Implement proper daemonization

The shell wrapper sends gocryptfs into the background and waits for SIGUSR1

all.bash

@@ -3,6 +3,4 @@
 set -eu
 
 cd gocryptfs_main
-echo -n "Compiling... "
 go build
-echo "done."

cryptfs/cryptfs.go

@@ -9,10 +9,11 @@ import (
 )
 
 const (
+	DEFAULT_PLAINBS = 4096
 	KEY_LEN         = 16
 	NONCE_LEN       = 12
 	AUTH_TAG_LEN    = 16
-	DEFAULT_PLAINBS = 4096
+	FILEID_LEN      = 16
 )
 
 type CryptFS struct {

gocryptfs

@@ -1,9 +1,13 @@
 #!/bin/bash
 
-# Simple wrapper that runs the gocryptfs process in the background
+# Shell wrapper that runs the gocryptfs process in the background
+# and exits on SIGUSR1
 
 set -eu
 
+trap "exit 0" SIGUSR1
+shopt -u huponexit
+
 dir=$(dirname "$0")
 main="$dir/gocryptfs_main/gocryptfs_main"
 
@@ -12,11 +16,8 @@ if [ ! -x $main ]; then
 	exit 1
 fi
 
-# This needs user input and cannot run in the background
-if [[ $* == *--init* ]]; then
-	"$main" $*
-else
-	"$main" $* &
-	sleep 0.1
-	disown
-fi
+# A backgrounded process gets /dev/null as stdin per default.
+# Explicitly set stdin to the current stdin so we can ask the user for input.
+"$main" $* < /proc/self/fd/0 & wait
+# The "& wait" is neccessary because bash only processes signals when
+# executing internal commands

gocryptfs_main/main.go

@@ -128,11 +128,20 @@ func main() {
 			fmt.Println(err)
 			os.Exit(ERREXIT_LOADCONF)
 		}
-		fmt.Printf("Success\n")
+		fmt.Printf("done.\n")
+	}
+
+	srv := pathfsFrontend(key, cipherdir, mountpoint, fusedebug)
+	fmt.Printf("Mounted.\n")
+
+	if zerokey == false {
 		printMasterKey(key)
 	}
 
-	pathfsFrontend(key, cipherdir, mountpoint, fusedebug)
+	// Send notification to our parent
+	sendSig()
+	// Jump into server loop
+	srv.Serve()
 }
 
 // printMasterKey - remind the user that he should store the master key in
@@ -143,12 +152,13 @@ func printMasterKey(key []byte) {
 	h = h[0:8] + "-" + h[8:16] + "-" + h[16:24] + "-" + h[24:32]
 
 	fmt.Printf(`
-WARNING:
-  If the gocryptfs config file becomes corrupted or you ever
-  forget your password, there is only one hope for recovery:
-  The master key. Print it to a piece of paper and store it in a drawer.
+ATTENTION:
 
-  Master key: %s
+  Your master key is: %s
+
+If the gocryptfs.conf file becomes corrupted or you ever forget your password,
+there is only one hope for recovery: The master key. Print it to a piece of
+paper and store it in a drawer.
 
 `, h)
 }
@@ -171,7 +181,7 @@ func readPassword() string {
 	fd := int(os.Stdin.Fd())
 	p, err := terminal.ReadPassword(fd)
 	if err != nil {
-		fmt.Printf("Error: Could not read password: %s\n")
+		fmt.Printf("Error: Could not read password: %v\n", err)
 		os.Exit(ERREXIT_PASSWORD)
 	}
 	return string(p)
@@ -189,7 +199,7 @@ func dirEmpty(dir string) bool {
 	return false
 }
 
-func pathfsFrontend(key []byte, cipherdir string, mountpoint string, debug bool) {
+func pathfsFrontend(key []byte, cipherdir string, mountpoint string, debug bool) *fuse.Server {
 
 	finalFs := pathfs_frontend.NewFS(key, cipherdir, USE_OPENSSL)
 	pathFsOpts := &pathfs.PathNodeFsOptions{ClientInodes: true}
@@ -210,13 +220,12 @@ func pathfsFrontend(key []byte, cipherdir string, mountpoint string, debug bool)
 	// Second column, "Type", will be shown as "fuse." + Name
 	mOpts.Name = "gocryptfs"
 
-	state, err := fuse.NewServer(conn.RawFS(), mountpoint, &mOpts)
+	srv, err := fuse.NewServer(conn.RawFS(), mountpoint, &mOpts)
 	if err != nil {
-		fmt.Printf("Mount fail: %v\n", err)
+		fmt.Printf("Mount failed: %v", err)
 		os.Exit(1)
 	}
-	state.SetDebug(debug)
+	srv.SetDebug(debug)
 
-	fmt.Println("Mounted.")
-	state.Serve()
+	return srv
 }

gocryptfs_main/sendsig.go

@@ -0,0 +1,42 @@
+package main
+
+import (
+	"syscall"
+	"bytes"
+	"fmt"
+	"os"
+	"io/ioutil"
+)
+
+// cmdline looks like this: /bin/bash \0 /path/to/gocryptfs \0 --zerokey \0 ...
+const (
+	WRAPPER_PREFIX =  "/bin/bash\000"
+	WRAPPER_CONTAINS = "gocryptfs\000"
+)
+
+// Send USR1 to the "gocryptfs" wrapper shell script. This notifies it that the
+// mounting has completed sucessfully.
+//
+// Checks /proc/$PPID/cmdline to make sure we do not kill an unrelated process.
+func sendSig() {
+	ppid := os.Getppid()
+	fn := fmt.Sprintf("/proc/%d/cmdline", ppid)
+	cmdline, err := ioutil.ReadFile(fn)
+	if err != nil {
+		fmt.Printf("sendSig: ReadFile: %v\n", err)
+		return
+	}
+	if bytes.HasPrefix(cmdline, []byte(WRAPPER_PREFIX)) && bytes.Contains(cmdline, []byte(WRAPPER_CONTAINS)) {
+		p, err := os.FindProcess(ppid)
+		if err != nil {
+			fmt.Printf("sendSig: FindProcess: %v\n", err)
+			return
+		}
+		err = p.Signal(syscall.SIGUSR1)
+		if err != nil {
+			fmt.Printf("sendSig: Signal: %v\n", err)
+		}
+	} else {
+		fmt.Printf("Not running under the gocryptfs wrapper - will not daemonize\n")
+	}
+}