Securing MongoDB Part 3: Database Auditing and Encryption

Mat Keep


Welcome back to our 4-part blog series presenting the best practices and controls available in MongoDB to help you create a secure, compliant database platform.

In this installment, we’ll be discussing database auditing and encryption.

As a quick recap, in part 1, we took a look at the general requirements for data security and regulatory compliance, and then in part 2, reviewed MongoDB access control enforcing authentication and authorization. In part 4, we’ll wrap up with environmental control and management.

If you want to get a head-start and learn about all of these topics in one installment, just go ahead and download the MongoDB Security Architecture guide.

MongoDB Auditing

The auditing framework provided as part of MongoDB Enterprise Advanced logs all access and actions executed against the database. The auditing framework captures administrative actions (DDL) such as schema operations as well as authentication and authorization activities, along with read and write (DML) operations to the database. Administrators can construct and filter audit trails for any operation against MongoDB, whether DML, DCL or DDL without having to rely on third party tools. For example, it is possible to log and audit the identities of users who retrieved specific documents, and any changes made to the database during their session.

**Figure 1**: MongoDB Maintains an Audit Trail of Administrative Actions Against the Database

Administrators can configure MongoDB to log all actions or apply filters to capture only specific events, users or roles. The audit log can be written to multiple destinations in a variety of formats including to the console and syslog (in JSON format), and to a file (JSON or BSON), which can then be loaded to MongoDB and analyzed to identify relevant events. MongoDB Enterprise Advanced also supports role-based auditing. It is possible to log and report activities by specific role, such as userAdmin or dbAdmin – coupled with any inherited roles each user has – rather than having to extract activity for each individual administrator.

Auditing adds performance overhead to a MongoDB system. The amount is dependent on several factors including which events are logged and where the audit log is maintained, such as on an external storage device and the audit log format. Users should consider the specific needs of their application for auditing and their performance goals in order to determine their optimal configuration.

Learn more from the MongoDB auditing documentation.

MongoDB Encryption

Administrators can encrypt MongoDB data in motion over the network and at rest in permanent storage.

Network Encryption

Support for SSL/TLS allows clients to connect to MongoDB over an encrypted channel. Clients are defined as any entity capable of connecting to the MongoDB server, including:

  • Users and administrators
  • Applications
  • MongoDB tools (e.g., mongodump, mongorestore, mongotop)
  • Nodes that make up a MongoDB cluster, such as replica set members, query routers and config servers.

It is possible to mix SSL/TLS with non-SSL/TLS connections on the same port, which can be useful when applying finer grained encryption controls for internal and external traffic, as well as avoiding downtime when upgrading a MongoDB cluster to support SSL.

The TLS protocol is also supported with x.509 certificates.

MongoDB Enterprise Advanced supports FIPS 140-2 encryption if run in FIPS Mode with a FIPS validated Cryptographic module. The mongod and mongos processes should be configured with the "sslFIPSMode" setting In addition, these processes should be deployed on systems with an OpenSSL library configured with the FIPS 140-2 module.

The MongoDB documentation includes a tutorial for configuring TLS/SSL connections.

Disk Encryption

There are multiple ways to encrypt data at rest with MongoDB. Encryption can implemented at the application level, or via external filesystem and disk encryption solutions. By introducing additional technology into the stack, both of these approaches can add cost and complexity.

With the introduction of the Encrypted storage engine in MongoDB 3.2, protection of data at-rest becomes an integral feature of the database. By natively encrypting database files on disk, administrators eliminate both the management and performance overhead of external encryption mechanisms. This new storage engine provides an additional level of defense, allowing only those staff with the appropriate database credentials access to encrypted data.

**Figure 2:** End to End Encryption – Data In-Flight and Data At-Rest

Using the Encrypted storage engine, the raw database content, referred to as plaintext, is encrypted using an algorithm that takes a random encryption key as input and generates ciphertext that can only be read if decrypted with the decryption key. The process is entirely transparent to the application. MongoDB supports a variety of encryption schema, with AES-256 (256 bit encryption) in CBC mode being the default. AES-256 in GCM mode is also supported. The encryption schema can be configured for FIPS 140-2 compliance.

The storage engine encrypts each database with a separate key. The key-wrapping scheme in MongoDB wraps all of the individual internal database keys with one external master key for each server. The Encrypted storage engine supports two key management options – in both cases, the only key being managed outside of MongoDB is the master key:

  • Local key management via a keyfile.
  • Integration with a third party key management appliance via the KMIP protocol (recommended).

Most regulatory requirements mandate that the encryption keys must be rotated and replaced with a new key at least once annually. MongoDB can achieve key rotation without incurring downtime by performing rolling restarts of the replica set. When using a KMIP appliance, the database files themselves do not need to be re-encrypted, thereby avoiding the significant performance overhead imposed by key rotation in other databases. Only the master key is rotated, and the internal database keystore is re-encrypted.

The Encrypted storage engine is designed for operational efficiency and performance:

  • Compatible with WiredTiger’s document level concurrency control and compression.
  • Support for Intel’s AES-NI equipped CPUs for acceleration of the encryption/decryption process.
  • As documents are modified, only updated storage blocks need to be encrypted, rather than the entire database.

Based on user testing, the Encrypted storage engine minimizes performance overhead to around 15% (this can vary, based on data types being encrypted), which can be much less than the observed overhead imposed by some filesystem encryption solutions.

The Encrypted storage engine is based on WiredTiger and available as part of MongoDB Enterprise Advanced. Refer to the documentation to learn more, and see a tutorial on how to configure the storage engine.

MongoDB Atlas Encryption

As discussed in Part 2 of the Securing MongoDB blog series, MongoDB Atlas is a database as a service for MongoDB, providing all of the features of the database, without the operational heavy lifting required for any application. MongoDB Atlas has been engineered to deliver robust encryption controls.

Data managed by the MongoDB Atlas service can be encrypted on the network and on disk. Support for TLS/SSL allows clients to connect to MongoDB over an encrypted channel. All data transfers across the cluster are also encrypted. Data at rest can be protected using encrypted data volumes. Note that this uses the cloud provider’s native volume encryption solution, rather than the MongoDB encrypted storage engine.

Review the MongoDB Atlas documentation for more information on configuring the in-built security controls.

Getting Started with MongoDB Security

With comprehensive controls for user rights management, auditing and encryption, coupled with management controls, MongoDB can meet the best practice and requirements discussed in this blog series. MongoDB Enterprise Advanced is the certified and supported production release of MongoDB, with advanced security features, including Kerberos and LDAP authentication, encryption of data at-rest, FIPS-compliance, and maintenance of audit logs. These capabilities extend MongoDB’s security framework, which includes Role-Based Access Control, PKI certificates, Field-Level Redaction, and SSL/TLS data transport encryption.

In the final part of this blog post series, we will dive into environmental control and database management.

You can learn about all of these capabilities now by reading the MongoDB Security Architecture guide. If you want to try them for yourself, [download MongoDB Enterprise](, free of charge for evaluation and development.
MongoDB security architecture

About the Author - Mat Keep

Mat is a director within the MongoDB product marketing team, responsible for building the vision, positioning and content for MongoDB’s products and services, including the analysis of market trends and customer requirements. Prior to MongoDB, Mat was director of product management at Oracle Corp. with responsibility for the MySQL database in web, telecoms, cloud and big data workloads. This followed a series of sales, business development and analyst / programmer positions with both technology vendors and end-user companies.