Merge pull request #29852 from nextcloud/backport/29835/stable22

[stable22] Fix getting subnet of ipv4 mapped ipv6 addresses

Author: PVince81

lib/private/Security/Normalizer/IpAddress.php

@@ -92,6 +92,38 @@ private function getIPv6Subnet(string $ip, int $maskBits = 48): string {
 		return \inet_ntop($binary).'/'.$maskBits;
 	}
 
+	/**
+	 * 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 (!$binary) {
+			return null;
+		}
+		for ($i = 0; $i <= 9; $i++) {
+			if (unpack('C', $binary[$i])[1] !== 0) {
+				return null;
+			}
+		}
+
+		for ($i = 10; $i <= 11; $i++) {
+			if (unpack('C', $binary[$i])[1] !== 255) {
+				return null;
+			}
+		}
+
+		$binary4 = '';
+		for ($i = 12; $i < 16; $i++) {
+			$binary4 .= $binary[$i];
+		}
+
+		return inet_ntop($binary4);
+	}
+
+
 	/**
 	 * Gets either the /32 (IPv4) or the /64 (IPv6) subnet of an IP address
 	 *
@@ -104,6 +136,15 @@ public function getSubnet(): string {
 				32
 			);
 		}
+
+		$ipv4 = $this->getEmbeddedIpv4($this->ip);
+		if ($ipv4 !== null) {
+			return $this->getIPv4Subnet(
+				$ipv4,
+				32
+			);
+		}
+
 		return $this->getIPv6Subnet(
 			$this->ip,
 			64

tests/lib/Security/Normalizer/IpAddressTest.php

@@ -38,6 +38,18 @@ public function subnetDataProvider() {
 				'192.168.0.123',
 				'192.168.0.123/32',
 			],
+			[
+				'::ffff:192.168.0.123',
+				'192.168.0.123/32',
+			],
+			[
+				'0:0:0:0:0:ffff:192.168.0.123',
+				'192.168.0.123/32',
+			],
+			[
+				'0:0:0:0:0:ffff:c0a8:7b',
+				'192.168.0.123/32',
+			],
 			[
 				'2001:0db8:85a3:0000:0000:8a2e:0370:7334',
 				'2001:db8:85a3::/64',