From 69ad7cc13bf2e2499c39daa4a2707421ad999762 Mon Sep 17 00:00:00 2001 From: Brendan Abolivier Date: Tue, 21 Apr 2020 16:33:01 +0200 Subject: [PATCH] Config option to inhibit 3PID errors on /requestToken Adds a request_token_inhibit_errors configuration flag (disabled by default) which, if enabled, change the behaviour of all /requestToken endpoints so that they return a 200 and a fake sid if the 3PID was/was not found associated with an account (depending on the endpoint), instead of an error. Co-Authored-By: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com> --- changelog.d/7315.feature | 1 + docs/sample_config.yaml | 10 +++++ synapse/config/server.py | 21 +++++++++ synapse/rest/client/v2_alpha/account.py | 17 +++++++- synapse/rest/client/v2_alpha/register.py | 12 +++++- tests/rest/client/v2_alpha/test_account.py | 16 +++++++ tests/rest/client/v2_alpha/test_register.py | 47 ++++++++++++++++++++- 7 files changed, 121 insertions(+), 3 deletions(-) create mode 100644 changelog.d/7315.feature diff --git a/changelog.d/7315.feature b/changelog.d/7315.feature new file mode 100644 index 000000000..ebcb4741b --- /dev/null +++ b/changelog.d/7315.feature @@ -0,0 +1 @@ +Allow `/requestToken` endpoints to hide the existence (or lack thereof) of 3PID associations on the homeserver. diff --git a/docs/sample_config.yaml b/docs/sample_config.yaml index 2ff0dd05a..abe03b226 100644 --- a/docs/sample_config.yaml +++ b/docs/sample_config.yaml @@ -409,6 +409,16 @@ retention: # longest_max_lifetime: 1y # interval: 1d +# Inhibits the /requestToken endpoints from returning an error that might leak +# information about whether an e-mail address is in use or not on this +# homeserver. +# Note that for some endpoints the error situation is the e-mail already being +# used, and for others the error is entering the e-mail being unused. +# If this option is enabled, instead of returning an error, these endpoints will +# act as if no error happened and return a fake session ID ('sid') to clients. +# +#request_token_inhibit_3pid_errors: true + ## TLS ## diff --git a/synapse/config/server.py b/synapse/config/server.py index 7525765fe..8acf3946e 100644 --- a/synapse/config/server.py +++ b/synapse/config/server.py @@ -507,6 +507,17 @@ class ServerConfig(Config): self.enable_ephemeral_messages = config.get("enable_ephemeral_messages", False) + # Inhibits the /requestToken endpoints from returning an error that might leak + # information about whether an e-mail address is in use or not on this + # homeserver, and instead return a 200 with a fake sid if this kind of error is + # met, without sending anything. + # This is a compromise between sending an email, which could be a spam vector, + # and letting the client know which email address is bound to an account and + # which one isn't. + self.request_token_inhibit_3pid_errors = config.get( + "request_token_inhibit_3pid_errors", False, + ) + def has_tls_listener(self) -> bool: return any(l["tls"] for l in self.listeners) @@ -967,6 +978,16 @@ class ServerConfig(Config): # - shortest_max_lifetime: 3d # longest_max_lifetime: 1y # interval: 1d + + # Inhibits the /requestToken endpoints from returning an error that might leak + # information about whether an e-mail address is in use or not on this + # homeserver. + # Note that for some endpoints the error situation is the e-mail already being + # used, and for others the error is entering the e-mail being unused. + # If this option is enabled, instead of returning an error, these endpoints will + # act as if no error happened and return a fake session ID ('sid') to clients. + # + #request_token_inhibit_3pid_errors: true """ % locals() ) diff --git a/synapse/rest/client/v2_alpha/account.py b/synapse/rest/client/v2_alpha/account.py index 631cc74cb..e2fdcda65 100644 --- a/synapse/rest/client/v2_alpha/account.py +++ b/synapse/rest/client/v2_alpha/account.py @@ -30,7 +30,7 @@ from synapse.http.servlet import ( ) from synapse.push.mailer import Mailer, load_jinja2_templates from synapse.util.msisdn import phone_number_to_msisdn -from synapse.util.stringutils import assert_valid_client_secret +from synapse.util.stringutils import assert_valid_client_secret, random_string from synapse.util.threepids import check_3pid_allowed from ._base import client_patterns, interactive_auth_handler @@ -100,6 +100,11 @@ class EmailPasswordRequestTokenRestServlet(RestServlet): ) if existing_user_id is None: + if self.config.request_token_inhibit_3pid_errors: + # Make the client think the operation succeeded. See the rationale in the + # comments for request_token_inhibit_3pid_errors. + return 200, {"sid": random_string(16)} + raise SynapseError(400, "Email not found", Codes.THREEPID_NOT_FOUND) if self.config.threepid_behaviour_email == ThreepidBehaviour.REMOTE: @@ -378,6 +383,11 @@ class EmailThreepidRequestTokenRestServlet(RestServlet): ) if existing_user_id is not None: + if self.config.request_token_inhibit_3pid_errors: + # Make the client think the operation succeeded. See the rationale in the + # comments for request_token_inhibit_3pid_errors. + return 200, {"sid": random_string(16)} + raise SynapseError(400, "Email is already in use", Codes.THREEPID_IN_USE) if self.config.threepid_behaviour_email == ThreepidBehaviour.REMOTE: @@ -441,6 +451,11 @@ class MsisdnThreepidRequestTokenRestServlet(RestServlet): existing_user_id = await self.store.get_user_id_by_threepid("msisdn", msisdn) if existing_user_id is not None: + if self.hs.config.request_token_inhibit_3pid_errors: + # Make the client think the operation succeeded. See the rationale in the + # comments for request_token_inhibit_3pid_errors. + return 200, {"sid": random_string(16)} + raise SynapseError(400, "MSISDN is already in use", Codes.THREEPID_IN_USE) if not self.hs.config.account_threepid_delegate_msisdn: diff --git a/synapse/rest/client/v2_alpha/register.py b/synapse/rest/client/v2_alpha/register.py index a09189b1b..416489ae5 100644 --- a/synapse/rest/client/v2_alpha/register.py +++ b/synapse/rest/client/v2_alpha/register.py @@ -49,7 +49,7 @@ from synapse.http.servlet import ( from synapse.push.mailer import load_jinja2_templates from synapse.util.msisdn import phone_number_to_msisdn from synapse.util.ratelimitutils import FederationRateLimiter -from synapse.util.stringutils import assert_valid_client_secret +from synapse.util.stringutils import assert_valid_client_secret, random_string from synapse.util.threepids import check_3pid_allowed from ._base import client_patterns, interactive_auth_handler @@ -135,6 +135,11 @@ class EmailRegisterRequestTokenRestServlet(RestServlet): ) if existing_user_id is not None: + if self.hs.config.request_token_inhibit_3pid_errors: + # Make the client think the operation succeeded. See the rationale in the + # comments for request_token_inhibit_3pid_errors. + return 200, {"sid": random_string(16)} + raise SynapseError(400, "Email is already in use", Codes.THREEPID_IN_USE) if self.config.threepid_behaviour_email == ThreepidBehaviour.REMOTE: @@ -202,6 +207,11 @@ class MsisdnRegisterRequestTokenRestServlet(RestServlet): ) if existing_user_id is not None: + if self.hs.config.request_token_inhibit_3pid_errors: + # Make the client think the operation succeeded. See the rationale in the + # comments for request_token_inhibit_3pid_errors. + return 200, {"sid": random_string(16)} + raise SynapseError( 400, "Phone number is already in use", Codes.THREEPID_IN_USE ) diff --git a/tests/rest/client/v2_alpha/test_account.py b/tests/rest/client/v2_alpha/test_account.py index c3facc00e..de72dc9a4 100644 --- a/tests/rest/client/v2_alpha/test_account.py +++ b/tests/rest/client/v2_alpha/test_account.py @@ -178,6 +178,22 @@ class PasswordResetTestCase(unittest.HomeserverTestCase): # Assert we can't log in with the new password self.attempt_wrong_password_login("kermit", new_password) + @unittest.override_config({"request_token_inhibit_3pid_errors": True}) + def test_password_reset_bad_email_inhibit_error(self): + """Test that triggering a password reset with an email address that isn't bound + to an account doesn't leak the lack of binding for that address if configured + that way. + """ + self.register_user("kermit", "monkey") + self.login("kermit", "monkey") + + email = "test@example.com" + + client_secret = "foobar" + session_id = self._request_token(email, client_secret) + + self.assertIsNotNone(session_id) + def _request_token(self, email, client_secret): request, channel = self.make_request( "POST", diff --git a/tests/rest/client/v2_alpha/test_register.py b/tests/rest/client/v2_alpha/test_register.py index d0c997e38..18527353f 100644 --- a/tests/rest/client/v2_alpha/test_register.py +++ b/tests/rest/client/v2_alpha/test_register.py @@ -33,7 +33,11 @@ from tests import unittest class RegisterRestServletTestCase(unittest.HomeserverTestCase): - servlets = [register.register_servlets] + servlets = [ + login.register_servlets, + register.register_servlets, + synapse.rest.admin.register_servlets, + ] url = b"/_matrix/client/r0/register" def default_config(self, name="test"): @@ -260,6 +264,47 @@ class RegisterRestServletTestCase(unittest.HomeserverTestCase): [["m.login.email.identity"]], (f["stages"] for f in flows) ) + @unittest.override_config( + { + "request_token_inhibit_3pid_errors": True, + "public_baseurl": "https://test_server", + "email": { + "smtp_host": "mail_server", + "smtp_port": 2525, + "notif_from": "sender@host", + }, + } + ) + def test_request_token_existing_email_inhibit_error(self): + """Test that requesting a token via this endpoint doesn't leak existing + associations if configured that way. + """ + user_id = self.register_user("kermit", "monkey") + self.login("kermit", "monkey") + + email = "test@example.com" + + # Add a threepid + self.get_success( + self.hs.get_datastore().user_add_threepid( + user_id=user_id, + medium="email", + address=email, + validated_at=0, + added_at=0, + ) + ) + + request, channel = self.make_request( + "POST", + b"register/email/requestToken", + {"client_secret": "foobar", "email": email, "send_attempt": 1}, + ) + self.render(request) + self.assertEquals(200, channel.code, channel.result) + + self.assertIsNotNone(channel.json_body.get("sid")) + class AccountValidityTestCase(unittest.HomeserverTestCase):