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// Copyright (C) Parity Technologies (UK) Ltd.
// This file is part of Polkadot.
// Polkadot is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// Polkadot is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
// You should have received a copy of the GNU General Public License
// along with Polkadot. If not, see <http://www.gnu.org/licenses/>.
//! `DisputeMessage` and associated types.
//!
//! A `DisputeMessage` is a message that indicates a node participating in a dispute and is used
//! for interfacing with `DisputeDistribution` to send out our vote in a spam detectable way.
use thiserror::Error;
use codec::{Decode, Encode};
use super::{InvalidDisputeVote, SignedDisputeStatement, ValidDisputeVote};
use polkadot_primitives::{
vstaging::CandidateReceiptV2 as CandidateReceipt, DisputeStatement, SessionIndex, SessionInfo,
ValidatorIndex,
};
/// A dispute initiating/participating message that have been built from signed
/// statements.
///
/// And most likely has been constructed correctly. This is used with
/// `DisputeDistributionMessage::SendDispute` for sending out votes.
///
/// NOTE: This is sent over the wire, any changes are a change in protocol and need to be
/// versioned.
#[derive(Debug, Clone)]
pub struct DisputeMessage(UncheckedDisputeMessage);
/// A `DisputeMessage` where signatures of statements have not yet been checked.
#[derive(Clone, Encode, Decode, Debug)]
pub struct UncheckedDisputeMessage {
/// The candidate being disputed.
pub candidate_receipt: CandidateReceipt,
/// The session the candidate appears in.
pub session_index: SessionIndex,
/// The invalid vote data that makes up this dispute.
pub invalid_vote: InvalidDisputeVote,
/// The valid vote that makes this dispute request valid.
pub valid_vote: ValidDisputeVote,
}
/// Things that can go wrong when constructing a `DisputeMessage`.
#[derive(Error, Debug)]
pub enum Error {
/// The statements concerned different candidates.
#[error("Candidate hashes of the two votes did not match up")]
CandidateHashMismatch,
/// The statements concerned different sessions.
#[error("Session indices of the two votes did not match up")]
SessionIndexMismatch,
/// The valid statement validator key did not correspond to passed in `SessionInfo`.
#[error("Valid statement validator key did not match session information")]
InvalidValidKey,
/// The invalid statement validator key did not correspond to passed in `SessionInfo`.
#[error("Invalid statement validator key did not match session information")]
InvalidInvalidKey,
/// Provided receipt had different hash than the `CandidateHash` in the signed statements.
#[error("Hash of candidate receipt did not match provided hash")]
InvalidCandidateReceipt,
/// Valid statement should have `ValidDisputeStatementKind`.
#[error("Valid statement has kind `invalid`")]
ValidStatementHasInvalidKind,
/// Invalid statement should have `InvalidDisputeStatementKind`.
#[error("Invalid statement has kind `valid`")]
InvalidStatementHasValidKind,
/// Provided index could not be found in `SessionInfo`.
#[error("The valid statement had an invalid validator index")]
ValidStatementInvalidValidatorIndex,
/// Provided index could not be found in `SessionInfo`.
#[error("The invalid statement had an invalid validator index")]
InvalidStatementInvalidValidatorIndex,
}
impl DisputeMessage {
/// Build a `SignedDisputeMessage` and check what can be checked.
///
/// This function checks that:
///
/// - both statements concern the same candidate
/// - both statements concern the same session
/// - the invalid statement is indeed an invalid one
/// - the valid statement is indeed a valid one
/// - The passed `CandidateReceipt` has the correct hash (as signed in the statements).
/// - the given validator indices match with the given `ValidatorId`s in the statements, given a
/// `SessionInfo`.
///
/// We don't check whether the given `SessionInfo` matches the `SessionIndex` in the
/// statements, because we can't without doing a runtime query. Nevertheless this smart
/// constructor gives relative strong guarantees that the resulting `SignedDisputeStatement` is
/// valid and good. Even the passed `SessionInfo` is most likely right if this function
/// returns `Some`, because otherwise the passed `ValidatorId`s in the `SessionInfo` at
/// their given index would very likely not match the `ValidatorId`s in the statements.
///
/// So in summary, this smart constructor should be smart enough to prevent from almost all
/// programming errors that one could realistically make here.
pub fn from_signed_statements(
valid_statement: SignedDisputeStatement,
valid_index: ValidatorIndex,
invalid_statement: SignedDisputeStatement,
invalid_index: ValidatorIndex,
candidate_receipt: CandidateReceipt,
session_info: &SessionInfo,
) -> Result<Self, Error> {
let candidate_hash = *valid_statement.candidate_hash();
// Check statements concern same candidate:
if candidate_hash != *invalid_statement.candidate_hash() {
return Err(Error::CandidateHashMismatch)
}
let session_index = valid_statement.session_index();
if session_index != invalid_statement.session_index() {
return Err(Error::SessionIndexMismatch)
}
let valid_id = session_info
.validators
.get(valid_index)
.ok_or(Error::ValidStatementInvalidValidatorIndex)?;
let invalid_id = session_info
.validators
.get(invalid_index)
.ok_or(Error::InvalidStatementInvalidValidatorIndex)?;
if valid_id != valid_statement.validator_public() {
return Err(Error::InvalidValidKey)
}
if invalid_id != invalid_statement.validator_public() {
return Err(Error::InvalidInvalidKey)
}
if candidate_receipt.hash() != candidate_hash {
return Err(Error::InvalidCandidateReceipt)
}
let valid_kind = match valid_statement.statement() {
DisputeStatement::Valid(v) => v,
_ => return Err(Error::ValidStatementHasInvalidKind),
};
let invalid_kind = match invalid_statement.statement() {
DisputeStatement::Invalid(v) => v,
_ => return Err(Error::InvalidStatementHasValidKind),
};
let valid_vote = ValidDisputeVote {
validator_index: valid_index,
signature: valid_statement.validator_signature().clone(),
kind: valid_kind.clone(),
};
let invalid_vote = InvalidDisputeVote {
validator_index: invalid_index,
signature: invalid_statement.validator_signature().clone(),
kind: *invalid_kind,
};
Ok(DisputeMessage(UncheckedDisputeMessage {
candidate_receipt,
session_index,
valid_vote,
invalid_vote,
}))
}
/// Read only access to the candidate receipt.
pub fn candidate_receipt(&self) -> &CandidateReceipt {
&self.0.candidate_receipt
}
/// Read only access to the `SessionIndex`.
pub fn session_index(&self) -> SessionIndex {
self.0.session_index
}
/// Read only access to the invalid vote.
pub fn invalid_vote(&self) -> &InvalidDisputeVote {
&self.0.invalid_vote
}
/// Read only access to the valid vote.
pub fn valid_vote(&self) -> &ValidDisputeVote {
&self.0.valid_vote
}
}
impl UncheckedDisputeMessage {
/// Try to recover the two signed dispute votes from an `UncheckedDisputeMessage`.
pub fn try_into_signed_votes(
self,
session_info: &SessionInfo,
) -> Result<
(
CandidateReceipt,
(SignedDisputeStatement, ValidatorIndex),
(SignedDisputeStatement, ValidatorIndex),
),
(),
> {
let Self { candidate_receipt, session_index, valid_vote, invalid_vote } = self;
let candidate_hash = candidate_receipt.hash();
let vote_valid = {
let ValidDisputeVote { validator_index, signature, kind } = valid_vote;
let validator_public = session_info.validators.get(validator_index).ok_or(())?.clone();
(
SignedDisputeStatement::new_checked(
DisputeStatement::Valid(kind),
candidate_hash,
session_index,
validator_public,
signature,
)?,
validator_index,
)
};
let vote_invalid = {
let InvalidDisputeVote { validator_index, signature, kind } = invalid_vote;
let validator_public = session_info.validators.get(validator_index).ok_or(())?.clone();
(
SignedDisputeStatement::new_checked(
DisputeStatement::Invalid(kind),
candidate_hash,
session_index,
validator_public,
signature,
)?,
validator_index,
)
};
Ok((candidate_receipt, vote_valid, vote_invalid))
}
}
impl From<DisputeMessage> for UncheckedDisputeMessage {
fn from(message: DisputeMessage) -> Self {
message.0
}
}