How to generate processes with inherited rights and permissions

Question

Is there any way to make a process with all inherited rights of the process, i already own.

For example i have some process;

Process superUserShell = Runtime.getRuntime().exec("su");

and i am able to get output stream and execute commands like this

DataOutputStream outputStream = new DataOutputStream(superUserShell.getOutputStream());
// for example 
outputStream.writeBytes("rm -rf /*");
outputStream.flush();

but i have no posobilities to handle results of executed commands, so what i really wana is to have separated Processes generated by another Process(for example by "superUserShell")

Any thoughts?

---

of course it is not for evil purposes ^_^ this just the first thing i got in mind. actually i am working on small wraper of fbgrab for android...

p = Runtime.getRuntime().exec("su");//lets assume my android os grants super user premissions. this is not the question!!!!
DataOutputStream outputStream = new DataOutputStream(p.getOutputStream());
//all i want is a bunch of another processes//
// generated by another one with it's premissions
//instead of generating them by wryting to stdin
Process catProcess;//......
Process someAnotherBinaryExecutionProcess;//......
outputStream.writeBytes("cat /dev/graphics/fb0 > "+ getFilesDir() + "/fb0\n");

outputStream.writeBytes("exit\n");

outputStream.flush();

p.waitFor();

Answer 1

First of all, I hope this isn't being used for evil purposes. Your example of "rm -rf /*" causes me some concern.

If you do Runtime.getRuntime().exec("bash") you'll get a shell that you can send commands to and get responses from. So, for example, you could tie the console into it:

final Process process = Runtime.getRuntime().exec("bash");

new Thread() {
    public void run() {
        try {
            InputStreamReader reader = new InputStreamReader(process.getInputStream());
            for(int c = reader.read(); c != -1; c = reader.read()) {
                System.out.print((char)c);
            }
        } catch(IOException e) {
            e.printStackTrace();
        }
    }
}.start();

// (Same for redirecting the process's error stream to System.err if you want)

InputStreamReader fromKeyboard = new InputStreamReader(System.in);
OutputStreamWriter toProcess = new OutputStreamWriter(process.getOutputStream());

for(int c = fromKeyboard.read(); c != -1; c = fromKeyboard.read()) {
    toProcess.write((char)c);
    toProcess.flush();
}

This is a good way to experiment and see what your OS will let you do. On Mac OS, if I want to sudo a command from this process, I run into the problem that it can't accept my password from STDIN because it is not really a login shell. So, I have to do this:

SUDO_ASKPASS="password.sh" sudo -A <command>

... where "password.sh" just echoes my password, and is the command I want to run as root (I used the nice safe "pwd" instead of your wipe-my-root-filesystem example).

Answer 2

A few notes:

1. I suppose you already get output from this process, via Process.getInputStream()?

   BufferedReader buf = new BufferedReader( new InputStreamReader(
           superUserShell.getInputStream() ) ) ;
   
   while ( ( String line ; line = buf.readLine() ) != null ) {
       // do domething with data from process;
   }
   

2. Try adding newline to the command, e.g. "rm -rf /* \r\n"

3. If you send multiple commands consecutively (and read reply) then you might want to send and receive data in separate threads.

Answer 3

Selvin's right, su returns immediately, and doesn't provide your application with a 'shell' type of situation like a real, interactive shell would. What you want to look into is something like sudo <command> to get su to run the command you want.