fusefrontend[_reverse]: move crypto init up to caller

Both fusefrontend and fusefrontend_reverse were doing
essentially the same thing, move it into main's
initFuseFrontend.

A side-effect is that we have a reference to cryptocore
in main, which will help with wiping the keys on exit
(https://github.com/rfjakob/gocryptfs/issues/211).

internal/fusefrontend/args.go

@@ -2,7 +2,6 @@ package fusefrontend
 
 import (
 	"github.com/hanwen/go-fuse/fuse"
-	"github.com/rfjakob/gocryptfs/internal/cryptocore"
 )
 
 // Args is a container for arguments that are passed from main() to fusefrontend
@@ -10,7 +9,6 @@ type Args struct {
 	// Cipherdir is the backing storage directory (absolute path).
 	// For reverse mode, Cipherdir actually contains *plaintext* files.
 	Cipherdir      string
-	CryptoBackend  cryptocore.AEADTypeEnum
 	PlaintextNames bool
 	LongNames      bool
 	// Should we chown a file after it has been created?
@@ -26,15 +24,8 @@ type Args struct {
 	// location. If it is false, reverse mode maps ".gocryptfs.reverse.conf"
 	// to "gocryptfs.conf" in the plaintext dir.
 	ConfigCustom bool
-	// Raw64 is true when RawURLEncoding (without padding) should be used for
-	// file names.
-	// Corresponds to the Raw64 feature flag introduced in gocryptfs v1.2.
-	Raw64 bool
 	// NoPrealloc disables automatic preallocation before writing
 	NoPrealloc bool
-	// Use HKDF key derivation.
-	// Corresponds to the HKDF feature flag introduced in gocryptfs v1.3.
-	HKDF bool
 	// Try to serialize read operations, "-serialize_reads"
 	SerializeReads bool
 	// Force decode even if integrity check fails (openSSL only)

internal/fusefrontend/fs.go

@@ -17,7 +17,6 @@ import (
 	"github.com/hanwen/go-fuse/fuse/pathfs"
 
 	"github.com/rfjakob/gocryptfs/internal/contentenc"
-	"github.com/rfjakob/gocryptfs/internal/cryptocore"
 	"github.com/rfjakob/gocryptfs/internal/nametransform"
 	"github.com/rfjakob/gocryptfs/internal/serialize_reads"
 	"github.com/rfjakob/gocryptfs/internal/syscallcompat"
@@ -44,20 +43,15 @@ type FS struct {
 var _ pathfs.FileSystem = &FS{} // Verify that interface is implemented.
 
 // NewFS returns a new encrypted FUSE overlay filesystem.
-func NewFS(masterkey []byte, args Args) *FS {
+func NewFS(args Args, c *contentenc.ContentEnc, n *nametransform.NameTransform) *FS {
-	cryptoCore := cryptocore.New(masterkey, args.CryptoBackend, contentenc.DefaultIVBits, args.HKDF, args.ForceDecode)
-	contentEnc := contentenc.New(cryptoCore, contentenc.DefaultBS, args.ForceDecode)
-	nameTransform := nametransform.New(cryptoCore.EMECipher, args.LongNames, args.Raw64)
-
 	if args.SerializeReads {
 		serialize_reads.InitSerializer()
 	}
-
 	return &FS{
 		FileSystem:    pathfs.NewLoopbackFileSystem(args.Cipherdir),
 		args:          args,
-		nameTransform: nameTransform,
+		nameTransform: n,
-		contentEnc:    contentEnc,
+		contentEnc:    c,
 	}
 }
 

internal/fusefrontend_reverse/rfs.go

@@ -2,7 +2,6 @@ package fusefrontend_reverse
 
 import (
 	"fmt"
-	"log"
 	"path/filepath"
 	"syscall"
 
@@ -42,22 +41,15 @@ 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(masterkey []byte, args fusefrontend.Args) *ReverseFS {
+func NewFS(args fusefrontend.Args, c *contentenc.ContentEnc, n *nametransform.NameTransform) *ReverseFS {
-	if args.CryptoBackend != cryptocore.BackendAESSIV {
-		log.Panic("reverse mode must use AES-SIV, everything else is insecure")
-	}
 	initLongnameCache()
-	cryptoCore := cryptocore.New(masterkey, args.CryptoBackend, contentenc.DefaultIVBits, args.HKDF, false)
-	contentEnc := contentenc.New(cryptoCore, contentenc.DefaultBS, false)
-	nameTransform := nametransform.New(cryptoCore.EMECipher, args.LongNames, args.Raw64)
-
 	return &ReverseFS{
 		// pathfs.defaultFileSystem returns ENOSYS for all operations
 		FileSystem:    pathfs.NewDefaultFileSystem(),
 		loopbackfs:    pathfs.NewLoopbackFileSystem(args.Cipherdir),
 		args:          args,
-		nameTransform: nameTransform,
+		nameTransform: n,
-		contentEnc:    contentEnc,
+		contentEnc:    c,
 	}
 }
 

mount.go

@@ -3,6 +3,7 @@ package main
 import (
 	"encoding/json"
 	"fmt"
+	"log"
 	"log/syslog"
 	"net"
 	"os"
@@ -21,11 +22,13 @@ import (
 	"github.com/hanwen/go-fuse/fuse/pathfs"
 
 	"github.com/rfjakob/gocryptfs/internal/configfile"
+	"github.com/rfjakob/gocryptfs/internal/contentenc"
 	"github.com/rfjakob/gocryptfs/internal/cryptocore"
 	"github.com/rfjakob/gocryptfs/internal/ctlsock"
 	"github.com/rfjakob/gocryptfs/internal/exitcodes"
 	"github.com/rfjakob/gocryptfs/internal/fusefrontend"
 	"github.com/rfjakob/gocryptfs/internal/fusefrontend_reverse"
+	"github.com/rfjakob/gocryptfs/internal/nametransform"
 	"github.com/rfjakob/gocryptfs/internal/readpassword"
 	"github.com/rfjakob/gocryptfs/internal/tlog"
 )
@@ -182,6 +185,13 @@ func setOpenFileLimit() {
 	}
 }
 
+// ctlsockFs satisfies both the pathfs.FileSystem and the ctlsock.Interface
+// interfaces
+type ctlsockFs interface {
+	pathfs.FileSystem
+	ctlsock.Interface
+}
+
 // initFuseFrontend - initialize gocryptfs/fusefrontend
 // Calls os.Exit on errors
 func initFuseFrontend(masterkey []byte, args *argContainer, confFile *configfile.ConfFile) *fuse.Server {
@@ -203,11 +213,8 @@ func initFuseFrontend(masterkey []byte, args *argContainer, confFile *configfile
 		Cipherdir:      args.cipherdir,
 		PlaintextNames: args.plaintextnames,
 		LongNames:      args.longnames,
-		CryptoBackend:  cryptoBackend,
 		ConfigCustom:   args._configCustom,
-		Raw64:          args.raw64,
 		NoPrealloc:     args.noprealloc,
-		HKDF:           args.hkdf,
 		SerializeReads: args.serialize_reads,
 		ForceDecode:    args.forcedecode,
 		ForceOwner:     args._forceOwner,
@@ -216,10 +223,10 @@ func initFuseFrontend(masterkey []byte, args *argContainer, confFile *configfile
 	if confFile != nil {
 		// Settings from the config file override command line args
 		frontendArgs.PlaintextNames = confFile.IsFeatureFlagSet(configfile.FlagPlaintextNames)
-		frontendArgs.Raw64 = confFile.IsFeatureFlagSet(configfile.FlagRaw64)
+		args.raw64 = confFile.IsFeatureFlagSet(configfile.FlagRaw64)
-		frontendArgs.HKDF = confFile.IsFeatureFlagSet(configfile.FlagHKDF)
+		args.hkdf = confFile.IsFeatureFlagSet(configfile.FlagHKDF)
 		if confFile.IsFeatureFlagSet(configfile.FlagAESSIV) {
-			frontendArgs.CryptoBackend = cryptocore.BackendAESSIV
+			cryptoBackend = cryptocore.BackendAESSIV
 		} else if args.reverse {
 			tlog.Fatal.Printf("AES-SIV is required by reverse mode, but not enabled in the config file")
 			os.Exit(exitcodes.Usage)
@@ -232,8 +239,6 @@ func initFuseFrontend(masterkey []byte, args *argContainer, confFile *configfile
 	}
 	jsonBytes, _ := json.MarshalIndent(frontendArgs, "", "\t")
 	tlog.Debug.Printf("frontendArgs: %s", string(jsonBytes))
-	var finalFs pathfs.FileSystem
-	var ctlSockBackend ctlsock.Interface
 	// pathFsOpts are passed into go-fuse/pathfs
 	pathFsOpts := &pathfs.PathNodeFsOptions{ClientInodes: true}
 	if args.sharedstorage {
@@ -242,21 +247,23 @@ func initFuseFrontend(masterkey []byte, args *argContainer, confFile *configfile
 		// https://github.com/rfjakob/gocryptfs/issues/156
 		pathFsOpts.ClientInodes = false
 	}
+	// Init crypto backend
+	cCore := cryptocore.New(masterkey, cryptoBackend, contentenc.DefaultIVBits, args.hkdf, args.forcedecode)
+	cEnc := contentenc.New(cCore, contentenc.DefaultBS, args.forcedecode)
+	nameTransform := nametransform.New(cCore.EMECipher, frontendArgs.LongNames, args.raw64)
+	// Spawn fusefrontend
+	var fs ctlsockFs
 	if args.reverse {
-		// The dance with the intermediate variables is because we need to
+		if cryptoBackend != cryptocore.BackendAESSIV {
-		// cast the FS into pathfs.FileSystem *and* ctlsock.Interface. This
+			log.Panic("reverse mode must use AES-SIV, everything else is insecure")
-		// avoids using interface{}.
+		}
-		fs := fusefrontend_reverse.NewFS(masterkey, frontendArgs)
+		fs = fusefrontend_reverse.NewFS(frontendArgs, cEnc, nameTransform)
-		finalFs = fs
-		ctlSockBackend = fs
 		// Reverse mode is read-only, so we don't need a working link().
 		// Disable hard link tracking to avoid strange breakage on duplicate
 		// inode numbers ( https://github.com/rfjakob/gocryptfs/issues/149 ).
 		pathFsOpts.ClientInodes = false
 	} else {
-		fs := fusefrontend.NewFS(masterkey, frontendArgs)
+		fs = fusefrontend.NewFS(frontendArgs, cEnc, nameTransform)
-		finalFs = fs
-		ctlSockBackend = fs
 	}
 	// fusefrontend / fusefrontend_reverse have initialized their crypto with
 	// derived keys (HKDF), we can purge the master key from memory.
@@ -266,9 +273,9 @@ func initFuseFrontend(masterkey []byte, args *argContainer, confFile *configfile
 	// We have opened the socket early so that we cannot fail here after
 	// asking the user for the password
 	if args._ctlsockFd != nil {
-		go ctlsock.Serve(args._ctlsockFd, ctlSockBackend)
+		go ctlsock.Serve(args._ctlsockFd, fs)
 	}
-	pathFs := pathfs.NewPathNodeFs(finalFs, pathFsOpts)
+	pathFs := pathfs.NewPathNodeFs(fs, pathFsOpts)
 	var fuseOpts *nodefs.Options
 	if args.sharedstorage {
 		// sharedstorage mode sets all cache timeouts to zero so changes to the