[R1] Hewlett Packard Network Automation RPCServlet Arbitrary Code Execution

HP Network Automation (HP NA) software, available for Windows or Linux, "automates the complete operational lifecycle of network devices from provisioning to policy-based change management, compliance, and security administration." Within HP NA, the RPCServlet or com.rendition.web.servlets.RpcServlet.class is an HTTP endpoint that can be invoked via GET or POST requests to the NA admin server at https://[target]/call. The sole purpose of the RPCServlet appears to be the invocation of arbitrary static functions by the client. This can be quite dangerous, but the servlet restricts access to specific IP addresses:

1. Two addresses are hardcoded into the servlet to always have access: 127.0.0.1 and 0:0:0:0:0:0:0:1 (aka localhost).
2. The “gateway/mesh/host” address in the configuration file is allowed access. By default, this value is not set.
3. All addresses in the “rpc/allowed_ips” configuration option. As far as we can tell this doesn’t even exist in the configuration by default.

So by default, the RPCServlet will only process requests from localhost. That prevents full-on remote code execution, but opens the door for phishing goodness. Similar to recent vulnerabilities found by Tavis Ormandy, if an attacker can get a user with HP NA installed on their machine to open a crafted webpage then the attacker can access RPCServlet and execute arbitrary commands. This vector is also exploitable via deserialization attacks. Two specific libraries are useful here: Commons-Collections and Commons-BeanUtils. We can leverage these libraries to create serialized objects to eventually execute Runtime.getRuntime().exec().