vercel-pow.js

const { webcrypto: crypto } = require("crypto");


// https://vercel.com/docs/security/attack-challenge-mode
(async () => {
    const hostname = "https://vercel-debug-xi.vercel.app";

    const _vcrct = await getReqToken();
    const solution = await computePOW(_vcrct);
    const resp = await postChallenge(hostname, _vcrct, solution);
    const solutionCookie = resp.headers.get("set-cookie").split("; ")[0];
    // console.log("solutionCookie:", solutionCookie);

    console.log("page:", await (await fetch(hostname, {
        headers: {
            "cookie": solutionCookie,
        },
    })).text());


    /**
     * @param {string} input
     * @returns {Promise<string>}
     */
    async function sha256(input) {
        const rawData = new TextEncoder().encode(input);
        const hashedData = await crypto.subtle.digest("SHA-256", rawData);
        const hashedDataArr = Array.from(new Uint8Array(hashedData));

        return hashedDataArr
            .map(x => x.toString(16).padStart(2, "0"))
            .join("");
    }

    /**
     * @param {string} prefix
     * @param {string} searchString
     * @returns {Promise<{key: string, hash: string}>}
     */
    async function computeSolution(prefix, searchString) {
        while(true) {
            const rnd = Math.random().toString(36).substring(2, 15);
            const hash = await sha256(prefix + rnd);
            if(hash.startsWith(searchString)) {
                return {
                    key: rnd,
                    hash: hash,
                };
            }
        }
    }

    /**
     * @param {string} vcrct 
     * @returns {Promise<string>}
     */
    async function computePOW(vcrct) {
        // "0.1709267488.60.ZjM0Y2Y0YjkxODZkMzZiMzBjZjE1YWRjNGNiZTZhNWU7NDRlNjQwNzk7MDAwMDsz.0a9072dba7fa6e57595d3d9cc6f98ca6"
        // ZjM0Y2Y0YjkxODZkMzZiMzBjZjE1YWRjNGNiZTZhNWU7NDRlNjQwNzk7MDAwMDsz
        const paramsString = atob(vcrct.split(".")[3]);

        // f34cf4b9186d36b30cf15adc4cbe6a5e;44e64079;0000;3
        const [, prefix, startSearchString, numSolutions] = paramsString.split(";");

        const results = [];
        let searchString = startSearchString;
        for(let i = 0; i < Number(numSolutions); i++) {
            const solution = await computeSolution(prefix, searchString);
            results.push(solution.key);

            searchString = solution.hash.slice(-searchString.length);
        }

        return results.join(";");
    }

    /**
     * @param {string} hostname
     * @param {string} token
     * @param {string} solution
     * @returns {Promise<Response>}
     */
    async function postChallenge(hostname, token, solution) {
        return fetch(hostname + "/.well-known/vercel/security/request-challenge", {
            method: "POST",
            headers: {
                "x-vercel-challenge-token": token,
                "x-vercel-challenge-solution": solution,
            },
        });
    }

    /**
     * @returns {Promise<string>}
     */
    async function getReqToken() {
        const initResp = await fetch(hostname);
        const initContent = await initResp.text();
        const initContentRe = initContent.match(/window\._vcrct="(?<token>.*?)"/);

        if(initContentRe === null) {
            return null;
        }

        const { token } = initContentRe.groups;

        return token;
    }
})();