Perl Net::SMTP force auth method - perl

Question

I'm trying to send mail using Perl Net::SMTP with auth method other than default picked GSSAPI (e.g. force PLAIN).
I have tried:
my $smtp;
$smtp = Net::SMTP::SSL->new($host, Port => $port);
$smtp->auth($user, $passwd);
and replacing last line with:
$smtp->auth('PLAIN', $user, $passwd);
or passing Authen::SASL object with selected mechanism to $smtp->auth(). None of the above work - debug (and mail server logs) says it still tries AUTH GSSAPI.
Does anyone know how to correctly force auth method in Net::SMTP?
My Perl version is 5.20.2-3+deb8u8 from Debian 8, packages version:
Net::SMTP - 2.33
Net::SMTP::SSL - 1.01
Authen::SASL - 2.16

Answer 1

Net::SMTP version above 3.00
Net::SMTP above version 3:
* does not overwrite mechanism in Authen::SASL parameter of auth method
* supports STARTTLS and smtps
use Net::SMTP;
use Authen::SASL;
my($host, $user, $pass) = ('...','...','...'); # fill correct data
my $smtp = Net::SMTP->new( $host, SSL=>1, Debug => 1 ); # SSL=>1 - use smtps
$smtp->auth(
Authen::SASL->new(
mechanism => 'PLAIN LOGIN',
callback => { user => $user, pass => $passwd }
)
);

Answer 2

Net::SMTP version below 3.00
Net::SMTP version 2.31_1 (newest pre 3.00 in libnet) overwrites mechanism in Authen::SASL with mechanism listed in EHLO reply. Below please find my UGLY fix.
use Net::SMTP::SSL;
use Authen::SASL;
my ( $host, $port, $user, $pass ) = ( '...', '...', '...', '...' ); # fill correct data
my $smtp = Net::SMTP::SSL->new( $host, Port => $port, Debug => 1 );
my $auth = Authen::SASL->new(
mechanism => 'PLAIN LOGIN',
callback => { user => $user, pass => $passwd }
);
{
no warnings 'redefine';
my $count;
local *Authen::SASL::mechanism = sub {
my $self = shift;
# Fix Begin
# ignore first setting of mechanism
if ( !$count++ && #_ && $Net::SMTP::VERSION =~ /^2\./ ) {
return;
}
# Fix End
#_
? $self->{mechanism} = shift
: $self->{mechanism};
};
$smtp->auth($auth);
}
Code requiring fixing - Net::SMTP 2.31_1 from libnet 1.22_01
sub auth {
my ($self, $username, $password) = #_;
...
my $mechanisms = $self->supports('AUTH', 500, ["Command unknown: 'AUTH'"]);
return unless defined $mechanisms;
my $sasl;
if (ref($username) and UNIVERSAL::isa($username, 'Authen::SASL')) {
$sasl = $username;
$sasl->mechanism($mechanisms); # <= HERE Authen::SASL mechanism overwrite
}