pyssb/ssb/feed/models.py

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# SPDX-License-Identifier: MIT
#
# Copyright (c) 2017 PySSB contributors (see AUTHORS for more details)
#
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
#
# The above copyright notice and this permission notice shall be included in all
# copies or substantial portions of the Software.
#
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
# SOFTWARE.
"""Feed models"""
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from base64 import b64encode
from collections import OrderedDict, namedtuple
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from datetime import datetime
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from hashlib import sha256
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
from typing_extensions import Self
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from ssb.util import tag
OrderedMsg = namedtuple("OrderedMsg", ("previous", "author", "sequence", "timestamp", "hash", "content"))
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class NoPrivateKeyException(Exception):
"""Exception to raise when a private key is not available"""
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def to_ordered(data: Dict[str, Any]) -> OrderedDict[str, Any]:
"""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)
def get_millis_1970() -> int:
"""Get the UNIX timestamp in milliseconds"""
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return int(datetime.utcnow().timestamp() * 1000)
class Feed:
"""Base class for feeds"""
def __init__(self, public_key: VerifyKey):
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self.public_key = public_key
@property
def id(self) -> str:
"""The identifier of the feed"""
return tag(self.public_key).decode("ascii")
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def sign(self, msg: bytes) -> bytes:
"""Sign a message"""
raise NoPrivateKeyException("Cannot use remote identity to sign (no private key!)")
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class LocalFeed(Feed):
"""Class representing a local feed"""
def __init__(self, private_key: SigningKey): # pylint: disable=super-init-not-called
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self.private_key = private_key
@property
def public_key(self) -> VerifyKey:
"""The public key of the feed"""
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return self.private_key.verify_key
@public_key.setter
def public_key(self, key: VerifyKey) -> None:
raise TypeError("Can not set only the public key for a local feed")
def sign(self, msg: bytes) -> bytes:
"""Sign a message for this feed"""
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return self.private_key.sign(msg).signature
class Message:
"""Base class for SSB messages"""
def __init__( # pylint: disable=too-many-arguments
self,
feed: Feed,
content: Dict[str, Any],
signature: Optional[str] = None,
sequence: int = 1,
timestamp: Optional[int] = None,
previous: Optional["Message"] = None,
):
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self.feed = feed
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self.content = content
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self.signature = signature
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self.previous = previous
self.timestamp = get_millis_1970() if timestamp is None else timestamp
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if self.previous:
self.sequence: int = self.previous.sequence + 1
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else:
self.sequence = sequence
self._check_signature()
def _check_signature(self) -> None:
if self.signature is None:
raise ValueError("signature can't be None")
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@classmethod
def parse(cls, data: bytes, feed: Feed) -> Self:
"""Parse raw message data"""
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obj = loads(data, object_pairs_hook=OrderedDict)
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:
"""Serialize the message"""
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]:
"""Convert the message to a dictionary"""
obj = to_ordered(
{
"previous": self.previous.key if self.previous else None,
"author": self.feed.id,
"sequence": self.sequence,
"timestamp": self.timestamp,
"hash": "sha256",
"content": self.content,
}
)
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if add_signature:
obj["signature"] = self.signature
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return obj
def verify(self, signature: str) -> bool:
"""Verify the signature of the message"""
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return self.signature == signature
@property
def hash(self) -> str:
"""The cryptographic hash of the message"""
hash_ = sha256(self.serialize()).digest()
return b64encode(hash_).decode("ascii") + ".sha256"
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@property
def key(self) -> str:
"""The key of the message"""
return "%" + self.hash
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class LocalMessage(Message):
"""Class representing a local message"""
feed: LocalFeed
previous: "LocalMessage"
def __init__( # pylint: disable=too-many-arguments
self,
feed: LocalFeed,
content: Dict[str, Any],
signature: Optional[str] = None,
sequence: int = 1,
timestamp: Optional[int] = None,
previous: Optional["LocalMessage"] = None,
):
super().__init__(feed, content, signature=signature, sequence=sequence, timestamp=timestamp, previous=previous)
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def _check_signature(self) -> None:
if self.signature is None:
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self.signature = self._sign()
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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)
return (b64encode(bytes(self.feed.sign(data))) + b".sig.ed25519").decode("ascii")