From 223e501fb9c2b6ae21b96054e20c4c31d94a5d96 Mon Sep 17 00:00:00 2001
From: Christian Heimes <christian@python.org>
Date: Mon, 24 Sep 2018 19:21:12 +0200
Subject: [PATCH] bpo-34791: xml package obeys ignore env flags (GH-9544)

The xml.sax and xml.dom.domreg modules now obey
sys.flags.ignore_environment.

Signed-off-by: Christian Heimes <christian@python.org>



https://bugs.python.org/issue34791
---
 Lib/xml/dom/domreg.py                                         | 4 +++-
 Lib/xml/sax/__init__.py                                       | 2 +-
 .../next/Security/2018-09-24-18-49-25.bpo-34791.78GmIG.rst    | 3 +++
 3 files changed, 7 insertions(+), 2 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Security/2018-09-24-18-49-25.bpo-34791.78GmIG.rst

diff --git a/Lib/xml/dom/domreg.py b/Lib/xml/dom/domreg.py
index 8c3d901acb0..69c17eebb26 100644
--- a/Lib/xml/dom/domreg.py
+++ b/Lib/xml/dom/domreg.py
@@ -6,6 +6,8 @@ registerDOMImplementation should be imported from xml.dom."""
 # should be published by posting to xml-sig@python.org, and are
 # subsequently recorded in this file.
 
+import sys
+
 well_known_implementations = {
     'minidom':'xml.dom.minidom',
     '4DOM': 'xml.dom.DOMImplementation',
@@ -55,7 +57,7 @@ def getDOMImplementation(name=None, features=()):
         return mod.getDOMImplementation()
     elif name:
         return registered[name]()
-    elif "PYTHON_DOM" in os.environ:
+    elif not sys.flags.ignore_environment and "PYTHON_DOM" in os.environ:
         return getDOMImplementation(name = os.environ["PYTHON_DOM"])
 
     # User did not specify a name, try implementations in arbitrary
diff --git a/Lib/xml/sax/__init__.py b/Lib/xml/sax/__init__.py
index ef67ae67a6b..13f6cf58d0d 100644
--- a/Lib/xml/sax/__init__.py
+++ b/Lib/xml/sax/__init__.py
@@ -58,7 +58,7 @@ if _false:
     import xml.sax.expatreader
 
 import os, sys
-if "PY_SAX_PARSER" in os.environ:
+if not sys.flags.ignore_environment and "PY_SAX_PARSER" in os.environ:
     default_parser_list = os.environ["PY_SAX_PARSER"].split(",")
 del os
 
diff --git a/Misc/NEWS.d/next/Security/2018-09-24-18-49-25.bpo-34791.78GmIG.rst b/Misc/NEWS.d/next/Security/2018-09-24-18-49-25.bpo-34791.78GmIG.rst
new file mode 100644
index 00000000000..afb59f8cb0e
--- /dev/null
+++ b/Misc/NEWS.d/next/Security/2018-09-24-18-49-25.bpo-34791.78GmIG.rst
@@ -0,0 +1,3 @@
+The xml.sax and xml.dom.domreg no longer use environment variables to
+override parser implementations when sys.flags.ignore_environment is set by
+-E or -I arguments.