gwpb_mda.php

#!/usr/bin/env php
<?php
// SPDX-License-Identifier: GPL-2.0-only

const LOCK_FILE = "/tmp/public_inbox.lock";

function clean_header_val(string $str): string
{
	$ex = explode("\n", $str);
	foreach ($ex as &$v)
		$v = trim($v);
	return implode(" ", $ex);
}

function fx(string $input): int
{
	$hdr = explode("\n\n", $input, 2);
	$hdr = trim($hdr[0]);

	if (!preg_match("/(?:^|\\n)from:\s+?(.+?)(?:\\n\S+\:|$)/si", $hdr, $m)) {
		printf("x: Cannot find the 'from' header in the email.\n");
		return 1;
	}
	$from = clean_header_val($m[1]);

	if (preg_match("/\\@turing\\.[\\w\\d\\.]+$/", $from)) {
		/*
		 * Drop any email from turing.bla domain
		 * where 'bla' can be anything. Note that
		 * it was not enough to block turing.com
		 * because their spam system has started
		 * expanding to other TLDs (not only .com).
		 */

		// Bounce the email.
		printf("x: The MDA detected /\\@turing\\.[\\w\\d\\.]+$/ pattern and it's globally recognized as spam. The email cannot be delivered.\n");
		return 1;
	}

	$uniq = date("Y_m_d_H_i_s_").rand().microtime(true);
	$tmpName = "/tmp/public_inbox_{$uniq}.txt";
	file_put_contents($tmpName, $input);
	$tmpName = escapeshellarg($tmpName);
	shell_exec("/usr/local/bin/public-inbox-mda < {$tmpName}");
	unlink($tmpName);
	return 0;
}


function main(): int
{
	$handle = fopen(LOCK_FILE, "a");
	if (!$handle) {
		printf("Cannot open the lock file: %s\n", LOCK_FILE);
		return 1;
	}
	flock($handle, LOCK_EX);
	$ret = fx(file_get_contents("php://stdin"));
	flock($handle, LOCK_UN);
	fclose($handle);
	return $ret;
}

exit(main());