Client-Side Field Level Encryption

New in MongoDB 4.2, client-side field level encryption allows administrators and developers to encrypt specific data fields in addition to other MongoDB encryption features.

With client-side field level encryption, developers can encrypt fields client-side without any server-side configuration or directives. Client-side field level encryption supports workloads where applications must guarantee that unauthorized parties, including server administrators, cannot read the encrypted data.

mongocryptd configuration

Client-side field level encryption requires the mongocryptd daemon / process to be running. If mongocryptd isn’t running, the driver will atempt to spawn an instance, utilizing the PATH environment variable. Alternatively, the path to mongocryptd can be specified by setting mongocryptdSpawnPath in extraOptions. A specific daemon / process URI can also be configured in the AutoEncryptionSettings class by setting mongocryptdURI in extraOptions.

More information about mongocryptd will soon be available from the official documentation.

Examples

Automatic client-side encryption

The following is a sample app that assumes the key and schema have already been created in MongoDB. The example uses a local key, however using AWS Key Management Service is also an option. The data in the encryptedField field is automatically encrypted on the insert and decrypted when using find on the client-side. The following example has been adapted from ClientSideEncryptionExamples.cs, which can be found on GitHub along with the driver source.

using System;
using System.Collections.Generic;
using MongoDB.Bson;
using MongoDB.Driver.Encryption;

namespace MongoDB.Driver.Examples
{
    public class ClientEncryptionExamples
    {
        private const string LocalMasterKey = "Mng0NCt4ZHVUYUJCa1kxNkVyNUR1QURhZ2h2UzR2d2RrZzh0cFBwM3R6NmdWMDFBMUN3YkQ5aXRRMkhGRGdQV09wOGVNYUMxT2k3NjZKelhaQmRCZGJkTXVyZG9uSjFk";

        public static void Main(string[] args)
        {
            var localMasterKey = Convert.FromBase64String(LocalMasterKey);

            var kmsProviders = new Dictionary<string, IReadOnlyDictionary<string, object>>();
            var localKey = new Dictionary<string, object>
            {
                { "key", localMasterKey }
            };
            kmsProviders.Add("local", localKey);

            var keyVaultNamespace = CollectionNamespace.FromFullName("encryption.__keyVault");
            var autoEncryptionOptions = new AutoEncryptionOptions(keyVaultNamespace, kmsProviders);

            var mongoClientSettings = new MongoClientSettings
            {
                AutoEncryptionOptions = autoEncryptionOptions
            };
            var client = new MongoClient(mongoClientSettings);
            var database = client.GetDatabase("test");
            database.DropCollection("coll");
            var collection = database.GetCollection<BsonDocument>("coll");

            collection.InsertOne(new BsonDocument("encryptedField", "123456789"));

            var result = collection.Find(FilterDefinition<BsonDocument>.Empty).First();
            Console.WriteLine(result.ToJson());
        }
    }
}

The following example shows how to configure the AutoEncryptionSettings instance to create a new key and how to set the json schema map. The following example has been adapted from ClientSideEncryptionExamples.cs, which can be found on Github along with the driver source.

using System;
using System.Collections.Generic;
using System.Threading;
using MongoDB.Bson;
using MongoDB.Driver.Encryption;

namespace MongoDB.Driver.Examples
{
    public class ClientEncryptionExamples
    {
        private const string LocalMasterKey = "Mng0NCt4ZHVUYUJCa1kxNkVyNUR1QURhZ2h2UzR2d2RrZzh0cFBwM3R6NmdWMDFBMUN3YkQ5aXRRMkhGRGdQV09wOGVNYUMxT2k3NjZKelhaQmRCZGJkTXVyZG9uSjFk";

        public static void Main(string[] args)
        {
            var localMasterKey = Convert.FromBase64String(LocalMasterKey);

            var kmsProviders = new Dictionary<string, IReadOnlyDictionary<string, object>>();
            var localKey = new Dictionary<string, object>
            {
                { "key", localMasterKey }
            };
            kmsProviders.Add("local", localKey);

            var keyVaultNamespace = CollectionNamespace.FromFullName("encryption.__keyVault");
            var keyVaultMongoClient = new MongoClient();
            var clientEncryptionSettings = new ClientEncryptionOptions(
                keyVaultMongoClient,
                keyVaultNamespace,
                kmsProviders);

            Guid dataKeyId;
            using (var clientEncryption = new ClientEncryption(clientEncryptionSettings))
            {
                dataKeyId = clientEncryption.CreateDataKey("local", new DataKeyOptions(), CancellationToken.None);
            }

            var base64DataKeyId = Convert.ToBase64String(GuidConverter.ToBytes(dataKeyId, GuidRepresentation.Standard));
            var collectionNamespace = CollectionNamespace.FromFullName("test.coll");

            var schemaMap = $@"{{
                properties: {{
                    encryptedField: {{
                        encrypt: {{
                            keyId: [{{
                                '$binary' : {{
                                    'base64' : '{base64DataKeyId}',
                                    'subType' : '04'
                                }}
                            }}],
                        bsonType: 'string',
                        algorithm: 'AEAD_AES_256_CBC_HMAC_SHA_512-Deterministic'
                        }}
                    }}
                }},
                'bsonType': 'object'
            }}";
            var autoEncryptionSettings = new AutoEncryptionOptions(
                keyVaultNamespace,
                kmsProviders,
                schemaMap: new Dictionary<string, BsonDocument>()
                {
                    { collectionNamespace.ToString(), BsonDocument.Parse(schemaMap) }
                });
            var clientSettings = new MongoClientSettings
            {
                AutoEncryptionOptions = autoEncryptionSettings
            };
            var client = new MongoClient(clientSettings);
            var database = client.GetDatabase("test");
            database.DropCollection("coll");
            var collection = database.GetCollection<BsonDocument>("coll");

            collection.InsertOne(new BsonDocument("encryptedField", "123456789"));

            var result = collection.Find(FilterDefinition<BsonDocument>.Empty).First();
            Console.WriteLine(result.ToJson());
        }
    }
}

Explicit Encryption and Decryption

Explicit encryption and decryption is a MongoDB Community Server feature and does not use the mongocryptd process. Explicit encryption is provided by the ClientEncryption class. The following example has been adapted from ExplicitEncryptionExamples.cs:

using System;
using System.Collections.Generic;
using System.Threading;
using MongoDB.Driver.Encryption;
using MongoDB.Libmongocrypt;

namespace MongoDB.Driver.Examples
{
    public class ExplicitEncryptionExamples
    {
        private const string LocalMasterKey = "Mng0NCt4ZHVUYUJCa1kxNkVyNUR1QURhZ2h2UzR2d2RrZzh0cFBwM3R6NmdWMDFBMUN3YkQ5aXRRMkhGRGdQV09wOGVNYUMxT2k3NjZKelhaQmRCZGJkTXVyZG9uSjFk";

        public static void Main(string[] args)
        {
            var localMasterKey = Convert.FromBase64String(LocalMasterKey);
            var kmsProviders = new Dictionary<string, IReadOnlyDictionary<string, object>>();
            var localKey = new Dictionary<string, object>
            {
                { "key", localMasterKey }
            };
            kmsProviders.Add("local", localKey);

            var keyVaultNamespace = CollectionNamespace.FromFullName("encryption.__keyVault");
            var keyVaultClient = new MongoClient("mongodb://localhost");
            var keyVaultDatabase = keyVaultClient.GetDatabase(keyVaultNamespace.DatabaseNamespace.DatabaseName);
            keyVaultDatabase.DropCollection(keyVaultNamespace.CollectionName);

            // Create the ClientEncryption instance
            var clientEncryptionSettings = new ClientEncryptionOptions(
                keyVaultClient,
                keyVaultNamespace,
                kmsProviders);
            using (var clientEncryption = new ClientEncryption(clientEncryptionSettings))
            {
                var dataKeyId = clientEncryption.CreateDataKey(
                    "local",
                    new DataKeyOptions(),
                    CancellationToken.None);

                var originalString = "123456789";
                Console.WriteLine($"Original string {originalString}.");

                // Explicitly encrypt a field
                var encryptOptions = new EncryptOptions(
                    EncryptionAlgorithm.AEAD_AES_256_CBC_HMAC_SHA_512_Deterministic.ToString(),
                    keyId: dataKeyId);
                var encryptedFieldValue = clientEncryption.Encrypt(
                    originalString,
                    encryptOptions,
                    CancellationToken.None);
                Console.WriteLine($"Encrypted value {encryptedFieldValue}.");

                // Explicitly decrypt the field
                var decryptedValue = clientEncryption.Decrypt(encryptedFieldValue, CancellationToken.None);
                Console.WriteLine($"Decrypted value {decryptedValue}.");
            }
        }
    }
}

Explicit Encryption and Auto Decryption

Although automatic encryption requires MongoDB 4.2 Enterprise Server or a MongoDB 4.2 Atlas cluster, automatic decryption is supported for all users. To configure automatic decryption without automatic encryption set bypassAutoEncryption=true. The following example has been adapted from ExplicitEncryptionExamples.cs:

using System;
using System.Collections.Generic;
using System.Threading;
using MongoDB.Bson;
using MongoDB.Driver.Encryption;
using MongoDB.Libmongocrypt;

namespace MongoDB.Driver.Examples
{
    public class ExplicitEncryptionAndAutoDecryptionExamples
    {
        private const string LocalMasterKey = "Mng0NCt4ZHVUYUJCa1kxNkVyNUR1QURhZ2h2UzR2d2RrZzh0cFBwM3R6NmdWMDFBMUN3YkQ5aXRRMkhGRGdQV09wOGVNYUMxT2k3NjZKelhaQmRCZGJkTXVyZG9uSjFk";

        public static void Main(string[] args)
        {
            var localMasterKey = Convert.FromBase64String(LocalMasterKey);
            var kmsProviders = new Dictionary<string, IReadOnlyDictionary<string, object>>();
            var localKey = new Dictionary<string, object>
            {
                { "key", localMasterKey }
            };
            kmsProviders.Add("local", localKey);

            var keyVaultNamespace = CollectionNamespace.FromFullName("encryption.__keyVault");
            var collectionNamespace = CollectionNamespace.FromFullName("test.coll");
            var autoEncryptionOptions = new AutoEncryptionOptions(
                keyVaultNamespace,
                kmsProviders,
                bypassAutoEncryption: true);
            var clientSettings = MongoClientSettings.FromConnectionString("mongodb://localhost");
            clientSettings.AutoEncryptionOptions = autoEncryptionOptions;
            var mongoClient = new MongoClient(clientSettings);
            var database = mongoClient.GetDatabase(collectionNamespace.DatabaseNamespace.DatabaseName);
            database.DropCollection(collectionNamespace.CollectionName);
            var collection = database.GetCollection<BsonDocument>(collectionNamespace.CollectionName);

            var keyVaultClient = new MongoClient("mongodb://localhost");
            var keyVaultDatabase = keyVaultClient.GetDatabase(keyVaultNamespace.DatabaseNamespace.DatabaseName);
            keyVaultDatabase.DropCollection(keyVaultNamespace.CollectionName);

            // Create the ClientEncryption instance
            var clientEncryptionSettings = new ClientEncryptionOptions(
                keyVaultClient,
                keyVaultNamespace,
                kmsProviders);
            using (var clientEncryption = new ClientEncryption(clientEncryptionSettings))
            {
                var dataKeyId = clientEncryption.CreateDataKey(
                    "local",
                    new DataKeyOptions(),
                    CancellationToken.None);

                var originalString = "123456789";
                Console.WriteLine($"Original string {originalString}.");

                // Explicitly encrypt a field
                var encryptOptions = new EncryptOptions(
                    EncryptionAlgorithm.AEAD_AES_256_CBC_HMAC_SHA_512_Deterministic.ToString(),
                    keyId: dataKeyId);
                var encryptedFieldValue = clientEncryption.Encrypt(
                    originalString,
                    encryptOptions,
                    CancellationToken.None);
                Console.WriteLine($"Encrypted value {encryptedFieldValue}.");

                collection.InsertOne(new BsonDocument("encryptedField", encryptedFieldValue));

                // Automatically decrypts the encrypted field.
                var decryptedValue = collection.Find(FilterDefinition<BsonDocument>.Empty).First();
                Console.WriteLine($"Decrypted document {decryptedValue.ToJson()}.");
            }
        }
    }
}