EL4121 Embedded System / mbed-os

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features/mbedtls/src/ecdh.c@0:b74591d5ab33, 2017-12-11 (annotated)

Committer:
be_bryan
Date:
Mon Dec 11 17:54:04 2017 +0000
Revision:
0:b74591d5ab33
motor ++

Who changed what in which revision?

UserRevisionLine numberNew contents of line
be_bryan 0:b74591d5ab33 1 /*
be_bryan 0:b74591d5ab33 2 * Elliptic curve Diffie-Hellman
be_bryan 0:b74591d5ab33 3 *
be_bryan 0:b74591d5ab33 4 * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
be_bryan 0:b74591d5ab33 5 * SPDX-License-Identifier: Apache-2.0
be_bryan 0:b74591d5ab33 6 *
be_bryan 0:b74591d5ab33 7 * Licensed under the Apache License, Version 2.0 (the "License"); you may
be_bryan 0:b74591d5ab33 8 * not use this file except in compliance with the License.
be_bryan 0:b74591d5ab33 9 * You may obtain a copy of the License at
be_bryan 0:b74591d5ab33 10 *
be_bryan 0:b74591d5ab33 11 * http://www.apache.org/licenses/LICENSE-2.0
be_bryan 0:b74591d5ab33 12 *
be_bryan 0:b74591d5ab33 13 * Unless required by applicable law or agreed to in writing, software
be_bryan 0:b74591d5ab33 14 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
be_bryan 0:b74591d5ab33 15 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
be_bryan 0:b74591d5ab33 16 * See the License for the specific language governing permissions and
be_bryan 0:b74591d5ab33 17 * limitations under the License.
be_bryan 0:b74591d5ab33 18 *
be_bryan 0:b74591d5ab33 19 * This file is part of mbed TLS (https://tls.mbed.org)
be_bryan 0:b74591d5ab33 20 */
be_bryan 0:b74591d5ab33 21
be_bryan 0:b74591d5ab33 22 /*
be_bryan 0:b74591d5ab33 23 * References:
be_bryan 0:b74591d5ab33 24 *
be_bryan 0:b74591d5ab33 25 * SEC1 http://www.secg.org/index.php?action=secg,docs_secg
be_bryan 0:b74591d5ab33 26 * RFC 4492
be_bryan 0:b74591d5ab33 27 */
be_bryan 0:b74591d5ab33 28
be_bryan 0:b74591d5ab33 29 #if !defined(MBEDTLS_CONFIG_FILE)
be_bryan 0:b74591d5ab33 30 #include "mbedtls/config.h"
be_bryan 0:b74591d5ab33 31 #else
be_bryan 0:b74591d5ab33 32 #include MBEDTLS_CONFIG_FILE
be_bryan 0:b74591d5ab33 33 #endif
be_bryan 0:b74591d5ab33 34
be_bryan 0:b74591d5ab33 35 #if defined(MBEDTLS_ECDH_C)
be_bryan 0:b74591d5ab33 36
be_bryan 0:b74591d5ab33 37 #include "mbedtls/ecdh.h"
be_bryan 0:b74591d5ab33 38
be_bryan 0:b74591d5ab33 39 #include <string.h>
be_bryan 0:b74591d5ab33 40
be_bryan 0:b74591d5ab33 41 /*
be_bryan 0:b74591d5ab33 42 * Generate public key: simple wrapper around mbedtls_ecp_gen_keypair
be_bryan 0:b74591d5ab33 43 */
be_bryan 0:b74591d5ab33 44 int mbedtls_ecdh_gen_public( mbedtls_ecp_group *grp, mbedtls_mpi *d, mbedtls_ecp_point *Q,
be_bryan 0:b74591d5ab33 45 int (*f_rng)(void *, unsigned char *, size_t),
be_bryan 0:b74591d5ab33 46 void *p_rng )
be_bryan 0:b74591d5ab33 47 {
be_bryan 0:b74591d5ab33 48 return mbedtls_ecp_gen_keypair( grp, d, Q, f_rng, p_rng );
be_bryan 0:b74591d5ab33 49 }
be_bryan 0:b74591d5ab33 50
be_bryan 0:b74591d5ab33 51 /*
be_bryan 0:b74591d5ab33 52 * Compute shared secret (SEC1 3.3.1)
be_bryan 0:b74591d5ab33 53 */
be_bryan 0:b74591d5ab33 54 int mbedtls_ecdh_compute_shared( mbedtls_ecp_group *grp, mbedtls_mpi *z,
be_bryan 0:b74591d5ab33 55 const mbedtls_ecp_point *Q, const mbedtls_mpi *d,
be_bryan 0:b74591d5ab33 56 int (*f_rng)(void *, unsigned char *, size_t),
be_bryan 0:b74591d5ab33 57 void *p_rng )
be_bryan 0:b74591d5ab33 58 {
be_bryan 0:b74591d5ab33 59 int ret;
be_bryan 0:b74591d5ab33 60 mbedtls_ecp_point P;
be_bryan 0:b74591d5ab33 61
be_bryan 0:b74591d5ab33 62 mbedtls_ecp_point_init( &P );
be_bryan 0:b74591d5ab33 63
be_bryan 0:b74591d5ab33 64 /*
be_bryan 0:b74591d5ab33 65 * Make sure Q is a valid pubkey before using it
be_bryan 0:b74591d5ab33 66 */
be_bryan 0:b74591d5ab33 67 MBEDTLS_MPI_CHK( mbedtls_ecp_check_pubkey( grp, Q ) );
be_bryan 0:b74591d5ab33 68
be_bryan 0:b74591d5ab33 69 MBEDTLS_MPI_CHK( mbedtls_ecp_mul( grp, &P, d, Q, f_rng, p_rng ) );
be_bryan 0:b74591d5ab33 70
be_bryan 0:b74591d5ab33 71 if( mbedtls_ecp_is_zero( &P ) )
be_bryan 0:b74591d5ab33 72 {
be_bryan 0:b74591d5ab33 73 ret = MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
be_bryan 0:b74591d5ab33 74 goto cleanup;
be_bryan 0:b74591d5ab33 75 }
be_bryan 0:b74591d5ab33 76
be_bryan 0:b74591d5ab33 77 MBEDTLS_MPI_CHK( mbedtls_mpi_copy( z, &P.X ) );
be_bryan 0:b74591d5ab33 78
be_bryan 0:b74591d5ab33 79 cleanup:
be_bryan 0:b74591d5ab33 80 mbedtls_ecp_point_free( &P );
be_bryan 0:b74591d5ab33 81
be_bryan 0:b74591d5ab33 82 return( ret );
be_bryan 0:b74591d5ab33 83 }
be_bryan 0:b74591d5ab33 84
be_bryan 0:b74591d5ab33 85 /*
be_bryan 0:b74591d5ab33 86 * Initialize context
be_bryan 0:b74591d5ab33 87 */
be_bryan 0:b74591d5ab33 88 void mbedtls_ecdh_init( mbedtls_ecdh_context *ctx )
be_bryan 0:b74591d5ab33 89 {
be_bryan 0:b74591d5ab33 90 memset( ctx, 0, sizeof( mbedtls_ecdh_context ) );
be_bryan 0:b74591d5ab33 91 }
be_bryan 0:b74591d5ab33 92
be_bryan 0:b74591d5ab33 93 /*
be_bryan 0:b74591d5ab33 94 * Free context
be_bryan 0:b74591d5ab33 95 */
be_bryan 0:b74591d5ab33 96 void mbedtls_ecdh_free( mbedtls_ecdh_context *ctx )
be_bryan 0:b74591d5ab33 97 {
be_bryan 0:b74591d5ab33 98 if( ctx == NULL )
be_bryan 0:b74591d5ab33 99 return;
be_bryan 0:b74591d5ab33 100
be_bryan 0:b74591d5ab33 101 mbedtls_ecp_group_free( &ctx->grp );
be_bryan 0:b74591d5ab33 102 mbedtls_ecp_point_free( &ctx->Q );
be_bryan 0:b74591d5ab33 103 mbedtls_ecp_point_free( &ctx->Qp );
be_bryan 0:b74591d5ab33 104 mbedtls_ecp_point_free( &ctx->Vi );
be_bryan 0:b74591d5ab33 105 mbedtls_ecp_point_free( &ctx->Vf );
be_bryan 0:b74591d5ab33 106 mbedtls_mpi_free( &ctx->d );
be_bryan 0:b74591d5ab33 107 mbedtls_mpi_free( &ctx->z );
be_bryan 0:b74591d5ab33 108 mbedtls_mpi_free( &ctx->_d );
be_bryan 0:b74591d5ab33 109 }
be_bryan 0:b74591d5ab33 110
be_bryan 0:b74591d5ab33 111 /*
be_bryan 0:b74591d5ab33 112 * Setup and write the ServerKeyExhange parameters (RFC 4492)
be_bryan 0:b74591d5ab33 113 * struct {
be_bryan 0:b74591d5ab33 114 * ECParameters curve_params;
be_bryan 0:b74591d5ab33 115 * ECPoint public;
be_bryan 0:b74591d5ab33 116 * } ServerECDHParams;
be_bryan 0:b74591d5ab33 117 */
be_bryan 0:b74591d5ab33 118 int mbedtls_ecdh_make_params( mbedtls_ecdh_context *ctx, size_t *olen,
be_bryan 0:b74591d5ab33 119 unsigned char *buf, size_t blen,
be_bryan 0:b74591d5ab33 120 int (*f_rng)(void *, unsigned char *, size_t),
be_bryan 0:b74591d5ab33 121 void *p_rng )
be_bryan 0:b74591d5ab33 122 {
be_bryan 0:b74591d5ab33 123 int ret;
be_bryan 0:b74591d5ab33 124 size_t grp_len, pt_len;
be_bryan 0:b74591d5ab33 125
be_bryan 0:b74591d5ab33 126 if( ctx == NULL || ctx->grp.pbits == 0 )
be_bryan 0:b74591d5ab33 127 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
be_bryan 0:b74591d5ab33 128
be_bryan 0:b74591d5ab33 129 if( ( ret = mbedtls_ecdh_gen_public( &ctx->grp, &ctx->d, &ctx->Q, f_rng, p_rng ) )
be_bryan 0:b74591d5ab33 130 != 0 )
be_bryan 0:b74591d5ab33 131 return( ret );
be_bryan 0:b74591d5ab33 132
be_bryan 0:b74591d5ab33 133 if( ( ret = mbedtls_ecp_tls_write_group( &ctx->grp, &grp_len, buf, blen ) )
be_bryan 0:b74591d5ab33 134 != 0 )
be_bryan 0:b74591d5ab33 135 return( ret );
be_bryan 0:b74591d5ab33 136
be_bryan 0:b74591d5ab33 137 buf += grp_len;
be_bryan 0:b74591d5ab33 138 blen -= grp_len;
be_bryan 0:b74591d5ab33 139
be_bryan 0:b74591d5ab33 140 if( ( ret = mbedtls_ecp_tls_write_point( &ctx->grp, &ctx->Q, ctx->point_format,
be_bryan 0:b74591d5ab33 141 &pt_len, buf, blen ) ) != 0 )
be_bryan 0:b74591d5ab33 142 return( ret );
be_bryan 0:b74591d5ab33 143
be_bryan 0:b74591d5ab33 144 *olen = grp_len + pt_len;
be_bryan 0:b74591d5ab33 145 return( 0 );
be_bryan 0:b74591d5ab33 146 }
be_bryan 0:b74591d5ab33 147
be_bryan 0:b74591d5ab33 148 /*
be_bryan 0:b74591d5ab33 149 * Read the ServerKeyExhange parameters (RFC 4492)
be_bryan 0:b74591d5ab33 150 * struct {
be_bryan 0:b74591d5ab33 151 * ECParameters curve_params;
be_bryan 0:b74591d5ab33 152 * ECPoint public;
be_bryan 0:b74591d5ab33 153 * } ServerECDHParams;
be_bryan 0:b74591d5ab33 154 */
be_bryan 0:b74591d5ab33 155 int mbedtls_ecdh_read_params( mbedtls_ecdh_context *ctx,
be_bryan 0:b74591d5ab33 156 const unsigned char **buf, const unsigned char *end )
be_bryan 0:b74591d5ab33 157 {
be_bryan 0:b74591d5ab33 158 int ret;
be_bryan 0:b74591d5ab33 159
be_bryan 0:b74591d5ab33 160 if( ( ret = mbedtls_ecp_tls_read_group( &ctx->grp, buf, end - *buf ) ) != 0 )
be_bryan 0:b74591d5ab33 161 return( ret );
be_bryan 0:b74591d5ab33 162
be_bryan 0:b74591d5ab33 163 if( ( ret = mbedtls_ecp_tls_read_point( &ctx->grp, &ctx->Qp, buf, end - *buf ) )
be_bryan 0:b74591d5ab33 164 != 0 )
be_bryan 0:b74591d5ab33 165 return( ret );
be_bryan 0:b74591d5ab33 166
be_bryan 0:b74591d5ab33 167 return( 0 );
be_bryan 0:b74591d5ab33 168 }
be_bryan 0:b74591d5ab33 169
be_bryan 0:b74591d5ab33 170 /*
be_bryan 0:b74591d5ab33 171 * Get parameters from a keypair
be_bryan 0:b74591d5ab33 172 */
be_bryan 0:b74591d5ab33 173 int mbedtls_ecdh_get_params( mbedtls_ecdh_context *ctx, const mbedtls_ecp_keypair *key,
be_bryan 0:b74591d5ab33 174 mbedtls_ecdh_side side )
be_bryan 0:b74591d5ab33 175 {
be_bryan 0:b74591d5ab33 176 int ret;
be_bryan 0:b74591d5ab33 177
be_bryan 0:b74591d5ab33 178 if( ( ret = mbedtls_ecp_group_copy( &ctx->grp, &key->grp ) ) != 0 )
be_bryan 0:b74591d5ab33 179 return( ret );
be_bryan 0:b74591d5ab33 180
be_bryan 0:b74591d5ab33 181 /* If it's not our key, just import the public part as Qp */
be_bryan 0:b74591d5ab33 182 if( side == MBEDTLS_ECDH_THEIRS )
be_bryan 0:b74591d5ab33 183 return( mbedtls_ecp_copy( &ctx->Qp, &key->Q ) );
be_bryan 0:b74591d5ab33 184
be_bryan 0:b74591d5ab33 185 /* Our key: import public (as Q) and private parts */
be_bryan 0:b74591d5ab33 186 if( side != MBEDTLS_ECDH_OURS )
be_bryan 0:b74591d5ab33 187 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
be_bryan 0:b74591d5ab33 188
be_bryan 0:b74591d5ab33 189 if( ( ret = mbedtls_ecp_copy( &ctx->Q, &key->Q ) ) != 0 ||
be_bryan 0:b74591d5ab33 190 ( ret = mbedtls_mpi_copy( &ctx->d, &key->d ) ) != 0 )
be_bryan 0:b74591d5ab33 191 return( ret );
be_bryan 0:b74591d5ab33 192
be_bryan 0:b74591d5ab33 193 return( 0 );
be_bryan 0:b74591d5ab33 194 }
be_bryan 0:b74591d5ab33 195
be_bryan 0:b74591d5ab33 196 /*
be_bryan 0:b74591d5ab33 197 * Setup and export the client public value
be_bryan 0:b74591d5ab33 198 */
be_bryan 0:b74591d5ab33 199 int mbedtls_ecdh_make_public( mbedtls_ecdh_context *ctx, size_t *olen,
be_bryan 0:b74591d5ab33 200 unsigned char *buf, size_t blen,
be_bryan 0:b74591d5ab33 201 int (*f_rng)(void *, unsigned char *, size_t),
be_bryan 0:b74591d5ab33 202 void *p_rng )
be_bryan 0:b74591d5ab33 203 {
be_bryan 0:b74591d5ab33 204 int ret;
be_bryan 0:b74591d5ab33 205
be_bryan 0:b74591d5ab33 206 if( ctx == NULL || ctx->grp.pbits == 0 )
be_bryan 0:b74591d5ab33 207 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
be_bryan 0:b74591d5ab33 208
be_bryan 0:b74591d5ab33 209 if( ( ret = mbedtls_ecdh_gen_public( &ctx->grp, &ctx->d, &ctx->Q, f_rng, p_rng ) )
be_bryan 0:b74591d5ab33 210 != 0 )
be_bryan 0:b74591d5ab33 211 return( ret );
be_bryan 0:b74591d5ab33 212
be_bryan 0:b74591d5ab33 213 return mbedtls_ecp_tls_write_point( &ctx->grp, &ctx->Q, ctx->point_format,
be_bryan 0:b74591d5ab33 214 olen, buf, blen );
be_bryan 0:b74591d5ab33 215 }
be_bryan 0:b74591d5ab33 216
be_bryan 0:b74591d5ab33 217 /*
be_bryan 0:b74591d5ab33 218 * Parse and import the client's public value
be_bryan 0:b74591d5ab33 219 */
be_bryan 0:b74591d5ab33 220 int mbedtls_ecdh_read_public( mbedtls_ecdh_context *ctx,
be_bryan 0:b74591d5ab33 221 const unsigned char *buf, size_t blen )
be_bryan 0:b74591d5ab33 222 {
be_bryan 0:b74591d5ab33 223 int ret;
be_bryan 0:b74591d5ab33 224 const unsigned char *p = buf;
be_bryan 0:b74591d5ab33 225
be_bryan 0:b74591d5ab33 226 if( ctx == NULL )
be_bryan 0:b74591d5ab33 227 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
be_bryan 0:b74591d5ab33 228
be_bryan 0:b74591d5ab33 229 if( ( ret = mbedtls_ecp_tls_read_point( &ctx->grp, &ctx->Qp, &p, blen ) ) != 0 )
be_bryan 0:b74591d5ab33 230 return( ret );
be_bryan 0:b74591d5ab33 231
be_bryan 0:b74591d5ab33 232 if( (size_t)( p - buf ) != blen )
be_bryan 0:b74591d5ab33 233 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
be_bryan 0:b74591d5ab33 234
be_bryan 0:b74591d5ab33 235 return( 0 );
be_bryan 0:b74591d5ab33 236 }
be_bryan 0:b74591d5ab33 237
be_bryan 0:b74591d5ab33 238 /*
be_bryan 0:b74591d5ab33 239 * Derive and export the shared secret
be_bryan 0:b74591d5ab33 240 */
be_bryan 0:b74591d5ab33 241 int mbedtls_ecdh_calc_secret( mbedtls_ecdh_context *ctx, size_t *olen,
be_bryan 0:b74591d5ab33 242 unsigned char *buf, size_t blen,
be_bryan 0:b74591d5ab33 243 int (*f_rng)(void *, unsigned char *, size_t),
be_bryan 0:b74591d5ab33 244 void *p_rng )
be_bryan 0:b74591d5ab33 245 {
be_bryan 0:b74591d5ab33 246 int ret;
be_bryan 0:b74591d5ab33 247
be_bryan 0:b74591d5ab33 248 if( ctx == NULL )
be_bryan 0:b74591d5ab33 249 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
be_bryan 0:b74591d5ab33 250
be_bryan 0:b74591d5ab33 251 if( ( ret = mbedtls_ecdh_compute_shared( &ctx->grp, &ctx->z, &ctx->Qp, &ctx->d,
be_bryan 0:b74591d5ab33 252 f_rng, p_rng ) ) != 0 )
be_bryan 0:b74591d5ab33 253 {
be_bryan 0:b74591d5ab33 254 return( ret );
be_bryan 0:b74591d5ab33 255 }
be_bryan 0:b74591d5ab33 256
be_bryan 0:b74591d5ab33 257 if( mbedtls_mpi_size( &ctx->z ) > blen )
be_bryan 0:b74591d5ab33 258 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
be_bryan 0:b74591d5ab33 259
be_bryan 0:b74591d5ab33 260 *olen = ctx->grp.pbits / 8 + ( ( ctx->grp.pbits % 8 ) != 0 );
be_bryan 0:b74591d5ab33 261 return mbedtls_mpi_write_binary( &ctx->z, buf, *olen );
be_bryan 0:b74591d5ab33 262 }
be_bryan 0:b74591d5ab33 263
be_bryan 0:b74591d5ab33 264 #endif /* MBEDTLS_ECDH_C */