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zulip-desktop/app/renderer/js/clipboard-decrypter.ts
Anders Kaseorg feb67e6c2d Deglobalize ElectronBridge type.
Signed-off-by: Anders Kaseorg <anders@zulip.com>
2021-09-01 14:04:51 -07:00

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import crypto from "crypto";
import {clipboard} from "electron";
// This helper is exposed via electron_bridge for use in the social
// login flow.
//
// It consists of a key and a promised token. The in-app page sends
// the key to the server, and opens the users browser to a page where
// they can log in and get a token encrypted to that key. When the
// user copies the encrypted token from their browser to the
// clipboard, we decrypt it and resolve the promise. The in-app page
// then uses the decrypted token to log the user in within the app.
//
// The encryption is authenticated (AES-GCM) to guarantee that we
// dont leak anything from the users clipboard other than the token
// intended for us.
export interface ClipboardDecrypter {
version: number;
key: Uint8Array;
pasted: Promise<string>;
}
export class ClipboardDecrypterImpl implements ClipboardDecrypter {
version: number;
key: Uint8Array;
pasted: Promise<string>;
constructor(_: number) {
// At this time, the only version is 1.
this.version = 1;
this.key = crypto.randomBytes(32);
this.pasted = new Promise((resolve) => {
let interval: NodeJS.Timeout | null = null;
const startPolling = () => {
if (interval === null) {
interval = setInterval(poll, 1000);
}
poll();
};
const stopPolling = () => {
if (interval !== null) {
clearInterval(interval);
interval = null;
}
};
const poll = () => {
let plaintext;
try {
const data = Buffer.from(clipboard.readText(), "hex");
const iv = data.slice(0, 12);
const ciphertext = data.slice(12, -16);
const authTag = data.slice(-16);
const decipher = crypto.createDecipheriv(
"aes-256-gcm",
this.key,
iv,
{authTagLength: 16},
);
decipher.setAuthTag(authTag);
plaintext =
decipher.update(ciphertext, undefined, "utf8") +
decipher.final("utf8");
} catch {
// If the parsing or decryption failed in any way,
// the correct token hasnt been copied yet; try
// again next time.
return;
}
window.removeEventListener("focus", startPolling);
window.removeEventListener("blur", stopPolling);
stopPolling();
resolve(plaintext);
};
window.addEventListener("focus", startPolling);
window.addEventListener("blur", stopPolling);
if (document.hasFocus()) {
startPolling();
}
});
}
}