Credential Stuffing in Nestjs with Api Keys

Credential stuffing is an automated attack where adversaries use large lists of known username and password pairs to gain unauthorized access. When an API relies solely on static API keys without additional protections, a compromised key can be reused at scale to impersonate a client or service. In a NestJS application, this risk increases if API keys are issued per user or client and are accepted without additional context (such as IP or behavioral signals).

A common pattern in NestJS is to validate API keys via a guard or an interceptor before allowing access to a route. If the key is treated as a bearer credential and no rate limiting or reuse detection is in place, attackers can automate submissions using credential stuffing techniques to test leaked keys across endpoints. Even though the attack surface is unauthenticated from the scanner’s perspective, the presence of key-based authentication does not prevent automated probing if the endpoints do not enforce strict throttling or key rotation policies.

Consider an endpoint that retrieves user profile data and accepts an API key via header. If the key is not bound to a specific scope, tenant, or rate limit, a single leaked key can be used to enumerate user data through mass enumeration or to escalate privileges by targeting administrative endpoints. The API’s OpenAPI spec may define the key as a security scheme, but if runtime protections are weak, the specification alone cannot prevent abuse.

Because middleBrick scans the unauthenticated attack surface, it can detect the absence of rate limiting, weak input validation, and excessive data exposure that make credential stuffing feasible. It also checks whether API key usage is consistent with defined permissions and whether sensitive endpoints lack additional authorization checks, highlighting findings mapped to OWASP API Top 10 and relevant compliance frameworks.

To reduce the risk of credential stuffing when using API keys in NestJS, combine strict validation, scoped permissions, and runtime protections. Avoid accepting API keys as the sole factor for privileged operations; instead, pair them with per-request checks and monitoring.

1. Use environment variables and typed configuration

Never hardcode keys. Use NestJS’s built-in ConfigModule to inject keys from environment variables and enforce validation at startup.

// config.module.ts
import { Module } from '@nestjs/common';
import { ConfigService } from '@nestjs/config';

@Module({
  imports: [],
  providers: [
    {
      provide: 'API_KEYS',
      useFactory: (config: ConfigService) => {
        const keys = config.get('API_KEYS')?.split(',') ?? [];
        if (!keys.length) {
          throw new Error('API_KEYS must be defined as a comma-separated list');
        }
        return new Set(keys);
      },
      inject: [ConfigService],
    },
  ],
  exports: ['API_KEYS'],
})
export class ConfigModule {}

2. Validate keys with a custom guard and scope binding

Create an API key guard that checks the key and enforces scope or tenant constraints. This prevents a key issued for read-only analytics from being used to access administrative routes.

// api-key.guard.ts
import { Injectable, CanActivate, ExecutionContext, ForbiddenException } from '@nestjs/common';
import { REQUEST } from '@nestjs/core';
import { ApiKeyScopesService } from './api-key-scopes.service';

@Injectable()
export class ApiKeyGuard implements CanActivate {
  constructor(
    private readonly scopeService: ApiKeyScopesService,
    @REQUEST() private readonly req: Request,
  ) {}

  async canActivate(context: ExecutionContext): Promise {
    const headerKey = this.req.headers['x-api-key'];
    const routeScopes = this.getRouteScopes(context);

    if (!headerKey) {
      throw new ForbiddenException('Missing API key');
    }

    const isValid = await this.scopeService.validateKeyAndScope(headerKey, routeScopes);
    if (!isValid) {
      throw new ForbiddenException('Invalid key or insufficient scope');
    }
    return true;
  }

  private getRouteScopes(context: ExecutionContext): string[] {
    const controllerScopes = context.getClass<{ scopes?: string[] }>()?.scopes || [];
    const methodScopes = context.getHandler<{ scopes?: string[] }>()?.scopes || [];
    return [...new Set([...controllerScopes, ...methodScopes])];
  }
}

3. Enforce rate limiting and reuse detection

Apply rate limiting per key using a token bucket or sliding window. Track recent request signatures to detect rapid enumeration patterns typical of credential stuffing.

// rate-limiting.middleware.ts
import { Injectable, NestMiddleware } from '@nestjs/common';
import { Request, Response, NextFunction } from 'express';
import { RateLimiterRedis } from 'rate-limiter-flexible';

@Injectable()
export class RateLimitingMiddleware implements NestMiddleware {
  private limiter = new RateLimiterRedis({
    storeClient: { host: '127.0.0.1', port: 6379 },
    keyPrefix: 'middlebrick_rl',
    points: 60,           // 60 requests
    duration: 60,         // per 60 seconds
    blockDuration: 300,   // block for 5 minutes on abuse
  });

  use(req: Request, res: Response, next: NextFunction) {
    const key = req.headers['x-api-key'] || req.ip;
    this.limiter.consume(key)
      .then(() => next())
      .catch(() => res.status(429).json({ error: 'Too many requests' }));
  }
}

4. Bind keys to metadata and rotate regularly

Store metadata such as owner, scope, and creation date alongside keys in a secure store. Rotate keys on a schedule and revoke compromised keys immediately. The validation step should compare the provided key against this metadata to ensure it matches expected usage patterns.

5. Combine with other security checks

Use input validation to reject malformed keys and ensure headers are normalized to avoid case-sensitivity issues. Apply encryption in transit and at rest for key storage, and log anomalous usage for audit and detection.