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package fusefrontend
import (
"path/filepath"
"strings"
"syscall"
"github.com/rfjakob/gocryptfs/internal/nametransform"
"github.com/rfjakob/gocryptfs/internal/syscallcompat"
)
// openBackingDir opens the parent ciphertext directory of plaintext path
// "relPath". It returns the dirfd (opened with O_PATH) and the encrypted
// basename.
//
// The caller should then use Openat(dirfd, cName, ...) and friends.
// For convenience, if relPath is "", cName is going to be ".".
//
// openBackingDir is secure against symlink races by using Openat and
// ReadDirIVAt.
func (fs *FS) openBackingDir(relPath string) (dirfd int, cName string, err error) {
dirRelPath := nametransform.Dir(relPath)
// With PlaintextNames, we don't need to read DirIVs. Easy.
if fs.args.PlaintextNames {
dirfd, err = syscallcompat.OpenDirNofollow(fs.args.Cipherdir, dirRelPath)
if err != nil {
return -1, "", err
}
// If relPath is empty, cName is ".".
cName = filepath.Base(relPath)
return dirfd, cName, nil
}
// Cache lookup
dirfd, iv := fs.dirCache.Lookup(dirRelPath)
if dirfd > 0 {
name := filepath.Base(relPath)
cName = fs.nameTransform.EncryptAndHashName(name, iv)
return dirfd, cName, nil
}
// Open cipherdir (following symlinks)
dirfd, err = syscall.Open(fs.args.Cipherdir, syscall.O_RDONLY|syscall.O_DIRECTORY|syscallcompat.O_PATH, 0)
if err != nil {
return -1, "", err
}
// If relPath is empty, cName is ".".
if relPath == "" {
return dirfd, ".", nil
}
// Walk the directory tree
parts := strings.Split(relPath, "/")
for i, name := range parts {
iv, err := nametransform.ReadDirIVAt(dirfd)
if err != nil {
syscall.Close(dirfd)
return -1, "", err
}
cName = fs.nameTransform.EncryptAndHashName(name, iv)
// Last part? We are done.
if i == len(parts)-1 {
fs.dirCache.Store(dirRelPath, dirfd, iv)
break
}
// Not the last part? Descend into next directory.
dirfd2, err := syscallcompat.Openat(dirfd, cName, syscall.O_RDONLY|syscall.O_NOFOLLOW|syscall.O_DIRECTORY|syscallcompat.O_PATH, 0)
syscall.Close(dirfd)
if err != nil {
return -1, "", err
}
dirfd = dirfd2
}
return dirfd, cName, nil
}
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