mbedtls/library/ecjpake.c
2015-09-07 12:43:09 +02:00

391 lines
12 KiB
C

/*
* Elliptic curve J-PAKE
*
* Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
* SPDX-License-Identifier: Apache-2.0
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may
* not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*
* This file is part of mbed TLS (https://tls.mbed.org)
*/
/*
* We implement EC-JPAKE as defined in Chapter 7.4 of the Thread v1.0
* Specification. References below are to this document.
*/
#if !defined(MBEDTLS_CONFIG_FILE)
#include "mbedtls/config.h"
#else
#include MBEDTLS_CONFIG_FILE
#endif
#if defined(MBEDTLS_ECJPAKE_C)
#include "mbedtls/ecjpake.h"
#include <string.h>
/*
* Write a point plus its length to a buffer
*/
static int ecjpake_write_len_point( unsigned char **p,
const unsigned char *end,
const mbedtls_ecp_group *grp,
const mbedtls_ecp_point *P )
{
int ret;
size_t len;
/* Need at least 4 for length plus 1 for point */
if( end < *p || end - *p < 5 )
return( MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL );
ret = mbedtls_ecp_point_write_binary( grp, P, MBEDTLS_ECP_PF_UNCOMPRESSED,
&len, *p + 4, end - ( *p + 4 ) );
if( ret != 0 )
return( ret );
(*p)[0] = (unsigned char)( ( len >> 24 ) & 0xFF );
(*p)[1] = (unsigned char)( ( len >> 16 ) & 0xFF );
(*p)[2] = (unsigned char)( ( len >> 8 ) & 0xFF );
(*p)[3] = (unsigned char)( ( len ) & 0xFF );
*p += 4 + len;
return( 0 );
}
/*
* Size of the temporary buffer for ecjpake_hash:
* 3 EC points plus their length, plus ID (6 bytes)
*/
#define ECJPAKE_HASH_BUF_LEN ( 3 * ( 4 + MBEDTLS_ECP_MAX_PT_LEN ) + 6 )
/*
* Compute hash for ZKP (7.4.2.2.2.1)
*/
static int ecjpake_hash( const mbedtls_md_info_t *md_info,
const mbedtls_ecp_group *grp,
const mbedtls_ecp_point *G,
const mbedtls_ecp_point *V,
const mbedtls_ecp_point *X,
const char *id,
mbedtls_mpi *h )
{
int ret;
unsigned char buf[ECJPAKE_HASH_BUF_LEN];
unsigned char *p = buf;
const unsigned char *end = buf + sizeof( buf );
const size_t id_len = strlen( id );
unsigned char hash[MBEDTLS_MD_MAX_SIZE];
/* Write things to temporary buffer */
MBEDTLS_MPI_CHK( ecjpake_write_len_point( &p, end, grp, G ) );
MBEDTLS_MPI_CHK( ecjpake_write_len_point( &p, end, grp, V ) );
MBEDTLS_MPI_CHK( ecjpake_write_len_point( &p, end, grp, X ) );
if( end < p || (size_t)( end - p ) < id_len )
return( MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL );
*p++ = (unsigned char)( ( id_len >> 24 ) & 0xFF );
*p++ = (unsigned char)( ( id_len >> 16 ) & 0xFF );
*p++ = (unsigned char)( ( id_len >> 8 ) & 0xFF );
*p++ = (unsigned char)( ( id_len ) & 0xFF );
memcpy( p, id, id_len );
p += id_len;
/* Compute hash */
mbedtls_md( md_info, buf, p - buf, hash );
/* Turn it into an integer mod n */
MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( h, hash,
mbedtls_md_get_size( md_info ) ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( h, h, &grp->N ) );
cleanup:
return( ret );
}
/*
* Generate ZKP (7.4.2.3.2) and write it as ECSchnorrZKP (7.4.2.2.2)
*/
static int ecjpake_zkp_write( const mbedtls_md_info_t *md_info,
const mbedtls_ecp_group *grp,
const mbedtls_ecp_point *G,
const mbedtls_mpi *x,
const mbedtls_ecp_point *X,
const char *id,
unsigned char **p,
const unsigned char *end,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng )
{
int ret;
mbedtls_ecp_point V;
mbedtls_mpi v;
mbedtls_mpi h; /* later recycled to hold r */
size_t len;
if( end < *p )
return( MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL );
mbedtls_ecp_point_init( &V );
mbedtls_mpi_init( &v );
mbedtls_mpi_init( &h );
/* Compute signature */
MBEDTLS_MPI_CHK( mbedtls_ecp_gen_keypair_base( (mbedtls_ecp_group *) grp,
G, &v, &V, f_rng, p_rng ) );
MBEDTLS_MPI_CHK( ecjpake_hash( md_info, grp, G, &V, X, id, &h ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &h, &h, x ) ); /* x*h */
MBEDTLS_MPI_CHK( mbedtls_mpi_sub_mpi( &h, &v, &h ) ); /* v - x*h */
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &h, &h, &grp->N ) ); /* r */
/* Write it out */
MBEDTLS_MPI_CHK( mbedtls_ecp_tls_write_point( grp, &V,
MBEDTLS_ECP_PF_UNCOMPRESSED, &len, *p, end - *p ) );
*p += len;
len = mbedtls_mpi_size( &h ); /* actually r */
if( end < *p || (size_t)( end - *p ) < 1 + len || len > 255 )
return( MBEDTLS_ERR_ECP_BUFFER_TOO_SMALL );
*(*p)++ = (unsigned char)( len & 0xFF );
MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &h, *p, len ) ); /* r */
*p += len;
cleanup:
mbedtls_ecp_point_free( &V );
mbedtls_mpi_free( &v );
mbedtls_mpi_free( &h );
return( ret );
}
/*
* Parse a ECShnorrZKP (7.4.2.2.2) and verify it (7.4.2.3.3)
*/
static int ecjpake_zkp_read( const mbedtls_md_info_t *md_info,
const mbedtls_ecp_group *grp,
const mbedtls_ecp_point *G,
const mbedtls_ecp_point *X,
const char *id,
unsigned char **p,
const unsigned char *end )
{
int ret;
mbedtls_ecp_point V, VV;
mbedtls_mpi r, h;
size_t r_len;
mbedtls_ecp_point_init( &V );
mbedtls_ecp_point_init( &VV );
mbedtls_mpi_init( &r );
mbedtls_mpi_init( &h );
/*
* struct {
* ECPoint V;
* opaque r<1..2^8-1>;
* } ECSchnorrZKP;
*/
if( end < *p )
return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
MBEDTLS_MPI_CHK( mbedtls_ecp_tls_read_point( grp, &V,
(const unsigned char **) p, end - *p ) );
if( end < *p || (size_t)( end - *p ) < 1 )
return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
r_len = *(*p)++;
if( end < *p || (size_t)( end - *p ) < r_len )
return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( &r, *p, r_len ) );
*p += r_len;
/*
* Verification
*/
MBEDTLS_MPI_CHK( ecjpake_hash( md_info, grp, G, &V, X, id, &h ) );
MBEDTLS_MPI_CHK( mbedtls_ecp_muladd( (mbedtls_ecp_group *) grp,
&VV, &h, X, &r, G ) );
if( mbedtls_ecp_point_cmp( &VV, &V ) != 0 )
return( MBEDTLS_ERR_ECP_VERIFY_FAILED );
cleanup:
mbedtls_ecp_point_free( &V );
mbedtls_ecp_point_free( &VV );
mbedtls_mpi_free( &r );
mbedtls_mpi_free( &h );
return( ret );
}
#if defined(MBEDTLS_SELF_TEST)
#if defined(MBEDTLS_PLATFORM_C)
#include "mbedtls/platform.h"
#else
#include <stdio.h>
#define mbedtls_printf printf
#endif
#if !defined(MBEDTLS_ECP_DP_SECP256R1_ENABLED) || \
!defined(MBEDTLS_SHA256_C)
int mbedtls_ecjpake_self_test( int verbose )
{
(void) verbose;
return( 0 );
}
#else
static const unsigned char ecjpake_test_X[] = {
0x04, 0xac, 0xcf, 0x01, 0x06, 0xef, 0x85, 0x8f, 0xa2, 0xd9, 0x19, 0x33,
0x13, 0x46, 0x80, 0x5a, 0x78, 0xb5, 0x8b, 0xba, 0xd0, 0xb8, 0x44, 0xe5,
0xc7, 0x89, 0x28, 0x79, 0x14, 0x61, 0x87, 0xdd, 0x26, 0x66, 0xad, 0xa7,
0x81, 0xbb, 0x7f, 0x11, 0x13, 0x72, 0x25, 0x1a, 0x89, 0x10, 0x62, 0x1f,
0x63, 0x4d, 0xf1, 0x28, 0xac, 0x48, 0xe3, 0x81, 0xfd, 0x6e, 0xf9, 0x06,
0x07, 0x31, 0xf6, 0x94, 0xa4
};
static const unsigned char ecjpake_test_zkp[] = {
0x41, 0x04, 0x1d, 0xd0, 0xbd, 0x5d, 0x45, 0x66, 0xc9, 0xbe, 0xd9, 0xce,
0x7d, 0xe7, 0x01, 0xb5, 0xe8, 0x2e, 0x08, 0xe8, 0x4b, 0x73, 0x04, 0x66,
0x01, 0x8a, 0xb9, 0x03, 0xc7, 0x9e, 0xb9, 0x82, 0x17, 0x22, 0x36, 0xc0,
0xc1, 0x72, 0x8a, 0xe4, 0xbf, 0x73, 0x61, 0x0d, 0x34, 0xde, 0x44, 0x24,
0x6e, 0xf3, 0xd9, 0xc0, 0x5a, 0x22, 0x36, 0xfb, 0x66, 0xa6, 0x58, 0x3d,
0x74, 0x49, 0x30, 0x8b, 0xab, 0xce, 0x20, 0x72, 0xfe, 0x16, 0x66, 0x29,
0x92, 0xe9, 0x23, 0x5c, 0x25, 0x00, 0x2f, 0x11, 0xb1, 0x50, 0x87, 0xb8,
0x27, 0x38, 0xe0, 0x3c, 0x94, 0x5b, 0xf7, 0xa2, 0x99, 0x5d, 0xda, 0x1e,
0x98, 0x34, 0x58
};
/* For tests we don't need a secure RNG;
* use the LGC from Numerical Recipes for simplicity */
static int ecjpake_lgc( void *p, unsigned char *out, size_t len )
{
static uint32_t x = 42;
(void) p;
while( len > 0 )
{
size_t use_len = len > 4 ? 4 : len;
x = 1664525 * x + 1013904223;
memcpy( out, &x, use_len );
out += use_len;
len -= use_len;
}
return( 0 );
}
/*
* Checkup routine
*/
int mbedtls_ecjpake_self_test( int verbose )
{
int ret;
mbedtls_ecp_group grp;
mbedtls_ecp_point X;
mbedtls_mpi x;
const mbedtls_md_info_t *md_info;
unsigned char buf[1000];
unsigned char *p;
const unsigned char *end;
mbedtls_ecp_group_init( &grp );
mbedtls_ecp_point_init( &X );
mbedtls_mpi_init( &x );
/* Common to all tests */
md_info = mbedtls_md_info_from_type( MBEDTLS_MD_SHA256 );
MBEDTLS_MPI_CHK( mbedtls_ecp_group_load( &grp, MBEDTLS_ECP_DP_SECP256R1 ) );
if( verbose != 0 )
mbedtls_printf( " ECJPAKE test #1 (zkp read): " );
MBEDTLS_MPI_CHK( mbedtls_ecp_point_read_binary( &grp, &X,
ecjpake_test_X,
sizeof( ecjpake_test_X ) ) );
p = (unsigned char *) ecjpake_test_zkp;
end = ecjpake_test_zkp + sizeof( ecjpake_test_zkp );
MBEDTLS_MPI_CHK( ecjpake_zkp_read( md_info, &grp, &grp.G, &X, "client",
&p, end ) );
/* Corrupt proof */
memcpy( buf, ecjpake_test_zkp, sizeof( ecjpake_test_zkp ) );
buf[sizeof( ecjpake_test_zkp ) - 1]--;
p = buf;
end = buf + sizeof( ecjpake_test_zkp );
ret = ecjpake_zkp_read( md_info, &grp, &grp.G, &X, "client", &p, end );
if( ret != MBEDTLS_ERR_ECP_VERIFY_FAILED )
{
ret = 1;
goto cleanup;
}
ret = 0;
if( verbose != 0 )
mbedtls_printf( "passed\n" );
if( verbose != 0 )
mbedtls_printf( " ECJPAKE test #2 (zkp write/read): " );
MBEDTLS_MPI_CHK( mbedtls_ecp_gen_keypair_base( &grp, &grp.G, &x, &X,
ecjpake_lgc, NULL ) );
p = buf;
MBEDTLS_MPI_CHK( ecjpake_zkp_write( md_info, &grp, &grp.G, &x, &X, "client",
&p, buf + sizeof( buf ),
ecjpake_lgc, NULL ) );
p = buf;
MBEDTLS_MPI_CHK( ecjpake_zkp_read( md_info, &grp, &grp.G, &X, "client",
&p, buf + sizeof( buf ) ) );
if( verbose != 0 )
mbedtls_printf( "passed\n" );
cleanup:
mbedtls_ecp_group_free( &grp );
mbedtls_ecp_point_free( &X );
mbedtls_mpi_free( &x );
if( ret != 0 )
{
if( verbose != 0 )
mbedtls_printf( "failed\n" );
ret = 1;
}
if( verbose != 0 )
mbedtls_printf( "\n" );
return( ret );
}
#endif /* MBEDTLS_ECP_DP_SECP256R1_ENABLED && MBEDTLS_SHA256_C */
#endif /* MBEDTLS_SELF_TEST */
#endif /* MBEDTLS_ECJPAKE_C */