How to Decrypt OpenSSL AES-256-CBC Encrypted Files in Java?

Decrypting File Encrypted with OpenSSL in Java Using AES

Challenge:

Users need to decrypt a file encrypted in UNIX using the openssl command with AES-256-CBC encryption in Java. The password is required as well.

OpenSSL Decryption with Java:

OpenSSL employs its own password-based key derivation method. The ciphertext is also implicitly encoded as Base64.

Cryptic Algorithm Defined:

salt = random(8)
keyAndIV = BytesToKey(password, salt, 48)
key = keyAndIV[0..31]
iv = keyAndIV[32..47]
ct = AES-256-CBC-encrypt(key, iv, plaintext)

Java Implementation:

import java.io.File;
import java.io.IOException;
import java.nio.charset.Charset;
import java.nio.file.Files;
import java.security.GeneralSecurityException;
import java.security.MessageDigest;
import java.util.Arrays;
import java.util.List;

import javax.crypto.BadPaddingException;
import javax.crypto.Cipher;
import javax.crypto.IllegalBlockSizeException;
import javax.crypto.spec.IvParameterSpec;
import javax.crypto.spec.SecretKeySpec;

import org.bouncycastle.util.encoders.Base64;

public class OpenSSLDecryptor {
    // ... Code as in the given answer ...
}

Notes:

• ASCII charset is specified, but the actual character set may vary.
• NIST-approved PBKDF2 algorithm should be used for improved security.
• OpenSSL 1.1.0c changed its digest algorithm. Specify it explicitly both in the command and in the Java code.

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