Broken Access Control in Buffalo

Broken Access Control (BAC) in Buffalo applications typically emerges through several common patterns. The most prevalent occurs in resource handlers where authorization checks are omitted or improperly implemented. Consider a typical Buffalo resource for managing user profiles:

type UserProfileResource struct {
  buffalo.Resource
}

func (u UserProfileResource) List(c buffalo.Context) error {
  // No authorization check - any authenticated user can list all profiles
  profiles, err := models.Profiles().All()
  return c.Render(200, r.JSON(profiles))
}

func (u UserProfileResource) Show(c buffalo.Context) error {
  // IDOR vulnerability - user can access any profile by ID
  profile := &models.UserProfile{}
  err := models.DB.Find(profile, c.Param("id"))
  return c.Render(200, r.JSON(profile))
}

Another common manifestation involves improper use of Buffalo's authentication middleware. Developers often assume that requiring authentication is sufficient, but fail to verify resource ownership:

func (u UserProfileResource) Update(c buffalo.Context) error {
  // Only checks authentication, not authorization
  profile := &models.UserProfile{}
  err := models.DB.Find(profile, c.Param("id"))
  
  // Any authenticated user can update any profile
  err = c.Bind(profile)
  return c.Render(200, r.JSON(profile))
}

BAC also appears in Buffalo applications through inadequate role-based access control (RBAC) implementation. Without proper role checks, users may access administrative functions:

func AdminDashboard(c buffalo.Context) error {
  // No role verification - any authenticated user can access admin dashboard
  return c.Render(200, r.HTML("admin/dashboard.plush.html"))
}

Property-level authorization failures are particularly subtle in Buffalo. Developers might authorize access to a resource but fail to filter sensitive properties:

func (u UserProfileResource) Show(c buffalo.Context) error {
  profile := &models.UserProfile{}
  err := models.DB.Find(profile, c.Param("id"))
  
  // Authorization check passed, but sensitive data still exposed
  return c.Render(200, r.JSON(profile))
}

Finally, broken access control can occur through improper use of Buffalo's Pop ORM, where queries don't properly scope data to the authenticated user:

func (u OrderResource) List(c buffalo.Context) error {
  // Returns all orders, not just user's orders
  orders := &models.Orders{}
  err := models.DB.All(orders)
  return c.Render(200, r.JSON(orders))
}

Detecting broken access control in Buffalo applications requires both static analysis and runtime testing. For static analysis, examine your resource handlers for missing authorization patterns. Look for handlers that:

• Accept resource IDs without ownership verification
• Lack role-based access checks for privileged operations
• Don't filter data by the authenticated user's context

middleBrick's black-box scanning approach is particularly effective for Buffalo applications because it tests the actual running API without requiring source code access. The scanner automatically:

• Tests IDOR vulnerabilities by manipulating resource identifiers
• Attempts privilege escalation by accessing admin endpoints
• Verifies property authorization by checking sensitive data exposure

For Buffalo applications, middleBrick specifically tests common endpoint patterns like:

GET /api/users/{id}/profile
PUT /api/orders/{id}/status
DELETE /api/admin/{resource}/purge
POST /api/users/{id}/promote

The scanner's 12 parallel security checks include authentication bypass attempts and authorization verification. For Buffalo apps using Pop ORM, middleBrick tests whether queries properly scope to the authenticated user's data.

middleBrick also analyzes OpenAPI specifications if provided, mapping defined security requirements against actual runtime behavior. This is particularly useful for Buffalo applications where the spec might declare "authenticated" endpoints that still have authorization gaps.

For development teams, the GitHub Action integration allows you to automatically scan your Buffalo API endpoints as part of your CI/CD pipeline. You can fail builds if broken access control risks are detected:

- name: Scan API Security
  uses: middleBrick/middlebrick-action@v1
  with:
    url: http://localhost:3000
    fail-on-severity: high

Buffalo provides several native mechanisms for implementing proper access control. The most straightforward approach uses middleware to enforce authorization at the handler level:

func AuthorizeUser(next buffalo.Handler) buffalo.Handler {
  return func(c buffalo.Context) error {
    // Get authenticated user
    user := c.Value("current_user").(*models.User)
    
    // Get resource ID from URL
    resourceID := c.Param("id")
    
    // Verify ownership
    ownsResource, err := user.OwnsResource(resourceID)
    if err != nil || !ownsResource {
      return c.Error(403, errors.New("access denied"))
    }
    
    return next(c)
  }
}

func (u UserProfileResource) Show(c buffalo.Context) error {
  return AuthorizeUser(func(c buffalo.Context) error {
    profile := &models.UserProfile{}
    err := models.DB.Find(profile, c.Param("id"))
    return c.Render(200, r.JSON(profile))
  })(c)
}

For role-based access control, Buffalo's authentication system integrates well with authorization checks:

func RequireRole(role string) buffalo.MiddlewareFunc {
  return func(next buffalo.Handler) buffalo.Handler {
    return func(c buffalo.Context) error {
      user := c.Value("current_user").(*models.User)
      
      if !user.HasRole(role) {
        return c.Error(403, errors.New("insufficient privileges"))
      }
      
      return next(c)
    }
  }
}

func AdminDashboard(c buffalo.Context) error {
  return c.Render(200, r.HTML("admin/dashboard.plush.html"))
}

// In routes setup:
admin := app.Group("/admin")
admin.Use(RequireRole("admin"))
admin.GET("/dashboard", AdminDashboard)

Property-level authorization in Buffalo can be implemented using struct tags and custom marshaling:

type UserProfile struct {
  ID        uuid.UUID `json:"id" db:"id"`
  UserID    uuid.UUID `json:"user_id" db:"user_id"`
  Email     string    `json:"email" db:"email"`
  SSN       string    `json:"-" db:"ssn" validate:"-"`
  Salary    int       `json:"-" db:"salary" validate:"-"`
  CreatedAt time.Time `json:"created_at" db:"created_at"`
}

func (u UserProfileResource) Show(c buffalo.Context) error {
  profile := &models.UserProfile{}
  err := models.DB.Find(profile, c.Param("id"))
  
  // Create sanitized response
  response := struct {
    ID         uuid.UUID `json:"id"`
    Email      string    `json:"email"`
    CreatedAt  time.Time `json:"created_at"`
  }{
    ID:        profile.ID,
    Email:     profile.Email,
    CreatedAt: profile.CreatedAt,
  }
  
  return c.Render(200, r.JSON(response))
}

For data scoping in Pop queries, use WHERE clauses to ensure users only access their own data:

func (u OrderResource) List(c buffalo.Context) error {
  user := c.Value("current_user").(*models.User)
  
  orders := &models.Orders{}
  err := models.DB.Where("user_id = ?", user.ID).All(orders)
  return c.Render(200, r.JSON(orders))
}

Buffalo's transaction support also helps with authorization by ensuring atomicity between authorization checks and data access:

func (u OrderResource) Update(c buffalo.Context) error {
  tx, ok := models.DB.Transaction(c)
  if !ok {
    return errors.New("no transaction found")
  }
  
  user := c.Value("current_user").(*models.User)
  orderID := c.Param("id")
  
  // Check authorization and get order in one transaction
  order := &models.Order{}
  err := tx.Where("id = ? AND user_id = ?", orderID, user.ID).First(order)
  if err != nil {
    return c.Error(404, err)
  }
  
  err = c.Bind(order)
  return tx.Update(order)
}