Eric Tsai / mbedtls

Modified mbed TLS headers for AES functionality only to reduce build size

Dependents:   BLE_Gateway_Linker_fix BLE_Gateway

Fork of mbedtls by sandbox

source/ecdsa.c@5:f09f5ed830ca, 2017-07-10 (annotated)

Committer:
electronichamsters
Date:
Mon Jul 10 04:00:25 2017 +0000
Revision:
5:f09f5ed830ca
Parent:
1:24750b9ad5ef 
working gateway

Who changed what in which revision?

UserRevisionLine numberNew contents of line
Christopher Haster 1:24750b9ad5ef 1 /*
Christopher Haster 1:24750b9ad5ef 2 * Elliptic curve DSA
Christopher Haster 1:24750b9ad5ef 3 *
Christopher Haster 1:24750b9ad5ef 4 * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
Christopher Haster 1:24750b9ad5ef 5 * SPDX-License-Identifier: Apache-2.0
Christopher Haster 1:24750b9ad5ef 6 *
Christopher Haster 1:24750b9ad5ef 7 * Licensed under the Apache License, Version 2.0 (the "License"); you may
Christopher Haster 1:24750b9ad5ef 8 * not use this file except in compliance with the License.
Christopher Haster 1:24750b9ad5ef 9 * You may obtain a copy of the License at
Christopher Haster 1:24750b9ad5ef 10 *
Christopher Haster 1:24750b9ad5ef 11 * http://www.apache.org/licenses/LICENSE-2.0
Christopher Haster 1:24750b9ad5ef 12 *
Christopher Haster 1:24750b9ad5ef 13 * Unless required by applicable law or agreed to in writing, software
Christopher Haster 1:24750b9ad5ef 14 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
Christopher Haster 1:24750b9ad5ef 15 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
Christopher Haster 1:24750b9ad5ef 16 * See the License for the specific language governing permissions and
Christopher Haster 1:24750b9ad5ef 17 * limitations under the License.
Christopher Haster 1:24750b9ad5ef 18 *
Christopher Haster 1:24750b9ad5ef 19 * This file is part of mbed TLS (https://tls.mbed.org)
Christopher Haster 1:24750b9ad5ef 20 */
Christopher Haster 1:24750b9ad5ef 21
Christopher Haster 1:24750b9ad5ef 22 /*
Christopher Haster 1:24750b9ad5ef 23 * References:
Christopher Haster 1:24750b9ad5ef 24 *
Christopher Haster 1:24750b9ad5ef 25 * SEC1 http://www.secg.org/index.php?action=secg,docs_secg
Christopher Haster 1:24750b9ad5ef 26 */
Christopher Haster 1:24750b9ad5ef 27
Christopher Haster 1:24750b9ad5ef 28 #if !defined(MBEDTLS_CONFIG_FILE)
Christopher Haster 1:24750b9ad5ef 29 #include "mbedtls/config.h"
Christopher Haster 1:24750b9ad5ef 30 #else
Christopher Haster 1:24750b9ad5ef 31 #include MBEDTLS_CONFIG_FILE
Christopher Haster 1:24750b9ad5ef 32 #endif
Christopher Haster 1:24750b9ad5ef 33
Christopher Haster 1:24750b9ad5ef 34 #if defined(MBEDTLS_ECDSA_C)
Christopher Haster 1:24750b9ad5ef 35
Christopher Haster 1:24750b9ad5ef 36 #include "mbedtls/ecdsa.h"
Christopher Haster 1:24750b9ad5ef 37 #include "mbedtls/asn1write.h"
Christopher Haster 1:24750b9ad5ef 38
Christopher Haster 1:24750b9ad5ef 39 #include <string.h>
Christopher Haster 1:24750b9ad5ef 40
Christopher Haster 1:24750b9ad5ef 41 #if defined(MBEDTLS_ECDSA_DETERMINISTIC)
Christopher Haster 1:24750b9ad5ef 42 #include "mbedtls/hmac_drbg.h"
Christopher Haster 1:24750b9ad5ef 43 #endif
Christopher Haster 1:24750b9ad5ef 44
Christopher Haster 1:24750b9ad5ef 45 /*
Christopher Haster 1:24750b9ad5ef 46 * Derive a suitable integer for group grp from a buffer of length len
Christopher Haster 1:24750b9ad5ef 47 * SEC1 4.1.3 step 5 aka SEC1 4.1.4 step 3
Christopher Haster 1:24750b9ad5ef 48 */
Christopher Haster 1:24750b9ad5ef 49 static int derive_mpi( const mbedtls_ecp_group *grp, mbedtls_mpi *x,
Christopher Haster 1:24750b9ad5ef 50 const unsigned char *buf, size_t blen )
Christopher Haster 1:24750b9ad5ef 51 {
Christopher Haster 1:24750b9ad5ef 52 int ret;
Christopher Haster 1:24750b9ad5ef 53 size_t n_size = ( grp->nbits + 7 ) / 8;
Christopher Haster 1:24750b9ad5ef 54 size_t use_size = blen > n_size ? n_size : blen;
Christopher Haster 1:24750b9ad5ef 55
Christopher Haster 1:24750b9ad5ef 56 MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( x, buf, use_size ) );
Christopher Haster 1:24750b9ad5ef 57 if( use_size * 8 > grp->nbits )
Christopher Haster 1:24750b9ad5ef 58 MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( x, use_size * 8 - grp->nbits ) );
Christopher Haster 1:24750b9ad5ef 59
Christopher Haster 1:24750b9ad5ef 60 /* While at it, reduce modulo N */
Christopher Haster 1:24750b9ad5ef 61 if( mbedtls_mpi_cmp_mpi( x, &grp->N ) >= 0 )
Christopher Haster 1:24750b9ad5ef 62 MBEDTLS_MPI_CHK( mbedtls_mpi_sub_mpi( x, x, &grp->N ) );
Christopher Haster 1:24750b9ad5ef 63
Christopher Haster 1:24750b9ad5ef 64 cleanup:
Christopher Haster 1:24750b9ad5ef 65 return( ret );
Christopher Haster 1:24750b9ad5ef 66 }
Christopher Haster 1:24750b9ad5ef 67
Christopher Haster 1:24750b9ad5ef 68 /*
Christopher Haster 1:24750b9ad5ef 69 * Compute ECDSA signature of a hashed message (SEC1 4.1.3)
Christopher Haster 1:24750b9ad5ef 70 * Obviously, compared to SEC1 4.1.3, we skip step 4 (hash message)
Christopher Haster 1:24750b9ad5ef 71 */
Christopher Haster 1:24750b9ad5ef 72 int mbedtls_ecdsa_sign( mbedtls_ecp_group *grp, mbedtls_mpi *r, mbedtls_mpi *s,
Christopher Haster 1:24750b9ad5ef 73 const mbedtls_mpi *d, const unsigned char *buf, size_t blen,
Christopher Haster 1:24750b9ad5ef 74 int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
Christopher Haster 1:24750b9ad5ef 75 {
Christopher Haster 1:24750b9ad5ef 76 int ret, key_tries, sign_tries, blind_tries;
Christopher Haster 1:24750b9ad5ef 77 mbedtls_ecp_point R;
Christopher Haster 1:24750b9ad5ef 78 mbedtls_mpi k, e, t;
Christopher Haster 1:24750b9ad5ef 79
Christopher Haster 1:24750b9ad5ef 80 /* Fail cleanly on curves such as Curve25519 that can't be used for ECDSA */
Christopher Haster 1:24750b9ad5ef 81 if( grp->N.p == NULL )
Christopher Haster 1:24750b9ad5ef 82 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
Christopher Haster 1:24750b9ad5ef 83
Christopher Haster 1:24750b9ad5ef 84 mbedtls_ecp_point_init( &R );
Christopher Haster 1:24750b9ad5ef 85 mbedtls_mpi_init( &k ); mbedtls_mpi_init( &e ); mbedtls_mpi_init( &t );
Christopher Haster 1:24750b9ad5ef 86
Christopher Haster 1:24750b9ad5ef 87 sign_tries = 0;
Christopher Haster 1:24750b9ad5ef 88 do
Christopher Haster 1:24750b9ad5ef 89 {
Christopher Haster 1:24750b9ad5ef 90 /*
Christopher Haster 1:24750b9ad5ef 91 * Steps 1-3: generate a suitable ephemeral keypair
Christopher Haster 1:24750b9ad5ef 92 * and set r = xR mod n
Christopher Haster 1:24750b9ad5ef 93 */
Christopher Haster 1:24750b9ad5ef 94 key_tries = 0;
Christopher Haster 1:24750b9ad5ef 95 do
Christopher Haster 1:24750b9ad5ef 96 {
Christopher Haster 1:24750b9ad5ef 97 MBEDTLS_MPI_CHK( mbedtls_ecp_gen_keypair( grp, &k, &R, f_rng, p_rng ) );
Christopher Haster 1:24750b9ad5ef 98 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( r, &R.X, &grp->N ) );
Christopher Haster 1:24750b9ad5ef 99
Christopher Haster 1:24750b9ad5ef 100 if( key_tries++ > 10 )
Christopher Haster 1:24750b9ad5ef 101 {
Christopher Haster 1:24750b9ad5ef 102 ret = MBEDTLS_ERR_ECP_RANDOM_FAILED;
Christopher Haster 1:24750b9ad5ef 103 goto cleanup;
Christopher Haster 1:24750b9ad5ef 104 }
Christopher Haster 1:24750b9ad5ef 105 }
Christopher Haster 1:24750b9ad5ef 106 while( mbedtls_mpi_cmp_int( r, 0 ) == 0 );
Christopher Haster 1:24750b9ad5ef 107
Christopher Haster 1:24750b9ad5ef 108 /*
Christopher Haster 1:24750b9ad5ef 109 * Step 5: derive MPI from hashed message
Christopher Haster 1:24750b9ad5ef 110 */
Christopher Haster 1:24750b9ad5ef 111 MBEDTLS_MPI_CHK( derive_mpi( grp, &e, buf, blen ) );
Christopher Haster 1:24750b9ad5ef 112
Christopher Haster 1:24750b9ad5ef 113 /*
Christopher Haster 1:24750b9ad5ef 114 * Generate a random value to blind inv_mod in next step,
Christopher Haster 1:24750b9ad5ef 115 * avoiding a potential timing leak.
Christopher Haster 1:24750b9ad5ef 116 */
Christopher Haster 1:24750b9ad5ef 117 blind_tries = 0;
Christopher Haster 1:24750b9ad5ef 118 do
Christopher Haster 1:24750b9ad5ef 119 {
Christopher Haster 1:24750b9ad5ef 120 size_t n_size = ( grp->nbits + 7 ) / 8;
Christopher Haster 1:24750b9ad5ef 121 MBEDTLS_MPI_CHK( mbedtls_mpi_fill_random( &t, n_size, f_rng, p_rng ) );
Christopher Haster 1:24750b9ad5ef 122 MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( &t, 8 * n_size - grp->nbits ) );
Christopher Haster 1:24750b9ad5ef 123
Christopher Haster 1:24750b9ad5ef 124 /* See mbedtls_ecp_gen_keypair() */
Christopher Haster 1:24750b9ad5ef 125 if( ++blind_tries > 30 )
Christopher Haster 1:24750b9ad5ef 126 return( MBEDTLS_ERR_ECP_RANDOM_FAILED );
Christopher Haster 1:24750b9ad5ef 127 }
Christopher Haster 1:24750b9ad5ef 128 while( mbedtls_mpi_cmp_int( &t, 1 ) < 0 ||
Christopher Haster 1:24750b9ad5ef 129 mbedtls_mpi_cmp_mpi( &t, &grp->N ) >= 0 );
Christopher Haster 1:24750b9ad5ef 130
Christopher Haster 1:24750b9ad5ef 131 /*
Christopher Haster 1:24750b9ad5ef 132 * Step 6: compute s = (e + r * d) / k = t (e + rd) / (kt) mod n
Christopher Haster 1:24750b9ad5ef 133 */
Christopher Haster 1:24750b9ad5ef 134 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( s, r, d ) );
Christopher Haster 1:24750b9ad5ef 135 MBEDTLS_MPI_CHK( mbedtls_mpi_add_mpi( &e, &e, s ) );
Christopher Haster 1:24750b9ad5ef 136 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &e, &e, &t ) );
Christopher Haster 1:24750b9ad5ef 137 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &k, &k, &t ) );
Christopher Haster 1:24750b9ad5ef 138 MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( s, &k, &grp->N ) );
Christopher Haster 1:24750b9ad5ef 139 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( s, s, &e ) );
Christopher Haster 1:24750b9ad5ef 140 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( s, s, &grp->N ) );
Christopher Haster 1:24750b9ad5ef 141
Christopher Haster 1:24750b9ad5ef 142 if( sign_tries++ > 10 )
Christopher Haster 1:24750b9ad5ef 143 {
Christopher Haster 1:24750b9ad5ef 144 ret = MBEDTLS_ERR_ECP_RANDOM_FAILED;
Christopher Haster 1:24750b9ad5ef 145 goto cleanup;
Christopher Haster 1:24750b9ad5ef 146 }
Christopher Haster 1:24750b9ad5ef 147 }
Christopher Haster 1:24750b9ad5ef 148 while( mbedtls_mpi_cmp_int( s, 0 ) == 0 );
Christopher Haster 1:24750b9ad5ef 149
Christopher Haster 1:24750b9ad5ef 150 cleanup:
Christopher Haster 1:24750b9ad5ef 151 mbedtls_ecp_point_free( &R );
Christopher Haster 1:24750b9ad5ef 152 mbedtls_mpi_free( &k ); mbedtls_mpi_free( &e ); mbedtls_mpi_free( &t );
Christopher Haster 1:24750b9ad5ef 153
Christopher Haster 1:24750b9ad5ef 154 return( ret );
Christopher Haster 1:24750b9ad5ef 155 }
Christopher Haster 1:24750b9ad5ef 156
Christopher Haster 1:24750b9ad5ef 157 #if defined(MBEDTLS_ECDSA_DETERMINISTIC)
Christopher Haster 1:24750b9ad5ef 158 /*
Christopher Haster 1:24750b9ad5ef 159 * Deterministic signature wrapper
Christopher Haster 1:24750b9ad5ef 160 */
Christopher Haster 1:24750b9ad5ef 161 int mbedtls_ecdsa_sign_det( mbedtls_ecp_group *grp, mbedtls_mpi *r, mbedtls_mpi *s,
Christopher Haster 1:24750b9ad5ef 162 const mbedtls_mpi *d, const unsigned char *buf, size_t blen,
Christopher Haster 1:24750b9ad5ef 163 mbedtls_md_type_t md_alg )
Christopher Haster 1:24750b9ad5ef 164 {
Christopher Haster 1:24750b9ad5ef 165 int ret;
Christopher Haster 1:24750b9ad5ef 166 mbedtls_hmac_drbg_context rng_ctx;
Christopher Haster 1:24750b9ad5ef 167 unsigned char data[2 * MBEDTLS_ECP_MAX_BYTES];
Christopher Haster 1:24750b9ad5ef 168 size_t grp_len = ( grp->nbits + 7 ) / 8;
Christopher Haster 1:24750b9ad5ef 169 const mbedtls_md_info_t *md_info;
Christopher Haster 1:24750b9ad5ef 170 mbedtls_mpi h;
Christopher Haster 1:24750b9ad5ef 171
Christopher Haster 1:24750b9ad5ef 172 if( ( md_info = mbedtls_md_info_from_type( md_alg ) ) == NULL )
Christopher Haster 1:24750b9ad5ef 173 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
Christopher Haster 1:24750b9ad5ef 174
Christopher Haster 1:24750b9ad5ef 175 mbedtls_mpi_init( &h );
Christopher Haster 1:24750b9ad5ef 176 mbedtls_hmac_drbg_init( &rng_ctx );
Christopher Haster 1:24750b9ad5ef 177
Christopher Haster 1:24750b9ad5ef 178 /* Use private key and message hash (reduced) to initialize HMAC_DRBG */
Christopher Haster 1:24750b9ad5ef 179 MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( d, data, grp_len ) );
Christopher Haster 1:24750b9ad5ef 180 MBEDTLS_MPI_CHK( derive_mpi( grp, &h, buf, blen ) );
Christopher Haster 1:24750b9ad5ef 181 MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &h, data + grp_len, grp_len ) );
Christopher Haster 1:24750b9ad5ef 182 mbedtls_hmac_drbg_seed_buf( &rng_ctx, md_info, data, 2 * grp_len );
Christopher Haster 1:24750b9ad5ef 183
Christopher Haster 1:24750b9ad5ef 184 ret = mbedtls_ecdsa_sign( grp, r, s, d, buf, blen,
Christopher Haster 1:24750b9ad5ef 185 mbedtls_hmac_drbg_random, &rng_ctx );
Christopher Haster 1:24750b9ad5ef 186
Christopher Haster 1:24750b9ad5ef 187 cleanup:
Christopher Haster 1:24750b9ad5ef 188 mbedtls_hmac_drbg_free( &rng_ctx );
Christopher Haster 1:24750b9ad5ef 189 mbedtls_mpi_free( &h );
Christopher Haster 1:24750b9ad5ef 190
Christopher Haster 1:24750b9ad5ef 191 return( ret );
Christopher Haster 1:24750b9ad5ef 192 }
Christopher Haster 1:24750b9ad5ef 193 #endif /* MBEDTLS_ECDSA_DETERMINISTIC */
Christopher Haster 1:24750b9ad5ef 194
Christopher Haster 1:24750b9ad5ef 195 /*
Christopher Haster 1:24750b9ad5ef 196 * Verify ECDSA signature of hashed message (SEC1 4.1.4)
Christopher Haster 1:24750b9ad5ef 197 * Obviously, compared to SEC1 4.1.3, we skip step 2 (hash message)
Christopher Haster 1:24750b9ad5ef 198 */
Christopher Haster 1:24750b9ad5ef 199 int mbedtls_ecdsa_verify( mbedtls_ecp_group *grp,
Christopher Haster 1:24750b9ad5ef 200 const unsigned char *buf, size_t blen,
Christopher Haster 1:24750b9ad5ef 201 const mbedtls_ecp_point *Q, const mbedtls_mpi *r, const mbedtls_mpi *s)
Christopher Haster 1:24750b9ad5ef 202 {
Christopher Haster 1:24750b9ad5ef 203 int ret;
Christopher Haster 1:24750b9ad5ef 204 mbedtls_mpi e, s_inv, u1, u2;
Christopher Haster 1:24750b9ad5ef 205 mbedtls_ecp_point R;
Christopher Haster 1:24750b9ad5ef 206
Christopher Haster 1:24750b9ad5ef 207 mbedtls_ecp_point_init( &R );
Christopher Haster 1:24750b9ad5ef 208 mbedtls_mpi_init( &e ); mbedtls_mpi_init( &s_inv ); mbedtls_mpi_init( &u1 ); mbedtls_mpi_init( &u2 );
Christopher Haster 1:24750b9ad5ef 209
Christopher Haster 1:24750b9ad5ef 210 /* Fail cleanly on curves such as Curve25519 that can't be used for ECDSA */
Christopher Haster 1:24750b9ad5ef 211 if( grp->N.p == NULL )
Christopher Haster 1:24750b9ad5ef 212 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
Christopher Haster 1:24750b9ad5ef 213
Christopher Haster 1:24750b9ad5ef 214 /*
Christopher Haster 1:24750b9ad5ef 215 * Step 1: make sure r and s are in range 1..n-1
Christopher Haster 1:24750b9ad5ef 216 */
Christopher Haster 1:24750b9ad5ef 217 if( mbedtls_mpi_cmp_int( r, 1 ) < 0 || mbedtls_mpi_cmp_mpi( r, &grp->N ) >= 0 ||
Christopher Haster 1:24750b9ad5ef 218 mbedtls_mpi_cmp_int( s, 1 ) < 0 || mbedtls_mpi_cmp_mpi( s, &grp->N ) >= 0 )
Christopher Haster 1:24750b9ad5ef 219 {
Christopher Haster 1:24750b9ad5ef 220 ret = MBEDTLS_ERR_ECP_VERIFY_FAILED;
Christopher Haster 1:24750b9ad5ef 221 goto cleanup;
Christopher Haster 1:24750b9ad5ef 222 }
Christopher Haster 1:24750b9ad5ef 223
Christopher Haster 1:24750b9ad5ef 224 /*
Christopher Haster 1:24750b9ad5ef 225 * Additional precaution: make sure Q is valid
Christopher Haster 1:24750b9ad5ef 226 */
Christopher Haster 1:24750b9ad5ef 227 MBEDTLS_MPI_CHK( mbedtls_ecp_check_pubkey( grp, Q ) );
Christopher Haster 1:24750b9ad5ef 228
Christopher Haster 1:24750b9ad5ef 229 /*
Christopher Haster 1:24750b9ad5ef 230 * Step 3: derive MPI from hashed message
Christopher Haster 1:24750b9ad5ef 231 */
Christopher Haster 1:24750b9ad5ef 232 MBEDTLS_MPI_CHK( derive_mpi( grp, &e, buf, blen ) );
Christopher Haster 1:24750b9ad5ef 233
Christopher Haster 1:24750b9ad5ef 234 /*
Christopher Haster 1:24750b9ad5ef 235 * Step 4: u1 = e / s mod n, u2 = r / s mod n
Christopher Haster 1:24750b9ad5ef 236 */
Christopher Haster 1:24750b9ad5ef 237 MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( &s_inv, s, &grp->N ) );
Christopher Haster 1:24750b9ad5ef 238
Christopher Haster 1:24750b9ad5ef 239 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &u1, &e, &s_inv ) );
Christopher Haster 1:24750b9ad5ef 240 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &u1, &u1, &grp->N ) );
Christopher Haster 1:24750b9ad5ef 241
Christopher Haster 1:24750b9ad5ef 242 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &u2, r, &s_inv ) );
Christopher Haster 1:24750b9ad5ef 243 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &u2, &u2, &grp->N ) );
Christopher Haster 1:24750b9ad5ef 244
Christopher Haster 1:24750b9ad5ef 245 /*
Christopher Haster 1:24750b9ad5ef 246 * Step 5: R = u1 G + u2 Q
Christopher Haster 1:24750b9ad5ef 247 *
Christopher Haster 1:24750b9ad5ef 248 * Since we're not using any secret data, no need to pass a RNG to
Christopher Haster 1:24750b9ad5ef 249 * mbedtls_ecp_mul() for countermesures.
Christopher Haster 1:24750b9ad5ef 250 */
Christopher Haster 1:24750b9ad5ef 251 MBEDTLS_MPI_CHK( mbedtls_ecp_muladd( grp, &R, &u1, &grp->G, &u2, Q ) );
Christopher Haster 1:24750b9ad5ef 252
Christopher Haster 1:24750b9ad5ef 253 if( mbedtls_ecp_is_zero( &R ) )
Christopher Haster 1:24750b9ad5ef 254 {
Christopher Haster 1:24750b9ad5ef 255 ret = MBEDTLS_ERR_ECP_VERIFY_FAILED;
Christopher Haster 1:24750b9ad5ef 256 goto cleanup;
Christopher Haster 1:24750b9ad5ef 257 }
Christopher Haster 1:24750b9ad5ef 258
Christopher Haster 1:24750b9ad5ef 259 /*
Christopher Haster 1:24750b9ad5ef 260 * Step 6: convert xR to an integer (no-op)
Christopher Haster 1:24750b9ad5ef 261 * Step 7: reduce xR mod n (gives v)
Christopher Haster 1:24750b9ad5ef 262 */
Christopher Haster 1:24750b9ad5ef 263 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &R.X, &R.X, &grp->N ) );
Christopher Haster 1:24750b9ad5ef 264
Christopher Haster 1:24750b9ad5ef 265 /*
Christopher Haster 1:24750b9ad5ef 266 * Step 8: check if v (that is, R.X) is equal to r
Christopher Haster 1:24750b9ad5ef 267 */
Christopher Haster 1:24750b9ad5ef 268 if( mbedtls_mpi_cmp_mpi( &R.X, r ) != 0 )
Christopher Haster 1:24750b9ad5ef 269 {
Christopher Haster 1:24750b9ad5ef 270 ret = MBEDTLS_ERR_ECP_VERIFY_FAILED;
Christopher Haster 1:24750b9ad5ef 271 goto cleanup;
Christopher Haster 1:24750b9ad5ef 272 }
Christopher Haster 1:24750b9ad5ef 273
Christopher Haster 1:24750b9ad5ef 274 cleanup:
Christopher Haster 1:24750b9ad5ef 275 mbedtls_ecp_point_free( &R );
Christopher Haster 1:24750b9ad5ef 276 mbedtls_mpi_free( &e ); mbedtls_mpi_free( &s_inv ); mbedtls_mpi_free( &u1 ); mbedtls_mpi_free( &u2 );
Christopher Haster 1:24750b9ad5ef 277
Christopher Haster 1:24750b9ad5ef 278 return( ret );
Christopher Haster 1:24750b9ad5ef 279 }
Christopher Haster 1:24750b9ad5ef 280
Christopher Haster 1:24750b9ad5ef 281 /*
Christopher Haster 1:24750b9ad5ef 282 * Convert a signature (given by context) to ASN.1
Christopher Haster 1:24750b9ad5ef 283 */
Christopher Haster 1:24750b9ad5ef 284 static int ecdsa_signature_to_asn1( const mbedtls_mpi *r, const mbedtls_mpi *s,
Christopher Haster 1:24750b9ad5ef 285 unsigned char *sig, size_t *slen )
Christopher Haster 1:24750b9ad5ef 286 {
Christopher Haster 1:24750b9ad5ef 287 int ret;
Christopher Haster 1:24750b9ad5ef 288 unsigned char buf[MBEDTLS_ECDSA_MAX_LEN];
Christopher Haster 1:24750b9ad5ef 289 unsigned char *p = buf + sizeof( buf );
Christopher Haster 1:24750b9ad5ef 290 size_t len = 0;
Christopher Haster 1:24750b9ad5ef 291
Christopher Haster 1:24750b9ad5ef 292 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &p, buf, s ) );
Christopher Haster 1:24750b9ad5ef 293 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &p, buf, r ) );
Christopher Haster 1:24750b9ad5ef 294
Christopher Haster 1:24750b9ad5ef 295 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &p, buf, len ) );
Christopher Haster 1:24750b9ad5ef 296 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &p, buf,
Christopher Haster 1:24750b9ad5ef 297 MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) );
Christopher Haster 1:24750b9ad5ef 298
Christopher Haster 1:24750b9ad5ef 299 memcpy( sig, p, len );
Christopher Haster 1:24750b9ad5ef 300 *slen = len;
Christopher Haster 1:24750b9ad5ef 301
Christopher Haster 1:24750b9ad5ef 302 return( 0 );
Christopher Haster 1:24750b9ad5ef 303 }
Christopher Haster 1:24750b9ad5ef 304
Christopher Haster 1:24750b9ad5ef 305 /*
Christopher Haster 1:24750b9ad5ef 306 * Compute and write signature
Christopher Haster 1:24750b9ad5ef 307 */
Christopher Haster 1:24750b9ad5ef 308 int mbedtls_ecdsa_write_signature( mbedtls_ecdsa_context *ctx, mbedtls_md_type_t md_alg,
Christopher Haster 1:24750b9ad5ef 309 const unsigned char *hash, size_t hlen,
Christopher Haster 1:24750b9ad5ef 310 unsigned char *sig, size_t *slen,
Christopher Haster 1:24750b9ad5ef 311 int (*f_rng)(void *, unsigned char *, size_t),
Christopher Haster 1:24750b9ad5ef 312 void *p_rng )
Christopher Haster 1:24750b9ad5ef 313 {
Christopher Haster 1:24750b9ad5ef 314 int ret;
Christopher Haster 1:24750b9ad5ef 315 mbedtls_mpi r, s;
Christopher Haster 1:24750b9ad5ef 316
Christopher Haster 1:24750b9ad5ef 317 mbedtls_mpi_init( &r );
Christopher Haster 1:24750b9ad5ef 318 mbedtls_mpi_init( &s );
Christopher Haster 1:24750b9ad5ef 319
Christopher Haster 1:24750b9ad5ef 320 #if defined(MBEDTLS_ECDSA_DETERMINISTIC)
Christopher Haster 1:24750b9ad5ef 321 (void) f_rng;
Christopher Haster 1:24750b9ad5ef 322 (void) p_rng;
Christopher Haster 1:24750b9ad5ef 323
Christopher Haster 1:24750b9ad5ef 324 MBEDTLS_MPI_CHK( mbedtls_ecdsa_sign_det( &ctx->grp, &r, &s, &ctx->d,
Christopher Haster 1:24750b9ad5ef 325 hash, hlen, md_alg ) );
Christopher Haster 1:24750b9ad5ef 326 #else
Christopher Haster 1:24750b9ad5ef 327 (void) md_alg;
Christopher Haster 1:24750b9ad5ef 328
Christopher Haster 1:24750b9ad5ef 329 MBEDTLS_MPI_CHK( mbedtls_ecdsa_sign( &ctx->grp, &r, &s, &ctx->d,
Christopher Haster 1:24750b9ad5ef 330 hash, hlen, f_rng, p_rng ) );
Christopher Haster 1:24750b9ad5ef 331 #endif
Christopher Haster 1:24750b9ad5ef 332
Christopher Haster 1:24750b9ad5ef 333 MBEDTLS_MPI_CHK( ecdsa_signature_to_asn1( &r, &s, sig, slen ) );
Christopher Haster 1:24750b9ad5ef 334
Christopher Haster 1:24750b9ad5ef 335 cleanup:
Christopher Haster 1:24750b9ad5ef 336 mbedtls_mpi_free( &r );
Christopher Haster 1:24750b9ad5ef 337 mbedtls_mpi_free( &s );
Christopher Haster 1:24750b9ad5ef 338
Christopher Haster 1:24750b9ad5ef 339 return( ret );
Christopher Haster 1:24750b9ad5ef 340 }
Christopher Haster 1:24750b9ad5ef 341
Christopher Haster 1:24750b9ad5ef 342 #if ! defined(MBEDTLS_DEPRECATED_REMOVED) && \
Christopher Haster 1:24750b9ad5ef 343 defined(MBEDTLS_ECDSA_DETERMINISTIC)
Christopher Haster 1:24750b9ad5ef 344 int mbedtls_ecdsa_write_signature_det( mbedtls_ecdsa_context *ctx,
Christopher Haster 1:24750b9ad5ef 345 const unsigned char *hash, size_t hlen,
Christopher Haster 1:24750b9ad5ef 346 unsigned char *sig, size_t *slen,
Christopher Haster 1:24750b9ad5ef 347 mbedtls_md_type_t md_alg )
Christopher Haster 1:24750b9ad5ef 348 {
Christopher Haster 1:24750b9ad5ef 349 return( mbedtls_ecdsa_write_signature( ctx, md_alg, hash, hlen, sig, slen,
Christopher Haster 1:24750b9ad5ef 350 NULL, NULL ) );
Christopher Haster 1:24750b9ad5ef 351 }
Christopher Haster 1:24750b9ad5ef 352 #endif
Christopher Haster 1:24750b9ad5ef 353
Christopher Haster 1:24750b9ad5ef 354 /*
Christopher Haster 1:24750b9ad5ef 355 * Read and check signature
Christopher Haster 1:24750b9ad5ef 356 */
Christopher Haster 1:24750b9ad5ef 357 int mbedtls_ecdsa_read_signature( mbedtls_ecdsa_context *ctx,
Christopher Haster 1:24750b9ad5ef 358 const unsigned char *hash, size_t hlen,
Christopher Haster 1:24750b9ad5ef 359 const unsigned char *sig, size_t slen )
Christopher Haster 1:24750b9ad5ef 360 {
Christopher Haster 1:24750b9ad5ef 361 int ret;
Christopher Haster 1:24750b9ad5ef 362 unsigned char *p = (unsigned char *) sig;
Christopher Haster 1:24750b9ad5ef 363 const unsigned char *end = sig + slen;
Christopher Haster 1:24750b9ad5ef 364 size_t len;
Christopher Haster 1:24750b9ad5ef 365 mbedtls_mpi r, s;
Christopher Haster 1:24750b9ad5ef 366
Christopher Haster 1:24750b9ad5ef 367 mbedtls_mpi_init( &r );
Christopher Haster 1:24750b9ad5ef 368 mbedtls_mpi_init( &s );
Christopher Haster 1:24750b9ad5ef 369
Christopher Haster 1:24750b9ad5ef 370 if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
Christopher Haster 1:24750b9ad5ef 371 MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 )
Christopher Haster 1:24750b9ad5ef 372 {
Christopher Haster 1:24750b9ad5ef 373 ret += MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
Christopher Haster 1:24750b9ad5ef 374 goto cleanup;
Christopher Haster 1:24750b9ad5ef 375 }
Christopher Haster 1:24750b9ad5ef 376
Christopher Haster 1:24750b9ad5ef 377 if( p + len != end )
Christopher Haster 1:24750b9ad5ef 378 {
Christopher Haster 1:24750b9ad5ef 379 ret = MBEDTLS_ERR_ECP_BAD_INPUT_DATA +
Christopher Haster 1:24750b9ad5ef 380 MBEDTLS_ERR_ASN1_LENGTH_MISMATCH;
Christopher Haster 1:24750b9ad5ef 381 goto cleanup;
Christopher Haster 1:24750b9ad5ef 382 }
Christopher Haster 1:24750b9ad5ef 383
Christopher Haster 1:24750b9ad5ef 384 if( ( ret = mbedtls_asn1_get_mpi( &p, end, &r ) ) != 0 ||
Christopher Haster 1:24750b9ad5ef 385 ( ret = mbedtls_asn1_get_mpi( &p, end, &s ) ) != 0 )
Christopher Haster 1:24750b9ad5ef 386 {
Christopher Haster 1:24750b9ad5ef 387 ret += MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
Christopher Haster 1:24750b9ad5ef 388 goto cleanup;
Christopher Haster 1:24750b9ad5ef 389 }
Christopher Haster 1:24750b9ad5ef 390
Christopher Haster 1:24750b9ad5ef 391 if( ( ret = mbedtls_ecdsa_verify( &ctx->grp, hash, hlen,
Christopher Haster 1:24750b9ad5ef 392 &ctx->Q, &r, &s ) ) != 0 )
Christopher Haster 1:24750b9ad5ef 393 goto cleanup;
Christopher Haster 1:24750b9ad5ef 394
Christopher Haster 1:24750b9ad5ef 395 if( p != end )
Christopher Haster 1:24750b9ad5ef 396 ret = MBEDTLS_ERR_ECP_SIG_LEN_MISMATCH;
Christopher Haster 1:24750b9ad5ef 397
Christopher Haster 1:24750b9ad5ef 398 cleanup:
Christopher Haster 1:24750b9ad5ef 399 mbedtls_mpi_free( &r );
Christopher Haster 1:24750b9ad5ef 400 mbedtls_mpi_free( &s );
Christopher Haster 1:24750b9ad5ef 401
Christopher Haster 1:24750b9ad5ef 402 return( ret );
Christopher Haster 1:24750b9ad5ef 403 }
Christopher Haster 1:24750b9ad5ef 404
Christopher Haster 1:24750b9ad5ef 405 /*
Christopher Haster 1:24750b9ad5ef 406 * Generate key pair
Christopher Haster 1:24750b9ad5ef 407 */
Christopher Haster 1:24750b9ad5ef 408 int mbedtls_ecdsa_genkey( mbedtls_ecdsa_context *ctx, mbedtls_ecp_group_id gid,
Christopher Haster 1:24750b9ad5ef 409 int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
Christopher Haster 1:24750b9ad5ef 410 {
Christopher Haster 1:24750b9ad5ef 411 return( mbedtls_ecp_group_load( &ctx->grp, gid ) ||
Christopher Haster 1:24750b9ad5ef 412 mbedtls_ecp_gen_keypair( &ctx->grp, &ctx->d, &ctx->Q, f_rng, p_rng ) );
Christopher Haster 1:24750b9ad5ef 413 }
Christopher Haster 1:24750b9ad5ef 414
Christopher Haster 1:24750b9ad5ef 415 /*
Christopher Haster 1:24750b9ad5ef 416 * Set context from an mbedtls_ecp_keypair
Christopher Haster 1:24750b9ad5ef 417 */
Christopher Haster 1:24750b9ad5ef 418 int mbedtls_ecdsa_from_keypair( mbedtls_ecdsa_context *ctx, const mbedtls_ecp_keypair *key )
Christopher Haster 1:24750b9ad5ef 419 {
Christopher Haster 1:24750b9ad5ef 420 int ret;
Christopher Haster 1:24750b9ad5ef 421
Christopher Haster 1:24750b9ad5ef 422 if( ( ret = mbedtls_ecp_group_copy( &ctx->grp, &key->grp ) ) != 0 ||
Christopher Haster 1:24750b9ad5ef 423 ( ret = mbedtls_mpi_copy( &ctx->d, &key->d ) ) != 0 ||
Christopher Haster 1:24750b9ad5ef 424 ( ret = mbedtls_ecp_copy( &ctx->Q, &key->Q ) ) != 0 )
Christopher Haster 1:24750b9ad5ef 425 {
Christopher Haster 1:24750b9ad5ef 426 mbedtls_ecdsa_free( ctx );
Christopher Haster 1:24750b9ad5ef 427 }
Christopher Haster 1:24750b9ad5ef 428
Christopher Haster 1:24750b9ad5ef 429 return( ret );
Christopher Haster 1:24750b9ad5ef 430 }
Christopher Haster 1:24750b9ad5ef 431
Christopher Haster 1:24750b9ad5ef 432 /*
Christopher Haster 1:24750b9ad5ef 433 * Initialize context
Christopher Haster 1:24750b9ad5ef 434 */
Christopher Haster 1:24750b9ad5ef 435 void mbedtls_ecdsa_init( mbedtls_ecdsa_context *ctx )
Christopher Haster 1:24750b9ad5ef 436 {
Christopher Haster 1:24750b9ad5ef 437 mbedtls_ecp_keypair_init( ctx );
Christopher Haster 1:24750b9ad5ef 438 }
Christopher Haster 1:24750b9ad5ef 439
Christopher Haster 1:24750b9ad5ef 440 /*
Christopher Haster 1:24750b9ad5ef 441 * Free context
Christopher Haster 1:24750b9ad5ef 442 */
Christopher Haster 1:24750b9ad5ef 443 void mbedtls_ecdsa_free( mbedtls_ecdsa_context *ctx )
Christopher Haster 1:24750b9ad5ef 444 {
Christopher Haster 1:24750b9ad5ef 445 mbedtls_ecp_keypair_free( ctx );
Christopher Haster 1:24750b9ad5ef 446 }
Christopher Haster 1:24750b9ad5ef 447
Christopher Haster 1:24750b9ad5ef 448 #endif /* MBEDTLS_ECDSA_C */