bpo-42988: Remove the pydoc getfile feature (GH-25015) (#25066)

CVE-2021-3426: Remove the "getfile" feature of the pydoc module which
could be abused to read arbitrary files on the disk (directory
traversal vulnerability). Moreover, even source code of Python
modules can contain sensitive data like passwords. Vulnerability
reported by David Schwörer.
(cherry picked from commit 9b999479c0022edfc9835a8a1f06e046f3881048)

Co-authored-by: Victor Stinner <vstinner@python.org>

Co-authored-by: Victor Stinner <vstinner@python.org>

3 files changed, 4 insertions, 24 deletions

diff --git a/Lib/pydoc.py b/Lib/pydoc.py
index 978e4cd0ba..9677c0d046 100644
--- a/Lib/pydoc.py
+++ b/Lib/pydoc.py
@@ -2348,9 +2348,6 @@ def _url_handler(url, content_type="text/html"):
 %s</head><body bgcolor="#f0f0f8">%s<div style="clear:both;padding-top:.5em;">%s</div>
 </body></html>''' % (title, css_link, html_navbar(), contents)
 
-        def filelink(self, url, path):
-            return '<a href="getfile?key=%s">%s</a>' % (url, path)
-
 
     html = _HTMLDoc()
 
@@ -2436,19 +2433,6 @@ def _url_handler(url, content_type="text/html"):
             'key = %s' % key, '#ffffff', '#ee77aa', '<br>'.join(results))
         return 'Search Results', contents
 
-    def html_getfile(path):
-        """Get and display a source file listing safely."""
-        path = urllib.parse.unquote(path)
-        with tokenize.open(path) as fp:
-            lines = html.escape(fp.read())
-        body = '<pre>%s</pre>' % lines
-        heading = html.heading(
-            '<big><big><strong>File Listing</strong></big></big>',
-            '#ffffff', '#7799ee')
-        contents = heading + html.bigsection(
-            'File: %s' % path, '#ffffff', '#ee77aa', body)
-        return 'getfile %s' % path, contents
-
     def html_topics():
         """Index of topic texts available."""
 
@@ -2540,8 +2524,6 @@ def _url_handler(url, content_type="text/html"):
                 op, _, url = url.partition('=')
                 if op == "search?key":
                     title, content = html_search(url)
-                elif op == "getfile?key":
-                    title, content = html_getfile(url)
                 elif op == "topic?key":
                     # try topics first, then objects.
                     try:
diff --git a/Lib/test/test_pydoc.py b/Lib/test/test_pydoc.py
index 198cea93eb..baad8212c5 100644
--- a/Lib/test/test_pydoc.py
+++ b/Lib/test/test_pydoc.py
@@ -1049,18 +1049,12 @@ class PydocUrlHandlerTest(PydocBaseTest):
             ("topic?key=def", "Pydoc: KEYWORD def"),
             ("topic?key=STRINGS", "Pydoc: TOPIC STRINGS"),
             ("foobar", "Pydoc: Error - foobar"),
-            ("getfile?key=foobar", "Pydoc: Error - getfile?key=foobar"),
             ]
 
         with self.restrict_walk_packages():
             for url, title in requests:
                 self.call_url_handler(url, title)
 
-            path = string.__file__
-            title = "Pydoc: getfile " + path
-            url = "getfile?key=" + path
-            self.call_url_handler(url, title)
-
 
 class TestHelper(unittest.TestCase):
     def test_keywords(self):
diff --git a/Misc/NEWS.d/next/Security/2021-03-24-14-16-56.bpo-42988.P2aNco.rst b/Misc/NEWS.d/next/Security/2021-03-24-14-16-56.bpo-42988.P2aNco.rst
new file mode 100644
index 0000000000..4b42dd0530
--- /dev/null
+++ b/Misc/NEWS.d/next/Security/2021-03-24-14-16-56.bpo-42988.P2aNco.rst
@@ -0,0 +1,4 @@
+CVE-2021-3426: Remove the ``getfile`` feature of the :mod:`pydoc` module which
+could be abused to read arbitrary files on the disk (directory traversal
+vulnerability). Moreover, even source code of Python modules can contain
+sensitive data like passwords. Vulnerability reported by David Schwörer.