127 lines
4.0 KiB
Go
127 lines
4.0 KiB
Go
package nametransform
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import (
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"io"
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"io/ioutil"
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"os"
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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/cryptocore"
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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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const (
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// DirIVLen is identical to AES block size
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DirIVLen = 16
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// DirIVFilename is the filename used to store directory IV.
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// Exported because we have to ignore this name in directory listing.
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DirIVFilename = "gocryptfs.diriv"
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)
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// ReadDirIV - read the "gocryptfs.diriv" file from "dir" (absolute ciphertext path)
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// This function is exported because it allows for an efficient readdir implementation.
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func ReadDirIV(dir string) (iv []byte, err error) {
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fd, err := os.Open(filepath.Join(dir, DirIVFilename))
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if err != nil {
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// Note: getting errors here is normal because of concurrent deletes.
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return nil, err
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}
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defer fd.Close()
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return fdReadDirIV(fd)
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}
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// ReadDirIVAt reads "gocryptfs.diriv" from the directory that is opened as "dirfd".
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// Using the dirfd makes it immune to concurrent renames of the directory.
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func ReadDirIVAt(dirfd *os.File) (iv []byte, err error) {
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fdRaw, err := syscallcompat.Openat(int(dirfd.Fd()), DirIVFilename, syscall.O_RDONLY, 0)
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if err != nil {
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tlog.Warn.Printf("ReadDirIVAt: opening %q in dir %q failed: %v",
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DirIVFilename, dirfd.Name(), err)
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return nil, err
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}
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fd := os.NewFile(uintptr(fdRaw), DirIVFilename)
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defer fd.Close()
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return fdReadDirIV(fd)
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}
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// fdReadDirIV reads and verifies the DirIV from an opened gocryptfs.diriv file.
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func fdReadDirIV(fd *os.File) (iv []byte, err error) {
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// We want to detect if the file is bigger than DirIVLen, so
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// make the buffer 1 byte bigger than necessary.
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iv = make([]byte, DirIVLen+1)
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n, err := fd.Read(iv)
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if err != nil && err != io.EOF {
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tlog.Warn.Printf("ReadDirIVAt: Read failed: %v", err)
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return nil, err
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}
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iv = iv[0:n]
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if len(iv) != DirIVLen {
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tlog.Warn.Printf("ReadDirIVAt: wanted %d bytes, got %d. Returning EINVAL.", DirIVLen, len(iv))
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return nil, syscall.EINVAL
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}
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return iv, nil
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}
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// WriteDirIV - create diriv file inside "dir" (absolute ciphertext path)
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// This function is exported because it is used from pathfs_frontend, main,
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// and also the automated tests.
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func WriteDirIV(dir string) error {
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iv := cryptocore.RandBytes(DirIVLen)
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file := filepath.Join(dir, DirIVFilename)
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err := ioutil.WriteFile(file, iv, 0400)
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if err != nil {
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tlog.Warn.Printf("WriteDirIV: %v", err)
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}
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return err
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}
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// EncryptPathDirIV - encrypt relative plaintext path using EME with DirIV.
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// Components that are longer than 255 bytes are hashed if be.longnames == true.
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func (be *NameTransform) EncryptPathDirIV(plainPath string, rootDir string) (cipherPath string, err error) {
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// Empty string means root directory
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if plainPath == "" {
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return plainPath, nil
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}
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// Reject names longer than 255 bytes already here. This relieves everybody
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// who uses hashed long names from checking for that later.
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baseName := filepath.Base(plainPath)
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if len(baseName) > syscall.NAME_MAX {
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return "", syscall.ENAMETOOLONG
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}
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// Check if the DirIV is cached
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parentDir := filepath.Dir(plainPath)
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iv, cParentDir := be.DirIVCache.lookup(parentDir)
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if iv != nil {
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cBaseName := be.EncryptName(baseName, iv)
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if be.longNames && len(cBaseName) > syscall.NAME_MAX {
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cBaseName = be.HashLongName(cBaseName)
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}
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cipherPath = filepath.Join(cParentDir, cBaseName)
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return cipherPath, nil
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}
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// Not cached - walk the directory tree
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var wd = rootDir
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var encryptedNames []string
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plainNames := strings.Split(plainPath, "/")
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for _, plainName := range plainNames {
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iv, err = ReadDirIV(wd)
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if err != nil {
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return "", err
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}
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encryptedName := be.EncryptName(plainName, iv)
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if be.longNames && len(encryptedName) > syscall.NAME_MAX {
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encryptedName = be.HashLongName(encryptedName)
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}
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encryptedNames = append(encryptedNames, encryptedName)
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wd = filepath.Join(wd, encryptedName)
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}
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cipherPath = filepath.Join(encryptedNames...)
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// Cache the final DirIV
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cParentDir = filepath.Dir(cipherPath)
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be.DirIVCache.store(parentDir, iv, cParentDir)
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return cipherPath, nil
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}
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