Queryable Encryption
This cookbook provides a tutorial on setting up and using Queryable Encryption (QE) with Doctrine MongoDB ODM to protect sensitive data in your documents.
Introduction
In many applications, you need to store sensitive information like social security numbers, financial data, or personal details. MongoDB's Queryable Encryption allows you to encrypt this data on the client-side, store it as fully randomized encrypted data, and still run expressive queries on it. This ensures that sensitive data is never exposed in an unencrypted state on the server, in system logs, or in backups.
This tutorial will guide you through the process of securing a document's fields using queryable encryption, from defining the document and configuring the connection to storing and querying the encrypted data.
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Queryable Encryption is only available on MongoDB Enterprise 7.0+ or MongoDB Atlas. |
The Scenario
We will model a Patient document that has an embedded PatientRecord.
This record contains sensitive information:
- A Social Security Number (
ssn), which we need to query for exact matches. - A
billingAmount, which should support range queries. - A
billingobject, which should be encrypted but not directly queryable.
Defining the Documents
First, let's define our Patient, PatientRecord, and Billing
classes. We use the #[Encrypt] attribute to mark
fields that require encryption.
<?phpnamespace Documents;use Doctrine\ODM\MongoDB\Mapping\Annotations as ODM;use Doctrine\ODM\MongoDB\Mapping\Annotations\Encrypt;use Doctrine\ODM\MongoDB\Mapping\Annotations\EncryptQuery;#[ODM\Document]class Patient{ #[ODM\Id] public string $id; #[ODM\EmbedOne(targetDocument: PatientRecord::class)] public PatientRecord $patientRecord;}#[ODM\EmbeddedDocument]class PatientRecord{ /** * Encrypted with equality queries. * This allows us to find a patient by their exact SSN. */ #[ODM\Field(type: 'string')] #[Encrypt(queryType: EncryptQuery::Equality)] public string $ssn; /** * The entire embedded document is encrypted as an object. * By not specifying a queryType, we make it non-queryable. */ #[ODM\EmbedOne(targetDocument: Billing::class)] #[Encrypt] public Billing $billing; /** * Encrypted with range queries. * This allows us to query for billing amounts within a certain range. */ #[ODM\Field(type: 'int')] #[Encrypt(queryType: EncryptQuery::Range, min: 0, max: 5000, sparsity: 1)] public int $billingAmount;}#[ODM\EmbeddedDocument]class Billing{ #[ODM\Field(type: 'string')] public string $creditCardNumber;}Configuration and Usage
The following example demonstrates how to configure the DocumentManager for
encryption and how to work with encrypted documents.
Step 1: Configure the DocumentManager
First, we configure the DocumentManager with autoEncryption options.
For more details on the available options, see the MongoDB\Driver\Manager
documentation. We'll use the local KMS provider for simplicity. For this
provider, you need a 96-byte master key.
The following code will look for the key in a local file (master-key.bin)
and generate it if it doesn't exist. In a production environment, you should
use a non-local key management service (KMS).
For each field marked with #[Encrypt], the MongoDB driver will generate
a Data Encryption Key (DEK), encrypt it with the master key, and store it in
the key vault collection. In Doctrine ODM, the key vault collection is set
to <database>.datakeys by default, but you can change it using the
keyVaultNamespace option.
<?phpuse Doctrine\ODM\MongoDB\Configuration;use Doctrine\ODM\MongoDB\Mapping\Driver\AttributeDriver;use MongoDB\BSON\Binary;// For the local KMS provider, we need a 96-byte master key.// We'll store it in a local file. If the file doesn't exist, we generate// one. In a production environment, ensure this key file is properly// secured.$keyFile = __DIR__ . '/master-key.bin';if (!file_exists($keyFile)) { file_put_contents($keyFile, random_bytes(96));}$masterKey = new Binary(file_get_contents($keyFile), Binary::TYPE_GENERIC);$config = new Configuration();// Enable auto encryption and set the KMS provider.$config->setAutoEncryption([ 'keyVaultNamespace' => 'encryption.datakeys']);$config->setKmsProvider([ 'type' => 'local', 'key' => new Binary($masterKey),]);// Other configuration$config->setProxyDir(__DIR__ . '/Proxies');$config->setProxyNamespace('Proxies');$config->setHydratorDir(__DIR__ . '/Hydrators');$config->setHydratorNamespace('Hydrators');$config->setPersistentCollectionDir(__DIR__ . '/PersistentCollections');$config->setPersistentCollectionNamespace('PersistentCollections');$config->setDefaultDB('my_db');$config->setMetadataDriverImpl(new AttributeDriver([__DIR__]));Step 2: Create the DocumentManager
The MongoDB\Client will be instantiated with the options from the
configuration.
<?phpuse Doctrine\ODM\MongoDB\DocumentManager;use MongoDB\Client;$client = new Client( uri: 'mongodb://localhost:27017/', uriOptions: [], driverOptions: $config->getDriverOptions(),);$documentManager = DocumentManager::create($client, $config);The driverOptions passed to the client contain the autoEncryption option
that was configured in the previous step.
Step 3: Create the Encrypted Collection
Next, we use the SchemaManager to create the collection with the necessary
encryption metadata. To make the example re-runnable, we can drop the collection
first.
<?php$schemaManager = $documentManager->getSchemaManager();$schemaManager->dropDocumentCollection(Patient::class);$schemaManager->createDocumentCollection(Patient::class);Step 4: Persist and Query Documents
Finally, we can persist and query documents as usual. The encryption and decryption will be handled automatically.
<?php$patient = new Patient();$patient->patientRecord = new PatientRecord();$patient->patientRecord->ssn = '123-456-7890';$patient->patientRecord->billingAmount = 1500;$patient->patientRecord->billing = new Billing();$patient->patientRecord->billing->creditCardNumber = '9876-5432-1098-7654';$documentManager->persist($patient);$documentManager->flush();$documentManager->clear();// Query the document using an encrypted field$foundPatient = $documentManager->getRepository(Patient::class)->findOneBy([ 'patientRecord.ssn' => '123-456-7890',]);// The document is retrieved and its fields are automatically decryptedassert($foundPatient instanceof Patient);assert($foundPatient->patientRecord->billingAmount === 1500);What the Document Looks Like in the Database
When you inspect the document directly in the database (e.g., using mongosh
or MongoDB Compass), you will see that the fields marked with #[Encrypt]
are stored as BSON binary data (subtype 6), not the original BSON type. The
driver also adds a __safeContent__ field to the document. For more details,
see the Queryable Encryption Fundamentals in the MongoDB manual.
{ "_id": ObjectId("..."), "patientRecord": { "ssn": Binary("...", 6), "billing": Binary("...", 6), "billingAmount": Binary("...", 6) }, "__safeContent__": [ Binary("...", 0) ]}Limitations
- The ODM simplifies configuration by supporting a single KMS provider per
DocumentManagerthroughConfiguration::setKmsProvider(). If you need to work with multiple KMS providers, you must manually configure thekmsProvidersarray and pass it as a driver option, bypassing the ODM's helper method. - Automatic generation of the
encryptedFieldsMapis not compatible withSINGLE_COLLECTIONinheritance. Because all classes in the hierarchy share a single collection, theSchemaManagercannot merge their encrypted fields before creating the collection. - Embedded documents and collections are encrypted as a whole. As such,
they cannot be partially updated. Only the
set*andatomicSet*collection strategies can be used. - For a complete list of limitations, please refer to the official Queryable Encryption Limitations documentation.