XSS概述
跨站脚本攻击(Cross Site Scripting)，缩写为XSS。恶意攻击者往Web页面里插入恶意Script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。
Servlet的方式
1、继承HttpServletRequestWrapper，实现对请求参数的过滤
/**
* xss请求适配器
*/
public class XssHttpServletRequestWrapper extends HttpServletRequestWrapper { public XssHttpServletRequestWrapper(HttpServletRequest request) {
super(request);
} /**
* 对数组参数进行特殊字符过滤
*/
@Override
public String[] getParameterValues(String name) {
String[] values = super.getParameterValues(name);
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;
} /**
* 对参数中特殊字符进行过滤
*/
@Override
public String getParameter(String name) {
String value = super.getParameter(name);
if (value == null) {
return null;
}
return cleanXSS(value);
} /**
* 获取attribute,特殊字符过滤
*/
@Override
public Object getAttribute(String name) {
Object value = super.getAttribute(name);
if (value != null && value instanceof String) {
cleanXSS((String) value);
}
return value;
} /**
* 对请求头部进行特殊字符过滤
*/
@Override
public String getHeader(String name) {
String value = super.getHeader(name);
if (value == null) {
return null;
}
return cleanXSS(value);
} /**
* 转义字符,使用该方法存在一定的弊端
*
* @param value
* @return
*/
private String cleanXSS2(String value) {
// 移除特殊标签
value = value.replaceAll("<", "<").replaceAll(">", ">");
value = value.replaceAll("\\(", "(").replaceAll("\\)", ")");
value = value.replaceAll("'", "'");
value = value.replaceAll("eval\\((.*)\\)", "");
value = value.replaceAll("[\\\"\\\'][\\s]*javascript:(.*)[\\\"\\\']", "\"\"");
value = value.replaceAll("script", "");
return value;
} private String cleanXSS(String value) {
if (value != null) {
//推荐使用ESAPI库来避免脚本攻击,value = ESAPI.encoder().canonicalize(value);
// 避免空字符串
value = value.replaceAll(" ", "");
// 避免script 标签
Pattern scriptPattern = Pattern.compile("<script>(.*?)</script>", Pattern.CASE_INSENSITIVE);
value = scriptPattern.matcher(value).replaceAll("");
// 避免src形式的表达式
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("");
// 删除单个的 </script> 标签
scriptPattern = Pattern.compile("</script>", Pattern.CASE_INSENSITIVE);
value = scriptPattern.matcher(value).replaceAll("");
// 删除单个的<script ...> 标签
scriptPattern = Pattern.compile("<script(.*?)>",
Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);
value = scriptPattern.matcher(value).replaceAll("");
// 避免 eval(...) 形式表达式
scriptPattern = Pattern.compile("eval\\((.*?)\\)",
Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);
value = scriptPattern.matcher(value).replaceAll("");
// 避免 expression(...) 表达式
scriptPattern = Pattern.compile("expression\\((.*?)\\)",
Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);
value = scriptPattern.matcher(value).replaceAll("");
// 避免 javascript: 表达式
scriptPattern = Pattern.compile("javascript:", Pattern.CASE_INSENSITIVE);
value = scriptPattern.matcher(value).replaceAll("");
// 避免 vbscript:表达式
scriptPattern = Pattern.compile("vbscript:", Pattern.CASE_INSENSITIVE);
value = scriptPattern.matcher(value).replaceAll("");
// 避免 onload= 表达式
scriptPattern = Pattern.compile("onload(.*?)=",
Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);
value = scriptPattern.matcher(value).replaceAll("");
}
return value;
} }
2、实现Filter，实现XSS过滤器
/**
* xss过滤器
*/
public class XssFilter implements Filter { FilterConfig filterConfig = null; @Override
public void init(FilterConfig filterConfig) throws ServletException {
this.filterConfig = filterConfig;
} @Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException {
//对请求进行拦截,防xss处理
chain.doFilter(new XssHttpServletRequestWrapper((HttpServletRequest) request), response);
} @Override
public void destroy() {
this.filterConfig = null;
} }
3、注入XSS过滤器，两种方式
第一种方式：配置web.xml
<!-- xss过滤器 -->
<filter>
<filter-name>XssSqlFilter</filter-name>
<filter-class>cn.aric.xss.XssFilter</filter-class>
</filter>
<filter-mapping>
<filter-name>XssSqlFilter</filter-name>
<url-pattern>/*</url-pattern>
<dispatcher>REQUEST</dispatcher>
<dispatcher>FORWARD</dispatcher>
</filter-mapping>
第二种方式：注解
/**
* 注入Xss过滤器(注解方式)
*/
public class WebInitializer implements WebApplicationInitializer{ @Override
public void onStartup(ServletContext servletContext) throws ServletException {
//添加监听器
servletContext.addListener(RequestContextListener.class);
//添加过滤器
Dynamic xssFilterRegistration = servletContext.addFilter("XssFilter", XssFilter.class);
//添加映射规则
xssFilterRegistration.addMappingForUrlPatterns(
EnumSet.of(DispatcherType.REQUEST,DispatcherType.FORWARD,DispatcherType.INCLUDE),
false,
"/*"); } }
Spring整合的方式
1、使用spring的HtmlUtils,可以使用StringEscapeUtils 中的过滤方法
/**
* 解决XSS跨站脚本攻击和sql注入攻击,使用spring的HtmlUtils,可以使用StringEscapeUtils 中的过滤方法
*/
public class XssSpringHttpServletRequestWrapper extends HttpServletRequestWrapper{ public XssSpringHttpServletRequestWrapper(HttpServletRequest request) {
super(request);
} /**
* 对数组参数进行特殊字符过滤
*/
@Override
public String[] getParameterValues(String name) {
String[] values = super.getParameterValues(name);
String[] newValues = new String[values.length];
for (int i = 0; i < values.length; i++) {
//spring的HtmlUtils进行转义
newValues[i] = HtmlUtils.htmlEscape(values[i]);
}
return newValues;
} /**
* 拦截参数,并对其进行字符转义
*/
@Override
public String getParameter(String name) {
return HtmlUtils.htmlEscape(name);
} /**
* 拦截参数,并对其进行字符转义
*/
@Override
public Object getAttribute(String name) {
return HtmlUtils.htmlEscape(name);
} }
2、实现XSS过滤器
/**
* spring方式xss过滤器
*/
public class XssSpringFilter implements Filter{ @Override
public void init(FilterConfig filterConfig) throws ServletException { } @Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException {
HttpServletRequest req = (HttpServletRequest) request;
chain.doFilter(new XssSpringHttpServletRequestWrapper(req), response);
} @Override
public void destroy() { } }
3、配置XSS过滤器
<!-- spring方式的xss过滤器 -->
<filter>
<filter-name>xssSpringFilter</filter-name>
<filter-class>cn.aric.xss.XssSpringHttpServletRequestWrapper</filter-class>
</filter>
<filter-mapping>
<filter-name>xssSpringFilter</filter-name>
<url-pattern>/*</url-pattern>
</filter-mapping>