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	try to decode some malicious xml on startup; if this succeeds, then force-disable all xml-based features (primarily WebDAV) this is paranoid future-proofing against unanticipated changes in future versions of python, specifically if the importlib or xml.etree.ET behavior changes in a way that somehow reenables entity expansion, which (still hypothetically) would probably be caused by failing to unload the `_elementtree` c-module no past or present python versions are affected by this change
		
			
				
	
	
		
			161 lines
		
	
	
		
			5.0 KiB
		
	
	
	
		
			Python
		
	
	
	
	
	
			
		
		
	
	
			161 lines
		
	
	
		
			5.0 KiB
		
	
	
	
		
			Python
		
	
	
	
	
	
#!/usr/bin/env python3
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# coding: utf-8
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from __future__ import print_function, unicode_literals
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import re
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import unittest
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from xml.etree import ElementTree as ET
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from copyparty.dxml import BadXML, mkenod, mktnod, parse_xml
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ET.register_namespace("D", "DAV:")
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def _parse(txt):
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    try:
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        parse_xml(txt)
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        raise Exception("unsafe")
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    except BadXML:
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        pass
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class TestDXML(unittest.TestCase):
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    def test_qbe(self):
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        # allowed by default; verify that we stopped it
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        txt = r"""<!DOCTYPE qbe [
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<!ENTITY a "nice_bakuretsu">
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]>
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<l>&a;&a;&a;&a;&a;&a;&a;&a;&a;</l>"""
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        _parse(txt)
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        ET.fromstring(txt)
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    def test_ent_file(self):
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        # NOT allowed by default; should still be blocked
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        txt = r"""<!DOCTYPE ext [
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<!ENTITY ee SYSTEM "file:///bin/bash">
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]>
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<root>ⅇ</root>"""
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        _parse(txt)
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        try:
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            ET.fromstring(txt)
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            raise Exception("unsafe2")
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        except ET.ParseError:
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            pass
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    def test_ent_ext(self):
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        # NOT allowed by default; should still be blocked
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        txt = r"""<!DOCTYPE ext [
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<!ENTITY ee SYSTEM "http://example.com/a.xml">
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]>
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<root>ⅇ</root>"""
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        _parse(txt)
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    def test_dtd(self):
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        # allowed by default; verify that we stopped it
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        txt = r"""<!DOCTYPE d SYSTEM "a.dtd">
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<root>a</root>"""
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        _parse(txt)
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        ET.fromstring(txt)
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    ##
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    ## end of negative/security tests; the rest is functional
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    ##
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    def test3(self):
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        txt = r"""<?xml version="1.0" ?>
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<propfind xmlns="DAV:">
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    <prop>
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        <name/>
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        <href/>
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    </prop>
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</propfind>
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"""
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        txt = txt.replace("\n", "\r\n")
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        ET.fromstring(txt)
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        el = parse_xml(txt)
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        self.assertListEqual(
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            [y.tag for y in el.findall(r"./{DAV:}prop/*")],
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            [r"{DAV:}name", r"{DAV:}href"],
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        )
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    def test4(self):
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        txt = r"""<?xml version="1.0" encoding="utf-8" ?>
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<D:propertyupdate xmlns:D="DAV:" xmlns:Z="urn:schemas-microsoft-com:">
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    <D:set>
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        <D:prop>
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            <Z:Win32CreationTime>Thu, 20 Oct 2022 02:16:33 GMT</Z:Win32CreationTime>
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            <Z:Win32LastAccessTime>Thu, 20 Oct 2022 02:16:35 GMT</Z:Win32LastAccessTime>
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            <Z:Win32LastModifiedTime>Thu, 20 Oct 2022 02:16:33 GMT</Z:Win32LastModifiedTime>
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            <Z:Win32FileAttributes>00000000</Z:Win32FileAttributes>
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        </D:prop>
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    </D:set>
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</D:propertyupdate>"""
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        ref = r"""<?xml version="1.0" encoding="UTF-8"?>
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<D:multistatus xmlns:D="DAV:">
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    <D:response>
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        <D:href>/d1/foo.txt</D:href>
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        <D:propstat>
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            <D:prop>
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                <Win32CreationTime xmlns="urn:schemas-microsoft-com:"></Win32CreationTime>
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                <Win32LastAccessTime xmlns="urn:schemas-microsoft-com:"></Win32LastAccessTime>
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                <Win32LastModifiedTime xmlns="urn:schemas-microsoft-com:"></Win32LastModifiedTime>
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                <Win32FileAttributes xmlns="urn:schemas-microsoft-com:"></Win32FileAttributes>
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            </D:prop>
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            <D:status>HTTP/1.1 403 Forbidden</D:status>
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        </D:propstat>
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    </D:response>
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</D:multistatus>"""
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        txt = re.sub("\n +", "\n", txt)
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        root = mkenod("a")
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        root.insert(0, parse_xml(txt))
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        prop = root.find(r"./{DAV:}propertyupdate/{DAV:}set/{DAV:}prop")
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        assert prop is not None
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        assert len(prop)
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        for el in prop:
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            el.clear()
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        res = ET.tostring(prop).decode("utf-8")
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        want = """<D:prop xmlns:D="DAV:" xmlns:ns1="urn:schemas-microsoft-com:">
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<ns1:Win32CreationTime /><ns1:Win32LastAccessTime /><ns1:Win32LastModifiedTime /><ns1:Win32FileAttributes /></D:prop>
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"""
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        self.assertEqual(res, want)
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    def test5(self):
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        txt = r"""<?xml version="1.0" encoding="utf-8" ?>
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<D:lockinfo xmlns:D="DAV:">
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    <D:lockscope><D:exclusive/></D:lockscope>
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    <D:locktype><D:write/></D:locktype>
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    <D:owner><D:href>DESKTOP-FRS9AO2\ed</D:href></D:owner>
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</D:lockinfo>"""
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        ref = r"""<?xml version="1.0" encoding="utf-8"?>
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<D:prop xmlns:D="DAV:"><D:lockdiscovery><D:activelock>
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    <D:locktype><D:write/></D:locktype>
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    <D:lockscope><D:exclusive/></D:lockscope>
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    <D:depth>infinity</D:depth>
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    <D:owner><D:href>DESKTOP-FRS9AO2\ed</D:href></D:owner>
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    <D:timeout>Second-3600</D:timeout>
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    <D:locktoken><D:href>1666199679</D:href></D:locktoken>
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    <D:lockroot><D:href>/d1/foo.txt</D:href></D:lockroot>
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</D:activelock></D:lockdiscovery></D:prop>"""
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        txt = re.sub("\n +", "\n", txt)
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        lk = parse_xml(txt)
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        self.assertEqual(lk.tag, "{DAV:}lockinfo")
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        if lk.find(r"./{DAV:}depth") is None:
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            lk.append(mktnod("D:depth", "infinity"))
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        lk.append(mkenod("D:timeout", mktnod("D:href", "Second-3600")))
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        lk.append(mkenod("D:locktoken", mktnod("D:href", "56709")))
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        lk.append(mkenod("D:lockroot", mktnod("D:href", "/foo/bar.txt")))
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        lk2 = mkenod("D:activelock")
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        root = mkenod("D:prop", mkenod("D:lockdiscovery", lk2))
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        for a in lk:
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            lk2.append(a)
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        print(ET.tostring(root).decode("utf-8"))
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