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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 d3bb7bb2f2
commit 96f0b3b1d3
5 changed files with 118 additions and 16 deletions
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44
include/psa/crypto_extra.h
View file

@ -62,6 +62,50 @@ extern "C" {
MBEDTLS_DEPRECATED_NUMERIC_CONSTANT( PSA_ERROR_INSUFFICIENT_DATA )
#endif
/** \addtogroup attributes
* @{
*/
/** \brief Declare the enrollment algorithm for a key.
*
* An operation on a key may indifferently use the algorithm set with
* psa_set_key_algorithm() or with this function.
*
* \param[out] attributes The attribute structure to write to.
* \param alg2 A second algorithm that the key may be used
* for, in addition to the algorithm set with
* psa_set_key_algorithm().
*
* \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.
*/
static inline void psa_set_key_enrollment_algorithm(
psa_key_attributes_t *attributes,
psa_algorithm_t alg2)
{
attributes->policy.alg2 = alg2;
}
/** Retrieve the enrollment algorithm policy from key attributes.
*
* \param[in] attributes The key attribute structure to query.
*
* \return The enrollment algorithm stored in the attribute structure.
*/
static inline psa_algorithm_t psa_get_key_enrollment_algorithm(
const psa_key_attributes_t *attributes)
{
return( attributes->policy.alg2 );
}
/**@}*/
/**
* \brief Library deinitialization.
*

5
include/psa/crypto_struct.h
View file

@ -251,10 +251,11 @@ struct psa_key_policy_s
{
psa_key_usage_t usage;
psa_algorithm_t alg;
psa_algorithm_t alg2;
};
typedef struct psa_key_policy_s psa_key_policy_t;
#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;
@ -272,7 +273,7 @@ struct psa_key_attributes_s
size_t domain_parameters_size;
};
#define PSA_KEY_ATTRIBUTES_INIT {0, 0, {0, 0}, 0, 0, NULL, 0}
#define PSA_KEY_ATTRIBUTES_INIT {0, 0, {0, 0, 0}, 0, 0, NULL, 0}
static inline struct psa_key_attributes_s psa_key_attributes_init( void )
{
const struct psa_key_attributes_s v = PSA_KEY_ATTRIBUTES_INIT;

40
library/psa_crypto.c
View file

@ -786,6 +786,25 @@ 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.
@ -793,20 +812,8 @@ 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.
@ -827,10 +834,15 @@ 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 );
}

8
tests/suites/test_suite_psa_crypto.data
View file

@ -516,6 +516,14 @@ PSA key policy: raw agreement, key only permits a KDF
depends_on:MBEDTLS_PK_PARSE_C:MBEDTLS_ECP_C:MBEDTLS_ECP_DP_SECP256R1_ENABLED:MBEDTLS_ECDH_C
raw_agreement_key_policy:PSA_KEY_USAGE_DERIVE:PSA_ALG_ECDH:PSA_KEY_TYPE_ECC_KEY_PAIR(PSA_ECC_CURVE_SECP256R1):"49c9a8c18c4b885638c431cf1df1c994131609b580d4fd43a0cab17db2f13eee":PSA_ALG_KEY_AGREEMENT(PSA_ALG_ECDH, PSA_ALG_HKDF(PSA_ALG_SHA_256))
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_KEY_PAIR(PSA_ECC_CURVE_SECP256R1):"49c9a8c18c4b885638c431cf1df1c994131609b580d4fd43a0cab17db2f13eee":PSA_KEY_USAGE_DERIVE | PSA_KEY_USAGE_SIGN | PSA_KEY_USAGE_VERIFY:PSA_ALG_ECDH:PSA_ALG_ECDSA_ANY
Copy key: raw, 0 bytes
copy_success:PSA_KEY_USAGE_COPY:0:PSA_KEY_TYPE_RAW_DATA:"":1:-1:-1:PSA_KEY_USAGE_COPY:0

37
tests/suites/test_suite_psa_crypto.function
View file

@ -1912,6 +1912,43 @@ 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_attributes_t attributes = PSA_KEY_ATTRIBUTES_INIT;
psa_key_attributes_t got_attributes = PSA_KEY_ATTRIBUTES_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_set_key_usage_flags( &attributes, usage );
psa_set_key_algorithm( &attributes, alg );
psa_set_key_enrollment_algorithm( &attributes, alg2 );
psa_set_key_type( &attributes, key_type );
PSA_ASSERT( psa_import_key( &attributes, key_data->x, key_data->len,
&handle ) );
PSA_ASSERT( psa_get_key_attributes( handle, &got_attributes ) );
TEST_EQUAL( psa_get_key_usage_flags( &got_attributes ), usage );
TEST_EQUAL( psa_get_key_algorithm( &got_attributes ), alg );
TEST_EQUAL( psa_get_key_enrollment_algorithm( &got_attributes ), 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 raw_agreement_key_policy( int policy_usage,
int policy_alg,