plugins: Allow the server to receive large messages (#4958)

logical/plugin/grpc_backend_client.go

@@ -3,6 +3,7 @@ package plugin
 import (
 	"context"
 	"errors"
+	"math"
 	"sync/atomic"
 
 	"google.golang.org/grpc"
@@ -195,6 +196,9 @@ func (b *backendGRPCPluginClient) Setup(ctx context.Context, config *logical.Bac
 
 	// Register the server in this closure.
 	serverFunc := func(opts []grpc.ServerOption) *grpc.Server {
+		opts = append(opts, grpc.MaxRecvMsgSize(math.MaxInt32))
+		opts = append(opts, grpc.MaxSendMsgSize(math.MaxInt32))
+
 		s := grpc.NewServer(opts...)
 		pb.RegisterSystemViewServer(s, sysView)
 		pb.RegisterStorageServer(s, storage)

logical/plugin/serve.go

@@ -2,8 +2,11 @@ package plugin
 
 import (
 	"crypto/tls"
+	"math"
 	"os"
 
+	"google.golang.org/grpc"
+
 	log "github.com/hashicorp/go-hclog"
 	"github.com/hashicorp/go-plugin"
 	"github.com/hashicorp/vault/helper/pluginutil"
@@ -54,7 +57,11 @@ func Serve(opts *ServeOpts) error {
 		Logger:          logger,
 
 		// A non-nil value here enables gRPC serving for this plugin...
-		GRPCServer: plugin.DefaultGRPCServer,
+		GRPCServer: func(opts []grpc.ServerOption) *grpc.Server {
+			opts = append(opts, grpc.MaxRecvMsgSize(math.MaxInt32))
+			opts = append(opts, grpc.MaxSendMsgSize(math.MaxInt32))
+			return plugin.DefaultGRPCServer(opts)
+		},
 	}
 
 	if !pluginutil.GRPCSupport() {