java 拦截器解决xss攻击
一、xss攻击
XSS攻击通常指的是通过利用网页开发时留下的漏洞,通过巧妙的方法注入恶意指令代码到网页,使用户加载并执行攻击者恶意制造的网页程序。这些恶意网页程序通常是JavaScript,但实际上也可以包括Java、 VBScript、ActiveX、 Flash 或者甚至是普通的HTML。攻击成功后,攻击者可能得到包括但不限于更高的权限(如执行一些操作)、私密网页内容、会话和cookie等各种内容。
简单说就是说,通过在输入框输入一些js代码,如在账号密码输入框中输入
<video src=1 onerror=alert(/xss/)/>
或者
<script>alert("@@") </script>
这样点击提交的时候就会触发alert弹窗,分别弹出 xss 和 @@ 的内容,这里只是做个简单的演示,弹了个窗口,还能存储病毒下载地址到服务端,进入的时候自动下载,或者修改你的cookie啥的,这里感兴趣可以百度查查xss攻击。
二、如何防御
解决思路对用户提交表单的参数进行转移,如把< 转换为 < 把 > 转换为 &rt;
java有很多的过滤工具类
<dependency> <groupId>commons-lang</groupId> <artifactId>commons-lang</artifactId> <version>2.6</version> </dependency>
然后通过下面的代码即可过滤
StringEscapeUtils.escapeHtml(string);
底层也是将一切标签进行转移,达到js调用不生效的作用。
这里使用的是filter过请求进行拦截处理。
过滤的内容报过get请求的参数、对象, post形式body中的参数
1)添加xss过滤器
<!-- xss过滤器 --> <filter> <filter-name>XssgFilter</filter-name> <filter-class>com.train.web.filter.XssFilter</filter-class> </filter> <filter-mapping> <filter-name>XssgFilter</filter-name> <url-pattern>/*</url-pattern> </filter-mapping>
这里过滤了所有的请求,其中XssFilter是我们自己过滤器
2)添加自己的过滤器,
import javax.servlet.*; import javax.servlet.http.HttpServletRequest; import java.io.IOException; public class XssFilter implements Filter { @Override public void init(FilterConfig filterConfig) throws ServletException { } @Override public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException { XssHttpServletRequestWrapper req=new XssHttpServletRequestWrapper((HttpServletRequest)servletRequest); filterChain.doFilter(req,servletResponse); } @Override public void destroy() { } }
3)定义自己的http包装类
public class XssHttpServletRequestWrapper extends HttpServletRequestWrapper { boolean isUpData = false;//判断是否是上传 上传忽略 public XssHttpServletRequestWrapper(HttpServletRequest servletRequest) { super(servletRequest); String contentType = servletRequest.getContentType (); if (null != contentType) isUpData =contentType.startsWith ("multipart"); } @Override public String[] getParameterValues(String parameter) { String[] values = super.getParameterValues(parameter); if (values==null) { return null; } int count = values.length; String[] encodedValues = new String[count]; for (int i = 0; i < count; i++) { encodedValues[i] = cleanXSS(values[i]); } return encodedValues; } @Override public String getParameter(String parameter) { String value = super.getParameter(parameter); if (value == null) { return null; } return cleanXSS(value); } /** * 获取request的属性时,做xss过滤 */ @Override public Object getAttribute(String name) { Object value = super.getAttribute(name); if (null != value && value instanceof String) { value = cleanXSS((String) value); } return value; } @Override public String getHeader(String name) { String value = super.getHeader(name); if (value == null) return null; return cleanXSS(value); } private static String cleanXSS(String value) { value = value.replaceAll("<", "<").replaceAll(">", ">"); value = value.replaceAll("%3C", "<").replaceAll("%3E", ">"); value = value.replaceAll("\\(", "(").replaceAll("\\)", ")"); value = value.replaceAll("%28", "(").replaceAll("%29", ")"); value = value.replaceAll("'", "'"); value = value.replaceAll("eval\\((.*)\\)", ""); value = value.replaceAll("[\\\"\\\'][\\s]*javascript:(.*)[\\\"\\\']", "\"\""); value = value.replaceAll("script", ""); return value; } @Override public ServletInputStream getInputStream () throws IOException { if (isUpData){ return super.getInputStream (); }else{ final ByteArrayInputStream bais = new ByteArrayInputStream(inputHandlers(super.getInputStream ()).getBytes ()); return new ServletInputStream() { @Override public int read() throws IOException { return bais.read(); } @Override public boolean isFinished() { return false; } @Override public boolean isReady() { return false; } @Override public void setReadListener(ReadListener readListener) { } }; } } public String inputHandlers(ServletInputStream servletInputStream){ StringBuilder sb = new StringBuilder(); BufferedReader reader = null; try { reader = new BufferedReader(new InputStreamReader (servletInputStream, Charset.forName("UTF-8"))); String line = ""; while ((line = reader.readLine()) != null) { sb.append(line); } } catch (IOException e) { e.printStackTrace(); } finally { if (servletInputStream != null) { try { servletInputStream.close(); } catch (IOException e) { e.printStackTrace(); } } if (reader != null) { try { reader.close(); } catch (IOException e) { e.printStackTrace(); } } } return cleanXSS(sb.toString ()); } }
但是这里有个问题,假如这里还有一些特殊的需求,有些html标签是希望在前端能显示的,前端通过一些已经防止了xss攻击的富文本控件输入信息,后台不希望将这些信息转义
三、添加一些额外的内容
1)希望能动态的开关
2)期待部分接口的接口的参数是能存在标签的
添加一个xss开关的控制类, 这里使用了配置中心
import org.springframework.beans.factory.annotation.Value; import org.springframework.stereotype.Component; @Component public class XSSFilterConfigUtil { public static Boolean openXssProtect; public static Boolean getOpenXssProtect() { return openXssProtect == null ? false : openXssProtect; } @Value("${open.xss.protect}") public void setOpenXssProtect(Boolean openXssProtect) { XSSFilterConfigUtil.openXssProtect = openXssProtect; } }
注意的是:
1. @Value无法为静态属性注入值,所以需要添加set方法为其注入值;
2. 工具类必须添加@Component或者@Service注解,否则@Value不起作用。
静态方法中注入了值以后,Filter中就可以直接使用了。
修改上面的http包装类,这里不对" 进行过滤,过滤的话,会把json的""个去除,使用@RequestBody没办法解析成为一个正常的对象
import com.alibaba.fastjson.JSONObject; import com.train.service.impl.XSSFilterConfigUtil; import org.apache.commons.lang.StringUtils; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import javax.servlet.ServletInputStream; import javax.servlet.http.HttpServletRequest; import javax.servlet.http.HttpServletRequestWrapper; import java.io.BufferedReader; import java.io.ByteArrayInputStream; import java.io.IOException; import java.io.InputStreamReader; import java.nio.charset.Charset; import java.util.HashMap; import java.util.Map; import java.util.regex.Matcher; import java.util.regex.Pattern; /** * 防护http处理 * 1.过滤xss */ public class XssHttpServletRequestWrapper extends HttpServletRequestWrapper { private static final Logger LOGGER = LoggerFactory.getLogger(XssHttpServletRequestWrapper.class); boolean isUpData = false;//判断是否是上传 上传忽略 //不期待被过滤的的链接和字段(管理后台使用了富文本,希望有可编辑的内容) HashMap<String, String> doNotFilterURLAndParamMap = new HashMap<String, String>() { { put("/api/v2/group/manage", "description"); put("/api/v1/sendNews", "content"); } }; /** * Constructs a request object wrapping the given request. * * @param request The request to wrap * @throws IllegalArgumentException if the request is null */ public XssHttpServletRequestWrapper(HttpServletRequest request) { super(request); String contentType = request.getContentType (); if (null != contentType) isUpData =contentType.startsWith ("multipart"); } /** * 过滤单个参数 * @param name * @return */ @Override public String getParameter(String name) { String parameter = super.getParameter(name); if(StringUtils.isNotBlank(parameter) && XSSFilterConfigUtil.getOpenXssProtect()){ //这里使用的阿帕奇的common-lang3中的转义html方法,也可以自己实现, String escapeParameter = this.cleanXSS(parameter); return escapeParameter; } return parameter; } /** * 过滤实体的每个参数 * @param name * @return */ @Override public String[] getParameterValues(String name) { String[] parameterValues = super.getParameterValues(name); if (parameterValues == null) { return null; } if (XSSFilterConfigUtil.getOpenXssProtect()) { for (int i = 0; i < parameterValues.length; ++i) { String value = parameterValues[i]; parameterValues[i] = this.cleanXSS(value); } } return parameterValues; } /** * 处理@RequestBody的形式传入的json数据 * @return * @throws IOException */ @Override public ServletInputStream getInputStream () throws IOException { if(!XSSFilterConfigUtil.getOpenXssProtect()) { return super.getInputStream (); } if (isUpData){ return super.getInputStream (); }else{ final ByteArrayInputStream bais = new ByteArrayInputStream(inputHandlers(super.getInputStream ()).getBytes ()); return new ServletInputStream() { @Override public int read() throws IOException { return bais.read(); } }; } } public String inputHandlers(ServletInputStream servletInputStream){ StringBuilder sb = new StringBuilder(); BufferedReader reader = null; try { reader = new BufferedReader(new InputStreamReader(servletInputStream, Charset.forName("UTF-8"))); String line = ""; while ((line = reader.readLine()) != null) { sb.append(line); } } catch (IOException e) { e.printStackTrace(); } finally { if (servletInputStream != null) { try { servletInputStream.close(); } catch (IOException e) { e.printStackTrace(); } } if (reader != null) { try { reader.close(); } catch (IOException e) { e.printStackTrace(); } } } String requestUrl = StringUtils.replaceOnce(this.getRequestURI(), this.getContextPath(), StringUtils.EMPTY); boolean needFilter = false; String key = ""; String param = ""; for(Map.Entry<String, String> entry : doNotFilterURLAndParamMap.entrySet()){ key = entry.getKey(); int index = StringUtils.indexOf(key, "*"); if (index > 0) { String[] array = key.split("\\*"); StringBuffer stringBuffer = new StringBuffer(); for (String s : array) { stringBuffer.append(s).append("(.*)"); } Pattern p = Pattern.compile(stringBuffer.toString()); Matcher m = p.matcher(requestUrl); if (m.find()) { needFilter = true; param = entry.getValue(); break; } } else { if (requestUrl.equals(key)) { needFilter = true; param = entry.getValue(); break; } } } if(needFilter) { //有需要特殊处理的字段,不希望过滤标签 try { /*String param = doNotFilterURLAndParamMap.get(requestUrl);*/ JSONObject jsonObject = JSONObject.parseObject(sb.toString()); if(jsonObject.containsKey(param)) { Object notFilterValue = jsonObject.get(param); String cleanXSSParams = cleanXSS(sb.toString ()); JSONObject filteredJson = JSONObject.parseObject(cleanXSSParams); filteredJson.put(param, notFilterValue); return filteredJson.toJSONString(); }else { return cleanXSS(sb.toString ()); } }catch (Exception e) { LOGGER.error("XssHttpServletRequestWrapper转换json数据失败",e); return cleanXSS(sb.toString ()); //异常时,就直接过滤,不管需要特殊处理的参数 } }else { return cleanXSS(sb.toString ()); } } /** * 过滤规则,这里不直接使用StringEscapeUtils.escapeHtml,因为获取的是一个json字符串,会将" 替换导致数据异常,没有""进行分割,无法正常注入到@RequestBody * @param value * @return */ private static String cleanXSS(String value) { value = value.replaceAll("<", "<").replaceAll(">", ">"); value = value.replaceAll("%3C", "<").replaceAll("%3E", ">"); // value = value.replaceAll("\\(", "(").replaceAll("\\)", ")"); value = value.replaceAll("%28", "(").replaceAll("%29", ")"); // value = value.replaceAll("'", "'"); /* value = value.replaceAll("eval\\((.*)\\)", ""); value = value.replaceAll("[\\\"\\\'][\\s]*javascript:(.*)[\\\"\\\']", "\"\""); value = value.replaceAll("script", "");*/ return value; } }
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