Merge pull request #1146 from uhoreg/reporting_olm_error

record, report, and notify about olm errors

spec/unit/crypto/algorithms/megolm.spec.js

@@ -453,6 +453,99 @@ describe("MegolmDecryption", function() {
         bobClient2.stopClient();
     });
 
+    it("notifies devices when unable to create olm session", async function() {
+        const aliceClient = (new TestClient(
+            "@alice:example.com", "alicedevice",
+        )).client;
+        const bobClient = (new TestClient(
+            "@bob:example.com", "bobdevice",
+        )).client;
+        await Promise.all([
+            aliceClient.initCrypto(),
+            bobClient.initCrypto(),
+        ]);
+        const aliceDevice = aliceClient._crypto._olmDevice;
+        const bobDevice = bobClient._crypto._olmDevice;
+
+        const encryptionCfg = {
+            "algorithm": "m.megolm.v1.aes-sha2",
+        };
+        const roomId = "!someroom";
+        const aliceRoom = new Room(roomId, aliceClient, "@alice:example.com", {});
+        const bobRoom = new Room(roomId, bobClient, "@bob:example.com", {});
+        aliceClient.store.storeRoom(aliceRoom);
+        bobClient.store.storeRoom(bobRoom);
+        await aliceClient.setRoomEncryption(roomId, encryptionCfg);
+        await bobClient.setRoomEncryption(roomId, encryptionCfg);
+
+        aliceRoom.getEncryptionTargetMembers = async () => {
+            return [
+                {
+                    userId: "@alice:example.com",
+                    membership: "join",
+                },
+                {
+                    userId: "@bob:example.com",
+                    membership: "join",
+                },
+            ];
+        };
+        const BOB_DEVICES = {
+            bobdevice: {
+                user_id: "@bob:example.com",
+                device_id: "bobdevice",
+                algorithms: [olmlib.OLM_ALGORITHM, olmlib.MEGOLM_ALGORITHM],
+                keys: {
+                    "ed25519:bobdevice": bobDevice.deviceEd25519Key,
+                    "curve25519:bobdevice": bobDevice.deviceCurve25519Key,
+                },
+                known: true,
+                verified: 1,
+            },
+        };
+
+        aliceClient._crypto._deviceList.storeDevicesForUser(
+            "@bob:example.com", BOB_DEVICES,
+        );
+        aliceClient._crypto._deviceList.downloadKeys = async function(userIds) {
+            return this._getDevicesFromStore(userIds);
+        };
+
+        aliceClient.claimOneTimeKeys = async () => {
+            // Bob has no one-time keys
+            return {
+                one_time_keys: {},
+            };
+        };
+
+        let run = false;
+        aliceClient.sendToDevice = async (msgtype, contentMap) => {
+            run = true;
+            expect(msgtype).toBe("org.matrix.room_key.withheld");
+            expect(contentMap).toStrictEqual({
+                '@bob:example.com': {
+                    bobdevice: {
+                        algorithm: "m.megolm.v1.aes-sha2",
+                        code: 'm.no_olm',
+                        reason: 'Unable to establish a secure channel.',
+                        sender_key: aliceDevice.deviceCurve25519Key,
+                    },
+                },
+            });
+        };
+
+        const event = new MatrixEvent({
+            type: "m.room.message",
+            sender: "@alice:example.com",
+            room_id: roomId,
+            event_id: "$event",
+            content: {},
+        });
+        await aliceClient._crypto.encryptEvent(event, aliceRoom);
+
+        expect(run).toBe(true);
+    });
+
     it("throws an error describing why it doesn't have a key", async function() {
         const aliceClient = (new TestClient(
             "@alice:example.com", "alicedevice",
@@ -495,4 +588,103 @@ describe("MegolmDecryption", function() {
             },
         }))).rejects.toThrow("The sender has blocked you.");
     });
+
+    it("throws an error describing the lack of an olm session", async function() {
+        const aliceClient = (new TestClient(
+            "@alice:example.com", "alicedevice",
+        )).client;
+        const bobClient = (new TestClient(
+            "@bob:example.com", "bobdevice",
+        )).client;
+        await Promise.all([
+            aliceClient.initCrypto(),
+            bobClient.initCrypto(),
+        ]);
+        const bobDevice = bobClient._crypto._olmDevice;
+
+        const roomId = "!someroom";
+
+        const now = Date.now();
+
+        aliceClient._crypto._onToDeviceEvent(new MatrixEvent({
+            type: "org.matrix.room_key.withheld",
+            sender: "@bob:example.com",
+            content: {
+                algorithm: "m.megolm.v1.aes-sha2",
+                room_id: roomId,
+                session_id: "session_id",
+                sender_key: bobDevice.deviceCurve25519Key,
+                code: "m.no_olm",
+                reason: "Unable to establish a secure channel.",
+            },
+        }));
+
+        await new Promise((resolve) => {
+            setTimeout(resolve, 100);
+        });
+
+        await expect(aliceClient._crypto.decryptEvent(new MatrixEvent({
+            type: "m.room.encrypted",
+            sender: "@bob:example.com",
+            event_id: "$event",
+            room_id: roomId,
+            content: {
+                algorithm: "m.megolm.v1.aes-sha2",
+                ciphertext: "blablabla",
+                device_id: "bobdevice",
+                sender_key: bobDevice.deviceCurve25519Key,
+                session_id: "session_id",
+            },
+            origin_server_ts: now,
+        }))).rejects.toThrow("The sender was unable to establish a secure channel.");
+    });
+
+    it("throws an error to indicate a wedged olm session", async function() {
+        const aliceClient = (new TestClient(
+            "@alice:example.com", "alicedevice",
+        )).client;
+        const bobClient = (new TestClient(
+            "@bob:example.com", "bobdevice",
+        )).client;
+        await Promise.all([
+            aliceClient.initCrypto(),
+            bobClient.initCrypto(),
+        ]);
+        const bobDevice = bobClient._crypto._olmDevice;
+
+        const roomId = "!someroom";
+
+        const now = Date.now();
+
+        // pretend we got an event that we can't decrypt
+        aliceClient._crypto._onToDeviceEvent(new MatrixEvent({
+            type: "m.room.encrypted",
+            sender: "@bob:example.com",
+            content: {
+                msgtype: "m.bad.encrypted",
+                algorithm: "m.megolm.v1.aes-sha2",
+                session_id: "session_id",
+                sender_key: bobDevice.deviceCurve25519Key,
+            },
+        }));
+
+        await new Promise((resolve) => {
+            setTimeout(resolve, 100);
+        });
+
+        await expect(aliceClient._crypto.decryptEvent(new MatrixEvent({
+            type: "m.room.encrypted",
+            sender: "@bob:example.com",
+            event_id: "$event",
+            room_id: roomId,
+            content: {
+                algorithm: "m.megolm.v1.aes-sha2",
+                ciphertext: "blablabla",
+                device_id: "bobdevice",
+                sender_key: bobDevice.deviceCurve25519Key,
+                session_id: "session_id",
+            },
+            origin_server_ts: now,
+        }))).rejects.toThrow("The secure channel with the sender was corrupted.");
+    });
 });

src/crypto/OlmDevice.js

@@ -674,6 +674,18 @@ OlmDevice.prototype.matchesSession = async function(
     return matches;
 };
 
+OlmDevice.prototype.recordSessionProblem = async function(deviceKey, type, fixed) {
+    await this._cryptoStore.storeEndToEndSessionProblem(deviceKey, type, fixed);
+};
+
+OlmDevice.prototype.sessionMayHaveProblems = async function(deviceKey, timestamp) {
+    return await this._cryptoStore.getEndToEndSessionProblem(deviceKey, timestamp);
+};
+
+OlmDevice.prototype.filterOutNotifiedErrorDevices = async function(devices) {
+    return await this._cryptoStore.filterOutNotifiedErrorDevices(devices);
+};
+
 
 // Outbound group session
 // ======================

src/crypto/algorithms/base.js

@@ -159,6 +159,16 @@ class DecryptionAlgorithm {
     shareKeysWithDevice(keyRequest) {
         throw new Error("shareKeysWithDevice not supported for this DecryptionAlgorithm");
     }
+
+    /**
+     * Retry decrypting all the events from a sender that haven't been
+     * decrypted yet.
+     *
+     * @param {string} senderKey the sender's key
+     */
+    async retryDecryptionFromSender(senderKey) {
+        // ignore by default
+    }
 }
 export {DecryptionAlgorithm}; // https://github.com/jsdoc3/jsdoc/issues/1272
 

src/crypto/algorithms/megolm.js

@@ -253,8 +253,10 @@ MegolmEncryption.prototype._ensureOutboundSession = async function(
             }
         }
 
+        const errorDevices = [];
+
         await self._shareKeyWithDevices(
-            session, shareMap,
+            session, shareMap, errorDevices,
         );
 
         // are there any new blocked devices that we need to notify?
@@ -281,6 +283,18 @@ MegolmEncryption.prototype._ensureOutboundSession = async function(
             }
         }
 
+
+        const filteredErrorDevices =
+              await self._olmDevice.filterOutNotifiedErrorDevices(errorDevices);
+        for (const {userId, deviceInfo} of filteredErrorDevices) {
+            blockedMap[userId] = blockedMap[userId] || [];
+            blockedMap[userId].push({
+                code: "m.no_olm",
+                reason: WITHHELD_MESSAGES["m.no_olm"],
+                deviceInfo,
+            });
+        }
+
         // notify blocked devices that they're blocked
         await self._notifyBlockedDevices(session, blockedMap);
     }
@@ -346,10 +360,14 @@ MegolmEncryption.prototype._prepareNewSession = async function() {
  * @param {object<string, module:crypto/deviceinfo[]>} devicesByUser
  *    map from userid to list of devices
  *
+ * @param {array<object>} errorDevices
+ *    array that will be populated with the devices that can't get an
+ *    olm session for
+ *
  * @return {array<object<userid, deviceInfo>>}
  */
 MegolmEncryption.prototype._splitUserDeviceMap = function(
-    session, chainIndex, devicemap, devicesByUser,
+    session, chainIndex, devicemap, devicesByUser, errorDevices,
 ) {
     const maxUsersPerRequest = 20;
 
@@ -381,6 +399,8 @@ MegolmEncryption.prototype._splitUserDeviceMap = function(
                 // to claim a one-time-key for dead devices on every message.
                 session.markSharedWithDevice(userId, deviceId, chainIndex);
 
+                errorDevices.push({userId, deviceInfo});
+
                 // ensureOlmSessionsForUsers has already done the logging,
                 // so just skip it.
                 continue;
@@ -550,6 +570,10 @@ MegolmEncryption.prototype._sendBlockedNotificationsToDevices = async function(
         const message = Object.assign({}, payload);
         message.code = blockedInfo.code;
         message.reason = blockedInfo.reason;
+        if (message.code === "m.no_olm") {
+            delete message.room_id;
+            delete message.session_id;
+        }
 
         if (!contentMap[userId]) {
             contentMap[userId] = {};
@@ -663,8 +687,14 @@ MegolmEncryption.prototype.reshareKeyWithDevice = async function(
  *
  * @param {object<string, module:crypto/deviceinfo[]>} devicesByUser
  *    map from userid to list of devices
+ *
+ * @param {array<object>} errorDevices
+ *    array that will be populated with the devices that we can't get an
+ *    olm session for
  */
-MegolmEncryption.prototype._shareKeyWithDevices = async function(session, devicesByUser) {
+MegolmEncryption.prototype._shareKeyWithDevices = async function(
+    session, devicesByUser, errorDevices,
+) {
     const key = this._olmDevice.getOutboundGroupSessionKey(session.sessionId);
     const payload = {
         type: "m.room_key",
@@ -682,7 +712,7 @@ MegolmEncryption.prototype._shareKeyWithDevices = async function(session, device
     );
 
     const userDeviceMaps = this._splitUserDeviceMap(
-        session, key.chain_index, devicemap, devicesByUser,
+        session, key.chain_index, devicemap, devicesByUser, errorDevices,
     );
 
     for (let i = 0; i < userDeviceMaps.length; i++) {
@@ -915,6 +945,11 @@ function MegolmDecryption(params) {
 }
 utils.inherits(MegolmDecryption, base.DecryptionAlgorithm);
 
+const PROBLEM_DESCRIPTIONS = {
+    no_olm: "The sender was unable to establish a secure channel.",
+    unknown: "The secure channel with the sender was corrupted.",
+};
+
 /**
  * @inheritdoc
  *
@@ -981,6 +1016,28 @@ MegolmDecryption.prototype.decryptEvent = async function(event) {
         // event is still in the pending list; if not, a retry will have been
         // scheduled, so we needn't send out the request here.)
         this._requestKeysForEvent(event);
+
+        // See if there was a problem with the olm session at the time the
+        // event was sent.  Use a fuzz factor of 2 minutes.
+        const problem = await this._olmDevice.sessionMayHaveProblems(
+            content.sender_key, event.getTs() - 120000,
+        );
+        if (problem) {
+            let problemDescription = PROBLEM_DESCRIPTIONS[problem.type]
+                  || PROBLEM_DESCRIPTIONS.unknown;
+            if (problem.fixed) {
+                problemDescription +=
+                    " Trying to create a new secure channel and re-requesting the keys.";
+            }
+            throw new base.DecryptionError(
+                "MEGOLM_UNKNOWN_INBOUND_SESSION_ID",
+                problemDescription,
+                {
+                    session: content.sender_key + '|' + content.session_id,
+                },
+            );
+        }
+
         throw new base.DecryptionError(
             "MEGOLM_UNKNOWN_INBOUND_SESSION_ID",
             "The sender's device has not sent us the keys for this message.",
@@ -1036,11 +1093,16 @@ MegolmDecryption.prototype._requestKeysForEvent = function(event) {
  */
 MegolmDecryption.prototype._addEventToPendingList = function(event) {
     const content = event.getWireContent();
-    const k = content.sender_key + "|" + content.session_id;
-    if (!this._pendingEvents[k]) {
-        this._pendingEvents[k] = new Set();
+    const senderKey = content.sender_key;
+    const sessionId = content.session_id;
+    if (!this._pendingEvents[senderKey]) {
+        this._pendingEvents[senderKey] = new Map();
     }
-    this._pendingEvents[k].add(event);
+    const senderPendingEvents = this._pendingEvents[senderKey];
+    if (!senderPendingEvents.has(sessionId)) {
+        senderPendingEvents.set(sessionId, new Set());
+    }
+    senderPendingEvents.get(sessionId).add(event);
 };
 
 /**
@@ -1052,14 +1114,20 @@ MegolmDecryption.prototype._addEventToPendingList = function(event) {
  */
 MegolmDecryption.prototype._removeEventFromPendingList = function(event) {
     const content = event.getWireContent();
-    const k = content.sender_key + "|" + content.session_id;
-    if (!this._pendingEvents[k]) {
+    const senderKey = content.sender_key;
+    const sessionId = content.session_id;
+    const senderPendingEvents = this._pendingEvents[senderKey];
+    const pendingEvents = senderPendingEvents && senderPendingEvents.get(sessionId);
+    if (!pendingEvents) {
         return;
     }
 
-    this._pendingEvents[k].delete(event);
-    if (this._pendingEvents[k].size === 0) {
-        delete this._pendingEvents[k];
+    pendingEvents.delete(event);
+    if (pendingEvents.size === 0) {
+        senderPendingEvents.delete(senderKey);
+    }
+    if (senderPendingEvents.size === 0) {
+        delete this._pendingEvents[senderKey];
     }
 };
 
@@ -1170,11 +1238,69 @@ MegolmDecryption.prototype.onRoomKeyEvent = function(event) {
  */
 MegolmDecryption.prototype.onRoomKeyWithheldEvent = async function(event) {
     const content = event.getContent();
+    const senderKey = content.sender_key;
 
+    if (content.code === "m.no_olm") {
+        const sender = event.getSender();
+        // if the sender says that they haven't been able to establish an olm
+        // session, let's proactively establish one
+
+        // Note: after we record that the olm session has had a problem, we
+        // trigger retrying decryption for all the messages from the sender's
+        // key, so that we can update the error message to indicate the olm
+        // session problem.
+
+        if (await this._olmDevice.getSessionIdForDevice(senderKey)) {
+            // a session has already been established, so we don't need to
+            // create a new one.
+            await this._olmDevice.recordSessionProblem(senderKey, "no_olm", true);
+            this.retryDecryptionFromSender(senderKey);
+            return;
+        }
+        const device = this._crypto._deviceList.getDeviceByIdentityKey(
+            content.algorithm, senderKey,
+        );
+        if (!device) {
+            logger.info(
+                "Couldn't find device for identity key " + senderKey +
+                    ": not establishing session",
+            );
+            await this._olmDevice.recordSessionProblem(senderKey, "no_olm", false);
+            this.retryDecryptionFromSender(senderKey);
+            return;
+        }
+        await olmlib.ensureOlmSessionsForDevices(
+            this._olmDevice, this._baseApis, {[sender]: [device]}, false,
+        );
+        const encryptedContent = {
+            algorithm: olmlib.OLM_ALGORITHM,
+            sender_key: this._olmDevice.deviceCurve25519Key,
+            ciphertext: {},
+        };
+        await olmlib.encryptMessageForDevice(
+            encryptedContent.ciphertext,
+            this._userId,
+            this._deviceId,
+            this._olmDevice,
+            sender,
+            device,
+            {type: "m.dummy"},
+        );
+
+        await this._olmDevice.recordSessionProblem(senderKey, "no_olm", true);
+        this.retryDecryptionFromSender(senderKey);
+
+        await this._baseApis.sendToDevice("m.room.encrypted", {
+            [sender]: {
+                [device.deviceId]: encryptedContent,
+            },
+        });
+    } else {
         await this._olmDevice.addInboundGroupSessionWithheld(
-        content.room_id, content.sender_key, content.session_id, content.code,
+            content.room_id, senderKey, content.session_id, content.code,
             content.reason,
         );
+    }
 };
 
 /**
@@ -1320,13 +1446,20 @@ MegolmDecryption.prototype.importRoomKey = function(session) {
  * @return {Boolean} whether all messages were successfully decrypted
  */
 MegolmDecryption.prototype._retryDecryption = async function(senderKey, sessionId) {
-    const k = senderKey + "|" + sessionId;
-    const pending = this._pendingEvents[k];
+    const senderPendingEvents = this._pendingEvents[senderKey];
+    if (!senderPendingEvents) {
+        return true;
+    }
+
+    const pending = senderPendingEvents.get(sessionId);
     if (!pending) {
         return true;
     }
 
-    delete this._pendingEvents[k];
+    pending.delete(sessionId);
+    if (pending.size === 0) {
+        this._pendingEvents[senderKey];
+    }
 
     await Promise.all([...pending].map(async (ev) => {
         try {
@@ -1336,7 +1469,32 @@ MegolmDecryption.prototype._retryDecryption = async function(senderKey, sessionI
         }
     }));
 
-    return !this._pendingEvents[k];
+    // ev.attemptDecryption will re-add to this._pendingEvents if an event
+    // couldn't be decrypted
+    return !((this._pendingEvents[senderKey] || {})[sessionId]);
+};
+
+MegolmDecryption.prototype.retryDecryptionFromSender = async function(senderKey) {
+    const senderPendingEvents = this._pendingEvents[senderKey];
+    logger.warn(senderPendingEvents);
+    if (!senderPendingEvents) {
+        return true;
+    }
+
+    delete this._pendingEvents[senderKey];
+
+    await Promise.all([...senderPendingEvents].map(async ([_sessionId, pending]) => {
+        await Promise.all([...pending].map(async (ev) => {
+            try {
+                logger.warn(ev.getId());
+                await ev.attemptDecryption(this._crypto);
+            } catch (e) {
+                // don't die if something goes wrong
+            }
+        }));
+    }));
+
+    return !this._pendingEvents[senderKey];
 };
 
 base.registerAlgorithm(

src/crypto/index.js

@@ -2502,16 +2502,31 @@ Crypto.prototype._onRoomKeyEvent = function(event) {
 Crypto.prototype._onRoomKeyWithheldEvent = function(event) {
     const content = event.getContent();
 
-    if (!content.room_id || !content.session_id || !content.algorithm
-        || !content.sender_key) {
+    if ((content.code !== "m.no_olm" && (!content.room_id || !content.session_id))
+        || !content.algorithm || !content.sender_key) {
         logger.error("key withheld event is missing fields");
         return;
     }
 
+    logger.info(
+        `Got room key withheld event from ${event.getSender()} (${content.sender_key}) `
+            + `for ${content.algorithm}/${content.room_id}/${content.session_id} `
+            + `with reason ${content.code} (${content.reason})`,
+    );
+
     const alg = this._getRoomDecryptor(content.room_id, content.algorithm);
     if (alg.onRoomKeyWithheldEvent) {
         alg.onRoomKeyWithheldEvent(event);
     }
+    if (!content.room_id) {
+        // retry decryption for all events sent by the sender_key.  This will
+        // update the events to show a message indicating that the olm session was
+        // wedged.
+        const roomDecryptors = this._getRoomDecryptors(content.algorithm);
+        for (const decryptor of roomDecryptors) {
+            decryptor.retryDecryptionFromSender(content.sender_key);
+        }
+    }
 };
 
 /**
@@ -2627,6 +2642,16 @@ Crypto.prototype._onToDeviceBadEncrypted = async function(event) {
     const algorithm = content.algorithm;
     const deviceKey = content.sender_key;
 
+    // retry decryption for all events sent by the sender_key.  This will
+    // update the events to show a message indicating that the olm session was
+    // wedged.
+    const retryDecryption = () => {
+        const roomDecryptors = this._getRoomDecryptors(olmlib.MEGOLM_ALGORITHM);
+        for (const decryptor of roomDecryptors) {
+            decryptor.retryDecryptionFromSender(deviceKey);
+        }
+    };
+
     if (sender === undefined || deviceKey === undefined || deviceKey === undefined) {
         return;
     }
@@ -2640,6 +2665,8 @@ Crypto.prototype._onToDeviceBadEncrypted = async function(event) {
             "New session already forced with device " + sender + ":" + deviceKey +
             " at " + lastNewSessionForced + ": not forcing another",
         );
+        await this._olmDevice.recordSessionProblem(deviceKey, "wedged", true);
+        retryDecryption();
         return;
     }
 
@@ -2653,6 +2680,8 @@ Crypto.prototype._onToDeviceBadEncrypted = async function(event) {
             "Couldn't find device for identity key " + deviceKey +
             ": not re-establishing session",
         );
+        await this._olmDevice.recordSessionProblem(deviceKey, "wedged", false);
+        retryDecryption();
         return;
     }
     const devicesByUser = {};
@@ -2684,6 +2713,9 @@ Crypto.prototype._onToDeviceBadEncrypted = async function(event) {
         {type: "m.dummy"},
     );
 
+    await this._olmDevice.recordSessionProblem(deviceKey, "wedged", true);
+    retryDecryption();
+
     await this._baseApis.sendToDevice("m.room.encrypted", {
         [sender]: {
             [device.deviceId]: encryptedContent,
@@ -2965,6 +2997,24 @@ Crypto.prototype._getRoomDecryptor = function(roomId, algorithm) {
 };
 
 
+/**
+ * Get all the room decryptors for a given encryption algorithm.
+ *
+ * @param {string} algorithm The encryption algorithm
+ *
+ * @return {array} An array of room decryptors
+ */
+Crypto.prototype._getRoomDecryptors = function(algorithm) {
+    const decryptors = [];
+    for (const d of Object.values(this._roomDecryptors)) {
+        if (algorithm in d) {
+            decryptors.push(d[algorithm]);
+        }
+    }
+    return decryptors;
+};
+
+
 /**
  * sign the given object with our ed25519 key
  *

src/crypto/store/indexeddb-crypto-store-backend.js

@@ -19,7 +19,7 @@ limitations under the License.
 import logger from '../../logger';
 import utils from '../../utils';
 
-export const VERSION = 8;
+export const VERSION = 9;
 
 /**
  * Implementation of a CryptoStore which is backed by an existing
@@ -426,6 +426,74 @@ export class Backend {
         });
     }
 
+    async storeEndToEndSessionProblem(deviceKey, type, fixed) {
+        const txn = this._db.transaction("session_problems", "readwrite");
+        const objectStore = txn.objectStore("session_problems");
+        objectStore.put({
+            deviceKey,
+            type,
+            fixed,
+            time: Date.now(),
+        });
+        return promiseifyTxn(txn);
+    }
+
+    async getEndToEndSessionProblem(deviceKey, timestamp) {
+        let result;
+        const txn = this._db.transaction("session_problems", "readwrite");
+        const objectStore = txn.objectStore("session_problems");
+        const index = objectStore.index("deviceKey");
+        const req = index.getAll(deviceKey);
+        req.onsuccess = (event) => {
+            const problems = req.result;
+            if (!problems.length) {
+                result = null;
+                return;
+            }
+            problems.sort((a, b) => {
+                return a.time - b.time;
+            });
+            const lastProblem = problems[problems.length - 1];
+            for (const problem of problems) {
+                if (problem.time > timestamp) {
+                    result = Object.assign({}, problem, {fixed: lastProblem.fixed});
+                    return;
+                }
+            }
+            if (lastProblem.fixed) {
+                result = null;
+            } else {
+                result = lastProblem;
+            }
+        };
+        await promiseifyTxn(txn);
+        return result;
+    }
+
+    // FIXME: we should probably prune this when devices get deleted
+    async filterOutNotifiedErrorDevices(devices) {
+        const txn = this._db.transaction("notified_error_devices", "readwrite");
+        const objectStore = txn.objectStore("notified_error_devices");
+
+        const ret = [];
+
+        await Promise.all(devices.map((device) => {
+            return new Promise((resolve) => {
+                const {userId, deviceInfo} = device;
+                const getReq = objectStore.get([userId, deviceInfo.deviceId]);
+                getReq.onsuccess = function() {
+                    if (!getReq.result) {
+                        objectStore.put({userId, deviceId: deviceInfo.deviceId});
+                        ret.push(device);
+                    }
+                    resolve();
+                };
+            });
+        }));
+
+        return ret;
+    }
+
     // Inbound group sessions
 
     getEndToEndInboundGroupSession(senderCurve25519Key, sessionId, txn, func) {
@@ -699,6 +767,16 @@ export function upgradeDatabase(db, oldVersion) {
             keyPath: ["senderCurve25519Key", "sessionId"],
         });
     }
+    if (oldVersion < 9) {
+        const problemsStore = db.createObjectStore("session_problems", {
+            keyPath: ["deviceKey", "time"],
+        });
+        problemsStore.createIndex("deviceKey", "deviceKey");
+
+        db.createObjectStore("notified_error_devices", {
+            keyPath: ["userId", "deviceId"],
+        });
+    }
     // Expand as needed.
 }
 

src/crypto/store/indexeddb-crypto-store.js

@@ -409,6 +409,24 @@ export default class IndexedDBCryptoStore {
         });
     }
 
+    storeEndToEndSessionProblem(deviceKey, type, fixed) {
+        return this._backendPromise.then(async (backend) => {
+            await backend.storeEndToEndSessionProblem(deviceKey, type, fixed);
+        });
+    }
+
+    getEndToEndSessionProblem(deviceKey, timestamp) {
+        return this._backendPromise.then(async (backend) => {
+            return await backend.getEndToEndSessionProblem(deviceKey, timestamp);
+        });
+    }
+
+    filterOutNotifiedErrorDevices(devices) {
+        return this._backendPromise.then(async (backend) => {
+            return await backend.filterOutNotifiedErrorDevices(devices);
+        });
+    }
+
     // Inbound group sessions
 
     /**

src/crypto/store/localStorage-crypto-store.js

@@ -31,6 +31,7 @@ import MemoryCryptoStore from './memory-crypto-store';
 const E2E_PREFIX = "crypto.";
 const KEY_END_TO_END_ACCOUNT = E2E_PREFIX + "account";
 const KEY_CROSS_SIGNING_KEYS = E2E_PREFIX + "cross_signing_keys";
+const KEY_NOTIFIED_ERROR_DEVICES = E2E_PREFIX + "notified_error_devices";
 const KEY_DEVICE_DATA = E2E_PREFIX + "device_data";
 const KEY_INBOUND_SESSION_PREFIX = E2E_PREFIX + "inboundgroupsessions/";
 const KEY_INBOUND_SESSION_WITHHELD_PREFIX = E2E_PREFIX + "inboundgroupsessions.withheld/";
@@ -41,6 +42,10 @@ function keyEndToEndSessions(deviceKey) {
     return E2E_PREFIX + "sessions/" + deviceKey;
 }
 
+function keyEndToEndSessionProblems(deviceKey) {
+    return E2E_PREFIX + "session.problems/" + deviceKey;
+}
+
 function keyEndToEndInboundGroupSession(senderKey, sessionId) {
     return KEY_INBOUND_SESSION_PREFIX + senderKey + "/" + sessionId;
 }
@@ -128,6 +133,58 @@ export default class LocalStorageCryptoStore extends MemoryCryptoStore {
         );
     }
 
+    async storeEndToEndSessionProblem(deviceKey, type, fixed) {
+        const key = keyEndToEndSessionProblems(deviceKey);
+        const problems = getJsonItem(this.store, key) || [];
+        problems.push({type, fixed, time: Date.now()});
+        problems.sort((a, b) => {
+            return a.time - b.time;
+        });
+        setJsonItem(this.store, key, problems);
+    }
+
+    async getEndToEndSessionProblem(deviceKey, timestamp) {
+        const key = keyEndToEndSessionProblems(deviceKey);
+        const problems = getJsonItem(this.store, key) || [];
+        if (!problems.length) {
+            return null;
+        }
+        const lastProblem = problems[problems.length - 1];
+        for (const problem of problems) {
+            if (problem.time > timestamp) {
+                return Object.assign({}, problem, {fixed: lastProblem.fixed});
+            }
+        }
+        if (lastProblem.fixed) {
+            return null;
+        } else {
+            return lastProblem;
+        }
+    }
+
+    async filterOutNotifiedErrorDevices(devices) {
+        const notifiedErrorDevices =
+              getJsonItem(this.store, KEY_NOTIFIED_ERROR_DEVICES) || {};
+        const ret = [];
+
+        for (const device of devices) {
+            const {userId, deviceInfo} = device;
+            if (userId in notifiedErrorDevices) {
+                if (!(deviceInfo.deviceId in notifiedErrorDevices[userId])) {
+                    ret.push(device);
+                    notifiedErrorDevices[userId][deviceInfo.deviceId] = true;
+                }
+            } else {
+                ret.push(device);
+                notifiedErrorDevices[userId] = {[deviceInfo.deviceId]: true };
+            }
+        }
+
+        setJsonItem(this.store, KEY_NOTIFIED_ERROR_DEVICES, notifiedErrorDevices);
+
+        return ret;
+    }
+
     // Inbound Group Sessions
 
     getEndToEndInboundGroupSession(senderCurve25519Key, sessionId, txn, func) {

src/crypto/store/memory-crypto-store.js

@@ -36,6 +36,10 @@ export default class MemoryCryptoStore {
 
         // Map of {devicekey -> {sessionId -> session pickle}}
         this._sessions = {};
+        // Map of {devicekey -> array of problems}
+        this._sessionProblems = {};
+        // Map of {userId -> deviceId -> true}
+        this._notifiedErrorDevices = {};
         // Map of {senderCurve25519Key+'/'+sessionId -> session data object}
         this._inboundGroupSessions = {};
         this._inboundGroupSessionsWithheld = {};
@@ -275,6 +279,53 @@ export default class MemoryCryptoStore {
         deviceSessions[sessionId] = sessionInfo;
     }
 
+    async storeEndToEndSessionProblem(deviceKey, type, fixed) {
+        const problems = this._sessionProblems[deviceKey]
+              = this._sessionProblems[deviceKey] || [];
+        problems.push({type, fixed, time: Date.now()});
+        problems.sort((a, b) => {
+            return a.time - b.time;
+        });
+    }
+
+    async getEndToEndSessionProblem(deviceKey, timestamp) {
+        const problems = this._sessionProblems[deviceKey] || [];
+        if (!problems.length) {
+            return null;
+        }
+        const lastProblem = problems[problems.length - 1];
+        for (const problem of problems) {
+            if (problem.time > timestamp) {
+                return Object.assign({}, problem, {fixed: lastProblem.fixed});
+            }
+        }
+        if (lastProblem.fixed) {
+            return null;
+        } else {
+            return lastProblem;
+        }
+    }
+
+    async filterOutNotifiedErrorDevices(devices) {
+        const notifiedErrorDevices = this._notifiedErrorDevices;
+        const ret = [];
+
+        for (const device of devices) {
+            const {userId, deviceInfo} = device;
+            if (userId in notifiedErrorDevices) {
+                if (!(deviceInfo.deviceId in notifiedErrorDevices[userId])) {
+                    ret.push(device);
+                    notifiedErrorDevices[userId][deviceInfo.deviceId] = true;
+                }
+            } else {
+                ret.push(device);
+                notifiedErrorDevices[userId] = {[deviceInfo.deviceId]: true };
+            }
+        }
+
+        return ret;
+    }
+
     // Inbound Group Sessions
 
     getEndToEndInboundGroupSession(senderCurve25519Key, sessionId, txn, func) {