web项目脚本过滤--XSS过滤器

XSS脚本过滤

脚本攻击经常是项目测试人员或者“不法分子”闲着没事干，想办法让你的程序不正常，最近项目中刚好用到所以就贴出来做个笔记。

1.思路

我们可以通过servlet规范中的过滤器，对每一次请求进行过滤 --> 将请求参数获取到对脚本数据进行转义处理后再进行持久化操作，比如< script > < /script>中的'<' ,'>'号。

2.配置过滤器

在项目中web.xml中添加:

  <filter>  
    <filter-name>XSSEscape</filter-name>  
    <filter-class>com.hp.up.front.xss.XSSFilter</filter-class>
</filter>  
<filter-mapping>  
    <filter-name>XSSEscape</filter-name>  
    <url-pattern>/*</url-pattern>  
    <dispatcher>REQUEST</dispatcher>  
</filter-mapping> 

其中com.hp.up.front.xss.XSSFilter就是过滤器路径

3.编写过滤器

自然是实现javax.servlet.Filter 重写doFilter了:

import java.io.IOException;
import javax.servlet.Filter;
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 Filter {  
    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
    }
    @Override
    public void destroy() {
    }
    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
        throws IOException, ServletException {
        chain.doFilter(new XSSRequestWrapper((HttpServletRequest) request), response);
    }
}

doFilter方法中传入XSSRequestWrapper对象，该类集成自HttpServletRequestWrapper，其实就是对HttpServletRequest中获取参数的方法的重写，从而实现对参数进行过滤、操作

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;

import org.apache.commons.lang.StringEscapeUtils;

public class XSSRequestWrapper extends HttpServletRequestWrapper{

public XSSRequestWrapper(HttpServletRequest request) {  
    super(request);  
}  

@Override  
public String getHeader(String name) {  
    return StringEscapeUtils.escapeHtml(super.getHeader(name));  
}  

@Override  
public String getQueryString() {  
    return StringEscapeUtils.escapeHtml(super.getQueryString());  
}  

@Override  
public String getParameter(String name) {  
    return StringEscapeUtils.escapeHtml(super.getParameter(name));  
}  

@Override  
public String[] getParameterValues(String name) {  
    String[] values = super.getParameterValues(name);  
    if(values != null) {  
        int length = values.length;  
        String[] escapseValues = new String[length];  
        for(int i = 0; i < length; i++){  
            escapseValues[i] = htmlEncode(values[i]);  
        }  
        return escapseValues;  
    }
    return super.getParameterValues(name);  
}

private static String htmlEncode(String source) {
    if (source == null) {
        return "";
    }
    String html = "";
    StringBuffer buffer = new StringBuffer();
    for (int i = 0; i < source.length(); i++) {
        char c = source.charAt(i);
        switch (c) {
        case '<':
            buffer.append("&lt;");
            break;
        case '>':
            buffer.append("&gt;");
            break;
        case '&':
            buffer.append("&amp;");
            break;
        case '"':
            buffer.append("&quot;");
            break;
        case 10:
        case 13:
            break;
        default:
            buffer.append(c);
        }
    }
    html = buffer.toString();
    return html;
 }  
}

最终发现每次提交数据拦截器都会对数据中的脚本进行转义后再存到数据库中: