Allow uploads up to 16 MB.

This fixes a regression due to a low Zope form memory limit of 1MB used since Plone 6.0.7.
You can use ``dos_protection`` settings in ``etc/zope.conf`` to change the limit.
See plone/Products.CMFPlone#3848 and zopefoundation/Zope#1142.

news/3848.bugfix

@@ -0,0 +1,5 @@
+Allow uploads up to 16 MB.
+This fixes a regression due to a low Zope form memory limit of 1MB used since Plone 6.0.7.
+You can use ``dos_protection`` settings in ``etc/zope.conf`` to change the limit.
+See `CMFPlone issue 3848 <https://github.com/plone/Products.CMFPlone/issues/3848>`_ and `Zope PR 1142 <https://github.com/zopefoundation/Zope/pull/1142>`_.
+@maurits

src/plone/restapi/__init__.py

@@ -1,3 +1,4 @@
+from . import patches
 from AccessControl import allow_module
 from AccessControl.Permissions import add_user_folders
 from plone.restapi.pas import plugin

src/plone/restapi/deserializer/__init__.py

@@ -4,6 +4,9 @@
 
 
 def json_body(request):
+    # TODO We should not read the complete request BODY in memory.
+    # Once we have fixed this, we can remove the temporary patches.py.
+    # See there for background information.
     try:
         data = json.loads(request.get("BODY") or "{}")
     except ValueError:

src/plone/restapi/patches.py

@@ -0,0 +1,20 @@
+# TEMPORARY patch for low form memory limit introduced in Zope 5.8.4.
+# See https://github.com/plone/Products.CMFPlone/issues/3848
+# and https://github.com/zopefoundation/Zope/pull/1180
+# Should be removed once `plone.restapi.deserializer.json_body` no longer
+# reads the complete request BODY in memory.
+from ZPublisher import HTTPRequest
+
+import logging
+
+
+logger = logging.getLogger(__name__)
+_attr = "FORM_MEMORY_LIMIT"
+_limit = getattr(HTTPRequest, _attr, None)
+if _limit and _limit == 2**20:
+    setattr(HTTPRequest, _attr, 2**24)
+    logger.info(
+        "PATCH: ZPublisher.HTTPRequest.%s is at a too low default of 1MB. "
+        "Increased it to 16MB to enable larger file uploads.",
+        _attr,
+    )