191 lines
5.1 KiB
Python
191 lines
5.1 KiB
Python
"""Feed models"""
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from base64 import b64encode
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from collections import OrderedDict, namedtuple
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import datetime
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from hashlib import sha256
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from typing import Any, Dict, Optional
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from nacl.signing import SigningKey, VerifyKey
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from simplejson import dumps, loads
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from typing_extensions import Self
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from ssb.util import tag
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OrderedMsg = namedtuple("OrderedMsg", ("previous", "author", "sequence", "timestamp", "hash", "content"))
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class NoPrivateKeyException(Exception):
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"""Exception to raise when a private key is not available"""
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def to_ordered(data: Dict[str, Any]) -> OrderedDict[str, Any]:
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"""Convert a dictionary to an ``OrderedDict``"""
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smsg = OrderedMsg(**data)
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return OrderedDict((k, getattr(smsg, k)) for k in smsg._fields)
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def get_millis_1970() -> int:
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"""Get the UNIX timestamp in milliseconds"""
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return int(datetime.datetime.utcnow().timestamp() * 1000)
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class Feed:
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"""Base class for feeds"""
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def __init__(self, public_key: VerifyKey):
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self.public_key = public_key
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@property
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def id(self) -> str:
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"""The identifier of the feed"""
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return tag(self.public_key).decode("ascii")
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def sign(self, msg: "Message") -> bytes:
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"""Sign a message"""
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raise NoPrivateKeyException("Cannot use remote identity to sign (no private key!)")
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class LocalFeed(Feed):
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"""Class representing a local feed"""
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def __init__(self, private_key: SigningKey): # pylint: disable=super-init-not-called
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self.private_key: SigningKey = private_key
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@property
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def public_key(self) -> VerifyKey:
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"""The public key of the feed"""
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return self.private_key.verify_key
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@public_key.setter
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def public_key(self, _: VerifyKey) -> None:
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raise TypeError("Cannot set just the public key of a local feed")
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def sign(self, msg: "Message") -> bytes:
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"""Sign a message for this feed"""
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return self.private_key.sign(msg).signature
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class Message:
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"""Base class for SSB messages"""
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def __init__( # pylint: disable=too-many-arguments
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self,
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feed: Feed,
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content: Dict[str, Any],
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signature: Optional[str] = None,
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sequence: int = 1,
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timestamp: Optional[int] = None,
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previous: Optional["Message"] = None,
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):
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self.feed = feed
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self.content = content
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if signature is None:
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raise ValueError("signature can't be None")
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self.signature = signature
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self.previous = previous
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if self.previous:
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self.sequence: int = self.previous.sequence + 1
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else:
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self.sequence = sequence
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self.timestamp = get_millis_1970() if timestamp is None else timestamp
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@classmethod
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def parse(cls, data: bytes, feed: Feed) -> Self:
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"""Parse raw message data"""
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obj = loads(data, object_pairs_hook=OrderedDict)
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msg = cls(feed, obj["content"], timestamp=obj["timestamp"])
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return msg
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def serialize(self, add_signature: bool = True) -> bytes:
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"""Serialize the message"""
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return dumps(self.to_dict(add_signature=add_signature), indent=2).encode("utf-8")
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def to_dict(self, add_signature: bool = True) -> OrderedDict[str, Any]:
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"""Convert the message to a dictionary"""
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obj = to_ordered(
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{
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"previous": self.previous.key if self.previous else None,
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"author": self.feed.id,
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"sequence": self.sequence,
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"timestamp": self.timestamp,
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"hash": "sha256",
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"content": self.content,
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}
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)
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if add_signature:
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obj["signature"] = self.signature
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return obj
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def verify(self, signature: str) -> bool:
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"""Verify the signature of the message"""
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return self.signature == signature
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@property
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def hash(self) -> str:
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"""The cryptographic hash of the message"""
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hash_ = sha256(self.serialize()).digest()
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return b64encode(hash_).decode("ascii") + ".sha256"
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@property
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def key(self) -> str:
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"""The key of the message"""
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return "%" + self.hash
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class LocalMessage(Message):
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"""Class representing a local message"""
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def __init__( # pylint: disable=too-many-arguments,super-init-not-called
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self,
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feed: Feed,
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content: Dict[str, Any],
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signature: Optional[str] = None,
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sequence: int = 1,
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timestamp: Optional[int] = None,
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previous: Optional[Message] = None,
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):
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self.feed = feed
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self.content = content
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self.previous = previous
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if self.previous:
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self.sequence = self.previous.sequence + 1
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else:
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self.sequence = sequence
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self.timestamp = get_millis_1970() if timestamp is None else timestamp
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if signature is None:
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self.signature = self._sign()
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else:
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self.signature = signature
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def _sign(self) -> str:
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# ensure ordering of keys and indentation of 2 characters, like ssb-keys
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data = self.serialize(add_signature=False)
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return (b64encode(bytes(self.feed.sign(data))) + b".sig.ed25519").decode("ascii")
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