Java 使用servlet过滤器修改请求参数_Java_Servlet Filters

Java 使用servlet过滤器修改请求参数

java

Java 使用servlet过滤器修改请求参数,java,servlet-filters,Java,Servlet Filters,现有的web应用程序正在Tomcat4.1上运行。页面存在XSS问题，但我无法修改源代码。我决定编写一个servlet过滤器，在页面看到参数之前对其进行清理我想写一个如下的过滤器类： import java.io.*; import javax.servlet.*; public final class XssFilter implements Filter { public void doFilter(ServletRequest request, ServletResponse r

现有的web应用程序正在Tomcat4.1上运行。页面存在XSS问题，但我无法修改源代码。我决定编写一个servlet过滤器，在页面看到参数之前对其进行清理

我想写一个如下的过滤器类：

import java.io.*;
import javax.servlet.*;

public final class XssFilter implements Filter {

  public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain)
      throws IOException, ServletException
  {
    String badValue = request.getParameter("dangerousParamName");
    String goodValue = sanitize(badValue);
    request.setParameter("dangerousParamName", goodValue);
    chain.doFilter(request, response);
  }

  public void destroy() {
  }

  public void init(FilterConfig filterConfig) {
  }
}

但是

ServletRequest.setParameter

不存在

在将请求向下传递到链之前，如何更改请求参数的值？

编写一个简单的类，该类使用getParameter（）方法对HttpServletRequestWrapper进行子类调用，该方法返回输入的净化版本。然后将

HttpServletRequestWrapper

的一个实例直接传递给

Filter.docain（）

而不是请求对象。

正如您所指出的

HttpServletRequest

没有setParameter方法。这是经过深思熟虑的，因为类表示来自客户端的请求，而修改参数并不表示这一点

一种解决方案是使用

HttpServletRequestWrapper

类，它允许您用一个请求包装另一个请求。您可以将其子类化，并重写

getParameter

方法以返回经过清理的值。然后，您可以将包装好的请求传递给

chain.doFilter

，而不是原始请求

这有点难看，但ServletAPI说您应该这样做。如果您试图将任何其他内容传递给

doFilter

，一些servlet容器会抱怨您违反了规范，并拒绝处理它

更优雅的解决方案是更多的工作—修改处理参数的原始servlet/JSP，使其期望的是请求属性而不是参数。过滤器检查参数，对其进行清理，并使用清理后的值设置属性（使用

request.setAttribute

）。没有子类化，没有欺骗，但确实需要修改应用程序的其他部分。

记录在案，下面是我最后编写的类：

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;
import javax.servlet.http.HttpServletRequestWrapper;

public final class XssFilter implements Filter {

    static class FilteredRequest extends HttpServletRequestWrapper {

        /* These are the characters allowed by the Javascript validation */
        static String allowedChars = "+-0123456789#*";

        public FilteredRequest(ServletRequest request) {
            super((HttpServletRequest)request);
        }

        public String sanitize(String input) {
            String result = "";
            for (int i = 0; i < input.length(); i++) {
                if (allowedChars.indexOf(input.charAt(i)) >= 0) {
                    result += input.charAt(i);
                }
            }
            return result;
        }

        public String getParameter(String paramName) {
            String value = super.getParameter(paramName);
            if ("dangerousParamName".equals(paramName)) {
                value = sanitize(value);
            }
            return value;
        }

        public String[] getParameterValues(String paramName) {
            String values[] = super.getParameterValues(paramName);
            if ("dangerousParamName".equals(paramName)) {
                for (int index = 0; index < values.length; index++) {
                    values[index] = sanitize(values[index]);
                }
            }
            return values;
        }
    }

    public void doFilter(ServletRequest request, ServletResponse response,
            FilterChain chain) throws IOException, ServletException {
        chain.doFilter(new FilteredRequest(request), response);
    }

    public void destroy() {
    }

    public void init(FilterConfig filterConfig) {
    }
}

import java.io.IOException；
导入javax.servlet.Filter；
导入javax.servlet.FilterChain；
导入javax.servlet.FilterConfig；
导入javax.servlet.ServletException；
导入javax.servlet.ServletRequest；
导入javax.servlet.ServletResponse；
导入javax.servlet.http.HttpServletRequest；
导入javax.servlet.http.HttpServletRequestWrapper；
公共最终类XssFilter实现了过滤器{
静态类FiltereRequest扩展了HttpServletRequestWrapper{
/*这些是Javascript验证所允许的字符*/
静态字符串allowedChars=“+-0123456789#*”；
公共筛选器请求（ServletRequest请求）{
超级（（HttpServletRequest）请求）；
}
公共字符串清理（字符串输入）{
字符串结果=”；
对于（int i=0；i=0）{
结果+=输入字符（i）；
}
}
返回结果；
}
公共字符串getParameter（字符串参数名）{
字符串值=super.getParameter（paramName）；
如果（“危险的参数名”。等于（参数名））{
值=消毒（值）；
}
返回值；
}
公共字符串[]getParameterValues（字符串paramName）{
字符串值[]=super.getParameterValues（paramName）；
如果（“危险的参数名”。等于（参数名））{
对于（int index=0；index

尝试

请求.setAttribute（“参数”，值）。这对我很管用
请查找此代码示例：
private void sanitizePrice(ServletRequest request){
        if(request.getParameterValues ("price") !=  null){
            String price[] = request.getParameterValues ("price");

            for(int i=0;i<price.length;i++){
                price[i] = price[i].replaceAll("[^\\dA-Za-z0-9- ]", "").trim();
                System.out.println(price[i]);
            }
            request.setAttribute("price", price);
            //request.getParameter("numOfBooks").re
        }
    }

private void sanitizePrice（ServletRequest）{
if（request.getParameterValues（“price”）！=null）{
字符串价格[]=request.getParameterValues（“价格”）；
对于（int i=0；i您可以使用正则表达式进行清理。在调用chain.doFilter（request，response）方法之前，在筛选器内部调用此代码。
以下是示例代码：
for (Enumeration en = request.getParameterNames(); en.hasMoreElements(); ) {
String name = (String)en.nextElement();
String values[] = request.getParameterValues(name);
int n = values.length;
    for(int i=0; i < n; i++) {
     values[i] = values[i].replaceAll("[^\\dA-Za-z ]","").replaceAll("\\s+","+").trim();   
    }
}

for（枚举en=request.getParameterNames（）；en.hasMoreElements（）；）{
字符串名称=（字符串）en.nextElement（）；
字符串值[]=request.getParameterValues（名称）；
int n=值。长度；
对于（int i=0；i
我也遇到了同样的问题（在筛选器中更改HTTP请求的参数）。我最终使用了线程本地
。在筛选器中，我有：
class MyFilter extends Filter {
    public static final ThreadLocal<String> THREAD_VARIABLE = new ThreadLocal<>();
    public void doFilter(HttpServletRequest request, HttpServletResponse response, FilterChain chain) {
        THREAD_VARIABLE.set("myVariableValue");
        chain.doFilter(request, response);
    }
}

优点：

比传递HTTP参数更通用（您可以传递POJO对象）
稍微快一点（无需解析URL来提取变量值）
比HttpServletRequestWrapper
样板更优雅
变量范围比HTTP请求（执行request.setAttribute（String，Object）
时的范围）更宽，也就是说，您可以在其他筛选器中访问变量

缺点：

只有当处理筛选器的线程与处理HTTP请求的线程相同时（我所知道的所有基于Java的服务器都是这种情况），才可以使用此方法。因此，当

执行HTTP重定向（因为浏览器执行新的HTTP请求，并且无法保证sam将处理该请求
...
String myVariable = MyFilter.THREAD_VARIABLE.get();
...

//import ../../Constants;

public class RequestFilter implements Filter {

    private static final Logger logger = LoggerFactory.getLogger(RequestFilter.class);

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

    @Override
    public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain)
        throws IOException, ServletException {
        try {
            CustomHttpServletRequest customHttpServletRequest = new CustomHttpServletRequest((HttpServletRequest) servletRequest);
            filterChain.doFilter(customHttpServletRequest, servletResponse);
        } finally {
            //do something here
        }
    }



    @Override
    public void destroy() {

    }

     public static Map<String, String[]> ADMIN_QUERY_PARAMS = new HashMap<String, String[]>() {
        {
            put("diagnostics", new String[]{"false"});
            put("skipCache", new String[]{"false"});
        }
    };

    /*
        This is a custom wrapper over the `HttpServletRequestWrapper` which 
        overrides the various header getter methods and query param getter methods.
        Changes to the request pojo are
        => A custom header is added whose value is a unique id
        => Admin query params are set to default values in the url
    */
    private class CustomHttpServletRequest extends HttpServletRequestWrapper {
        public CustomHttpServletRequest(HttpServletRequest request) {
            super(request);
            //create custom id (to be returned) when the value for a
            //particular header is asked for
            internalRequestId = RandomStringUtils.random(10, true, true) + "-local";
        }

        public String getHeader(String name) {
            String value = super.getHeader(name);
            if(Strings.isNullOrEmpty(value) && isRequestIdHeaderName(name)) {
                value = internalRequestId;
            }
            return value;
        }

        private boolean isRequestIdHeaderName(String name) {
            return Constants.RID_HEADER.equalsIgnoreCase(name) || Constants.X_REQUEST_ID_HEADER.equalsIgnoreCase(name);
        }

        public Enumeration<String> getHeaders(String name) {
            List<String> values = Collections.list(super.getHeaders(name));
            if(values.size()==0 && isRequestIdHeaderName(name)) {
                values.add(internalRequestId);
            }
            return Collections.enumeration(values);
        }

        public Enumeration<String> getHeaderNames() {
            List<String> names = Collections.list(super.getHeaderNames());
            names.add(Constants.RID_HEADER);
            names.add(Constants.X_REQUEST_ID_HEADER);
            return Collections.enumeration(names);
        }

        public String getParameter(String name) {
            if (ADMIN_QUERY_PARAMS.get(name) != null) {
                return ADMIN_QUERY_PARAMS.get(name)[0];
            }
            return super.getParameter(name);
        }

        public Map<String, String[]> getParameterMap() {
            Map<String, String[]> paramsMap = new HashMap<>(super.getParameterMap());
            for (String paramName : ADMIN_QUERY_PARAMS.keySet()) {
                if (paramsMap.get(paramName) != null) {
                    paramsMap.put(paramName, ADMIN_QUERY_PARAMS.get(paramName));
                }
            }
            return paramsMap;
        }

        public String[] getParameterValues(String name) {
            if (ADMIN_QUERY_PARAMS.get(name) != null) {
                return ADMIN_QUERY_PARAMS.get(name);
            }
            return super.getParameterValues(name);
        }

        public String getQueryString() {
            Map<String, String[]> map = getParameterMap();
            StringBuilder builder = new StringBuilder();
            for (String param: map.keySet()) {
                for (String value: map.get(param)) {
                    builder.append(param).append("=").append(value).append("&");
                }
            }
            builder.deleteCharAt(builder.length() - 1);
            return builder.toString();
        }
    }
}

 private final class CustomHttpServletRequest extends HttpServletRequestWrapper {

    private final Map<String, String[]> queryParameterMap;
    private final Charset requestEncoding;

    public CustomHttpServletRequest(HttpServletRequest request) {
        super(request);
        queryParameterMap = getCommonQueryParamFromLegacy(request.getParameterMap());

        String encoding = request.getCharacterEncoding();
        requestEncoding = (encoding != null ? Charset.forName(encoding) : StandardCharsets.UTF_8);
    }

    private final Map<String, String[]> getCommonQueryParamFromLegacy(Map<String, String[]> paramMap) {
        Objects.requireNonNull(paramMap);

        Map<String, String[]> commonQueryParamMap = new LinkedHashMap<>(paramMap);

        commonQueryParamMap.put(CommonQueryParams.PATIENT_ID, new String[] { paramMap.get(LEGACY_PARAM_PATIENT_ID)[0] });
        commonQueryParamMap.put(CommonQueryParams.PATIENT_BIRTHDATE, new String[] { paramMap.get(LEGACY_PARAM_PATIENT_BIRTHDATE)[0] });
        commonQueryParamMap.put(CommonQueryParams.KEYWORDS, new String[] { paramMap.get(LEGACY_PARAM_STUDYTYPE)[0] });

        String lowerDateTime = null;
        String upperDateTime = null;

        try {
            String studyDateTime = new SimpleDateFormat("yyyy-MM-dd").format(new SimpleDateFormat("dd-MM-yyyy").parse(paramMap.get(LEGACY_PARAM_STUDY_DATE_TIME)[0]));

            lowerDateTime = studyDateTime + "T23:59:59";
            upperDateTime = studyDateTime + "T00:00:00";

        } catch (ParseException e) {
            LOGGER.error("Can't parse StudyDate from query parameters : {}", e.getLocalizedMessage());
        }

        commonQueryParamMap.put(CommonQueryParams.LOWER_DATETIME, new String[] { lowerDateTime });
        commonQueryParamMap.put(CommonQueryParams.UPPER_DATETIME, new String[] { upperDateTime });

        legacyQueryParams.forEach(commonQueryParamMap::remove);
        return Collections.unmodifiableMap(commonQueryParamMap);

    }

    @Override
    public String getParameter(String name) {
        String[] params = queryParameterMap.get(name);
        return params != null ? params[0] : null;
    }

    @Override
    public String[] getParameterValues(String name) {
        return queryParameterMap.get(name);
    }

    @Override
    public Map<String, String[]> getParameterMap() {
            return queryParameterMap; // unmodifiable to uphold the interface contract.
        }

        @Override
        public Enumeration<String> getParameterNames() {
            return Collections.enumeration(queryParameterMap.keySet());
        }

        @Override
        public String getQueryString() {
            // @see : https://stackoverflow.com/a/35831692/9869013
            // return queryParameterMap.entrySet().stream().flatMap(entry -> Stream.of(entry.getValue()).map(value -> entry.getKey() + "=" + value)).collect(Collectors.joining("&")); // without encoding !!
            return queryParameterMap.entrySet().stream().flatMap(entry -> encodeMultiParameter(entry.getKey(), entry.getValue(), requestEncoding)).collect(Collectors.joining("&"));
        }

        private Stream<String> encodeMultiParameter(String key, String[] values, Charset encoding) {
            return Stream.of(values).map(value -> encodeSingleParameter(key, value, encoding));
        }

        private String encodeSingleParameter(String key, String value, Charset encoding) {
            return urlEncode(key, encoding) + "=" + urlEncode(value, encoding);
        }

        private String urlEncode(String value, Charset encoding) {
            try {
                return URLEncoder.encode(value, encoding.name());
            } catch (UnsupportedEncodingException e) {
                throw new IllegalArgumentException("Cannot url encode " + value, e);
            }
        }

        @Override
        public ServletInputStream getInputStream() throws IOException {
            throw new UnsupportedOperationException("getInputStream() is not implemented in this " + CustomHttpServletRequest.class.getSimpleName() + " wrapper");
        }

    }