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Improve FREE_LOCAL_INPUT() and FREE_LOCAL_OUTPUT()

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* Set swapped pointers to NULL when the buffers are freed.
* Change example name <buffer> to <input> and <output> to reduce
  confusion.
* Document assumptions of FREE_LOCAL_ macros.
* Add comment on error case in FREE_LOCAL_OUTPUT(), explaining why it's
  okay to mask the existing status code.

Signed-off-by: David Horstmann <david.horstmann@arm.com>
This commit is contained in:
David Horstmann 2023-12-08 14:08:18 +00:00
parent b7a5b6ed35
commit 3e72db4f51
1 changed files with 25 additions and 2 deletions
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27
library/psa_crypto.c
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@ -115,7 +115,7 @@ mbedtls_psa_drbg_context_t *const mbedtls_psa_random_state =
* Assumptions:
* - psa_status_t status exists
* - An exit label is declared
* - The name <buffer>_copy is not used for the given value of <buffer>
* - The name <input>_copy is not used for the given value of <input>
*/
#define SWAP_FOR_LOCAL_INPUT(input, length) \
psa_crypto_local_input_t input ## _copy = PSA_CRYPTO_LOCAL_INPUT_INIT; \
@ -125,14 +125,23 @@ mbedtls_psa_drbg_context_t *const mbedtls_psa_random_state =
} \
input = input ## _copy.buffer;
/* Free the substituted input buffer copy created by SWAP_FOR_LOCAL_INPUT().
* Note that this does not restore the pointer to the original buffer.
* Assumptions:
* - psa_crypto_local_input_t <input>_copy exists, for the given value of
* <input>
* - <input>_copy was previously allocated by psa_crypto_local_input_alloc()
* - <input> points to <input>_copy.buffer
*/
#define FREE_LOCAL_INPUT(input) \
input = NULL; \
psa_crypto_local_input_free(&input ## _copy);
/* Substitute an output buffer for a local copy of itself.
* Assumptions:
* - psa_status_t status exists
* - An exit label is declared
* - The name <buffer>_copy is not used for the given value of <buffer>
* - The name <output>_copy is not used for the given value of <output>
*/
#define SWAP_FOR_LOCAL_OUTPUT(output, length) \
psa_crypto_local_output_t output ## _copy = PSA_CRYPTO_LOCAL_OUTPUT_INIT; \
@ -142,10 +151,24 @@ mbedtls_psa_drbg_context_t *const mbedtls_psa_random_state =
} \
output = output ## _copy.buffer;
/* Free the substituted output buffer copy created by SWAP_FOR_LOCAL_OUTPUT()
* after first copying back its contents to the original buffer.
* Note that this does not restore the pointer to the original buffer.
* Assumptions:
* - psa_crypto_local_output_t <output>_copy exists, for the given value of
* <output>
* - <output>_copy was previously allocated by psa_crypto_local_output_alloc()
* - <output> points to <output>_copy.buffer
* - psa_status_t status exists
*/
#define FREE_LOCAL_OUTPUT(output) \
output = NULL; \
psa_status_t local_output_free_status; \
local_output_free_status = psa_crypto_local_output_free(&output ## _copy); \
if (local_output_free_status != PSA_SUCCESS) { \
/* Since this error case is an internal error, it's more serious than \
* any existing error code and so it's fine to overwrite the existing \
* status. */ \
status = local_output_free_status; \
}
#else /* MBEDTLS_PSA_COPY_CALLER_BUFFERS */