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[crypto] Force caller to provide temporary storage for modular calculations

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bigint_mod_multiply() and bigint_mod_exp() require a fixed amount of
temporary storage for intermediate results.  (The amount of temporary
storage required depends upon the size of the integers involved.)

When performing calculations for 4096-bit RSA the amount of temporary
storage space required will exceed 2.5kB, which is too much to
allocate on the stack.  Avoid this problem by forcing the caller to
allocate temporary storage.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
This commit is contained in:
Michael Brown
2012-03-18 20:02:25 +00:00
parent 5af9e62196
commit 3ec773cd2b
5 changed files with 99 additions and 40 deletions
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19
src/tests/bigint_test.c
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@@ -162,7 +162,8 @@ void bigint_mod_multiply_sample ( const bigint_element_t *multiplicand0,
const bigint_element_t *multiplier0,
const bigint_element_t *modulus0,
bigint_element_t *result0,
unsigned int size ) {
unsigned int size,
void *tmp ) {
const bigint_t ( size ) *multiplicand __attribute__ (( may_alias ))
= ( ( const void * ) multiplicand0 );
const bigint_t ( size ) *multiplier __attribute__ (( may_alias ))
@@ -172,14 +173,15 @@ void bigint_mod_multiply_sample ( const bigint_element_t *multiplicand0,
bigint_t ( size ) *result __attribute__ (( may_alias ))
= ( ( void * ) result0 );
bigint_mod_multiply ( multiplicand, multiplier, modulus, result );
bigint_mod_multiply ( multiplicand, multiplier, modulus, result, tmp );
}
void bigint_mod_exp_sample ( const bigint_element_t *base0,
const bigint_element_t *modulus0,
const bigint_element_t *exponent0,
bigint_element_t *result0,
unsigned int size, unsigned int exponent_size ) {
unsigned int size, unsigned int exponent_size,
void *tmp ) {
const bigint_t ( size ) *base __attribute__ (( may_alias ))
= ( ( const void * ) base0 );
const bigint_t ( size ) *modulus __attribute__ (( may_alias ))
@@ -189,7 +191,7 @@ void bigint_mod_exp_sample ( const bigint_element_t *base0,
bigint_t ( size ) *result __attribute__ (( may_alias ))
= ( ( void * ) result0 );
bigint_mod_exp ( base, modulus, exponent, result );
bigint_mod_exp ( base, modulus, exponent, result, tmp );
}
/**
@@ -471,6 +473,8 @@ void bigint_mod_exp_sample ( const bigint_element_t *base0,
bigint_t ( size ) multiplier_temp; \
bigint_t ( size ) modulus_temp; \
bigint_t ( size ) result_temp; \
size_t tmp_len = bigint_mod_multiply_tmp_len ( &modulus_temp ); \
uint8_t tmp[tmp_len]; \
{} /* Fix emacs alignment */ \
\
assert ( bigint_size ( &multiplier_temp ) == \
@@ -490,7 +494,7 @@ void bigint_mod_exp_sample ( const bigint_element_t *base0,
DBG_HDA ( 0, &multiplier_temp, sizeof ( multiplier_temp ) ); \
DBG_HDA ( 0, &modulus_temp, sizeof ( modulus_temp ) ); \
bigint_mod_multiply ( &multiplicand_temp, &multiplier_temp, \
&modulus_temp, &result_temp ); \
&modulus_temp, &result_temp, tmp ); \
DBG_HDA ( 0, &result_temp, sizeof ( result_temp ) ); \
bigint_done ( &result_temp, result_raw, sizeof ( result_raw ) );\
\
@@ -520,6 +524,9 @@ void bigint_mod_exp_sample ( const bigint_element_t *base0,
bigint_t ( size ) modulus_temp; \
bigint_t ( exponent_size ) exponent_temp; \
bigint_t ( size ) result_temp; \
size_t tmp_len = bigint_mod_exp_tmp_len ( &modulus_temp, \
&exponent_temp ); \
uint8_t tmp[tmp_len]; \
{} /* Fix emacs alignment */ \
\
assert ( bigint_size ( &modulus_temp ) == \
@@ -536,7 +543,7 @@ void bigint_mod_exp_sample ( const bigint_element_t *base0,
DBG_HDA ( 0, &modulus_temp, sizeof ( modulus_temp ) ); \
DBG_HDA ( 0, &exponent_temp, sizeof ( exponent_temp ) ); \
bigint_mod_exp ( &base_temp, &modulus_temp, &exponent_temp, \
&result_temp ); \
&result_temp, tmp ); \
DBG_HDA ( 0, &result_temp, sizeof ( result_temp ) ); \
bigint_done ( &result_temp, result_raw, sizeof ( result_raw ) );\
\