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/**
* @license
* Copyright 2025 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
import { OAuth2Client, Credentials } from 'google-auth-library';
import * as http from 'http';
import url from 'url';
import crypto from 'crypto';
import * as net from 'net';
import open from 'open';
import path from 'node:path';
import { promises as fs } from 'node:fs';
import * as os from 'os';
// OAuth Client ID used to initiate OAuth2Client class.
const OAUTH_CLIENT_ID =
'681255809395-oo8ft2oprdrnp9e3aqf6av3hmdib135j.apps.googleusercontent.com';
// OAuth Secret value used to initiate OAuth2Client class.
// Note: It's ok to save this in git because this is an installed application
// as described here: https://developers.google.com/identity/protocols/oauth2#installed
// "The process results in a client ID and, in some cases, a client secret,
// which you embed in the source code of your application. (In this context,
// the client secret is obviously not treated as a secret.)"
const OAUTH_CLIENT_SECRET = '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';
// OAuth Scopes for Cloud Code authorization.
const OAUTH_SCOPE = [
'https://www.googleapis.com/auth/cloud-platform',
'https://www.googleapis.com/auth/userinfo.email',
'https://www.googleapis.com/auth/userinfo.profile',
];
const HTTP_REDIRECT = 301;
const SIGN_IN_SUCCESS_URL =
'https://developers.google.com/gemini-code-assist/auth_success_gemini';
const SIGN_IN_FAILURE_URL =
'https://developers.google.com/gemini-code-assist/auth_failure_gemini';
const GEMINI_DIR = '.gemini';
const CREDENTIAL_FILENAME = 'oauth_creds.json';
/**
* An Authentication URL for updating the credentials of a Oauth2Client
* as well as a promise that will resolve when the credentials have
* been refreshed (or which throws error when refreshing credentials failed).
*/
export interface OauthWebLogin {
authUrl: string;
loginCompletePromise: Promise<void>;
}
export async function getOauthClient(): Promise<OAuth2Client> {
const client = new OAuth2Client({
clientId: OAUTH_CLIENT_ID,
clientSecret: OAUTH_CLIENT_SECRET,
});
if (await loadCachedCredentials(client)) {
// Found valid cached credentials.
return client;
}
const webLogin = await authWithWeb(client);
console.log(
`\n\nCode Assist login required.\n` +
`Attempting to open authentication page in your browser.\n` +
`Otherwise navigate to:\n\n${webLogin.authUrl}\n\n`,
);
await open(webLogin.authUrl);
console.log('Waiting for authentication...');
await webLogin.loginCompletePromise;
return client;
}
async function authWithWeb(client: OAuth2Client): Promise<OauthWebLogin> {
const port = await getAvailablePort();
const redirectUri = `http://localhost:${port}/oauth2callback`;
const state = crypto.randomBytes(32).toString('hex');
const authUrl: string = client.generateAuthUrl({
redirect_uri: redirectUri,
access_type: 'offline',
scope: OAUTH_SCOPE,
state,
});
const loginCompletePromise = new Promise<void>((resolve, reject) => {
const server = http.createServer(async (req, res) => {
try {
if (req.url!.indexOf('/oauth2callback') === -1) {
res.writeHead(HTTP_REDIRECT, { Location: SIGN_IN_FAILURE_URL });
res.end();
reject(new Error('Unexpected request: ' + req.url));
}
// acquire the code from the querystring, and close the web server.
const qs = new url.URL(req.url!, 'http://localhost:3000').searchParams;
if (qs.get('error')) {
res.writeHead(HTTP_REDIRECT, { Location: SIGN_IN_FAILURE_URL });
res.end();
reject(new Error(`Error during authentication: ${qs.get('error')}`));
} else if (qs.get('state') !== state) {
res.end('State mismatch. Possible CSRF attack');
reject(new Error('State mismatch. Possible CSRF attack'));
} else if (qs.get('code')) {
const { tokens } = await client.getToken({
code: qs.get('code')!,
redirect_uri: redirectUri,
});
client.setCredentials(tokens);
await cacheCredentials(client.credentials);
res.writeHead(HTTP_REDIRECT, { Location: SIGN_IN_SUCCESS_URL });
res.end();
resolve();
} else {
reject(new Error('No code found in request'));
}
} catch (e) {
reject(e);
} finally {
server.close();
}
});
server.listen(port);
});
return {
authUrl,
loginCompletePromise,
};
}
export function getAvailablePort(): Promise<number> {
return new Promise((resolve, reject) => {
let port = 0;
try {
const server = net.createServer();
server.listen(0, () => {
const address = server.address()! as net.AddressInfo;
port = address.port;
});
server.on('listening', () => {
server.close();
server.unref();
});
server.on('error', (e) => reject(e));
server.on('close', () => resolve(port));
} catch (e) {
reject(e);
}
});
}
async function loadCachedCredentials(client: OAuth2Client): Promise<boolean> {
try {
const keyFile =
process.env.GOOGLE_APPLICATION_CREDENTIALS || getCachedCredentialPath();
const creds = await fs.readFile(keyFile, 'utf-8');
client.setCredentials(JSON.parse(creds));
// This will verify locally that the credentials look good.
const { token } = await client.getAccessToken();
if (!token) {
return false;
}
// This will check with the server to see if it hasn't been revoked.
await client.getTokenInfo(token);
return true;
} catch (_) {
return false;
}
}
async function cacheCredentials(credentials: Credentials) {
const filePath = getCachedCredentialPath();
await fs.mkdir(path.dirname(filePath), { recursive: true });
const credString = JSON.stringify(credentials, null, 2);
await fs.writeFile(filePath, credString);
}
function getCachedCredentialPath(): string {
return path.join(os.homedir(), GEMINI_DIR, CREDENTIAL_FILENAME);
}
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