From 0545c1f0c52c6c3d7025040298d4546ddfe41e72 Mon Sep 17 00:00:00 2001
From: Bruno Windels <brunow@matrix.org>
Date: Wed, 2 Sep 2020 17:37:48 +0200
Subject: [PATCH] extract verifying a signed object from the device tracker

---
 src/matrix/e2ee/DeviceTracker.js | 27 +++++----------------------
 src/matrix/e2ee/common.js        | 23 +++++++++++++++++++++++
 2 files changed, 28 insertions(+), 22 deletions(-)

diff --git a/src/matrix/e2ee/DeviceTracker.js b/src/matrix/e2ee/DeviceTracker.js
index b085be80..095730ff 100644
--- a/src/matrix/e2ee/DeviceTracker.js
+++ b/src/matrix/e2ee/DeviceTracker.js
@@ -14,13 +14,11 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import anotherjson from "../../../lib/another-json/index.js";
+import {verifyEd25519Signature, SIGNATURE_ALGORITHM} from "./common.js";
 
 const TRACKING_STATUS_OUTDATED = 0;
 const TRACKING_STATUS_UPTODATE = 1;
 
-const DEVICE_KEYS_SIGNATURE_ALGORITHM = "ed25519";
-
 // map 1 device from /keys/query response to DeviceIdentity
 function deviceKeysAsDeviceIdentity(deviceSection) {
     const deviceId = deviceSection["device_id"];
@@ -200,7 +198,7 @@ export class DeviceTracker {
                 if (deviceIdOnKeys !== deviceId) {
                     return false;
                 }
-                return this._verifyUserDeviceKeys(deviceKeys);
+                return this._hasValidSignature(deviceKeys);
             });
             const verifiedKeys = verifiedEntries.map(([, deviceKeys]) => deviceKeys);
             return {userId, verifiedKeys};
@@ -208,26 +206,11 @@ export class DeviceTracker {
         return verifiedKeys;
     }
 
-    _verifyUserDeviceKeys(deviceSection) {
+    _hasValidSignature(deviceSection) {
         const deviceId = deviceSection["device_id"];
         const userId = deviceSection["user_id"];
-        const clone = Object.assign({}, deviceSection);
-        delete clone.unsigned;
-        delete clone.signatures;
-        const canonicalJson = anotherjson.stringify(clone);
-        const key = deviceSection?.keys?.[`${DEVICE_KEYS_SIGNATURE_ALGORITHM}:${deviceId}`];
-        const signature = deviceSection?.signatures?.[userId]?.[`${DEVICE_KEYS_SIGNATURE_ALGORITHM}:${deviceId}`];
-        try {
-            if (!signature) {
-                throw new Error("no signature");
-            }
-            // throws when signature is invalid
-            this._olmUtil.ed25519_verify(key, canonicalJson, signature);
-            return true;
-        } catch (err) {
-            console.warn("Invalid device signature, ignoring device.", key, canonicalJson, signature, err);
-            return false;
-        }
+        const ed25519Key = deviceSection?.keys?.[`${SIGNATURE_ALGORITHM}:${deviceId}`];
+        return verifyEd25519Signature(this._olmUtil, userId, deviceId, ed25519Key, deviceSection);
     }
 
     /**
diff --git a/src/matrix/e2ee/common.js b/src/matrix/e2ee/common.js
index c5e7399f..9b3b2f26 100644
--- a/src/matrix/e2ee/common.js
+++ b/src/matrix/e2ee/common.js
@@ -14,6 +14,8 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
+import anotherjson from "../../../lib/another-json/index.js";
+
 // use common prefix so it's easy to clear properties that are not e2ee related during session clear
 export const SESSION_KEY_PREFIX = "e2ee:";
 export const OLM_ALGORITHM = "m.olm.v1.curve25519-aes-sha2";
@@ -27,3 +29,24 @@ export class DecryptionError extends Error {
         this.details = detailsObj;
     }
 }
+
+export const SIGNATURE_ALGORITHM = "ed25519";
+
+export function verifyEd25519Signature(olmUtil, userId, deviceOrKeyId, ed25519Key, value) {
+    const clone = Object.assign({}, value);
+    delete clone.unsigned;
+    delete clone.signatures;
+    const canonicalJson = anotherjson.stringify(clone);
+    const signature = value?.signatures?.[userId]?.[`${SIGNATURE_ALGORITHM}:${deviceOrKeyId}`];
+    try {
+        if (!signature) {
+            throw new Error("no signature");
+        }
+        // throws when signature is invalid
+        this._olmUtil.ed25519_verify(ed25519Key, canonicalJson, signature);
+        return true;
+    } catch (err) {
+        console.warn("Invalid signature, ignoring.", ed25519Key, canonicalJson, signature, err);
+        return false;
+    }
+}