postfix-sender-login: Better hardening.

Run as a dedicated user, not ‘postfix’.

1 files changed, 7 insertions, 6 deletions

diff --git a/roles/MSA/files/usr/local/bin/postfix-sender-login.pl b/roles/MSA/files/usr/local/bin/postfix-sender-login.pl
index 374cc70..a37f872 100755
--- a/roles/MSA/files/usr/local/bin/postfix-sender-login.pl
+++ b/roles/MSA/files/usr/local/bin/postfix-sender-login.pl
@@ -1,89 +1,90 @@
 #!/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>
+# Copyright © 2017,2020 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 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 $nProc       = 2;                        # number of pre-forked servers
+my $maxRequests = 32;                       # maximum number of requests per worker
+my $POSTMASTER  = 'postmaster@fripost.org'; # returned for forbidden envelope sender addresses
 
-my $BASEDN  = 'ou=virtual,dc=fripost,dc=org';
+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/';
+my $LDAPI   = "ldapi://";
 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++) {
+    for (my $n = 0; $n < $maxRequests; $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: $!";