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Make psa_key_policy_algorithm_intersection MAC-length aware

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This makes it more in-line with how psa_key_policy_permits works. It
also adds consistency: the intersection of MAC with default length and
MAC with exact-length is now computed correctly in case the exact length
equals the default length of the algorithm when used with the given
key type.

Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
This commit is contained in:
Steven Cooreman 2021-03-02 16:34:49 +01:00
parent 15472f8c70
commit 1ac5ce3b91
1 changed files with 48 additions and 18 deletions
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62
library/psa_crypto.c
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@ -719,6 +719,7 @@ psa_status_t psa_import_key_into_slot(
* Return 0 (which allows no operation) on incompatibility.
*/
static psa_algorithm_t psa_key_policy_algorithm_intersection(
psa_key_type_t key_type,
psa_algorithm_t alg1,
psa_algorithm_t alg2 )
{
@ -772,8 +773,28 @@ static psa_algorithm_t psa_key_policy_algorithm_intersection(
( PSA_ALG_FULL_LENGTH_MAC( alg1 ) ==
PSA_ALG_FULL_LENGTH_MAC( alg2 ) ) )
{
size_t alg1_len = PSA_MAC_TRUNCATED_LENGTH( alg1 );
size_t alg2_len = PSA_MAC_TRUNCATED_LENGTH( alg2 );
/* Calculate the actual requested output length for both sides. In case
* of at-least-this-length wildcard algorithms, the requested output
* length is the shortest allowed length. */
size_t alg1_len = 0;
size_t alg2_len = 0;
if( PSA_SUCCESS != psa_get_mac_output_length(
PSA_ALG_TRUNCATED_MAC( alg1,
PSA_MAC_TRUNCATED_LENGTH( alg1 ) ),
key_type,
&alg1_len ) )
{
return( 0 );
}
if( PSA_SUCCESS != psa_get_mac_output_length(
PSA_ALG_TRUNCATED_MAC( alg2,
PSA_MAC_TRUNCATED_LENGTH( alg2 ) ),
key_type,
&alg2_len ) )
{
return( 0 );
}
size_t max_len = alg1_len > alg2_len ? alg1_len : alg2_len;
/* If both are wildcards, return most restrictive wildcard */
@ -782,22 +803,26 @@ static psa_algorithm_t psa_key_policy_algorithm_intersection(
{
return( PSA_ALG_AT_LEAST_THIS_LENGTH_MAC( alg1, max_len ) );
}
/* If only one is a wildcard, return specific algorithm if compatible.
* Special case: specific MAC algorithm with '0' as length means full-
* length MAC, which is always allowed by a wildcard with the same
* base algorithm. */
if( ( ( alg1 & PSA_ALG_MAC_AT_LEAST_THIS_LENGTH_FLAG ) != 0 ) &&
( ( alg1_len <= alg2_len ) ||
( alg2 == PSA_ALG_FULL_LENGTH_MAC( alg1 ) ) ) )
/* If only one is a wildcard, return specific algorithm if compatible. */
if( ( alg1 & PSA_ALG_MAC_AT_LEAST_THIS_LENGTH_FLAG ) != 0 )
{
if( alg1_len <= alg2_len )
return( alg2 );
else
return( 0 );
}
if( ( ( alg2 & PSA_ALG_MAC_AT_LEAST_THIS_LENGTH_FLAG ) != 0 ) &&
( ( alg2_len <= alg1_len ) ||
( alg1 == PSA_ALG_FULL_LENGTH_MAC( alg2 ) ) ) )
if( ( alg2 & PSA_ALG_MAC_AT_LEAST_THIS_LENGTH_FLAG ) != 0 )
{
if( alg2_len <= alg1_len )
return( alg1 );
else
return( 0 );
}
/* If none of them are wildcards, check whether we can match
* default-length with exact-length, and return exact-length in that
* case. */
if( alg1_len == alg2_len )
return( PSA_ALG_TRUNCATED_MAC( alg1, alg1_len ) );
}
/* If the policies are incompatible, allow nothing. */
return( 0 );
@ -919,6 +944,7 @@ static psa_status_t psa_key_policy_permits( const psa_key_policy_t *policy,
/** Restrict a key policy based on a constraint.
*
* \param[in] key_type The key type for which to restrict the policy
* \param[in,out] policy The policy to restrict.
* \param[in] constraint The policy constraint to apply.
*
@ -926,17 +952,20 @@ static psa_status_t psa_key_policy_permits( const psa_key_policy_t *policy,
* \c *policy contains the intersection of the original value of
* \c *policy and \c *constraint.
* \retval #PSA_ERROR_INVALID_ARGUMENT
* \c *policy and \c *constraint are incompatible.
* \c key_type, \c *policy and \c *constraint are incompatible.
* \c *policy is unchanged.
*/
static psa_status_t psa_restrict_key_policy(
psa_key_type_t key_type,
psa_key_policy_t *policy,
const psa_key_policy_t *constraint )
{
psa_algorithm_t intersection_alg =
psa_key_policy_algorithm_intersection( policy->alg, constraint->alg );
psa_key_policy_algorithm_intersection( key_type, policy->alg,
constraint->alg );
psa_algorithm_t intersection_alg2 =
psa_key_policy_algorithm_intersection( policy->alg2, constraint->alg2 );
psa_key_policy_algorithm_intersection( key_type, policy->alg2,
constraint->alg2 );
if( intersection_alg == 0 && policy->alg != 0 && constraint->alg != 0 )
return( PSA_ERROR_INVALID_ARGUMENT );
if( intersection_alg2 == 0 && policy->alg2 != 0 && constraint->alg2 != 0 )
@ -2089,7 +2118,8 @@ psa_status_t psa_copy_key( mbedtls_svc_key_id_t source_key,
if( status != PSA_SUCCESS )
goto exit;
status = psa_restrict_key_policy( &actual_attributes.core.policy,
status = psa_restrict_key_policy( source_slot->attr.type,
&actual_attributes.core.policy,
&source_slot->attr.policy );
if( status != PSA_SUCCESS )
goto exit;