Feign Client Signed Endpoint

Question

I am using Spring Feign Client to access Binance API.

Certain APIs such as SIGNED Endpoint Examples for POST /api/v3/order require to be signed using -sha256 -hmac.

The documentation tells how do call the signed API using cURL + OpenSSL

Example 1: As a request body

requestBody:

symbol=LTCBTC&side=BUY&type=LIMIT&timeInForce=GTC&quantity=1&price=0.1&recvWindow=5000&timestamp=1499827319559

HMAC SHA256 signature:

[linux]$ echo -n "symbol=LTCBTC&side=BUY&type=LIMIT&timeInForce=GTC&quantity=1&price=0.1&recvWindow=5000&timestamp=1499827319559" | openssl dgst -sha256 -hmac "NhqPtmdSJYdKjVHjA7PZj4Mge3R5YNiP1e3UZjInClVN65XAbvqqM6A7H5fATj0j"
(stdin)= c8db56825ae71d6d79447849e617115f4a920fa2acdcab2b053c4b2838bd6b71

curl command:

(HMAC SHA256)
[linux]$ curl -H "X-MBX-APIKEY: vmPUZE6mv9SD5VNHk4HlWFsOr6aKE2zvsw0MuIgwCIPy6utIco14y7Ju91duEh8A" -X POST 'https://api.binance.com/api/v3/order' -d 'symbol=LTCBTC&side=BUY&type=LIMIT&timeInForce=GTC&quantity=1&price=0.1&recvWindow=5000&timestamp=1499827319559&signature=c8db56825ae71d6d79447849e617115f4a920fa2acdcab2b053c4b2838bd6b71'

How can I do it using FeignClient?

Do I have to create a RequestInterceptor?

Any advice would be greatly appreciated.

Regards,

Flávio Oliva

Answer 1

This is my final solution:

I am using spring-boot 2.3.3.

@FeignClient(name = "order", url = "${binance.api.url}", decode404 = true, configuration = SignedEndpointFeignConfiguration.class)
public interface OrderApi {


    @PostMapping(value = "/api/v3/order", consumes = {MediaType.APPLICATION_FORM_URLENCODED_VALUE})
    ResponseEntity<String> newOrder(@SpringQueryMap OrderRequest orderRequest);

}

@Slf4j
public class SignedEndpointFeignConfiguration extends BinanceDefaultFeignConfiguration {

    public SignedEndpointFeignConfiguration(ApplicationProperties.BinanceApi binanceApi) {
        super(binanceApi);
    }

    @Bean
    public RequestInterceptor requestInterceptor() {
        return new SignatureInterceptor(binanceApi);
    }

}

@Slf4j
public class BinanceDefaultFeignConfiguration {

    protected final ApplicationProperties.BinanceApi binanceApi;

    public BinanceDefaultFeignConfiguration(ApplicationProperties.BinanceApi binanceApi) {
        this.binanceApi = binanceApi;
    }

    @Bean
    public ErrorDecoder errorDecoder() {
        return new FeignErrorDecoder();
    }

    @Bean
    public Logger.Level logger() {
        return Logger.Level.FULL;
    }

    @Bean
    public Encoder encoder() {
        return new JacksonEncoder();
    }

    @Bean
    public Decoder decoder() {
        return new ResponseEntityDecoder(new SpringDecoder(feignHttpMessageConverter()));
    }

    public ObjectFactory<HttpMessageConverters> feignHttpMessageConverter() {
        final HttpMessageConverters httpMessageConverters = new HttpMessageConverters(new GateWayMappingJackson2HttpMessageConverter());
        return () -> httpMessageConverters;
    }

    public static class GateWayMappingJackson2HttpMessageConverter extends MappingJackson2HttpMessageConverter {
        GateWayMappingJackson2HttpMessageConverter() {
            List<MediaType> mediaTypes = new ArrayList<>();
            mediaTypes.add(MediaType.APPLICATION_JSON);
            setSupportedMediaTypes(mediaTypes);
        }
    }

    @Bean
    public RequestInterceptor requestInterceptor() {
        return (RequestTemplate template) -> template.header("X-MBX-APIKEY", binanceApi.apiKey);
    }
}

@Slf4j
@AllArgsConstructor
public class SignatureInterceptor implements RequestInterceptor {

    protected final ApplicationProperties.BinanceApi binanceApi;

    @Override
    public void apply(RequestTemplate template) {
        addApiKeyToHeader(template);
        addSignatureToQueryParams(template);
    }

    private void addApiKeyToHeader(RequestTemplate template) {
        template.header("X-MBX-APIKEY", binanceApi.apiKey);
    }

    private void addSignatureToQueryParams(RequestTemplate template) {
        final String signature = Signature.encode(binanceApi.secretKey, getQueryLineWithoutQuestionMark(template));
        log.debug("Signature: {}", signature);
        template.query("signature", signature);
    }


    private static String getQueryLineWithoutQuestionMark(RequestTemplate template) {
        final String queryLineWithoutQuestionMark = template.queryLine().substring(1);
        log.debug("Request Params: {}", queryLineWithoutQuestionMark);
        return template.queryLine().substring(1);
    }

}

import org.apache.commons.codec.binary.Hex;

import javax.crypto.Mac;
import javax.crypto.spec.SecretKeySpec;
import java.nio.charset.StandardCharsets;

/**
 * Utility class used to sign a provided data.
 */
public class Signature {
    /**
     * @param key the key used to sign the data.
     * @param data the data to be signed in UTF-8 format.
     * @return the data signature.
     */
    public static String encode(String key, String data) {
        try {
            Mac hmac = Mac.getInstance("HmacSHA256");
            SecretKeySpec secret_key = new SecretKeySpec(key.getBytes(StandardCharsets.UTF_8), "HmacSHA256");
            hmac.init(secret_key);
            return new String(Hex.encodeHex(hmac.doFinal(data.getBytes(StandardCharsets.UTF_8))));
        } catch (Exception e) {
            throw new RuntimeException(e);
        }
    }
}

@Component
@PropertySource(value = "classpath:/application.yml")
public class ApplicationProperties {

    @Component
    @ConfigurationProperties(value = "binance.api")
    public static class BinanceApi {

        @Value("${url}")
        public String url;

        @Value("${apiKey}")
        public String apiKey;

        @Value("${secretKey}")
        public String secretKey;

    }

}

binance:
  api:
    url: https://api.binance.com
    apiKey: abc
    secretKey: xyz


logging:
  level:
    org.springframework: INFO