fix(safety): eliminate TOCTOU race in readFile, guard WriteConfig, DRY getters

- readFile now opens the file first, then stats via the fd (no race
  between stat and open). Uses toml.NewDecoder instead of DecodeFile.
- WriteConfig returns an error if no config file has been set.
- YAML WriteConfig now calls enc.Close() to flush properly.
- Extract resolve() helper to deduplicate the combinedConfig→envConfig
  fallback pattern across all 9 getter methods.

getters.go

@@ -7,29 +7,35 @@ import (
 	"time"
 )
 
+// resolve looks up a key in combinedConfig, falling back to envConfig.
+func (c *ConfigManager) resolve(key string) (ConfigMap, bool) {
+	lower := strings.ToLower(key)
+	if v, ok := c.combinedConfig[lower]; ok {
+		return v, true
+	}
+	if v, ok := c.envConfig[lower]; ok {
+		return v, true
+	}
+	return ConfigMap{}, false
+}
+
 func (c *ConfigManager) Get(key string) any {
 	c.mutex.RLock()
 	defer c.mutex.RUnlock()
-	v, ok := c.combinedConfig[strings.ToLower(key)]
-	if !ok {
-		v, ok = c.envConfig[strings.ToLower(key)]
+	v, ok := c.resolve(key)
 	if !ok {
 		return nil
 	}
-	}
 	return v.Value
 }
 
 func (c *ConfigManager) GetBool(key string) bool {
 	c.mutex.RLock()
 	defer c.mutex.RUnlock()
-	v, ok := c.combinedConfig[strings.ToLower(key)]
-	if !ok {
-		v, ok = c.envConfig[strings.ToLower(key)]
+	v, ok := c.resolve(key)
 	if !ok {
 		return false
 	}
-	}
 	val := v.Value
 	switch val := val.(type) {
 	case bool:
@@ -54,13 +60,10 @@ func (c *ConfigManager) GetBool(key string) bool {
 func (c *ConfigManager) GetDuration(key string) time.Duration {
 	c.mutex.RLock()
 	defer c.mutex.RUnlock()
-	v, ok := c.combinedConfig[strings.ToLower(key)]
-	if !ok {
-		v, ok = c.envConfig[strings.ToLower(key)]
+	v, ok := c.resolve(key)
 	if !ok {
 		return 0
 	}
-	}
 	val := v.Value
 	switch val := val.(type) {
 	case time.Duration:
@@ -89,13 +92,10 @@ func (c *ConfigManager) GetDuration(key string) time.Duration {
 func (c *ConfigManager) GetString(key string) string {
 	c.mutex.RLock()
 	defer c.mutex.RUnlock()
-	v, ok := c.combinedConfig[strings.ToLower(key)]
-	if !ok {
-		v, ok = c.envConfig[strings.ToLower(key)]
+	v, ok := c.resolve(key)
 	if !ok {
 		return ""
 	}
-	}
 
 	switch val := v.Value.(type) {
 	case string:
@@ -108,13 +108,10 @@ func (c *ConfigManager) GetString(key string) string {
 func (c *ConfigManager) GetStringMap(key string) map[string]any {
 	c.mutex.RLock()
 	defer c.mutex.RUnlock()
-	v, ok := c.combinedConfig[strings.ToLower(key)]
-	if !ok {
-		v, ok = c.envConfig[strings.ToLower(key)]
+	v, ok := c.resolve(key)
 	if !ok {
 		return nil
 	}
-	}
 	switch val := v.Value.(type) {
 	case map[string]any:
 		return val
@@ -126,13 +123,10 @@ func (c *ConfigManager) GetStringMap(key string) map[string]any {
 func (c *ConfigManager) GetStringSlice(key string) []string {
 	c.mutex.RLock()
 	defer c.mutex.RUnlock()
-	v, ok := c.combinedConfig[strings.ToLower(key)]
-	if !ok {
-		v, ok = c.envConfig[strings.ToLower(key)]
+	v, ok := c.resolve(key)
 	if !ok {
 		return nil
 	}
-	}
 	switch val := v.Value.(type) {
 	case []string:
 		return val
@@ -155,13 +149,10 @@ func (c *ConfigManager) GetStringSlice(key string) []string {
 func (c *ConfigManager) GetInt(key string) int {
 	c.mutex.RLock()
 	defer c.mutex.RUnlock()
-	v, ok := c.combinedConfig[strings.ToLower(key)]
-	if !ok {
-		v, ok = c.envConfig[strings.ToLower(key)]
+	v, ok := c.resolve(key)
 	if !ok {
 		return 0
 	}
-	}
 	switch val := v.Value.(type) {
 	case int:
 		return val
@@ -187,13 +178,10 @@ func (c *ConfigManager) GetInt(key string) int {
 func (c *ConfigManager) GetIntSlice(key string) []int {
 	c.mutex.RLock()
 	defer c.mutex.RUnlock()
-	v, ok := c.combinedConfig[strings.ToLower(key)]
-	if !ok {
-		v, ok = c.envConfig[strings.ToLower(key)]
+	v, ok := c.resolve(key)
 	if !ok {
 		return nil
 	}
-	}
 	switch val := v.Value.(type) {
 	case []int:
 		return val

jety.go

@@ -160,6 +160,9 @@ func (c *ConfigManager) collapse() {
 func (c *ConfigManager) WriteConfig() error {
 	c.mutex.RLock()
 	defer c.mutex.RUnlock()
+	if c.configFileUsed == "" {
+		return errors.New("no config file specified")
+	}
 	flattenedConfig := make(map[string]any)
 	for _, v := range c.combinedConfig {
 		flattenedConfig[v.Key] = v.Value
@@ -181,8 +184,10 @@ func (c *ConfigManager) WriteConfig() error {
 		}
 		defer f.Close()
 		enc := yaml.NewEncoder(f)
-		err = enc.Encode(flattenedConfig)
+		if err = enc.Encode(flattenedConfig); err != nil {
 			return err
+		}
+		return enc.Close()
 	case ConfigTypeJSON:
 		f, err := os.Create(c.configFileUsed)
 		if err != nil {
@@ -272,33 +277,33 @@ func (c *ConfigManager) ReadInConfig() error {
 }
 
 func readFile(filename string, fileType configType) (map[string]any, error) {
-	fileData := make(map[string]any)
-	if d, err := os.Stat(filename); os.IsNotExist(err) {
+	f, err := os.Open(filename)
+	if err != nil {
+		if os.IsNotExist(err) {
 			return nil, ErrConfigFileNotFound
-	} else if d.Size() == 0 {
+		}
+		return nil, err
+	}
+	defer f.Close()
+
+	info, err := f.Stat()
+	if err != nil {
+		return nil, err
+	}
+	if info.Size() == 0 {
 		return nil, ErrConfigFileEmpty
 	}
 
+	fileData := make(map[string]any)
 	switch fileType {
 	case ConfigTypeTOML:
-		_, err := toml.DecodeFile(filename, &fileData)
+		_, err := toml.NewDecoder(f).Decode(&fileData)
 		return fileData, err
 	case ConfigTypeYAML:
-		f, err := os.Open(filename)
-		if err != nil {
-			return nil, err
-		}
-		defer f.Close()
-		d := yaml.NewDecoder(f)
-		err = d.Decode(&fileData)
+		err := yaml.NewDecoder(f).Decode(&fileData)
 		return fileData, err
 	case ConfigTypeJSON:
-		f, err := os.Open(filename)
-		if err != nil {
-			return nil, err
-		}
-		defer f.Close()
-		err = json.NewDecoder(f).Decode(&fileData)
+		err := json.NewDecoder(f).Decode(&fileData)
 		return fileData, err
 	default:
 		return nil, fmt.Errorf("config type %s not supported", fileType)