InvalidKeySpecException 数据不是对象 ID（标记 = -96）

Question

我在 Azure 门户免费订阅上获得了一个访问令牌，标题是：

{
  "typ": "JWT",
  "alg": "RS256",
  "x5t": "7_Zuf1tvkwLxYaHS3q6lUjUYIGw",
  "kid": "7_Zuf1tvkwLxYaHS3q6lUjUYIGw"
}

所以我从here 得到了 x5c，然后把

-----开始证书----- MIIDBTCCAe......cNpO9oReBUsX -----结束证书-----

    ze7xq1zGljQihJgcNpO9oReBUsX

在https://jwt.io/，签名已验证。

但是，当我尝试使用 jjwt 和 jose4j 使用 JDK1.8 验证签名时，按照this refrence 中的步骤，我在线上遇到了以下异常

PublicKey publicKey = keyFactory.generatePublic(keySpec);

java.security.spec.InvalidKeySpecException: java.security.InvalidKeyException: IOException: ObjectIdentifier() -- data isn't an object ID (tag = -96)
at java.base/sun.security.rsa.RSAKeyFactory.engineGeneratePublic(RSAKeyFactory.java:204)
at java.base/java.security.KeyFactory.generatePublic(KeyFactory.java:352)
at com.ipscape.api.v1_0.external.other.JwtExample.decodeJwt(JwtExample.java:41)
at com.ipscape.api.v1_0.external.other.JwtExample.main(JwtExample.java:72)
Caused by: java.security.InvalidKeyException: IOException: ObjectIdentifier() -- data isn't an object ID (tag = -96)
at java.base/sun.security.x509.X509Key.decode(X509Key.java:396)
at java.base/sun.security.x509.X509Key.decode(X509Key.java:401)
at java.base/sun.security.rsa.RSAPublicKeyImpl.<init>(RSAPublicKeyImpl.java:86)
at java.base/sun.security.rsa.RSAKeyFactory.generatePublic(RSAKeyFactory.java:297)
at java.base/sun.security.rsa.RSAKeyFactory.engineGeneratePublic(RSAKeyFactory.java:200)

使用 jose4j 的代码：

        String publicKeyPEM =
        "MIIDBTCCAe2gAwIBAgIQE7nbxEiAlqhFdKnsKV+nuTANBgkqhkiG9w0BAQsFADAtMSswKQYDVQQDEyJhY2NvdW50cy5hY2Nlc3Njb250cm9sLndpbmRvd3MubmV0MB4XDTE4MDYyMTAwMDAwMFoXDTIwMDYyMTAwMDAwMFowLTErMCkGA1UEAxMiYWNjb3VudHMuYWNjZXNzY29udHJvbC53aW5kb3dzLm5ldDCCASIwDQYJKoZIhvcNAQEBBQADggEPADCCAQoCggEBAL1cxvfI3wPu1HFGZL6wnSHfcqX6DlvezLF1wbqUs6/DS5GhxtvHk6+9nKyNuCjznkEKql6bTIgnUbvTPr0UUKa3hezq/D9nkGu4qX8LVONVWkb53mjnN45lnVfOLh6VQ7J8/9Ut/ybbnhcn2a12vWiR0c6899TgtRp+i0bkT9dYl+3/wfP8+bBqmolwno7yojv/DxMz86mzhS7lW6mS9zzYtdsy6IHcF2P9XIac2TaP0efUpLrQY81wuTE3gUh2s6j7tqNH7aKK2PNAuxXtyGtZ9r+bg0gMrDXXVKJylQO9m4Z5J0vuz8xgCElLg3uJPOI8q/j0YrLe5rHy67ACg0MCAwEAAaMhMB8wHQYDVR0OBBYEFDnSNW3pMmrshl3iBAS4OSLCu/7GMA0GCSqGSIb3DQEBCwUAA4IBAQAFs3C5sfXSfoi7ea62flYEukqyVMhrDrpxRlvIuXqL11g8KEXlk8pS8gEnRtU6NBeHhMrhYSuiqj7/2jUT1BR3zJ2bChEyEpIgOFaiTUxq6tXdpWi/M7ibf8O/1sUtjgYktwJlSL6FEVAMFH82TxCoTWp2g5i2lmZQ7KxiKhG+Vl9nw1bPX57hkWWhR7Hpes0MbpGNZI2IEpZSjNG1IWPPOBcaOh4ed2WBQcLcaTuAaELlaxanQaC0B3029To80MnzpZuadaul3+jN7JQg0MpHdJJ8GMHAWe/IjXc0evJNhVUcKON41hzTu0R+Sze7xq1zGljQihJgcNpO9oReBUsX";

    X509EncodedKeySpec keySpec = new X509EncodedKeySpec(Base64.getDecoder().decode(publicKeyPEM.getBytes()));
    KeyFactory keyFactory = KeyFactory.getInstance("RSA");
    PublicKey publicKey = keyFactory.generatePublic(keySpec);

    JwtConsumer jwtConsumer = new JwtConsumerBuilder()
        .setRequireExpirationTime()
        .setVerificationKey(publicKey)
        .build();

Answer 1

这行得通：

        JwtConsumer jwtConsumer = new JwtConsumerBuilder()
        .setRequireExpirationTime()
        .setExpectedAudience("https://example.com/")
        .setVerificationKey(publicKey)
        .build();

    JwtClaims jwtDecoded = null;
    jwtDecoded = jwtConsumer.processToClaims(token);

    Map<String, Object> jwtClaims = jwtDecoded.getClaimsMap();
    String iss = (String) jwtClaims.get("iss");

Answer 2

x5c is a (X.509) certificate, not a public key. 实际上它是一个证书数组，必要时形成一个链，虽然这个例子是一个单一的自签名证书。证书的 PEM 标题和尾行应该全部大写“BEGIN CERTIFICATE”和“END CERTIFICATE”，并且 base64 应该添加换行符，这与 JWT 格式不同，后者是 base64 但不是 PEM。

要阅读证书，请使用java.security.cert.CertificateFactory。 （这也可以处理一个链，作为它调用 PkiPath 的证书序列，或一个标准的（通常称为 p7b 或 p7c）的（普通）PKCS7 消息。）要么给它正确 PEM 格式，或正确的二进制/DER 格式；后者更容易，因为它只是对 JWT x5c 格式进行 base64 解码（正如您现在所做的那样，在将其放入错误的密钥规范之前，但 java.util.Base64.Decoder 不需要以字节为单位的 base64，它可能需要String)。如果您只需要公钥，则可以从证书中获取它。执行以下操作：

String certb64 = "...";
byte[] certder = Base64.getDecoder().decode(certb64);
InputStream certstream = new ByteArrayInputStream (certder);
Certificate cert = CertificateFactory.getInstance("X.509").generateCertificate(certstream);
PublicKey key = cert.getPublicKey();