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package fusefrontend_reverse
import (
"encoding/base64"
"log"
"path/filepath"
"strings"
"syscall"
"github.com/rfjakob/gocryptfs/internal/nametransform"
"github.com/rfjakob/gocryptfs/internal/pathiv"
"github.com/rfjakob/gocryptfs/internal/syscallcompat"
"github.com/rfjakob/gocryptfs/internal/tlog"
)
// rDecryptName decrypts the ciphertext name "cName", given the dirIV of the
// directory "cName" lies in. The relative plaintext path to the directory
// "pDir" is used if a "gocryptfs.longname.XYZ.name" must be resolved.
func (rfs *RootNode) rDecryptName(cName string, dirIV []byte, pDir string) (pName string, err error) {
nameType := nametransform.NameType(cName)
if nameType == nametransform.LongNameNone {
pName, err = rfs.nameTransform.DecryptName(cName, dirIV)
if err != nil {
// We get lots of decrypt requests for names like ".Trash" that
// are invalid base64. Convert them to ENOENT so the correct
// error gets returned to the user.
if _, ok := err.(base64.CorruptInputError); ok {
return "", syscall.ENOENT
}
// Stat attempts on the link target of encrypted symlinks.
// These are always valid base64 but the length is not a
// multiple of 16.
if err == syscall.EBADMSG {
return "", syscall.ENOENT
}
return "", err
}
} else if nameType == nametransform.LongNameContent {
dirfd, err := syscallcompat.OpenDirNofollow(rfs.args.Cipherdir, filepath.Dir(pDir))
if err != nil {
return "", err
}
defer syscall.Close(dirfd)
fd, err := syscallcompat.Openat(dirfd, filepath.Base(pDir), syscall.O_RDONLY|syscall.O_DIRECTORY|syscall.O_NOFOLLOW, 0)
if err != nil {
return "", err
}
defer syscall.Close(fd)
var errno syscall.Errno
pName, _, errno = rfs.findLongnameParent(fd, dirIV, cName)
if errno != 0 {
return "", errno
}
} else {
// It makes no sense to decrypt a ".name" file. This is a virtual file
// that has no representation in the plaintext filesystem. ".name"
// files should have already been handled in virtualfile.go.
tlog.Warn.Printf("rDecryptName: cannot decrypt virtual file %q", cName)
return "", syscall.EINVAL
}
return pName, nil
}
// decryptPath decrypts a relative ciphertext path to a relative plaintext
// path.
func (rn *RootNode) decryptPath(cPath string) (string, error) {
if rn.args.PlaintextNames || cPath == "" {
return cPath, nil
}
parts := strings.Split(cPath, "/")
var transformedParts []string
for i := range parts {
// Start at the top and recurse
currentCipherDir := filepath.Join(parts[:i]...)
currentPlainDir := filepath.Join(transformedParts[:i]...)
dirIV := rn.deriveDirIV(currentCipherDir)
transformedPart, err := rn.rDecryptName(parts[i], dirIV, currentPlainDir)
if err != nil {
return "", err
}
transformedParts = append(transformedParts, transformedPart)
}
pRelPath := filepath.Join(transformedParts...)
return pRelPath, nil
}
// deriveDirIV wraps pathiv.Derive but takes DeterministicNames into account.
func (rn *RootNode) deriveDirIV(cPath string) []byte {
if rn.args.PlaintextNames {
log.Panic("BUG: deriveDirIV called but PlaintextNames is set")
}
if rn.args.DeterministicNames {
return make([]byte, nametransform.DirIVLen)
}
return pathiv.Derive(cPath, pathiv.PurposeDirIV)
}
// openBackingDir receives an already decrypted relative path
// "pRelPath", opens the directory that contains the target file/dir
// and returns the fd to the directory and the decrypted name of the
// target file. The fd/name pair is intended for use with fchownat and
// friends.
func (rn *RootNode) openBackingDir(cPath string) (dirfd int, pPath string, err error) {
defer func() {
tlog.Debug.Printf("openBackingDir %q -> %d %q %v\n", cPath, dirfd, pPath, err)
}()
dirfd = -1
pPath, err = rn.decryptPath(cPath)
if err != nil {
return
}
if rn.isExcludedPlain(pPath) {
err = syscall.EPERM
return
}
// Open directory, safe against symlink races
pDir := filepath.Dir(pPath)
dirfd, err = syscallcompat.OpenDirNofollow(rn.args.Cipherdir, pDir)
if err != nil {
return
}
return dirfd, pPath, nil
}
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