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 := ""

internal/music/naming.go

@@ -8,7 +8,14 @@ import (
 )
 
 func GenerateStem(fileName, prefix string, used map[string]struct{}) (string, error) {
-	maxCore := MaxStemLen - len(prefix)
+	return GenerateStemWithMax(fileName, prefix, MaxStemLen, used)
+}
+
+func GenerateStemWithMax(fileName, prefix string, maxStemLen int, used map[string]struct{}) (string, error) {
+	if maxStemLen <= 0 {
+		maxStemLen = MaxStemLen
+	}
+	maxCore := maxStemLen - len(prefix)
 	if maxCore < 3 {
 		return "", fmt.Errorf("prefix too long: %q", prefix)
 	}
@@ -19,11 +26,11 @@ func GenerateStem(fileName, prefix string, used map[string]struct{}) (string, er
 		sum := sha1.Sum([]byte(fileName))
 		core = fmt.Sprintf("%x", sum[:])[:maxCore]
 	}
-	stem := strings.TrimRight((prefix + core)[:Min(MaxStemLen, len(prefix)+len(core))], "_")
+	stem := strings.TrimRight((prefix + core)[:Min(maxStemLen, len(prefix)+len(core))], "_")
 	if stem == "" {
 		return "", fmt.Errorf("could not derive music stem for %s", fileName)
 	}
-	return UniqueName(stem, used), nil
+	return UniqueNameWithMax(stem, maxStemLen, used), nil
 }
 
 func SlugWords(value string) []string {
@@ -119,13 +126,20 @@ func AbbreviateWord(word string, maxLen int) string {
 }
 
 func UniqueName(stem string, used map[string]struct{}) string {
+	return UniqueNameWithMax(stem, MaxStemLen, used)
+}
+
+func UniqueNameWithMax(stem string, maxStemLen int, used map[string]struct{}) string {
+	if maxStemLen <= 0 {
+		maxStemLen = MaxStemLen
+	}
 	if _, exists := used[stem]; !exists {
 		used[stem] = struct{}{}
 		return stem
 	}
 	for index := 1; ; index++ {
 		suffix := fmt.Sprintf("_%d", index)
-		prefixLen := Min(len(stem), Max(0, MaxStemLen-len(suffix)))
+		prefixLen := Min(len(stem), Max(0, maxStemLen-len(suffix)))
 		candidate := strings.TrimRight(stem[:prefixLen], "_") + suffix
 		if _, exists := used[candidate]; exists {
 			continue
@@ -148,16 +162,27 @@ func ReserveName(stem string, used map[string]struct{}) error {
 }
 
 func ValidateManualOutputFile(name string) error {
+	return ValidateManualOutputFileWithRules(name, ".bmu", MaxStemLen)
+}
+
+func ValidateManualOutputFileWithRules(name, extension string, maxStemLen int) error {
 	name = strings.ToLower(strings.TrimSpace(name))
-	if !strings.HasSuffix(name, ".bmu") {
-		return fmt.Errorf("output file must end with .bmu")
+	extension = strings.ToLower(strings.TrimSpace(extension))
+	if extension == "" {
+		extension = ".bmu"
 	}
-	stem := strings.TrimSuffix(name, ".bmu")
+	if maxStemLen <= 0 {
+		maxStemLen = MaxStemLen
+	}
+	if !strings.HasSuffix(name, extension) {
+		return fmt.Errorf("output file must end with %s", extension)
+	}
+	stem := strings.TrimSuffix(name, extension)
 	if stem == "" {
 		return fmt.Errorf("output file stem is empty")
 	}
-	if len(stem) > MaxStemLen {
-		return fmt.Errorf("output file stem %q exceeds %d characters", stem, MaxStemLen)
+	if len(stem) > maxStemLen {
+		return fmt.Errorf("output file stem %q exceeds %d characters", stem, maxStemLen)
 	}
 	for _, r := range stem {
 		switch {