Merge pull request #1312 from matrix-org/bwindels/fixresetkeys

Clear cross-signing keys when detecting the keys have changed
matrix-org · Apr 9, 2020 · d1c9030 · d1c9030
2 parents bad09fe + 70071ee
commit d1c9030
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Showing 2 changed files with 22 additions and 6 deletions.
diff --git a/src/crypto/CrossSigning.js b/src/crypto/CrossSigning.js
@@ -310,6 +310,13 @@ 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
@@ -1145,13 +1145,18 @@ 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);
+            // 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);
@@ -1307,7 +1312,11 @@ 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) => {