feat(process): add listening pid resolver

Signed-off-by: Vitor Mattos <1079143+vitormattos@users.noreply.github.com>

Author: vitormattos

lib/Service/Process/ListeningPidResolver.php

@@ -0,0 +1,211 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * SPDX-FileCopyrightText: 2026 LibreCode coop and contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OCA\Libresign\Service\Process;
+
+use OCA\Libresign\Vendor\Symfony\Component\Process\Process;
+
+class ListeningPidResolver {
+	/**
+	 * @return int[]
+	 */
+	public function findListeningPids(int $port): array {
+		if ($port <= 0) {
+			throw new \RuntimeException('Invalid port to inspect process listeners.');
+		}
+
+		$usedStrategy = false;
+		$pids = [];
+
+		$ss = $this->findListeningPidsUsingSs($port);
+		if ($ss !== null) {
+			$usedStrategy = true;
+			$pids = array_merge($pids, $ss);
+		}
+
+		$lsof = $this->findListeningPidsUsingLsof($port);
+		if ($lsof !== null) {
+			$usedStrategy = true;
+			$pids = array_merge($pids, $lsof);
+		}
+
+		$proc = $this->findListeningPidsUsingProc($port);
+		if ($proc !== null) {
+			$usedStrategy = true;
+			$pids = array_merge($pids, $proc);
+		}
+
+		if (!$usedStrategy) {
+			throw new \RuntimeException('Unable to inspect listening process PIDs: no strategy available.');
+		}
+
+		return array_values(array_filter(
+			array_unique(array_map('intval', $pids)),
+			static fn (int $pid): bool => $pid > 0,
+		));
+	}
+
+	/**
+	 * @return int[]|null null means strategy unavailable
+	 */
+	protected function findListeningPidsUsingSs(int $port): ?array {
+		if (!$this->commandIsAvailable('ss')) {
+			return null;
+		}
+
+		$process = $this->createProcess(['ss', '-ltnp', 'sport = :' . $port]);
+		$process->run();
+		if (!$process->isSuccessful()) {
+			return [];
+		}
+
+		$output = $process->getOutput();
+		preg_match_all('/pid=(\d+)/', $output, $matches);
+		if (!isset($matches[1]) || !is_array($matches[1])) {
+			return [];
+		}
+
+		return array_map('intval', $matches[1]);
+	}
+
+	/**
+	 * @return int[]|null null means strategy unavailable
+	 */
+	protected function findListeningPidsUsingLsof(int $port): ?array {
+		if (!$this->commandIsAvailable('lsof')) {
+			return null;
+		}
+
+		$process = $this->createProcess(['lsof', '-ti', 'tcp:' . $port, '-sTCP:LISTEN']);
+		$process->run();
+		if (!$process->isSuccessful()) {
+			return [];
+		}
+
+		$lines = preg_split('/\R/', trim($process->getOutput()));
+		if (!is_array($lines)) {
+			return [];
+		}
+
+		return array_map('intval', array_filter($lines, static fn (string $line): bool => $line !== ''));
+	}
+
+	/**
+	 * @return int[]|null null means strategy unavailable
+	 */
+	protected function findListeningPidsUsingProc(int $port): ?array {
+		if (PHP_OS_FAMILY !== 'Linux') {
+			return null;
+		}
+
+		if (!is_readable('/proc/net/tcp') && !is_readable('/proc/net/tcp6')) {
+			return null;
+		}
+
+		$inodesByPort = $this->getListeningSocketInodesByPort($port);
+		if (empty($inodesByPort)) {
+			return [];
+		}
+
+		$fdPaths = glob('/proc/[0-9]*/fd/[0-9]*');
+		if (!is_array($fdPaths)) {
+			return [];
+		}
+
+		$pids = [];
+		foreach ($fdPaths as $fdPath) {
+			$target = @readlink($fdPath);
+			if (!is_string($target) || !preg_match('/^socket:\\[(\\d+)\\]$/', $target, $matches)) {
+				continue;
+			}
+
+			$inode = $matches[1] ?? '';
+			if ($inode === '' || !isset($inodesByPort[$inode])) {
+				continue;
+			}
+
+			if (preg_match('#^/proc/([0-9]+)/fd/[0-9]+$#', $fdPath, $pidMatches)) {
+				$pids[] = (int)$pidMatches[1];
+			}
+		}
+
+		return $pids;
+	}
+
+	/**
+	 * @return array<string, true>
+	 */
+	protected function getListeningSocketInodesByPort(int $port): array {
+		$portHex = strtoupper(str_pad(dechex($port), 4, '0', STR_PAD_LEFT));
+		$inodes = [];
+
+		foreach (['/proc/net/tcp', '/proc/net/tcp6'] as $path) {
+			foreach ($this->readListeningInodesFromProcTable($path, $portHex) as $inode) {
+				$inodes[$inode] = true;
+			}
+		}
+
+		return $inodes;
+	}
+
+	/**
+	 * @return string[]
+	 */
+	protected function readListeningInodesFromProcTable(string $path, string $portHex): array {
+		if (!is_readable($path)) {
+			return [];
+		}
+
+		$lines = file($path, FILE_IGNORE_NEW_LINES | FILE_SKIP_EMPTY_LINES);
+		if (!is_array($lines) || count($lines) <= 1) {
+			return [];
+		}
+
+		$inodes = [];
+		foreach (array_slice($lines, 1) as $line) {
+			$columns = preg_split('/\s+/', trim($line));
+			if (!is_array($columns) || count($columns) < 10) {
+				continue;
+			}
+
+			$localAddress = $columns[1];
+			$state = $columns[3];
+			$inode = $columns[9] ?? '';
+
+			if ($state !== '0A' || !is_string($inode) || $inode === '') {
+				continue;
+			}
+
+			$addressParts = explode(':', $localAddress);
+			if (count($addressParts) !== 2) {
+				continue;
+			}
+
+			if (strtoupper($addressParts[1]) !== $portHex) {
+				continue;
+			}
+
+			$inodes[] = $inode;
+		}
+
+		return $inodes;
+	}
+
+	protected function commandIsAvailable(string $command): bool {
+		$process = $this->createProcess(['/bin/sh', '-lc', 'command -v ' . escapeshellarg($command) . ' >/dev/null 2>&1']);
+		$process->run();
+		return $process->isSuccessful();
+	}
+
+	/**
+	 * @param string[] $command
+	 */
+	protected function createProcess(array $command): Process {
+		return new Process($command);
+	}
+}