Refactor cli argument handling

Also, add the "-config" option for storing gocryptfs.conf
outside of CIPHERDIR.

5 files changed, 153 insertions, 114 deletions

diff --git a/MANPAGE.md b/MANPAGE.md
index 3dde852..7ed5e1e 100644
--- a/MANPAGE.md
+++ b/MANPAGE.md
@@ -23,7 +23,7 @@ gocryptfs [OPTIONS] CIPHERDIR MOUNTPOINT
 Change password
 ---------------
 
-gocryptfs -passwd CIPHERDIR
+gocryptfs -passwd [OPTIONS] CIPHERDIR
 
 DESCRIPTION
 ===========
diff --git a/checkdir.go b/checkdir.go
index 9614d7d..6f7f75d 100644
--- a/checkdir.go
+++ b/checkdir.go
@@ -6,6 +6,7 @@ import (
 	"os"
 )
 
+// checkDirEmpty - check if "dir" exists and is an empty directory
 func checkDirEmpty(dir string) error {
 	err := checkDir(dir)
 	if err != nil {
@@ -21,6 +22,7 @@ func checkDirEmpty(dir string) error {
 	return fmt.Errorf("directory %s not empty", dir)
 }
 
+// checkDir - check if "dir" exists and is a directory
 func checkDir(dir string) error {
 	fi, err := os.Stat(dir)
 	if err != nil {
diff --git a/daemonize.go b/daemonize.go
index 4f09164..a65bd11 100644
--- a/daemonize.go
+++ b/daemonize.go
@@ -9,17 +9,18 @@ import (
 )
 
 // The child sends us USR1 if the mount was successful
-func waitForUsr1() {
+func exitOnUsr1() {
 	c := make(chan os.Signal, 1)
 	signal.Notify(c, syscall.SIGUSR1)
 	<-c
 	os.Exit(0)
 }
 
-// daemonize - execute ourselves once again, this time with the "-f" flag, and
-// wait for SIGUSR1.
-func daemonize() {
-	go waitForUsr1()
+// forkChild - execute ourselves once again, this time with the "-f" flag, and
+// wait for SIGUSR1 or child exit.
+// This is a workaround for the missing true fork function in Go.
+func forkChild() {
+	go exitOnUsr1()
 	name := os.Args[0]
 	notifyArg := fmt.Sprintf("-notifypid=%d", os.Getpid())
 	newArgs := []string{"-f", notifyArg}
@@ -30,7 +31,7 @@ func daemonize() {
 	c.Stdin = os.Stdin
 	err := c.Start()
 	if err != nil {
-		fmt.Printf("daemonize: starting %s failed: %v\n", name, err)
+		fmt.Printf("forkChild: starting %s failed: %v\n", name, err)
 		os.Exit(1)
 	}
 	err = c.Wait()
@@ -40,7 +41,7 @@ func daemonize() {
 				os.Exit(waitstat.ExitStatus())
 			}
 		}
-		fmt.Printf("daemonize: wait returned an unknown error: %v\n", err)
+		fmt.Printf("forkChild: wait returned an unknown error: %v\n", err)
 		os.Exit(1)
 	}
 	// The child exited with 0 - let's do the same.
diff --git a/main.go b/main.go
index 0f3fb4f..ece032e 100644
--- a/main.go
+++ b/main.go
@@ -36,19 +36,16 @@ const (
 // GitVersion will be set by the build script "build.bash"
 var GitVersion = "[version not set - please compile using ./build.bash]"
 
-func initDir(dirArg string, plaintextNames bool) {
-	dir, _ := filepath.Abs(dirArg)
-
-	err := checkDirEmpty(dir)
+func initDir(args *argContainer) {
+	err := checkDirEmpty(args.cipherdir)
 	if err != nil {
 		fmt.Printf("Invalid CIPHERDIR: %v\n", err)
 		os.Exit(ERREXIT_INIT)
 	}
 
-	confName := filepath.Join(dir, cryptfs.ConfDefaultName)
 	cryptfs.Info.Printf("Choose a password for protecting your files.\n")
 	password := readPasswordTwice()
-	err = cryptfs.CreateConfFile(confName, password, plaintextNames)
+	err = cryptfs.CreateConfFile(args.config, password, args.plaintextnames)
 	if err != nil {
 		fmt.Println(err)
 		os.Exit(ERREXIT_INIT)
@@ -58,23 +55,71 @@ func initDir(dirArg string, plaintextNames bool) {
 }
 
 func usageText() {
-	fmt.Fprintf(os.Stderr, "Usage: %s -init [OPTIONS] CIPHERDIR\n", PROGRAM_NAME)
-	fmt.Fprintf(os.Stderr, "       %s [OPTIONS] CIPHERDIR MOUNTPOINT\n", PROGRAM_NAME)
-	fmt.Fprintf(os.Stderr, "\nOptions:\n")
+	printVersion()
+	fmt.Printf("\n")
+	fmt.Printf("Usage: %s -init|-passwd [OPTIONS] CIPHERDIR\n", PROGRAM_NAME)
+	fmt.Printf("  or   %s [OPTIONS] CIPHERDIR MOUNTPOINT\n", PROGRAM_NAME)
+	fmt.Printf("\nOptions:\n")
 	flagSet.PrintDefaults()
 }
 
 type argContainer struct {
 	debug, init, zerokey, fusedebug, openssl, passwd, foreground, version,
 	plaintextnames, quiet bool
-	masterkey, mountpoint, cipherdir, cpuprofile string
+	masterkey, mountpoint, cipherdir, cpuprofile, config string
 	notifypid                                    int
 }
 
 var flagSet *flag.FlagSet
 
+// loadConfig - load the config file "filename", prompting the user for the password
+func loadConfig(filename string) (masterkey []byte, confFile *cryptfs.ConfFile) {
+	// Check if the file exists at all before prompting for a password
+	_, err := os.Stat(filename)
+	if err != nil {
+		fmt.Print(err)
+		os.Exit(ERREXIT_LOADCONF)
+	}
+	fmt.Printf("Password: ")
+	pw := readPassword()
+	cryptfs.Info.Printf("Decrypting master key... ")
+	cryptfs.Warn.Disable() // Silence DecryptBlock() error messages on incorrect password
+	masterkey, confFile, err = cryptfs.LoadConfFile(filename, pw)
+	cryptfs.Warn.Enable()
+	if err != nil {
+		fmt.Println(err)
+		fmt.Println("Wrong password.")
+		os.Exit(ERREXIT_LOADCONF)
+	}
+	cryptfs.Info.Printf("done.\n")
+
+	return masterkey, confFile
+}
+
+// changePassword - change the password of config file "filename"
+func changePassword(filename string) {
+	masterkey, confFile := loadConfig(filename)
+	fmt.Printf("Please enter your new password.\n")
+	newPw := readPasswordTwice()
+	confFile.EncryptKey(masterkey, newPw)
+	err := confFile.WriteFile()
+	if err != nil {
+		fmt.Println(err)
+		os.Exit(ERREXIT_INIT)
+	}
+	cryptfs.Info.Printf("Password changed.\n")
+	os.Exit(0)
+}
+
+// printVersion - print a version string like
+// "gocryptfs v0.3.1-31-g6736212-dirty; on-disk format 2"
+func printVersion() {
+	fmt.Printf("%s %s; on-disk format %d\n", PROGRAM_NAME, GitVersion, cryptfs.HEADER_CURRENT_VERSION)
+}
+
 func main() {
 	runtime.GOMAXPROCS(4)
+	var err error
 
 	// Parse command line arguments
 	var args argContainer
@@ -93,20 +138,54 @@ func main() {
 	flagSet.BoolVar(&args.quiet, "q", false, "Quiet - silence informational messages")
 	flagSet.StringVar(&args.masterkey, "masterkey", "", "Mount with explicit master key")
 	flagSet.StringVar(&args.cpuprofile, "cpuprofile", "", "Write cpu profile to specified file")
+	flagSet.StringVar(&args.config, "config", "", "Use specified config file instead of CIPHERDIR/gocryptfs.conf")
 	flagSet.IntVar(&args.notifypid, "notifypid", 0, "Send USR1 to the specified process after "+
 		"successful mount - used internally for daemonization")
 	flagSet.Parse(os.Args[1:])
 
+	if args.debug {
+		cryptfs.Debug.Enable()
+		cryptfs.Debug.Printf("Debug output enabled\n")
+	}
+	// By default, let the child handle everything.
+	// The parent *could* handle operations that do not require backgrounding by
+	// itself, but that would make the code paths more complicated.
+	if !args.foreground {
+		forkChild() // does not return
+	}
+	// Getting here means we *are* the child
+	// "-v"
 	if args.version {
-		fmt.Printf("%s %s; on-disk format %d\n", PROGRAM_NAME, GitVersion, cryptfs.HEADER_CURRENT_VERSION)
+		printVersion()
 		os.Exit(0)
 	}
+	// Every operation below requires CIPHERDIR. Check that we have it.
+	if flagSet.NArg() >= 1 {
+		args.cipherdir, _ = filepath.Abs(flagSet.Arg(0))
+		err := checkDir(args.cipherdir)
+		if err != nil {
+			fmt.Printf("Invalid CIPHERDIR: %v\n", err)
+			os.Exit(ERREXIT_CIPHERDIR)
+		}
+	} else {
+		usageText()
+		os.Exit(ERREXIT_USAGE)
+	}
+	// "-q"
 	if args.quiet {
 		cryptfs.Info.Disable()
 	}
-	if !args.foreground {
-		daemonize() // does not return
+	// "-config"
+	if args.config != "" {
+		args.config, err = filepath.Abs(args.config)
+		if err != nil {
+			fmt.Printf("Invalid \"-config\" setting: %v\n", err)
+		}
+		cryptfs.Info.Printf("Using config file at custom location %s\n", args.config)
+	} else {
+		args.config = filepath.Join(args.cipherdir, cryptfs.ConfDefaultName)
 	}
+	// "-cpuprofile"
 	if args.cpuprofile != "" {
 		f, err := os.Create(args.cpuprofile)
 		if err != nil {
@@ -117,123 +196,79 @@ func main() {
 		pprof.StartCPUProfile(f)
 		defer pprof.StopCPUProfile()
 	}
-	if args.debug {
-		cryptfs.Debug.Enable()
-		cryptfs.Debug.Printf("Debug output enabled\n")
-	}
+	// "-openssl"
 	if args.openssl == false {
 		cryptfs.Info.Printf("Openssl disabled\n")
 	}
+	// Operation flags: init, passwd or mount
+	// "-init"
 	if args.init {
-		if flagSet.NArg() != 1 && args.plaintextnames == false {
-			fmt.Printf("Usage: %s --init [--plaintextnames] CIPHERDIR\n", PROGRAM_NAME)
+		if flagSet.NArg() > 1 {
+			fmt.Printf("Usage: %s -init [OPTIONS] CIPHERDIR\n", PROGRAM_NAME)
 			os.Exit(ERREXIT_USAGE)
 		}
-		initDir(flagSet.Arg(0), args.plaintextnames) // does not return
+		initDir(&args) // does not return
 	}
+	// "-passwd"
 	if args.passwd {
-		if flagSet.NArg() != 1 {
-			fmt.Printf("Usage: %s --passwd CIPHERDIR\n", PROGRAM_NAME)
-			os.Exit(ERREXIT_USAGE)
-		}
-	} else {
-		// Normal mount
-		if flagSet.NArg() < 2 {
-			usageText()
+		if flagSet.NArg() > 1 {
+			fmt.Printf("Usage: %s -passwd [OPTIONS] CIPHERDIR\n", PROGRAM_NAME)
 			os.Exit(ERREXIT_USAGE)
 		}
-		args.mountpoint, _ = filepath.Abs(flagSet.Arg(1))
-		err := checkDirEmpty(args.mountpoint)
-		if err != nil {
-			fmt.Printf("Invalid MOUNTPOINT: %v\n", err)
-			os.Exit(ERREXIT_MOUNTPOINT)
-		}
+		changePassword(args.config) // does not return
 	}
-	args.cipherdir, _ = filepath.Abs(flagSet.Arg(0))
-	err := checkDir(args.cipherdir)
-	if err != nil {
-		fmt.Printf("Invalid CIPHERDIR: %v\n", err)
-		os.Exit(ERREXIT_CIPHERDIR)
-	}
-
-	var plaintextNames bool
-	var cf *cryptfs.ConfFile
-	var currentPassword string
-	key := make([]byte, cryptfs.KEY_LEN)
-	if args.zerokey {
-		cryptfs.Info.Printf("Zerokey mode active: using all-zero dummy master key.\n")
-		plaintextNames = args.plaintextnames
-	} else if len(args.masterkey) > 0 {
-		key = parseMasterKey(args.masterkey)
-		cryptfs.Info.Printf("Using explicit master key.\n")
-	} else {
-		// Load config file
-		cfname := filepath.Join(args.cipherdir, cryptfs.ConfDefaultName)
-		_, err = os.Stat(cfname)
-		if err != nil {
-			fmt.Printf("Error: %s not found in CIPHERDIR\n", cryptfs.ConfDefaultName)
-			fmt.Printf("Please run \"%s --init %s\" first\n", os.Args[0], flagSet.Arg(0))
-			os.Exit(ERREXIT_LOADCONF)
-		}
-		if args.passwd == true {
-			fmt.Printf("Old password: ")
-		} else {
-			fmt.Printf("Password: ")
-		}
-		currentPassword = readPassword()
-		cryptfs.Info.Printf("Decrypting master key... ")
-		cryptfs.Warn.Disable() // Silence DecryptBlock() error messages on incorrect password
-		key, cf, err = cryptfs.LoadConfFile(cfname, currentPassword)
-		cryptfs.Warn.Enable()
-		if err != nil {
-			fmt.Println(err)
-			os.Exit(ERREXIT_LOADCONF)
-		}
-		cryptfs.Info.Printf("done.\n")
+	// Mount
+	// Check mountpoint
+	if flagSet.NArg() < 2 {
+		usageText()
+		os.Exit(ERREXIT_USAGE)
 	}
-	if args.passwd == true {
-		fmt.Printf("Please enter the new password.\n")
-		newPassword := readPasswordTwice()
-		if newPassword == currentPassword {
-			fmt.Printf("New and old passwords are identical\n")
-			os.Exit(ERREXIT_PASSWORD)
-		}
-		cf.EncryptKey(key, newPassword)
-		err := cf.WriteFile()
-		if err != nil {
-			fmt.Println(err)
-			os.Exit(ERREXIT_INIT)
-		}
-		cryptfs.Info.Printf("Password changed.\n")
-		os.Exit(0)
+	args.mountpoint, err = filepath.Abs(flagSet.Arg(1))
+	if err != nil {
+		fmt.Printf("Invalid MOUNTPOINT: %v\n", err)
+		os.Exit(ERREXIT_MOUNTPOINT)
 	}
-
-	if cf != nil {
-		plaintextNames = cf.PlaintextNames()
+	err = checkDirEmpty(args.mountpoint)
+	if err != nil {
+		fmt.Printf("Invalid MOUNTPOINT: %v\n", err)
+		os.Exit(ERREXIT_MOUNTPOINT)
 	}
-	srv := pathfsFrontend(key, args.cipherdir, args.mountpoint, args.fusedebug, args.openssl, plaintextNames)
-
-	if args.zerokey == false && len(args.masterkey) == 0 {
-		printMasterKey(key)
-	} else if args.zerokey == true {
-		cryptfs.Info.Printf("ZEROKEY MODE PROVIDES NO SECURITY AT ALL AND SHOULD ONLY BE USED FOR TESTING.\n")
-	} else if len(args.masterkey) > 0 {
+	// Get master key
+	var masterkey []byte
+	if args.masterkey != "" {
+		// "-masterkey"
+		cryptfs.Info.Printf("Using explicit master key.\n")
+		masterkey = parseMasterKey(args.masterkey)
 		cryptfs.Info.Printf("THE MASTER KEY IS VISIBLE VIA \"ps -auxwww\", ONLY USE THIS MODE FOR EMERGENCIES.\n")
+	} else if args.zerokey {
+		// "-zerokey"
+		cryptfs.Info.Printf("Using all-zero dummy master key.\n")
+		cryptfs.Info.Printf("ZEROKEY MODE PROVIDES NO SECURITY AT ALL AND SHOULD ONLY BE USED FOR TESTING.\n")
+		masterkey = make([]byte, cryptfs.KEY_LEN)
+	} else {
+		// Load master key from config file
+		var confFile *cryptfs.ConfFile
+		masterkey, confFile = loadConfig(args.config)
+		printMasterKey(masterkey)
+		args.plaintextnames = confFile.PlaintextNames()
 	}
-
+	// Initialize FUSE server
+	srv := pathfsFrontend(masterkey, args.cipherdir, args.mountpoint, args.fusedebug, args.openssl, args.plaintextnames)
 	cryptfs.Info.Println("Filesystem ready.")
-	// Send USR1 notification
+	// We are ready - send USR1 signal to our parent
 	if args.notifypid > 0 {
 		sendUsr1(args.notifypid)
 	}
-	// Wait for SIGING in the background and unmount ourselves if we get it
-	// This prevents a dangling "Transport endpoint is not connected" mountpoint
+	// Wait for SIGINT in the background and unmount ourselves if we get it.
+	// This prevents a dangling "Transport endpoint is not connected" mountpoint.
 	handleSigint(srv, args.mountpoint)
 	// Jump into server loop. Returns when it gets an umount request from the kernel.
 	srv.Serve()
-	// main returns with code 0
+	// main exits with code 0
 }
 
+// pathfsFrontend - initialize FUSE server based on go-fuse's PathFS
+// Calls os.Exit on errors
 func pathfsFrontend(key []byte, cipherdir string, mountpoint string,
 	debug bool, openssl bool, plaintextNames bool) *fuse.Server {
 
diff --git a/masterkey.go b/masterkey.go
index a1889b4..2062997 100644
--- a/masterkey.go
+++ b/masterkey.go
@@ -37,7 +37,8 @@ paper and store it in a drawer.
 `, hChunked)
 }
 
-// Parse a hex-encoded master key that was passed on the command line
+// parseMasterKey - Parse a hex-encoded master key that was passed on the command line
+// Calls os.Exit on failure
 func parseMasterKey(masterkey string) []byte {
 	masterkey = strings.Replace(masterkey, "-", "", -1)
 	key, err := hex.DecodeString(masterkey)