Migrate the ban-sync component from matrix-appservice-irc

src/components/ban-sync.ts

@@ -0,0 +1,273 @@
+
+
+import { Intent, MatrixUser, WeakStateEvent, Logger, MatrixHostResolver } from "..";
+import { MatrixGlob } from "matrix-bot-sdk";
+import axios from "axios";
+
+const log = new Logger("MatrixBanSync");
+
+const CACHE_HOMESERVER_PROPERTIES_FOR_MS = 1000 * 60 * 30; // 30 minutes
+
+export interface MatrixBanSyncConfig {
+    rooms?: string[];
+    blockByRegistrationStatus: RegistrationStatus[];
+}
+
+enum BanEntityType {
+    Server = "m.policy.rule.server",
+    User = "m.policy.rule.user"
+}
+
+interface BanEntity {
+    matcher: MatrixGlob;
+    entityType: BanEntityType;
+    reason: string;
+}
+
+interface MPolicyContent {
+    entity: string;
+    reason: string;
+    recommendation: "m.ban";
+}
+
+function eventTypeToBanEntityType(eventType: string): BanEntityType|null {
+    switch (eventType) {
+        case "m.policy.rule.user":
+        case "org.matrix.mjolnir.rule.user":
+            return BanEntityType.User;
+        case "m.policy.rule.server":
+        case "org.matrix.mjolnir.rule.server":
+            return BanEntityType.Server
+        default:
+            return null;
+    }
+}
+
+const supportedRecommendations = [
+    "org.matrix.mjolnir.ban", // Used historically.
+    "m.ban"
+];
+
+interface MatrixRegistrationResponse {
+    flows: {
+        stages: string[],
+    }[],
+}
+
+enum RegistrationStatus {
+    Unknown = 0,
+    Open = 1,
+    ProtectedEmail = 2,
+    ProtectedCaptcha = 3,
+    Closed = 4,
+}
+
+const AuthTypeRecaptcha = 'm.login.recaptcha';
+const AuthTypeEmail = 'm.login.email.identity';
+
+/**
+ * Synchronises Matrix `m.policy.rule` events with the bridge to filter specific
+ * users from using the service.
+ */
+export class MatrixBanSync {
+    private readonly homeserverPropertiesCache = new Map<string, {
+        registrationStatus: RegistrationStatus; ts: number;
+    }>();
+    private readonly bannedEntites = new Map<string, BanEntity>();
+    private readonly subscribedRooms = new Set<string>();
+    private readonly hostResolver = new MatrixHostResolver();
+    constructor(private config: MatrixBanSyncConfig) {
+
+    }
+
+    /**
+     * Determine the state of the homeservers user registration system.
+     *
+     * @param url The base URL for the C-S API of the homeserver.
+     * @returns A status enum.
+     */
+    private static async getRegistrationStatus(url: URL): Promise<RegistrationStatus> {
+        let registrationResponse = await axios.post(new URL('/_matrix/client/v3/register', url).toString(), { });
+        if (registrationResponse.status === 404) {
+            // Fallback to old APIs
+            registrationResponse = await axios.post(new URL('/_matrix/client/r0/register', url).toString(), { });
+        }
+
+
+        if (registrationResponse.status === 403 && registrationResponse.data.errcode === 'M_FORBIDDEN') {
+            // Explicitly forbidden private server -> great!
+            return RegistrationStatus.Closed;
+        }
+
+        if (registrationResponse.status === 404) {
+            // Endpoint is not connected, probably also great!
+            return RegistrationStatus.Closed;
+        }
+
+        if (registrationResponse.status === 401) {
+            // Look at the flows.
+            const { flows } = registrationResponse.data as MatrixRegistrationResponse;
+            if (!flows) {
+                // Invalid response
+                return RegistrationStatus.Unknown;
+            }
+
+            if (flows.length === 0) {
+                // No available flows, so closed.
+                return RegistrationStatus.Closed;
+            }
+
+            let openReg = RegistrationStatus.Unknown;
+            // Check the flows
+            for (const flow of flows) {
+                // A flow with recaptcha
+                if (openReg > RegistrationStatus.ProtectedCaptcha && flow.stages.includes(AuthTypeRecaptcha)) {
+                    openReg = RegistrationStatus.ProtectedCaptcha;
+                }
+                // A flow without any recaptcha stages
+                if (openReg > RegistrationStatus.ProtectedEmail &&
+                    flow.stages.includes(AuthTypeEmail) && !flow.stages.includes(AuthTypeRecaptcha)) {
+                    openReg = RegistrationStatus.ProtectedEmail;
+                }
+                // A flow without any email or recaptcha stages
+                if (openReg > RegistrationStatus.Open &&
+                    !flow.stages.includes(AuthTypeEmail) && !flow.stages.includes(AuthTypeRecaptcha)) {
+                    openReg = RegistrationStatus.Open;
+                    // Already as bad as it gets
+                    break;
+                }
+            }
+            return openReg;
+        }
+
+        return RegistrationStatus.Unknown;
+    }
+
+    /**
+     * Get properties about a given homeserver that may influence the rules
+     * applied to it.
+     * @param serverName The homeserver name.
+     * @returns A set of properties.
+     * @throws This will fail if the client does not provide a well-known. Callers should
+     * make their own assumptions about the state of the host in this case.
+     */
+    public async getHomeserverProperties(serverName: string) {
+        const hsData = this.homeserverPropertiesCache.get(serverName);
+        // Slightly fuzz the ttl.
+        const ttl = Date.now() + CACHE_HOMESERVER_PROPERTIES_FOR_MS + (Math.random()*60000);
+        if (hsData && hsData.ts < ttl) {
+            return hsData;
+        }
+        const url = await this.hostResolver.resolveMatrixClient(serverName, true);
+
+        const hsProps = {
+            registrationStatus: await MatrixBanSync.getRegistrationStatus(url),
+            ts: Date.now(),
+        };
+        this.homeserverPropertiesCache.set(serverName, hsProps);
+        return hsProps;
+    }
+
+    /**
+     * Perform joins against all the configured ban list rooms, and pull all ban state.
+     * This can be quite expensive to run if there is lots of state to pull.
+     * @param intent The client intent to pull the state via.
+     */
+    public async syncRules(intent: Intent) {
+        this.bannedEntites.clear();
+        this.subscribedRooms.clear();
+        for (const roomIdOrAlias of this.config.rooms || []) {
+            try {
+                const roomId = await intent.join(roomIdOrAlias);
+                this.subscribedRooms.add(roomId);
+                const roomState = await intent.roomState(roomId, false) as WeakStateEvent[];
+                for (const evt of roomState) {
+                    this.handleIncomingState(evt, roomId);
+                }
+            }
+            catch (ex) {
+                log.error(`Failed to read ban list from ${roomIdOrAlias}`, ex);
+            }
+        }
+    }
+
+    /**
+     * Is the given room considered part of the bridge's ban list set.
+     * @param roomId A Matrix room ID.
+     * @returns true if state should be handled from the room, false otherwise.
+     */
+    public isTrackingRoomState(roomId: string): boolean {
+        return this.subscribedRooms.has(roomId);
+    }
+
+    /**
+     * Checks to see if the incoming state is a recommendation entry.
+     * @param evt A Matrix state event. Unknown state events will be filtered out.
+     * @param roomId The Matrix roomID where the event came from.
+     * @returns `true` if the event was a new ban, and existing clients should be checked. `false` otherwise.
+     */
+    public handleIncomingState(evt: WeakStateEvent, roomId: string) {
+        const content = evt.content as unknown as MPolicyContent;
+        const entityType = eventTypeToBanEntityType(evt.type);
+        if (!entityType) {
+            return false;
+        }
+        const key = `${roomId}:${evt.state_key}`;
+        if (evt.content.entity === undefined) {
+            // Empty, delete instead.
+            log.info(`Deleted ban rule ${evt.type}/$ matching ${key}`);
+            this.bannedEntites.delete(key);
+            return false;
+        }
+        if (!supportedRecommendations.includes(content.recommendation)) {
+            return false;
+        }
+        if (typeof content.entity !== "string" || content.entity === "") {
+            throw Error('`entity` key is not valid, must be a non-empty string');
+        }
+        this.bannedEntites.set(key, {
+            matcher: new MatrixGlob(content.entity),
+            entityType,
+            reason: content.reason || "No reason given",
+        });
+        log.info(`New ban rule ${evt.type} matching ${content.entity}`);
+        return true;
+    }
+
+    /**
+     * Check if a user is banned by via a ban list.
+     * @param user A userId string or a MatrixUser object.
+     * @returns Either a string reason for the ban, or false if the user was not banned.
+     */
+    public async isUserBanned(user: MatrixUser|string): Promise<string|false> {
+        const matrixUser = typeof user === "string" ? new MatrixUser(user) : user;
+        for (const entry of this.bannedEntites.values()) {
+            if (entry.entityType === BanEntityType.Server && entry.matcher.test(matrixUser.host)) {
+                return entry.reason;
+            }
+            if (entry.entityType === BanEntityType.User && entry.matcher.test(matrixUser.userId)) {
+                return entry.reason;
+            }
+        }
+
+        if (this.config.blockByRegistrationStatus) {
+            // Check the user's homeserver.
+            const { registrationStatus } = await this.getHomeserverProperties(matrixUser.host);
+            if (this.config.blockByRegistrationStatus.includes(registrationStatus)) {
+                const statusName = RegistrationStatus[registrationStatus];
+                return `${matrixUser.host} has ${statusName} registration, which is blocked by this bridge.`
+            }
+        }
+        return false;
+    }
+
+    /**
+     * Should be called when the bridge config has been updated.
+     * @param config The new config.
+     * @param intent The bot user intent.
+     */
+    public async updateConfig(config: MatrixBanSyncConfig, intent: Intent) {
+        this.config = config;
+        await this.syncRules(intent);
+    }
+}

src/index.ts

@@ -28,6 +28,7 @@ export * from "./components/room-upgrade-handler";
 export * from "./components/app-service-bot";
 export * from "./components/state-lookup";
 export * from "./components/activity-tracker";
+export * from "./components/ban-sync";
 
 // Config and CLI
 export * from "./components/cli";