Arcrun/.component-builds/auth_service_account/src/index.ts

/**
 * arcrun auth_service_account Worker
 *
 * POST / → JSON input {action, api_key, service} → WASM (WASI preview1 stdin/stdout) → JSON output
 *
 * 方案 A:直接 import cypher-executor/src/lib/wasi-shim.ts 的 shim + host function factory,
 * 確保 AES-GCM 解密 / RS256 sign 邏輯只存在於一個檔案(rule 02 §2.2)。
 *
 * 這個 Worker 比 auth_static_key 多一個 host function:http_request(token exchange 用)。
 * http_request 不是 crypto,不受 rule 02 §2.2 約束;在此檔內聚合提供即可。
 *
 * 安全邊界:
 *   - api_key 經 stdin 傳進 WASM,同時綁到 host function 的 kv_get 做越權檢查
 *   - ENCRYPTION_KEY 只存在於 host function 的 closure 中,不會進入 WASM 記憶體
 *   - private key 只以 PKCS8 bytes 傳給 crypto_sign_rs256 host function,decrypt 後 plaintext 不離開 WASM
 */

import componentWasm from '../component.wasm' assert { type: 'webassembly' };
import { Hono } from 'hono';
import { cors } from 'hono/cors';
import {
  createWasiShim,
  createArcrunHostFunctions,
  type ArcrunHostEnv,
  type WasiHostFunctions,
} from '../../../cypher-executor/src/lib/wasi-shim';

type Env = ArcrunHostEnv;

const app = new Hono<{ Bindings: Env }>();
app.use('*', cors());

app.get('/', (c) => c.json({ ok: true, component: 'auth_service_account' }));

app.post('/', async (c) => {
  let input: Record<string, unknown>;
  try {
    input = await c.req.json();
  } catch {
    return c.json({ success: false, error: 'request body must be JSON' }, 400);
  }

  const apiKey = typeof input.api_key === 'string' ? input.api_key : '';
  if (!apiKey) {
    return c.json({ success: false, error: 'api_key 必填' }, 400);
  }

  try {
    const result = await runWasm(c.env, apiKey, input);
    return c.json(result);
  } catch (e) {
    return c.json(
      { success: false, error: e instanceof Error ? e.message : String(e) },
      500,
    );
  }
});

export default app;

// ── WASM runner ──────────────────────────────────────────────────────────────

async function runWasm(env: Env, apiKey: string, input: unknown): Promise<unknown> {
  const stdinData = JSON.stringify(input);
  const baseHost = createArcrunHostFunctions(env, apiKey);
  const hostFunctions: WasiHostFunctions = {
    ...baseHost,
    http_request: async (url, method, headersJson, body) => {
      const headers: Record<string, string> = {};
      if (headersJson) {
        try {
          const parsed = JSON.parse(headersJson);
          if (parsed && typeof parsed === 'object') {
            for (const [k, v] of Object.entries(parsed as Record<string, unknown>)) {
              if (typeof v === 'string') headers[k] = v;
            }
          }
        } catch {
          // 忽略 header parse 錯誤,當作沒 header
        }
      }
      const init: RequestInit = { method, headers };
      if (body && method.toUpperCase() !== 'GET' && method.toUpperCase() !== 'HEAD') {
        init.body = body;
      }
      const res = await fetch(url, init);
      // WASM 端(main.go)直接 json.Unmarshal 回傳內容找 access_token,
      // 因此只回傳 response body 原文。非 2xx 也回原文,讓 WASM 從 {error, error_description} 判斷
      return await res.text();
    },
  };

  const shim = createWasiShim(stdinData, hostFunctions);

  const instance = await WebAssembly.instantiate(
    componentWasm as WebAssembly.Module,
    shim.imports,
  );
  shim.setMemory(instance.exports.memory as WebAssembly.Memory);
  await shim.run(instance);

  const stdout = shim.getStdout().trim();
  if (!stdout) throw new Error('WASM component produced no output');
  return JSON.parse(stdout);
}