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[rng] Add ANS X9.82 mandatory start-up tests 

ANS X9.82 specifies that the start-up tests shall consist of at least
one full cycle of the continuous tests.

Signed-off-by: Michael Brown <mcb30@ipxe.org>
pull/5/head
Michael Brown 2012-02-20 19:26:04 +00:00
parent a3b116cea1
commit c6b0b3424b
1 changed files with 32 additions and 0 deletions
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32
src/crypto/entropy.c
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@ -351,6 +351,31 @@ static int get_entropy ( entropy_sample_t *entropy ) {
return 0;
}
/**
* Calculate number of samples required for startup tests
*
* @ret num_samples Number of samples required
*
* ANS X9.82 Part 2 (October 2011 Draft) Section 8.5.2.1.5 requires
* that at least one full cycle of the continuous tests must be
* performed at start-up.
*/
static inline __attribute__ (( always_inline )) unsigned int
startup_test_count ( void ) {
unsigned int num_samples;
/* At least max(N,C) samples shall be generated by the noise
* source for start-up testing.
*/
num_samples = repetition_count_cutoff();
if ( num_samples < adaptive_proportion_cutoff() )
num_samples = adaptive_proportion_cutoff();
linker_assert ( __builtin_constant_p ( num_samples ),
startup_test_count_not_constant );
return num_samples;
}
/**
* Create next nonce value
*
@ -387,6 +412,7 @@ static uint32_t make_next_nonce ( void ) {
*/
int get_entropy_input_tmp ( unsigned int num_samples, uint8_t *tmp,
size_t tmp_len ) {
static unsigned int startup_tested = 0;
struct {
uint32_t nonce;
entropy_sample_t sample;
@ -398,6 +424,12 @@ int get_entropy_input_tmp ( unsigned int num_samples, uint8_t *tmp,
/* Enable entropy gathering */
entropy_enable();
/* Perform mandatory startup tests, if not yet performed */
for ( ; startup_tested < startup_test_count() ; startup_tested++ ) {
if ( ( rc = get_entropy ( &data.sample ) ) != 0 )
goto err_get_entropy;
}
/* 3. entropy_total = 0
*
* (Nothing to do; the number of entropy samples required has