feat(middleware/csrf): TrustedOrigins using https://*.example.com style subdomains

docs/api/middleware/csrf.md

@@ -116,7 +116,7 @@ func (h *Handler) DeleteToken(c fiber.Ctx) error
 | Storage           | `fiber.Storage`                    | Store is used to store the state of the middleware.                                                                                                                                                                                                                                          | `nil`                        |
 | Session           | `*session.Store`                   | Session is used to store the state of the middleware. Overrides Storage if set.                                                                                                                                                                                                              | `nil`                        |
 | SessionKey        | `string`                           | SessionKey is the key used to store the token in the session.                                                                                                                                                                                                                                | "csrfToken"                  |
-| TrustedOrigins    | `[]string`                         | TrustedOrigins is a list of trusted origins for unsafe requests. This supports subdomain matching, so you can use a value like "https://.example.com" to allow any subdomain of example.com to submit requests.                                                                              | `[]`                         |
+| TrustedOrigins    | `[]string`                         | TrustedOrigins is a list of trusted origins for unsafe requests. This supports subdomain matching, so you can use a value like "https://*.example.com" to allow any subdomain of example.com to submit requests.                                                                             | `[]`                         |
 
 ### Default Config
 
@@ -154,6 +154,36 @@ var ConfigDefault = Config{
 }
 ```
 
+### Trusted Origins
+
+The `TrustedOrigins` option is used to specify a list of trusted origins for unsafe requests. This is useful when you want to allow requests from other origins. This supports matching subdomains at any level. This means you can use a value like `"https://*.example.com"` to allow any subdomain of `example.com` to submit requests, including multiple subdomain levels such as `"https://sub.sub.example.com"`.
+
+To ensure that the provided `TrustedOrigins` origins are correctly formatted, this middleware validates and normalizes them. It checks for valid schemes, i.e., HTTP or HTTPS, and it will automatically remove trailing slashes. If the provided origin is invalid, the middleware will panic.
+
+#### Example with Explicit Origins
+
+In the following example, the CSRF middleware will allow requests from `trusted.example.com`, in addition to the current host.
+
+```go
+app.Use(csrf.New(csrf.Config{
+	TrustedOrigins: []string{"https://trusted.example.com"},
+}))
+```
+
+#### Example with Subdomain Matching
+
+In the following example, the CSRF middleware will allow requests from any subdomain of `example.com`, in addition to the current host.
+
+```go
+app.Use(csrf.New(csrf.Config{
+	TrustedOrigins: []string{"https://*.example.com"},
+}))
+```
+
+::caution
+When using `TrustedOrigins` with subdomain matching, make sure you control and trust all the subdomains, including all subdomain levels. If not, an attacker could create a subdomain under a trusted origin and use it to send harmful requests.
+:::
+
 ## Constants
 
 ```go
@@ -273,7 +303,6 @@ When HTTPS requests are protected by CSRF, referer checking is always carried ou
 The Referer header is automatically included in requests by all modern browsers, including those made using the JS Fetch API. However, if you're making use of this middleware with a custom client, it's important to ensure that the client sends a valid Referer header.
 :::
 
-
 ### Token Lifecycle
 
 Tokens are valid until they expire or until they are deleted. By default, tokens are valid for 1 hour, and each subsequent request extends the expiration by 1 hour. The token only expires if the user doesn't make a request for the duration of the expiration time.

middleware/csrf/csrf.go

@@ -24,7 +24,7 @@
 
 // Handler for CSRF middleware
 type Handler struct {
-	config         *Config
+	config         Config
 	sessionManager *sessionManager
 	storageManager *storageManager
 }
@@ -56,6 +56,36 @@
 		storageManager = newStorageManager(cfg.Storage)
 	}
 
+	// Pre-parse trusted origins
+	trustedOrigins := []string{}
+	trustedSubOrigins := []subdomain{}
+
+	for _, origin := range cfg.TrustedOrigins {
+		if i := strings.Index(origin, "://*."); i != -1 {
+			trimmedOrigin := strings.TrimSpace(origin[:i+3] + origin[i+4:])
+			isValid, normalizedOrigin := normalizeOrigin(trimmedOrigin)
+			if !isValid {
+				panic("[CSRF] Invalid origin format in configuration:" + origin)
+			}
+			sd := subdomain{prefix: normalizedOrigin[:i+3], suffix: normalizedOrigin[i+3:]}
+			trustedSubOrigins = append(trustedSubOrigins, sd)
+		} else {
+			trimmedOrigin := strings.TrimSpace(origin)
+			isValid, normalizedOrigin := normalizeOrigin(trimmedOrigin)
+			if !isValid {
+				panic("[CSRF] Invalid origin format in configuration:" + origin)
+			}
+			trustedOrigins = append(trustedOrigins, normalizedOrigin)
+		}
+	}
+
+	// Create the handler outside of the returned function
+	handler := &Handler{
+		config:         cfg,
+		sessionManager: sessionManager,
+		storageManager: storageManager,
+	}
+
 	// Return new handler
 	return func(c fiber.Ctx) error {
 		// Don't execute middleware if Next returns true
@@ -64,11 +94,7 @@
 		}
 
 		// Store the CSRF handler in the context
-		c.Locals(handlerKey, &Handler{
-			config:         &cfg,
-			sessionManager: sessionManager,
-			storageManager: storageManager,
-		})
+		c.Locals(handlerKey, handler)
 
 		var token string
 
@@ -88,12 +114,12 @@
 			// Assume that anything not defined as 'safe' by RFC7231 needs protection
 
 			// Enforce an origin check for unsafe requests.
-			err := originMatchesHost(c, cfg.TrustedOrigins)
+			err := originMatchesHost(c, trustedOrigins, trustedSubOrigins)
 
 			// If there's no origin, enforce a referer check for HTTPS connections.
 			if errors.Is(err, errOriginNotFound) {
 				if c.Scheme() == "https" {
-					err = refererMatchesHost(c, cfg.TrustedOrigins)
+					err = refererMatchesHost(c, trustedOrigins, trustedSubOrigins)
 				} else {
 					// If it's not HTTPS, clear the error to allow the request to proceed.
 					err = nil
@@ -237,20 +263,15 @@
 // DeleteToken removes the token found in the context from the storage
 // and expires the CSRF cookie
 func (handler *Handler) DeleteToken(c fiber.Ctx) error {
-	// Get the config from the context
-	config := handler.config
-	if config == nil {
-		panic("CSRF Handler config not found in context")
-	}
 	// Extract token from the client request cookie
-	cookieToken := c.Cookies(config.CookieName)
+	cookieToken := c.Cookies(handler.config.CookieName)
 	if cookieToken == "" {
-		return config.ErrorHandler(c, ErrTokenNotFound)
+		return handler.config.ErrorHandler(c, ErrTokenNotFound)
 	}
 	// Remove the token from storage
-	deleteTokenFromStorage(c, cookieToken, *config, handler.sessionManager, handler.storageManager)
+	deleteTokenFromStorage(c, cookieToken, handler.config, handler.sessionManager, handler.storageManager)
 	// Expire the cookie
-	expireCSRFCookie(c, *config)
+	expireCSRFCookie(c, handler.config)
 	return nil
 }
 
@@ -262,8 +283,8 @@
 // originMatchesHost checks that the origin header matches the host header
 // returns an error if the origin header is not present or is invalid
 // returns nil if the origin header is valid
-func originMatchesHost(c fiber.Ctx, trustedOrigins []string) error {
-	origin := c.Get(fiber.HeaderOrigin)
+func originMatchesHost(c fiber.Ctx, trustedOrigins []string, trustedSubOrigins []subdomain) error {
+	origin := strings.ToLower(c.Get(fiber.HeaderOrigin))
 	if origin == "" || origin == "null" { // "null" is set by some browsers when the origin is a secure context https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Origin#description
 		return errOriginNotFound
 	}
@@ -273,23 +294,31 @@
 		return ErrOriginInvalid
 	}
 
-	if originURL.Host != c.Host() {
-		for _, trustedOrigin := range trustedOrigins {
-			if isTrustedSchemeAndDomain(trustedOrigin, origin) {
-				return nil
-			}
+	if originURL.Scheme == c.Scheme() && originURL.Host == c.Host() {
+		return nil
+	}
+
+	for _, trustedOrigin := range trustedOrigins {
+		if origin == trustedOrigin {
+			return nil
 		}
-		return ErrOriginNoMatch
 	}
 
-	return nil
+	for _, trustedSubOrigin := range trustedSubOrigins {
+		if trustedSubOrigin.match(origin) {
+			return nil
+		}
+	}
+
+	return ErrOriginNoMatch
 }
 
 // refererMatchesHost checks that the referer header matches the host header
 // returns an error if the referer header is not present or is invalid
 // returns nil if the referer header is valid
-func refererMatchesHost(c fiber.Ctx, trustedOrigins []string) error {
-	referer := c.Get(fiber.HeaderReferer)
+func refererMatchesHost(c fiber.Ctx, trustedOrigins []string, trustedSubOrigins []subdomain) error {
+	referer := strings.ToLower(c.Get(fiber.HeaderReferer))
+
 	if referer == "" {
 		return ErrRefererNotFound
 	}
@@ -299,41 +328,23 @@
 		return ErrRefererInvalid
 	}
 
-	if refererURL.Host != c.Host() {
-		for _, trustedOrigin := range trustedOrigins {
-			if isTrustedSchemeAndDomain(trustedOrigin, referer) {
-				return nil
-			}
-		}
-		return ErrRefererNoMatch
-	}
-
-	return nil
-}
-
-// isTrustedSchemeAndDomain checks if the trustedProtoDomain is the same as the protoDomain
-// or if the protoDomain is a subdomain of the trustedProtoDomain where trustedProtoDomain
-// is prefixed with "https://." or "http://."
-func isTrustedSchemeAndDomain(trustedProtoDomain, protoDomain string) bool {
-	if trustedProtoDomain == protoDomain {
-		return true
+	if refererURL.Scheme == c.Scheme() && refererURL.Host == c.Host() {
+		return nil
 	}
 
-	// Use constant prefixes for better readability and avoid magic numbers.
-	const httpsPrefix = "https://."
-	const httpPrefix = "http://."
+	referer = refererURL.String()
 
-	if strings.HasPrefix(trustedProtoDomain, httpsPrefix) {
-		trustedProtoDomain = trustedProtoDomain[len(httpsPrefix):]
-		protoDomain = strings.TrimPrefix(protoDomain, "https://")
-		return strings.HasSuffix(protoDomain, "."+trustedProtoDomain)
+	for _, trustedOrigin := range trustedOrigins {
+		if referer == trustedOrigin {
+			return nil
+		}
 	}
 
-	if strings.HasPrefix(trustedProtoDomain, httpPrefix) {
-		trustedProtoDomain = trustedProtoDomain[len(httpPrefix):]
-		protoDomain = strings.TrimPrefix(protoDomain, "http://")
-		return strings.HasSuffix(protoDomain, "."+trustedProtoDomain)
+	for _, trustedSubOrigin := range trustedSubOrigins {
+		if trustedSubOrigin.match(referer) {
+			return nil
+		}
 	}
 
-	return false
+	return ErrRefererNoMatch
 }