ES256 JWT验证-SignatureException：签名的无效编码：java.io.IOException：序列标记错误

时间：2019-12-07 18:18:28

标签： java cryptography elliptic-curve java-security jwt-auth

嗨，我有一个使用椭圆曲线ES256签名的JWT正在尝试对其进行验证：

eyJhbGciOiJFUzI1NiIsInR5cCI6IkpXVCIsImtpZCI6IjEyMzQifQ.eyJpc3MiOiJodHRwczovL2p3dC1pZHAuZXhhbXBsZS5jb20iLCJzdWIiOiJtYWlsdG86bWlrZUBleGFtcGxlLmNvbSIsIm5iZiI6MTU3NTY1NjY3NCwiZXhwIjoxOTI0OTkxOTk5LCJpYXQiOjE1NzU2NTY2NzQsImp0aSI6ImlkMTIzNDU2IiwidHlwIjoiaHR0cHM6Ly9leGFtcGxlLmNvbS9yZWdpc3RlciJ9.kcj0QQrERKIfny1TfHY-Z9iDFazr84xCssTDuXtV1n1dvY7CYXuP5ZBvpi9ArOQjsS8YCd0bKsWaQ-17VnF_1A

使用此公共密钥：

-----BEGIN PUBLIC KEY-----
MFkwEwYHKoZIzj0CAQYIKoZIzj0DAQcDQgAEoBUyo8CQAFPeYPvv78ylh5MwFZjT
CLQeb042TjiMJxG+9DLFmRSMlBQ9T/RsLLc+PmpB1+7yPAR+oR5gZn3kJQ==
-----END PUBLIC KEY-----

只是

{
  "kty": "EC",
  "use": "sig",
  "crv": "P-256",
  "kid": "1234",
  "x": "oBUyo8CQAFPeYPvv78ylh5MwFZjTCLQeb042TjiMJxE=",
  "y": "vvQyxZkUjJQUPU/0bCy3Pj5qQdfu8jwEfqEeYGZ95CU=",
  "alg": "ES256"
}

它可以在https://jwt.io/上正确验证，但是当我尝试使用本机Java对其进行验证时，它会引发错误：


java.security.SignatureException: invalid encoding for signature: java.io.IOException: Sequence tag error
    at com.ibm.crypto.provider.AbstractSHAwithECDSA.engineVerify(Unknown Source)
    at java.security.Signature$Delegate.engineVerify(Signature.java:1219)
    at java.security.Signature.verify(Signature.java:652)
    at curam.platforminfrastructure.outbound.oauth2.impl.ValidateJWT.validateEllipticCurve(ValidateJWT.java:235)
    at curam.platforminfrastructure.outbound.oauth2.impl.ValidateJWT.validateJWT(ValidateJWT.java:88)
    at curam.platforminfrastructure.outbound.oauth2.impl.ValidateJWT.testJWT(ValidateJWT.java:53)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:44)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:15)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:41)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:20)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:76)
    at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:50)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:193)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:52)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:191)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:42)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:184)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:236)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:89)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:41)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:541)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:763)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:463)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:209)

我的代码如下：

import com.fasterxml.jackson.databind.JsonNode;
import com.fasterxml.jackson.databind.ObjectMapper;
import java.io.IOException;
import java.math.BigInteger;
import java.security.AlgorithmParameters;
import java.security.InvalidKeyException;
import java.security.KeyFactory;
import java.security.NoSuchAlgorithmException;
import java.security.Signature;
import java.security.SignatureException;
import java.security.interfaces.ECPublicKey;
import java.security.spec.ECGenParameterSpec;
import java.security.spec.ECParameterSpec;
import java.security.spec.ECPoint;
import java.security.spec.ECPublicKeySpec;
import java.security.spec.InvalidKeySpecException;
import java.security.spec.InvalidParameterSpecException;
import java.util.Base64;
import java.util.Base64.Decoder;
import java.util.Base64.Encoder;

public class ValidateJWT {

  final Decoder urlDecoder = Base64.getUrlDecoder();
  final Encoder urlEncoder = Base64.getUrlEncoder();
  final Decoder decoder = Base64.getDecoder();
  final Encoder encoder = Base64.getEncoder();
  final ObjectMapper objectMapper = new ObjectMapper();

  public boolean validateEllipticCurve(final String JWT, final String PUBLICKEY)
      throws IOException {
    final String[] at_arr = JWT.split("\\.");
    final String headerB64u = at_arr[0];
    final String payloadB64u = at_arr[1];
    final String signed_data = headerB64u + "." + payloadB64u;
    final byte[] signature = urlDecoder.decode(at_arr[2]);
    final byte[] at_headerJSON = urlDecoder.decode(headerB64u);

    final JsonNode pkRoot = objectMapper.readTree(PUBLICKEY);
    final String xStr = pkRoot.get("x").textValue();
    final String yStr = pkRoot.get("y").textValue();
    final byte xArr[] = decoder.decode(xStr);
    final byte yArr[] = decoder.decode(yStr);
    final BigInteger x = new BigInteger(xArr);
    final BigInteger y = new BigInteger(yArr);

    try {
      final AlgorithmParameters parameters = AlgorithmParameters
          .getInstance("EC");
      parameters.init(new ECGenParameterSpec("secp256k1"));
      final ECParameterSpec ecParameterSpec = parameters
          .getParameterSpec(ECParameterSpec.class);
      final KeyFactory keyFactory = KeyFactory.getInstance("EC");

      final ECPoint ecPoint = new ECPoint(x, y);
      final ECPublicKeySpec keySpec = new ECPublicKeySpec(ecPoint,
          ecParameterSpec);
      final ECPublicKey publicKey = (ECPublicKey) keyFactory
          .generatePublic(keySpec);

      final JsonNode key_root = objectMapper.readTree(at_headerJSON);
      final String alg = key_root.get("alg").textValue();

      Signature dataVerifyingInstance = null;
      switch (alg) {
      case "ES256":
        dataVerifyingInstance = Signature.getInstance("SHA256withECDSA");
        break;
      case "ES384":
        dataVerifyingInstance = Signature.getInstance("SHA384withECDSA");
        break;
      case "ES512":
        dataVerifyingInstance = Signature.getInstance("SHA512withECDSA");
        break;
      }

      dataVerifyingInstance.initVerify(publicKey);
      dataVerifyingInstance.update(signed_data.getBytes());
      final boolean verification = dataVerifyingInstance.verify(signature);
      return verification;
    } catch (final SignatureException | InvalidKeySpecException
        | InvalidKeyException | InvalidParameterSpecException
        | NoSuchAlgorithmException ex) {
      ex.printStackTrace();
      return false;
    }
  }

}

最后一行似乎引发了异常。

final boolean verification = dataVerifyingInstance.verify(signature);// <== here

我不确定是否通过使用错误的曲线（secp256k1，secp256r1，secp256v1）引起问题，或者可能是其他原因。任何提示将不胜感激。

1 个答案:

答案 0 :(得分：2)

问题在于，为JWS计算的签名（在椭圆曲线的情况下）是RFC7515中指定的R和S值的原始串联。因此，这是32 + 32 = 64字节（如果是256位曲线）。

但是，Java实现期望此签名采用DER序列形式。这就是为什么您遇到此异常的原因-您的签名（R和S值）没有经过DER编码。您甚至可以检查负责解码签名（sun.security.ec.ECDSASignature::decodeSignature）和编码签名（用于签名操作-sun.security.ec.ECDSASignature::encodeSignature）的代码。从源代码中可以看到，它们使用sun.ec包中的内部类进行DER编码。并且不建议自己使用这些类。

您的最佳选择是将原始签名转换为DER编码的签名。如果需要，可以使用BouncyCastle，它具有DER编码处理功能。这是将您的EC原始签名转换为DER编码的原始签名的方法：

private static byte[] toDerSignature(byte[] jwsSig) throws IOException {

    byte[] rBytes = Arrays.copyOfRange(jwsSig, 0, 32);
    byte[] sBytes = Arrays.copyOfRange(jwsSig, 32, 64);

    BigInteger r = new BigInteger(1, rBytes);
    BigInteger s = new BigInteger(1, sBytes);

    DERSequence sequence = new DERSequence(new ASN1Encodable[] {
            new ASN1Integer(r),
            new ASN1Integer(s)
    });

    return sequence.getDEREncoded();
}

并使用此签名进行验证。

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