security.py 文件源码

def calculate_digest(secret, message, salt):
    """Calculate a SHA-256 HMAC digest for the given data."""
    assert isinstance(secret, bytes), "%r is not a byte string." % (secret,)
    assert isinstance(message, bytes), "%r is not byte string." % (message,)
    assert isinstance(salt, bytes), "%r is not a byte string." % (salt,)
    hmacr = HMAC(secret, digestmod=sha256)
    hmacr.update(message)
    hmacr.update(salt)
    return hmacr.digest()


# Cache the Fernet pre-shared key, since it's expensive to derive the key.
# Note: this will need to change to become a dictionary if salts are supported.