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Smack API for XEP-0373: OpenPGP for XMPP.
/**
*
* Copyright 2018 Paul Schaub.
*
* Licensed under the Apache License, Version 2.0 (the "License");
* you may not use this file except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.jivesoftware.smackx.ox.util;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.util.Set;
import org.jivesoftware.smack.util.StringUtils;
import org.jivesoftware.smack.util.stringencoder.Base64;
import org.jivesoftware.smackx.ox.OpenPgpSecretKeyBackupPassphrase;
import org.jivesoftware.smackx.ox.crypto.OpenPgpProvider;
import org.jivesoftware.smackx.ox.element.SecretkeyElement;
import org.jivesoftware.smackx.ox.exception.InvalidBackupCodeException;
import org.jivesoftware.smackx.ox.exception.MissingOpenPgpKeyException;
import org.bouncycastle.openpgp.PGPException;
import org.bouncycastle.openpgp.PGPSecretKeyRing;
import org.bouncycastle.util.io.Streams;
import org.jxmpp.jid.BareJid;
import org.pgpainless.PGPainless;
import org.pgpainless.algorithm.SymmetricKeyAlgorithm;
import org.pgpainless.decryption_verification.ConsumerOptions;
import org.pgpainless.decryption_verification.DecryptionStream;
import org.pgpainless.encryption_signing.EncryptionOptions;
import org.pgpainless.encryption_signing.EncryptionStream;
import org.pgpainless.encryption_signing.ProducerOptions;
import org.pgpainless.exception.MissingDecryptionMethodException;
import org.pgpainless.key.OpenPgpV4Fingerprint;
import org.pgpainless.util.Passphrase;
/**
* Helper class which provides some functions needed for backup/restore of the users secret key to/from their private
* PubSub node.
*/
public class SecretKeyBackupHelper {
/**
* Generate a secure backup code.
* This code can be used to encrypt a secret key backup and follows the form described in XEP-0373 §5.3.
*
* @see
* XEP-0373 §5.4 Encrypting the Secret Key Backup
*
* @return backup code
*/
public static OpenPgpSecretKeyBackupPassphrase generateBackupPassword() {
return new OpenPgpSecretKeyBackupPassphrase(StringUtils.secureOfflineAttackSafeRandomString());
}
/**
* Create a {@link SecretkeyElement} which contains the secret keys listed in {@code fingerprints} and is encrypted
* symmetrically using the {@code backupCode}.
*
* @param provider {@link OpenPgpProvider} for symmetric encryption.
* @param owner owner of the secret keys (usually our jid).
* @param fingerprints set of {@link OpenPgpV4Fingerprint}s of the keys which are going to be backed up.
* @param backupCode passphrase for symmetric encryption.
* @return {@link SecretkeyElement}
*
* @throws PGPException PGP is brittle
* @throws IOException IO is dangerous
* @throws MissingOpenPgpKeyException in case one of the keys whose fingerprint is in {@code fingerprints} is
* not accessible.
*/
public static SecretkeyElement createSecretkeyElement(OpenPgpProvider provider,
BareJid owner,
Set fingerprints,
OpenPgpSecretKeyBackupPassphrase backupCode)
throws PGPException, IOException, MissingOpenPgpKeyException {
ByteArrayOutputStream buffer = new ByteArrayOutputStream();
for (OpenPgpV4Fingerprint fingerprint : fingerprints) {
PGPSecretKeyRing key = provider.getStore().getSecretKeyRing(owner, fingerprint);
if (key == null) {
throw new MissingOpenPgpKeyException(owner, fingerprint);
}
byte[] bytes = key.getEncoded();
buffer.write(bytes);
}
return createSecretkeyElement(buffer.toByteArray(), backupCode);
}
/**
* Create a {@link SecretkeyElement} which contains the secret keys which are serialized in {@code keys} and is
* symmetrically encrypted using the {@code backupCode}.
*
* @see
* XEP-0373 §5.4 Encrypting the Secret Key Backup
*
* @param keys serialized OpenPGP secret keys in transferable key format
* @param backupCode passphrase for symmetric encryption
* @return {@link SecretkeyElement}
*
* @throws PGPException PGP is brittle
* @throws IOException IO is dangerous
*/
public static SecretkeyElement createSecretkeyElement(byte[] keys,
OpenPgpSecretKeyBackupPassphrase backupCode)
throws PGPException, IOException {
InputStream keyStream = new ByteArrayInputStream(keys);
ByteArrayOutputStream cryptOut = new ByteArrayOutputStream();
EncryptionOptions encOpts = new EncryptionOptions()
.addPassphrase(Passphrase.fromPassword(backupCode.toString()));
encOpts.overrideEncryptionAlgorithm(SymmetricKeyAlgorithm.AES_256);
EncryptionStream encryptionStream = PGPainless.encryptAndOrSign()
.onOutputStream(cryptOut)
.withOptions(ProducerOptions.encrypt(encOpts)
.setAsciiArmor(false));
Streams.pipeAll(keyStream, encryptionStream);
encryptionStream.close();
return new SecretkeyElement(Base64.encode(cryptOut.toByteArray()));
}
/**
* Decrypt a secret key backup and return the {@link PGPSecretKeyRing} contained in it.
* TODO: Return a PGPSecretKeyRingCollection instead?
*
* @param backup encrypted {@link SecretkeyElement} containing the backup
* @param backupCode passphrase for decrypting the {@link SecretkeyElement}.
* @return the TODO javadoc me please
* @throws InvalidBackupCodeException in case the provided backup code is invalid.
* @throws IOException IO is dangerous.
* @throws PGPException PGP is brittle.
*/
public static PGPSecretKeyRing restoreSecretKeyBackup(SecretkeyElement backup, OpenPgpSecretKeyBackupPassphrase backupCode)
throws InvalidBackupCodeException, IOException, PGPException {
byte[] encrypted = Base64.decode(backup.getB64Data());
InputStream encryptedIn = new ByteArrayInputStream(encrypted);
ByteArrayOutputStream plaintextOut = new ByteArrayOutputStream();
try {
DecryptionStream decryptionStream = PGPainless.decryptAndOrVerify()
.onInputStream(encryptedIn)
.withOptions(new ConsumerOptions()
.addDecryptionPassphrase(Passphrase.fromPassword(backupCode.toString())));
Streams.pipeAll(decryptionStream, plaintextOut);
decryptionStream.close();
} catch (MissingDecryptionMethodException e) {
throw new InvalidBackupCodeException("Could not decrypt secret key backup. Possibly wrong passphrase?", e);
}
byte[] decrypted = plaintextOut.toByteArray();
return PGPainless.readKeyRing().secretKeyRing(decrypted);
}
}