Phishing Api Keys in Chi

Phishing API keys in Chi applications typically exploit the framework's dynamic configuration system and environment variable handling. Attackers often target Chi's middleware chain, injecting malicious API keys through request headers or query parameters that override legitimate configuration values.

A common attack pattern involves exploiting Chi's URL parameter parsing. Consider this vulnerable endpoint:

router.Get("/api/:key/resource", func(w http.ResponseWriter, r *http.Request) {
    key := chi.URLParam(r, "key")
    // No validation of key format or source
    processRequest(w, r, key)
})

Attackers can craft URLs like /api/PHISHING_KEY/resource to bypass authentication checks. The malicious key appears legitimate to downstream services because Chi's parameter extraction doesn't distinguish between user input and configuration values.

Another manifestation occurs in Chi's middleware composition. Attackers exploit the order of middleware execution:

router.Use(middleware.Timeout(30 * time.Second))
router.Use(middleware.Logger)
router.Use(middleware.RealIP)
// No authentication middleware applied globally

Without proper authentication middleware applied before business logic, API keys passed in custom headers can reach sensitive endpoints. The RealIP middleware, for instance, can be manipulated to spoof client identities when combined with forged API keys.

Chi's context-based request handling also creates vulnerabilities. Attackers leverage context injection:

func handler(w http.ResponseWriter, r *http.Request) {
    ctx := r.Context()
    // Malicious key stored in context without validation
    ctx = context.WithValue(ctx, "api_key", r.Header.Get("X-API-Key"))
    processSensitiveOperation(ctx)
}

The context propagation mechanism allows phishing keys to flow through the entire request lifecycle, potentially reaching database connections or external API calls without proper validation.

Detecting phishing API keys in Chi applications requires examining both code patterns and runtime behavior. Start with static analysis of your middleware chain:

// Check for missing authentication middleware
for _, m := range router.Middlewares() {
    if !isAuthMiddleware(m) && isSensitiveEndpoint(m) {
        log.Println("Missing auth middleware on sensitive endpoint")
    }
}

// Validate API key extraction patterns
func validateKeyExtraction(r *http.Request) error {
    key := r.Header.Get("X-API-Key")
    if key == "" {
        return errors.New("missing API key")
    }
    if !isValidKeyFormat(key) {
        return errors.New("suspicious API key format")
    }
    return nil
}

Runtime detection should monitor for anomalous API key patterns. Implement request logging that flags unusual key characteristics:

func loggingMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        key := r.Header.Get("X-API-Key")
        if key != "" && !isKnownKeyPattern(key) {
            log.Printf("Suspicious API key detected: %s from %s", key, r.RemoteAddr)
        }
        next.ServeHTTP(w, r)
    })
}

For comprehensive detection, use middleBrick's CLI to scan your Chi application:

middlebrick scan http://localhost:3000 --api chi --checks authentication,bolia,idor

middleBrick specifically tests Chi's URL parameter handling and middleware composition, identifying endpoints vulnerable to phishing key injection. The scanner checks for unauthenticated endpoints that might accept API keys through various channels.

Automated testing should include fuzzing API key inputs:

func fuzzApiKeyEndpoint(t *testing.T) {
    testCases := []string{
        "phishing-key-123",
        "malicious-key-456",
        "attacker-controlled-789",
    }
    
    for _, key := range testCases {
        req := httptest.NewRequest("GET", "/api/resource", nil)
        req.Header.Set("X-API-Key", key)
        rr := httptest.NewRecorder()
        
        router.ServeHTTP(rr, req)
        
        if rr.Code == http.StatusOK {
            t.Errorf("Endpoint accepted phishing key: %s", key)
        }
    }
}

Remediating phishing API key vulnerabilities in Chi requires a defense-in-depth approach. Start with strict API key validation using Chi's context system:

func validateAPIKey(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        key := r.Header.Get("X-API-Key")
        if key == "" || !isValidKeyFormat(key) {
            http.Error(w, "Invalid API key", http.StatusUnauthorized)
            return
        }
        
        // Verify key against known patterns and databases
        if !isKnownValidKey(key) {
            http.Error(w, "Unauthorized", http.StatusUnauthorized)
            return
        }
        
        // Store validated key in context for downstream use
        ctx := context.WithValue(r.Context(), "validated_key", key)
        next.ServeHTTP(w, r.WithContext(ctx))
    })
}

// Apply globally to all routes
router.Use(validateAPIKey)

Implement API key rotation and versioning to prevent phishing attacks on stale keys:

type apiVersion struct {
    Version string
    Key     string
    Expires time.Time
}

var validKeys = map[string]apiVersion{
    "v1-valid-key-123": {Version: "v1", Key: "v1-valid-key-123", Expires: time.Now().Add(24 * time.Hour)},
    // ... other valid keys
}

func isKnownValidKey(key string) bool {
    if ver, exists := validKeys[key]; exists {
        return ver.Expires.After(time.Now())
    }
    return false
}

Use Chi's route groups to enforce authentication at the appropriate level:

apiGroup := router.Route("/api", func(r chi.Router) {
    r.Use(validateAPIKey)
    
    r.Get("/resource", func(w http.ResponseWriter, r *http.Request) {
        // Only reached if API key is validated
        w.Write([]byte("Authorized access"))
    })
    
    r.Post("/sensitive", func(w http.ResponseWriter, r *http.Request) {
        // Additional validation can be applied here
        if !hasRequiredScope(r.Context(), "sensitive:read") {
            http.Error(w, "Insufficient permissions", http.StatusForbidden)
            return
        }
        w.Write([]byte("Sensitive data accessed"))
    })
})

Implement rate limiting and anomaly detection at the API key level:

type keyUsage struct {
    Count   int
    LastUse time.Time
}

var keyTracker = sync.Map{}

func rateLimitMiddleware(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        key := r.Context().Value("validated_key").(string)
        
        usage, _ := keyTracker.LoadOrStore(key, &keyUsage{})
        usage.(*keyUsage).Count++
        usage.(*keyUsage).LastUse = time.Now()
        
        if usage.(*keyUsage).Count > 100 { // 100 requests per period
            http.Error(w, "Rate limit exceeded", http.StatusTooManyRequests)
            return
        }
        
        next.ServeHTTP(w, r)
    })
}

router.Use(rateLimitMiddleware)