Missing Authentication in Buffalo

Missing authentication in Buffalo applications often occurs when developers assume certain endpoints are internal or don't require protection. This manifests in several Buffalo-specific patterns that create critical security vulnerabilities.

The most common manifestation appears in Buffalo's resource routing. When developers use buffalo.Resource without applying authentication middleware to specific actions, endpoints become publicly accessible:

app.Resource("/users", UsersResource{}) // All actions exposed without auth

This exposes endpoints like GET /users/:id for retrieving user data, PUT /users/:id for updating profiles, and DELETE /users/:id for account deletion—all without authentication checks.

Another Buffalo-specific pattern involves the SkipAuth flag on resource actions:

func (v UsersResource) SkipAuth() []string {
    return []string{"Create", "Login"} // Only these actions skip auth
}

When this list is incomplete or improperly maintained, attackers can exploit unlisted actions. A common mistake is omitting destructive actions like Delete or Update.

Buffalo's middleware stack can also create authentication gaps. Developers sometimes apply authentication middleware too late in the chain:

app.Use(middleware.RequestLogger) // Logging first
app.Use(auth.Middleware) // Auth applied afterward
app.GET("/admin", AdminHandler) // Admin endpoint exposed before auth check

This ordering allows unauthenticated requests to reach handlers before the authentication middleware can block them.

Buffalo's pop/soda ORM integration creates another vulnerability vector. When developers write direct database queries without checking user context:

func getUser(c buffalo.Context) error {
    id := c.Param("id")
    user := &User{}
    err := models.DB.Find(user, id) // No ownership verification
    return c.Render(200, r.JSON(user))
}

This allows any authenticated (or even unauthenticated) user to retrieve any user's data by ID—a classic Broken Object Level Authorization (BOLA) scenario that stems from missing authentication context.

Detecting missing authentication in Buffalo applications requires examining both the routing configuration and middleware stack. Start by auditing your resource definitions:

// Check all resources for authentication gaps
for _, resource := range app.Routes() {
    if resource.RequiresAuth == false {
        log.Printf("Potential auth gap: %s %s", resource.Method, resource.Path)
    }
}

Buffalo's built-in middleware inspection helps identify where authentication is applied:

// List middleware stack for each route
for _, route := range app.Routes() {
    middlewareStack := route.MiddlewareStack
    hasAuth := false
    for _, mw := range middlewareStack {
        if mw.Name() == "auth.Middleware" {
            hasAuth = true
            break
        }
    }
    if !hasAuth {
        log.Printf("Route %s missing auth middleware", route.Path)
    }
}

Automated scanning with middleBrick provides comprehensive detection without code access. The scanner tests endpoints by attempting unauthenticated requests and analyzing responses:

middlebrick scan https://your-buffalo-app.com

middleBrick's black-box approach tests the actual runtime behavior, identifying endpoints that respond to unauthenticated requests when they shouldn't. The scanner specifically checks for:

• Resource endpoints without authentication middleware
• Actions listed in SkipAuth() that shouldn't be public
• Middleware ordering issues allowing pre-auth access
• Direct database queries without ownership verification

For OpenAPI specification analysis, middleBrick resolves $ref references and cross-references spec definitions with runtime findings, identifying mismatches between documented authentication requirements and actual implementation.

Remediating missing authentication in Buffalo applications requires a systematic approach using Buffalo's native authentication features. The most robust solution uses Buffalo's middleware system to protect entire resource groups:

// Create a protected app group
authApp := app.Group("/api")
authApp.Use(auth.Middleware) // Apply auth to all routes in this group

// Add authenticated resources
authApp.Resource("/users", UsersResource{})
authApp.Resource("/posts", PostsResource{})

This ensures all endpoints under /api/* require authentication, eliminating gaps from individual resource definitions.

For selective authentication, use Buffalo's SkipAuth method correctly:

func (v UsersResource) SkipAuth() []string {
    return []string{"Create", "Login", "ForgotPassword"} // Only truly public actions
}

// Explicitly require auth on other actions
func (v UsersResource) AuthRequired() []string {
    return []string{"Show", "Update", "Delete"} // These always require auth
}

Implement ownership verification for data access:

func (v UsersResource) Show(c buffalo.Context) error {
    id := c.Param("id")
    currentUser := c.Value("current_user").(*models.User)
    
    // Verify ownership or admin role
    if id != fmt.Sprintf("%d", currentUser.ID) && !currentUser.IsAdmin {
        return c.Error(403, errors.New("unauthorized"))
    }
    
    user := &models.User{}
    err := models.DB.Find(user, id)
    if err != nil {
        return c.Error(404, err)
    }
    return c.Render(200, r.JSON(user))
}

For middleware ordering issues, ensure authentication is the first middleware applied:

app.Use(auth.Middleware) // First: block unauthenticated requests
app.Use(middleware.RequestLogger) // Second: log authenticated requests only
app.Use(middleware.CORS) // Third: apply CORS after auth

Integrate authentication checks into your CI/CD pipeline using middleBrick's GitHub Action:

- name: Scan API Security
  uses: middlebrick/middlebrick-action@v1
  with:
    url: https://staging.your-buffalo-app.com
    fail-on-severity: high

This automatically catches authentication regressions before deployment, ensuring your Buffalo application maintains proper security controls throughout development.