mirror of https://github.com/status-im/consul.git
245 lines
10 KiB
Plaintext
245 lines
10 KiB
Plaintext
---
|
|
layout: docs
|
|
page_title: Service-to-service permissions - Intentions
|
|
description: >-
|
|
Intentions define access control for services via Connect and are used to
|
|
control which services may establish connections or make requests.
|
|
---
|
|
|
|
# Intentions
|
|
|
|
-> **1.9.0 and later:** This guide only applies in Consul versions 1.9.0 and
|
|
later. The documentation for the legacy intentions system is
|
|
[here](/docs/connect/intentions-legacy).
|
|
|
|
Intentions define access control for services via Connect and are used to
|
|
control which services may establish connections or make requests. Intentions
|
|
can be managed via the API, CLI, or UI.
|
|
|
|
Intentions are enforced on inbound connections or requests by the
|
|
[proxy](/docs/connect/proxies) or within a [natively integrated
|
|
application](/docs/connect/native).
|
|
|
|
Depending upon the [protocol] in use by the destination service, you can define
|
|
intentions to control Connect traffic authorization either at networking layer
|
|
4 (e.g. TCP) and networking layer 7 (e.g. HTTP):
|
|
|
|
- **Identity-based** - All intentions may enforce access based on identities
|
|
encoded within [TLS
|
|
certificates](/docs/connect/connect-internals#mutual-transport-layer-security-mtls).
|
|
This allows for coarse all-or-nothing access control between pairs of
|
|
services. These work with for services with any [protocol] as they only
|
|
require awareness of the TLS handshake that wraps the opaque TCP connection.
|
|
These can also be thought of as **L4 intentions**.
|
|
|
|
- **Application-aware** - Some intentions may additionally enforce access based
|
|
on [L7 request
|
|
attributes](/docs/connect/config-entries/service-intentions#permissions) in
|
|
addition to connection identity. These may only be defined for services with
|
|
a [protocol] that is HTTP-based. These can also be thought of as **L7
|
|
intentions**.
|
|
|
|
At any given point in time, between any pair of services **only one intention
|
|
controls authorization**. This may be either an L4 intention or an L7
|
|
intention, but at any given point in time only one of those applies.
|
|
|
|
The [intention match API](/api/connect/intentions#list-matching-intentions)
|
|
should be periodically called to retrieve all relevant intentions for the
|
|
target destination. After verifying the TLS client certificate, the cached
|
|
intentions should be consulted for each incoming connection/request to
|
|
determine if it should be accepted or rejected.
|
|
|
|
The default intention behavior is defined by the default [ACL
|
|
policy](/docs/agent/options#acl_default_policy). If the default ACL policy is
|
|
"allow all", then all Connect connections are allowed by default. If the
|
|
default ACL policy is "deny all", then all Connect connections or requests are
|
|
denied by default.
|
|
|
|
## Intention Basics
|
|
|
|
Intentions are managed primarily via
|
|
[`service-intentions`](/docs/connect/config-entries/service-intentions) config
|
|
entries or the UI. Some simpler tasks can also be achieved with the older
|
|
[API](/api-docs/connect/intentions) or [CLI](/commands/intention). Please see
|
|
the respective documentation for each for full details on options, flags, etc.
|
|
|
|
Below is an example of a basic
|
|
[`service-intentions`](/docs/connect/config-entries/service-intentions) config
|
|
entry representing two simple intentions. The full data model complete with
|
|
more examples can be found in the
|
|
[`service-intentions`](/docs/connect/config-entries/service-intentions) config
|
|
entry documentation.
|
|
|
|
```hcl
|
|
Kind = "service-intentions"
|
|
Name = "db"
|
|
Sources = [
|
|
{
|
|
Name = "web"
|
|
Action = "deny"
|
|
},
|
|
{
|
|
Name = "api"
|
|
Action = "allow"
|
|
}
|
|
]
|
|
```
|
|
|
|
This config entry defines two intentions with a common destination of "db". The
|
|
first intention above is a deny intention with a source of "web". This says
|
|
that connections from web to db are not allowed and the connection will be
|
|
rejected. The second intention is an allow intention with a source of "api".
|
|
This says that connections from api to db are allowed and connections will be
|
|
accepted.
|
|
|
|
### Wildcard Intentions
|
|
|
|
An intention source or destination may also be the special wildcard
|
|
value `*`. This matches _any_ value and is used as a catch-all.
|
|
|
|
This example says that the "web" service cannot connect to _any_ service:
|
|
|
|
```hcl
|
|
Kind = "service-intentions"
|
|
Name = "*"
|
|
Sources = [
|
|
{
|
|
Name = "web"
|
|
Action = "deny"
|
|
}
|
|
]
|
|
```
|
|
|
|
And this example says that _no_ service can connect to the "db" service:
|
|
|
|
```hcl
|
|
Kind = "service-intentions"
|
|
Name = "db"
|
|
Sources = [
|
|
{
|
|
Name = "*"
|
|
Action = "deny"
|
|
}
|
|
]
|
|
```
|
|
|
|
### Enforcement
|
|
|
|
For services that define their [protocol] as TCP, intentions mediate the
|
|
ability to **establish new connections**. When an intention is modified,
|
|
existing connections will not be affected. This means that changing a
|
|
connection from "allow" to "deny" today _will not_ kill the connection.
|
|
|
|
For services that define their protocol as HTTP-based, intentions mediate the
|
|
ability to **issue new requests**.
|
|
|
|
When an intention is modified, requests received after the modification will
|
|
use the latest intention rules to enforce access. This means that though
|
|
changing a connection from "allow" to "deny" today will not kill the
|
|
connection, it will correctly block new requests from being processed.
|
|
|
|
## Precedence and Match Order
|
|
|
|
Intentions are matched in an implicit order based on specificity, preferring
|
|
deny over allow. Specificity is determined by whether a value is an exact
|
|
specified value or is the wildcard value `*`.
|
|
The full precedence table is shown below and is evaluated
|
|
top to bottom, with larger numbers being evaluated first.
|
|
|
|
| Source Namespace | Source Name | Destination Namespace | Destination Name | Precedence |
|
|
| ---------------- | ----------- | --------------------- | ---------------- | ---------- |
|
|
| Exact | Exact | Exact | Exact | 9 |
|
|
| Exact | `*` | Exact | Exact | 8 |
|
|
| `*` | `*` | Exact | Exact | 7 |
|
|
| Exact | Exact | Exact | `*` | 6 |
|
|
| Exact | `*` | Exact | `*` | 5 |
|
|
| `*` | `*` | Exact | `*` | 4 |
|
|
| Exact | Exact | `*` | `*` | 3 |
|
|
| Exact | `*` | `*` | `*` | 2 |
|
|
| `*` | `*` | `*` | `*` | 1 |
|
|
|
|
The precedence value can be read from a
|
|
[field](/docs/connect/config-entries/service-intentions#precedence) on the
|
|
`service-intentions` config entry after it is modified. Precedence cannot be
|
|
manually overridden today.
|
|
|
|
The numbers in the table above are not stable. Their ordering will remain
|
|
fixed but the actual number values may change in the future.
|
|
|
|
-> <EnterpriseAlert inline /> - Namespaces are an Enterprise feature. In Consul
|
|
OSS the only allowable value for either namespace field is `"default"`. Other
|
|
rows in this table are not applicable.
|
|
|
|
## Intention Management Permissions
|
|
|
|
Intention management can be protected by [ACLs](/docs/security/acl).
|
|
Permissions for intentions are _destination-oriented_, meaning the ACLs
|
|
for managing intentions are looked up based on the destination value
|
|
of the intention, not the source.
|
|
|
|
Intention permissions are by default implicitly granted at `read` level
|
|
when granting `service:read` or `service:write`. This is because a
|
|
service registered that wants to use Connect needs `intentions:read`
|
|
for its own service name in order to know whether or not to authorize
|
|
connections. The following ACL policy will implicitly grant `intentions:read`
|
|
(note _read_) for service `web`.
|
|
|
|
```hcl
|
|
service "web" {
|
|
policy = "write"
|
|
}
|
|
```
|
|
|
|
It is possible to explicitly specify intention permissions. For example,
|
|
the following policy will allow a service to be discovered without granting
|
|
access to read intentions for it.
|
|
|
|
```hcl
|
|
service "web" {
|
|
policy = "read"
|
|
intentions = "deny"
|
|
}
|
|
```
|
|
|
|
Note that `intentions:read` is required for a token that a Connect-enabled
|
|
service uses to register itself or its proxy. If the token used does not
|
|
have `intentions:read` then the agent will be unable to resolve intentions
|
|
for the service and so will not be able to authorize any incoming connections.
|
|
|
|
~> **Security Note:** Explicitly allowing `intentions:write` on the token you
|
|
provide to a service instance at registration time opens up a significant
|
|
additional vulnerability. Although you may trust the service _team_ to define
|
|
which inbound connections they accept, using a combined token for registration
|
|
allows a compromised instance to to redefine the intentions which allows many
|
|
additional attack vectors and may be hard to detect. We strongly recommend only
|
|
delegating `intentions:write` using tokens that are used by operations teams or
|
|
orchestrators rather than spread via application config, or only manage
|
|
intentions with management tokens.
|
|
|
|
## Performance and Intention Updates
|
|
|
|
The intentions for services registered with a Consul agent are cached
|
|
locally on that agent. They are then updated via a background blocking query
|
|
against the Consul servers.
|
|
|
|
Supported [proxies] (such as [Envoy]) also cache this data within their own
|
|
configuration so that inbound connections or requests require no Consul agent
|
|
involvement during authorization. All actions in the data path of connections
|
|
happen within the proxy.
|
|
|
|
Updates to intentions are propagated nearly instantly to agents since agents
|
|
maintain a continuous blocking query in the background for intention updates
|
|
for registered services. Proxies similarly use blocking queries to update
|
|
their local configurations quickly.
|
|
|
|
Because all the intention data is cached locally, the agents or proxies can
|
|
fail static. Even if the agents are severed completely from the Consul servers,
|
|
or the proxies are severed completely from their local Consul agent, inbound
|
|
connection authorization continues to work indefinitely. Changes to intentions
|
|
will not be picked up until the partition heals, but will then automatically
|
|
take effect when connectivity is restored.
|
|
|
|
[protocol]: /docs/connect/config-entries/service-defaults#protocol
|
|
[proxies]: /docs/connect/proxies
|
|
[envoy]: /docs/connect/proxies/envoy
|