Allow logging in by IP address

There are many situations that this commit is untested against. Not
ready for merging yet.

Author: jalsol

dmoj/settings.py

@@ -687,6 +687,7 @@
     'social_core.backends.facebook.FacebookOAuth2',
     'judge.social_auth.GitHubSecureEmailOAuth2',
     'django.contrib.auth.backends.ModelBackend',
+    'judge.ip_based_auth.IPBasedAuthBackend',
 )
 
 SOCIAL_AUTH_PIPELINE = (

judge/forms.py

@@ -6,6 +6,7 @@
 import webauthn
 from django import forms
 from django.conf import settings
+from django.contrib.auth import authenticate
 from django.contrib.auth.forms import AuthenticationForm
 from django.contrib.auth.models import User
 from django.core.exceptions import ValidationError
@@ -47,6 +48,15 @@
 }
 
 
+def get_client_ip(request):
+    x_forwarded_for = request.META.get('HTTP_X_FORWARDED_FOR')
+    if x_forwarded_for:
+        ip = x_forwarded_for.split(',')[0]
+    else:
+        ip = request.META.get('REMOTE_ADDR')
+    return ip
+
+
 class ProfileForm(ModelForm):
     if newsletter_id is not None:
         newsletter = forms.BooleanField(label=_('Subscribe to contest updates'), initial=False, required=False)
@@ -428,13 +438,37 @@ def _has_social_auth(self, key):
                 getattr(settings, 'SOCIAL_AUTH_%s_SECRET' % key, None))
 
     def clean(self):
-        username = self.cleaned_data.get('username')
+        is_ip_login = self.request.POST.get('ip-login', 'false') == 'true'
+
         try:
-            user = User.objects.get(username=username)
-        except User.DoesNotExist:
+            if is_ip_login:
+                ip = get_client_ip(self.request)
+                user = Profile.objects.filter(ip=ip).select_related('user').first().user
+            else:
+                username = self.cleaned_data.get('username')
+                user = User.objects.get(username=username)
+        except (Profile.DoesNotExist, User.DoesNotExist):
             user = None
+
         if user is not None:
             self.confirm_login_allowed(user)
+
+        if is_ip_login:
+            # a hack to remove the username/password errors, since we don't need them
+            del self.errors['username']
+            del self.errors['password']
+
+            # set the password to the user's password to pass the form_valid check
+            self.cleaned_data['password'] = user.password
+
+            # super.clean() will skip the check, since there is no username/password when logging in by IP address,
+            # so this is a hack to process that manually
+            self.user_cache = authenticate(self.request, ip_address=ip)
+            if self.user_cache is None:
+                raise self.get_invalid_login_error()
+            else:
+                self.confirm_login_allowed(self.user_cache)
+
         return super(CustomAuthenticationForm, self).clean()
 
     def confirm_login_allowed(self, user):

judge/ip_based_auth.py

@@ -0,0 +1,12 @@
+from django.contrib.auth.backends import ModelBackend
+
+from judge.models import Profile
+
+
+class IPBasedAuthBackend(ModelBackend):
+    def authenticate(self, request, ip_address=None):
+        try:
+            user = Profile.objects.filter(ip=ip_address).select_related('user').first().user
+        except Profile.DoesNotExist:
+            user = None
+        return user

templates/registration/login.html

@@ -26,6 +26,16 @@
     </style>
 {% endblock %}
 
+{% block js_media %}
+<script>
+    $(document).ready(function () {
+        $("#ip-login-button").click(function () {
+            $("input[name='ip-login']").val("true");
+        });
+    });
+</script>
+{% endblock %}
+
 {% block body %}
     <div class="auth-flow-form">
         <form action="" method="post" class="form-area">
@@ -57,7 +67,10 @@
             </table>
             <hr>
             <button style="float:right;" type="submit">{{ _('Login!') }}</button>
+            <!-- TODO: enabled if allowing login by ip address -->
+            <button style="float:right; margin-right: 0.5em" type="submit" id="ip-login-button" formnovalidate>{{_('Login by IP Address!')}}</button>
             <input type="hidden" name="next" value="{{ next }}">
+            <input type="hidden" name="ip-login" value="false">
         </form>
         <a href="{{ url('password_reset') }}">{{ _('Forgot your password?') }}</a>