Shield WAF reference
Arcjet Shield WAF protects your application against common attacks, including the OWASP Top 10.
Configuration
Section titled “Configuration”Shield is configured by specifying which mode you want it to run in.
The arcjet client can be configured with one or more Shield rules, which are
constructed with the shield(options: ShieldOptions) function and configured by
ShieldOptions:
type ShieldOptions = { mode?: ArcjetMode | undefined;};type ArcjetMode = "LIVE" | "DRY_RUN";Per route versus hooks
Bot protection rules can be configured in two ways:
- Per route: The rule is defined in the route handler itself. This allows you to configure the rule alongside the code it is protecting which is useful if you want to use the decision to add context to your own code. However, it means rules are not located in a single place.
- Hooks: The rule is defined as a hook. This lets you configure rules in a single place or apply them globally to all routes, but it means the rules are not located alongside the code they are protecting.
Per route
This configures bot protection on a single route.
import { env } from "$env/dynamic/private";import arcjet, { shield } from "@arcjet/sveltekit";import { error, type RequestEvent } from "@sveltejs/kit";
const aj = arcjet({ key: env.ARCJET_KEY!, // Get your site key from https://console.arcjet.com rules: [ // Protect against common attacks with Arcjet Shield shield({ mode: "LIVE", // will block requests. Use "DRY_RUN" to log only }), ],});
export async function load(event: RequestEvent) { const decision = await aj.protect(event);
if (decision.isDenied()) { return error(403, "You are suspicious!"); }
return {};}import { env } from "$env/dynamic/private";import arcjet, { shield } from "@arcjet/sveltekit";import { error } from "@sveltejs/kit";
const aj = arcjet({ key: env.ARCJET_KEY, // Get your site key from https://console.arcjet.com rules: [ // Protect against common attacks with Arcjet Shield shield({ mode: "LIVE", // will block requests. Use "DRY_RUN" to log only }), ],});
export async function load(event) { const decision = await aj.protect(event);
if (decision.isDenied()) { return error(403, "You are suspicious!"); }
return {};}/>
Hooks
This runs on every request to your SvelteKit app – see the SvelteKit Hooks docs for details.
import { env } from "$env/dynamic/private";import arcjet, { shield } from "@arcjet/sveltekit";import { error } from "@sveltejs/kit";
const aj = arcjet({ key: env.ARCJET_KEY, // Get your site key from https://console.arcjet.com rules: [ // Protect against common attacks with Arcjet Shield shield({ mode: "LIVE", // will block requests. Use "DRY_RUN" to log only }), ],});
export async function handle({ event, resolve }) { const decision = await aj.protect(event);
if (decision.isDenied()) { return error(403, "Forbidden"); }
return resolve(event);}import { env } from "$env/dynamic/private";import arcjet, { shield } from "@arcjet/sveltekit";import { error, type RequestEvent } from "@sveltejs/kit";
const aj = arcjet({ key: env.ARCJET_KEY!, // Get your site key from https://console.arcjet.com rules: [ // Protect against common attacks with Arcjet Shield shield({ mode: "LIVE", // will block requests. Use "DRY_RUN" to log only }), ],});
export async function handle({ event, resolve,}: { event: RequestEvent; resolve: (event: RequestEvent) => Response | Promise<Response>;}): Promise<Response> { const decision = await aj.protect(event);
if (decision.isDenied()) { return error(403, "Forbidden"); }
return resolve(event);}Avoid double protection with hooks
If you use Arcjet in hooks and individual routes, you need to be careful that Arcjet is not running multiple times per request. This can be avoided by excluding the individual routes before running Arcjet in the hook.
For example, if you already have a shield rule defined in the API route
at /api/arcjet, you can exclude it from the hook like this:
import { env } from "$env/dynamic/private";import arcjet, { shield } from "@arcjet/sveltekit";import { error } from "@sveltejs/kit";
const aj = arcjet({ key: env.ARCJET_KEY, // Get your site key from https://console.arcjet.com rules: [ // Protect against common attacks with Arcjet Shield shield({ mode: "LIVE", // will block requests. Use "DRY_RUN" to log only }), ],});
export async function handle({ event, resolve }) { // Ignore routes that extend the Arcjet rules // - they will call `.protect` themselves const filteredRoutes = ["/api/arcjet"]; if (filteredRoutes.includes(event.url.pathname)) { // return - route will handle protecttion return resolve(event); }
// Ensure every other route is protected with shield const decision = await aj.protect(event);
if (decision.isDenied()) { return error(403, "Forbidden"); }
// Continue with the route return resolve(event);}import { env } from "$env/dynamic/private";import arcjet, { shield } from "@arcjet/sveltekit";import { error, type RequestEvent } from "@sveltejs/kit";
const aj = arcjet({ key: env.ARCJET_KEY!, // Get your site key from https://console.arcjet.com rules: [ // Protect against common attacks with Arcjet Shield shield({ mode: "LIVE", // will block requests. Use "DRY_RUN" to log only }), ],});
export async function handle({ event, resolve,}: { event: RequestEvent; resolve: (event: RequestEvent) => Response | Promise<Response>;}): Promise<Response> { // Ignore routes that extend the Arcjet rules // - they will call `.protect` themselves const filteredRoutes = ["/api/arcjet"]; if (filteredRoutes.includes(event.url.pathname)) { // return - route will handle protection return resolve(event); }
// Ensure every other route is protected with shield const decision = await aj.protect(event);
if (decision.isDenied()) { return error(403, "Forbidden"); }
// Continue with the route return resolve(event);}Decision
Section titled “Decision”Arcjet provides a single protect function that is used to execute your
protection rules. This requires a RequestEvent property which is the event
context as passed to the request handler.
This function returns a Promise that resolves to an
ArcjetDecision object. This contains the following properties:
id(string) – The unique ID for the request. This can be used to look up the request in the Arcjet dashboard. It is prefixed withreq_for decisions involving the Arcjet cloud API. For decisions taken locally, the prefix islreq_.conclusion(ArcjetConclusion) – The final conclusion based on evaluating each of the configured rules. If you wish to accept Arcjet’s recommended action based on the configured rules then you can use this property.reason(ArcjetReason) – An object containing more detailed information about the conclusion.results(ArcjetRuleResult[]) – An array ofArcjetRuleResultobjects containing the results of each rule that was executed.ip(ArcjetIpDetails) – An object containing Arcjet’s analysis of the client IP address. For more information, see the SDK reference.
To check whether a shield rule returned a deny conclusion, use
decision.isDenied() and decision.reason.isShield() (JS) /
decision.is_denied() and decision.reason_v2.type == "SHIELD" (Python).
You can iterate through the results and check whether a shield rule was applied:
for (const result of decision.results) { console.log("Rule Result", result);}for result in decision.results: print("Rule Result", result)This example logs the full result as well as the shield rule:
import { env } from "$env/dynamic/private";import arcjet, { fixedWindow, shield } from "@arcjet/sveltekit";import { error, json, type RequestEvent } from "@sveltejs/kit";
const aj = arcjet({ key: env.ARCJET_KEY!, rules: [ fixedWindow({ mode: "LIVE", window: "1h", max: 60, }), shield({ mode: "LIVE", }), ],});
export async function GET(event: RequestEvent) { const decision = await aj.protect(event);
for (const result of decision.results) { console.log("Rule Result", result);
if (result.reason.isRateLimit()) { console.log("Rate limit rule", result); }
if (result.reason.isShield()) { console.log("Shield rule", result); } }
if (decision.isDenied()) { return error(403, "Forbidden"); }
return json({ message: "Hello world" });}import arcjet, { fixedWindow, shield } from "@arcjet/sveltekit";import { error, json } from "@sveltejs/kit";
const aj = arcjet({ key: env.ARCJET_KEY, rules: [ fixedWindow({ mode: "LIVE", window: "1h", max: 60, }), shield({ mode: "LIVE", }), ],});
export async function GET(event) { const decision = await aj.protect(event);
for (const result of decision.results) { console.log("Rule Result", result);
if (result.reason.isRateLimit()) { console.log("Rate limit rule", result); }
if (result.reason.isShield()) { console.log("Shield rule", result); } }
if (decision.isDenied()) { return error(403, "Forbidden"); }
return json({ message: "Hello world" });}Error handling
Section titled “Error handling”Arcjet is designed to fail open so that a service issue or misconfiguration does not block all requests. The SDK also times out and fails open after 2000 ms by default. However, in most cases, the response time is less than 20 ms to 30 ms.
If there is an error condition when processing the rule, Arcjet returns an
ERROR result for that rule and you can check the message property on the
rule’s error result for more information.
If all other rules that were run returned an ALLOW result, then the final
Arcjet conclusion is ERROR.
import { env } from "$env/dynamic/private";import arcjet, { shield } from "@arcjet/sveltekit";import { error, json, type RequestEvent } from "@sveltejs/kit";
const aj = arcjet({ key: env.ARCJET_KEY!, rules: [ shield({ mode: "LIVE", }), ],});
export async function GET(event: RequestEvent) { const decision = await aj.protect(event);
for (const { reason } of decision.results) { if (reason.isError()) { // Fail open by logging the error and continuing console.warn("Arcjet error", reason.message); // You could also fail closed here for very sensitive routes //return error(503, { message: "Service unavailable" }); } }
if (decision.isDenied()) { return error(403, { message: "You are suspicious!" }); }
return json({ message: "Hello world" });}import { env } from "$env/dynamic/private";import arcjet, { shield } from "@arcjet/sveltekit";import { error, json } from "@sveltejs/kit";
const aj = arcjet({ key: env.ARCJET_KEY, rules: [ shield({ mode: "LIVE", }), ],});
export async function GET(event) { const decision = await aj.protect(event);
for (const { reason } of decision.results) { if (reason.isError()) { // Fail open by logging the error and continuing console.warn("Arcjet error", reason.message); // You could also fail closed here for very sensitive routes //return error(503, { message: "Service unavailable" }); } }
if (decision.isDenied()) { return error(403, { message: "You are suspicious!" }); }
return json({ message: "Hello world" });}Testing
Section titled “Testing”Arcjet runs the same in any environment, including locally and in CI. You can
use the mode set to DRY_RUN to log the results of rule execution without
blocking any requests.
We have an example test framework you can use to automatically test your rules. Arcjet can also be triggered based using a sample of your traffic.
For details, see the Testing section of the docs.