安全

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概述

This document is an analysis and explanation of the WordPress core software development and its related security processes, as well as an examination of the inherent security built directly into the software. Decision makers evaluating WordPress as a content management system or web application framework should use this document in their analysis and decision-making, and for developers to refer to it to familiarize themselves with the security components and best practices of the software.

The information in this document is up-to-date for the latest stable release of the software, WordPress 4.7 at time of publication, but should be considered relevant also to the most recent versions of the software as backwards compatibility is a strong focus for the WordPress development team. Specific security measures and changes will be noted as they have been added to the core software in specific releases. It is strongly encouraged to always be running the latest stable version of WordPress to ensure the most secure experience possible.

执行摘要

WordPress is a dynamic open-source content management system which is used to power millions of websites, web applications, and blogs. It currently powers more than 35% of the top 10 million websites on the Internet. WordPress’ usability, extensibility, and mature development community make it a popular and secure choice for websites of all sizes.

自2003年成立以来，WordPress经历了不断的加强，其核心软件能够处理和减轻常见的安全威胁，包括在开放Web应用程序安全项目(OWASP)中列出的十大常见安全漏洞，本文将对此进行讨论。

The WordPress Security Team, in collaboration with the WordPress Core Leadership Team and backed by the WordPress global community, works to identify and resolve security issues in the core software available for distribution and installation at WordPress.org, as well as recommending and documenting security best practices for third-party plugin and theme authors.

Site developers and administrators should pay particular attention to the correct use of core APIs and underlying server configuration which have been the source of common vulnerabilities, as well as ensuring all users employ strong passwords to access WordPress.

WordPress 概要

WordPress is a free and open source content management system (CMS). It is the most widely-used CMS software in the world and it powers more than 35% of the top 10 million websites1, giving it an estimated 62% market share of all sites using a CMS.

WordPress is licensed under the General Public License (GPLv2 or later) which provides four core freedoms, and can be considered as the WordPress “bill of rights”:

  1. 为任何目的运行程序的自由。
  2. 可以自由地研究程序的工作原理，并对其进行更改以使其按您的意愿进行。
  3. 重新分发的自由。
  4. 将您修改后的版本分发给他人的自由。

WordPress 核心领导团队

The WordPress project is a meritocracy, run by a core leadership team, and led by its co-creator and lead developer, Matt Mullenweg. The team governs all aspects of the project, including core development, WordPress.org, and community initiatives.

The Core Leadership Team consists of Matt Mullenweg, five lead developers, and more than a dozen core developers with permanent commit access. These developers have final authority on technical decisions, and lead architecture discussions and implementation efforts.

WordPress has a number of contributing developers. Some of these are former or current committers, and some are likely future committers. These contributing developers are trusted and veteran contributors to WordPress who have earned a great deal of respect among their peers. As needed, WordPress also has guest committers, individuals who are granted commit access, sometimes for a specific component, on a temporary or trial basis.

The core and contributing developers primarily guide WordPress development. Every version, hundreds of developers contribute code to WordPress. These core contributors are volunteers who contribute to the core codebase in some way.

WordPress 发布周期

Each WordPress release cycle is led by one or more of the core WordPress developers. A release cycle usually lasts around 4 months from the initial scoping meeting to launch of the version.

A release cycle follows the following pattern2:

  • Phase 1: Planning and securing team leads. This is done in the #core chat room on Slack. The release lead discusses features for the next release of WordPress. WordPress contributors get involved with that discussion. The release lead will identify team leads for each of the features.
  • Phase 2: Development work begins. Team leads assemble teams and work on their assigned features. Regular chats are scheduled to ensure the development keeps moving forward.
  • Phase 3: Beta. Betas are released, and beta-testers are asked to start reporting bugs. No more commits for new enhancements or feature requests are carried out from this phase on. Third-party plugin and theme authors are encouraged to test their code against the upcoming changes.
  • Phase 4: Release Candidate. There is a string freeze for translatable strings from this point on. Work is targeted on regressions and blockers only.
  • Phase 5: Launch. WordPress version is launched and made available in the WordPress Admin for updates.

版本编号和安全发行

A major WordPress version is dictated by the first two sequences. For example, 3.5 is a major release, as is 3.6, 3.7, or 4.0. There isn’t a “WordPress 3” or “WordPress 4” and each major release is referred to by its numbering, e.g., “WordPress 3.9.”

Major releases may add new user features and developer APIs. Though typically in the software world, a “major” version means you can break backwards compatibility, WordPress strives to never break backwards compatibility. Backwards compatibility is one of the project’s most important philosophies, with the aim of making updates much easier on users and developers alike.

A minor WordPress version is dictated by the third sequence. Version 3.5.1 is a minor release, as is 3.4.23. A minor release is reserved for fixing security vulnerabilities and addressing critical bugs only. Since new versions of WordPress are released so frequently — the aim is every 4-5 months for a major release, and minor releases happen as needed — there is only a need for major and minor releases.

Version Backwards Compatibility

The WordPress project has a strong commitment to backwards compatibility. This commitment means that themes, plugins, and custom code continues to function when WordPress core software is updated, encouraging site owners to keep their WordPress version updated to the latest secure release.

WordPress 和安全性

WordPress 安全团队

The WordPress Security Team is made up of approximately 50 experts including lead developers and security researchers — about half are employees of Automattic (makers of WordPress.com, the earliest and largest WordPress hosting platform on the web), and a number work in the web security field. The team consults with well-known and trusted security researchers and hosting companies3.

The WordPress Security Team often collaborates with other security teams to address issues in common dependencies, such as resolving the vulnerability in the PHP XML parser, used by the XML-RPC API that ships with WordPress, in WordPress 3.9.24. This vulnerability resolution was a result of a joint effort by both WordPress and Drupal security teams.

WordPress 安全风险，进程，和历史

The WordPress Security Team believes in Responsible Disclosure by alerting the security team immediately of any potential vulnerabilities. Potential security vulnerabilities can be signaled to the Security Team via the WordPress HackerOne5. The Security Team communicates amongst itself via a private Slack channel, and works on a walled-off, private Trac for tracking, testing, and fixing bugs and security problems.

Each security report is acknowledged upon receipt, and the team works to verify the vulnerability and determine its severity. If confirmed, the security team then plans for a patch to fix the problem which can be committed to an upcoming release of the WordPress software or it can be pushed as an immediate security release, depending on the severity of the issue.

For an immediate security release, an advisory is published by the Security Team to the WordPress.org News site6 announcing the release and detailing the changes. Credit for the responsible disclosure of a vulnerability is given in the advisory to encourage and reinforce continued responsible reporting in the future.

当有新版本可用时，WordPress软件的管理员会在其网站仪表盘上看到一条有关升级的通知，并且在进行手动升级后，用户将被重定向到“关于WordPress”屏幕，其中会对改进进行详细介绍。 如果管理员启用了自动后台更新，则他们将在升级完成后收到一封电子邮件。

安全发行版本的自动后台更新

从3.7版开始，WordPress为所有次要版本7（例如3.7.1和3.7.2）引入了自动后台更新。 WordPress安全团队可以识别，修复和推出针对WordPress的自动化安全增强功能，而站点所有者无需在终端上做任何事情，并且该安全更新将自动安装。

When a security update is pushed for the current stable release of WordPress, the core team will also push security updates for all the releases that are capable of background updates (since WordPress 3.7), so these older but still recent versions of WordPress will receive security enhancements.

Individual site owners can opt to remove automatic background updates through a simple change in their configuration file, but keeping the functionality is strongly recommended by the core team, as well as running the latest stable release of WordPress.

2013 OWASP Top 10

The Open Web Application Security Project (OWASP) is an online community dedicated to web application security. The OWASP Top 10 list8 focuses on identifying the most serious application security risks for a broad array of organizations. The Top 10 items are selected and prioritized in combination with consensus estimates of exploitability, detectability, and impact estimates.

The following sections discuss the APIs, resources, and policies that WordPress uses to strengthen the core software and 3rd party plugins and themes against these potential risks.

A1 - 注入

There is a set of functions and APIs available in WordPress to assist developers in making sure unauthorized code cannot be injected, and help them validate and sanitize data. Best practices and documentation are available9 on how to use these APIs to protect, validate, or sanitize input and output data in HTML, URLs, HTTP headers, and when interacting with the database and filesystem. Administrators can also further restrict the types of file which can be uploaded via filters.

A2-中断的身份验证和会话管理

WordPress core software manages user accounts and authentication and details such as the user ID, name, and password are managed on the server-side, as well as the authentication cookies. Passwords are protected in the database using standard salting and stretching techniques. Existing sessions are destroyed upon logout for versions of WordPress after 4.0.

A3 - 跨站脚本（XSS）

WordPress provides a range of functions which can help ensure that user-supplied data is safe10. Trusted users, that is administrators and editors on a single WordPress installation, and network administrators only in WordPress Multisite, can post unfiltered HTML or JavaScript as they need to, such as inside a post or page. Untrusted users and user-submitted content is filtered by default to remove dangerous entities, using the KSES library through the wp_kses function.

As an example, the WordPress core team noticed before the release of WordPress 2.3 that the function the_search_query() was being misused by most theme authors, who were not escaping the function’s output for use in HTML. In a very rare case of slightly breaking backward compatibility, the function’s output was changed in WordPress 2.3 to be pre-escaped.

A4-不安全的直接对象引用

WordPress often provides direct object reference, such as unique numeric identifiers of user accounts or content available in the URL or form fields. While these identifiers disclose direct system information, WordPress’ rich permissions and access control system prevent unauthorized requests.

A5 - 安全性配置错误

The majority of the WordPress security configuration operations are limited to a single authorized administrator. Default settings for WordPress are continually evaluated at the core team level, and the WordPress core team provides documentation and best practices to tighten security for server configuration for running a WordPress site11.

A6 - 敏感数据泄露

WordPress user account passwords are salted and hashed based on the Portable PHP Password Hashing Framework12. WordPress’ permission system is used to control access to private information such an registered users’ PII, commenters’ email addresses, privately published content, etc. In WordPress 3.7, a password strength meter was included in the core software providing additional information to users setting their passwords and hints on increasing strength. WordPress also has an optional configuration setting for requiring HTTPS.

A7 - Missing Function Level Access Control

WordPress checks for proper authorization and permissions for any function level access requests prior to the action being executed. Access or visualization of administrative URLs, menus, and pages without proper authentication is tightly integrated with the authentication system to prevent access from unauthorized users.

A8 - 跨站请求伪造攻击

WordPress uses cryptographic tokens, called nonces13, to validate intent of action requests from authorized users to protect against potential CSRF threats. WordPress provides an API for the generation of these tokens to create and verify unique and temporary tokens, and the token is limited to a specific user, a specific action, a specific object, and a specific time period, which can be added to forms and URLs as needed. Additionally, all nonces are invalidated upon logout.

A9 - 使用具有已知漏洞的组件

The WordPress core team closely monitors the few included libraries and frameworks WordPress integrates with for core functionality. In the past the core team has made contributions to several third-party components to make them more secure, such as the update to fix a cross-site vulnerability in TinyMCE in WordPress 3.5.214.

If necessary, the core team may decide to fork or replace critical external components, such as when the SWFUpload library was officially replaced by the Plupload library in 3.5.2, and a secure fork of SWFUpload was made available by the security team<15 for those plugins who continued to use SWFUpload in the short-term.

A10 - 未经验证的重定向和转发

WordPress’ internal access control and authentication system will protect against attempts to direct users to unwanted destinations or automatic redirects. This functionality is also made available to plugin developers via an API, wp_safe_redirect()16.

进一步的安全风险和担忧

XXE (XML eXternal Entity) processing attacks

When processing XML, WordPress disables the loading of custom XML entities to prevent both External Entity and Entity Expansion attacks. Beyond PHP’s core functionality, WordPress does not provide additional secure XML processing API for plugin authors.

SSRF（服务端请求伪造）攻击

HTTP requests issued by WordPress are filtered to prevent access to loopback and private IP addresses. Additionally, access is only allowed to certain standard HTTP ports.

WordPress 插件和主题安全

默认主题

WordPress requires a theme to be enabled to render content visible on the frontend. The default theme which ships with core WordPress (currently "Twenty Twenty") has been vigorously reviewed and tested for security reasons by both the team of theme developers plus the core development team.

The default theme can serve as a starting point for custom theme development, and site developers can create a child theme which includes some customization but falls back on the default theme for most functionality and security. The default theme can be easily removed by an administrator if not needed.

WordPress.org 主题和插件代码仓库

There are approximately 50,000+ plugins and 5,000+ themes listed on the WordPress.org site. These themes and plugins are submitted for inclusion and are manually reviewed by volunteers before making them available on the repository.

Inclusion of plugins and themes in the repository is not a guarantee that they are free from security vulnerabilities. Guidelines are provided for plugin authors to consult prior to submission for inclusion in the repository17, and extensive documentation about how to do WordPress theme development18 is provided on the WordPress.org site.

Each plugin and theme has the ability to be continually developed by the plugin or theme owner, and any subsequent fixes or feature development can be uploaded to the repository and made available to users with that plugin or theme installed with a description of that change. Site administrators are notified of plugins which need to be updated via their administration dashboard.

When a plugin vulnerability is discovered by the WordPress Security Team, they contact the plugin author and work together to fix and release a secure version of the plugin. If there is a lack of response from the plugin author or if the vulnerability is severe, the plugin/theme is pulled from the public directory, and in some cases, fixed and updated directly by the Security Team.

主题审核团队

The Theme Review Team is a group of volunteers, led by key and established members of the WordPress community, who review and approve themes submitted to be included in the official WordPress Theme directory. The Theme Review Team maintains the official Theme Review Guidelines19, the Theme Unit Test Datas20, and the Theme Check Plugins21, and attempts to engage and educate the WordPress Theme developer community regarding development best practices. Inclusion in the group is moderated by core committers of the WordPress development team.

The Role of the Hosting Provider in WordPress Security

WordPress can be installed on a multitude of platforms. Though WordPress core software provides many provisions for operating a secure web application, which were covered in this document, the configuration of the operating system and the underlying web server hosting the software is equally important to keep the WordPress applications secure.

A Note about WordPress.com and WordPress security

WordPress.com is the largest WordPress installation in the world, and is owned and managed by Automattic, Inc., which was founded by Matt Mullenweg, the WordPress project co-creator. WordPress.com runs on the core WordPress software, and has its own security processes, risks, and solutions22. This document refers to security regarding the self-hosted, downloadable open source WordPress software available from WordPress.org and installable on any server in the world.

附录

核心 WordPress APIs

The WordPress Core Application Programming Interface (API) is comprised of several individual APIs23, each one covering the functions involved in, and use of, a given set of functionality. Together, these form the project interface which allows plugins and themes to interact with, alter, and extend WordPress core functionality safely and securely.

While each WordPress API provides best practices and standardized ways to interact with and extend WordPress core software, the following WordPress APIs are the most pertinent to enforcing and hardening WordPress security:

数据库 API

WordPress 0.71中添加的数据库API24提供了正确的方法来访问数据库层中存储的命名值数据。

文件系统 API

WordPress 2.626中添加的文件系统 API25最初是为WordPress自己的自动更新功能创建的。在各种主机类型上，文件系统 API提取了安全地完成将本地文件读写到文件系统所需的功能。

It does this through the WP_Filesystem_Base class, and several subclasses which implement different ways of connecting to the local filesystem, depending on individual host support. Any theme or plugin that needs to write files locally should do so using the WP_Filesystem family of classes.

HTTP API

The HTTP API27, added in WordPress 2.728 and extended further in WordPress 2.8, standardizes the HTTP requests for WordPress. The API handles cookies, gzip encoding and decoding, chunk decoding (if HTTP 1.1), and various other HTTP protocol implementations. The API standardizes requests, tests each method prior to sending, and, based on your server configuration, uses the appropriate method to make the request.

权限和当前用户 API

The permissions and current user API29 is a set of functions which will help verify the current user’s permissions and authority to perform any task or operation being requested, and can protect further against unauthorized users accessing or performing functions beyond their permitted capabilities.

White paper content License

The text in this document (not including the WordPress logo or trademark) is licensed under CC0 1.0 Universal (CC0 1.0) Public Domain Dedication. You can copy, modify, distribute and perform the work, even for commercial purposes, all without asking permission.

A special thank you to Drupal’s security white paper, which provided some inspiration.

附加阅读

作者 Sara Rosso

Contributions from Barry Abrahamson, Michael Adams, Jon Cave, Helen Hou-Sandí, Dion Hulse, Mo Jangda, Paul Maiorana

Version 1.0 March 2015

脚注