Create sdk/ and api/ submodules (#6583)

sdk/plugin/serve.go

@@ -0,0 +1,92 @@
+package plugin
+
+import (
+	"crypto/tls"
+	"math"
+	"os"
+
+	"google.golang.org/grpc"
+
+	log "github.com/hashicorp/go-hclog"
+	plugin "github.com/hashicorp/go-plugin"
+	"github.com/hashicorp/vault/sdk/helper/pluginutil"
+	"github.com/hashicorp/vault/sdk/logical"
+)
+
+// BackendPluginName is the name of the plugin that can be
+// dispensed from the plugin server.
+const BackendPluginName = "backend"
+
+type TLSProviderFunc func() (*tls.Config, error)
+
+type ServeOpts struct {
+	BackendFactoryFunc logical.Factory
+	TLSProviderFunc    TLSProviderFunc
+	Logger             log.Logger
+}
+
+// Serve is a helper function used to serve a backend plugin. This
+// should be ran on the plugin's main process.
+func Serve(opts *ServeOpts) error {
+	logger := opts.Logger
+	if logger == nil {
+		logger = log.New(&log.LoggerOptions{
+			Level:      log.Trace,
+			Output:     os.Stderr,
+			JSONFormat: true,
+		})
+	}
+
+	// pluginMap is the map of plugins we can dispense.
+	pluginSets := map[int]plugin.PluginSet{
+		// Version 3 used to supports both protocols. We want to keep it around
+		// since it's possible old plugins built against this version will still
+		// work with gRPC. There is currently no difference between version 3
+		// and version 4.
+		3: plugin.PluginSet{
+			"backend": &GRPCBackendPlugin{
+				Factory: opts.BackendFactoryFunc,
+				Logger:  logger,
+			},
+		},
+		4: plugin.PluginSet{
+			"backend": &GRPCBackendPlugin{
+				Factory: opts.BackendFactoryFunc,
+				Logger:  logger,
+			},
+		},
+	}
+
+	err := pluginutil.OptionallyEnableMlock()
+	if err != nil {
+		return err
+	}
+
+	serveOpts := &plugin.ServeConfig{
+		HandshakeConfig:  handshakeConfig,
+		VersionedPlugins: pluginSets,
+		TLSProvider:      opts.TLSProviderFunc,
+		Logger:           logger,
+
+		// A non-nil value here enables gRPC serving for this plugin...
+		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)
+		},
+	}
+
+	plugin.Serve(serveOpts)
+
+	return nil
+}
+
+// handshakeConfigs are used to just do a basic handshake between
+// a plugin and host. If the handshake fails, a user friendly error is shown.
+// This prevents users from executing bad plugins or executing a plugin
+// directory. It is a UX feature, not a security feature.
+var handshakeConfig = plugin.HandshakeConfig{
+	ProtocolVersion:  4,
+	MagicCookieKey:   "VAULT_BACKEND_PLUGIN",
+	MagicCookieValue: "6669da05-b1c8-4f49-97d9-c8e5bed98e20",
+}