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Reuse PSA_MAC_LENGTH in psa_get_mac_output_length

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Avoid code duplication. Also update the guarantees made by the function
doc to match the guarantees given by PSA_MAC_LENGTH.

Signed-off-by: Steven Cooreman <steven.cooreman@silabs.com>
This commit is contained in:
Steven Cooreman 2021-03-02 21:29:45 +01:00
parent 5a17267442
commit 7d4b0d778f
1 changed files with 18 additions and 28 deletions
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46
library/psa_crypto.c
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@ -547,7 +547,7 @@ static inline size_t psa_get_key_slot_bits( const psa_key_slot_t *slot )
/** Return the output MAC length of a MAC algorithm, in bytes /** Return the output MAC length of a MAC algorithm, in bytes
* *
* \param[in] algorithm The specific MAC algorithm * \param[in] algorithm The specific (non-wildcard) MAC algorithm.
* \param[in] key_type The key type of the key to be used with the * \param[in] key_type The key type of the key to be used with the
* \p algorithm. * \p algorithm.
* \param[out] length The calculated output length of the given MAC * \param[out] length The calculated output length of the given MAC
@ -556,41 +556,31 @@ static inline size_t psa_get_key_slot_bits( const psa_key_slot_t *slot )
* *
* \retval #PSA_SUCCESS * \retval #PSA_SUCCESS
* The \p length has been successfully calculated * The \p length has been successfully calculated
* \retval #PSA_ERROR_NOT_SUPPORTED
* \p algorithm is a MAC algorithm, but ubsupported by this PSA core.
* \retval #PSA_ERROR_INVALID_ARGUMENT * \retval #PSA_ERROR_INVALID_ARGUMENT
* \p algorithm is not a valid, specific MAC algorithm or \p key_type * \p algorithm is not a valid, specific MAC algorithm recognized and
* describes a key incompatible with the specified \p algorithm. * supported by this core, or \p key_type describes a key which is
* inconsistent with the specified \p algorithm.
* \retval #PSA_ERROR_INVALID_ARGUMENT
* \p algorithm tries to truncate the MAC to a size which would be
* larger than the underlying algorithm's maximum output length.
*/ */
static psa_status_t psa_get_mac_output_length( psa_algorithm_t algorithm, static psa_status_t psa_get_mac_output_length( psa_algorithm_t algorithm,
psa_key_type_t key_type, psa_key_type_t key_type,
size_t *length ) size_t *length )
{ {
if( !PSA_ALG_IS_MAC( algorithm ) || PSA_ALG_IS_WILDCARD( algorithm ) ) /* Get the default length for the algorithm and key combination. None of the
* currently supported algorithms have a default output length dependent on
* key size, so setting it to a bogus value is OK. */
size_t default_length = PSA_MAC_LENGTH( key_type, 0,
PSA_ALG_FULL_LENGTH_MAC( algorithm ) );
/* PSA_MAC_LENGTH, when called on a full-length algorithm identifier, can
* currently return either 0 (unknown algorithm) or 1 (cipher-MAC with
* stream cipher) in cases where the key type / algorithm combination would
* be invalid. */
if( default_length == 0 || default_length == 1 )
return( PSA_ERROR_INVALID_ARGUMENT ); return( PSA_ERROR_INVALID_ARGUMENT );
size_t default_length = 0;
if( PSA_ALG_FULL_LENGTH_MAC( algorithm ) == PSA_ALG_CMAC ||
PSA_ALG_FULL_LENGTH_MAC( algorithm ) == PSA_ALG_CBC_MAC )
{
default_length = PSA_BLOCK_CIPHER_BLOCK_LENGTH( key_type );
/* CMAC and CBC-MAC are only defined on block ciphers */
if( default_length == 0 )
return( PSA_ERROR_INVALID_ARGUMENT );
}
else if( PSA_ALG_IS_HMAC( algorithm ) )
{
/* HMAC output length is dictated by the underlying hash operation */
psa_algorithm_t hash_alg = PSA_ALG_HMAC_GET_HASH( algorithm );
default_length = PSA_HASH_LENGTH( hash_alg );
if( hash_alg == 0 || default_length == 0 )
return( PSA_ERROR_INVALID_ARGUMENT );
}
else
return( PSA_ERROR_NOT_SUPPORTED );
/* Output the expected (potentially truncated) length as long as it can /* Output the expected (potentially truncated) length as long as it can
* actually be output by the algorithm */ * actually be output by the algorithm */
if( PSA_ALG_FULL_LENGTH_MAC( algorithm ) == algorithm ) if( PSA_ALG_FULL_LENGTH_MAC( algorithm ) == algorithm )