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