» KV Secrets Engine - Version 2

The kv secrets engine is used to store arbitrary secrets within the configured physical storage for Vault.

Key names must always be strings. If you write non-string values directly via the CLI, they will be converted into strings. However, you can preserve non-string values by writing the key/value pairs to Vault from a JSON file or using the HTTP API.

This secrets engine honors the distinction between the create and update capabilities inside ACL policies.

» Setup

Most secrets engines must be configured in advance before they can perform their functions. These steps are usually completed by an operator or configuration management tool.

A v2 kv secrets engine can be enabled by:

$ vault secrets enable -version=2 kv

Additionally, when running a dev-mode server, the v2 kv secrets engine is enabled by default at the path secret/ (for non-dev serers, it is currently v1). It can be disabled, moved, or enabled multiple times at different paths. Each instance of the KV secrets engine is isolated and unique.

» Upgrading from Version 1

An existing version 1 kv store can be upgraded to a version 2 kv store via the CLI or API, as shown below. This will start an upgrade process to upgrade the existing key/value data to a versioned format. The mount will be inaccessible during this process. This process could take a long time, so plan accordingly.

Once upgraded to version 2, the former paths at which the data was accessible will no longer suffice. You will need to adjust user policies to add access to the version 2 paths as detailed in the ACL Rules section below. Similarly, users/applications will need to update the paths at which they interact with the kv data once it has been upgraded to version 2.

An existing version 1 kv can be upgraded to a version 2 KV store with the CLI command:

$ vault kv enable-versioning secret/
Success! Tuned the secrets engine at: secret/

or via the API:

$ cat payload.json
{
  "options": {
      "version": "2"
  }
}

$ curl \
    --header "X-Vault-Token: ..." \
    --request POST \
    --data @payload.json \
    http://127.0.0.1:8200/v1/sys/mounts/secret/tune

» ACL Rules

The version 2 kv store uses a prefixed API, which is different from the version 1 API. Before upgrading from a version 1 kv the ACL rules should be changed. Also different paths in the version 2 API can be ACL'ed differently.

Writing and reading versions are prefixed with the data/ path. This policy that worked for the version 1 kv:

path "secret/dev/team-1/*" {
  capabilities = ["create", "update", "read"]
}

Should be changed to:

path "secret/data/dev/team-1/*" {
  capabilities = ["create", "update", "read"]
}

There are different levels of data deletion for this backend. To grant a policy the permissions to delete the latest version of a key:

path "secret/data/dev/team-1/*" {
  capabilities = ["delete"]
}

To allow the policy to delete any version of a key:

path "secret/delete/dev/team-1/*" {
  capabilities = ["update"]
}

To allow a policy to undelete data:

path "secret/undelete/dev/team-1/*" {
  capabilities = ["update"]
}

To allow a policy to destroy versions:

path "secret/destroy/dev/team-1/*" {
  capabilities = ["update"]
}

To allow a policy to list keys:

path "secret/metadata/dev/team-1/*" {
  capabilities = ["list"]
}

To allow a policy to view metadata for each version:

path "secret/metadata/dev/team-1/*" {
  capabilities = ["read"]
}

To allow a policy to permanently remove all versions and metadata for a key:

path "secret/metadata/dev/team-1/*" {
  capabilities = ["delete"]
}

See the API Specification for more information.

» Usage

After the secrets engine is configured and a user/machine has a Vault token with the proper permission, it can generate credentials. The kv secrets engine allows for writing keys with arbitrary values.

» Writing/Reading arbitrary data

  1. Write arbitrary data:

    $ vault kv put secret/my-secret my-value=s3cr3t
    Key              Value
    ---              -----
    created_time     2018-03-30T22:11:48.589157362Z
    deletion_time    n/a
    destroyed        false
    version          1
    
  2. Read arbitrary data:

    $ vault kv get secret/my-secret
    ====== Metadata ======
    Key              Value
    ---              -----
    created_time     2018-03-30T22:11:48.589157362Z
    deletion_time    n/a
    destroyed        false
    version          1
    
    ====== Data ======
    Key         Value
    ---         -----
    my-value    s3cr3t
    
  3. Write another version, the previous version will still be accessible. The -cas flag can optionally be passed to perform a check-and-set operation. If not set the write will be allowed. If set to -cas=0 a write will only be allowed if the key doesn’t exist. If the index is non-zero the write will only be allowed if the key’s current version matches the version specified in the cas parameter.

    $ vault kv put -cas=1 secret/my-secret my-value=new-s3cr3t
    Key              Value
    ---              -----
    created_time     2018-03-30T22:18:37.124228658Z
    deletion_time    n/a
    destroyed        false
    version          2
    
  4. Reading now will return the newest version of the data:

    $ vault kv get secret/my-secret
    ====== Metadata ======
    Key              Value
    ---              -----
    created_time     2018-03-30T22:18:37.124228658Z
    deletion_time    n/a
    destroyed        false
    version          2
    
    ====== Data ======
    Key         Value
    ---         -----
    my-value    new-s3cr3t
    
  5. Previous versions can be accessed with the -version flag:

    $ vault kv get -version=1 secret/my-secret
    ====== Metadata ======
    Key              Value
    ---              -----
    created_time     2018-03-30T22:16:39.808909557Z
    deletion_time    n/a
    destroyed        false
    version          1
    
    ====== Data ======
    Key         Value
    ---         -----
    my-value    s3cr3t
    

» Deleting and Destroying Data

When deleting data the standard vault kv delete command will perform a soft delete. It will mark the version as deleted and populate a deletion_time timestamp. Soft deletes do not remove the underlying version data from storage, which allows the version to be undeleted. The vault kv undelete commmand handles undeleting versions.

A version's data is permanently deleted only when the key has more versions than are allowed by the max-versions setting, or when using vault kv destroy. When the destroy command is used the underlying version data will be removed and the key metadata will be marked as destroyed. If a version is cleaned up by going over max-versions the version metadata will also be removed from the key.

See the commands below for more information:

  1. The latest version of a key can be deleted with the delete command, this also takes a -versions flag to delete prior versions:

    $ vault kv delete secret/my-secret
    Success! Data deleted (if it existed) at: secret/my-secret
    
  2. Versions can be undeleted:

    $ vault kv undelete -versions=2 secret/my-secret
    Success! Data written to: secret/undelete/my-secret
    
    $ vault kv get secret/my-secret
    ====== Metadata ======
    Key              Value
    ---              -----
    created_time     2018-03-30T22:18:37.124228658Z
    deletion_time    n/a
    destroyed        false
    version          2
    
    ====== Data ======
    Key         Value
    ---         -----
    my-value    new-s3cr3t
    
  3. Destroying a version permanently deletes the underlying data:

    $ vault kv destroy -versions=2 secret/my-secret
    Success! Data written to: secret/destroy/my-secret
    

» Key Metadata

All versions and key metadata can be tracked with the metadata command & API. Deleting the metadata key will cause all metadata and versions for that key to be permanently removed.

See the commands below for more information:

  1. All metadata and versions for a key can be viewed:

    $ vault kv metadata get secret/my-secret
    ======= Metadata =======
    Key                Value
    ---                -----
    created_time       2018-03-30T22:16:39.808909557Z
    current_version    2
    max_versions       0
    oldest_version     0
    updated_time       2018-03-30T22:18:37.124228658Z
    
    ====== Version 1 ======
    Key              Value
    ---              -----
    created_time     2018-03-30T22:16:39.808909557Z
    deletion_time    n/a
    destroyed        false
    
    ====== Version 2 ======
    Key              Value
    ---              -----
    created_time     2018-03-30T22:18:37.124228658Z
    deletion_time    n/a
    destroyed        true
    
  2. The metadata settings for a key can be configured:

    $ vault kv metadata put -max-versions 1 secret/my-secret
    Success! Data written to: secret/metadata/my-secret
    

    Max versions changes will be applied on next write:

    $ vault kv put secret/my-secret my-value=newer-s3cr3t
    Key              Value
    ---              -----
    created_time     2018-03-30T22:41:09.193643571Z
    deletion_time    n/a
    destroyed        false
    version          3
    

    Once a key has more versions than max versions the oldest versions are cleaned up:

    $ vault kv metadata get secret/my-secret
    ======= Metadata =======
    Key                Value
    ---                -----
    created_time       2018-03-30T22:16:39.808909557Z
    current_version    3
    max_versions       1
    oldest_version     3
    updated_time       2018-03-30T22:41:09.193643571Z
    
    ====== Version 3 ======
    Key              Value
    ---              -----
    created_time     2018-03-30T22:41:09.193643571Z
    deletion_time    n/a
    destroyed        false
    
  3. Permanently delete all metadata and versions for a key:

    $ vault kv metadata delete secret/my-secret
    Success! Data deleted (if it existed) at: secret/metadata/my-secret
    

» API

The KV secrets engine has a full HTTP API. Please see the KV secrets engine API for more details.