/*
* Derive and export the shared secret (G^Y)^X mod P
*/
int dhm_calc_secret( dhm_context *ctx,
unsigned char *output, size_t *olen )
{
int ret;
if( ctx == NULL || *olen < ctx->len )
return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
MPI_CHK( mpi_exp_mod( &ctx->K, &ctx->GY, &ctx->X,
&ctx->P, &ctx->RP ) );
if( ( ret = dhm_check_range( &ctx->GY, &ctx->P ) ) != 0 )
return( ret );
*olen = mpi_size( &ctx->K );
MPI_CHK( mpi_write_binary( &ctx->K, output, *olen ) );
cleanup:
if( ret != 0 )
return( POLARSSL_ERR_DHM_CALC_SECRET_FAILED + ret );
return( 0 );
}
/*
* Parse the ServerKeyExchange parameters
*/
int dhm_read_params( dhm_context *ctx,
unsigned char **p,
const unsigned char *end )
{
int ret, n;
memset( ctx, 0, sizeof( dhm_context ) );
if( ( ret = dhm_read_bignum( &ctx->P, p, end ) ) != 0 ||
( ret = dhm_read_bignum( &ctx->G, p, end ) ) != 0 ||
( ret = dhm_read_bignum( &ctx->GY, p, end ) ) != 0 )
return( ret );
if( ( ret = dhm_check_range( &ctx->GY, &ctx->P ) ) != 0 )
return( ret );
ctx->len = mpi_size( &ctx->P );
if( end - *p < 2 )
return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
n = ( (*p)[0] << 8 ) | (*p)[1];
(*p) += 2;
if( end != *p + n )
return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
return( 0 );
}
/*
* Create own private value X and export G^X
*/
int dhm_make_public( dhm_context *ctx, int x_size,
unsigned char *output, size_t olen,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng )
{
int ret, n;
if( ctx == NULL || olen < 1 || olen > ctx->len )
return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
/*
* generate X and calculate GX = G^X mod P
*/
n = x_size / sizeof( t_uint ) + 1;
mpi_fill_random( &ctx->X, n, f_rng, p_rng );
while( mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 )
mpi_shift_r( &ctx->X, 1 );
MPI_CHK( mpi_exp_mod( &ctx->GX, &ctx->G, &ctx->X,
&ctx->P , &ctx->RP ) );
if( ( ret = dhm_check_range( &ctx->GX, &ctx->P ) ) != 0 )
return( ret );
MPI_CHK( mpi_write_binary( &ctx->GX, output, olen ) );
cleanup:
if( ret != 0 )
return( POLARSSL_ERR_DHM_MAKE_PUBLIC_FAILED + ret );
return( 0 );
}
/*
* Setup and write the ServerKeyExchange parameters
*/
int dhm_make_params( dhm_context *ctx, int x_size,
unsigned char *output, size_t *olen,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng )
{
int ret, n;
size_t n1, n2, n3;
unsigned char *p;
/*
* Generate X as large as possible ( < P )
*/
n = x_size / sizeof( t_uint ) + 1;
mpi_fill_random( &ctx->X, n, f_rng, p_rng );
while( mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 )
mpi_shift_r( &ctx->X, 1 );
/*
* Calculate GX = G^X mod P
*/
MPI_CHK( mpi_exp_mod( &ctx->GX, &ctx->G, &ctx->X,
&ctx->P , &ctx->RP ) );
if( ( ret = dhm_check_range( &ctx->GX, &ctx->P ) ) != 0 )
return( ret );
/*
* export P, G, GX
*/
#define DHM_MPI_EXPORT(X,n) \
MPI_CHK( mpi_write_binary( X, p + 2, n ) ); \
*p++ = (unsigned char)( n >> 8 ); \
*p++ = (unsigned char)( n ); p += n;
n1 = mpi_size( &ctx->P );
n2 = mpi_size( &ctx->G );
n3 = mpi_size( &ctx->GX );
p = output;
DHM_MPI_EXPORT( &ctx->P , n1 );
DHM_MPI_EXPORT( &ctx->G , n2 );
DHM_MPI_EXPORT( &ctx->GX, n3 );
*olen = p - output;
ctx->len = n1;
cleanup:
if( ret != 0 )
return( POLARSSL_ERR_DHM_MAKE_PARAMS_FAILED + ret );
return( 0 );
}
/*
* Create own private value X and export G^X
*/
int mbedtls_dhm_make_public( mbedtls_dhm_context *ctx, int x_size,
unsigned char *output, size_t olen,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng )
{
int ret, count = 0;
if( ctx == NULL || olen < 1 || olen > ctx->len )
return( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
if( mbedtls_mpi_cmp_int( &ctx->P, 0 ) == 0 )
return( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
/*
* generate X and calculate GX = G^X mod P
*/
do
{
mbedtls_mpi_fill_random( &ctx->X, x_size, f_rng, p_rng );
while( mbedtls_mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 )
MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( &ctx->X, 1 ) );
if( count++ > 10 )
return( MBEDTLS_ERR_DHM_MAKE_PUBLIC_FAILED );
}
while( dhm_check_range( &ctx->X, &ctx->P ) != 0 );
MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &ctx->GX, &ctx->G, &ctx->X,
&ctx->P , &ctx->RP ) );
if( ( ret = dhm_check_range( &ctx->GX, &ctx->P ) ) != 0 )
return( ret );
MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &ctx->GX, output, olen ) );
cleanup:
if( ret != 0 )
return( MBEDTLS_ERR_DHM_MAKE_PUBLIC_FAILED + ret );
return( 0 );
}
/*
* Derive and export the shared secret (G^Y)^X mod P
*/
int mbedtls_dhm_calc_secret( mbedtls_dhm_context *ctx,
unsigned char *output, size_t output_size, size_t *olen,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng )
{
int ret;
mbedtls_mpi GYb;
if( ctx == NULL || output_size < ctx->len )
return( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
if( ( ret = dhm_check_range( &ctx->GY, &ctx->P ) ) != 0 )
return( ret );
mbedtls_mpi_init( &GYb );
/* Blind peer's value */
if( f_rng != NULL )
{
MBEDTLS_MPI_CHK( dhm_update_blinding( ctx, f_rng, p_rng ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &GYb, &ctx->GY, &ctx->Vi ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &GYb, &GYb, &ctx->P ) );
}
else
MBEDTLS_MPI_CHK( mbedtls_mpi_copy( &GYb, &ctx->GY ) );
/* Do modular exponentiation */
MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &ctx->K, &GYb, &ctx->X,
&ctx->P, &ctx->RP ) );
/* Unblind secret value */
if( f_rng != NULL )
{
MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &ctx->K, &ctx->K, &ctx->Vf ) );
MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &ctx->K, &ctx->K, &ctx->P ) );
}
*olen = mbedtls_mpi_size( &ctx->K );
MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &ctx->K, output, *olen ) );
cleanup:
mbedtls_mpi_free( &GYb );
if( ret != 0 )
return( MBEDTLS_ERR_DHM_CALC_SECRET_FAILED + ret );
return( 0 );
}
/*
* Parse the ServerKeyExchange parameters
*/
int mbedtls_dhm_read_params( mbedtls_dhm_context *ctx,
unsigned char **p,
const unsigned char *end )
{
int ret;
if( ( ret = dhm_read_bignum( &ctx->P, p, end ) ) != 0 ||
( ret = dhm_read_bignum( &ctx->G, p, end ) ) != 0 ||
( ret = dhm_read_bignum( &ctx->GY, p, end ) ) != 0 )
return( ret );
if( ( ret = dhm_check_range( &ctx->GY, &ctx->P ) ) != 0 )
return( ret );
ctx->len = mbedtls_mpi_size( &ctx->P );
return( 0 );
}
/*
* Derive and export the shared secret (G^Y)^X mod P
*/
int dhm_calc_secret_no_export(dhm_context *ctx)
{
int ret;
if( ctx == NULL )
return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
MPI_CHK( mpi_exp_mod( &ctx->K, &ctx->GY, &ctx->X,
&ctx->P, &ctx->RP ) );
if( ( ret = dhm_check_range( &ctx->GY, &ctx->P ) ) != 0 )
return( ret );
cleanup:
if( ret != 0 )
return( POLARSSL_ERR_DHM_CALC_SECRET_FAILED + ret );
return( 0 );
}
/*
* Setup and write the ServerKeyExchange parameters
*/
int mbedtls_dhm_make_params( mbedtls_dhm_context *ctx, int x_size,
unsigned char *output, size_t *olen,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng )
{
int ret, count = 0;
size_t n1, n2, n3;
unsigned char *p;
if( mbedtls_mpi_cmp_int( &ctx->P, 0 ) == 0 )
return( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
/*
* Generate X as large as possible ( < P )
*/
do
{
mbedtls_mpi_fill_random( &ctx->X, x_size, f_rng, p_rng );
while( mbedtls_mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 )
MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( &ctx->X, 1 ) );
if( count++ > 10 )
return( MBEDTLS_ERR_DHM_MAKE_PARAMS_FAILED );
}
while( dhm_check_range( &ctx->X, &ctx->P ) != 0 );
/*
* Calculate GX = G^X mod P
*/
MBEDTLS_MPI_CHK( mbedtls_mpi_exp_mod( &ctx->GX, &ctx->G, &ctx->X,
&ctx->P , &ctx->RP ) );
if( ( ret = dhm_check_range( &ctx->GX, &ctx->P ) ) != 0 )
return( ret );
/*
* export P, G, GX
*/
#define DHM_MPI_EXPORT(X,n) \
MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( X, p + 2, n ) ); \
*p++ = (unsigned char)( n >> 8 ); \
*p++ = (unsigned char)( n ); p += n;
n1 = mbedtls_mpi_size( &ctx->P );
n2 = mbedtls_mpi_size( &ctx->G );
n3 = mbedtls_mpi_size( &ctx->GX );
p = output;
DHM_MPI_EXPORT( &ctx->P , n1 );
DHM_MPI_EXPORT( &ctx->G , n2 );
DHM_MPI_EXPORT( &ctx->GX, n3 );
*olen = p - output;
ctx->len = n1;
cleanup:
if( ret != 0 )
return( MBEDTLS_ERR_DHM_MAKE_PARAMS_FAILED + ret );
return( 0 );
}
