Broken Authentication in Loopback with Dynamodb

Loopback is a widely used Node.js framework that supports multiple authentication strategies, including local and token-based flows. When integrating with DynamoDB as the user store, misconfiguration can expose authentication logic and enable account takeover. A common pattern is to store user records in a DynamoDB table keyed by a unique identifier such as userId or email. If the API exposes an endpoint like /api/users/me that retrieves the caller’s profile using a request context (e.g., req.accessToken.userId) without re-verifying ownership, it can lead to Insecure Direct Object References (IDOR) and Broken Authentication.

For example, an attacker authenticated as one user might manipulate the request to reference another user’s userId. If the Loopback controller directly uses this value to perform a DynamoDB GetItem or Query without ensuring the authenticated subject matches the requested resource, the attacker can read or modify other users’ data. This is a BOLA/IDOR issue nested within a Broken Authentication flow, because the framework’s authentication middleware may have issued a valid token but authorization boundaries are not enforced at the data-access layer.

DynamoDB-specific risk arises when access patterns rely on client-supplied keys without server-side mapping checks. Suppose a Loopback model is configured with a datasource pointing to DynamoDB and a model definition like User maps to a table with userId as the partition key. If a controller action uses User.findById(req.params.id) and req.params.id is not reconciled with the authenticated subject, the unauthenticated attack surface includes enumeration or tampering. Moreover, if tokens are not rotated or invalidated properly (e.g., missing short-lived tokens or refresh token revocation), stolen credentials remain valid longer than necessary, increasing the window for exploitation.

Another vector involves credential storage. If passwords are stored in DynamoDB without proper hashing and salting (e.g., using plain text or a weak scheme), an attacker who gains read access via IDOR can recover credentials. MiddleBrick scans this attack surface by testing unauthenticated endpoints and inspecting authentication mechanisms; it flags missing ownership validation and weak session handling. Findings map to OWASP API Top 10 2023: Broken Authentication and Security Misconfiguration, and can be aligned with compliance frameworks such as SOC2 and GDPR.

Real-world patterns include endpoints that accept a user identifier in the URL path or body without correlating it to the authenticated context. For instance, a PUT /api/users/{id} that updates profile attributes should ensure id matches the authenticated subject. Without this check, the API implicitly trusts the client-supplied identifier, enabling privilege escalation or account manipulation. middleBrick’s checks for BOLA/IDOR and Authentication are designed to surface these gaps during black-box scanning in 5–15 seconds.

To remediate Broken Authentication in Loopback with DynamoDB, enforce strict ownership checks and avoid direct use of client-provided identifiers. Below are concrete code examples that demonstrate secure patterns.

1. Ensure authenticated subject matches requested resource

Instead of allowing a generic findById that accepts any id, bind the request’s authenticated subject to the query. Assume you have a Loopback controller method handling profile retrieval.

// Good: controller/me.controller.js
const {repository} = require('loopback-datasource-juggler');

module.exports = function(MeController) {
  MeController.prototype.getMyProfile = async function(ctx) {
    const userId = ctx.req.accessToken.userId; // from auth token
    if (!userId) {
      const err = new Error('Authentication required');
      err.statusCode = 401;
      throw err;
    }
    const User = ctx.models.User;
    const user = await User.findOne({where: {userId}});
    if (!user) {
      const err = new Error('Not found');
      err.statusCode = 404;
      throw err;
    }
    return user;
  };
};

This ensures the authenticated subject from the token is used as the query filter, preventing IDOR. The DynamoDB connector in Loopback translates findOne into a Query with a filter on the partition key derived from the token, not from user input.

2. Parameterize DynamoDB queries and avoid concatenation

When interacting directly with the AWS SDK, use parameter objects and never concatenate identifiers into the request.

// Good: services/user.service.js using AWS SDK v3
const {DynamoDBClient, GetItemCommand} = require('@aws-sdk/client-dynamodb');
const {marshall, unmarshall} = require('@aws-sdk/util-dynamodb');

const client = new DynamoDBClient({region: 'us-east-1'});

async function getUserByUserId(userId) {
  const params = {
    TableName: process.env.USERS_TABLE,
    Key: marshall({userId}),
  };
  const command = new GetItemCommand(params);
  const response = await client.send(command);
  return response.Item ? unmarshall(response.Item) : null;
}

In a Loopback context, wrap such logic in a repository or service and ensure the userId passed is derived from the authenticated token, not from req.params.id when handling generic endpoints.

3. Hash credentials and enforce token hygiene

Store passwords using a strong, adaptive hash (e.g., bcrypt). Do not store secrets in DynamoDB in plain text.

// Good: models/user.json — ensure password hash field is not exposed
{
  "name": "User",
  "base": "User",
  "idInjection": true,
  "options": {
    "validateUpsert": true
  },
  "properties": {
    "email": {"type": "string", "required": true},
    "password": {"type": "string", "required": true},
    "userId": {"type": "string", "required": true}
  },
  "acls": [
    {
      "principalType": "ROLE",
      "principalId": "$everyone",
      "permission": "DENY"
    }
  ]
}

In your user registration or login flow, hash the password before persisting:

// Good: common/models/user.js — hook to hash password
module.exports = function(User) {
  User.observe('before save', async (ctx, next) => {
    if (ctx.instance && ctx.instance.password) {
      const bcrypt = require('bcrypt');
      const saltRounds = 10;
      ctx.instance.password = await bcrypt.hash(ctx.instance.password, saltRounds);
    }
    next();
  });
};

For session security, set short expiration on access tokens and implement token revocation checks. In combination with DynamoDB TTL for forgotten sessions, this reduces the impact of token leakage. middleBrick’s Continuous Monitoring (Pro plan) can detect weak session handling and prompt rotation issues across scanned APIs.

4. Use the GitHub Action to enforce thresholds in CI/CD

Add API security checks to your CI/CD pipeline so that a failing score blocks deployment. With the GitHub Action, you can set a score threshold and fail the build if risk levels exceed your policy.

# .github/workflows/api-security.yml
name: API Security Check
on: [push, pull_request]
jobs:
  security:
    runs-on: ubuntu-latest  
    steps:
      - uses: actions/checkout@v4
      - name: Run middleBrick scan
        uses: middlebread/action@v1
        with:
          url: 'https://api.example.com/openapi.json'
          threshold: 'C'

This ensures Broken Authentication issues are caught before reaching production, complementing runtime protections.