csrf-error view

src/zope/formlib/configure.zcml

@@ -13,16 +13,23 @@
       permission="zope.Public"
       template="widget_macros.pt"
       />
-  
+
   <adapter factory=".form.default_page_template" name="default" />
   <adapter factory=".form.default_subpage_template" name="default" />
   <adapter factory=".form.render_submit_button" name="render" />
 
   <!-- Error view for 'Invalid' -->
   <adapter
-      factory=".errors.InvalidErrorView"
-      permission="zope.Public"
-      />
+    factory=".errors.InvalidErrorView"
+    permission="zope.Public"
+  />
+
+  <!-- Error view for 'CSRF protection errors' -->
+  <adapter
+    factory=".errors.InvalidCSRFTokenErrorView"
+    provides="zope.publisher.interfaces.browser.IBrowserPage"
+    permission="zope.Public"
+  />
 
   <!-- For security proxied views -->
   <class class=".form.Widgets">
@@ -295,7 +302,7 @@
       permission="zope.Public"
       />
 
-  <!-- 
+  <!--
 
        Need to repeat the above for Sequence to avoid being overridden by a
        DAV widget.  This suggests that we should be getting something
@@ -412,7 +419,7 @@
       factory=".widgets.ChoiceCollectionInputWidget"
       permission="zope.Public"
       />
-  
+
   <!-- FrozenSet + Choice -->
   <adapter
       for="zope.schema.interfaces.IFrozenSet
@@ -462,7 +469,7 @@
       factory=".source.SourceMultiSelectSetWidget"
       permission="zope.Public"
       />
-  
+
   <adapter
       for="zope.schema.interfaces.IFrozenSet
            zope.schema.interfaces.IIterableSource
@@ -501,7 +508,7 @@
       factory=".widgets.MultiSelectSetWidget"
       permission="zope.Public"
       />
-      
+
   <adapter
       for="zope.schema.interfaces.IFrozenSet
            zope.schema.interfaces.IVocabularyTokenized
@@ -573,7 +580,7 @@
       factory=".source.SourceSequenceDisplayWidget"
       permission="zope.Public"
       />
-  
+
     <adapter
       for="zope.schema.interfaces.IAbstractSet
            zope.schema.interfaces.ISource

src/zope/formlib/errors.py

@@ -20,8 +20,11 @@
 from zope.i18n import Message
 from zope.i18n import translate
 
-from zope.formlib.interfaces import IWidgetInputErrorView
 from zope.publisher.interfaces.browser import IBrowserRequest
+from zope.publisher.interfaces.browser import IBrowserPage
+from zope.publisher.browser import BrowserPage
+from zope.formlib.interfaces import IWidgetInputErrorView
+from zope.formlib.interfaces import IInvalidCSRFTokenError
 
 
 @implementer(IWidgetInputErrorView)
@@ -45,3 +48,23 @@ def snippet(self):
         if isinstance(msg, Message):
             msg = translate(msg, context=self.request)
         return u'<span class="error">%s</span>' % escape(msg)
+
+
+@implementer(IBrowserPage)
+@adapter(IInvalidCSRFTokenError, IBrowserRequest)
+class InvalidCSRFTokenErrorView(BrowserPage):
+
+    def update(self):
+        self.request.response.setStatus(403)
+        self.request.response.setHeader(
+            'Expires', 'Jan, 1 Jan 1970 00:00:00 GMT')
+        self.request.response.setHeader(
+            'Cache-Control', 'no-store, no-cache, must-revalidate')
+        self.request.response.setHeader(
+            'Pragma', 'no-cache')
+
+    def render(self):
+        msg = self.context.doc
+        if isinstance(msg, Message):
+            msg = translate(msg, context=self.request)
+        return escape(msg)

src/zope/formlib/form.py

@@ -44,7 +44,7 @@
 from zope.formlib.interfaces import IInputWidget, IDisplayWidget
 from zope.formlib.interfaces import WidgetsError, MissingInputError
 from zope.formlib.interfaces import InputErrors, WidgetInputError
-from zope.formlib.interfaces import InvalidFormError
+from zope.formlib.interfaces import InvalidFormError, InvalidCSRFTokenError
 
 from zope.formlib import interfaces
 from zope.i18nmessageid import MessageFactory
@@ -784,11 +784,11 @@ def checkToken(self):
         if cookietoken is None:
             # CSRF is enabled, so we really should get a token from the
             # cookie. We didn't get it, so this submit is invalid!
-            raise InvalidFormError('CSRF token incorrect')
+            raise InvalidCSRFTokenError(_('Invalid CSRF token'))
         if cookietoken != self.request.form.get('__csrftoken__', None):
             # The token in the cookie is different from the one in the
             # form data. This submit is invalid!
-            raise InvalidFormError('CSRF token incorrect')
+            raise InvalidCSRFTokenError(_('Invalid CSRF token'))
 
     def setUpWidgets(self, ignore_request=False):
         self.adapters = {}

src/zope/formlib/form.txt

@@ -2058,7 +2058,7 @@ If for some reason the cookie is not set, the form will raise an error::
     >>> _ = myform()   #doctest: +IGNORE_EXCEPTION_DETAIL
     Traceback (most recent call last):
     ...
-    InvalidFormError: CSRF token incorrect
+    InvalidCSRFTokenError: Invalid CSRF token
 
 As an attacker cannot read the cookie value, he can only guess the
 corresponding form value, that is hard get right, so most proably wrong::
@@ -2072,7 +2072,7 @@ corresponding form value, that is hard get right, so most proably wrong::
     >>> _ = myform()  #doctest: +IGNORE_EXCEPTION_DETAIL
     Traceback (most recent call last):
     ...
-    InvalidFormError: CSRF token incorrect
+    InvalidCSRFTokenError: Invalid CSRF token
 
 When the form value is missing altogether, the form obviously raises an error
 too::
@@ -2085,7 +2085,7 @@ too::
     >>> _ = myform()   #doctest: +IGNORE_EXCEPTION_DETAIL
     Traceback (most recent call last):
     ...
-    InvalidFormError: CSRF token incorrect
+    InvalidCSRFTokenError: Invalid CSRF token
 
 To repeat: this protection works as long as the cookie value is identical to
 the submitted form value. No state is kept on the server. We can demonstrate

src/zope/formlib/interfaces.py

@@ -31,9 +31,19 @@ def doc():
 @implementer(IInvalidFormError)
 class InvalidFormError(Exception):
     """The form submit could not be validated.
+    """
+
+class IInvalidCSRFTokenError(Interface):
+
+    def doc():
+        """The form submit could not be handled as the CSRF token is missing
+        or incorrect.
+        """
 
-    For example when the CSRF token is incorrect or does not existed
-    for "protected" form components.
+@implementer(IInvalidCSRFTokenError)
+class InvalidCSRFTokenError(InvalidFormError):
+    """The form submit could not be handled as the CSRF token is missing
+    or incorrect.
     """
 
 class IWidgetInputError(Interface):