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