2 * Elliptic curve Diffie-Hellman
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4 * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
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5 * SPDX-License-Identifier: Apache-2.0
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7 * Licensed under the Apache License, Version 2.0 (the "License"); you may
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8 * not use this file except in compliance with the License.
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9 * You may obtain a copy of the License at
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11 * http://www.apache.org/licenses/LICENSE-2.0
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13 * Unless required by applicable law or agreed to in writing, software
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14 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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15 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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16 * See the License for the specific language governing permissions and
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17 * limitations under the License.
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19 * This file is part of mbed TLS (https://tls.mbed.org)
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25 * SEC1 http://www.secg.org/index.php?action=secg,docs_secg
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29 #if !defined(MBEDTLS_CONFIG_FILE)
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30 #include "mbedtls/config.h"
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32 #include MBEDTLS_CONFIG_FILE
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35 #if defined(MBEDTLS_ECDH_C)
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37 #include "mbedtls/ecdh.h"
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38 #include "mbedtls/platform_util.h"
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42 /* Parameter validation macros based on platform_util.h */
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43 #define ECDH_VALIDATE_RET( cond ) \
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44 MBEDTLS_INTERNAL_VALIDATE_RET( cond, MBEDTLS_ERR_ECP_BAD_INPUT_DATA )
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45 #define ECDH_VALIDATE( cond ) \
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46 MBEDTLS_INTERNAL_VALIDATE( cond )
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48 #if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
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49 typedef mbedtls_ecdh_context mbedtls_ecdh_context_mbed;
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52 static mbedtls_ecp_group_id mbedtls_ecdh_grp_id(
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53 const mbedtls_ecdh_context *ctx )
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55 #if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
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56 return( ctx->grp.id );
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58 return( ctx->grp_id );
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62 #if !defined(MBEDTLS_ECDH_GEN_PUBLIC_ALT)
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64 * Generate public key (restartable version)
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66 * Note: this internal function relies on its caller preserving the value of
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67 * the output parameter 'd' across continuation calls. This would not be
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68 * acceptable for a public function but is OK here as we control call sites.
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70 static int ecdh_gen_public_restartable( mbedtls_ecp_group *grp,
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71 mbedtls_mpi *d, mbedtls_ecp_point *Q,
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72 int (*f_rng)(void *, unsigned char *, size_t),
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74 mbedtls_ecp_restart_ctx *rs_ctx )
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78 /* If multiplication is in progress, we already generated a privkey */
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79 #if defined(MBEDTLS_ECP_RESTARTABLE)
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80 if( rs_ctx == NULL || rs_ctx->rsm == NULL )
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82 MBEDTLS_MPI_CHK( mbedtls_ecp_gen_privkey( grp, d, f_rng, p_rng ) );
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84 MBEDTLS_MPI_CHK( mbedtls_ecp_mul_restartable( grp, Q, d, &grp->G,
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85 f_rng, p_rng, rs_ctx ) );
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92 * Generate public key
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94 int mbedtls_ecdh_gen_public( mbedtls_ecp_group *grp, mbedtls_mpi *d, mbedtls_ecp_point *Q,
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95 int (*f_rng)(void *, unsigned char *, size_t),
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98 ECDH_VALIDATE_RET( grp != NULL );
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99 ECDH_VALIDATE_RET( d != NULL );
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100 ECDH_VALIDATE_RET( Q != NULL );
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101 ECDH_VALIDATE_RET( f_rng != NULL );
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102 return( ecdh_gen_public_restartable( grp, d, Q, f_rng, p_rng, NULL ) );
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104 #endif /* !MBEDTLS_ECDH_GEN_PUBLIC_ALT */
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106 #if !defined(MBEDTLS_ECDH_COMPUTE_SHARED_ALT)
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108 * Compute shared secret (SEC1 3.3.1)
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110 static int ecdh_compute_shared_restartable( mbedtls_ecp_group *grp,
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112 const mbedtls_ecp_point *Q, const mbedtls_mpi *d,
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113 int (*f_rng)(void *, unsigned char *, size_t),
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115 mbedtls_ecp_restart_ctx *rs_ctx )
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118 mbedtls_ecp_point P;
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120 mbedtls_ecp_point_init( &P );
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122 MBEDTLS_MPI_CHK( mbedtls_ecp_mul_restartable( grp, &P, d, Q,
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123 f_rng, p_rng, rs_ctx ) );
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125 if( mbedtls_ecp_is_zero( &P ) )
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127 ret = MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
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131 MBEDTLS_MPI_CHK( mbedtls_mpi_copy( z, &P.X ) );
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134 mbedtls_ecp_point_free( &P );
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140 * Compute shared secret (SEC1 3.3.1)
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142 int mbedtls_ecdh_compute_shared( mbedtls_ecp_group *grp, mbedtls_mpi *z,
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143 const mbedtls_ecp_point *Q, const mbedtls_mpi *d,
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144 int (*f_rng)(void *, unsigned char *, size_t),
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147 ECDH_VALIDATE_RET( grp != NULL );
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148 ECDH_VALIDATE_RET( Q != NULL );
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149 ECDH_VALIDATE_RET( d != NULL );
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150 ECDH_VALIDATE_RET( z != NULL );
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151 return( ecdh_compute_shared_restartable( grp, z, Q, d,
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152 f_rng, p_rng, NULL ) );
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154 #endif /* !MBEDTLS_ECDH_COMPUTE_SHARED_ALT */
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156 static void ecdh_init_internal( mbedtls_ecdh_context_mbed *ctx )
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158 mbedtls_ecp_group_init( &ctx->grp );
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159 mbedtls_mpi_init( &ctx->d );
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160 mbedtls_ecp_point_init( &ctx->Q );
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161 mbedtls_ecp_point_init( &ctx->Qp );
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162 mbedtls_mpi_init( &ctx->z );
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164 #if defined(MBEDTLS_ECP_RESTARTABLE)
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165 mbedtls_ecp_restart_init( &ctx->rs );
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170 * Initialize context
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172 void mbedtls_ecdh_init( mbedtls_ecdh_context *ctx )
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174 ECDH_VALIDATE( ctx != NULL );
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176 #if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
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177 ecdh_init_internal( ctx );
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178 mbedtls_ecp_point_init( &ctx->Vi );
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179 mbedtls_ecp_point_init( &ctx->Vf );
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180 mbedtls_mpi_init( &ctx->_d );
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182 memset( ctx, 0, sizeof( mbedtls_ecdh_context ) );
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184 ctx->var = MBEDTLS_ECDH_VARIANT_NONE;
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186 ctx->point_format = MBEDTLS_ECP_PF_UNCOMPRESSED;
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187 #if defined(MBEDTLS_ECP_RESTARTABLE)
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188 ctx->restart_enabled = 0;
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192 static int ecdh_setup_internal( mbedtls_ecdh_context_mbed *ctx,
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193 mbedtls_ecp_group_id grp_id )
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197 ret = mbedtls_ecp_group_load( &ctx->grp, grp_id );
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200 return( MBEDTLS_ERR_ECP_FEATURE_UNAVAILABLE );
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209 int mbedtls_ecdh_setup( mbedtls_ecdh_context *ctx, mbedtls_ecp_group_id grp_id )
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211 ECDH_VALIDATE_RET( ctx != NULL );
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213 #if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
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214 return( ecdh_setup_internal( ctx, grp_id ) );
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219 ctx->point_format = MBEDTLS_ECP_PF_UNCOMPRESSED;
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220 ctx->var = MBEDTLS_ECDH_VARIANT_MBEDTLS_2_0;
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221 ctx->grp_id = grp_id;
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222 ecdh_init_internal( &ctx->ctx.mbed_ecdh );
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223 return( ecdh_setup_internal( &ctx->ctx.mbed_ecdh, grp_id ) );
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228 static void ecdh_free_internal( mbedtls_ecdh_context_mbed *ctx )
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230 mbedtls_ecp_group_free( &ctx->grp );
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231 mbedtls_mpi_free( &ctx->d );
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232 mbedtls_ecp_point_free( &ctx->Q );
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233 mbedtls_ecp_point_free( &ctx->Qp );
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234 mbedtls_mpi_free( &ctx->z );
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236 #if defined(MBEDTLS_ECP_RESTARTABLE)
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237 mbedtls_ecp_restart_free( &ctx->rs );
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241 #if defined(MBEDTLS_ECP_RESTARTABLE)
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243 * Enable restartable operations for context
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245 void mbedtls_ecdh_enable_restart( mbedtls_ecdh_context *ctx )
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247 ECDH_VALIDATE( ctx != NULL );
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249 ctx->restart_enabled = 1;
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256 void mbedtls_ecdh_free( mbedtls_ecdh_context *ctx )
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261 #if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
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262 mbedtls_ecp_point_free( &ctx->Vi );
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263 mbedtls_ecp_point_free( &ctx->Vf );
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264 mbedtls_mpi_free( &ctx->_d );
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265 ecdh_free_internal( ctx );
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269 case MBEDTLS_ECDH_VARIANT_MBEDTLS_2_0:
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270 ecdh_free_internal( &ctx->ctx.mbed_ecdh );
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276 ctx->point_format = MBEDTLS_ECP_PF_UNCOMPRESSED;
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277 ctx->var = MBEDTLS_ECDH_VARIANT_NONE;
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278 ctx->grp_id = MBEDTLS_ECP_DP_NONE;
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282 static int ecdh_make_params_internal( mbedtls_ecdh_context_mbed *ctx,
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283 size_t *olen, int point_format,
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284 unsigned char *buf, size_t blen,
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285 int (*f_rng)(void *,
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289 int restart_enabled )
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292 size_t grp_len, pt_len;
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293 #if defined(MBEDTLS_ECP_RESTARTABLE)
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294 mbedtls_ecp_restart_ctx *rs_ctx = NULL;
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297 if( ctx->grp.pbits == 0 )
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298 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
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300 #if defined(MBEDTLS_ECP_RESTARTABLE)
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301 if( restart_enabled )
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304 (void) restart_enabled;
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308 #if defined(MBEDTLS_ECP_RESTARTABLE)
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309 if( ( ret = ecdh_gen_public_restartable( &ctx->grp, &ctx->d, &ctx->Q,
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310 f_rng, p_rng, rs_ctx ) ) != 0 )
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313 if( ( ret = mbedtls_ecdh_gen_public( &ctx->grp, &ctx->d, &ctx->Q,
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314 f_rng, p_rng ) ) != 0 )
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316 #endif /* MBEDTLS_ECP_RESTARTABLE */
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318 if( ( ret = mbedtls_ecp_tls_write_group( &ctx->grp, &grp_len, buf,
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325 if( ( ret = mbedtls_ecp_tls_write_point( &ctx->grp, &ctx->Q, point_format,
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326 &pt_len, buf, blen ) ) != 0 )
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329 *olen = grp_len + pt_len;
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334 * Setup and write the ServerKeyExhange parameters (RFC 4492)
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336 * ECParameters curve_params;
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338 * } ServerECDHParams;
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340 int mbedtls_ecdh_make_params( mbedtls_ecdh_context *ctx, size_t *olen,
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341 unsigned char *buf, size_t blen,
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342 int (*f_rng)(void *, unsigned char *, size_t),
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345 int restart_enabled = 0;
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346 ECDH_VALIDATE_RET( ctx != NULL );
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347 ECDH_VALIDATE_RET( olen != NULL );
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348 ECDH_VALIDATE_RET( buf != NULL );
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349 ECDH_VALIDATE_RET( f_rng != NULL );
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351 #if defined(MBEDTLS_ECP_RESTARTABLE)
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352 restart_enabled = ctx->restart_enabled;
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354 (void) restart_enabled;
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357 #if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
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358 return( ecdh_make_params_internal( ctx, olen, ctx->point_format, buf, blen,
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359 f_rng, p_rng, restart_enabled ) );
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363 case MBEDTLS_ECDH_VARIANT_MBEDTLS_2_0:
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364 return( ecdh_make_params_internal( &ctx->ctx.mbed_ecdh, olen,
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365 ctx->point_format, buf, blen,
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367 restart_enabled ) );
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369 return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
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374 static int ecdh_read_params_internal( mbedtls_ecdh_context_mbed *ctx,
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375 const unsigned char **buf,
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376 const unsigned char *end )
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378 return( mbedtls_ecp_tls_read_point( &ctx->grp, &ctx->Qp, buf,
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383 * Read the ServerKeyExhange parameters (RFC 4492)
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385 * ECParameters curve_params;
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387 * } ServerECDHParams;
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389 int mbedtls_ecdh_read_params( mbedtls_ecdh_context *ctx,
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390 const unsigned char **buf,
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391 const unsigned char *end )
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394 mbedtls_ecp_group_id grp_id;
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395 ECDH_VALIDATE_RET( ctx != NULL );
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396 ECDH_VALIDATE_RET( buf != NULL );
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397 ECDH_VALIDATE_RET( *buf != NULL );
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398 ECDH_VALIDATE_RET( end != NULL );
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400 if( ( ret = mbedtls_ecp_tls_read_group_id( &grp_id, buf, end - *buf ) )
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404 if( ( ret = mbedtls_ecdh_setup( ctx, grp_id ) ) != 0 )
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407 #if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
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408 return( ecdh_read_params_internal( ctx, buf, end ) );
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412 case MBEDTLS_ECDH_VARIANT_MBEDTLS_2_0:
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413 return( ecdh_read_params_internal( &ctx->ctx.mbed_ecdh,
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416 return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
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421 static int ecdh_get_params_internal( mbedtls_ecdh_context_mbed *ctx,
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422 const mbedtls_ecp_keypair *key,
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423 mbedtls_ecdh_side side )
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427 /* If it's not our key, just import the public part as Qp */
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428 if( side == MBEDTLS_ECDH_THEIRS )
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429 return( mbedtls_ecp_copy( &ctx->Qp, &key->Q ) );
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431 /* Our key: import public (as Q) and private parts */
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432 if( side != MBEDTLS_ECDH_OURS )
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433 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
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435 if( ( ret = mbedtls_ecp_copy( &ctx->Q, &key->Q ) ) != 0 ||
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436 ( ret = mbedtls_mpi_copy( &ctx->d, &key->d ) ) != 0 )
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443 * Get parameters from a keypair
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445 int mbedtls_ecdh_get_params( mbedtls_ecdh_context *ctx,
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446 const mbedtls_ecp_keypair *key,
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447 mbedtls_ecdh_side side )
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450 ECDH_VALIDATE_RET( ctx != NULL );
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451 ECDH_VALIDATE_RET( key != NULL );
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452 ECDH_VALIDATE_RET( side == MBEDTLS_ECDH_OURS ||
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453 side == MBEDTLS_ECDH_THEIRS );
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455 if( mbedtls_ecdh_grp_id( ctx ) == MBEDTLS_ECP_DP_NONE )
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457 /* This is the first call to get_params(). Set up the context
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458 * for use with the group. */
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459 if( ( ret = mbedtls_ecdh_setup( ctx, key->grp.id ) ) != 0 )
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464 /* This is not the first call to get_params(). Check that the
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465 * current key's group is the same as the context's, which was set
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466 * from the first key's group. */
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467 if( mbedtls_ecdh_grp_id( ctx ) != key->grp.id )
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468 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
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471 #if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
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472 return( ecdh_get_params_internal( ctx, key, side ) );
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476 case MBEDTLS_ECDH_VARIANT_MBEDTLS_2_0:
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477 return( ecdh_get_params_internal( &ctx->ctx.mbed_ecdh,
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480 return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
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485 static int ecdh_make_public_internal( mbedtls_ecdh_context_mbed *ctx,
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486 size_t *olen, int point_format,
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487 unsigned char *buf, size_t blen,
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488 int (*f_rng)(void *,
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492 int restart_enabled )
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495 #if defined(MBEDTLS_ECP_RESTARTABLE)
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496 mbedtls_ecp_restart_ctx *rs_ctx = NULL;
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499 if( ctx->grp.pbits == 0 )
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500 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
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502 #if defined(MBEDTLS_ECP_RESTARTABLE)
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503 if( restart_enabled )
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506 (void) restart_enabled;
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509 #if defined(MBEDTLS_ECP_RESTARTABLE)
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510 if( ( ret = ecdh_gen_public_restartable( &ctx->grp, &ctx->d, &ctx->Q,
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511 f_rng, p_rng, rs_ctx ) ) != 0 )
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514 if( ( ret = mbedtls_ecdh_gen_public( &ctx->grp, &ctx->d, &ctx->Q,
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515 f_rng, p_rng ) ) != 0 )
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517 #endif /* MBEDTLS_ECP_RESTARTABLE */
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519 return mbedtls_ecp_tls_write_point( &ctx->grp, &ctx->Q, point_format, olen,
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524 * Setup and export the client public value
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526 int mbedtls_ecdh_make_public( mbedtls_ecdh_context *ctx, size_t *olen,
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527 unsigned char *buf, size_t blen,
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528 int (*f_rng)(void *, unsigned char *, size_t),
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531 int restart_enabled = 0;
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532 ECDH_VALIDATE_RET( ctx != NULL );
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533 ECDH_VALIDATE_RET( olen != NULL );
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534 ECDH_VALIDATE_RET( buf != NULL );
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535 ECDH_VALIDATE_RET( f_rng != NULL );
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537 #if defined(MBEDTLS_ECP_RESTARTABLE)
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538 restart_enabled = ctx->restart_enabled;
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541 #if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
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542 return( ecdh_make_public_internal( ctx, olen, ctx->point_format, buf, blen,
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543 f_rng, p_rng, restart_enabled ) );
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547 case MBEDTLS_ECDH_VARIANT_MBEDTLS_2_0:
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548 return( ecdh_make_public_internal( &ctx->ctx.mbed_ecdh, olen,
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549 ctx->point_format, buf, blen,
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551 restart_enabled ) );
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553 return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
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558 static int ecdh_read_public_internal( mbedtls_ecdh_context_mbed *ctx,
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559 const unsigned char *buf, size_t blen )
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562 const unsigned char *p = buf;
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564 if( ( ret = mbedtls_ecp_tls_read_point( &ctx->grp, &ctx->Qp, &p,
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568 if( (size_t)( p - buf ) != blen )
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569 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
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575 * Parse and import the client's public value
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577 int mbedtls_ecdh_read_public( mbedtls_ecdh_context *ctx,
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578 const unsigned char *buf, size_t blen )
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580 ECDH_VALIDATE_RET( ctx != NULL );
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581 ECDH_VALIDATE_RET( buf != NULL );
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583 #if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
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584 return( ecdh_read_public_internal( ctx, buf, blen ) );
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588 case MBEDTLS_ECDH_VARIANT_MBEDTLS_2_0:
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589 return( ecdh_read_public_internal( &ctx->ctx.mbed_ecdh,
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592 return MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
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597 static int ecdh_calc_secret_internal( mbedtls_ecdh_context_mbed *ctx,
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598 size_t *olen, unsigned char *buf,
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600 int (*f_rng)(void *,
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604 int restart_enabled )
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607 #if defined(MBEDTLS_ECP_RESTARTABLE)
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608 mbedtls_ecp_restart_ctx *rs_ctx = NULL;
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611 if( ctx == NULL || ctx->grp.pbits == 0 )
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612 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
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614 #if defined(MBEDTLS_ECP_RESTARTABLE)
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615 if( restart_enabled )
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618 (void) restart_enabled;
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621 #if defined(MBEDTLS_ECP_RESTARTABLE)
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622 if( ( ret = ecdh_compute_shared_restartable( &ctx->grp, &ctx->z, &ctx->Qp,
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623 &ctx->d, f_rng, p_rng,
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629 if( ( ret = mbedtls_ecdh_compute_shared( &ctx->grp, &ctx->z, &ctx->Qp,
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630 &ctx->d, f_rng, p_rng ) ) != 0 )
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634 #endif /* MBEDTLS_ECP_RESTARTABLE */
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636 if( mbedtls_mpi_size( &ctx->z ) > blen )
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637 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
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639 *olen = ctx->grp.pbits / 8 + ( ( ctx->grp.pbits % 8 ) != 0 );
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641 if( mbedtls_ecp_get_type( &ctx->grp ) == MBEDTLS_ECP_TYPE_MONTGOMERY )
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642 return mbedtls_mpi_write_binary_le( &ctx->z, buf, *olen );
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644 return mbedtls_mpi_write_binary( &ctx->z, buf, *olen );
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648 * Derive and export the shared secret
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650 int mbedtls_ecdh_calc_secret( mbedtls_ecdh_context *ctx, size_t *olen,
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651 unsigned char *buf, size_t blen,
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652 int (*f_rng)(void *, unsigned char *, size_t),
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655 int restart_enabled = 0;
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656 ECDH_VALIDATE_RET( ctx != NULL );
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657 ECDH_VALIDATE_RET( olen != NULL );
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658 ECDH_VALIDATE_RET( buf != NULL );
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660 #if defined(MBEDTLS_ECP_RESTARTABLE)
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661 restart_enabled = ctx->restart_enabled;
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664 #if defined(MBEDTLS_ECDH_LEGACY_CONTEXT)
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665 return( ecdh_calc_secret_internal( ctx, olen, buf, blen, f_rng, p_rng,
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666 restart_enabled ) );
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670 case MBEDTLS_ECDH_VARIANT_MBEDTLS_2_0:
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671 return( ecdh_calc_secret_internal( &ctx->ctx.mbed_ecdh, olen, buf,
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672 blen, f_rng, p_rng,
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673 restart_enabled ) );
\r
675 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
\r
680 #endif /* MBEDTLS_ECDH_C */
\r