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/**
 * Upgrade API: Core_Upgrader class
 *
 * @package WordPress
 * @subpackage Upgrader
 * @since 4.6.0
 */

/**
 * Core class used for updating core.
 *
 * It allows for WordPress to upgrade itself in combination with
 * the wp-admin/includes/update-core.php file.
 *
 * Note: Newly introduced functions and methods cannot be used here.
 * All functions must be present in the previous version being upgraded from
 * as this file is used there too.
 *
 * @since 2.8.0
 * @since 4.6.0 Moved to its own file from wp-admin/includes/class-wp-upgrader.php.
 *
 * @see WP_Upgrader
 */
class Core_Upgrader extends WP_Upgrader {

	/**
	 * Initializes the upgrade strings.
	 *
	 * @since 2.8.0
	 */
	public function upgrade_strings() {
		$this-&gt;strings['up_to_date'] = __( 'WordPress is at the latest version.' );
		$this-&gt;strings['locked']     = __( 'Another update is currently in progress.' );
		$this-&gt;strings['no_package'] = __( 'Update package not available.' );
		/* translators: %s: Package URL. */
		$this-&gt;strings['downloading_package']   = sprintf( __( 'Downloading update from %s&amp;#8230;' ), '&lt;span class=&quot;code pre&quot;&gt;%s&lt;/span&gt;' );
		$this-&gt;strings['unpack_package']        = __( 'Unpacking the update&amp;#8230;' );
		$this-&gt;strings['copy_failed']           = __( 'Could not copy files.' );
		$this-&gt;strings['copy_failed_space']     = __( 'Could not copy files. You may have run out of disk space.' );
		$this-&gt;strings['start_rollback']        = __( 'Attempting to restore the previous version.' );
		$this-&gt;strings['rollback_was_required'] = __( 'Due to an error during updating, WordPress has been restored to your previous version.' );
	}

	/**
	 * Upgrades WordPress core.
	 *
	 * @since 2.8.0
	 *
	 * @global WP_Filesystem_Base $wp_filesystem                WordPress filesystem subclass.
	 * @global callable           $_wp_filesystem_direct_method
	 *
	 * @param object $current Response object for whether WordPress is current.
	 * @param array  $args {
	 *     Optional. Arguments for upgrading WordPress core. Default empty array.
	 *
	 *     @type bool $pre_check_md5    Whether to check the file checksums before
	 *                                  attempting the upgrade. Default true.
	 *     @type bool $attempt_rollback Whether to attempt to rollback the chances if
	 *                                  there is a problem. Default false.
	 *     @type bool $do_rollback      Whether to perform this &quot;upgrade&quot; as a rollback.
	 *                                  Default false.
	 * }
	 * @return string|false|WP_Error New WordPress version on success, false or WP_Error on failure.
	 */
	public function upgrade( $current, $args = array() ) {
		global $wp_filesystem;

		require ABSPATH . WPINC . '/version.php'; // $wp_version;

		$start_time = time();

		$defaults    = array(
			'pre_check_md5'                =&gt; true,
			'attempt_rollback'             =&gt; false,
			'do_rollback'                  =&gt; false,
			'allow_relaxed_file_ownership' =&gt; false,
		);
		$parsed_args = wp_parse_args( $args, $defaults );

		$this-&gt;init();
		$this-&gt;upgrade_strings();

		// Is an update available?
		if ( ! isset( $current-&gt;response ) || 'latest' === $current-&gt;response ) {
			return new WP_Error( 'up_to_date', $this-&gt;strings['up_to_date'] );
		}

		$res = $this-&gt;fs_connect( array( ABSPATH, WP_CONTENT_DIR ), $parsed_args['allow_relaxed_file_ownership'] );
		if ( ! $res || is_wp_error( $res ) ) {
			return $res;
		}

		$wp_dir = trailingslashit( $wp_filesystem-&gt;abspath() );

		$partial = true;
		if ( $parsed_args['do_rollback'] ) {
			$partial = false;
		} elseif ( $parsed_args['pre_check_md5'] &amp;&amp; ! $this-&gt;check_files() ) {
			$partial = false;
		}

		/*
		 * If partial update is returned from the API, use that, unless we're doing
		 * a reinstallation. If we cross the new_bundled version number, then use
		 * the new_bundled zip. Don't though if the constant is set to skip bundled items.
		 * If the API returns a no_content zip, go with it. Finally, default to the full zip.
		 */
		if ( $parsed_args['do_rollback'] &amp;&amp; $current-&gt;packages-&gt;rollback ) {
			$to_download = 'rollback';
		} elseif ( $current-&gt;packages-&gt;partial &amp;&amp; 'reinstall' !== $current-&gt;response &amp;&amp; $wp_version === $current-&gt;partial_version &amp;&amp; $partial ) {
			$to_download = 'partial';
		} elseif ( $current-&gt;packages-&gt;new_bundled &amp;&amp; version_compare( $wp_version, $current-&gt;new_bundled, '&lt;' )
			&amp;&amp; ( ! defined( 'CORE_UPGRADE_SKIP_NEW_BUNDLED' ) || ! CORE_UPGRADE_SKIP_NEW_BUNDLED ) ) {
			$to_download = 'new_bundled';
		} elseif ( $current-&gt;packages-&gt;no_content ) {
			$to_download = 'no_content';
		} else {
			$to_download = 'full';
		}

		// Lock to prevent multiple Core Updates occurring.
		$lock = WP_Upgrader::create_lock( 'core_updater', 15 * MINUTE_IN_SECONDS );
		if ( ! $lock ) {
			return new WP_Error( 'locked', $this-&gt;strings['locked'] );
		}

		$download = $this-&gt;download_package( $current-&gt;packages-&gt;$to_download, false );

		/*
		 * Allow for signature soft-fail.
		 * WARNING: This may be removed in the future.
		 */
		if ( is_wp_error( $download ) &amp;&amp; $download-&gt;get_error_data( 'softfail-filename' ) ) {
			// Output the failure error as a normal feedback, and not as an error:
			/** This filter is documented in wp-admin/includes/update-core.php */
			apply_filters( 'update_feedback', $download-&gt;get_error_message() );

			// Report this failure back to WordPress.org for debugging purposes.
			wp_version_check(
				array(
					'signature_failure_code' =&gt; $download-&gt;get_error_code(),
					'signature_failure_data' =&gt; $download-&gt;get_error_data(),
				)
			);

			// Pretend this error didn't happen.
			$download = $download-&gt;get_error_data( 'softfail-filename' );
		}

		if ( is_wp_error( $download ) ) {
			WP_Upgrader::release_lock( 'core_updater' );
			return $download;
		}

		$working_dir = $this-&gt;unpack_package( $download );
		if ( is_wp_error( $working_dir ) ) {
			WP_Upgrader::release_lock( 'core_updater' );
			return $working_dir;
		}

		// Copy update-core.php from the new version into place.
		if ( ! $wp_filesystem-&gt;copy( $working_dir . '/wordpress/wp-admin/includes/update-core.php', $wp_dir . 'wp-admin/includes/update-core.php', true ) ) {
			$wp_filesystem-&gt;delete( $working_dir, true );
			WP_Upgrader::release_lock( 'core_updater' );
			return new WP_Error( 'copy_failed_for_update_core_file', __( 'The update cannot be installed because some files could not be copied. This is usually due to inconsistent file permissions.' ), 'wp-admin/includes/update-core.php' );
		}
		$wp_filesystem-&gt;chmod( $wp_dir . 'wp-admin/includes/update-core.php', FS_CHMOD_FILE );

		wp_opcache_invalidate( ABSPATH . 'wp-admin/includes/update-core.php' );
		require_once ABSPATH . 'wp-admin/includes/update-core.php';

		if ( ! function_exists( 'update_core' ) ) {
			WP_Upgrader::release_lock( 'core_updater' );
			return new WP_Error( 'copy_failed_space', $this-&gt;strings['copy_failed_space'] );
		}

		$result = update_core( $working_dir, $wp_dir );

		// In the event of an issue, we may be able to roll back.
		if ( $parsed_args['attempt_rollback'] &amp;&amp; $current-&gt;packages-&gt;rollback &amp;&amp; ! $parsed_args['do_rollback'] ) {
			$try_rollback = false;
			if ( is_wp_error( $result ) ) {
				$error_code = $result-&gt;get_error_code();
				/*
				 * Not all errors are equal. These codes are critical: copy_failed__copy_dir,
				 * mkdir_failed__copy_dir, copy_failed__copy_dir_retry, and disk_full.
				 * do_rollback allows for update_core() to trigger a rollback if needed.
				 */
				if ( str_contains( $error_code, 'do_rollback' ) ) {
					$try_rollback = true;
				} elseif ( str_contains( $error_code, '__copy_dir' ) ) {
					$try_rollback = true;
				} elseif ( 'disk_full' === $error_code ) {
					$try_rollback = true;
				}
			}

			if ( $try_rollback ) {
				/** This filter is documented in wp-admin/includes/update-core.php */
				apply_filters( 'update_feedback', $result );

				/** This filter is documented in wp-admin/includes/update-core.php */
				apply_filters( 'update_feedback', $this-&gt;strings['start_rollback'] );

				$rollback_result = $this-&gt;upgrade( $current, array_merge( $parsed_args, array( 'do_rollback' =&gt; true ) ) );

				$original_result = $result;
				$result          = new WP_Error(
					'rollback_was_required',
					$this-&gt;strings['rollback_was_required'],
					(object) array(
						'update'   =&gt; $original_result,
						'rollback' =&gt; $rollback_result,
					)
				);
			}
		}

		/** This action is documented in wp-admin/includes/class-wp-upgrader.php */
		do_action(
			'upgrader_process_complete',
			$this,
			array(
				'action' =&gt; 'update',
				'type'   =&gt; 'core',
			)
		);

		// Clear the current updates.
		delete_site_transient( 'update_core' );

		if ( ! $parsed_args['do_rollback'] ) {
			$stats = array(
				'update_type'      =&gt; $current-&gt;response,
				'success'          =&gt; true,
				'fs_method'        =&gt; $wp_filesystem-&gt;method,
				'fs_method_forced' =&gt; defined( 'FS_METHOD' ) || has_filter( 'filesystem_method' ),
				'fs_method_direct' =&gt; ! empty( $GLOBALS['_wp_filesystem_direct_method'] ) ? $GLOBALS['_wp_filesystem_direct_method'] : '',
				'time_taken'       =&gt; time() - $start_time,
				'reported'         =&gt; $wp_version,
				'attempted'        =&gt; $current-&gt;version,
			);

			if ( is_wp_error( $result ) ) {
				$stats['success'] = false;
				// Did a rollback occur?
				if ( ! empty( $try_rollback ) ) {
					$stats['error_code'] = $original_result-&gt;get_error_code();
					$stats['error_data'] = $original_result-&gt;get_error_data();
					// Was the rollback successful? If not, collect its error too.
					$stats['rollback'] = ! is_wp_error( $rollback_result );
					if ( is_wp_error( $rollback_result ) ) {
						$stats['rollback_code'] = $rollback_result-&gt;get_error_code();
						$stats['rollback_data'] = $rollback_result-&gt;get_error_data();
					}
				} else {
					$stats['error_code'] = $result-&gt;get_error_code();
					$stats['error_data'] = $result-&gt;get_error_data();
				}
			}

			wp_version_check( $stats );
		}

		WP_Upgrader::release_lock( 'core_updater' );

		return $result;
	}

	/**
	 * Determines if this WordPress Core version should update to an offered version or not.
	 *
	 * @since 3.7.0
	 *
	 * @param string $offered_ver The offered version, of the format x.y.z.
	 * @return bool True if we should update to the offered version, otherwise false.
	 */
	public static function should_update_to_version( $offered_ver ) {
		require ABSPATH . WPINC . '/version.php'; // $wp_version; // x.y.z

		$current_branch = implode( '.', array_slice( preg_split( '/[.-]/', $wp_version ), 0, 2 ) ); // x.y
		$new_branch     = implode( '.', array_slice( preg_split( '/[.-]/', $offered_ver ), 0, 2 ) ); // x.y

		$current_is_development_version = (bool) strpos( $wp_version, '-' );

		// Defaults:
		$upgrade_dev   = get_site_option( 'auto_update_core_dev', 'enabled' ) === 'enabled';
		$upgrade_minor = get_site_option( 'auto_update_core_minor', 'enabled' ) === 'enabled';
		$upgrade_major = get_site_option( 'auto_update_core_major', 'unset' ) === 'enabled';

		// WP_AUTO_UPDATE_CORE = true (all), 'beta', 'rc', 'development', 'branch-development', 'minor', false.
		if ( defined( 'WP_AUTO_UPDATE_CORE' ) ) {
			if ( false === WP_AUTO_UPDATE_CORE ) {
				// Defaults to turned off, unless a filter allows it.
				$upgrade_dev   = false;
				$upgrade_minor = false;
				$upgrade_major = false;
			} elseif ( true === WP_AUTO_UPDATE_CORE
				|| in_array( WP_AUTO_UPDATE_CORE, array( 'beta', 'rc', 'development', 'branch-development' ), true )
			) {
				// ALL updates for core.
				$upgrade_dev   = true;
				$upgrade_minor = true;
				$upgrade_major = true;
			} elseif ( 'minor' === WP_AUTO_UPDATE_CORE ) {
				// Only minor updates for core.
				$upgrade_dev   = false;
				$upgrade_minor = true;
				$upgrade_major = false;
			}
		}

		// 1: If we're already on that version, not much point in updating?
		if ( $offered_ver === $wp_version ) {
			return false;
		}

		// 2: If we're running a newer version, that's a nope.
		if ( version_compare( $wp_version, $offered_ver, '&gt;' ) ) {
			return false;
		}

		$failure_data = get_site_option( 'auto_core_update_failed' );
		if ( $failure_data ) {
			// If this was a critical update failure, cannot update.
			if ( ! empty( $failure_data['critical'] ) ) {
				return false;
			}

			// Don't claim we can update on update-core.php if we have a non-critical failure logged.
			if ( $wp_version === $failure_data['current'] &amp;&amp; str_contains( $offered_ver, '.1.next.minor' ) ) {
				return false;
			}

			/*
			 * Cannot update if we're retrying the same A to B update that caused a non-critical failure.
			 * Some non-critical failures do allow retries, like download_failed.
			 * 3.7.1 =&gt; 3.7.2 resulted in files_not_writable, if we are still on 3.7.1 and still trying to update to 3.7.2.
			 */
			if ( empty( $failure_data['retry'] ) &amp;&amp; $wp_version === $failure_data['current'] &amp;&amp; $offered_ver === $failure_data['attempted'] ) {
				return false;
			}
		}

		// 3: 3.7-alpha-25000 -&gt; 3.7-alpha-25678 -&gt; 3.7-beta1 -&gt; 3.7-beta2.
		if ( $current_is_development_version ) {

			/**
			 * Filters whether to enable automatic core updates for development versions.
			 *
			 * @since 3.7.0
			 *
			 * @param bool $upgrade_dev Whether to enable automatic updates for
			 *                          development versions.
			 */
			if ( ! apply_filters( 'allow_dev_auto_core_updates', $upgrade_dev ) ) {
				return false;
			}
			// Else fall through to minor + major branches below.
		}

		// 4: Minor in-branch updates (3.7.0 -&gt; 3.7.1 -&gt; 3.7.2 -&gt; 3.7.4).
		if ( $current_branch === $new_branch ) {

			/**
			 * Filters whether to enable minor automatic core updates.
			 *
			 * @since 3.7.0
			 *
			 * @param bool $upgrade_minor Whether to enable minor automatic core updates.
			 */
			return apply_filters( 'allow_minor_auto_core_updates', $upgrade_minor );
		}

		// 5: Major version updates (3.7.0 -&gt; 3.8.0 -&gt; 3.9.1).
		if ( version_compare( $new_branch, $current_branch, '&gt;' ) ) {

			/**
			 * Filters whether to enable major automatic core updates.
			 *
			 * @since 3.7.0
			 *
			 * @param bool $upgrade_major Whether to enable major automatic core updates.
			 */
			return apply_filters( 'allow_major_auto_core_updates', $upgrade_major );
		}

		// If we're not sure, we don't want it.
		return false;
	}

	/**
	 * Compares the disk file checksums against the expected checksums.
	 *
	 * @since 3.7.0
	 *
	 * @global string $wp_version       The WordPress version string.
	 * @global string $wp_local_package Locale code of the package.
	 *
	 * @return bool True if the checksums match, otherwise false.
	 */
	public function check_files() {
		global $wp_version, $wp_local_package;

		$checksums = get_core_checksums( $wp_version, isset( $wp_local_package ) ? $wp_local_package : 'en_US' );

		if ( ! is_array( $checksums ) ) {
			return false;
		}

		foreach ( $checksums as $file =&gt; $checksum ) {
			// Skip files which get updated.
			if ( str_starts_with( $file, 'wp-content' ) ) {
				continue;
			}
			if ( ! file_exists( ABSPATH . $file ) || md5_file( ABSPATH . $file ) !== $checksum ) {
				return false;
			}
		}

		return true;
	}
}
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