Simon Cooksey / mbed-os

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features/mbedtls/src/ecdh.c@0:fb7af294d5d9, 2016-11-17 (annotated)

Committer:
Simon Cooksey
Date:
Thu Nov 17 16:43:53 2016 +0000
Revision:
0:fb7af294d5d9
Initial commit

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Simon Cooksey 0:fb7af294d5d9 1 /*
Simon Cooksey 0:fb7af294d5d9 2 * Elliptic curve Diffie-Hellman
Simon Cooksey 0:fb7af294d5d9 3 *
Simon Cooksey 0:fb7af294d5d9 4 * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
Simon Cooksey 0:fb7af294d5d9 5 * SPDX-License-Identifier: Apache-2.0
Simon Cooksey 0:fb7af294d5d9 6 *
Simon Cooksey 0:fb7af294d5d9 7 * Licensed under the Apache License, Version 2.0 (the "License"); you may
Simon Cooksey 0:fb7af294d5d9 8 * not use this file except in compliance with the License.
Simon Cooksey 0:fb7af294d5d9 9 * You may obtain a copy of the License at
Simon Cooksey 0:fb7af294d5d9 10 *
Simon Cooksey 0:fb7af294d5d9 11 * http://www.apache.org/licenses/LICENSE-2.0
Simon Cooksey 0:fb7af294d5d9 12 *
Simon Cooksey 0:fb7af294d5d9 13 * Unless required by applicable law or agreed to in writing, software
Simon Cooksey 0:fb7af294d5d9 14 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
Simon Cooksey 0:fb7af294d5d9 15 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
Simon Cooksey 0:fb7af294d5d9 16 * See the License for the specific language governing permissions and
Simon Cooksey 0:fb7af294d5d9 17 * limitations under the License.
Simon Cooksey 0:fb7af294d5d9 18 *
Simon Cooksey 0:fb7af294d5d9 19 * This file is part of mbed TLS (https://tls.mbed.org)
Simon Cooksey 0:fb7af294d5d9 20 */
Simon Cooksey 0:fb7af294d5d9 21
Simon Cooksey 0:fb7af294d5d9 22 /*
Simon Cooksey 0:fb7af294d5d9 23 * References:
Simon Cooksey 0:fb7af294d5d9 24 *
Simon Cooksey 0:fb7af294d5d9 25 * SEC1 http://www.secg.org/index.php?action=secg,docs_secg
Simon Cooksey 0:fb7af294d5d9 26 * RFC 4492
Simon Cooksey 0:fb7af294d5d9 27 */
Simon Cooksey 0:fb7af294d5d9 28
Simon Cooksey 0:fb7af294d5d9 29 #if !defined(MBEDTLS_CONFIG_FILE)
Simon Cooksey 0:fb7af294d5d9 30 #include "mbedtls/config.h"
Simon Cooksey 0:fb7af294d5d9 31 #else
Simon Cooksey 0:fb7af294d5d9 32 #include MBEDTLS_CONFIG_FILE
Simon Cooksey 0:fb7af294d5d9 33 #endif
Simon Cooksey 0:fb7af294d5d9 34
Simon Cooksey 0:fb7af294d5d9 35 #if defined(MBEDTLS_ECDH_C)
Simon Cooksey 0:fb7af294d5d9 36
Simon Cooksey 0:fb7af294d5d9 37 #include "mbedtls/ecdh.h"
Simon Cooksey 0:fb7af294d5d9 38
Simon Cooksey 0:fb7af294d5d9 39 #include <string.h>
Simon Cooksey 0:fb7af294d5d9 40
Simon Cooksey 0:fb7af294d5d9 41 /*
Simon Cooksey 0:fb7af294d5d9 42 * Generate public key: simple wrapper around mbedtls_ecp_gen_keypair
Simon Cooksey 0:fb7af294d5d9 43 */
Simon Cooksey 0:fb7af294d5d9 44 int mbedtls_ecdh_gen_public( mbedtls_ecp_group *grp, mbedtls_mpi *d, mbedtls_ecp_point *Q,
Simon Cooksey 0:fb7af294d5d9 45 int (*f_rng)(void *, unsigned char *, size_t),
Simon Cooksey 0:fb7af294d5d9 46 void *p_rng )
Simon Cooksey 0:fb7af294d5d9 47 {
Simon Cooksey 0:fb7af294d5d9 48 return mbedtls_ecp_gen_keypair( grp, d, Q, f_rng, p_rng );
Simon Cooksey 0:fb7af294d5d9 49 }
Simon Cooksey 0:fb7af294d5d9 50
Simon Cooksey 0:fb7af294d5d9 51 /*
Simon Cooksey 0:fb7af294d5d9 52 * Compute shared secret (SEC1 3.3.1)
Simon Cooksey 0:fb7af294d5d9 53 */
Simon Cooksey 0:fb7af294d5d9 54 int mbedtls_ecdh_compute_shared( mbedtls_ecp_group *grp, mbedtls_mpi *z,
Simon Cooksey 0:fb7af294d5d9 55 const mbedtls_ecp_point *Q, const mbedtls_mpi *d,
Simon Cooksey 0:fb7af294d5d9 56 int (*f_rng)(void *, unsigned char *, size_t),
Simon Cooksey 0:fb7af294d5d9 57 void *p_rng )
Simon Cooksey 0:fb7af294d5d9 58 {
Simon Cooksey 0:fb7af294d5d9 59 int ret;
Simon Cooksey 0:fb7af294d5d9 60 mbedtls_ecp_point P;
Simon Cooksey 0:fb7af294d5d9 61
Simon Cooksey 0:fb7af294d5d9 62 mbedtls_ecp_point_init( &P );
Simon Cooksey 0:fb7af294d5d9 63
Simon Cooksey 0:fb7af294d5d9 64 /*
Simon Cooksey 0:fb7af294d5d9 65 * Make sure Q is a valid pubkey before using it
Simon Cooksey 0:fb7af294d5d9 66 */
Simon Cooksey 0:fb7af294d5d9 67 MBEDTLS_MPI_CHK( mbedtls_ecp_check_pubkey( grp, Q ) );
Simon Cooksey 0:fb7af294d5d9 68
Simon Cooksey 0:fb7af294d5d9 69 MBEDTLS_MPI_CHK( mbedtls_ecp_mul( grp, &P, d, Q, f_rng, p_rng ) );
Simon Cooksey 0:fb7af294d5d9 70
Simon Cooksey 0:fb7af294d5d9 71 if( mbedtls_ecp_is_zero( &P ) )
Simon Cooksey 0:fb7af294d5d9 72 {
Simon Cooksey 0:fb7af294d5d9 73 ret = MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
Simon Cooksey 0:fb7af294d5d9 74 goto cleanup;
Simon Cooksey 0:fb7af294d5d9 75 }
Simon Cooksey 0:fb7af294d5d9 76
Simon Cooksey 0:fb7af294d5d9 77 MBEDTLS_MPI_CHK( mbedtls_mpi_copy( z, &P.X ) );
Simon Cooksey 0:fb7af294d5d9 78
Simon Cooksey 0:fb7af294d5d9 79 cleanup:
Simon Cooksey 0:fb7af294d5d9 80 mbedtls_ecp_point_free( &P );
Simon Cooksey 0:fb7af294d5d9 81
Simon Cooksey 0:fb7af294d5d9 82 return( ret );
Simon Cooksey 0:fb7af294d5d9 83 }
Simon Cooksey 0:fb7af294d5d9 84
Simon Cooksey 0:fb7af294d5d9 85 /*
Simon Cooksey 0:fb7af294d5d9 86 * Initialize context
Simon Cooksey 0:fb7af294d5d9 87 */
Simon Cooksey 0:fb7af294d5d9 88 void mbedtls_ecdh_init( mbedtls_ecdh_context *ctx )
Simon Cooksey 0:fb7af294d5d9 89 {
Simon Cooksey 0:fb7af294d5d9 90 memset( ctx, 0, sizeof( mbedtls_ecdh_context ) );
Simon Cooksey 0:fb7af294d5d9 91 }
Simon Cooksey 0:fb7af294d5d9 92
Simon Cooksey 0:fb7af294d5d9 93 /*
Simon Cooksey 0:fb7af294d5d9 94 * Free context
Simon Cooksey 0:fb7af294d5d9 95 */
Simon Cooksey 0:fb7af294d5d9 96 void mbedtls_ecdh_free( mbedtls_ecdh_context *ctx )
Simon Cooksey 0:fb7af294d5d9 97 {
Simon Cooksey 0:fb7af294d5d9 98 if( ctx == NULL )
Simon Cooksey 0:fb7af294d5d9 99 return;
Simon Cooksey 0:fb7af294d5d9 100
Simon Cooksey 0:fb7af294d5d9 101 mbedtls_ecp_group_free( &ctx->grp );
Simon Cooksey 0:fb7af294d5d9 102 mbedtls_ecp_point_free( &ctx->Q );
Simon Cooksey 0:fb7af294d5d9 103 mbedtls_ecp_point_free( &ctx->Qp );
Simon Cooksey 0:fb7af294d5d9 104 mbedtls_ecp_point_free( &ctx->Vi );
Simon Cooksey 0:fb7af294d5d9 105 mbedtls_ecp_point_free( &ctx->Vf );
Simon Cooksey 0:fb7af294d5d9 106 mbedtls_mpi_free( &ctx->d );
Simon Cooksey 0:fb7af294d5d9 107 mbedtls_mpi_free( &ctx->z );
Simon Cooksey 0:fb7af294d5d9 108 mbedtls_mpi_free( &ctx->_d );
Simon Cooksey 0:fb7af294d5d9 109 }
Simon Cooksey 0:fb7af294d5d9 110
Simon Cooksey 0:fb7af294d5d9 111 /*
Simon Cooksey 0:fb7af294d5d9 112 * Setup and write the ServerKeyExhange parameters (RFC 4492)
Simon Cooksey 0:fb7af294d5d9 113 * struct {
Simon Cooksey 0:fb7af294d5d9 114 * ECParameters curve_params;
Simon Cooksey 0:fb7af294d5d9 115 * ECPoint public;
Simon Cooksey 0:fb7af294d5d9 116 * } ServerECDHParams;
Simon Cooksey 0:fb7af294d5d9 117 */
Simon Cooksey 0:fb7af294d5d9 118 int mbedtls_ecdh_make_params( mbedtls_ecdh_context *ctx, size_t *olen,
Simon Cooksey 0:fb7af294d5d9 119 unsigned char *buf, size_t blen,
Simon Cooksey 0:fb7af294d5d9 120 int (*f_rng)(void *, unsigned char *, size_t),
Simon Cooksey 0:fb7af294d5d9 121 void *p_rng )
Simon Cooksey 0:fb7af294d5d9 122 {
Simon Cooksey 0:fb7af294d5d9 123 int ret;
Simon Cooksey 0:fb7af294d5d9 124 size_t grp_len, pt_len;
Simon Cooksey 0:fb7af294d5d9 125
Simon Cooksey 0:fb7af294d5d9 126 if( ctx == NULL || ctx->grp.pbits == 0 )
Simon Cooksey 0:fb7af294d5d9 127 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
Simon Cooksey 0:fb7af294d5d9 128
Simon Cooksey 0:fb7af294d5d9 129 if( ( ret = mbedtls_ecdh_gen_public( &ctx->grp, &ctx->d, &ctx->Q, f_rng, p_rng ) )
Simon Cooksey 0:fb7af294d5d9 130 != 0 )
Simon Cooksey 0:fb7af294d5d9 131 return( ret );
Simon Cooksey 0:fb7af294d5d9 132
Simon Cooksey 0:fb7af294d5d9 133 if( ( ret = mbedtls_ecp_tls_write_group( &ctx->grp, &grp_len, buf, blen ) )
Simon Cooksey 0:fb7af294d5d9 134 != 0 )
Simon Cooksey 0:fb7af294d5d9 135 return( ret );
Simon Cooksey 0:fb7af294d5d9 136
Simon Cooksey 0:fb7af294d5d9 137 buf += grp_len;
Simon Cooksey 0:fb7af294d5d9 138 blen -= grp_len;
Simon Cooksey 0:fb7af294d5d9 139
Simon Cooksey 0:fb7af294d5d9 140 if( ( ret = mbedtls_ecp_tls_write_point( &ctx->grp, &ctx->Q, ctx->point_format,
Simon Cooksey 0:fb7af294d5d9 141 &pt_len, buf, blen ) ) != 0 )
Simon Cooksey 0:fb7af294d5d9 142 return( ret );
Simon Cooksey 0:fb7af294d5d9 143
Simon Cooksey 0:fb7af294d5d9 144 *olen = grp_len + pt_len;
Simon Cooksey 0:fb7af294d5d9 145 return( 0 );
Simon Cooksey 0:fb7af294d5d9 146 }
Simon Cooksey 0:fb7af294d5d9 147
Simon Cooksey 0:fb7af294d5d9 148 /*
Simon Cooksey 0:fb7af294d5d9 149 * Read the ServerKeyExhange parameters (RFC 4492)
Simon Cooksey 0:fb7af294d5d9 150 * struct {
Simon Cooksey 0:fb7af294d5d9 151 * ECParameters curve_params;
Simon Cooksey 0:fb7af294d5d9 152 * ECPoint public;
Simon Cooksey 0:fb7af294d5d9 153 * } ServerECDHParams;
Simon Cooksey 0:fb7af294d5d9 154 */
Simon Cooksey 0:fb7af294d5d9 155 int mbedtls_ecdh_read_params( mbedtls_ecdh_context *ctx,
Simon Cooksey 0:fb7af294d5d9 156 const unsigned char **buf, const unsigned char *end )
Simon Cooksey 0:fb7af294d5d9 157 {
Simon Cooksey 0:fb7af294d5d9 158 int ret;
Simon Cooksey 0:fb7af294d5d9 159
Simon Cooksey 0:fb7af294d5d9 160 if( ( ret = mbedtls_ecp_tls_read_group( &ctx->grp, buf, end - *buf ) ) != 0 )
Simon Cooksey 0:fb7af294d5d9 161 return( ret );
Simon Cooksey 0:fb7af294d5d9 162
Simon Cooksey 0:fb7af294d5d9 163 if( ( ret = mbedtls_ecp_tls_read_point( &ctx->grp, &ctx->Qp, buf, end - *buf ) )
Simon Cooksey 0:fb7af294d5d9 164 != 0 )
Simon Cooksey 0:fb7af294d5d9 165 return( ret );
Simon Cooksey 0:fb7af294d5d9 166
Simon Cooksey 0:fb7af294d5d9 167 return( 0 );
Simon Cooksey 0:fb7af294d5d9 168 }
Simon Cooksey 0:fb7af294d5d9 169
Simon Cooksey 0:fb7af294d5d9 170 /*
Simon Cooksey 0:fb7af294d5d9 171 * Get parameters from a keypair
Simon Cooksey 0:fb7af294d5d9 172 */
Simon Cooksey 0:fb7af294d5d9 173 int mbedtls_ecdh_get_params( mbedtls_ecdh_context *ctx, const mbedtls_ecp_keypair *key,
Simon Cooksey 0:fb7af294d5d9 174 mbedtls_ecdh_side side )
Simon Cooksey 0:fb7af294d5d9 175 {
Simon Cooksey 0:fb7af294d5d9 176 int ret;
Simon Cooksey 0:fb7af294d5d9 177
Simon Cooksey 0:fb7af294d5d9 178 if( ( ret = mbedtls_ecp_group_copy( &ctx->grp, &key->grp ) ) != 0 )
Simon Cooksey 0:fb7af294d5d9 179 return( ret );
Simon Cooksey 0:fb7af294d5d9 180
Simon Cooksey 0:fb7af294d5d9 181 /* If it's not our key, just import the public part as Qp */
Simon Cooksey 0:fb7af294d5d9 182 if( side == MBEDTLS_ECDH_THEIRS )
Simon Cooksey 0:fb7af294d5d9 183 return( mbedtls_ecp_copy( &ctx->Qp, &key->Q ) );
Simon Cooksey 0:fb7af294d5d9 184
Simon Cooksey 0:fb7af294d5d9 185 /* Our key: import public (as Q) and private parts */
Simon Cooksey 0:fb7af294d5d9 186 if( side != MBEDTLS_ECDH_OURS )
Simon Cooksey 0:fb7af294d5d9 187 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
Simon Cooksey 0:fb7af294d5d9 188
Simon Cooksey 0:fb7af294d5d9 189 if( ( ret = mbedtls_ecp_copy( &ctx->Q, &key->Q ) ) != 0 ||
Simon Cooksey 0:fb7af294d5d9 190 ( ret = mbedtls_mpi_copy( &ctx->d, &key->d ) ) != 0 )
Simon Cooksey 0:fb7af294d5d9 191 return( ret );
Simon Cooksey 0:fb7af294d5d9 192
Simon Cooksey 0:fb7af294d5d9 193 return( 0 );
Simon Cooksey 0:fb7af294d5d9 194 }
Simon Cooksey 0:fb7af294d5d9 195
Simon Cooksey 0:fb7af294d5d9 196 /*
Simon Cooksey 0:fb7af294d5d9 197 * Setup and export the client public value
Simon Cooksey 0:fb7af294d5d9 198 */
Simon Cooksey 0:fb7af294d5d9 199 int mbedtls_ecdh_make_public( mbedtls_ecdh_context *ctx, size_t *olen,
Simon Cooksey 0:fb7af294d5d9 200 unsigned char *buf, size_t blen,
Simon Cooksey 0:fb7af294d5d9 201 int (*f_rng)(void *, unsigned char *, size_t),
Simon Cooksey 0:fb7af294d5d9 202 void *p_rng )
Simon Cooksey 0:fb7af294d5d9 203 {
Simon Cooksey 0:fb7af294d5d9 204 int ret;
Simon Cooksey 0:fb7af294d5d9 205
Simon Cooksey 0:fb7af294d5d9 206 if( ctx == NULL || ctx->grp.pbits == 0 )
Simon Cooksey 0:fb7af294d5d9 207 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
Simon Cooksey 0:fb7af294d5d9 208
Simon Cooksey 0:fb7af294d5d9 209 if( ( ret = mbedtls_ecdh_gen_public( &ctx->grp, &ctx->d, &ctx->Q, f_rng, p_rng ) )
Simon Cooksey 0:fb7af294d5d9 210 != 0 )
Simon Cooksey 0:fb7af294d5d9 211 return( ret );
Simon Cooksey 0:fb7af294d5d9 212
Simon Cooksey 0:fb7af294d5d9 213 return mbedtls_ecp_tls_write_point( &ctx->grp, &ctx->Q, ctx->point_format,
Simon Cooksey 0:fb7af294d5d9 214 olen, buf, blen );
Simon Cooksey 0:fb7af294d5d9 215 }
Simon Cooksey 0:fb7af294d5d9 216
Simon Cooksey 0:fb7af294d5d9 217 /*
Simon Cooksey 0:fb7af294d5d9 218 * Parse and import the client's public value
Simon Cooksey 0:fb7af294d5d9 219 */
Simon Cooksey 0:fb7af294d5d9 220 int mbedtls_ecdh_read_public( mbedtls_ecdh_context *ctx,
Simon Cooksey 0:fb7af294d5d9 221 const unsigned char *buf, size_t blen )
Simon Cooksey 0:fb7af294d5d9 222 {
Simon Cooksey 0:fb7af294d5d9 223 int ret;
Simon Cooksey 0:fb7af294d5d9 224 const unsigned char *p = buf;
Simon Cooksey 0:fb7af294d5d9 225
Simon Cooksey 0:fb7af294d5d9 226 if( ctx == NULL )
Simon Cooksey 0:fb7af294d5d9 227 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
Simon Cooksey 0:fb7af294d5d9 228
Simon Cooksey 0:fb7af294d5d9 229 if( ( ret = mbedtls_ecp_tls_read_point( &ctx->grp, &ctx->Qp, &p, blen ) ) != 0 )
Simon Cooksey 0:fb7af294d5d9 230 return( ret );
Simon Cooksey 0:fb7af294d5d9 231
Simon Cooksey 0:fb7af294d5d9 232 if( (size_t)( p - buf ) != blen )
Simon Cooksey 0:fb7af294d5d9 233 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
Simon Cooksey 0:fb7af294d5d9 234
Simon Cooksey 0:fb7af294d5d9 235 return( 0 );
Simon Cooksey 0:fb7af294d5d9 236 }
Simon Cooksey 0:fb7af294d5d9 237
Simon Cooksey 0:fb7af294d5d9 238 /*
Simon Cooksey 0:fb7af294d5d9 239 * Derive and export the shared secret
Simon Cooksey 0:fb7af294d5d9 240 */
Simon Cooksey 0:fb7af294d5d9 241 int mbedtls_ecdh_calc_secret( mbedtls_ecdh_context *ctx, size_t *olen,
Simon Cooksey 0:fb7af294d5d9 242 unsigned char *buf, size_t blen,
Simon Cooksey 0:fb7af294d5d9 243 int (*f_rng)(void *, unsigned char *, size_t),
Simon Cooksey 0:fb7af294d5d9 244 void *p_rng )
Simon Cooksey 0:fb7af294d5d9 245 {
Simon Cooksey 0:fb7af294d5d9 246 int ret;
Simon Cooksey 0:fb7af294d5d9 247
Simon Cooksey 0:fb7af294d5d9 248 if( ctx == NULL )
Simon Cooksey 0:fb7af294d5d9 249 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
Simon Cooksey 0:fb7af294d5d9 250
Simon Cooksey 0:fb7af294d5d9 251 if( ( ret = mbedtls_ecdh_compute_shared( &ctx->grp, &ctx->z, &ctx->Qp, &ctx->d,
Simon Cooksey 0:fb7af294d5d9 252 f_rng, p_rng ) ) != 0 )
Simon Cooksey 0:fb7af294d5d9 253 {
Simon Cooksey 0:fb7af294d5d9 254 return( ret );
Simon Cooksey 0:fb7af294d5d9 255 }
Simon Cooksey 0:fb7af294d5d9 256
Simon Cooksey 0:fb7af294d5d9 257 if( mbedtls_mpi_size( &ctx->z ) > blen )
Simon Cooksey 0:fb7af294d5d9 258 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
Simon Cooksey 0:fb7af294d5d9 259
Simon Cooksey 0:fb7af294d5d9 260 *olen = ctx->grp.pbits / 8 + ( ( ctx->grp.pbits % 8 ) != 0 );
Simon Cooksey 0:fb7af294d5d9 261 return mbedtls_mpi_write_binary( &ctx->z, buf, *olen );
Simon Cooksey 0:fb7af294d5d9 262 }
Simon Cooksey 0:fb7af294d5d9 263
Simon Cooksey 0:fb7af294d5d9 264 #endif /* MBEDTLS_ECDH_C */