feat(#707): secure Discord service ingress

apps/gateway/src/chat/chat.gateway-auth.ts

@@ -1,3 +1,4 @@
+import { timingSafeEqual } from 'node:crypto';
 import type { IncomingHttpHeaders } from 'node:http';
 import { fromNodeHeaders } from 'better-auth/node';
 
@@ -12,6 +13,19 @@ export interface SessionAuth {
   };
 }
 
+export function validateDiscordServiceToken(
+  candidate: unknown,
+  expected: string | undefined,
+): boolean {
+  if (typeof candidate !== 'string' || !expected) return false;
+  const candidateBuffer = Buffer.from(candidate);
+  const expectedBuffer = Buffer.from(expected);
+  return (
+    candidateBuffer.length === expectedBuffer.length &&
+    timingSafeEqual(candidateBuffer, expectedBuffer)
+  );
+}
+
 export async function validateSocketSession(
   headers: IncomingHttpHeaders,
   auth: SessionAuth,

apps/gateway/src/chat/chat.gateway.ts

@@ -11,6 +11,11 @@ import {
 } from '@nestjs/websockets';
 import { Server, Socket } from 'socket.io';
 import type { AgentSessionEvent } from '@mariozechner/pi-coding-agent';
+import {
+  verifyDiscordIngressEnvelope,
+  type DiscordIngressEnvelope,
+  type DiscordIngressPayload,
+} from '@mosaicstack/discord-plugin';
 import type { Auth } from '@mosaicstack/auth';
 import type { Brain } from '@mosaicstack/brain';
 import type {
@@ -28,7 +33,8 @@ import { CommandExecutorService } from '../commands/command-executor.service.js'
 import { RoutingEngineService } from '../agent/routing/routing-engine.service.js';
 import { v4 as uuid } from 'uuid';
 import { ChatSocketMessageDto } from './chat.dto.js';
-import { validateSocketSession } from './chat.gateway-auth.js';
+import { validateDiscordServiceToken, validateSocketSession } from './chat.gateway-auth.js';
+import { DiscordReplayProtector } from '../plugin/discord-replay-protector.js';
 
 /** Per-client state tracking streaming accumulation for persistence. */
 interface ClientSession {
@@ -50,6 +56,37 @@ interface ClientSession {
  */
 const modelOverrides = new Map<string, string>();
 
+function isDiscordIngressEnvelope(value: unknown): value is DiscordIngressEnvelope {
+  if (typeof value !== 'object' || value === null) return false;
+  const envelope = value as { payload?: unknown; signature?: unknown };
+  if (
+    typeof envelope.signature !== 'string' ||
+    typeof envelope.payload !== 'object' ||
+    envelope.payload === null
+  ) {
+    return false;
+  }
+  const payload = envelope.payload as Record<string, unknown>;
+  return [
+    payload['correlationId'],
+    payload['messageId'],
+    payload['guildId'],
+    payload['channelId'],
+    payload['userId'],
+    payload['conversationId'],
+    payload['content'],
+  ].every((field: unknown): boolean => typeof field === 'string');
+}
+
+function isChatSocketMessage(value: unknown): value is ChatSocketMessageDto {
+  if (typeof value !== 'object' || value === null) return false;
+  const payload = value as { content?: unknown; conversationId?: unknown };
+  return (
+    typeof payload.content === 'string' &&
+    (payload.conversationId === undefined || typeof payload.conversationId === 'string')
+  );
+}
+
 @WebSocketGateway({
   cors: {
     origin: process.env['GATEWAY_CORS_ORIGIN'] ?? 'http://localhost:3000',
@@ -62,6 +99,7 @@ export class ChatGateway implements OnGatewayInit, OnGatewayConnection, OnGatewa
 
   private readonly logger = new Logger(ChatGateway.name);
   private readonly clientSessions = new Map<string, ClientSession>();
+  private readonly discordReplayProtector = new DiscordReplayProtector();
 
   constructor(
     @Inject(AgentService) private readonly agentService: AgentService,
@@ -77,6 +115,13 @@ export class ChatGateway implements OnGatewayInit, OnGatewayConnection, OnGatewa
   }
 
   async handleConnection(client: Socket): Promise<void> {
+    const serviceToken = client.handshake.auth['discordServiceToken'];
+    if (validateDiscordServiceToken(serviceToken, process.env['DISCORD_SERVICE_TOKEN'])) {
+      client.data.discordService = true;
+      this.logger.log(`Authenticated Discord service connected: ${client.id}`);
+      return;
+    }
+
     const session = await validateSocketSession(client.handshake.headers, this.auth);
     if (!session) {
       this.logger.warn(`Rejected unauthenticated WebSocket client: ${client.id}`);
@@ -87,8 +132,6 @@ export class ChatGateway implements OnGatewayInit, OnGatewayConnection, OnGatewa
     client.data.user = session.user;
     client.data.session = session.session;
     this.logger.log(`Client connected: ${client.id}`);
-
-    // Broadcast command manifest to the newly connected client
     client.emit('commands:manifest', { manifest: this.commandRegistry.getManifest() });
   }
 
@@ -105,12 +148,41 @@ export class ChatGateway implements OnGatewayInit, OnGatewayConnection, OnGatewa
   @SubscribeMessage('message')
   async handleMessage(
     @ConnectedSocket() client: Socket,
-    @MessageBody() data: ChatSocketMessageDto,
+    @MessageBody() rawData: unknown,
   ): Promise<void> {
+    let discordIngress: DiscordIngressPayload | null = null;
+    let data: ChatSocketMessageDto;
+    if (client.data.discordService) {
+      if (!isDiscordIngressEnvelope(rawData)) {
+        this.logger.warn(`Rejected malformed Discord ingress from ${client.id}`);
+        return;
+      }
+      discordIngress = this.resolveDiscordIngress(client, rawData);
+      if (!discordIngress) return;
+      data = { conversationId: discordIngress.conversationId, content: discordIngress.content };
+    } else {
+      if (!isChatSocketMessage(rawData)) {
+        this.logger.warn(`Rejected malformed chat message from ${client.id}`);
+        return;
+      }
+      data = rawData;
+    }
     const conversationId = data.conversationId ?? uuid();
-    const userId = (client.data.user as { id: string } | undefined)?.id;
+    const discordServiceUserId = process.env['DISCORD_SERVICE_USER_ID'];
+    if (discordIngress && !discordServiceUserId) {
+      this.logger.warn(
+        `Rejected Discord ingress without configured service owner from ${client.id}`,
+      );
+      return;
+    }
+    const userId = discordIngress
+      ? discordServiceUserId
+      : (client.data.user as { id: string } | undefined)?.id;
+    const correlationId = discordIngress?.correlationId;
 
-    this.logger.log(`Message from ${client.id} in conversation ${conversationId}`);
+    this.logger.log(
+      `Message from ${client.id} in conversation ${conversationId}${correlationId ? ` correlation=${correlationId}` : ''}`,
+    );
 
     // Ensure agent session exists for this conversation
     let sessionRoutingDecision: RoutingDecisionInfo | undefined;
@@ -213,6 +285,13 @@ export class ChatGateway implements OnGatewayInit, OnGatewayConnection, OnGatewa
             content: data.content,
             metadata: {
               timestamp: new Date().toISOString(),
+              ...(correlationId
+                ? {
+                    correlationId,
+                    discordMessageId: discordIngress?.messageId,
+                    discordUserId: discordIngress?.userId,
+                  }
+                : {}),
             },
           },
           userId,
@@ -271,7 +350,17 @@ export class ChatGateway implements OnGatewayInit, OnGatewayConnection, OnGatewa
     }
 
     // Send acknowledgment
-    client.emit('message:ack', { conversationId, messageId: uuid() });
+    client.emit('message:ack', {
+      conversationId,
+      messageId: uuid(),
+      ...(correlationId
+        ? {
+            correlationId,
+            discordMessageId: discordIngress?.messageId,
+            discordUserId: discordIngress?.userId,
+          }
+        : {}),
+    });
 
     // Dispatch to agent
     try {
@@ -442,6 +531,39 @@ export class ChatGateway implements OnGatewayInit, OnGatewayConnection, OnGatewa
    * Creates it if absent — safe to call concurrently since a duplicate insert
    * would fail on the PK constraint and be caught here.
    */
+  private resolveDiscordIngress(
+    client: Socket,
+    envelope: DiscordIngressEnvelope,
+  ): DiscordIngressPayload | null {
+    const payload = verifyDiscordIngressEnvelope(
+      envelope,
+      process.env['DISCORD_SERVICE_TOKEN'] ?? '',
+      {
+        guildIds: this.readDiscordAllowlist('DISCORD_ALLOWED_GUILD_IDS'),
+        channelIds: this.readDiscordAllowlist('DISCORD_ALLOWED_CHANNEL_IDS'),
+        userIds: this.readDiscordAllowlist('DISCORD_ALLOWED_USER_IDS'),
+      },
+    );
+    if (!payload) {
+      this.logger.warn(`Rejected invalid Discord ingress envelope from ${client.id}`);
+      return null;
+    }
+    if (!this.discordReplayProtector.claim(payload.messageId)) {
+      this.logger.warn(
+        `Rejected replayed Discord message=${payload.messageId} correlation=${payload.correlationId}`,
+      );
+      return null;
+    }
+    return payload;
+  }
+
+  private readDiscordAllowlist(name: string): string[] {
+    return (process.env[name] ?? '')
+      .split(',')
+      .map((id: string): string => id.trim())
+      .filter((id: string): boolean => id.length > 0);
+  }
+
   private async ensureConversation(conversationId: string, userId: string): Promise<void> {
     try {
       const existing = await this.brain.conversations.findById(conversationId, userId);

apps/gateway/src/plugin/discord-ingress.security.spec.ts

@@ -0,0 +1,89 @@
+import { describe, expect, it } from 'vitest';
+import {
+  createDiscordIngressEnvelope,
+  verifyDiscordIngressEnvelope,
+  type DiscordIngressPayload,
+} from '@mosaicstack/discord-plugin';
+import { validateDiscordServiceToken } from '../chat/chat.gateway-auth.js';
+import { DiscordReplayProtector } from './discord-replay-protector.js';
+
+const SERVICE_TOKEN = 'test-service-token';
+
+function createPayload(overrides: Partial<DiscordIngressPayload> = {}): DiscordIngressPayload {
+  return {
+    correlationId: 'correlation-001',
+    messageId: 'discord-message-001',
+    guildId: 'guild-001',
+    channelId: 'channel-001',
+    userId: 'user-001',
+    conversationId: 'discord-channel-001',
+    content: 'hello Tess',
+    ...overrides,
+  };
+}
+
+describe('Discord ingress security', () => {
+  it('accepts only the configured Discord service identity', () => {
+    expect(validateDiscordServiceToken(SERVICE_TOKEN, SERVICE_TOKEN)).toBe(true);
+    expect(validateDiscordServiceToken('wrong-service-token', SERVICE_TOKEN)).toBe(false);
+    expect(validateDiscordServiceToken(undefined, SERVICE_TOKEN)).toBe(false);
+  });
+
+  it('rejects unauthenticated or tampered service envelopes', () => {
+    const envelope = createDiscordIngressEnvelope(createPayload(), SERVICE_TOKEN);
+
+    expect(verifyDiscordIngressEnvelope(envelope, SERVICE_TOKEN)).toEqual(createPayload());
+    expect(verifyDiscordIngressEnvelope(envelope, 'wrong-service-token')).toBeNull();
+    expect(
+      verifyDiscordIngressEnvelope(
+        { ...envelope, payload: { ...envelope.payload, content: 'forged command' } },
+        SERVICE_TOKEN,
+      ),
+    ).toBeNull();
+  });
+
+  it.each([
+    ['guild', { guildId: 'unlisted-guild' }],
+    ['channel', { channelId: 'unlisted-channel' }],
+    ['user', { userId: 'unlisted-user' }],
+  ])(
+    'rejects an unallowlisted Discord %s',
+    (_kind: string, overrides: Partial<DiscordIngressPayload>) => {
+      const envelope = createDiscordIngressEnvelope(createPayload(overrides), SERVICE_TOKEN);
+
+      expect(
+        verifyDiscordIngressEnvelope(envelope, SERVICE_TOKEN, {
+          guildIds: ['guild-001'],
+          channelIds: ['channel-001'],
+          userIds: ['user-001'],
+        }),
+      ).toBeNull();
+    },
+  );
+
+  it('retains Discord message and correlation IDs after authenticated allowlisted validation', () => {
+    const payload = createPayload({
+      correlationId: 'correlation-trace-123',
+      messageId: 'discord-snowflake-987',
+    });
+    const envelope = createDiscordIngressEnvelope(payload, SERVICE_TOKEN);
+
+    expect(
+      verifyDiscordIngressEnvelope(envelope, SERVICE_TOKEN, {
+        guildIds: ['guild-001'],
+        channelIds: ['channel-001'],
+        userIds: ['user-001'],
+      }),
+    ).toEqual(payload);
+  });
+
+  it('rejects a replayed Discord message ID while retaining bounded replay state', () => {
+    const replayProtector = new DiscordReplayProtector(60_000, 2);
+
+    expect(replayProtector.claim('discord-message-001')).toBe(true);
+    expect(replayProtector.claim('discord-message-001')).toBe(false);
+    expect(replayProtector.claim('discord-message-002')).toBe(true);
+    expect(replayProtector.claim('discord-message-003')).toBe(true);
+    expect(replayProtector.size).toBe(2);
+  });
+});

apps/gateway/src/plugin/discord-replay-protector.ts

@@ -0,0 +1,40 @@
+/**
+ * Bounded replay cache for Discord's globally unique native message IDs.
+ * Durable ingress idempotency is added with Tess's canonical inbox/outbox work.
+ */
+export class DiscordReplayProtector {
+  private readonly claimedAt = new Map<string, number>();
+
+  constructor(
+    private readonly ttlMs = 15 * 60 * 1000,
+    private readonly maxEntries = 10_000,
+  ) {}
+
+  get size(): number {
+    return this.claimedAt.size;
+  }
+
+  /** Claims an ID exactly once within its bounded retention window. */
+  claim(messageId: string, now = Date.now()): boolean {
+    this.prune(now);
+    if (this.claimedAt.has(messageId)) return false;
+
+    this.claimedAt.set(messageId, now);
+    this.evictOverflow();
+    return true;
+  }
+
+  private prune(now: number): void {
+    for (const [messageId, claimedAt] of this.claimedAt) {
+      if (now - claimedAt >= this.ttlMs) this.claimedAt.delete(messageId);
+    }
+  }
+
+  private evictOverflow(): void {
+    while (this.claimedAt.size > this.maxEntries) {
+      const oldestMessageId = this.claimedAt.keys().next().value;
+      if (oldestMessageId === undefined) return;
+      this.claimedAt.delete(oldestMessageId);
+    }
+  }
+}

apps/gateway/src/plugin/plugin.module.ts

@@ -50,19 +50,41 @@ class TelegramChannelPluginAdapter implements IChannelPlugin {
 
 const DEFAULT_GATEWAY_URL = 'http://localhost:14242';
 
+function requiredDiscordAllowlist(name: string): string[] {
+  const value = process.env[name]
+    ?.split(',')
+    .map((id: string): string => id.trim())
+    .filter((id: string): boolean => id.length > 0);
+  if (!value || value.length === 0) {
+    throw new Error(`${name} is required when DISCORD_BOT_TOKEN is configured`);
+  }
+  return value;
+}
+
 function createPluginRegistry(): IChannelPlugin[] {
   const plugins: IChannelPlugin[] = [];
   const discordToken = process.env['DISCORD_BOT_TOKEN'];
   const discordGuildId = process.env['DISCORD_GUILD_ID'];
   const discordGatewayUrl = process.env['DISCORD_GATEWAY_URL'] ?? DEFAULT_GATEWAY_URL;
+  const discordServiceToken = process.env['DISCORD_SERVICE_TOKEN'];
+  const discordServiceUserId = process.env['DISCORD_SERVICE_USER_ID'];
 
   if (discordToken) {
+    if (!discordServiceToken || !discordServiceUserId) {
+      throw new Error(
+        'DISCORD_SERVICE_TOKEN and DISCORD_SERVICE_USER_ID are required when DISCORD_BOT_TOKEN is configured',
+      );
+    }
     plugins.push(
       new DiscordChannelPluginAdapter(
         new DiscordPlugin({
           token: discordToken,
           guildId: discordGuildId,
           gatewayUrl: discordGatewayUrl,
+          serviceToken: discordServiceToken,
+          allowedGuildIds: requiredDiscordAllowlist('DISCORD_ALLOWED_GUILD_IDS'),
+          allowedChannelIds: requiredDiscordAllowlist('DISCORD_ALLOWED_CHANNEL_IDS'),
+          allowedUserIds: requiredDiscordAllowlist('DISCORD_ALLOWED_USER_IDS'),
         }),
       ),
     );