今天研究的内容，是CoAP这个协议在EMQ消息队列的支持，CoAP是一个受限资源的协议，基于UDP实现的多用于物联网环境的通信协议。相关介绍不多说，可以看RFC。
CoAP协议下，基于DTLS通信，同样因为协议的产生背景原因，所以，对秘钥大小有有一些要求，尽量的小，所以ECC（椭圆曲线）秘钥算法成为了首先，比RSA秘钥短很多，但是加密安全强度不比RSA对应较长的秘钥安全性低。所以，EC加密算法研究成为了本博文的重点，另外，CoAP的证书中签名算法，也是有所限制的，用的是ECDSA，因为签名算法和秘钥加密算法是对应着工作的。
相关验证逻辑，可以基于CoAP的开发工具Californium的java三件套（core，connector，scandium），可以用证书进行验证。
《一》. 下面看看基于OpenSSL工具创建EC证书的过程
[root@tkwh-kfcs-app2 coaps]# openssl ecparam -out coapCA.key -name secp521r1 -genkey [root@tkwh-kfcs-app2 coaps]# openssl req -new -key coapCA.key -out coapCA.csr [root@tkwh-kfcs-app2 coaps]# openssl x509 -req -days 365 -in coapCA.csr -signkey coapCA.key -out coapCA.crt [root@tkwh-kfcs-app2 coaps]# openssl ecparam -out coapApp.key -name secp521r1 -genkey [root@tkwh-kfcs-app2 coaps]# openssl req -new -key coapApp.key -out coapApp.csr [root@tkwh-kfcs-app2 coaps]# openssl x509 -req -days 365 -in coapApp.csr -signkey coapApp.key -out coapApp.crt
从这个指令过程看，证书创建的步骤，EC算法和RSA算法没有什么太大的区别，也是三步走（1. 自签名根证书，2.生成CSR证书签名请求，3.生成对应目标证书）
《二》下面基于JAVA原生JDK的工具创建ECC的证书全流程进行分享，直接上相关的代码，希望能给到相关朋友一些帮助，有什么不清楚，可以参考我前面的博文，关于RSA证书的创建过程。
1.创建秘钥对
/** * algo: e.g. ECC * signAlgo: e.g. secp256r1 * @param algo * @param signAlgo * @return */ public static KeyPair getKeyPair(String algo, String signAlgo) { KeyPairGenerator keyPairGenerator = null; try { keyPairGenerator = KeyPairGenerator.getInstance(algo); ECGenParameterSpec ecGenParameterSpec = new ECGenParameterSpec(signAlgo); keyPairGenerator.initialize(ecGenParameterSpec, new SecureRandom()); KeyPair keyPair = keyPairGenerator.generateKeyPair(); return keyPair; } catch (NoSuchAlgorithmException e) { e.printStackTrace(); } catch (InvalidAlgorithmParameterException e) { e.printStackTrace(); } return null; }
2.创建自签名证书（CA）
/** * 生成自签名证书 * * @param publicKey 公钥对象 * @param privateKey 私钥对象 * @param subj 证书主体描述信息 * @param notBefore 有效期起始日期 * @param validDays 有效期长度 * @return * @throws Exception */ public static X509Certificate createRootCert(PublicKey publicKey, PrivateKey privateKey, String subj, Date notBefore, long validDays) throws Exception{ String algo = "SHA256WITHECDSA"; try { //证书拥有者subject的描述name sun.security.x509.X500Name subject = new sun.security.x509.X500Name(subj); CertificateExtensions certExts = new CertificateExtensions(); certExts.set(SubjectKeyIdentifierExtension.NAME, new SubjectKeyIdentifierExtension((new KeyIdentifier(publicKey)).getIdentifier())); certExts.set(AuthorityKeyIdentifierExtension.NAME, new AuthorityKeyIdentifierExtension(new KeyIdentifier(publicKey), null, null)); //设置是否根证书 BasicConstraintsExtension bce = new BasicConstraintsExtension(true, -1); certExts.set(BasicConstraintsExtension.NAME, new BasicConstraintsExtension(false, bce.getExtensionValue())); //配置证书的有效期,并生成根证书（自签名证书） X509CertInfo x509CertInfo = new X509CertInfo(); //设置证书的版本号 x509CertInfo.set(X509CertInfo.VERSION, new CertificateVersion(CertificateVersion.V3)); AlgorithmId algorithmId = AlgorithmId.get(algo); x509CertInfo.set(X509CertInfo.ALGORITHM_ID, new CertificateAlgorithmId(algorithmId)); //设置证书的签发者信息 x509CertInfo.set(X509CertInfo.ISSUER, subject); //设置证书的拥有者信息 x509CertInfo.set(X509CertInfo.SUBJECT, subject); //设置证书的序列号，基于当前时间计算 x509CertInfo.set(X509CertInfo.SERIAL_NUMBER, new CertificateSerialNumber((int) (System.currentTimeMillis() / 1000L))); //设置证书的公钥 x509CertInfo.set(X509CertInfo.KEY, new CertificateX509Key(publicKey)); //设置证书有效期 Date endDate = new Date(notBefore.getTime() + validDays * 24 * 60 * 60 * 1000L); CertificateValidity cv = new CertificateValidity(notBefore, endDate); x509CertInfo.set(X509CertInfo.VALIDITY, cv); x509CertInfo.set(CertificateExtensions.NAME, certExts); X509CertImpl cert = new X509CertImpl(x509CertInfo); try { cert.sign(privateKey, algo); } catch (InvalidKeyException | CertificateException | NoSuchAlgorithmException | NoSuchProviderException | SignatureException e3) { e3.printStackTrace(); } return cert; } catch (NoSuchAlgorithmException e) { e.printStackTrace(); } catch (CertificateException e) { e.printStackTrace(); } catch (IOException e) { e.printStackTrace(); } catch (Exception e) { e.printStackTrace(); } return null; }
3.创建用户证书（用2中的证书签发客户证书）
/** * 基于根证书签发客户证书（非CA证书），即intermediate certificate * * @param ca 根证书文件对象 * @param caKey 根证书对应的私钥 * @param publicKey 待签发证书的公钥 * @param subj 待签发证书的主体描述信息 * @param notBefore 证书有效期起点 * @param validDays 证书有效期长度 * @param sginAlgo 证书签名算法 * @return */ public static X509Certificate createUserCert(X509Certificate ca, PrivateKey caKey, PublicKey publicKey, String subj, Date notBefore, long validDays, String sginAlgo) { //获取ca证书 X509Certificate caCert = ca; X509CertInfo x509CertInfo = new X509CertInfo(); try { //设置证书的版本号 x509CertInfo.set(X509CertInfo.VERSION, new CertificateVersion(CertificateVersion.V3)); //设置证书的序列号，基于当前时间计算 x509CertInfo.set(X509CertInfo.SERIAL_NUMBER, new CertificateSerialNumber((int) (System.currentTimeMillis() / 1000L))); /** * 下面这个设置算法ID的代码，是错误的，会导致证书验证失败，但是报错不是很明确。 若将生成的证书存为keystore，让后keytool转换 * 会出现异常。 * * 重点： AlgorithmId的参数设置要和后面的证书签名中用到的算法信息一致。 */ AlgorithmId algorithmId = AlgorithmId.get(sginAlgo); x509CertInfo.set(X509CertInfo.ALGORITHM_ID, new CertificateAlgorithmId(algorithmId)); //设置证书的签发者信息 sun.security.x509.X500Name issuer = new sun.security.x509.X500Name(caCert.getIssuerX500Principal().toString()); x509CertInfo.set(X509CertInfo.ISSUER, issuer); //设置证书的拥有者信息 sun.security.x509.X500Name subject = new sun.security.x509.X500Name(subj); x509CertInfo.set(X509CertInfo.SUBJECT, subject); //设置证书的公钥 x509CertInfo.set(X509CertInfo.KEY, new CertificateX509Key(publicKey)); //设置证书有效期 Date endDate = new Date(notBefore.getTime() + validDays * 24 * 60 * 60 * 1000L); CertificateValidity cv = new CertificateValidity(notBefore, endDate); x509CertInfo.set(X509CertInfo.VALIDITY, cv); CertificateExtensions exts = new CertificateExtensions(); exts.set(SubjectKeyIdentifierExtension.NAME, new SubjectKeyIdentifierExtension((new KeyIdentifier(publicKey)).getIdentifier())); exts.set(AuthorityKeyIdentifierExtension.NAME, new AuthorityKeyIdentifierExtension(new KeyIdentifier(ca.getPublicKey()), null, null)); exts.set(BasicConstraintsExtension.NAME, new BasicConstraintsExtension(false,false,-1)); x509CertInfo.set(CertificateExtensions.NAME, exts); } catch (CertificateException cee) { cee.printStackTrace(); } catch (IOException eio) { eio.printStackTrace(); } catch (NoSuchAlgorithmException e) { e.printStackTrace(); } // 获取CA私钥 PrivateKey caPrivateKey = caKey; //用CA的私钥给当前证书进行签名，获取最终的下游证书（证书链的下一节点） X509CertImpl cert = new X509CertImpl(x509CertInfo); try { cert.sign(caPrivateKey, sginAlgo); } catch (InvalidKeyException | CertificateException | NoSuchAlgorithmException | NoSuchProviderException | SignatureException e3) { e3.printStackTrace(); } return cert; }
4. 证书的导出和导入相关方法
/** * 导出ECC私钥文件存入文件，PEM格式，PKCS#8编码 * @param privateKey * @param keyPath * @throws Exception */ public static void savePrivateKeyAsPEM(PrivateKey privateKey, String keyPath) throws Exception { String content = Base64Util.encode(privateKey.getEncoded()); File file = new File(keyPath); try (RandomAccessFile randomAccessFile = new RandomAccessFile(file, "rw")) { randomAccessFile.write(BEGIN_EC_PRIVATE_KEY.getBytes()); randomAccessFile.write(NEW_LINE.getBytes()); int i = 0; for (; i<(content.length() - (content.length() % 64)); i+=64) { randomAccessFile.write(content.substring(i, i + 64).getBytes()); randomAccessFile.write(NEW_LINE.getBytes()); } randomAccessFile.write(content.substring(i).getBytes()); randomAccessFile.write(NEW_LINE.getBytes()); randomAccessFile.write(END_EC_PRIVATE_KEY.getBytes()); } }
/** * 导出ECC公钥文件存入文件，PEM格式，PKCS#8编码 * * @param publicKey * @param name * @throws Exception */ public static void savePublicKeyAsPEM(PublicKey publicKey, String name) throws Exception { String content = Base64Util.encode(publicKey.getEncoded()); File file = new File(name); try (RandomAccessFile randomAccessFile = new RandomAccessFile(file, "rw")) { randomAccessFile.write(BEGIN_EC_PUBLIC_KEY.getBytes()); randomAccessFile.write(NEW_LINE.getBytes()); int i = 0; for (; i<(content.length() - (content.length() % 64)); i+=64) { randomAccessFile.write(content.substring(i, i + 64).getBytes()); randomAccessFile.write(NEW_LINE.getBytes()); } randomAccessFile.write(content.substring(i).getBytes()); randomAccessFile.write(NEW_LINE.getBytes()); randomAccessFile.write(END_EC_PUBLIC_KEY.getBytes()); } }
这里需要说明的是，写入文件后，文件格式中的头部和尾部信息如下：
private static final String BEGIN_EC_PRIVATE_KEY = "-----BEGIN PRIVATE KEY-----"; private static final String END_EC_PRIVATE_KEY = "-----END PRIVATE KEY-----"; private static final String BEGIN_EC_PUBLIC_KEY = "-----BEGIN PUBLIC KEY-----"; private static final String END_EC_PUBLIC_KEY = "-----END PUBLIC KEY-----";
用OPENSSL创建的EC证书私钥，默认情况下会含有EC PARAMETERS的描述，这个部分，JAVA生成过程中，目前没有弄清楚，如何能做到和OPENSSL一样，不过，不考虑EC PARAMETERS部分，整个证书运行逻辑没有问题。（若有知道的博友，可以给我留言，告知我JAVA代码如何实现openssl生成的EC证书私钥模式的文件），下面给予一个对比，OPENSSL的EC私钥内容和用上述JAVA生成的EC私钥内容：
OPENSSL（PKCS#1编码）：
openssl ecparam -out coapApp.key -name secp521r1 -genkey
-----BEGIN EC PARAMETERS----- BgUrgQQAIw== -----END EC PARAMETERS----- -----BEGIN EC PRIVATE KEY----- MIHcAgEBBEIBHpCev79KIY4T9lMyheMD9A+kXUXxmhbTdQO+bA9PCeLeXpUuHiPU dgJ31MjWYBe/5lr9Vr9kwZ20CAErIPDgttCgBwYFK4EEACOhgYkDgYYABAGhKHT6 J6aihJyNgjdGNDP2yaCGDZjmuQw2JIs9l0C27B6KHytxOV5qZfvA80s8kq/a1FBn lUlHHjsEaVi20wWTmAFMgs75xAU+VjXEU9i03GaQuwC73mySAHWPWVQXmFu0b+Bz wfvBf8so3Qew054UFbmg1zvcjZM0rBhn6GZtp7LOZw== -----END EC PRIVATE KEY-----
查看具体内容：
[root@ws2 opt]# openssl ec -in coapApp.key -noout -text read EC key Private-Key: (521 bit) priv: 01:1e:90:9e:bf:bf:4a:21:8e:13:f6:53:32:85:e3: 03:f4:0f:a4:5d:45:f1:9a:16:d3:75:03:be:6c:0f: 4f:09:e2:de:5e:95:2e:1e:23:d4:76:02:77:d4:c8: d6:60:17:bf:e6:5a:fd:56:bf:64:c1:9d:b4:08:01: 2b:20:f0:e0:b6:d0 pub: 04:01:a1:28:74:fa:27:a6:a2:84:9c:8d:82:37:46: 34:33:f6:c9:a0:86:0d:98:e6:b9:0c:36:24:8b:3d: 97:40:b6:ec:1e:8a:1f:2b:71:39:5e:6a:65:fb:c0: f3:4b:3c:92:af:da:d4:50:67:95:49:47:1e:3b:04: 69:58:b6:d3:05:93:98:01:4c:82:ce:f9:c4:05:3e: 56:35:c4:53:d8:b4:dc:66:90:bb:00:bb:de:6c:92: 00:75:8f:59:54:17:98:5b:b4:6f:e0:73:c1:fb:c1: 7f:cb:28:dd:07:b0:d3:9e:14:15:b9:a0:d7:3b:dc: 8d:93:34:ac:18:67:e8:66:6d:a7:b2:ce:67 ASN1 OID: secp521r1 NIST CURVE: P-521
JAVA（PKCS#8编码）：
ECGenParameterSpec ecGenParameterSpec = new ECGenParameterSpec(“secp256r1”);
-----BEGIN PRIVATE KEY----- MEECAQAwEwYHKoZIzj0CAQYIKoZIzj0DAQcEJzAlAgEBBCAoWE90so3R0wAj/kWS p43qZEHS2WcdZZAehpPtfZyV6A== -----END PRIVATE KEY-----
查看具体内容：
[root@ws2 opt]# openssl ec -in eccDevCertPem.key -noout -text read EC key Private-Key: (256 bit) priv: 28:58:4f:74:b2:8d:d1:d3:00:23:fe:45:92:a7:8d: ea:64:41:d2:d9:67:1d:65:90:1e:86:93:ed:7d:9c: 95:e8 pub: 04:af:74:c5:4f:53:69:76:51:0d:c7:0a:9d:36:62: f0:4c:ab:f1:42:5c:cf:68:28:e8:9c:c7:13:b4:61: b0:a9:52:2a:66:57:2e:35:fe:92:dc:1c:8f:c9:cb: fa:2f:88:6a:bb:c3:54:d2:3d:34:ad:d5:9c:20:f5: 1d:1e:9d:87:3b ASN1 OID: prime256v1 NIST CURVE: P-256
5. JAVA创建证书的DEMO
public void fromZeroToStart() throws Exception { String subjCA = "OU=TaiKang,O=TKCloud,L=Wuhan,ST=Hubei,C=CN,CN=IOT_" + "ECC_CA"; String subjSVR = "OU=TaiKang,O=TKCloud,L=Wuhan,ST=Hubei,C=CN,CN=" + "10.95.197.8"; String subjDev = "OU=TaiKang,O=TKCloud,L=Wuhan,ST=Hubei,C=CN,CN=IOT_" + "Device"; KeyPair eccCaKey = CertUtils.getKeyPair("EC", "secp256r1"); KeyPair eccEmKey = CertUtils.getKeyPair("EC", "secp256r1"); KeyPair eccDvKey = CertUtils.getKeyPair("EC", "secp256r1"); //自签发根证书 Date notBefore = new Date(); X509Certificate crt = CertUtils.createRootCert(eccCaKey.getPublic(), eccCaKey.getPrivate(), subjCA, notBefore,365, SIGN_ALGO); //根证书签发生成实体证书 X509Certificate eccEmqCert = CertUtils.createUserCert(crt, eccCaKey.getPrivate(), eccEmKey.getPublic(), subjSVR, notBefore, 365, SIGN_ALGO); //写入证书到文件 SSLUtils.exportPemCrtFile(crt.getEncoded(),basePath + "eccRootCert.crt"); SSLUtils.exportDerKeyFile(eccCaKey.getPrivate().getEncoded(),basePath + "eccRootCert.key"); SSLUtils.savePrivateKeyAsPEM(eccCaKey.getPrivate(), basePath + "eccRootCertPem.key"); SSLUtils.exportPemCrtFile(eccEmqCert.getEncoded(),basePath + "eccEmqCert.crt"); SSLUtils.exportDerKeyFile(eccEmKey.getPrivate().getEncoded(),basePath + "eccEmqCert.key"); SSLUtils.savePrivateKeyAsPEM(eccEmKey.getPrivate(), basePath + "eccEmqCertPem.key"); }
6. 遇到的小麻烦
1）证书的有效时间和验证服务器的时间不同步导致异常
[root@mq2 ecc]# openssl verify -CAfile eccRootCert.crt eccEmqCert.crt eccEmqCert.crt: CN = IOT_ECC_CA, C = CN, ST = Hubei, L = Wuhan, O = TKCloud, OU = TaiKang error 9 at 1 depth lookup:certificate is not yet valid
等一会后，同样的证书，同样的操作，就可以了（生成的证书里面设置的有效时间范围，和当前验证操作，即执行openssl的服务的时间没有同步，服务器时间慢了点）
[root@mq2 ecc]# openssl verify -CAfile eccRootCert.crt eccEmqCert.crt
eccEmqCert.crt: OK
[root@ws2 ecc]# mosquitto_pub -d -h 10.95.197.8 -p 8883 -t taikang/rulee -i client18 --cafile /opt/ecc/eccRootCert.crt --cert /opt/ecc/eccDevCert.crt --key /opt/ecc/eccDevCertPem.key -u shihuc -P shihuc -m "are you ok, emqttd" Client client18 sending CONNECT OpenSSL Error: error:14090086:SSL routines:ssl3_get_server_certificate:certificate verify failed Error: A TLS error occurred.
上述错误信息，也是证书的有效时间和服务器时间不同步，参照上面的错误。
2）openssl的版本不同导致的查看证书出现异常
[root@mq2 ecc]# openssl x509 -in eccRootCert.crt -noout -text Certificate: Data: Version: 3 (0x2) Serial Number: 1556080738 (0x5cbfe862) Signature Algorithm: ecdsa-with-SHA256 Issuer: CN=IOT_ECC_CA, C=CN, ST=Hubei, L=Wuhan, O=TKCloud, OU=TaiKang Validity Not Before: Apr 24 04:38:58 2019 GMT Not After : Apr 23 04:38:58 2020 GMT Subject: CN=IOT_ECC_CA, C=CN, ST=Hubei, L=Wuhan, O=TKCloud, OU=TaiKang Subject Public Key Info: Public Key Algorithm: id-ecPublicKey Public-Key: (256 bit) pub: 04:65:49:e6:46:8d:28:b2:49:d2:45:26:04:f9:d5: b3:f4:84:f9:38:2e:ad:43:d1:14:92:af:ad:c3:0a: 3c:35:21:f3:25:39:85:41:a9:b9:51:d7:b3:20:6b: 5d:09:23:c6:66:b5:22:f3:fb:dd:a6:1c:74:43:19: c1:b0:50:5c:44 ASN1 OID: prime256v1 NIST CURVE: P-256 X509v3 extensions: X509v3 Authority Key Identifier: keyid:0F:62:52:44:B1:7F:AA:23:BE:55:70:E3:05:F1:0F:EE:96:CB:C1:E9 X509v3 Basic Constraints: CA:TRUE X509v3 Subject Key Identifier: 0F:62:52:44:B1:7F:AA:23:BE:55:70:E3:05:F1:0F:EE:96:CB:C1:E9 Signature Algorithm: ecdsa-with-SHA256 30:44:02:20:02:f5:d5:3b:59:8a:42:af:c7:9a:15:06:f9:4b: 03:09:0d:bb:28:59:dc:eb:91:38:65:99:64:45:91:33:2d:d5: 02:20:51:f6:c3:ff:8e:76:32:cd:f2:a9:a9:23:18:37:d3:0a: 18:9a:94:94:16:00:b4:fc:7c:cc:11:e8:99:18:81:21 [root@mq2 ecc]# openssl version OpenSSL 1.0.2k-fips 26 Jan 2017
同一个证书，在另外一个服务器上查看：
[root@tkwh-kfcs-app2 java]# openssl x509 -in eccRootCert.crt -noout -text Certificate: Data: Version: 3 (0x2) Serial Number: 1556066987 (0x5cbfb2ab) Signature Algorithm: ecdsa-with-SHA256 Issuer: CN=IOT_ECC_CA, C=CN, ST=Hubei, L=Wuhan, O=TKCloud, OU=TaiKang Validity Not Before: Apr 24 00:49:35 2019 GMT Not After : Apr 23 00:49:35 2020 GMT Subject: CN=IOT_ECC_CA, C=CN, ST=Hubei, L=Wuhan, O=TKCloud, OU=TaiKang Subject Public Key Info: Public Key Algorithm: id-ecPublicKey Unable to load Public Key 139880214046624:error:100AE081:elliptic curve routines:EC_GROUP_new_by_curve_name:unknown group:ec_curve.c:371: 139880214046624:error:100D7010:elliptic curve routines:ECKEY_PUB_DECODE:EC lib:ec_ameth.c:206: 139880214046624:error:0B07707D:x509 certificate routines:X509_PUBKEY_get:public key decode error:x_pubkey.c:164: X509v3 extensions: X509v3 Authority Key Identifier: keyid:06:67:AB:58:41:C5:DA:BD:23:73:9C:BA:E5:45:79:28:73:1C:E2:AF X509v3 Basic Constraints: CA:TRUE X509v3 Subject Key Identifier: 06:67:AB:58:41:C5:DA:BD:23:73:9C:BA:E5:45:79:28:73:1C:E2:AF Signature Algorithm: ecdsa-with-SHA256 30:44:02:20:5e:f6:fa:30:42:6f:20:1e:f6:34:1f:66:2c:a3: c7:a8:25:27:a1:8f:83:73:96:23:f2:e4:0d:e5:4b:a8:d2:a5: 02:20:4c:6f:8b:2b:d4:5d:23:b3:fd:ba:3e:18:66:30:69:dc: 48:f5:a9:88:7e:2f:e8:e9:7b:7b:4c:85:e0:bc:d5:01 [root@tkwh-kfcs-app2 java]# openssl version OpenSSL 1.0.1e-fips 11 Feb 2013
好了，到这里，ECC证书创建和基本的验证过程，到此结束，有相关需求或者探讨的，可以关注我的博客，一起深入。
