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authorJakob Unterwurzacher2020-08-01 20:47:59 +0200
committerJakob Unterwurzacher2020-08-01 21:14:10 +0200
commit13dc7657ba0aac4da3f4b80ba231a919fdfae0f5 (patch)
treed13781bacb4a02327f519d399e946f83fd13e5c7 /internal/fusefrontend_reverse_v1api/reverse_longnames.go
parentdd3d8c100bc9e84c44b2efb55e536b2fc0ded37e (diff)
v2api/reverse: move old fusefrontend_reverse out of the way
fusefrontend_reverse -> fusefrontend_reverse_v1api
Diffstat (limited to 'internal/fusefrontend_reverse_v1api/reverse_longnames.go')
-rw-r--r--internal/fusefrontend_reverse_v1api/reverse_longnames.go126
1 files changed, 126 insertions, 0 deletions
diff --git a/internal/fusefrontend_reverse_v1api/reverse_longnames.go b/internal/fusefrontend_reverse_v1api/reverse_longnames.go
new file mode 100644
index 0000000..f1576d2
--- /dev/null
+++ b/internal/fusefrontend_reverse_v1api/reverse_longnames.go
@@ -0,0 +1,126 @@
+package fusefrontend_reverse
+
+import (
+ "log"
+ "path/filepath"
+ "sync"
+ "syscall"
+ "time"
+
+ "golang.org/x/sys/unix"
+
+ "github.com/hanwen/go-fuse/v2/fuse"
+ "github.com/hanwen/go-fuse/v2/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
+ }
+ dirfd, err := syscallcompat.OpenDirNofollow(rfs.args.Cipherdir, filepath.Dir(dir))
+ if err != nil {
+ tlog.Warn.Printf("findLongnameParent: OpenDirNofollow failed: %v\n", err)
+ return "", err
+ }
+ fd, err := syscallcompat.Openat(dirfd, filepath.Base(dir), syscall.O_RDONLY|syscall.O_DIRECTORY|syscall.O_NOFOLLOW, 0)
+ syscall.Close(dirfd)
+ if err != nil {
+ tlog.Warn.Printf("findLongnameParent: Openat 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 := nametransform.RemoveLongNameSuffix(dotName) // 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, inoTagNameFile)
+}