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CTR_DRBG entropy usage: test the exact amount of consumed entropy

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This commit is contained in:
Gilles Peskine 2019-10-22 19:10:01 +02:00
parent 97f59ab527
commit 58b56ce444
1 changed files with 13 additions and 13 deletions
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26
tests/suites/test_suite_ctr_drbg.function
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@ -197,7 +197,7 @@ void ctr_drbg_entropy_usage( )
unsigned char entropy[1024];
mbedtls_ctr_drbg_context ctx;
size_t i, reps = 10;
size_t last_idx;
size_t expected_idx = 0;
mbedtls_ctr_drbg_init( &ctx );
test_offset_idx = 0;
@ -207,20 +207,19 @@ void ctr_drbg_entropy_usage( )
memset( add, 0, sizeof( add ) );
/* Init must use entropy */
last_idx = test_offset_idx;
TEST_ASSERT( mbedtls_ctr_drbg_seed( &ctx, mbedtls_test_entropy_func, entropy, NULL, 0 ) == 0 );
TEST_ASSERT( last_idx < test_offset_idx );
expected_idx += MBEDTLS_CTR_DRBG_ENTROPY_LEN;
TEST_EQUAL( test_offset_idx, expected_idx );
/* By default, PR is off and reseed_interval is large,
* so the next few calls should not use entropy */
last_idx = test_offset_idx;
for( i = 0; i < reps; i++ )
{
TEST_ASSERT( mbedtls_ctr_drbg_random( &ctx, out, sizeof( out ) - 4 ) == 0 );
TEST_ASSERT( mbedtls_ctr_drbg_random_with_add( &ctx, out, sizeof( out ) - 4,
add, sizeof( add ) ) == 0 );
}
TEST_ASSERT( last_idx == test_offset_idx );
TEST_EQUAL( test_offset_idx, expected_idx );
/* While at it, make sure we didn't write past the requested length */
TEST_ASSERT( out[sizeof( out ) - 4] == 0 );
@ -232,17 +231,17 @@ void ctr_drbg_entropy_usage( )
* so the next call should reseed */
mbedtls_ctr_drbg_set_reseed_interval( &ctx, 2 * reps );
TEST_ASSERT( mbedtls_ctr_drbg_random( &ctx, out, sizeof( out ) ) == 0 );
TEST_ASSERT( last_idx < test_offset_idx );
expected_idx += MBEDTLS_CTR_DRBG_ENTROPY_LEN;
TEST_EQUAL( test_offset_idx, expected_idx );
/* The new few calls should not reseed */
last_idx = test_offset_idx;
for( i = 0; i < reps / 2; i++ )
{
TEST_ASSERT( mbedtls_ctr_drbg_random( &ctx, out, sizeof( out ) ) == 0 );
TEST_ASSERT( mbedtls_ctr_drbg_random_with_add( &ctx, out, sizeof( out ) ,
add, sizeof( add ) ) == 0 );
}
TEST_ASSERT( last_idx == test_offset_idx );
TEST_EQUAL( test_offset_idx, expected_idx );
/* Call update with too much data (sizeof entropy > MAX(_SEED)_INPUT).
* Make sure it's detected as an error and doesn't cause memory
@ -253,18 +252,19 @@ void ctr_drbg_entropy_usage( )
/* Now enable PR, so the next few calls should all reseed */
mbedtls_ctr_drbg_set_prediction_resistance( &ctx, MBEDTLS_CTR_DRBG_PR_ON );
TEST_ASSERT( mbedtls_ctr_drbg_random( &ctx, out, sizeof( out ) ) == 0 );
TEST_ASSERT( last_idx < test_offset_idx );
expected_idx += MBEDTLS_CTR_DRBG_ENTROPY_LEN;
TEST_EQUAL( test_offset_idx, expected_idx );
/* Finally, check setting entropy_len */
mbedtls_ctr_drbg_set_entropy_len( &ctx, 42 );
last_idx = test_offset_idx;
TEST_ASSERT( mbedtls_ctr_drbg_random( &ctx, out, sizeof( out ) ) == 0 );
TEST_ASSERT( test_offset_idx - last_idx == 42 );
expected_idx += 42;
TEST_EQUAL( test_offset_idx, expected_idx );
mbedtls_ctr_drbg_set_entropy_len( &ctx, 13 );
last_idx = test_offset_idx;
TEST_ASSERT( mbedtls_ctr_drbg_random( &ctx, out, sizeof( out ) ) == 0 );
TEST_ASSERT( test_offset_idx - last_idx == 13 );
expected_idx += 13;
TEST_EQUAL( test_offset_idx, expected_idx );
exit:
mbedtls_ctr_drbg_free( &ctx );