Java防止xss攻击

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首先说一下思路,防止这种类似于注入攻击,就是使用拦截器(Filter)处理特殊字符或过滤特殊字符 今天介绍一个方法,利用覆盖Servlet的getParameter方法达到处理特殊字符的目的来解决(防止)Xss攻击 web.xml

<filter> 
    <filter-name>XssEscape</filter-name> 
    <filter-class>cn.wuzhuti.filter.XssFilter</filter-class> 
</filter> 
<filter-mapping> 
    <filter-name>XssEscape</filter-name> 
    <url-pattern>/*</url-pattern> 
    <dispatcher>REQUEST</dispatcher> 
</filter-mapping>

Filter类(XssFilter.java)

package cn.wuzhuti.filter;

import java.io.IOException;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;

public class XssFilter implements javax.servlet.Filter {

    @Override
    public void destroy() {
        // TODO Auto-generated method stub
    }
    
    @Override
    public void doFilter(ServletRequest request, ServletResponse response,
        FilterChain filterChain) throws IOException, ServletException {
     
        XssHttpServletRequestWrapper xssRequest = new XssHttpServletRequestWrapper((HttpServletRequest) request);
        filterChain.doFilter(xssRequest, response);
    }
    
    @Override
    public void init(FilterConfig arg0) throws ServletException {
        // TODO Auto-generated method stub
    }

}

最关键的类(XssHttpServletRequestWrapper.java) 继承servlet的HttpServletRequestWrapper,并重写相应的几个有可能带xss攻击的方法

package cn.wuzhuti.filter;

import java.io.StringReader;
import java.io.StringWriter;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;
import com.blogspot.radialmind.html.HTMLParser;
import com.blogspot.radialmind.xss.XSSFilter;

public class XssHttpServletRequestWrapper extends HttpServletRequestWrapper {
 
    HttpServletRequest orgRequest = null;

    public XssHttpServletRequestWrapper(HttpServletRequest request) {
        super(request);
        orgRequest = request;
    }

    /**
    * 覆盖getParameter方法,将参数名和参数值都做xss过滤。
    * 如果需要获得原始的值,则通过super.getParameterValues(name)来获取
    * getParameterNames,getParameterValues和getParameterMap也可能需要覆盖
    */
    @Override
    public String getParameter(String name) {
        String value = super.getParameter(xssEncode(name));
        if (value != null) {
            value = xssEncode(value);
        }
        return value;
    }

    /**
    * 覆盖getHeader方法,将参数名和参数值都做xss过滤。
    * 如果需要获得原始的值,则通过super.getHeaders(name)来获取
    * getHeaderNames 也可能需要覆盖
    */
    @Override
    public String getHeader(String name) {

    String value = super.getHeader(xssEncode(name));
        if (value != null) {
        value = xssEncode(value);
        }
        return value;
    }

    /**
    * 将容易引起xss漏洞的半角字符直接替换成全角字符
    * 
    * @param s
    * @return
    */
    private static String xssEncode(String s) {
        if (s == null || s.isEmpty()) {
            return s;
        }

        StringReader reader = new StringReader(s);
        StringWriter writer = new StringWriter();
        try {
            HTMLParser.process(reader, writer, new XSSFilter(), true);
            String result = writer.toString();
            System.out.println("xssEncode-------------------------" + s + " = " + result);
     
            return result;
        } catch (NullPointerException e) {
            return s;
        } catch (Exception ex) {
            ex.printStackTrace();
        }
        
        return null;
        
    }

    /**
    * 获取最原始的request
    * 
    * @return
    */
    public HttpServletRequest getOrgRequest() {
        return orgRequest;
    }
    
    /**
    * 获取最原始的request的静态方法
    * 
    * @return
    */
    public static HttpServletRequest getOrgRequest(HttpServletRequest req) {
        if (req instanceof XssHttpServletRequestWrapper) {
            return ((XssHttpServletRequestWrapper) req).getOrgRequest();
        }
    
        return req;
    }
}

通过重写getParameter()等方法,实现简单的过滤,从而防止Xss攻击 依赖jar包

百度网盘下载
xssProtect-0.1.jar
antlr-runtime-3.0.1.jar

其他连接
http://code.google.com/p/xssprotect/
http://xssprotect.googlecode.com/svn/trunk/

大家如果有更好的想法欢迎大家留言讨论。

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