open-consul/website/content/docs/security/acl/acl-system.mdx

---
layout: docs
page_title: ACL System
description: >-
  Consul provides an optional Access Control List (ACL) system which can be used
  to control access to data and APIs. The ACL system is a Capability-based
  system that relies on tokens which can have fine grained rules applied to
  them. It is very similar to AWS IAM in many ways.
---

# ACL System

-> **1.4.0 and later:** This guide only applies in Consul versions 1.4.0 and later. The documentation for the legacy ACL system is [here](/docs/acl/acl-legacy).

Consul provides an optional Access Control List (ACL) system which can be used to control access to data and APIs.
The ACL is [Capability-based](https://en.wikipedia.org/wiki/Capability-based_security), relying on tokens which
are associated with policies to determine which fine grained rules can be applied. Consul's capability based
ACL system is very similar to the design of [AWS IAM](https://aws.amazon.com/iam/).

To learn how to setup the ACL system on an existing Consul datacenter, use the [Bootstrapping The ACL System tutorial](https://learn.hashicorp.com/tutorials/consul/access-control-setup?utm_source=consul.io&utm_medium=docs).

## ACL System Overview

The ACL system is designed to be easy to use and fast to enforce while providing administrative insight.
The diagram below shows the relationships between most of the components of the ACL system:

![ACL system component relationships](/img/acl-token-policy-rule-relationship.png)

At the highest level, there are two major components to the ACL system:

- **ACL Policies** - Policies allow the grouping of a set of rules into a logical unit that can be reused and linked with
  many tokens.

- **ACL Tokens** - Requests to Consul are authorized by using bearer token. Each ACL token has a public
  Accessor ID which is used to name a token, and a Secret ID which is used as the bearer token used to
  make requests to Consul.

For many scenarios policies and tokens are sufficient, but more advanced setups
may benefit from additional components in the ACL system:

- **ACL Roles** - Roles allow for the grouping of a set of policies and service
  identities into a reusable higher-level entity that can be applied to many
  tokens. (Added in Consul 1.5.0)

- **ACL Service Identities** - Service identities are a policy template for
  expressing a link to a policy suitable for use in [Consul
  Connect](/docs/connect). At authorization time this acts like an
  additional policy was attached, the contents of which are described further
  below. These are directly attached to tokens and roles and are not
  independently configured. (Added in Consul 1.5.0)

- **ACL Node Identities** - Node identities are a policy template for
  expressing a link to a policy suitable for use as an [Consul `agent` token
  ](/docs/agent/options#acl_tokens_agent). At authorization time this acts like an
  additional policy was attached, the contents of which are described further
  below. These are directly attached to tokens and roles and are not
  independently configured. (Added in Consul 1.8.1)

- **ACL Auth Methods and Binding Rules** - To learn more about these topics,
  see the [auth methods documentation page](/docs/acl/auth-methods).

ACL tokens, policies, roles, auth methods, and binding rules are managed by
Consul operators via Consul's [ACL API](/api/acl/acl),
[ACL CLI](/commands/acl), or systems like
[HashiCorp's Vault](https://www.vaultproject.io/docs/secrets/consul).

If the ACL system becomes inoperable, you can follow the
[reset procedure](https://learn.hashicorp.com/tutorials/consul/access-control-troubleshoot#reset-the-acl-system) at any time.

### ACL Policies

An ACL policy (not to be confused with [policy dispositions](/docs/security/acl/acl-rules#policy-dispositions)) is a named set of rules and several attributes that define the policy domain. The ID is generated when policy is created, but you can specify the attributes when creating the policy. Refer to the [ACL policy command line](https://www.consul.io/commands/acl/policy) documentation or [ACL policy API](/api-docs/acl/policies) documentation for additional information on how to create policies.

ACL policies can have the following attributes:

| Attribute | Description | Required | Default |
| ---       | ---         | ---      | ---     |
| `ID` | The policy's auto-generated public identifier. | N/A | N/A |
| `name` | Unique name for the policy. | Required | none |
| `description` | Human readable description of the policy. | Optional | none |
| `rules` | Set of rules granting or denying permissions. See the [Rule Specification](/docs/acl/acl-rules#rule-specification) documentation for more details. | Optional | none |
| `datacenter` | Datacenter in which the policy is valid. More than one datacenter can be specified. | Optional | none | 
| `namespace` | <EnterpriseAlert inline /> Namespace in which the policy is valid. Added in Consul Enterprise 1.7.0. | Optional | `default` |
| `partition` | <EnterpriseAlert inline /> Admin partition in which the policy is valid. Added in Consul Enterprise 1.11.0 | Optional | `default` |

-> **Non-default Namespaces and Partitions** - Rules defined in a policy tied to an namespace or admin partition other than `default` can only grant a subset of privileges that affect the namespace or partition. See [Namespace Rules](/docs/acl/acl-rules#namespace-rules) and [Admin Partition Rules](/docs/acl/acl-rules#admin-partition-rules) for additional information.

You can view the current ACL policies on the command line or through the API. The following example demonstrates the command line usage:

```shell-session
$ consul acl policy list -format json -token <token_id>
[
    {
        "ID": "56595ec1-52e4-d6de-e566-3b78696d5459",
        "Name": "b-policy",
        "Description": "",
        "Datacenters": null,
        "Hash": "ULwaXlI6Ecqb9YSPegXWgVL1LlwctY9TeeAOhp5HGBA=",
        "CreateIndex": 126,
        "ModifyIndex": 126,
        "Namespace": "default",
        "Partition": "default"
    },
    {
        "ID": "00000000-0000-0000-0000-000000000001",
        "Name": "global-management",
        "Description": "Builtin Policy that grants unlimited access",
        "Datacenters": null,
        "Hash": "W1bQuDAlAlxEb4ZWwnVHplnt3I5oPKOZJQITh79Xlog=",
        "CreateIndex": 70,
        "ModifyIndex": 70,
        "Namespace": "default",
        "Partition": "default"
    }
]
```

Note that the `Hash`, `CreateIndex`, and `ModifyIndex` attributes are also printed. These attributes are printed for all responses and are not specific to ACL policies. 

#### Builtin Policies

- **Global Management** - Grants unrestricted privileges to any token that uses it. When created it will be named `global-management`
  and will be assigned the reserved ID of `00000000-0000-0000-0000-000000000001`. This policy can be renamed but modification
  of anything else including the rule set and datacenter scoping will be prevented by Consul.

- **Namespace Management** - <EnterpriseAlert inline /> - Every namespace created will have a policy injected with the name `namespace-management`. This policy gets injected with a randomized UUID and may be managed like any other user-defined policy
  within the Namespace. (Added in Consul Enterprise 1.7.0)

### ACL Service Identities

-> Added in Consul 1.5.0

An ACL service identity is an [ACL policy](/docs/acl/acl-system#acl-policies) template for expressing a link to a policy
suitable for use in [Consul Connect](/docs/connect). They are usable
on both tokens and roles and are composed of the following elements:

- **Service Name** - The name of the service.
- **Datacenters** - A list of datacenters the effective policy is valid within. (Optional)

Services participating in the service mesh will need privileges to both _be
discovered_ and to _discover other healthy service instances_. Suitable
policies tend to all look nearly identical so a service identity is a policy
template to aid in avoiding boilerplate policy creation.

During the authorization process, the configured service identity is automatically
applied as a policy with the following preconfigured [ACL
rules](/docs/acl/acl-system#acl-rules-and-scope):

```hcl
# Allow the service and its sidecar proxy to register into the catalog.
service "<Service Name>" {
	policy = "write"
}
service "<Service Name>-sidecar-proxy" {
	policy = "write"
}

# Allow for any potential upstreams to be resolved.
service_prefix "" {
	policy = "read"
}
node_prefix "" {
	policy = "read"
}
```

The [API documentation for roles](/api/acl/roles#sample-payload) has some
examples of using a service identity.

-> **Service Scope for Namespace and Admin Partition** - Service identity rules in Consul Enterprise are scoped to the namespace or admin partition within which the corresponding ACL token or role resides.

### ACL Node Identities

-> Added in Consul 1.8.1

An ACL node identity is an [ACL policy](/docs/acl/acl-system#acl-policies) template for expressing a link to a policy
suitable for use as an [Consul `agent` token](/docs/agent/options#acl_tokens_agent). They are usable
on both tokens and roles and are composed of the following elements:

- **Node Name** - The name of the node to grant access to.
- **Datacenter** - The datacenter that the node resides within.

During the authorization process, the configured node identity is automatically
applied as a policy with the following preconfigured [ACL
rules](/docs/acl/acl-system#acl-rules-and-scope):

```hcl
# Allow the agent to register its own node in the Catalog and update its network coordinates
node "<Node Name>" {
  policy = "write"
}

# Allows the agent to detect and diff services registered to itself. This is used during
# anti-entropy to reconcile difference between the agents knowledge of registered
# services and checks in comparison with what is known in the Catalog.
service_prefix "" {
  policy = "read"
}
```

-> **Consul Enterprise Namespacing** - Node Identities can only be applied to tokens and roles in the `default` namespace.
The synthetic policy rules allow for `service:read` permissions on all services in all namespaces.

### ACL Roles

-> Added in Consul 1.5.0

An ACL role is a named set of policies and service identities and is composed
of the following elements:

- **ID** - The role's auto-generated public identifier.
- **Name** - A unique meaningful name for the role.
- **Description** - A human readable description of the role. (Optional)
- **Policy Set** - The list of policies that are applicable for the role.
- **Service Identity Set** - The list of service identities that are applicable for the role.
- **Namespace** <EnterpriseAlert inline /> - The namespace this policy resides within. (Added in Consul Enterprise 1.7.0)

-> **Linking Roles to Policies in Consul Enterprise** - Roles can only be linked to policies that are defined in the same namespace or admin partition. 

### ACL Tokens

Consul uses ACL tokens to determine if the caller is authorized to perform an action. An ACL token is composed of several attributes that you can specify when creating the token. Refer to the [ACL token command line](https://www.consul.io/commands/acl/token) documentation or [ACL token API](/api-docs/acl/tokens) documentation for additional information on how to create policies.:

- **Accessor ID** - The token's public identifier.
- **Secret ID** -The bearer token used when making requests to Consul.
- **Policy Set** - The list of policies that are applicable for the token.
- **Role Set** - The list of roles that are applicable for the token. Added in Consul 1.5.0.
- **Service Identity Set** - The list of service identities that are applicable for the token. Added in Consul 1.5.0
- **Local** - Indicates whether the token is local to the datacenter in which it was created. The attribute also can specify if the token was created in the primary datacenter and globally replicated.
- **CreateTime** - Timestamp indicating when the token was created. 
- **Expiration Time** - The time at which this token is revoked. This attribute is option when creating a token. Added in Consul 1.5.0.
- **Namespace** <EnterpriseAlert inline /> - The namespace in which the policy resides. Added in Consul Enterprise 1.7.0.
- **Partition** <EnterpriseAlert inline /> - The partition in which the policy resides. Added in Consul Enterprise 1.11.0.

-> **Linking Tokens to Policies in Consul Enterprise** - Tokens can only be linked to policies that are defined in the same namespace or admin partition. 

You can view the current ACL tokens on the command line or through the API. The following example demonstrates the command line usage:

```shell-session
$ consul acl token list -format json -token <token_id>
[
    {
        "CreateIndex": 75,
        "ModifyIndex": 75,
        "AccessorID": "c3274caa-fbe4-b457-f4af-c05ba89a048d",
        "SecretID": "105c016a-ae9c-2006-ce23-4ef8823ba2af",
        "Description": "Bootstrap Token (Global Management)",
        "Policies": [
            {
                "ID": "00000000-0000-0000-0000-000000000001",
                "Name": "global-management"
            }
        ],
        "Local": false,
        "CreateTime": "2021-12-16T10:22:08.906291-08:00",
        "Hash": "Wda9obh/gvreyTbVhbyJ3ipX0M/apF4kpqowPQQx+u8=",
        "Legacy": false,
        "Namespace": "default",
        "Partition": "default"
    },
    {
        "CreateIndex": 71,
        "ModifyIndex": 71,
        "AccessorID": "00000000-0000-0000-0000-000000000002",
        "SecretID": "anonymous",
        "Description": "Anonymous Token",
        "Local": false,
        "CreateTime": "2021-12-16T10:21:11.996298-08:00",
        "Hash": "tgCOyeidw+oaoZXQ9mHy6+EnY7atKoGaBzg2ndTwXl0=",
        "Legacy": false,
        "Namespace": "default",
        "Partition": "default"
    }
]
```

Note that the `CreateIndex`, `ModifyIndex`, and `Hash` attributes are also printed. These attributes are printed for all responses and are not specific to ACL tokens. 

#### Builtin Tokens

During cluster bootstrapping when ACLs are enabled both the special `anonymous` and the `initial_management` token will be
injected.

- **Anonymous Token** - The anonymous token is used when a request is made to Consul without specifying a bearer token.
  The anonymous token's description and policies may be updated but Consul will prevent this token's deletion. When created,
  it will be assigned `00000000-0000-0000-0000-000000000002` for its Accessor ID and `anonymous` for its Secret ID.

- **Initial Management Token** - When an initial management token is present within the Consul configuration, it is created
  and will be linked with the builtin Global Management policy giving it unrestricted privileges. The initial management
  token is created with the Secret ID set to the value of the configuration entry.
  In Consul 1.4 - 1.10, this was called the `master` token. It was renamed to `initial_management` token in Consul 1.11.

#### Authorization

The token Secret ID is passed along with each RPC request to the servers. Consul's
[HTTP endpoints](/api) can accept tokens via the `token`
query string parameter, the `X-Consul-Token` request header, or an
[RFC6750](https://tools.ietf.org/html/rfc6750) authorization bearer token. Consul's
[CLI commands](/docs/commands) can accept tokens via the
`token` argument, or the `CONSUL_HTTP_TOKEN` environment variable. The CLI
commands can also accept token values stored in files with the `token-file`
argument, or the `CONSUL_HTTP_TOKEN_FILE` environment variable.

If no token is provided for an HTTP request then Consul will use the default ACL token
if it has been configured. If no default ACL token was configured then the anonymous
token will be used.

#### ACL Rules and Scope

The rules from all policies, roles, and service identities linked with a token are combined to form that token's
effective rule set. Policy rules can be defined in either an allowlist or denylist
mode depending on the configuration of [`acl_default_policy`](/docs/agent/options#acl_default_policy).
If the default policy is to "deny" access to all resources, then policy rules can be set to
allowlist access to specific resources. Conversely, if the default policy is “allow” then policy rules can
be used to explicitly deny access to resources.

The following table summarizes the ACL resources that are available for constructing
rules:

| Resource                                            | Scope                                                                                                                                                                                                    |
| --------------------------------------------------- | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| [`acl`](/docs/acl/acl-rules#acl-resource-rules)     | Operations for managing the ACL system [ACL API](/api/acl/acl)                                                                                                                                           |
| [`agent`](/docs/acl/acl-rules#agent-rules)          | Utility operations in the [Agent API](/api/agent), other than service and check registration                                                                                                             |
| [`event`](/docs/acl/acl-rules#event-rules)          | Listing and firing events in the [Event API](/api/event)                                                                                                                                                 |
| [`key`](/docs/acl/acl-rules#key-value-rules)        | Key/value store operations in the [KV Store API](/api/kv)                                                                                                                                                |
| [`keyring`](/docs/acl/acl-rules#keyring-rules)      | Keyring operations in the [Keyring API](/api/operator/keyring)                                                                                                                                           |
| [`node`](/docs/acl/acl-rules#node-rules)            | Node-level catalog operations in the [Catalog API](/api/catalog), [Health API](/api/health), [Prepared Query API](/api/query), [Network Coordinate API](/api/coordinate), and [Agent API](/api/agent)    |
| [`operator`](/docs/acl/acl-rules#operator-rules)    | Cluster-level operations in the [Operator API](/api/operator), other than the [Keyring API](/api/operator/keyring)                                                                                       |
| [`query`](/docs/acl/acl-rules#prepared-query-rules) | Prepared query operations in the [Prepared Query API](/api/query)                                                                                                                                        |
| [`service`](/docs/acl/acl-rules#service-rules)      | Service-level catalog operations in the [Catalog API](/api/catalog), [Health API](/api/health), [Intentions API](/api/connect/intentions), [Prepared Query API](/api/query), and [Agent API](/api/agent) |
| [`session`](/docs/acl/acl-rules#session-rules)      | Session operations in the [Session API](/api/session)                                                                                                                                                    |

Since Consul snapshots actually contain ACL tokens, the [Snapshot API](/api/snapshot)
requires a token with "write" privileges for the ACL system.

The following resources are not covered by ACL policies:

1. The [Status API](/api/status) is used by servers when bootstrapping and exposes
   basic IP and port information about the servers, and does not allow modification
   of any state.

2. The datacenter listing operation of the
   [Catalog API](/api/catalog#list-datacenters) similarly exposes the names of known
   Consul datacenters, and does not allow modification of any state.

3. The [connect CA roots endpoint](/api/connect/ca#list-ca-root-certificates) exposes just the public TLS certificate which other systems can use to verify the TLS connection with Consul.

Constructing rules from these policies is covered in detail on the
[ACL Rules](/docs/acl/acl-rules) page.

-> **Consul Enterprise Namespacing** - In addition to directly linked policies, roles and service identities, Consul Enterprise
will include the ACL policies and roles defined in the [Namespaces definition](/docs/enterprise/namespaces#namespace-definition). (Added in Consul Enterprise 1.7.0)

## Configuring ACLs

ACLs are configured using several different configuration options. These are marked
as to whether they are set on servers, clients, or both.

| Configuration Option                                           | Servers    | Clients    | Purpose                                                                |
| -------------------------------------------------------------- | ---------- | ---------- | ---------------------------------------------------------------------- |
| [`acl.enabled`](/docs/agent/options#acl_enabled)               | `REQUIRED` | `REQUIRED` | Controls whether ACLs are enabled                                      |
| [`acl.default_policy`](/docs/agent/options#acl_default_policy) | `OPTIONAL` | `N/A`      | Determines allowlist or denylist mode                                  |
| [`acl.down_policy`](/docs/agent/options#acl_down_policy)       | `OPTIONAL` | `OPTIONAL` | Determines what to do when the remote token or policy resolution fails |
| [`acl.role_ttl`](/docs/agent/options#acl_role_ttl)             | `OPTIONAL` | `OPTIONAL` | Determines time-to-live for cached ACL Roles                           |
| [`acl.policy_ttl`](/docs/agent/options#acl_policy_ttl)         | `OPTIONAL` | `OPTIONAL` | Determines time-to-live for cached ACL Policies                        |
| [`acl.token_ttl`](/docs/agent/options#acl_token_ttl)           | `OPTIONAL` | `OPTIONAL` | Determines time-to-live for cached ACL Tokens                          |

A number of special tokens can also be configured which allow for bootstrapping the ACL
system, or accessing Consul in special situations:

| Special Token                                                                        | Servers    | Clients    | Purpose                                                                                                                                                                                                                                                                   |
| ------------------------------------------------------------------------------------ | ---------- | ---------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| [`acl.tokens.agent_recovery`](/docs/agent/options#acl_tokens_agent_recovery)         | `OPTIONAL` | `OPTIONAL` | Special token that can be used to access [Agent API](/api/agent) when remote bearer token resolution fails; used for setting up the cluster such as doing initial join operations, see the [ACL Agent Recovery Token](#acl-agent-recovery-token) section for more details |
| [`acl.tokens.agent`](/docs/agent/options#acl_tokens_agent)                           | `OPTIONAL` | `OPTIONAL` | Special token that is used for an agent's internal operations, see the [ACL Agent Token](#acl-agent-token) section for more details                                                                                                                                       |
| [`acl.tokens.initial_management`](/docs/agent/options#acl_tokens_initial_management) | `OPTIONAL` | `N/A`      | Special token used to bootstrap the ACL system, check the [Bootstrapping ACLs](https://learn.hashicorp.com/tutorials/consul/access-control-setup-production) tutorial for more details                                                                                    |
| [`acl.tokens.default`](/docs/agent/options#acl_tokens_default)                       | `OPTIONAL` | `OPTIONAL` | Default token to use for client requests where no token is supplied; this is often configured with read-only access to services to enable DNS service discovery on agents                                                                                                 |

All of these tokens except the `initial_management` token can all be introduced or updated via the [/v1/agent/token API](/api/agent#update-acl-tokens).

In Consul 1.4 - 1.10, the following special tokens were known by different names:

| New Name (1.11+)                                                                     | Old Name (1.4 - 1.10)                                                    |
| ------------------------------------------------------------------------------------ | ------------------------------------------------------------------------ |
| [`acl.tokens.agent_recovery`](/docs/agent/options#acl_tokens_agent_recovery)         | [`acl.tokens.agent_master`](/docs/agent/options#acl_tokens_agent_master) |
| [`acl.tokens.initial_management`](/docs/agent/options#acl_tokens_initial_management) | [`acl.tokens.master`](/docs/agent/options#acl_tokens_master)             |

#### ACL Agent Recovery Token

Since the [`acl.tokens.agent_recovery`](/docs/agent/options#acl_tokens_agent_recovery) is designed to be used when the Consul servers are not available, its policy is managed locally on the agent and does not need to have a token defined on the Consul servers via the ACL API. Once set, it implicitly has the following policy associated with it

In Consul 1.4 - 1.10, this was called the `agent_master` token. It was renamed to `agent_recovery` token in Consul 1.11.

```hcl
agent "<node name of agent>" {
  policy = "write"
}
node_prefix "" {
  policy = "read"
}
```

#### ACL Agent Token

The [`acl.tokens.agent`](/docs/agent/options#acl_tokens_agent) is a special token that is used for an agent's internal operations. It isn't used directly for any user-initiated operations like the [`acl.tokens.default`](/docs/agent/options#acl_tokens_default), though if the `acl.tokens.agent` isn't configured the `acl.tokens.default` will be used. The ACL agent token is used for the following operations by the agent:

1. Updating the agent's node entry using the [Catalog API](/api/catalog), including updating its node metadata, tagged addresses, and network coordinates
2. Performing [anti-entropy](/docs/internals/anti-entropy) syncing, in particular reading the node metadata and services registered with the catalog
3. Reading and writing the special `_rexec` section of the KV store when executing [`consul exec`](/commands/exec) commands

Here's an example policy sufficient to accomplish the above for a node called `mynode`:

```hcl
node "mynode" {
  policy = "write"
}
service_prefix "" {
  policy = "read"
}
key_prefix "_rexec" {
  policy = "write"
}
```

The `service_prefix` policy needs read access for any services that can be registered on the agent. If [remote exec is disabled](/docs/agent/options#disable_remote_exec), the default, then the `key_prefix` policy can be omitted.

## Next Steps

Setup ACLs with the [Bootstrapping the ACL System tutorial](https://learn.hashicorp.com/tutorials/consul/access-control-setup-production?utm_source=consul.io&utm_medium=docs) or continue reading about
[ACL rules](/docs/acl/acl-rules).