Fix Improper Error Handling in Buffalo

In Buffalo, improper error handling usually manifests as leaking internal system details—like database schema, file paths, or stack traces—directly to the client via the default error handler. This is a classic Information Exposure (CWE-209) vulnerability. As an AppSec researcher, your goal is to ensure that internal failures stay in the logs and only sanitized, generic messages reach the end-user.

The Vulnerable Pattern

func UserShow(c buffalo.Context) error {
	u := &models.User{}
	err := models.DB.Find(u, c.Param("user_id"))
	if err != nil {
		// VULNERABILITY: Passing the raw 'err' object to c.Error
		// If the ID is malformed or DB is down, this leaks SQL state/logic.
		return c.Error(500, err)
	}
	return c.Render(200, r.JSON(u))
}

The Secure Implementation

The vulnerability occurs when the application returns the raw error object (often containing SQL syntax, table names, or pointer addresses) to the HTTP response. Attackers use this data to map the backend infrastructure or perform SQL injection. The fix involves two layers: 1) Action-level sanitization, where specific errors are caught and replaced with generic user-facing messages, and 2) Global Error Handlers in the Buffalo App configuration to ensure that even unhandled panics or unexpected errors return a uniform, non-descriptive JSON/HTML response instead of a stack trace.

func UserShow(c buffalo.Context) error {
	u := &models.User{}
	err := models.DB.Find(u, c.Param("user_id"))
	if err != nil {
		// SECURE: Log the actual error for devops, return generic message to client
		c.Logger().Errorf("DB Error: %v", err)
		return c.Error(404, fmt.Errorf("the requested resource could not be found"))
	}
	return c.Render(200, r.JSON(u))
}
// Globally in actions/app.go:
app.ErrorHandlers[500] = func(status int, err error, c buffalo.Context) error {
return c.Render(status, r.JSON(map[string]string{“error”: “Internal Server Error”}))
}