:9fca2b23d0ba 433 * Initialize context
marcozecchini 0:9fca2b23d0ba 434 */
marcozecchini 0:9fca2b23d0ba 435 void mbedtls_ecdsa_init( mbedtls_ecdsa_context *ctx )
marcozecchini 0:9fca2b23d0ba 436 {
marcozecchini 0:9fca2b23d0ba 437 mbedtls_ecp_keypair_init( ctx );
marcozecchini 0:9fca2b23d0ba 438 }
marcozecchini 0:9fca2b23d0ba 439
marcozecchini 0:9fca2b23d0ba 440 /*
marcozecchini 0:9fca2b23d0ba 441 * Free context
marcozecchini 0:9fca2b23d0ba 442 */
marcozecchini 0:9fca2b23d0ba 443 void mbedtls_ecdsa_free( mbedtls_ecdsa_context *ctx )
marcozecchini 0:9fca2b23d0ba 444 {
marcozecchini 0:9fca2b23d0ba 445 mbedtls_ecp_keypair_free( ctx );
marcozecchini 0:9fca2b23d0ba 446 }
marcozecchini 0:9fca2b23d0ba 447
marcozecchini 0:9fca2b23d0ba 448 #endif /* MBEDTLS_ECDSA_C */