---
layout: docs
page_title: Secrets sync
description: Secrets sync allows you to safely sync Vault-managed secrets with external destinations.
---


# Secrets sync

<EnterpriseAlert product="vault" />

In certain circumstances, fetching secrets directly from Vault is impossible or impractical. To help with this challenge,
Vault can maintain a one-way sync for KVv2 secrets into various destinations that are easier to access for some clients.
With this, Vault remains the system of records but can cache a subset of secrets on various external systems acting as
trusted last-mile delivery systems.

A secret that is associated from a Vault KVv2 Secrets Engine into an external destination is actively managed by a continuous
process. If the secret value is updated in Vault, the secret is updated in the destination as well. If the secret is deleted
from Vault, it is deleted on the external system as well. This process is asynchronous and event-based. Vault propagates
modifications into the proper destinations automatically in a handful of seconds.

<Note title="Not related to HCP Vault Secrets">

  Secrets sync is a Vault Enterprise feature. For information on secrets sync
  with [HCP Vault Secrets](/hcp/docs/vault-secrets), refer to the HashiCorp Cloud
  Platform documentation for
  [Vault Secrets integrations](/hcp/docs/vault-secrets/integrations).

</Note>

## Activating the feature

The secrets sync feature requires manual activation through a one-time trigger. If a sync-related endpoint is called prior to
activation, an error response will be received indicating that the feature has not been activated yet. Be sure to understand the
potential [client count impacts](#client-counts) of using secrets sync before proceeding.

Activating the feature can be done through one of several methods:

  1. Activation directly through the UI.
  
  1. Acitvation through the CLI:
    
    ```shell-session
    vault write -f sys/activation-flags/secrets-sync/activate
    ``` 

  1. Activation through a POST or PUT request:

    ```shell-session
    $ curl \
      --request PUT \
      --header "X-Vault-Token: ..." \
      http://127.0.0.1:8200/v1/sys/activation-flags/secrets-sync/activate
    ```

## Destinations

Secrets can be synced into various external systems, called destinations. The supported destinations are:
* [AWS Secrets Manager](/vault/docs/sync/awssm)
* [Azure Key Vault](/vault/docs/sync/azurekv)
* [GCP Secret Manager](/vault/docs/sync/gcpsm)
* [GitHub Repository Actions](/vault/docs/sync/github)
* [Vercel Projects](/vault/docs/sync/vercelproject)

## Associations

Syncing a secret into one of the external systems is done by creating a connection between it and a destination, which is
called an association. These associations are created via Vault's API by adding a KVv2 secret target to one of the configured
destinations. Each association keeps track of that secret's current sync status, the timestamp of its last status change, and
the error code of the last sync or unsync operation if it failed. Each destination can have any number of secret associations.

## Sync statuses

There are several sync statuses which relay information about the outcome of the latest sync
operation to have occurred on that secret. The status information is stored inside each
association object returned by the endpoint and, upon failure, includes an error code describing the cause of the failure.

| Status                   | Description                                                                                     |
|:-------------------------|:------------------------------------------------------------------------------------------------|
| `UNKNOWN`                | Vault is unable to determine the current state of the secret in regard to the external service. |
| `PENDING`                | An operation is queued for that secret and has not been processed yet.                          |
| `SYNCED`                 | The sync operation was successful and sent the secret to the external destination.              |
| `UNSYNCED`               | The unsync operation was successful and removed the secret from the external destination.       |
| `INTERNAL_VAULT_ERROR`   | The operation failed due to an issue internal to Vault.                                         |
| `CLIENT_SIDE_ERROR`      | The operation failed due to a configuration error such as invalid privileges.                   |
| `EXTERNAL_SERVICE_ERROR` | The operation failed due to an issue with the external service such as a temporary downtime.    |

## Name template

By default, the name of synced secrets follows this format: `vault/<accessor>/<secret-path>`. The casing and delimiters
may change as they are normalized according to the valid character set of each destination type. This pattern was chosen to
prevent accidental name collisions and to clearly identify where the secret is coming from.

Every destination allows you to customize this name pattern by configuring a `secret_name_template` field to best suit
individual use cases. The templates use a subset of the go-template syntax for extra flexibility.

The following placeholders are available:

| Placeholder         | Description                                                                                                 |
|:--------------------|:------------------------------------------------------------------------------------------------------------|
| `DestinationType`   | The type of the destination, e.g. "aws-sm"                                                                  |
| `DestinationName`   | The name of the destination                                                                                 |
| `NamespacePath`     | The full namespace path where the secret being synced is located                                            |
| `NamespaceBaseName` | The segment following the last `/` character from the full path                                             |
| `NamespaceID`       | The internal unique ID identifying the namespace, e.g. `RQegM`                                              |
| `MountPath`         | The full mount path where the secret being synced is located                                                |
| `MountBaseName`     | The segment following the last `/` character from the full path                                             |
| `MountAccessor`     | The internal unique ID identifying the mount, e.g. `kv_1234`                                                |
| `SecretPath`        | The full secret path                                                                                        |
| `SecretBaseName`    | The segment following the last `/` character from the full path                                             |
| `SecretKey`         | The individual secret key being synced, only available if the destination uses the `secret-key` granularity |

Let's assume we want to sync the following secret:

  <CodeBlockConfig hideClipboard>

    $ VAULT_NAMESPACE=ns1/ns2 vault kv get -mount=path/to/kv1 path/to/secret1

    ========== Secret Path ==========
    path/to/kv1/data/path/to/secret1

    ======= Metadata =======
    (...)

    === Data ===
    Key    Value
    ---    -----
    foo    bar

  </CodeBlockConfig>

Let's look at some name template examples and the resulting secret name at the sync destination.

| Name template                            | Result                 |
|:-----------------------------------------|:-----------------------|
| prefix-{{ .SecretPath }}                 | prefix-path/to/secret1 |
| {{ .SecretBaseName \| uppercase }}       | SECRET1                |
| {{ .MountAccessor }}_{{ .SecretKey }}    | kv_1234_foo            |
| {{ .SecretPath \| replace \"/\" \"_\" }} | path_to_secret1        |

Name templates can be updated. The new template is only effective for new secrets associated with the destination and does
not affect the secrets synced with the previous template. It is possible to update an association to force a recreate operation.
The secret synced with the old template will be deleted and a new secret using the new template version will be synced.

## Custom tags

A destination can also have custom tags so that every secret associated to it that is synced will share that same set of tags.
Additionally, a default tag value of `hashicorp:vault` is used to denote any secret that is synced via Vault Enterprise. Similar
to secret names, tag keys and values are normalized according to the valid character set of each destination type.

## Granularity

Vault KV-v2 secrets are multi-value and their data is represented in JSON. Multi-value secrets are useful to bundle closely
related information together like a username & password pair. However, most secret management systems only support single-value
entries. Secrets sync allows you to choose the granularity that best suits your use case for each destination by specifying a `granularity`
field.

The `secret-path` granularity syncs the entire JSON content of the Vault secret as a single entry at the destination. If
the destination does not support multi-value secret the JSON is encoded as a single-value JSON-string.

The `secret-key` granularity syncs each Vault key-value pair as a distinct entry at the destination. If the value itself is a list or map
it is encoded as a JSON blob.

Granularity can be updated. The new granularity only affects secrets newly associated with the destination and does
not modify the previously synced secrets. It is possible to update an association to force a recreate operation.
The secret synced with the old granularity will be deleted and new secrets will be synced according to the new granularity.

## Security

~> Note: Vault does not control the permissions at the destination. It is the responsibility
of the operator to configure and maintain proper access controls on the external system so synced
secrets are not accessed unintentionally.

### Vault access requirements

Vault verifies the client has read access on the secret before syncing it with any destination. This additional check is
there to prevent users from maliciously or unintentionally leveraging elevated permissions on an external system to access
secrets they normally wouldn't be able to.

Let's assume we have a secret located at `path/to/data/secret1` and a user with write access to the sync feature,
but no read access to that secret. This scenario is equivalent to this ACL policy:

  <CodeBlockConfig hideClipboard>

    # Allow full access to the sync feature
    path "sys/sync/*" {
      capabilities = ["read", "list", "create", "update", "delete"]
    }

    # Allow read access to the secret mount path/to
    path "path/to/*" {
      capabilities = ["read"]
    }

    # Deny access to a specific secret
    path "path/to/data/my-secret-1" {
      capabilities = ["deny"]
    }

  </CodeBlockConfig>

If a client with this policy tries to read this secret they will receive an unauthorized error:

  <CodeBlockConfig hideClipboard>

    $ vault kv get -mount=path/to my-secret-1

    Error reading path/to/data/my-secret-1: Error making API request.

    URL: GET http://127.0.0.1:8200/v1/path/to/data/my-secret-1
    Code: 403. Errors:

    * 1 error occurred:
      * permission denied

  </CodeBlockConfig>

Likewise, if the client tries to sync this secret to any destination they will receive a similar unauthorized error:

  <CodeBlockConfig hideClipboard>

    $ vault write sys/sync/destinations/$TYPE/$NAME/associations/set \
    mount="path/to" \
    secret_name="my-secret-1"

    Error writing data to sys/sync/destinations/$TYPE/$NAME/associations/set: Error making API request.

    URL: PUT http://127.0.0.1:8200/v1/sys/sync/destinations/$TYPE/$NAME/associations/set
    Code: 403. Errors:

    * permission denied to read the content of the secret my-secret-1 in mount path/to

  </CodeBlockConfig>

This read access verification is only done when creating or updating an association. Once the association is created, revoking
read access to the policy that was used to sync the secret has no effect.

### Collisions and overwrites

Secrets Sync operates with a last-write-wins strategy. If a secret with the same name already exists at the destination,
Vault overwrites it when syncing a secret. There are also no automatic mechanisms to prevent a principal with sufficient
privileges at the destination from overwriting a secret synced by Vault.

To prevent Vault from accidentally overwriting existing secrets, it is recommended to use either a name pattern or
built-in tags as an extra policy condition on the role used to configure a Vault sync destination. A negative condition on other
policies may be used to prevent out-of-band overwrites to Vault secrets from non-Vault roles.

To see examples of policies that provide this type of restriction, refer to the access management section of the documentation
for each destination type below:

* [AWS Access Management](/vault/docs/sync/awssm#access-management)
* [GCP Access Management](/vault/docs/sync/gcpsm#access-management)

## Reconciliation

Vault Secrets Sync is designed to automatically recover from transient failures
in two ways: operation retries and reconciliation scans.

Operation retries happen when a sync operation fails. Vault automatically
retries the operation with exponential backoff. Operation retries help in
situations where your network becomes unreliable or overwhelmed.

Reconciliation scans happen periodically in a background thread. Vault scans all
secrets currently managed by the sync system to identify and update out-of-date
secrets, and to ensure that any configured destinations are up-to-date.
Reconciliation scans help in situations where there are external service downtimes
that are outside of your control and provide a way to automatically recover and self-heal.

Operation retries and reconciliation scans are both enabled by default.

Note that reconciliation process do not protect from out-of-band updates
that occur directly in the external service. The secrets sync system is designed to be
one-way and does not support bidirectional sync at this time.

## Client counts

Each secret that is synced with one or more destinations is counted as a
distinct client in Vault's client counting. See [entity assignments with secret
sync](/vault/docs/concepts/client-count#secret-sync-clients)
for more information.

## API

Please see the [secrets sync API](/vault/api-docs/system/secrets-sync) for more details.
