Merge pull request #21654 from nextcloud/backport/21653/stable18

[stable18] Fix IPv6 remote addresses from X_FORWARDED_FOR headers before validating

Author: kesselb

lib/private/AppFramework/Http/Request.php

@@ -659,6 +659,12 @@ public function getRemoteAddress(): string {
 				if(isset($this->server[$header])) {
 					foreach(explode(',', $this->server[$header]) as $IP) {
 						$IP = trim($IP);
+
+						// remove brackets from IPv6 addresses
+						if (strpos($IP, '[') === 0 && substr($IP, -1) === ']') {
+							$IP = substr($IP, 1, -1);
+						}
+
 						if (filter_var($IP, FILTER_VALIDATE_IP) !== false) {
 							return $IP;
 						}

tests/lib/AppFramework/Http/RequestTest.php

@@ -634,6 +634,34 @@ public function testGetRemoteAddressWithNotMatchingCidrTrustedRemote() {
 		$this->assertSame('192.168.3.99', $request->getRemoteAddress());
 	}
 
+	public function testGetRemoteAddressWithXForwardedForIPv6() {
+		$this->config
+			->expects($this->at(0))
+			->method('getSystemValue')
+			->with('trusted_proxies')
+			->willReturn(['192.168.2.0/24']);
+		$this->config
+			->expects($this->at(1))
+			->method('getSystemValue')
+			->with('forwarded_for_headers')
+			->willReturn(['HTTP_X_FORWARDED_FOR']);
+
+		$request = new Request(
+			[
+				'server' => [
+					'REMOTE_ADDR' => '192.168.2.99',
+					'HTTP_X_FORWARDED_FOR' => '[2001:db8:85a3:8d3:1319:8a2e:370:7348]',
+				],
+			],
+			$this->secureRandom,
+			$this->config,
+			$this->csrfTokenManager,
+			$this->stream
+		);
+
+		$this->assertSame('2001:db8:85a3:8d3:1319:8a2e:370:7348', $request->getRemoteAddress());
+	}
+
 	/**
 	 * @return array
 	 */