113 lines
3.3 KiB
Go
113 lines
3.3 KiB
Go
package fusefrontend_reverse
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import (
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"crypto/sha256"
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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/tlog"
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)
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// saneDir is like filepath.Dir but returns "" instead of "."
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func saneDir(path string) string {
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d := filepath.Dir(path)
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if d == "." {
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return ""
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}
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return d
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}
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type ivPurposeType string
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const (
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ivPurposeDirIV ivPurposeType = "DIRIV"
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ivPurposeFileID ivPurposeType = "FILEID"
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ivPurposeSymlinkIV ivPurposeType = "SYMLINKIV"
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ivPurposeBlock0IV ivPurposeType = "BLOCK0IV"
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)
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// derivePathIV derives an IV from an encrypted path by hashing it with sha256
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func derivePathIV(path string, purpose ivPurposeType) []byte {
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// Use null byte as separator as it cannot occur in the path
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extended := []byte(path + "\000" + string(purpose))
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hash := sha256.Sum256(extended)
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return hash[:nametransform.DirIVLen]
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}
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func (rfs *ReverseFS) 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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func (rfs *ReverseFS) 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.EINVAL {
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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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pName, err = rfs.findLongnameParent(pDir, dirIV, cName)
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if err != nil {
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return "", err
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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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func (rfs *ReverseFS) decryptPath(relPath string) (string, error) {
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if rfs.args.PlaintextNames || relPath == "" {
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return relPath, nil
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}
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// Check if the parent dir is in the cache
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cDir := saneDir(relPath)
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dirIV, pDir := rPathCache.lookup(cDir)
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if dirIV != nil {
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cName := filepath.Base(relPath)
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pName, err := rfs.rDecryptName(cName, dirIV, pDir)
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if err != nil {
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return "", err
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}
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return filepath.Join(pDir, pName), nil
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}
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parts := strings.Split(relPath, "/")
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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 = derivePathIV(currentCipherDir, ivPurposeDirIV)
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transformedPart, err := rfs.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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rPathCache.store(cDir, dirIV, saneDir(pRelPath))
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return pRelPath, nil
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}
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