ctfdefcon

gistfile1.c

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>

typedef struct _llist {
   struct _llist *next;
   uint32_t tag;
   char data[100];
}llist;

char *answer;
//function pointer
char *(*func)();
llist *head;

char* userBuf(llist* p)
{
		//holds address to p
	llist* nextp = p;
	char* d;
	//traverse llist p
	while(1){
		if(nextp->tag == 0x41414100){
			//tag matches magic tag
			//not sure if necessary but lets replace address of p with nextp, holding current tag/data
			p = nextp;
			//return the data at this index
			d = nextp->data;
		}else{
			//incrmement to next item in list
			nextp = nextp->next;
		}
	}
	return d;
}

void send_string(answer){
	printf("The answer is: %s", answer);
}

 int main(int argc, char* argv[])
 {
 	func = (char *(*)(llist *))userBuf;
 	answer = (char *)(*func)(head);
 	send_string(answer);

 	exit(0);
 }