Broken Authentication in Chi

Broken authentication in Chi applications typically emerges through improper session management and flawed credential handling. The most common vulnerability occurs when developers rely on client-side session tokens without proper server-side validation. For example, Chi's default middleware stack doesn't include authentication by default, leaving developers to implement their own solutions.

A critical vulnerability pattern in Chi applications involves session fixation attacks. When developers store session identifiers in cookies without regenerating them after login, attackers can hijack user sessions. Here's a vulnerable pattern:

router := chi.NewRouter()
router.Use(middleware.Logger)
router.Use(middleware.Recoverer)

// Vulnerable: no session regeneration
router.Post("/login", func(w http.ResponseWriter, r *http.Request) {
    // Authenticate user
    if authenticateUser(r.FormValue("username"), r.FormValue("password")) {
        session := getSession(r)
        session.Values["user_id"] = userID
        session.Save(r, w)
        // Session ID remains unchanged - vulnerable to fixation
    }
})

Another Chi-specific manifestation involves improper middleware ordering. When authentication middleware isn't positioned correctly in the chain, unauthenticated requests can bypass security checks. Consider this flawed ordering:

router := chi.NewRouter()
router.Use(middleware.Logger) // Logging first
router.Use(middleware.Recoverer)
router.Post("/api/private", requireAuth, privateHandler) // Auth middleware applied per-route

The problem: if a developer forgets to add requireAuth to a new route, it becomes publicly accessible. A more robust approach uses a base router with authentication enforced globally, then creates subrouters for public endpoints.

Credential stuffing vulnerabilities also appear in Chi applications when rate limiting isn't properly implemented. Without per-IP or per-account rate limiting, automated tools can brute-force credentials. Chi's middleware ecosystem requires manual implementation of these protections:

router.Use(middleware.RateLimiter(10, time.Minute)) // Global rate limiting only

This global approach fails to protect against targeted attacks on specific user accounts, a common exploitation vector in Chi-based APIs.

Detecting broken authentication in Chi applications requires both static analysis and runtime scanning. Static analysis should focus on middleware configuration and session handling patterns. Look for these specific indicators:

• Missing or improperly configured authentication middleware in route chains
• Session tokens stored without HttpOnly or Secure flags
• Lack of session regeneration after privilege escalation
• Hardcoded credentials or API keys in configuration files
• Insecure default middleware configurations

Runtime detection with middleBrick specifically targets Chi's middleware architecture. The scanner identifies vulnerable patterns by analyzing HTTP responses and request flows. For Chi applications, middleBrick checks:

middlebrick scan https://api.example.com --output json
{
  "authentication": {
    "risk_score": 65,
    "findings": [
      {
        "severity": "high",
        "title": "Missing session regeneration",
        "description": "Chi application fails to regenerate session IDs after authentication",
        "remediation": "Implement session regeneration using gorilla/sessions with regenerateID()"
      }
    ]
  }
}

middleBrick's black-box scanning approach is particularly effective for Chi applications because it tests the actual HTTP surface without requiring source code access. The scanner sends crafted requests to identify authentication bypass opportunities, including testing for default credential acceptance and session fixation vulnerabilities.

For comprehensive Chi security assessment, combine middleBrick's automated scanning with manual testing of authentication flows. Pay special attention to:

• CSRF token validation in forms
• Password reset functionality (often vulnerable to account takeover)
• Remember-me cookie implementation
• API key rotation and expiration policies

Securing Chi applications against authentication vulnerabilities requires implementing defense-in-depth strategies. Start with proper middleware configuration and session management. Here's a secure Chi authentication pattern:

import (
    "github.com/go-chi/chi/v5/middleware"
    "github.com/gorilla/sessions"
    "net/http"
)

var store = sessions.NewCookieStore([]byte("strong-secret-key"))

func authMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        session, _ := store.Get(r, "auth-session")
        
        // Check for valid session
        if auth, ok := session.Values["authenticated"].(bool); !ok || !auth {
            http.Error(w, "Unauthorized", http.StatusUnauthorized)
            return
        }
        
        next.ServeHTTP(w, r)
    })
}

// Secure login handler with session regeneration
router.Post("/login", func(w http.ResponseWriter, r *http.Request) {
    // Authenticate credentials
    if username, password := r.FormValue("username"), r.FormValue("password"); authenticate(username, password) {
        session, _ := store.Get(r, "auth-session")
        
        // Regenerate session ID to prevent fixation
        session.Values["authenticated"] = true
        session.Values["user_id"] = userID
        session.Save(r, w)
        
        http.Redirect(w, r, "/dashboard", http.StatusSeeOther)
    } else {
        http.Error(w, "Invalid credentials", http.StatusUnauthorized)
    }
})

For API endpoints, implement token-based authentication with proper validation:

func tokenAuthMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        token := r.Header.Get("Authorization")
        if token == "" || !validateToken(token) {
            http.Error(w, "Missing or invalid token", http.StatusUnauthorized)
            return
        }
        next.ServeHTTP(w, r)
    })
}

// Apply to API group
apiRouter := chi.NewRouter()
apiRouter.Use(tokenAuthMiddleware)
apiRouter.Get("/users/{id}", getUserHandler)

Implement rate limiting at the Chi router level to prevent credential stuffing:

import "github.com/ulule/limiter/v7"

rateLimitMiddleware := middleware.RateLimiter(limiter.NewRateLimiter(limiter.NewRate(10, time.Minute)))
router.Use(rateLimitMiddleware)

// Per-IP rate limiting for login attempts
loginRouter := chi.NewRouter()
loginRouter.Use(func(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        limiter := limiter.NewIPRateLimiter(5, time.Minute) // 5 attempts per minute
        limitCtx, err := limiter.GetIPRateLimitContext(r.Context(), r)
        if err != nil {
            http.Error(w, "Too many attempts", http.StatusTooManyRequests)
            return
        }
        next.ServeHTTP(w, r.WithContext(limitCtx))
    })
})
loginRouter.Post("/login", loginHandler)

Finally, implement comprehensive logging and monitoring for authentication events. Track failed login attempts, session creations, and privilege changes to detect suspicious patterns early.