noiseprotocol/noise/noise_protocol.py

from functools import partial
from typing import Tuple

from noise.exceptions import NoiseProtocolNameError, NoisePSKError
from noise.state import HandshakeState
from .constants import MAX_PROTOCOL_NAME_LEN, Empty
from .functions import dh_map, cipher_map, hash_map, keypair_map, hmac_hash, hkdf
from .patterns import patterns_map


class NoiseProtocol(object):
    """
    TODO: Document
    """
    methods = {
        'pattern': patterns_map,
        'dh': dh_map,
        'cipher': cipher_map,
        'hash': hash_map,
        'keypair': keypair_map
    }

    def __init__(self, protocol_name: bytes):
        if not isinstance(protocol_name, bytes):
            raise NoiseProtocolNameError('Protocol name has to be of type "bytes" not {}'.format(type(protocol_name)))
        if len(protocol_name) > MAX_PROTOCOL_NAME_LEN:
            raise NoiseProtocolNameError('Protocol name too long, has to be at most '
                                         '{} chars long'.format(MAX_PROTOCOL_NAME_LEN))

        self.name = protocol_name
        mappings, pattern_modifiers = self._parse_protocol_name()

        # A valid Pattern instance (see Section 7 of specification (rev 32))
        self.pattern = mappings['pattern']()
        self.pattern_modifiers = pattern_modifiers
        if self.pattern_modifiers:
            self.pattern.apply_pattern_modifiers(pattern_modifiers)

        # Handle PSK handshake options
        self.psks = None
        self.is_psk_handshake = any([modifier.startswith('psk') for modifier in self.pattern_modifiers])

        self.dh_fn = mappings['dh']
        self.cipher_fn = mappings['cipher']
        self.hash_fn = mappings['hash']
        self.keypair_fn = mappings['keypair']
        self.hmac = partial(hmac_hash, algorithm=self.hash_fn.fn)
        self.hkdf = partial(hkdf, hmac_hash_fn=self.hmac)

        self.prologue = None
        self.initiator = None
        self.one_way = False
        self.handshake_hash = None

        self.handshake_state = Empty()
        self.symmetric_state = Empty()
        self.cipher_state_handshake = Empty()
        self.cipher_state_encrypt = Empty()
        self.cipher_state_decrypt = Empty()

        self.keypairs = {'s': None, 'e': None, 'rs': None, 're': None}

    def _parse_protocol_name(self) -> Tuple[dict, list]:
        unpacked = self.name.decode().split('_')
        if unpacked[0] != 'Noise':
            raise NoiseProtocolNameError('Noise Protocol name shall begin with Noise! Provided: {}'.format(self.name))

        # Extract pattern name and pattern modifiers
        pattern = ''
        modifiers_str = None
        for i, char in enumerate(unpacked[1]):
            if char.isupper():
                pattern += char
            else:
                # End of pattern, now look for modifiers
                modifiers_str = unpacked[1][i:]  # Will be empty string if it exceeds string size
                break
        modifiers = modifiers_str.split('+') if modifiers_str else []

        data = {'pattern': 'Pattern' + pattern,
                'dh': unpacked[2],
                'cipher': unpacked[3],
                'hash': unpacked[4],
                'keypair': unpacked[2],
                'pattern_modifiers': modifiers}

        mapped_data = {}

        # Validate if we know everything that Noise Protocol is supposed to use and map appropriate functions
        for key, map_dict in self.methods.items():
            func = map_dict.get(data[key])
            if not func:
                raise NoiseProtocolNameError('Unknown {} in Noise Protocol name, given {}, known {}'.format(
                                             key, data[key], " ".join(map_dict)))
            mapped_data[key] = func

        return mapped_data, modifiers

    def handshake_done(self):
        if self.pattern.one_way:
            if self.initiator:
                self.cipher_state_decrypt = None
            else:
                self.cipher_state_encrypt = None
        self.handshake_hash = self.symmetric_state.h
        del self.handshake_state
        del self.symmetric_state
        del self.cipher_state_handshake
        del self.prologue
        del self.initiator
        del self.dh_fn
        del self.hash_fn
        del self.keypair_fn

    def validate(self):
        if self.is_psk_handshake:
            if any([len(psk) != 32 for psk in self.psks]):
                raise NoisePSKError('Invalid psk length! Has to be 32 bytes long')
            if len(self.psks) != self.pattern.psk_count:
                raise NoisePSKError('Bad number of PSKs provided to this protocol! {} are required, '
                                    'given {}'.format(self.pattern.psk_count, len(self.psks)))

        # TODO: Validate keypairs
        # TODO: Validate initiator set
        # TODO: Validate buffers set
        # TODO: Warn about ephemerals

    def initialise_handshake_state(self):
        kwargs = {'initiator': self.initiator}
        if self.prologue:
            kwargs['prologue'] = self.prologue
        for keypair, value in self.keypairs.items():
            if value:
                kwargs[keypair] = value
        self.handshake_state = HandshakeState.initialize(self, **kwargs)
        self.symmetric_state = self.handshake_state.symmetric_state