Anti cross-site scripting (XSS) filter for Java web apps_java filter cross-site scripting-优快云博客

本文介绍了一个为Java web应用程序编写的安全改进型跨站脚本攻击(XSS)过滤器，它能从请求参数中移除可疑字符串，防止攻击。该过滤器作为链中第一个过滤器配置，适用于捕获所有站点请求。

摘要生成于 C知道，由 DeepSeek-R1 满血版支持，前往体验 >

Here is a good and simple anti cross-site scripting (XSS) filter written for Java web applications. What it basically does is remove all suspicious strings from request parameters before returning them to the application. It’s an improvement over my previous post on the topic.

You should configure it as the first filter in your chain (web.xml) and it’s generally a good idea to let it catch every request made to your site.

The actual implementation consists of two classes, the actual filter is quite simple, it wraps the HTTP request object in a specialized HttpServletRequestWrapper that will perform our filtering.

 
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);
 
    }
 
 
 
}

The wrapper overrides the getParameterValues(), getParameter() and getHeader() methods to execute the filtering before returning the desired field to the caller. The actual XSS checking and striping is performed in the stripXSS() private method.

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