Secure element keys: save the key size #191
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This commit blindingly copies the size from the attributes. This is not correct for copy and import.
Add a parameter to the key import method of a secure element driver to make it report the key size in bits. This is necessary (otherwise the core has no idea what the bit-size is), and making import report it is easier than adding a separate method (for other key creation methods, this information is an input, not an output).
For a key in a secure element, save the bit size alongside the slot number. This is a quick-and-dirty implementation where the storage format depends on sizeof(size_t), which is fragile. This should be replaced by a more robust implementation before going into production.
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This was referenced Jul 31, 2019
yanesca
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Aug 2, 2019
k-stachowiak
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Aug 5, 2019
| @@ -1035,6 +1035,11 @@ psa_status_t psa_destroy_key( psa_key_handle_t handle ) | |||
| /* Return the size of the key in the given slot, in bits. */ | |||
| static size_t psa_get_key_slot_bits( const psa_key_slot_t *slot ) | |||
| { | |||
| #if defined(MBEDTLS_PSA_CRYPTO_SE_C) | |||
| if( psa_get_se_driver( slot->lifetime, NULL, NULL ) ) | |||
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nitpick: For the sake of consistency, this could be tested for equality explicitly.
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This function returns a boolean with the type int (since we're still not using stdbool). Mbed TLS usually (but not fully consistently) uses explicit comparison to 0 even for booleans, but PSA crypto code doesn't.
| @@ -445,6 +480,9 @@ void key_creation_import_export( int min_slot, int restart ) | |||
| /* Test that the key was created in the expected slot. */ | |||
| TEST_ASSERT( ram_slots[min_slot].type == PSA_KEY_TYPE_RAW_DATA ); | |||
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| /* Test the key attributes and the key data. */ | |||
| if( ! check_key_attributes( handle, &attributes ) ) | |||
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Why isn't this put inside an assertion macro?
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The assertion macros are in check_key_attributes. That function returns ok/not-ok, and if it returns not-ok, the test failure data has already been recorded, so test_fail should not be called again.
k-stachowiak
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For a key in a secure element, the core has no way to compute the bit size. Store it as part of the key metadata in memory and in persistent storage. When importing a key, ask the driver what the bit size is.
Extracted from #183