policies/expression: validate syntax on form clean

passbook/policies/expression/evaluator.py

@@ -56,10 +56,8 @@ class Evaluator:
         kwargs["pb_is_group_member"] = Evaluator.jinja2_func_is_group_member
         kwargs["pb_logger"] = get_logger()
         kwargs["requests"] = Session()
+        kwargs["pb_is_sso_flow"] = request.context.get(PLAN_CONTEXT_SSO, False)
         if request.http_request:
-            kwargs["pb_is_sso_flow"] = request.http_request.session.get(
-                PLAN_CONTEXT_SSO, False
-            )
             kwargs["pb_client_ip"] = (
                 get_client_ip(request.http_request) or "255.255.255.255"
             )

passbook/policies/expression/forms.py

@@ -3,6 +3,7 @@
 from django import forms
 
 from passbook.admin.fields import CodeMirrorWidget
+from passbook.policies.expression.evaluator import Evaluator
 from passbook.policies.expression.models import ExpressionPolicy
 from passbook.policies.forms import GENERAL_FIELDS
 
@@ -12,6 +13,12 @@ class ExpressionPolicyForm(forms.ModelForm):
 
     template_name = "policy/expression/form.html"
 
+    def clean_expression(self):
+        """Test Jinja2 Syntax"""
+        expression = self.cleaned_data.get("expression")
+        Evaluator().validate(expression)
+        return expression
+
     class Meta:
 
         model = ExpressionPolicy