Bug in 'auth'?

[sub-qp-smtpd]

        I'm using a modified auth plugin as supplied in 0.32. The
arguments are passed:

my ( $self, $transaction, $method, $user, $passClear, $passHash, $ticket )  = 
@_ ;

        And the test condition, there should be a match on the second
'and' pair:

    if (
        ( ( defined $passClear ) and ( $auth eq $passClear ) ) or
        ( ( defined $passHash ) and ( $passHash eq hmac_md5_hex( $ticket, $auth 
) ) )
    ) {

        Although the correct password is supplied, it ends up that
$passHash is empty (undefined):

Use of uninitialized value in subroutine entry at
/usr/lib/perl5/vendor_perl/5.8.5/Digest/HMAC.pm line 59.

        Is this something that has been corrected, and I just missed it?
For some reason, this seems very inconsistent, as many auth connections go
through fine.

        I'm basically using auth_flat_file for AUTH CRAM-MD5 and AUTH
LOGIN (it's the latter that's showing the problem right now), and a custom
password lookup.

        Thanks for any help.