From 78eb31baf3a34ba255701c249d71dda7fd0d75e5 Mon Sep 17 00:00:00 2001 From: Sadeep Madurange Date: Mon, 10 Aug 2026 11:12:33 +0800 Subject: Verify GPG signature. --- lex.cgi | 142 +++++++++++++++++++++++++++++++++++++++++++++------------------- 1 file changed, 100 insertions(+), 42 deletions(-) (limited to 'lex.cgi') diff --git a/lex.cgi b/lex.cgi index f6fb12d..e4a1994 100755 --- a/lex.cgi +++ b/lex.cgi @@ -8,12 +8,18 @@ use Email::MIME; use OpenBSD::Pledge; use OpenBSD::Unveil; -unveil("/tmp", "rwc") or die "unveil /tmp failed: $!"; -unveil() or die "unveil lock failed: $!"; +my $base_dir = "/var/lex"; +my $keyring_file = "$base_dir/pubring.gpg"; -pledge('stdio rpath wpath cpath') or die "pledge failed: $!"; +unveil("/usr/local/bin/gpg", "rx") or die "unveil gpg failed: $!"; +unveil("/dev/null", "rw") or die "unveil /dev/null failed: $!"; +unveil("/tmp", "rwc") or die "unveil /tmp failed: $!"; +unveil($base_dir, "rwc") or die "unveil $base_dir failed: $!"; +unveil() or die "unveil lock failed: $!"; -my $log_file = "/tmp/lex.log"; +pledge('stdio rpath wpath cpath proc exec') or die "pledge failed: $!"; + +my $log_file = "$base_dir/debug.log"; my $max_log_bytes = 1024 * 1024; # 1 MB cap sub log_msg { @@ -28,7 +34,13 @@ sub log_msg { my $lh; if (open($lh, '>>', $log_file)) { - my $timestamp = sprintf("%d", time()); + my $tz_offset = 8 * 3600; + my ($sec, $min, $hour, $mday, $mon, $year) = gmtime(time() + $tz_offset); + + my $timestamp = sprintf( + "%04d-%02d-%02d %02d:%02d:%02d", + $year + 1900, $mon + 1, $mday, $hour, $min, $sec + ); print $lh "[$timestamp] [$$] $msg\n"; close($lh); } @@ -41,10 +53,84 @@ sub respond_ok { exit 0; } -my $content_type = $ENV{'CONTENT_TYPE'} // ''; +sub verify_pgp_signature { + my ($signed_data, $signature) = @_; + + unless (-f $keyring_file) { + log_msg("ERROR: Keyring missing at $keyring_file"); + return 0; + } + + my $tmp_dir = "/tmp/lex"; + unless (-d $tmp_dir) { + make_path($tmp_dir); + } + + my $msg_id = sprintf("msg_%.6f_$$", time()); + my $tmp_data = "${tmp_dir}/${msg_id}.mime"; + my $tmp_sig = "${tmp_dir}/${msg_id}.sig"; + + # Ensure CRLF line endings on the signed data block + $signed_data =~ s/\r?\n/\r\n/g; + + my $dh; + unless (open($dh, '>:raw', $tmp_data)) { + log_msg("ERROR: Could not create temp data file: $!"); + return 0; + } + print $dh $signed_data; + close($dh); + + # Write sig file with trailing CRLF + my $sh; + unless (open($sh, '>:raw', $tmp_sig)) { + log_msg("ERROR: Could not create temp sig file: $!"); + unlink($tmp_data); + return 0; + } + print $sh $signature . "\r\n"; + close($sh); + + my $pipe; + my $gpg_output = ""; + my $pid = open($pipe, "-|") // die "Cannot fork: $!"; + + if ($pid == 0) { + open(STDERR, '>&', STDOUT); + exec( + '/usr/local/bin/gpg', + '--batch', + '--no-default-keyring', + '--keyring', $keyring_file, + '--trust-model', 'always', + '--verify', + $tmp_sig, + $tmp_data + ) or exit(127); + } + + while (my $line = <$pipe>) { + $gpg_output .= $line; + } + close($pipe); + my $exit_code = $? >> 8; + + unlink($tmp_data, $tmp_sig); + + if ($exit_code == 0) { + return 1; + } else { + $gpg_output =~ s/\r?\n/ /g; + log_msg("DEBUG: gpg output: $gpg_output"); + log_msg("DEBUG: gpg exited with code $exit_code"); + return 0; + } +} + +my $content_type = $ENV{'CONTENT_TYPE'} // ''; my $content_length = $ENV{'CONTENT_LENGTH'} // 0; -my $remote_ip = $ENV{'REMOTE_ADDR'} // 'unknown'; +my $remote_ip = $ENV{'REMOTE_ADDR'} // 'unknown'; my $user_agent = $ENV{'HTTP_USER_AGENT'} // 'unknown'; log_msg("INFO: Request received from $remote_ip [$user_agent]"); @@ -57,7 +143,6 @@ binmode(STDIN); my $raw_data = ''; read(STDIN, $raw_data, $content_length); -# Parse application/x-www-form-urlencoded payload unless ($content_type =~ /application\/x-www-form-urlencoded/i) { log_msg("WARN: Content-Type is not urlencoded: '$content_type'"); respond_ok(); @@ -78,7 +163,6 @@ for my $pair (split(/&/, $raw_data)) { $params{$key} //= $val; } -# Extract MIME message for PGP check my $mime_raw = $params{'body-mime'} // ''; if ($mime_raw eq '') { log_msg("WARN: 'body-mime' parameter is empty or missing"); @@ -89,19 +173,15 @@ if ($mime_raw eq '') { my $parsed = Email::MIME->new($mime_raw); my @parts = $parsed->parts; -# Signed content + PGP signature must be present unless (@parts >= 2) { log_msg("WARN: MIME parts count < 2 (found " . scalar(@parts) . ")"); respond_ok(); } -# Part 0: canonical signed content (headers + body) +# Extract canonical signed part directly (Part 0 string representation) my $signed_part = $parts[0]->as_string; -# Normalize line endings to \r\n for canonical PGP verification -$signed_part =~ s/\r?\n/\r\n/g; - -# Part 1: detached PGP signature +# Extract PGP signature block my $sig_part_raw = $parts[1]->body_raw // ''; my ($pgp_sig) = $sig_part_raw =~ /(-----BEGIN PGP SIGNATURE-----[\s\S]*?-----END PGP SIGNATURE-----)/; @@ -115,34 +195,11 @@ unless (length($signed_part) > 0 && $pgp_sig) { respond_ok(); } -my $dir = "/tmp/lex"; -unless (-d $dir) { - make_path($dir); -} - -my $msg_id = sprintf("msg_%.6f_$$", time()); -my $sig_file = "${dir}/${msg_id}.sig"; -my $mime_file = "${dir}/${msg_id}.mime"; - -# Write MIME file -my $mfh; -unless (open($mfh, '>:raw', $mime_file)) { - log_msg("ERROR: Failed to write $mime_file: $!"); - respond_ok(); -} -print $mfh $signed_part; -close($mfh); - -# Write sig file -my $sfh; -unless (open($sfh, '>:raw', $sig_file)) { - log_msg("ERROR: Failed to write $sig_file: $!"); +unless (verify_pgp_signature($signed_part, $pgp_sig)) { + log_msg("WARN: PGP signature verification failed"); respond_ok(); } -print $sfh $pgp_sig . "\r\n"; -close($sfh); -# Extract body, strip signature block, leading and trailing whitespaces my $plain_text = $parts[0]->body_str // ''; $plain_text =~ s/\r\n/\n/g; $plain_text =~ s/\n-- \n.*$//s; @@ -153,8 +210,7 @@ unless (length($plain_text) > 0) { respond_ok(); } -# Append plain text to queue file -my $queue_file = "/tmp/lex_queue.txt"; +my $queue_file = "$base_dir/queue.txt"; my $qfh; unless (open($qfh, '>>:utf8', $queue_file)) { log_msg("ERROR: Failed to append to $queue_file: $!"); @@ -163,6 +219,8 @@ unless (open($qfh, '>>:utf8', $queue_file)) { print $qfh $plain_text . "\n"; close($qfh); +my $msg_id = sprintf("msg_%.6f_$$", time()); my $content_length_kb = sprintf("%.2f KB", $content_length / 1024); log_msg("INFO: Processed $msg_id successfully ($content_length_kb)"); respond_ok(); + -- cgit v1.2.3