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+
+                        <h1 id="sso-mapping-providers"><a class="header" href="#sso-mapping-providers">SSO Mapping Providers</a></h1>
+<p>A mapping provider is a Python class (loaded via a Python module) that
+works out how to map attributes of a SSO response to Matrix-specific
+user attributes. Details such as user ID localpart, displayname, and even avatar
+URLs are all things that can be mapped from talking to a SSO service.</p>
+<p>As an example, a SSO service may return the email address
+&quot;john.smith@example.com&quot; for a user, whereas Synapse will need to figure out how
+to turn that into a displayname when creating a Matrix user for this individual.
+It may choose <code>John Smith</code>, or <code>Smith, John [Example.com]</code> or any number of
+variations. As each Synapse configuration may want something different, this is
+where SAML mapping providers come into play.</p>
+<p>SSO mapping providers are currently supported for OpenID and SAML SSO
+configurations. Please see the details below for how to implement your own.</p>
+<p>It is up to the mapping provider whether the user should be assigned a predefined
+Matrix ID based on the SSO attributes, or if the user should be allowed to
+choose their own username.</p>
+<p>In the first case - where users are automatically allocated a Matrix ID - it is
+the responsibility of the mapping provider to normalise the SSO attributes and
+map them to a valid Matrix ID. The <a href="https://matrix.org/docs/spec/appendices#user-identifiers">specification for Matrix
+IDs</a> has some
+information about what is considered valid.</p>
+<p>If the mapping provider does not assign a Matrix ID, then Synapse will
+automatically serve an HTML page allowing the user to pick their own username.</p>
+<p>External mapping providers are provided to Synapse in the form of an external
+Python module. You can retrieve this module from <a href="https://pypi.org">PyPI</a> or elsewhere,
+but it must be importable via Synapse (e.g. it must be in the same virtualenv
+as Synapse). The Synapse config is then modified to point to the mapping provider
+(and optionally provide additional configuration for it).</p>
+<h2 id="openid-mapping-providers"><a class="header" href="#openid-mapping-providers">OpenID Mapping Providers</a></h2>
+<p>The OpenID mapping provider can be customized by editing the
+<code>oidc_config.user_mapping_provider.module</code> config option.</p>
+<p><code>oidc_config.user_mapping_provider.config</code> allows you to provide custom
+configuration options to the module. Check with the module's documentation for
+what options it provides (if any). The options listed by default are for the
+user mapping provider built in to Synapse. If using a custom module, you should
+comment these options out and use those specified by the module instead.</p>
+<h3 id="building-a-custom-openid-mapping-provider"><a class="header" href="#building-a-custom-openid-mapping-provider">Building a Custom OpenID Mapping Provider</a></h3>
+<p>A custom mapping provider must specify the following methods:</p>
+<ul>
+<li><code>def __init__(self, parsed_config)</code>
+<ul>
+<li>Arguments:
+<ul>
+<li><code>parsed_config</code> - A configuration object that is the return value of the
+<code>parse_config</code> method. You should set any configuration options needed by
+the module here.</li>
+</ul>
+</li>
+</ul>
+</li>
+<li><code>def parse_config(config)</code>
+<ul>
+<li>This method should have the <code>@staticmethod</code> decoration.</li>
+<li>Arguments:
+<ul>
+<li><code>config</code> - A <code>dict</code> representing the parsed content of the
+<code>oidc_config.user_mapping_provider.config</code> homeserver config option.
+Runs on homeserver startup. Providers should extract and validate
+any option values they need here.</li>
+</ul>
+</li>
+<li>Whatever is returned will be passed back to the user mapping provider module's
+<code>__init__</code> method during construction.</li>
+</ul>
+</li>
+<li><code>def get_remote_user_id(self, userinfo)</code>
+<ul>
+<li>Arguments:
+<ul>
+<li><code>userinfo</code> - A <code>authlib.oidc.core.claims.UserInfo</code> object to extract user
+information from.</li>
+</ul>
+</li>
+<li>This method must return a string, which is the unique, immutable identifier
+for the user. Commonly the <code>sub</code> claim of the response.</li>
+</ul>
+</li>
+<li><code>async def map_user_attributes(self, userinfo, token, failures)</code>
+<ul>
+<li>This method must be async.</li>
+<li>Arguments:
+<ul>
+<li><code>userinfo</code> - A <code>authlib.oidc.core.claims.UserInfo</code> object to extract user
+information from.</li>
+<li><code>token</code> - A dictionary which includes information necessary to make
+further requests to the OpenID provider.</li>
+<li><code>failures</code> - An <code>int</code> that represents the amount of times the returned
+mxid localpart mapping has failed.  This should be used
+to create a deduplicated mxid localpart which should be
+returned instead. For example, if this method returns
+<code>john.doe</code> as the value of <code>localpart</code> in the returned
+dict, and that is already taken on the homeserver, this
+method will be called again with the same parameters but
+with failures=1. The method should then return a different
+<code>localpart</code> value, such as <code>john.doe1</code>.</li>
+</ul>
+</li>
+<li>Returns a dictionary with two keys:
+<ul>
+<li><code>localpart</code>: A string, used to generate the Matrix ID. If this is
+<code>None</code>, the user is prompted to pick their own username. This is only used
+during a user's first login. Once a localpart has been associated with a
+remote user ID (see <code>get_remote_user_id</code>) it cannot be updated.</li>
+<li><code>displayname</code>: An optional string, the display name for the user.</li>
+</ul>
+</li>
+</ul>
+</li>
+<li><code>async def get_extra_attributes(self, userinfo, token)</code>
+<ul>
+<li>
+<p>This method must be async.</p>
+</li>
+<li>
+<p>Arguments:</p>
+<ul>
+<li><code>userinfo</code> - A <code>authlib.oidc.core.claims.UserInfo</code> object to extract user
+information from.</li>
+<li><code>token</code> - A dictionary which includes information necessary to make
+further requests to the OpenID provider.</li>
+</ul>
+</li>
+<li>
+<p>Returns a dictionary that is suitable to be serialized to JSON. This
+will be returned as part of the response during a successful login.</p>
+<p>Note that care should be taken to not overwrite any of the parameters
+usually returned as part of the <a href="https://matrix.org/docs/spec/client_server/latest#post-matrix-client-r0-login">login response</a>.</p>
+</li>
+</ul>
+</li>
+</ul>
+<h3 id="default-openid-mapping-provider"><a class="header" href="#default-openid-mapping-provider">Default OpenID Mapping Provider</a></h3>
+<p>Synapse has a built-in OpenID mapping provider if a custom provider isn't
+specified in the config. It is located at
+<a href="https://github.com/matrix-org/synapse/blob/develop/synapse/handlers/oidc.py"><code>synapse.handlers.oidc.JinjaOidcMappingProvider</code></a>.</p>
+<h2 id="saml-mapping-providers"><a class="header" href="#saml-mapping-providers">SAML Mapping Providers</a></h2>
+<p>The SAML mapping provider can be customized by editing the
+<code>saml2_config.user_mapping_provider.module</code> config option.</p>
+<p><code>saml2_config.user_mapping_provider.config</code> allows you to provide custom
+configuration options to the module. Check with the module's documentation for
+what options it provides (if any). The options listed by default are for the
+user mapping provider built in to Synapse. If using a custom module, you should
+comment these options out and use those specified by the module instead.</p>
+<h3 id="building-a-custom-saml-mapping-provider"><a class="header" href="#building-a-custom-saml-mapping-provider">Building a Custom SAML Mapping Provider</a></h3>
+<p>A custom mapping provider must specify the following methods:</p>
+<ul>
+<li><code>def __init__(self, parsed_config, module_api)</code>
+<ul>
+<li>Arguments:
+<ul>
+<li><code>parsed_config</code> - A configuration object that is the return value of the
+<code>parse_config</code> method. You should set any configuration options needed by
+the module here.</li>
+<li><code>module_api</code> - a <code>synapse.module_api.ModuleApi</code> object which provides the
+stable API available for extension modules.</li>
+</ul>
+</li>
+</ul>
+</li>
+<li><code>def parse_config(config)</code>
+<ul>
+<li><strong>This method should have the <code>@staticmethod</code> decoration.</strong></li>
+<li>Arguments:
+<ul>
+<li><code>config</code> - A <code>dict</code> representing the parsed content of the
+<code>saml_config.user_mapping_provider.config</code> homeserver config option.
+Runs on homeserver startup. Providers should extract and validate
+any option values they need here.</li>
+</ul>
+</li>
+<li>Whatever is returned will be passed back to the user mapping provider module's
+<code>__init__</code> method during construction.</li>
+</ul>
+</li>
+<li><code>def get_saml_attributes(config)</code>
+<ul>
+<li><strong>This method should have the <code>@staticmethod</code> decoration.</strong></li>
+<li>Arguments:
+<ul>
+<li><code>config</code> - A object resulting from a call to <code>parse_config</code>.</li>
+</ul>
+</li>
+<li>Returns a tuple of two sets. The first set equates to the SAML auth
+response attributes that are required for the module to function, whereas
+the second set consists of those attributes which can be used if available,
+but are not necessary.</li>
+</ul>
+</li>
+<li><code>def get_remote_user_id(self, saml_response, client_redirect_url)</code>
+<ul>
+<li>Arguments:
+<ul>
+<li><code>saml_response</code> - A <code>saml2.response.AuthnResponse</code> object to extract user
+information from.</li>
+<li><code>client_redirect_url</code> - A string, the URL that the client will be
+redirected to.</li>
+</ul>
+</li>
+<li>This method must return a string, which is the unique, immutable identifier
+for the user. Commonly the <code>uid</code> claim of the response.</li>
+</ul>
+</li>
+<li><code>def saml_response_to_user_attributes(self, saml_response, failures, client_redirect_url)</code>
+<ul>
+<li>
+<p>Arguments:</p>
+<ul>
+<li><code>saml_response</code> - A <code>saml2.response.AuthnResponse</code> object to extract user
+information from.</li>
+<li><code>failures</code> - An <code>int</code> that represents the amount of times the returned
+mxid localpart mapping has failed.  This should be used
+to create a deduplicated mxid localpart which should be
+returned instead. For example, if this method returns
+<code>john.doe</code> as the value of <code>mxid_localpart</code> in the returned
+dict, and that is already taken on the homeserver, this
+method will be called again with the same parameters but
+with failures=1. The method should then return a different
+<code>mxid_localpart</code> value, such as <code>john.doe1</code>.</li>
+<li><code>client_redirect_url</code> - A string, the URL that the client will be
+redirected to.</li>
+</ul>
+</li>
+<li>
+<p>This method must return a dictionary, which will then be used by Synapse
+to build a new user. The following keys are allowed:</p>
+<ul>
+<li><code>mxid_localpart</code> - A string, the mxid localpart of the new user. If this is
+<code>None</code>, the user is prompted to pick their own username. This is only used
+during a user's first login. Once a localpart has been associated with a
+remote user ID (see <code>get_remote_user_id</code>) it cannot be updated.</li>
+<li><code>displayname</code> - The displayname of the new user. If not provided, will default to
+the value of <code>mxid_localpart</code>.</li>
+<li><code>emails</code> - A list of emails for the new user. If not provided, will
+default to an empty list.</li>
+</ul>
+<p>Alternatively it can raise a <code>synapse.api.errors.RedirectException</code> to
+redirect the user to another page. This is useful to prompt the user for
+additional information, e.g. if you want them to provide their own username.
+It is the responsibility of the mapping provider to either redirect back
+to <code>client_redirect_url</code> (including any additional information) or to
+complete registration using methods from the <code>ModuleApi</code>.</p>
+</li>
+</ul>
+</li>
+</ul>
+<h3 id="default-saml-mapping-provider"><a class="header" href="#default-saml-mapping-provider">Default SAML Mapping Provider</a></h3>
+<p>Synapse has a built-in SAML mapping provider if a custom provider isn't
+specified in the config. It is located at
+<a href="https://github.com/matrix-org/synapse/blob/develop/synapse/handlers/saml.py"><code>synapse.handlers.saml.DefaultSamlMappingProvider</code></a>.</p>
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