index.js

"use strict";
var __awaiter = (this && this.__awaiter) || function (thisArg, _arguments, P, generator) {
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                case 0: case 1: t = op; break;
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exports.__esModule = true;
exports.verify = void 0;
var jsrsasign_1 = require("jsrsasign");
function verify(userToken) {
    return __awaiter(this, void 0, void 0, function () {
        var jwt, jwKey, isValid;
        return __generator(this, function (_a) {
            switch (_a.label) {
                case 0:
                    jwt = decodeJWT(userToken);
                    return [4 /*yield*/, fetchPublicKey(jwt.header.kid)];
                case 1:
                    jwKey = _a.sent();
                    isValid = jsrsasign_1.jws.JWS.verifyJWT(userToken, jwKey, {
                        alg: ['RS256'], iss: 'https://securetoken.google.com/incentive-success-fifth-benito',
                        aud: 'incentive-success-fifth-benito'
                    });
                    return [2 /*return*/, isValid];
            }
        });
    });
}
exports.verify = verify;
function decodeJWT(jwtString) {
    // @ts-ignore
    var jwt = jwtString.match(/(?<header>[^.]+)\.(?<payload>[^.]+)\.(?<signature>[^.]+)/).groups;
    // @ts-ignore
    jwt.header = JSON.parse(atob(jwt.header));
    // @ts-ignore
    jwt.payload = JSON.parse(atob(jwt.payload));
    return jwt;
}
function fetchPublicKey(kid) {
    return __awaiter(this, void 0, void 0, function () {
        var key;
        return __generator(this, function (_a) {
            switch (_a.label) {
                case 0: return [4 /*yield*/, fetch('https://www.googleapis.com/robot/v1/metadata/x509/securetoken@system.gserviceaccount.com')];
                case 1: return [4 /*yield*/, (_a.sent()).json()];
                case 2:
                    key = _a.sent();
                    key = key[kid];
                    return [2 /*return*/, key];
            }
        });
    });
}