class ara::crypto::cryp::WriteableKeySlot

The interface ara::crypto::cryp::WriteableKeySlot serves in AUTOSAR Adaptive as a writable abstraction for key storage locations in a crypto provider. Instances can neither be copied nor moved ([SWS_CRYPT_50170], [SWS_CRYPT_50168]), but are instead referenced via the smart pointer type Sptr [SWS_CRYPT_50172]. Via the thread-safe method Clear(), the content of the key slot is cleared, with rollback semantics taking effect in error cases such as kBusyResource or kUnsupported [SWS_CRYPT_30405].

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Context

The interface ara::crypto::cryp::WriteableKeySlot defines a writable storage location for cryptographic keys within the AUTOSAR Adaptive Platform in the context of a crypto provider. It directly derives from the base interface KeySlot and represents a standardized abstraction to selectively clear managed key slots and control their lifecycle. Applications of the crypto stack act as primary interaction partners as consumers, as does the concrete crypto provider, which manages the binding to physical or logical key storage. The creation of concrete instances is likely performed via higher-level factory or provider methods, since the interface functions as a purely abstract base class. Question Q-5c3b13bb35c3ff53 (open)

Lifecycle

The resource and ownership model of ara::crypto::cryp::WriteableKeySlot strictly prevents duplicating key references via value semantics. For this purpose, both the copy constructor [SWS_CRYPT_50170] and the move constructor [SWS_CRYPT_50171] are explicitly deleted (=delete). Likewise, the deleted declarations of the copy assignment operator [SWS_CRYPT_50168] and the move assignment operator [SWS_CRYPT_50169] prevent any subsequent assignment.

Referential passing and shared management are instead handled via the defined smart pointer type alias Sptr, which is instantiated as std::shared_ptr<WriteableKeySlot> [SWS_CRYPT_50172]. Destruction of the instance is safeguarded by a virtual default destructor that is specified as exception-safe (exception safe) and emits no exceptions (noexcept=default) [SWS_CRYPT_50167]. This allows safe polymorphic deallocation via pointers to the interface. In terms of state, a slot can be occupied or empty. Occupying the slot is likely performed via separate interfaces of the crypto provider, whereas clearing is realized via the thread-safe method Clear() [SWS_CRYPT_30405]. Question Q-72dfcb17eb3e2d25 (open)

State diagram: State transitions of the key content through Clear() and error handling. Sources: [SWS_CRYPT_30405]

Usage Path

The central usage path focuses on the controlled resetting or clearing of stored key material:

• Referencing: The caller accesses the instance via a shared pointer of type WriteableKeySlot::Sptr [SWS_CRYPT_50172].
• Clear call: Calling the pure virtual method Clear() triggers the clearing process for the current content of the key slot [SWS_CRYPT_30405]. Because the method is thread-safe, the call can also be made in concurrent contexts [SWS_CRYPT_30405].
• Result verification: The operation returns an ara::core::Result<void> [SWS_CRYPT_30405]. If the key slot was already empty beforehand or the content was removed without error, the result represents a successful state with an empty value [SWS_CRYPT_30405].

Error Scenarios

The method Clear() is declared exception-safe and noexcept; error situations are transported via ara::core::Result according to the error model of AUTOSAR Adaptive [SWS_CRYPT_30405]. Possible error codes comprise:

• ara::crypto::CryptoErrc::kUnsupported: Occurs if the concrete manifestation of the key slot does not support clearing [SWS_CRYPT_30405]. For this case, the interface guarantees rollback semantics so that the state remains unchanged [SWS_CRYPT_30405].
• ara::crypto::CryptoErrc::kBusyResource: Returned if the clear operation cannot be performed temporarily [SWS_CRYPT_30405]. This is likely typically caused by concurrent accesses to hardware-bound storage resources. Question (open) Here as well, rollback semantics ensure that no partial changes remain [SWS_CRYPT_30405].