Display a warning when an unverified user's identity changes

res/css/_components.pcss

@@ -319,6 +319,7 @@
 @import "./views/rooms/_ThirdPartyMemberInfo.pcss";
 @import "./views/rooms/_ThreadSummary.pcss";
 @import "./views/rooms/_TopUnreadMessagesBar.pcss";
+@import "./views/rooms/_UserIdentityWarning.pcss";
 @import "./views/rooms/_VoiceRecordComposerTile.pcss";
 @import "./views/rooms/_WhoIsTypingTile.pcss";
 @import "./views/rooms/wysiwyg_composer/_EditWysiwygComposer.pcss";

res/css/views/rooms/_UserIdentityWarning.pcss

@@ -0,0 +1,26 @@
+/*
+Copyright 2024 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only
+Please see LICENSE files in the repository root for full details.
+*/
+
+.mx_UserIdentityWarning {
+    border-top: 1px solid $separator;
+    padding-top: 5px;
+    margin-left: calc(-42px + var(--RoomView_MessageList-padding));
+    display: flex;
+    align-items: center;
+
+    .mx_BaseAvatar {
+        margin-left: 8px;
+    }
+    .mx_UserIdentityWarning_main {
+        margin-left: 24px;
+        flex-grow: 1;
+    }
+}
+
+.mx_MessageComposer.mx_MessageComposer--compact > .mx_UserIdentityWarning {
+    margin-left: calc(-25px + var(--RoomView_MessageList-padding));
+}

src/components/views/rooms/MessageComposer.tsx

@@ -30,6 +30,7 @@ import E2EIcon from "./E2EIcon";
 import SettingsStore from "../../../settings/SettingsStore";
 import { aboveLeftOf, MenuProps } from "../../structures/ContextMenu";
 import ReplyPreview from "./ReplyPreview";
+import UserIdentityWarning from "./UserIdentityWarning";
 import { UPDATE_EVENT } from "../../../stores/AsyncStore";
 import VoiceRecordComposerTile from "./VoiceRecordComposerTile";
 import { VoiceRecordingStore } from "../../../stores/VoiceRecordingStore";
@@ -671,6 +672,7 @@ export class MessageComposer extends React.Component<IProps, IState> {
                 <div className={classes} ref={this.ref} role="region" aria-label={_t("a11y|message_composer")}>
                     {recordingTooltip}
                     <div className="mx_MessageComposer_wrapper">
+                        <UserIdentityWarning room={this.props.room} />
                         <ReplyPreview
                             replyToEvent={this.props.replyToEvent}
                             permalinkCreator={this.props.permalinkCreator}

src/components/views/rooms/UserIdentityWarning.tsx

@@ -0,0 +1,308 @@
+/*
+Copyright 2024 New Vector Ltd.
+
+SPDX-License-Identifier: AGPL-3.0-only OR GPL-3.0-only
+Please see LICENSE files in the repository root for full details.
+*/
+
+import React from "react";
+import {
+    CryptoEvent,
+    EventType,
+    KnownMembership,
+    MatrixEvent,
+    Room,
+    RoomStateEvent,
+    RoomMember,
+} from "matrix-js-sdk/src/matrix";
+import { logger } from "matrix-js-sdk/src/logger";
+
+import type { CryptoApi, UserVerificationStatus } from "matrix-js-sdk/src/crypto-api";
+import { _t } from "../../../languageHandler";
+import AccessibleButton, { ButtonEvent } from "../elements/AccessibleButton";
+import MemberAvatar from "../avatars/MemberAvatar";
+import { MatrixClientPeg } from "../../../MatrixClientPeg";
+import { SDKContext } from "../../../contexts/SDKContext";
+
+interface IProps {
+    // The current room being viewed.
+    room: Room;
+}
+
+interface IState {
+    // The current room member that we are prompting the user to approve.
+    currentPrompt: RoomMember | undefined;
+}
+
+// Does the given user's identity need to be approved?
+async function userNeedsApproval(crypto: CryptoApi, userId: string): Promise<boolean> {
+    const verificationStatus = await crypto.getUserVerificationStatus(userId);
+    return verificationStatus.needsUserApproval;
+}
+
+/**
+ * Displays a banner warning when there is an issue with a user's identity.
+ *
+ * Warns when an unverified user's identity has changed, and gives the user a
+ * button to acknowledge the change.
+ */
+export default class UserIdentityWarning extends React.Component<IProps, IState> {
+    // Which room members need their identity approved.
+    private membersNeedingApproval: Map<string, RoomMember>;
+    // Whether we got a verification status update while we were fetching a
+    // user's verification status.
+    //
+    // We set the entry for a user to `false` when we fetch a user's
+    // verification status, and remove the user's entry when we are done
+    // fetching.  When we receive a verification status update, if the entry for
+    // the user is `false`, we set it to `true`.  After we have finished
+    // fetching the user's verification status, if the entry for the user is
+    // `true`, rather than `false`, we know that we got an update, and so we
+    // discard the value that we fetched.  We always use the value from the
+    // update and consider it as the most up-to-date version.  If the fetched
+    // value is more up-to-date, then we should be getting a new update soon
+    // with the newer value, so it will fix itself in the end.
+    private gotVerificationStatusUpdate: Map<string, boolean>;
+    private mounted: boolean;
+    private initialised: boolean;
+    public constructor(props: IProps, context: React.ContextType<typeof SDKContext>) {
+        super(props, context);
+        this.state = {
+            currentPrompt: undefined,
+        };
+        this.membersNeedingApproval = new Map();
+        this.gotVerificationStatusUpdate = new Map();
+        this.mounted = true;
+        this.initialised = false;
+        this.addListeners();
+    }
+
+    public componentDidMount(): void {
+        if (!MatrixClientPeg.safeGet().getCrypto()) return;
+        if (this.props.room.hasEncryptionStateEvent()) {
+            this.initialise().catch((e) => {
+                logger.error("Error initialising UserIdentityWarning:", e);
+            });
+        }
+    }
+
+    public componentWillUnmount(): void {
+        this.mounted = false;
+        this.removeListeners();
+    }
+
+    // Select a new user to display a warning for.  This is called after the
+    // current prompted user no longer needs their identity approved.
+    private selectCurrentPrompt(): void {
+        if (this.membersNeedingApproval.size === 0) {
+            this.setState({
+                currentPrompt: undefined,
+            });
+            return;
+        }
+        // We return the user with the smallest user ID.
+        const keys = Array.from(this.membersNeedingApproval.keys()).sort((a, b) => a.localeCompare(b));
+        this.setState({
+            currentPrompt: this.membersNeedingApproval.get(keys[0]!),
+        });
+    }
+
+    // Initialise the component.  Get the room members, check which ones need
+    // their identity approved, and pick one to display.
+    public async initialise(): Promise<void> {
+        if (!this.mounted || this.initialised) {
+            return;
+        }
+        this.initialised = true;
+
+        const crypto = MatrixClientPeg.safeGet().getCrypto()!;
+        const members = await this.props.room.getEncryptionTargetMembers();
+        if (!this.mounted) {
+            return;
+        }
+
+        for (const member of members) {
+            const userId = member.userId;
+            if (this.gotVerificationStatusUpdate.has(userId)) {
+                // We're already checking their verification status, so we don't
+                // need to do anything here.
+                continue;
+            }
+            this.gotVerificationStatusUpdate.set(userId, false);
+            if (await userNeedsApproval(crypto, userId)) {
+                if (
+                    !this.membersNeedingApproval.has(userId) &&
+                    this.gotVerificationStatusUpdate.get(userId) === false
+                ) {
+                    this.membersNeedingApproval.set(userId, member);
+                }
+            }
+            this.gotVerificationStatusUpdate.delete(userId);
+        }
+        if (!this.mounted) {
+            return;
+        }
+
+        this.selectCurrentPrompt();
+    }
+
+    private addMemberNeedingApproval(userId: string): void {
+        if (userId === MatrixClientPeg.safeGet().getUserId()) {
+            // We always skip our own user, because we can't pin our own identity.
+            return;
+        }
+        const member = this.props.room.getMember(userId);
+        if (member) {
+            this.membersNeedingApproval.set(userId, member);
+            if (!this.state.currentPrompt) {
+                // If we're not currently displaying a prompt, then we should
+                // display a prompt for this user.
+                this.selectCurrentPrompt();
+            }
+        }
+    }
+
+    private removeMemberNeedingApproval(userId: string): void {
+        this.membersNeedingApproval.delete(userId);
+
+        // If we removed the currently displayed user, we need to pick a new one
+        // to display.
+        if (this.state.currentPrompt?.userId === userId) {
+            this.selectCurrentPrompt();
+        }
+    }
+
+    private addListeners(): void {
+        const cli = MatrixClientPeg.safeGet();
+        cli.on(CryptoEvent.UserTrustStatusChanged, this.onUserTrustStatusChanged);
+        cli.on(RoomStateEvent.Events, this.onRoomStateEvent);
+    }
+
+    private removeListeners(): void {
+        const cli = MatrixClientPeg.get();
+        if (cli) {
+            cli.removeListener(CryptoEvent.UserTrustStatusChanged, this.onUserTrustStatusChanged);
+            cli.removeListener(RoomStateEvent.Events, this.onRoomStateEvent);
+        }
+    }
+
+    private onUserTrustStatusChanged = (userId: string, verificationStatus: UserVerificationStatus): void => {
+        // Handle a change in user trust.  If the user's identity now needs
+        // approval, make sure that a warning is shown.  If the user's identity
+        // doesn't need approval, remove the warning (if any).
+
+        if (!this.initialised) {
+            return;
+        }
+
+        if (this.gotVerificationStatusUpdate.has(userId)) {
+            this.gotVerificationStatusUpdate.set(userId, true);
+        }
+
+        if (verificationStatus.needsUserApproval) {
+            this.addMemberNeedingApproval(userId);
+        } else {
+            this.removeMemberNeedingApproval(userId);
+        }
+    };
+
+    private onRoomStateEvent = async (event: MatrixEvent): Promise<void> => {
+        if (event.getRoomId() !== this.props.room.roomId) {
+            return;
+        }
+
+        const eventType = event.getType();
+        if (eventType === EventType.RoomEncryption && event.getStateKey() === "") {
+            // Room is now encrypted, so we can initialise the component.
+            return this.initialise().catch((e) => {
+                logger.error("Error initialising UserIdentityWarning:", e);
+            });
+        } else if (eventType !== EventType.RoomMember) {
+            return;
+        }
+
+        if (!this.initialised) {
+            return;
+        }
+
+        const userId = event.getStateKey();
+
+        if (!userId) return;
+
+        if (
+            event.getContent().membership === KnownMembership.Join ||
+            (event.getContent().membership === KnownMembership.Join && this.props.room.shouldEncryptForInvitedMembers())
+        ) {
+            // Someone's membership changed and we will now encrypt to them.  If
+            // their identity needs approval, show a warning.
+            if (this.gotVerificationStatusUpdate.has(userId)) {
+                // We're already checking their verification status, so we don't
+                // need to do anything here.
+                return;
+            }
+            this.gotVerificationStatusUpdate.set(userId, false);
+            const crypto = MatrixClientPeg.safeGet().getCrypto()!;
+            if (await userNeedsApproval(crypto, userId)) {
+                if (
+                    !this.membersNeedingApproval.has(userId) &&
+                    this.gotVerificationStatusUpdate.get(userId) === false
+                ) {
+                    this.addMemberNeedingApproval(userId);
+                }
+            }
+            this.gotVerificationStatusUpdate.delete(userId);
+        } else {
+            // Someone's membership changed and we no longer encrypt to them.
+            // If we're showing a warning about them, we don't need to any more.
+            this.removeMemberNeedingApproval(userId);
+        }
+    };
+
+    // Callback for when the user hits the "OK" button
+    public confirmIdentity = async (ev: ButtonEvent): Promise<void> => {
+        if (this.state.currentPrompt) {
+            await MatrixClientPeg.safeGet().getCrypto()!.pinCurrentUserIdentity(this.state.currentPrompt.userId);
+        }
+    };
+
+    public render(): React.ReactNode {
+        const { currentPrompt } = this.state;
+        if (currentPrompt) {
+            const substituteATag = (sub: string): React.ReactNode => (
+                <a href="https://element.io/help#encryption18" target="_blank" rel="noreferrer noopener">
+                    {sub}
+                </a>
+            );
+            const substituteBTag = (sub: string): React.ReactNode => <b>{sub}</b>;
+            return (
+                <div className="mx_UserIdentityWarning">
+                    <MemberAvatar member={currentPrompt} title={currentPrompt.userId} size="30px" />
+                    <span className="mx_UserIdentityWarning_main">
+                        {currentPrompt.rawDisplayName === currentPrompt.userId
+                            ? _t(
+                                  "encryption|pinned_identity_changed_no_displayname",
+                                  { userId: currentPrompt.userId },
+                                  {
+                                      a: substituteATag,
+                                      b: substituteBTag,
+                                  },
+                              )
+                            : _t(
+                                  "encryption|pinned_identity_changed",
+                                  { displayName: currentPrompt.rawDisplayName, userId: currentPrompt.userId },
+                                  {
+                                      a: substituteATag,
+                                      b: substituteBTag,
+                                  },
+                              )}
+                    </span>
+                    <AccessibleButton kind="primary" onClick={this.confirmIdentity}>
+                        {_t("action|ok")}
+                    </AccessibleButton>
+                </div>
+            );
+        } else {
+            return null;
+        }
+    }
+}

src/i18n/strings/en_EN.json

@@ -909,6 +909,8 @@
             "warning": "If you didn't set the new recovery method, an attacker may be trying to access your account. Change your account password and set a new recovery method immediately in Settings."
         },
         "not_supported": "<not supported>",
+        "pinned_identity_changed": "%(displayName)s's (<b>%(userId)s</b>) identity appears to have changed. <a>Learn more</a>",
+        "pinned_identity_changed_no_displayname": "<b>%(userId)s</b>'s identity appears to have changed. <a>Learn more</a>",
         "recovery_method_removed": {
             "description_1": "This session has detected that your Security Phrase and key for Secure Messages have been removed.",
             "description_2": "If you did this accidentally, you can setup Secure Messages on this session which will re-encrypt this session's message history with a new recovery method.",