package com.system.filter;

import java.io.IOException;
import java.util.Enumeration;

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;
import javax.servlet.http.HttpServletResponse;

import org.apache.log4j.Logger;
/** 
 * 非法字符过滤器 
 * 1.所有非法字符配置在web.xml中，如需添加新字符，请自行配置 
 * 2.请注意请求与相应的编码格式设置
 * @author lee 
 * 
 */  
public class XSSFilter implements Filter{
	private static final Logger log = Logger.getLogger(XSSFilter.class);
    private String encoding;  
    private String[] illegalChars;  
    private final String str="<,>";
	@Override
	public void destroy() {
		// TODO Auto-generated method stub
		encoding = null;  
        illegalChars = null;  
	}

	@Override
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain)
			throws IOException, ServletException {
		// TODO Auto-generated method stub
		HttpServletRequest req = (HttpServletRequest)request;  
        HttpServletResponse res = (HttpServletResponse) response;  
          
        //必须手动指定编码格式  
        req.setCharacterEncoding(encoding);  
        String tempURL = req.getRequestURI();   
        log.info(tempURL);  
        Enumeration params = req.getParameterNames();  
          
        //是否执行过滤  true：执行过滤  false：不执行过滤  
        boolean executable = true;  
          
        //非法状态  true：非法  false；不非法  
        boolean illegalStatus = false;  
        String illegalChar = "";  
        //对参数名与参数进行判断  
        w:while(params.hasMoreElements()){  
              
            String paramName = (String) params.nextElement();  
              
            executable = true;  
              
            //密码不过滤  
            if(paramName.toLowerCase().contains("password")){  
                executable = false;  
            }
              
            if(executable){  
                String[] paramValues = req.getParameterValues(paramName); 
                  
                f1:for(int i=0;i<paramValues.length;i++){  
                      
                    String paramValue = paramValues[i];  
                      
                    f2:for(int j=0;j<illegalChars.length;j++){  
                          
                        illegalChar = illegalChars[j];  
                        if(paramValue.indexOf(illegalChar) != -1){  
                            illegalStatus = true;//非法状态  
                            break f2;  
                        }  
                    }  
                      
                    if(illegalStatus){  
                        break f1;  
                    }  
                      
                }  
            }  
              
            if(illegalStatus){  
                break w;  
            }  
        }  
        if(illegalStatus){  
            //必须手动指定编码格式  
            res.setContentType("text/html;charset="+encoding);  
            res.setCharacterEncoding(encoding);  
            res.getWriter().print("<script>window.alert('当前链接中存在非法字符');window.history.go(-1);</script>");  
        }else{  
            filterChain.doFilter(request, response);  
        }  
	}

	@Override
	public void init(FilterConfig filterConfig) throws ServletException {
		// TODO Auto-generated method stub
		encoding = filterConfig.getInitParameter("encoding");  
        illegalChars = str.split(",");  
	}
}