From 1f0c6a6dc9f14137b8b7348f0d33aff5b92a725f Mon Sep 17 00:00:00 2001
From: Florian Duros <florianduros@element.io>
Date: Tue, 21 Feb 2023 17:13:43 +0100
Subject: [PATCH] Add easy way to determine if the decryption failure is due to
 "DecryptionError: The sender has disabled encrypting to unverified devices."
 (#3167)

* Add isEncryptedDisabledForUnverifiedDevices in event.ts

* Add Tests

* Add isEncryptedDisabledForUnverifiedDevices properties to event

* Use WITHHELD_MESSAGES instead of hardcoded string

* Use getter instead of function

* Add documentation
---
 spec/unit/models/event.spec.ts | 19 +++++++++++++++++++
 src/@types/crypto.ts           |  4 ++++
 src/models/event.ts            | 17 +++++++++++++++++
 3 files changed, 40 insertions(+)

diff --git a/spec/unit/models/event.spec.ts b/spec/unit/models/event.spec.ts
index 244f9214521..dd21893a52c 100644
--- a/spec/unit/models/event.spec.ts
+++ b/spec/unit/models/event.spec.ts
@@ -126,12 +126,31 @@ describe("MatrixEvent", () => {
             expect(encryptedEvent.isEncrypted()).toBeTruthy();
             expect(encryptedEvent.isBeingDecrypted()).toBeFalsy();
             expect(encryptedEvent.isDecryptionFailure()).toBeTruthy();
+            expect(encryptedEvent.isEncryptedDisabledForUnverifiedDevices).toBeFalsy();
             expect(encryptedEvent.getContent()).toEqual({
                 msgtype: "m.bad.encrypted",
                 body: "** Unable to decrypt: Error: test error **",
             });
         });
 
+        it(`should report "DecryptionError: The sender has disabled encrypting to unverified devices."`, async () => {
+            const crypto = {
+                decryptEvent: jest
+                    .fn()
+                    .mockRejectedValue("DecryptionError: The sender has disabled encrypting to unverified devices."),
+            } as unknown as Crypto;
+
+            await encryptedEvent.attemptDecryption(crypto);
+            expect(encryptedEvent.isEncrypted()).toBeTruthy();
+            expect(encryptedEvent.isBeingDecrypted()).toBeFalsy();
+            expect(encryptedEvent.isDecryptionFailure()).toBeTruthy();
+            expect(encryptedEvent.isEncryptedDisabledForUnverifiedDevices).toBeTruthy();
+            expect(encryptedEvent.getContent()).toEqual({
+                msgtype: "m.bad.encrypted",
+                body: "** Unable to decrypt: DecryptionError: The sender has disabled encrypting to unverified devices. **",
+            });
+        });
+
         it("should retry decryption if a retry is queued", async () => {
             const eventAttemptDecryptionSpy = jest.spyOn(encryptedEvent, "attemptDecryption");
 
diff --git a/src/@types/crypto.ts b/src/@types/crypto.ts
index a81ea57da0c..77118401436 100644
--- a/src/@types/crypto.ts
+++ b/src/@types/crypto.ts
@@ -44,6 +44,10 @@ export interface IEventDecryptionResult {
      */
     claimedEd25519Key?: string;
     untrusted?: boolean;
+    /**
+     * The sender doesn't authorize the unverified devices to decrypt his messages
+     */
+    encryptedDisabledForUnverifiedDevices?: boolean;
 }
 
 interface Extensible {
diff --git a/src/models/event.ts b/src/models/event.ts
index 5e0c1276123..d4baa5b224b 100644
--- a/src/models/event.ts
+++ b/src/models/event.ts
@@ -36,6 +36,7 @@ import { TypedEventEmitter } from "./typed-event-emitter";
 import { EventStatus } from "./event-status";
 import { DecryptionError } from "../crypto/algorithms";
 import { CryptoBackend } from "../common-crypto/CryptoBackend";
+import { WITHHELD_MESSAGES } from "../crypto/OlmDevice";
 
 export { EventStatus } from "./event-status";
 
@@ -272,6 +273,12 @@ export class MatrixEvent extends TypedEventEmitter<MatrixEventEmittedEvents, Mat
     private thread?: Thread;
     private threadId?: string;
 
+    /*
+     * True if this event is an encrypted event which we failed to decrypt, the receiver's device is unverified and
+     * the sender has disabled encrypting to unverified devices.
+     */
+    private encryptedDisabledForUnverifiedDevices = false;
+
     /* Set an approximate timestamp for the event relative the local clock.
      * This will inherently be approximate because it doesn't take into account
      * the time between the server putting the 'age' field on the event as it sent
@@ -704,6 +711,14 @@ export class MatrixEvent extends TypedEventEmitter<MatrixEventEmittedEvents, Mat
         return this.clearEvent?.content?.msgtype === "m.bad.encrypted";
     }
 
+    /*
+     * True if this event is an encrypted event which we failed to decrypt, the receiver's device is unverified and
+     * the sender has disabled encrypting to unverified devices.
+     */
+    public get isEncryptedDisabledForUnverifiedDevices(): boolean {
+        return this.isDecryptionFailure() && this.encryptedDisabledForUnverifiedDevices;
+    }
+
     public shouldAttemptDecryption(): boolean {
         if (this.isRedacted()) return false;
         if (this.isBeingDecrypted()) return false;
@@ -899,6 +914,7 @@ export class MatrixEvent extends TypedEventEmitter<MatrixEventEmittedEvents, Mat
                     body: "** Unable to decrypt: " + reason + " **",
                 },
             },
+            encryptedDisabledForUnverifiedDevices: reason === `DecryptionError: ${WITHHELD_MESSAGES["m.unverified"]}`,
         };
     }
 
@@ -920,6 +936,7 @@ export class MatrixEvent extends TypedEventEmitter<MatrixEventEmittedEvents, Mat
         this.claimedEd25519Key = decryptionResult.claimedEd25519Key ?? null;
         this.forwardingCurve25519KeyChain = decryptionResult.forwardingCurve25519KeyChain || [];
         this.untrusted = decryptionResult.untrusted || false;
+        this.encryptedDisabledForUnverifiedDevices = decryptionResult.encryptedDisabledForUnverifiedDevices || false;
         this.invalidateExtensibleEvent();
     }