从 Bouncy Castle 中的 ASN.1 编码中检索 CMSSignedData

Question

在以下代码中，我使用 Bouncy Castle 签署了一条消息：

import org.bouncycastle.cms.CMSProcessableByteArray;
import org.bouncycastle.cms.CMSSignedData;
import org.bouncycastle.cms.CMSSignedDataGenerator;
import org.bouncycastle.cms.CMSTypedData;
import org.bouncycastle.cms.jcajce.JcaSignerInfoGeneratorBuilder;
import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.operator.ContentSigner;
import org.bouncycastle.operator.jcajce.JcaContentSignerBuilder;
import org.bouncycastle.operator.jcajce.JcaDigestCalculatorProviderBuilder;
import org.bouncycastle.util.encoders.Base64;

import java.io.FileInputStream;

import java.nio.file.Files;
import java.nio.file.Path;
import java.nio.file.Paths;
import java.security.KeyFactory;
import java.security.PrivateKey;
import java.security.Security;
import java.security.cert.CertificateFactory;
import java.security.cert.X509Certificate;
import java.security.spec.PKCS8EncodedKeySpec;

public class Sign {

    public static void main(String[] args) throws Exception {
        Security.addProvider(new BouncyCastleProvider());

        String certPath = "certPath";
        FileInputStream inPublic = new FileInputStream(certPath);
        CertificateFactory factory = CertificateFactory.getInstance("X.509");
        X509Certificate cert = (X509Certificate) factory.generateCertificate(inPublic);


        String keyPrivatePath = "keyPath";
        Path path = Paths.get(keyPrivatePath);
        Files.readAllBytes(Paths.get(keyPrivatePath));
        PKCS8EncodedKeySpec spec = new PKCS8EncodedKeySpec(Files.readAllBytes(Paths.get(keyPrivatePath)));
        KeyFactory kf = KeyFactory.getInstance("RSA");
        PrivateKey privateKey = kf.generatePrivate(spec);

        CMSProcessableByteArray msg = new CMSProcessableByteArray("My message".getBytes());
        CMSSignedDataGenerator sGen = new CMSSignedDataGenerator();

        ContentSigner sha1Signer = new JcaContentSignerBuilder("SHA1withRSA").setProvider("BC").build(privateKey);
        sGen.addSignerInfoGenerator(
                new JcaSignerInfoGeneratorBuilder(
                        new JcaDigestCalculatorProviderBuilder().setProvider("BC").build()
                ).build(sha1Signer, cert)
        );

        CMSSignedData sd = sGen.generate(msg);

        CMSTypedData cmsBytes = new CMSProcessableByteArray(sd.getEncoded());
        // How to reconstruct a CMSSignedData from cmsBytes again?
        byte[] bytes = (byte[]) cmsBytes.getContent();
        CMSSignedData retrieved = new CMSSignedData(bytes);
        System.out.println(retrieved.getSignedContent()); // Doesn't work, is null
    }
}

我的问题是如何仅使用此对象的 ASN.1 编码的字节数组来检索原始CMSSignedData（想读取原始消息并进行验证）。

我问这个的原因是我想解密某个加密和签名的消息。我能够解密此消息，但它会生成一个 ASN.1 编码字节数组（它确实对应于我的原始消息），但我无法进一步处理此解密消息。

Answer 1

您可以使用org.bouncycastle.asn1.cms.ContentInfo 和org.bouncycastle.asn1.ASN1Sequence 类：

CMSTypedData cmsBytes = new CMSProcessableByteArray(sd.getEncoded());
byte[] bytes = (byte[]) cmsBytes.getContent();

// reconstruct CMSSignedData from the byte array
ContentInfo ci = ContentInfo.getInstance(ASN1Sequence.fromByteArray(bytes));
CMSSignedData sig = new CMSSignedData(ci);

另外请注意，您必须创建一个CMSSignedData，其内容封装在签名中，因此您必须更改此内容：

CMSSignedData sd = sGen.generate(msg);

到这里：

CMSSignedData sd = sGen.generate(msg, true);