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Code Issues Releases Wiki Activity

Implement exploratory support for custom decryption factories

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This may enable decryption of messages with hardware-backed keys
This commit is contained in:
Paul Schaub 2022-09-23 16:17:42 +02:00
parent 6c8d226926
commit 3a96b6abbb
5 changed files with 221 additions and 47 deletions
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24
pgpainless-core/src/main/java/org/pgpainless/decryption_verification/ConsumerOptions.java
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@ -22,6 +22,7 @@ import org.bouncycastle.openpgp.PGPPublicKeyRingCollection;
import org.bouncycastle.openpgp.PGPSecretKeyRing;
import org.bouncycastle.openpgp.PGPSecretKeyRingCollection;
import org.bouncycastle.openpgp.PGPSignature;
import org.bouncycastle.openpgp.operator.PublicKeyDataDecryptorFactory;
import org.pgpainless.decryption_verification.cleartext_signatures.InMemoryMultiPassStrategy;
import org.pgpainless.decryption_verification.cleartext_signatures.MultiPassStrategy;
import org.pgpainless.key.protection.SecretKeyRingProtector;
@ -48,7 +49,7 @@ public class ConsumerOptions {
// Session key for decryption without passphrase/key
private SessionKey sessionKey = null;
private HardwareSecurity.DecryptionCallback hardwareDecryptionCallback = null;
private Map<Set<Long>, PublicKeyDataDecryptorFactory> customPublicKeyDataDecryptorFactories = new HashMap<>();
private final Map<PGPSecretKeyRing, SecretKeyRingProtector> decryptionKeys = new HashMap<>();
private final Set<Passphrase> decryptionPassphrases = new HashSet<>();
@ -239,11 +240,28 @@ public class ConsumerOptions {
return this;
}
public ConsumerOptions setHardwareDecryptionCallback(HardwareSecurity.DecryptionCallback callback) {
this.hardwareDecryptionCallback = callback;
/**
* Add a custom {@link PublicKeyDataDecryptorFactory} which enable decryption of messages, e.g. using
* hardware-backed secret keys.
* (See e.g. {@link org.pgpainless.decryption_verification.HardwareSecurity.HardwareDataDecryptorFactory}).
*
* The set of key-ids determines, whether the decryptor factory shall be consulted to decrypt a given session key.
* See for example {@link HardwareSecurity#getIdsOfHardwareBackedKeys(PGPSecretKeyRing)}.
*
* @param keyIds set of key-ids for which the factory shall be consulted
* @param decryptorFactory decryptor factory
* @return options
*/
public ConsumerOptions addCustomDecryptorFactory(
@Nonnull Set<Long> keyIds, @Nonnull PublicKeyDataDecryptorFactory decryptorFactory) {
this.customPublicKeyDataDecryptorFactories.put(keyIds, decryptorFactory);
return this;
}
Map<Set<Long>, PublicKeyDataDecryptorFactory> getCustomDecryptorFactories() {
return new HashMap<>(customPublicKeyDataDecryptorFactories);
}
public @Nonnull Set<PGPSecretKeyRing> getDecryptionKeys() {
return Collections.unmodifiableSet(decryptionKeys.keySet());
}

28
pgpainless-core/src/main/java/org/pgpainless/decryption_verification/DecryptionStreamFactory.java
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@ -408,6 +408,34 @@ public final class DecryptionStreamFactory {
}
}
// Try custom PublicKeyDataDecryptorFactories (e.g. hardware-backed).
Map<Set<Long>, PublicKeyDataDecryptorFactory> customFactories = options.getCustomDecryptorFactories();
for (PGPPublicKeyEncryptedData publicKeyEncryptedData : publicKeyProtected) {
Long keyId = publicKeyEncryptedData.getKeyID();
for (Set<Long> keyIds : customFactories.keySet()) {
if (!keyIds.contains(keyId)) {
continue;
}
PublicKeyDataDecryptorFactory decryptorFactory = customFactories.get(keyIds);
try {
InputStream decryptedDataStream = publicKeyEncryptedData.getDataStream(decryptorFactory);
PGPSessionKey pgpSessionKey = publicKeyEncryptedData.getSessionKey(decryptorFactory);
SessionKey sessionKey = new SessionKey(pgpSessionKey);
resultBuilder.setSessionKey(sessionKey);
throwIfAlgorithmIsRejected(sessionKey.getAlgorithm());
integrityProtectedEncryptedInputStream =
new IntegrityProtectedInputStream(decryptedDataStream, publicKeyEncryptedData, options);
return integrityProtectedEncryptedInputStream;
} catch (PGPException e) {
LOGGER.debug("Decryption with custom PublicKeyDataDecryptorFactory failed", e);
}
}
}
// Then try decryption with public key encryption
for (PGPPublicKeyEncryptedData publicKeyEncryptedData : publicKeyProtected) {
PGPPrivateKey privateKey = null;

91
pgpainless-core/src/main/java/org/pgpainless/decryption_verification/HardwareSecurity.java
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@ -1,8 +1,23 @@
// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
//
// SPDX-License-Identifier: Apache-2.0
package org.pgpainless.decryption_verification;
import org.bouncycastle.openpgp.PGPPublicKeyEncryptedData;
import org.pgpainless.util.SessionKey;
import org.bouncycastle.bcpg.S2K;
import org.bouncycastle.openpgp.PGPException;
import org.bouncycastle.openpgp.PGPSecretKey;
import org.bouncycastle.openpgp.PGPSecretKeyRing;
import org.bouncycastle.openpgp.operator.PGPDataDecryptor;
import org.bouncycastle.openpgp.operator.PublicKeyDataDecryptorFactory;
import org.bouncycastle.openpgp.operator.bc.BcPublicKeyDataDecryptorFactory;
import java.util.HashSet;
import java.util.Set;
/**
* Enable integration of hardware-backed OpenPGP keys.
*/
public class HardwareSecurity {
public interface DecryptionCallback {
@ -13,15 +28,81 @@ public class HardwareSecurity {
*
* If decryption fails for some reason, a subclass of the {@link HardwareSecurityException} is thrown.
*
* @param pkesk public-key-encrypted session key
* @param keyAlgorithm algorithm
* @param sessionKeyData encrypted session key
*
* @return decrypted session key
* @throws HardwareSecurityException exception
*/
SessionKey decryptSessionKey(PGPPublicKeyEncryptedData pkesk) throws HardwareSecurityException;
byte[] decryptSessionKey(int keyAlgorithm, byte[] sessionKeyData)
throws HardwareSecurityException;
}
public static class HardwareSecurityException extends Exception {
/**
* Return the key-ids of all keys which appear to be stored on a hardware token / smartcard.
*
* @param secretKeys secret keys
* @return set of keys with S2K type DIVERT_TO_CARD or GNU_DUMMY_S2K
*/
public static Set<Long> getIdsOfHardwareBackedKeys(PGPSecretKeyRing secretKeys) {
Set<Long> hardwareBackedKeys = new HashSet<>();
for (PGPSecretKey secretKey : secretKeys) {
S2K s2K = secretKey.getS2K();
if (s2K == null) {
continue;
}
int type = s2K.getType();
// TODO: Is GNU_DUMMY_S2K appropriate?
if (type == S2K.GNU_PROTECTION_MODE_DIVERT_TO_CARD || type == S2K.GNU_DUMMY_S2K) {
hardwareBackedKeys.add(secretKey.getKeyID());
}
}
return hardwareBackedKeys;
}
/**
* Implementation of {@link PublicKeyDataDecryptorFactory} which delegates decryption of encrypted session keys
* to a {@link DecryptionCallback}.
* Users can provide such a callback to delegate decryption of messages to hardware security SDKs.
*/
public static class HardwareDataDecryptorFactory implements PublicKeyDataDecryptorFactory {
private final DecryptionCallback callback;
// luckily we can instantiate the BcPublicKeyDataDecryptorFactory with null as argument.
private final PublicKeyDataDecryptorFactory factory =
new BcPublicKeyDataDecryptorFactory(null);
/**
* Create a new {@link HardwareDataDecryptorFactory}.
*
* @param callback decryption callback
*/
public HardwareDataDecryptorFactory(DecryptionCallback callback) {
this.callback = callback;
}
@Override
public byte[] recoverSessionData(int keyAlgorithm, byte[][] secKeyData)
throws PGPException {
try {
// delegate decryption to the callback
return callback.decryptSessionKey(keyAlgorithm, secKeyData[0]);
} catch (HardwareSecurityException e) {
throw new PGPException("Hardware-backed decryption failed.", e);
}
}
@Override
public PGPDataDecryptor createDataDecryptor(boolean withIntegrityPacket, int encAlgorithm, byte[] key)
throws PGPException {
return factory.createDataDecryptor(withIntegrityPacket, encAlgorithm, key);
}
}
public static class HardwareSecurityException
extends Exception {
}
}

86
pgpainless-core/src/test/java/org/pgpainless/decryption_verification/CustomPublicKeyDataDecryptorFactoryTest.java Normal file
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@ -0,0 +1,86 @@
// SPDX-FileCopyrightText: 2022 Paul Schaub <vanitasvitae@fsfe.org>
//
// SPDX-License-Identifier: Apache-2.0
package org.pgpainless.decryption_verification;
import org.bouncycastle.openpgp.PGPException;
import org.bouncycastle.openpgp.PGPPrivateKey;
import org.bouncycastle.openpgp.PGPPublicKey;
import org.bouncycastle.openpgp.PGPPublicKeyRing;
import org.bouncycastle.openpgp.PGPSecretKey;
import org.bouncycastle.openpgp.PGPSecretKeyRing;
import org.bouncycastle.openpgp.operator.PublicKeyDataDecryptorFactory;
import org.bouncycastle.openpgp.operator.bc.BcPublicKeyDataDecryptorFactory;
import org.bouncycastle.util.io.Streams;
import org.junit.jupiter.api.Test;
import org.pgpainless.PGPainless;
import org.pgpainless.algorithm.EncryptionPurpose;
import org.pgpainless.encryption_signing.EncryptionOptions;
import org.pgpainless.encryption_signing.EncryptionStream;
import org.pgpainless.encryption_signing.ProducerOptions;
import org.pgpainless.key.info.KeyRingInfo;
import org.pgpainless.key.protection.UnlockSecretKey;
import org.pgpainless.util.Passphrase;
import java.io.ByteArrayInputStream;
import java.io.ByteArrayOutputStream;
import java.io.IOException;
import java.nio.charset.StandardCharsets;
import java.security.InvalidAlgorithmParameterException;
import java.security.NoSuchAlgorithmException;
import java.util.Collections;
import static org.junit.jupiter.api.Assertions.assertEquals;
public class CustomPublicKeyDataDecryptorFactoryTest {
@Test
public void testDecryptionWithEmulatedHardwareDecryptionCallback()
throws PGPException, IOException, InvalidAlgorithmParameterException, NoSuchAlgorithmException {
PGPSecretKeyRing secretKey = PGPainless.generateKeyRing().modernKeyRing("Alice");
PGPPublicKeyRing cert = PGPainless.extractCertificate(secretKey);
KeyRingInfo info = PGPainless.inspectKeyRing(secretKey);
PGPPublicKey encryptionKey = info.getEncryptionSubkeys(EncryptionPurpose.ANY).get(0);
// Encrypt a test message
String plaintext = "Hello, World!\n";
ByteArrayOutputStream ciphertextOut = new ByteArrayOutputStream();
EncryptionStream encryptionStream = PGPainless.encryptAndOrSign()
.onOutputStream(ciphertextOut)
.withOptions(ProducerOptions.encrypt(EncryptionOptions.get()
.addRecipient(cert)));
encryptionStream.write(plaintext.getBytes(StandardCharsets.UTF_8));
encryptionStream.close();
HardwareSecurity.DecryptionCallback hardwareDecryptionCallback = new HardwareSecurity.DecryptionCallback() {
@Override
public byte[] decryptSessionKey(int keyAlgorithm, byte[] sessionKeyData)
throws HardwareSecurity.HardwareSecurityException {
// Emulate hardware decryption.
try {
PGPSecretKey decryptionKey = secretKey.getSecretKey(encryptionKey.getKeyID());
PGPPrivateKey privateKey = UnlockSecretKey.unlockSecretKey(decryptionKey, Passphrase.emptyPassphrase());
PublicKeyDataDecryptorFactory internal = new BcPublicKeyDataDecryptorFactory(privateKey);
return internal.recoverSessionData(keyAlgorithm, new byte[][] {sessionKeyData});
} catch (PGPException e) {
throw new HardwareSecurity.HardwareSecurityException();
}
}
};
// Decrypt
DecryptionStream decryptionStream = PGPainless.decryptAndOrVerify()
.onInputStream(new ByteArrayInputStream(ciphertextOut.toByteArray()))
.withOptions(ConsumerOptions.get()
.addCustomDecryptorFactory(
Collections.singleton(encryptionKey.getKeyID()),
new HardwareSecurity.HardwareDataDecryptorFactory(hardwareDecryptionCallback)));
ByteArrayOutputStream decryptedOut = new ByteArrayOutputStream();
Streams.pipeAll(decryptionStream, decryptedOut);
decryptionStream.close();
assertEquals(plaintext, decryptedOut.toString());
}
}

39
pgpainless-core/src/test/java/org/pgpainless/decryption_verification/HardwareSecurityCallbackTest.java
View file

@ -1,39 +0,0 @@
package org.pgpainless.decryption_verification;
import org.bouncycastle.openpgp.PGPException;
import org.bouncycastle.openpgp.PGPPublicKeyEncryptedData;
import org.junit.jupiter.api.Test;
import org.pgpainless.PGPainless;
import org.pgpainless.util.SessionKey;
import java.io.ByteArrayInputStream;
import java.io.IOException;
public class HardwareSecurityCallbackTest {
@Test
public void test() throws PGPException, IOException {
PGPainless.decryptAndOrVerify()
.onInputStream(new ByteArrayInputStream(new byte[0]))
.withOptions(ConsumerOptions.get()
.setHardwareDecryptionCallback(new HardwareSecurity.DecryptionCallback() {
@Override
public SessionKey decryptSessionKey(PGPPublicKeyEncryptedData pkesk) throws HardwareSecurity.HardwareSecurityException {
/*
pkesk.getSessionKey(new PublicKeyDataDecryptorFactory() {
@Override
public byte[] recoverSessionData(int keyAlgorithm, byte[][] secKeyData) throws PGPException {
return new byte[0];
}
@Override
public PGPDataDecryptor createDataDecryptor(boolean withIntegrityPacket, int encAlgorithm, byte[] key) throws PGPException {
return null;
}
});
*/
return null;
}
}));
}
}