Broken Authentication in Fiber

Broken Authentication in Fiber applications typically emerges through several critical patterns that developers should recognize. The most common manifestation occurs when session management is improperly configured or when JWT tokens are mishandled. In Fiber, this often happens when developers use the default session middleware without understanding its security implications.

A classic vulnerability appears when session cookies lack the Secure and HttpOnly flags. Consider this insecure pattern:

app := fiber.New()

Without explicit configuration, session cookies default to insecure settings that expose applications to session hijacking. Attackers can intercept these cookies over unencrypted connections or exploit cross-site scripting (XSS) vulnerabilities to steal them.

Another Fiber-specific issue arises with JWT token handling. Many developers store JWTs in localStorage or expose them to client-side JavaScript, creating opportunities for XSS attacks. The improper use of fiber.Context().JSON() to return tokens without proper validation can lead to authentication bypass.

Role-based access control (RBAC) implementation flaws are particularly dangerous in Fiber applications. Developers often create middleware like this:

func RequireRole(role string) fiber.Handler {
    return func(c *fiber.Ctx) error {
        userRole := c.Locals("role").(string)
        if userRole != role {
            return c.Status(403).SendString("Forbidden")
        }
        return c.Next()
    }
}

While this looks correct, it fails to validate that the user is authenticated at all. An attacker can bypass this by simply not being logged in, as the middleware doesn't check for authentication status before checking roles.

Time-based authentication bypasses are another Fiber-specific vulnerability. When using middleware that checks authentication, developers sometimes forget to call c.Next() in all code paths:

func AuthMiddleware(c *fiber.Ctx) error {
    token := c.Get("Authorization")
    if token == "" {
        return c.Status(401).SendString("Unauthorized")
    }
    // Missing c.Next() call in some branches
    return c.Next()
}

This creates situations where unauthenticated requests might proceed to protected endpoints.

Credential management issues in Fiber often involve hardcoded secrets or weak password policies. Developers might store API keys directly in configuration files or use predictable password reset tokens. The lack of rate limiting on authentication endpoints makes Fiber applications vulnerable to credential stuffing attacks.

Detecting Broken Authentication in Fiber applications requires a multi-layered approach. Manual code review should focus on authentication middleware implementation, session configuration, and JWT handling patterns.

Start by examining session middleware configuration:

store := memory.New()

Check if the session store uses secure defaults and whether session cookies have appropriate security flags. Look for missing Secure, HttpOnly, and SameSite attributes.

For JWT implementations, audit token generation and validation:

token := jwt.New(jwt.SigningMethodHS256)
claims := token.Claims.(jwt.MapClaims)
claims["sub"] = userID
claims["exp"] = time.Now().Add(time.Hour * 72).Unix()
tokenString, _ := token.SignedString(secretKey)

Verify that tokens use strong signing algorithms, have appropriate expiration times, and are transmitted securely. Check for hardcoded secrets and ensure proper key rotation policies.

Automated scanning with middleBrick provides comprehensive detection of authentication vulnerabilities. The scanner identifies common Fiber-specific issues including:

• Insecure session cookie configurations
• Missing authentication checks in middleware chains
• Weak JWT implementations
• Exposed authentication endpoints without rate limiting
• Predictable token generation patterns

middleBrick's black-box scanning approach tests the actual runtime behavior of your Fiber application, identifying vulnerabilities that static analysis might miss. The scanner attempts to bypass authentication mechanisms, test session fixation vulnerabilities, and probe for broken access control patterns.

Integration with middleBrick's GitHub Action allows continuous monitoring of authentication security. The action can be configured to scan your Fiber API endpoints as part of your CI/CD pipeline:

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

This ensures that authentication vulnerabilities are caught before deployment to production.

Remediating Broken Authentication in Fiber applications requires implementing security best practices specific to Go and the Fiber framework. Start with proper session configuration:

store := memory.New()
app.Use(sessions.New(sessions.Config{
    Store: store,
    Secret: "strong-random-secret",
    Cookie: sessions.CookieConfig{
        Secure: true,
        HttpOnly: true,
        SameSite: "Lax",
    },
}))

This configuration ensures session cookies are only transmitted over HTTPS, cannot be accessed by client-side JavaScript, and have appropriate same-site restrictions.

For JWT implementation, use a robust approach with proper validation:

func GenerateJWT(userID string) (string, error) {
    token := jwt.NewWithClaims(jwt.SigningMethodHS256, jwt.MapClaims{
        "sub": userID,
        "exp": time.Now().Add(24 * time.Hour).Unix(),
    })
    return token.SignedString(jwtKey)
}

func ValidateJWT(c *fiber.Ctx) error {
    authHeader := c.Get("Authorization")
    if authHeader == "" {
        return c.Status(401).SendString("Missing token")
    }
    
    tokenString := strings.TrimPrefix(authHeader, "Bearer ")
    token, err := jwt.ParseWithClaims(tokenString, jwt.MapClaims{}, func(token *jwt.Token) (interface{}, error) {
        return jwtKey, nil
    })
    
    if err != nil || !token.Valid {
        return c.Status(401).SendString("Invalid token")
    }
    
    claims, ok := token.Claims.(jwt.MapClaims)
    if !ok || !token.Valid {
        return c.Status(401).SendString("Invalid claims")
    }
    
    c.Locals("user_id", claims["sub"])
    return c.Next()
}

This implementation includes proper error handling, claim validation, and user context setting for downstream middleware.

Implement comprehensive authentication middleware that checks both authentication and authorization:

func RequireAuthAndRole(requiredRole string) fiber.Handler {
    return func(c *fiber.Ctx) error {
        // Check authentication first
        authHeader := c.Get("Authorization")
        if authHeader == "" {
            return c.Status(401).SendString("Unauthorized")
        }
        
        // Validate token
        tokenString := strings.TrimPrefix(authHeader, "Bearer ")
        token, err := jwt.ParseWithClaims(tokenString, jwt.MapClaims{}, func(token *jwt.Token) (interface{}, error) {
            return jwtKey, nil
        })
        
        if err != nil || !token.Valid {
            return c.Status(401).SendString("Invalid token")
        }
        
        // Check role
        claims, _ := token.Claims.(jwt.MapClaims)
        userRole := claims["role"].(string)
        if userRole != requiredRole {
            return c.Status(403).SendString("Forbidden")
        }
        
        return c.Next()
    }
}

This middleware ensures users are both authenticated and authorized before accessing protected resources.

Add rate limiting to authentication endpoints to prevent brute force attacks:

app.Use(rateLimit.New(rateLimit.Config{
    Filter: func(c *fiber.Ctx) bool {
        return c.Path() == "/login" || c.Path() == "/auth"
    },
    TimeWindow: 1 * time.Minute,
    MaxRequests: 5,
}))

This configuration limits authentication attempts to 5 requests per minute per IP address, significantly reducing the risk of credential stuffing attacks.

Implement proper password policies and secure credential storage. Use bcrypt for password hashing and enforce minimum complexity requirements:

func HashPassword(password string) (string, error) {
    bytes, err := bcrypt.GenerateFromPassword([]byte(password), 14)
    return string(bytes), err
}

func CheckPasswordHash(password, hash string) bool {
    err := bcrypt.CompareHashAndPassword([]byte(hash), []byte(password))
    return err == nil
}

These functions ensure passwords are stored securely and verified correctly during authentication.