package Qpsmtpd::Auth;

# See the documentation in 'perldoc docs/authentication.pod'

use strict;
use warnings;

use Qpsmtpd::Constants;

use Digest::HMAC_MD5 qw(hmac_md5_hex);
use MIME::Base64;

sub e64 {
    my ($arg) = @_;
    my $res = encode_base64($arg);
    chomp($res);
    return ($res);
}

sub SASL {

    # $DB::single = 1;
    my ($session, $mechanism, $prekey) = @_;
    my ($user, $passClear, $passHash, $ticket, $loginas);

    if ($mechanism eq 'plain') {
        ($loginas, $user, $passClear) =
          get_auth_details_plain($session, $prekey);
        return DECLINED if !$user || !$passClear;
    }
    elsif ($mechanism eq 'login') {
        ($user, $passClear) = get_auth_details_login($session, $prekey);
        return DECLINED if !$user || !$passClear;
    }
    elsif ($mechanism eq 'cram-md5') {
        ($ticket, $user, $passHash) = get_auth_details_cram_md5($session);
        return DECLINED if !$user || !$passHash;
    }
    else {
        #this error is now caught in SMTP.pm's sub auth
        $session->respond(500, "Internal server error");
        return DECLINED;
    }

    # try running the specific hooks first
    my ($rc, $msg) =
      $session->run_hooks("auth-$mechanism", $mechanism, $user, $passClear,
                          $passHash, $ticket);

    # try running the polymorphous hooks next
    if (!$rc || $rc == DECLINED) {
        ($rc, $msg) =
          $session->run_hooks("auth",     $mechanism, $user,
                              $passClear, $passHash,  $ticket);
    }

    if ($rc == OK) {
        $msg =
            uc($mechanism)
          . " authentication successful for $user"
          . ($msg ? " - $msg" : '');
        $session->respond(235, $msg);
        $session->connection->relay_client(1);
        if ($session->connection->notes('naughty')) {
            $session->log(LOGINFO, "auth success cleared naughty");
            $session->connection->notes('naughty', 0);
        }
        $session->log(LOGDEBUG, $msg);    # already logged by $session->respond

        $session->{_auth_user}      = $user;
        $session->{_auth_mechanism} = $mechanism;
        s/[\r\n].*//s for ($session->{_auth_user}, $session->{_auth_mechanism});

        return OK;
    }
    else {
        $msg =
            uc($mechanism)
          . " authentication failed for $user"
          . ($msg ? " - $msg" : '');
        $session->respond(535, $msg);
        $session->log(LOGDEBUG, $msg);    # already logged by $session->respond
        return DENY;
    }
}

sub get_auth_details_plain {
    my ($session, $prekey) = @_;

    if (!$prekey) {
        $session->respond(334, ' ');
        $prekey = <STDIN>;
    }

    my ($loginas, $user, $passClear) = split /\x0/, decode_base64($prekey);

    if (!$user) {
        if ($loginas) {
            $session->respond(535, "Authentication invalid ($loginas)");
        }
        else {
            $session->respond(535, "Authentication invalid");
        }
        return;
    }

    # Authorization ID must not be different from Authentication ID
    if ($loginas ne '' && $loginas ne $user) {
        $session->respond(535, "Authentication invalid for $user");
        return;
    }

    return ($loginas, $user, $passClear);
}

sub get_auth_details_login {
    my ($session, $prekey) = @_;

    my $user;

    if ($prekey) {
        $user = decode_base64($prekey);
    }
    else {
        $user = get_base64_response($session, 'Username:') or return;
    }

    my $passClear = get_base64_response($session, 'Password:') or return;

    return ($user, $passClear);
}

sub get_auth_details_cram_md5 {
    my ($session, $ticket) = @_;

    if (!$ticket) {    # ticket is only passed in during testing
          # rand() is not cryptographic, but we only need to generate a globally
         # unique number.  The rand() is there in case the user logs in more than
         # once in the same second, or if the clock is skewed.
        $ticket =
          sprintf('<%x.%x@%s>', rand(1000000), time(), $session->config('me'));
    }

    # send the base64 encoded ticket
    $session->respond(334, encode_base64($ticket, ''));
    my $line = <STDIN>;

    if ($line eq '*') {
        $session->respond(501, "Authentication canceled");
        return;
    }

    my ($user, $passHash) = split(/ /, decode_base64($line));
    unless ($user && $passHash) {
        $session->respond(504, "Invalid authentication string");
        return;
    }

    $session->{auth}{ticket} = $ticket;
    return ($ticket, $user, $passHash);
}

sub get_base64_response {
    my ($session, $question) = @_;

    $session->respond(334, e64($question));
    my $answer = decode_base64(<STDIN>);
    if ($answer eq '*') {
        $session->respond(501, "Authentication canceled");
        return;
    }
    return $answer;
}

sub validate_password {
    my ($self, %a) = @_;

    my ($pkg, $file, $line) = caller();
    $file = (split /\//, $file)[-1];    # strip off the path

    my $src_clear     = $a{src_clear};
    my $src_crypt     = $a{src_crypt};
    my $attempt_clear = $a{attempt_clear};
    my $attempt_hash  = $a{attempt_hash};
    my $method        = $a{method} or die "missing method";
    my $ticket        = $a{ticket} || $self->{auth}{ticket};
    my $deny          = $a{deny} || DENY;

    if (!$src_crypt && !$src_clear) {
        $self->log(LOGINFO, "fail: missing password");
        return ($deny, "$file - no such user");
    }

    if (!$src_clear && $method =~ /CRAM-MD5/i) {
        $self->log(LOGINFO, "skip: cram-md5 not supported w/o clear pass");
        return (DECLINED, $file);
    }

    if (defined $attempt_clear) {
        if ($src_clear && $src_clear eq $attempt_clear) {
            $self->log(LOGINFO, "pass: clear match");
            return (OK, $file);
        }

        if ($src_crypt && $src_crypt eq crypt($attempt_clear, $src_crypt)) {
            $self->log(LOGINFO, "pass: crypt match");
            return (OK, $file);
        }
    }

    if (defined $attempt_hash && $src_clear) {
        if (!$ticket) {
            $self->log(LOGERROR, "skip: missing ticket");
            return (DECLINED, $file);
        }

        if ($attempt_hash eq hmac_md5_hex($ticket, $src_clear)) {
            $self->log(LOGINFO, "pass: hash match");
            return (OK, $file);
        }
    }

    $self->log(LOGINFO, "fail: wrong password");
    return ($deny, "$file - wrong password");
}

# tag: qpsmtpd plugin that sets RELAYCLIENT when the user authenticates

1;