Configuration hardening

internal/music/music.go

@@ -78,6 +78,13 @@ type CreditsOverlay struct {
 }
 
 func ResolveFFmpeg() (string, error) {
+	return ResolveFFmpegWithConfig("")
+}
+
+func ResolveFFmpegWithConfig(configuredPath string) (string, error) {
+	if configured := strings.TrimSpace(configuredPath); configured != "" {
+		return configured, nil
+	}
 	if configured := strings.TrimSpace(os.Getenv("SOW_FFMPEG")); configured != "" {
 		return configured, nil
 	}
@@ -89,6 +96,13 @@ func ResolveFFmpeg() (string, error) {
 }
 
 func ResolveFFprobe() (string, error) {
+	return ResolveFFprobeWithConfig("")
+}
+
+func ResolveFFprobeWithConfig(configuredPath string) (string, error) {
+	if configured := strings.TrimSpace(configuredPath); configured != "" {
+		return configured, nil
+	}
 	if configured := strings.TrimSpace(os.Getenv("SOW_FFPROBE")); configured != "" {
 		return configured, nil
 	}
@@ -104,6 +118,15 @@ func IsMusicAssetPath(rel string) bool {
 	return rel == "envi/music" || strings.HasPrefix(rel, "envi/music/")
 }
 
+func PathIsUnder(root, rel string) bool {
+	root = TrimSlashes(filepath.ToSlash(root))
+	rel = TrimSlashes(filepath.ToSlash(rel))
+	if root == "" || rel == "" {
+		return false
+	}
+	return rel == root || strings.HasPrefix(rel, root+"/")
+}
+
 func PrefixForDir(prefixes map[string]string, dir string) string {
 	dir = TrimSlashes(filepath.ToSlash(dir))
 	bestPrefix := ""