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Fundamentals

Automatic Encryption

On this page

  • How Encrypted Writes and Reads Work
  • Encrypted Writes
  • Encrypted Reads
  • Enabling Automatic Client-Side Field Level Encryption
  • Server-Side Field Level Encryption Enforcement

MongoDB supports automatically encrypting fields in read and write operations when using Client-Side Field Level Encryption. You can perform automatic encryption using mongosh and official MongoDB drivers which are compatible with version 4.2 and later. For a complete list of official compatible drivers with support for CSFLE, see Driver Compatibility Compatibility.

How Encrypted Writes and Reads Work

The following diagrams show how the client application and driver write and read field-level encrypted data.

Encrypted Writes

For write operations, the driver encrypts field values prior to writing to the MongoDB database.

The following diagram shows the steps taken by the client application and driver to perform a write of field-level encrypted data:

Diagram that shows the data flow for a write of field-level encrypted data

Encrypted Reads

For read operations, the driver encrypts field values in the query prior to issuing the read operation.

For read operations that return encrypted fields, the driver automatically decrypts the encrypted values only if the driver was configured with access to the Customer Master Key (CMK) and Data Encryption Keys (DEK) used to encrypt those values.

The following diagram shows the steps taken by the client application and driver to query and decrypt field-level encrypted data:

Diagram that shows the data flow for querying and reading field-level encrypted data

Enabling Automatic Client-Side Field Level Encryption

To enable automatic encryption, specify automatic encryption settings in your client's MongoClient instance.

The following code snippets show how to create a client with automatic encryption enabled in mongosh and MongoDB drivers:

var autoEncryptionOpts =
{
   "keyVaultNamespace" : "<database>.<collection>",
   "kmsProviders" : { ... },
   "schemaMap" : { ... }
}
cluster = Mongo(
  "<Your Connection String>",
  autoEncryptionOpts
);

Tip

Environment Variables

If possible, consider defining the credentials provided in kmsProviders as environment variables, and then passing them to mongosh using the --eval option. This minimizes the chances of credentials leaking into logs.

var clientSettings = MongoClientSettings.FromConnectionString(_connectionString);
var autoEncryptionOptions = new AutoEncryptionOptions(
    keyVaultNamespace: keyVaultNamespace,
    kmsProviders: kmsProviders,
    schemaMap: schemaMap,
    extraOptions: extraOptions);
clientSettings.AutoEncryptionOptions = autoEncryptionOptions;
var client = new MongoClient(clientSettings);
autoEncryptionOpts := options.AutoEncryption().
	SetKmsProviders(provider.Credentials()).
	SetKeyVaultNamespace(keyVaultNamespace).
	SetSchemaMap(schemaMap).
	SetExtraOptions(extraOptions)
client, err := mongo.Connect(context.TODO(), options.Client().ApplyURI(uri).SetAutoEncryptionOptions(autoEncryptionOpts))
MongoClientSettings clientSettings = MongoClientSettings.builder()
    .applyConnectionString(new ConnectionString("mongodb://localhost:27017"))
    .autoEncryptionSettings(AutoEncryptionSettings.builder()
        .keyVaultNamespace(keyVaultNamespace)
        .kmsProviders(kmsProviders)
        .schemaMap(schemaMap)
        .extraOptions(extraOptions)
        .build())
    .build();
MongoClient mongoClient = MongoClients.create(clientSettings);
const secureClient = new MongoClient(connectionString, {
  useNewUrlParser: true,
  useUnifiedTopology: true,
  monitorCommands: true,
  autoEncryption: {
    keyVaultNamespace,
    kmsProviders,
    schemaMap: patientSchema,
    extraOptions: extraOptions,
  },
});
fle_opts = AutoEncryptionOpts(
  kms_providers,
  key_vault_namespace,
  schema_map=patient_schema,
  **extra_options
)
client = MongoClient(connection_string, auto_encryption_opts=fle_opts)

For more information on CSFLE-specific MongoClient settings, see CSFLE-Specific MongoClient Options.

Server-Side Field Level Encryption Enforcement

MongoDB supports using schema validation to enforce encryption of specific fields in a collection. Clients performing automatic Client-Side Field Level Encryption have specific behavior depending on the database connection configuration:

  • If the connection autoEncryptionOpts schemaMap object contains a key for the specified collection, the client uses that object to perform automatic field level encryption and ignores the remote schema. At minimum, the local rules must encrypt those fields that the remote schema marks as requiring encryption.

  • If the connection autoEncryptionOpts schemaMap object does not contain a key for the specified collection, the client downloads the server-side remote schema for the collection and uses it to perform automatic field level encryption.

    Important

    Behavior Considerations

    When autoEncryptionOpts does not contain a key for the specified collection:

    • The client trusts that the server has a valid schema with respect to automatic field level encryption.

    • The client uses the remote schema to perform automatic CSFLE only. The client does not enforce any other validation rules specified in the schema.

To learn how to set up server-side CSFLE enforcement, see Server-Side Schema Enforcement.

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