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| layout | page_title | sidebar_current | description |
|---|---|---|---|
| docs | Secret Backends | docs-secrets | Secret backends are mountable backends that store or generate secrets in Vault. |
Secret Backends
Secret backends are the components in Vault which store and generate secrets.
Some secret backends, such as "generic", simply store and read secrets verbatim. Other secret backends, such as "aws", create dynamic secrets: secrets that are made on demand.
Secret backends are part of the mount system in Vault. They behave very similarly to a virtual filesystem: any read/write/delete is sent to the secret backend, and the secret backend can choose to react to that operation however it sees fit.
For example, the "generic" backend passes through any operation back to the configured storage backend for Vault. A "read" turns into a "read" of the storage backend at the same path, a "write" turns into a write, etc. This is a lot like a normal filesystem.
The "aws" backend, on the other hand, behaves differently. When you
write to aws/config/root, it expects a certain format and stores that
information as configuration. You can't read from this path. When you
read from aws/<name>, it looks up an IAM policy named <name> and
generates AWS access credentials on demand and returns them. It doesn't
behave at all like a typical filesystem: you're not simply storing and
retrieving values, you're interacting with an API.
Mounting/Unmounting Secret Backends
Secret backends can be mounted/unmounted using the CLI or the API. There are three operations that can be performed with a secret backend with regards to mounting:
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Mount - This mounts a new secret backend. Multiple secret backends of the same type can be mounted at the same time by specifying different mount points. By default, secret backends are mounted to the same path as their name. This is what you want most of the time.
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Unmount - This unmounts an existing secret backend. When a secret backend is unmounted, all of its secrets are revoked (if they support it), and all of the data stored for that backend in the physical storage layer is deleted.
-
Remount - This moves the mount point for an existing secret backend. This revokes all secrets, since secret leases are tied to the path they were created at. The data stored for the backend won't be deleted.
Once a secret backend is mounted, you can interact with it directly
at its mount point according to its own API. You can use the vault help
system to determine the paths it responds to.
Barrier View
An important concept around secret backends is that they receive a barrier view to the configured Vault physical storage. This is a lot like a chroot.
Whenever a secret backend is mounted, a random UUID is generated. This
becomes the data root for that backend. Whenever that backend writes to
the physical storage layer, it is prefixed with that UUID folder. Since
the Vault storage layer doesn't support relative access (such as ..),
this makes it impossible for a mounted backend to access any other data.
This is an important security feature in Vault: even a malicious backend can't access the data from any other backend.