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package fusefrontend_reverse
import (
"fmt"
"os"
"path/filepath"
"syscall"
"github.com/hanwen/go-fuse/fuse"
"github.com/hanwen/go-fuse/fuse/nodefs"
"github.com/hanwen/go-fuse/fuse/pathfs"
"github.com/rfjakob/gocryptfs/internal/contentenc"
"github.com/rfjakob/gocryptfs/internal/cryptocore"
"github.com/rfjakob/gocryptfs/internal/fusefrontend"
"github.com/rfjakob/gocryptfs/internal/nametransform"
)
const (
DirIVMode = syscall.S_IFREG | 0400
)
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
nameTransform *nametransform.NameTransform
// Content encryption helper
contentEnc *contentenc.ContentEnc
}
// Encrypted FUSE overlay filesystem
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 &reverseFS{
// pathfs.defaultFileSystem returns ENOSYS for all operations
FileSystem: pathfs.NewDefaultFileSystem(),
loopbackfs: pathfs.NewLoopbackFileSystem(args.Cipherdir),
args: args,
nameTransform: nameTransform,
contentEnc: contentEnc,
}
}
// relDir is identical to filepath.Dir excepts that it returns "" when
// filepath.Dir would return ".".
// In the FUSE API, the root directory is called "", and we actually want that.
func relDir(path string) string {
dir := filepath.Dir(path)
if dir == "." {
return ""
}
return dir
}
// dirIVAttr handles GetAttr requests for the virtual gocryptfs.diriv files.
func (rfs *reverseFS) dirIVAttr(relPath string, context *fuse.Context) (*fuse.Attr, fuse.Status) {
cDir := relDir(relPath)
dir, err := rfs.decryptPath(cDir)
if err != nil {
fmt.Printf("decrypt err %q\n", cDir)
return nil, fuse.ToStatus(err)
}
// Does the parent dir exist?
a, status := rfs.loopbackfs.GetAttr(dir, context)
if !status.Ok() {
fmt.Printf("missing parent\n")
return nil, status
}
// Is it a dir at all?
if !a.IsDir() {
fmt.Printf("not isdir\n")
return nil, fuse.ENOTDIR
}
// Does the user have execute permissions?
if a.Mode&syscall.S_IXUSR == 0 {
fmt.Printf("not exec")
return nil, fuse.EPERM
}
// All good. Let's fake the file.
// We use the inode number of the parent dir (can this cause problems?).
a.Mode = DirIVMode
a.Size = nametransform.DirIVLen
a.Nlink = 1
return a, fuse.OK
}
// isDirIV determines if the path points to a gocryptfs.diriv file
func isDirIV(relPath string) bool {
return filepath.Base(relPath) == nametransform.DirIVFilename
}
func (rfs *reverseFS) GetAttr(relPath string, context *fuse.Context) (*fuse.Attr, fuse.Status) {
if isDirIV(relPath) {
return rfs.dirIVAttr(relPath, context)
}
if rfs.isFiltered(relPath) {
return nil, fuse.EPERM
}
relPath, err := rfs.decryptPath(relPath)
if err != nil {
return nil, fuse.ToStatus(err)
}
a, status := rfs.loopbackfs.GetAttr(relPath, context)
if !status.Ok() {
return nil, status
}
// Calculate encrypted file size
if a.IsRegular() {
a.Size = rfs.contentEnc.PlainSizeToCipherSize(a.Size)
}
return a, fuse.OK
}
func (rfs *reverseFS) Access(relPath string, mode uint32, context *fuse.Context) fuse.Status {
if isDirIV(relPath) {
return fuse.OK
}
if rfs.isFiltered(relPath) {
return fuse.EPERM
}
absPath, err := rfs.abs(rfs.decryptPath(relPath))
if err != nil {
return fuse.ToStatus(err)
}
return fuse.ToStatus(syscall.Access(absPath, mode))
}
func (rfs *reverseFS) Open(relPath string, flags uint32, context *fuse.Context) (fuseFile nodefs.File, status fuse.Status) {
if isDirIV(relPath) {
return NewDirIVFile(relDir(relPath))
}
if rfs.isFiltered(relPath) {
return nil, fuse.EPERM
}
absPath, err := rfs.abs(rfs.decryptPath(relPath))
if err != nil {
return nil, fuse.ToStatus(err)
}
f, err := os.OpenFile(absPath, int(flags), 0666)
if err != nil {
return nil, fuse.ToStatus(err)
}
return NewFile(f, rfs.contentEnc)
}
func (rfs *reverseFS) OpenDir(cipherPath string, context *fuse.Context) ([]fuse.DirEntry, fuse.Status) {
relPath, err := rfs.decryptPath(cipherPath)
if err != nil {
return nil, fuse.ToStatus(err)
}
// Read plaintext dir
entries, status := rfs.loopbackfs.OpenDir(relPath, context)
if entries == nil {
return nil, status
}
// Encrypt names
dirIV := deriveDirIV(cipherPath)
for i := range entries {
entries[i].Name = rfs.nameTransform.EncryptName(entries[i].Name, dirIV)
}
// Add virtual gocryptfs.diriv
entries = append(entries, fuse.DirEntry{syscall.S_IFREG | 0400, nametransform.DirIVFilename})
return entries, fuse.OK
}
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