# Source code for acme.jose.jwa

    """JSON Web Algorithm.

    https://tools.ietf.org/html/draft-ietf-jose-json-web-algorithms-40

    """
    import abc
    import collections
    import logging

    import cryptography.exceptions
    from cryptography.hazmat.backends import default_backend
    from cryptography.hazmat.primitives import hashes
    from cryptography.hazmat.primitives import hmac
    from cryptography.hazmat.primitives.asymmetric import padding

    from acme.jose import errors
    from acme.jose import interfaces
    from acme.jose import jwk

    logger = logging.getLogger(__name__)

    class JWA(interfaces.JSONDeSerializable):  # pylint: disable=abstract-method
        # pylint: disable=too-few-public-methods
        # for some reason disable=abstract-method has to be on the line
        # above...
        """JSON Web Algorithm."""

    class JWASignature(JWA, collections.Hashable):
        """JSON Web Signature Algorithm."""
        SIGNATURES = {}

        def __init__(self, name):
            self.name = name

        def __eq__(self, other):
            if not isinstance(other, JWASignature):
                return NotImplemented
            return self.name == other.name

        def __hash__(self):
            return hash((self.__class__, self.name))

        def __ne__(self, other):
            return not self == other

        @classmethod
        def register(cls, signature_cls):
            """Register class for JSON deserialization."""
            cls.SIGNATURES[signature_cls.name] = signature_cls
            return signature_cls

        def to_partial_json(self):
            return self.name

        @classmethod
        def from_json(cls, jobj):
            return cls.SIGNATURES[jobj]

        @abc.abstractmethod
        def sign(self, key, msg):  # pragma: no cover
            """Sign the ``msg`` using ``key``."""
            raise NotImplementedError()

        @abc.abstractmethod
        def verify(self, key, msg, sig):  # pragma: no cover
            """Verify the ``msg` and ``sig`` using ``key``."""
            raise NotImplementedError()

        def __repr__(self):
            return self.name

    class _JWAHS(JWASignature):

        kty = jwk.JWKOct

        def __init__(self, name, hash_):
            super(_JWAHS, self).__init__(name)
            self.hash = hash_()

        def sign(self, key, msg):
            signer = hmac.HMAC(key, self.hash, backend=default_backend())
            signer.update(msg)
            return signer.finalize()

        def verify(self, key, msg, sig):
            verifier = hmac.HMAC(key, self.hash, backend=default_backend())
            verifier.update(msg)
            try:
                verifier.verify(sig)
            except cryptography.exceptions.InvalidSignature as error:
                logger.debug(error, exc_info=True)
                return False
            else:
                return True

    class _JWARSA(object):

        kty = jwk.JWKRSA
        padding = NotImplemented
        hash = NotImplemented

        def sign(self, key, msg):
            """Sign the ``msg`` using ``key``."""
            try:
                signer = key.signer(self.padding, self.hash)
            except AttributeError as error:
                logger.debug(error, exc_info=True)
                raise errors.Error("Public key cannot be used for signing")
            except ValueError as error:  # digest too large
                logger.debug(error, exc_info=True)
                raise errors.Error(str(error))
            signer.update(msg)
            try:
                return signer.finalize()
            except ValueError as error:
                logger.debug(error, exc_info=True)
                raise errors.Error(str(error))

        def verify(self, key, msg, sig):
            """Verify the ``msg` and ``sig`` using ``key``."""
            verifier = key.verifier(sig, self.padding, self.hash)
            verifier.update(msg)
            try:
                verifier.verify()
            except cryptography.exceptions.InvalidSignature as error:
                logger.debug(error, exc_info=True)
                return False
            else:
                return True

    class _JWARS(_JWARSA, JWASignature):

        def __init__(self, name, hash_):
            super(_JWARS, self).__init__(name)
            self.padding = padding.PKCS1v15()
            self.hash = hash_()

    class _JWAPS(_JWARSA, JWASignature):

        def __init__(self, name, hash_):
            super(_JWAPS, self).__init__(name)
            self.padding = padding.PSS(
                mgf=padding.MGF1(hash_()),
                salt_length=padding.PSS.MAX_LENGTH)
            self.hash = hash_()

    class _JWAES(JWASignature):  # pylint: disable=abstract-class-not-used

        # TODO: implement ES signatures

        def sign(self, key, msg):  # pragma: no cover
            raise NotImplementedError()

        def verify(self, key, msg, sig):  # pragma: no cover
            raise NotImplementedError()

    HS256 = JWASignature.register(_JWAHS('HS256', hashes.SHA256))
    HS384 = JWASignature.register(_JWAHS('HS384', hashes.SHA384))
    HS512 = JWASignature.register(_JWAHS('HS512', hashes.SHA512))

    RS256 = JWASignature.register(_JWARS('RS256', hashes.SHA256))
    RS384 = JWASignature.register(_JWARS('RS384', hashes.SHA384))
    RS512 = JWASignature.register(_JWARS('RS512', hashes.SHA512))

    PS256 = JWASignature.register(_JWAPS('PS256', hashes.SHA256))
    PS384 = JWASignature.register(_JWAPS('PS384', hashes.SHA384))
    PS512 = JWASignature.register(_JWAPS('PS512', hashes.SHA512))

    ES256 = JWASignature.register(_JWAES('ES256'))
    ES384 = JWASignature.register(_JWAES('ES384'))
    ES512 = JWASignature.register(_JWAES('ES512'))