x25519.c (5937B)
1 /* 2 * ECDH with curve-optimized implementation multiplexing 3 * 4 * Copyright 2016-2018 INRIA and Microsoft Corporation 5 * SPDX-License-Identifier: Apache-2.0 6 * 7 * Licensed under the Apache License, Version 2.0 (the "License"); you may 8 * not use this file except in compliance with the License. 9 * You may obtain a copy of the License at 10 * 11 * http://www.apache.org/licenses/LICENSE-2.0 12 * 13 * Unless required by applicable law or agreed to in writing, software 14 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT 15 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 16 * See the License for the specific language governing permissions and 17 * limitations under the License. 18 * 19 * This file is part of Mbed TLS (https://tls.mbed.org) 20 */ 21 22 #include "common.h" 23 24 #if defined(MBEDTLS_ECDH_C) && defined(MBEDTLS_ECDH_VARIANT_EVEREST_ENABLED) 25 26 #include <mbedtls/ecdh.h> 27 28 #if !(defined(__SIZEOF_INT128__) && (__SIZEOF_INT128__ == 16)) 29 #define KRML_VERIFIED_UINT128 30 #endif 31 32 #include <Hacl_Curve25519.h> 33 #include <mbedtls/platform_util.h> 34 35 #include "x25519.h" 36 37 #include <string.h> 38 39 /* 40 * Initialize context 41 */ 42 void mbedtls_x25519_init( mbedtls_x25519_context *ctx ) 43 { 44 mbedtls_platform_zeroize( ctx, sizeof( mbedtls_x25519_context ) ); 45 } 46 47 /* 48 * Free context 49 */ 50 void mbedtls_x25519_free( mbedtls_x25519_context *ctx ) 51 { 52 if( ctx == NULL ) 53 return; 54 55 mbedtls_platform_zeroize( ctx->our_secret, MBEDTLS_X25519_KEY_SIZE_BYTES ); 56 mbedtls_platform_zeroize( ctx->peer_point, MBEDTLS_X25519_KEY_SIZE_BYTES ); 57 } 58 59 int mbedtls_x25519_make_params( mbedtls_x25519_context *ctx, size_t *olen, 60 unsigned char *buf, size_t blen, 61 int( *f_rng )(void *, unsigned char *, size_t), 62 void *p_rng ) 63 { 64 int ret = 0; 65 66 uint8_t base[MBEDTLS_X25519_KEY_SIZE_BYTES] = {0}; 67 68 if( ( ret = f_rng( p_rng, ctx->our_secret, MBEDTLS_X25519_KEY_SIZE_BYTES ) ) != 0 ) 69 return ret; 70 71 *olen = MBEDTLS_X25519_KEY_SIZE_BYTES + 4; 72 if( blen < *olen ) 73 return( MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL ); 74 75 *buf++ = MBEDTLS_ECP_TLS_NAMED_CURVE; 76 *buf++ = MBEDTLS_ECP_TLS_CURVE25519 >> 8; 77 *buf++ = MBEDTLS_ECP_TLS_CURVE25519 & 0xFF; 78 *buf++ = MBEDTLS_X25519_KEY_SIZE_BYTES; 79 80 base[0] = 9; 81 Hacl_Curve25519_crypto_scalarmult( buf, ctx->our_secret, base ); 82 83 base[0] = 0; 84 if( memcmp( buf, base, MBEDTLS_X25519_KEY_SIZE_BYTES) == 0 ) 85 return MBEDTLS_ERR_ECP_RANDOM_FAILED; 86 87 return( 0 ); 88 } 89 90 int mbedtls_x25519_read_params( mbedtls_x25519_context *ctx, 91 const unsigned char **buf, const unsigned char *end ) 92 { 93 if( end - *buf < MBEDTLS_X25519_KEY_SIZE_BYTES + 1 ) 94 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA ); 95 96 if( ( *(*buf)++ != MBEDTLS_X25519_KEY_SIZE_BYTES ) ) 97 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA ); 98 99 memcpy( ctx->peer_point, *buf, MBEDTLS_X25519_KEY_SIZE_BYTES ); 100 *buf += MBEDTLS_X25519_KEY_SIZE_BYTES; 101 return( 0 ); 102 } 103 104 int mbedtls_x25519_get_params( mbedtls_x25519_context *ctx, const mbedtls_ecp_keypair *key, 105 mbedtls_x25519_ecdh_side side ) 106 { 107 size_t olen = 0; 108 109 switch( side ) { 110 case MBEDTLS_X25519_ECDH_THEIRS: 111 return mbedtls_ecp_point_write_binary( &key->grp, &key->Q, MBEDTLS_ECP_PF_COMPRESSED, &olen, ctx->peer_point, MBEDTLS_X25519_KEY_SIZE_BYTES ); 112 case MBEDTLS_X25519_ECDH_OURS: 113 return mbedtls_mpi_write_binary_le( &key->d, ctx->our_secret, MBEDTLS_X25519_KEY_SIZE_BYTES ); 114 default: 115 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA ); 116 } 117 } 118 119 int mbedtls_x25519_calc_secret( mbedtls_x25519_context *ctx, size_t *olen, 120 unsigned char *buf, size_t blen, 121 int( *f_rng )(void *, unsigned char *, size_t), 122 void *p_rng ) 123 { 124 /* f_rng and p_rng are not used here because this implementation does not 125 need blinding since it has constant trace. */ 126 (( void )f_rng); 127 (( void )p_rng); 128 129 *olen = MBEDTLS_X25519_KEY_SIZE_BYTES; 130 131 if( blen < *olen ) 132 return( MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL ); 133 134 Hacl_Curve25519_crypto_scalarmult( buf, ctx->our_secret, ctx->peer_point); 135 136 /* Wipe the DH secret and don't let the peer chose a small subgroup point */ 137 mbedtls_platform_zeroize( ctx->our_secret, MBEDTLS_X25519_KEY_SIZE_BYTES ); 138 139 if( memcmp( buf, ctx->our_secret, MBEDTLS_X25519_KEY_SIZE_BYTES) == 0 ) 140 return MBEDTLS_ERR_ECP_RANDOM_FAILED; 141 142 return( 0 ); 143 } 144 145 int mbedtls_x25519_make_public( mbedtls_x25519_context *ctx, size_t *olen, 146 unsigned char *buf, size_t blen, 147 int( *f_rng )(void *, unsigned char *, size_t), 148 void *p_rng ) 149 { 150 int ret = 0; 151 unsigned char base[MBEDTLS_X25519_KEY_SIZE_BYTES] = { 0 }; 152 153 if( ctx == NULL ) 154 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA ); 155 156 if( ( ret = f_rng( p_rng, ctx->our_secret, MBEDTLS_X25519_KEY_SIZE_BYTES ) ) != 0 ) 157 return ret; 158 159 *olen = MBEDTLS_X25519_KEY_SIZE_BYTES + 1; 160 if( blen < *olen ) 161 return(MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL); 162 *buf++ = MBEDTLS_X25519_KEY_SIZE_BYTES; 163 164 base[0] = 9; 165 Hacl_Curve25519_crypto_scalarmult( buf, ctx->our_secret, base ); 166 167 base[0] = 0; 168 if( memcmp( buf, base, MBEDTLS_X25519_KEY_SIZE_BYTES ) == 0 ) 169 return MBEDTLS_ERR_ECP_RANDOM_FAILED; 170 171 return( ret ); 172 } 173 174 int mbedtls_x25519_read_public( mbedtls_x25519_context *ctx, 175 const unsigned char *buf, size_t blen ) 176 { 177 if( blen < MBEDTLS_X25519_KEY_SIZE_BYTES + 1 ) 178 return(MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL); 179 if( (*buf++ != MBEDTLS_X25519_KEY_SIZE_BYTES) ) 180 return(MBEDTLS_ERR_ECP_BAD_INPUT_DATA); 181 memcpy( ctx->peer_point, buf, MBEDTLS_X25519_KEY_SIZE_BYTES ); 182 return( 0 ); 183 } 184 185 186 #endif /* MBEDTLS_ECDH_C && MBEDTLS_ECDH_VARIANT_EVEREST_ENABLED */