nametransform: check name validity on encryption

xfstests generic/523 discovered that we allowed to set
xattrs with "/" in the name, but did not allow to read
them later.

With this change we do not allow to set them in the first
place.

3 files changed, 22 insertions, 8 deletions

diff --git a/internal/fusefrontend/node_xattr.go b/internal/fusefrontend/node_xattr.go
index 3855b55..925dcbf 100644
--- a/internal/fusefrontend/node_xattr.go
+++ b/internal/fusefrontend/node_xattr.go
@@ -56,12 +56,14 @@ func (n *Node) Getxattr(ctx context.Context, attr string, dest []byte) (uint32,
 		}
 	} else {
 		// encrypted user xattr
-		cAttr := rn.encryptXattrName(attr)
+		cAttr, err := rn.encryptXattrName(attr)
+		if err != nil {
+			return minus1, syscall.EIO
+		}
 		cData, errno := n.getXAttr(cAttr)
 		if errno != 0 {
 			return 0, errno
 		}
-		var err error
 		data, err = rn.decryptXattrValue(cData)
 		if err != nil {
 			tlog.Warn.Printf("GetXAttr: %v", err)
@@ -91,7 +93,10 @@ func (n *Node) Setxattr(ctx context.Context, attr string, data []byte, flags uin
 		return n.setXAttr(attr, data, flags)
 	}
 
-	cAttr := rn.encryptXattrName(attr)
+	cAttr, err := rn.encryptXattrName(attr)
+	if err != nil {
+		return syscall.EINVAL
+	}
 	cData := rn.encryptXattrValue(data)
 	return n.setXAttr(cAttr, cData, flags)
 }
@@ -107,7 +112,10 @@ func (n *Node) Removexattr(ctx context.Context, attr string) syscall.Errno {
 		return n.removeXAttr(attr)
 	}
 
-	cAttr := rn.encryptXattrName(attr)
+	cAttr, err := rn.encryptXattrName(attr)
+	if err != nil {
+		return syscall.EINVAL
+	}
 	return n.removeXAttr(cAttr)
 }
 
diff --git a/internal/fusefrontend/root_node.go b/internal/fusefrontend/root_node.go
index e998e9d..a830cc4 100644
--- a/internal/fusefrontend/root_node.go
+++ b/internal/fusefrontend/root_node.go
@@ -311,10 +311,13 @@ func (rn *RootNode) decryptXattrValue(cData []byte) (data []byte, err error) {
 }
 
 // encryptXattrName transforms "user.foo" to "user.gocryptfs.a5sAd4XAa47f5as6dAf"
-func (rn *RootNode) encryptXattrName(attr string) (cAttr string) {
+func (rn *RootNode) encryptXattrName(attr string) (string, error) {
 	// xattr names are encrypted like file names, but with a fixed IV.
-	cAttr = xattrStorePrefix + rn.nameTransform.EncryptName(attr, xattrNameIV)
-	return cAttr
+	cAttr, err := rn.nameTransform.EncryptName(attr, xattrNameIV)
+	if err != nil {
+		return "", err
+	}
+	return xattrStorePrefix + cAttr, nil
 }
 
 func (rn *RootNode) decryptXattrName(cAttr string) (attr string, err error) {
diff --git a/internal/fusefrontend/xattr_unit_test.go b/internal/fusefrontend/xattr_unit_test.go
index f6c0469..a0cf4c8 100644
--- a/internal/fusefrontend/xattr_unit_test.go
+++ b/internal/fusefrontend/xattr_unit_test.go
@@ -33,7 +33,10 @@ func newTestFS(args Args) *RootNode {
 func TestEncryptDecryptXattrName(t *testing.T) {
 	fs := newTestFS(Args{})
 	attr1 := "user.foo123456789"
-	cAttr := fs.encryptXattrName(attr1)
+	cAttr, err := fs.encryptXattrName(attr1)
+	if err != nil {
+		t.Fatal(err)
+	}
 	t.Logf("cAttr=%v", cAttr)
 	attr2, err := fs.decryptXattrName(cAttr)
 	if attr1 != attr2 || err != nil {