Springboot详解如何实现SQL注入过滤器过程
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场景：以过滤器(Filter)的方式，对所有http请求的入参拦截，使用正则表达式匹配入参中的字符串。存在SQL注入风险的参数，中断请求，并立即返回提示信息。不存在SQL注入风险的参数，校验通过后，放入过滤器链，继续后续业务。
环境：本例是基于springboot的web工程，版本：springboot 2.6.3
1.过滤器SqlInjectFilter
SqlInjectFilter，实现javax.servlet.Filter接口。即在doFilter方法中实现具体逻辑。
@Slf4j
public class SqlInjectFilter implements Filter {
private static final String SQL_REG_EXP = ".*(\\b(select|insert|into|update|delete|from|where|and|or|trancate" +
"|drop|execute|like|grant|use|union|order|by)\\b).*";
@Override
public void doFilter(ServletRequest servletRequest, ServletResponse servletResponse, FilterChain filterChain) throws IOException, ServletException {
HttpServletRequest request = (HttpServletRequest) servletRequest;
CustomRequestWrapper requestWrapper = new CustomRequestWrapper(request);
Map<String, Object> parameterMap = new HashMap<>();
parameterMap =getParameterMap(parameterMap, request, requestWrapper);
// 正则校验是否有SQL关键字
for (Object obj : parameterMap.entrySet()) {
Map.Entry entry = (Map.Entry) obj;
Object value = entry.getValue();
if (value != null) {
boolean isValid = isSqlInject(value.toString(), servletResponse);
if (!isValid) {
return;
}
}
}
filterChain.doFilter(requestWrapper, servletResponse);
}
private Map<String, Object> getParameterMap(Map<String, Object> paramMap, HttpServletRequest request, CustomRequestWrapper requestWrapper) {
// 1.POST请求获取参数
if ("POST".equals(request.getMethod().toUpperCase())) {
String body = requestWrapper.getBody();
paramMap = JSONObject.parseObject(body, HashMap.class);
} else {
Map<String, String[]> parameterMap = requestWrapper.getParameterMap();
//普通的GET请求
if (parameterMap != null && parameterMap.size() > 0) {
Set<Map.Entry<String, String[]>> entries = parameterMap.entrySet();
for (Map.Entry<String, String[]> next : entries) {
paramMap.put(next.getKey(), next.getValue()[0]);
}
} else {
//GET请求,参数在URL路径型式,比如server/{var1}/{var2}
String afterDecodeUrl = null;
try {
//编码过URL需解码解码还原字符
afterDecodeUrl = URLDecoder.decode(request.getRequestURI(), "UTF-8");
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
}
paramMap.put("pathVar", afterDecodeUrl);
}
}
return paramMap;
}
private boolean isSqlInject(String value, ServletResponse servletResponse) throws IOException {
if (null != value && value.toLowerCase().matches(SQL_REG_EXP)) {
log.info("入参中有非法字符: " + value);
HttpServletResponse response = (HttpServletResponse) servletResponse;
Map<String, String> responseMap = new HashMap<>();
// 匹配到非法字符,立即返回
responseMap.put("code", "999");
responseMap.put("message","入参中有非法字符");
response.setContentType("application/json;charset=UTF-8");
response.setStatus(HttpStatus.OK.value());
response.getWriter().write(JSON.toJSONString(responseMap));
response.getWriter().flush();
response.getWriter().close();
return false;
}
return true;
}
}2.请求装饰类CustomRequestWrapper
在拦截请求时，会读取HttpServletRequest的InputStream，而这种数据流一旦读取后，就没了。那么直接把请求放入过滤器链，后续的环节就读取不到数据了。因此，需要一个装饰类，读取了InputStream数据后，还得回写到请求中。然后把数据完整的装饰类放入过滤器链。这样拦截了请求，读取了数据，并回写了数据，数据完整性得到保证。
public class CustomRequestWrapper extends HttpServletRequestWrapper {
private final String body;
public CustomRequestWrapper(HttpServletRequest request) throws IOException {
super(request);
StringBuilder sb = new StringBuilder();
BufferedReader bufferedReader = null;
try {
InputStream inputStream = request.getInputStream();
if (inputStream != null) {
bufferedReader = new BufferedReader(new InputStreamReader(inputStream, StandardCharsets.UTF_8));
char[] charBuffer = new char[512];
int bytesRead = -1;
while ((bytesRead = bufferedReader.read(charBuffer)) > 0) {
sb.append(charBuffer, 0, bytesRead);
}
} else {
sb.append("");
}
} catch (IOException e) {
e.printStackTrace();
throw e;
} finally {
if (bufferedReader != null) {
try {
bufferedReader.close();
} catch (IOException e) {
e.printStackTrace();
throw e;
}
}
}
body = sb.toString();
}
@Override
public ServletInputStream getInputStream() throws IOException {
final ByteArrayInputStream bais = new ByteArrayInputStream(body.getBytes("UTF-8"));
return new ServletInputStream() {
@Override
public boolean isFinished() {
return false;
}
@Override
public boolean isReady() {
return false;
}
@Override
public void setReadListener(ReadListener readListener) {
}
@Override
public int read() {
return bais.read();
}
};
}
@Override
public BufferedReader getReader() throws IOException {
return new BufferedReader(new InputStreamReader(this.getInputStream(), StandardCharsets.UTF_8));
}
public String getBody() {
return this.body;
}
@Override
public String getParameter(String name) {
return super.getParameter(name);
}
@Override
public Map<String, String[]> getParameterMap() {
return super.getParameterMap();
}
@Override
public Enumeration<String> getParameterNames() {
return super.getParameterNames();
}
@Override
public String[] getParameterValues(String name) {
return super.getParameterValues(name);
}
}3.过滤器注册
过滤器生效，需注册。
@Configuration
public class FilterConfiguration {
@Bean("sqlFilter")
public SqlInjectFilter sqlInjectFilter() {
return new SqlInjectFilter();
}
@Bean
public FilterRegistrationBean<SqlInjectFilter> sqlFilterRegistrationBean() {
FilterRegistrationBean<SqlInjectFilter> filterReg = new FilterRegistrationBean<>();
filterReg.setFilter(sqlInjectFilter());
filterReg.addUrlPatterns("/*");
filterReg.setOrder(1);
return filterReg;
}
}4.测试辅助类
4.1 结果对象ResultObj
Restful请求返回格式统一。
@Data
@NoArgsConstructor
@AllArgsConstructor
@Builder
public class ResultObj {
private String code;
private String message;
}4.2 Restful的Controller类
SqlInjectionController，包括POST请求和GET请求测试。
@RestController
@Slf4j
@RequestMapping("/inject")
public class SqlInjectionController {
@PostMapping("/f1")
public Object f1(@RequestBody Object obj) {
log.info("SqlInjectionController->f1,接收参数,obj = " + obj.toString());
log.info("SqlInjectionController->f1,返回.");
return ResultObj.builder().code("200").message("成功").build();
}
@GetMapping("/f2")
public Object f2(@RequestParam(name = "var") String var) {
log.info("SqlInjectionController->f2,接收参数,var = " + var);
log.info("SqlInjectionController->f2,返回.");
return ResultObj.builder().code("200").message("成功").build();
}
@GetMapping("/f3/{var}")
public Object f3(@PathVariable("var") String var) {
log.info("SqlInjectionController->f3,接收参数,var = " + var);
log.info("SqlInjectionController->f3,返回.");
return ResultObj.builder().code("200").message("成功").build();
}
}5.测试
5.1 POST请求测试
URL: http://127.0.0.1:18081/server/inject/f1
入参：
{
"userName": "Hangzhou select",
"password": "202206112219"
}
返回：
{
"code": "999",
"message": "入参中有非法字符"
}
5.2 GET请求测试1
URL: http://127.0.0.1:18081/server/inject/f2?var=56622 INSert
返回：
{
"code": "999",
"message": "入参中有非法字符"
}
5.3 GET请求测试2
URL: http://127.0.0.1:18081/server/inject/f3/123 delete
返回：
{
"code": "999",
"message": "入参中有非法字符"
}
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