XSS跨站点脚本攻击

XSS攻击：跨站脚本攻击(Cross Site 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。

以下为Java web项目中的解决方案：

Filter代码：

import java.io.IOException;

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 org.apache.commons.lang.StringUtils;

import com.fengling.core.web.util.URLHelper;

public class XssFilter implements Filter {
    private String filterChar;
    private String replaceChar;
    private String splitChar;
    private String excludeUrls;
    FilterConfig filterConfig = null;
    public void init(FilterConfig filterConfig) throws ServletException {
        this.filterChar=filterConfig.getInitParameter("FilterChar");
        this.replaceChar=filterConfig.getInitParameter("ReplaceChar");
        this.splitChar=filterConfig.getInitParameter("SplitChar");
        this.excludeUrls=filterConfig.getInitParameter("excludeUrls");
        this.filterConfig = filterConfig;
    }

    public void destroy() {
        this.filterConfig = null;
    }

    public void doFilter(ServletRequest request, ServletResponse response,

    FilterChain chain) throws IOException, ServletException {
        if(isExcludeUrl(request)){
            chain.doFilter(request, response);
        }else{
            chain.doFilter(new XssHttpServletRequestWrapper((HttpServletRequest) request,filterChar,replaceChar,splitChar), response);
        }
    }
    
    
    private boolean isExcludeUrl(ServletRequest request){
        boolean exclude=false;
        if(StringUtils.isNotBlank(excludeUrls)){
             String[]excludeUrl=excludeUrls.split(splitChar);
             if(excludeUrl!=null&&excludeUrl.length>0){
                 for(String url:excludeUrl){
                     if(URLHelper.getURI((HttpServletRequest)request).startsWith(url)){
                         exclude=true;
                     }
                 }
             }
        }
        return exclude;
    }

}

XssHttpServletRequestWrapper代码：

import java.io.UnsupportedEncodingException;
import java.net.URLDecoder;

import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletRequestWrapper;


public class XssHttpServletRequestWrapper extends HttpServletRequestWrapper {
    private String[]filterChars;
    private String[]replaceChars;
    public XssHttpServletRequestWrapper(HttpServletRequest request,String filterChar,String replaceChar,String splitChar) {
        super(request);
        if(filterChar!=null&&filterChar.length()>0){
            filterChars=filterChar.split(splitChar);
        }
        if(replaceChar!=null&&replaceChar.length()>0){
            replaceChars=replaceChar.split(splitChar);
        }
    }
    public String getQueryString() {
        String value = super.getQueryString();
        if (value != null) {
            value = xssEncode(value);
        }
        return value;
    }
    
    /**
     * 覆盖getParameter方法，将参数名和参数值都做xss过滤。<br/>
     * 如果需要获得原始的值，则通过super.getParameterValues(name)来获取<br/>
     * getParameterNames,getParameterValues和getParameterMap也可能需要覆盖
     */
    public String getParameter(String name) {
        String value = super.getParameter(xssEncode(name));
        if (value != null) {
            value = xssEncode(value);
        }
        return value;
    }
    
    public String[] getParameterValues(String name) {
        String[]parameters=super.getParameterValues(name);
        if (parameters==null||parameters.length == 0) {
            return null;
        }
        for (int i = 0; i < parameters.length; i++) {
            parameters[i] = xssEncode(parameters[i]);
        }
        return parameters;
    }
    
    /**
     * 覆盖getHeader方法，将参数名和参数值都做xss过滤。<br/>
     * 如果需要获得原始的值，则通过super.getHeaders(name)来获取<br/> getHeaderNames 也可能需要覆盖
     */
    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  String xssEncode(String s) {
        if (s == null || s.equals("")) {
            return s;
        }
        try {
            s = URLDecoder.decode(s, "UTF8");
        } catch (UnsupportedEncodingException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
        for (int i = 0; i < filterChars.length; i++) {
            if(s.contains(filterChars[i])){
                s=s.replace(filterChars[i], replaceChars[i]);
            }
        }
        return s;
    }
}

web.xml中配置：

<!--@分隔-->
    <filter>
        <filter-name>XssFilter</filter-name>
        <filter-class>com.fengling.common.web.XssFilter</filter-class>
        <init-param>
            <param-name>excludeUrls</param-name>
            <param-value>/member/contribute@/admin/fengling@/flow_statistic</param-value>
        </init-param>
        <init-param>
            <param-name>SplitChar</param-name>
            <param-value>@</param-value>
        </init-param>
        <init-param>
            <param-name>FilterChar</param-name>
            <param-value>'@"@@#@:@%@;@></param-value>
        </init-param>
        <init-param>
            <param-name>ReplaceChar</param-name>
            <param-value>‘@“@＼@＃@：@％@；@＞</param-value>
        </init-param>
    </filter>

    <filter-mapping>
        <filter-name>XssFilter</filter-name>
        <url-pattern>/*</url-pattern>
    </filter-mapping>