longnames part I: Create and OpenDir work with long filenames > 176 bytes

Todo: Rename, Unlink, Rmdir, Mknod, Mkdir

1 files changed, 68 insertions, 0 deletions

diff --git a/internal/nametransform/longnames.go b/internal/nametransform/longnames.go
new file mode 100644
index 0000000..e442b64
--- /dev/null
+++ b/internal/nametransform/longnames.go
@@ -0,0 +1,68 @@
+package nametransform
+
+import (
+	"syscall"
+	"path/filepath"
+	"io/ioutil"
+	"crypto/sha256"
+	"encoding/base64"
+	"strings"
+
+	"github.com/rfjakob/gocryptfs/internal/toggledlog"
+)
+
+// Files with long names are stored in two files:
+// gocryptfs.longname.[sha256]       <--- File content
+// gocryptfs.longname.[sha256].name  <--- File name
+const longNamePrefix = "gocryptfs.longname."
+const longNameSuffix = ".name"
+
+// HashLongName - take the hash of a long string "name" and return
+// "gocryptfs.longname.[sha256]"
+func HashLongName(name string) string {
+	hashBin := sha256.Sum256([]byte(name))
+	hashBase64 := base64.URLEncoding.EncodeToString(hashBin[:])
+	return longNamePrefix + hashBase64
+}
+
+// IsLongName - detect if cName is
+// gocryptfs.longname.* ........ 1
+// gocryptfs.longname.*.name ... 2
+// else ........................ 0
+func IsLongName(cName string) int {
+	if !strings.HasPrefix(cName, longNamePrefix) {
+		return 0
+	}
+	if strings.HasSuffix(cName, longNameSuffix) {
+		return 2
+	}
+	return 1
+}
+
+// ReadLongName - read "path".name
+func ReadLongName(path string) (string, error) {
+	content, err := ioutil.ReadFile(path+longNameSuffix)
+	if err != nil {
+		toggledlog.Warn.Printf("ReadLongName: %v", err)
+	}
+	return string(content), err
+}
+
+// WriteLongName -
+func (n *NameTransform) WriteLongName(cDir string, hashedName string, plainName string) (err error) {
+	if len(plainName) > syscall.NAME_MAX {
+		return syscall.ENAMETOOLONG
+	}
+
+	dirIV, err := ReadDirIV(cDir)
+	if err != nil {
+		toggledlog.Warn.Printf("WriteLongName: %v", err)
+		return err
+	}
+	cName := n.EncryptName(plainName, dirIV)
+	err = ioutil.WriteFile(filepath.Join(cDir, hashedName + longNameSuffix), []byte(cName), 0600)
+	if err != nil {
+		toggledlog.Warn.Printf("WriteLongName: %v", err)
+	}
+	return err
+}