Nothing has been saved to disk yet, but there is stale data in
psa_crypto_transaction. This stale data should not be reused, but do
wipe it to reduce the risk of it mattering somehow in the future.
Introduce a new function psa_get_transparent_key which returns
NOT_SUPPORTED if the key is in a secure element. Use this function in
functions that don't support keys in a secure element.
After this commit, all functions that access a key slot directly via
psa_get_key_slot or psa_get_key_from_slot rather than via
psa_get_transparent_key have at least enough support for secure
elements not to crash or otherwise cause undefined behavior. Lesser
bad behavior such as wrong results or resource leakage is still
possible in error cases.
The following provides more information on this PR:
- PSA stands for Platform Security Architecture.
- Add support for use of psa_trusted_storage_api internal_trusted_storage.h v1.0.0
as the interface to the psa_trusted_storage_linux backend (i.e. for persistent
storage when MBEDTLS_PSA_ITS_FILE_C is not defined). This requires changes
to psa_crypto_its.h and psa_crypto_storage.c to migrate to the new API.
Stored keys must contain lifetime information. The lifetime used to be
implied by the location of the key, back when applications supplied
the lifetime value when opening the key. Now that all keys' metadata
are stored in a central location, this location needs to store the
lifetime explicitly.
Pass information via a key attribute structure rather than as separate
parameters to psa_crypto_storage functions. This makes it easier to
maintain the code when the metadata of a key evolves.
This has negligible impact on code size (+4B with "gcc -Os" on x86_64).
Key creation and key destruction for a key in a secure element both
require updating three pieces of data: the key data in the secure
element, the key metadata in internal storage, and the SE driver's
persistent data. Perform these actions in a transaction so that
recovery is possible if the action is interrupted midway.
Implement a transaction record that can be used for actions that
modify more than one piece of persistent data (whether in the
persistent storage or elsewhere such as in a secure element).
While performing a transaction, the transaction file is present in
storage. If the system starts with an ongoing transaction, it must
complete the transaction (not implemented yet).
In the generic message digest abstraction, instead of storing method
pointers in the per-algorithm data structure and using wrapper
functions as those methods, call the per-algorithm function directly.
This saves some code size (2336B -> 2043B for md with all algorithms
enabled on M0+ with gcc -Os). This should also make it easier to
optimize the case when a single algorithm is supported. In addition,
this is a very slight security improvement since it removes one
opportunity for a buffer overflow to directly turn into letting the
attacker overwrite a pointer to a function pointer.
This commit does not modify the documented API. However, it removes
the possibility for users to define their own hash implementations and
use them by building their own md_info.
Changing mbedtls_md_context to contain a md type identifier rather
than a pointer to an info structure would save a few more bytes and a
few more runtime memory accesses, but would be a major API break since
a lot of code uses `const mbedtls_md_info *` to keep track of which
hash is in use.
All modules using restartable ECC operations support passing `NULL`
as the restart context as a means to not use the feature.
The restart contexts for ECDSA and ECP are nested, and when calling
restartable ECP operations from restartable ECDSA operations, the
address of the ECP restart context to use is calculated by adding
the to the address of the ECDSA restart context the offset the of
the ECP restart context.
If the ECP restart context happens to not reside at offset `0`, this
leads to a non-`NULL` pointer being passed to restartable ECP
operations from restartable ECDSA-operations; those ECP operations
will hence assume that the pointer points to a valid ECP restart
address and likely run into a segmentation fault when trying to
dereference the non-NULL but close-to-NULL address.
The problem doesn't arise currently because luckily the ECP restart
context has offset 0 within the ECDSA restart context, but we should
not rely on it.
This commit fixes the passage from restartable ECDSA to restartable ECP
operations by propagating NULL as the restart context pointer.
Apart from being fragile, the previous version could also lead to
NULL pointer dereference failures in ASanDbg builds which dereferenced
the ECDSA restart context even though it's not needed to calculate the
address of the offset'ed ECP restart context.
All modules using restartable ECC operations support passing `NULL`
as the restart context as a means to not use the feature.
The restart contexts for ECDSA and ECP are nested, and when calling
restartable ECP operations from restartable ECDSA operations, the
address of the ECP restart context to use is calculated by adding
the to the address of the ECDSA restart context the offset the of
the ECP restart context.
If the ECP restart context happens to not reside at offset `0`, this
leads to a non-`NULL` pointer being passed to restartable ECP
operations from restartable ECDSA-operations; those ECP operations
will hence assume that the pointer points to a valid ECP restart
address and likely run into a segmentation fault when trying to
dereference the non-NULL but close-to-NULL address.
The problem doesn't arise currently because luckily the ECP restart
context has offset 0 within the ECDSA restart context, but we should
not rely on it.
This commit fixes the passage from restartable ECDSA to restartable ECP
operations by propagating NULL as the restart context pointer.
Apart from being fragile, the previous version could also lead to
NULL pointer dereference failures in ASanDbg builds which dereferenced
the ECDSA restart context even though it's not needed to calculate the
address of the offset'ed ECP restart context.
dummy
Replace some frequently-used macros by inline functions: instead of
calling MOD_{ADD,SUB,MUL} after the mbedtls_mpi_{add,sub,mul}_mpi,
call a function mbedtls_mpi_xxx_mod that does the same.
In the baremetal config, with "gcc -Os -mthumb -mcpu=cortex-m0plus",
ecp.o goes down from 13878 bytes to 12234.
No noticeable performance change for benchmarks on x86_64 with either
"gcc -O2" or "gcc -Os".
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.
Expose the type of an entry in the SE driver table as an opaque type
to other library modules. Soon, driver table entries will have state,
and callers will need to be able to access this state through
functions using this opaque type.
Provide functions to look up a driver by its lifetime and to retrieve
the method table from an entry.
