Overview

The purpose of this module is to connect with an external REST API and delegate the authentication operations to it whenever possible. The component must implement the API described in one of the next sections for ejabberd_auth_http to work out of the box.

The module can be especially useful for users maintaining their own central user database which is shared with other services. It fits perfectly when client application uses custom authentication token and MongooseIM has to validate it externally.

Configuration

How to enable

For full reference please check Advanced-configuration#authentication. The simplest way is to just replace default auth_method option in rel/files/ejabberd.cfg with {auth_method, http}.

Enabling the module is not enough! Please follow instructions below.

Configuration options

ejabberd_auth_http requires some parameters to function properly. The following options can be set in auth_opts tuple in rel/files/ejabberd.cfg:

  • host (mandatory, string) - consists of protocol, hostname (or IP) and port (optional). Examples:
    • {host, "http://localhost:12000"}
    • {host, "https://10.20.30.40"}
  • connection_pool_size (optional, integer, default: 10) - the number of connections open to auth service
  • connection_opts (optional, default: []) - extra options for hackers: http://erlang.org/doc/man/gen_tcp.html#type-connect_option
  • basic_auth (optional, default: "") - HTTP Basic Authentication in format "username:password"; auth service doesn't have to require authentication for HTTP auth to work
  • path_prefix (optional, default: "/") - a path prefix to be inserted between host and method name; must be terminated with /

Example: TODO

SCRAM support

ejabberd_auth_http can use the SCRAM method. When SCRAM is enabled, the passwords sent to the auth service are serialised and the same serialised format is expected when fetching a password from the component.

It is transparent when MongooseIM is responsible for all DB operations such as password setting, account creation etc.

The service CAN perform the (de)serialisation of SCRAM-encoded passwords, using a format that will be described in near future in separate document.

Authentication service API

URL format

All GET requests include the following URL-encoded query string: ?user=<username>&server=<domain>&pass=<password>.

All POST requests have the following URL-encoded string in the request body: user=<username>&server=<domain>&pass=<password>.

If certain method does not need a password, the value of pass is undefined, so it shouldn't be used.

Return codes

For the best integration, the return code range should not exceed the list below:

  • 500 - internal server error
  • 409 - conflict
  • 404 - not found
  • 403 - not allowed
  • 401 - not authorised
  • 400 - other error, should be sent in response body
  • 204 - success, no return data
  • 201 - created
  • 200 - success, return value in response body

Whenever the specification says "anything else", service should use one of the codes from the list above.

Some requests consider multiple return codes a "success". It is up to the server-side developer to pick one of the codes.

HTTP header Content-Length

IMPORTANT: The authentication server MUST include a Content-Length HTTP header in the response. A body can be missing in the first data chunk read from a socket, leading to strange authentication errors.

Method register

  • Description: Creates a user account.
  • HTTP method: POST
  • Type: mandatory when mod_register is enabled
  • Return values:
    • 201 - success
    • 409 - user already exists
    • anything else - will be treated as failure

Method check_password

  • Description: Must respond if the password is valid for user.
  • HTTP method: GET
  • Type: mandatory when SCRAM is not used
  • Return values:
    • 200, true or false in body
    • anything else - will be treated as false

Method get_password

  • Description: Must return the user's password in plaintext or in the SCRAM serialised form.
  • HTTP method: GET
  • Type: mandatory when SCRAM or DIGEST SASL mechanism is used
  • Return values:
    • 200, password in the body
    • anything else - get_password will fail

Method user_exists

  • Description: Must return the information whether the user exists in DB.
  • HTTP method: GET
  • Type: mandatory
  • Return values:
    • 200, true or false in body
    • anything else - will be treated as false

Method set_password

  • Description: Must set user's password in the internal database to a provided value. The value should not be transformed (except for URL-decoding) before writing into DB.
  • HTTP method: POST
  • Type: mandatory when mod_register is enabled
  • Return values:
    • 200 or 201 or 204 - success
    • anything else - will be treated as false

Method remove_user

  • Description: Removes a user account.
  • HTTP method: POST
  • Type: mandatory when mod_register is enabled
  • Return values:
    • 200 or 201 or 204 - success
    • 404 - user does not exist
    • 403 - not allowed for some reason
    • 40X - will be treated as bad request

Method remove_user_validate

  • Description: Removes a user account only if provided password is valid.
  • HTTP method: POST
  • Type: mandatory when mod_register is enabled
  • Return values:
    • 200 or 201 or 204 - success
    • 404 - user does not exist
    • 403 - invalid user password or not allowed for other reason
    • 40X - will be treated as bad request

Authentication service API recipes

Below are some examples of the auth service APIs and MongooseIM-side configuration along with use cases.

System using common, custom auth token

An Auth token is provided as a password.

  • Service implements: check_password, user_exists
  • MongooseIM config: password format: plain, mod_register disabled
  • Client side: MUST NOT use DIGEST-MD5 mechanism; use PLAIN

Central database of plaintext passwords

  • Service implements: check_password, get_password, user_exists
  • MongooseIM config: password format: plain, mod_register disabled
  • Client side: May use any available auth method

Central database able to process SCRAM

  • Service implements: get_password, user_exists
  • MongooseIM config: password format: scram, mod_register disabled
  • Client side: May use any available auth method

Godlike MongooseIM

  • Service implements: all methods
  • MongooseIM config: password format: scram (recommended) or plain, mod_register enabled
  • Client side: May use any available auth method