Using Secret Store Plugins in Barbican

Summary

By default, Barbican is configured to use one active secret store plugin in a deployment. This means that all of the new secrets are going to be stored via same plugin mechanism (i.e. same storage backend).

In Newton OpenStack release, support for configuring multiple secret store plugin backends is added (Spec Link). As part of this change, client can choose to select preferred plugin backend for storing their secret at a project level.

Enabling Multiple Barbican Backends

Multiple backends support may be needed in specific deployment/ use-case scenarios and can be enabled via configuration.

For this, a Barbican deployment may have more than one secret storage backend added in service configuration. Project administrators will have choice of pre-selecting one backend as the preferred choice for secrets created under that project. Any new secret created under that project will use the preferred backend to store its key material. When there is no project level storage backend selected, then new secret will use the global secret storage backend.

Multiple plugin configuration can be defined as follows.

[secretstore]
# Set to True when multiple plugin backends support is needed
enable_multiple_secret_stores = True
stores_lookup_suffix = software, kmip, pkcs11, dogtag

[secretstore:software]
secret_store_plugin = store_crypto
crypto_plugin = simple_crypto

[secretstore:kmip]
secret_store_plugin = kmip_plugin
global_default = True

[secretstore:dogtag]
secret_store_plugin = dogtag_plugin

[secretstore:pkcs11]
secret_store_plugin = store_crypto
crypto_plugin = p11_crypto

When enable_multiple_secret_stores is enabled (True), then list property stores_lookup_suffix is used for looking up supported plugin names in configuration section. This section name is constructed using pattern ‘secretstore:{one_of_suffix}’. One of the plugin must be explicitly identified as global default i.e. global_default = True. Ordering of suffix and label used does not matter as long as there is a matching section defined in service configuration.

Note

For existing Barbican deployment case, its recommended to keep existing secretstore and crypto plugin (if applicable) name combination to be used as global default secret store. This is needed to be consistent with existing behavior.

Warning

When multiple plugins support is enabled, then enabled_secretstore_plugins and enabled_crypto_plugins values are not used to instantiate relevant plugins. Only above mentioned mechanism is used to identify and instantiate store and crypto plugins.

Multiple backend can be useful in following type of usage scenarios.

• In a deployment, a deployer may be okay in storing their dev/test resources using a low-security secret store, such as one backend using software-only crypto, but may want to use an HSM-backed secret store for production resources.
• In a deployment, for certain use cases where a client requires high concurrent access of stored keys, HSM might not be a good storage backend. Also scaling them horizontally to provide higher scalability is a costly approach with respect to database.
• HSM devices generally have limited storage capacity so a deployment will have to watch its stored keys size proactively to remain under the limit constraint. This is more applicable in KMIP backend than with PKCS11 backend because of plugin’s different storage apporach. This aspect can also result from above use case scenario where deployment is storing non-sensitive (from dev/test environment) encryption keys in HSM.
• Barbican running as IaaS service or platform component where some class of client services have strict compliance requirements (e.g. FIPS) so will use HSM backed plugins whereas others may be okay storing keys in software-only crypto plugin.