From a800603561c0cb58727474035b6b27ed9e5fc277 Mon Sep 17 00:00:00 2001
From: Andrew Morgan <1342360+anoadragon453@users.noreply.github.com>
Date: Mon, 1 Feb 2021 15:54:39 +0000
Subject: [PATCH] Prevent email UIA failures from raising a LoginError (#9265)

Context, Fixes: https://github.com/matrix-org/synapse/issues/9263

In the past to fix an issue with old Riots re-requesting threepid validation tokens, we raised a `LoginError` during UIA instead of `InteractiveAuthIncompleteError`. This is now breaking the way Tchap logs in - which isn't standard, but also isn't disallowed by the spec.

An easy fix is just to remove the 4 year old workaround.
---
 changelog.d/9265.bugfix  |  1 +
 synapse/handlers/auth.py | 10 ----------
 2 files changed, 1 insertion(+), 10 deletions(-)
 create mode 100644 changelog.d/9265.bugfix

diff --git a/changelog.d/9265.bugfix b/changelog.d/9265.bugfix
new file mode 100644
index 000000000000..34f7bd8ddd06
--- /dev/null
+++ b/changelog.d/9265.bugfix
@@ -0,0 +1 @@
+Prevent password hashes from getting dropped if a client failed threepid validation during a User Interactive Auth stage. Removes a workaround for an ancient bug in Riot Web <v0.7.4.
\ No newline at end of file
diff --git a/synapse/handlers/auth.py b/synapse/handlers/auth.py
index 0e98db22b3b1..31273579648a 100644
--- a/synapse/handlers/auth.py
+++ b/synapse/handlers/auth.py
@@ -567,16 +567,6 @@ async def check_ui_auth(
                         session.session_id, login_type, result
                     )
             except LoginError as e:
-                if login_type == LoginType.EMAIL_IDENTITY:
-                    # riot used to have a bug where it would request a new
-                    # validation token (thus sending a new email) each time it
-                    # got a 401 with a 'flows' field.
-                    # (https://github.com/vector-im/vector-web/issues/2447).
-                    #
-                    # Grandfather in the old behaviour for now to avoid
-                    # breaking old riot deployments.
-                    raise
-
                 # this step failed. Merge the error dict into the response
                 # so that the client can have another go.
                 errordict = e.error_dict()