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psa: Implement persistent keys

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Allow use of persistent keys, including configuring them, importing and
exporting them, and destroying them.

When getting a slot using psa_get_key_slot, there are 3 scenarios that
can occur if the keys lifetime is persistent:

1. Key type is PSA_KEY_TYPE_NONE, no persistent storage entry:
   -  The key slot is treated as a standard empty key slot
2. Key type is PSA_KEY_TYPE_NONE, persistent storage entry exists:
   -  Attempt to load the key from persistent storage
3. Key type is not PSA_KEY_TYPE_NONE:
   -  As checking persistent storage on every use of the key could
      be expensive, the persistent key is assumed to be saved in
      persistent storage, the in-memory key is continued to be used.
This commit is contained in:
Darryl Green
2018-06-18 17:27:26 +01:00
parent 40225ba709
commit d49a499d03
9 changed files with 599 additions and 5 deletions
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83
library/psa_crypto.c
View File

@ -43,6 +43,10 @@
#include "psa/crypto.h"
/* Include internal declarations that are useful for implementing persistently
* stored keys. */
#include "psa_crypto_storage.h"
#include <stdlib.h>
#include <string.h>
#if defined(MBEDTLS_PLATFORM_C)
@ -702,6 +706,27 @@ static psa_status_t psa_import_key_into_slot( key_slot_t *slot,
return( PSA_SUCCESS );
}
#if defined(MBEDTLS_PSA_CRYPTO_STORAGE_C)
static psa_status_t psa_load_persistent_key_into_slot( psa_key_slot_t key,
key_slot_t *p_slot )
{
psa_status_t status = PSA_SUCCESS;
uint8_t *key_data = NULL;
size_t key_data_length = 0;
status = psa_load_persistent_key( key, &( p_slot )->type,
&( p_slot )->policy, &key_data,
&key_data_length );
if( status != PSA_SUCCESS )
goto exit;
status = psa_import_key_into_slot( p_slot,
key_data, key_data_length );
exit:
psa_free_persistent_key_data( key_data, key_data_length );
return( status );
}
#endif /* defined(MBEDTLS_PSA_CRYPTO_STORAGE_C) */
/* Retrieve a key slot, occupied or not. */
static psa_status_t psa_get_key_slot( psa_key_slot_t key,
key_slot_t **p_slot )
@ -715,6 +740,23 @@ static psa_status_t psa_get_key_slot( psa_key_slot_t key,
return( PSA_ERROR_INVALID_ARGUMENT );
*p_slot = &global_data.key_slots[key - 1];
#if defined(MBEDTLS_PSA_CRYPTO_STORAGE_C)
if( ( *p_slot )->lifetime == PSA_KEY_LIFETIME_PERSISTENT )
{
/* There are two circumstances this can occur: the key material has
* not yet been created, or the key exists in storage but has not yet
* been loaded into memory. */
if( ( *p_slot )->type == PSA_KEY_TYPE_NONE )
{
psa_status_t status = PSA_SUCCESS;
status = psa_load_persistent_key_into_slot( key, *p_slot );
if( status != PSA_ERROR_EMPTY_SLOT )
return( status );
}
}
#endif /* defined(MBEDTLS_PSA_CRYPTO_STORAGE_C) */
return( PSA_SUCCESS );
}
@ -830,18 +872,44 @@ psa_status_t psa_import_key( psa_key_slot_t key,
return( status );
}
return( PSA_SUCCESS );
#if defined(MBEDTLS_PSA_CRYPTO_STORAGE_C)
if( slot->lifetime == PSA_KEY_LIFETIME_PERSISTENT )
{
/* Store in file location */
status = psa_save_persistent_key( key, slot->type, &slot->policy, data,
data_length );
if( status != PSA_SUCCESS )
{
(void) psa_remove_key_data_from_memory( slot );
slot->type = PSA_KEY_TYPE_NONE;
}
}
#endif /* defined(MBEDTLS_PSA_CRYPTO_STORAGE_C) */
return( status );
}
psa_status_t psa_destroy_key( psa_key_slot_t key )
{
key_slot_t *slot;
psa_status_t status;
psa_status_t status = PSA_SUCCESS;
psa_status_t storage_status = PSA_SUCCESS;
status = psa_get_key_slot( key, &slot );
if( status != PSA_SUCCESS )
return( status );
return( psa_remove_key_from_memory( slot ) );
#if defined(MBEDTLS_PSA_CRYPTO_STORAGE_C)
if( slot->lifetime == PSA_KEY_LIFETIME_PERSISTENT )
{
storage_status = psa_destroy_persistent_key( key );
}
#endif /* defined(MBEDTLS_PSA_CRYPTO_STORAGE_C) */
status = psa_remove_key_data_from_memory( slot );
/* Zeroize the slot to wipe metadata such as policies. */
mbedtls_zeroize( slot, sizeof( *slot ) );
if( status != PSA_SUCCESS )
return( status );
return( storage_status );
}
/* Return the size of the key in the given slot, in bits. */
@ -2974,16 +3042,21 @@ psa_status_t psa_set_key_lifetime( psa_key_slot_t key,
if( lifetime != PSA_KEY_LIFETIME_VOLATILE &&
lifetime != PSA_KEY_LIFETIME_PERSISTENT &&
lifetime != PSA_KEY_LIFETIME_WRITE_ONCE)
lifetime != PSA_KEY_LIFETIME_WRITE_ONCE )
return( PSA_ERROR_INVALID_ARGUMENT );
status = psa_get_empty_key_slot( key, &slot );
if( status != PSA_SUCCESS )
return( status );
if( lifetime != PSA_KEY_LIFETIME_VOLATILE )
if( lifetime == PSA_KEY_LIFETIME_WRITE_ONCE )
return( PSA_ERROR_NOT_SUPPORTED );
#if !defined(MBEDTLS_PSA_CRYPTO_STORAGE_C)
if( lifetime == PSA_KEY_LIFETIME_PERSISTENT )
return( PSA_ERROR_NOT_SUPPORTED );
#endif
slot->lifetime = lifetime;
return( PSA_SUCCESS );