---
layout: docs
page_title: Use Vault Proxy as an API proxy
description: >-
  Use auto-authentication and configure Vault Proxy as a proxy for the Vault API.
---

# Use Vault Proxy as an API proxy

Vault Proxy's API Proxy functionality allows you to use Vault Proxy's API as a proxy
for Vault's API.

## Functionality

The [`listener` stanza](/vault/docs/agent-and-proxy/proxy#listener-stanza) for Vault Proxy configures a listener for Vault Proxy. If
its `role` is not set to `metrics_only`, it will act as a proxy for the Vault server that
has been configured in the [`vault` stanza](/vault/docs/agent-and-proxy/proxy#vault-stanza) of Proxy. This enables access to the Vault
API from the Proxy API, and can be configured to optionally allow or force the automatic use of
the Auto-Auth token for these requests, as described below.

If a `listener` has been configured alongside a `cache` stanza, the API Proxy will
first attempt to utilize the cache subsystem for qualifying requests, before forwarding the
request to Vault. See the [caching docs](/vault/docs/agent-and-proxy/proxy/caching) for more information on caching.

## Using Auto-Auth token

Vault Proxy allows for easy authentication to Vault in a wide variety of
environments using [Auto-Auth](/vault/docs/agent-and-proxy/autoauth). By setting the
`use_auto_auth_token` (see below) configuration, clients will not be required
to provide a Vault token to the requests made to the Proxy. When this
configuration is set, if the request doesn't already bear a token, then the
auto-auth token will be used to forward the request to the Vault server. This
configuration will be overridden if the request already has a token attached,
in which case, the token present in the request will be used to forward the
request to the Vault server.

## Forcing Auto-Auth token

Vault Proxy can be configured to force the use of the auto-auth token by using
the value `force` for the `use_auto_auth_token` option. This configuration
overrides the default behavior described above in [Using Auto-Auth
Token](/vault/docs/agent-and-proxy/proxy/apiproxy#using-auto-auth-token), and instead ignores any
existing Vault token in the request and instead uses the auto-auth token.


## Configuration (`api_proxy`)

The top level `api_proxy` block has the following configuration entries:

- `use_auto_auth_token` `(bool/string: false)` - If set, the requests made to Proxy
without a Vault token will be forwarded to the Vault server with the
auto-auth token attached. If the requests already bear a token, this
configuration will be overridden and the token in the request will be used to
forward the request to the Vault server. If set to `"force"` Proxy will use the
auto-auth token, overwriting the attached Vault token if set.

~> **Note**: When using the proxy's auto-auth token with the `use_auto_auth_token`
   configuration, one proxy per application is very strongly recommended, as Vault will
   unable to distinguish requests coming from multiple applications through a single proxy.
   In situations where a single proxy is shared by multiple applications, setting `use_auto_auth_token`
   to `false` (the default) is recommended.

- `prepend_configured_namespace` `(bool: false)` - If set, when Proxy has a
  namespace configured, such as through the
  [Vault stanza](/vault/docs/agent-and-proxy/proxy#vault-stanza), all requests
  proxied to Vault will have the configured namespace prepended to the namespace
  header. If Proxy's namespace is set to `ns1` and Proxy is sent a request with the
  namespace `ns2`, the request will go to the `ns1/ns2` namespace. Likewise, if Proxy
  is sent a request without a namespace, the request will go to the `ns1` namespace.
  In essence, what this means is that all proxied requests must go to the configured
  namespace or to its child namespaces.

The following two `api_proxy` options are only useful when making requests to a Vault
Enterprise cluster, and are documented as part of its
[Eventual Consistency](/vault/docs/enterprise/consistency#vault-proxy-and-consistency-headers)
page.

- `enforce_consistency` `(string: "never")` - Set to one of `"always"`
or `"never"`.

- `when_inconsistent` `(string: optional)` - Set to one of `"fail"`, `"retry"`,
or `"forward"`.

### Example configuration

Here is an example of a `listener` configuration alongside `api_proxy` configuration to force the use of the auto_auth token
and enforce consistency for a proxy dedicated to a single application.

```hcl
# Other Vault Proxy configuration blocks
# ...

api_proxy {
  use_auto_auth_token = "force"
  enforce_consistency = "always"
}

listener "unix" {
    address = "/var/run/vault-proxy.sock
}
```