Merge pull request #3257 from matrix-org/rav/fonx_on_no_consent

Reject attempts to send event before privacy consent is given

2 files changed, 79 insertions, 1 deletions

diff --git a/synapse/api/errors.py b/synapse/api/errors.py
index a9ff5576f3..aca804280c 100644
--- a/synapse/api/errors.py
+++ b/synapse/api/errors.py
@@ -19,6 +19,7 @@ import logging
 
 import simplejson as json
 from six import iteritems
+from six.moves import http_client
 
 logger = logging.getLogger(__name__)
 
@@ -51,6 +52,7 @@ class Codes(object):
     THREEPID_DENIED = "M_THREEPID_DENIED"
     INVALID_USERNAME = "M_INVALID_USERNAME"
     SERVER_NOT_TRUSTED = "M_SERVER_NOT_TRUSTED"
+    CONSENT_NOT_GIVEN = "M_CONSENT_NOT_GIVEN"
 
 
 class CodeMessageException(RuntimeError):
@@ -138,6 +140,32 @@ class SynapseError(CodeMessageException):
         return res
 
 
+class ConsentNotGivenError(SynapseError):
+    """The error returned to the client when the user has not consented to the
+    privacy policy.
+    """
+    def __init__(self, msg, consent_uri):
+        """Constructs a ConsentNotGivenError
+
+        Args:
+            msg (str): The human-readable error message
+            consent_url (str): The URL where the user can give their consent
+        """
+        super(ConsentNotGivenError, self).__init__(
+            code=http_client.FORBIDDEN,
+            msg=msg,
+            errcode=Codes.CONSENT_NOT_GIVEN
+        )
+        self._consent_uri = consent_uri
+
+    def error_dict(self):
+        return cs_error(
+            self.msg,
+            self.errcode,
+            consent_uri=self._consent_uri
+        )
+
+
 class RegistrationError(SynapseError):
     """An error raised when a registration event fails."""
     pass
@@ -292,7 +320,7 @@ def cs_error(msg, code=Codes.UNKNOWN, **kwargs):
 
     Args:
         msg (str): The error message.
-        code (int): The error code.
+        code (str): The error code.
         kwargs : Additional keys to add to the response.
     Returns:
         A dict representing the error response JSON.
diff --git a/synapse/api/urls.py b/synapse/api/urls.py
index 91a33a3402..bb46b5da8a 100644
--- a/synapse/api/urls.py
+++ b/synapse/api/urls.py
@@ -1,5 +1,6 @@
 # -*- coding: utf-8 -*-
 # Copyright 2014-2016 OpenMarket Ltd
+# Copyright 2018 New Vector Ltd.
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
 # you may not use this file except in compliance with the License.
@@ -14,6 +15,12 @@
 # limitations under the License.
 
 """Contains the URL paths to prefix various aspects of the server with. """
+from hashlib import sha256
+import hmac
+
+from six.moves.urllib.parse import urlencode
+
+from synapse.config import ConfigError
 
 CLIENT_PREFIX = "/_matrix/client/api/v1"
 CLIENT_V2_ALPHA_PREFIX = "/_matrix/client/v2_alpha"
@@ -25,3 +32,46 @@ SERVER_KEY_PREFIX = "/_matrix/key/v1"
 SERVER_KEY_V2_PREFIX = "/_matrix/key/v2"
 MEDIA_PREFIX = "/_matrix/media/r0"
 LEGACY_MEDIA_PREFIX = "/_matrix/media/v1"
+
+
+class ConsentURIBuilder(object):
+    def __init__(self, hs_config):
+        """
+        Args:
+            hs_config (synapse.config.homeserver.HomeServerConfig):
+        """
+        if hs_config.form_secret is None:
+            raise ConfigError(
+                "form_secret not set in config",
+            )
+        if hs_config.public_baseurl is None:
+            raise ConfigError(
+                "public_baseurl not set in config",
+            )
+
+        self._hmac_secret = hs_config.form_secret.encode("utf-8")
+        self._public_baseurl = hs_config.public_baseurl
+
+    def build_user_consent_uri(self, user_id):
+        """Build a URI which we can give to the user to do their privacy
+        policy consent
+
+        Args:
+            user_id (str): mxid or username of user
+
+        Returns
+            (str) the URI where the user can do consent
+        """
+        mac = hmac.new(
+            key=self._hmac_secret,
+            msg=user_id,
+            digestmod=sha256,
+        ).hexdigest()
+        consent_uri = "%s_matrix/consent?%s" % (
+            self._public_baseurl,
+            urlencode({
+                "u": user_id,
+                "h": mac
+            }),
+        )
+        return consent_uri