Decrypt gpg in Java without using Java.Runtime

问题

I have a .gpg file and a RSA private key. How can I programatically decrypt it without using operating system? e.g. without using something like Runtime.getRuntime().exec("gpg -decrypt.....");

Libraries I've found all run operating system. Like GnuPG or gnugpg-for-java.

回答1:

The Bouncy Castle library provides (among other features) an OpenPGP implementation. The package org.bouncycastle.openpgp.examples contains several usage examples, one of them showing how to encrypt/decrypt a file using a public/secret key pair (there is no browseable sourcecode on the bouncycastle homepage, but you can have a look at the examples on GrepCode).

回答2:

As Skyr mentioned: Bouncy Castle is the way to go.

What do you want to do with this key? If your goal is to en- or decrypt files you might want to take a look at bouncy-gpg (shameless plug: I wrote it).

Using secret keys is actually three steps

Parse the key and put it into a PGPSecretKeyRing
Extract the secret key from the keyring
Decrypt it with the password

1. Parsing the exported key

In any case look here for the part that parses keys:

class ...

private PGPSecretKeyRingCollection secretKeyRings = new PGPSecretKeyRingCollection(EMPTY_LIST);

 ...

/**
 * Add a new secret keyring to the public keyrings.
 * .
 * Can read the result of "gpg --export" and "gpg --export -a keyid"
 * .
 * E.g. "gpg --export-secret-key -a keyid":
 * addSecretKey("-----BEGIN PGP PRIVATE KEY BLOCK----- ....".getBytes("US-ASCII")
 * <p>
 * The password is queried via the callback (decryptionSecretKeyPassphraseForSecretKeyId).
 *
 * @param encodedPrivateKey the key ascii armored or binary
 * @throws IOException  IO is dangerous
 * @throws PGPException E.g. this is nor a valid key
 */
public void addSecretKey(byte[] encodedPrivateKey) throws IOException, PGPException {

    if (encodedPrivateKey == null) {
        throw new NullPointerException("encodedPrivateKey must not be null");
    }

    try (
            final InputStream raw = new ByteArrayInputStream(encodedPrivateKey);
            final InputStream decoded = org.bouncycastle.openpgp.PGPUtil.getDecoderStream(raw)
    ) {
        PGPSecretKeyRing pgpPrivate = new PGPSecretKeyRing(decoded, getKeyFingerPrintCalculator());
        this.secretKeyRings = PGPSecretKeyRingCollection.addSecretKeyRing(this.secretKeyRings, pgpPrivate);
    }
}

2. Getting the key from the keyring

       final PGPSecretKeyRingCollection pgpSec = ...
       final PGPSecretKey encryptedKey = pgpSec.getSecretKey(keyID);

3. Decrypting the key

Later you have to decrypt the key using a password like so:

 /**
 * Decrypt an encrypted PGP secret key.
 *
 * @param encryptedKey An encrypted key
 * @param passphrase   The passphrase for the key
 * @return the decrypted secret key
 * @throws PGPException E.g. wrong passphrase
 */
public static PGPPrivateKey extractPrivateKey(PGPSecretKey encryptedKey, final char[] passphrase) throws PGPException {
    LOGGER.debug("Extracting secret key with key ID '0x{}'", Long.toHexString(encryptedKey.getKeyID()));

    PGPDigestCalculatorProvider calcProvider = new JcaPGPDigestCalculatorProviderBuilder()
            .setProvider(BouncyCastleProvider.PROVIDER_NAME).build();

    PBESecretKeyDecryptor decryptor = new JcePBESecretKeyDecryptorBuilder(
            calcProvider).setProvider(BouncyCastleProvider.PROVIDER_NAME)
            .build(passphrase);

    return encryptedKey.extractPrivateKey(decryptor);
}

回答3:

there are too many examples that I've tried on Bouncy Castle with PGP. The common issue is keyID can't be found in KeyRing.

So, I found @Jens' bouncy-gpg (not sure if he still maintains it.)

Here is his documentation from github.io. It's simple to follow and works! https://neuhalje.github.io/bouncy-gpg/

来源：https://stackoverflow.com/questions/16244372/decrypt-gpg-in-java-without-using-java-runtime

标签

java

rsa

gnupg