#!/usr/bin/perl -w

my $benutzername = "test";
my $passwordold = "password";
my $passwordnew = "freeSt19"; 


$pwd = (getpwnam($benutzername))[1];

#check, if the user knows his old password: 
if (crypt($passwordold, $pwd) ne $pwd) {
	die "Sorry...\n";
} else {
	print "ok\n";
}


my $cryptedShadowString = `echo "$passwordnew"|openssl passwd -1 -stdin`;
chomp($cryptedShadowString);


my @Zeilen = ("");
open(DATA, "</etc/shadow") || die "Datei mit E-Mails nicht gefunden\n";
while(<DATA>)
 {
  push(@Zeilen,$_);
 }
close(DATA);


#Write the new shadow-file
open(SHADOW, ">/etc/shadow");
for(@Zeilen){
	if( $_ =~ m/^$benutzername/){
		my @pwField = split( /:/, $_);
		$pwField[1] = $cryptedShadowString;
		print SHADOW $pwField[0].":".$pwField[1].":".$pwField[2].":".$pwField[3].":".$pwField[4].":".$pwField[5].":".$pwField[6].":".$pwField[7].":".$pwField[8];
		
	}else{
		print SHADOW $_;
	}	

}
close(SHADOW);

$mode = 0640;
chmod $mode, "/etc/shadow";
`chown root /etc/shadow`;
`chgrp shadow /etc/shadow`;