Unable to execute a simple “whoami” unix command using java program on the server

Question

Im facing this strange issue of not being able to execute a simple "whoami" unix command on a AIX server. I have a webapplication that is deployed on an AIX server. Now I want to see under which WAS user my webapplication is currently running. So I added the below code:

    public String whoami() throws Exception {
        Process p = Runtime.getRuntime().exec("whoami");
        BufferedReader in = new BufferedReader(new InputStreamReader(p.getInputStream()));
        String line;
        String output = "";

        while ((line = in.readLine()) != null) {
            //System.out.println(line);
            output += line;
        }
        in.close();
        p.destroy();
        return output;
    }
}

The above code is added in a jar file which is referred by a JSP. The JSP has to receive the output of the code above and it displays the WAS User name. But when i deploy the webapplication on the server and try to observe the output, im getting an error message like

Error 500: access denied (java.io.FilePermission <> execute)

However, When I remove the above code and run my webapplication, everything runs fine. What wron am i doing here. Did I miss doing anything? Please help. This is the first time im working on UNIX

Answer 1

It looks like your web server has been configured with a Java security policy that prohibits executing external applications.

See http://java.sun.com/developer/onlineTraining/Programming/JDCBook/appA.html for information about Java Security Policies, and the documentation for your web server.

You will need to supply (or edit) a policy file to contain something like:

grant {
  permission java.io.FilePermission 
    "/usr/bin/whoami", "execute";
};

Answer 2

Just out of curiosity Have you considered to use:

user.name 

System property in Java?

Answer 3

AFAIK whoami is a shell command and Runtime#exec() executes programs only.

you can try Runtime.getRuntime().exec(new String[]{"sh","-c","whoami"}) to call sh and let it execute whoami

another thing: do you need to destroy the process after reading?

Answer 4

You can use the ProcessBuilder class instead of getRuntime().exec("whoami") .

Here is sample code

import java.io.*;
import java.util.*;

public class DoProcessBuilder {

    public static void main(String args[]) throws IOException {
        if (args.length <= 0) {
            System.err.println("Need command to run");
            System.exit(-1);
        }
        Process process = new ProcessBuilder(args).start();
        InputStream is = process.getInputStream();
        InputStreamReader isr = new InputStreamReader(is);
        BufferedReader br = new BufferedReader(isr);
        String line;
        System.out.printf("Output of running &#37;s is:", Arrays.toString(args));
        while ((line = br.readLine()) != null) {
            System.out.println(line);
        }
    }
}