Add ProtecingKeymanager interface and calls (#4982)

* Add ProtectedKeymanager interface and calls

* Rename interface

Co-authored-by: Raul Jordan <raul@prysmaticlabs.com>

validator/client/BUILD.bazel

@@ -19,6 +19,7 @@ go_library(
         "//beacon-chain/core/helpers:go_default_library",
         "//proto/beacon/rpc/v1:go_default_library",
         "//proto/slashing:go_default_library",
+        "//shared/bls:go_default_library",
         "//shared/bytesutil:go_default_library",
         "//shared/featureconfig:go_default_library",
         "//shared/hashutil:go_default_library",

validator/client/validator_attest.go

@@ -12,10 +12,12 @@ import (
 	"github.com/prysmaticlabs/go-bitfield"
 	"github.com/prysmaticlabs/go-ssz"
 	slashpb "github.com/prysmaticlabs/prysm/proto/slashing"
+	"github.com/prysmaticlabs/prysm/shared/bls"
 	"github.com/prysmaticlabs/prysm/shared/bytesutil"
 	"github.com/prysmaticlabs/prysm/shared/featureconfig"
 	"github.com/prysmaticlabs/prysm/shared/hashutil"
 	"github.com/prysmaticlabs/prysm/shared/params"
+	"github.com/prysmaticlabs/prysm/validator/keymanager"
 	"github.com/sirupsen/logrus"
 	"go.opencensus.io/trace"
 )
@@ -209,7 +211,12 @@ func (v *validator) signAtt(ctx context.Context, pubKey [48]byte, data *ethpb.At
 		return nil, err
 	}
 
-	sig, err := v.keyManager.Sign(pubKey, root, domain.SignatureDomain)
+	var sig *bls.Signature
+	if protectingKeymanager, supported := v.keyManager.(keymanager.ProtectingKeyManager); supported {
+		sig, err = protectingKeymanager.SignAttestation(pubKey, domain.SignatureDomain, data)
+	} else {
+		sig, err = v.keyManager.Sign(pubKey, root, domain.SignatureDomain)
+	}
 	if err != nil {
 		return nil, err
 	}

validator/client/validator_propose.go

@@ -12,9 +12,11 @@ import (
 	ethpb "github.com/prysmaticlabs/ethereumapis/eth/v1alpha1"
 	"github.com/prysmaticlabs/go-ssz"
 	slashpb "github.com/prysmaticlabs/prysm/proto/slashing"
+	"github.com/prysmaticlabs/prysm/shared/bls"
 	"github.com/prysmaticlabs/prysm/shared/bytesutil"
 	"github.com/prysmaticlabs/prysm/shared/featureconfig"
 	"github.com/prysmaticlabs/prysm/shared/params"
+	"github.com/prysmaticlabs/prysm/validator/keymanager"
 	"github.com/sirupsen/logrus"
 	"go.opencensus.io/trace"
 )
@@ -196,7 +198,12 @@ func (v *validator) signBlock(ctx context.Context, pubKey [48]byte, epoch uint64
 	if err != nil {
 		return nil, errors.Wrap(err, "could not get signing root")
 	}
-	sig, err := v.keyManager.Sign(pubKey, root, domain.SignatureDomain)
+	var sig *bls.Signature
+	if protectingKeymanager, supported := v.keyManager.(keymanager.ProtectingKeyManager); supported {
+		sig, err = protectingKeymanager.SignProposal(pubKey, domain.SignatureDomain, b)
+	} else {
+		sig, err = v.keyManager.Sign(pubKey, root, domain.SignatureDomain)
+	}
 	if err != nil {
 		return nil, errors.Wrap(err, "could not get signing root")
 	}

validator/keymanager/BUILD.bazel

@@ -19,6 +19,7 @@ go_library(
         "//shared/bytesutil:go_default_library",
         "//shared/interop:go_default_library",
         "//validator/accounts:go_default_library",
+        "@com_github_prysmaticlabs_ethereumapis//eth/v1alpha1:go_default_library",
         "@com_github_sirupsen_logrus//:go_default_library",
         "@com_github_wealdtech_go_eth2_wallet//:go_default_library",
         "@com_github_wealdtech_go_eth2_wallet_store_filesystem//:go_default_library",

validator/keymanager/keymanager.go

@@ -3,6 +3,7 @@ package keymanager
 import (
 	"errors"
 
+	ethpb "github.com/prysmaticlabs/ethereumapis/eth/v1alpha1"
 	"github.com/prysmaticlabs/prysm/shared/bls"
 )
 
@@ -12,10 +13,22 @@ var ErrNoSuchKey = errors.New("no such key")
 // ErrCannotSign is returned whenever a signing attempt fails.
 var ErrCannotSign = errors.New("cannot sign")
 
+// ErrCouldSlash is returned whenever a signing attempt is refused due to a potential slashing event.
+var ErrCouldSlash = errors.New("could result in a slashing event")
+
 // KeyManager controls access to private keys by the validator.
 type KeyManager interface {
 	// FetchValidatingKeys fetches the list of public keys that should be used to validate with.
 	FetchValidatingKeys() ([][48]byte, error)
 	// Sign signs a message for the validator to broadcast.
 	Sign(pubKey [48]byte, root [32]byte, domain uint64) (*bls.Signature, error)
 }
+
+// ProtectingKeyManager provides access to a keymanager that protects its clients from slashing events.
+type ProtectingKeyManager interface {
+	// SignProposal signs a block proposal for the validator to broadcast.
+	SignProposal(pubKey [48]byte, domain uint64, data *ethpb.BeaconBlock) (*bls.Signature, error)
+
+	// SignAttestation signs an attestation for the validator to broadcast.
+	SignAttestation(pubKey [48]byte, domain uint64, data *ethpb.AttestationData) (*bls.Signature, error)
+}