-
Notifications
You must be signed in to change notification settings - Fork 9
/
CVE-2020-26258.html
213 lines (179 loc) · 11 KB
/
CVE-2020-26258.html
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<!--
Copyright (C) 2005, 2006 Joe Walnes.
Copyright (C) 2006, 2007, 2008, 2021 XStream committers.
All rights reserved.
The software in this package is published under the terms of the BSD
style license a copy of which has been included with this distribution in
the LICENSE.txt file.
Created on 29. January 2005 by Joe Walnes
-->
<head>
<title>XStream - CVE-2020-26258</title>
<link rel="stylesheet" type="text/css" href="style.css"/>
<!-- Google analytics -->
<script src="http://www.google-analytics.com/urchin.js" type="text/javascript">
</script>
<script type="text/javascript">
_uacct = "UA-110973-2";
urchinTracker();
</script>
</head>
<body>
<div id="banner">
<a href="index.html"><img id="logo" src="logo.gif" alt="XStream"/></a>
</div>
<div id="center" class="Content2Column"> <!-- Content3Column for index -->
<div id="content">
<h1 class="FirstChild">CVE-2020-26258</h1>
<h2 id="vulnerability">Vulnerability</h2>
<p>CVE-2020-26258: A Server-Side Forgery Request can be activated unmarshalling with XStream to access data streams
from an arbitrary URL referencing a resource in an intranet or the local host.</p>
<h2 id="affected_versions">Affected Versions</h2>
<p>All versions until and including version 1.4.14 are affected running in a Java environment below Java 15, if
using the version out of the box. No user is affected, who followed the recommendation to setup
<a href="security.html#framework">XStream's security framework</a> with a whitelist.</p>
<h2 id="description">Description</h2>
<p>The processed stream at unmarshalling time contains type information to recreate the formerly written objects.
XStream creates therefore new instances based on these type information. An attacker can manipulate the processed
input stream and replace or inject objects, that result in a server-side forgery request.</p>
<h2 id="reproduction">Steps to Reproduce</h2>
<p>Create a simple HashMap and use XStream to marshal it to XML. Replace the XML with following snippet and
unmarshal it again with XStream:</p>
<div class="Source XML"><pre><map>
<entry>
<jdk.nashorn.internal.objects.NativeString>
<flags>0</flags>
<value class='com.sun.xml.internal.bind.v2.runtime.unmarshaller.Base64Data'>
<dataHandler>
<dataSource class='javax.activation.URLDataSource'>
<url>http://localhost:8080/internal/:</url>
</dataSource>
<transferFlavors/>
</dataHandler>
<dataLen>0</dataLen>
</value>
</jdk.nashorn.internal.objects.NativeString>
<string>test</string>
</entry>
</map>
</pre></div>
<div class="Source Java"><pre>XStream xstream = new XStream();
xstream.fromXML(xml);
</pre></div>
<p>As soon as the XML gets unmarshalled, the payload gets executed and the data from the URL location is collected.</p>
<p>Note, this example uses XML, but the attack can be performed for any supported format, e.g. JSON.</p>
<h2 id="impact">Impact</h2>
<p>The vulnerability may allow a remote attacker to request data from internal resources that are not publicly
available only by manipulating the processed input stream.</p>
<h2 id="workaround">Workaround</h2>
<p>As recommended, use XStream's security framework to implement a whitelist for the allowed types.</p>
<p>Users of XStream 1.4.14 who insist to use XStream default blacklist - despite that clear recommendation - can
simply add two lines to XStream's setup code:</p>
<div class="Source Java"><pre>xstream.denyTypes(new String[]{ "jdk.nashorn.internal.objects.NativeString" });
xstream.denyTypesByRegExp(new String[]{ ".*\\.ReadAllStream\\$FileStream" });
</pre></div>
<p>Users of XStream 1.4.13 who want to use XStream default blacklist can simply add three lines to XStream's setup
code:</p>
<div class="Source Java"><pre>xstream.denyTypes(new String[]{ "javax.imageio.ImageIO$ContainsFilter", "jdk.nashorn.internal.objects.NativeString" });
xstream.denyTypes(new Class[]{ java.lang.ProcessBuilder.class });
xstream.denyTypesByRegExp(new String[]{ ".*\\.ReadAllStream\\$FileStream" });
</pre></div>
<p>Users of XStream 1.4.12 to 1.4.7 who want to use XStream with a blacklist will have to setup such a list from
scratch and deny at least the following types: <em>javax.imageio.ImageIO$ContainsFilter</em>,
<em>java.beans.EventHandler</em>, <em>java.lang.ProcessBuilder</em>, <em>jdk.nashorn.internal.objects.NativeString</em>,
<em>java.lang.Void</em> and <em>void</em> and deny several types by name pattern.</p>
<div class="Source Java"><pre>xstream.denyTypes(new String[]{ "javax.imageio.ImageIO$ContainsFilter", "jdk.nashorn.internal.objects.NativeString" });
xstream.denyTypes(new Class[]{ java.lang.ProcessBuilder.class, java.beans.EventHandler.class, java.lang.ProcessBuilder.class, java.lang.Void.class, void.class });
xstream.denyTypesByRegExp(new String[]{ ".*\\$LazyIterator", "javax\\.crypto\\..*", ".*\\.ReadAllStream\\$FileStream" });
</pre></div>
<p>Users of XStream 1.4.6 or below can register an own converter to prevent the unmarshalling of the currently
know critical types of the Java runtime. It is in fact an updated version of the workaround for CVE-2013-7285:</p>
<div class="Source Java"><pre>xstream.registerConverter(new Converter() {
public boolean canConvert(Class type) {
return type != null && (type == java.beans.EventHandler.class || type == java.lang.ProcessBuilder.class
|| type.getName().equals("javax.imageio.ImageIO$ContainsFilter") || type.getName().equals("jdk.nashorn.internal.objects.NativeString")
|| type == java.lang.Void.class || void.class || Proxy.isProxy(type)
|| type.getName().startsWith("javax.crypto.") || type.getName().endsWith("$LazyIterator") || type.getName().endsWith(".ReadAllStream$FileStream"));
}
public Object unmarshal(HierarchicalStreamReader reader, UnmarshallingContext context) {
throw new ConversionException("Unsupported type due to security reasons.");
}
public void marshal(Object source, HierarchicalStreamWriter writer, MarshallingContext context) {
throw new ConversionException("Unsupported type due to security reasons.");
}
}, XStream.PRIORITY_VERY_HIGH);
</pre></div>
<h2 id="credits">Credits</h2>
<p>钟潦贵 (Liaogui Zhong) found and reported the issue to XStream and provided the required information to reproduce it.</p>
<br/>
</div>
</div>
<div class="SidePanel" id="left">
<div class="MenuGroup">
<h1>Software</h1>
<ul>
<li><a href="index.html">About XStream</a></li>
<li><a href="news.html">News</a></li>
<li><a href="changes.html">Change History</a></li>
<li><a href="security.html">Security Aspects</a></li>
<li><a href="versioning.html">About Versioning</a></li>
</ul>
</div>
<div class="MenuGroup">
<h1>Evaluating XStream</h1>
<ul>
<li><a href="tutorial.html">Two Minute Tutorial</a></li>
<li><a href="license.html">License</a></li>
<li><a href="download.html">Download</a></li>
<li><a href="references.html">References</a></li>
<li><a href="benchmarks.html">Benchmarks</a></li>
<li><a href="https://www.openhub.net/p/xstream">Code Statistics</a></li>
</ul>
</div>
<div class="MenuGroup">
<h1>Using XStream</h1>
<ul>
<li><a href="architecture.html">Architecture Overview</a></li>
<li><a href="graphs.html">Object references</a></li>
<li><a href="manual-tweaking-output.html">Tweaking the Output</a></li>
<li><a href="converters.html">Converters</a></li>
<li><a href="faq.html">Frequently Asked Questions</a></li>
<li><a href="mailing-lists.html">Mailing Lists</a></li>
<li><a href="issues.html">Reporting Issues</a></li>
</ul>
</div>
<div class="MenuGroup">
<h1>Javadoc</h1>
<ul>
<li><a href="javadoc/index.html">XStream Core</a></li>
<li><a href="hibernate-javadoc/index.html">Hibernate Extensions</a></li>
<li><a href="jmh-javadoc/index.html">JMH Module</a></li>
</ul>
</div>
<div class="MenuGroup">
<h1>Tutorials</h1>
<ul>
<li><a href="tutorial.html">Two Minute Tutorial</a></li>
<li><a href="alias-tutorial.html">Alias Tutorial</a></li>
<li><a href="annotations-tutorial.html">Annotations Tutorial</a></li>
<li><a href="converter-tutorial.html">Converter Tutorial</a></li>
<li><a href="objectstream.html">Object Streams Tutorial</a></li>
<li><a href="persistence-tutorial.html">Persistence API Tutorial</a></li>
<li><a href="json-tutorial.html">JSON Tutorial</a></li>
<li><a href="http://www.studytrails.com/java/xml/xstream/xstream-introduction.jsp">StudyTrails</a></li>
</ul>
</div>
<div class="MenuGroup">
<h1>Developing XStream</h1>
<ul>
<li><a href="how-to-contribute.html">How to Contribute</a></li>
<li><a href="team.html">Development Team</a></li>
<li><a href="repository.html">Source Repository</a></li>
<li><a href="https://travis-ci.org/x-stream/xstream/branches">Continuous Integration</a></li>
</ul>
</div>
</div>
</body>
</html>