fusefrontend: allow slashes in xattr names

xattr names have fewer restrictions than file names,
relax the validation.

Fixes https://github.com/rfjakob/gocryptfs/issues/627

1 files changed, 47 insertions, 0 deletions

diff --git a/internal/nametransform/xattr.go b/internal/nametransform/xattr.go
new file mode 100644
index 0000000..0aa0fd8
--- /dev/null
+++ b/internal/nametransform/xattr.go
@@ -0,0 +1,47 @@
+package nametransform
+
+import (
+	"fmt"
+	"strings"
+	"syscall"
+
+	"github.com/rfjakob/gocryptfs/v2/internal/tlog"
+)
+
+// xattr names are encrypted like file names, but with a fixed IV.
+// Padded with "_xx" for length 16.
+var xattrNameIV = []byte("xattr_name_iv_xx")
+
+func isValidXattrName(name string) error {
+	if name == "" {
+		return fmt.Errorf("empty input")
+	}
+	if strings.Contains(name, "\000") {
+		return fmt.Errorf("contains forbidden null byte")
+	}
+	return nil
+}
+
+// EncryptXattrName encrypts an extended attribute (xattr) name.
+// xattr names are encrypted like file names, but with a fixed IV, and fewer
+// naming restriction.
+func (n *NameTransform) EncryptXattrName(plainName string) (cipherName64 string, err error) {
+	if err := isValidXattrName(plainName); err != nil {
+		tlog.Warn.Printf("EncryptXattrName %q: invalid plainName: %v", plainName, err)
+		return "", syscall.EBADMSG
+	}
+	return n.encryptName(plainName, xattrNameIV), nil
+}
+
+// DecryptName calls decryptName to try and decrypt a base64-encoded encrypted
+// filename "cipherName", and failing that checks if it can be bypassed
+func (n *NameTransform) DecryptXattrName(cipherName string) (plainName string, err error) {
+	if plainName, err = n.decryptName(cipherName, xattrNameIV); err != nil {
+		return "", err
+	}
+	if err := isValidXattrName(plainName); err != nil {
+		tlog.Warn.Printf("DecryptXattrName %q: invalid name after decryption: %v", cipherName, err)
+		return "", syscall.EBADMSG
+	}
+	return plainName, err
+}