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.
Add a new function mbedtls_ctr_drbg_set_nonce_len() which configures
the DRBG instance to call f_entropy a second time during the initial
seeding to grab a nonce.
The default nonce length is 0, so there is no behavior change unless
the user calls the new function.
Add a new function mbedtls_ctr_drbg_set_nonce_len() which configures
the DRBG instance to call f_entropy a second time during the initial
seeding to grab a nonce.
The default nonce length is 0, so there is no behavior change unless
the user calls the new function.
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.
Move the definitions of mbedtls_ctr_drbg_seed_entropy_len() and
mbedtls_ctr_drbg_seed() to after they are used. This makes the code
easier to read and to maintain.
mbedtls_hmac_drbg_seed() always set the entropy length to the default,
so a call to mbedtls_hmac_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().
Consolidate the invalid-handle tests from test_suite_psa_crypto and
test_suite_psa_crypto_slot_management. Start with the code in
test_suite_psa_crypto_slot_management and adapt it to test one invalid
handle value per run of the test function.
Fix a signed int overflow in mbedtls_asn1_get_int() for numbers
between INT_MAX+1 and UINT_MAX (typically 0x80000000..0xffffffff).
This was undefined behavior which in practice would typically have
resulted in an incorrect value, but which may plausibly also have
caused the postcondition (*p == initial<*p> + len) to be violated.
Credit to OSS-Fuzz.
mbedtls_asn1_get_int() and mbedtls_asn1_get_mpi() behave differently
on negative INTEGERs (0200). Don't change the library behavior for now
because this might break interoperability in some applications. Change
the test function to the library behavior.
Fix the test data with negative INTEGERs. These test cases were
previously not run (they were introduced but deliberately deactivated
in 27d806fab4). The test data was
actually wrong: ASN.1 uses two's complement, which has no negative 0,
and some encodings were wrong. Now the tests have correct data, and
the test code rectifies the expected data to match the library
behavior.
mbedtls_asn1_get_int() and mbedtls_asn1_get_mpi() behave differently
on an empty INTEGER (0200). Don't change the library behavior for now
because this might break interoperability in some applications. Write
a test function that matches the library behavior.
When the asn1parse module is enabled but the bignum module is
disabled, the asn1parse test suite did not work. Fix this.
* Fix a syntax error in get_integer() (label immediately followed by a
closing brace).
* Fix an unused variable in get_integer().
* Fix `TEST_ASSERT( *p == q );` in nested_parse() failing because `*p`
was not set.
* Fix nested_parse() not outputting the length of what it parsed.
Document that passing 0 to a close/destroy function does nothing and
returns PSA_SUCCESS.
Although this was not written explicitly, the specification strongly
suggested that this would return PSA_ERROR_INVALID_HANDLE. While
returning INVALID_HANDLE makes sense, it was awkward for a very common
programming style where applications can store 0 in a handle variable
to indicate that the handle has been closed or has never been open:
applications had to either check if (handle != 0) before calling
psa_close_key(handle) or psa_destroy_key(handle), or ignore errors
from the close/destroy function. Now applications following this style
can just call psa_close_key(handle) or psa_destroy_key(handle).
The documentation of HMAC_DRBG erroneously claimed that
mbedtls_hmac_drbg_set_entropy_len() had an impact on the initial
seeding. This is in fact not the case: mbedtls_hmac_drbg_seed() forces
the entropy length to its chosen value. Fix the documentation.
The documentation of CTR_DRBG erroneously claimed that
mbedtls_ctr_drbg_set_entropy_len() had an impact on the initial
seeding. This is in fact not the case: mbedtls_ctr_drbg_seed() forces
the initial seeding to grab MBEDTLS_CTR_DRBG_ENTROPY_LEN bytes of
entropy. Fix the documentation and rewrite the discussion of the
entropy length and the security strength accordingly.
Explain how MBEDTLS_CTR_DRBG_ENTROPY_LEN is set next to the security
strength statement, rather than giving a partial explanation (current
setting only) in the documentation of MBEDTLS_CTR_DRBG_ENTROPY_LEN.
NIST and many other sources call it a "personalization string", and
certainly not "device-specific identifiers" which is actually somewhat
misleading since this is just one of many things that might go into a
personalization string.
