The default entropy nonce length is either zero or nonzero depending
on the desired security strength and the entropy length.
The implementation calculates the actual entropy nonce length from the
actual entropy length, and therefore it doesn't need a constant that
indicates the default entropy nonce length. A portable application may
be interested in this constant, however. And our test code could
definitely use it.
Define a constant MBEDTLS_CTR_DRBG_ENTROPY_NONCE_LEN and use it in
test code. Previously, test_suite_ctr_drbg had knowledge about the
default entropy nonce length built in and test_suite_psa_crypto_init
failed. Now both use MBEDTLS_CTR_DRBG_ENTROPY_NONCE_LEN.
This change means that the test ctr_drbg_entropy_usage no longer
validates that the default entropy nonce length is sensible. So add a
new test that checks that the default entropy length and the default
entropy nonce length are sufficient to ensure the expected security
strength.
Change the default entropy nonce length to be nonzero in some cases.
Specifically, the default nonce length is now set in such a way that
the entropy input during the initial seeding always contains enough
entropy to achieve the maximum possible security strength per
NIST SP 800-90A given the key size and entropy length.
If MBEDTLS_CTR_DRBG_ENTROPY_LEN is kept to its default value,
mbedtls_ctr_drbg_seed() now grabs extra entropy for a nonce if
MBEDTLS_CTR_DRBG_USE_128_BIT_KEY is disabled and either
MBEDTLS_ENTROPY_FORCE_SHA256 is enabled or MBEDTLS_SHA512_C is
disabled. If MBEDTLS_CTR_DRBG_USE_128_BIT_KEY is enabled, or if
the entropy module uses SHA-512, then the default value of
MBEDTLS_CTR_DRBG_ENTROPY_LEN does not require a second call to the
entropy function to achieve the maximum security strength.
This choice of default nonce size guarantees NIST compliance with the
maximum security strength while keeping backward compatibility and
performance high: in configurations that do not require grabbing more
entropy, the code will not grab more entropy than before.
mbedtls_ctr_drbg_seed() always set the entropy length to the default,
so a call to mbedtls_ctr_drbg_set_entropy_len() before seed() had no
effect. Change this to the more intuitive behavior that
set_entropy_len() sets the entropy length and seed() respects that and
only uses the default entropy length if there was no call to
set_entropy_len().
This removes the need for the test-only function
mbedtls_ctr_drbg_seed_entropy_len(). Just call
mbedtls_ctr_drbg_set_entropy_len() followed by
mbedtls_ctr_drbg_seed(), it works now.
previously a single function was used for most test cases (ctr_drbg_validate) making it harder to understand what the exact scenario is as a result it was split into easier to understand functions.
the testing functions were re-factored so that the common code was extracted to a single static function (removing the need for unclear goto statements).
As part of the re-factor the test functions now use data_t for parameters (support for this was introduced in previous rebase),
Unify the three existing validation functions (with prediction
resistance, with manual reseeding between generations, and with no
reseeding) into a single function that supports these three scenarios
plus a fourth one (reseed before the first generation).
The four supported scenarios cover the three scenarios from the
current CAVP test vectors (no reseed, reseed before generating,
prediction resistance) plus a fourth scenario used by the existing
test vectors (reseed after generating).
(cherry picked from commit cee9bedee6bc1a8e2b22fa8a31647b62ebb8a0a4)
The ctr_drbg_validate_xxx test functions had hard-coded sizes for the
entropy and the output size. Generalize the sizes.
Keep track of the current entropy size.
Unhexify the expected output and compare with the actual output,
rather than hexifying the actual output and comparing the hex.
Change function in tests named mbedtls_entropy_func to
mbedtls_test_entropy_func to avoid getting error from the linker when
calling the mbedtls_entropy_func elsewhere.
Fix potential integer overflows in the following functions:
* mbedtls_md2_update() to be bypassed and cause
* mbedtls_cipher_update()
* mbedtls_ctr_drbg_reseed()
This overflows would mainly be exploitable in 32-bit systems and could
cause buffer bound checks to be bypassed.
- As a consequence all error code that were positive were changed. A lot of MALLOC_FAILED and FILE_IO_ERROR error codes added for different modules.
- Programs and tests were adapted accordingly
