Data security in Boundary
Boundary has multiple mechanisms to ensure secure end-to-end behavior of the system. A key part of this is support for various Key Management Systems that protect the base encryption keys used for various functions. This page describes the various KMS key purposes that Boundary supports and how they are used within the system.
The worker-auth-storage KMS key
The worker-auth-storage KMS key is used by a PKI
Worker for storage of authentication
keys. It is optional for PKI workers; if not specified the authentication keys
will not be encrypted on disk. This is not used by KMS workers.
The root KMS key and per-scope KEK/DEKs OSS only
Following best practices of using different encryption keys for different purposes, Boundary has a number of encryption keys generated within each scope. Each key further contains versions, which hold the key material used to encrypt data. You can create new key versions by rotating the keys. A key version can be destroyed, which will re-encrypt any existing data before destroying the key material permanently.
The root KMS key acts as a KEK (Key Encrypting Key) for the scope-specific
KEKs (also referred to as the scope's root key). The scope's root KEK
and the various DEKs (Data Encryption Keys) are created when a scope is created.
The DEKs are encrypted with the scope's root KEK, and this is in turn
encrypted with the KMS key marked for the root purpose.
The current scoped DEKs and their purposes are detailed below:
audit: This is used to encrypt secret values in the event log. For more information about the event log, refer to the events config.database: This is the general-purpose DEK used to encrypt values within the database. Values that are encrypted are those generally considered to be secret, such as API keys, third-party tokens, certificate private keys, and so on.oidc: This is used to encrypt OIDC information in cookies and authentication requests.oplog: This is used for encrypting oplog (operation log) values for the given scope.tokens: This is used for encrypting tokens generated by auth methods within the given scope.sessions: This is used as a base key against which to derive session-specific encryption keys.
Key version lifecycle management
You can control the lifecycles of the per-scope KEK and DEKs via the CLI or
API using the key endpoints under the scopes section. To rotate all the keys
in a scope, use the rotate-keys endpoint:
This endpoint creates new key versions for all keys in the scope
p_A4jfDjZ9jf, and makes these key versions the active key versions for
encrypting new data. The previous key version(s) will continue to be used for
decrypting existing data. You can use the -rewrap flag to immediately rewrap
all DEK versions with the new KEK version. Otherwise, the DEK versions remain
encrypted by the prior KEK version from when they were created.
To list all keys in a scope and their versions, use the list-keys endpoint:
To destroy a key version, use the destroy-key-version endpoint:
The latest key version cannot be destroyed, so if you want to destroy the
latest key version, you will need to call the rotate-keys endpoint first,
to create a new set of key versions. The oplog purpose key versions also
cannot be destroyed at this time.
Destroying a key version sometimes requires background work before it can be
completed. This is because DEK versions that currently encrypt data
necessitate re-encrypting that data with the latest DEK version for each
purpose before they can be deleted. You can monitor the progress of this
re-encryption job via the list-key-destruction-jobs endpoint:
Once the job disappears from this list, the associated key version will have been destroyed and any existing data will have been re-encrypted.
The bsr KMS key HCP/ENT
The bsr KMS key is required for session recording.
If you do not add a bsr key to your controller configuration, you will receive an error when you attempt to enable session recording.
The key is used for encrypting data and checking the integrity of recordings.
The previous-root KMS key OSS only
The previous-root KMS key is used when migrating to a new root key. Adding
the previous-root KMS key to your configuration informs the Controller to use
it for decrypting the existing information in the database, allowing you to
rotate and rewrap the KEKs to complete the migration to the new root key.
The worker-auth KMS key OSS only
The worker-auth KMS key is a key shared by the Controller and Worker in order
to authenticate a Worker to the Controller. Specifics of this mechanism can be
found on the Connections/TLS page. If
a worker is used with PKI
authentication this is unnecessary.
The recovery KMS key OSS only
The recovery KMS key is used for rescue/recovery operations that can be used
by a client to authenticate almost any operation within Boundary. Its mechanism
of operation is very similar to the worker-auth flow in terms of using a
shared KMS between the client and the Controller for authentication. A nonce and
creation time are included as an encrypted payload, formatted as a token and
sent to the Controller. The time and nonce are used to ensure that a value
cannot be replayed by an adversary, and also to ensure that each operation must
be individually authenticated by a client so that revoking access to the KMS has
an immediate result.
Note: It is not required for this kms configuration block to exist in the
Controller's configuration file. It's best practice to leave it out except when
actually needed, and to use change control capabilities to ensure that the
configuration file modification is authorized. After it's no longer needed, the
block should be removed.
On the client side, a user can use the -recovery-config flag with any
operation on the CLI to specify a configuration file containing a suitable kms
block. This functionality is also accessible via the Go SDK.
Note: Requests authorized via this mechanism will show a user of u_recovery. This
mechanism cannot be used to authorize a session, as there is no uniquely
identifying user information available.
There are some other situations where this mechanism can be useful. For example,
it is possible to use this mechanism, along with some defaults in the Terraform
provider, to ensure that everything in Boundary is created through Terraform,
with the exception of resources that cannot themselves be deleted. (This
consists of built-in anonymous (u_anon), authenticated (u_auth), and
recovery (u_recovery) users and the global scope.). By initializing Boundary
with the options to skip creating default resources, Terraform can be used to
create the specific resources needed instead, with the recovery KMS used to
authenticate setting up the initial auth method(s).
The config KMS key OSS only
This key can be used to encrypt values within Boundary's configuration file. By
sharing this block between Boundary and an operator, the operator can put
sensitive or secret values (such as cloud API keys for KMSes) in Boundary's
configuration file, run boundary config encrypt to encrypt the file, and then
safely pass the file to a change control system. Only another operator or system
with access to that KMS can decrypt the values. Boundary will check for a
config KMS block on startup, and if it exists, will use it to decrypt any
encrypted values found at startup time.