The TLS 1.2 pseudorandom function does a lot of distinct HMAC operations
with the same key. To save the battery and CPU cycles spent on
calculating the paddings and hashing the inner padding, we keep the
hash context in the status right after the inner padding having been
hashed and clone it as needed.
Technically we could have reused the old one for the new API, but then
we had to set an extra field during setup. The new version works when
all the fields that haven't been set explicitely are zero-initialised.
The specific key derivation input functions support a subset of the
input options and need to check it anyway. Checking it at the top level
is redundant, it brings a very little value and comes with a cost in
code size and maintainability.
This change affects the psa_key_derivation_s structure. With the buffer
removed from the union, it is empty if MBEDTLS_MD_C is not defined.
We can avoid undefined behaviour by adding a new dummy field that is
always present or make the whole union conditional on MBEDTLS_MD_C.
In this latter case the initialiser macro has to depend on MBEDTLS_MD_C
as well. Furthermore the first structure would be either
psa_hkdf_key_derivation_t or psa_tls12_prf_key_derivation_t both of
which are very deep and would make the initialisation macro difficult
to maintain, therefore we go with the first option.
Part of the tests are adapted in this commit, another part is already
covered by the derive_input tests and some of them are not applicable to
the new API (the new API does not request capacity at the setup stage).
The test coverage temporarily drops with this commit, the two test cases
conserning capacity will be re-added in a later commit.
In the 1.0 API some functionality has been split from the
psa_key_derivation_setup() function and is now done with the
psa_key_derivation_input_*() functions. The new tests maintain the
existing test coverage of this functionality.
We want to make the PRF context structure depend on this flag, but
crypto_extra.h is included after crypto_struct.h and having the
option at its original place would not affect crypto_struct.h.
Some key derivation operation contexts (like
psa_tls12_prf_key_derivation_t) directly contain buffers with parts of
the derived key. Erase them safely as part of the abort.
Add the compile time option PSA_PRE_1_0_KEY_DERIVATION. If this is not
turned on, then the function `psa_key_derivation()` is removed.
Most of the tests regarding key derivation haven't been adapted to the
new API yet and some of them have only been adapted partially. When this
new option is turned off, the tests using the old API and test cases
using the old API of partially adapted tests are skipped.
The sole purpose of this option is to make the transition to the new API
smoother. Once the transition is complete it can and should be removed
along with the old API and its implementation.
From the implementation point of view does not make much difference to
constrain the input order.
We constrain it because, this way the code is easier to review, the data
flow easier to understand and the implementations in general are easier
to validate.
The new PSA helper headers are needed at build time. When building
Mbed OS tests, the source files are copied to a directory under TESTS.
The required header files need to be present in this directory.
Create a new header file psa_helpers.h and put the one helper macro
that isn't specific to PSA crypto there. Use this header file in the
ITS test suite.
This file isn't like the other .function files: it isn't concatenated
by a separate preprocessing script, but included via C preprocessing.
Rename this file to .h. This isn't a normal C header, because it
defines auxiliary functions. But the functions aren't big and we only
have one compilation unit per executable, so this is good enough for
what we're doing.
Replace all calls to mbedtls_psa_crypto_free in tests by PSA_DONE.
This is correct for most tests, because most tests close open keys. A
few tests now fail; these tests need to be reviewed and switched back
to mbedtls_psa_crypto_free if they genuinely expected to end with some
slots still in use.
The new macro PSA_DONE calls mbedtls_psa_crypto_free, but before that,
it checks that no key slots are in use. The goal is to allow tests to
verify that functions like psa_close_key properly mark slots as
unused, and more generally to detect key slot leaks. We call
mbedtls_psa_crypto_free at the end of each test case, which could mask
a bug whereby slots are not freed when they should be, but their
content is correctly reclaimed by mbedtls_psa_crypto_free.
Create a specific file for helper functions that are related to the
PSA API. The reason for a separate file is so that it can include
<psa/crypto.h>, without forcing this header inclusion into every test
suite. In this commit, psa_helpers.function doesn't need psa/crypto.h
yet, but this will be the case in a subsequent commit.
Move PSA_ASSERT to psa_helpers.function, since that's the sort of
things it's for.
Include "psa_helpers.function" from the PSA crypto tests.
In the ITS test, don't include "psa_helpers". The ITS tests are
meant to stand alone from the rest of the library.
