feat(privval): expose GetPubKey over gRPC (#2881)

## Description

While working on the Fibre side implementation I realised that I needed
to expose the `GetPubKey` method as well
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Author: ninabarbakadze

privval/grpc_server.go

@@ -3,7 +3,9 @@ package privval
 import (
 	"context"
 
+	cryptoenc "github.com/cometbft/cometbft/crypto/encoding"
 	"github.com/cometbft/cometbft/libs/log"
+	"github.com/cometbft/cometbft/proto/tendermint/crypto"
 	privvalproto "github.com/cometbft/cometbft/proto/tendermint/privval"
 	"github.com/cometbft/cometbft/types"
 )
@@ -47,3 +49,36 @@ func (s *PrivValidatorGRPCServer) SignRawBytes(
 		Signature: sig,
 	}, nil
 }
+
+func (s *PrivValidatorGRPCServer) GetPubKey(
+	_ context.Context,
+	req *privvalproto.PubKeyRequest,
+) (*privvalproto.PubKeyResponse, error) {
+	pubKey, err := s.privVal.GetPubKey()
+	if err != nil {
+		s.logger.Error("GetPubKey failed", "err", err)
+		return &privvalproto.PubKeyResponse{
+			PubKey: crypto.PublicKey{},
+			Error: &privvalproto.RemoteSignerError{
+				Code:        0,
+				Description: err.Error(),
+			},
+		}, nil
+	}
+
+	pk, err := cryptoenc.PubKeyToProto(pubKey)
+	if err != nil {
+		s.logger.Error("GetPubKey failed", "err", err)
+		return &privvalproto.PubKeyResponse{
+			PubKey: crypto.PublicKey{},
+			Error: &privvalproto.RemoteSignerError{
+				Code:        0,
+				Description: err.Error(),
+			},
+		}, nil
+	}
+
+	return &privvalproto.PubKeyResponse{
+		PubKey: pk,
+	}, nil
+}

privval/grpc_server_test.go

@@ -18,11 +18,9 @@ import (
 
 const testChainID = "test-chain"
 
-func setupGRPCServer(t *testing.T) (privvalproto.PrivValidatorAPIClient, types.PrivValidator) {
+func setupGRPCServerWithPV(t *testing.T, pv types.PrivValidator) privvalproto.PrivValidatorAPIClient {
 	t.Helper()
 
-	pv := types.NewMockPV()
-
 	lis, err := net.Listen("tcp", "127.0.0.1:0")
 	require.NoError(t, err)
 
@@ -41,11 +39,12 @@ func setupGRPCServer(t *testing.T) (privvalproto.PrivValidatorAPIClient, types.P
 	require.NoError(t, err)
 	t.Cleanup(func() { _ = conn.Close() })
 
-	return privvalproto.NewPrivValidatorAPIClient(conn), pv
+	return privvalproto.NewPrivValidatorAPIClient(conn)
 }
 
 func TestGRPCServerSignRawBytes(t *testing.T) {
-	client, pv := setupGRPCServer(t)
+	pv := types.NewMockPV()
+	client := setupGRPCServerWithPV(t, pv)
 
 	rawBytes := []byte("test commitment data")
 	uniqueID := "fiber-commitment"
@@ -66,31 +65,27 @@ func TestGRPCServerSignRawBytes(t *testing.T) {
 }
 
 func TestGRPCServerSignRawBytesError(t *testing.T) {
-	pv := types.NewErroringMockPV()
-
-	lis, err := net.Listen("tcp", "127.0.0.1:0")
-	require.NoError(t, err)
-
-	srv := grpc.NewServer()
-	privvalproto.RegisterPrivValidatorAPIServer(srv, privval.NewPrivValidatorGRPCServer(
-		pv,
-		log.NewNopLogger(),
-	))
-	go func() { _ = srv.Serve(lis) }()
-	t.Cleanup(srv.Stop)
-
-	conn, err := grpc.NewClient(
-		lis.Addr().String(),
-		grpc.WithTransportCredentials(insecure.NewCredentials()),
-	)
-	require.NoError(t, err)
-	t.Cleanup(func() { _ = conn.Close() })
+	client := setupGRPCServerWithPV(t, types.NewErroringMockPV())
 
-	client := privvalproto.NewPrivValidatorAPIClient(conn)
 	resp, err := client.SignRawBytes(context.Background(), &privvalproto.SignRawBytesRequest{
 		RawBytes: []byte("test data"),
 		UniqueId: "fiber-commitment",
 	})
 	require.NoError(t, err)
 	require.NotNil(t, resp.Error)
 }
+
+func TestGRPCServerGetPubKey(t *testing.T) {
+	pv := types.NewMockPV()
+	client := setupGRPCServerWithPV(t, pv)
+
+	resp, err := client.GetPubKey(context.Background(), &privvalproto.PubKeyRequest{
+		ChainId: testChainID,
+	})
+	require.NoError(t, err)
+	assert.Nil(t, resp.Error)
+
+	expectedPubKey, err := pv.GetPubKey()
+	require.NoError(t, err)
+	assert.Equal(t, expectedPubKey.Bytes(), resp.PubKey.GetEd25519())
+}

proto/tendermint/privval/types.pb.go

@@ -78,6 +78,7 @@ message PingResponse {}
 // from the node's privval without direct access to the key.
 service PrivValidatorAPI {
   rpc SignRawBytes(SignRawBytesRequest) returns (SignedRawBytesResponse);
+  rpc GetPubKey(PubKeyRequest) returns (PubKeyResponse);
 }
 
 message Message {