Fix inconsistent handling of upper and lower cases of email addresses. (#7021)

fixes #7016

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, random_string
-from synapse.util.threepids import check_3pid_allowed
+from synapse.util.threepids import canonicalise_email, check_3pid_allowed
 
 from ._base import client_patterns, interactive_auth_handler
 
@@ -83,7 +83,15 @@ class EmailPasswordRequestTokenRestServlet(RestServlet):
         client_secret = body["client_secret"]
         assert_valid_client_secret(client_secret)
 
-        email = body["email"]
+        # Canonicalise the email address. The addresses are all stored canonicalised
+        # in the database. This allows the user to reset his password without having to
+        # know the exact spelling (eg. upper and lower case) of address in the database.
+        # Stored in the database "foo@bar.com"
+        # User requests with "FOO@bar.com" would raise a Not Found error
+        try:
+            email = canonicalise_email(body["email"])
+        except ValueError as e:
+            raise SynapseError(400, str(e))
         send_attempt = body["send_attempt"]
         next_link = body.get("next_link")  # Optional param
 
@@ -94,6 +102,10 @@ class EmailPasswordRequestTokenRestServlet(RestServlet):
                 Codes.THREEPID_DENIED,
             )
 
+        # 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
+        # canonicalisation, matches the one in our database.
         existing_user_id = await self.hs.get_datastore().get_user_id_by_threepid(
             "email", email
         )
@@ -274,10 +286,13 @@ class PasswordRestServlet(RestServlet):
                 if "medium" not in threepid or "address" not in threepid:
                     raise SynapseError(500, "Malformed threepid")
                 if threepid["medium"] == "email":
-                    # For emails, transform the address to lowercase.
-                    # We store all email addreses as lowercase in the DB.
+                    # For emails, canonicalise the address.
+                    # We store all email addresses canonicalised in the DB.
                     # (See add_threepid in synapse/handlers/auth.py)
-                    threepid["address"] = threepid["address"].lower()
+                    try:
+                        threepid["address"] = canonicalise_email(threepid["address"])
+                    except ValueError as e:
+                        raise SynapseError(400, str(e))
                 # if using email, we must know about the email they're authing with!
                 threepid_user_id = await self.datastore.get_user_id_by_threepid(
                     threepid["medium"], threepid["address"]
@@ -392,7 +407,16 @@ class EmailThreepidRequestTokenRestServlet(RestServlet):
         client_secret = body["client_secret"]
         assert_valid_client_secret(client_secret)
 
-        email = body["email"]
+        # Canonicalise the email address. The addresses are all stored canonicalised
+        # in the database.
+        # This ensures that the validation email is sent to the canonicalised address
+        # as it will later be entered into the database.
+        # Otherwise the email will be sent to "FOO@bar.com" and stored as
+        # "foo@bar.com" in database.
+        try:
+            email = canonicalise_email(body["email"])
+        except ValueError as e:
+            raise SynapseError(400, str(e))
         send_attempt = body["send_attempt"]
         next_link = body.get("next_link")  # Optional param
 
@@ -403,9 +427,7 @@ class EmailThreepidRequestTokenRestServlet(RestServlet):
                 Codes.THREEPID_DENIED,
             )
 
-        existing_user_id = await self.store.get_user_id_by_threepid(
-            "email", body["email"]
-        )
+        existing_user_id = await self.store.get_user_id_by_threepid("email", email)
 
         if existing_user_id is not None:
             if self.config.request_token_inhibit_3pid_errors: