mirror of
https://github.com/bulwarkmail/webmail.git
synced 2026-11-02 08:15:55 +00:00
Linus Rath
db5ac82f53
Settings > Backup & reset gets "Keep mail on this device", off until the user turns it on in this browser. While it is on: - the JMAP client hands the server's answers to an encrypted cache in IndexedDB (AES-GCM, non-extractable key) and answers from it when the network is gone: the folder list, the last 30 days of the Inbox and of the folders the user opened, bodies and attachments, at most 250 MB, oldest out first; a background sync keeps it current - read, flag, tags and moves made offline are queued and sent in order when the server answers again; deleting for good and emptying a folder are refused offline - the composer, quick reply and the S/MIME and PGP plugins' sends that complete the composer's go to an outbox once every step up to the transport ran (checks, label, signature, plugin send checks); only the finished send waits, with files attached offline - the service worker keeps this build's app shell, so the app also starts offline from the kept session and the last policy - a full sign-out, the idle sign-out and signing one account out delete it, a sign-out the user starts asks first when mail is unsent, and the login page names what an automatic sign-out deleted; a policy fetch that forbids it (devices.noOffline) wipes that account Not in Lite.
60 lines
2.1 KiB
TypeScript
60 lines
2.1 KiB
TypeScript
/**
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* Encryption at rest for offline mode (#523): AES-GCM with a 256-bit key
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* the browser generates as non-extractable and keeps in the offline
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* database. Script on this origin can't read the key's bytes, only use it.
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*
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* What it protects against: someone who copies the browser profile's files
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* (a backup, a stolen disk image) without being able to run this site in
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* that profile. What it doesn't: someone using the unlocked browser profile,
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* or a script running on this origin, can decrypt everything. The docs say
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* so and recommend disk encryption.
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*/
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import { idbGet, idbWrite } from './db';
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export interface Sealed {
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iv: Uint8Array;
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data: ArrayBuffer;
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}
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let keyPromise: Promise<CryptoKey> | null = null;
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async function loadOrCreateKey(): Promise<CryptoKey> {
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const stored = await idbGet<{ id: string; key: CryptoKey }>('keys', 'aes');
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if (stored?.key) return stored.key;
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const key = await crypto.subtle.generateKey({ name: 'AES-GCM', length: 256 }, false, ['encrypt', 'decrypt']);
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await idbWrite([{ store: 'keys', put: { id: 'aes', key } }]);
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return key;
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}
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function deviceKey(): Promise<CryptoKey> {
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if (!keyPromise) {
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keyPromise = loadOrCreateKey();
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keyPromise.catch(() => { keyPromise = null; });
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}
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return keyPromise;
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}
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/** Forget the key in memory (the database with it was deleted). */
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export function forgetDeviceKey(): void {
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keyPromise = null;
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}
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export async function sealBytes(bytes: ArrayBuffer | Uint8Array): Promise<Sealed> {
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const iv = crypto.getRandomValues(new Uint8Array(12));
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const data = await crypto.subtle.encrypt({ name: 'AES-GCM', iv }, await deviceKey(), bytes as BufferSource);
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return { iv, data };
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}
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export async function openBytes(sealed: Sealed): Promise<ArrayBuffer> {
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return crypto.subtle.decrypt({ name: 'AES-GCM', iv: sealed.iv as BufferSource }, await deviceKey(), sealed.data);
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}
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export async function sealJson(value: unknown): Promise<Sealed> {
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return sealBytes(new TextEncoder().encode(JSON.stringify(value)));
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}
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export async function openJson<T>(sealed: Sealed): Promise<T> {
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return JSON.parse(new TextDecoder().decode(await openBytes(sealed))) as T;
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}
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