diff --git a/website/source/docs/internals/acl.html.markdown b/website/source/docs/internals/acl.html.markdown index cdb952b41c..275a6ec50e 100644 --- a/website/source/docs/internals/acl.html.markdown +++ b/website/source/docs/internals/acl.html.markdown @@ -9,78 +9,84 @@ description: |- # ACL System 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](http://en.wikipedia.org/wiki/Capability-based_security) that relies +access to data and APIs. The ACL is +[Capability-based](http://en.wikipedia.org/wiki/Capability-based_security), relying on tokens to which fine grained rules can be applied. It is very similar to [AWS IAM](http://aws.amazon.com/iam/) in many ways. +## Scope + +When the ACL system was launched in Consul 0.4, it was only possible to specify +policies for the KV store. In Consul 0.5, ACL policies were extended to service +registrations. + ## ACL Design -The ACL system is designed to be easy to use, fast to enforce, flexible to new -policies, all while providing administrative insight. It has been modeled on -the AWS IAM system, as well as the more general object-capability model. The system -is modeled around "tokens". +The ACL system is designed to be easy to use, fast to enforce, and flexible to new +policies, all while providing administrative insight. -Every token has an ID, name, type and rule set. The ID is a randomly generated -UUID, making it unfeasible to guess. The name is opaque and human readable. -The type is either "client" meaning it cannot modify ACL rules, and is restricted -by the provided rules, or is "management" and is allowed to perform all actions. +Every token has an ID, name, type, and rule set. The ID is a randomly generated +UUID, making it unfeasible to guess. The name is opaque to Consul and human readable. +The type is either "client" (meaning the token cannot modify ACL rules) or "management" +(meaning the token is allowed to perform all actions). The token ID is passed along with each RPC request to the servers. Agents can be configured with an [`acl_token`](/docs/agent/options.html#acl_token) property to provide a default token, but the token can also be specified by a client on a -[per-request basis](/docs/agent/http.html). ACLs are new as of Consul 0.4, meaning +[per-request basis](/docs/agent/http.html). ACLs were added in Consul 0.4, meaning prior versions do not provide a token. This is handled by the special "anonymous" -token. Anytime there is no token provided, the rules defined by that token are +token. If no token provided, the rules associated with the anonymous token are automatically applied. This allows policy to be enforced on legacy clients. Enforcement is always done by the server nodes. All servers must be configured to provide an [`acl_datacenter`](/docs/agent/options.html#acl_datacenter) which enables ACL enforcement but also specifies the authoritative datacenter. Consul does not -replicate data cross-WAN, and instead relies on [RPC forwarding](/docs/internal/architecture.html) -to support Multi-Datacenter configurations. However, because requests can be -made across datacenter boundaries, ACL tokens must be valid globally. To avoid +replicate data cross-WAN and instead relies on [RPC forwarding](/docs/internal/architecture.html) +to support Multi-Datacenter configurations. However, because requests can be made +across datacenter boundaries, ACL tokens must be valid globally. To avoid replication issues, a single datacenter is considered authoritative and stores all the tokens. -When a request is made to any non-authoritative server with a token, it must -be resolved into the appropriate policy. This is done by reading the token -from the authoritative server and caching a configurable +When a request is made to a server in a non-authoritative datacenter server, it +must be resolved into the appropriate policy. This is done by reading the token +from the authoritative server and caching the result for a configurable [`acl_ttl`](/docs/agent/options.html#acl_ttl). The implication of caching is that the cache TTL is an upper bound on the staleness of policy that is enforced. It is possible to set a zero TTL, but this has adverse -performance impacts, as every request requires refreshing the policy. +performance impacts, as every request requires refreshing the policy via a +cross-datacenter WAN call. -Another possible issue is an outage of the +The Consul ACL center is also built to accommodate for an outage of the [`acl_datacenter`](/docs/agent/options.html#acl_datacenter) or networking -issues preventing access. In this case, it may be impossible for non-authoritative -servers to resolve tokens. Consul provides a number of configurable -[`acl_down_policy`](/docs/agent/options.html#acl_down_policy) -choices to tune behavior. It is possible to deny or permit all actions, or to ignore -cache TTLs and enter a fail-safe mode. +issues preventing access to it. In this case, it may be impossible for +servers in non-authoritative datacenters to resolve tokens. Consul provides +a number of configurable [`acl_down_policy`](/docs/agent/options.html#acl_down_policy) +choices to tune behavior. It is possible to deny or permit all actions or to ignore +cache TTLs and enter a fail-safe mode. The default is to ignore cache TTLs +for any previously resolved tokens and to deny any uncached tokens. ACLs can also act in either a whitelist or blacklist mode depending on the configuration of [`acl_default_policy`](/docs/agent/options.html#acl_default_policy). If the default policy is to deny all actions, then token rules can be set to allow or whitelist -actions. In the inverse, the allow all default behavior is a blacklist, -where rules are used to prohibit actions. +actions. In the inverse, the allow all default behavior is a blacklist +where rules are used to prohibit actions. By default, Consul will allow all +actions. ### Blacklist mode and `consul exec` If you set [`acl_default_policy`](/docs/agent/options.html#acl_default_policy) -to `deny`, the `anonymous` token won't have the permission to read the default -`_rexec` prefix, and therefore token-less Consul agents (using the `anonymous` token) +to `deny`, the `anonymous` token won't have permission to read the default +`_rexec` prefix; therefore, Consul agents using the `anonymous` token won't be able to perform [`consul exec`](/docs/commands/exec.html) actions. -There is a subtle interaction there. The agents will need permission to -read/write to the `_rexec` prefix for [`consul exec`](/docs/commands/exec.html) to -work properly. They use that as the transport for most data, only the edge trigger -uses the event system. +Here's why: the agents need read/write permission to the `_rexec` prefix for +[`consul exec`](/docs/commands/exec.html) to work properly. They use that prefix +as the transport for most data. -You can do this by allowing the `anonymous` token to access that prefix, or by -providing tokens to the agents that enable it. The former can be done by giving -this rule to the `anonymous` token: +You can enable [`consul exec`](/docs/commands/exec.html) from agents that are not +configured with a token by allowing the `anonymous` token to access that prefix. +This can be done by giving this rule to the `anonymous` token: ```javascript key "_rexec/" { @@ -88,10 +94,14 @@ key "_rexec/" { } ``` +Alternatively, you can, of course, add an explicit +[`acl_token`](/docs/agent/options.html#acl_token) to each agent, giving it access +to that prefix. + ### Bootstrapping ACLs Bootstrapping the ACL system is done by providing an initial [`acl_master_token` -configuration](/docs/agent/options.html#acl_master_token), which will be created +configuration](/docs/agent/options.html#acl_master_token) which will be created as a "management" type token if it does not exist. Note that the [`acl_master_token` ](/docs/agent/options.html#acl_master_token) is only installed when a server acquires cluster leadership. If you would like to install or change the @@ -101,14 +111,33 @@ for all servers. Once this is done, restart the current leader to force a leader ## Rule Specification -A core part of the ACL system is a rule language which is used -to describe the policy that must be enforced. We make use of +A core part of the ACL system is a rule language which is used to describe the policy +that must be enforced. Consul supports ACLs for both [K/Vs](/intro/getting-started/kv.html) +and [services](/intro/getting-started/services.html). + +Key policies are defined by coupling a prefix with a policy. The rules are enforced +using a longest-prefix match policy; Consul picks the most specific policy possible. The +policy is either "read", "write" or "deny". A "write" policy implies "read", and there is no +way to specify write-only. If there is no applicable rule, the +[`acl_default_policy`](/docs/agent/options.html#acl_default_policy) is applied. + +Service policies are defined by coupling a service name and a policy. The rules are +enforced using an exact match policy. The default rule, applied to any service that doesn't +have a matching policy, is provided using the empty string. The policy is either "read", +"write", or "deny". A "write" policy implies "read", and there is no way to specify write-only. +If there is no applicable rule, the +[`acl_default_policy`](/docs/agent/options.html#acl_default_policy) is +applied. Currently, only the "write" level is enforced for registration of +services; services can always be read. + +The policy for the "consul" service is always "write" as it is managed internally by Consul. + +We make use of the [HashiCorp Configuration Language (HCL)](https://github.com/hashicorp/hcl/) to specify policy. This language is human readable and interoperable -with JSON making it easy to machine generate. +with JSON making it easy to machine-generate. -As of Consul 0.4, it is only possible to specify policies for the -KV store. Specification in the HCL format looks like: +Specification in the HCL format looks like: ```javascript # Default all keys to read-only @@ -119,17 +148,17 @@ key "foo/" { policy = "write" } key "foo/private/" { - # Deny access to the private dir + # Deny access to the dir "foo/private" policy = "deny" } -# Default all services to allowing registration +# Default all services to allow registration service "" { policy = "write" } service "secure" { - # Deny registration access to secure service + # Deny registration access to service named "secure" policy = "read" } ``` @@ -160,20 +189,3 @@ This is equivalent to the following JSON input: } ``` -Key policies provide both a prefix and a policy. The rules are enforced -using a longest-prefix match policy. This means we pick the most specific -policy possible. The policy is either "read", "write" or "deny". A "write" -policy implies "read", and there is no way to specify write-only. If there -is no applicable rule, the -[`acl_default_policy`](/docs/agent/options.html#acl_default_policy) is applied. - -Services policies provide both a service name and a policy. The rules are -enforced using an exact match policy. The default rule is provided using -the empty string. The policy is either "read", "write", or "deny". A "write" -policy implies "read", and there is no way to specify write-only. If there -is no applicable rule, the -[`acl_default_policy`](/docs/agent/options.html#acl_default_policy) is -applied. Currently, only the "write" level is enforced for registration of -services. The policy for the "consul" service is always "write" as it is -managed internally. -