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DKG messages between participants are now signed and verified
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,84 @@ | ||
| package dkg | ||
|
|
||
| import ( | ||
| "errors" | ||
|
|
||
| "github.com/drand/drand/util" | ||
|
|
||
| "github.com/drand/drand/key" | ||
| "github.com/drand/drand/protobuf/drand" | ||
| "google.golang.org/protobuf/types/known/timestamppb" | ||
| ) | ||
|
|
||
| func (d *DKGProcess) signMessage(beaconID, messageType string, proposal *drand.ProposalTerms) (*drand.DKGMetadata, error) { | ||
| kp, err := d.beaconIdentifier.KeypairFor(beaconID) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
||
| sig, err := kp.Scheme().AuthScheme.Sign(kp.Key, messageForProto(proposal, messageType, beaconID)) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| return &drand.DKGMetadata{ | ||
| BeaconID: beaconID, | ||
| Address: kp.Public.Address(), | ||
| Signature: sig, | ||
| }, nil | ||
| } | ||
|
|
||
| func (d *DKGProcess) verifyMessage(messageType string, metadata *drand.DKGMetadata, proposal *drand.ProposalTerms) error { | ||
| participants := util.Concat(proposal.Remaining, proposal.Joining) | ||
| // signing is done before the metadata is attached, so we must remove it before we perform verification | ||
| proposal.Metadata = nil | ||
|
|
||
| // find the participant the signature is allegedly from | ||
| var p *drand.Participant | ||
| for _, participant := range participants { | ||
| if participant.Address == metadata.Address { | ||
| p = participant | ||
| break | ||
| } | ||
| } | ||
| if p == nil { | ||
| return errors.New("no such participant") | ||
| } | ||
|
|
||
| // get the scheme for the network so we can correctly unmarshal the public key | ||
| kp, err := d.beaconIdentifier.KeypairFor(metadata.BeaconID) | ||
| if err != nil { | ||
| return err | ||
| } | ||
|
|
||
| // use that scheme to verify the message came from the alleged author | ||
| pubPoint := kp.Scheme().KeyGroup.Point() | ||
| err = pubPoint.UnmarshalBinary(p.PubKey) | ||
| if err != nil { | ||
| return key.ErrInvalidKeyScheme | ||
| } | ||
| return kp.Scheme().AuthScheme.Verify(pubPoint, messageForProto(proposal, messageType, metadata.BeaconID), metadata.Signature) | ||
| } | ||
|
|
||
| func messageForProto(proposal *drand.ProposalTerms, messageType, beaconID string) []byte { | ||
| return []byte(proposal.String() + messageType + beaconID) | ||
| } | ||
|
|
||
| // used for determining the message that was signed for verifying packet authenticity | ||
| func termsFromState(state *DBState) *drand.ProposalTerms { | ||
| return &drand.ProposalTerms{ | ||
| BeaconID: state.BeaconID, | ||
| Threshold: state.Threshold, | ||
| Epoch: state.Epoch, | ||
| SchemeID: state.SchemeID, | ||
| BeaconPeriodSeconds: uint32(state.BeaconPeriod.Seconds()), | ||
| CatchupPeriodSeconds: uint32(state.CatchupPeriod.Seconds()), | ||
| GenesisTime: timestamppb.New(state.GenesisTime), | ||
| GenesisSeed: state.GenesisSeed, | ||
| TransitionTime: timestamppb.New(state.TransitionTime), | ||
| Timeout: timestamppb.New(state.Timeout), | ||
| Leader: state.Leader, | ||
| Joining: state.Joining, | ||
| Remaining: state.Remaining, | ||
| Leaving: state.Leaving, | ||
| } | ||
| } |
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