We are technically allowed to use all possible values of key slice index
that will fit into the bit width we have allocated, so allow all values.
Signed-off-by: David Horstmann <david.horstmann@arm.com>
The persistent key cache slice is the last slice (not the first as
previously stated). Update the numbering-related comments accordingly.
Signed-off-by: David Horstmann <david.horstmann@arm.com>
Reassure both humans and compilers that the places where we assign an
integer to a smaller type are safe.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
We were only testing the static key store (MBEDTLS_PSA_KEY_STORE_DYNAMIC
disabled) with configs/*.h. Add a component with the static key store and
everything else (including built-in keys), and a component with the static
key store and CTR_DBRG using PSA for AES (which means PSA uses a volatile
key internally).
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Add a practical way to fill the dynamic key store by artificially limiting
the slice length through a test hook.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
When MBEDTLS_PSA_KEY_STORE_DYNAMIC is enabled, key slots are now organized in
multiple slices. The slices are allocated on demand, which allows the key
store to grow. The size of slices grows exponentially, which allows reaching
a large number of slots with a small (static) number of slices without too
much overhead.
Maintain a linked list of free slots in each slice. This way, allocating a
slot takes O(1) time unless a slice needs to be allocated.
In this commit, slices are only ever freed when deinitializing the key
store. This should be improved in the future to free empty slices.
To avoid growing the persistent key cache without control, the persistent
key cache has a fixed size (reusing MBEDTLS_PSA_KEY_SLOT_COUNT to avoid
creating yet another option).
When MBEDTLS_PSA_KEY_STORE_DYNAMIC is disabled. no semantic change and
minimal changes to the code.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Place some fields of psa_key_slot_t in a union, to prepare for a new field
in free slots that should not require extra memory.
For occupied slots, place only the registered_readers field in the union,
not other fields, to minimize textual changes. All fields could move to the
union except state (also needed in free slots) and attr (which must stay
first to reduce the code size, because it is accessed at many call sites).
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
It's impractical to fill the key store when it can grow to accommodate
millions of keys.
A later commit will restore those tests in test configurations with the
dynamic key store.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Add some abstractions around code that traverses the key store, in
preparation for adding support for MBEDTLS_PSA_KEY_STORE_DYNAMIC.
No intended behavior change. The generated machine code should be
almost the same with an optimizing compiler (in principle, it could be the
same with sufficient constant folding and inlining, but in practice it will
likely be a few byes larger),
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Create a new compilation option for a dynamically resized key store. The
implementation will follow in subsequent commits.
This option is off by default with custom configuration files, which is best
for typical deployments on highly constrained platforms. This option is on
by default with the provided configuration file, which is best for typical
deployments on relatively high-end platforms.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
