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Website: GH-730 for docs/internals/acl.html.

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Ryan Breen 2015-03-22 11:44:16 -04:00
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@ -27,16 +27,16 @@ The type is either "client" meaning it cannot modify ACL rules, and is restricte
by the provided rules, or is "management" and is allowed to perform all actions.
The token ID is passed along with each RPC request to the servers. Agents
[can be configured](/docs/agent/options.html) with `acl_token` 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 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 automatically applied. This allows
policy to be enforced on legacy clients.
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
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
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](/docs/agent/options.html) an `acl_datacenter`, which enables
ACL enforcement but also specifies the authoritative datacenter. Consul does not
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
@ -45,34 +45,38 @@ 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 `acl_ttl`. The implication
from the authoritative server and caching 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.
Another possible issue is an outage of the `acl_datacenter` or networking
Another possible issue is 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`
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.
ACLs can also act in either a whitelist or blacklist mode depending
on the configuration of `acl_default_policy`. If the default policy is
to deny all actions, then token rules can be set to allow or whitelist
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.
### Blacklist mode and `consul exec`
If you set `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) won't be able to perform `consul exec`
actions.
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)
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` to work properly. They use
that as the transport for most data, only the edge trigger uses the event
system.
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.
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
@ -88,11 +92,12 @@ key "_rexec/" {
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
as a "management" type token if it does not exist. Note that the `acl_master_token`
is only installed when a server acquires cluster leadership. If you would
like to install or change the `acl_master_token`, set the new value for
`acl_master_token` in the configuration for all servers. Once this is done, restart the
current leader to force a leader election.
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
[`acl_master_token`](/docs/agent/options.html#acl_master_token), set the new value for
[`acl_master_token`](/docs/agent/options.html#acl_master_token) in the configuration
for all servers. Once this is done, restart the current leader to force a leader election.
## Rule Specification
@ -159,13 +164,16 @@ 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` is applied.
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` 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.
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.