java - response.getOutputStream().write(buffer) 的 Servlet 类中的 XSS 漏洞问题

Question

我正在针对我的模块的代码审计报告修复问题。问题是 XSS 漏洞。它报告了语法问题response.getOutputStream().write(缓冲区);如何解决？功课做足了，发现OWASP推荐的ESAPI可以帮我修复，但是怎么实现呢？问题出在 servlet 类中？或任何其他 api 或其他任何可以帮助我修复它的东西？请分享您的相关经验。

FileOutputStream fos = null;
        FileInputStream fileInuptStream =null;
        BufferedInputStream bufferedInputStream = null;
        ByteArrayOutputStream byteArrayOutputStream =null;
        try{
           ServletContext servletContext = request.getSession().getServletContext();
            File attachmentDir = new File(servletContext.getRealPath("")+File.separator+"Reports" );
            String uploadDir=attachmentDir.getPath();
            if (!attachmentDir.exists()) {
                attachmentDir.mkdirs();
            }

            HSSFWorkbook wb= new HSSFWorkbook();
             AAAA  aaa=new AAAA();          
            wb=aaa.getExportXLS(request, response, fileName, wb);
             if(request.getSession().getAttribute("SESSION_AAAAA")!=null){
                    request.getSession().removeAttribute("SESSION_AAAAA");
            }           
              fos=new FileOutputStream(uploadDir+File.separator+fileName);
            wb.write(fos);

            File fileXls=new File(uploadDir+File.separator+fileName);
              fileInuptStream = new FileInputStream(fileXls);
              bufferedInputStream = new BufferedInputStream(fileInuptStream);
              byteArrayOutputStream = new ByteArrayOutputStream();
            int start = INT_ZERO;
            int length = ONE_ZERO_TWO_FOUR;
            int offset = MINUS_ONE;
            byte [] buffer = new byte [length];
            while ((offset = bufferedInputStream.read(buffer, start, length)) != -1)
                byteArrayOutputStream.write(buffer, start, offset);


            buffer = byteArrayOutputStream.toByteArray();

            response.setHeader("Expires", "0");
            response.setHeader("Cache-Control", "must-revalidate, post-check=0, pre-check=0");
            response.setHeader("Pragma", "public");
            response.setContentType("application/xls");
            response.setHeader("Content-disposition","attachment; filename="+fileName );
            response.setContentLength((int ) fileXls.length());
            response.getOutputStream().write(buffer);  --- REPORTED AT THIS LINE
            response.getOutputStream().flush(); 

Answer 1

这是一个误报。此 servlet 返回一个由 Apache POI 创建的 XLS 文件，而不是 HTML 文档。不可能有 XSS 攻击的手段。

然而，这段代码相当笨拙且效率低下。它在扩展的 WAR 文件夹中创建一个文件(当重新部署 WAR 时该文件无论如何都会丢失)，然后将其全部内容完全复制到服务器的内存中，而不是直接写入响应。可能这种笨拙的方法混淆了审计工具。您应该只是将 HttpServletResponse#getOutputStream() 传递给 Workbook#write()。

这是基于目前发布的代码的完整重写:

HSSFWorkbook wb = new HSSFWorkbook();
AAAA aaa = new AAAA();          
wb = aaa.getExportXLS(request, response, fileName, wb);
response.setHeader("Expires", "0");
response.setHeader("Cache-Control", "must-revalidate, post-check=0, pre-check=0");
response.setHeader("Pragma", "public");
response.setContentType("application/xls");
response.setHeader("Content-disposition", "attachment; filename=" + fileName);
wb.write(response.getOutputStream());