Java实现XSS防御

XSS概述

跨站脚本攻击(Cross Site Scripting)，缩写为XSS。恶意攻击者往Web页面里插入恶意Script代码，当用户浏览该页之时，嵌入其中Web里面的Script代码会被执行，从而达到恶意攻击用户的目的。

Servlet的方式

1、继承HttpServletRequestWrapper，实现对请求参数的过滤

/**

 * xss请求适配器

 */

public class XssHttpServletRequestWrapper extends HttpServletRequestWrapper {

    public XssHttpServletRequestWrapper(HttpServletRequest request) {

        super(request);

    }

    /**

     * 对数组参数进行特殊字符过滤

     */

    @Override

    public String[] getParameterValues(String name) {

        String[] values = super.getParameterValues(name);

        if (values == null) {

            return null;

        }

        int count = values.length;

        String[] encodedValues = new String[count];

        for (int i = 0; i < count; i++) {

            encodedValues[i] = cleanXSS(values[i]);

        }

        return encodedValues;

    }

    /**

     * 对参数中特殊字符进行过滤

     */

    @Override

    public String getParameter(String name) {

        String value = super.getParameter(name);

        if (value == null) {

            return null;

        }

        return cleanXSS(value);

    }

    /**

     * 获取attribute,特殊字符过滤

     */

    @Override

    public Object getAttribute(String name) {

        Object value = super.getAttribute(name);

        if (value != null && value instanceof String) {

            cleanXSS((String) value);

        }

        return value;

    }

    /**

     * 对请求头部进行特殊字符过滤

     */

    @Override

    public String getHeader(String name) {

        String value = super.getHeader(name);

        if (value == null) {

            return null;

        }

        return cleanXSS(value);

    }

    /**

     * 转义字符,使用该方法存在一定的弊端

     *

     * @param value

     * @return

     */

    private String cleanXSS2(String value) {

        // 移除特殊标签

        value = value.replaceAll("<", "&lt;").replaceAll(">", "&gt;");

        value = value.replaceAll("\\(", "(").replaceAll("\\)", ")");

        value = value.replaceAll("'", "'");

        value = value.replaceAll("eval\\((.*)\\)", "");

        value = value.replaceAll("[\\\"\\\'][\\s]*javascript:(.*)[\\\"\\\']", "\"\"");

        value = value.replaceAll("script", "");

        return value;

    }

    private String cleanXSS(String value) {

        if (value != null) {

            //推荐使用ESAPI库来避免脚本攻击,value = ESAPI.encoder().canonicalize(value);

            // 避免空字符串

            value = value.replaceAll(" ", "");

            // 避免script 标签

            Pattern scriptPattern = Pattern.compile("<script>(.*?)</script>", Pattern.CASE_INSENSITIVE);

            value = scriptPattern.matcher(value).replaceAll("");

            // 避免src形式的表达式

            scriptPattern = Pattern.compile("src[\r\n]*=[\r\n]*\\\'(.*?)\\\'",

                    Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);

            value = scriptPattern.matcher(value).replaceAll("");

            scriptPattern = Pattern.compile("src[\r\n]*=[\r\n]*\\\"(.*?)\\\"",

                    Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);

            value = scriptPattern.matcher(value).replaceAll("");

            // 删除单个的 </script> 标签

            scriptPattern = Pattern.compile("</script>", Pattern.CASE_INSENSITIVE);

            value = scriptPattern.matcher(value).replaceAll("");

            // 删除单个的<script ...> 标签

            scriptPattern = Pattern.compile("<script(.*?)>",

                    Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);

            value = scriptPattern.matcher(value).replaceAll("");

            // 避免 eval(...) 形式表达式

            scriptPattern = Pattern.compile("eval\\((.*?)\\)",

                    Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);

            value = scriptPattern.matcher(value).replaceAll("");

            // 避免 expression(...) 表达式

            scriptPattern = Pattern.compile("expression\\((.*?)\\)",

                    Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);

            value = scriptPattern.matcher(value).replaceAll("");

            // 避免 javascript: 表达式

            scriptPattern = Pattern.compile("javascript:", Pattern.CASE_INSENSITIVE);

            value = scriptPattern.matcher(value).replaceAll("");

            // 避免 vbscript:表达式

            scriptPattern = Pattern.compile("vbscript:", Pattern.CASE_INSENSITIVE);

            value = scriptPattern.matcher(value).replaceAll("");

            // 避免 onload= 表达式

            scriptPattern = Pattern.compile("onload(.*?)=",

                    Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);

            value = scriptPattern.matcher(value).replaceAll("");

        }

        return value;

    }

}

2、实现Filter，实现XSS过滤器

/**

 * xss过滤器

 */

public class XssFilter implements Filter {

    FilterConfig filterConfig = null;

    @Override

    public void init(FilterConfig filterConfig) throws ServletException {

        this.filterConfig = filterConfig;

    }

    @Override

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)

            throws IOException, ServletException {

        //对请求进行拦截,防xss处理

        chain.doFilter(new XssHttpServletRequestWrapper((HttpServletRequest) request), response);

    }

    @Override

    public void destroy() {

        this.filterConfig = null;

    }

}

3、注入XSS过滤器，两种方式
第一种方式：配置web.xml

<!-- xss过滤器 -->

<filter>

    <filter-name>XssSqlFilter</filter-name>

    <filter-class>cn.aric.xss.XssFilter</filter-class>

</filter>

<filter-mapping>

    <filter-name>XssSqlFilter</filter-name>

    <url-pattern>/*</url-pattern>

    <dispatcher>REQUEST</dispatcher>

    <dispatcher>FORWARD</dispatcher>

</filter-mapping>

第二种方式：注解

/**

 * 注入Xss过滤器(注解方式)

 */

public class WebInitializer implements WebApplicationInitializer{

    @Override

    public void onStartup(ServletContext servletContext) throws ServletException {

        //添加监听器

        servletContext.addListener(RequestContextListener.class);

        //添加过滤器

        Dynamic xssFilterRegistration = servletContext.addFilter("XssFilter", XssFilter.class);

        //添加映射规则

        xssFilterRegistration.addMappingForUrlPatterns(

                EnumSet.of(DispatcherType.REQUEST,DispatcherType.FORWARD,DispatcherType.INCLUDE),

                false,

                "/*");

    }

}

Spring整合的方式

1、使用spring的HtmlUtils,可以使用StringEscapeUtils 中的过滤方法

/**

 * 解决XSS跨站脚本攻击和sql注入攻击,使用spring的HtmlUtils,可以使用StringEscapeUtils 中的过滤方法

 */

public class XssSpringHttpServletRequestWrapper extends HttpServletRequestWrapper{

    public XssSpringHttpServletRequestWrapper(HttpServletRequest request) {

        super(request);

    }

    /**

     * 对数组参数进行特殊字符过滤

     */

    @Override

    public String[] getParameterValues(String name) {

        String[] values = super.getParameterValues(name);

        String[] newValues = new String[values.length];

        for (int i = 0; i < values.length; i++) {

            //spring的HtmlUtils进行转义

            newValues[i] = HtmlUtils.htmlEscape(values[i]);

        }

        return newValues;

    }

    /**

     * 拦截参数,并对其进行字符转义

     */

    @Override

    public String getParameter(String name) {

        return HtmlUtils.htmlEscape(name);

    }

    /**

     * 拦截参数,并对其进行字符转义

     */

    @Override

    public Object getAttribute(String name) {

        return HtmlUtils.htmlEscape(name);

    }

}

2、实现XSS过滤器

/**

 * spring方式xss过滤器

 */

public class XssSpringFilter implements Filter{

    @Override

    public void init(FilterConfig filterConfig) throws ServletException {

    }

    @Override

    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)

            throws IOException, ServletException {

        HttpServletRequest req = (HttpServletRequest) request;

        chain.doFilter(new XssSpringHttpServletRequestWrapper(req), response);

    }

    @Override

    public void destroy() {

    }

}

3、配置XSS过滤器

<!-- spring方式的xss过滤器 -->

<filter>

    <filter-name>xssSpringFilter</filter-name>

    <filter-class>cn.aric.xss.XssSpringHttpServletRequestWrapper</filter-class>

</filter>

<filter-mapping>

    <filter-name>xssSpringFilter</filter-name>

    <url-pattern>/*</url-pattern>

</filter-mapping>

巴特西

Java实现XSS防御

XSS概述

Servlet的方式

Spring整合的方式

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