How read a PKCS8 encrypted Private key which is also encoded in DER with bouncycastle?

Question

I have tried answers of these questions:

Bouncy Castle : PEMReader => PEMParser

Read an encrypted private key with bouncycastle/spongycastle

However as my encrypted key is encoded in DER when I call

Object object = pemParser.readObject(); 

object is null.

I can convert it to PEM with this openssl's command (it decrypts the key too)

openssl pkcs8 -inform der -in pkey.key -out pkey.pem 

but I need to read the key in its original file

Answer 1

Both those Qs are about parsing, and decrypting, files using OpenSSL's 'legacy PEM' encryption. You are using PKCS8 encryption which is different though similar, so Reading PKCS8 in PEM format: Cannot find provider is closer. You can use most of the approach there, but skipping the PEM parse:

import org.bouncycastle.asn1.ASN1Sequence;
import org.bouncycastle.asn1.pkcs.EncryptedPrivateKeyInfo; // NOT the 
import org.bouncycastle.asn1.pkcs.PrivateKeyInfo;       // javax ones!
import org.bouncycastle.openssl.jcajce.JcaPEMKeyConverter;
import org.bouncycastle.openssl.jcajce.JceOpenSSLPKCS8DecryptorProviderBuilder;
import org.bouncycastle.operator.InputDecryptorProvider;
import org.bouncycastle.pkcs.PKCS8EncryptedPrivateKeyInfo;

    // args[0] = filename args[1] = password
    FileInputStream fis = new FileInputStream(args[0]);
    byte[] buff = new byte[9999]; int len = fis.read(buff); fis.close();
    // could use File.readAllBytes in j8 but my dev machine is old

    // create what PEMParser would have 
    ASN1Sequence derseq = ASN1Sequence.getInstance (Arrays.copyOf(buff,len));
    PKCS8EncryptedPrivateKeyInfo encobj = new PKCS8EncryptedPrivateKeyInfo(EncryptedPrivateKeyInfo.getInstance(derseq));
    // decrypt and convert key
    JcaPEMKeyConverter converter = new JcaPEMKeyConverter();
    InputDecryptorProvider decryptionProv = new JceOpenSSLPKCS8DecryptorProviderBuilder().build(args[1].toCharArray());
    PrivateKeyInfo keyInfo = encobj.decryptPrivateKeyInfo(decryptionProv);
    PrivateKey key = converter.getPrivateKey(keyInfo);

    // now actually use key, this is just a dummy
    System.out.println (key.getAlgorithm());