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Implement delayed deletion in psa_destroy_key and some cleanup

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Signed-off-by: Ryan Everett <ryan.everett@arm.com>
This commit is contained in:
Ryan Everett 2024-01-17 11:39:09 +00:00
parent 1d32a57764
commit 7ed542e0f1
1 changed files with 53 additions and 27 deletions
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80
library/psa_crypto.c
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@ -987,18 +987,41 @@ psa_status_t psa_wipe_key_slot(psa_key_slot_t *slot)
/*
* As the return error code may not be handled in case of multiple errors,
* do our best to report an unexpected amount of registered readers.
* Assert with MBEDTLS_TEST_HOOK_TEST_ASSERT that registered_readers is
* equal to one:
* do our best to report an unexpected amount of registered readers or
* an unexpected state.
* Assert with MBEDTLS_TEST_HOOK_TEST_ASSERT that the slot is valid for
* wiping.
* if the MBEDTLS_TEST_HOOKS configuration option is enabled and the
* function is called as part of the execution of a test suite, the
* execution of the test suite is stopped in error if the assertion fails.
*/
if (((slot->state == PSA_SLOT_FULL) ||
(slot->state == PSA_SLOT_PENDING_DELETION)) &&
(slot->registered_readers != 1)) {
MBEDTLS_TEST_HOOK_TEST_ASSERT(slot->registered_readers == 1);
status = PSA_ERROR_CORRUPTION_DETECTED;
switch (slot->state) {
case PSA_SLOT_FULL:
/* In this state psa_wipe_key_slot() must only be called if the
* caller is the last reader. */
case PSA_SLOT_PENDING_DELETION:
/* In this state psa_wipe_key_slot() must only be called if the
* caller is the last reader. */
if (slot->registered_readers != 1) {
MBEDTLS_TEST_HOOK_TEST_ASSERT(slot->registered_readers == 1);
status = PSA_ERROR_CORRUPTION_DETECTED;
}
break;
case PSA_SLOT_FILLING:
/* In this state registered_readers must be 0. */
if (slot->registered_readers != 0) {
MBEDTLS_TEST_HOOK_TEST_ASSERT(slot->registered_readers == 0);
status = PSA_ERROR_CORRUPTION_DETECTED;
}
break;
case PSA_SLOT_EMPTY:
/* The slot is already empty, it cannot be wiped. */
MBEDTLS_TEST_HOOK_TEST_ASSERT(slot->state != PSA_SLOT_EMPTY);
status = PSA_ERROR_CORRUPTION_DETECTED;
break;
default:
/* The slot's state is invalid. */
status = PSA_ERROR_CORRUPTION_DETECTED;
}
/* Multipart operations may still be using the key. This is safe
@ -1028,29 +1051,25 @@ psa_status_t psa_destroy_key(mbedtls_svc_key_id_t key)
}
/*
* Get the description of the key in a key slot. In case of a persistent
* key, this will load the key description from persistent memory if not
* done yet. We cannot avoid this loading as without it we don't know if
* Get the description of the key in a key slot, and register to read it.
* In the case of a persistent key, this will load the key description
* from persistent memory if not done yet.
* We cannot avoid this loading as without it we don't know if
* the key is operated by an SE or not and this information is needed by
* the current implementation.
*/
* the current implementation. */
status = psa_get_and_lock_key_slot(key, &slot);
if (status != PSA_SUCCESS) {
return status;
}
/*
* If the key slot containing the key description is under access by the
* library (apart from the present access), the key cannot be destroyed
* yet. For the time being, just return in error. Eventually (to be
* implemented), the key should be destroyed when all accesses have
* stopped.
*/
if (slot->registered_readers > 1) {
psa_unregister_read(slot);
return PSA_ERROR_GENERIC_ERROR;
}
/* Set the key slot containing the key description's state to
* PENDING_DELETION. This stops new operations from registering
* to read the slot. Current readers can safely continue to access
* the key within the slot; the last registered reader will
* automatically wipe the slot when they call psa_unregister_read().
* If the key is persistent, we can now delete the copy of the key
* from memory. If the key is opaque, we require the driver to
* deal with the deletion. */
slot->state = PSA_SLOT_PENDING_DELETION;
if (PSA_KEY_LIFETIME_IS_READ_ONLY(slot->attr.lifetime)) {
@ -1099,6 +1118,9 @@ psa_status_t psa_destroy_key(mbedtls_svc_key_id_t key)
#if defined(MBEDTLS_PSA_CRYPTO_STORAGE_C)
if (!PSA_KEY_LIFETIME_IS_VOLATILE(slot->attr.lifetime)) {
/* Destroy the copy of the persistent key from memory.
* The slot will still hold a copy of the key until the last reader
* unregisters. */
status = psa_destroy_persistent_key(slot->attr.id);
if (overall_status == PSA_SUCCESS) {
overall_status = status;
@ -1125,8 +1147,11 @@ psa_status_t psa_destroy_key(mbedtls_svc_key_id_t key)
#endif /* MBEDTLS_PSA_CRYPTO_SE_C */
exit:
status = psa_wipe_key_slot(slot);
/* Prioritize CORRUPTION_DETECTED from wiping over a storage error */
/* Unregister from reading the slot. If we are the last active reader
* then this will wipe the slot. */
status = psa_unregister_read(slot);
/* Prioritize CORRUPTION_DETECTED from unregistering over
* a storage error. */
if (status != PSA_SUCCESS) {
overall_status = status;
}
@ -1825,6 +1850,7 @@ static void psa_fail_key_creation(psa_key_slot_t *slot,
* itself. */
(void) psa_crypto_stop_transaction();
#endif /* MBEDTLS_PSA_CRYPTO_SE_C */
psa_wipe_key_slot(slot);
}