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round_change.go
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round_change.go
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package qbft
import (
"bytes"
"github.com/bloxapp/ssv-spec/types"
"github.com/pkg/errors"
)
// uponRoundChange process round change messages.
// Assumes round change message is valid!
func (i *Instance) uponRoundChange(
instanceStartValue []byte,
signedRoundChange *SignedMessage,
roundChangeMsgContainer *MsgContainer,
valCheck ProposedValueCheckF,
) error {
hasQuorumBefore := HasQuorum(i.State.Share, roundChangeMsgContainer.MessagesForRound(signedRoundChange.Message.
Round))
// Currently, even if we have a quorum of round change messages, we update the container
addedMsg, err := roundChangeMsgContainer.AddFirstMsgForSignerAndRound(signedRoundChange)
if err != nil {
return errors.Wrap(err, "could not add round change msg to container")
}
if !addedMsg {
return nil // message was already added from signer
}
if hasQuorumBefore {
return nil // already changed round
}
justifiedRoundChangeMsg, valueToPropose, err := hasReceivedProposalJustificationForLeadingRound(
i.State,
i.config,
instanceStartValue,
signedRoundChange,
roundChangeMsgContainer,
valCheck)
if err != nil {
return errors.Wrap(err, "could not get proposal justification for leading round")
}
if justifiedRoundChangeMsg != nil {
roundChangeJustification, _ := justifiedRoundChangeMsg.Message.GetRoundChangeJustifications() // no need to check error, check on isValidRoundChange
proposal, err := CreateProposal(
i.State,
i.config,
valueToPropose,
roundChangeMsgContainer.MessagesForRound(i.State.Round), // TODO - might be optimized to include only necessary quorum
roundChangeJustification,
)
if err != nil {
return errors.Wrap(err, "failed to create proposal")
}
if err := i.Broadcast(proposal); err != nil {
return errors.Wrap(err, "failed to broadcast proposal message")
}
} else if partialQuorum, rcs := hasReceivedPartialQuorum(i.State, roundChangeMsgContainer); partialQuorum {
newRound := minRound(rcs)
if newRound <= i.State.Round {
return nil // no need to advance round
}
err := i.uponChangeRoundPartialQuorum(newRound, instanceStartValue)
if err != nil {
return err
}
}
return nil
}
func (i *Instance) uponChangeRoundPartialQuorum(newRound Round, instanceStartValue []byte) error {
i.State.Round = newRound
i.State.ProposalAcceptedForCurrentRound = nil
i.config.GetTimer().TimeoutForRound(i.State.Round)
roundChange, err := CreateRoundChange(i.State, i.config, newRound, instanceStartValue)
if err != nil {
return errors.Wrap(err, "failed to create round change message")
}
if err := i.Broadcast(roundChange); err != nil {
return errors.Wrap(err, "failed to broadcast round change message")
}
return nil
}
func hasReceivedPartialQuorum(state *State, roundChangeMsgContainer *MsgContainer) (bool, []*SignedMessage) {
all := roundChangeMsgContainer.AllMessaged()
rc := make([]*SignedMessage, 0)
for _, msg := range all {
if msg.Message.Round > state.Round {
rc = append(rc, msg)
}
}
return HasPartialQuorum(state.Share, rc), rc
}
// hasReceivedProposalJustificationForLeadingRound returns
// if first round or not received round change msgs with prepare justification - returns first rc msg in container and value to propose
// if received round change msgs with prepare justification - returns the highest prepare justification round change msg and value to propose
// (all the above considering the operator is a leader for the round
func hasReceivedProposalJustificationForLeadingRound(
state *State,
config IConfig,
instanceStartValue []byte,
signedRoundChange *SignedMessage,
roundChangeMsgContainer *MsgContainer,
valCheck ProposedValueCheckF,
) (*SignedMessage, []byte, error) {
roundChanges := roundChangeMsgContainer.MessagesForRound(signedRoundChange.Message.Round)
// optimization, if no round change quorum can return false
if !HasQuorum(state.Share, roundChanges) {
return nil, nil, nil
}
// Important!
// We iterate on all round chance msgs for liveliness in case the last round change msg is malicious.
for _, msg := range roundChanges {
// Chose proposal value.
// If justifiedRoundChangeMsg has no prepare justification chose state value
// If justifiedRoundChangeMsg has prepare justification chose prepared value
valueToPropose := instanceStartValue
if msg.Message.RoundChangePrepared() {
valueToPropose = signedRoundChange.FullData
}
roundChangeJustification, _ := msg.Message.GetRoundChangeJustifications() // no need to check error, checked on isValidRoundChange
if isProposalJustificationForLeadingRound(
state,
config,
msg,
roundChanges,
roundChangeJustification,
valueToPropose,
valCheck,
signedRoundChange.Message.Round,
) == nil {
// not returning error, no need to
return msg, valueToPropose, nil
}
}
return nil, nil, nil
}
// isProposalJustificationForLeadingRound - returns nil if we have a quorum of round change msgs and highest justified value for leading round
func isProposalJustificationForLeadingRound(
state *State,
config IConfig,
roundChangeMsg *SignedMessage,
roundChanges []*SignedMessage,
roundChangeJustifications []*SignedMessage,
value []byte,
valCheck ProposedValueCheckF,
newRound Round,
) error {
if err := isReceivedProposalJustification(
state,
config,
roundChanges,
roundChangeJustifications,
roundChangeMsg.Message.Round,
value,
valCheck); err != nil {
return err
}
if proposer(state, config, roundChangeMsg.Message.Round) != state.Share.OperatorID {
return errors.New("not proposer")
}
currentRoundProposal := state.ProposalAcceptedForCurrentRound == nil && state.Round == newRound
futureRoundProposal := newRound > state.Round
if !currentRoundProposal && !futureRoundProposal {
return errors.New("proposal round mismatch")
}
return nil
}
// isReceivedProposalJustification - returns nil if we have a quorum of round change msgs and highest justified value
func isReceivedProposalJustification(
state *State,
config IConfig,
roundChanges, prepares []*SignedMessage,
newRound Round,
value []byte,
valCheck ProposedValueCheckF,
) error {
if err := isProposalJustification(
state,
config,
roundChanges,
prepares,
state.Height,
newRound,
value,
valCheck,
); err != nil {
return errors.Wrap(err, "proposal not justified")
}
return nil
}
func validRoundChangeForDataIgnoreSignature(
state *State,
config IConfig,
signedMsg *SignedMessage,
height Height,
round Round,
fullData []byte,
) error {
if signedMsg.Message.MsgType != RoundChangeMsgType {
return errors.New("round change msg type is wrong")
}
if signedMsg.Message.Height != height {
return errors.New("wrong msg height")
}
if signedMsg.Message.Round != round {
return errors.New("wrong msg round")
}
if len(signedMsg.GetSigners()) != 1 {
return errors.New("msg allows 1 signer")
}
if err := signedMsg.Validate(); err != nil {
return errors.Wrap(err, "roundChange invalid")
}
if !signedMsg.CheckSignersInCommittee(state.Share.Committee) {
return errors.New("signer not in committee")
}
// Addition to formal spec
// We add this extra tests on the msg itself to filter round change msgs with invalid justifications, before they are inserted into msg containers
if signedMsg.Message.RoundChangePrepared() {
r, err := HashDataRoot(fullData)
if err != nil {
return errors.Wrap(err, "could not hash input data")
}
// validate prepare message justifications
prepareMsgs, _ := signedMsg.Message.GetRoundChangeJustifications() // no need to check error, checked on signedMsg.Message.Validate()
for _, pm := range prepareMsgs {
if err := validSignedPrepareForHeightRoundAndRootVerifySignature(
config,
pm,
state.Height,
signedMsg.Message.DataRound,
signedMsg.Message.Root,
state.Share.Committee); err != nil {
return errors.Wrap(err, "round change justification invalid")
}
}
if !bytes.Equal(r[:], signedMsg.Message.Root[:]) {
return errors.New("H(data) != root")
}
if !HasQuorum(state.Share, prepareMsgs) {
return errors.New("no justifications quorum")
}
if signedMsg.Message.DataRound > round {
return errors.New("prepared round > round")
}
return nil
}
return nil
}
func validRoundChangeForDataVerifySignature(
state *State,
config IConfig,
signedMsg *SignedMessage,
height Height,
round Round,
fullData []byte,
) error {
if err := validRoundChangeForDataIgnoreSignature(state, config, signedMsg, height, round, fullData); err != nil {
return err
}
// Verify signature
if err := signedMsg.Signature.VerifyByOperators(signedMsg, config.GetSignatureDomainType(), types.QBFTSignatureType, state.Share.Committee); err != nil {
return errors.Wrap(err, "msg signature invalid")
}
return nil
}
// highestPrepared returns a round change message with the highest prepared round, returns nil if none found
func highestPrepared(roundChanges []*SignedMessage) (*SignedMessage, error) {
var ret *SignedMessage
for _, rc := range roundChanges {
if !rc.Message.RoundChangePrepared() {
continue
}
if ret == nil {
ret = rc
} else {
if ret.Message.DataRound < rc.Message.DataRound {
ret = rc
}
}
}
return ret, nil
}
// returns the min round number out of the signed round change messages and the current round
func minRound(roundChangeMsgs []*SignedMessage) Round {
ret := NoRound
for _, msg := range roundChangeMsgs {
if ret == NoRound || ret > msg.Message.Round {
ret = msg.Message.Round
}
}
return ret
}
func getRoundChangeData(state *State, config IConfig, instanceStartValue []byte) (Round, [32]byte, []byte, []*SignedMessage, error) {
if state.LastPreparedRound != NoRound && state.LastPreparedValue != nil {
justifications, err := getRoundChangeJustification(state, config, state.PrepareContainer)
if err != nil {
return NoRound, [32]byte{}, nil, nil, errors.Wrap(err, "could not get round change justification")
}
r, err := HashDataRoot(state.LastPreparedValue)
if err != nil {
return NoRound, [32]byte{}, nil, nil, errors.Wrap(err, "could not hash input data")
}
return state.LastPreparedRound, r, state.LastPreparedValue, justifications, nil
}
return NoRound, [32]byte{}, nil, nil, nil
}
// CreateRoundChange
/**
RoundChange(
signRoundChange(
UnsignedRoundChange(
|current.blockchain|,
newRound,
digestOptionalBlock(current.lastPreparedBlock),
current.lastPreparedRound),
current.id),
current.lastPreparedBlock,
getRoundChangeJustification(current)
)
*/
func CreateRoundChange(state *State, config IConfig, newRound Round, instanceStartValue []byte) (*SignedMessage, error) {
round, root, fullData, justifications, err := getRoundChangeData(state, config, instanceStartValue)
if err != nil {
return nil, errors.Wrap(err, "could not generate round change data")
}
justificationsData, err := MarshalJustifications(justifications)
if err != nil {
return nil, errors.Wrap(err, "could not marshal justifications")
}
msg := &Message{
MsgType: RoundChangeMsgType,
Height: state.Height,
Round: newRound,
Identifier: state.ID,
Root: root,
DataRound: round,
RoundChangeJustification: justificationsData,
}
sig, err := config.GetShareSigner().SignRoot(msg, types.QBFTSignatureType, state.Share.SharePubKey)
if err != nil {
return nil, errors.Wrap(err, "failed signing prepare msg")
}
signedMsg := &SignedMessage{
Signature: sig,
Signers: []types.OperatorID{state.Share.OperatorID},
Message: *msg,
FullData: fullData,
}
return signedMsg, nil
}