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diff --git a/docs/howto/create_plugin.rst b/docs/howto/create_plugin.rst new file mode 100644 index 00000000..437374c7 --- /dev/null +++ b/docs/howto/create_plugin.rst @@ -0,0 +1,682 @@ +.. _create-plugin: + +Creating a Slixmpp Plugin +=========================== + +One of the goals of Slixmpp is to provide support for every draft or final +XMPP extension (`XEP <http://xmpp.org/extensions/>`_). To do this, Slixmpp has a +plugin mechanism for adding the functionalities required by each XEP. But even +though plugins were made to quickly implement and prototype the official XMPP +extensions, there is no reason you can't create your own plugin to implement +your own custom XMPP-based protocol. + +This guide will help walk you through the steps to +implement a rudimentary version of `XEP-0077 In-band +Registration <http://xmpp.org/extensions/xep-0077.html>`_. In-band registration +was implemented in example 14-6 (page 223) of `XMPP: The Definitive +Guide <http://oreilly.com/catalog/9780596521271>`_ because there was no Slixmpp +plugin for XEP-0077 at the time of writing. We will partially fix that issue +here by turning the example implementation from *XMPP: The Definitive Guide* +into a plugin. Again, note that this will not a complete implementation, and a +different, more robust, official plugin for XEP-0077 may be added to Slixmpp +in the future. + +.. note:: + + The example plugin created in this guide is for the server side of the + registration process only. It will **NOT** be able to register new accounts + on an XMPP server. + +First Steps +----------- +Every plugin inherits from the class :mod:`BasePlugin <slixmpp.plugins.base.BasePlugin`, +and must include a ``plugin_init`` method. While the +plugins distributed with Slixmpp must be placed in the plugins directory +``slixmpp/plugins`` to be loaded, custom plugins may be loaded from any +module. To do so, use the following form when registering the plugin: + +.. code-block:: python + + self.register_plugin('myplugin', module=mod_containing_my_plugin) + +The plugin name must be the same as the plugin's class name. + +Now, we can open our favorite text editors and create ``xep_0077.py`` in +``Slixmpp/slixmpp/plugins``. We want to do some basic house-keeping and +declare the name and description of the XEP we are implementing. If you +are creating your own custom plugin, you don't need to include the ``xep`` +attribute. + +.. code-block:: python + + """ + Creating a Slixmpp Plugin + + This is a minimal implementation of XEP-0077 to serve + as a tutorial for creating Slixmpp plugins. + """ + + from slixmpp.plugins.base import BasePlugin + + class xep_0077(BasePlugin): + """ + XEP-0077 In-Band Registration + """ + + def plugin_init(self): + self.description = "In-Band Registration" + self.xep = "0077" + +Now that we have a basic plugin, we need to edit +``slixmpp/plugins/__init__.py`` to include our new plugin by adding +``'xep_0077'`` to the ``__all__`` declaration. + +Interacting with Other Plugins +------------------------------ + +In-band registration is a feature that should be advertised through `Service +Discovery <http://xmpp.org/extensions/xep-0030.html>`_. To do that, we tell the +``xep_0030`` plugin to add the ``"jabber:iq:register"`` feature. We put this +call in a method named ``post_init`` which will be called once the plugin has +been loaded; by doing so we advertise that we can do registrations only after we +finish activating the plugin. + +The ``post_init`` method needs to call ``BasePlugin.post_init(self)`` +which will mark that ``post_init`` has been called for the plugin. Once the +Slixmpp object begins processing, ``post_init`` will be called on any plugins +that have not already run ``post_init``. This allows you to register plugins and +their dependencies without needing to worry about the order in which you do so. + +**Note:** by adding this call we have introduced a dependency on the XEP-0030 +plugin. Be sure to register ``'xep_0030'`` as well as ``'xep_0077'``. Slixmpp +does not automatically load plugin dependencies for you. + +.. code-block:: python + + def post_init(self): + BasePlugin.post_init(self) + self.xmpp['xep_0030'].add_feature("jabber:iq:register") + +Creating Custom Stanza Objects +------------------------------ + +Now, the IQ stanzas needed to implement our version of XEP-0077 are not very +complex, and we could just interact with the XML objects directly just like +in the *XMPP: The Definitive Guide* example. However, creating custom stanza +objects is good practice. + +We will create a new ``Registration`` stanza. Following the *XMPP: The +Definitive Guide* example, we will add support for a username and password +field. We also need two flags: ``registered`` and ``remove``. The ``registered`` +flag is sent when an already registered user attempts to register, along with +their registration data. The ``remove`` flag is a request to unregister a user's +account. + +Adding additional `fields specified in +XEP-0077 <http://xmpp.org/extensions/xep-0077.html#registrar-formtypes-register>`_ +will not be difficult and is left as an exercise for the reader. + +Our ``Registration`` class needs to start with a few descriptions of its +behaviour: + +* ``namespace`` + The namespace our stanza object lives in. In this case, + ``"jabber:iq:register"``. + +* ``name`` + The name of the root XML element. In this case, the ``query`` element. + +* ``plugin_attrib`` + The name to access this type of stanza. In particular, given a + registration stanza, the ``Registration`` object can be found using: + ``iq_object['register']``. + +* ``interfaces`` + A list of dictionary-like keys that can be used with the stanza object. + When using ``"key"``, if there exists a method of the form ``getKey``, + ``setKey``, or``delKey`` (depending on context) then the result of calling + that method will be returned. Otherwise, the value of the attribute ``key`` + of the main stanza element is returned if one exists. + + **Note:** The accessor methods currently use title case, and not camel case. + Thus if you need to access an item named ``"methodName"`` you will need to + use ``getMethodname``. This naming convention might change to full camel + case in a future version of Slixmpp. + +* ``sub_interfaces`` + A subset of ``interfaces``, but these keys map to the text of any + subelements that are direct children of the main stanza element. Thus, + referencing ``iq_object['register']['username']`` will either execute + ``getUsername`` or return the value in the ``username`` element of the + query. + + If you need to access an element, say ``elem``, that is not a direct child + of the main stanza element, you will need to add ``getElem``, ``setElem``, + and ``delElem``. See the note above about naming conventions. + +.. code-block:: python + + from slixmpp.xmlstream import ElementBase, ET, JID, register_stanza_plugin + from slixmpp import Iq + + class Registration(ElementBase): + namespace = 'jabber:iq:register' + name = 'query' + plugin_attrib = 'register' + interfaces = {'username', 'password', 'registered', 'remove'} + sub_interfaces = interfaces + + def getRegistered(self): + present = self.xml.find('{%s}registered' % self.namespace) + return present is not None + + def getRemove(self): + present = self.xml.find('{%s}remove' % self.namespace) + return present is not None + + def setRegistered(self, registered): + if registered: + self.addField('registered') + else: + del self['registered'] + + def setRemove(self, remove): + if remove: + self.addField('remove') + else: + del self['remove'] + + def addField(self, name): + itemXML = ET.Element('{%s}%s' % (self.namespace, name)) + self.xml.append(itemXML) + +Setting a ``sub_interface`` attribute to ``""`` will remove that subelement. +Since we want to include empty registration fields in our form, we need the +``addField`` method to add the empty elements. + +Since the ``registered`` and ``remove`` elements are just flags, we need to add +custom logic to enforce the binary behavior. + +Extracting Stanzas from the XML Stream +-------------------------------------- + +Now that we have a custom stanza object, we need to be able to detect when we +receive one. To do this, we register a stream handler that will pattern match +stanzas off of the XML stream against our stanza object's element name and +namespace. To do so, we need to create a ``Callback`` object which contains +an XML fragment that can identify our stanza type. We can add this handler +registration to our ``plugin_init`` method. + +Also, we need to associate our ``Registration`` class with IQ stanzas; +that requires the use of the ``register_stanza_plugin`` function (in +``slixmpp.xmlstream.stanzabase``) which takes the class of a parent stanza +type followed by the substanza type. In our case, the parent stanza is an IQ +stanza, and the substanza is our registration query. + +The ``__handleRegistration`` method referenced in the callback will be our +handler function to process registration requests. + +.. code-block:: python + + def plugin_init(self): + self.description = "In-Band Registration" + self.xep = "0077" + + self.xmpp.register_handler( + Callback('In-Band Registration', + MatchXPath('{%s}iq/{jabber:iq:register}query' % self.xmpp.default_ns), + self.__handleRegistration)) + register_stanza_plugin(Iq, Registration) + +Handling Incoming Stanzas and Triggering Events +----------------------------------------------- +There are six situations that we need to handle to finish our implementation of +XEP-0077. + +**Registration Form Request from a New User:** + + .. code-block:: xml + + <iq type="result"> + <query xmlns="jabber:iq:register"> + <username /> + <password /> + </query> + </iq> + +**Registration Form Request from an Existing User:** + + .. code-block:: xml + + <iq type="result"> + <query xmlns="jabber:iq:register"> + <registered /> + <username>Foo</username> + <password>hunter2</password> + </query> + </iq> + +**Unregister Account:** + + .. code-block:: xml + + <iq type="result"> + <query xmlns="jabber:iq:register" /> + </iq> + +**Incomplete Registration:** + + .. code-block:: xml + + <iq type="error"> + <query xmlns="jabber:iq:register"> + <username>Foo</username> + </query> + <error code="406" type="modify"> + <not-acceptable xmlns="urn:ietf:params:xml:ns:xmpp-stanzas" /> + </error> + </iq> + +**Conflicting Registrations:** + + .. code-block:: xml + + <iq type="error"> + <query xmlns="jabber:iq:register"> + <username>Foo</username> + <password>hunter2</password> + </query> + <error code="409" type="cancel"> + <conflict xmlns="urn:ietf:params:xml:ns:xmpp-stanzas" /> + </error> + </iq> + +**Successful Registration:** + + .. code-block:: xml + + <iq type="result"> + <query xmlns="jabber:iq:register" /> + </iq> + +Cases 1 and 2: Registration Requests +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +Responding to registration requests depends on if the requesting user already +has an account. If there is an account, the response should include the +``registered`` flag and the user's current registration information. Otherwise, +we just send the fields for our registration form. + +We will handle both cases by creating a ``sendRegistrationForm`` method that +will create either an empty of full form depending on if we provide it with +user data. Since we need to know which form fields to include (especially if we +add support for the other fields specified in XEP-0077), we will also create a +method ``setForm`` which will take the names of the fields we wish to include. + +.. code-block:: python + + def plugin_init(self): + self.description = "In-Band Registration" + self.xep = "0077" + self.form_fields = ('username', 'password') + ... remainder of plugin_init + + ... + + def __handleRegistration(self, iq): + if iq['type'] == 'get': + # Registration form requested + userData = self.backend[iq['from'].bare] + self.sendRegistrationForm(iq, userData) + + def setForm(self, *fields): + self.form_fields = fields + + def sendRegistrationForm(self, iq, userData=None): + reg = iq['register'] + if userData is None: + userData = {} + else: + reg['registered'] = True + + for field in self.form_fields: + data = userData.get(field, '') + if data: + # Add field with existing data + reg[field] = data + else: + # Add a blank field + reg.addField(field) + + iq.reply().set_payload(reg.xml) + iq.send() + +Note how we are able to access our ``Registration`` stanza object with +``iq['register']``. + +A User Backend +++++++++++++++ +You might have noticed the reference to ``self.backend``, which is an object +that abstracts away storing and retrieving user information. Since it is not +much more than a dictionary, we will leave the implementation details to the +final, full source code example. + +Case 3: Unregister an Account +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +The next simplest case to consider is responding to a request to remove +an account. If we receive a ``remove`` flag, we instruct the backend to +remove the user's account. Since your application may need to know about +when users are registered or unregistered, we trigger an event using +``self.xmpp.event('unregister_user', iq)``. See the component examples below for +how to respond to that event. + +.. code-block:: python + + def __handleRegistration(self, iq): + if iq['type'] == 'get': + # Registration form requested + userData = self.backend[iq['from'].bare] + self.sendRegistrationForm(iq, userData) + elif iq['type'] == 'set': + # Remove an account + if iq['register']['remove']: + self.backend.unregister(iq['from'].bare) + self.xmpp.event('unregistered_user', iq) + iq.reply().send() + return + +Case 4: Incomplete Registration +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +For the next case we need to check the user's registration to ensure it has all +of the fields we wanted. The simple option that we will use is to loop over the +field names and check each one; however, this means that all fields we send to +the user are required. Adding optional fields is left to the reader. + +Since we have received an incomplete form, we need to send an error message back +to the user. We have to send a few different types of errors, so we will also +create a ``_sendError`` method that will add the appropriate ``error`` element +to the IQ reply. + +.. code-block:: python + + def __handleRegistration(self, iq): + if iq['type'] == 'get': + # Registration form requested + userData = self.backend[iq['from'].bare] + self.sendRegistrationForm(iq, userData) + elif iq['type'] == 'set': + if iq['register']['remove']: + # Remove an account + self.backend.unregister(iq['from'].bare) + self.xmpp.event('unregistered_user', iq) + iq.reply().send() + return + + for field in self.form_fields: + if not iq['register'][field]: + # Incomplete Registration + self._sendError(iq, '406', 'modify', 'not-acceptable' + "Please fill in all fields.") + return + + ... + + def _sendError(self, iq, code, error_type, name, text=''): + iq.reply().set_payload(iq['register'].xml) + iq.error() + iq['error']['code'] = code + iq['error']['type'] = error_type + iq['error']['condition'] = name + iq['error']['text'] = text + iq.send() + +Cases 5 and 6: Conflicting and Successful Registration +~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ +We are down to the final decision on if we have a successful registration. We +send the user's data to the backend with the ``self.backend.register`` method. +If it returns ``True``, then registration has been successful. Otherwise, +there has been a conflict with usernames and registration has failed. Like +with unregistering an account, we trigger an event indicating that a user has +been registered by using ``self.xmpp.event('registered_user', iq)``. See the +component examples below for how to respond to this event. + +.. code-block:: python + + def __handleRegistration(self, iq): + if iq['type'] == 'get': + # Registration form requested + userData = self.backend[iq['from'].bare] + self.sendRegistrationForm(iq, userData) + elif iq['type'] == 'set': + if iq['register']['remove']: + # Remove an account + self.backend.unregister(iq['from'].bare) + self.xmpp.event('unregistered_user', iq) + iq.reply().send() + return + + for field in self.form_fields: + if not iq['register'][field]: + # Incomplete Registration + self._sendError(iq, '406', 'modify', 'not-acceptable', + "Please fill in all fields.") + return + + if self.backend.register(iq['from'].bare, iq['register']): + # Successful registration + self.xmpp.event('registered_user', iq) + iq.reply().set_payload(iq['register'].xml) + iq.send() + else: + # Conflicting registration + self._sendError(iq, '409', 'cancel', 'conflict', + "That username is already taken.") + +Example Component Using the XEP-0077 Plugin +------------------------------------------- +Alright, the moment we've been working towards - actually using our plugin to +simplify our other applications. Here is a basic component that simply manages +user registrations and sends the user a welcoming message when they register, +and a farewell message when they delete their account. + +Note that we have to register the ``'xep_0030'`` plugin first, +and that we specified the form fields we wish to use with +``self.xmpp.plugin['xep_0077'].setForm('username', 'password')``. + +.. code-block:: python + + import slixmpp.componentxmpp + + class Example(slixmpp.componentxmpp.ComponentXMPP): + + def __init__(self, jid, password): + slixmpp.componentxmpp.ComponentXMPP.__init__(self, jid, password, 'localhost', 8888) + + self.register_plugin('xep_0030') + self.register_plugin('xep_0077') + self.plugin['xep_0077'].setForm('username', 'password') + + self.add_event_handler("registered_user", self.reg) + self.add_event_handler("unregistered_user", self.unreg) + + def reg(self, iq): + msg = "Welcome! %s" % iq['register']['username'] + self.send_message(iq['from'], msg, mfrom=self.fulljid) + + def unreg(self, iq): + msg = "Bye! %s" % iq['register']['username'] + self.send_message(iq['from'], msg, mfrom=self.fulljid) + +**Congratulations!** We now have a basic, functioning implementation of +XEP-0077. + +Complete Source Code for XEP-0077 Plugin +---------------------------------------- +Here is a copy of a more complete implementation of the plugin we created, but +with some additional registration fields implemented. + +.. code-block:: python + + """ + Creating a Slixmpp Plugin + + This is a minimal implementation of XEP-0077 to serve + as a tutorial for creating Slixmpp plugins. + """ + + from slixmpp.plugins.base import BasePlugin + from slixmpp.xmlstream.handler.callback import Callback + from slixmpp.xmlstream.matcher.xpath import MatchXPath + from slixmpp.xmlstream import ElementBase, ET, JID, register_stanza_plugin + from slixmpp import Iq + import copy + + + class Registration(ElementBase): + namespace = 'jabber:iq:register' + name = 'query' + plugin_attrib = 'register' + interfaces = {'username', 'password', 'email', 'nick', 'name', + 'first', 'last', 'address', 'city', 'state', 'zip', + 'phone', 'url', 'date', 'misc', 'text', 'key', + 'registered', 'remove', 'instructions'} + sub_interfaces = interfaces + + def getRegistered(self): + present = self.xml.find('{%s}registered' % self.namespace) + return present is not None + + def getRemove(self): + present = self.xml.find('{%s}remove' % self.namespace) + return present is not None + + def setRegistered(self, registered): + if registered: + self.addField('registered') + else: + del self['registered'] + + def setRemove(self, remove): + if remove: + self.addField('remove') + else: + del self['remove'] + + def addField(self, name): + itemXML = ET.Element('{%s}%s' % (self.namespace, name)) + self.xml.append(itemXML) + + + class UserStore(object): + def __init__(self): + self.users = {} + + def __getitem__(self, jid): + return self.users.get(jid, None) + + def register(self, jid, registration): + username = registration['username'] + + def filter_usernames(user): + return user != jid and self.users[user]['username'] == username + + conflicts = filter(filter_usernames, self.users.keys()) + if conflicts: + return False + + self.users[jid] = registration + return True + + def unregister(self, jid): + del self.users[jid] + + class xep_0077(BasePlugin): + """ + XEP-0077 In-Band Registration + """ + + def plugin_init(self): + self.description = "In-Band Registration" + self.xep = "0077" + self.form_fields = ('username', 'password') + self.form_instructions = "" + self.backend = UserStore() + + self.xmpp.register_handler( + Callback('In-Band Registration', + MatchXPath('{%s}iq/{jabber:iq:register}query' % self.xmpp.default_ns), + self.__handleRegistration)) + register_stanza_plugin(Iq, Registration) + + def post_init(self): + BasePlugin.post_init(self) + self.xmpp['xep_0030'].add_feature("jabber:iq:register") + + def __handleRegistration(self, iq): + if iq['type'] == 'get': + # Registration form requested + userData = self.backend[iq['from'].bare] + self.sendRegistrationForm(iq, userData) + elif iq['type'] == 'set': + if iq['register']['remove']: + # Remove an account + self.backend.unregister(iq['from'].bare) + self.xmpp.event('unregistered_user', iq) + iq.reply().send() + return + + for field in self.form_fields: + if not iq['register'][field]: + # Incomplete Registration + self._sendError(iq, '406', 'modify', 'not-acceptable', + "Please fill in all fields.") + return + + if self.backend.register(iq['from'].bare, iq['register']): + # Successful registration + self.xmpp.event('registered_user', iq) + reply = iq.reply() + reply.set_payload(iq['register'].xml) + reply.send() + else: + # Conflicting registration + self._sendError(iq, '409', 'cancel', 'conflict', + "That username is already taken.") + + def setForm(self, *fields): + self.form_fields = fields + + def setInstructions(self, instructions): + self.form_instructions = instructions + + def sendRegistrationForm(self, iq, userData=None): + reg = iq['register'] + if userData is None: + userData = {} + else: + reg['registered'] = True + + if self.form_instructions: + reg['instructions'] = self.form_instructions + + for field in self.form_fields: + data = userData.get(field, '') + if data: + # Add field with existing data + reg[field] = data + else: + # Add a blank field + reg.addField(field) + + reply = iq.reply() + reply.set_payload(reg.xml) + reply.send() + + def _sendError(self, iq, code, error_type, name, text=''): + reply = iq.reply() + reply.set_payload(iq['register'].xml) + reply.error() + reply['error']['code'] = code + reply['error']['type'] = error_type + reply['error']['condition'] = name + reply['error']['text'] = text + reply.send() |