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Improve psa_wipe_output_buffer

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Change name and document to ensure suitability only for "tags" is explicit. Add
support for output size of zero in PSA_SUCCESS case.

Signed-off-by: Paul Elliott <paul.elliott@arm.com>
This commit is contained in:
Paul Elliott 2023-02-21 15:07:40 +00:00
parent f8e5b56ad8
commit 59200a22aa
1 changed files with 28 additions and 21 deletions
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49
library/psa_crypto.c
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@ -2684,34 +2684,41 @@ static psa_status_t psa_sign_verify_check_alg(int input_is_message,
}
/**
* \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.
* \brief For output buffers which contain "tags"
* (outputs that may be checked for validity like
* Hashes, MACs and signatures), 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 tag (barring an
* attack on the tag 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
* 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)
static void psa_wipe_tag_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);
size_t offset = 0;
if (output_buffer_size == 0) {
/* 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 */
return;
}
/* 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.*/
if (status == PSA_SUCCESS) {
offset = output_buffer_length;
}
memset(output_buffer + offset, '!', output_buffer_size - offset);
}
static psa_status_t psa_sign_internal(mbedtls_svc_key_id_t key,
@ -2776,8 +2783,8 @@ static psa_status_t psa_sign_internal(mbedtls_svc_key_id_t key,
exit:
psa_wipe_output_buffer(signature, status, signature_size,
*signature_length);
psa_wipe_tag_output_buffer(signature, status, signature_size,
*signature_length);
unlock_status = psa_unlock_key_slot(slot);
@ -3293,8 +3300,8 @@ psa_status_t psa_sign_hash_complete(
exit:
psa_wipe_output_buffer(signature, status, signature_size,
*signature_length);
psa_wipe_tag_output_buffer(signature, status, signature_size,
*signature_length);
if (status != PSA_OPERATION_INCOMPLETE) {
if (status != PSA_SUCCESS) {