XSSRequestWrapper.java

package testcode.xss;

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


/**
 * Taken from :
 * <a href="http://java.dzone.com/articles/stronger-anti-cross-site"></a>
 */
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;
    }
}