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Filename : jws.py
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"""JSON Web Signature."""
import argparse
import base64
import sys

import OpenSSL

from josepy import b64, errors, json_util, jwa, jwk, util


class MediaType:
    """MediaType field encoder/decoder."""

    PREFIX = 'application/'
    """MIME Media Type and Content Type prefix."""

    @classmethod
    def decode(cls, value):
        """Decoder."""
        # 4.1.10
        if '/' not in value:
            if ';' in value:
                raise errors.DeserializationError('Unexpected semi-colon')
            return cls.PREFIX + value
        return value

    @classmethod
    def encode(cls, value):
        """Encoder."""
        # 4.1.10
        if ';' not in value:
            assert value.startswith(cls.PREFIX)
            return value[len(cls.PREFIX):]
        return value


class Header(json_util.JSONObjectWithFields):
    """JOSE Header.

    .. warning:: This class supports **only** Registered Header
        Parameter Names (as defined in section 4.1 of the
        protocol). If you need Public Header Parameter Names (4.2)
        or Private Header Parameter Names (4.3), you must subclass
        and override :meth:`from_json` and :meth:`to_partial_json`
        appropriately.

    .. warning:: This class does not support any extensions through
        the "crit" (Critical) Header Parameter (4.1.11) and as a
        conforming implementation, :meth:`from_json` treats its
        occurrence as an error. Please subclass if you seek for
        a different behaviour.

    :ivar x5tS256: "x5t#S256"
    :ivar str typ: MIME Media Type, inc. :const:`MediaType.PREFIX`.
    :ivar str cty: Content-Type, inc. :const:`MediaType.PREFIX`.

    """
    alg = json_util.Field(
        'alg', decoder=jwa.JWASignature.from_json, omitempty=True)
    jku = json_util.Field('jku', omitempty=True)
    jwk = json_util.Field('jwk', decoder=jwk.JWK.from_json, omitempty=True)
    kid = json_util.Field('kid', omitempty=True)
    x5u = json_util.Field('x5u', omitempty=True)
    x5c = json_util.Field('x5c', omitempty=True, default=())
    x5t = json_util.Field(
        'x5t', decoder=json_util.decode_b64jose, omitempty=True)
    x5tS256 = json_util.Field(
        'x5t#S256', decoder=json_util.decode_b64jose, omitempty=True)
    typ = json_util.Field('typ', encoder=MediaType.encode,
                          decoder=MediaType.decode, omitempty=True)
    cty = json_util.Field('cty', encoder=MediaType.encode,
                          decoder=MediaType.decode, omitempty=True)
    crit = json_util.Field('crit', omitempty=True, default=())

    def not_omitted(self):
        """Fields that would not be omitted in the JSON object."""
        return {name: getattr(self, name)
                for name, field in self._fields.items()
                if not field.omit(getattr(self, name))}

    def __add__(self, other):
        if not isinstance(other, type(self)):
            raise TypeError('Header cannot be added to: {0}'.format(
                type(other)))

        not_omitted_self = self.not_omitted()
        not_omitted_other = other.not_omitted()

        if set(not_omitted_self).intersection(not_omitted_other):
            raise TypeError('Addition of overlapping headers not defined')

        not_omitted_self.update(not_omitted_other)
        return type(self)(**not_omitted_self)  # pylint: disable=star-args

    def find_key(self):
        """Find key based on header.

        .. todo:: Supports only "jwk" header parameter lookup.

        :returns: (Public) key found in the header.
        :rtype: .JWK

        :raises josepy.errors.Error: if key could not be found

        """
        if self.jwk is None:
            raise errors.Error('No key found')
        return self.jwk

    @crit.decoder  # type: ignore
    def crit(unused_value):
        # pylint: disable=missing-docstring,no-self-argument,no-self-use
        raise errors.DeserializationError(
            '"crit" is not supported, please subclass')

    # x5c does NOT use JOSE Base64 (4.1.6)

    @x5c.encoder  # type: ignore
    def x5c(value):  # pylint: disable=missing-docstring,no-self-argument
        return [base64.b64encode(OpenSSL.crypto.dump_certificate(
            OpenSSL.crypto.FILETYPE_ASN1, cert.wrapped)) for cert in value]

    @x5c.decoder  # type: ignore
    def x5c(value):  # pylint: disable=missing-docstring,no-self-argument
        try:
            return tuple(util.ComparableX509(OpenSSL.crypto.load_certificate(
                OpenSSL.crypto.FILETYPE_ASN1,
                base64.b64decode(cert))) for cert in value)
        except OpenSSL.crypto.Error as error:
            raise errors.DeserializationError(error)


class Signature(json_util.JSONObjectWithFields):
    """JWS Signature.

    :ivar combined: Combined Header (protected and unprotected,
        :class:`Header`).
    :ivar unicode protected: JWS protected header (Jose Base-64 decoded).
    :ivar header: JWS Unprotected Header (:class:`Header`).
    :ivar str signature: The signature.

    """
    header_cls = Header

    __slots__ = ('combined',)
    protected = json_util.Field('protected', omitempty=True, default='')
    header = json_util.Field(
        'header', omitempty=True, default=header_cls(),
        decoder=header_cls.from_json)
    signature = json_util.Field(
        'signature', decoder=json_util.decode_b64jose,
        encoder=json_util.encode_b64jose)

    @protected.encoder  # type: ignore
    def protected(value):  # pylint: disable=missing-docstring,no-self-argument
        # wrong type guess (Signature, not bytes) | pylint: disable=no-member
        return json_util.encode_b64jose(value.encode('utf-8'))

    @protected.decoder  # type: ignore
    def protected(value):  # pylint: disable=missing-docstring,no-self-argument
        return json_util.decode_b64jose(value).decode('utf-8')

    def __init__(self, **kwargs):
        if 'combined' not in kwargs:
            kwargs = self._with_combined(kwargs)
        super().__init__(**kwargs)
        assert self.combined.alg is not None

    @classmethod
    def _with_combined(cls, kwargs):
        assert 'combined' not in kwargs
        header = kwargs.get('header', cls._fields['header'].default)
        protected = kwargs.get('protected', cls._fields['protected'].default)

        if protected:
            combined = header + cls.header_cls.json_loads(protected)
        else:
            combined = header

        kwargs['combined'] = combined
        return kwargs

    @classmethod
    def _msg(cls, protected, payload):
        return (b64.b64encode(protected.encode('utf-8')) + b'.' +
                b64.b64encode(payload))

    def verify(self, payload, key=None):
        """Verify.

        :param JWK key: Key used for verification.

        """
        key = self.combined.find_key() if key is None else key
        return self.combined.alg.verify(
            key=key.key, sig=self.signature,
            msg=self._msg(self.protected, payload))

    @classmethod
    def sign(cls, payload, key, alg, include_jwk=True,
             protect=frozenset(), **kwargs):
        """Sign.

        :param JWK key: Key for signature.

        """
        assert isinstance(key, alg.kty)

        header_params = kwargs
        header_params['alg'] = alg
        if include_jwk:
            header_params['jwk'] = key.public_key()

        assert set(header_params).issubset(cls.header_cls._fields)
        assert protect.issubset(cls.header_cls._fields)

        protected_params = {}
        for header in protect:
            if header in header_params:
                protected_params[header] = header_params.pop(header)
        if protected_params:
            # pylint: disable=star-args
            protected = cls.header_cls(**protected_params).json_dumps()
        else:
            protected = ''

        header = cls.header_cls(**header_params)  # pylint: disable=star-args
        signature = alg.sign(key.key, cls._msg(protected, payload))

        return cls(protected=protected, header=header, signature=signature)

    def fields_to_partial_json(self):
        fields = super().fields_to_partial_json()
        if not fields['header'].not_omitted():
            del fields['header']
        return fields

    @classmethod
    def fields_from_json(cls, jobj):
        fields = super().fields_from_json(jobj)
        fields_with_combined = cls._with_combined(fields)
        if 'alg' not in fields_with_combined['combined'].not_omitted():
            raise errors.DeserializationError('alg not present')
        return fields_with_combined


class JWS(json_util.JSONObjectWithFields):
    """JSON Web Signature.

    :ivar str payload: JWS Payload.
    :ivar str signature: JWS Signatures.

    """
    __slots__ = ('payload', 'signatures')

    signature_cls = Signature

    def verify(self, key=None):
        """Verify."""
        return all(sig.verify(self.payload, key) for sig in self.signatures)

    @classmethod
    def sign(cls, payload, **kwargs):
        """Sign."""
        return cls(payload=payload, signatures=(
            cls.signature_cls.sign(payload=payload, **kwargs),))

    @property
    def signature(self):
        """Get a singleton signature.

        :rtype: :class:`JWS.signature_cls`

        """
        assert len(self.signatures) == 1
        return self.signatures[0]

    def to_compact(self):
        """Compact serialization.

        :rtype: bytes

        """
        assert len(self.signatures) == 1

        assert 'alg' not in self.signature.header.not_omitted()
        # ... it must be in protected

        return (
            b64.b64encode(self.signature.protected.encode('utf-8')) +
            b'.' +
            b64.b64encode(self.payload) +
            b'.' +
            b64.b64encode(self.signature.signature))

    @classmethod
    def from_compact(cls, compact):
        """Compact deserialization.

        :param bytes compact:

        """
        try:
            protected, payload, signature = compact.split(b'.')
        except ValueError:
            raise errors.DeserializationError(
                'Compact JWS serialization should comprise of exactly'
                ' 3 dot-separated components')

        sig = cls.signature_cls(
            protected=b64.b64decode(protected).decode('utf-8'),
            signature=b64.b64decode(signature))
        return cls(payload=b64.b64decode(payload), signatures=(sig,))

    def to_partial_json(self, flat=True):  # pylint: disable=arguments-differ
        assert self.signatures
        payload = json_util.encode_b64jose(self.payload)

        if flat and len(self.signatures) == 1:
            ret = self.signatures[0].to_partial_json()
            ret['payload'] = payload
            return ret
        else:
            return {
                'payload': payload,
                'signatures': self.signatures,
            }

    @classmethod
    def from_json(cls, jobj):
        if 'signature' in jobj and 'signatures' in jobj:
            raise errors.DeserializationError('Flat mixed with non-flat')
        elif 'signature' in jobj:  # flat
            return cls(payload=json_util.decode_b64jose(jobj.pop('payload')),
                       signatures=(cls.signature_cls.from_json(jobj),))
        else:
            return cls(payload=json_util.decode_b64jose(jobj['payload']),
                       signatures=tuple(cls.signature_cls.from_json(sig)
                                        for sig in jobj['signatures']))


class CLI:
    """JWS CLI."""

    @classmethod
    def sign(cls, args):
        """Sign."""
        key = args.alg.kty.load(args.key.read())
        args.key.close()
        if args.protect is None:
            args.protect = []
        if args.compact:
            args.protect.append('alg')

        sig = JWS.sign(payload=sys.stdin.read().encode(), key=key, alg=args.alg,
                       protect=set(args.protect))

        if args.compact:
            print(sig.to_compact().decode('utf-8'))
        else:  # JSON
            print(sig.json_dumps_pretty())

    @classmethod
    def verify(cls, args):
        """Verify."""
        if args.compact:
            sig = JWS.from_compact(sys.stdin.read().encode())
        else:  # JSON
            try:
                sig = JWS.json_loads(sys.stdin.read())
            except errors.Error as error:
                print(error)
                return -1

        if args.key is not None:
            assert args.kty is not None
            key = args.kty.load(args.key.read()).public_key()
            args.key.close()
        else:
            key = None

        sys.stdout.write(sig.payload)
        return not sig.verify(key=key)

    @classmethod
    def _alg_type(cls, arg):
        return jwa.JWASignature.from_json(arg)

    @classmethod
    def _header_type(cls, arg):
        assert arg in Signature.header_cls._fields
        return arg

    @classmethod
    def _kty_type(cls, arg):
        assert arg in jwk.JWK.TYPES
        return jwk.JWK.TYPES[arg]

    @classmethod
    def run(cls, args=None):
        """Parse arguments and sign/verify."""
        if args is None:
            args = sys.argv[1:]
        parser = argparse.ArgumentParser()
        parser.add_argument('--compact', action='store_true')

        subparsers = parser.add_subparsers()
        parser_sign = subparsers.add_parser('sign')
        parser_sign.set_defaults(func=cls.sign)
        parser_sign.add_argument(
            '-k', '--key', type=argparse.FileType('rb'), required=True)
        parser_sign.add_argument(
            '-a', '--alg', type=cls._alg_type, default=jwa.RS256)
        parser_sign.add_argument(
            '-p', '--protect', action='append', type=cls._header_type)

        parser_verify = subparsers.add_parser('verify')
        parser_verify.set_defaults(func=cls.verify)
        parser_verify.add_argument(
            '-k', '--key', type=argparse.FileType('rb'), required=False)
        parser_verify.add_argument(
            '--kty', type=cls._kty_type, required=False)

        parsed = parser.parse_args(args)
        return parsed.func(parsed)


if __name__ == '__main__':
    exit(CLI.run())  # pragma: no cover