When creating a key with a lifetime that places it in a secure
element, retrieve the appropriate driver table entry.
This commit doesn't yet achieve behavior: so far the code only
retrieves the driver, it doesn't call the driver.
The psa_tls12_prf_set_seed() and psa_tls12_prf_set_label() functions did
not work on platforms where malloc(0) returns NULL.
It does not affect the TLS use case but these PRFs are used in other
protocols as well and might not be used the same way. For example EAP
uses the TLS PRF with an empty secret. (This would not trigger the bug,
but is a strong indication that it is not safe to assume that certain
inputs to this function are not zero length.)
The conditional block includes the memcpy() call as well to avoid
passing a NULL pointer as a parameter resulting in undefined behaviour.
The current tests are already using zero length label and seed, there is
no need to add new test for this bug.
Secure element support has its own source file, and in addition
requires many hooks in other files. This is a nontrivial amount of
code, so make it optional (but default on).
PSA_ERROR_BAD_STATE means that the function was called on a context in a
bad state.
This error is something that can't happen while only using the PSA API and
therefore a PSA_ERROR_CORRUPTION_DETECTED is a more appropriate error
code.
The macro initialiser might leave bytes in the union unspecified.
Zeroising it in setup makes sure that the behaviour is the same
independently of the initialisation method used.
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.
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.
Now that psa_allocate_key() is no longer a public function, expose
psa_internal_allocate_key_slot() instead, which provides a pointer to
the slot to its caller.
Remove the key creation functions from before the attribute-based API,
i.e. the key creation functions that worked by allocating a slot, then
setting metadata through the handle and finally creating key material.
generate_key is a more classical name. The longer name was only
introduced to avoid confusion with getting a key from a generator,
which is key derivation, but we no longer use the generator
terminology so this reason no longer applies.
perl -i -pe 's/psa_generate_random_key/psa_generate_key/g' $(git ls-files)
“Tampering detected” was misleading because in the real world it can
also arise due to a software bug. “Corruption detected” is neutral and
more precisely reflects what can trigger the error.
perl -i -pe 's/PSA_ERROR_TAMPERING_DETECTED/PSA_ERROR_CORRUPTION_DETECTED/gi' $(git ls-files)
Generators are mostly about key derivation (currently: only about key
derivation). "Generator" is not a commonly used term in cryptography.
So favor "derivation" as terminology. Call a generator a key
derivation operation structure, since it behaves like other multipart
operation structures. Furthermore, the function names are not fully
consistent.
In this commit, I rename the functions to consistently have the prefix
"psa_key_derivation_". I used the following command:
perl -i -pe '%t = (
psa_crypto_generator_t => "psa_key_derivation_operation_t",
psa_crypto_generator_init => "psa_key_derivation_init",
psa_key_derivation_setup => "psa_key_derivation_setup",
psa_key_derivation_input_key => "psa_key_derivation_input_key",
psa_key_derivation_input_bytes => "psa_key_derivation_input_bytes",
psa_key_agreement => "psa_key_derivation_key_agreement",
psa_set_generator_capacity => "psa_key_derivation_set_capacity",
psa_get_generator_capacity => "psa_key_derivation_get_capacity",
psa_generator_read => "psa_key_derivation_output_bytes",
psa_generate_derived_key => "psa_key_derivation_output_key",
psa_generator_abort => "psa_key_derivation_abort",
PSA_CRYPTO_GENERATOR_INIT => "PSA_KEY_DERIVATION_OPERATION_INIT",
PSA_GENERATOR_UNBRIDLED_CAPACITY => "PSA_KEY_DERIVATION_UNLIMITED_CAPACITY",
); s/\b(@{[join("|", keys %t)]})\b/$t{$1}/ge' $(git ls-files)
