Jwt Misconfiguration in Chi

Jwt misconfiguration in Chi manifests through several specific attack vectors that stem from the framework's middleware-based architecture. The most common issue occurs when developers use Chi's middleware function without proper token validation, allowing attackers to bypass authentication entirely.

A typical vulnerable pattern looks like this:

r := chi.NewRouter()
r.Use(middleware.Logger)
r.Use(middleware.Recoverer)
r.Use(middleware.GetHead)

// Vulnerable: no actual JWT validation
r.Use(middleware.JWT("secret")) // hardcoded secret!
r.Group(func(r chi.Router) {
    r.Use(RequireAuth) // but this middleware doesn't validate
    r.Get("/api/users", getUsers)
})

The middleware.JWT function from the go-chi/jwtauth package requires careful configuration. Common misconfigurations include:

• Hardcoded secrets in source code instead of environment variables
• Using HS256 with weak secrets that can be brute-forced
• Missing token expiration validation
• Accepting tokens from any issuer without verification
• Ignoring token audience claims

Chi's middleware chain execution makes certain attacks particularly effective. Since middleware executes in order, placing JWT middleware after authorization checks creates a window where unauthenticated requests can access protected resources:

r := chi.NewRouter()
r.Use(RequireAuth) // executes first, but doesn't validate JWT
r.Use(middleware.JWT("secret")) // executes second, but too late

Another Chi-specific vulnerability arises from improper context handling. The middleware.JWT middleware stores tokens in the request context, but if subsequent handlers don't properly extract and validate the token, the authentication state becomes meaningless:

func RequireAuth(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        // BUG: never checks if token is actually valid
        next.ServeHTTP(w, r)
    })
}

Attackers can exploit these misconfigurations through token manipulation, including changing the kid header to reference non-existent keys, modifying expiration claims, or crafting tokens with altered scope claims that grant excessive permissions.

Detecting JWT misconfigurations in Chi applications requires both static analysis and runtime scanning. middleBrick's black-box scanning approach is particularly effective because it tests the actual authentication surface without requiring source code access.

middleBrick scans Chi APIs for JWT issues by:

• Testing for unauthenticated access to endpoints that should require authentication
• Analyzing HTTP response patterns to detect missing authentication headers
• Checking for predictable error messages that reveal implementation details
• Testing token replay attacks with expired or malformed tokens

For Chi applications, middleBrick specifically looks for these Chi-specific patterns:

CHI-JWT-001: Missing JWT middleware on protected routes
CHI-JWT-002: Hardcoded secrets in middleware configuration
CHI-JWT-003: Improper middleware ordering allowing authentication bypass
CHI-JWT-004: Context token extraction without validation
CHI-JWT-005: Missing token expiration enforcement

Developers can also perform manual detection using Chi's middleware chain inspection. The following diagnostic middleware helps identify JWT configuration issues:

func DebugJWT(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        ctx := r.Context()
        
        // Check if JWT middleware ran
        if token, _, err := jwtauth.FromContext(ctx); err != nil {
            log.Printf("No JWT token found in context: %v", err)
        } else if token == nil {
            log.Println("JWT middleware present but no token extracted")
        }
        
        // Check middleware chain
        chiCtx := chi.RouteContext(ctx)
        if chiCtx != nil {
            middlewareNames := chiCtx.Middlewares()
            hasJWT := false
            for _, mw := range middlewareNames {
                if strings.Contains(mw, "jwt") {
                    hasJWT = true
                    break
                }
            }
            if !hasJWT {
                log.Println("Warning: Protected route missing JWT middleware")
            }
        }
        
        next.ServeHTTP(w, r)
    })
}

middleBrick's CLI tool provides quick scanning capabilities for Chi applications:

middlebrick scan https://api.example.com --target chi --output json

The scanner will identify Chi-specific JWT issues and provide remediation guidance tailored to the framework's middleware architecture.

Remediating JWT misconfigurations in Chi requires leveraging the framework's native middleware patterns and proper token handling. The correct approach uses Chi's go-chi/jwtauth package with proper secret management and validation.

First, implement proper secret management using environment variables:

type Config struct {
    JWTSecret string
    JWTAlgo   string
    JWTIssuer string
}

func LoadConfig() Config {
    return Config{
        JWTSecret: os.Getenv("JWT_SECRET"),
        JWTAlgo:   "HS256",
        JWTIssuer: "your-app",
    }
}

func NewJWTMiddleware(cfg Config) func(http.Handler) http.Handler {
    key := []byte(cfg.JWTSecret)
    return middleware.JWTWithConfig(middleware.JWTConfig{
        ValidationKeyGetter: func(token *jwt.Token) (interface{}, error) {
            return key, nil
        },
        SigningMethod: jwt.GetSigningMethod(cfg.JWTAlgo),
        Issuer:        cfg.JWTIssuer,
        ExpirationTime: 15 * time.Minute, // short expiration for security
    })
}

Apply middleware in the correct order with proper validation:

func main() {
    cfg := LoadConfig()
    r := chi.NewRouter()
    
    // Order matters: JWT validation before authorization
    r.Use(middleware.Logger)
    r.Use(middleware.Recoverer)
    r.Use(NewJWTMiddleware(cfg))
    
    // Protected routes
    r.Group(func(r chi.Router) {
        r.Use(ValidateJWT) // ensure token is present and valid
        r.Get("/api/users", getUsers)
        r.Post("/api/orders", createOrder)
    })
    
    http.ListenAndServe(":3000", r)
}

func ValidateJWT(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        token, claims, err := jwtauth.FromContext(r.Context())
        if err != nil || token == nil || !token.Valid {
            http.Error(w, "Unauthorized", http.StatusUnauthorized)
            return
        }
        
        // Additional validation
        if claims.Subject == "" {
            http.Error(w, "Invalid token subject", http.StatusUnauthorized)
            return
        }
        
        next.ServeHTTP(w, r)
    })
}

For role-based access control in Chi, use context values to store user information:

func WithUser(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        token, claims, _ := jwtauth.FromContext(r.Context())
        
        // Extract user info from claims
        userID := claims.Subject
        role := claims["role"].(string)
        
        // Store in context for downstream handlers
        ctx := context.WithValue(r.Context(), "userID", userID)
        ctx = context.WithValue(ctx, "userRole", role)
        
        next.ServeHTTP(w, r.WithContext(ctx))
    })
}

func RequireRole(role string) func(http.Handler) http.Handler {
    return func(next http.Handler) http.Handler {
        return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
            userRole := r.Context().Value("userRole")
            if userRole != role {
                http.Error(w, "Forbidden", http.StatusForbidden)
                return
            }
            next.ServeHTTP(w, r)
        })
    }
}

Implement comprehensive error handling to avoid information leakage:

func ErrorHandler(next http.Handler) http.Handler {
    return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
        defer func() {
            if err := recover(); err != nil {
                log.Printf("Panic recovered: %v", err)
                http.Error(w, "Internal Server Error", http.StatusInternalServerError)
            }
        }()
        
        next.ServeHTTP(w, r)
    })
}