Stratis now supports per-pool encryption of the devices that form a pool's data tier. A pool may be encrypted, or its constituent encrypted devices may be activated, by means of a key stored in the kernel keyring.
- Name: Dennis Keefe, Anne Mulhern, John Baublitz
- Email: firstname.lastname@example.org, email@example.com, firstname.lastname@example.org
- Targeted release: Fedora 33
- Last updated: 2020-08-05
- FESCo issue: #2455
- Tracker bug: #1866521
- Release notes tracker: #543
Stratis 2.1.0 introduces support for encryption.
It supports per-pool encryption of the devices that form a pool's data tier. A pool may be encrypted, or its constituent encrypted devices may be activated, by means of a key stored in the kernel keyring.
This release implements encryption support and adds several new D-Bus interfaces to administer or monitor that support.
It implements encryption support in the following way:
- A single instance of stratisd can support both encrypted and unencrypted pools.
The choice to encrypt a pool must be made at the time a pool is created.
- At present, the use of a cache and of encryption are mutually exclusive; if the pool is created with encryption enabled, then it is not possible to create a cache.
- Each pool may be encrypted by means of a key in the kernel keyring; each encrypted pool may make use of a different key, but all devices in a pool are encrypted with a single key.
- Any additional devices that are added to an encrypted pool's data tier will be encrypted using the key that was specified when the pool was initialized.
stratisd 2.1.0 supplies several new D-Bus interfaces:
- org.storage.stratis2.manager.r1: This interface supplies an extended CreatePool method, to support an optional argument for encryption. In addition, it supplies a number of methods for key management.
- org.storage.stratis2.pool.r1: This interface supports explicit initialization of a cache tier. Previously, a cache was initialized as a side-effect of the addition of the first device to the cache tier. It also supports the new Encrypted property.
- org.storage.stratis2.FetchProperties.r1: This interface supports an additional HasCache property.
- org.storage.stratis2.Report.r1: This interface supports a set of ad-hoc reports about Stratis. The interface is unstable; the names by which the reports can be accesed are not guaranteed to remain stable, and the format of any report is only guaranteed to be valid JSON.
Please consult the D-Bus API Reference for the precise D-Bus specification.
The following are significant implementation details:
- Each block device in an encrypted pool's data tier is encrypted with a distinct, randomly chosen MEK (Media Encryption Key) on initialization.
- All devices belonging to a single encrypted pool share a single passphrase, supplied via the kernel keyring.
- The release requires cryptsetup version 2.3.
This release requires stratisd 2.1.0. The user will observe the following changes:
- The pool create command has been extended to allow encryption.
- There is a new pool init_cache command for initializing a cache.
- There is a new subcommand, key, for key management tasks.
- There is a new subcommand, report, which allows the display of certain reports generated by stratisd.
- The output of pool list now includes a Properties column; each entry in the column is a string encoding the following properties of the pool: (1) whether or not it has a cache, (2) whether or not it is encrypted.
- All commands now verify that stratis is communicating with a compatible version of stratisd and will fail with an appropriate error if stratisd is found to have an incompatible version.
To create an encrypted pool, a user must first ensure that a key is placed in the kernel keyring. We strongly encourage using the commands available via the stratis "key" subcommand for this task. This key, which is secret, has a corresponding key description, which is public.
An encrypted pool is then created by specifying the key description when using the pool create command.
It is necessary that the correct key and corresponding key description be set in the kernel keyring in order to set up a previously encrypted pool. Setting up a previously encrypted pool requires an explicit pool unlock command from the user. This command will attempt to unlock the devices belonging to any previously encrypted pool; it can only unlock all devices if a key for every encrypted pool is in the keyring. Once the devices belonging to a previously encrypted pool have been unlocked, the pool will be set up, and can be used in exactly the same manner as an unencrypted pool.
Benefits to Fedora
- A new feature that allows users to create pools that encrypt all data devices and consequently securely store all user data.
- Proposal owners:
- Package Rust crate libcryptsetup-rs
- Update existing stratis-cli package to specify new release
- Update existing stratisd package to specify new release
- Other developers: N/A
- Release engineering: Self Contained
- Policies guidelines: N/A
- Trademark approval: N/A
How To Test
- Testing encryption can be done using the CLI provided by stratis-cli or the D-Bus API provided by stratisd.
- Basic testing of encrypted pool and filesystem create and destroy via stratis-cli:
stratis key set --keyfile-path keyfile k1 # requires that the file keyfile contains a key stratis pool create --key-desc k1 p1 /dev/sdb stratis fs create p1 fs1 # from here you can mount /stratis/p1/fs1 and write and read data stratis blockdev list stratis pool list stratis fs list stratis fs destroy p1 fs1 stratis pool destroy p1
Users with existing filesystems will not notice any changes. Users creating new pools can read the documentation on how to make use of the new encryption feature as well as the new mechanism for instantiating a cache.
We are not aware of any packages that depend on stratisd besides stratis-cli which we are releasing with the necessary updates. In any case, such a package would continue to work with stratisd because of stratisd's support for versioned D-Bus interfaces. stratisd added a new dependency on libcryptsetup-rs; this crate has been packaged and is available in rawhide.
- Contingency mechanism:
- Contingency deadline: N/A
- Blocks release? No
- Blocks product? No
Please see https://stratis-storage.github.io/ for design documents and API reference.
Development and issue tracking is at https://github.com/stratis-storage/stratisd
Includes recent version of Stratis which supports encryption.