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Element-R: pass pickleKey in as raw key for indexeddb encryption (#12543)

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* Element-R: pass pickleKey in as raw key for indexeddb encryption

Currently, we pass the `pickleKey` to the rust library for use as a passphrase
for encrypting its crypto store. The Rust libary then passes that passphrase
through 200000 rounds of PBKDF2 to generate an encryption key, which is
(deliberately) slow.

However, the pickleKey is actually 32 bytes of random data (base64-encoded). By
passing the raw key into the rust library, we can therefore save the PBKDF
operation.

Backwards-compatibility with existing sessions is maintained, because if the
rust library discovers that the store was previously encrypted with a key based
on a PBKDF, it will re-base64 and PBKDF the key we provide, thus reconstructing
the right key.

* Update src/Lifecycle.ts

Co-authored-by: Florian Duros <florianduros@element.io>

* Lifecycle-test: clean up test setup

Rely less on the unit under test for setting up the test preconditions -- not
least because we don't really want to fire up matrix clients and the like
during test setup.

* Factor out "encryptPickleKey" method

For a start it makes it easier to grok what's going on, but also I went to use
this in a test

* Improve tests for `Lifecycle.restoreFromLocalStorage`

---------

Co-authored-by: Florian Duros <florianduros@element.io>
This commit is contained in:
Richard van der Hoff 2024-06-05 09:52:28 +01:00 • committed by GitHub
parent 5004456d82
commit 0a01320fca
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6 changed files with 233 additions and 64 deletions
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22
src/BasePlatform.ts
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@ -38,7 +38,7 @@ import { idbLoad, idbSave, idbDelete } from "./utils/StorageAccess";
import { ViewRoomPayload } from "./dispatcher/payloads/ViewRoomPayload";
import { IConfigOptions } from "./IConfigOptions";
import SdkConfig from "./SdkConfig";
import { buildAndEncodePickleKey, getPickleAdditionalData } from "./utils/tokens/pickling";
import { buildAndEncodePickleKey, encryptPickleKey } from "./utils/tokens/pickling";
export const SSO_HOMESERVER_URL_KEY = "mx_sso_hs_url";
export const SSO_ID_SERVER_URL_KEY = "mx_sso_is_url";
@ -378,24 +378,16 @@ export default abstract class BasePlatform {
* support storing pickle keys.
*/
public async createPickleKey(userId: string, deviceId: string): Promise<string | null> {
if (!window.crypto || !window.crypto.subtle) {
return null;
}
const crypto = window.crypto;
const randomArray = new Uint8Array(32);
crypto.getRandomValues(randomArray);
const cryptoKey = await crypto.subtle.generateKey({ name: "AES-GCM", length: 256 }, false, [
"encrypt",
"decrypt",
]);
const iv = new Uint8Array(32);
crypto.getRandomValues(iv);
const additionalData = getPickleAdditionalData(userId, deviceId);
const encrypted = await crypto.subtle.encrypt({ name: "AES-GCM", iv, additionalData }, cryptoKey, randomArray);
const data = await encryptPickleKey(randomArray, userId, deviceId);
if (data === undefined) {
// no crypto support
return null;
}
try {
await idbSave("pickleKey", [userId, deviceId], { encrypted, iv, cryptoKey });
await idbSave("pickleKey", [userId, deviceId], data);
} catch (e) {
return null;
}