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DHM refactoring: unify mbedtls_dhm_make_{params,public}

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Unify the common parts of mbedtls_dhm_make_params and mbedtls_dhm_make_public.

No intended behavior change, except that the exact error code may
change in some corner cases which are too exotic for the existing unit
tests.

Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This commit is contained in:
Gilles Peskine 2021-03-31 22:35:13 +02:00
parent 33ec863570
commit 0853bb2bea
1 changed files with 39 additions and 47 deletions
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86
library/dhm.c
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@ -150,21 +150,11 @@ int mbedtls_dhm_read_params( mbedtls_dhm_context *ctx,
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 )
static int dhm_make_common( mbedtls_dhm_context *ctx, int x_size,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng )
{
int ret, count = 0;
size_t n1, n2, n3;
unsigned char *p;
DHM_VALIDATE_RET( ctx != NULL );
DHM_VALIDATE_RET( output != NULL );
DHM_VALIDATE_RET( olen != NULL );
DHM_VALIDATE_RET( f_rng != NULL );
if( mbedtls_mpi_cmp_int( &ctx->P, 0 ) == 0 )
return( MBEDTLS_ERR_DHM_BAD_INPUT_DATA );
@ -193,6 +183,30 @@ int mbedtls_dhm_make_params( mbedtls_dhm_context *ctx, int x_size,
if( ( ret = dhm_check_range( &ctx->GX, &ctx->P ) ) != 0 )
return( ret );
cleanup:
return( ret );
}
/*
* 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;
size_t n1, n2, n3;
unsigned char *p;
DHM_VALIDATE_RET( ctx != NULL );
DHM_VALIDATE_RET( output != NULL );
DHM_VALIDATE_RET( olen != NULL );
DHM_VALIDATE_RET( f_rng != NULL );
ret = dhm_make_common( ctx, x_size, f_rng, p_rng );
if( ret != 0 )
goto cleanup;
/*
* export P, G, GX
*/
@ -220,11 +234,9 @@ int mbedtls_dhm_make_params( mbedtls_dhm_context *ctx, int x_size,
ctx->len = n1;
cleanup:
if( ret != 0 )
return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_DHM_MAKE_PARAMS_FAILED, ret ) );
return( 0 );
if( ret != 0 && ret > -128 )
ret = MBEDTLS_ERROR_ADD( MBEDTLS_ERR_DHM_MAKE_PARAMS_FAILED, ret );
return( ret );
}
/*
@ -276,7 +288,7 @@ int mbedtls_dhm_make_public( mbedtls_dhm_context *ctx, int x_size,
int (*f_rng)(void *, unsigned char *, size_t),
void *p_rng )
{
int ret, count = 0;
int ret;
DHM_VALIDATE_RET( ctx != NULL );
DHM_VALIDATE_RET( output != NULL );
DHM_VALIDATE_RET( f_rng != NULL );
@ -284,38 +296,18 @@ int mbedtls_dhm_make_public( mbedtls_dhm_context *ctx, int x_size,
if( 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_CHK( 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 );
ret = dhm_make_common( ctx, x_size, f_rng, p_rng );
if( ret == MBEDTLS_ERR_DHM_MAKE_PARAMS_FAILED )
return( MBEDTLS_ERR_DHM_MAKE_PUBLIC_FAILED );
if( ret != 0 )
goto cleanup;
MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &ctx->GX, output, olen ) );
cleanup:
if( ret != 0 )
return( MBEDTLS_ERROR_ADD( MBEDTLS_ERR_DHM_MAKE_PUBLIC_FAILED, ret ) );
return( 0 );
if( ret != 0 && ret > -128 )
ret = MBEDTLS_ERROR_ADD( MBEDTLS_ERR_DHM_MAKE_PUBLIC_FAILED, ret );
return( ret );
}
/*