作者：三烽
概述
物聯網平臺支持CoAP協議連接通信。CoAP協議適用在資源受限的低功耗設備上，尤其是NB-IoT的設備使用。本文介紹基於開源的CoAP協議進行對稱加密自主接入的流程，並提供java示例代碼。
官方鏈接
流程
一、連接CoAP服務器
endpoint地址為：{port}
：您的產品的。{port}：端口。使用對稱加密時端口為5682。
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二、進行設備認證
具體請求參數詳見官方文檔
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三、上報數據
具體請求參數詳見官方文檔
示例代碼
一、pom.xml依賴
<dependency>
<groupId>org.eclipse.californium</groupId>
<artifactId>californium-core</artifactId>
<version>2.0.0-M17</version>
</dependency>
<dependency>
<groupId>org.apache.commons</groupId>
<artifactId>commons-lang3</artifactId>
<version>3.5</version>
</dependency>
<dependency>
<groupId>commons-codec</groupId>
<artifactId>commons-codec</artifactId>
<version>1.13</version>
</dependency>
<dependency>
<groupId>com.alibaba</groupId>
<artifactId>fastjson</artifactId>
<version>1.2.61</version>
</dependency>
二、代碼
/*
* Copyright © 2019 Alibaba. All rights reserved.
*/
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.security.MessageDigest;
import java.security.NoSuchAlgorithmException;
import java.util.Set;
import java.util.SortedMap;
import java.util.TreeMap;
import javax.crypto.Cipher;
import javax.crypto.Mac;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;
import org.apache.commons.codec.DecoderException;
import org.apache.commons.codec.binary.Hex;
import org.apache.commons.lang3.RandomUtils;
import org.eclipse.californium.core.CoapClient;
import org.eclipse.californium.core.CoapResponse;
import org.eclipse.californium.core.Utils;
import org.eclipse.californium.core.coap.CoAP;
import org.eclipse.californium.core.coap.CoAP.Code;
import org.eclipse.californium.core.coap.CoAP.Type;
import org.eclipse.californium.core.coap.MediaTypeRegistry;
import org.eclipse.californium.core.coap.Option;
import org.eclipse.californium.core.coap.OptionNumberRegistry;
import org.eclipse.californium.core.coap.OptionSet;
import org.eclipse.californium.core.coap.Request;
import org.eclipse.californium.elements.exception.ConnectorException;
import com.alibaba.fastjson.JSONObject;
/**
* CoAP客戶端連接阿里雲物聯網平臺，基於eclipse californium開發。
* 自主接入開發流程及參數填寫，請參見：
* https://help.aliyun.com/document_detail/57697.html [使用對稱加密自主接入]
*/
public class IotCoapClientWithAes {
// ===================需要用戶填寫的參數，開始===========================
// 地域ID，當前僅支持華東2
private static String regionId = "cn-shanghai";
// 產品productKey
private static String productKey = "a1fBBLKhpwv";
// 設備名成deviceName
private static String deviceName = "AirC";
// 設備密鑰deviceSecret
private static String deviceSecret = "LL6VoF5L49EbMdoGvdwRppOgHWuwE9bL";
//發送的消息內容payload
private static String payload = "hello coap!!";
// ===================需要用戶填寫的參數，結束===========================
// 定義加密方式 MAC算法可選以下多種算法 HmacMD5 HmacSHA1，需與signmethod一致。
private static final String HMAC_ALGORITHM = "hmacsha1";
// CoAP接入地址，對稱加密端口號是5682。
private static String serverURI = "coap://" + productKey + ".coap." + regionId + ".link.aliyuncs.com:5682";
// 發送消息用的Topic。需要在控制檯自定義Topic，設備操作權限需選擇為“發佈”。
private static String updateTopic = "/" + productKey + "/" + deviceName + "/user/update";
// token option
private static final int COAP2_OPTION_TOKEN = 2088;
// seq option
private static final int COAP2_OPTION_SEQ = 2089;
// 加密算法sha256
private static final String SHA_256 = "SHA-256";
private static final int DIGITAL_16 = 16;
private static final int DIGITAL_48 = 48;
// CoAP客戶端
private CoapClient coapClient = new CoapClient();
// token 7天有效，失效後需要重新獲取。
private String token = null;
private String random = null;
@SuppressWarnings("unused")
private long seqOffset = 0;
/**
* 初始化CoAP客戶端
*
* @param productKey 產品key
* @param deviceName 設備名稱
* @param deviceSecret 設備密鑰
*/
public void conenct(String productKey, String deviceName, String deviceSecret) {
try {
// 認證uri，/auth
String uri = serverURI + "/auth";
// 只支持POST方法
Request request = new Request(Code.POST, Type.CON);
// 設置option
OptionSet optionSet = new OptionSet();
optionSet.addOption(new Option(OptionNumberRegistry.CONTENT_FORMAT, MediaTypeRegistry.APPLICATION_JSON));
optionSet.addOption(new Option(OptionNumberRegistry.ACCEPT, MediaTypeRegistry.APPLICATION_JSON));
request.setOptions(optionSet);
// 設置認證uri
request.setURI(uri);
// 設置認證請求payload
request.setPayload(authBody(productKey, deviceName, deviceSecret));
// 發送認證請求
CoapResponse response = coapClient.advanced(request);
System.out.println(Utils.prettyPrint(response));
System.out.println();
// 解析請求響應
JSONObject json = JSONObject.parseObject(response.getResponseText());
token = json.getString("token");
random = json.getString("random");
seqOffset = json.getLongValue("seqOffset");
} catch (ConnectorException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
}
/**
* 發送消息
*
* @param topic 發送消息的Topic
* @param payload 消息內容
*/
public void publish(String topic, byte[] payload) {
try {
// 消息發佈uri，/topic/${topic}
String uri = serverURI + "/topic" + topic;
// AES加密seq，seq=RandomUtils.nextInt()
String shaKey = encod(deviceSecret + "," + random);
byte[] keys = Hex.decodeHex(shaKey.substring(DIGITAL_16, DIGITAL_48));
byte[] seqBytes = encrypt(String.valueOf(RandomUtils.nextInt()).getBytes(StandardCharsets.UTF_8), keys);
// 只支持POST方法
Request request = new Request(CoAP.Code.POST, CoAP.Type.CON);
// 設置option
OptionSet optionSet = new OptionSet();
optionSet.addOption(new Option(OptionNumberRegistry.CONTENT_FORMAT, MediaTypeRegistry.APPLICATION_JSON));
optionSet.addOption(new Option(OptionNumberRegistry.ACCEPT, MediaTypeRegistry.APPLICATION_JSON));
optionSet.addOption(new Option(COAP2_OPTION_TOKEN, token));
optionSet.addOption(new Option(COAP2_OPTION_SEQ, seqBytes));
request.setOptions(optionSet);
// 設置消息發佈uri
request.setURI(uri);
// 設置消息payload
request.setPayload(encrypt(payload, keys));
// 發送消息
CoapResponse response = coapClient.advanced(request);
System.out.println("----------------");
System.out.println(request.getPayload().length);
System.out.println("----------------");
System.out.println(Utils.prettyPrint(response));
// 解析消息發送結果
String result = null;
if (response.getPayload() != null) {
result = new String(decrypt(response.getPayload(), keys));
}
System.out.println("payload: " + result);
System.out.println();
} catch (ConnectorException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
} catch (DecoderException e) {
e.printStackTrace();
}
}
/**
* 生成認證請求內容
*
* @param productKey 產品key
* @param deviceName 設備名字
* @param deviceSecret 設備密鑰
* @return 認證請求
*/
private String authBody(String productKey, String deviceName, String deviceSecret) {
// 構建認證請求
JSONObject body = new JSONObject();
body.put("productKey", productKey);
body.put("deviceName", deviceName);
body.put("clientId", productKey + "." + deviceName);
body.put("timestamp", String.valueOf(System.currentTimeMillis()));
body.put("signmethod", HMAC_ALGORITHM);
body.put("seq", DIGITAL_16);
body.put("sign", sign(body, deviceSecret));
System.out.println("----- auth body -----");
System.out.println(body.toJSONString());
return body.toJSONString();
}
/**
* 設備端簽名
*
* @param params 簽名參數
* @param deviceSecret 設備密鑰
* @return 簽名十六進制字符串
*/
private String sign(JSONObject params, String deviceSecret) {
// 請求參數按字典順序排序
Set<String> keys = getSortedKeys(params);
// sign、signmethod、version、resources除外
keys.remove("sign");
keys.remove("signmethod");
keys.remove("version");
keys.remove("resources");
// 組裝簽名明文
StringBuffer content = new StringBuffer();
for (String key : keys) {
content.append(key);
content.append(params.getString(key));
}
// 計算簽名
String sign = encrypt(content.toString(), deviceSecret);
System.out.println("sign content=" + content);
System.out.println("sign result=" + sign);
return sign;
}
/**
* 獲取JSON對象排序後的key集合
*
* @param json 需要排序的JSON對象
* @return 排序後的key集合
*/
private Set<String> getSortedKeys(JSONObject json) {
SortedMap<String, String> map = new TreeMap<String, String>();
for (String key : json.keySet()) {
String vlaue = json.getString(key);
map.put(key, vlaue);
}
return map.keySet();
}
/**
* 使用 HMAC_ALGORITHM 加密
*
* @param content 明文
* @param secret 密鑰
* @return 密文
*/
private String encrypt(String content, String secret) {
try {
byte[] text = content.getBytes(StandardCharsets.UTF_8);
byte[] key = secret.getBytes(StandardCharsets.UTF_8);
SecretKeySpec secretKey = new SecretKeySpec(key, HMAC_ALGORITHM);
Mac mac = Mac.getInstance(secretKey.getAlgorithm());
mac.init(secretKey);
return Hex.encodeHexString(mac.doFinal(text));
} catch (Exception e) {
e.printStackTrace();
return null;
}
}
/**
* SHA-256
*
* @param str 待加密的報文
*/
private String encod(String str) {
MessageDigest messageDigest;
String encdeStr = "";
try {
messageDigest = MessageDigest.getInstance(SHA_256);
byte[] hash = messageDigest.digest(str.getBytes(StandardCharsets.UTF_8));
encdeStr = Hex.encodeHexString(hash);
} catch (NoSuchAlgorithmException e) {
System.out.println(String.format("Exception@encod: str=%s;", str));
e.printStackTrace();
return null;
}
return encdeStr;
}
// AES 加解密算法
private static final String IV = "543yhjy97ae7fyfg";
private static final String TRANSFORM = "AES/CBC/PKCS5Padding";
private static final String ALGORITHM = "AES";
/**
* key length = 16 bits
*/
private byte[] encrypt(byte[] content, byte[] key) {
return encrypt(content, key, IV);
}
/**
* key length = 16 bits
*/
private byte[] decrypt(byte[] content, byte[] key) {
return decrypt(content, key, IV);
}
/**
* aes 128 cbc key length = 16 bits
*/
private byte[] encrypt(byte[] content, byte[] key, String ivContent) {
try {
SecretKeySpec keySpec = new SecretKeySpec(key, ALGORITHM);
Cipher cipher = Cipher.getInstance(TRANSFORM);
IvParameterSpec iv = new IvParameterSpec(ivContent.getBytes(StandardCharsets.UTF_8));
cipher.init(Cipher.ENCRYPT_MODE, keySpec, iv);
return cipher.doFinal(content);
} catch (Exception ex) {
System.out.println(
String.format("AES encrypt error, %s, %s, %s", content, Hex.encodeHex(key), ex.getMessage()));
return null;
}
}
/**
* aes 128 cbc key length = 16 bits
*/
private byte[] decrypt(byte[] content, byte[] key, String ivContent) {
try {
SecretKeySpec keySpec = new SecretKeySpec(key, ALGORITHM);
Cipher cipher = Cipher.getInstance(TRANSFORM);
IvParameterSpec iv = new IvParameterSpec(ivContent.getBytes(StandardCharsets.UTF_8));
cipher.init(Cipher.DECRYPT_MODE, keySpec, iv);
return cipher.doFinal(content);
} catch (Exception ex) {
System.out.println(String.format("AES decrypt error, %s, %s, %s", Hex.encodeHex(content),
Hex.encodeHex(key), ex.getMessage()));
return null;
}
}
public static void main(String[] args) throws InterruptedException {
IotCoapClientWithAes client = new IotCoapClientWithAes();
client.conenct(productKey, deviceName, deviceSecret);
client.publish(updateTopic, payload.getBytes(StandardCharsets.UTF_8));
}
}
注意事項
1、coap協議是短連接，和mqtt長連接不同，所以在控制檯的設備行為分析日誌裡看不到記錄，需要注意。
2、coap協議發送的payload有大小限制，不能超過1KB，如果超過的話這個請求會被拒絕，消息發不到平臺。代碼中System.out.println(request.getPayload().length);就是用來打印payload長度的。
3、目前只有華東2地域的設備支持使用coap協議接入。