From 9e1ba992e3d97664e801e10a5346f65de9bf6c8b Mon Sep 17 00:00:00 2001
From: Bruno Windels <brunow@matrix.org>
Date: Thu, 9 Apr 2020 12:24:29 +0200
Subject: [PATCH 1/4] Clear cross-signing keys when detecting the keys have
 changed

---
 src/crypto/CrossSigning.js |  5 +++++
 src/crypto/index.js        | 20 ++++++++++++++------
 2 files changed, 19 insertions(+), 6 deletions(-)

diff --git a/src/crypto/CrossSigning.js b/src/crypto/CrossSigning.js
index c0633e958af..732f6070e51 100644
--- a/src/crypto/CrossSigning.js
+++ b/src/crypto/CrossSigning.js
@@ -310,6 +310,11 @@ export class CrossSigningInfo extends EventEmitter {
         }
     }
 
+    /** unsets the keys, used when another session has reset the keys, to disable cross-signing */
+    clearKeys() {
+        this.keys = {};
+    }
+
     setKeys(keys) {
         const signingKeys = {};
         if (keys.master) {
diff --git a/src/crypto/index.js b/src/crypto/index.js
index b8b02fba3f2..cf8f874f26c 100644
--- a/src/crypto/index.js
+++ b/src/crypto/index.js
@@ -1145,13 +1145,17 @@ Crypto.prototype._onDeviceListUserCrossSigningUpdated = async function(userId) {
             // If it's not changed, just make sure everything is up to date
             await this.checkOwnCrossSigningTrust();
         } else {
-            this.emit("crossSigning.keysChanged", {});
             // We'll now be in a state where cross-signing on the account is not trusted
             // because our locally stored cross-signing keys will not match the ones
-            // on the server for our account. The app must call checkOwnCrossSigningTrust()
-            // to fix this.
-            // XXX: Do we need to do something to emit events saying every device has become
-            // untrusted?
+            // on the server for our account. So we clear our own stored cross-signing keys,
+            // effectively disabling cross-signing until the user gets verified by the device
+            // that reset the keys
+            this._storeTrustedSelfKeys(null);
+            // XXX this event doesn't seem to be used anywhere
+            // the DeviceListener in react-sdl does recheck though,
+            // as `crypto.devicesUpdated`` and `accountData` are
+            // emitted on the client when this case happens.
+            this.emit("crossSigning.keysChanged", {});
         }
     } else {
         await this._checkDeviceVerifications(userId);
@@ -1307,7 +1311,11 @@ Crypto.prototype.checkOwnCrossSigningTrust = async function() {
  * @param {object} keys The new trusted set of keys
  */
 Crypto.prototype._storeTrustedSelfKeys = async function(keys) {
-    this._crossSigningInfo.setKeys(keys);
+    if (keys) {
+        this._crossSigningInfo.setKeys(keys);
+    } else {
+        this._crossSigningInfo.clearKeys();
+    }
     await this._cryptoStore.doTxn(
         'readwrite', [IndexedDBCryptoStore.STORE_ACCOUNT],
         (txn) => {

From c8fb4af369133c8994a85d643be2af14fb2cb754 Mon Sep 17 00:00:00 2001
From: Bruno Windels <brunow@matrix.org>
Date: Thu, 9 Apr 2020 13:13:17 +0200
Subject: [PATCH 2/4] fix comment style

---
 src/crypto/CrossSigning.js | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/src/crypto/CrossSigning.js b/src/crypto/CrossSigning.js
index 732f6070e51..6d86d1bd9ce 100644
--- a/src/crypto/CrossSigning.js
+++ b/src/crypto/CrossSigning.js
@@ -310,7 +310,9 @@ export class CrossSigningInfo extends EventEmitter {
         }
     }
 
-    /** unsets the keys, used when another session has reset the keys, to disable cross-signing */
+    /**
+     * unsets the keys, used when another session has reset the keys, to disable cross-signing
+     */
     clearKeys() {
         this.keys = {};
     }

From 65dd56f53a13fc6495a47c487527c0736d3f77ad Mon Sep 17 00:00:00 2001
From: Bruno Windels <brunow@matrix.org>
Date: Thu, 9 Apr 2020 13:27:13 +0200
Subject: [PATCH 3/4] remove obsolete comment

---
 src/crypto/index.js | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/src/crypto/index.js b/src/crypto/index.js
index cf8f874f26c..ebe5bcd714d 100644
--- a/src/crypto/index.js
+++ b/src/crypto/index.js
@@ -1151,10 +1151,6 @@ Crypto.prototype._onDeviceListUserCrossSigningUpdated = async function(userId) {
             // effectively disabling cross-signing until the user gets verified by the device
             // that reset the keys
             this._storeTrustedSelfKeys(null);
-            // XXX this event doesn't seem to be used anywhere
-            // the DeviceListener in react-sdl does recheck though,
-            // as `crypto.devicesUpdated`` and `accountData` are
-            // emitted on the client when this case happens.
             this.emit("crossSigning.keysChanged", {});
         }
     } else {

From 70071eef410f5fc09dabea76847c0d02afc638a0 Mon Sep 17 00:00:00 2001
From: Bruno Windels <brunow@matrix.org>
Date: Thu, 9 Apr 2020 14:09:51 +0200
Subject: [PATCH 4/4] also emit user trust has changed

---
 src/crypto/index.js | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/src/crypto/index.js b/src/crypto/index.js
index ebe5bcd714d..29123ee7f16 100644
--- a/src/crypto/index.js
+++ b/src/crypto/index.js
@@ -1151,7 +1151,12 @@ Crypto.prototype._onDeviceListUserCrossSigningUpdated = async function(userId) {
             // effectively disabling cross-signing until the user gets verified by the device
             // that reset the keys
             this._storeTrustedSelfKeys(null);
+            // emit cross-signing has been disabled
             this.emit("crossSigning.keysChanged", {});
+            // as the trust for our own user has changed,
+            // also emit an event for this
+            this.emit("userTrustStatusChanged",
+                this._userId, this.checkUserTrust(userId));
         }
     } else {
         await this._checkDeviceVerifications(userId);