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Move output buffer wiping code to seperate function.

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Signed-off-by: Paul Elliott <paul.elliott@arm.com>
This commit is contained in:
Paul Elliott 2023-02-07 12:15:24 +00:00
parent 1243f93cca
commit 939bd9485d
1 changed files with 35 additions and 25 deletions
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60
library/psa_crypto.c
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@ -2683,6 +2683,37 @@ static psa_status_t psa_sign_verify_check_alg(int input_is_message,
return PSA_SUCCESS;
}
/**
* \brief Fill the unused part of the output buffer(the
* whole buffer on error, the trailing part on
* success) with something that isn't a valid
* signature (barring an attack on the signature
* and deliberately-crafted input), in case the
* caller doesn't check the return status properly.
*
* \param output_buffer pointer to buffer to wipe. May not be NULL
* unless /p output_buffer_size is zero.
* \param status status of function called to generate
* output_buffer originally
* \param output_buffer_size Size of output buffer. If zero, /p output_buffer
* could be NULL
* \param output_buffer_length Length of data written to output_buffer, must be
* less than /p output_buffer_size
*/
static void psa_wipe_output_buffer(uint8_t *output_buffer, psa_status_t status,
size_t output_buffer_size, size_t output_buffer_length)
{
if (status == PSA_SUCCESS) {
memset(output_buffer + output_buffer_length, '!',
output_buffer_size - output_buffer_length);
} else if (output_buffer_size > 0) {
memset(output_buffer, '!', output_buffer_size);
}
/* If output_buffer_size is 0 then we have nothing to do. We must
* not call memset because output_buffer may be NULL in this
* case.*/
}
static psa_status_t psa_sign_internal(mbedtls_svc_key_id_t key,
int input_is_message,
psa_algorithm_t alg,
@ -2745,18 +2776,8 @@ static psa_status_t psa_sign_internal(mbedtls_svc_key_id_t key,
exit:
/* Fill the unused part of the output buffer (the whole buffer on error,
* the trailing part on success) with something that isn't a valid signature
* (barring an attack on the signature and deliberately-crafted input),
* in case the caller doesn't check the return status properly. */
if (status == PSA_SUCCESS) {
memset(signature + *signature_length, '!',
signature_size - *signature_length);
} else {
memset(signature, '!', signature_size);
}
/* If signature_size is 0 then we have nothing to do. We must not call
* memset because signature may be NULL in this case. */
psa_wipe_output_buffer(signature, status, signature_size,
*signature_length);
unlock_status = psa_unlock_key_slot(slot);
@ -3268,19 +3289,8 @@ exit:
operation->num_ops += psa_driver_wrapper_sign_hash_get_num_ops(operation);
if (status != PSA_OPERATION_INCOMPLETE) {
/* Fill the unused part of the output buffer (the whole buffer on error,
* the trailing part on success) with something that isn't a valid
* signature (barring an attack on the signature and
* deliberately-crafted input), in case the caller doesn't check the
* return status properly.*/
if (status == PSA_SUCCESS) {
memset(signature + *signature_length, '!',
signature_size - *signature_length);
} else if (signature_size > 0) {
memset(signature, '!', signature_size);
}
/* If signature_size is 0 then we have nothing to do. We must not
* call memset because signature may be NULL in this case.*/
psa_wipe_output_buffer(signature, status, signature_size,
*signature_length);
if (status != PSA_SUCCESS) {
operation->error_occurred = 1;