Bola Idor in Dynamodb

BOLA (Broken Object Level Authorization) and IDOR (Insecure Direct Object References) vulnerabilities in DynamoDB often stem from improper handling of partition keys and sort keys in API endpoints. These attacks exploit the trust relationship between authenticated users and the database layer, allowing attackers to access or modify resources belonging to other users.

In DynamoDB, the most common BOLA/IDOR patterns involve:

• Directly passing user-controlled partition keys from request parameters to DynamoDB operations
• Missing authorization checks before database operations
• Using predictable resource identifiers that can be enumerated
• Improper validation of user ownership before CRUD operations

Consider this vulnerable DynamoDB pattern in Node.js:

app.get('/api/users/:userId', async (req, res) => {
  const userId = req.params.userId;
  const params = {
    TableName: 'Users',
    Key: {
      userId: userId
    }
  };
  const user = await dynamodb.get(params).promise();
  res.json(user);
});

The critical flaw here is that any authenticated user can request any userId, and the API will return the corresponding record without verifying ownership. An attacker simply needs to iterate through numeric or UUID user IDs to access other users' data.

Another common DynamoDB-specific pattern involves Global Secondary Indexes (GSIs) used for filtering:

app.get('/api/orders', async (req, res) => {
  const userId = req.query.userId || req.user.id; // Insecure default
  const params = {
    TableName: 'Orders',
    IndexName: 'UserOrdersIndex',
    KeyConditionExpression: 'userId = :userId',
    ExpressionAttributeValues: {
      ':userId': userId
    }
  };
  const orders = await dynamodb.query(params).promise();
  res.json(orders);
});

Here, if the userId parameter is not properly validated against the authenticated user's ID, attackers can access any user's orders by manipulating the query parameter.

Scan operations present another vulnerability vector:

app.get('/api/scans/:scanId', async (req, res) => {
  const scanId = req.params.scanId;
  const params = {
    TableName: 'Scans',
    Key: {
      scanId: scanId
    }
  };
  const scan = await dynamodb.get(params).promise();
  res.json(scan);
});

Without verifying that the authenticated user owns the scanId, this endpoint allows complete enumeration of all scan records in the database.

Detecting BOLA/IDOR vulnerabilities in DynamoDB requires both static code analysis and dynamic runtime testing. The key is identifying where user-controlled input flows directly to DynamoDB operations without proper authorization checks.

Static analysis patterns to look for:

• Request parameters directly used as partition keys or sort keys
• Missing authorization middleware before database operations
• Predictable resource identifiers (sequential integers, short UUIDs)
• GSI queries using user-controlled partition keys
• Scan operations without user filtering

Dynamic testing involves attempting authenticated requests with manipulated identifiers:

const axios = require('axios');
const userId = 'user-123';
const maliciousIds = ['user-124', 'user-125', 'user-000', 'admin'];

for (const testId of maliciousIds) {
  try {
    const response = await axios.get(`https://api.example.com/users/${testId}`, {
      headers: { Authorization: `Bearer ${token}` }
    });
    if (response.status === 200) {
      console.log(`Vulnerability detected: accessed ${testId}`);
    }
  } catch (error) {
    // Handle error
  }
}

middleBrick's DynamoDB-specific scanning includes:

middleBrick's CLI tool can scan DynamoDB-backed APIs with a single command:

npx middlebrick scan https://api.example.com --dynamodb

The tool automatically identifies DynamoDB-specific patterns and tests for authorization bypasses without requiring credentials or access to your infrastructure.

Remediating BOLA/IDOR vulnerabilities in DynamoDB requires implementing proper authorization checks and secure data access patterns. The core principle is always verifying resource ownership before database operations.

Secure DynamoDB access pattern:

app.get('/api/users/:userId', async (req, res) => {
  const requestedUserId = req.params.userId;
  const authenticatedUserId = req.user.id;
  
  // Authorization check
  if (requestedUserId !== authenticatedUserId) {
    return res.status(403).json({ 
      error: 'Access to this resource is not authorized' 
    });
  }
  
  const params = {
    TableName: 'Users',
    Key: {
      userId: requestedUserId
    }
  };
  
  try {
    const user = await dynamodb.get(params).promise();
    if (!user || !user.Item) {
      return res.status(404).json({ error: 'User not found' });
    }
    res.json(user.Item);
  } catch (error) {
    res.status(500).json({ error: 'Database error' });
  }
});

For GSI queries, implement user-scoped filtering:

app.get('/api/orders', async (req, res) => {
  const authenticatedUserId = req.user.id;
  const params = {
    TableName: 'Orders',
    IndexName: 'UserOrdersIndex',
    KeyConditionExpression: 'userId = :userId',
    ExpressionAttributeValues: {
      ':userId': authenticatedUserId
    }
  };
  
  try {
    const result = await dynamodb.query(params).promise();
    res.json(result.Items);
  } catch (error) {
    res.status(500).json({ error: 'Database error' });
  }
});

Using DynamoDB's built-in features for security:

• Condition Expressions to prevent unauthorized updates
• Fine-grained access control with IAM policies
• Encryption at rest for sensitive data

Conditional update example:

app.put('/api/users/:userId', async (req, res) => {
  const authenticatedUserId = req.user.id;
  const requestedUserId = req.params.userId;
  
  if (authenticatedUserId !== requestedUserId) {
    return res.status(403).json({ error: 'Unauthorized' });
  }
  
  const params = {
    TableName: 'Users',
    Key: {
      userId: requestedUserId
    },
    UpdateExpression: 'set #name = :name, #email = :email',
    ExpressionAttributeNames: {
      '#name': 'name',
      '#email': 'email'
    },
    ExpressionAttributeValues: {
      ':name': req.body.name,
      ':email': req.body.email
    },
    ConditionExpression: 'userId = :userId',
    ExpressionAttributeValues: {
      ':userId': authenticatedUserId
    }
  };
  
  try {
    await dynamodb.update(params).promise();
    res.json({ success: true });
  } catch (error) {
    if (error.code === 'ConditionalCheckFailedException') {
      return res.status(403).json({ error: 'Unauthorized' });
    }
    res.status(500).json({ error: 'Database error' });
  }
});

Implementing comprehensive authorization middleware:

const authorizeResource = async (req, res, next) => {
  const { userId, resourceId } = req.params;
  const authenticatedUserId = req.user.id;
  
  // Check if user owns the resource
  const params = {
    TableName: 'ResourceOwnership',
    Key: {
      userId: authenticatedUserId,
      resourceId: resourceId
    }
  };
  
  try {
    const result = await dynamodb.get(params).promise();
    if (!result.Item) {
      return res.status(403).json({ error: 'Access denied' });
    }
    next();
  } catch (error) {
    res.status(500).json({ error: 'Authorization check failed' });
  }
};

// Usage
app.get('/api/resources/:resourceId', 
  authorizeResource, 
  async (req, res) => {
    // Authorized code here
  }
);