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 */
mbedtls_x25519_init(mbedtls_x25519_context * ctx)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 */
mbedtls_x25519_free(mbedtls_x25519_context * ctx)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
mbedtls_x25519_make_params(mbedtls_x25519_context * ctx,size_t * olen,unsigned char * buf,size_t blen,int (* f_rng)(void *,unsigned char *,size_t),void * p_rng)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
mbedtls_x25519_read_params(mbedtls_x25519_context * ctx,const unsigned char ** buf,const unsigned char * end)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
mbedtls_x25519_get_params(mbedtls_x25519_context * ctx,const mbedtls_ecp_keypair * key,mbedtls_x25519_ecdh_side side)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
mbedtls_x25519_calc_secret(mbedtls_x25519_context * ctx,size_t * olen,unsigned char * buf,size_t blen,int (* f_rng)(void *,unsigned char *,size_t),void * p_rng)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
mbedtls_x25519_make_public(mbedtls_x25519_context * ctx,size_t * olen,unsigned char * buf,size_t blen,int (* f_rng)(void *,unsigned char *,size_t),void * p_rng)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
mbedtls_x25519_read_public(mbedtls_x25519_context * ctx,const unsigned char * buf,size_t blen)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 */
187
