•  03-04-2022
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Pregunta

We are trying to use ESAPI in our web app. We have following function in servlet.

        protected void doGet(HttpServletRequest request,
        HttpServletResponse response) throws ServletException, IOException {

        response.setContentType("text/html;charset=UTF-8");

        response.setHeader(SearchConstants.CACHE_CONTROL_HEADER,

                    SearchConstants.MAX_AGE_ZERO);

        response.setHeader(SearchConstants.CACHE_CONTROL_HEADER,

                    SearchConstants.NO_CACHE);

        response.setDateHeader(SearchConstants.EXPIRES_HEADER, 0);

        response.setHeader(SearchConstants.PRAGMA_HEADER, "no cache");

        result = processRequest(request, response);

        if (SearchConstants.XSLT_ERROR_MSG.equals(result)) {

              LOGGER.error("XSLT ERROR FOR QUERY STRING: "

                          + request.getQueryString());

              response.sendError(HttpServletResponse.SC_INTERNAL_SERVER_ERROR);

        } else if (SearchConstants.SEARCH_PAGE_MISSING_MSG.equals(result)) {

              LOGGER.error("NOT FOUND ERROR FOR QUERY STRING: "

                          + request.getQueryString());

              response.sendError(HttpServletResponse.SC_NOT_FOUND);

        } else {

              final PrintWriter out = response.getWriter();
              out.println(result); // this works
              // out.println(ESAPI.encoder().encodeForHTML(result));

        }

  }

In above code if I use out.println(ESAPI.encoder().encodeForHTML(result));, this actually prints html as text on browser. i.e. it's showing like simple text <html> other contents.. </html>, instead of rendering html page. result is nothing but html contents which needs to get rendred on client. We are doing something wrong over here. Please provide some pointers. How we can achieve encoding over here?

¿Fue útil?

Solución

The Solution for your problem is not encoding but to rendere Safe HTMl.. below is the solution

import org.owasp.validator.html.*; // Import AntiSamy

String POLICY_FILE_LOCATION = "antisamy-1.4.1.xml"; // Path to policy file

String dirtyInput = "<div><script>alert(1);</script></div>"; // Your HTML RESPONSE

Policy policy = Policy.getInstance(POLICY_FILE_LOCATION); // Create Policy object

AntiSamy as = new AntiSamy(); // Create AntiSamy object
CleanResults cr = as.scan(dirtyInput, policy, AntiSamy.SAX); // Scan dirtyInput

System.out.println(cr.getCleanHTML()); // Do something with your clean output!

Before you write this code ensure that you have following: antisamy.jar.

This jar needs below dependent jars:

  1. xercesImpl.jar
  2. batik.jar
  3. nekohtml.jar

You will also need policy.xml file.

Otros consejos

Sorry, I don't have time to go into details, and it appears that you already have a decent answer.

There is a way to do this in ESAPI. I suggest that calling Validator.getValidSafeHTML() method might be one way to do it. That method actually uses AntiSamy. Looking through the TestValidator.java JUnit tests should show how it's used. Unfortunately, documentation in that area is sorely lacking and it's code that I've had occasion or need to use.

Another way to go if you don't want to use ESAPI is to use the OWASP Java HTML Sanitizer Project. It is faster than AntiSamy, better maintained, and has minimal dependencies (maybe zero).

Hope that helps, -kevin

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