2021-06-08 21:25:50 +02:00
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package main
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import (
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"C"
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"fmt"
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"io"
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"strings"
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"syscall"
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"unsafe"
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"golang.org/x/sys/unix"
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2021-10-24 10:48:44 +02:00
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"libgocryptfs/v2/allocator"
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"libgocryptfs/v2/internal/configfile"
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"libgocryptfs/v2/internal/cryptocore"
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"libgocryptfs/v2/internal/nametransform"
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"libgocryptfs/v2/internal/syscallcompat"
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2021-06-08 21:25:50 +02:00
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)
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func mkdirWithIv(dirfd int, cName string, mode uint32) error {
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// Between the creation of the directory and the creation of gocryptfs.diriv
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// the directory is inconsistent. Take the lock to prevent other readers
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// from seeing it.
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err := unix.Mkdirat(dirfd, cName, mode)
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if err != nil {
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return err
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}
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dirfd2, err := syscallcompat.Openat(dirfd, cName, syscall.O_DIRECTORY|syscall.O_NOFOLLOW|syscallcompat.O_PATH, 0)
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if err == nil {
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// Create gocryptfs.diriv
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err = nametransform.WriteDirIVAt(dirfd2)
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syscall.Close(dirfd2)
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}
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if err != nil {
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// Delete inconsistent directory (missing gocryptfs.diriv!)
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syscallcompat.Unlinkat(dirfd, cName, unix.AT_REMOVEDIR)
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}
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return err
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}
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//export gcf_list_dir
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func gcf_list_dir(sessionID int, dirName string) (*C.char, *C.int, C.int) {
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volume := OpenedVolumes[sessionID]
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parentDirFd, cDirName, err := volume.prepareAtSyscall(dirName)
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if err != nil {
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return nil, nil, 0
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}
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defer syscall.Close(parentDirFd)
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// Read ciphertext directory
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fd, err := syscallcompat.Openat(parentDirFd, cDirName, syscall.O_RDONLY|syscall.O_DIRECTORY|syscall.O_NOFOLLOW, 0)
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if err != nil {
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return nil, nil, 0
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}
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defer syscall.Close(fd)
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cipherEntries, err := syscallcompat.Getdents(fd)
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if err != nil {
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return nil, nil, 0
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}
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// Get DirIV (stays nil if PlaintextNames is used)
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var cachedIV []byte
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if !OpenedVolumes[sessionID].plainTextNames {
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// Read the DirIV from disk
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2021-08-29 12:46:32 +02:00
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cachedIV, err = volume.nameTransform.ReadDirIVAt(fd)
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2021-06-08 21:25:50 +02:00
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if err != nil {
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return nil, nil, 0
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}
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}
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// Decrypted directory entries
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var plain strings.Builder
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var modes []uint32
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// Filter and decrypt filenames
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for i := range cipherEntries {
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cName := cipherEntries[i].Name
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if dirName == "" && cName == configfile.ConfDefaultName {
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// silently ignore "gocryptfs.conf" in the top level dir
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continue
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}
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if OpenedVolumes[sessionID].plainTextNames {
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plain.WriteString(cipherEntries[i].Name + "\x00")
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modes = append(modes, cipherEntries[i].Mode)
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continue
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}
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if cName == nametransform.DirIVFilename {
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// silently ignore "gocryptfs.diriv" everywhere if dirIV is enabled
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continue
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}
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// Handle long file name
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isLong := nametransform.NameType(cName)
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if isLong == nametransform.LongNameContent {
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cNameLong, err := nametransform.ReadLongNameAt(fd, cName)
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if err != nil {
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continue
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}
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cName = cNameLong
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} else if isLong == nametransform.LongNameFilename {
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// ignore "gocryptfs.longname.*.name"
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continue
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}
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name, err := OpenedVolumes[sessionID].nameTransform.DecryptName(cName, cachedIV)
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if err != nil {
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continue
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}
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// Override the ciphertext name with the plaintext name but reuse the rest
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// of the structure
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cipherEntries[i].Name = name
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plain.WriteString(cipherEntries[i].Name + "\x00")
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modes = append(modes, cipherEntries[i].Mode)
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}
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p := allocator.Malloc(len(modes))
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for i := 0; i < len(modes); i++ {
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offset := C.sizeof_int * uintptr(i)
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*(*C.int)(unsafe.Pointer(uintptr(p) + offset)) = (C.int)(modes[i])
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}
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return C.CString(plain.String()), (*C.int)(p), (C.int)(len(modes))
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}
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//export gcf_mkdir
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func gcf_mkdir(sessionID int, path string, mode uint32) bool {
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volume := OpenedVolumes[sessionID]
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dirfd, cName, err := volume.prepareAtSyscall(path)
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if err != nil {
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return false
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}
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defer syscall.Close(dirfd)
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if volume.plainTextNames {
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err = unix.Mkdirat(dirfd, cName, mode)
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if err != nil {
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return false
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}
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var ust unix.Stat_t
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err = syscallcompat.Fstatat(dirfd, cName, &ust, unix.AT_SYMLINK_NOFOLLOW)
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if err != nil {
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return false
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}
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} else {
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// We need write and execute permissions to create gocryptfs.diriv.
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// Also, we need read permissions to open the directory (to avoid
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// race-conditions between getting and setting the mode).
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origMode := mode
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mode := mode | 0700
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// Handle long file name
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if nametransform.IsLongContent(cName) {
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// Create ".name"
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err = OpenedVolumes[sessionID].nameTransform.WriteLongNameAt(dirfd, cName, path)
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if err != nil {
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return false
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}
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// Create directory
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err = mkdirWithIv(dirfd, cName, mode)
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if err != nil {
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nametransform.DeleteLongNameAt(dirfd, cName)
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return false
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}
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} else {
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err = mkdirWithIv(dirfd, cName, mode)
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if err != nil {
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return false
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}
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}
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fd, err := syscallcompat.Openat(dirfd, cName,
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syscall.O_RDONLY|syscall.O_DIRECTORY|syscall.O_NOFOLLOW, 0)
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if err != nil {
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return false
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}
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defer syscall.Close(fd)
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var st syscall.Stat_t
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err = syscall.Fstat(fd, &st)
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if err != nil {
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return false
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}
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// Fix permissions
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if origMode != mode {
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// Preserve SGID bit if it was set due to inheritance.
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origMode = uint32(st.Mode&^0777) | origMode
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syscall.Fchmod(fd, origMode)
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}
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}
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return true
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}
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//export gcf_rmdir
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func gcf_rmdir(sessionID int, relPath string) bool {
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volume := OpenedVolumes[sessionID]
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parentDirFd, cName, err := volume.openBackingDir(relPath)
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if err != nil {
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return false
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}
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defer syscall.Close(parentDirFd)
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if volume.plainTextNames {
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// Unlinkat with AT_REMOVEDIR is equivalent to Rmdir
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err = unix.Unlinkat(parentDirFd, cName, unix.AT_REMOVEDIR)
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return errToBool(err)
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}
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dirfd, err := syscallcompat.Openat(parentDirFd, cName, syscall.O_RDONLY|syscall.O_DIRECTORY|syscall.O_NOFOLLOW, 0)
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if err != nil {
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return false
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}
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defer syscall.Close(dirfd)
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// Check directory contents
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children, err := syscallcompat.Getdents(dirfd)
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if err == io.EOF {
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// The directory is empty
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err = unix.Unlinkat(parentDirFd, cName, unix.AT_REMOVEDIR)
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return errToBool(err)
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}
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if err != nil {
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return false
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}
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// If the directory is not empty besides gocryptfs.diriv, do not even
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// attempt the dance around gocryptfs.diriv.
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if len(children) > 1 {
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return false
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}
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// Move "gocryptfs.diriv" to the parent dir as "gocryptfs.diriv.rmdir.XYZ"
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tmpName := fmt.Sprintf("%s.rmdir.%d", nametransform.DirIVFilename, cryptocore.RandUint64())
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err = syscallcompat.Renameat(dirfd, nametransform.DirIVFilename, parentDirFd, tmpName)
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if err != nil {
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return false
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}
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// Actual Rmdir
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err = syscallcompat.Unlinkat(parentDirFd, cName, unix.AT_REMOVEDIR)
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if err != nil {
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// This can happen if another file in the directory was created in the
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// meantime, undo the rename
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syscallcompat.Renameat(parentDirFd, tmpName, dirfd, nametransform.DirIVFilename)
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return errToBool(err)
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}
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// Delete "gocryptfs.diriv.rmdir.XYZ"
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syscallcompat.Unlinkat(parentDirFd, tmpName, 0)
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// Delete .name file
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if nametransform.IsLongContent(cName) {
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nametransform.DeleteLongNameAt(parentDirFd, cName)
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}
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return true
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}
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