servnest/fn/common.php

<?php declare(strict_types=1);

function output(int $code, string $msg = '', array $logs = [''], array $data = []): never {
	http_response_code($code);
	$shortCode = intval($code / 100);
	if ($shortCode === 5)
		error_log('Internal error: ' . strip_tags($msg) . implode(LF, $logs));
	$final_message = match ($shortCode) {
		2 => ($msg === '') ? '' : '<p><output>' . _('<strong>Success</strong>: ') . '<em>' . $msg . '</em></output></p>' . LF,
		4 => '<p><output>' . _('<strong>User error</strong>: ') . '<em>' . $msg . '</em></output></p>' . LF,
		5 => '<p><output>' . _('<strong>Server error</strong>: ') . '<em>' . $msg . '</em></output></p>' . LF,
	};
	if (is_callable('displayPage'))
		displayPage(array_merge(['final_message' => $final_message], $data));
	echo $final_message;
	exit();
}

function exescape(array $args, array &$output = NULL, int &$result_code = NULL): int {
	exec('2>&1 ' . implode(' ', array_map('escapeshellarg', $args)), $output, $result_code);
	return $result_code;
}

class KdigException extends Exception {};
function kdig(string $name, string $type, string $server = NULL): array {
	exescape([
		CONF['dns']['kdig_path'],
		'+json',
		'+timeout=5',
		'+retry=0',
		'-q',
		$name,
		'-t',
		$type,
		...(isset($server) ? ['@' . $server] : []),
	], $output, $code);
	if ($code !== 0)
		throw new KdigException();
	return json_decode(implode(LF, $output), true, flags: JSON_THROW_ON_ERROR);
}

function insert(string $table, array $values): void {
	$query = 'INSERT INTO "' . $table . '"(';

	foreach ($values as $key => $val) {
		if ($key === array_key_last($values))
			$query .= "$key";
		else
			$query .= "$key, ";
	}

	$query .= ') VALUES(';
	foreach ($values as $key => $val) {
		if ($key === array_key_last($values))
			$query .= ":$key";
		else
			$query .= ":$key, ";
	}
	$query .= ')';

	DB->prepare($query)
	->execute($values);
}

function query(string $action, string $table, array $conditions = [], string $column = NULL): array {

	$query = match ($action) {
		'select' => 'SELECT *',
		'delete' => 'DELETE',
	};

	$query .= ' FROM "' . $table . '"';

	foreach ($conditions as $key => $val) {
		if ($key === array_key_first($conditions))
			$query .= " WHERE $key = :$key";
		else
			$query .= " AND $key = :$key";
	}

	$stmt = DB->prepare($query);
	$stmt->execute($conditions);

	return array_column($stmt->fetchAll(PDO::FETCH_ASSOC), $column);
}

function displayIndex(): void { ?>
<nav>
	<dl>
<?php foreach (PAGES[SERVICE] as $pageId => $page) {
	if ($pageId === 'index') continue;
?>
		<dt><a href="<?= $pageId ?>"><?= $page['title'] ?></a></dt>
		<dd>
			<?= $page['description'] ?>
		</dd>
<?php } ?>
	</dl>
</nav>
<?php
}

function redirUrl(string $pageId): string {
	return CONF['common']['prefix'] . '/' . $pageId . '?redir=' . PAGE_URL;
}

function redir(string $redir_to = NULL): never {
	$redir_to ??= $_GET['redir'] ?? NULL;

	if ($redir_to === NULL) {
		header('Location: ' . CONF['common']['prefix'] . '/');
		exit();
	}
	if (preg_match('/^[0-9a-z\/-]{0,128}$/D', $redir_to) !== 1)
		output(403, 'Wrong character in <code>redir</code>.');
	header('Location: ' . CONF['common']['prefix'] . '/' . $redir_to);
	exit();
}

// PHP rmdir() only works on empty directories
function removeDirectory(string $dir): void {
	$dirObj = new RecursiveDirectoryIterator($dir, RecursiveDirectoryIterator::SKIP_DOTS);
	$files = new RecursiveIteratorIterator($dirObj, RecursiveIteratorIterator::CHILD_FIRST);
	foreach ($files as $file)
		$file->isDir() && !$file->isLink() ? rmdir($file->getPathname()) : unlink($file->getPathname());
	if (rmdir($dir) !== true)
		output(500, 'Unable to remove directory.');
}

function equalArrays(array $a, array $b): bool {
	return array_diff($a, $b) === [] AND array_diff($b, $a) === [];
}

/*
	This token authenticates the user to the server through a public communication (the DNS).
	It is therefore also designed to keep private:
	- the user's id
	- that a same user used a token multiple times (by using a unique salt for each token)
*/
if (time() - query('select', 'params', ['name' => 'secret_key_last_change'], 'value')[0] >= 86400 * 20) {
	DB->prepare("UPDATE params SET value = :secret_key WHERE name = 'secret_key';")
	->execute([':secret_key' => bin2hex(random_bytes(32))]);
	DB->prepare("UPDATE params SET value = :last_change WHERE name = 'secret_key_last_change';")
	->execute([':last_change' => time()]);
}
define('SECRET_KEY', hex2bin(query('select', 'params', ['name' => 'secret_key'], 'value')[0]));
function getAuthToken(): string {
	$salt = bin2hex(random_bytes(4));
	$hash = hash_hmac('sha256', $salt . ($_SESSION['id'] ?? ''), SECRET_KEY);
	return $salt . '-' .  substr($hash, 0, 32);
}
function checkAuthToken(string $salt, string $hash): void {
	$correctProof = substr(hash_hmac('sha256', $salt . $_SESSION['id'], SECRET_KEY), 0, 32);
	if (hash_equals($correctProof, $hash) !== true)
		output(403, _('Wrong proof.'));
}