Question

我正在编写一个请求包装器类来修复跨站点脚本问题。我遇到的问题是当我调用chain.dofilter（wrapperclass）时，getParameterValues（）方法没有被调用。任何人都可以帮助我为什么这个方法没有被触发？

    import java.util.regex.Pattern;
    import javax.servlet.http.HttpServletRequest;
    import javax.servlet.http.HttpServletRequestWrapper;

    public class XSSRequestWrapper extends HttpServletRequestWrapper {

        private static Pattern[] patterns = new Pattern[]{
            // Script fragments
            Pattern.compile("<script>(.*?)</script>", Pattern.CASE_INSENSITIVE),
            // src='...'
            Pattern.compile("src[\r\n]*=[\r\n]*\\\'(.*?)\\\'", Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL),
            Pattern.compile("src[\r\n]*=[\r\n]*\\\"(.*?)\\\"", Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL),
            // lonely script tags
            Pattern.compile("</script>", Pattern.CASE_INSENSITIVE),
            Pattern.compile("<script(.*?)>", Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL),
            // eval(...)
            Pattern.compile("eval\\((.*?)\\)", Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL),
            // expression(...)
            Pattern.compile("expression\\((.*?)\\)", Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL),
            // javascript:...
            Pattern.compile("javascript:", Pattern.CASE_INSENSITIVE),
            // vbscript:...
            Pattern.compile("vbscript:", Pattern.CASE_INSENSITIVE),
            // onload(...)=...
            Pattern.compile("onload(.*?)=", Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL)
        };

        public XSSRequestWrapper(HttpServletRequest servletRequest) {
            super(servletRequest);
        }

        @Override
        public String[] getParameterValues(String parameter) {
            String[] values = super.getParameterValues(parameter);

            if (values == null) {
                return null;
            }

            int count = values.length;
            String[] encodedValues = new String[count];
            for (int i = 0; i < count; i++) {
                encodedValues[i] = stripXSS(values[i]);
            }

            return encodedValues;
        }

        @Override
        public String getParameter(String parameter) {
            String value = super.getParameter(parameter);

            return stripXSS(value);
        }

        @Override
        public String getHeader(String name) {
            String value = super.getHeader(name);
            return stripXSS(value);
        }

        private String stripXSS(String value) {
            if (value != null) {
                // NOTE: It's highly recommended to use the ESAPI library and uncomment the following line to
                // avoid encoded attacks.
                // value = ESAPI.encoder().canonicalize(value);

                // Avoid null characters
                value = value.replaceAll("\0", "");

                // Remove all sections that match a pattern
                for (Pattern scriptPattern : patterns){
                    value = scriptPattern.matcher(value).replaceAll("");
                }
            }
            return value;
        }
    }



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;

public final class XSSFilter implements Filter {

    @Override
    public void init(FilterConfig arg0) throws ServletException {
    }

    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {
        XSSRequestWrapper requestWrapper = new XSSRequestWrapper((HttpServletRequest) request);
         chain.doFilter(requestWrapper, response);
    }

    @Override
    public void destroy() {
    }
}

Answer 1

Servlet API提供了多种方法来从ServletRequest中提取参数。特定的Servlet实现可以使用这些方法中的任何一种来提取参数。如果您没有看到ServletRequest#getParameterValues(String)的任何调用，那么您过滤的底层servlet可能不会调用该方法。也许它会调用其他方法。

为了完成，我建议您的请求包装器覆盖所有这些方法：

HttpServletResponseWrapper的getParamertervalues（）没有被调用

1 个答案: