Turnstile を使った Nuxt フォームのスパム対策

app/
  components/
    ContactForm.vue
  composables/
    useTurnstile.ts
server/
  api/
    contact.post.ts
  utils/
    spam.ts
nuxt.config.ts
.env

NUXT_PUBLIC_TURNSTILE_SITE_KEY=1x00000000000000000000AA
NUXT_TURNSTILE_SECRET_KEY=1x0000000000000000000000000000000AA
NUXT_IKIFORM_SECRET_KEY=ik_sk_your_secret_key
NUXT_CLIENT_IP_HEADER=x-forwarded-for

const policy = [
  "default-src 'self'",
  "script-src 'self' 'unsafe-inline' https://challenges.cloudflare.com",
  "frame-src https://challenges.cloudflare.com",
  "object-src 'none'",
  "base-uri 'self'",
].join("; ");

export default defineNuxtConfig({
  runtimeConfig: {
    turnstileSecretKey: "",
    ikiformSecretKey: "",
    clientIpHeader: "x-forwarded-for",
    public: {
      turnstileSiteKey: "",
    },
  },
  routeRules: {
    "/contact": { headers: { "Content-Security-Policy": policy } },
  },
  $production: {
    nitro: {
      storage: {
        ratelimit: { driver: "upstash" },
      },
    },
  },
});

import type { H3Event } from "h3";

const WINDOW_SECONDS = 60;
const LIMIT = 5;

export function clientIp(event: H3Event) {
  const header = useRuntimeConfig(event).clientIpHeader;
  return getRequestHeader(event, header)?.split(",")[0]?.trim() || "unknown";
}

export async function secondsToWait(ip: string) {
  const storage = useStorage("ratelimit");
  const window = Math.floor(Date.now() / 1000 / WINDOW_SECONDS);
  const key = `contact:${ip}:${window}`;
  const count = ((await storage.getItem<number>(key)) ?? 0) + 1;
  await storage.setItem(key, count);
  if (count <= LIMIT) return 0;
  return (window + 1) * WINDOW_SECONDS - Math.floor(Date.now() / 1000);
}

export async function isHuman(event: H3Event, token: string, ip: string) {
  if (!token || token.length > 2048) return false;
  try {
    const verdict = await $fetch<{ success: boolean; hostname?: string; action?: string }>("https://challenges.cloudflare.com/turnstile/v0/siteverify", {
      method: "POST",
      body: { secret: useRuntimeConfig(event).turnstileSecretKey, response: token, remoteip: ip },
    });
    return verdict.success && verdict.action === "contact" && (import.meta.dev || verdict.hostname === getRequestHost(event));
  } catch {
    return false;
  }
}

interface ContactBody {
  name?: string;
  email?: string;
  company?: string;
  message?: string;
  _gotcha?: string;
  "cf-turnstile-response"?: string;
}

export default defineEventHandler(async (event) => {
  const ip = clientIp(event);
  const wait = await secondsToWait(ip);
  if (wait) throw createError({ status: 429, message: `Too many messages. Try again in ${wait} seconds.` });

  const body = await readBody<ContactBody>(event);
  const fields = {
    name: body.name?.trim().slice(0, 120) ?? "",
    email: body.email?.trim() ?? "",
    company: body.company?.trim().slice(0, 120) ?? "",
    message: body.message?.trim().slice(0, 5000) ?? "",
    _gotcha: body._gotcha ?? "",
  };
  if (!fields.email.includes("@")) throw createError({ status: 400, message: "Enter an address we can reply to." });
  if (!(await isHuman(event, body["cf-turnstile-response"] ?? "", ip))) {
    throw createError({ status: 403, message: "We couldn't confirm you're human. Try again." });
  }

  const origin = getRequestHeader(event, "origin");
  await $fetch("https://ikiform.com/f/frm_xxxxxxxxxxxxxxxx", {
    method: "POST",
    headers: {
      Accept: "application/json",
      Authorization: `Bearer ${useRuntimeConfig(event).ikiformSecretKey}`,
      ...(origin ? { Origin: origin } : {}),
    },
    body: fields,
  }).catch((failure) => {
    throw createError({
      status: failure.status ?? 502,
      message: failure.data?.error?.message ?? "Your message didn't send. Try again.",
    });
  });
  return { sent: true };
});

interface TurnstileApi {
  render(
    container: HTMLElement,
    options: { sitekey: string; action: string; callback: (token: string) => void; "expired-callback": () => void },
  ): string;
  reset(widgetId: string): void;
  remove(widgetId: string): void;
}

let loading: Promise<TurnstileApi> | undefined;

function load() {
  loading ??= new Promise<TurnstileApi>((resolve, reject) => {
    const script = document.createElement("script");
    script.src = "https://challenges.cloudflare.com/turnstile/v0/api.js?render=explicit";
    script.async = true;
    script.onload = () => {
      const api = (window as Window & { turnstile?: TurnstileApi }).turnstile;
      if (api) resolve(api);
      else reject(new Error("Turnstile did not load"));
    };
    script.onerror = () => reject(new Error("Turnstile did not load"));
    document.head.append(script);
  });
  return loading;
}

export function useTurnstile(action: string) {
  const { turnstileSiteKey } = useRuntimeConfig().public;
  const box = ref<HTMLElement>();
  const token = ref("");
  let api: TurnstileApi | undefined;
  let widgetId: string | undefined;

  onMounted(async () => {
    api = await load();
    if (!box.value) return;
    widgetId = api.render(box.value, {
      sitekey: turnstileSiteKey,
      action,
      callback: (value) => (token.value = value),
      "expired-callback": () => (token.value = ""),
    });
  });

  onBeforeUnmount(() => {
    if (widgetId) api?.remove(widgetId);
  });

  function reset() {
    token.value = "";
    if (widgetId) api?.reset(widgetId);
  }

  return { box, token, reset };
}

<script setup lang="ts">
const fields = reactive({ name: "", email: "", company: "", message: "", _gotcha: "" });
const { box, token, reset } = useTurnstile("contact");
const status = ref<"idle" | "sending" | "sent">("idle");
const error = ref("");

async function send() {
  status.value = "sending";
  error.value = "";
  try {
    await $fetch("/api/contact", { method: "POST", body: { ...fields, "cf-turnstile-response": token.value } });
    status.value = "sent";
  } catch (failure) {
    error.value = (failure as { data?: { message?: string } }).data?.message ?? "Couldn't send your message. Try again.";
    status.value = "idle";
    reset();
  }
}
</script>

<template>
  <p v-if="status === 'sent'" role="status">Thanks. We'll reply by email.</p>
  <form v-else @submit.prevent="send">
    <label for="name">Name</label>
    <input id="name" v-model="fields.name" autocomplete="name" required maxlength="120" />
    <label for="email">Email</label>
    <input id="email" v-model="fields.email" type="email" autocomplete="email" required />
    <label for="company">Company <span>(optional)</span></label>
    <input id="company" v-model="fields.company" autocomplete="organization" maxlength="120" />
    <label for="message">Message</label>
    <textarea id="message" v-model="fields.message" rows="5" required minlength="10" />
    <div class="hp" aria-hidden="true">
      <label for="hp-field">Leave this empty</label>
      <input id="hp-field" v-model="fields._gotcha" type="text" tabindex="-1" autocomplete="off" />
    </div>
    <div ref="box" />
    <p v-if="error" role="alert">{{ error }}</p>
    <button :disabled="status === 'sending' || !token">{{ status === "sending" ? "Sending" : "Send message" }}</button>
  </form>
</template>

for i in 1 2 3 4 5 6; do
  curl -s -o /dev/null -w "%{http_code}\n" -X POST http://localhost:3000/api/contact \
    -H "Content-Type: application/json" -d '{"email":"test@example.com"}'
done