package fusefrontend_reverse import ( "encoding/base64" "fmt" "os" "path/filepath" "sync" "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/configfile" "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 // Inode number generator inoGen *inoGenT // Maps backing files device+inode pairs to user-facing unique inode numbers inoMap map[devIno]uint64 // Protects map access inoMapLock sync.Mutex } // Encrypted FUSE overlay filesystem func NewFS(args fusefrontend.Args) *reverseFS { cryptoCore := cryptocore.New(args.Masterkey, args.CryptoBackend, contentenc.IVBitLen) 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, inoGen: NewInoGen(), inoMap: map[devIno]uint64{}, } } // 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 timestamps from the parent dir. a.Mode = DirIVMode a.Size = nametransform.DirIVLen a.Nlink = 1 a.Ino = rfs.inoGen.next() 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 } // isNameFile determines if the path points to a gocryptfs.longname.*.name // file func isNameFile(relPath string) bool { fileType := nametransform.NameType(filepath.Base(relPath)) return fileType == nametransform.LongNameFilename } func (rfs *reverseFS) inoAwareStat(relPlainPath string) (*fuse.Attr, fuse.Status) { absPath, err := rfs.abs(relPlainPath, nil) if err != nil { return nil, fuse.ToStatus(err) } var fi os.FileInfo if relPlainPath == "" { // Look through symlinks for the root dir fi, err = os.Stat(absPath) } else { fi, err = os.Lstat(absPath) } if err != nil { return nil, fuse.ToStatus(err) } st := fi.Sys().(*syscall.Stat_t) // The file has hard links. We have to give it a stable inode number so // tar or rsync can find them. if fi.Mode().IsRegular() && st.Nlink > 1 { di := devIno{st.Dev, st.Ino} rfs.inoMapLock.Lock() stableIno := rfs.inoMap[di] if stableIno == 0 { rfs.inoMap[di] = rfs.inoGen.next() } rfs.inoMapLock.Unlock() st.Ino = stableIno } else { st.Ino = rfs.inoGen.next() } a := &fuse.Attr{} a.FromStat(st) return a, fuse.OK } // GetAttr - FUSE call func (rfs *reverseFS) GetAttr(relPath string, context *fuse.Context) (*fuse.Attr, fuse.Status) { if relPath == configfile.ConfDefaultName { return rfs.inoAwareStat(configfile.ConfReverseName) } if rfs.isFiltered(relPath) { return nil, fuse.EPERM } // Handle virtual files var f nodefs.File var status fuse.Status virtual := false if isDirIV(relPath) { virtual = true f, status = rfs.newDirIVFile(relPath) } if isNameFile(relPath) { virtual = true f, status = rfs.newNameFile(relPath) } if virtual { if !status.Ok() { fmt.Printf("GetAttr %q: newXFile failed: %v\n", relPath, status) return nil, status } var a fuse.Attr status = f.GetAttr(&a) return &a, status } cPath, err := rfs.decryptPath(relPath) if err != nil { return nil, fuse.ToStatus(err) } a, status := rfs.inoAwareStat(cPath) if !status.Ok() { return nil, status } // Calculate encrypted file size if a.IsRegular() { a.Size = rfs.contentEnc.PlainSizeToCipherSize(a.Size) } return a, fuse.OK } // Access - FUSE call 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)) } // Open - FUSE call func (rfs *reverseFS) Open(relPath string, flags uint32, context *fuse.Context) (fuseFile nodefs.File, status fuse.Status) { if relPath == configfile.ConfDefaultName { // gocryptfs.conf maps to .gocryptfs.reverse.conf in the plaintext directory return rfs.loopbackfs.Open(configfile.ConfReverseName, flags, context) } if isDirIV(relPath) { return rfs.newDirIVFile(relPath) } if isNameFile(relPath) { return rfs.newNameFile(relPath) } if rfs.isFiltered(relPath) { return nil, fuse.EPERM } return rfs.NewFile(relPath, flags) } // OpenDir - FUSE readdir call 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 } // Allocate maximum possible number of virtual files. // If all files have long names we need a virtual ".name" file for each, // plus one for gocryptfs.diriv. virtualFiles := make([]fuse.DirEntry, len(entries)+1) // Virtual gocryptfs.diriv file virtualFiles[0] = fuse.DirEntry{syscall.S_IFREG | 0400, nametransform.DirIVFilename} // Actually used entries nVirtual := 1 // Encrypt names dirIV := derivePathIV(cipherPath) for i := range entries { var cName string // ".gocryptfs.reverse.conf" in the root directory is mapped to "gocryptfs.conf" if cipherPath == "" && entries[i].Name == configfile.ConfReverseName { cName = configfile.ConfDefaultName } else { cName = rfs.nameTransform.EncryptName(entries[i].Name, dirIV) if len(cName) > syscall.NAME_MAX { cName = nametransform.HashLongName(cName) dotNameFile := fuse.DirEntry{syscall.S_IFREG | 0600, cName + nametransform.LongNameSuffix} virtualFiles[nVirtual] = dotNameFile nVirtual++ } } entries[i].Name = cName } entries = append(entries, virtualFiles[:nVirtual]...) return entries, fuse.OK } // StatFs - FUSE call func (rfs *reverseFS) StatFs(name string) *fuse.StatfsOut { return rfs.loopbackfs.StatFs(name) } // Readlink - FUSE call func (rfs *reverseFS) Readlink(cipherPath string, context *fuse.Context) (string, fuse.Status) { absPath, err := rfs.abs(rfs.decryptPath(cipherPath)) if err != nil { return "", fuse.ToStatus(err) } plainTarget, err := os.Readlink(absPath) if err != nil { return "", fuse.ToStatus(err) } if rfs.args.PlaintextNames { return plainTarget, fuse.OK } nonce := derivePathIV(cipherPath) // Symlinks are encrypted like file contents and base64-encoded cBinTarget := rfs.contentEnc.EncryptBlock([]byte(plainTarget), 0, nil, contentenc.ExternalNonce, nonce) cTarget := base64.URLEncoding.EncodeToString(cBinTarget) return cTarget, fuse.OK }