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-rw-r--r--internal/nametransform/diriv.go143
1 files changed, 143 insertions, 0 deletions
diff --git a/internal/nametransform/diriv.go b/internal/nametransform/diriv.go
new file mode 100644
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+++ b/internal/nametransform/diriv.go
@@ -0,0 +1,143 @@
+package nametransform
+
+import (
+ "errors"
+ "io/ioutil"
+ "os"
+ "path/filepath"
+ "strings"
+ "syscall"
+
+ "github.com/rfjakob/gocryptfs/internal/cryptocore"
+ "github.com/rfjakob/gocryptfs/internal/tlog"
+)
+
+const (
+ // identical to AES block size
+ dirIVLen = 16
+ // dirIV is stored in this file. Exported because we have to ignore this
+ // name in directory listing.
+ DirIVFilename = "gocryptfs.diriv"
+)
+
+// ReadDirIV - read the "gocryptfs.diriv" file from "dir" (absolute ciphertext path)
+// This function is exported because it allows for an efficient readdir implementation.
+func ReadDirIV(dir string) (iv []byte, err error) {
+ dirfd, err := os.Open(dir)
+ if err != nil {
+ return nil, err
+ }
+ defer dirfd.Close()
+
+ return ReadDirIVAt(dirfd)
+}
+
+// ReadDirIVAt reads "gocryptfs.diriv" from the directory that is opened as "dirfd".
+// Using the dirfd makes it immune to concurrent renames of the directory.
+func ReadDirIVAt(dirfd *os.File) (iv []byte, err error) {
+ fdRaw, err := syscall.Openat(int(dirfd.Fd()), DirIVFilename, syscall.O_RDONLY, 0)
+ if err != nil {
+ tlog.Warn.Printf("ReadDirIVAt: opening %q in dir %q failed: %v",
+ DirIVFilename, dirfd.Name(), err)
+ return nil, err
+ }
+ fd := os.NewFile(uintptr(fdRaw), DirIVFilename)
+ defer fd.Close()
+
+ iv = make([]byte, dirIVLen+1)
+ n, err := fd.Read(iv)
+ if err != nil {
+ tlog.Warn.Printf("ReadDirIVAt: Read failed: %v", err)
+ return nil, err
+ }
+ iv = iv[0:n]
+ if len(iv) != dirIVLen {
+ tlog.Warn.Printf("ReadDirIVAt: wanted %d bytes, got %d", dirIVLen, len(iv))
+ return nil, errors.New("invalid iv length")
+ }
+ return iv, nil
+}
+
+// WriteDirIV - create diriv file inside "dir" (absolute ciphertext path)
+// This function is exported because it is used from pathfs_frontend, main,
+// and also the automated tests.
+func WriteDirIV(dir string) error {
+ iv := cryptocore.RandBytes(dirIVLen)
+ file := filepath.Join(dir, DirIVFilename)
+ err := ioutil.WriteFile(file, iv, 0400)
+ if err != nil {
+ tlog.Warn.Printf("WriteDirIV: %v", err)
+ }
+ return err
+}
+
+// EncryptPathDirIV - encrypt relative plaintext path using EME with DirIV.
+// Components that are longer than 255 bytes are hashed if be.longnames == true.
+func (be *NameTransform) EncryptPathDirIV(plainPath string, rootDir string) (cipherPath string, err error) {
+ // Empty string means root directory
+ if plainPath == "" {
+ return plainPath, nil
+ }
+ // Reject names longer than 255 bytes already here. This relieves everybody
+ // who uses hashed long names from checking for that later.
+ baseName := filepath.Base(plainPath)
+ if len(baseName) > syscall.NAME_MAX {
+ return "", syscall.ENAMETOOLONG
+ }
+ // Check if the DirIV is cached
+ parentDir := filepath.Dir(plainPath)
+ found, iv, cParentDir := be.DirIVCache.lookup(parentDir)
+ if found {
+ cBaseName := be.EncryptName(baseName, iv)
+ if be.longNames && len(cBaseName) > syscall.NAME_MAX {
+ cBaseName = HashLongName(cBaseName)
+ }
+ cipherPath = cParentDir + "/" + cBaseName
+ return cipherPath, nil
+ }
+ // Not cached - walk the directory tree
+ var wd = rootDir
+ var encryptedNames []string
+ plainNames := strings.Split(plainPath, "/")
+ for _, plainName := range plainNames {
+ iv, err = ReadDirIV(wd)
+ if err != nil {
+ return "", err
+ }
+ encryptedName := be.EncryptName(plainName, iv)
+ if be.longNames && len(encryptedName) > syscall.NAME_MAX {
+ encryptedName = HashLongName(encryptedName)
+ }
+ encryptedNames = append(encryptedNames, encryptedName)
+ wd = filepath.Join(wd, encryptedName)
+ }
+ cipherPath = strings.Join(encryptedNames, "/")
+ // Cache the final DirIV
+ cParentDir = filepath.Dir(cipherPath)
+ be.DirIVCache.store(parentDir, iv, cParentDir)
+ return cipherPath, nil
+}
+
+// DecryptPathDirIV - decrypt path using EME with DirIV
+//
+// TODO This has only a single user, Readlink(), and only for compatability with
+// gocryptfs v0.5. Drop?
+func (be *NameTransform) DecryptPathDirIV(encryptedPath string, rootDir string) (string, error) {
+ var wd = rootDir
+ var plainNames []string
+ encryptedNames := strings.Split(encryptedPath, "/")
+ tlog.Debug.Printf("DecryptPathDirIV: decrypting %v\n", encryptedNames)
+ for _, encryptedName := range encryptedNames {
+ iv, err := ReadDirIV(wd)
+ if err != nil {
+ return "", err
+ }
+ plainName, err := be.DecryptName(encryptedName, iv)
+ if err != nil {
+ return "", err
+ }
+ plainNames = append(plainNames, plainName)
+ wd = filepath.Join(wd, encryptedName)
+ }
+ return filepath.Join(plainNames...), nil
+}