fiber/docs/middleware/csrf.md

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csrf

CSRF

The CSRF middleware provides protection against Cross-Site Request Forgery attacks. It validates tokens on unsafe HTTP methods (POST, PUT, DELETE, etc.) and returns 403 Forbidden if an attack is detected.

Table of Contents

• Quick Start
• Best Practices & Production Requirements
• Configuration by Application Type
• Recipes for Common Use Cases
• Using CSRF Tokens
• Security Model
• Token Extractors
• Advanced Configuration
• API Reference
• Config Properties
• Error Types
• Constants

Quick Start

import (
    "github.com/gofiber/fiber/v3"
    "github.com/gofiber/fiber/v3/middleware/csrf"
)

// Default config (development only)
app.Use(csrf.New())

// Production config
app.Use(csrf.New(csrf.Config{
    CookieName:        "__Host-csrf_",
    CookieSecure:      true,
    CookieHTTPOnly:    true,  // false for SPAs
    CookieSameSite:    "Lax",
    CookieSessionOnly: true,
    Extractor:         csrf.FromHeader("X-Csrf-Token"),
    Session:           sessionStore,
}))

Best Practices & Production Requirements

:::danger Production Requirements

• CookieSecure: true (HTTPS only)
• CookieSameSite: "Lax" or "Strict"
• Use Session store for better security

:::

1. Always use HTTPS in production
2. Use sessions for authenticated applications
3. Set CookieSecure: true and appropriate SameSite values
4. Implement XSS protection alongside CSRF
5. Regenerate tokens after auth changes
6. Use __Host- cookie prefix when possible

:::warning BREACH Protection To mitigate BREACH attacks, ensure your pages are served over HTTPS, disable HTTP compression, and implement rate limiting for requests. The CSRF token is sent as a header on every request, so if you include the token in a page that is vulnerable to BREACH, an attacker may be able to extract the token. :::

Configuration by Application Type

Server-Side Rendered Apps

app.Use(csrf.New(csrf.Config{
    CookieName:        "__Host-csrf_",
    CookieSecure:      true,
    CookieHTTPOnly:    true,        // Secure - blocks JavaScript
    CookieSameSite:    "Lax",
    CookieSessionOnly: true,
    Extractor:         csrf.FromForm("_csrf"),
    Session:           sessionStore,
}))

Single Page Applications (SPAs)

app.Use(csrf.New(csrf.Config{
    CookieName:        "__Host-csrf_",
    CookieSecure:      true,
    CookieHTTPOnly:    false,       // Required for JavaScript access to tokens
    CookieSameSite:    "Lax",
    CookieSessionOnly: true,
    Extractor:         csrf.FromHeader("X-Csrf-Token"),
    Session:           sessionStore,
}))

:::warning SPA Security Trade-off SPAs require CookieHTTPOnly: false to access tokens via JavaScript. This slightly increases XSS risk but is necessary for SPA functionality. :::

Recipes for Common Use Cases

• Without Sessions: CSRF Recipe - Simple Double Submit Cookie pattern
• With Sessions: CSRF with Session Recipe - More secure Synchronizer Token pattern

Using CSRF Tokens

Server-Side Forms

func formHandler(c fiber.Ctx) error {
    token := csrf.TokenFromContext(c)
    
    return c.SendString(fmt.Sprintf(`
        <form method="POST" action="/submit">
            <input type="hidden" name="_csrf" value="%s">
            <input type="text" name="message" required>
            <button type="submit">Submit</button>
        </form>
    `, token))
}

Single Page Applications

func apiHandler(c fiber.Ctx) error {
    token := csrf.TokenFromContext(c)
    
    return c.JSON(fiber.Map{
        "csrf_token": token,
        "data":       "your data",
    })
}

// Get CSRF token from cookie
function getCsrfToken() {
    const value = `; ${document.cookie}`;
    const parts = value.split(`; __Host-csrf_=`);
    if (parts.length === 2) return parts.pop().split(';').shift();
}

// Use with fetch API
async function makeRequest(url, data) {
    const csrfToken = getCsrfToken();
    
    const response = await fetch(url, {
        method: 'POST',
        headers: {
            'Content-Type': 'application/json',
            'X-Csrf-Token': csrfToken
        },
        body: JSON.stringify(data)
    });
    
    if (!response.ok) {
        throw new Error(`HTTP ${response.status}: ${response.statusText}`);
    }
    
    return response.json();
}

Security Model

The middleware employs a robust, defense-in-depth strategy to protect against CSRF attacks. The primary defense is token-based validation, which operates in one of two modes depending on your configuration. This is supplemented by a mandatory secondary check on the request's origin.

1. Token Validation Patterns

Double Submit Cookie (Default Mode)

This is the default pattern, used when a Session store is not configured. It is a "semi-stateless" approach; while it doesn't tie tokens to a specific user session, the server still maintains a record of all validly issued tokens.

• How it Works:

  1. On a user's first visit (or a safe request like GET), the middleware generates a unique token.
  2. This token is sent to the client in a Set-Cookie header.
  3. A record of this token is also kept on the server (in-memory by default, or in your configured Storage). This proves the token was generated by the server and is not expired, but does not link it to a specific user.
  4. For any subsequent unsafe request (e.g., POST, PUT), the client application must read the token from the cookie and send it back in a different location, such as the X-CSRF-Token header.

• Validation: The middleware validates three things: that the token from the header/form exactly matches the token from the cookie, that the token exists in the server-side storage, and that it has not expired.

• Why it's Secure: An attacker on a malicious domain cannot read the victim's cookie to forge a matching header. Furthermore, they cannot invent a token, because it wouldn't exist in the server's storage registry.

Synchronizer Token (Session-Based Mode)

This is a more secure, stateful pattern that is automatically enabled when you provide a Session store in the configuration.

• How it Works:

  1. A unique token is generated and stored directly within the user's session data on the server.
  2. The token is also sent to the client as a cookie.
  3. For unsafe requests, the client sends the token back in a header or form field.

• Validation: The middleware performs a multi-step validation:

  1. It first performs the standard Double Submit Cookie check: the token from the header/form must exactly match the token from the cookie. This is a fast and efficient first line of defense, and there is little benefit of skipping it.
  2. It then validates that this token exists and is valid within the user's server-side session. This is the authoritative check that ties the token to the authenticated user.

• Why it's More Secure: Tying the token to the server-side session provides the strongest CSRF protection, as the token is then guaranteed to have been generated for the specific user. While browsers handle sending the required cookie automatically, it's important to note that custom API clients must also remember to send the cookie with their requests for validation to succeed.

// Enable the more secure Synchronizer Token pattern
app.Use(csrf.New(csrf.Config{
    Session: sessionStore, // Providing a session store activates this mode
}))

2. Origin & Referer Validation

As a crucial second layer of defense, the middleware always performs Origin and Referer header checks for unsafe requests (when the connection is HTTPS).

• The request's Origin (for cross-origin requests) or Referer (for same-origin requests) header must match the application's Host header or be explicitly allowed in the TrustedOrigins list.
• This check is performed in addition to token validation and provides strong protection because these headers are reliably set by browsers and cannot be programmatically controlled by an attacker from a malicious site.

Token Extractors

Built-in Extractors

Secure (Recommended):

• csrf.FromHeader("X-Csrf-Token") - Most secure, preferred for APIs
• csrf.FromForm("_csrf") - Secure for form submissions

Acceptable:

• csrf.FromQuery("csrf_token") - URL parameters
• csrf.FromParam("csrf") - Route parameters

Using Route-Specific Extractors

There are cases where you might want to use different extractors for different routes:

// API routes - header only
api := app.Group("/api")
api.Use(csrf.New(csrf.Config{
    Extractor: csrf.FromHeader("X-Csrf-Token"),
}))

// Form routes - form only  
forms := app.Group("/forms")
forms.Use(csrf.New(csrf.Config{
    Extractor: csrf.FromForm("_csrf"),
}))

Custom Extractor

You can create a custom extractor to handle specific cases:

:::danger Never Extract from Cookies NEVER create custom extractors that read from cookies using the same CookieName as your CSRF configuration. This completely defeats CSRF protection by making the extracted token always match the cookie value, allowing any CSRF attack to succeed.

// ❌ NEVER DO THIS - Completely defeats CSRF protection
func BadExtractor(c fiber.Ctx) (string, error) {
    return c.Cookies("csrf_"), nil  // Always passes validation!
}

// ✅ DO THIS - Extract from different source than cookie
app.Use(csrf.New(csrf.Config{
    CookieName: "csrf_",
    Extractor: csrf.FromHeader("X-Csrf-Token"), // Header vs cookie comparison
}))

The middleware uses the Double Submit Cookie pattern - it compares the extracted token against the cookie value. If your extractor reads from the same cookie, they will always match and provide zero CSRF protection. :::

Bearer Token Embedding

// Extract CSRF token embedded in JWT Authorization header
// Useful for APIs that combine JWT auth with CSRF protection
func BearerTokenExtractor(c fiber.Ctx) (string, error) {
    // Extract from "Authorization: Bearer <jwt>:<csrf>"
    auth := c.Get("Authorization")
    if !strings.HasPrefix(auth, "Bearer ") {
        return "", csrf.ErrTokenNotFound
    }
    
    parts := strings.SplitN(strings.TrimPrefix(auth, "Bearer "), ":", 2)
    if len(parts) != 2 || parts[1] == "" {
        return "", csrf.ErrTokenNotFound
    }
    
    return parts[1], nil
}

Chain Extractor (Advanced)

For edge cases requiring multiple token sources, use the Chain extractor:

// Only if you absolutely need multiple sources
app.Use(csrf.New(csrf.Config{
    Extractor: csrf.Chain(
        csrf.FromHeader("X-Csrf-Token"),   // Try header first
        csrf.FromForm("_csrf"),            // Fallback to form
    ),
}))

:::danger Security Risk Chaining extractors increases attack surface and complexity. Most applications should use a single, appropriate extractor for their use case. :::

Advanced Configuration

Trusted Origins

app.Use(csrf.New(csrf.Config{
    TrustedOrigins: []string{
        "https://trusted.example.com",
        "https://*.example.com", // Wildcard subdomains
    },
}))

Custom Error Handler

app.Use(csrf.New(csrf.Config{
    ErrorHandler: func(c fiber.Ctx, err error) error {
        accepts := c.Accepts("html", "json")
        path := c.Path()
        if accepts == "json" || strings.HasPrefix(path, "/api/") {
            return c.Status(fiber.StatusForbidden).JSON(fiber.Map{
                "error": "Forbidden",
            })
        }
        return c.Status(fiber.StatusForbidden).Render("error", fiber.Map{
            "Title": "Forbidden",
            "Status": fiber.StatusForbidden,
        }, "layouts/main")
    },
}))

Custom Storage/Database

You can use any storage from our storage package.

storage := sqlite3.New() // From github.com/gofiber/storage/sqlite3
app.Use(csrf.New(csrf.Config{
    Storage: storage,
}))

Token Management

// Delete token (e.g., on logout)
handler := csrf.HandlerFromContext(c)
if handler != nil {
    if err := handler.DeleteToken(c); err != nil {
        // handle error, e.g. log it
    }
}

// With session middleware
session.Destroy()  // Also deletes CSRF token

API Reference

// Create middleware
func New(config ...csrf.Config) fiber.Handler

// Get token from context
func TokenFromContext(c fiber.Ctx) string

// Get handler from context
func HandlerFromContext(c fiber.Ctx) *csrf.Handler

// Delete token
func (h *csrf.Handler) DeleteToken(c fiber.Ctx) error

Config Properties

Property	Type	Description	Default
Next	func(fiber.Ctx) bool	Skip middleware when returns true	nil
CookieName	string	CSRF cookie name	"csrf_"
CookieDomain	string	CSRF cookie domain	""
CookiePath	string	CSRF cookie path	""
CookieSecure	bool	HTTPS only cookie (required for production)	false
CookieHTTPOnly	bool	Prevent JavaScript access (use false for SPAs)	false
CookieSameSite	string	SameSite attribute (use "Lax" or "Strict")	"Lax"
CookieSessionOnly	bool	Session-only cookie (expires on browser close)	false
IdleTimeout	time.Duration	Token expiration time	30 * time.Minute
KeyGenerator	func() string	Token generation function	utils.UUIDv4
ErrorHandler	fiber.ErrorHandler	Custom error handler	defaultErrorHandler
Extractor	func(fiber.Ctx) (string, error)	Token extraction method	FromHeader("X-Csrf-Token")
Session	*session.Store	Session store (recommended for production)	nil
Storage	fiber.Storage	Token storage (overridden by Session)	nil
TrustedOrigins	[]string	Trusted origins for cross-origin requests	[]
SingleUseToken	bool	Generate new token after each use	false

Error Types

var (
    ErrTokenNotFound   = errors.New("csrf: token not found")
    ErrTokenInvalid    = errors.New("csrf: token invalid")
    ErrRefererNotFound = errors.New("csrf: referer header missing")
    ErrRefererInvalid  = errors.New("csrf: referer header invalid")
    ErrRefererNoMatch  = errors.New("csrf: referer does not match host or trusted origins")
    ErrOriginInvalid   = errors.New("csrf: origin header invalid")
    ErrOriginNoMatch   = errors.New("csrf: origin does not match host or trusted origins")
)

Constants

const (
    HeaderName = "X-Csrf-Token"
)