XSS是一种经常出现在web应用中的计算机安全漏洞，具体信息请自行Google。本文只分享在Spring Cloud Gateway中执行通用的XSS防范。首次作文，全是代码，若有遗漏不明之处，请各位看官原谅指点。
使用版本
- Spring Cloud版本为 Greenwich.SR4
- Spring Boot版本为 2.1.11.RELEASE
1.创建一个Filter
特别注意的是在处理完成之后需要重新构造请求，否则后续业务无法获得参数。
import io.netty.buffer.ByteBufAllocator;
import lombok.AllArgsConstructor;
import lombok.Builder;
import lombok.Data;
import lombok.NoArgsConstructor;
import lombok.extern.slf4j.Slf4j;
import org.springframework.boot.context.properties.ConfigurationProperties;
import org.springframework.cloud.gateway.filter.GatewayFilterChain;
import org.springframework.cloud.gateway.filter.GlobalFilter;
import org.springframework.core.Ordered;
import org.springframework.core.io.buffer.DataBuffer;
import org.springframework.core.io.buffer.DataBufferUtils;
import org.springframework.core.io.buffer.NettyDataBufferFactory;
import org.springframework.http.HttpHeaders;
import org.springframework.http.HttpMethod;
import org.springframework.http.server.reactive.ServerHttpRequest;
import org.springframework.http.server.reactive.ServerHttpRequestDecorator;
import org.springframework.stereotype.Component;
import org.springframework.util.Assert;
import org.springframework.util.DigestUtils;
import org.springframework.validation.annotation.Validated;
import org.springframework.web.server.ServerWebExchange;
import reactor.core.publisher.Flux;
import reactor.core.publisher.Mono;
import javax.validation.constraints.NotEmpty;
import java.net.URI;
import java.nio.charset.StandardCharsets;
import java.util.List;
import java.util.Optional;
@Component
@Slf4j
@ConfigurationProperties("config.xss")
@Data
public class XssFilter implements GlobalFilter, Ordered {
private List<XssWhiteUrl> whiteUrls;
@Override
public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
ServerHttpRequest request = exchange.getRequest();
URI uri = request.getURI();
String method = request.getMethodValue();
// 判断是否在白名单中
if (this.white(uri.getPath(), method)) {
return chain.filter(exchange);
}
// 只拦截POST和PUT请求
if ((HttpMethod.POST.name().equals(method) || HttpMethod.PUT.name().equals(method))) {
return DataBufferUtils.join(request.getBody())
.flatMap(dataBuffer -> {
// 取出body中的参数
byte[] oldBytes = new byte[dataBuffer.readableByteCount()];
dataBuffer.read(oldBytes);
String bodyString = new String(oldBytes, StandardCharsets.UTF_8);
log.debug("原请求参数为：{}", bodyString);
// 执行XSS清理
bodyString = XssUtil.INSTANCE.cleanXss(bodyString);
log.debug("修改后参数为：{}", bodyString);
ServerHttpRequest newRequest = request.mutate().uri(uri).build();
// 重新构造body
byte[] newBytes = bodyString.getBytes(StandardCharsets.UTF_8);
DataBuffer bodyDataBuffer = toDataBuffer(newBytes);
Flux<DataBuffer> bodyFlux = Flux.just(bodyDataBuffer);
// 重新构造header
HttpHeaders headers = new HttpHeaders();
headers.putAll(request.getHeaders());
// 由于修改了传递参数，需要重新设置CONTENT_LENGTH，长度是字节长度，不是字符串长度
int length = newBytes.length;
headers.remove(HttpHeaders.CONTENT_LENGTH);
headers.setContentLength(length);
headers.set(HttpHeaders.CONTENT_TYPE, "application/json;charset=utf8");
// 重写ServerHttpRequestDecorator，修改了body和header，重写getBody和getHeaders方法
newRequest = new ServerHttpRequestDecorator(newRequest) {
@Override
public Flux<DataBuffer> getBody() {
return bodyFlux;
}
@Override
public HttpHeaders getHeaders() {
return headers;
}
};
return chain.filter(exchange.mutate().request(newRequest).build());
});
} else {
return chain.filter(exchange);
}
}
private boolean white(String url, String method) {
return whiteUrls != null && whiteUrls.contains(XssWhiteUrl.builder().url(url).method(method).build());
}
private DataBuffer toDataBuffer(byte[] bytes) {
NettyDataBufferFactory nettyDataBufferFactory = new NettyDataBufferFactory(ByteBufAllocator.DEFAULT);
DataBuffer buffer = nettyDataBufferFactory.allocateBuffer(bytes.length);
buffer.write(bytes);
return buffer;
}
public static final int ORDER = 10;
@Override
public int getOrder() {
return ORDER;
}
@Data
@Validated
@AllArgsConstructor
@NoArgsConstructor
private static class XssWhiteUrl {
@NotEmpty
private String url;
@NotEmpty
private String method;
}
}
2. 处理XSS字符串
这里大范围采用Jsoup处理，然后根据自己的业务做了一部分定制。较为特殊的是，我们将字符串中含有'</'标示为这段文本是富文本。在清除xss攻击字符串方法时优化空间较大。
import com.alibaba.fastjson.JSONObject;
import org.jsoup.Jsoup;
import org.jsoup.nodes.Document;
import org.jsoup.safety.Whitelist;
import java.util.ArrayList;
import java.util.List;
import java.util.Map;
import java.util.Objects;
public enum XssUtil {
INSTANCE;
private final static String RICH_TEXT = "</";
private final static Whitelist CUSTOM_WHITELIST = Whitelist.relaxed()
.addAttributes("video", "width", "height", "controls", "alt", "src")
.addAttributes(":all", "style", "class");
private final static Document.OutputSettings OUTPUT_SETTINGS = new Document.OutputSettings().prettyPrint(false);
private String cleanObj(String val) {
JSONObject jsonObject = JSONObject.parseObject(val);
for (Map.Entry<String, Object> entry : jsonObject.entrySet()) {
if (entry.getValue() != null && entry.getValue() instanceof String) {
String str = (String) entry.getValue();
str = this.cleanXss(str);
entry.setValue(str);
}
}
return jsonObject.toJSONString();
}
private String cleanArr(String val) {
List<String> list = JSONObject.parseArray(val, String.class);
List<String> result = new ArrayList<>(list.size());
for (String str : list) {
str = this.cleanXss(str);
result.add(str);
}
return JSONObject.toJSONString(result);
}
public String cleanXss(String str) {
if (JsonUtil.INSTANCE.isJsonObj(str)) {
str = this.cleanObj(str);
} else if (JsonUtil.INSTANCE.isJsonArr(str)) {
str = this.cleanArr(str);
} else {
boolean richText = this.richText(str);
if (!richText) {
str = str.trim();
str = str.replaceAll(" +", " ");
}
String afterClean = Jsoup.clean(str, "", CUSTOM_WHITELIST, OUTPUT_SETTINGS);
if (paramError(richText, afterClean, str)) {
throw new BizRunTimeException(ApiCode.PARAM_ERROR, "参数包含特殊字符");
}
str = richText ? afterClean : this.backSpecialStr(afterClean);
}
return str;
}
private boolean richText(String str) {
return str.contains(RICH_TEXT);
}
private boolean paramError(boolean richText, String afterClean, String str) {
// 如果包含富文本字符，那么不是参数错误
if (richText) {
return false;
}
// 如果清理后的字符和清理前的字符匹配，那么不是参数错误
if (Objects.equals(str, afterClean)) {
return false;
}
// 如果仅仅包含可以通过的特殊字符，那么不是参数错误
if (Objects.equals(str, this.backSpecialStr(afterClean))) {
return false;
}
// 如果还有......
return true;
}
private String backSpecialStr(String str) {
return str.replaceAll("&", "&");
}
}
3.其它使用到的工具
import com.alibaba.fastjson.JSONObject;
import org.springframework.util.StringUtils;
public enum JsonUtil {
INSTANCE;
private final static String JSON_OBJECT_START = "{";
private final static String JSON_OBJECT_END = "}";
private final static String JSON_ARRAY_START = "[";
private final static String JSON_ARRAY_END = "]";
public boolean isJsonObj(String val) {
if (StringUtils.isEmpty(val)) {
return false;
}
val = val.trim();
if (val.startsWith(JSON_OBJECT_START) && val.endsWith(JSON_OBJECT_END)) {
try {
JSONObject.parseObject(val);
return true;
} catch (Exception e) {
return false;
}
}
return false;
}
public boolean isJsonArr(String val) {
if (StringUtils.isEmpty(val)) {
return false;
}
val = val.trim();
if (StringUtils.isEmpty(val)) {
return false;
}
val = val.trim();
if (val.startsWith(JSON_ARRAY_START) && val.endsWith(JSON_ARRAY_END)) {
try {
JSONObject.parseArray(val);
return true;
} catch (Exception e) {
return false;
}
}
return false;
}
public boolean isJsonObj(Object obj) {
String str = JSONObject.toJSONString(obj);
return this.isJsonObj(str);
}
public boolean isJson(String str) {
if (StringUtils.isEmpty(str)) {
return false;
}
return this.isJsonObj(str) || this.isJsonArr(str);
}
}
大功告成。
----------------手动分隔----------------
修改
感谢@chang_p_x的指正，在第一步创建Filter时有问题，原因是使用了新旧代码的问题，现已经将元代码放在正文，新代码如下
@Override
public Mono<Void> filter(ServerWebExchange exchange, GatewayFilterChain chain) {
ServerHttpRequest request = exchange.getRequest();
URI uri = request.getURI();
String method = request.getMethodValue();
if (this.white(uri.getPath(), method)) {
return chain.filter(exchange);
}
if ((HttpMethod.POST.name().equals(method) || HttpMethod.PUT.name().equals(method))) {
return DataBufferUtils.join(request.getBody()).flatMap(d -> Mono.just(Optional.of(d))).defaultIfEmpty(Optional.empty())
.flatMap(optional -> {
// 取出body中的参数
String bodyString = "";
if (optional.isPresent()) {
byte[] oldBytes = new byte[optional.get().readableByteCount()];
optional.get().read(oldBytes);
bodyString = new String(oldBytes, StandardCharsets.UTF_8);
}
HttpHeaders httpHeaders = request.getHeaders();
// 执行XSS清理
log.debug("{} - [{}：{}] XSS处理前参数：{}", method, uri.getPath(), bodyString);
bodyString = XssUtil.INSTANCE.cleanXss(bodyString);
log.info("{} - [{}：{}] 参数：{}", method, uri.getPath(), bodyString);
ServerHttpRequest newRequest = request.mutate().uri(uri).build();
// 重新构造body
byte[] newBytes = bodyString.getBytes(StandardCharsets.UTF_8);
DataBuffer bodyDataBuffer = toDataBuffer(newBytes);
Flux<DataBuffer> bodyFlux = Flux.just(bodyDataBuffer);
// 重新构造header
HttpHeaders headers = new HttpHeaders();
headers.putAll(httpHeaders);
// 由于修改了传递参数，需要重新设置CONTENT_LENGTH，长度是字节长度，不是字符串长度
int length = newBytes.length;
headers.remove(HttpHeaders.CONTENT_LENGTH);
headers.setContentLength(length);
headers.set(HttpHeaders.CONTENT_TYPE, "application/json;charset=utf8");
// 重写ServerHttpRequestDecorator，修改了body和header，重写getBody和getHeaders方法
newRequest = new ServerHttpRequestDecorator(newRequest) {
@Override
public Flux<DataBuffer> getBody() {
return bodyFlux;
}
@Override
public HttpHeaders getHeaders() {
return headers;
}
};
return chain.filter(exchange.mutate().request(newRequest).build());
});
} else {
return chain.filter(exchange);
}
}
以上为个人经验，希望能给大家一个参考，也希望大家多多支持编程网。
