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- Added extra sanity check to DHM values

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This commit is contained in:
Paul Bakker 2012-04-26 18:59:59 +00:00
parent c9b3e1e783
commit aec37cb653
1 changed files with 27 additions and 13 deletions

28
library/dhm.c
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@ -61,15 +61,15 @@ static int dhm_read_bignum( mpi *X,
} }
/* /*
* Verify sanity of public parameter with regards to P * Verify sanity of parameter with regards to P
* *
* Public parameter should be: 2 <= public_param <= P - 2 * Parameter should be: 2 <= public_param <= P - 2
* *
* For more information on the attack, see: * For more information on the attack, see:
* http://www.cl.cam.ac.uk/~rja14/Papers/psandqs.pdf * http://www.cl.cam.ac.uk/~rja14/Papers/psandqs.pdf
* http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2005-2643 * http://web.nvd.nist.gov/view/vuln/detail?vulnId=CVE-2005-2643
*/ */
static int dhm_check_range( const mpi *public_param, const mpi *P ) static int dhm_check_range( const mpi *param, const mpi *P )
{ {
mpi L, U; mpi L, U;
int ret = POLARSSL_ERR_DHM_BAD_INPUT_DATA; int ret = POLARSSL_ERR_DHM_BAD_INPUT_DATA;
@ -78,8 +78,8 @@ static int dhm_check_range( const mpi *public_param, const mpi *P )
mpi_lset( &L, 2 ); mpi_lset( &L, 2 );
mpi_sub_int( &U, P, 2 ); mpi_sub_int( &U, P, 2 );
if( mpi_cmp_mpi( public_param, &L ) >= 0 && if( mpi_cmp_mpi( param, &L ) >= 0 &&
mpi_cmp_mpi( public_param, &U ) <= 0 ) mpi_cmp_mpi( param, &U ) <= 0 )
{ {
ret = 0; ret = 0;
} }
@ -124,18 +124,25 @@ int dhm_make_params( dhm_context *ctx, int x_size,
int (*f_rng)(void *, unsigned char *, size_t), int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng ) void *p_rng )
{ {
int ret; int ret, count = 0;
size_t n1, n2, n3; size_t n1, n2, n3;
unsigned char *p; unsigned char *p;
/* /*
* Generate X as large as possible ( < P ) * Generate X as large as possible ( < P )
*/ */
do
{
mpi_fill_random( &ctx->X, x_size, f_rng, p_rng ); mpi_fill_random( &ctx->X, x_size, f_rng, p_rng );
while( mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 ) while( mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 )
mpi_shift_r( &ctx->X, 1 ); mpi_shift_r( &ctx->X, 1 );
if( count++ > 10 )
return( POLARSSL_ERR_DHM_MAKE_PARAMS_FAILED );
}
while( dhm_check_range( &ctx->X, &ctx->P ) != 0 );
/* /*
* Calculate GX = G^X mod P * Calculate GX = G^X mod P
*/ */
@ -199,7 +206,7 @@ int dhm_make_public( dhm_context *ctx, int x_size,
int (*f_rng)(void *, unsigned char *, size_t), int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng ) void *p_rng )
{ {
int ret; int ret, count = 0;
if( ctx == NULL || olen < 1 || olen > ctx->len ) if( ctx == NULL || olen < 1 || olen > ctx->len )
return( POLARSSL_ERR_DHM_BAD_INPUT_DATA ); return( POLARSSL_ERR_DHM_BAD_INPUT_DATA );
@ -207,11 +214,18 @@ int dhm_make_public( dhm_context *ctx, int x_size,
/* /*
* generate X and calculate GX = G^X mod P * generate X and calculate GX = G^X mod P
*/ */
do
{
mpi_fill_random( &ctx->X, x_size, f_rng, p_rng ); mpi_fill_random( &ctx->X, x_size, f_rng, p_rng );
while( mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 ) while( mpi_cmp_mpi( &ctx->X, &ctx->P ) >= 0 )
mpi_shift_r( &ctx->X, 1 ); mpi_shift_r( &ctx->X, 1 );
if( count++ > 10 )
return( POLARSSL_ERR_DHM_MAKE_PUBLIC_FAILED );
}
while( dhm_check_range( &ctx->X, &ctx->P ) != 0 );
MPI_CHK( mpi_exp_mod( &ctx->GX, &ctx->G, &ctx->X, MPI_CHK( mpi_exp_mod( &ctx->GX, &ctx->G, &ctx->X,
&ctx->P , &ctx->RP ) ); &ctx->P , &ctx->RP ) );