.. _status-codes:

PSA status codes
================

Status type
-----------

.. typedef:: int32_t psa_status_t

    .. summary::
        Function return status.

    This is either `PSA_SUCCESS`, which is zero, indicating success; or a small negative value indicating that an error occurred. Errors are encoded as one of the ``PSA_ERROR_xxx`` values defined here.

Success codes
-------------

.. macro:: PSA_SUCCESS
    :definition: ((psa_status_t)0)

    .. summary::
        The action was completed successfully.

Error codes
-----------

.. macro:: PSA_ERROR_GENERIC_ERROR
    :definition: ((psa_status_t)-132)

    .. summary::
        An error occurred that does not correspond to any defined failure cause.

    Implementations can use this error code if none of the other standard error codes are applicable.

.. macro:: PSA_ERROR_NOT_SUPPORTED
    :definition: ((psa_status_t)-134)

    .. summary::
        The requested operation or a parameter is not supported by this implementation.

    It is recommended that implementations return this error code when an enumeration parameter such as a key type, algorithm, etc. is not recognized. If a combination of parameters is recognized and identified as not valid, return `PSA_ERROR_INVALID_ARGUMENT` instead.

.. macro:: PSA_ERROR_NOT_PERMITTED
    :definition: ((psa_status_t)-133)

    .. summary::
        The requested action is denied by a policy.

    It is recommended that implementations return this error code when the parameters are recognized as valid and supported, and a policy explicitly denies the requested operation.

    If a subset of the parameters of a function call identify a forbidden operation, and another subset of the parameters are not valid or not supported, it is unspecified whether the function returns `PSA_ERROR_NOT_PERMITTED`, `PSA_ERROR_NOT_SUPPORTED` or `PSA_ERROR_INVALID_ARGUMENT`.

.. macro:: PSA_ERROR_BUFFER_TOO_SMALL
    :definition: ((psa_status_t)-138)

    .. summary::
        An output buffer is too small.

    Applications can call the ``PSA_xxx_SIZE`` macro listed in the function description to determine a sufficient buffer size.

    It is recommended that implementations only return this error code in cases when performing the operation with a larger output buffer would succeed. However, implementations can also return this error if a function has invalid or unsupported parameters in addition to an insufficient output buffer size.

.. macro:: PSA_ERROR_ALREADY_EXISTS
    :definition: ((psa_status_t)-139)

    .. summary::
        Asking for an item that already exists.

    It is recommended that implementations return this error code when attempting to write to a location where a key is already present.

.. macro:: PSA_ERROR_DOES_NOT_EXIST
    :definition: ((psa_status_t)-140)

    .. summary::
        Asking for an item that doesn't exist.

    It is recommended that implementations return this error code if a requested key does not exist.

.. macro:: PSA_ERROR_BAD_STATE
    :definition: ((psa_status_t)-137)

    .. summary::
        The requested action cannot be performed in the current state.

    Multi-part operations return this error when one of the functions is called out of sequence. Refer to the function descriptions for permitted sequencing of functions.

    Implementations must not return this error code to indicate that a key either exists or not, but must instead return `PSA_ERROR_ALREADY_EXISTS` or `PSA_ERROR_DOES_NOT_EXIST` as applicable.

    Implementations must not return this error code to indicate that a key identifier is invalid, but must return `PSA_ERROR_INVALID_HANDLE` instead.

.. macro:: PSA_ERROR_INVALID_ARGUMENT
    :definition: ((psa_status_t)-135)

    .. summary::
        The parameters passed to the function are invalid.

    Implementations can return this error any time a parameter or combination of parameters are recognized as invalid.

    Implementations must not return this error code to indicate that a key identifier is invalid, but must return `PSA_ERROR_INVALID_HANDLE` instead.

.. macro:: PSA_ERROR_INSUFFICIENT_MEMORY
    :definition: ((psa_status_t)-141)

    .. summary::
        There is not enough runtime memory.

    If the action is carried out across multiple security realms, this error can refer to available memory in any of the security realms.

.. macro:: PSA_ERROR_INSUFFICIENT_STORAGE
    :definition: ((psa_status_t)-142)

    .. summary::
        There is not enough persistent storage.

    Functions that modify the key storage return this error code if there is insufficient storage space on the host media. In addition, many functions that do not otherwise access storage might return this error code if the implementation requires a mandatory log entry for the requested action and the log storage space is full.

.. macro:: PSA_ERROR_COMMUNICATION_FAILURE
    :definition: ((psa_status_t)-145)

    .. summary::
        There was a communication failure inside the implementation.

    This can indicate a communication failure between the application and an external cryptoprocessor or between the cryptoprocessor and an external volatile or persistent memory. A communication failure can be transient or permanent depending on the cause.

    .. warning::
        If a function returns this error, it is undetermined whether the requested action has completed. Returning `PSA_SUCCESS` is recommended on successful completion whenever possible, however functions can return `PSA_ERROR_COMMUNICATION_FAILURE` if the requested action was completed successfully in an external cryptoprocessor but there was a breakdown of communication before the cryptoprocessor could report the status to the application.

.. macro:: PSA_ERROR_STORAGE_FAILURE
    :definition: ((psa_status_t)-146)

    .. summary::
        There was a storage failure that might have led to data loss.

    This error indicates that some persistent storage could not be read or written by the implementation. It does not indicate the following situations, which have specific error codes:

    * A corruption of volatile memory - use `PSA_ERROR_CORRUPTION_DETECTED`.
    * A communication error between the cryptoprocessor and its external storage - use `PSA_ERROR_COMMUNICATION_FAILURE`.
    * When the storage is in a valid state but is full - use `PSA_ERROR_INSUFFICIENT_STORAGE`.
    * When the storage or stored data is corrupted - use `PSA_ERROR_DATA_CORRUPT`.
    * When the stored data is not valid - use `PSA_ERROR_DATA_INVALID`.

    A storage failure does not indicate that any data that was previously read is invalid. However this previously read data might no longer be readable from storage.

    When a storage failure occurs, it is no longer possible to ensure the global integrity of the keystore. Depending on the global integrity guarantees offered by the implementation, access to other data might fail even if the data is still readable but its integrity cannot be guaranteed.

    It is recommended to only use this error code to report a permanent storage corruption. However application writers must keep in mind that transient errors while reading the storage might be reported using this error code.

.. macro:: PSA_ERROR_DATA_CORRUPT
    :definition: ((psa_status_t)-152)

    .. summary::
        Stored data has been corrupted.

    This error indicates that some persistent storage has suffered corruption.  It does not indicate the following situations, which have specific error codes:

    * A corruption of volatile memory - use `PSA_ERROR_CORRUPTION_DETECTED`.
    * A communication error between the cryptoprocessor and its external storage - use `PSA_ERROR_COMMUNICATION_FAILURE`.
    * When the storage is in a valid state but is full - use `PSA_ERROR_INSUFFICIENT_STORAGE`.
    * When the storage fails for other reasons - use `PSA_ERROR_STORAGE_FAILURE`.
    * When the stored data is not valid - use `PSA_ERROR_DATA_INVALID`.

    Note that a storage corruption does not indicate that any data that was previously read is invalid. However this previously read data might no longer be readable from storage.

    When a storage failure occurs, it is no longer possible to ensure the global integrity of the keystore. Depending on the global integrity guarantees offered by the implementation, access to other data might fail even if the data is still readable but its integrity cannot be guaranteed.

    It is recommended to only use this error code to report when a storage component indicates that the stored data is corrupt, or fails an integrity check. For example, in situations that the PSA Internal Trusted Storage API reports `PSA_ERROR_DATA_CORRUPT` or `PSA_ERROR_INVALID_SIGNATURE`.

.. macro:: PSA_ERROR_DATA_INVALID
    :definition: ((psa_status_t)-153)

    .. summary::
        Data read from storage is not valid for the implementation.

    This error indicates that some data read from storage does not have a valid format. It does not indicate the following situations, which have specific error codes:

    * When the storage or stored data is corrupted - use `PSA_ERROR_DATA_CORRUPT`.
    * When the storage fails for other reasons - use `PSA_ERROR_STORAGE_FAILURE`.
    * An invalid argument to the API - use `PSA_ERROR_INVALID_ARGUMENT`.

    This error is typically a result of an integration failure, where the implementation reading the data is not compatible with the implementation that stored the data.

    It is recommended to only use this error code to report when data that is successfully read from storage is invalid.

.. macro:: PSA_ERROR_HARDWARE_FAILURE
    :definition: ((psa_status_t)-147)

    .. summary::
        A hardware failure was detected.

    A hardware failure can be transient or permanent depending on the cause.

.. macro:: PSA_ERROR_CORRUPTION_DETECTED
    :definition: ((psa_status_t)-151)

    .. summary::
        A tampering attempt was detected.

    If an application receives this error code, there is no guarantee that previously accessed or computed data was correct and remains confidential. In this situation, it is recommended that applications perform no further security functions and enter a safe failure state.

    Implementations can return this error code if they detect an invalid state that cannot happen during normal operation and that indicates that the implementation's security guarantees no longer hold. Depending on the implementation architecture and on its security and safety goals, the implementation might forcibly terminate the application.

    This error code is intended as a last resort when a security breach is detected and it is unsure whether the keystore data is still protected. Implementations must only return this error code to report an alarm from a tampering detector, to indicate that the confidentiality of stored data can no longer be guaranteed, or to indicate that the integrity of previously returned data is now considered compromised. Implementations must not use this error code to indicate a hardware failure that merely makes it impossible to perform the requested operation, instead use `PSA_ERROR_COMMUNICATION_FAILURE`, `PSA_ERROR_STORAGE_FAILURE`, `PSA_ERROR_HARDWARE_FAILURE`, `PSA_ERROR_INSUFFICIENT_ENTROPY` or other applicable error code.

    This error indicates an attack against the application. Implementations must not return this error code as a consequence of the behavior of the application itself.

.. macro:: PSA_ERROR_INSUFFICIENT_ENTROPY
    :definition: ((psa_status_t)-148)

    .. summary::
        There is not enough entropy to generate random data needed for the requested action.

    This error indicates a failure of a hardware random generator. Application writers must note that this error can be returned not only by functions whose purpose is to generate random data, such as key, IV or nonce generation, but also by functions that execute an algorithm with a randomized result, as well as functions that use randomization of intermediate computations as a countermeasure to certain attacks.

    It is recommended that implementations do not return this error after `psa_crypto_init()` has succeeded. This can be achieved if the implementation generates sufficient entropy during initialization and subsequently a cryptographically secure pseudorandom generator (PRNG) is used. However, implementations might return this error at any time, for example, if a policy requires the PRNG to be reseeded during normal operation.

.. macro:: PSA_ERROR_INVALID_SIGNATURE
    :definition: ((psa_status_t)-149)

    .. summary::
        The signature, MAC or hash is incorrect.

    Verification functions return this error if the verification calculations completed successfully, and the value to be verified was determined to be incorrect.

    If the value to verify has an invalid size, implementations can return either `PSA_ERROR_INVALID_ARGUMENT` or `PSA_ERROR_INVALID_SIGNATURE`.

.. macro:: PSA_ERROR_INVALID_PADDING
    :definition: ((psa_status_t)-150)

    .. summary::
        The decrypted padding is incorrect.

    .. warning::
        In some protocols, when decrypting data, it is essential that the behavior of the application does not depend on whether the padding is correct, down to precise timing. Protocols that use authenticated encryption are recommended for use by applications, rather than plain encryption. If the application must perform a decryption of unauthenticated data, the application writer must take care not to reveal whether the padding is invalid.

    Implementations must handle padding carefully, aiming to make it impossible for an external observer to distinguish between valid and invalid padding. In particular, it is recommended that the timing of a decryption operation does not depend on the validity of the padding.

.. macro:: PSA_ERROR_INSUFFICIENT_DATA
    :definition: ((psa_status_t)-143)

    .. summary::
        Return this error when there's insufficient data when attempting to read from a resource.

.. macro:: PSA_ERROR_INVALID_HANDLE
    :definition: ((psa_status_t)-136)

    .. summary::
        The key identifier is not valid.

    See also :title:`key-ids`.
