Question

我在java web应用程序中实现了过滤器。这里getHeader被执行但getParameter没有被执行。我想防止对参数的xss攻击。

这是我的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 {
        chain.doFilter(new XSSRequestWrapper((HttpServletRequest) request), response);
    }

}

这是XSSRequestWrapper.java

public class XSSRequestWrapper extends HttpServletRequestWrapper {

    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("", "");

            // Avoid anything between script tags
            Pattern scriptPattern = Pattern.compile("<script>(.*?)</script>", Pattern.CASE_INSENSITIVE);
            value = scriptPattern.matcher(value).replaceAll("");

            // Avoid anything in a src='...' type of expression
            scriptPattern = Pattern.compile("src[\r\n]*=[\r\n]*\\\'(.*?)\\\'", Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);
            value = scriptPattern.matcher(value).replaceAll("");

            scriptPattern = Pattern.compile("src[\r\n]*=[\r\n]*\\\"(.*?)\\\"", Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);
            value = scriptPattern.matcher(value).replaceAll("");

            // Remove any lonesome </script> tag
            scriptPattern = Pattern.compile("</script>", Pattern.CASE_INSENSITIVE);
            value = scriptPattern.matcher(value).replaceAll("");

            // Remove any lonesome <script ...> tag
            scriptPattern = Pattern.compile("<script(.*?)>", Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);
            value = scriptPattern.matcher(value).replaceAll("");

            // Avoid eval(...) expressions
            scriptPattern = Pattern.compile("eval\\((.*?)\\)", Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);
            value = scriptPattern.matcher(value).replaceAll("");

            // Avoid expression(...) expressions
            scriptPattern = Pattern.compile("expression\\((.*?)\\)", Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);
            value = scriptPattern.matcher(value).replaceAll("");

            // Avoid javascript:... expressions
            scriptPattern = Pattern.compile("javascript:", Pattern.CASE_INSENSITIVE);
            value = scriptPattern.matcher(value).replaceAll("");

            // Avoid vbscript:... expressions
            scriptPattern = Pattern.compile("vbscript:", Pattern.CASE_INSENSITIVE);
            value = scriptPattern.matcher(value).replaceAll("");

            // Avoid onload= expressions
            scriptPattern = Pattern.compile("onload(.*?)=", Pattern.CASE_INSENSITIVE | Pattern.MULTILINE | Pattern.DOTALL);
            value = scriptPattern.matcher(value).replaceAll("");
        }
        return value;
    }
}

这是我的web.xml

 <filter>
  <filter-name>xss</filter-name>
  <filter-class>com.lfr.filters.XSSFilter</filter-class>
  </filter>
  <filter-mapping>
  <filter-name>xss</filter-name>
  <url-pattern>/*</url-pattern>
  </filter-mapping>

Answer 1

对我来说还不错。你确定servlet / jsp实际上正在使用任何参数。如果不是，那么这些方法是否正常被调用？

也许写一个显式调用getParameter的servlet，然后调试它以查看它的结束位置。

HttpServletRequestWrapper仅检查不是请求参数的请求标头

1 个答案: