Mitigate pesquisar-sessao DDoS and fix page= param pollution

Coordinated DDoS attack used repeated page= params
(?page=3&page=2&page=3&...) as a scraping fingerprint, likely
harvested from SAPL's own paginated search links which had a
long-standing bug producing those polluted URLs.

Reject duplicate page= at the middleware layer:
  RateLimitMiddleware.__call__ returns 400 (param_pollution) if
  request.GET.getlist('page') has more than one value — before any
  Redis or DB work runs, covering all paths universally.
  PesquisarSessaoPlenariaView.get has the same check as a backstop.

Fix the root cause — page= leaking into filter_url on 9 search views:
  All affected views built filter_url from the raw QUERY_STRING and
  guarded with startswith("&page"), which only strips page= when it
  is the first param. With ?filter=X&page=2 the page= leaked through
  and paginacao.html produced ?page=N&filter=X&page=2 on every link.
  Replaced with qr = request.GET.copy(); qr.pop('page', None).
  Views fixed: PesquisarStatusTramitacaoView, PesquisarAssuntoNormaView,
  PesquisarAuditLogView, PesquisarParlamentarView, PesquisarColigacaoView,
  PesquisarPartidoView, ProtocoloPesquisaView,
  PesquisarDocumentoAdministrativoView, PesquisarSessaoPlenariaView.

Cache anonymous GET on PesquisarSessaoPlenariaView (2 min TTL) to
reduce ORM load from repeated identical queries.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

docker/config/nginx/sapl.conf

@@ -158,6 +158,7 @@ server {
         proxy_pass http://sapl_server;
     }
 
+
     # ----------------------------------------------------------------
     # Scanner extension probes (.php, .asp, etc.) — SAPL never serves
     # these. Drop the connection before reaching Gunicorn.

sapl/base/views.py

@@ -1458,12 +1458,9 @@ class PesquisarAuditLogView(PermissionRequiredMixin, FilterView):
 
         data = self.filterset.data
 
-        url = ''
-
-        if data:
-            url = '&' + str(self.request.META["QUERY_STRING"])
-            if url.startswith("&page"):
-                url = ''
+        qr = self.request.GET.copy()
+        qr.pop('page', None)
+        url = ('&' + qr.urlencode()) if qr else ''
 
         resultados = self.object_list
         # if 'page' in self.request.META['QUERY_STRING']:

sapl/materia/views.py

@@ -396,12 +396,9 @@ class PesquisarStatusTramitacaoView(FilterView):
 
         data = self.filterset.data
 
-        url = ''
-
-        if data:
-            url = '&' + str(self.request.META["QUERY_STRING"])
-            if url.startswith("&page"):
-                url = ''
+        qr = self.request.GET.copy()
+        qr.pop('page', None)
+        url = ('&' + qr.urlencode()) if qr else ''
 
         if 'descricao' in self.request.META['QUERY_STRING'] or\
                 'page' in self.request.META['QUERY_STRING']:

sapl/middleware/ratelimit.py

@@ -402,6 +402,19 @@ class RateLimitMiddleware:
         if any(p.match(request.path) for p in self._bypass_paths):
             return self.get_response(request)
 
+        # Reject parameter pollution: the `page` param must appear at most once.
+        # Duplicate page= values (e.g. ?page=3&page=2&page=3) are a bot
+        # fingerprint — no legitimate browser or script sends this.
+        if len(request.GET.getlist('page')) > 1:
+            logger.warning(
+                'ratelimit_block layer=django reason=param_pollution ip=%s path=%s',
+                get_client_ip(request), request.path,
+            )
+            self._inc_block_metric('param_pollution')
+            response = HttpResponse(status=400)
+            response['X-RateLimit-Reason'] = 'param_pollution'
+            return response
+
         if request.path.startswith('/api/'):
             return self._handle_api(request)
 

sapl/middleware/test_ratelimiter.py

@@ -549,6 +549,31 @@ def test_call_pass_forwards_request_to_get_response():
     mw.get_response.assert_called_once_with(request)
 
 
+def test_call_rejects_duplicate_page_param_with_400():
+    mw, _ = _make_middleware()
+    request = _factory.get('/sessao/pesquisar-sessao', data={'page': ['3', '2', '3']})
+    response = mw(request)
+    assert response.status_code == 400
+    assert response['X-RateLimit-Reason'] == 'param_pollution'
+    mw.get_response.assert_not_called()
+
+
+def test_call_allows_single_page_param():
+    mw, _ = _make_middleware()
+    mw._evaluate = MagicMock(return_value={'action': 'pass', 'ip': '1.2.3.4'})
+    request = _factory.get('/sessao/pesquisar-sessao', data={'page': '2'})
+    mw(request)
+    mw.get_response.assert_called_once_with(request)
+
+
+def test_call_allows_no_page_param():
+    mw, _ = _make_middleware()
+    mw._evaluate = MagicMock(return_value={'action': 'pass', 'ip': '1.2.3.4'})
+    request = _factory.get('/sessao/pesquisar-sessao')
+    mw(request)
+    mw.get_response.assert_called_once_with(request)
+
+
 # ---------------------------------------------------------------------------
 # _is_same_origin
 # ---------------------------------------------------------------------------

sapl/norma/views.py

@@ -104,12 +104,9 @@ class PesquisarAssuntoNormaView(FilterView):
 
         data = self.filterset.data
 
-        url = ''
-
-        if data:
-            url = '&' + str(self.request.META["QUERY_STRING"])
-            if url.startswith("&page"):
-                url = ''
+        qr = self.request.GET.copy()
+        qr.pop('page', None)
+        url = ('&' + qr.urlencode()) if qr else ''
 
         if 'assunto' in self.request.META['QUERY_STRING'] or\
                 'page' in self.request.META['QUERY_STRING']:

sapl/parlamentares/views.py

@@ -232,11 +232,9 @@ class PesquisarParlamentarView(FilterView):
         super(PesquisarParlamentarView, self).get(request)
 
         data = self.filterset.data
-        url = ''
-        if data:
-            url = "&" + str(self.request.META['QUERY_STRING'])
-            if url.startswith("&page"):
-                url = ''
+        qr = self.request.GET.copy()
+        qr.pop('page', None)
+        url = ('&' + qr.urlencode()) if qr else ''
 
         if 'nome_parlamentar' in self.request.META['QUERY_STRING'] or\
                 'page' in self.request.META['QUERY_STRING']:
@@ -292,11 +290,9 @@ class PesquisarColigacaoView(FilterView):
         super(PesquisarColigacaoView, self).get(request)
 
         data = self.filterset.data
-        url = ''
-        if data:
-            url = "&" + str(self.request.META['QUERY_STRING'])
-            if url.startswith("&page"):
-                url = ''
+        qr = self.request.GET.copy()
+        qr.pop('page', None)
+        url = ('&' + qr.urlencode()) if qr else ''
 
         if 'nome' in self.request.META['QUERY_STRING'] or\
                 'page' in self.request.META['QUERY_STRING']:
@@ -351,11 +347,9 @@ class PesquisarPartidoView(FilterView):
         super(PesquisarPartidoView, self).get(request)
 
         data = self.filterset.data
-        url = ''
-        if data:
-            url = "&" + str(self.request.META['QUERY_STRING'])
-            if url.startswith("&page"):
-                url = ''
+        qr = self.request.GET.copy()
+        qr.pop('page', None)
+        url = ('&' + qr.urlencode()) if qr else ''
 
         if 'nome' in self.request.META['QUERY_STRING'] or\
                 'page' in self.request.META['QUERY_STRING']:

sapl/protocoloadm/views.py

@@ -570,10 +570,9 @@ class ProtocoloPesquisaView(PermissionRequiredMixin, FilterView):
         # Então a ordem da URL está diferente
         data = self.filterset.data
         if data and data.get('numero') is not None:
-            url = "&" + str(self.request.environ['QUERY_STRING'])
-            if url.startswith("&page"):
-                ponto_comeco = url.find('numero=') - 1
-                url = url[ponto_comeco:]
+            qr = self.request.GET.copy()
+            qr.pop('page', None)
+            url = ('&' + qr.urlencode()) if qr else ''
         else:
             url = ''
 
@@ -1100,10 +1099,9 @@ class PesquisarDocumentoAdministrativoView(DocumentoAdministrativoMixin,
         # Então a ordem da URL está diferente
         data = self.filterset.data
         if data and data.get('tipo') is not None:
-            url = "&" + str(self.request.environ['QUERY_STRING'])
-            if url.startswith("&page"):
-                ponto_comeco = url.find('tipo=') - 1
-                url = url[ponto_comeco:]
+            qr = self.request.GET.copy()
+            qr.pop('page', None)
+            url = ('&' + qr.urlencode()) if qr else ''
         else:
             url = ''
         self.filterset.form.fields['o'].label = _('Ordenação')

sapl/sessao/views.py

@@ -11,7 +11,7 @@ from django.contrib.auth.mixins import PermissionRequiredMixin
 from django.core.exceptions import ObjectDoesNotExist
 from django.db.models import Max, Prefetch, Q
 from django.http import JsonResponse
-from django.http.response import Http404, HttpResponseRedirect
+from django.http.response import Http404, HttpResponseBadRequest, HttpResponseRedirect
 from django.urls import reverse
 from django.urls.base import reverse_lazy
 from django.utils import timezone
@@ -20,6 +20,7 @@ from django.utils.decorators import method_decorator
 from django.utils.encoding import force_text
 from django.utils.html import strip_tags
 from django.utils.translation import ugettext_lazy as _
+from django.views.decorators.cache import cache_page
 from django.views.decorators.csrf import csrf_exempt
 from django.views.generic import (FormView, ListView, TemplateView)
 from django.views.generic.base import RedirectView
@@ -4085,6 +4086,7 @@ class PautaSessaoDetailView(PautaMultiFormatOutputMixin, DetailView):
                             rate=smart_rate,
                             block=True),
                   name='dispatch')
+@method_decorator(cache_page(60 * 2), name='get')
 class PesquisarSessaoPlenariaView(MultiFormatOutputMixin, FilterView):
     model = SessaoPlenaria
     filterset_class = SessaoPlenariaFilterSet
@@ -4144,17 +4146,17 @@ class PesquisarSessaoPlenariaView(MultiFormatOutputMixin, FilterView):
 
         data = self.filterset.data
         if data and data.get('data_inicio__year') is not None:
-            url = "&" + str(self.request.META['QUERY_STRING'])
-            if url.startswith("&page"):
-                ponto_comeco = url.find('data_inicio__year=') - 1
-                url = url[ponto_comeco:]
-            context['filter_url'] = url
+            qr = self.request.GET.copy()
+            qr.pop('page', None)
+            context['filter_url'] = ('&' + qr.urlencode()) if qr else ''
 
         context['numero_res'] = len(self.object_list)
 
         return context
 
     def get(self, request, *args, **kwargs):
+        if len(request.GET.getlist('page')) > 1:
+            return HttpResponseBadRequest()
 
         r = super().get(request)