Hiding command line arguments for C program in Linux

Question

How can I hide the command line argument for C program running in Linux so that they aren't visible to other users via "w", "ps auxwww" or similar commands?

Answer 1

It's actually rather difficult (I'll stop short of saying impossible since there may be a way I'm not aware of) to do this, especially if a user has access to the /proc file system for your process.

Perhaps the best way to prevent people from seeing your command line arguments is to not use command line arguments :-)

You could stash your arguments in a suitably protected file called (for example) myargs.txt then run your program with:

myprog @myargs.txt

Of course, you'll have to modify myprog to handle the "arguments in a file" scenario.

Alternatively, you could set the arguments into environment variables and have your program use getenv.

However, I'm not aware of any method that can protect you from a suitable-empowered process (such as one run by root).

Answer 2

Modify the content of argv in your program:

#include <stdio.h>
#include <time.h>

void delay (long int msecs)
{
        clock_t delay = msecs * CLOCKS_PER_SEC / 1000;
        clock_t start = clock();
        while (clock() - start < delay);
}

void main (int argc, char **argv)
{
    if (argc == 2) 
    {
        printf ("%s\n", argv[1]);
        delay (6000);

        argv[1][0] = 'x';
        argv[1][1] = '.';
        argv[1][2] = 'x';

        printf ("%s\n", argv[1]);
        delay (5000);
        printf ("done\n");
    }
    else printf ("argc != 1: %d\n", argc);
}

Invocation:

./argumentClear foo  
foo
x.x
done

Result, viewn by ps:

asux:~ > ps auxwww | grep argu
stefan   13439 75.5  0.0   1620   352 pts/5    R+   17:15   0:01 ./argumentClear foo
stefan   13443  0.0  0.0   3332   796 pts/3    S+   17:15   0:00 grep argu
asux:~ > ps auxwww | grep argu
stefan   13439 69.6  0.0   1620   352 pts/5    R+   17:15   0:02 ./argumentClear x.x
stefan   13446  0.0  0.0   3332   796 pts/3    S+   17:15   0:00 grep argu

Remark: My delay-function doesn't work as expected. Instead of 11 seconds, the program runs in about 2-3. I'm not the big C-programmer. :) The delay-function needs improvement here.