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Encryption at Rest

Encryption at Rest¶

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Encrypted Storage Engine
Application Level Encryption

Encryption at rest, when used in conjunction with transport encryption and good security policies that protect relevant accounts, passwords, and encryption keys, can help ensure compliance with security and privacy standards, including HIPAA, PCI-DSS, and FERPA.

Encrypted Storage Engine¶

New in version 3.2.

Enterprise Feature

Available in MongoDB Enterprise only.

Important

Available for the WiredTiger Storage Engine only.

MongoDB Enterprise 3.2 introduces a native encryption option for the WiredTiger storage engine. This feature allows MongoDB to encrypt data files such that only parties with the decryption key can decode and read the data.

Encryption Process¶

Changed in version 4.0

MongoDB Enterprise on Windows no longer supports AES256-GCM. This cipher is now available only on Linux.

If encryption is enabled, the default encryption mode that MongoDB Enterprise uses is the AES256-CBC (or 256-bit Advanced Encryption Standard in Cipher Block Chaining mode) via OpenSSL. AES-256 uses a symmetric key; i.e. the same key to encrypt and decrypt text. MongoDB Enterprise for Linux also supports authenticated encryption AES256-GCM (or 256-bit Advanced Encryption Standard in Galois/Counter Mode). FIPS mode encryption is also available.

AES256-GCM and Filesystem Backups

For encrypted storage engines that use AES256-GCM encryption mode, AES256-GCM requires that every process use a unique counter block value with the key.

For encrypted storage engine configured with AES256-GCM cipher:

Restoring from Hot Backup

Starting in 4.2, if you restore from files taken via “hot” backup (i.e. the mongod is running), MongoDB can detect “dirty” keys on startup and automatically rollover the database key to avoid IV (Initialization Vector) reuse.
Restoring from Cold Backup

However, if you restore from files taken via “cold” backup (i.e. the mongod is not running), MongoDB cannot detect “dirty” keys on startup, and reuse of IV voids confidentiality and integrity guarantees.

Starting in 4.2, to avoid the reuse of the keys after restoring from a cold filesystem snapshot, MongoDB adds a new command-line option --eseDatabaseKeyRollover. When started with the --eseDatabaseKeyRollover option, the mongod instance rolls over the database keys configured with AES256-GCM cipher and exits.

Tip

In general, if using filesystem based backups for MongoDB Enterprise 4.2+, use the “hot” backup feature, if possible.
For MongoDB Enterprise versions 4.0 and earlier, if you use AES256-GCM encryption mode, do not make copies of your data files or restore from filesystem snapshots (“hot” or “cold”).

The data encryption process includes:

Generating a master key.
Generating keys for each database.
Encrypting data with the database keys.
Encrypting the database keys with the master key.

The encryption occurs transparently in the storage layer; i.e. all data files are fully encrypted from a filesystem perspective, and data only exists in an unencrypted state in memory and during transmission.

To encrypt all of MongoDB’s network traffic, you can use TLS/SSL (Transport Layer Security/Secure Sockets Layer). See Configure mongod and mongos for TLS/SSL and TLS/SSL Configuration for Clients.

Key Management¶

Important

Secure management of the encryption keys is critical.

The database keys are internal to the server and are only paged to disk in an encrypted format. MongoDB never pages the master key to disk under any circumstances.

Only the master key is external to the server (i.e. kept separate from the data and the database keys), and requires external management. To manage the master key, MongoDB’s encrypted storage engine supports two key management options:

Integration with a third party key management appliance via the Key Management Interoperability Protocol (KMIP). Recommended
Local key management via a keyfile.

To configure MongoDB for encryption and use one of the two key management options, see Configure Encryption.

Encryption and Replication¶

Encryption is not a part of replication:

Master keys and database keys are not replicated, and
Data is not natively encrypted over the wire.

Although you could reuse the same key for the nodes, MongoDB recommends the use of individual keys for each node as well as the use of transport encryption.

For details, see Rotate Encryption Keys.

Logging¶

New in version 3.4: Available in MongoDB Enterprise only

The log file is not encrypted as a part of MongoDB’s encrypted storage engine. A mongod running with logging may output potentially sensitive information to log files as a part of normal operations, depending on the configured log verbosity.

MongoDB 3.4 Enterprise provides the security.redactClientLogData setting to prevent potentially sensitive information from entering the mongod process log. redactClientLogData reduces detail in the log and may complicate log diagnostics.

See the log redaction manual entry for more information.

Application Level Encryption¶

Application Level Encryption provides encryption on a per-field or per-document basis within the application layer.

New in version 4.2: MongoDB 4.2-series drivers provides a client-side field level encryption framework. For more information, see Client-Side Field Level Encryption.

To encrypt full documents, write custom encryption and decryption routines or use a commercial solution.

For a list of MongoDB’s certified partners, refer to the Partners List. To view security partners, select “Security” from the Technology filter, and “Certified” from the Certified filter.

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