sandbox / mbedtls

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Fork of mbedtls by Christopher Haster

source/ecdh.c@1:24750b9ad5ef, 2016-01-22 (annotated)

Committer:
Christopher Haster
Date:
Fri Jan 22 16:44:49 2016 -0600
Revision:
1:24750b9ad5ef
Initial move of mbedtls to mercurial

Who changed what in which revision?

UserRevisionLine numberNew contents of line
Christopher Haster 1:24750b9ad5ef 1 /*
Christopher Haster 1:24750b9ad5ef 2 * Elliptic curve Diffie-Hellman
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 * RFC 4492
Christopher Haster 1:24750b9ad5ef 27 */
Christopher Haster 1:24750b9ad5ef 28
Christopher Haster 1:24750b9ad5ef 29 #if !defined(MBEDTLS_CONFIG_FILE)
Christopher Haster 1:24750b9ad5ef 30 #include "mbedtls/config.h"
Christopher Haster 1:24750b9ad5ef 31 #else
Christopher Haster 1:24750b9ad5ef 32 #include MBEDTLS_CONFIG_FILE
Christopher Haster 1:24750b9ad5ef 33 #endif
Christopher Haster 1:24750b9ad5ef 34
Christopher Haster 1:24750b9ad5ef 35 #if defined(MBEDTLS_ECDH_C)
Christopher Haster 1:24750b9ad5ef 36
Christopher Haster 1:24750b9ad5ef 37 #include "mbedtls/ecdh.h"
Christopher Haster 1:24750b9ad5ef 38
Christopher Haster 1:24750b9ad5ef 39 #include <string.h>
Christopher Haster 1:24750b9ad5ef 40
Christopher Haster 1:24750b9ad5ef 41 /*
Christopher Haster 1:24750b9ad5ef 42 * Generate public key: simple wrapper around mbedtls_ecp_gen_keypair
Christopher Haster 1:24750b9ad5ef 43 */
Christopher Haster 1:24750b9ad5ef 44 int mbedtls_ecdh_gen_public( mbedtls_ecp_group *grp, mbedtls_mpi *d, mbedtls_ecp_point *Q,
Christopher Haster 1:24750b9ad5ef 45 int (*f_rng)(void *, unsigned char *, size_t),
Christopher Haster 1:24750b9ad5ef 46 void *p_rng )
Christopher Haster 1:24750b9ad5ef 47 {
Christopher Haster 1:24750b9ad5ef 48 return mbedtls_ecp_gen_keypair( grp, d, Q, f_rng, p_rng );
Christopher Haster 1:24750b9ad5ef 49 }
Christopher Haster 1:24750b9ad5ef 50
Christopher Haster 1:24750b9ad5ef 51 /*
Christopher Haster 1:24750b9ad5ef 52 * Compute shared secret (SEC1 3.3.1)
Christopher Haster 1:24750b9ad5ef 53 */
Christopher Haster 1:24750b9ad5ef 54 int mbedtls_ecdh_compute_shared( mbedtls_ecp_group *grp, mbedtls_mpi *z,
Christopher Haster 1:24750b9ad5ef 55 const mbedtls_ecp_point *Q, const mbedtls_mpi *d,
Christopher Haster 1:24750b9ad5ef 56 int (*f_rng)(void *, unsigned char *, size_t),
Christopher Haster 1:24750b9ad5ef 57 void *p_rng )
Christopher Haster 1:24750b9ad5ef 58 {
Christopher Haster 1:24750b9ad5ef 59 int ret;
Christopher Haster 1:24750b9ad5ef 60 mbedtls_ecp_point P;
Christopher Haster 1:24750b9ad5ef 61
Christopher Haster 1:24750b9ad5ef 62 mbedtls_ecp_point_init( &P );
Christopher Haster 1:24750b9ad5ef 63
Christopher Haster 1:24750b9ad5ef 64 /*
Christopher Haster 1:24750b9ad5ef 65 * Make sure Q is a valid pubkey before using it
Christopher Haster 1:24750b9ad5ef 66 */
Christopher Haster 1:24750b9ad5ef 67 MBEDTLS_MPI_CHK( mbedtls_ecp_check_pubkey( grp, Q ) );
Christopher Haster 1:24750b9ad5ef 68
Christopher Haster 1:24750b9ad5ef 69 MBEDTLS_MPI_CHK( mbedtls_ecp_mul( grp, &P, d, Q, f_rng, p_rng ) );
Christopher Haster 1:24750b9ad5ef 70
Christopher Haster 1:24750b9ad5ef 71 if( mbedtls_ecp_is_zero( &P ) )
Christopher Haster 1:24750b9ad5ef 72 {
Christopher Haster 1:24750b9ad5ef 73 ret = MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
Christopher Haster 1:24750b9ad5ef 74 goto cleanup;
Christopher Haster 1:24750b9ad5ef 75 }
Christopher Haster 1:24750b9ad5ef 76
Christopher Haster 1:24750b9ad5ef 77 MBEDTLS_MPI_CHK( mbedtls_mpi_copy( z, &P.X ) );
Christopher Haster 1:24750b9ad5ef 78
Christopher Haster 1:24750b9ad5ef 79 cleanup:
Christopher Haster 1:24750b9ad5ef 80 mbedtls_ecp_point_free( &P );
Christopher Haster 1:24750b9ad5ef 81
Christopher Haster 1:24750b9ad5ef 82 return( ret );
Christopher Haster 1:24750b9ad5ef 83 }
Christopher Haster 1:24750b9ad5ef 84
Christopher Haster 1:24750b9ad5ef 85 /*
Christopher Haster 1:24750b9ad5ef 86 * Initialize context
Christopher Haster 1:24750b9ad5ef 87 */
Christopher Haster 1:24750b9ad5ef 88 void mbedtls_ecdh_init( mbedtls_ecdh_context *ctx )
Christopher Haster 1:24750b9ad5ef 89 {
Christopher Haster 1:24750b9ad5ef 90 memset( ctx, 0, sizeof( mbedtls_ecdh_context ) );
Christopher Haster 1:24750b9ad5ef 91 }
Christopher Haster 1:24750b9ad5ef 92
Christopher Haster 1:24750b9ad5ef 93 /*
Christopher Haster 1:24750b9ad5ef 94 * Free context
Christopher Haster 1:24750b9ad5ef 95 */
Christopher Haster 1:24750b9ad5ef 96 void mbedtls_ecdh_free( mbedtls_ecdh_context *ctx )
Christopher Haster 1:24750b9ad5ef 97 {
Christopher Haster 1:24750b9ad5ef 98 if( ctx == NULL )
Christopher Haster 1:24750b9ad5ef 99 return;
Christopher Haster 1:24750b9ad5ef 100
Christopher Haster 1:24750b9ad5ef 101 mbedtls_ecp_group_free( &ctx->grp );
Christopher Haster 1:24750b9ad5ef 102 mbedtls_ecp_point_free( &ctx->Q );
Christopher Haster 1:24750b9ad5ef 103 mbedtls_ecp_point_free( &ctx->Qp );
Christopher Haster 1:24750b9ad5ef 104 mbedtls_ecp_point_free( &ctx->Vi );
Christopher Haster 1:24750b9ad5ef 105 mbedtls_ecp_point_free( &ctx->Vf );
Christopher Haster 1:24750b9ad5ef 106 mbedtls_mpi_free( &ctx->d );
Christopher Haster 1:24750b9ad5ef 107 mbedtls_mpi_free( &ctx->z );
Christopher Haster 1:24750b9ad5ef 108 mbedtls_mpi_free( &ctx->_d );
Christopher Haster 1:24750b9ad5ef 109 }
Christopher Haster 1:24750b9ad5ef 110
Christopher Haster 1:24750b9ad5ef 111 /*
Christopher Haster 1:24750b9ad5ef 112 * Setup and write the ServerKeyExhange parameters (RFC 4492)
Christopher Haster 1:24750b9ad5ef 113 * struct {
Christopher Haster 1:24750b9ad5ef 114 * ECParameters curve_params;
Christopher Haster 1:24750b9ad5ef 115 * ECPoint public;
Christopher Haster 1:24750b9ad5ef 116 * } ServerECDHParams;
Christopher Haster 1:24750b9ad5ef 117 */
Christopher Haster 1:24750b9ad5ef 118 int mbedtls_ecdh_make_params( mbedtls_ecdh_context *ctx, size_t *olen,
Christopher Haster 1:24750b9ad5ef 119 unsigned char *buf, size_t blen,
Christopher Haster 1:24750b9ad5ef 120 int (*f_rng)(void *, unsigned char *, size_t),
Christopher Haster 1:24750b9ad5ef 121 void *p_rng )
Christopher Haster 1:24750b9ad5ef 122 {
Christopher Haster 1:24750b9ad5ef 123 int ret;
Christopher Haster 1:24750b9ad5ef 124 size_t grp_len, pt_len;
Christopher Haster 1:24750b9ad5ef 125
Christopher Haster 1:24750b9ad5ef 126 if( ctx == NULL || ctx->grp.pbits == 0 )
Christopher Haster 1:24750b9ad5ef 127 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
Christopher Haster 1:24750b9ad5ef 128
Christopher Haster 1:24750b9ad5ef 129 if( ( ret = mbedtls_ecdh_gen_public( &ctx->grp, &ctx->d, &ctx->Q, f_rng, p_rng ) )
Christopher Haster 1:24750b9ad5ef 130 != 0 )
Christopher Haster 1:24750b9ad5ef 131 return( ret );
Christopher Haster 1:24750b9ad5ef 132
Christopher Haster 1:24750b9ad5ef 133 if( ( ret = mbedtls_ecp_tls_write_group( &ctx->grp, &grp_len, buf, blen ) )
Christopher Haster 1:24750b9ad5ef 134 != 0 )
Christopher Haster 1:24750b9ad5ef 135 return( ret );
Christopher Haster 1:24750b9ad5ef 136
Christopher Haster 1:24750b9ad5ef 137 buf += grp_len;
Christopher Haster 1:24750b9ad5ef 138 blen -= grp_len;
Christopher Haster 1:24750b9ad5ef 139
Christopher Haster 1:24750b9ad5ef 140 if( ( ret = mbedtls_ecp_tls_write_point( &ctx->grp, &ctx->Q, ctx->point_format,
Christopher Haster 1:24750b9ad5ef 141 &pt_len, buf, blen ) ) != 0 )
Christopher Haster 1:24750b9ad5ef 142 return( ret );
Christopher Haster 1:24750b9ad5ef 143
Christopher Haster 1:24750b9ad5ef 144 *olen = grp_len + pt_len;
Christopher Haster 1:24750b9ad5ef 145 return( 0 );
Christopher Haster 1:24750b9ad5ef 146 }
Christopher Haster 1:24750b9ad5ef 147
Christopher Haster 1:24750b9ad5ef 148 /*
Christopher Haster 1:24750b9ad5ef 149 * Read the ServerKeyExhange parameters (RFC 4492)
Christopher Haster 1:24750b9ad5ef 150 * struct {
Christopher Haster 1:24750b9ad5ef 151 * ECParameters curve_params;
Christopher Haster 1:24750b9ad5ef 152 * ECPoint public;
Christopher Haster 1:24750b9ad5ef 153 * } ServerECDHParams;
Christopher Haster 1:24750b9ad5ef 154 */
Christopher Haster 1:24750b9ad5ef 155 int mbedtls_ecdh_read_params( mbedtls_ecdh_context *ctx,
Christopher Haster 1:24750b9ad5ef 156 const unsigned char **buf, const unsigned char *end )
Christopher Haster 1:24750b9ad5ef 157 {
Christopher Haster 1:24750b9ad5ef 158 int ret;
Christopher Haster 1:24750b9ad5ef 159
Christopher Haster 1:24750b9ad5ef 160 if( ( ret = mbedtls_ecp_tls_read_group( &ctx->grp, buf, end - *buf ) ) != 0 )
Christopher Haster 1:24750b9ad5ef 161 return( ret );
Christopher Haster 1:24750b9ad5ef 162
Christopher Haster 1:24750b9ad5ef 163 if( ( ret = mbedtls_ecp_tls_read_point( &ctx->grp, &ctx->Qp, buf, end - *buf ) )
Christopher Haster 1:24750b9ad5ef 164 != 0 )
Christopher Haster 1:24750b9ad5ef 165 return( ret );
Christopher Haster 1:24750b9ad5ef 166
Christopher Haster 1:24750b9ad5ef 167 return( 0 );
Christopher Haster 1:24750b9ad5ef 168 }
Christopher Haster 1:24750b9ad5ef 169
Christopher Haster 1:24750b9ad5ef 170 /*
Christopher Haster 1:24750b9ad5ef 171 * Get parameters from a keypair
Christopher Haster 1:24750b9ad5ef 172 */
Christopher Haster 1:24750b9ad5ef 173 int mbedtls_ecdh_get_params( mbedtls_ecdh_context *ctx, const mbedtls_ecp_keypair *key,
Christopher Haster 1:24750b9ad5ef 174 mbedtls_ecdh_side side )
Christopher Haster 1:24750b9ad5ef 175 {
Christopher Haster 1:24750b9ad5ef 176 int ret;
Christopher Haster 1:24750b9ad5ef 177
Christopher Haster 1:24750b9ad5ef 178 if( ( ret = mbedtls_ecp_group_copy( &ctx->grp, &key->grp ) ) != 0 )
Christopher Haster 1:24750b9ad5ef 179 return( ret );
Christopher Haster 1:24750b9ad5ef 180
Christopher Haster 1:24750b9ad5ef 181 /* If it's not our key, just import the public part as Qp */
Christopher Haster 1:24750b9ad5ef 182 if( side == MBEDTLS_ECDH_THEIRS )
Christopher Haster 1:24750b9ad5ef 183 return( mbedtls_ecp_copy( &ctx->Qp, &key->Q ) );
Christopher Haster 1:24750b9ad5ef 184
Christopher Haster 1:24750b9ad5ef 185 /* Our key: import public (as Q) and private parts */
Christopher Haster 1:24750b9ad5ef 186 if( side != MBEDTLS_ECDH_OURS )
Christopher Haster 1:24750b9ad5ef 187 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
Christopher Haster 1:24750b9ad5ef 188
Christopher Haster 1:24750b9ad5ef 189 if( ( ret = mbedtls_ecp_copy( &ctx->Q, &key->Q ) ) != 0 ||
Christopher Haster 1:24750b9ad5ef 190 ( ret = mbedtls_mpi_copy( &ctx->d, &key->d ) ) != 0 )
Christopher Haster 1:24750b9ad5ef 191 return( ret );
Christopher Haster 1:24750b9ad5ef 192
Christopher Haster 1:24750b9ad5ef 193 return( 0 );
Christopher Haster 1:24750b9ad5ef 194 }
Christopher Haster 1:24750b9ad5ef 195
Christopher Haster 1:24750b9ad5ef 196 /*
Christopher Haster 1:24750b9ad5ef 197 * Setup and export the client public value
Christopher Haster 1:24750b9ad5ef 198 */
Christopher Haster 1:24750b9ad5ef 199 int mbedtls_ecdh_make_public( mbedtls_ecdh_context *ctx, size_t *olen,
Christopher Haster 1:24750b9ad5ef 200 unsigned char *buf, size_t blen,
Christopher Haster 1:24750b9ad5ef 201 int (*f_rng)(void *, unsigned char *, size_t),
Christopher Haster 1:24750b9ad5ef 202 void *p_rng )
Christopher Haster 1:24750b9ad5ef 203 {
Christopher Haster 1:24750b9ad5ef 204 int ret;
Christopher Haster 1:24750b9ad5ef 205
Christopher Haster 1:24750b9ad5ef 206 if( ctx == NULL || ctx->grp.pbits == 0 )
Christopher Haster 1:24750b9ad5ef 207 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
Christopher Haster 1:24750b9ad5ef 208
Christopher Haster 1:24750b9ad5ef 209 if( ( ret = mbedtls_ecdh_gen_public( &ctx->grp, &ctx->d, &ctx->Q, f_rng, p_rng ) )
Christopher Haster 1:24750b9ad5ef 210 != 0 )
Christopher Haster 1:24750b9ad5ef 211 return( ret );
Christopher Haster 1:24750b9ad5ef 212
Christopher Haster 1:24750b9ad5ef 213 return mbedtls_ecp_tls_write_point( &ctx->grp, &ctx->Q, ctx->point_format,
Christopher Haster 1:24750b9ad5ef 214 olen, buf, blen );
Christopher Haster 1:24750b9ad5ef 215 }
Christopher Haster 1:24750b9ad5ef 216
Christopher Haster 1:24750b9ad5ef 217 /*
Christopher Haster 1:24750b9ad5ef 218 * Parse and import the client's public value
Christopher Haster 1:24750b9ad5ef 219 */
Christopher Haster 1:24750b9ad5ef 220 int mbedtls_ecdh_read_public( mbedtls_ecdh_context *ctx,
Christopher Haster 1:24750b9ad5ef 221 const unsigned char *buf, size_t blen )
Christopher Haster 1:24750b9ad5ef 222 {
Christopher Haster 1:24750b9ad5ef 223 int ret;
Christopher Haster 1:24750b9ad5ef 224 const unsigned char *p = buf;
Christopher Haster 1:24750b9ad5ef 225
Christopher Haster 1:24750b9ad5ef 226 if( ctx == NULL )
Christopher Haster 1:24750b9ad5ef 227 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
Christopher Haster 1:24750b9ad5ef 228
Christopher Haster 1:24750b9ad5ef 229 if( ( ret = mbedtls_ecp_tls_read_point( &ctx->grp, &ctx->Qp, &p, blen ) ) != 0 )
Christopher Haster 1:24750b9ad5ef 230 return( ret );
Christopher Haster 1:24750b9ad5ef 231
Christopher Haster 1:24750b9ad5ef 232 if( (size_t)( p - buf ) != blen )
Christopher Haster 1:24750b9ad5ef 233 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
Christopher Haster 1:24750b9ad5ef 234
Christopher Haster 1:24750b9ad5ef 235 return( 0 );
Christopher Haster 1:24750b9ad5ef 236 }
Christopher Haster 1:24750b9ad5ef 237
Christopher Haster 1:24750b9ad5ef 238 /*
Christopher Haster 1:24750b9ad5ef 239 * Derive and export the shared secret
Christopher Haster 1:24750b9ad5ef 240 */
Christopher Haster 1:24750b9ad5ef 241 int mbedtls_ecdh_calc_secret( mbedtls_ecdh_context *ctx, size_t *olen,
Christopher Haster 1:24750b9ad5ef 242 unsigned char *buf, size_t blen,
Christopher Haster 1:24750b9ad5ef 243 int (*f_rng)(void *, unsigned char *, size_t),
Christopher Haster 1:24750b9ad5ef 244 void *p_rng )
Christopher Haster 1:24750b9ad5ef 245 {
Christopher Haster 1:24750b9ad5ef 246 int ret;
Christopher Haster 1:24750b9ad5ef 247
Christopher Haster 1:24750b9ad5ef 248 if( ctx == NULL )
Christopher Haster 1:24750b9ad5ef 249 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
Christopher Haster 1:24750b9ad5ef 250
Christopher Haster 1:24750b9ad5ef 251 if( ( ret = mbedtls_ecdh_compute_shared( &ctx->grp, &ctx->z, &ctx->Qp, &ctx->d,
Christopher Haster 1:24750b9ad5ef 252 f_rng, p_rng ) ) != 0 )
Christopher Haster 1:24750b9ad5ef 253 {
Christopher Haster 1:24750b9ad5ef 254 return( ret );
Christopher Haster 1:24750b9ad5ef 255 }
Christopher Haster 1:24750b9ad5ef 256
Christopher Haster 1:24750b9ad5ef 257 if( mbedtls_mpi_size( &ctx->z ) > blen )
Christopher Haster 1:24750b9ad5ef 258 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
Christopher Haster 1:24750b9ad5ef 259
Christopher Haster 1:24750b9ad5ef 260 *olen = ctx->grp.pbits / 8 + ( ( ctx->grp.pbits % 8 ) != 0 );
Christopher Haster 1:24750b9ad5ef 261 return mbedtls_mpi_write_binary( &ctx->z, buf, *olen );
Christopher Haster 1:24750b9ad5ef 262 }
Christopher Haster 1:24750b9ad5ef 263
Christopher Haster 1:24750b9ad5ef 264 #endif /* MBEDTLS_ECDH_C */