1 files changed, 105 insertions, 0 deletions
diff --git a/lib/private/Security/Normalizer/IpAddress.php b/lib/private/Security/Normalizer/IpAddress.php
new file mode 100644
index 00000000000..4d33a7bd632
--- /dev/null
+++ b/lib/private/Security/Normalizer/IpAddress.php
@@ -0,0 +1,105 @@
+<?php
+
+declare(strict_types=1);
+
+/**
+ * SPDX-FileCopyrightText: 2017 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+namespace OC\Security\Normalizer;
+
+use OCP\IConfig;
+
+/**
+ * Class IpAddress is used for normalizing IPv4 and IPv6 addresses in security
+ * relevant contexts in Nextcloud.
+ *
+ * @package OC\Security\Normalizer
+ */
+class IpAddress {
+	/**
+	 * @param string $ip IP to normalize
+	 */
+	public function __construct(
+		private string $ip,
+	) {
+	}
+
+	/**
+	 * Return the given subnet for an IPv6 address
+	 * Rely on security.ipv6_normalized_subnet_size, defaults to 56
+	 */
+	private function getIPv6Subnet(string $ip): string {
+		if ($ip[0] === '[' && $ip[-1] === ']') { // If IP is with brackets, for example [::1]
+			$ip = substr($ip, 1, strlen($ip) - 2);
+		}
+		$pos = strpos($ip, '%'); // if there is an explicit interface added to the IP, e.g. fe80::ae2d:d1e7:fe1e:9a8d%enp2s0
+		if ($pos !== false) {
+			$ip = substr($ip, 0, $pos - 1);
+		}
+
+		$config = \OCP\Server::get(IConfig::class);
+		$maskSize = min(64, $config->getSystemValueInt('security.ipv6_normalized_subnet_size', 56));
+		$maskSize = max(32, $maskSize);
+		if (PHP_INT_SIZE === 4) {
+			if ($maskSize === 64) {
+				$value = -1;
+			} elseif ($maskSize === 63) {
+				$value = PHP_INT_MAX;
+			} else {
+				$value = (1 << $maskSize - 32) - 1;
+			}
+			// as long as we support 32bit PHP we cannot use the `P` pack formatter (and not overflow 32bit integer)
+			$mask = pack('VVVV', -1, $value, 0, 0);
+		} else {
+			$mask = pack('VVP', (1 << 32) - 1, (1 << $maskSize - 32) - 1, 0);
+		}
+
+		$binary = \inet_pton($ip);
+		return inet_ntop($binary & $mask) . '/' . $maskSize;
+	}
+
+	/**
+	 * Returns the IPv4 address embedded in an IPv6 if applicable.
+	 * The detected format is "::ffff:x.x.x.x" using the binary form.
+	 *
+	 * @return string|null embedded IPv4 string or null if none was found
+	 */
+	private function getEmbeddedIpv4(string $ipv6): ?string {
+		$binary = inet_pton($ipv6);
+		if (!$binary) {
+			return null;
+		}
+
+		$mask = inet_pton('::FFFF:FFFF');
+		if (($binary & ~$mask) !== inet_pton('::FFFF:0.0.0.0')) {
+			return null;
+		}
+
+		return inet_ntop(substr($binary, -4));
+	}
+
+
+	/**
+	 * Gets either the /32 (IPv4) or the /56 (default for IPv6) subnet of an IP address
+	 */
+	public function getSubnet(): string {
+		if (filter_var($this->ip, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4)) {
+			return $this->ip . '/32';
+		}
+
+		$ipv4 = $this->getEmbeddedIpv4($this->ip);
+		if ($ipv4 !== null) {
+			return $ipv4 . '/32';
+		}
+
+		return $this->getIPv6Subnet($this->ip);
+	}
+
+	/**
+	 * Returns the specified IP address
+	 */
+	public function __toString(): string {
+		return $this->ip;
+	}
+}