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Document better what wiping a key slot does not do

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When a key slot is wiped, a copy of the key material may remain in
operations. This is undesirable, but does not violate the safety of
the code. Tracked in https://github.com/ARMmbed/mbed-crypto/issues/86
This commit is contained in:
Gilles Peskine 2019-08-13 15:01:08 +02:00
parent b4e73e9747
commit 3f7cd62ff5
1 changed files with 5 additions and 7 deletions
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12
library/psa_crypto.c
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@ -994,18 +994,16 @@ static psa_status_t psa_remove_key_data_from_memory( psa_key_slot_t *slot )
return( PSA_SUCCESS );
}
static void psa_abort_operations_using_key( psa_key_slot_t *slot )
{
/*FIXME how to implement this?*/
(void) slot;
}
/** Completely wipe a slot in memory, including its policy.
* Persistent storage is not affected. */
psa_status_t psa_wipe_key_slot( psa_key_slot_t *slot )
{
psa_status_t status = psa_remove_key_data_from_memory( slot );
psa_abort_operations_using_key( slot );
/* Multipart operations may still be using the key. This is safe
* because all multipart operation objects are independent from
* the key slot: if they need to access the key after the setup
* phase, they have a copy of the key. Note that this means that
* key material can linger until all operations are completed. */
/* At this point, key material and other type-specific content has
* been wiped. Clear remaining metadata. We can call memset and not
* zeroize because the metadata is not particularly sensitive. */