From 672a668ecf1b5df644b5eb1297516dbc15e64adc Mon Sep 17 00:00:00 2001
From: Ms6RB <33758164+ms6rb@users.noreply.github.com>
Date: Sun, 8 Mar 2026 18:45:08 +0200
Subject: [PATCH] feat(skills): add NestJS security testing module (#348)

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+---
+name: nestjs
+description: Security testing playbook for NestJS applications covering guards, pipes, decorators, module boundaries, and multi-transport auth
+---
+
+# NestJS
+
+Security testing for NestJS applications. Focus on guard gaps across decorator stacks, validation pipe bypasses, module boundary leaks, and inconsistent auth enforcement across HTTP, WebSocket, and microservice transports.
+
+## Attack Surface
+
+**Decorator Pipeline**
+- Guards: `@UseGuards`, `CanActivate`, execution context (HTTP/WS/RPC), `Reflector` metadata
+- Pipes: `ValidationPipe` (whitelist, transform, forbidNonWhitelisted), `ParseIntPipe`, custom pipes
+- Interceptors: response mapping, caching, logging, timeout — can modify request/response flow
+- Filters: exception filters that may leak information
+- Metadata: `@SetMetadata`, `@Public()`, `@Roles()`, `@Permissions()`
+
+**Module System**
+- `@Module` boundaries, provider scoping (DEFAULT/REQUEST/TRANSIENT)
+- Dynamic modules: `forRoot`/`forRootAsync`, global modules
+- DI container: provider overrides, custom providers
+
+**Controllers & Transports**
+- REST: `@Controller`, versioning (URI/Header/MediaType)
+- GraphQL: `@Resolver`, playground/sandbox exposure
+- WebSocket: `@WebSocketGateway`, gateway guards, room authorization
+- Microservices: TCP, Redis, NATS, MQTT, gRPC, Kafka — often lack HTTP-level auth
+
+**Data Layer**
+- TypeORM: repositories, QueryBuilder, raw queries, relations
+- Prisma: `$queryRaw`, `$queryRawUnsafe`
+- Mongoose: operator injection, `$where`, `$regex`
+
+**Auth & Config**
+- `@nestjs/passport` strategies, `@nestjs/jwt`, session-based auth
+- `@nestjs/config`, ConfigService, `.env` files
+- `@nestjs/throttler`, rate limiting with `@SkipThrottle`
+
+**API Documentation**
+- `@nestjs/swagger`: OpenAPI exposure, DTO schemas, auth schemes
+
+## High-Value Targets
+
+- Swagger/OpenAPI endpoints in production (`/api`, `/api-docs`, `/api-json`, `/swagger`)
+- Auth endpoints: login, register, token refresh, password reset, OAuth callbacks
+- Admin controllers decorated with `@Roles('admin')` — test with user-level tokens
+- File upload endpoints using `FileInterceptor`/`FilesInterceptor`
+- WebSocket gateways sharing business logic with HTTP controllers
+- Microservice handlers (`@MessagePattern`, `@EventPattern`) — often unguarded
+- CRUD generators (`@nestjsx/crud`) with auto-generated endpoints
+- Background jobs and scheduled tasks (`@nestjs/schedule`)
+- Health/metrics endpoints (`@nestjs/terminus`, `/health`, `/metrics`)
+- GraphQL playground/sandbox in production (`/graphql`)
+
+## Reconnaissance
+
+**Swagger Discovery**
+```
+GET /api
+GET /api-docs
+GET /api-json
+GET /swagger
+GET /docs
+GET /v1/api-docs
+GET /api/v2/docs
+```
+
+Extract: paths, parameter schemas, DTOs, auth schemes, example values. Swagger may reveal internal endpoints, deprecated routes, and admin-only paths not visible in the UI.
+
+**Guard Mapping**
+
+For each controller and method, identify:
+- Global guards (applied in `main.ts` or app module)
+- Controller-level guards (`@UseGuards` on the class)
+- Method-level guards (`@UseGuards` on individual handlers)
+- `@Public()` or `@SkipThrottle()` decorators that bypass protection
+
+## Key Vulnerabilities
+
+### Guard Bypass
+
+**Decorator Stack Gaps**
+- Guards execute: global → controller → method. A method missing `@UseGuards` when siblings have it is the #1 finding.
+- `@Public()` metadata causing global `AuthGuard` to skip enforcement — check if applied too broadly.
+- New methods added to existing controllers without inheriting the expected guard.
+
+**ExecutionContext Switching**
+- Guards handling only HTTP context (`getRequest()`) may fail silently on WebSocket or RPC, returning `true` by default.
+- Test same business logic through alternate transports to find context-specific bypasses.
+
+**Reflector Mismatches**
+- Guard reads `SetMetadata('roles', [...])` but decorator sets `'role'` (singular) — guard sees no metadata, defaults to allow.
+- `applyDecorators()` compositions accidentally overriding stricter guards with permissive ones.
+
+### Validation Pipe Exploits
+
+**Whitelist Bypass**
+- `whitelist: true` without `forbidNonWhitelisted: true`: extra properties silently stripped but may have been processed by earlier middleware/interceptors.
+- Missing `@Type(() => ChildDto)` on nested objects: `@ValidateNested()` without `@Type` means nested payload is never validated.
+- Array elements: `@IsArray()` doesn't validate elements without `@ValidateNested({ each: true })` and `@Type`.
+
+**Type Coercion**
+- `transform: true` enables implicit coercion: strings → numbers, `"true"` → `true`, `"null"` → `null`.
+- Exploit truthiness assumptions in business logic downstream.
+
+**Conditional Validation**
+- `@ValidateIf()` and validation groups creating paths where fields skip validation entirely.
+
+**Missing Parse Pipes**
+- `@Param('id')` without `ParseIntPipe`/`ParseUUIDPipe` — string values reach ORM queries directly.
+
+### Auth & Passport
+
+**JWT Strategy**
+- Check `ignoreExpiration` is false, `algorithms` is pinned (no `none` or HS/RS confusion)
+- Weak `secretOrKey` values
+- Cross-service token reuse when audience/issuer not enforced
+
+**Passport Strategy Issues**
+- `validate()` return value becomes `req.user` — if it returns full DB record, sensitive fields leak downstream
+- Multiple strategies (JWT + session): one may bypass restrictions of the other
+- Custom guards returning `true` for unauthenticated as "optional auth"
+
+**Timing Attacks**
+- Plain string comparison instead of bcrypt/argon2 in local strategy
+
+### Serialization Leaks
+
+**Missing ClassSerializerInterceptor**
+- If not applied globally, `@Exclude()` fields (passwords, internal IDs) returned in responses.
+- `@Expose()` with groups: admin-only fields exposed when groups not enforced per-request.
+
+**Circular Relations**
+- Eager-loaded TypeORM/Prisma relations exposing entire object graph without careful serialization.
+
+### Interceptor Abuse
+
+**Cache Poisoning**
+- `CacheInterceptor` without user/tenant identity in cache key — responses from one user served to another.
+- Test: authenticated request, then unauthenticated request returning cached data.
+
+**Response Mapping**
+- Transformation interceptors may leak internal entity fields if mapping is incomplete.
+
+### Module Boundary Leaks
+
+**Global Module Exposure**
+- `@Global()` modules expose all providers to every module without explicit imports.
+- Sensitive services (admin operations, internal APIs) accessible from untrusted modules.
+
+**Config Leaks**
+- `forRoot`/`forRootAsync` configuration secrets accessible via `ConfigService` injection in any module.
+
+**Scope Issues**
+- Request-scoped providers (`Scope.REQUEST`) incorrectly scoped as DEFAULT (singleton) — request context leaks across concurrent requests.
+
+### WebSocket Gateway
+
+- HTTP guards don't automatically apply to WebSocket gateways — `@UseGuards` must be explicit.
+- Authentication deferred from `handleConnection` to message handlers allows unauthenticated message sending.
+- Room/namespace authorization: users joining rooms they shouldn't access.
+- `@SubscribeMessage()` handlers relying on connection-level auth instead of per-message validation.
+
+### Microservice Transport
+
+- `@MessagePattern`/`@EventPattern` handlers often lack guards (considered "internal").
+- If transport (Redis, NATS, Kafka) is network-accessible, messages can be injected bypassing all HTTP security.
+- `ValidationPipe` may only be configured for HTTP — microservice payloads skip validation.
+
+### ORM Injection
+
+**TypeORM**
+- `QueryBuilder` and `.query()` with template literal interpolation → SQL injection.
+- Relations: API allowing specification of which relations to load via query params.
+
+**Mongoose**
+- Query operator injection: `{ password: { $gt: "" } }` via unsanitized request body.
+- `$where` and `$regex` operators from user input.
+
+**Prisma**
+- `$queryRaw`/`$executeRaw` with string interpolation (but not tagged template).
+- `$queryRawUnsafe` usage.
+
+### Rate Limiting
+
+- `@SkipThrottle()` on sensitive endpoints (login, password reset, OTP).
+- In-memory throttler storage: resets on restart, doesn't work across instances.
+- Behind proxy without `trust proxy`: all requests share same IP, or header spoofable.
+
+### CRUD Generators
+
+- Auto-generated CRUD endpoints may not inherit manual guard configurations.
+- Bulk operations (`createMany`, `updateMany`) bypassing per-entity authorization.
+- Query parameter injection in CRUD libraries: `filter`, `sort`, `join`, `select` exposing unauthorized data.
+
+## Bypass Techniques
+
+- `@Public()` / skip-metadata applied via composed decorators at method level causing global guards to skip via `Reflector` metadata checks
+- Route param pollution: `/users/123?id=456` — which `id` wins in guards vs handlers?
+- Version routing: v1 of endpoint may still be registered without the guard added to v2
+- `X-HTTP-Method-Override` or `_method` processed by Express before guards
+- Content-type switching: `application/x-www-form-urlencoded` instead of JSON to bypass JSON-specific validation
+- Exception filter differences: guard throwing results in generic error that leaks route existence info
+
+## Testing Methodology
+
+1. **Enumerate** — Fetch Swagger/OpenAPI, map all controllers, resolvers, and gateways
+2. **Guard audit** — Map decorator stack per method: which guards, pipes, interceptors are applied at each level
+3. **Matrix testing** — Test each endpoint across: unauth/user/admin × HTTP/WS/microservice
+4. **Validation probing** — Send extra fields, wrong types, nested objects, arrays to find pipe gaps
+5. **Transport parity** — Same operation via HTTP, WebSocket, and microservice transport
+6. **Module boundaries** — Check if providers from one module are accessible without proper imports
+7. **Serialization check** — Compare raw entity fields with API response fields
+
+## Validation Requirements
+
+- Guard bypass: request to guarded endpoint succeeding without auth, showing guard chain break point
+- Validation bypass: payload with extra/malformed fields affecting business logic
+- Cross-transport inconsistency: same action authorized via HTTP but exploitable via WebSocket/microservice
+- Module boundary leak: accessing provider or data across unauthorized module boundaries
+- Serialization leak: response containing excluded fields (passwords, internal metadata)
+- IDOR: side-by-side requests from different users showing unauthorized data access
+- ORM injection: raw query with user-controlled input returning unauthorized data, or error-based evidence of query structure
+- Cache poisoning: response from unauthenticated or different-user request matching a prior authenticated user's cached response