fix: enumeration attack vector on login form

core/templates/core/login.jinja

@@ -26,9 +26,11 @@
     {% endif %}
   {% endif %}
 
-  <form method="post" action="{{ url('core:login') }}">
+  <form method="post" action="{{ url('core:login') }}" id="login-form">
     {% if form.errors %}
-      <p class="alert alert-red">{% trans %}Your username and password didn't match. Please try again.{% endtrans %}</p>
+      <p class="alert alert-red">
+        {% trans %}Your credentials didn't match. Please try again.{% endtrans %}
+      </p>
     {% endif %}
 
     {% csrf_token %}

core/tests/test_core.py

@@ -38,6 +38,7 @@ from core.markdown import markdown
 from core.models import AnonymousUser, Group, Page, User
 from core.utils import get_semester_code, get_start_of_semester
 from core.views import AllowFragment
+from counter.models import Customer
 from sith import settings
 
 
@@ -151,24 +152,44 @@ class TestUserLogin:
     def user(self) -> User:
         return baker.make(User, password=make_password("plop"))
 
-    def test_login_fail(self, client, user):
+    @pytest.mark.parametrize(
+        "identifier_getter",
+        [
+            lambda user: user.username,
+            lambda user: user.email,
+            lambda user: Customer.get_or_create(user)[0].account_id,
+        ],
+    )
+    def test_login_fail(self, client, user, identifier_getter):
         """Should not login a user correctly."""
+        identifier = identifier_getter(user)
         response = client.post(
             reverse("core:login"),
-            {"username": user.username, "password": "wrong-password"},
+            {"username": identifier, "password": "wrong-password"},
         )
         assert response.status_code == 200
-        assert (
-            '<p class="alert alert-red">Votre nom d\'utilisateur '
-            "et votre mot de passe ne correspondent pas. Merci de réessayer.</p>"
-        ) in response.text
         assert response.wsgi_request.user.is_anonymous
+        soup = BeautifulSoup(response.text, "lxml")
+        form = soup.find(id="login-form")
+        assert (
+            form.find(class_="alert alert-red").get_text(strip=True)
+            == "Vos identifiants ne correspondent pas. Veuillez réessayer."
+        )
+        assert form.find("input", attrs={"name": "username"}).get("value") == identifier
 
-    def test_login_success(self, client, user):
+    @pytest.mark.parametrize(
+        "identifier_getter",
+        [
+            lambda user: user.username,
+            lambda user: user.email,
+            lambda user: Customer.get_or_create(user)[0].account_id,
+        ],
+    )
+    def test_login_success(self, client, user, identifier_getter):
         """Should login a user correctly."""
         response = client.post(
             reverse("core:login"),
-            {"username": user.username, "password": "plop"},
+            {"username": identifier_getter(user), "password": "plop"},
         )
         assertRedirects(response, reverse("core:index"))
         assert response.wsgi_request.user == user

core/views/forms.py

@@ -132,29 +132,31 @@ class FutureDateTimeField(forms.DateTimeField):
 
 class LoginForm(AuthenticationForm):
     def __init__(self, *arg, **kwargs):
-        if "data" in kwargs:
-            from counter.models import Customer
-
-            data = kwargs["data"].copy()
-            account_code = re.compile(r"^[0-9]+[A-Za-z]$")
-            try:
-                if account_code.match(data["username"]):
-                    user = (
-                        Customer.objects.filter(account_id__iexact=data["username"])
-                        .first()
-                        .user
-                    )
-                elif "@" in data["username"]:
-                    user = User.objects.filter(email__iexact=data["username"]).first()
-                else:
-                    user = User.objects.filter(username=data["username"]).first()
-                data["username"] = user.username
-            except:  # noqa E722 I don't know what error is supposed to be raised here
-                pass
-            kwargs["data"] = data
         super().__init__(*arg, **kwargs)
         self.fields["username"].label = _("Username, email, or account number")
 
+    def clean_username(self):
+        identifier: str = self.cleaned_data["username"]
+        account_code = re.compile(r"^[0-9]+[A-Za-z]$")
+        if account_code.match(identifier):
+            qs_filter = "customer__account_id__iexact"
+        elif identifier.count("@") == 1:
+            qs_filter = "email"
+        else:
+            qs_filter = None
+        if qs_filter:
+            # if the user gave an email or an account code instead of
+            # a username, retrieve and return the corresponding username.
+            # If there is no username, return an empty string, so that
+            # Django will properly handle the error when failing the authentication
+            identifier = (
+                User.objects.filter(**{qs_filter: identifier})
+                .values_list("username", flat=True)
+                .first()
+                or ""
+            )
+        return identifier
+
 
 class RegisteringForm(UserCreationForm):
     error_css_class = "error"

locale/fr/LC_MESSAGES/django.po

@@ -6,7 +6,7 @@
 msgid ""
 msgstr ""
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2025-06-16 14:54+0200\n"
+"POT-Creation-Date: 2025-06-25 16:29+0200\n"
 "PO-Revision-Date: 2016-07-18\n"
 "Last-Translator: Maréchal <thomas.girod@utbm.fr\n"
 "Language-Team: AE info <ae.info@utbm.fr>\n"
@@ -2015,10 +2015,8 @@ msgid "Please login or create an account to see this page."
 msgstr "Merci de vous identifier ou de créer un compte pour voir cette page."
 
 #: core/templates/core/login.jinja
-msgid "Your username and password didn't match. Please try again."
+msgid "Your credentials didn't match. Please try again."
-msgstr ""
+msgstr "Vos identifiants ne correspondent pas. Veuillez réessayer."
-"Votre nom d'utilisateur et votre mot de passe ne correspondent pas. Merci de "
-"réessayer."
 
 #: core/templates/core/login.jinja
 msgid "Lost password?"