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psa_export_key: Always set a valid data length

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Make psa_export_key() always set a valid data_length when exporting,
even when there are errors. This makes the API easier to use for buggy
programs (like our test code).

Our test code previously used exported_length uninitialized when
checking to see that the buffer returned was all zero in import_export()
in the case where an error was returned from psa_export_key().
Initialize exported_length to an invalid length, and check that it gets
set properly by psa_export_key(), to avoid this using export_length
uninitialized. Note that the mem_is_zero() check is still valid when
psa_export_key() returns an error, e.g. where exported_length is 0, as
we want to check that nothing was written to the buffer on error.

Out test code also previous passed NULL for the data_length parameter of
psa_export_key() when it expected a failure (in key_policy_fail()).
However, data_length is not allowed to be NULL, especially now that we
write to data_length from psa_export_key() even when there are errors.
Update the test code to not pass in a NULL data_length.
This commit is contained in:
Jaeden Amero 2018-06-27 17:20:43 +01:00 committed by itayzafrir
parent 74e2cd088c
commit f24c7f80a0
2 changed files with 19 additions and 2 deletions
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6
library/psa_crypto.c
View file

@ -636,6 +636,12 @@ static psa_status_t psa_internal_export_key( psa_key_slot_t key,
{
key_slot_t *slot;
/* Set the key to empty now, so that even when there are errors, we always
* set data_length to a value between 0 and data_size. On error, setting
* the key to empty is a good choice because an empty key representation is
* unlikely to be accepted anywhere. */
*data_length = 0;
if( key == 0 || key > PSA_KEY_SLOT_COUNT )
return( PSA_ERROR_EMPTY_SLOT );
slot = &global_data.key_slots[key];

15
tests/suites/test_suite_psa_crypto.function
View file

@ -8,6 +8,9 @@
#define PSA_CRYPTO_TEST_SIZE_T_RANGE( x ) 1
#endif
/** An invalid export length that will never be set by psa_export_key(). */
static const size_t INVALID_EXPORT_LENGTH = ~0U;
/** Test if a buffer is not all-bits zero.
*
* \param buffer Pointer to the beginning of the buffer.
@ -320,7 +323,7 @@ void import_export( data_t *data,
unsigned char *exported = NULL;
unsigned char *reexported = NULL;
size_t export_size;
size_t exported_length;
size_t exported_length = INVALID_EXPORT_LENGTH;
size_t reexported_length;
psa_key_type_t got_type;
size_t got_bits;
@ -358,6 +361,13 @@ void import_export( data_t *data,
exported, export_size,
&exported_length );
TEST_ASSERT( status == expected_export_status );
/* The exported length must be set by psa_export_key() to a value between 0
* and export_size. On errors, the exported length must be 0. */
TEST_ASSERT( exported_length != INVALID_EXPORT_LENGTH );
TEST_ASSERT( status == PSA_SUCCESS || exported_length == 0 );
TEST_ASSERT( exported_length <= export_size );
TEST_ASSERT( mem_is_zero( exported + exported_length,
export_size - exported_length ) );
if( status != PSA_SUCCESS )
@ -536,13 +546,14 @@ void key_policy_fail( int usage_arg, int alg_arg, int expected_status,
if( usage & PSA_KEY_USAGE_SIGN )
{
size_t data_length;
TEST_ASSERT( keypair != NULL );
TEST_ASSERT( PSA_CRYPTO_TEST_SIZE_T_RANGE( keypair->len ) );
TEST_ASSERT( psa_import_key( key_slot,
PSA_KEY_TYPE_RSA_KEYPAIR,
keypair->x,
keypair->len ) == PSA_SUCCESS );
actual_status = psa_export_key( key_slot, NULL, 0, NULL );
actual_status = psa_export_key( key_slot, NULL, 0, &data_length );
}
TEST_ASSERT( actual_status == expected_status );