reverse: rename types to reverseXYZ

...to prevent confusion with the forward variants.

FS   -> reverseFS
file -> reverseFile

Also add an incomplete read implementation.

3 files changed, 119 insertions, 36 deletions

diff --git a/internal/fusefrontend_reverse/rfile.go b/internal/fusefrontend_reverse/rfile.go
index 746a0d6..15f2764 100644
--- a/internal/fusefrontend_reverse/rfile.go
+++ b/internal/fusefrontend_reverse/rfile.go
@@ -1,27 +1,79 @@
 package fusefrontend_reverse
 
 import (
+	"fmt"
+	"io"
 	"os"
 
 	"github.com/hanwen/go-fuse/fuse"
 	"github.com/hanwen/go-fuse/fuse/nodefs"
 
 	"github.com/rfjakob/gocryptfs/internal/contentenc"
+	"github.com/rfjakob/gocryptfs/internal/tlog"
 )
 
-type file struct {
+var zeroFileId []byte
+
+func init() {
+	zeroFileId = make([]byte, 16)
+}
+
+type reverseFile struct {
+	// Embed nodefs.defaultFile for a ENOSYS implementation of all methods
+	nodefs.File
+	// Backing FD
 	fd *os.File
 	// Content encryption helper
 	contentEnc *contentenc.ContentEnc
-
-	// nodefs.defaultFile returns ENOSYS for all operations
-	nodefs.File
 }
 
 func NewFile(fd *os.File, contentEnc *contentenc.ContentEnc) (nodefs.File, fuse.Status) {
-	return &file{
+	return &reverseFile{
+		File:       nodefs.NewDefaultFile(),
 		fd:         fd,
 		contentEnc: contentEnc,
-		File:       nodefs.NewDefaultFile(),
 	}, fuse.OK
 }
+
+// GetAttr - FUSE call
+func (rf *reverseFile) GetAttr(*fuse.Attr) fuse.Status {
+	fmt.Printf("reverseFile.GetAttr fd=%d\n", rf.fd.Fd())
+	return fuse.ENOSYS
+}
+
+// Read - FUSE call
+func (rf *reverseFile) Read(buf []byte, off int64) (resultData fuse.ReadResult, status fuse.Status) {
+	// TODO prefix file header
+
+	length := uint64(len(buf))
+	blocks := rf.contentEnc.ExplodeCipherRange(uint64(off), length)
+
+	// Read the backing plaintext in one go
+	alignedOffset, alignedLength := contentenc.JointPlaintextRange(blocks)
+	tlog.Warn.Printf("alignedOffset=%d, alignedLength=%d\n", alignedOffset, alignedLength)
+	plaintext := make([]byte, int(alignedLength))
+	n, err := rf.fd.ReadAt(plaintext, int64(alignedOffset))
+	if err != nil && err != io.EOF {
+		tlog.Warn.Printf("reverseFile.Read: ReadAt: %s", err.Error())
+		return nil, fuse.ToStatus(err)
+	}
+	// Truncate buffer down to actually read bytes
+	plaintext = plaintext[0:n]
+
+	// Encrypt blocks
+	ciphertext := rf.contentEnc.EncryptBlocks(plaintext, blocks[0].BlockNo, zeroFileId)
+
+	// Crop down to the relevant part
+	var out []byte
+	lenHave := len(ciphertext)
+	skip := blocks[0].Skip
+	endWant := int(skip + length)
+	if lenHave > endWant {
+		out = plaintext[skip:endWant]
+	} else if lenHave > int(skip) {
+		out = plaintext[skip:lenHave]
+	}
+	// else: out stays empty, file was smaller than the requested offset
+
+	return fuse.ReadResultData(out), fuse.OK
+}
diff --git a/internal/fusefrontend_reverse/rfs.go b/internal/fusefrontend_reverse/rfs.go
index 914dccb..68a5ac8 100644
--- a/internal/fusefrontend_reverse/rfs.go
+++ b/internal/fusefrontend_reverse/rfs.go
@@ -2,6 +2,7 @@ package fusefrontend_reverse
 
 import (
 	"os"
+	"syscall"
 
 	"github.com/hanwen/go-fuse/fuse"
 	"github.com/hanwen/go-fuse/fuse/nodefs"
@@ -13,9 +14,11 @@ import (
 	"github.com/rfjakob/gocryptfs/internal/nametransform"
 )
 
-type FS struct {
-	// loopbackFileSystem, see go-fuse/fuse/pathfs/loopback.go
+type reverseFS struct {
+	// Embed pathfs.defaultFileSystem for a ENOSYS implementation of all methods
 	pathfs.FileSystem
+	// pathfs.loopbackFileSystem, see go-fuse/fuse/pathfs/loopback.go
+	loopbackfs pathfs.FileSystem
 	// Stores configuration arguments
 	args fusefrontend.Args
 	// Filename encryption helper
@@ -25,43 +28,56 @@ type FS struct {
 }
 
 // Encrypted FUSE overlay filesystem
-func NewFS(args fusefrontend.Args) *FS {
+func NewFS(args fusefrontend.Args) *reverseFS {
 	cryptoCore := cryptocore.New(args.Masterkey, args.OpenSSL, true)
 	contentEnc := contentenc.New(cryptoCore, contentenc.DefaultBS)
 	nameTransform := nametransform.New(cryptoCore, args.LongNames)
 
-	return &FS{
-		FileSystem:    pathfs.NewLoopbackFileSystem(args.Cipherdir),
+	return &reverseFS{
+		// pathfs.defaultFileSystem returns ENOSYS for all operations
+		FileSystem:    pathfs.NewDefaultFileSystem(),
+		loopbackfs:    pathfs.NewLoopbackFileSystem(args.Cipherdir),
 		args:          args,
 		nameTransform: nameTransform,
 		contentEnc:    contentEnc,
 	}
 }
 
-func (fs *FS) GetAttr(relPath string, context *fuse.Context) (*fuse.Attr, fuse.Status) {
-	if fs.isFiltered(relPath) {
+func (rfs *reverseFS) GetAttr(relPath string, context *fuse.Context) (*fuse.Attr, fuse.Status) {
+	if rfs.isFiltered(relPath) {
 		return nil, fuse.EPERM
 	}
-	relPath, err := fs.decryptPath(relPath)
+	relPath, err := rfs.decryptPath(relPath)
 	if err != nil {
 		return nil, fuse.ToStatus(err)
 	}
-	a, status := fs.FileSystem.GetAttr(relPath, context)
+	a, status := rfs.loopbackfs.GetAttr(relPath, context)
 	if a == nil {
 		return a, status
 	}
 	// Calculate encrypted file size
 	if a.IsRegular() {
-		a.Size = fs.contentEnc.PlainSizeToCipherSize(a.Size)
+		a.Size = rfs.contentEnc.PlainSizeToCipherSize(a.Size)
 	}
 	return a, fuse.OK
 }
 
-func (fs *FS) Open(relPath string, flags uint32, context *fuse.Context) (fuseFile nodefs.File, status fuse.Status) {
-	if fs.isFiltered(relPath) {
+func (rfs *reverseFS) Access(relPath string, mode uint32, context *fuse.Context) fuse.Status {
+	if rfs.isFiltered(relPath) {
+		return fuse.EPERM
+	}
+	cPath, err := rfs.abs(rfs.encryptPath(relPath))
+	if err != nil {
+		return fuse.ToStatus(err)
+	}
+	return fuse.ToStatus(syscall.Access(cPath, mode))
+}
+
+func (rfs *reverseFS) Open(relPath string, flags uint32, context *fuse.Context) (fuseFile nodefs.File, status fuse.Status) {
+	if rfs.isFiltered(relPath) {
 		return nil, fuse.EPERM
 	}
-	absPath, err := fs.abs(fs.decryptPath(relPath))
+	absPath, err := rfs.abs(rfs.decryptPath(relPath))
 	if err != nil {
 		return nil, fuse.ToStatus(err)
 	}
@@ -69,22 +85,22 @@ func (fs *FS) Open(relPath string, flags uint32, context *fuse.Context) (fuseFil
 	if err != nil {
 		return nil, fuse.ToStatus(err)
 	}
-	return NewFile(f, fs.contentEnc)
+	return NewFile(f, rfs.contentEnc)
 }
 
-func (fs *FS) OpenDir(relPath string, context *fuse.Context) ([]fuse.DirEntry, fuse.Status) {
-	relPath, err := fs.decryptPath(relPath)
+func (rfs *reverseFS) OpenDir(relPath string, context *fuse.Context) ([]fuse.DirEntry, fuse.Status) {
+	relPath, err := rfs.decryptPath(relPath)
 	if err != nil {
 		return nil, fuse.ToStatus(err)
 	}
 	// Read plaintext dir
-	entries, status := fs.FileSystem.OpenDir(relPath, context)
+	entries, status := rfs.loopbackfs.OpenDir(relPath, context)
 	if entries == nil {
 		return nil, status
 	}
 	// Encrypt names
 	for i := range entries {
-		entries[i].Name, err = fs.encryptPath(entries[i].Name)
+		entries[i].Name, err = rfs.encryptPath(entries[i].Name)
 		if err != nil {
 			return nil, fuse.ToStatus(err)
 		}
diff --git a/internal/fusefrontend_reverse/rpath.go b/internal/fusefrontend_reverse/rpath.go
index 9377958..7e11ca3 100644
--- a/internal/fusefrontend_reverse/rpath.go
+++ b/internal/fusefrontend_reverse/rpath.go
@@ -1,15 +1,24 @@
 package fusefrontend_reverse
 
 import (
+	"encoding/base64"
+	"fmt"
 	"path/filepath"
 	"strings"
+	"syscall"
 )
 
-func (fs *FS) abs(relPath string, err error) (string, error) {
+var zeroDirIV []byte
+
+func init() {
+	zeroDirIV = make([]byte, 16)
+}
+
+func (rfs *reverseFS) abs(relPath string, err error) (string, error) {
 	if err != nil {
 		return "", err
 	}
-	return filepath.Join(fs.args.Cipherdir, relPath), nil
+	return filepath.Join(rfs.args.Cipherdir, relPath), nil
 }
 
 const (
@@ -17,30 +26,36 @@ const (
 	DECRYPT
 )
 
-func (fs *FS) encryptPath(relPath string) (string, error) {
-	return fs.transformPath(relPath, ENCRYPT)
+func (rfs *reverseFS) encryptPath(relPath string) (string, error) {
+	return rfs.transformPath(relPath, ENCRYPT)
 }
 
-func (fs *FS) decryptPath(relPath string) (string, error) {
-	return fs.transformPath(relPath, DECRYPT)
+func (rfs *reverseFS) decryptPath(relPath string) (string, error) {
+	return rfs.transformPath(relPath, DECRYPT)
 }
 
-func (fs *FS) transformPath(relPath string, direction int) (string, error) {
-	if fs.args.PlaintextNames {
+func (rfs *reverseFS) transformPath(relPath string, direction int) (string, error) {
+	if rfs.args.PlaintextNames || relPath == "" {
 		return relPath, nil
 	}
 	var err error
 	var transformedParts []string
-	iv := make([]byte, 16)
 	parts := strings.Split(relPath, "/")
 	for _, part := range parts {
 		var transformedPart string
 		switch direction {
 		case ENCRYPT:
-			transformedPart = fs.nameTransform.EncryptName(part, iv)
+			transformedPart = rfs.nameTransform.EncryptName(part, zeroDirIV)
 		case DECRYPT:
-			transformedPart, err = fs.nameTransform.DecryptName(part, iv)
+			transformedPart, err = rfs.nameTransform.DecryptName(part, zeroDirIV)
 			if err != nil {
+				// We get lots of decrypt requests for names like ".Trash" that
+				// are invalid base64. Convert them to ENOENT so the correct
+				// error gets returned to the user.
+				if _, ok := err.(base64.CorruptInputError); ok {
+					fmt.Printf("converting to ENOENT\n")
+					return "", syscall.ENOENT
+				}
 				return "", err
 			}
 		default:
@@ -51,6 +66,6 @@ func (fs *FS) transformPath(relPath string, direction int) (string, error) {
 	return filepath.Join(transformedParts...), nil
 }
 
-func (fs *FS) isFiltered(relPath string) bool {
+func (rfs *reverseFS) isFiltered(relPath string) bool {
 	return false
 }