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#!/usr/bin/perl -T
#----------------------------------------------------------------------
# socketmap lookup table returning the SASL login name(s) owning a given
# sender address
# Copyright © 2017 Guilhem Moulin <guilhem@fripost.org>
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program. If not, see <http://www.gnu.org/licenses/>.
#----------------------------------------------------------------------
use warnings;
use strict;
use Errno 'EINTR';
use Socket qw/PF_UNIX SOCK_STREAM SHUT_RDWR/;
use Net::LDAPI ();
use Net::LDAP::Util qw/ldap_explode_dn escape_dn_value escape_filter_value/;
use Net::LDAP::Constant qw/LDAP_NO_SUCH_OBJECT/;
use Authen::SASL ();
# clean up PATH
$ENV{PATH} = join ':', qw{/usr/bin /bin};
delete @ENV{qw/IFS CDPATH ENV BASH_ENV/};
my $nProc = 2; # number of pre-forked servers
my $POSTMASTER = 'postmaster@fripost.org'; # returned for forbidden envelope sender addresses
my $BASEDN = 'ou=virtual,dc=fripost,dc=org';
my $BUFSIZE = 65536; # try to read that many bytes at the time
my $LDAPI = 'ldapi://%2Fvar%2Fspool%2Fpostfix-msa%2Fprivate%2Fldapi/';
sub server();
# fdopen(3) the file descriptor FD
die "This service must be socket-activated.\n"
unless defined $ENV{LISTEN_PID} and $ENV{LISTEN_PID} == $$
and defined $ENV{LISTEN_FDS} and $ENV{LISTEN_FDS} == 1;
open my $S, '+<&=', 3 or die "fdopen: $!";
my @CHILDREN;
for (my $i = 0; $i < $nProc-1; $i++) {
my $pid = fork() // die "fork: $!";
if ($pid) {
push @CHILDREN, $pid;
} else {
server(); # child, never return
exit;
}
}
server();
waitpid $_ => 0 foreach @CHILDREN;
exit $?;
#############################################################################
sub server() {
for (my $n = 0; $n < 32; $n++) {
accept(my $conn, $S) or do {
next if $! == EINTR;
die "accept: $!";
};
my $reply = process_request($conn);
# encode the reply as a netstring and send it back
# https://cr.yp.to/proto/netstrings.txt
$reply = length($reply).':'.$reply.',';
my $len = length($reply);
for (my $i = 0; $i < $len;) {
my $n = syswrite($conn, $reply, $len-$i, $i) // do {
next if $! == EINTR;
warn "Can't write: $!";
last;
};
$i += $n;
}
close $conn or warn "Can't close: $!";
}
}
sub process_request($) {
my $conn = shift;
my ($buf, $offset) = (undef, 0);
# keep reading until the request length is determined
do {
my $n = sysread($conn, $buf, $BUFSIZE, $offset) // do {
next if $! == EINTR;
return "TEMP can't read: $!";
};
return "TEMP EOF" if $n == 0;
$offset += $n;
} until ($buf =~ /\A(0|[1-9][0-9]*):/);
# keep reading until the whole request is buffered
my $strlen = length("$1") + 1; # [len]":"
my $len = $strlen + $1 + 1; # [len]":"[string]","
while ($offset < $len) {
my $n = sysread($conn, $buf, $BUFSIZE, $offset) // do {
next if $! == EINTR;
return "TEMP can't read: $!";
};
return "TEMP EOF" if $n == 0;
$offset += $n;
}
# requests are of the form $name <space> $key, cf. socketmap_table(5)
my $i = index($buf, ' ', $strlen);
return "TEMP invalid input: $buf" unless $i > $strlen and substr($buf,-1) eq ',';
my $name = substr($buf, $strlen, $i-$strlen);
my $key = substr($buf, $i, -1);
return "TEMP invalid name: $name" unless $name eq 'sender_login';
$key =~ /\A(.+)@([^\@]+)\z/ or return "NOTFOUND "; # invalid sender address
my ($localpart, $domainpart) = ($1, $2);
my $ldap = Net::LDAPI::->new( $LDAPI ) //
return "TEMP couldn't create Net::LDAPI object";
$ldap->bind( undef, sasl => Authen::SASL::->new(mechanism => 'EXTERNAL') ) or
return "TEMP LDAP: couldn't bind";
my $reply = lookup_sender($ldap, $localpart, $domainpart);
$ldap->unbind();
return $reply;
}
sub lookup_sender($$$) {
my ($ldap, $l, $d) = @_;
my $filter = '(&(objectClass=FripostVirtualDomain)(fvd='.escape_filter_value($d).'))';
my $mesg = $ldap->search( base => $BASEDN, scope => 'one', deref => 'never'
, filter => $filter
, attrs => [qw/objectClass fripostOwner fripostPostmaster/]
);
return "TEMP LDAP error: ".$mesg->error() if $mesg->code;
my $entry = $mesg->pop_entry() // return "NOTFOUND "; # not a domain we know
return "TEMP LDAP error: multiple entry founds" if defined $mesg->pop_entry(); # sanity check
# domain postmasters are allowed to use any sender address
my @logins = $entry->get_value('fripostPostmaster', asref => 0);
my @owners = $entry->get_value('fripostOwner', asref => 0);
if (grep { $_ eq 'FripostVirtualAliasDomain' } $entry->get_value('objectClass', asref => 0)) {
# so are alias domain owners
push @logins, @owners;
} else {
my $dn = 'fvd='.escape_dn_value($d).','.$BASEDN;
my $filter = '(&(|(objectClass=FripostVirtualAlias)(objectClass=FripostVirtualList)(objectClass=FripostVirtualUser))(fvl='.escape_filter_value($l).'))';
my $mesg = $ldap->search( base => $dn, scope => 'one', deref => 'never'
, filter => $filter
, attrs => [qw/objectClass fripostOwner/]
);
unless ($mesg->code == 0 and defined ($entry = $mesg->pop_entry())) {
# domains owners are allowed to use any unkwown localpart as sender address
push @logins, @owners;
} else {
return "TEMP LDAP error: multiple entry founds" if defined $mesg->pop_entry(); # sanity check
if (grep { $_ eq 'FripostVirtualUser' } $entry->get_value('objectClass', asref => 0)) {
push @logins, $entry->dn();
} else {
# alias/list owners can use the address as sender, and so are the domains owners
push @logins, @owners, $entry->get_value('fripostOwner', asref => 0);
}
}
}
# convert DNs to SASL login names
my %logins;
foreach my $dn (@logins) {
next unless defined $dn;
$dn = ldap_explode_dn($dn, casefold => 'lower');
next unless defined $dn and $#$dn == 4;
my $l = $dn->[0]->{fvl} // next;
my $d = $dn->[1]->{fvd} // next;
$logins{$l.'@'.$d} = 1;
}
# if the entry is found in LDAP but doesn't have an owner, only
# $POSTMASTER is allowed to use it as sender address
my $reply = %logins ? join(',', keys %logins) : $POSTMASTER;
return "OK $reply";
}
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