Sensitive information

Sensitive information is information that either requires additional permissions for read/write operations or is meant to be accessed only programmatically for various reasons. Examples of sensitive information include customer passwords, addresses, date of birth, and the number of orders for a product.

Exposing sensitive information to users without permissions

Let's focus on the case when an endpoint, or a page, is configured only for authenticated customers or admin users with certain permissions, yet still exposes information that it shouldn't.

Customer information example

Imagine a page or an endpoint that allows admin users to read data of a customer with the specified ID. The controller/endpoint is properly configured to be accessible only by admin users that have Magento_Customer::read_customer permission for their role. When developing this functionality, a responsible service would probably look something like this:

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interface CustomerQueryServiceInterface {
    public function findById(string $id): CustomerInterface;
}
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interface CustomerQueryServiceInterface {
    public function findById(string $id): CustomerInterface;
}

The service is really abstract. Most likely, it's actively used in other places where there's a need to get customer data by ID. However, the dob and addresses properties also require the Magento_Customer::personal_info permission, which is intended for the most trusted admin users only. This creates a problem for the customer read endpoint/page: CustomerQueryServiceInterface::findById() always returns the full set of customer info, including dob and addresses.

Here's how the sensitive information will be exposed through various interfaces.

REST web API

The application framework serializes all properties defined in CustomerInterface into JSON and exposes them. If the endpoint is configured to require Magento_Customer::personal_info, then admin users without it won't be able to read basic customer data. If it is configured to require Magento_Customer::read_customer, then admin users without Magento_Customer::personal_info can see dob and addresses.

GraphQL

If there are dob and addresses nodes available in the schema.graphqls, then these properties will be exposed to all admin users.

HTML page using blocks

A block gets all customer data from CustomerQueryServiceInterface with a high chance that the necessary authorization that occurs before rendering any HTML code that contains dob and addresses will be forgotten.

HTML page using UI components

UI components read data from a global JS object that contains all data retrieved from data providers. The object is rendered into JS on the backend and is available in response HTML. The data provider that uses CustomerQueryServiceInterface will expose full customer data inside the response HTML.

A solution for the example

The solution is to have operation-specific DTOs and a case-specific service.

The first step is to make a case-specific service for customer data retrieval by admin users:

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interface AdminCustomerQueryServiceInterface {}
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interface AdminCustomerQueryServiceInterface {}

The second step is to define operation specific DTOs:

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interface ReadCustomerDataInterface {
    public function getId(): string;
    public function getName(): string;
}

interface ReadPersonalCustomerDataInterface {
    public function getId(): string;
    public function getDob(): \DateTime;
    public function getAddresses(): array;
}
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interface ReadCustomerDataInterface {
    public function getId(): string;
    public function getName(): string;
}

interface ReadPersonalCustomerDataInterface {
    public function getId(): string;
    public function getDob(): \DateTime;
    public function getAddresses(): array;
}

The final step is to define case-specific operations:

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interface AdminCustomerQueryServiceInterface {
    public function findById(string $id): ReadCustomerDataInterface;
    public function findPersonalDataById(string $id): ReadPersonalCustomerDataInterface;
}
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interface AdminCustomerQueryServiceInterface {
    public function findById(string $id): ReadCustomerDataInterface;
    public function findPersonalDataById(string $id): ReadPersonalCustomerDataInterface;
}

This service belongs in the business logic layer, so inside both these methods, you might use the same repository::method from the persistence layer. To avoid redundant calls to the repository, consider having an identity-map with full customer info to reuse when findPersonalDataById() is executed after findById() with the same ID.

With this approach, it is harder to expose the sensitive data accidentally. findPersonalDataById() will only be called when there's an explicit need to read sensitive data.

Here's how it will work for different interfaces.

HTML rendered with backend blocks

The block will have a condition: when the user has Magento_Customer::personal_info, call thefindPersonalDataById() method. Otherwise, leave the personal data empty.

HTML rendered on frontend

Inside the data provider for the UI component, the same condition listed above is present.

REST/SOAP web API

Both findById() and findPersonalDataById() have their own endpoints. The first requires Magento_Customer::read_customer, while the second requires Magento_Customer::personal_info. A client that wants to render the customer info page will issue two requests:

1. Fetch basic customer data from the findById() endpoint
2. Fetch personal customer data from the findPersonalDataById() endpoint

The second may fail with a 403 status. In this case, the client ignores the status and displays basic customer data only, assuming the current admin user does not have access to Magento_Customer::personal_info.

GraphQL

The dob and addresses fields have their own resolvers, which will validate access to Magento_Customer::personal_info. If successful, the resolvers call findPersonalDataById() and return the results.

Exposing sensitive information through a persistent storage

There is always a possibility of bad actors gaining access to persistent storage either through injection attacks, through misconfigured environment, or any other way. For that reason, you must protect sensitive information while it's in storage and while it's being transported by APIs or a HTML interface.

Hashed sensitive information

Sensitive information that is never exposed in plain text after creation and is only used for comparison can be safely stored in the form of a hash.

Good examples include passwords, tokens, and secrets. After a password (or similar entity) is created, there is no need to ever display it to a user again. Later on, there's only a need to compare user input to the existing password. A hash allows allows you to compare a value to a hashed one and to avoid exposing the original value. A salt is often used with hashes for passwords to prevent attacks using rainbow tables.

\Magento\Framework\Encryption\EncryptorInterface helps with hashes. Use getHash() method to generate a hash with or without a salt, depending on the second argument. (Using a salt is recommended.) Subsequently, use isValidHash() to compare the user-provided value to an existing hash. These methods handle salts, choose a secure algorithm, and will work after the encryption key is updated by an admin user.

Encrypted sensitive information

Extremely sensitive information that is only accessible to authorized users must be stored encrypted.

Private information such as addresses are good candidates for encryption, depending on your application requirements. Encrypting such information involves having an encryption key that is not stored in the same storage as the encrypted information.

The application handles encryption with \Magento\Framework\Encryption\EncryptorInterface. The encrypt() and decrypt() methods use the encryption key for encryption and choose the most secure algorithm with decent performance. It also handles old and new encryption keys and emerging best practices to encryption with regards to the algorithm.

Last updated 9/8/2023

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