使用springMVC通过Filter实现防止xss注入

springMVC Filter防止xss注入

跨站脚本工具(cross 斯特scripting),为不和层叠样式表(cascading style sheets,CSS)的缩写混淆,故将跨站脚本攻击缩写为XSS。

恶意攻击者往web页面里插入恶意scriptScript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。

防止XSS攻击简单的预防就是对Request请求中的一些参数去掉一些比较敏感的脚本命令。

原本是打算通过springMVC的HandlerInterceptor机制来实现的,通过获取request然后对request中的参数进行修改,结果虽然值修改了,但在Controller中获取的数值还是没有修改的。没办法就是要Filter来完成。

简单来说就是创建一个新的httpRequest类XsslHttpServletRequestWrapper,然后重写一些get方法(获取参数时对参数进行XSS判断预防)。

@WebFilter(filterName="xssMyfilter",urlPatterns="/*") 
public class MyXssFilter implements Filter{ 
	@Override
	public void init(FilterConfig filterConfig) throws ServletException {		
	}
 
	@Override
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
	        throws IOException, ServletException {
		XsslHttpServletRequestWrapper xssRequest = new XsslHttpServletRequestWrapper((HttpServletRequest)request);
		chain.doFilter(xssRequest , response); 
	}
	
	@Override
	public void destroy() {		
	}	
}

XSS代码的过滤是在XsslHttpServletRequestWrapper中实现的,主要是覆盖实现了getParameter,getParameterValues,getHeader这几个方法,然后对获取的value值进行XSS处理。

public class XsslHttpServletRequestWrapper extends HttpServletRequestWrapper { 
  HttpServletRequest xssRequest = null;  
 public XsslHttpServletRequestWrapper(HttpServletRequest request) {
  super(request);
  xssRequest = request;
 } 
 
  @Override  
  public String getParameter(String name) {  
       String value = super.getParameter(replaceXSS(name));  
         if (value != null) {  
             value = replaceXSS(value);  
         }  
         return value;  
  }  
  
  @Override
 public String[] getParameterValues(String name) {
   String[] values = super.getParameterValues(replaceXSS(name));
   if(values != null && values.length > 0){
    for(int i =0; i< values.length ;i++){
     values[i] = replaceXSS(values[i]);
    }
   }
  return values;
  }
  
  @Override  
  public String getHeader(String name) {  
   
         String value = super.getHeader(replaceXSS(name));  
         if (value != null) {  
             value = replaceXSS(value);  
         }  
         return value;  
     } 
  /**
   * 去除待带script、src的语句,转义替换后的value值
   */
 public static String replaceXSS(String value) {
     if (value != null) {
         try{
          value = value.replace("+","%2B");   //'+' replace to '%2B'
          value = URLDecoder.decode(value, "utf-8");
         }catch(UnsupportedEncodingException e){
         }catch(IllegalArgumentException e){
     }
         
   // Avoid null characters
   value = value.replaceAll("\0", "");
 
   // Avoid anything between script tags
   Pattern scriptPattern = Pattern.compile("", Pattern.CASE_INSENSITIVE);
   value = scriptPattern.matcher(value).replaceAll("");
 
   // Avoid anything in a src='...' type of e­xpression
   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("");
 
   // Remove any lonesome  tag
   scriptPattern = Pattern.compile("", Pattern.CASE_INSENSITIVE);
   value = scriptPattern.matcher(value).replaceAll("");
 
   // Remove any lonesome 
                    
                    

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