# Overview

This plugin provides the ability for your RabbitMQ server to perform
authentication (determining who can log in) and authorisation
(determining what permissions they have) by making requests to an HTTP
server.

This plugin can put a significant amount of load on its backing service.
We recommend using it together with [rabbitmq_auth_backend_cache](http://github.com/rabbitmq/rabbitmq-auth-backend-cache)
with a reasonable caching interval (e.g. 1-3 minutes).

## RabbitMQ Version Requirements

This plugin is distributed with RabbitMQ.

## Enabling the Plugin

Like all RabbitMQ plugins, this plugin must be enabled before it can be used:

``` shell
rabbitmq-plugins enable rabbitmq_auth_backend_http
```

## Configuring the Plugin

To use this backend exclusively, use the following snippet in `rabbitmq.conf` (currently
in master)

``` ini
auth_backends.1 = http
```

Or, in the classic config format (`rabbitmq.config`, prior to 3.7.0) or `advanced.config`:

``` erl
[{rabbit, [{auth_backends, [rabbit_auth_backend_http]}]}].
```

See [RabbitMQ Configuration guide](http://www.rabbitmq.com/configure.html) and
[Access Control guide](http://rabbitmq.com/access-control.html) for more information.

You need to configure the plugin to know which URIs to point at
and which HTTP method to use.

Below is a minimal configuration file example.

In `rabbitmq.conf`:

``` ini
auth_backends.1 = http
auth_http.http_method   = post
auth_http.user_path     = http://some-server/auth/user
auth_http.vhost_path    = http://some-server/auth/vhost
auth_http.resource_path = http://some-server/auth/resource
auth_http.topic_path    = http://some-server/auth/topic
```

In the [`advanced.config` format](https://www.rabbitmq.com/configure.html#advanced-config-file):

``` erl
[
    {rabbit, [{auth_backends, [rabbit_auth_backend_http]}]},
    {rabbitmq_auth_backend_http,
    [{http_method,   post},
    {user_path,     "http(s)://some-server/auth/user"},
    {vhost_path,    "http(s)://some-server/auth/vhost"},
    {resource_path, "http(s)://some-server/auth/resource"},
    {topic_path,    "http(s)://some-server/auth/topic"}]}
].
```

By default `http_method` configuration is `GET` for backwards compatibility. It's recommended
to use `POST` requests to avoid credentials logging.

## What Must My Web Server Do?

This plugin requires that your web server respond to requests in a
certain predefined format. It will make GET (by default) or POST requests
against the URIs listed in the configuration file. It will add query string
(for `GET` requests) or a URL-encoded request body (for `POST` requests) parameters as follows:

### user_path

* `username`: the name of the user
* `password`: the password provided (may be missing if e.g. rabbitmq-auth-mechanism-ssl is used)

Note: This request may include additional http request parameters in addition to the ones listed above.
For instance, if the user accessed RabbitMQ via the MQTT protocol, it is expected `client_id` and `vhost` request parameters too.

### vhost_path

* `username`: the name of the user
* `vhost`: the name of the virtual host being accessed
* `ip`: the client ip address

Note that you cannot create arbitrary virtual hosts using this plugin; you can only determine whether your users can see / access the ones that exist.

### resource_path

* `username`: the name of the user
* `vhost`: the name of the virtual host containing the resource
* `resource`: the type of resource (`exchange`, `queue`, `topic`)
* `name`: the name of the resource
* `permission`:the access level to the resource (`configure`, `write`, `read`): see [the Access Control guide](http://www.rabbitmq.com/access-control.html) for their meaning

Note: This request may include additional http request parameters in addition to the ones listed above.
For instance, if the user accessed RabbitMQ via the MQTT protocol, it is expected `client_id` request parameter too.

### topic_path

* `username`: the name of the user
* `vhost`: the name of the virtual host containing the resource
* `resource`: the type of resource (`topic` in this case)
* `name`: the name of the exchange
* `permission`: the access level to the resource (`write` or `read`)
* `routing_key`: the routing key of a published message (when the permission is `write`)
or routing key of the queue binding (when the permission is `read`)

See [topic authorisation](http://www.rabbitmq.com/access-control.html#topic-authorisation) for more information
about topic authorisation.

Your web server should always return HTTP 200 OK, with a body
containing:

* `deny`: deny access to the user / vhost / resource
* `allow`: allow access to the user / vhost / resource
* `allow [list of tags]` (for `user_path` only): allow access, and mark the user as an having the tags listed

## Using TLS/HTTPS

If your Web server uses HTTPS and certificate verification, you need to
configure the plugin to use a CA and client certificate/key pair using the `rabbitmq_auth_backend_http.ssl_options` config variable:

``` erl
[
    {rabbit, [{auth_backends, [rabbit_auth_backend_http]}]},
    {rabbitmq_auth_backend_http,
    [{http_method,   post},
    {user_path,     "https://some-server/auth/user"},
    {vhost_path,    "https://some-server/auth/vhost"},
    {resource_path, "https://some-server/auth/resource"},
    {topic_path,    "https://some-server/auth/topic"},
    {ssl_options,
        [{cacertfile, "/path/to/cacert.pem"},
        {certfile,   "/path/to/client/cert.pem"},
        {keyfile,    "/path/to/client/key.pem"},
        {verify,     verify_peer},
        {fail_if_no_peer_cert, true}]}]}
].
```

It is recommended to use TLS for authentication and enable peer verification.

### Wildcard Certificates

If the certificate of your Web Server should be matched against a wildcard certificate in your `cacertfile`, the following option must be added to the `ssl_options`:

``` erl
{customize_hostname_check, [{match_fun,public_key:pkix_verify_hostname_match_fun(https)}]}
```

## Debugging

[Enable debug logging](https://rabbitmq.com/logging.html#debug-logging) to see what the backend service receives.
Look for log messages containing "rabbit_auth_backend_http
failed".

## Example Apps

There are [example backend services](./examples) available in Python, PHP, Spring Boot, ASP.NET Web API.

See [examples README](./examples/README.md) for more information.
