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// Copyright (C) 2019-2023 Algorand, Inc.
// This file is part of go-algorand
//
// go-algorand is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as
// published by the Free Software Foundation, either version 3 of the
// License, or (at your option) any later version.
//
// go-algorand 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 Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with go-algorand. If not, see <https://www.gnu.org/licenses/>.
package agreement
import (
"fmt"
"time"
"github.com/algorand/go-algorand/crypto"
"github.com/algorand/go-algorand/data/basics"
"github.com/algorand/go-algorand/data/committee"
"github.com/algorand/go-algorand/logging"
"github.com/algorand/go-algorand/protocol"
)
type (
// rawVote is the inner struct which is authenticated with keys
rawVote struct {
_struct struct{} `codec:",omitempty,omitemptyarray"`
Sender basics.Address `codec:"snd"`
Round basics.Round `codec:"rnd"`
Period period `codec:"per"`
Step step `codec:"step"`
Proposal proposalValue `codec:"prop"`
}
// unauthenticatedVote is a vote which has not been verified
unauthenticatedVote struct {
_struct struct{} `codec:",omitempty,omitemptyarray"`
R rawVote `codec:"r"`
Cred committee.UnauthenticatedCredential `codec:"cred"`
Sig crypto.OneTimeSignature `codec:"sig,omitempty,omitemptycheckstruct"`
}
// A vote is an endorsement of a particular proposal in Algorand
vote struct {
_struct struct{} `codec:",omitempty,omitemptyarray"`
R rawVote `codec:"r"`
Cred committee.Credential `codec:"cred"`
Sig crypto.OneTimeSignature `codec:"sig,omitempty,omitemptycheckstruct"`
// validatedAt indicates the time at which this vote was verified (as a voteVerified messageEvent),
// relative to the zero of that round. It is only set for step 0.
validatedAt time.Duration
}
// unauthenticatedEquivocationVote is a pair of votes which has not
// been verified to be equivocating.
unauthenticatedEquivocationVote struct {
_struct struct{} `codec:",omitempty,omitemptyarray"`
Sender basics.Address `codec:"snd"`
Round basics.Round `codec:"rnd"`
Period period `codec:"per"`
Step step `codec:"step"`
Cred committee.UnauthenticatedCredential `codec:"cred"`
Proposals [2]proposalValue `codec:"props"`
Sigs [2]crypto.OneTimeSignature `codec:"sigs"`
}
// An equivocationVote is a pair of votes from the same sender that
// votes for two different hashes.
//
// These pairs are necessarily generated by a faulty node. However, if
// we ever receive such a pair, we must count this as a single
// "wildcard" vote to avoid violating vote propagation assumptions and
// causing a fork.
equivocationVote struct {
_struct struct{} `codec:",omitempty,omitemptyarray"`
Sender basics.Address `codec:"snd"`
Round basics.Round `codec:"rnd"`
Period period `codec:"per"`
Step step `codec:"step"`
Cred committee.Credential `codec:"cred"`
Proposals [2]proposalValue `codec:"props"`
Sigs [2]crypto.OneTimeSignature `codec:"sigs"`
}
// UnauthenticatedVote exported for dumping textual versions of messages
UnauthenticatedVote = unauthenticatedVote
)
// verify verifies that a vote that was received from the network is valid.
func (uv unauthenticatedVote) verify(l LedgerReader) (vote, error) {
rv := uv.R
m, err := membership(l, rv.Sender, rv.Round, rv.Period, rv.Step)
if err != nil {
return vote{}, fmt.Errorf("unauthenticatedVote.verify: could not get membership parameters: %w", err)
}
switch rv.Step {
case propose:
if rv.Period == rv.Proposal.OriginalPeriod && rv.Sender != rv.Proposal.OriginalProposer {
return vote{}, fmt.Errorf("unauthenticatedVote.verify: proposal-vote sender mismatches with proposal-value: %v != %v", rv.Sender, rv.Proposal.OriginalProposer)
}
// The following check could apply to all steps, but it's sufficient to only check in the propose step.
if rv.Proposal.OriginalPeriod > rv.Period {
return vote{}, fmt.Errorf("unauthenticatedVote.verify: proposal-vote in period %d claims to repropose block from future period %d", rv.Period, rv.Proposal.OriginalPeriod)
}
fallthrough
case soft:
fallthrough
case cert:
if rv.Proposal == bottom {
return vote{}, fmt.Errorf("unauthenticatedVote.verify: votes from step %d cannot validate bottom", rv.Step)
}
}
proto, err := l.ConsensusParams(ParamsRound(rv.Round))
if err != nil {
return vote{}, fmt.Errorf("unauthenticatedVote.verify: could not get consensus params for round %d: %v", ParamsRound(rv.Round), err)
}
if rv.Round < m.Record.VoteFirstValid {
return vote{}, fmt.Errorf("unauthenticatedVote.verify: vote by %v in round %d before VoteFirstValid %d: %+v", rv.Sender, rv.Round, m.Record.VoteFirstValid, uv)
}
if m.Record.VoteLastValid != 0 && rv.Round > m.Record.VoteLastValid {
return vote{}, fmt.Errorf("unauthenticatedVote.verify: vote by %v in round %d after VoteLastValid %d: %+v", rv.Sender, rv.Round, m.Record.VoteLastValid, uv)
}
ephID := basics.OneTimeIDForRound(rv.Round, m.Record.KeyDilution(proto))
voteID := m.Record.VoteID
if !voteID.Verify(ephID, rv, uv.Sig) {
return vote{}, fmt.Errorf("unauthenticatedVote.verify: could not verify FS signature on vote by %v given %v: %+v", rv.Sender, voteID, uv)
}
cred, err := uv.Cred.Verify(proto, m)
if err != nil {
return vote{}, fmt.Errorf("unauthenticatedVote.verify: got a vote, but sender was not selected: %v", err)
}
return vote{R: rv, Cred: cred, Sig: uv.Sig}, nil
}
// makeVote creates a new unauthenticated vote from its constituent components.
//
// makeVote returns an error it it fails.
func makeVote(rv rawVote, voting crypto.OneTimeSigner, selection *crypto.VRFSecrets, l Ledger) (unauthenticatedVote, error) {
m, err := membership(l, rv.Sender, rv.Round, rv.Period, rv.Step)
if err != nil {
return unauthenticatedVote{}, fmt.Errorf("makeVote: could not get membership parameters: %v", err)
}
proto, err := l.ConsensusParams(ParamsRound(rv.Round))
if err != nil {
return unauthenticatedVote{}, fmt.Errorf("makeVote: could not get consensus params for round %d: %v", ParamsRound(rv.Round), err)
}
switch rv.Step {
case propose, soft, cert, late, redo:
if rv.Proposal == bottom {
logging.Base().Panicf("makeVote: votes from step %d cannot validate bottom", rv.Step)
}
case down:
if rv.Proposal != bottom {
logging.Base().Panicf("makeVote: votes from step %d must validate bottom", rv.Step)
}
}
ephID := basics.OneTimeIDForRound(rv.Round, voting.KeyDilution(proto.DefaultKeyDilution))
sig := voting.Sign(ephID, rv)
if (sig == crypto.OneTimeSignature{}) {
return unauthenticatedVote{}, fmt.Errorf("makeVote: got back empty signature for vote")
}
cred := committee.MakeCredential(&selection.SK, m.Selector)
return unauthenticatedVote{R: rv, Cred: cred, Sig: sig}, nil
}
// ToBeHashed implements the Hashable interface.
func (rv rawVote) ToBeHashed() (protocol.HashID, []byte) {
return protocol.Vote, protocol.Encode(&rv)
}
func (v vote) u() unauthenticatedVote {
return unauthenticatedVote{R: v.R, Cred: v.Cred.UnauthenticatedCredential, Sig: v.Sig}
}
func (pair unauthenticatedEquivocationVote) verify(l LedgerReader) (equivocationVote, error) {
if pair.Proposals[0] == pair.Proposals[1] {
return equivocationVote{}, fmt.Errorf("isEquivocationPair: not an equivocation pair: identical vote (block hash %v == %v)", pair.Proposals[0], pair.Proposals[1])
}
rv0 := rawVote{Sender: pair.Sender, Round: pair.Round, Period: pair.Period, Step: pair.Step, Proposal: pair.Proposals[0]}
rv1 := rawVote{Sender: pair.Sender, Round: pair.Round, Period: pair.Period, Step: pair.Step, Proposal: pair.Proposals[1]}
uv0 := unauthenticatedVote{R: rv0, Cred: pair.Cred, Sig: pair.Sigs[0]}
uv1 := unauthenticatedVote{R: rv1, Cred: pair.Cred, Sig: pair.Sigs[1]}
v0, err := uv0.verify(l)
if err != nil {
return equivocationVote{}, fmt.Errorf("unauthenticatedEquivocationVote.verify: failed to verify pair 0: %w", err)
}
_, err = uv1.verify(l)
if err != nil {
return equivocationVote{}, fmt.Errorf("unauthenticatedEquivocationVote.verify: failed to verify pair 1: %w", err)
}
return equivocationVote{
Sender: pair.Sender,
Round: pair.Round,
Period: pair.Period,
Step: pair.Step,
Cred: v0.Cred,
Proposals: pair.Proposals,
Sigs: pair.Sigs,
}, nil
}
// the first member of the equivocation pair
func (pair equivocationVote) v0() vote {
rv := rawVote{Sender: pair.Sender, Round: pair.Round, Period: pair.Period, Step: pair.Step, Proposal: pair.Proposals[0]}
return vote{R: rv, Cred: pair.Cred, Sig: pair.Sigs[0]}
}
// the second member of the equivocation pair
func (pair equivocationVote) v1() vote {
rv := rawVote{Sender: pair.Sender, Round: pair.Round, Period: pair.Period, Step: pair.Step, Proposal: pair.Proposals[1]}
return vote{R: rv, Cred: pair.Cred, Sig: pair.Sigs[1]}
}
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