如何在 java 过滤器中更改 servlet 请求 body？

Question

如何更改 java 过滤器中的请求 body 以防止 XSS 攻击？我构建 HttpServletRequestWrapper 并使用 getparameter 进行更改 body 但是获取流关闭异常。

Answer 1

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);
  }
}

Answer 2

由于我没有足够的声誉来添加评论，所以我将其添加为答案。 3 年后，我找到了公认的答案来节省我的时间。同时，我不得不解决一些问题，因此添加了...

(1) 一个错误（缺少对 rawData 的分配）

public void resetInputStream(byte[] newRawData) {
    rawData = newRawData;
    servletStream.stream = new ByteArrayInputStream(newRawData);
}

(2) 随着时间的推移需要进行更改。参考：

如何在 java 过滤器中更改 servlet 请求 body？

How to change servlet request body in java filter?

java

xss

servlets

servlet-filters

XSSFilter.java

XSSRequestWrapper .java

XSSUtils .java