a2677bce2a
Makes it robust against symlink races. Final piece, closes https://github.com/rfjakob/gocryptfs/issues/165
119 lines
3.6 KiB
Go
119 lines
3.6 KiB
Go
package fusefrontend_reverse
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import (
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"log"
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"path/filepath"
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"sync"
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"syscall"
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"time"
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"github.com/hanwen/go-fuse/fuse"
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"github.com/hanwen/go-fuse/fuse/nodefs"
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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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const (
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// File names are padded to 16-byte multiples, encrypted and
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// base64-encoded. We can encode at most 176 bytes to stay below the 255
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// bytes limit:
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// * base64(176 bytes) = 235 bytes
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// * base64(192 bytes) = 256 bytes (over 255!)
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// But the PKCS#7 padding is at least one byte. This means we can only use
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// 175 bytes for the file name.
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shortNameMax = 175
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)
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// longnameParentCache maps dir+"/"+longname to plaintextname.
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// Yes, the combination of relative plaintext dir path and encrypted
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// longname is strange, but works fine as a map index.
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var longnameParentCache map[string]string
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var longnameCacheLock sync.Mutex
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// Very simple cache cleaner: Nuke it every hour
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func longnameCacheCleaner() {
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for {
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time.Sleep(time.Hour)
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longnameCacheLock.Lock()
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longnameParentCache = map[string]string{}
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longnameCacheLock.Unlock()
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}
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}
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func initLongnameCache() {
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if longnameParentCache != nil {
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return
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}
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longnameParentCache = map[string]string{}
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go longnameCacheCleaner()
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}
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// findLongnameParent converts "longname" = "gocryptfs.longname.XYZ" to the
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// plaintext name. "dir" = relative plaintext path to the directory the
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// longname file is in, "dirIV" = directory IV of the directory.
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func (rfs *ReverseFS) findLongnameParent(dir string, dirIV []byte, longname string) (plaintextName string, err error) {
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longnameCacheLock.Lock()
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hit := longnameParentCache[dir+"/"+longname]
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longnameCacheLock.Unlock()
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if hit != "" {
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return hit, nil
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}
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fd, err := syscallcompat.OpenNofollow(rfs.args.Cipherdir, dir, syscall.O_RDONLY|syscall.O_DIRECTORY, 0)
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if err != nil {
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tlog.Warn.Printf("findLongnameParent: opendir failed: %v\n", err)
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return "", err
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}
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dirEntries, err := syscallcompat.Getdents(fd)
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syscall.Close(fd)
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if err != nil {
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tlog.Warn.Printf("findLongnameParent: Getdents failed: %v\n", err)
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return "", err
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}
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longnameCacheLock.Lock()
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defer longnameCacheLock.Unlock()
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for _, entry := range dirEntries {
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plaintextName := entry.Name
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if len(plaintextName) <= shortNameMax {
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continue
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}
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cName := rfs.nameTransform.EncryptName(plaintextName, dirIV)
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if len(cName) <= syscall.NAME_MAX {
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// Entry should have been skipped by the "continue" above
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log.Panic("logic error or wrong shortNameMax constant?")
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}
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hName := rfs.nameTransform.HashLongName(cName)
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longnameParentCache[dir+"/"+hName] = plaintextName
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if longname == hName {
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hit = plaintextName
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}
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}
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if hit == "" {
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return "", syscall.ENOENT
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}
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return hit, nil
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}
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func (rfs *ReverseFS) newNameFile(relPath string) (nodefs.File, fuse.Status) {
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dotName := filepath.Base(relPath) // gocryptfs.longname.XYZ.name
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longname := dotName[:len(dotName)-len(nametransform.LongNameSuffix)] // gocryptfs.longname.XYZ
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// cipher directory
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cDir := nametransform.Dir(relPath)
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// plain directory
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pDir, err := rfs.decryptPath(cDir)
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if err != nil {
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return nil, fuse.ToStatus(err)
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}
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dirIV := pathiv.Derive(cDir, pathiv.PurposeDirIV)
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// plain name
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pName, err := rfs.findLongnameParent(pDir, dirIV, longname)
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if err != nil {
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return nil, fuse.ToStatus(err)
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}
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content := []byte(rfs.nameTransform.EncryptName(pName, dirIV))
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parentFile := filepath.Join(pDir, pName)
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return rfs.newVirtualFile(content, rfs.args.Cipherdir, parentFile, inoBaseNameFile)
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}
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