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Use new error codes for UTDs from historical events
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@richvdh
richvdh committed Apr 16, 2024
1 parent a16906b commit 38a508a
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Showing 4 changed files with 155 additions and 7 deletions.
98 changes: 95 additions & 3 deletions spec/integ/crypto/crypto.spec.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -480,11 +480,17 @@ describe.each(Object.entries(CRYPTO_BACKENDS))("crypto (%s)", (backend: string,
// A promise which resolves, with the MatrixEvent which wraps the event, once the decryption fails.
const awaitDecryption = emitPromise(aliceClient, MatrixEventEvent.Decrypted);

// Ensure that the timestamp post-dates the creation of our device
const encryptedEvent = {
...testData.ENCRYPTED_EVENT,
origin_server_ts: Date.now(),
};

const syncResponse = {
next_batch: 1,
rooms: {
join: {
[testData.TEST_ROOM_ID]: { timeline: { events: [testData.ENCRYPTED_EVENT] } },
[testData.TEST_ROOM_ID]: { timeline: { events: [encryptedEvent] } },
},
},
};
Expand All @@ -504,12 +510,17 @@ describe.each(Object.entries(CRYPTO_BACKENDS))("crypto (%s)", (backend: string,

await aliceClient.getCrypto()!.importRoomKeys([testData.RATCHTED_MEGOLM_SESSION_DATA]);

// Alice gets both the events in a single sync
// Ensure that the timestamp post-dates the creation of our device
const encryptedEvent = {
...testData.ENCRYPTED_EVENT,
origin_server_ts: Date.now(),
};

const syncResponse = {
next_batch: 1,
rooms: {
join: {
[testData.TEST_ROOM_ID]: { timeline: { events: [testData.ENCRYPTED_EVENT] } },
[testData.TEST_ROOM_ID]: { timeline: { events: [encryptedEvent] } },
},
},
};
Expand All @@ -521,6 +532,87 @@ describe.each(Object.entries(CRYPTO_BACKENDS))("crypto (%s)", (backend: string,
expect(ev.decryptionFailureReason).toEqual(DecryptionFailureCode.OLM_UNKNOWN_MESSAGE_INDEX);
});

describe("Historical events", () => {
async function sendEventAndAwaitDecryption(): Promise<MatrixEvent> {
// A promise which resolves, with the MatrixEvent which wraps the event, once the decryption fails.
const awaitDecryption = emitPromise(aliceClient, MatrixEventEvent.Decrypted);

// Ensure that the timestamp pre-dates the creation of our device: set it to 24 hours ago
const encryptedEvent = {
...testData.ENCRYPTED_EVENT,
origin_server_ts: Date.now() - 24 * 3600 * 1000,
};

const syncResponse = {
next_batch: 1,
rooms: {
join: {
[testData.TEST_ROOM_ID]: { timeline: { events: [encryptedEvent] } },
},
},
};

syncResponder.sendOrQueueSyncResponse(syncResponse);
return await awaitDecryption;
}

newBackendOnly("fails with HISTORICAL_MESSAGE_BACKUP_NO_BACKUP when there is no backup", async () => {
fetchMock.get("path:/_matrix/client/v3/room_keys/version", {
status: 404,
body: { errcode: "M_NOT_FOUND", error: "No current backup version." },
});
expectAliceKeyQuery({ device_keys: { "@alice:localhost": {} }, failures: {} });
await startClientAndAwaitFirstSync();

const ev = await sendEventAndAwaitDecryption();
expect(ev.decryptionFailureReason).toEqual(DecryptionFailureCode.HISTORICAL_MESSAGE_NO_KEY_BACKUP);
});

newBackendOnly("fails with HISTORICAL_MESSAGE_BACKUP_UNCONFIGURED when the backup is broken", async () => {
fetchMock.get("path:/_matrix/client/v3/room_keys/version", {});
expectAliceKeyQuery({ device_keys: { "@alice:localhost": {} }, failures: {} });
await startClientAndAwaitFirstSync();

const ev = await sendEventAndAwaitDecryption();
expect(ev.decryptionFailureReason).toEqual(
DecryptionFailureCode.HISTORICAL_MESSAGE_BACKUP_UNCONFIGURED,
);
});

newBackendOnly("fails with HISTORICAL_MESSAGE_WORKING_BACKUP when backup is working", async () => {
// The test backup data is signed by a dummy device. We'll need to tell Alice about the device, and
// later, tell her to trust it, so that she trusts the backup.
const e2eResponder = new E2EKeyResponder(aliceClient.getHomeserverUrl());
e2eResponder.addDeviceKeys(testData.SIGNED_TEST_DEVICE_DATA);
fetchMock.get("path:/_matrix/client/v3/room_keys/version", testData.SIGNED_BACKUP_DATA);
await startClientAndAwaitFirstSync();

await aliceClient
.getCrypto()!
.storeSessionBackupPrivateKey(
Buffer.from(testData.BACKUP_DECRYPTION_KEY_BASE64, "base64"),
testData.SIGNED_BACKUP_DATA.version!,
);

// Tell Alice to trust the dummy device that signed the backup
const devices = await aliceClient.getCrypto()!.getUserDeviceInfo([TEST_USER_ID]);
expect(devices.get(TEST_USER_ID)!.keys()).toContain(testData.TEST_DEVICE_ID);
await aliceClient.getCrypto()!.setDeviceVerified(testData.TEST_USER_ID, testData.TEST_DEVICE_ID);

// Tell Alice to check and enable backup
await aliceClient.getCrypto()!.checkKeyBackupAndEnable();

// Sanity: Alice should now have working backup.
expect(await aliceClient.getCrypto()!.getActiveSessionBackupVersion()).toEqual(
testData.SIGNED_BACKUP_DATA.version,
);

// Finally! we can check what happens when we get an event.
const ev = await sendEventAndAwaitDecryption();
expect(ev.decryptionFailureReason).toEqual(DecryptionFailureCode.HISTORICAL_MESSAGE_WORKING_BACKUP);
});
});

it("Decryption fails with Unable to decrypt for other errors", async () => {
expectAliceKeyQuery({ device_keys: { "@alice:localhost": {} }, failures: {} });
await startClientAndAwaitFirstSync();
Expand Down
8 changes: 7 additions & 1 deletion spec/integ/crypto/megolm-backup.spec.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -45,6 +45,7 @@ import { KeyBackupInfo, KeyBackupSession } from "../../../src/crypto-api/keyback
import { IKeyBackup } from "../../../src/crypto/backup";
import { flushPromises } from "../../test-utils/flushPromises";
import { defer, IDeferred } from "../../../src/utils";
import { DecryptionFailureCode } from "../../../src/crypto-api";

const ROOM_ID = testData.TEST_ROOM_ID;

Expand Down Expand Up @@ -242,8 +243,13 @@ describe.each(Object.entries(CRYPTO_BACKENDS))("megolm-keys backup (%s)", (backe

const room = aliceClient.getRoom(ROOM_ID)!;
const event = room.getLiveTimeline().getEvents()[0];
await advanceTimersUntil(awaitDecryption(event, { waitOnDecryptionFailure: true }));

// On the first decryption attempt, decryption fails.
await awaitDecryption(event);
expect(event.decryptionFailureReason).toEqual(DecryptionFailureCode.HISTORICAL_MESSAGE_WORKING_BACKUP);

Check failure on line 249 in spec/integ/crypto/megolm-backup.spec.ts

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GitHub Actions / Jest [integ] (Node 18)

megolm-keys backup (libolm) › Key backup check on UTD message › Alice checks key backups when receiving a message she can't decrypt 

expect(received).toEqual(expected) // deep equality

Expected: "HISTORICAL_MESSAGE_WORKING_BACKUP"
Received: "MEGOLM_UNKNOWN_INBOUND_SESSION_ID"

    at Object.toEqual (spec/integ/crypto/megolm-backup.spec.ts:249:51)

Check failure on line 249 in spec/integ/crypto/megolm-backup.spec.ts

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GitHub Actions / Jest [integ] (Node lts/*)

megolm-keys backup (libolm) › Key backup check on UTD message › Alice checks key backups when receiving a message she can't decrypt 

expect(received).toEqual(expected) // deep equality

Expected: "HISTORICAL_MESSAGE_WORKING_BACKUP"
Received: "MEGOLM_UNKNOWN_INBOUND_SESSION_ID"

    at Object.toEqual (spec/integ/crypto/megolm-backup.spec.ts:249:51)

Check failure on line 249 in spec/integ/crypto/megolm-backup.spec.ts

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GitHub Actions / Jest [integ] (Node 21)

megolm-keys backup (libolm) › Key backup check on UTD message › Alice checks key backups when receiving a message she can't decrypt 

expect(received).toEqual(expected) // deep equality

Expected: "HISTORICAL_MESSAGE_WORKING_BACKUP"
Received: "MEGOLM_UNKNOWN_INBOUND_SESSION_ID"

    at Object.toEqual (spec/integ/crypto/megolm-backup.spec.ts:249:51)

// Eventually, decryption succeeds.
await awaitDecryption(event, { waitOnDecryptionFailure: true });
expect(event.getContent()).toEqual(testData.CLEAR_EVENT.content);
});

Expand Down
18 changes: 18 additions & 0 deletions src/crypto-api.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -542,6 +542,24 @@ export enum DecryptionFailureCode {
/** Message was encrypted with a Megolm session which has been shared with us, but in a later ratchet state. */
OLM_UNKNOWN_MESSAGE_INDEX = "OLM_UNKNOWN_MESSAGE_INDEX",

/**
* Message was sent before the current device was created; there is no key backup on the server, so this
* decryption failure is expected.
*/
HISTORICAL_MESSAGE_NO_KEY_BACKUP = "HISTORICAL_MESSAGE_NO_KEY_BACKUP",

/**
* Message was sent before the current device was created; there was a key backup on the server, but we don't
* seem to have access to the backup. (Probably we don't have the right key.)
*/
HISTORICAL_MESSAGE_BACKUP_UNCONFIGURED = "HISTORICAL_MESSAGE_BACKUP_UNCONFIGURED",

/**
* Message was sent before the current device was created; there was a (usable) key backup on the server, but we
* still can't decrypt. (Either the session isn't in the backup, or we just haven't gotten around to checking yet.)
*/
HISTORICAL_MESSAGE_WORKING_BACKUP = "HISTORICAL_MESSAGE_WORKING_BACKUP",

/** Unknown or unclassified error. */
UNKNOWN_ERROR = "UNKNOWN_ERROR",

Expand Down
38 changes: 35 additions & 3 deletions src/rust-crypto/rust-crypto.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -1707,7 +1707,7 @@ class EventDecryptor {
};
} catch (err) {
if (err instanceof RustSdkCryptoJs.MegolmDecryptionError) {
this.onMegolmDecryptionError(event, err);
this.onMegolmDecryptionError(event, err, await this.perSessionBackupDownloader.getServerBackupInfo());
} else {
throw new DecryptionError(DecryptionFailureCode.UNKNOWN_ERROR, "Unknown error");
}
Expand All @@ -1718,19 +1718,51 @@ class EventDecryptor {
* Handle a `MegolmDecryptionError` returned by the rust SDK.
*
* Fires off a request to the `perSessionBackupDownloader`, if appropriate, and then throws a `DecryptionError`.
*
* @param event - The event which could not be decrypted.
* @param err - The error from the Rust SDK.
* @param serverBackupInfo - Details about the current backup from the server. `null` if there is no backup.
* `undefined` if our attempt to check failed.
*/
private onMegolmDecryptionError(event: MatrixEvent, err: RustSdkCryptoJs.MegolmDecryptionError): never {
private onMegolmDecryptionError(
event: MatrixEvent,
err: RustSdkCryptoJs.MegolmDecryptionError,
serverBackupInfo: KeyBackupInfo | null | undefined,
): never {
const content = event.getWireContent();
const errorDetails = { session: content.sender_key + "|" + content.session_id };

// If the error looks like it might be recoverable from backup, queue up a request to try that.
if (
err.code === RustSdkCryptoJs.DecryptionErrorCode.MissingRoomKey ||
err.code === RustSdkCryptoJs.DecryptionErrorCode.UnknownMessageIndex
) {
this.perSessionBackupDownloader.onDecryptionKeyMissingError(event.getRoomId()!, content.session_id!);

// If the event was sent before this device was created, we use some different error codes.
if (event.getTs() <= this.olmMachine.deviceCreationTimeMs) {
if (serverBackupInfo === null) {
throw new DecryptionError(
DecryptionFailureCode.HISTORICAL_MESSAGE_NO_KEY_BACKUP,
"This message was sent before this device logged in, and there is no key backup on the server.",
errorDetails,
);
} else if (!this.perSessionBackupDownloader.isKeyBackupDownloadConfigured()) {
throw new DecryptionError(
DecryptionFailureCode.HISTORICAL_MESSAGE_BACKUP_UNCONFIGURED,
"This message was sent before this device logged in, and key backup is not working.",
errorDetails,
);
} else {
throw new DecryptionError(
DecryptionFailureCode.HISTORICAL_MESSAGE_WORKING_BACKUP,
"This message was sent before this device logged in. Key backup is working, but we still do not (yet) have the key.",
errorDetails,
);
}
}
}

const errorDetails = { session: content.sender_key + "|" + content.session_id };
switch (err.code) {
case RustSdkCryptoJs.DecryptionErrorCode.MissingRoomKey:
throw new DecryptionError(
Expand Down

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