(should be trivial) GCC skipping arg vector conditions?

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March 10th, 2013, 08:38 PM

macaswell

Contributing User

Join Date: Jul 2010

Posts: 49

Time spent in forums: 10 h 29 m 15 sec
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(should be trivial) GCC skipping arg vector conditions?

I have a simple program that is supposed to either do its thing or, given the correct arguments, return a flag so that the parent process (a much, much more complex and advanced program...) can decide whether this process (called a cell) is safe to run, or if it's been flagged as unsafe because a proprietary virus (part of this complex process) has infected this cell and marked it with the flag 0xBADF. Btw, I say virus because precisely what it does is act as a lytic or lysogenic process which either infects a "cell," giving it the flag that says the cell could be harmful/shouldn't be loaded or executed, or injects a copy of itself into a cell process so that the cell process could itself become one of these cell checker viruses. It's confusing, but I assure you that it does not even work without this framework I've developed. Anyway, my test cell file that I want to try to change the flag on won't even correctly work anyway.

The source is:

Code:

/* 
 * cf1.c
 * cell flag to test labeling for use in VAIS and other NOXIS classes
*/

#include<stdio.h>

int main(int argc, char** argv){
  if(argv[1] == "?"){
    if(argv[2] == "CELL_FLAG"){
      return 0x5afe; // 5AFE is safe
    }
  }else{
    printf("The default CELL_FLAG for this cell is 0x5AFE.\n");
    return 0;
  }
}

The command line is:

Code:

$ gcc -o cf1 cf1.c
$ ./cf1 ? CELL_FLAG

The process should return 0x5AFE, as denoted by the mac os x (I don't know if other unix systems use $?).

But instead, it ignores the input and does it's thing.

What's goin' on here?

EDIT: Just to clarify and ease your mind, I say "virus" but it's only a modified version of Jingle Bell, from this article:
http://www.kernelthread.com/publications/security/vunix.html

March 10th, 2013, 08:48 PM

macaswell

Contributing User

Join Date: Jul 2010

Posts: 49

Time spent in forums: 10 h 29 m 15 sec
Reputation Power: 13

On another note, the same thing is happening to other processes with the argv conditions.

March 10th, 2013, 09:00 PM

macaswell

Contributing User

Join Date: Jul 2010

Posts: 49

Time spent in forums: 10 h 29 m 15 sec
Reputation Power: 13

Sorry, it was extremely trivial. I need to use strcmp()...I'm switching between languages constantly and these things are always confused. Anyway, the fixed (and more proper) source code is:

Code:

#include<stdio.h>
#include<string.h>

int main(int argc, char** argv){
  while(argc > 1){
    if(strcmp(argv[1], "?") == 0){
      if(strcmp(argv[1], "CELL_FLAG") == 0){
        return 0x5afe; // 0x5AFE is safe
      }
    }
    break;
  }

  printf("The default CELL_FLAG for this cell is 0x5AFE.\n");
  return 0;
}

(should be trivial) GCC skipping arg vector conditions?

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