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