dhm_make_common includes a piece of code that is identical to
dhm_random_below except for returning a different error code in one
case. Call dhm_random_below instead of repeating the code.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
P-1 is as bad as 1 as a blinding value. Don't accept it.
The chance that P-1 would be randomly generated is infinitesimal, so
this is not a practical issue, but it makes the code cleaner. It was
inconsistent to accept P-1 as a blinding value but not as a private key.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Unify the common parts of mbedtls_dhm_make_params and mbedtls_dhm_make_public.
No intended behavior change, except that the exact error code may
change in some corner cases which are too exotic for the existing unit
tests.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Instead of generating blinding values in a not-quite-uniform way
(https://github.com/ARMmbed/mbedtls/issues/4245) with copy-pasted
code, use mbedtls_mpi_random().
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Since mbedtls_mpi_random() is not specific to ECC code, move it from
the ECP module to the bignum module.
This increases the code size in builds without short Weierstrass
curves (including builds without ECC at all) that do not optimize out
unused functions.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Rename mbedtls_ecp_gen_privkey_sw to mbedtls_mpi_random since it has
no particular connection to elliptic curves beyond the fact that its
operation is defined by the deterministic ECDSA specification. This is
a generic function that generates a random MPI between 1 inclusive and
N exclusive.
Slightly generalize the function to accept a different lower bound,
which adds a negligible amount of complexity.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
mbedtls_ecp_gen_privkey_mx generates a random number with a certain
top bit set. Depending on the size, it would either generate a number
with that top bit being random, then forcibly set the top bit to
1 (when high_bit is not a multiple of 8); or generate a number with
that top bit being 0, then set the top bit to 1 (when high_bit is a
multiple of 8). Change it to always generate the top bit randomly
first.
This doesn't make any difference in practice: the probability
distribution is the same either way, and no supported or plausible
curve has a size of the form 8n+1 anyway. But it slightly simplifies
reasoning about the behavior of this function.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Don't calculate the bit-size of the initially generated random number.
This is not necessary to reach the desired distribution of private
keys, and creates a (tiny) side channel opportunity.
This changes the way the result is derived from the random number, but
does not affect the resulting distribution.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
The library rejected an RNG input of all-bits-zero, which led to the
key 2^{254} (for Curve25519) having a 31/32 chance of being generated
compared to other keys. This had no practical impact because the
probability of non-compliance was 2^{-256}, but needlessly
complicated the code.
The exception was added in 98e28a74e3 to
avoid the case where b - 1 wraps because b is 0. Instead, change the
comparison code to avoid calculating b - 1.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
For Montgomery keys, n_bits is actually the position of the highest
bit and not the number of bits, which would be 1 more (fence vs
posts). Rename the variable accordingly to lessen the confusion.
No semantic change.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Put the Montgomery and short Weierstrass implementations of
mbedtls_ecp_gen_privkey into their own function which can be tested
independently, but will not be part of the public ABI/API.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
When mbedtls_nist_kw_wrap was called with output=NULL and out_size=0, it
performed arithmetic on the null pointer before detecting that the output
buffer is too small and returning an error code. This was unlikely to have
consequences on real-world hardware today, but it is undefined behavior and
UBSan with Clang 10 flagged it. So fix it (fix#4025).
Fix a similar-looking pattern in unwrap, though I haven't verified that it's
reachable there.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
The persistence level PSA_KEY_PERSISTENCE_READ_ONLY can now only be used
as intended, for keys that cannot be modified through normal use of the API.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
mbedtls_psa_get_stats() was written back before lifetimes were
structured as persistence and location. Fix its classification of
volatile external keys and internal keys with a non-default
persistence.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
On space-constrained platforms, it is a useful configuration to be able
to import/export and perform RSA key pair operations, but to exclude RSA
key generation, potentially saving flash space. It is not possible to
express this with the PSA_WANT_ configuration system at the present
time. However, in previous versions of Mbed TLS (v2.24.0 and earlier) it
was possible to configure a software PSA implementation which was
capable of making RSA signatures but not capable of generating RSA keys.
To do this, one unset MBEDTLS_GENPRIME.
Since the addition of MBEDTLS_PSA_BUILTIN_KEY_TYPE_RSA_KEY_PAIR, this
expressivity was lost. Expressing that you wanted to work with RSA key
pairs forced you to include the ability to generate key pairs as well.
Change psa_crypto_rsa.c to only call mbedtls_rsa_gen_key() if
MBEDTLS_GENPRIME is also set. This restores the configuration behavior
present in Mbed TLS v2.24.0 and earlier versions.
It left as a future exercise to add the ability to PSA to be able to
express a desire for a software or accelerator configuration that
includes RSA key pair operations, like signature, but excludes key pair
generation.
Without this change, linker errors will occur when attempts to call,
which doesn't exist when MBEDTLS_GENPRIME is unset.
psa_crypto_rsa.c.obj: in function `rsa_generate_key':
psa_crypto_rsa.c:320: undefined reference to `mbedtls_rsa_gen_key'
Fixes#4512
Signed-off-by: Jaeden Amero <jaeden.amero@arm.com>
TLS code specific to SHA-384 was gated on MBEDTLS_SHA512_C. But SHA-384 also
requires that MBEDTLS_SHA512_NO_SHA384 is not defined. This lead to dead
code in TLS when MBEDTLS_SHA512_C and MBEDTLS_SHA512_NO_SHA384 were both
defined (i.e. when SHA-512 was enabled but not SHA-384).
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
They depended on MBEDTLS_SHA512_C only. A check for !MBEDTLS_SHA512_NO_SHA384
was missing.
Fix#4499.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
The sequence of calls starts-update-starts-update-finish is not a
guaranteed valid way to abort an operation and start a new one. Our
software implementation just happens to support it, but alt
implementations may very well not support it.
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
Session-ID based session resumption requires that the resumed session
is consistent with the client's ClientHello in terms of choice of
ciphersuite and choice of compression.
This check was previously assumed to be performed in the session cache
implementation, which seems wrong: The session cache should be an id-based
lookup only, and protocol specific checks should be left to Mbed TLS.
This commit
- adds an explicit ciphersuite and compression consistency check after
the SSL session cache has been queried
- removes the ciphersuite and compression consistency check from
Mbed TLS' session cache reference implementation.
Don't use ssl_check_xxx() for functions with void return
Signed-off-by: Hanno Becker <hanno.becker@arm.com>
Prepare to isolate the Montgomery and short Weierstrass
implementations of mbedtls_ecp_gen_privkey into their own function.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
A previous fix in d596ca8a1e worked with
beta versions of GCC 11, but not with the final 11.1 release.
This time, just disable the warning locally.
Fix#4130
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Zephyr's native posix port define _POSIX_C_SOURCE with a higher value
during the build, so when mbedTLS defines it with a different value
breaks the build.
As Zephyr is already defining a higher value is guaranteed that mbedTLS
required features will be available. So, just define it in case it was
not defined before.
[taken from Zephyr mbedtls module:
76dcd6eeca]
Signed-off-by: Flavio Ceolin <flavio.ceolin@intel.com>
Signed-off-by: David Brown <david.brown@linaro.org>
Since they became equivalent after moving the is_sign checking back to
the PSA core, they're now redundant, and the generic mac_setup function
can just be called directly.
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
Since a valid mac operation context would guarantee that the stored
mac size is >= 4, it wasn't immediately obvious that the zero-length
check is meant for static analyzers and a bit of robustness.
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
The PSA core checks the key type and algorithm combination before
calling the driver, so the driver doesn't have to do this once more.
The PSA core will also not start an operation with a requested length
which is larger than the full MAC output size, so the output length check
in the driver isn't needed as long as the driver returns an error on
mac_setup if it doesn't support the underlying hash algorithm.
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
It makes sense to do the length checking in the core rather than expect
each driver to deal with it themselves. This puts the onus on the core to
dictate which algorithm/key combinations are valid before calling a driver.
Additionally, this commit also updates the psa_mac_sign_finish function
to better deal with output buffer sanitation, as per the review comments
on #4247.
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
As psa_mac_sign_finish / psa_mac_verify_finish already checks that the
operation structure is valid (id is non-zero), the driver itself doesn't
have to check for that anymore. If the operation has a driver ID assigned,
it means that driver has returned success from its setup function, so the
algorithm value will be set correctly.
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
The key passed to the driver has been imported by the PSA Core, meaning
its length has already been verified, and the driver can rely on the
buffer length and key attributes being consistent.
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
This means there is no longer a need to have an internal HMAC API, so
it is being removed in this commit as well.
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
Prefix with 'mbedtls_psa' as per the other types which implement some
sort of algorithm in software.
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
Now renamed to mbedtls_psa_safer_memcmp, it provides a single location
for buffer comparison.
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
The purpose of key_set was to guard the operation structure from being
used for update/finish before a key was set. Now that the implementation
fully adheres to the PSA API, that function is covered by the `alg`
variable instead. It's set to the algorithm in use when a key is set, and
is zero when the operation is reset/invalid.
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
* Early return since there's nothing to clean up
* Get rid of unnecessary local variable
* Check algorithm validity for MAC in the PSA core instead of in the driver
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
Apparently it was at some point assumed that there would be
support for MAC algorithms with IV, but that hasn't been
implemented yet. Until that time, these context structure
members are superfluous and can be removed.
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
Typedef'ed structures are suffixed _t
Also updated the initialiser macro with content that actually
matches the structure's content.
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
Since HMAC moved into its own compilation unit, the internal API needed
to be documented and finalized. This means no more reaching deep into
the operation structure from within the PSA Crypto core. This will make
future refactoring work easier, since internal HMAC is now opaque to the
core.
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
Step 3/x in moving the driver. Separate commits should make for easier
review.
Additional changes on top of code movement:
* Copied the implementation of safer_memcmp from psa_crypto into
psa_cipher_mac since the mac_verify driver implementation
depends on it, and it isn't available through external linkage
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
Step 2/x in moving the driver. Separate commits should make for easier
review.
Additional changes on top of code movement:
* Early-return success on input with zero-length to mac_update, to
avoid NULL pointers getting passed into the driver dispatch
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
Step 1/x in moving the driver. Separate commits should make for easier
review.
Additional changes on top of just moving code:
* Added a sanity check on the key buffer size for CMAC.
* Transfered responsibility for resetting the core members of the
PSA MAC operation structure back to the core (from the driver
wrapper layer)
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
This is a temporary measure. Other operations in the PSA Core which rely
on this internal HMAC API should be rewritten to use the MAC API instead,
since they can then leverage accelerated HMAC should a platform provide
such acceleration support.
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
The changed logic is to try a sign-message driver (opaque or transparent);
if there isn't one, fallback to builtin sofware and do the hashing,
then try a sign-hash driver. This will enable to the opaque driver
to fallback to software.
Signed-off-by: gabor-mezei-arm <gabor.mezei@arm.com>
To avoid code duplication of the old-style SE interface usage
call psa_driver_wrapper_sign/verify_hash function instead of
the direct internal functions.
Signed-off-by: gabor-mezei-arm <gabor.mezei@arm.com>
Use common funtion for psa_sign_hash and psa_sign_message and one for
psa_verify_hash and psa_verify_message to unify them.
Signed-off-by: gabor-mezei-arm <gabor.mezei@arm.com>
Move the key buffer size calculation code under
tests to avoid check-names.sh to complain about
"likely macros with typos".
This removes the calculation of key buffer
sizes for the test driver from the wrapper based on
static size data. But the code is still there in test
code to be used when we go back to work on the
generation of the driver wrapper.
Signed-off-by: Ronald Cron <ronald.cron@arm.com>
pk_get_pk_alg will either return 0 or a pk error code. This means that
the error code will always be a high level module ID and so we just
return ret.
Signed-off-by: Chris Jones <christopher.jones@arm.com>
Add implementation for MBEDTLS_PSA_CRYPTO_BUILTIN_KEYS
Merging as it has been ready for four days now and I prefer not having to go through other rebases especially given the coming change of scope of development (3.0 rather than 2.2x).
Improve comments explaining error code checking, fix incorrect comments
and make a small formatting fix.
Signed-off-by: Chris Jones <christopher.jones@arm.com>
* group setting of attributes before calling get_builtin_key
* return early instead of going to exit when no resources are allocated yet
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
Leverage the fact that the get_builtin_key entrypoint returns a key's
attributes, such that a proper size for the builtin key's buffer can
be calculated through the driver's get_key_buffer_size hook.
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
Since the loading attempt of a builtin key might be followed by trying
to load a persistent key, we can only wipe the allocated key data, not
the associated metadata.
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
The macro always meant 'location', but was mistakenly named 'lifetime'.
Naming it location instead makes much more sense, and drives home the
conceptual differences between location and lifetime values.
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
Instead of the full attributes struct, it now only takes/returns what it
actually needs to.
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
Builtin key support for the test driver is always compiled in, and no
longer guarded by MBEDTLS_PSA_CRYPTO_BUILTIN_KEYS.
Parsing the key slot from the buffer by cast and assign instead of memcmp.
For exporting keys, the test driver no longer reaches into the key
identifier in order to check whether a key is builtin, but rather
assumes so based on the key buffer length. It's the driver's
responsibility to be able to detect the key material it returned as part
of the get_builtin_key operation.
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
As part of test_psa_crypto_drivers, define a builtin symmetric
plus an ECC key on the test driver lifetime.
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
According to the design in psa-driver-interface.md. Compiles without
issue in test_psa_crypto_drivers.
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
This reverts commit c75d9f589b.
This was merged by mistake in development instead of development_3.0.
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
This reverts commit 48f6d0d6e5.
This was merged by mistake in development instead of development_3.0.
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
This reverts commit 9a86843470.
This was merged by mistake in development instead of development_3.0.
Signed-off-by: Manuel Pégourié-Gonnard <manuel.pegourie-gonnard@arm.com>
An incorrect error code addition was spotted by the new invasive testing
infrastructure whereby pk_get_pk_alg will always return a high level
error or zero and pk_parse_key_pkcs8_unencrypted_der will try to add
another high level error, resulting in a garbage error code.
Apply the same fix from ae3741e8a to fix the bug.
Signed-off-by: Chris Jones <christopher.jones@arm.com>
Replace all occurences of error code addition in the library with the new
MBEDTLS_ERROR_ADD macro.
Signed-off-by: Chris Jones <christopher.jones@arm.com>
Add a missing guard for the definition and declaration of
mbedtls_test_hook_error_add.
Also make the declaration always visible when MBEDTLS_TEST_HOOKS is
enabled. This fixes an issue when MBEDTLS_ERROR_C is not defined but
MBEDTLS_TEST_HOOKS is.
Signed-off-by: Chris Jones <christopher.jones@arm.com>
Fix unused parameter warnings when MBEDTLS_TEST_HOOKS is not enabled.
A few issues were caught by check-names.sh namely:
- mbedtls_error_add was not capitalised.
- mbedtls_test_hook_error_add was being defined multiple times as the
definition was in a header.
Signed-off-by: Chris Jones <christopher.jones@arm.com>
The previous implementation of the error addition interface did not comply
with the invasive testing architecture guidelines. This commit fixes that
by:
- Renaming functions/macros/variables to follow the mbedtls_error_xxx or
mbedtls_test_hook_xxx convention.
- Making mbedtls_test_hook_error_add a global variable that can be set
by the testing code.
- Using a static inline function call, as opposed to macro, to keep
discrepancies between debug and production version to a minimum.
Signed-off-by: Chris Jones <christopher.jones@arm.com>
Change the signature of the `hook` parameter of `mbedtls_set_err_add_hook`
to use the actual signature of the function as opposed to `void *`. This
fixes a warning when compiling with clang `-pedantic`.
Signed-off-by: Chris Jones <christopher.jones@arm.com>
`error.c` and error.h are the more logical place to keep this code and it
prevents issues with building `common.c` and conflicts with other projects
that use mbedtls (such as mbedOS).
`error.c` has been automatically generated by first adding the code to
`error.fmt` and then running `./scripts/generate_errors.pl`.
Also add parenthesis to the addition in `MBEDTLS_ERR_ADD`.
Signed-off-by: Chris Jones <christopher.jones@arm.com>
Fix building by adding `common.c` to the build scripts (both make and Cmake).
Also reworks the hook function pointer (also renamed to `err_add_hook`) to be
a static local to `common.c` with a setter function to set the pointer to a
checking function.
Signed-off-by: Chris Jones <christopher.jones@arm.com>
`error.c` is a file generated from `error.h` and thus cannot contain the code
that was previously added. This commit fixes that issue by moving the
`MBEDTLS_ERR_ADD` macro and associated function and function pointer into
`common.h` and `common.c`.
Also fix a typo in `tests/include/test/helpers.h` where tabs were accidentally
used instead of spaces.
Signed-off-by: Chris Jones <christopher.jones@arm.com>
All occurences of manual error code addition/combination, in `rsa.c`, have
been replaced with the `MBEDTLS_ERR_ADD` macro.
Signed-off-by: Chris Jones <christopher.jones@arm.com>
Adds a macro (`MBEDTLS_ERR_ADD`) to add error codes together and check that the
result will not be corrupted. This additional check is only enabled during
testing when `MBEDTLS_TEST_HOOKS` is defined.
Also includes a reference usage example in `rsa.c` where two high-level error
codes could be incorrectly added together under the right conditions. This now
ensures that when this error occurs during testing it will be correctly
reported.
Signed-off-by: Chris Jones <christopher.jones@arm.com>
Corresponds better to the validation done in other modules of PSA Crypto.
Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
Signed-off-by: Ronald Cron <ronald.cron@arm.com>
Capitalise the MPS trace macros, as per the coding style (and make a slight
change to naming convention to avoid a name collision).
Signed-off-by: Dave Rodgman <dave.rodgman@arm.com>
As we want to do Mbed TLS aead operations as a
driver does, aead operations should not access
the key slot as key slots are not available to
drivers.
Second step in this PR: do not unlock the key slot
as part of operation abort.
Signed-off-by: Ronald Cron <ronald.cron@arm.com>
As we want to do Mbed TLS aead operations as a
driver does, aead operations should not access
the key slot as key slots are not available to
drivers.
First step in this PR: move key resolution from
aead operation setup to psa_aead_encrypt/decrypt
APIs.
Signed-off-by: Ronald Cron <ronald.cron@arm.com>
Fix the subtraction in fix_negative, which was incorrectly not looking
for a carry. This caused the result to be wrong when the least
significant limb of N was 0. Fix#4296.
The bug was introduced by d10e8fae9e
"Optimize fix_negative". Thanks to Philippe Antoine (catenacyber) for
reporting the bug which was found by his EC differential fuzzer.
Credit to OSS-Fuzz.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
This header file will contain declarations of functions that are not
part of the public ABI/API, and must not be called from other modules,
but can be called from unit tests.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
Move the handling of the sign out of the base-specific loops. This
both simplifies the code, and corrects an edge case: the code in the
non-hexadecimal case depended on mbedtls_mpi_mul_int() preserving the
sign bit when multiplying a "negative zero" MPI by an integer, which
used to be the case but stopped with PR #2512.
Fix#4295. Thanks to Guido Vranken for analyzing the cause of the bug.
Credit to OSS-Fuzz.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
In a TLS client, enforce the Diffie-Hellman minimum parameter size
set with mbedtls_ssl_conf_dhm_min_bitlen() precisely. Before, the
minimum size was rounded down to the nearest multiple of 8.
Signed-off-by: Gilles Peskine <Gilles.Peskine@arm.com>
When creating a persistent key or registering a key
with an invalid key identifier return
PSA_ERROR_INVALID_ARGUMENT instead of
PSA_ERROR_INVALID_HANDLE.
Signed-off-by: Ronald Cron <ronald.cron@arm.com>
This check was added earlier to avoid useless calls to `memcpy()`
with length `0` in the _frequent_ case where we're not accumulating.
By now, the whole code path has been moved to a branch which is only
executed if the reader is accumulating, and the only time this check
would be relevant is if we happen to feed an empty fragment to the
reader. In this case, the call to memcpy() could be removed, but
since this case is exceptional and the call to memcpy() is still
correct even for a length 0 copy, we remove the check for simplicity
of the code.
Signed-off-by: Hanno Becker <hanno.becker@arm.com>
Previously, the semantics of mbedtls_mps_reader_commit() was to invalidate
all buffers previously fetched via mbedtls_mps_reader_get(), forbidding
any further use by the 'consumer'. This was in fact a necessary constraint
for the current implementation, which did some memory moving in
mbedtls_mps_reader_commit().
This commit simplifies the reader's semantics and implementation in
the following way:
- API: A call to mbedtls_mps_reader_commit() does no longer invalidate
the buffers previously obtained via mbedtls_mps_reader_get().
Instead, they can continue to be used until
mbedtls_mps_reader_reclaim() is called.
Calling mbedtls_mps_reader_commit() now only sets a marker
indicating which parts of the data received through
mbedtls_mps_reader_get() need not be backed up once
mbedtls_mps_reader_reclaim() is called. Allowing the user
to call mbedtls_mbedtls_reader_commit() multiple times
before mbedtls_mps_reader_reclaim() is mere convenience:
We'd get exactly the same functionality if instead of
mbedtls_mps_reader_commit(), there was an additional argument
to mbedtls_mps_reader_reclaim() indicating how much data
to retain. However, the present design is more convenient
for the user and doesn't appear to introduce any unnecessary
complexity (anymore), so we stick with it for now.
- Implementation: mbedtls_mps_reader_commit() is now a 1-liner,
setting the 'commit-marker', but doing nothing else.
Instead, the complexity of mbedtls_mp_reader_reclaim()
slightly increases because it has to deal with creating
backups from both the accumulator and the current
fragment. In the previous implementation, which shifted
the accumulator content with every call to
mbedtls_mps_reader_commit(), only the backup from the
fragment was necessary; with the new implementation
which doesn't shift anything in
mbedtls_mps_reader_commit(), we need to do the
accumulator shift in mbedtls_mps_reader_reclaim().
Signed-off-by: Hanno Becker <hanno.becker@arm.com>
