如何使用AES解密用openssl命令加密的Java文件？

Z时代
2024-01-10
分类：问答

我需要使用以下命令在JAVA中解密在UNIX中加密的文件：

openssl aes-256-cbc -a -salt -in password.txt -out password.txt.enc mypass mypass

我必须像在UNIX中一样在Java中解密

openssl aes-256-cbc -d -a -in password.txt.enc -out password.txt.new mypass

有人可以给我一个Java代码来执行此操作吗？

回答：

OpenSSL通常使用自己的基于密码的密钥派生方法，该方法在中指定EVP_BytesToKey，请参见下面的代码。此外，它会在多行中隐式地将密文编码为base 64，以便在邮件正文中发送密文。

因此，结果是伪代码：

salt = random(8)
keyAndIV = BytesToKey(password, salt, 48)
key = keyAndIV[0..31]
iv = keyAndIV[32..47]
ct = AES-256-CBC-encrypt(key, iv, plaintext)
res = base64MimeEncode("Salted__" | salt | ct))

因此解密为：

(salt, ct) = base64MimeDecode(res)
key = keyAndIV[0..31]
iv = keyAndIV[32..47]
pt = AES-256-CBC-decrypt(key, iv, plaintext)

可以像这样在Java中实现：

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 {
    private static final Charset ASCII = Charset.forName("ASCII");
    private static final int INDEX_KEY = 0;
    private static final int INDEX_IV = 1;
    private static final int ITERATIONS = 1;
    private static final int ARG_INDEX_FILENAME = 0;
    private static final int ARG_INDEX_PASSWORD = 1;
    private static final int SALT_OFFSET = 8;
    private static final int SALT_SIZE = 8;
    private static final int CIPHERTEXT_OFFSET = SALT_OFFSET + SALT_SIZE;
    private static final int KEY_SIZE_BITS = 256;
    /**
     * Thanks go to Ola Bini for releasing this source on his blog.
     * The source was obtained from <a href="http://olabini.com/blog/tag/evp_bytestokey/">here</a> .
     */
    public static byte[][] EVP_BytesToKey(int key_len, int iv_len, MessageDigest md,
            byte[] salt, byte[] data, int count) {
        byte[][] both = new byte[2][];
        byte[] key = new byte[key_len];
        int key_ix = 0;
        byte[] iv = new byte[iv_len];
        int iv_ix = 0;
        both[0] = key;
        both[1] = iv;
        byte[] md_buf = null;
        int nkey = key_len;
        int niv = iv_len;
        int i = 0;
        if (data == null) {
            return both;
        }
        int addmd = 0;
        for (;;) {
            md.reset();
            if (addmd++ > 0) {
                md.update(md_buf);
            }
            md.update(data);
            if (null != salt) {
                md.update(salt, 0, 8);
            }
            md_buf = md.digest();
            for (i = 1; i < count; i++) {
                md.reset();
                md.update(md_buf);
                md_buf = md.digest();
            }
            i = 0;
            if (nkey > 0) {
                for (;;) {
                    if (nkey == 0)
                        break;
                    if (i == md_buf.length)
                        break;
                    key[key_ix++] = md_buf[i];
                    nkey--;
                    i++;
                }
            }
            if (niv > 0 && i != md_buf.length) {
                for (;;) {
                    if (niv == 0)
                        break;
                    if (i == md_buf.length)
                        break;
                    iv[iv_ix++] = md_buf[i];
                    niv--;
                    i++;
                }
            }
            if (nkey == 0 && niv == 0) {
                break;
            }
        }
        for (i = 0; i < md_buf.length; i++) {
            md_buf[i] = 0;
        }
        return both;
    }
    public static void main(String[] args) {
        try {
            // --- read base 64 encoded file ---
            File f = new File(args[ARG_INDEX_FILENAME]);
            List<String> lines = Files.readAllLines(f.toPath(), ASCII);
            StringBuilder sb = new StringBuilder();
            for (String line : lines) {
                sb.append(line.trim());
            }
            String dataBase64 = sb.toString();
            byte[] headerSaltAndCipherText = Base64.decode(dataBase64);
            // --- extract salt & encrypted ---
            // header is "Salted__", ASCII encoded, if salt is being used (the default)
            byte[] salt = Arrays.copyOfRange(
                    headerSaltAndCipherText, SALT_OFFSET, SALT_OFFSET + SALT_SIZE);
            byte[] encrypted = Arrays.copyOfRange(
                    headerSaltAndCipherText, CIPHERTEXT_OFFSET, headerSaltAndCipherText.length);
            // --- specify cipher and digest for EVP_BytesToKey method ---
            Cipher aesCBC = Cipher.getInstance("AES/CBC/PKCS5Padding");
            MessageDigest md5 = MessageDigest.getInstance("MD5");
            // --- create key and IV  ---
            // the IV is useless, OpenSSL might as well have use zero's
            final byte[][] keyAndIV = EVP_BytesToKey(
                    KEY_SIZE_BITS / Byte.SIZE,
                    aesCBC.getBlockSize(),
                    md5,
                    salt,
                    args[ARG_INDEX_PASSWORD].getBytes(ASCII),
                    ITERATIONS);
            SecretKeySpec key = new SecretKeySpec(keyAndIV[INDEX_KEY], "AES");
            IvParameterSpec iv = new IvParameterSpec(keyAndIV[INDEX_IV]);
            // --- initialize cipher instance and decrypt ---
            aesCBC.init(Cipher.DECRYPT_MODE, key, iv);
            byte[] decrypted = aesCBC.doFinal(encrypted);
            String answer = new String(decrypted, ASCII);
            System.out.println(answer);
        } catch (BadPaddingException e) {
            // AKA "something went wrong"
            throw new IllegalStateException(
                    "Bad password, algorithm, mode or padding;" +
                    " no salt, wrong number of iterations or corrupted ciphertext.");
        } catch (IllegalBlockSizeException e) {
            throw new IllegalStateException(
                    "Bad algorithm, mode or corrupted (resized) ciphertext.");
        } catch (GeneralSecurityException e) {
            throw new IllegalStateException(e);
        } catch (IOException e) {
            throw new IllegalStateException(e);
        }
    }        
}