1--- 2layout: docs 3page_title: ACL System 4description: >- 5 Consul provides an optional Access Control List (ACL) system which can be used 6 to control access to data and APIs. The ACL system is a Capability-based 7 system that relies on tokens which can have fine grained rules applied to 8 them. It is very similar to AWS IAM in many ways. 9--- 10 11# ACL System 12 13-> **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). 14 15Consul provides an optional Access Control List (ACL) system which can be used to control access to data and APIs. 16The ACL is [Capability-based](https://en.wikipedia.org/wiki/Capability-based_security), relying on tokens which 17are associated with policies to determine which fine grained rules can be applied. Consul's capability based 18ACL system is very similar to the design of [AWS IAM](https://aws.amazon.com/iam/). 19 20To 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). 21 22## ACL System Overview 23 24The ACL system is designed to be easy to use and fast to enforce while providing administrative insight. 25At the highest level, there are two major components to the ACL system: 26 27- **ACL Policies** - Policies allow the grouping of a set of rules into a logical unit that can be reused and linked with 28 many tokens. 29 30- **ACL Tokens** - Requests to Consul are authorized by using bearer token. Each ACL token has a public 31 Accessor ID which is used to name a token, and a Secret ID which is used as the bearer token used to 32 make requests to Consul. 33 34For many scenarios policies and tokens are sufficient, but more advanced setups 35may benefit from additional components in the ACL system: 36 37- **ACL Roles** - Roles allow for the grouping of a set of policies and service 38 identities into a reusable higher-level entity that can be applied to many 39 tokens. (Added in Consul 1.5.0) 40 41- **ACL Service Identities** - Service identities are a policy template for 42 expressing a link to a policy suitable for use in [Consul 43 Connect](/docs/connect). At authorization time this acts like an 44 additional policy was attached, the contents of which are described further 45 below. These are directly attached to tokens and roles and are not 46 independently configured. (Added in Consul 1.5.0) 47 48- **ACL Node Identities** - Node identities are a policy template for 49 expressing a link to a policy suitable for use as an [Consul `agent` token 50 ](/docs/agent/options#acl_tokens_agent). At authorization time this acts like an 51 additional policy was attached, the contents of which are described further 52 below. These are directly attached to tokens and roles and are not 53 independently configured. (Added in Consul 1.8.1) 54 55- **ACL Auth Methods and Binding Rules** - To learn more about these topics, 56 see the [auth methods documentation page](/docs/acl/auth-methods). 57 58ACL tokens, policies, roles, auth methods, and binding rules are managed by 59Consul operators via Consul's [ACL API](/api/acl/acl), 60[ACL CLI](/commands/acl), or systems like 61[HashiCorp's Vault](https://www.vaultproject.io/docs/secrets/consul). 62 63If the ACL system becomes inoperable, you can follow the 64[reset procedure](https://learn.hashicorp.com/tutorials/consul/access-control-troubleshoot#reset-the-acl-system) at any time. 65 66### ACL Policies 67 68An ACL policy is a named set of rules and is composed of the following elements: 69 70- **ID** - The policy's auto-generated public identifier. 71- **Name** - A unique meaningful name for the policy. 72- **Description** - A human readable description of the policy. (Optional) 73- **Rules** - Set of rules granting or denying permissions. See the [Rule Specification](/docs/acl/acl-rules#rule-specification) documentation for more details. 74- **Datacenters** - A list of datacenters the policy is valid within. 75- **Namespace** - <EnterpriseAlert inline /> - The namespace this policy resides within. (Added in Consul Enterprise 1.7.0) 76 77-> **Consul Enterprise Namespacing** - Rules defined in a policy in any namespace other than `default` will be [restricted](/docs/acl/acl-rules#namespace-rules) to being able to grant a subset of the overall privileges and only affecting that single namespace. 78 79#### Builtin Policies 80 81- **Global Management** - Grants unrestricted privileges to any token that uses it. When created it will be named `global-management` 82 and will be assigned the reserved ID of `00000000-0000-0000-0000-000000000001`. This policy can be renamed but modification 83 of anything else including the rule set and datacenter scoping will be prevented by Consul. 84 85- **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 86 within the Namespace. (Added in Consul Enterprise 1.7.0) 87 88### ACL Service Identities 89 90-> Added in Consul 1.5.0 91 92An ACL service identity is an [ACL policy](/docs/acl/acl-system#acl-policies) template for expressing a link to a policy 93suitable for use in [Consul Connect](/docs/connect). They are usable 94on both tokens and roles and are composed of the following elements: 95 96- **Service Name** - The name of the service. 97- **Datacenters** - A list of datacenters the effective policy is valid within. (Optional) 98 99Services participating in the service mesh will need privileges to both _be 100discovered_ and to _discover other healthy service instances_. Suitable 101policies tend to all look nearly identical so a service identity is a policy 102template to aid in avoiding boilerplate policy creation. 103 104During the authorization process, the configured service identity is automatically 105applied as a policy with the following preconfigured [ACL 106rules](/docs/acl/acl-system#acl-rules-and-scope): 107 108```hcl 109# Allow the service and its sidecar proxy to register into the catalog. 110service "<Service Name>" { 111 policy = "write" 112} 113service "<Service Name>-sidecar-proxy" { 114 policy = "write" 115} 116 117# Allow for any potential upstreams to be resolved. 118service_prefix "" { 119 policy = "read" 120} 121node_prefix "" { 122 policy = "read" 123} 124``` 125 126The [API documentation for roles](/api/acl/roles#sample-payload) has some 127examples of using a service identity. 128 129-> **Consul Enterprise Namespacing** - Service Identity rules will be scoped to the single namespace that 130the corresponding ACL Token or Role resides within. 131 132### ACL Node Identities 133 134-> Added in Consul 1.8.1 135 136An ACL node identity is an [ACL policy](/docs/acl/acl-system#acl-policies) template for expressing a link to a policy 137suitable for use as an [Consul `agent` token](/docs/agent/options#acl_tokens_agent). They are usable 138on both tokens and roles and are composed of the following elements: 139 140- **Node Name** - The name of the node to grant access to. 141- **Datacenter** - The datacenter that the node resides within. 142 143During the authorization process, the configured node identity is automatically 144applied as a policy with the following preconfigured [ACL 145rules](/docs/acl/acl-system#acl-rules-and-scope): 146 147```hcl 148# Allow the agent to register its own node in the Catalog and update its network coordinates 149node "<Node Name>" { 150 policy = "write" 151} 152 153# Allows the agent to detect and diff services registered to itself. This is used during 154# anti-entropy to reconcile difference between the agents knowledge of registered 155# services and checks in comparison with what is known in the Catalog. 156service_prefix "" { 157 policy = "read" 158} 159``` 160 161-> **Consul Enterprise Namespacing** - Node Identities can only be applied to tokens and roles in the `default` namespace. 162The synthetic policy rules allow for `service:read` permissions on all services in all namespaces. 163 164### ACL Roles 165 166-> Added in Consul 1.5.0 167 168An ACL role is a named set of policies and service identities and is composed 169of the following elements: 170 171- **ID** - The role's auto-generated public identifier. 172- **Name** - A unique meaningful name for the role. 173- **Description** - A human readable description of the role. (Optional) 174- **Policy Set** - The list of policies that are applicable for the role. 175- **Service Identity Set** - The list of service identities that are applicable for the role. 176- **Namespace** <EnterpriseAlert inline /> - The namespace this policy resides within. (Added in Consul Enterprise 1.7.0) 177 178-> **Consul Enterprise Namespacing** - Roles may only link to policies defined in the same namespace as the role itself. 179 180### ACL Tokens 181 182ACL tokens are used to determine if the caller is authorized to perform an action. An ACL token is composed of the following 183elements: 184 185- **Accessor ID** - The token's public identifier. 186- **Secret ID** -The bearer token used when making requests to Consul. 187- **Description** - A human readable description of the token. (Optional) 188- **Policy Set** - The list of policies that are applicable for the token. 189- **Role Set** - The list of roles that are applicable for the token. (Added in Consul 1.5.0) 190- **Service Identity Set** - The list of service identities that are applicable for the token. (Added in Consul 1.5.0) 191- **Locality** - Indicates whether the token should be local to the datacenter it was created within or created in 192 the primary datacenter and globally replicated. 193- **Expiration Time** - The time at which this token is revoked. (Optional; Added in Consul 1.5.0) 194- **Namespace** <EnterpriseAlert inline /> - The namespace this policy resides within. (Added in Consul Enterprise 1.7.0) 195 196-> **Consul Enterprise Namespacing** - Tokens may only link to policies and roles defined in the same namespace as 197the token itself. 198 199#### Builtin Tokens 200 201During cluster bootstrapping when ACLs are enabled both the special `anonymous` and the `master` token will be 202injected. 203 204- **Anonymous Token** - The anonymous token is used when a request is made to Consul without specifying a bearer token. 205 The anonymous token's description and policies may be updated but Consul will prevent this token's deletion. When created, 206 it will be assigned `00000000-0000-0000-0000-000000000002` for its Accessor ID and `anonymous` for its Secret ID. 207 208- **Master Token** - When a master token is present within the Consul configuration, it is created and will be linked 209 With the builtin Global Management policy giving it unrestricted privileges. The master token is created with the Secret ID 210 set to the value of the configuration entry. 211 212#### Authorization 213 214The token Secret ID is passed along with each RPC request to the servers. Consul's 215[HTTP endpoints](/api) can accept tokens via the `token` 216query string parameter, the `X-Consul-Token` request header, or an 217[RFC6750](https://tools.ietf.org/html/rfc6750) authorization bearer token. Consul's 218[CLI commands](/docs/commands) can accept tokens via the 219`token` argument, or the `CONSUL_HTTP_TOKEN` environment variable. The CLI 220commands can also accept token values stored in files with the `token-file` 221argument, or the `CONSUL_HTTP_TOKEN_FILE` environment variable. 222 223If no token is provided for an HTTP request then Consul will use the default ACL token 224if it has been configured. If no default ACL token was configured then the anonymous 225token will be used. 226 227#### ACL Rules and Scope 228 229The rules from all policies, roles, and service identities linked with a token are combined to form that token's 230effective rule set. Policy rules can be defined in either an allowlist or denylist 231mode depending on the configuration of [`acl_default_policy`](/docs/agent/options#acl_default_policy). 232If the default policy is to "deny" access to all resources, then policy rules can be set to 233allowlist access to specific resources. Conversely, if the default policy is “allow” then policy rules can 234be used to explicitly deny access to resources. 235 236The following table summarizes the ACL resources that are available for constructing 237rules: 238 239| Resource | Scope | 240| --------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | 241| [`acl`](/docs/acl/acl-rules#acl-resource-rules) | Operations for managing the ACL system [ACL API](/api/acl/acl) | 242| [`agent`](/docs/acl/acl-rules#agent-rules) | Utility operations in the [Agent API](/api/agent), other than service and check registration | 243| [`event`](/docs/acl/acl-rules#event-rules) | Listing and firing events in the [Event API](/api/event) | 244| [`key`](/docs/acl/acl-rules#key-value-rules) | Key/value store operations in the [KV Store API](/api/kv) | 245| [`keyring`](/docs/acl/acl-rules#keyring-rules) | Keyring operations in the [Keyring API](/api/operator/keyring) | 246| [`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) | 247| [`operator`](/docs/acl/acl-rules#operator-rules) | Cluster-level operations in the [Operator API](/api/operator), other than the [Keyring API](/api/operator/keyring) | 248| [`query`](/docs/acl/acl-rules#prepared-query-rules) | Prepared query operations in the [Prepared Query API](/api/query) | 249| [`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) | 250| [`session`](/docs/acl/acl-rules#session-rules) | Session operations in the [Session API](/api/session) | 251 252Since Consul snapshots actually contain ACL tokens, the [Snapshot API](/api/snapshot) 253requires a token with "write" privileges for the ACL system. 254 255The following resources are not covered by ACL policies: 256 2571. The [Status API](/api/status) is used by servers when bootstrapping and exposes 258 basic IP and port information about the servers, and does not allow modification 259 of any state. 260 2612. The datacenter listing operation of the 262 [Catalog API](/api/catalog#list-datacenters) similarly exposes the names of known 263 Consul datacenters, and does not allow modification of any state. 264 2653. 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. 266 267Constructing rules from these policies is covered in detail on the 268[ACL Rules](/docs/acl/acl-rules) page. 269 270-> **Consul Enterprise Namespacing** - In addition to directly linked policies, roles and service identities, Consul Enterprise 271will include the ACL policies and roles defined in the [Namespaces definition](/docs/enterprise/namespaces#namespace-definition). (Added in Consul Enterprise 1.7.0) 272 273## Configuring ACLs 274 275ACLs are configured using several different configuration options. These are marked 276as to whether they are set on servers, clients, or both. 277 278| Configuration Option | Servers | Clients | Purpose | 279| -------------------------------------------------------------- | ---------- | ---------- | ---------------------------------------------------------------------- | 280| [`acl.enabled`](/docs/agent/options#acl_enabled) | `REQUIRED` | `REQUIRED` | Controls whether ACLs are enabled | 281| [`acl.default_policy`](/docs/agent/options#acl_default_policy) | `OPTIONAL` | `N/A` | Determines allowlist or denylist mode | 282| [`acl.down_policy`](/docs/agent/options#acl_down_policy) | `OPTIONAL` | `OPTIONAL` | Determines what to do when the remote token or policy resolution fails | 283| [`acl.role_ttl`](/docs/agent/options#acl_role_ttl) | `OPTIONAL` | `OPTIONAL` | Determines time-to-live for cached ACL Roles | 284| [`acl.policy_ttl`](/docs/agent/options#acl_policy_ttl) | `OPTIONAL` | `OPTIONAL` | Determines time-to-live for cached ACL Policies | 285| [`acl.token_ttl`](/docs/agent/options#acl_token_ttl) | `OPTIONAL` | `OPTIONAL` | Determines time-to-live for cached ACL Tokens | 286 287A number of special tokens can also be configured which allow for bootstrapping the ACL 288system, or accessing Consul in special situations: 289 290| Special Token | Servers | Clients | Purpose | 291| ------------------------------------------------------------------------ | ---------- | ---------- | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | 292| [`acl.tokens.agent_master`](/docs/agent/options#acl_tokens_agent_master) | `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 Master Token](#acl-agent-master-token) section for more details | 293| [`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 | 294| [`acl.tokens.master`](/docs/agent/options#acl_tokens_master) | `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 | 295| [`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 | 296 297All of these tokens except the `master` token can all be introduced or updated via the [/v1/agent/token API](/api/agent#update-acl-tokens). 298 299#### ACL Agent Master Token 300 301Since the [`acl.tokens.agent_master`](/docs/agent/options#acl_tokens_agent_master) 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 302 303```hcl 304agent "<node name of agent>" { 305 policy = "write" 306} 307node_prefix "" { 308 policy = "read" 309} 310``` 311 312#### ACL Agent Token 313 314The [`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: 315 3161. Updating the agent's node entry using the [Catalog API](/api/catalog), including updating its node metadata, tagged addresses, and network coordinates 3172. Performing [anti-entropy](/docs/internals/anti-entropy) syncing, in particular reading the node metadata and services registered with the catalog 3183. Reading and writing the special `_rexec` section of the KV store when executing [`consul exec`](/commands/exec) commands 319 320Here's an example policy sufficient to accomplish the above for a node called `mynode`: 321 322```hcl 323node "mynode" { 324 policy = "write" 325} 326service_prefix "" { 327 policy = "read" 328} 329key_prefix "_rexec" { 330 policy = "write" 331} 332``` 333 334The `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. 335 336## Next Steps 337 338Setup 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 339[ACL rules](/docs/acl/acl-rules). 340