Lab Help Please With Linux C Progam Race Condition

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Someone please help me with my lab! I have a lab where I have to use this SeedUbuntu virtual machine for a race condition vulnerability. There is C program that I need to utilize to create the attack so I can access the shadow file. Here is the link to the lab with the programs and PDF information: http://ift.tt/1f5pAYl What I am confused about is exactly how to approach this. I can compile and run the vulp.c program and the shell script in seperate terminals but what do I do next? I know I need symbolic links but where does all this come into play? I also increased the length of delay by a lot so I would have more time. Please help me understand this step by step. I'm so fascinated by it but I want to get it right!

/*  vulp.c  */

#include <stdio.h>
#include<unistd.h>

#define DELAY 10000

int main()
{
   char * fn = "/tmp/XYZ";
   char buffer[60];
   FILE *fp;
   long int  i;

   /* get user input */
   scanf("%50s", buffer );

   if(!access(fn, W_OK)){
       /* simulating delay */
        for (i=0; i < DELAY; i++){
           int a = i^2; 
        }

        fp = fopen(fn, "a+");
        fwrite("\n", sizeof(char), 1, fp);
        fwrite(buffer, sizeof(char), strlen(buffer), fp);
        fclose(fp);
   }
   else printf("No permission \n");
}

asked 1 min ago

user3294617

4