<?php

/**

 * SSL utilities for Requests

 *

 * @package Requests\Utilities

 */

namespace WpOrg\Requests;

use WpOrg\Requests\Exception\InvalidArgument;

use WpOrg\Requests\Utility\InputValidator;

/**

 * SSL utilities for Requests

 *

 * Collection of utilities for working with and verifying SSL certificates.

 *

 * @package Requests\Utilities

 */

final class Ssl {

	/**

	 * Verify the certificate against common name and subject alternative names

	 *

	 * Unfortunately, PHP doesn't check the certificate against the alternative

	 * names, leading things like 'https://www.github.com/' to be invalid.

	 *

	 * @link https://tools.ietf.org/html/rfc2818#section-3.1 RFC2818, Section 3.1

	 *

	 * @param string|Stringable $host Host name to verify against

	 * @param array $cert Certificate data from openssl_x509_parse()

	 * @return bool

	 * @throws \WpOrg\Requests\Exception\InvalidArgument When the passed $host argument is not a string or a stringable object.

	 * @throws \WpOrg\Requests\Exception\InvalidArgument When the passed $cert argument is not an array or array accessible.

	 */

	public static function verify_certificate($host, $cert) {

		if (InputValidator::is_string_or_stringable($host) === false) {

			throw InvalidArgument::create(1, '$host', 'string|Stringable', gettype($host));

		}

		if (InputValidator::has_array_access($cert) === false) {

			throw InvalidArgument::create(2, '$cert', 'array|ArrayAccess', gettype($cert));

		}

		$has_dns_alt = false;

		// Check the subjectAltName

		if (!empty($cert['extensions']['subjectAltName'])) {

			$altnames = explode(',', $cert['extensions']['subjectAltName']);

			foreach ($altnames as $altname) {

				$altname = trim($altname);

				if (strpos($altname, 'DNS:') !== 0) {

					continue;

				}

				$has_dns_alt = true;

				// Strip the 'DNS:' prefix and trim whitespace

				$altname = trim(substr($altname, 4));

				// Check for a match

				if (self::match_domain($host, $altname) === true) {

					return true;

				}

			}

			if ($has_dns_alt === true) {

				return false;

			}

		}

		// Fall back to checking the common name if we didn't get any dNSName

		// alt names, as per RFC2818

		if (!empty($cert['subject']['CN'])) {

			// Check for a match

			return (self::match_domain($host, $cert['subject']['CN']) === true);

		}

		return false;

	}

	/**

	 * Verify that a reference name is valid

	 *

	 * Verifies a dNSName for HTTPS usage, (almost) as per Firefox's rules:

	 * - Wildcards can only occur in a name with more than 3 components

	 * - Wildcards can only occur as the last character in the first

	 *   component

	 * - Wildcards may be preceded by additional characters

	 *

	 * We modify these rules to be a bit stricter and only allow the wildcard

	 * character to be the full first component; that is, with the exclusion of

	 * the third rule.

	 *

	 * @param string|Stringable $reference Reference dNSName

	 * @return boolean Is the name valid?

	 * @throws \WpOrg\Requests\Exception\InvalidArgument When the passed argument is not a string or a stringable object.

	 */

	public static function verify_reference_name($reference) {

		if (InputValidator::is_string_or_stringable($reference) === false) {

			throw InvalidArgument::create(1, '$reference', 'string|Stringable', gettype($reference));

		}

		if ($reference === '') {

			return false;

		}

		if (preg_match('`\s`', $reference) > 0) {

			// Whitespace detected. This can never be a dNSName.

			return false;

		}

		$parts = explode('.', $reference);

		if ($parts !== array_filter($parts)) {

			// DNSName cannot contain two dots next to each other.

			return false;

		}

		// Check the first part of the name

		$first = array_shift($parts);

		if (strpos($first, '*') !== false) {

			// Check that the wildcard is the full part

			if ($first !== '*') {

				return false;

			}

			// Check that we have at least 3 components (including first)

			if (count($parts) < 2) {

				return false;

			}

		}

		// Check the remaining parts

		foreach ($parts as $part) {

			if (strpos($part, '*') !== false) {

				return false;

			}

		}

		// Nothing found, verified!

		return true;

	}

	/**

	 * Match a hostname against a dNSName reference

	 *

	 * @param string|Stringable $host Requested host

	 * @param string|Stringable $reference dNSName to match against

	 * @return boolean Does the domain match?

	 * @throws \WpOrg\Requests\Exception\InvalidArgument When either of the passed arguments is not a string or a stringable object.

	 */

	public static function match_domain($host, $reference) {

		if (InputValidator::is_string_or_stringable($host) === false) {

			throw InvalidArgument::create(1, '$host', 'string|Stringable', gettype($host));

		}

		// Check if the reference is blocklisted first

		if (self::verify_reference_name($reference) !== true) {

			return false;

		}

		// Check for a direct match

		if ((string) $host === (string) $reference) {

			return true;

		}

		// Calculate the valid wildcard match if the host is not an IP address

		// Also validates that the host has 3 parts or more, as per Firefox's ruleset,

		// as a wildcard reference is only allowed with 3 parts or more, so the

		// comparison will never match if host doesn't contain 3 parts or more as well.

		if (ip2long($host) === false) {

			$parts    = explode('.', $host);

			$parts[0] = '*';

			$wildcard = implode('.', $parts);

			if ($wildcard === (string) $reference) {

				return true;

			}

		}

		return false;

	}

}