=head1 NAME

kpwvalid - Checks quality of new password

=head1 SYNOPSIS

=for html
<div class="synopsis">

B<kpwvalid>

=for html
</div>

=head1 DESCRIPTION

The B<kpwvalid> command checks the quality of a new password passed to it
from the B<kpasswd> or B<kas setpassword> command. It is optional. If it
exists, it must reside in the same AFS directory as the binaries for the
B<kpasswd> and B<kas> command suites (create a symbolic link from the
client machine's local disk to this directory). The directory's ACL must
extend the C<a> (administer) and C<w> (write) permissions to the
system:administrators group only. These requirements prevent unauthorized
users from substituting a spurious B<kpwvalid> binary.

The AFS distribution includes an example B<kpwvalid> program that checks
that the password is at least eight characters long; the code for it
appears in L<EXAMPLES> below.

The script or program must accept a sequence of password strings, one per
line, on the standard input stream. The first is the current password and
is ignored. Each subsequent string is a candidate password to be
checked. The program must write the following to the standard output
stream for each one:

=over 4

=item *

C<0> (zero) and a newline character to indicate that the password is
acceptable.

=item *

A non-zero decimal number and a newline character to indicate that the
password is not acceptable.

=back

Further, it must write any error messages only to the standard error
stream, not to the standard output stream.

=head1 EXAMPLES

The following example program, included in the AFS distribution, verifies
that the requested password includes eight or more characters.

   #include <stdio.h>
   /* prints 0 if the password is long enough, otherwise non-zero */
   main()
   {
   char oldpassword[512];
   char password[512];

   if (fgets(oldpassword, 512, stdin))
      while (fgets(password, 512, stdin)) {
         if (strlen(password) > 8) { /* password includes a newline */
            fputs("0\n",stdout);
            fflush(stdout);
         }
         else {
            fputs("Passwords must contain at least 8 characters.\n",
                  stderr);
            fputs("1\n",stdout);
            fflush(stdout);
         }
   return 0;
   }


=head1 SEE ALSO

L<kas_setpassword(8)>,
L<kpasswd(1)>

=head1 COPYRIGHT

IBM Corporation 2000. <http://www.ibm.com/> All Rights Reserved.

This documentation is covered by the IBM Public License Version 1.0.  It was
converted from HTML to POD by software written by Chas Williams and Russ
Allbery, based on work by Alf Wachsmann and Elizabeth Cassell.
