Add Matrix utility function to register users on Dendrite

CHANGELOG.md

@@ -7,6 +7,9 @@
 * Add `federation.hostmeta` generators for Matrix client and server well-known files. 
   Django views and url configuration also included for convenience.
 
+* Add `register_dendrite_user` Matrix protocol utility to register users on Dendrite
+  homeservers using a shared registration secret.
+
 ## [0.21.0] - 2020-12-20
 
 ### Added

docs/usage.rst

@@ -239,6 +239,8 @@ Some settings need to be set in Django settings. An example is below:
       "client_wellknown_other_keys": {
         "org.foo.key" "barfoo",
       },
+      # (Optional) registration shared secret
+      "registration_shared_secret": "supersecretstring",
     }
 
 * ``nodeinfo2_function`` (optional) function that returns data for generating a `NodeInfo2 document <https://github.com/jaywink/nodeinfo2>`_. Once configured the path ``/.well-known/x-nodeinfo2`` will automatically generate a NodeInfo2 document. The function should return a ``dict`` corresponding to the NodeInfo2 schema, with the following minimum items:
@@ -296,6 +298,11 @@ Diaspora
 .. autofunction:: federation.utils.diaspora.retrieve_diaspora_hcard
 .. autofunction:: federation.utils.diaspora.retrieve_diaspora_host_meta
 
+Matrix
+......
+
+.. autofunction:: federation.utils.matrix.register_dendrite_user
+
 Network
 .......
 

federation/utils/matrix.py

@@ -0,0 +1,75 @@
+import hashlib
+import hmac
+import uuid
+from typing import Dict
+
+import requests
+
+from federation.utils.django import get_function_from_config
+
+
+def generate_dendrite_mac(shared_secret: str, username: str, password: str, admin: bool) -> str:
+    """
+    Generate a MAC for using in registering users with Dendrite.
+    """
+    # From: https://github.com/matrix-org/dendrite/blob/master/clientapi/routing/register.go
+    mac = hmac.new(
+      key=shared_secret.encode('utf8'),
+      digestmod=hashlib.sha1,
+    )
+
+    mac.update(username.encode('utf8'))
+    mac.update(b"\x00")
+    mac.update(password.encode('utf8'))
+    mac.update(b"\x00")
+    mac.update(b"admin" if admin else b"notadmin")
+    return mac.hexdigest()
+
+
+def register_dendrite_user(username: str) -> Dict:
+    """
+    Shared secret registration for Dendrite.
+
+    Note uses the legacy route, see
+    https://github.com/matrix-org/dendrite/issues/1669
+
+    Currently compatible with Django apps only.
+
+    Returns:
+        {
+            'user_id': '@username:domain.tld',
+            'access_token': 'randomaccesstoken',
+            'home_server': 'domain.tld',
+            'device_id': 'randomdevice'
+        }
+    """
+    try:
+        matrix_config_func = get_function_from_config("matrix_config_function")
+    except AttributeError:
+        raise AttributeError("Not configured for Matrix support")
+    matrix_config = matrix_config_func()
+
+    password = str(uuid.uuid4())
+    mac = generate_dendrite_mac(
+        matrix_config["registration_shared_secret"],
+        username,
+        password,
+        False,
+    )
+
+    # Register using shared secret
+    response = requests.post(
+        f"{matrix_config['homeserver_base_url']}/_matrix/client/api/v1/register?kind=user",
+        json={
+            "type": "org.matrix.login.shared_secret",
+            "mac": mac,
+            "password": password,
+            "user": username,
+            "admin": False,
+        },
+        headers={
+            "Content-Type": "application/json",
+        },
+    )
+    response.raise_for_status()
+    return response.json()