Password auth provider callbacks

Password auth providers offer a way for server administrators to integrate their Synapse installation with an external authentication system. The callbacks can be registered by using the Module API's register_password_auth_provider_callbacks method.

Callbacks

`auth_checkers`

First introduced in Synapse v1.46.0

auth_checkers: Dict[Tuple[str, Tuple[str, ...]], Callable]

A dict mapping from tuples of a login type identifier (such as m.login.password) and a tuple of field names (such as ("password", "secret_thing")) to authentication checking callbacks, which should be of the following form:

async def check_auth(
    user: str,
    login_type: str,
    login_dict: "synapse.module_api.JsonDict",
) -> Optional[
    Tuple[
        str, 
        Optional[Callable[["synapse.module_api.LoginResponse"], Awaitable[None]]]
    ]
]

The login type and field names should be provided by the user in the request to the /login API. The Matrix specification defines some types, however user defined ones are also allowed.

The callback is passed the user field provided by the client (which might not be in @username:server form), the login type, and a dictionary of login secrets passed by the client.

If the authentication is successful, the module must return the user's Matrix ID (e.g. @alice:example.com) and optionally a callback to be called with the response to the /login request. If the module doesn't wish to return a callback, it must return None instead.

If the authentication is unsuccessful, the module must return None.

If multiple modules register an auth checker for the same login type but with different fields, Synapse will refuse to start.

If multiple modules register an auth checker for the same login type with the same fields, then the callbacks will be executed in order, until one returns a Matrix User ID (and optionally a callback). In that case, the return value of that callback will be accepted and subsequent callbacks will not be fired. If every callback returns None, then the authentication fails.

`check_3pid_auth`

First introduced in Synapse v1.46.0

async def check_3pid_auth(
    medium: str, 
    address: str,
    password: str,
) -> Optional[
    Tuple[
        str, 
        Optional[Callable[["synapse.module_api.LoginResponse"], Awaitable[None]]]
    ]
]

Called when a user attempts to register or log in with a third party identifier, such as email. It is passed the medium (eg. email), an address (eg. jdoe@example.com) and the user's password.

If the authentication is unsuccessful, the module must return None.

If multiple modules implement this callback, they will be considered in order. If a callback returns None, Synapse falls through to the next one. The value of the first callback that does not return None will be used. If this happens, Synapse will not call any of the subsequent implementations of this callback. If every callback return None, the authentication is denied.

`on_logged_out`

First introduced in Synapse v1.46.0

async def on_logged_out(
    user_id: str,
    device_id: Optional[str],
    access_token: str
) -> None

Called during a logout request for a user. It is passed the qualified user ID, the ID of the deactivated device (if any: access tokens are occasionally created without an associated device ID), and the (now deactivated) access token.

If multiple modules implement this callback, Synapse runs them all in order.

`get_username_for_registration`

First introduced in Synapse v1.52.0

async def get_username_for_registration(
    uia_results: Dict[str, Any],
    params: Dict[str, Any],
) -> Optional[str]

Called when registering a new user. The module can return a username to set for the user being registered by returning it as a string, or None if it doesn't wish to force a username for this user. If a username is returned, it will be used as the local part of a user's full Matrix ID (e.g. it's alice in @alice:example.com).

This callback is called once User-Interactive Authentication has been completed by the user. It is not called when registering a user via SSO. It is passed two dictionaries, which include the information that the user has provided during the registration process.

The first dictionary contains the results of the User-Interactive Authentication flow followed by the user. Its keys are the identifiers of every step involved in the flow, associated with either a boolean value indicating whether the step was correctly completed, or additional information (e.g. email address, phone number...). A list of most existing identifiers can be found in the Matrix specification. Here's an example featuring all currently supported keys:

{
    "m.login.dummy": True,  # Dummy authentication
    "m.login.terms": True,  # User has accepted the terms of service for the homeserver
    "m.login.recaptcha": True,  # User has completed the recaptcha challenge
    "m.login.email.identity": {  # User has provided and verified an email address
        "medium": "email",
        "address": "alice@example.com",
        "validated_at": 1642701357084,
    },
    "m.login.msisdn": {  # User has provided and verified a phone number
        "medium": "msisdn",
        "address": "33123456789",
        "validated_at": 1642701357084,
    },
    "org.matrix.msc3231.login.registration_token": "sometoken",  # User has registered through the flow described in MSC3231
}

The second dictionary contains the parameters provided by the user's client in the request to /_matrix/client/v3/register. See the Matrix specification for a complete list of these parameters.

If the module cannot, or does not wish to, generate a username for this user, it must return None.

Example

The example module below implements authentication checkers for two different login types:

my.login.type
- Expects a my_field field to be sent to /login
- Is checked by the method: self.check_my_login
m.login.password (defined in the spec)
- Expects a password field to be sent to /login
- Is checked by the method: self.check_pass

from typing import Awaitable, Callable, Optional, Tuple

import synapse
from synapse import module_api


class MyAuthProvider:
    def __init__(self, config: dict, api: module_api):

        self.api = api

        self.credentials = {
            "bob": "building",
            "@scoop:matrix.org": "digging",
        }

        api.register_password_auth_provider_callbacks(
            auth_checkers={
                ("my.login_type", ("my_field",)): self.check_my_login,
                ("m.login.password", ("password",)): self.check_pass,
            },
        )

    async def check_my_login(
        self,
        username: str,
        login_type: str,
        login_dict: "synapse.module_api.JsonDict",
    ) -> Optional[
        Tuple[
            str,
            Optional[Callable[["synapse.module_api.LoginResponse"], Awaitable[None]]],
        ]
    ]:
        if login_type != "my.login_type":
            return None

        if self.credentials.get(username) == login_dict.get("my_field"):
            return self.api.get_qualified_user_id(username)

    async def check_pass(
        self,
        username: str,
        login_type: str,
        login_dict: "synapse.module_api.JsonDict",
    ) -> Optional[
        Tuple[
            str,
            Optional[Callable[["synapse.module_api.LoginResponse"], Awaitable[None]]],
        ]
    ]:
        if login_type != "m.login.password":
            return None

        if self.credentials.get(username) == login_dict.get("password"):
            return self.api.get_qualified_user_id(username)