1 files changed, 87 insertions, 0 deletions
diff --git a/apps/settings/lib/SetupChecks/ForwardedForHeaders.php b/apps/settings/lib/SetupChecks/ForwardedForHeaders.php
new file mode 100644
index 00000000000..8238ce07554
--- /dev/null
+++ b/apps/settings/lib/SetupChecks/ForwardedForHeaders.php
@@ -0,0 +1,87 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2023 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OCA\Settings\SetupChecks;
+
+use OCP\IConfig;
+use OCP\IL10N;
+use OCP\IRequest;
+use OCP\IURLGenerator;
+use OCP\SetupCheck\ISetupCheck;
+use OCP\SetupCheck\SetupResult;
+
+class ForwardedForHeaders implements ISetupCheck {
+	public function __construct(
+		private IL10N $l10n,
+		private IConfig $config,
+		private IURLGenerator $urlGenerator,
+		private IRequest $request,
+	) {
+	}
+
+	public function getCategory(): string {
+		return 'security';
+	}
+
+	public function getName(): string {
+		return $this->l10n->t('Forwarded for headers');
+	}
+
+	public function run(): SetupResult {
+		$trustedProxies = $this->config->getSystemValue('trusted_proxies', []);
+		$remoteAddress = $this->request->getHeader('REMOTE_ADDR');
+		$detectedRemoteAddress = $this->request->getRemoteAddress();
+
+		if (!\is_array($trustedProxies)) {
+			return SetupResult::error($this->l10n->t('Your "trusted_proxies" setting is not correctly set, it should be an array.'));
+		}
+
+		foreach ($trustedProxies as $proxy) {
+			$addressParts = explode('/', $proxy, 2);
+			if (filter_var($addressParts[0], FILTER_VALIDATE_IP) === false || !ctype_digit($addressParts[1] ?? '24')) {
+				return SetupResult::error(
+					$this->l10n->t('Your "trusted_proxies" setting is not correctly set, it should be an array of IP addresses - optionally with range in CIDR notation.'),
+					$this->urlGenerator->linkToDocs('admin-reverse-proxy'),
+				);
+			}
+		}
+
+		if (($remoteAddress === '') && ($detectedRemoteAddress === '')) {
+			if (\OC::$CLI) {
+				/* We were called from CLI */
+				return SetupResult::info($this->l10n->t('Your remote address could not be determined.'));
+			} else {
+				/* Should never happen */
+				return SetupResult::error($this->l10n->t('Your remote address could not be determined.'));
+			}
+		}
+
+		if (empty($trustedProxies) && $this->request->getHeader('X-Forwarded-Host') !== '') {
+			return SetupResult::error(
+				$this->l10n->t('The reverse proxy header configuration is incorrect. This is a security issue and can allow an attacker to spoof their IP address as visible to the Nextcloud.'),
+				$this->urlGenerator->linkToDocs('admin-reverse-proxy')
+			);
+		}
+
+		if (\in_array($remoteAddress, $trustedProxies, true) && ($remoteAddress !== '127.0.0.1')) {
+			if ($remoteAddress !== $detectedRemoteAddress) {
+				/* Remote address was successfuly fixed */
+				return SetupResult::success($this->l10n->t('Your IP address was resolved as %s', [$detectedRemoteAddress]));
+			} else {
+				return SetupResult::warning(
+					$this->l10n->t('The reverse proxy header configuration is incorrect, or you are accessing Nextcloud from a trusted proxy. If not, this is a security issue and can allow an attacker to spoof their IP address as visible to the Nextcloud.'),
+					$this->urlGenerator->linkToDocs('admin-reverse-proxy')
+				);
+			}
+		}
+
+		/* Either not enabled or working correctly */
+		return SetupResult::success();
+	}
+}