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authorGuilhem Moulin <guilhem@fripost.org>2017-05-31 21:42:32 +0200
committerGuilhem Moulin <guilhem@fripost.org>2017-06-01 01:09:00 +0200
commit6e39bad3fbe75b88fca4c2e2aad8eb51af14b1be (patch)
tree87898c1653a36f1b23efbef55d6f876d8bc83444 /roles/MSA/files/usr/local
parente136d3edbdb6749d4559939dc9fcbc11d166e34c (diff)
Don't let authenticated client use arbitrary sender addresses.
The following policy is now implemented: * users can use their SASL login name as sender address; * alias and/or list owners can use the address as envelope sender; * domain postmasters can use arbitrary sender addresses under their domains; * domain owners can use arbitrary sender addresses under their domains, unless it is also an existing account name; * for known domains without owner or postmasters, other sender addresses are not allowed; and * arbitrary sender addresses under unknown domains are allowed.
Diffstat (limited to 'roles/MSA/files/usr/local')
-rwxr-xr-xroles/MSA/files/usr/local/bin/postfix-sender-login.pl171
1 files changed, 171 insertions, 0 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
new file mode 100755
index 0000000..58cbf9d
--- /dev/null
+++ b/roles/MSA/files/usr/local/bin/postfix-sender-login.pl
@@ -0,0 +1,171 @@
+#!/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/};
+
+# returned for forbidden envelope sender addresses
+my $POSTMASTER = 'postmaster@fripost.org';
+
+# 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 $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 process_request($);
+
+while(1) {
+ accept(my $conn, $S) or do {
+ # try again if accept(2) was interrupted by a signal
+ 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 {
+ 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) // 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) // 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";
+}