static int32_t hmacFinal()

in source/sigv4.c [2456:2522]
47 lines of code
6 McCabe index (conditional complexity)

static int32_t hmacFinal( HmacContext_t * pHmacContext,
                          char * pMac,
                          size_t macLen )
{
    int32_t returnStatus = -1;
    uint8_t innerHashDigest[ SIGV4_HASH_MAX_DIGEST_LENGTH ];
    size_t i = 0U;
    const SigV4CryptoInterface_t * pCryptoInterface = NULL;

    assert( pHmacContext != NULL );
    assert( pHmacContext->key != NULL );
    assert( pHmacContext->pCryptoInterface != NULL );
    /* Note that we must have a block-sized derived key before calling this function. */
    assert( pHmacContext->pCryptoInterface->hashInit != NULL );
    assert( pHmacContext->pCryptoInterface->hashUpdate != NULL );
    assert( pHmacContext->pCryptoInterface->hashFinal != NULL );

    pCryptoInterface = pHmacContext->pCryptoInterface;

    /* Write the inner hash. */
    returnStatus = pCryptoInterface->hashFinal( pCryptoInterface->pHashContext,
                                                innerHashDigest,
                                                pCryptoInterface->hashDigestLen );

    if( returnStatus == 0 )
    {
        /* Create the outer-padded key by retrieving the original key from
         * the inner-padded key (by XORing with ipad byte) and then XOR with opad
         * to generate the outer-padded key. As XOR is associative, one way to do
         * this is by performing XOR on each byte of the inner-padded key (ipad ^ opad).  */
        for( i = 0U; i < pCryptoInterface->hashBlockLen; i++ )
        {
            pHmacContext->key[ i ] ^= HMAX_IPAD_XOR_OPAD_BYTE;
        }

        returnStatus = pCryptoInterface->hashInit( pCryptoInterface->pHashContext );
    }

    if( returnStatus == 0 )
    {
        /* Update hash using the outer-padded key. */
        returnStatus = pCryptoInterface->hashUpdate( pCryptoInterface->pHashContext,
                                                     pHmacContext->key,
                                                     pCryptoInterface->hashBlockLen );
    }

    if( returnStatus == 0 )
    {
        /* Update hash using the inner digest. */
        returnStatus = pCryptoInterface->hashUpdate( pCryptoInterface->pHashContext,
                                                     innerHashDigest,
                                                     pCryptoInterface->hashDigestLen );
    }

    if( returnStatus == 0 )
    {
        /* Write the final HMAC value. */
        returnStatus = pCryptoInterface->hashFinal( pCryptoInterface->pHashContext,
                                                    ( uint8_t * ) pMac,
                                                    macLen );
    }

    /* Reset the HMAC context. */
    pHmacContext->keyLen = 0U;

    return returnStatus;
}