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More refactoring: consolidate attribute validation

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Consolidate attribute validation at the beginning of key creation into
a single function. Improve comments.
This commit is contained in:
Gilles Peskine 2019-07-31 17:21:46 +02:00
parent 3825e14e65
commit 1b8594a218
1 changed files with 66 additions and 25 deletions
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91
library/psa_crypto.c
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@ -1403,10 +1403,14 @@ psa_status_t psa_export_public_key( psa_key_handle_t handle,
data_length, 1 ) );
}
static psa_status_t psa_check_key_slot_policy(
const psa_key_slot_t *slot )
/** Validate that a key policy is internally well-formed.
*
* This function only rejects invalid policies. It does not validate the
* consistency of the policy with respect to other attributes of the key
* such as the key type.
*/
static psa_status_t psa_validate_key_policy( const psa_key_policy_t *policy )
{
const psa_key_policy_t *policy = &slot->attr.policy;
if( ( policy->usage & ~( PSA_KEY_USAGE_EXPORT |
PSA_KEY_USAGE_COPY |
PSA_KEY_USAGE_ENCRYPT |
@ -1419,6 +1423,48 @@ static psa_status_t psa_check_key_slot_policy(
return( PSA_SUCCESS );
}
/** Validate the internal consistency of key attributes.
*
* This function only rejects invalid attribute values. If does not
* validate the consistency of the attributes with any key data that may
* be involved in the creation of the key.
*
* Call this function early in the key creation process.
*
* \param[in] attributes Key attributes for the new key.
* \param[out] p_drv On any return, the driver for the key, if any.
* NULL for a transparent key.
*
*/
static psa_status_t psa_validate_key_attributes(
const psa_key_attributes_t *attributes,
psa_se_drv_table_entry_t **p_drv )
{
psa_status_t status;
if( attributes->core.lifetime != PSA_KEY_LIFETIME_VOLATILE )
{
status = psa_validate_persistent_key_parameters(
attributes->core.lifetime, attributes->core.id,
p_drv, 1 );
if( status != PSA_SUCCESS )
return( status );
}
status = psa_validate_key_policy( &attributes->core.policy );
if( status != PSA_SUCCESS )
return( status );
/* Refuse to create overly large keys.
* Note that this doesn't trigger on import if the attributes don't
* explicitly specify a size (so psa_get_key_bits returns 0), so
* psa_import_key() needs its own checks. */
if( psa_get_key_bits( attributes ) > PSA_MAX_KEY_BITS )
return( PSA_ERROR_NOT_SUPPORTED );
return( PSA_SUCCESS );
}
/** Prepare a key slot to receive key material.
*
* This function allocates a key slot and sets its metadata.
@ -1455,26 +1501,15 @@ static psa_status_t psa_start_key_creation(
*p_drv = NULL;
status = psa_validate_key_attributes( attributes, p_drv );
if( status != PSA_SUCCESS )
return( status );
status = psa_internal_allocate_key_slot( handle, p_slot );
if( status != PSA_SUCCESS )
return( status );
slot = *p_slot;
if( attributes->core.lifetime != PSA_KEY_LIFETIME_VOLATILE )
{
status = psa_validate_persistent_key_parameters( attributes->core.lifetime,
attributes->core.id,
p_drv, 1 );
if( status != PSA_SUCCESS )
return( status );
}
/* Refuse to create overly large keys.
* Note that this doesn't trigger on import if the attributes don't
* explicitly specify a size (so psa_get_key_bits returns 0), so
* psa_import_key() needs its own checks. */
if( psa_get_key_bits( attributes ) > PSA_MAX_KEY_BITS )
return( PSA_ERROR_NOT_SUPPORTED );
/* We're storing the declared bit-size of the key. It's up to each
* creation mechanism to verify that this information is correct.
* It's automatically correct for mechanisms that use the bit-size as
@ -1483,10 +1518,6 @@ static psa_status_t psa_start_key_creation(
slot->attr = attributes->core;
status = psa_check_key_slot_policy( slot );
if( status != PSA_SUCCESS )
return( status );
#if defined(MBEDTLS_PSA_CRYPTO_SE_C)
/* For a key in a secure element, we need to do three things:
* create the key file in internal storage, create the
@ -1647,7 +1678,16 @@ static void psa_fail_key_creation( psa_key_slot_t *slot,
psa_wipe_key_slot( slot );
}
static psa_status_t psa_check_key_slot_attributes(
/** Validate optional attributes during key creation.
*
* Some key attributes are optional during key creation. If they are
* specified in the attributes structure, check that they are consistent
* with the data in the slot.
*
* This function should be called near the end of key creation, after
* the slot in memory is fully populated but before saving persistent data.
*/
static psa_status_t psa_validate_optional_attributes(
const psa_key_slot_t *slot,
const psa_key_attributes_t *attributes )
{
@ -1746,7 +1786,7 @@ psa_status_t psa_import_key( const psa_key_attributes_t *attributes,
if( status != PSA_SUCCESS )
goto exit;
}
status = psa_check_key_slot_attributes( slot, attributes );
status = psa_validate_optional_attributes( slot, attributes );
if( status != PSA_SUCCESS )
goto exit;
@ -1801,7 +1841,8 @@ psa_status_t psa_copy_key( psa_key_handle_t source_handle,
if( status != PSA_SUCCESS )
goto exit;
status = psa_check_key_slot_attributes( source_slot, specified_attributes );
status = psa_validate_optional_attributes( source_slot,
specified_attributes );
if( status != PSA_SUCCESS )
goto exit;