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Keys may allow a second algorithm

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Add a second permitted algorithm to key policies.

This commit includes smoke tests that do not cover psa_copy_key.
This commit is contained in:
Gilles Peskine 2019-05-10 19:33:38 +02:00
parent 8bf196b303
commit d6f371b1ba
5 changed files with 124 additions and 15 deletions
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39
include/psa/crypto_extra.h
View file

@ -62,6 +62,45 @@ extern "C" {
MBEDTLS_DEPRECATED_NUMERIC_CONSTANT( PSA_ERROR_INSUFFICIENT_DATA )
#endif
/** \addtogroup policy
* @{
*/
/** \brief Set the enrollment algorithm in a key policy.
*
* An operation on a key may indifferently use the algorithm set with
* psa_key_policy_set_usage() or with this function.
*
* \param[in,out] policy The key policy to modify. It must have been
* initialized as per the documentation for
* #psa_key_policy_t.
* \param alg2 A second algorithm that the key may be used for,
* in addition to the algorithm set with
* psa_key_policy_set_usage().
*
* \warning Setting an enrollment algorithm is not recommended, because
* using the same key with different algorithms can allow some
* attacks based on arithmetic relations between different
* computations made with the same key, or can escalate harmless
* side channels into exploitable ones. Use this function only
* if it is necessary to support a protocol for which is has been
* verified that the usage of the key with multiple algorithms
* is safe.
*/
void psa_key_policy_set_enrollment_algorithm(psa_key_policy_t *policy,
psa_algorithm_t alg2);
/** \brief Retrieve the enrollment algorithm field of a policy structure.
*
* \param[in] policy The policy object to query.
*
* \return The enrollment algorithm for a key with this policy.
*/
psa_algorithm_t psa_key_policy_get_enrollment_algorithm(
const psa_key_policy_t *policy);
/**@}*/
/**
* \brief Library deinitialization.
*

3
include/psa/crypto_struct.h
View file

@ -228,9 +228,10 @@ struct psa_key_policy_s
{
psa_key_usage_t usage;
psa_algorithm_t alg;
psa_algorithm_t alg2;
};
#define PSA_KEY_POLICY_INIT {0, 0}
#define PSA_KEY_POLICY_INIT {0, 0, 0}
static inline struct psa_key_policy_s psa_key_policy_init( void )
{
const struct psa_key_policy_s v = PSA_KEY_POLICY_INIT;

52
library/psa_crypto.c
View file

@ -763,6 +763,25 @@ static psa_algorithm_t psa_key_policy_algorithm_intersection(
return( 0 );
}
static int psa_key_algorithm_permits( psa_algorithm_t policy_alg,
psa_algorithm_t requested_alg )
{
/* Common case: the policy only allows alg. */
if( requested_alg == policy_alg )
return( 1 );
/* If policy_alg is a hash-and-sign with a wildcard for the hash,
* and alg is the same hash-and-sign family with any hash,
* then alg is compliant with policy_alg. */
if( PSA_ALG_IS_HASH_AND_SIGN( requested_alg ) &&
PSA_ALG_SIGN_GET_HASH( policy_alg ) == PSA_ALG_ANY_HASH )
{
return( ( policy_alg & ~PSA_ALG_HASH_MASK ) ==
( requested_alg & ~PSA_ALG_HASH_MASK ) );
}
/* If it isn't permitted, it's forbidden. */
return( 0 );
}
/** Test whether a policy permits an algorithm.
*
* The caller must test usage flags separately.
@ -770,20 +789,8 @@ static psa_algorithm_t psa_key_policy_algorithm_intersection(
static int psa_key_policy_permits( const psa_key_policy_t *policy,
psa_algorithm_t alg )
{
/* Common case: the policy only allows alg. */
if( alg == policy->alg )
return( 1 );
/* If policy->alg is a hash-and-sign with a wildcard for the hash,
* and alg is the same hash-and-sign family with any hash,
* then alg is compliant with policy->alg. */
if( PSA_ALG_IS_HASH_AND_SIGN( alg ) &&
PSA_ALG_SIGN_GET_HASH( policy->alg ) == PSA_ALG_ANY_HASH )
{
return( ( policy->alg & ~PSA_ALG_HASH_MASK ) ==
( alg & ~PSA_ALG_HASH_MASK ) );
}
/* If it isn't permitted, it's forbidden. */
return( 0 );
return( psa_key_algorithm_permits( policy->alg, alg ) ||
psa_key_algorithm_permits( policy->alg2, alg ) );
}
/** Restrict a key policy based on a constraint.
@ -804,10 +811,15 @@ static psa_status_t psa_restrict_key_policy(
{
psa_algorithm_t intersection_alg =
psa_key_policy_algorithm_intersection( policy->alg, constraint->alg );
psa_algorithm_t intersection_alg2 =
psa_key_policy_algorithm_intersection( 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 )
return( PSA_ERROR_INVALID_ARGUMENT );
policy->usage &= constraint->usage;
policy->alg = intersection_alg;
policy->alg2 = intersection_alg2;
return( PSA_SUCCESS );
}
@ -3218,6 +3230,18 @@ psa_algorithm_t psa_key_policy_get_algorithm( const psa_key_policy_t *policy )
{
return( policy->alg );
}
void psa_key_policy_set_enrollment_algorithm( psa_key_policy_t *policy,
psa_algorithm_t alg2 )
{
policy->alg2 = alg2;
}
psa_algorithm_t psa_key_policy_get_enrollment_algorithm(
const psa_key_policy_t *policy )
{
return( policy->alg2 );
}
#endif /* !defined(MBEDTLS_PSA_CRYPTO_SPM) */
psa_status_t psa_set_key_policy( psa_key_handle_t handle,

8
tests/suites/test_suite_psa_crypto.data
View file

@ -492,6 +492,14 @@ PSA key policy: agreement, wrong algorithm
depends_on:MBEDTLS_PK_PARSE_C:MBEDTLS_ECP_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_ECDH_C
agreement_key_policy:PSA_KEY_USAGE_DERIVE:PSA_ALG_ECDH(PSA_ALG_SELECT_RAW):PSA_KEY_TYPE_ECC_KEYPAIR(PSA_ECC_CURVE_SECP256R1):"49c9a8c18c4b885638c431cf1df1c994131609b580d4fd43a0cab17db2f13eee":PSA_ALG_FFDH(PSA_ALG_SELECT_RAW)
PSA key policy algorithm2: CTR, CBC
depends_on:MBEDTLS_AES_C:MBEDTLS_CIPHER_MODE_CTR:MBEDTLS_CIPHER_MODE_CBC_NOPAD
key_policy_alg2:PSA_KEY_TYPE_AES:"aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa":PSA_KEY_USAGE_ENCRYPT:PSA_ALG_CTR:PSA_ALG_CBC_NO_PADDING
PSA key policy algorithm2: ECDH, ECDSA
depends_on:MBEDTLS_PK_PARSE_C:MBEDTLS_ECP_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_ECDH_C:MBEDTLS_ECDSA_C
key_policy_alg2:PSA_KEY_TYPE_ECC_KEYPAIR(PSA_ECC_CURVE_SECP256R1):"49c9a8c18c4b885638c431cf1df1c994131609b580d4fd43a0cab17db2f13eee":PSA_KEY_USAGE_DERIVE | PSA_KEY_USAGE_SIGN | PSA_KEY_USAGE_VERIFY:PSA_ALG_ECDH(PSA_ALG_SELECT_RAW):PSA_ALG_ECDSA_ANY
Copy key: raw, 0 bytes
copy_key_policy:0:0:PSA_KEY_TYPE_RAW_DATA:"":0:0:-1:-1:0:0

37
tests/suites/test_suite_psa_crypto.function
View file

@ -1932,6 +1932,43 @@ exit:
}
/* END_CASE */
/* BEGIN_CASE */
void key_policy_alg2( int key_type_arg, data_t *key_data,
int usage_arg, int alg_arg, int alg2_arg )
{
psa_key_handle_t handle = 0;
psa_key_type_t key_type = key_type_arg;
psa_key_policy_t policy = PSA_KEY_POLICY_INIT;
psa_key_policy_t got_policy = PSA_KEY_POLICY_INIT;
psa_key_usage_t usage = usage_arg;
psa_algorithm_t alg = alg_arg;
psa_algorithm_t alg2 = alg2_arg;
PSA_ASSERT( psa_crypto_init( ) );
PSA_ASSERT( psa_allocate_key( &handle ) );
psa_key_policy_set_usage( &policy, usage, alg );
psa_key_policy_set_enrollment_algorithm( &policy, alg2 );
PSA_ASSERT( psa_set_key_policy( handle, &policy ) );
PSA_ASSERT( psa_import_key( handle, key_type,
key_data->x, key_data->len ) );
PSA_ASSERT( psa_get_key_policy( handle, &got_policy ) );
TEST_EQUAL( psa_key_policy_get_usage( &got_policy ), usage );
TEST_EQUAL( psa_key_policy_get_algorithm( &got_policy ), alg );
TEST_EQUAL( psa_key_policy_get_enrollment_algorithm( &got_policy ), alg2 );
if( ! exercise_key( handle, usage, alg ) )
goto exit;
if( ! exercise_key( handle, usage, alg2 ) )
goto exit;
exit:
psa_destroy_key( handle );
mbedtls_psa_crypto_free( );
}
/* END_CASE */
/* BEGIN_CASE */
void copy_key_policy( int source_usage_arg, int source_alg_arg,
int type_arg, data_t *material,