ctlsock: add initial limited implementation

At the moment, in forward mode you can only encrypt paths
and in reverse mode you can only decrypt paths.

5 files changed, 177 insertions, 2 deletions

diff --git a/internal/ctlsock/ctlsock_serve.go b/internal/ctlsock/ctlsock_serve.go
new file mode 100644
index 0000000..571260d
--- /dev/null
+++ b/internal/ctlsock/ctlsock_serve.go
@@ -0,0 +1,137 @@
+// Package ctlsock implementes the control socket interface that can be
+// activated by passing "-ctlsock" on the command line.
+package ctlsock
+
+import (
+	"encoding/json"
+	"errors"
+	"io"
+	"net"
+	"os"
+	"syscall"
+
+	"github.com/rfjakob/gocryptfs/internal/tlog"
+)
+
+// Interface should be implemented by fusefrontend[_reverse]
+type Interface interface {
+	EncryptPath(string) (string, error)
+	DecryptPath(string) (string, error)
+}
+
+// RequestStruct is sent by a client
+type RequestStruct struct {
+	EncryptPath string
+	DecryptPath string
+}
+
+// ResponseStruct is sent by us as response to a request
+type ResponseStruct struct {
+	// Result is the resulting decrypted or encrypted path. Empty on error.
+	Result string
+	// ErrNo is the error number as defined in errno.h.
+	// 0 means success and -1 means that the error number is not known
+	// (look at ErrText in this case).
+	ErrNo int32
+	// ErrText is a detailed error message.
+	ErrText string
+}
+
+type ctlSockHandler struct {
+	fs     Interface
+	socket *net.UnixListener
+}
+
+// CreateAndServe creates an unix socket at "path" and serves incoming
+// connections in a new goroutine.
+func CreateAndServe(path string, fs Interface) error {
+	sock, err := net.Listen("unix", path)
+	if err != nil {
+		return err
+	}
+	handler := ctlSockHandler{
+		fs:     fs,
+		socket: sock.(*net.UnixListener),
+	}
+	go handler.acceptLoop()
+	return nil
+}
+
+func (ch *ctlSockHandler) acceptLoop() {
+	for {
+		conn, err := ch.socket.Accept()
+		if err != nil {
+			tlog.Warn.Printf("ctlsock: Accept error: %v", err)
+			break
+		}
+		go ch.handleConnection(conn.(*net.UnixConn))
+	}
+}
+
+func (ch *ctlSockHandler) handleConnection(conn *net.UnixConn) {
+	// 2*PATH_MAX is definitely big enough for requests to decrypt or
+	// encrypt paths.
+	buf := make([]byte, 2*syscall.PathMax)
+	for {
+		n, err := conn.Read(buf)
+		if err == io.EOF {
+			conn.Close()
+			return
+		} else if err != nil {
+			tlog.Warn.Printf("ctlsock: Read error: %#v", err)
+			conn.Close()
+			return
+		}
+		buf = buf[:n]
+		var in RequestStruct
+		err = json.Unmarshal(buf, &in)
+		if err != nil {
+			tlog.Warn.Printf("ctlsock: Unmarshal error: %#v", err)
+			errorMsg := ResponseStruct{
+				ErrNo:   int32(syscall.EINVAL),
+				ErrText: err.Error(),
+			}
+			sendResponse(&errorMsg, conn)
+		}
+		ch.handleRequest(&in, conn)
+		// Restore original size.
+		buf = buf[:cap(buf)]
+	}
+}
+
+func (ch *ctlSockHandler) handleRequest(in *RequestStruct, conn *net.UnixConn) {
+	var err error
+	var out ResponseStruct
+	if in.DecryptPath != "" && in.EncryptPath != "" {
+		err = errors.New("Ambigous")
+	} else if in.DecryptPath == "" && in.EncryptPath == "" {
+		err = errors.New("No operation")
+	} else if in.DecryptPath != "" {
+		out.Result, err = ch.fs.DecryptPath(in.DecryptPath)
+	} else if in.EncryptPath != "" {
+		out.Result, err = ch.fs.EncryptPath(in.EncryptPath)
+	}
+	if err != nil {
+		out.ErrText = err.Error()
+		out.ErrNo = -1
+		// Try to extract the actual error number
+		if pe, ok := err.(*os.PathError); ok {
+			if se, ok := pe.Err.(syscall.Errno); ok {
+				out.ErrNo = int32(se)
+			}
+		}
+	}
+	sendResponse(&out, conn)
+}
+
+func sendResponse(msg *ResponseStruct, conn *net.UnixConn) {
+	jsonMsg, err := json.Marshal(msg)
+	if err != nil {
+		tlog.Warn.Printf("ctlsock: Marshal failed: %v", err)
+		return
+	}
+	_, err = conn.Write(jsonMsg)
+	if err != nil {
+		tlog.Warn.Printf("ctlsock: Write failed: %v", err)
+	}
+}
diff --git a/internal/fusefrontend/ctlsock_interface.go b/internal/fusefrontend/ctlsock_interface.go
new file mode 100644
index 0000000..c22dce6
--- /dev/null
+++ b/internal/fusefrontend/ctlsock_interface.go
@@ -0,0 +1,19 @@
+package fusefrontend
+
+import (
+	"errors"
+
+	"github.com/rfjakob/gocryptfs/internal/ctlsock"
+)
+
+var _ ctlsock.Interface = &FS{} // Verify that interface is implemented.
+
+// EncryptPath implements ctlsock.Backend
+func (fs *FS) EncryptPath(plainPath string) (string, error) {
+	return fs.encryptPath(plainPath)
+}
+
+// DecryptPath implements ctlsock.Backend
+func (fs *FS) DecryptPath(plainPath string) (string, error) {
+	return "", errors.New("Not implemented")
+}
diff --git a/internal/fusefrontend/write_lock.go b/internal/fusefrontend/write_lock.go
index 7394994..3addfd6 100644
--- a/internal/fusefrontend/write_lock.go
+++ b/internal/fusefrontend/write_lock.go
@@ -21,7 +21,7 @@ var wlock wlockMap
 // 2) lock ... unlock ...
 // 3) unregister
 type wlockMap struct {
-	// Counts lock() calls. As every operation that modifies a file should
+	// opCount counts lock() calls. As every operation that modifies a file should
 	// call it, this effectively serves as a write-operation counter.
 	// The variable is accessed without holding any locks so atomic operations
 	// must be used. It must be the first element of the struct to guarantee
diff --git a/internal/fusefrontend_reverse/ctlsock_interface.go b/internal/fusefrontend_reverse/ctlsock_interface.go
new file mode 100644
index 0000000..448663f
--- /dev/null
+++ b/internal/fusefrontend_reverse/ctlsock_interface.go
@@ -0,0 +1,19 @@
+package fusefrontend_reverse
+
+import (
+	"errors"
+
+	"github.com/rfjakob/gocryptfs/internal/ctlsock"
+)
+
+var _ ctlsock.Interface = &reverseFS{} // Verify that interface is implemented.
+
+// EncryptPath implements ctlsock.Backend
+func (rfs *reverseFS) EncryptPath(plainPath string) (string, error) {
+	return "", errors.New("Not implemented")
+}
+
+// DecryptPath implements ctlsock.Backend
+func (rfs *reverseFS) DecryptPath(plainPath string) (string, error) {
+	return rfs.decryptPath(plainPath)
+}
diff --git a/internal/fusefrontend_reverse/rfs.go b/internal/fusefrontend_reverse/rfs.go
index 87a2602..84348f7 100644
--- a/internal/fusefrontend_reverse/rfs.go
+++ b/internal/fusefrontend_reverse/rfs.go
@@ -49,7 +49,7 @@ var _ pathfs.FileSystem = &reverseFS{}
 // NewFS returns an encrypted FUSE overlay filesystem.
 // In this case (reverse mode) the backing directory is plain-text and
 // reverseFS provides an encrypted view.
-func NewFS(args fusefrontend.Args) pathfs.FileSystem {
+func NewFS(args fusefrontend.Args) *reverseFS {
 	if args.CryptoBackend != cryptocore.BackendAESSIV {
 		panic("reverse mode must use AES-SIV, everything else is insecure")
 	}