diff --git a/synapse/config/server.py b/synapse/config/server.py
index e85c6a0840..532b910470 100644
--- a/synapse/config/server.py
+++ b/synapse/config/server.py
@@ -19,7 +19,7 @@ import logging
import os.path
import re
from textwrap import indent
-from typing import Any, Dict, Iterable, List, Optional
+from typing import Any, Dict, Iterable, List, Optional, Set
import attr
import yaml
@@ -542,6 +542,19 @@ class ServerConfig(Config):
users_new_default_push_rules
) # type: set
+ # Whitelist of domain names that given next_link parameters must have
+ next_link_domain_whitelist = config.get(
+ "next_link_domain_whitelist"
+ ) # type: Optional[List[str]]
+
+ self.next_link_domain_whitelist = None # type: Optional[Set[str]]
+ if next_link_domain_whitelist is not None:
+ if not isinstance(next_link_domain_whitelist, list):
+ raise ConfigError("'next_link_domain_whitelist' must be a list")
+
+ # Turn the list into a set to improve lookup speed.
+ self.next_link_domain_whitelist = set(next_link_domain_whitelist)
+
def has_tls_listener(self) -> bool:
return any(listener.tls for listener in self.listeners)
@@ -1014,6 +1027,24 @@ class ServerConfig(Config):
# act as if no error happened and return a fake session ID ('sid') to clients.
#
#request_token_inhibit_3pid_errors: true
+
+ # A list of domains that the domain portion of 'next_link' parameters
+ # must match.
+ #
+ # This parameter is optionally provided by clients while requesting
+ # validation of an email or phone number, and maps to a link that
+ # users will be automatically redirected to after validation
+ # succeeds. Clients can make use this parameter to aid the validation
+ # process.
+ #
+ # The whitelist is applied whether the homeserver or an
+ # identity server is handling validation.
+ #
+ # The default value is no whitelist functionality; all domains are
+ # allowed. Setting this value to an empty list will instead disallow
+ # all domains.
+ #
+ #next_link_domain_whitelist: ["matrix.org"]
"""
% locals()
)
diff --git a/synapse/rest/client/v2_alpha/account.py b/synapse/rest/client/v2_alpha/account.py
index 3481477731..455051ac46 100644
--- a/synapse/rest/client/v2_alpha/account.py
+++ b/synapse/rest/client/v2_alpha/account.py
@@ -17,6 +17,11 @@
import logging
import random
from http import HTTPStatus
+from typing import TYPE_CHECKING
+from urllib.parse import urlparse
+
+if TYPE_CHECKING:
+ from synapse.app.homeserver import HomeServer
from synapse.api.constants import LoginType
from synapse.api.errors import (
@@ -98,6 +103,9 @@ class EmailPasswordRequestTokenRestServlet(RestServlet):
Codes.THREEPID_DENIED,
)
+ # Raise if the provided next_link value isn't valid
+ assert_valid_next_link(self.hs, next_link)
+
# The email will be sent to the stored address.
# This avoids a potential account hijack by requesting a password reset to
# an email address which is controlled by the attacker but which, after
@@ -446,6 +454,9 @@ class EmailThreepidRequestTokenRestServlet(RestServlet):
Codes.THREEPID_DENIED,
)
+ # Raise if the provided next_link value isn't valid
+ assert_valid_next_link(self.hs, next_link)
+
existing_user_id = await self.store.get_user_id_by_threepid("email", email)
if existing_user_id is not None:
@@ -517,6 +528,9 @@ class MsisdnThreepidRequestTokenRestServlet(RestServlet):
Codes.THREEPID_DENIED,
)
+ # Raise if the provided next_link value isn't valid
+ assert_valid_next_link(self.hs, next_link)
+
existing_user_id = await self.store.get_user_id_by_threepid("msisdn", msisdn)
if existing_user_id is not None:
@@ -603,15 +617,10 @@ class AddThreepidEmailSubmitTokenServlet(RestServlet):
# Perform a 302 redirect if next_link is set
if next_link:
- if next_link.startswith("file:///"):
- logger.warning(
- "Not redirecting to next_link as it is a local file: address"
- )
- else:
- request.setResponseCode(302)
- request.setHeader("Location", next_link)
- finish_request(request)
- return None
+ request.setResponseCode(302)
+ request.setHeader("Location", next_link)
+ finish_request(request)
+ return None
# Otherwise show the success template
html = self.config.email_add_threepid_template_success_html_content
@@ -875,6 +884,45 @@ class ThreepidDeleteRestServlet(RestServlet):
return 200, {"id_server_unbind_result": id_server_unbind_result}
+def assert_valid_next_link(hs: "HomeServer", next_link: str):
+ """
+ Raises a SynapseError if a given next_link value is invalid
+
+ next_link is valid if the scheme is http(s) and the next_link.domain_whitelist config
+ option is either empty or contains a domain that matches the one in the given next_link
+
+ Args:
+ hs: The homeserver object
+ next_link: The next_link value given by the client
+
+ Raises:
+ SynapseError: If the next_link is invalid
+ """
+ valid = True
+
+ # Parse the contents of the URL
+ next_link_parsed = urlparse(next_link)
+
+ # Scheme must not point to the local drive
+ if next_link_parsed.scheme == "file":
+ valid = False
+
+ # If the domain whitelist is set, the domain must be in it
+ if (
+ valid
+ and hs.config.next_link_domain_whitelist is not None
+ and next_link_parsed.hostname not in hs.config.next_link_domain_whitelist
+ ):
+ valid = False
+
+ if not valid:
+ raise SynapseError(
+ 400,
+ "'next_link' domain not included in whitelist, or not http(s)",
+ errcode=Codes.INVALID_PARAM,
+ )
+
+
class WhoamiRestServlet(RestServlet):
PATTERNS = client_patterns("/account/whoami$")
|
