Issue
How can I change request body in java filter to protect from XSS attack?
I build HttpServletRequestWrapper and use getparameter for change body but
get stream close exception.
Solution
XSSFilter.java
public class XSSFilter implements Filter {
@Override
public void init(FilterConfig filterConfig) throws ServletException {
}
@Override
public void destroy() {
}
@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
throws IOException, ServletException {
XSSRequestWrapper wrappedRequest = new XSSRequestWrapper(
(HttpServletRequest) request);
String body = IOUtils.toString(wrappedRequest.getReader());
if(!"".equals(body))
{
JSONObject oldJsonObject = new JSONObject(body);
JSONObject newJsonObject = new JSONObject();
for(String key : oldJsonObject.keySet())
{
newJsonObject.put(key, XSSUtils.stripXSS(oldJsonObject.get(key).toString()));
}
wrappedRequest.resetInputStream(newJsonObject.toString().getBytes());
}
chain.doFilter(wrappedRequest, response);
}
}
XSSRequestWrapper .java
public class XSSRequestWrapper extends HttpServletRequestWrapper {
private byte[] rawData;
private HttpServletRequest request;
private ResettableServletInputStream servletStream;
public XSSRequestWrapper(HttpServletRequest request) {
super(request);
this.request = request;
this.servletStream = new ResettableServletInputStream();
}
public void resetInputStream(byte[] newRawData) {
servletStream.stream = new ByteArrayInputStream(newRawData);
}
@Override
public ServletInputStream getInputStream() throws IOException {
if (rawData == null) {
rawData = IOUtils.toByteArray(this.request.getReader());
servletStream.stream = new ByteArrayInputStream(rawData);
}
return servletStream;
}
@Override
public BufferedReader getReader() throws IOException {
if (rawData == null) {
rawData = IOUtils.toByteArray(this.request.getReader());
servletStream.stream = new ByteArrayInputStream(rawData);
}
return new BufferedReader(new InputStreamReader(servletStream));
}
private class ResettableServletInputStream extends ServletInputStream {
private InputStream stream;
@Override
public int read() throws IOException {
return stream.read();
}
}
}
XSSUtils .java
public class XSSUtils {
private XSSUtils()
{
}
public static String stripXSS(String value) {
return value == null ? value : escapeHtml4(value);
}
}
Answered By - Neda Esmaeili
Answer Checked By - Marilyn (JavaFixing Volunteer)
