osbuild/device: use systemd-escape like escaping for mountable paths

Previously, the function used to escape filesystem paths of mountable
entities, which are used as device names, could generate the same name
for different devices. Specifically, it returned `root` as the device
name for entity with `/` and `/root` mount point. This results in
invalid osbuild manifests being generated.

Rework the escaping function by implementing a similar escaping
algorithm as used by systemd-escape, which will ensure that we always
generate a unique device name for devices with different mountpoints,
while still generating the same device name for the same device (with
the same mountponit path).

Signed-off-by: Tomáš Hozza <[email protected]>

pkg/osbuild/device.go

@@ -153,7 +153,7 @@ func deviceName(p disk.Entity) string {
 
 	switch payload := p.(type) {
 	case disk.Mountable:
-		return pathdot(payload.GetMountpoint())
+		return pathEscape(payload.GetMountpoint())
 	case *disk.LUKSContainer:
 		return "luks-" + payload.UUID[:4]
 	case *disk.LVMVolumeGroup:
@@ -206,12 +206,21 @@ func getDevices(path []disk.Entity, filename string, lockLoopback bool) (map[str
 	return do, parent
 }
 
-func pathdot(path string) string {
-	if path == "/" {
-		return "root"
+// pathEscape implements similar path escaping as used by systemd-escape
+// https://github.com/systemd/systemd/blob/c57ff6230e4e199d40f35a356e834ba99f3f8420/src/basic/unit-name.c#L389
+func pathEscape(path string) string {
+	if len(path) == 0 || path == "/" {
+		return "-"
 	}
 
-	path = strings.TrimLeft(path, "/")
+	path = strings.Trim(path, "/")
 
-	return strings.ReplaceAll(path, "/", ".")
+	escapeChars := func(s, char string) string {
+		return strings.ReplaceAll(s, char, fmt.Sprintf("\\x%x", char[0]))
+	}
+
+	path = escapeChars(path, "\\")
+	path = escapeChars(path, "-")
+
+	return strings.ReplaceAll(path, "/", "-")
 }

pkg/osbuild/device_test.go

@@ -140,3 +140,29 @@ func TestGenDeviceFinishStagesOrderWithLVMClevisBind(t *testing.T) {
 	// followed by "org.osbuild.luks2.remove-key"
 	assert.Equal("org.osbuild.luks2.remove-key", luks.Type)
 }
+
+func TestPathEscape(t *testing.T) {
+	testCases := []struct {
+		path     string
+		expected string
+	}{
+		{"", "-"},
+		{"/", "-"},
+		{"/root", "root"},
+		{"/root/", "root"},
+		{"/home/shadowman", "home-shadowman"},
+		{"/home/s.o.s", "home-s.o.s"},
+		{"/path/to/dir", "path-to-dir"},
+		{"/path/with\\backslash", "path-with\\x5cbackslash"},
+		{"/path-with-dash", "path\\x2dwith\\x2ddash"},
+	}
+
+	for _, tc := range testCases {
+		t.Run(tc.path, func(t *testing.T) {
+			result := pathEscape(tc.path)
+			if result != tc.expected {
+				t.Errorf("pathEscape(%q) = %q; expected %q", tc.path, result, tc.expected)
+			}
+		})
+	}
+}