fix(security): close Critical auth gaps (C1/C2/C3)

C1: replace fragile path.endsWith() guard whitelist with a metadata
    @Public() decorator + Reflector (no more path-shape bypass surface).
C2: CenterApiKeyGuard attaches the authenticated GuildNode; introspect
    & resolve-names now reject when body.guildNodeId != that node
    (stops one node probing/enumerating another guild's identities).
C3: heartbeat/status are self-only (a node can't revoke/hijack another);
    GET /nodes no longer returns apiKeyHash (credential-hash leak).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/auth/auth.controller.ts

@@ -1,9 +1,11 @@
-import { Body, Controller, Get, Headers, Param, Patch, Post, UnauthorizedException } from '@nestjs/common';
+import { Body, Controller, ForbiddenException, Get, Headers, Param, Patch, Post, Req, UnauthorizedException } from '@nestjs/common';
 import { AuthService } from './auth.service.js';
 import { LoginDto } from './dto.login.dto.js';
 import { RefreshDto } from './dto.refresh.dto.js';
 import { LogoutDto } from './dto.logout.dto.js';
 import { UpdateMeDto } from './dto.update-me.dto.js';
+import { Public } from '../common/public.decorator.js';
+import type { AuthedGuildNode } from '../common/center-api-key.guard.js';
 
 function bearer(authorization?: string): string {
   return authorization?.startsWith('Bearer ') ? authorization.slice(7) : '';
@@ -13,21 +15,25 @@ function bearer(authorization?: string): string {
 export class AuthController {
   constructor(private readonly authService: AuthService) {}
 
+  @Public()
   @Post('login')
   login(@Body() body: LoginDto) {
     return this.authService.login(body);
   }
 
+  @Public()
   @Post('refresh')
   refresh(@Body() body: RefreshDto) {
     return this.authService.refresh(body.refreshToken);
   }
 
+  @Public()
   @Post('logout')
   logout(@Body() body: LogoutDto) {
     return this.authService.logout(body.refreshToken);
   }
 
+  @Public()
   @Get('me')
   me(@Headers('authorization') authorization?: string) {
     const token = bearer(authorization);
@@ -35,6 +41,7 @@ export class AuthController {
     return this.authService.getMe(token);
   }
 
+  @Public()
   @Patch('me')
   updateMe(@Headers('authorization') authorization: string | undefined, @Body() body: UpdateMeDto) {
     const token = bearer(authorization);
@@ -42,41 +49,64 @@ export class AuthController {
     return this.authService.updateMe(token, body.name);
   }
 
+  @Public()
   @Get('me/guilds')
   meGuilds(@Headers('authorization') authorization?: string) {
-    const token = authorization?.startsWith('Bearer ') ? authorization.slice(7) : '';
+    const token = bearer(authorization);
     if (!token) throw new UnauthorizedException('missing bearer token');
     return this.authService.listMyGuilds(token);
   }
 
+  @Public()
   @Post('me/guilds/join')
   joinGuild(@Headers('authorization') authorization: string | undefined, @Body() body: { guildNodeId?: string }) {
-    const token = authorization?.startsWith('Bearer ') ? authorization.slice(7) : '';
+    const token = bearer(authorization);
     if (!token) throw new UnauthorizedException('missing bearer token');
     return this.authService.joinGuild(token, String(body?.guildNodeId ?? ''));
   }
 
+  @Public()
   @Get('guilds/:guildNodeId/members')
   guildMembers(@Headers('authorization') authorization: string | undefined, @Param('guildNodeId') guildNodeId: string) {
-    const token = authorization?.startsWith('Bearer ') ? authorization.slice(7) : '';
+    const token = bearer(authorization);
     if (!token) throw new UnauthorizedException('missing bearer token');
     return this.authService.listGuildMembers(token, guildNodeId);
   }
 
+  @Public()
   @Post('agent/login')
   agentLogin(@Body() body: { apiKey?: string }) {
     return this.authService.agentLogin(String(body?.apiKey ?? ''));
   }
 
+  // Not @Public(): requires a guild node api key. The guard attaches the
+  // authenticated node; a node may only introspect tokens for its own
+  // guild (Center C2 — prevents cross-tenant identity probing).
   @Post('introspect')
-  introspect(@Body() body: { token?: string; guildNodeId?: string }) {
-    return this.authService.introspectGuildToken(body?.token ?? '', body?.guildNodeId ?? '');
+  introspect(
+    @Req() req: { guildNode?: AuthedGuildNode },
+    @Body() body: { token?: string; guildNodeId?: string },
+  ) {
+    const requested = String(body?.guildNodeId ?? '');
+    if (!req.guildNode || req.guildNode.nodeId !== requested) {
+      throw new ForbiddenException('api key not authorized for this guild node');
+    }
+    return this.authService.introspectGuildToken(body?.token ?? '', requested);
   }
 
+  // Not @Public(): same node-ownership rule as introspect (Center C2 —
+  // prevents one node enumerating another guild's member identities).
   @Post('resolve-names')
-  resolveNames(@Body() body: { guildNodeId?: string; names?: string[] }) {
+  resolveNames(
+    @Req() req: { guildNode?: AuthedGuildNode },
+    @Body() body: { guildNodeId?: string; names?: string[] },
+  ) {
+    const requested = String(body?.guildNodeId ?? '');
+    if (!req.guildNode || req.guildNode.nodeId !== requested) {
+      throw new ForbiddenException('api key not authorized for this guild node');
+    }
     return this.authService.resolveNames(
-      String(body?.guildNodeId ?? ''),
+      requested,
       Array.isArray(body?.names) ? body.names : [],
     );
   }

src/common/center-api-key.guard.ts

@@ -1,43 +1,36 @@
 import { CanActivate, ExecutionContext, Injectable, UnauthorizedException } from '@nestjs/common';
+import { Reflector } from '@nestjs/core';
 import { InjectRepository } from '@nestjs/typeorm';
 import { Repository } from 'typeorm';
 import bcrypt from 'bcryptjs';
 import { GuildNode } from '../entities/guild-node.entity.js';
+import { IS_PUBLIC_KEY } from './public.decorator.js';
+
+// The authenticated guild node, attached to the request by this guard so
+// downstream handlers can enforce node-ownership (a node may only act on
+// its own nodeId / introspect tokens for its own guild).
+export type AuthedGuildNode = { id: string; nodeId: string };
 
 @Injectable()
 export class CenterApiKeyGuard implements CanActivate {
   constructor(
     @InjectRepository(GuildNode)
     private readonly nodeRepo: Repository<GuildNode>,
+    private readonly reflector: Reflector,
   ) {}
 
   async canActivate(context: ExecutionContext): Promise<boolean> {
+    const isPublic = this.reflector.getAllAndOverride<boolean>(IS_PUBLIC_KEY, [
+      context.getHandler(),
+      context.getClass(),
+    ]);
+    if (isPublic) return true;
+
     const req = context.switchToHttp().getRequest<{
-      path?: string;
-      method?: string;
       headers: Record<string, string | string[] | undefined>;
+      guildNode?: AuthedGuildNode;
     }>();
 
-    const path = req.path ?? '';
-    const method = (req.method ?? 'GET').toUpperCase();
-
-    const noApiKeyRequired =
-      path === '/healthz' ||
-      path.endsWith('/healthz') ||
-      (method === 'POST' && (path === '/auth/login' || path.endsWith('/auth/login'))) ||
-      (method === 'POST' && (path === '/auth/agent/login' || path.endsWith('/auth/agent/login'))) ||
-      (method === 'POST' && (path === '/auth/refresh' || path.endsWith('/auth/refresh'))) ||
-      (method === 'POST' && (path === '/auth/logout' || path.endsWith('/auth/logout'))) ||
-      (method === 'GET' && (path === '/auth/me' || path.endsWith('/auth/me'))) ||
-      (method === 'PATCH' && (path === '/auth/me' || path.endsWith('/auth/me'))) ||
-      (method === 'GET' && (path === '/auth/me/guilds' || path.endsWith('/auth/me/guilds'))) ||
-      (method === 'POST' && (path === '/auth/me/guilds/join' || path.endsWith('/auth/me/guilds/join'))) ||
-      (method === 'GET' && (path.includes('/auth/guilds/') && path.endsWith('/members')));
-
-    if (noApiKeyRequired) {
-      return true;
-    }
-
     const received = req.headers['x-api-key'];
     const apiKey = Array.isArray(received) ? received[0] : received;
     if (!apiKey) throw new UnauthorizedException('missing api key');
@@ -46,7 +39,12 @@ export class CenterApiKeyGuard implements CanActivate {
     for (const node of nodes) {
       if (!node.apiKeyHash) continue;
       const ok = await bcrypt.compare(apiKey, node.apiKeyHash);
-      if (ok) return true;
+      if (ok) {
+        // Identify which node this key belongs to so handlers can enforce
+        // that a node only acts within its own scope (Center C2/C3).
+        req.guildNode = { id: node.id, nodeId: node.nodeId };
+        return true;
+      }
     }
 
     throw new UnauthorizedException('invalid api key');

src/common/health.controller.ts

@@ -1,6 +1,8 @@
 import { Controller, Get, ServiceUnavailableException } from '@nestjs/common';
 import { DataSource } from 'typeorm';
+import { Public } from './public.decorator.js';
 
+@Public()
 @Controller('healthz')
 export class HealthController {
   constructor(private readonly dataSource: DataSource) {}

src/common/public.decorator.ts

@@ -0,0 +1,8 @@
+import { SetMetadata } from '@nestjs/common';
+
+// Routes annotated with @Public() skip the global CenterApiKeyGuard
+// (api-key + node-identity) check. This is metadata-driven on purpose:
+// the previous string-matching whitelist (path.endsWith(...)) was a
+// bypass surface. Only the route's own decorator opens it.
+export const IS_PUBLIC_KEY = 'fabric:isPublic';
+export const Public = () => SetMetadata(IS_PUBLIC_KEY, true);

src/nodes/nodes.controller.ts

@@ -2,6 +2,7 @@ import {
   Body,
   Controller,
   DefaultValuePipe,
+  ForbiddenException,
   Get,
   NotFoundException,
   Param,
@@ -9,12 +10,14 @@ import {
   Patch,
   Post,
   Query,
+  Req,
 } from '@nestjs/common';
 import { InjectRepository } from '@nestjs/typeorm';
 import { Repository } from 'typeorm';
 import { GuildNode } from '../entities/guild-node.entity.js';
 import { AuditService } from '../audit/audit.service.js';
 import { UpdateNodeStatusDto } from './dto.update-node-status.dto.js';
+import type { AuthedGuildNode } from '../common/center-api-key.guard.js';
 
 @Controller('nodes')
 export class NodesController {
@@ -24,8 +27,21 @@ export class NodesController {
     private readonly audit: AuditService,
   ) {}
 
+  // A node may only act on itself. The guard authenticates the caller via
+  // its api key and attaches the matching node; reject if it tries to
+  // touch any other nodeId (Center C3 — prevents node hijack/DoS).
+  private assertSelf(req: { guildNode?: AuthedGuildNode }, nodeId: string) {
+    if (!req.guildNode || req.guildNode.nodeId !== nodeId) {
+      throw new ForbiddenException('api key not authorized for this node');
+    }
+  }
+
   @Post(':nodeId/heartbeat')
-  async heartbeat(@Param('nodeId') nodeId: string) {
+  async heartbeat(
+    @Req() req: { guildNode?: AuthedGuildNode },
+    @Param('nodeId') nodeId: string,
+  ) {
+    this.assertSelf(req, nodeId);
     const node = await this.nodeRepo.findOne({ where: { nodeId } });
     if (!node) {
       throw new NotFoundException('node not found');
@@ -53,9 +69,11 @@ export class NodesController {
 
   @Patch(':nodeId/status')
   async updateStatus(
+    @Req() req: { guildNode?: AuthedGuildNode },
     @Param('nodeId') nodeId: string,
     @Body() body: UpdateNodeStatusDto,
   ) {
+    this.assertSelf(req, nodeId);
     const node = await this.nodeRepo.findOne({ where: { nodeId } });
     if (!node) {
       throw new NotFoundException('node not found');
@@ -93,7 +111,18 @@ export class NodesController {
     });
 
     return {
-      items,
+      // Never expose apiKeyHash (Center C3 — credential hash leak / offline
+      // brute-force). Project to an explicit safe shape.
+      items: items.map((n: GuildNode) => ({
+        id: n.id,
+        nodeId: n.nodeId,
+        name: n.name,
+        endpoint: n.endpoint,
+        status: n.status,
+        lastHeartbeatAt: n.lastHeartbeatAt,
+        createdAt: n.createdAt,
+        updatedAt: n.updatedAt,
+      })),
       page: safePage,
       pageSize: safePageSize,
       total,