从RSA .pem文件中获取私钥

Question

给定此.pem文件（使用openssl生成并使用密码加密）：

-----BEGIN RSA PRIVATE KEY-----
Proc-Type: 4,ENCRYPTED
DEK-Info: DES-EDE3-CBC,AC009672952033EB

2wegzxf3MtncXS1CY3c.....
....
....
-----END RSA PRIVATE KEY-----

如何PrivateKey使用Java 获取对象？我编写了以下代码，但是找不到正确的方法来获取KeySpec：

PrivateKey readFromPem(File keyFile, String password){
    PemReader r = new PemReader(new InputStreamReader(new FileInputStream(keyFile)));
    PemObject pemObject = r.readPemObject();
    byte[] encodedKey = pemObject.getContent();

    KeySpec keySpec = ???? // how to get this?

    KeyFactory keyFactory = KeyFactory.getInstance("RSA");
    PrivateKey key = keyFactory.generatePrivate(keySpec);
    return key;
}

我想我应该构建一个RSAPrivateKeySpec，但我不知道如何。我尝试了这个答案和另一个答案中的方法，但是它们在解析字节数组时都导致错误。

Answer 1

我正在使用 BouncyCastle 1.57 （bcprov-jdk15on，bcmail-jdk15on和bcpkix-jdk15on）和
Java 7 。

您可以使用JcaPEMKeyConverter该类读取私钥。以下代码适用于带有和不带有密码的密钥：

import org.bouncycastle.jce.provider.BouncyCastleProvider;
import org.bouncycastle.openssl.PEMDecryptorProvider;
import org.bouncycastle.openssl.PEMEncryptedKeyPair;
import org.bouncycastle.openssl.PEMKeyPair;
import org.bouncycastle.openssl.PEMParser;
import org.bouncycastle.openssl.jcajce.JcaPEMKeyConverter;
import org.bouncycastle.openssl.jcajce.JcePEMDecryptorProviderBuilder;

// don't forget to add the provider
Security.addProvider(new BouncyCastleProvider());
String password = "your password";

// reads your key file
PEMParser pemParser = new PEMParser(new FileReader(keyFile));
Object object = pemParser.readObject();
JcaPEMKeyConverter converter = new JcaPEMKeyConverter().setProvider("BC");

KeyPair kp;
if (object instanceof PEMEncryptedKeyPair) {
    // Encrypted key - we will use provided password
    PEMEncryptedKeyPair ckp = (PEMEncryptedKeyPair) object;
    // uses the password to decrypt the key
    PEMDecryptorProvider decProv = new JcePEMDecryptorProviderBuilder().build(password.toCharArray());
    kp = converter.getKeyPair(ckp.decryptKeyPair(decProv));
} else {
    // Unencrypted key - no password needed
    PEMKeyPair ukp = (PEMKeyPair) object;
    kp = converter.getKeyPair(ukp);
}

// RSA
KeyFactory keyFac = KeyFactory.getInstance("RSA");
RSAPrivateCrtKeySpec privateKey = keyFac.getKeySpec(kp.getPrivate(), RSAPrivateCrtKeySpec.class);

System.out.println(privateKey.getClass());

所述privateKey的类将是java.security.spec.RSAPrivateCrtKeySpec（延伸RSAPrivateKeySpec）。