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)
+}