Clean up status code handling inside psa_destroy_key
Adopt a simple method for tracking whether there was a failure: each
fallible operation sets overall_status, unless overall_status is
already non-successful. Thus in case of multiple failures, the
function always reports whatever failed first. This may not always be
the right thing, but it's simple.
This revealed a bug whereby if the only failure was the call to
psa_destroy_se_key(), i.e. if the driver reported a failure or if the
driver lacked support for destroying keys, psa_destroy_key() would
ignore that failure.
For a key in a secure element, if creating a transaction file fails,
don't touch storage, but close the key in memory. This may not be
right, but it's no wronger than it was before. Tracked in
https://github.com/ARMmbed/mbed-crypto/issues/215
diff --git a/library/psa_crypto.c b/library/psa_crypto.c
index 66c5151..bce777b 100644
--- a/library/psa_crypto.c
+++ b/library/psa_crypto.c
@@ -1014,8 +1014,8 @@
psa_status_t psa_destroy_key( psa_key_handle_t handle )
{
psa_key_slot_t *slot;
- psa_status_t status = PSA_SUCCESS;
- psa_status_t storage_status = PSA_SUCCESS;
+ psa_status_t status; /* status of the last operation */
+ psa_status_t overall_status = PSA_SUCCESS;
#if defined(MBEDTLS_PSA_CRYPTO_SE_C)
psa_se_drv_table_entry_t *driver;
#endif /* MBEDTLS_PSA_CRYPTO_SE_C */
@@ -1041,18 +1041,30 @@
if( status != PSA_SUCCESS )
{
(void) psa_crypto_stop_transaction( );
- /* TOnogrepDO: destroy what can be destroyed anyway */
- return( status );
+ /* We should still try to destroy the key in the secure
+ * element and the key metadata in storage. This is especially
+ * important if the error is that the storage is full.
+ * But how to do it exactly without risking an inconsistent
+ * state after a reset?
+ * https://github.com/ARMmbed/mbed-crypto/issues/215
+ */
+ overall_status = status;
+ goto exit;
}
status = psa_destroy_se_key( driver, slot->data.se.slot_number );
+ if( overall_status == PSA_SUCCESS )
+ overall_status = status;
}
#endif /* MBEDTLS_PSA_CRYPTO_SE_C */
#if defined(MBEDTLS_PSA_CRYPTO_STORAGE_C)
if( slot->attr.lifetime != PSA_KEY_LIFETIME_VOLATILE )
{
- storage_status = psa_destroy_persistent_key( slot->attr.id );
+ status = psa_destroy_persistent_key( slot->attr.id );
+ if( overall_status == PSA_SUCCESS )
+ overall_status = status;
+
/* TODO: other slots may have a copy of the same key. We should
* invalidate them.
* https://github.com/ARMmbed/mbed-crypto/issues/214
@@ -1063,23 +1075,23 @@
#if defined(MBEDTLS_PSA_CRYPTO_SE_C)
if( driver != NULL )
{
- psa_status_t status2;
status = psa_save_se_persistent_data( driver );
- status2 = psa_crypto_stop_transaction( );
- if( status == PSA_SUCCESS )
- status = status2;
- if( status != PSA_SUCCESS )
- {
- /* TOnogrepDO: destroy what can be destroyed anyway */
- return( status );
- }
+ if( overall_status == PSA_SUCCESS )
+ overall_status = status;
+ status = psa_crypto_stop_transaction( );
+ if( overall_status == PSA_SUCCESS )
+ overall_status = status;
}
#endif /* MBEDTLS_PSA_CRYPTO_SE_C */
+#if defined(MBEDTLS_PSA_CRYPTO_SE_C)
+exit:
+#endif /* MBEDTLS_PSA_CRYPTO_SE_C */
status = psa_wipe_key_slot( slot );
- if( status != PSA_SUCCESS )
- return( status );
- return( storage_status );
+ /* Prioritize CORRUPTION_DETECTED from wiping over a storage error */
+ if( overall_status == PSA_SUCCESS )
+ overall_status = status;
+ return( overall_status );
}
void psa_reset_key_attributes( psa_key_attributes_t *attributes )
