Data-at-Rest Encryption Overview
Overview
Having tables encrypted makes it almost impossible for someone to access or steal a hard disk and get access to the original data. This functionality is also known as Transparent Data Encryption (TDE).
All of the following assumes that encryption keys are stored on another system.
Encryption and Decryption Lifecycle
MariaDB performs data-at-rest encryption at specific points during disk I/O operations. When data is written to disk, encryption usually takes place; when data is read back into memory, decryption takes place. Data stored in memory (for example, in buffer pools) is often decrypted while in use.
Which Storage Engines Does MariaDB Encryption Support?
MariaDB encryption is fully supported for the InnoDB storage engines. Encryption is also supported for the Aria storage engine, but only for tables created with ROW_FORMAT=PAGE (the default), and for the binary log (replication log).
MariaDB allows the user to configure flexibly what to encrypt. In or InnoDB, one can choose to encrypt:
everything — all tablespaces (with all tables) (with innodb_encrypt_tables=1)
individual tables
everything, excluding individual tables
Additionally, one can choose to encrypt InnoDB log files (recommended, with innodb_encrypt_log=1) and InnoDB Temporary Tables (with innodb_encrypt_temporary_tables=1).
When innodb_encrypt_log=1 or innodb_encrypt_temporary_tables=1 an encryption key of 1 must be defined. See Enabling InnoDB Encryption.
Limitations
These limitations exist in the data-at-rest encryption implementation:
Only data and only at rest is encrypted. Metadata (for example
.frmfiles) and data sent to the client are not encrypted (but see Secure Connections).Only the MariaDB server knows how to decrypt the data, in particular
mariadb-binlog can read encrypted binary logs only when --read-from-remote-server is used (MDEV-8813).
Percona XtraBackup cannot back up instances that use encrypted InnoDB. However, MariaDB's fork, MariaDB Backup, can back up encrypted instances.
The Audit plugin cannot create encrypted output. Send it to syslog and configure the protection there instead.
File-based general query log and slow query log cannot be encrypted (MDEV-9639).
The Aria log is not encrypted (MDEV-8587). This affects only non-temporary Aria tables though.
The MariaDB error log is not encrypted. The error log can contain query text and data in some cases, including crashes, assertion failures, and cases where InnoDB write monitor output to the log to aid in debugging. It can sent to syslog too, if needed.
Encryption Key Management
MariaDB's data-at-rest encryption requires the use of a key management and encryption plugin. These plugins are responsible both for the management of encryption keys and for the actual encryption and decryption of data.
MariaDB supports the use of multiple encryption keys. Each encryption key uses a 32-bit integer as a key identifier. If the specific plugin supports key rotation, then encryption keys can also be rotated, which creates a new version of the encryption key.
How MariaDB manages encryption keys depends on which encryption key management solution you choose. Currently, MariaDB has three options:
Once you have an key management and encryption plugin set up and configured for your server, you can begin using encryption options to better secure your data.
Encrypting Data
Encryption occurs whenever MariaDB writes pages to disk. Encrypting table data requires that you install a key management and encryption plugin, such as the File Key Management plugin. Once you have a plugin set up and configured, you can enable encryption for your InnoDB and Aria tables.
Encrypting Table Data
MariaDB supports data-at-rest encryption for InnoDB and Aria storage engines. Additionally, it supports encrypting the InnoDB redo log and internal on-disk temporary tables that use the Aria storage engine..
Encrypting Temporary Files
MariaDB also creates temporary files on disk. For example, a binary log cache will be written to a temporary file if the binary log cache exceeds binlog_cache_size or binlog_stmt_cache_size, and temporary files are also often used for filesorts during query execution. These temporary files can also be encrypted if encrypt_tmp_files=ON is set.
Temporary files created internally by InnoDB, such as those used for merge sorts and row logs can also be encrypted if innodb_encrypt_log=ON is set. These files are encrypted regardless of whether the tables involved are encrypted or not, and regardless of whether encrypt_tmp_files is set or not.
Encrypting Binary Logs
MariaDB can also encrypt binary logs (including relay logs).
Binary and Relay Log Encryption Behavior
When is an event encrypted?
When binary log and relay log events are written to the IO_CACHE, they are encrypted. This happens regardless of whether the cache is stored on disk or in memory, depending on the transaction size and the values of binlog_cache_size and binlog_stmt_cache_size. Hence, before events are written to the actual binary log and relay log files, they are encrypted.
When is an event decrypted?
When a START_ENCRYPTION_EVENT appears in the binary log or relay log, events are decrypted as they are read. This event comes right after the FORMAT_DESCRIPTION_EVENT in encrypted binary logs and relay logs, making it the second event in the log file.
Encryption and Page Compression
Data-at-rest encryption and InnoDB page compression can be used together. When they are used together, data is first compressed, and then it is encrypted. In this case you save space and still have your data protected.
Thanks
Tablespace encryption was donated to the MariaDB project by Google.
We are grateful to these companies for their support of MariaDB!
See Also
A blog post about table encryption with benchmark results
This page is licensed: CC BY-SA / Gnu FDL
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