Add basic message validator

Author: jannikluhn

rolling-shutter/gnosisaccessnode/decryptionkeyshandler.go

@@ -0,0 +1,83 @@
+package gnosisaccessnode
+
+import (
+	"context"
+	"math"
+
+	pubsub "github.com/libp2p/go-libp2p-pubsub"
+	"github.com/pkg/errors"
+
+	"github.com/shutter-network/rolling-shutter/rolling-shutter/p2pmsg"
+)
+
+const (
+	// TODO: pull these from keyper set manager
+	n         = 7
+	threshold = 5
+)
+
+type DecryptionKeysHandler struct {
+	config *Config
+}
+
+func NewDecryptionKeysHandler(config *Config) *DecryptionKeysHandler {
+	return &DecryptionKeysHandler{
+		config: config,
+	}
+}
+
+func (*DecryptionKeysHandler) MessagePrototypes() []p2pmsg.Message {
+	return []p2pmsg.Message{&p2pmsg.DecryptionKeys{}}
+}
+
+func (handler *DecryptionKeysHandler) ValidateMessage(_ context.Context, msg p2pmsg.Message) (pubsub.ValidationResult, error) {
+	key := msg.(*p2pmsg.DecryptionKeys)
+	result, err := handler.validateCommonFields(key)
+	if result != pubsub.ValidationAccept || err != nil {
+		return result, err
+	}
+	result, err = handler.validateGnosisFields(key)
+	if result != pubsub.ValidationAccept || err != nil {
+		return result, err
+	}
+	return pubsub.ValidationAccept, nil
+}
+
+func (handler *DecryptionKeysHandler) validateCommonFields(key *p2pmsg.DecryptionKeys) (pubsub.ValidationResult, error) {
+	if key.InstanceID != handler.config.InstanceID {
+		return pubsub.ValidationReject,
+			errors.Errorf("instance ID mismatch (want=%d, have=%d)", handler.config.InstanceID, key.GetInstanceID())
+	}
+	if key.Eon > math.MaxInt64 {
+		return pubsub.ValidationReject, errors.Errorf("eon %d overflows int64", key.Eon)
+	}
+
+	if len(key.Keys) == 0 {
+		return pubsub.ValidationReject, errors.New("no keys in message")
+	}
+	if len(key.Keys) > int(handler.config.MaxNumKeysPerMessage) {
+		return pubsub.ValidationReject, errors.Errorf(
+			"too many keys in message (%d > %d)",
+			len(key.Keys),
+			handler.config.MaxNumKeysPerMessage,
+		)
+	}
+	return pubsub.ValidationAccept, nil
+}
+
+func (handler *DecryptionKeysHandler) validateGnosisFields(keys *p2pmsg.DecryptionKeys) (pubsub.ValidationResult, error) {
+	extraWrapped, ok := keys.Extra.(*p2pmsg.DecryptionKeys_Gnosis)
+	if !ok {
+		return pubsub.ValidationReject, errors.Errorf("unexpected extra type %T, expected Gnosis", keys.Extra)
+	}
+	extra := extraWrapped.Gnosis
+	if extra == nil {
+		return pubsub.ValidationReject, errors.New("missing extra Gnosis data")
+	}
+
+	return pubsub.ValidationAccept, nil
+}
+
+func (handler *DecryptionKeysHandler) HandleMessage(_ context.Context, _ p2pmsg.Message) ([]p2pmsg.Message, error) {
+	return nil, nil
+}

rolling-shutter/gnosisaccessnode/node.go

@@ -3,7 +3,10 @@ package gnosisaccessnode
 import (
 	"context"
 
+	"github.com/pkg/errors"
+
 	"github.com/shutter-network/rolling-shutter/rolling-shutter/medley/service"
+	"github.com/shutter-network/rolling-shutter/rolling-shutter/p2p"
 )
 
 type GnosisAccessNode struct {
@@ -17,5 +20,10 @@ func New(config *Config) *GnosisAccessNode {
 }
 
 func (node *GnosisAccessNode) Start(ctx context.Context, runner service.Runner) error {
-	return nil
+	messageSender, err := p2p.New(node.config.P2P)
+	if err != nil {
+		return errors.Wrap(err, "failed to initialize p2p messaging")
+	}
+	messageSender.AddMessageHandler(NewDecryptionKeysHandler(node.config))
+	return runner.StartService(messageSender)
 }