Single use secret in Hashicorp vault - hashicorp-vault

Question

Is it possible with any secret engine to have a "single use" password?
I have a command that generates an rsa keypair for users, and would like them to retrieve their private key. I can obviously print it out, or write to file etc, but thought it would be nice if it was stored in a "single use" place in vault? Then the user could retrieve it via the UI, and know that no-one else has viewed it. If someone else viewed it they would need to regenerate.
Basically can we have a vault key that can only be read once?

Answer 1

You can create a policy that only has access to that secret, for example
# policy: rsa
path "secret/rsa" {
capabilities = ["read"]
}
and then create a wrapped token for that policy, for example
$ vault token create -policy=rsa -num_uses=1 -wrap-ttl=120
Key Value
--- -----
wrapping_token: s.9QFJ8mRxGJD0e7kFfFIbdpDM
wrapping_accessor: S0zKNUr2ENbnCtj0YyriO31b
wrapping_token_ttl: 2m
wrapping_token_creation_time: 2019-12-17 09:45:42.537057 -0800 PST
wrapping_token_creation_path: auth/token/create
wrapped_accessor: VmBKXoc19ZLZlHGl0nQCvV6r
This will generate a wrapped token.
You can give that to your end user and they can unwrap it with
VAULT_TOKEN="s.3Kf3Xfn58Asr3bSDkRXATHrw" vault unwrap
which will generate a token.
With that token, the user will be able to login to vault and retrieve the rsa creds only once since the token will be invalid afterwards.
You can now guarantee that the creds have only been used from the target user as the wrapped token can be unwrapped only once.
Note: you might need to adjust num_uses when you create the token if your end user goes through the UI as the UI might use the token to perform more than one actions.
more info