tor: remove Onion Service upon shutdown

This commit adds a new method to call DEL_ONION when lnd is shutting
down. Tor controller will now be aware of the active serviceID and
removes the service upon shutdown.

tor/cmd_onion.go

@@ -0,0 +1,301 @@
+package tor
+
+import (
+	"errors"
+	"fmt"
+	"io/ioutil"
+	"os"
+)
+
+var (
+	// ErrNoPrivateKey is an error returned by the OnionStore.PrivateKey
+	// method when a private key hasn't yet been stored.
+	ErrNoPrivateKey = errors.New("private key not found")
+)
+
+// OnionType denotes the type of the onion service.
+type OnionType int
+
+const (
+	// V2 denotes that the onion service is V2.
+	V2 OnionType = iota
+
+	// V3 denotes that the onion service is V3.
+	V3
+)
+
+// OnionStore is a store containing information about a particular onion
+// service.
+type OnionStore interface {
+	// StorePrivateKey stores the private key according to the
+	// implementation of the OnionStore interface.
+	StorePrivateKey(OnionType, []byte) error
+
+	// PrivateKey retrieves a stored private key. If it is not found, then
+	// ErrNoPrivateKey should be returned.
+	PrivateKey(OnionType) ([]byte, error)
+
+	// DeletePrivateKey securely removes the private key from the store.
+	DeletePrivateKey(OnionType) error
+}
+
+// OnionFile is a file-based implementation of the OnionStore interface that
+// stores an onion service's private key.
+type OnionFile struct {
+	privateKeyPath string
+	privateKeyPerm os.FileMode
+}
+
+// A compile-time constraint to ensure OnionFile satisfies the OnionStore
+// interface.
+var _ OnionStore = (*OnionFile)(nil)
+
+// NewOnionFile creates a file-based implementation of the OnionStore interface
+// to store an onion service's private key.
+func NewOnionFile(privateKeyPath string,
+	privateKeyPerm os.FileMode) *OnionFile {
+
+	return &OnionFile{
+		privateKeyPath: privateKeyPath,
+		privateKeyPerm: privateKeyPerm,
+	}
+}
+
+// StorePrivateKey stores the private key at its expected path.
+func (f *OnionFile) StorePrivateKey(_ OnionType, privateKey []byte) error {
+	return ioutil.WriteFile(f.privateKeyPath, privateKey, f.privateKeyPerm)
+}
+
+// PrivateKey retrieves the private key from its expected path. If the file
+// does not exist, then ErrNoPrivateKey is returned.
+func (f *OnionFile) PrivateKey(_ OnionType) ([]byte, error) {
+	if _, err := os.Stat(f.privateKeyPath); os.IsNotExist(err) {
+		return nil, ErrNoPrivateKey
+	}
+	return ioutil.ReadFile(f.privateKeyPath)
+}
+
+// DeletePrivateKey removes the file containing the private key.
+func (f *OnionFile) DeletePrivateKey(_ OnionType) error {
+	return os.Remove(f.privateKeyPath)
+}
+
+// AddOnionConfig houses all of the required parameters in order to
+// successfully create a new onion service or restore an existing one.
+type AddOnionConfig struct {
+	// Type denotes the type of the onion service that should be created.
+	Type OnionType
+
+	// VirtualPort is the externally reachable port of the onion address.
+	VirtualPort int
+
+	// TargetPorts is the set of ports that the service will be listening
+	// on locally. The Tor server will use choose a random port from this
+	// set to forward the traffic from the virtual port.
+	//
+	// NOTE: If nil/empty, the virtual port will be used as the only target
+	// port.
+	TargetPorts []int
+
+	// Store is responsible for storing all onion service related
+	// information.
+	//
+	// NOTE: If not specified, then nothing will be stored, making onion
+	// services unrecoverable after shutdown.
+	Store OnionStore
+}
+
+// prepareKeyparam takes a config and prepares the key param to be used inside
+// ADD_ONION.
+func (c *Controller) prepareKeyparam(cfg AddOnionConfig) (string, error) {
+	// We'll start off by checking if the store contains an existing
+	// private key. If it does not, then we should request the server to
+	// create a new onion service and return its private key. Otherwise,
+	// we'll request the server to recreate the onion server from our
+	// private key.
+	var keyParam string
+	switch cfg.Type {
+	// TODO(yy): drop support for v2.
+	case V2:
+		keyParam = "NEW:RSA1024"
+	case V3:
+		keyParam = "NEW:ED25519-V3"
+	}
+
+	if cfg.Store != nil {
+		privateKey, err := cfg.Store.PrivateKey(cfg.Type)
+		switch err {
+		// Proceed to request a new onion service.
+		case ErrNoPrivateKey:
+
+		// Recover the onion service with the private key found.
+		case nil:
+			keyParam = string(privateKey)
+
+		default:
+			return "", err
+		}
+	}
+
+	return keyParam, nil
+}
+
+// prepareAddOnion constructs a cmd command string based on the specified
+// config.
+func (c *Controller) prepareAddOnion(cfg AddOnionConfig) (string, error) {
+	// Create the keyParam.
+	keyParam, err := c.prepareKeyparam(cfg)
+	if err != nil {
+		return "", err
+	}
+
+	// Now, we'll create a mapping from the virtual port to each target
+	// port. If no target ports were specified, we'll use the virtual port
+	// to provide a one-to-one mapping.
+	var portParam string
+
+	// Helper function which appends the correct Port param depending on
+	// whether the user chose to use a custom target IP address or not.
+	pushPortParam := func(targetPort int) {
+		if c.targetIPAddress == "" {
+			portParam += fmt.Sprintf("Port=%d,%d ", cfg.VirtualPort,
+				targetPort)
+		} else {
+			portParam += fmt.Sprintf("Port=%d,%s:%d ",
+				cfg.VirtualPort, c.targetIPAddress, targetPort)
+		}
+	}
+
+	if len(cfg.TargetPorts) == 0 {
+		pushPortParam(cfg.VirtualPort)
+	} else {
+		for _, targetPort := range cfg.TargetPorts {
+			pushPortParam(targetPort)
+		}
+	}
+
+	// Send the command to create the onion service to the Tor server and
+	// await its response.
+	cmd := fmt.Sprintf("ADD_ONION %s %s", keyParam, portParam)
+
+	return cmd, nil
+}
+
+// AddOnion creates an ephemeral onion service and returns its onion address.
+// Once created, the new onion service will remain active until either,
+//   - the onion service is removed via `DEL_ONION`.
+//   - the Tor daemon terminates.
+//   - the controller connection that originated the `ADD_ONION` is closed.
+// Each connection can only see its own ephemeral services. If a service needs
+// to survive beyond current controller connection, use the "Detach" flag when
+// creating new service via `ADD_ONION`.
+func (c *Controller) AddOnion(cfg AddOnionConfig) (*OnionAddr, error) {
+	// Before sending the request to create an onion service to the Tor
+	// server, we'll make sure that it supports V3 onion services if that
+	// was the type requested.
+	// TODO(yy): drop support for v2.
+	if cfg.Type == V3 {
+		if err := supportsV3(c.version); err != nil {
+			return nil, err
+		}
+	}
+
+	// Construct the cmd command.
+	cmd, err := c.prepareAddOnion(cfg)
+	if err != nil {
+		return nil, err
+	}
+
+	// Send the command to create the onion service to the Tor server and
+	// await its response.
+	_, reply, err := c.sendCommand(cmd)
+	if err != nil {
+		return nil, err
+	}
+
+	// If successful, the reply from the server should be of the following
+	// format, depending on whether a private key has been requested:
+	//
+	//	C: ADD_ONION RSA1024:[Blob Redacted] Port=80,8080
+	//	S: 250-ServiceID=testonion1234567
+	//	S: 250 OK
+	//
+	//	C: ADD_ONION NEW:RSA1024 Port=80,8080
+	//	S: 250-ServiceID=testonion1234567
+	//	S: 250-PrivateKey=RSA1024:[Blob Redacted]
+	//	S: 250 OK
+	//
+	// We're interested in retrieving the service ID, which is the public
+	// name of the service, and the private key if requested.
+	replyParams := parseTorReply(reply)
+	serviceID, ok := replyParams["ServiceID"]
+	if !ok {
+		return nil, errors.New("service id not found in reply")
+	}
+
+	// If a new onion service was created and an onion store was provided,
+	// we'll store its private key to disk in the event that it needs to be
+	// recreated later on.
+	if privateKey, ok := replyParams["PrivateKey"]; cfg.Store != nil && ok {
+		err := cfg.Store.StorePrivateKey(cfg.Type, []byte(privateKey))
+		if err != nil {
+			return nil, fmt.Errorf("unable to write private key "+
+				"to file: %v", err)
+		}
+	}
+
+	c.activeServiceID = serviceID
+	log.Debugf("serviceID:%s added to tor controller", serviceID)
+
+	// Finally, we'll return the onion address composed of the service ID,
+	// along with the onion suffix, and the port this onion service can be
+	// reached at externally.
+	return &OnionAddr{
+		OnionService: serviceID + ".onion",
+		Port:         cfg.VirtualPort,
+	}, nil
+}
+
+// DelOnion tells the Tor daemon to remove an onion service, which satisfies
+// either,
+//   - the onion service was created on the same control connection as the
+//     "DEL_ONION" command.
+//   - the onion service was created using the "Detach" flag.
+func (c *Controller) DelOnion(serviceID string) error {
+	log.Debugf("removing serviceID:%s from tor controller", serviceID)
+
+	cmd := fmt.Sprintf("DEL_ONION %s", serviceID)
+
+	// Send the command to create the onion service to the Tor server and
+	// await its response.
+	code, _, err := c.sendCommand(cmd)
+
+	// Tor replies with "250 OK" on success, or a 512 if there are an
+	// invalid number of arguments, or a 552 if it doesn't recognize the
+	// ServiceID.
+	switch code {
+	// Replied 250 OK.
+	case success:
+		return nil
+
+	// Replied 512 for invalid arguments. This is most likely that the
+	// serviceID is not set(empty string).
+	case invalidNumOfArguments:
+		return fmt.Errorf("invalid arguments: %w", err)
+
+	// Replied 552, which means either,
+	//   - the serviceID is invalid.
+	//   - the onion service is not owned by the current control connection
+	//     and,
+	//   - the onion service is not a detached service.
+	// In either case, we will ignore the error and log a warning as there
+	// not much we can do from the controller side.
+	case serviceIDNotRecognized:
+		log.Warnf("removing serviceID:%v not found", serviceID)
+		return nil
+
+	default:
+		return fmt.Errorf("undefined response code: %v, err: %w",
+			code, err)
+	}
+}