[PATCH 9/9] lei-daemon: do not leak FDs on bogus requests

[Eric Wong <e@80x24.org>]

If a client passes us the incorrect number of FDs, we'll vivify
them into PerlIO objects so they can be auto-closed.  Using
POSIX::close was considered, but it would've been more code to
handle an uncommon case.
---
 lib/PublicInbox/LEI.pm | 15 +++++++--------
 t/lei-daemon.t         | 29 +++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+), 8 deletions(-)

diff --git a/lib/PublicInbox/LEI.pm b/lib/PublicInbox/LEI.pm
index 878685f1..e5211764 100644
--- a/lib/PublicInbox/LEI.pm
+++ b/lib/PublicInbox/LEI.pm
@@ -981,17 +981,16 @@ sub accept_dispatch { # Listener {post_accept} callback
 		return send($sock, 'timed out waiting to recv FDs', MSG_EOR);
 	# (4096 * 33) >MAX_ARG_STRLEN
 	my @fds = $recv_cmd->($sock, my $buf, 4096 * 33) or return; # EOF
-	if (scalar(@fds) == 4) {
-		for my $i (0..3) {
-			my $fd = shift(@fds);
-			open($self->{$i}, '+<&=', $fd) and next;
-			send($sock, "open(+<&=$fd) (FD=$i): $!", MSG_EOR);
-		}
-	} elsif (!defined($fds[0])) {
+	if (!defined($fds[0])) {
 		warn(my $msg = "recv_cmd failed: $!");
 		return send($sock, $msg, MSG_EOR);
 	} else {
-		return;
+		my $i = 0;
+		for my $fd (@fds) {
+			open($self->{$i++}, '+<&=', $fd) and next;
+			send($sock, "open(+<&=$fd) (FD=$i): $!", MSG_EOR);
+		}
+		return if scalar(@fds) != 4;
 	}
 	$self->{2}->autoflush(1); # keep stdout buffered until x_it|DESTROY
 	# $ENV_STR = join('', map { "\0$_=$ENV{$_}" } keys %ENV);
diff --git a/t/lei-daemon.t b/t/lei-daemon.t
index c30e5ac1..35e059b9 100644
--- a/t/lei-daemon.t
+++ b/t/lei-daemon.t
@@ -2,8 +2,16 @@
 # Copyright (C) 2020-2021 all contributors <meta@public-inbox.org>
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
 use strict; use v5.10.1; use PublicInbox::TestCommon;
+use Socket qw(AF_UNIX SOCK_SEQPACKET MSG_EOR pack_sockaddr_un);
+use PublicInbox::Spawn qw(which);
 
 test_lei({ daemon_only => 1 }, sub {
+	my $send_cmd = PublicInbox::Spawn->can('send_cmd4') // do {
+		require PublicInbox::CmdIPC4;
+		PublicInbox::CmdIPC4->can('send_cmd4');
+	};
+	$send_cmd or BAIL_OUT 'started testing lei-daemon w/o send_cmd4!';
+
 	my $sock = "$ENV{XDG_RUNTIME_DIR}/lei/5.seq.sock";
 	my $err_log = "$ENV{XDG_RUNTIME_DIR}/lei/errors.log";
 	lei_ok('daemon-pid');
@@ -22,6 +30,27 @@ test_lei({ daemon_only => 1 }, sub {
 	is($pid, $pid_again, 'daemon-pid idempotent');
 	like($lei_err, qr/phail/, 'got mock "phail" error previous run');
 
+	SKIP: {
+		skip 'only testing open files on Linux', 1 if $^O ne 'linux';
+		my $d = "/proc/$pid/fd";
+		skip "no $d on Linux" unless -d $d;
+		my @before = sort(glob("$d/*"));
+		my $addr = pack_sockaddr_un($sock);
+		open my $null, '<', '/dev/null' or BAIL_OUT "/dev/null: $!";
+		my @fds = map { fileno($null) } (0..2);
+		for (0..10) {
+			socket(my $c, AF_UNIX, SOCK_SEQPACKET, 0) or
+							BAIL_OUT "socket: $!";
+			connect($c, $addr) or BAIL_OUT "connect: $!";
+			$send_cmd->($c, \@fds, 'hi',  MSG_EOR);
+		}
+		lei_ok('daemon-pid');
+		chomp($pid = $lei_out);
+		is($pid, $pid_again, 'pid unchanged after failed reqs');
+		my @after = sort(glob("$d/*"));
+		is_deeply(\@before, \@after, 'open files unchanged') or
+			diag explain([\@before, \@after]);;
+	}
 	lei_ok(qw(daemon-kill));
 	is($lei_out, '', 'no output from daemon-kill');
 	is($lei_err, '', 'no error from daemon-kill');