Broken Access Control in Chi

Broken Access Control in Chi applications typically emerges through improper handling of user permissions and resource ownership verification. The most common manifestation occurs when developers rely solely on client-side state or URL parameters to determine resource access, rather than validating the authenticated user's actual permissions against the requested resource.

A critical vulnerability pattern in Chi applications involves route handlers that accept resource identifiers without verifying ownership. For example, an endpoint like /api/users/:userId/orders/:orderId might retrieve an order without confirming whether the authenticated user actually owns that order or has permission to view it. This creates a classic Insecure Direct Object Reference (IDOR) scenario where attackers can enumerate IDs to access other users' data.

Another Chi-specific manifestation occurs in middleware chains where authorization checks are applied inconsistently. Developers might secure certain routes with authentication middleware but forget to add authorization checks that verify resource ownership. This is particularly problematic in applications with complex role hierarchies or multi-tenant architectures where users should only access their own organizational data.

Session fixation attacks also represent a broken access control vector in Chi applications. If session management isn't properly implemented, attackers can force a user's session ID, gaining unauthorized access to authenticated resources. This is especially dangerous in applications that don't implement proper session invalidation on privilege changes or logout.

Chi's middleware-based architecture, while powerful, can inadvertently create access control gaps when developers chain middleware without understanding the complete request lifecycle. For instance, a middleware that sets user context might be bypassed if not properly ordered, allowing subsequent handlers to operate without proper user context.

Detecting broken access control in Chi applications requires both manual code review and automated scanning. When using middleBrick's API security scanner, the tool specifically tests for authorization bypasses by attempting to access resources with different user contexts and analyzing the application's responses.

middleBrick's black-box scanning approach is particularly effective for Chi applications because it doesn't require access to source code. The scanner sends authenticated requests with varying user permissions to test whether resource boundaries are properly enforced. For example, it will attempt to access another user's order history by manipulating URL parameters while maintaining different authentication contexts.

The scanner's BOLA (Broken Object Level Authorization) checks specifically target Chi's route parameter handling. It tests endpoints like /api/users/:id/profile by substituting different user IDs to see if the application returns data for users other than the authenticated one. This directly addresses one of the most common broken access control patterns in Chi applications.

middleBrick also analyzes OpenAPI specifications alongside runtime behavior, which is crucial for Chi applications since many use code-first development with auto-generated specs. The tool cross-references the documented security requirements with actual endpoint behavior, identifying discrepancies where endpoints appear secured in documentation but lack proper authorization checks in implementation.

For LLM/AI security, middleBrick's unique capability includes testing for excessive agency patterns in Chi applications that integrate AI features. This involves checking whether AI endpoints properly restrict access to sensitive operations based on user permissions, preventing privilege escalation through AI tool calls.

Developers should also implement logging and monitoring to detect suspicious access patterns, such as users accessing resources outside their normal behavior patterns or rapid enumeration attempts on resource IDs.

Remediating broken access control in Chi applications requires implementing proper authorization checks at the resource level, not just authentication. The most effective approach is to create a middleware that verifies resource ownership before processing requests that access user-specific data.

// Chi-specific authorization middleware
func authorizeUserResource(next http.Handler, getResourceOwner func(context.Context, string) (int, error)) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        userID, err := getUserIDFromContext(r.Context())
        if err != nil {
            http.Error(w, "Unauthorized", http.StatusUnauthorized)
            return
        }

        resourceID := chi.URLParam(r, "resourceId")
        ownerID, err := getResourceOwner(r.Context(), resourceID)
        if err != nil || ownerID != userID {
            http.Error(w, "Forbidden", http.StatusForbidden)
            return
        }
        
        next.ServeHTTP(w, r)
    })
}

// Usage in route
router.Get("/users/{userId}/orders/{orderId}", 
    authorizeUserResource(getOrderOwner, getOrderByID),
    getOrderHandler)

This middleware pattern ensures that every request to access user-specific resources validates ownership before proceeding. The getResourceOwner function should query the database to verify the authenticated user actually owns the requested resource.

For applications with role-based access control, implement a more sophisticated authorization middleware that checks both ownership and role permissions:

func authorizeWithRoles(next http.Handler, rbac RBACService) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        user := getUserFromContext(r.Context())
        resource := getResourceFromRequest(r)
        action := getActionFromRequest(r)
        
        if !rbac.CanAccess(user.Role, resource, action) {
            http.Error(w, "Forbidden", http.StatusForbidden)
            return
        }
        
        next.ServeHTTP(w, r)
    })
}

Chi's context-based request handling makes it ideal for passing user and authorization information through middleware chains. Always extract user context early in the middleware chain and make it available to all subsequent handlers.

Implement proper session management by using secure, http-only cookies and implementing session rotation on privilege changes. Chi integrates well with Go's standard net/http session libraries, allowing you to implement secure session handling without introducing vulnerabilities.

For multi-tenant applications, add tenant verification middleware that ensures users can only access resources within their assigned tenant, preventing cross-tenant data access.