source: cgi-scripts/dovecot-changepw@ 209

#!/usr/bin/perl -w
#
# $Id$
# 
# Simple CGI script to change your password, currently 'configured' 
# for dovecotpw, but could easy be ported to something else.
# 
# License: BSDLike
# Rick van der Zwet <info@rickvanderzwet.nl>

use CGI;
$q = CGI->new;

$MIN_PASSWD_LENGTH=8;

$PASSWDFILE='/usr/local/etc/dovecot.passwd';
$DOVECOTPW='/usr/local/sbin/dovecotpw';

if (! -w $PASSWDFILE || ! -x $DOVECOTPW) { 
  print $q->header(-status=>$error);
  print $q->start_html('Problems');
  print $q->h2('Not able to open internals (database or binary)');
  exit 1;
};


# Message 'buffer', entries in here will be pushed on top of form
@messages = ();


#
# Verify validity of CGI input
sub check_cgi() {
  if ($q->request_method() eq "POST") {
    if (! ($q->param('username') && $q->param('old_password') && 
        $q->param('new_password') && $q->param('verify_password'))) { 
      push(@messages, "Not all fields are provided");
      return 1;
    } 
    if ($q->param('new_password') ne $q->param('verify_password')) {
      push(@messages, 'New passwords does not match');
      return 1;
    }
    if ($q->param('new_password') eq $q->param('old_password')) {
      push(@messages, 'New password equal to old password not changing');
      return 1;
    }
    if (length($q->param('new_password')) < $MIN_PASSWD_LENGTH) {
      push(@messages, "New password to short (minimal $MIN_PASSWD_LENGTH characters)");
      return 1;
    }
  return 0;
  }
  return 1;
}


# 
# Process CGI, assuming all values are correct
sub process_cgi_for_dovecotpw() {
  my $username = $q->param('username');
  my $old_password = $q->param('old_password');
  my $new_password = $q->param('new_password');

  # XXX: Untested LOCK setup
  open(LOCK, '>> /tmp/changepw.lock');
  flock LOCK, 2;
  my $password = `$DOVECOTPW -p $old_password`;
  open(FH, "<$PASSWDFILE");
  my @users = <FH>;
  close(FH);
  # Find all lines _NOT_ matching this entry
  my @lines = grep (!/^$username:$password/, @users);
  # If we still have the same amount of lines we did not remove anything
  if ((scalar(@lines) - scalar(@users)) == 0) {
    push(@messages, "Username or password invalid");
    flock LOCK, 2;
    close(LOCK);
    return;
  }
  $password = `$DOVECOTPW -p $new_password`;
  push(@lines,"$username:$password");

  open(FH, ">$PASSWDFILE");
  print FH sort(@lines); 
  close(FH);
  push(@messages, "Password changed");
  flock LOCK, 2;
  close(LOCK);
}

# Only process if field are valid
if (check_cgi() == 0) {
 process_cgi_for_dovecotpw();
}

print $q->header;
print $q->start_html('Change Email Password');
print $q->start_center();
if (@messages) {
  print $q->h2($q->ul({-style => 'list-style-type: none'}, $q->li(@messages)));
};
print $q->start_form();
print $q->table($q->caption($q->h2('Please provide your values to change password')),
  $q->Tr([$q->td(['username', $q->textfield('username','somebody@example.org')])]),
  $q->Tr([$q->td(['old password', $q->password_field('old_password')])]),
  $q->Tr([$q->td(['new password', $q->password_field('new_password')])]),
  $q->Tr([$q->td(['verify new password', $q->password_field('verify_password')])]),
  $q->Tr([$q->td({-colspan=>2,-align=>'center'},[$q->submit('submit', 'Change Password')])])
);
print '</table>';
print $q->end_form();
print $q->end_center();
print $q->end_html;