fix(gateway): security hardening — auth guards, ownership checks, validation, rate limiting

apps/gateway/src/conversations/conversations.controller.ts

@@ -16,7 +16,8 @@ import type { Brain } from '@mosaic/brain';
 import { BRAIN } from '../brain/brain.tokens.js';
 import { AuthGuard } from '../auth/auth.guard.js';
 import { CurrentUser } from '../auth/current-user.decorator.js';
-import type {
+import { assertOwner } from '../auth/resource-ownership.js';
+import {
   CreateConversationDto,
   UpdateConversationDto,
   SendMessageDto,
@@ -33,10 +34,8 @@ export class ConversationsController {
   }
 
   @Get(':id')
-  async findOne(@Param('id') id: string) {
-    const conversation = await this.brain.conversations.findById(id);
-    if (!conversation) throw new NotFoundException('Conversation not found');
-    return conversation;
+  async findOne(@Param('id') id: string, @CurrentUser() user: { id: string }) {
+    return this.getOwnedConversation(id, user.id);
   }
 
   @Post()
@@ -49,7 +48,12 @@ export class ConversationsController {
   }
 
   @Patch(':id')
-  async update(@Param('id') id: string, @Body() dto: UpdateConversationDto) {
+  async update(
+    @Param('id') id: string,
+    @Body() dto: UpdateConversationDto,
+    @CurrentUser() user: { id: string },
+  ) {
+    await this.getOwnedConversation(id, user.id);
     const conversation = await this.brain.conversations.update(id, dto);
     if (!conversation) throw new NotFoundException('Conversation not found');
     return conversation;
@@ -57,22 +61,25 @@ export class ConversationsController {
 
   @Delete(':id')
   @HttpCode(HttpStatus.NO_CONTENT)
-  async remove(@Param('id') id: string) {
+  async remove(@Param('id') id: string, @CurrentUser() user: { id: string }) {
+    await this.getOwnedConversation(id, user.id);
     const deleted = await this.brain.conversations.remove(id);
     if (!deleted) throw new NotFoundException('Conversation not found');
   }
 
   @Get(':id/messages')
-  async listMessages(@Param('id') id: string) {
-    const conversation = await this.brain.conversations.findById(id);
-    if (!conversation) throw new NotFoundException('Conversation not found');
+  async listMessages(@Param('id') id: string, @CurrentUser() user: { id: string }) {
+    await this.getOwnedConversation(id, user.id);
     return this.brain.conversations.findMessages(id);
   }
 
   @Post(':id/messages')
-  async addMessage(@Param('id') id: string, @Body() dto: SendMessageDto) {
-    const conversation = await this.brain.conversations.findById(id);
-    if (!conversation) throw new NotFoundException('Conversation not found');
+  async addMessage(
+    @Param('id') id: string,
+    @Body() dto: SendMessageDto,
+    @CurrentUser() user: { id: string },
+  ) {
+    await this.getOwnedConversation(id, user.id);
     return this.brain.conversations.addMessage({
       conversationId: id,
       role: dto.role,
@@ -80,4 +87,11 @@ export class ConversationsController {
       metadata: dto.metadata,
     });
   }
+
+  private async getOwnedConversation(id: string, userId: string) {
+    const conversation = await this.brain.conversations.findById(id);
+    if (!conversation) throw new NotFoundException('Conversation not found');
+    assertOwner(conversation.userId, userId, 'Conversation');
+    return conversation;
+  }
 }

apps/gateway/src/conversations/conversations.dto.ts

@@ -1,15 +1,36 @@
-export interface CreateConversationDto {
+import { IsIn, IsObject, IsOptional, IsString, IsUUID, MaxLength } from 'class-validator';
+
+export class CreateConversationDto {
+  @IsOptional()
+  @IsString()
+  @MaxLength(255)
   title?: string;
+
+  @IsOptional()
+  @IsUUID()
   projectId?: string;
 }
 
-export interface UpdateConversationDto {
+export class UpdateConversationDto {
+  @IsOptional()
+  @IsString()
+  @MaxLength(255)
   title?: string;
+
+  @IsOptional()
+  @IsUUID()
   projectId?: string | null;
 }
 
-export interface SendMessageDto {
-  role: 'user' | 'assistant' | 'system';
-  content: string;
+export class SendMessageDto {
+  @IsIn(['user', 'assistant', 'system'])
+  role!: 'user' | 'assistant' | 'system';
+
+  @IsString()
+  @MaxLength(10_000)
+  content!: string;
+
+  @IsOptional()
+  @IsObject()
   metadata?: Record<string, unknown>;
 }