485 lines
16 KiB
Python
485 lines
16 KiB
Python
from dataclasses import dataclass
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import io
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import itertools
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from typing import Optional, Tuple
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import multihash
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from libp2p.crypto.authenticated_encryption import (
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EncryptionParameters as AuthenticatedEncryptionParameters,
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)
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from libp2p.crypto.authenticated_encryption import (
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initialize_pair as initialize_pair_for_encryption,
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)
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from libp2p.crypto.authenticated_encryption import InvalidMACException
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from libp2p.crypto.authenticated_encryption import MacAndCipher as Encrypter
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from libp2p.crypto.ecc import ECCPublicKey
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from libp2p.crypto.exceptions import MissingDeserializerError
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from libp2p.crypto.key_exchange import create_ephemeral_key_pair
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from libp2p.crypto.keys import PrivateKey, PublicKey
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from libp2p.crypto.serialization import deserialize_public_key
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from libp2p.io.exceptions import DecryptionFailedException, IOException
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from libp2p.io.msgio import MsgIOReadWriter
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from libp2p.network.connection.raw_connection_interface import IRawConnection
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from libp2p.peer.id import ID as PeerID
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from libp2p.security.base_session import BaseSession
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from libp2p.security.base_transport import BaseSecureTransport
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from libp2p.security.secure_conn_interface import ISecureConn
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from libp2p.typing import TProtocol
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from .exceptions import (
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IncompatibleChoices,
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InconsistentNonce,
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InvalidSignatureOnExchange,
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PeerMismatchException,
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SecioException,
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SedesException,
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SelfEncryption,
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)
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from .pb.spipe_pb2 import Exchange, Propose
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ID = TProtocol("/secio/1.0.0")
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NONCE_SIZE = 16 # bytes
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# NOTE: the following is only a subset of allowable parameters according to the
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# `secio` specification.
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DEFAULT_SUPPORTED_EXCHANGES = "P-256"
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DEFAULT_SUPPORTED_CIPHERS = "AES-128"
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DEFAULT_SUPPORTED_HASHES = "SHA256"
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class SecureSession(BaseSession):
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buf: io.BytesIO
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low_watermark: int
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high_watermark: int
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def __init__(
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self,
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local_peer: PeerID,
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local_private_key: PrivateKey,
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local_encryption_parameters: AuthenticatedEncryptionParameters,
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remote_peer: PeerID,
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remote_encryption_parameters: AuthenticatedEncryptionParameters,
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conn: MsgIOReadWriter,
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is_initiator: bool,
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) -> None:
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super().__init__(local_peer, local_private_key, is_initiator, remote_peer)
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self.conn = conn
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self.local_encryption_parameters = local_encryption_parameters
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self.remote_encryption_parameters = remote_encryption_parameters
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self._initialize_authenticated_encryption_for_local_peer()
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self._initialize_authenticated_encryption_for_remote_peer()
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self._reset_internal_buffer()
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def _initialize_authenticated_encryption_for_local_peer(self) -> None:
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self.local_encrypter = Encrypter(self.local_encryption_parameters)
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def _initialize_authenticated_encryption_for_remote_peer(self) -> None:
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self.remote_encrypter = Encrypter(self.remote_encryption_parameters)
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async def next_msg_len(self) -> int:
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return await self.conn.next_msg_len()
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def _reset_internal_buffer(self) -> None:
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self.buf = io.BytesIO()
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self.low_watermark = 0
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self.high_watermark = 0
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def _drain(self, n: int) -> bytes:
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if self.low_watermark == self.high_watermark:
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return bytes()
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data = self.buf.getbuffer()[self.low_watermark : self.high_watermark]
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if n is None:
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n = len(data)
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result = data[:n].tobytes()
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self.low_watermark += len(result)
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if self.low_watermark == self.high_watermark:
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del data # free the memoryview so we can free the underlying BytesIO
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self.buf.close()
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self._reset_internal_buffer()
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return result
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async def _fill(self) -> None:
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msg = await self.read_msg()
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self.buf.write(msg)
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self.low_watermark = 0
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self.high_watermark = len(msg)
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async def read(self, n: int = None) -> bytes:
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if n == 0:
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return bytes()
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data_from_buffer = self._drain(n)
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if len(data_from_buffer) > 0:
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return data_from_buffer
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next_length = await self.next_msg_len()
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if n < next_length:
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await self._fill()
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return self._drain(n)
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else:
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return await self.read_msg()
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async def read_msg(self) -> bytes:
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msg = await self.conn.read_msg()
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try:
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decrypted_msg = self.remote_encrypter.decrypt_if_valid(msg)
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except InvalidMACException as e:
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raise DecryptionFailedException() from e
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return decrypted_msg
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async def write(self, data: bytes) -> None:
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await self.write_msg(data)
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async def write_msg(self, msg: bytes) -> None:
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encrypted_data = self.local_encrypter.encrypt(msg)
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tag = self.local_encrypter.authenticate(encrypted_data)
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await self.conn.write_msg(encrypted_data + tag)
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@dataclass(frozen=True)
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class Proposal:
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"""A ``Proposal`` represents the set of session parameters one peer in a
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pair of peers attempting to negotiate a `secio` channel prefers."""
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nonce: bytes
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public_key: PublicKey
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exchanges: str = DEFAULT_SUPPORTED_EXCHANGES # comma separated list
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ciphers: str = DEFAULT_SUPPORTED_CIPHERS # comma separated list
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hashes: str = DEFAULT_SUPPORTED_HASHES # comma separated list
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def serialize(self) -> bytes:
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protobuf = Propose(
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rand=self.nonce,
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public_key=self.public_key.serialize(),
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exchanges=self.exchanges,
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ciphers=self.ciphers,
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hashes=self.hashes,
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)
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return protobuf.SerializeToString()
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@classmethod
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def deserialize(cls, protobuf_bytes: bytes) -> "Proposal":
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protobuf = Propose.FromString(protobuf_bytes)
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nonce = protobuf.rand
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public_key_protobuf_bytes = protobuf.public_key
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try:
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public_key = deserialize_public_key(public_key_protobuf_bytes)
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except MissingDeserializerError as error:
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raise SedesException() from error
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exchanges = protobuf.exchanges
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ciphers = protobuf.ciphers
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hashes = protobuf.hashes
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return cls(nonce, public_key, exchanges, ciphers, hashes)
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def calculate_peer_id(self) -> PeerID:
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return PeerID.from_pubkey(self.public_key)
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@dataclass
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class EncryptionParameters:
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permanent_public_key: PublicKey
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curve_type: str
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cipher_type: str
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hash_type: str
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ephemeral_public_key: PublicKey
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def __init__(self) -> None:
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pass
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@dataclass
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class SessionParameters:
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local_peer: PeerID
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local_encryption_parameters: EncryptionParameters
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remote_peer: PeerID
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remote_encryption_parameters: EncryptionParameters
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# order is a comparator used to break the symmetry b/t each pair of peers
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order: int
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shared_key: bytes
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def __init__(self) -> None:
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pass
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async def _response_to_msg(read_writer: MsgIOReadWriter, msg: bytes) -> bytes:
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await read_writer.write_msg(msg)
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return await read_writer.read_msg()
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def _mk_multihash_sha256(data: bytes) -> bytes:
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return multihash.digest(data, "sha2-256")
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def _mk_score(public_key: PublicKey, nonce: bytes) -> bytes:
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return _mk_multihash_sha256(public_key.serialize() + nonce)
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def _select_parameter_from_order(
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order: int, supported_parameters: str, available_parameters: str
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) -> str:
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if order < 0:
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first_choices = available_parameters.split(",")
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second_choices = supported_parameters.split(",")
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elif order > 0:
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first_choices = supported_parameters.split(",")
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second_choices = available_parameters.split(",")
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else:
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return supported_parameters.split(",")[0]
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for first, second in itertools.product(first_choices, second_choices):
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if first == second:
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return first
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raise IncompatibleChoices()
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def _select_encryption_parameters(
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local_proposal: Proposal, remote_proposal: Proposal
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) -> Tuple[str, str, str, int]:
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first_score = _mk_score(remote_proposal.public_key, local_proposal.nonce)
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second_score = _mk_score(local_proposal.public_key, remote_proposal.nonce)
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order = 0
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if first_score < second_score:
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order = -1
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elif second_score < first_score:
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order = 1
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if order == 0:
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raise SelfEncryption()
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return (
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_select_parameter_from_order(
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order, DEFAULT_SUPPORTED_EXCHANGES, remote_proposal.exchanges
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),
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_select_parameter_from_order(
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order, DEFAULT_SUPPORTED_CIPHERS, remote_proposal.ciphers
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),
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_select_parameter_from_order(
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order, DEFAULT_SUPPORTED_HASHES, remote_proposal.hashes
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),
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order,
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)
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async def _establish_session_parameters(
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local_peer: PeerID,
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local_private_key: PrivateKey,
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remote_peer: Optional[PeerID],
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conn: MsgIOReadWriter,
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nonce: bytes,
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) -> Tuple[SessionParameters, bytes]:
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# establish shared encryption parameters
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session_parameters = SessionParameters()
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session_parameters.local_peer = local_peer
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local_encryption_parameters = EncryptionParameters()
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session_parameters.local_encryption_parameters = local_encryption_parameters
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local_public_key = local_private_key.get_public_key()
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local_encryption_parameters.permanent_public_key = local_public_key
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local_proposal = Proposal(nonce, local_public_key)
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serialized_local_proposal = local_proposal.serialize()
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serialized_remote_proposal = await _response_to_msg(conn, serialized_local_proposal)
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remote_encryption_parameters = EncryptionParameters()
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session_parameters.remote_encryption_parameters = remote_encryption_parameters
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remote_proposal = Proposal.deserialize(serialized_remote_proposal)
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remote_encryption_parameters.permanent_public_key = remote_proposal.public_key
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remote_peer_from_proposal = remote_proposal.calculate_peer_id()
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if not remote_peer:
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remote_peer = remote_peer_from_proposal
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elif remote_peer != remote_peer_from_proposal:
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raise PeerMismatchException(
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{
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"expected_remote_peer": remote_peer,
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"received_remote_peer": remote_peer_from_proposal,
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}
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)
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session_parameters.remote_peer = remote_peer
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curve_param, cipher_param, hash_param, order = _select_encryption_parameters(
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local_proposal, remote_proposal
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)
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local_encryption_parameters.curve_type = curve_param
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local_encryption_parameters.cipher_type = cipher_param
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local_encryption_parameters.hash_type = hash_param
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remote_encryption_parameters.curve_type = curve_param
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remote_encryption_parameters.cipher_type = cipher_param
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remote_encryption_parameters.hash_type = hash_param
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session_parameters.order = order
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# exchange ephemeral pub keys
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local_ephemeral_public_key, shared_key_generator = create_ephemeral_key_pair(
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curve_param
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)
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local_encryption_parameters.ephemeral_public_key = local_ephemeral_public_key
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local_selection = (
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serialized_local_proposal
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+ serialized_remote_proposal
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+ local_ephemeral_public_key.to_bytes()
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)
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exchange_signature = local_private_key.sign(local_selection)
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local_exchange = Exchange(
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ephemeral_public_key=local_ephemeral_public_key.to_bytes(),
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signature=exchange_signature,
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)
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serialized_local_exchange = local_exchange.SerializeToString()
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serialized_remote_exchange = await _response_to_msg(conn, serialized_local_exchange)
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remote_exchange = Exchange()
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remote_exchange.ParseFromString(serialized_remote_exchange)
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remote_ephemeral_public_key_bytes = remote_exchange.ephemeral_public_key
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remote_ephemeral_public_key = ECCPublicKey.from_bytes(
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remote_ephemeral_public_key_bytes, curve_param
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)
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remote_encryption_parameters.ephemeral_public_key = remote_ephemeral_public_key
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remote_selection = (
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serialized_remote_proposal
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+ serialized_local_proposal
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+ remote_ephemeral_public_key_bytes
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)
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valid_signature = remote_encryption_parameters.permanent_public_key.verify(
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remote_selection, remote_exchange.signature
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)
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if not valid_signature:
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raise InvalidSignatureOnExchange()
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shared_key = shared_key_generator(remote_ephemeral_public_key_bytes)
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session_parameters.shared_key = shared_key
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return session_parameters, remote_proposal.nonce
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def _mk_session_from(
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local_private_key: PrivateKey,
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session_parameters: SessionParameters,
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conn: MsgIOReadWriter,
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is_initiator: bool,
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) -> SecureSession:
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key_set1, key_set2 = initialize_pair_for_encryption(
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session_parameters.local_encryption_parameters.cipher_type,
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session_parameters.local_encryption_parameters.hash_type,
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session_parameters.shared_key,
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)
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if session_parameters.order < 0:
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key_set1, key_set2 = key_set2, key_set1
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session = SecureSession(
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session_parameters.local_peer,
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local_private_key,
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key_set1,
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session_parameters.remote_peer,
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key_set2,
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conn,
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is_initiator,
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)
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return session
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async def _finish_handshake(session: SecureSession, remote_nonce: bytes) -> bytes:
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await session.write_msg(remote_nonce)
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return await session.read_msg()
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async def create_secure_session(
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local_nonce: bytes,
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local_peer: PeerID,
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local_private_key: PrivateKey,
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conn: IRawConnection,
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remote_peer: PeerID = None,
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) -> ISecureConn:
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"""
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Attempt the initial `secio` handshake with the remote peer.
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If successful, return an object that provides secure communication
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to the ``remote_peer``. Raise `SecioException` when `conn` closed.
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Raise `InconsistentNonce` when handshake failed
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"""
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msg_io = MsgIOReadWriter(conn)
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try:
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session_parameters, remote_nonce = await _establish_session_parameters(
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local_peer, local_private_key, remote_peer, msg_io, local_nonce
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)
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except SecioException as e:
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await conn.close()
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raise e
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# `IOException` includes errors raised while read from/write to raw connection
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except IOException as e:
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raise SecioException("connection closed") from e
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is_initiator = remote_peer is not None
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session = _mk_session_from(
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local_private_key, session_parameters, msg_io, is_initiator
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)
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try:
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received_nonce = await _finish_handshake(session, remote_nonce)
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# `IOException` includes errors raised while read from/write to raw connection
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except IOException as e:
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raise SecioException("connection closed") from e
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if received_nonce != local_nonce:
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await conn.close()
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raise InconsistentNonce()
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return session
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class Transport(BaseSecureTransport):
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"""``Transport`` provides a security upgrader for a ``IRawConnection``,
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following the `secio` protocol defined in the libp2p specs."""
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def get_nonce(self) -> bytes:
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return self.secure_bytes_provider(NONCE_SIZE)
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async def secure_inbound(self, conn: IRawConnection) -> ISecureConn:
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"""
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Secure the connection, either locally or by communicating with opposing
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node via conn, for an inbound connection (i.e. we are not the
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initiator)
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:return: secure connection object (that implements secure_conn_interface)
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"""
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local_nonce = self.get_nonce()
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local_peer = self.local_peer
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local_private_key = self.local_private_key
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return await create_secure_session(
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local_nonce, local_peer, local_private_key, conn
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)
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async def secure_outbound(
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self, conn: IRawConnection, peer_id: PeerID
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) -> ISecureConn:
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"""
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Secure the connection, either locally or by communicating with opposing
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node via conn, for an inbound connection (i.e. we are the initiator)
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:return: secure connection object (that implements secure_conn_interface)
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"""
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local_nonce = self.get_nonce()
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local_peer = self.local_peer
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local_private_key = self.local_private_key
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return await create_secure_session(
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local_nonce, local_peer, local_private_key, conn, peer_id
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)
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