实用：防止SQL、XSS等注入攻击的Filter

本文主要原理是转换过滤或拦截请求中的非法字符

FILTER代码：

XssFilter.java

/**
 * {@link CharLimitFilter}
 *
 * 拦截防止XSS注入
 *
 * @author Administrator
 */
public class XssFilter implements Filter {


	/* (non-Javadoc)
	 * @see javax.servlet.Filter#doFilter(javax.servlet.ServletRequest, javax.servlet.ServletResponse, javax.servlet.FilterChain)
	 */
	public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain) throws IOException,
			ServletException {
		
			XssHttpServletRequestWrapper xssRequest = new XssHttpServletRequestWrapper(
			(HttpServletRequest) request);
			filterChain.doFilter(xssRequest, response);
		
	}
	
	 public void init(FilterConfig conf) throws ServletException { 
		 System.out.println("PreventXSSInject Filter staring..."); 
         System.out.println(); 
	 }
	 
	 public void destroy() { 
         
	 } 

}

SqlInjectFilter.java

public class SqlInjectFilter implements Filter {
	private static List invalidsql = new ArrayList(); 
    private static String error = "/sqlerrors.jsp"; 
    private static boolean debug = false; 
     
    public void destroy() { 
         
    } 
    public void doFilter(ServletRequest req, ServletResponse res, 
            FilterChain fc) throws IOException, ServletException { 
       //防sql关键字注入
    	if(debug){ 
            System.out.println("prevent sql inject filter works"); 
        } 
        HttpServletRequest request = (HttpServletRequest)req; 
        HttpServletResponse response = (HttpServletResponse)res; 
        Map params = request.getParameterMap(); 
        Set keys = params.keySet(); 
        for(String key : keys){ 
            String value = request.getParameter(key); 
            if(debug){ 
                System.out.println("process params : <"+key+", "+value+">"); 
            } 
            for(String word : invalidsql){ 
                if(word.equalsIgnoreCase(value) || value.contains(word)){ 
                    if(value.contains("<")){ 
                        value = value.replace("<", "<"); 
                    } 
                    if(value.contains(">")){ 
                        value = value.replace(">", ">"); 
                    } 
                    if(value.contains("(")){ 
                    	value = value.replace("(", "（"); 
                    }
                    if(value.contains(")")){ 
                    	value = value.replace(")", "）"); 
                    }
                    request.getSession().setAttribute("sqlInjectError", "您输入的参数值  \""+value+"\" 中包含关键字: \""+word+"\""); 
                    response.sendRedirect(request.getContextPath()+error); 
                    return; 
                } 
            } 
        } 
        fc.doFilter(req, res);
    } 
    public void init(FilterConfig conf) throws ServletException { 
        String sql = conf.getInitParameter("invalidsql"); 
        String errorpage = conf.getInitParameter("error"); 
        String de = conf.getInitParameter("debug"); 
        if(errorpage != null){ 
            error = errorpage; 
        } 
        if(sql != null){ 
            //invalidsql = Arrays.asList(sql.split(" ")); 
        	String[] sqlarr = sql.split(" ");
        	for(String sqlword:sqlarr){
        		invalidsql.add(sqlword);
        	}
        	invalidsql.add("<");
            invalidsql.add(">");
            invalidsql.add("(");
            invalidsql.add(")");
        } 
        if(de != null && Boolean.parseBoolean(de)){ 
            debug = true; 
            System.out.println("PreventSQLInject Filter staring..."); 
            System.out.println("print filter details"); 
            System.out.println("invalid words as fllows (split with blank):"); 
            for(String s : invalidsql){ 
                System.out.print(s+" "); 
            } 
            System.out.println(); 
            System.out.println("error page as fllows"); 
            System.out.println(error); 
            System.out.println(); 
        }
    }
}

XSS包装器：

XssHttpServletRequestWrapper.java

/**
 * {@link XssHttpServletRequestWrapper}
 *
 * TODO : document me
 *
 * @author Administrator
 */
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 || "".equals(s)) {
			return s;
		}
		StringBuilder sb = new StringBuilder(s.length() + 16);
		for (int i = 0; i < s.length(); i++) {
			char c = s.charAt(i);
			switch (c) {
			case '>':
				sb.append('＞');//全角大于号
				break;
			case '<':
				sb.append('＜');//全角小于号
				break;
			case '\'':
				sb.append('‘');//全角单引号
				break;
			case '\"':
				sb.append('“');//全角双引号
				break;
			case '&':
				sb.append('＆');//全角
				break;
			case '\\':
				sb.append('＼');//全角斜线
				break;
			case '#':
				sb.append('＃');//全角井号
				break;
			case '(':
				sb.append('（');//全角井号
				break;
			case ')':
				sb.append('）');//全角井号
				break;
			default:
				sb.append(c);
				break;
			}
		}
		return sb.toString();
	}

	/**
	* 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;
	}

}

在WEB.XML中配置FILTER

	
	    XssFilter
	    
	        com.megait.jgjz.web.filter.XssFilter
	    
	
	
	    XssFilter
	    /*
	
	
   
     PreventSqlInject 
     com.megait.jgjz.web.filter.SqlInjectFilter 
      
      
         invalidsql 
         select insert delete from update create where union destory drop alter and or like exec count chr mid master truncate char declare ; - ' % | $ % @ " + cr lf , . script document eval 
      
      
      
         error 
         /sqlerrors.jsp 
      
          
      
         debug 
         true 
      
    
    
     PreventSqlInject 
     /* 
    

在应用里添加注入报错页面

sqlerrors.jsp

<%@ page language="java" import="java.util.*" pageEncoding="utf-8"%> 
 <% 
 String path = request.getContextPath(); 
 %> 
  
  
    
   	
      
    
    
    
     这个是防sql注入系统，自动过滤您的请求，请更换请求字符串。 
     <%=session.getAttribute("sqlInjectError")%>