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Add S2KUsageFix class and tests to switch secret keys encrypted with USAGE_CHECKSUM over to USAGE_SHA1

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This commit is contained in:
Paul Schaub 2021-09-09 20:31:02 +02:00
parent 657e3e3301
commit c851457ef8
Signed by: vanitasvitae
GPG key ID: 62BEE9264BF17311
4 changed files with 261 additions and 0 deletions
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4
pgpainless-core/src/main/java/org/pgpainless/exception/WrongPassphraseException.java
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@ -19,6 +19,10 @@ import org.bouncycastle.openpgp.PGPException;
public class WrongPassphraseException extends PGPException {
public WrongPassphraseException(String message) {
super(message);
}
public WrongPassphraseException(long keyId, PGPException cause) {
this("Wrong passphrase provided for key " + Long.toHexString(keyId), cause);
}

103
pgpainless-core/src/main/java/org/pgpainless/key/protection/fixes/S2KUsageFix.java Normal file
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@ -0,0 +1,103 @@
/*
* Copyright 2021 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.pgpainless.key.protection.fixes;
import org.bouncycastle.bcpg.SecretKeyPacket;
import org.bouncycastle.openpgp.PGPException;
import org.bouncycastle.openpgp.PGPPrivateKey;
import org.bouncycastle.openpgp.PGPSecretKey;
import org.bouncycastle.openpgp.PGPSecretKeyRing;
import org.bouncycastle.openpgp.operator.PBESecretKeyEncryptor;
import org.bouncycastle.openpgp.operator.PGPDigestCalculator;
import org.pgpainless.algorithm.HashAlgorithm;
import org.pgpainless.exception.WrongPassphraseException;
import org.pgpainless.implementation.ImplementationFactory;
import org.pgpainless.key.protection.SecretKeyRingProtector;
import org.pgpainless.key.protection.UnlockSecretKey;
/**
* Repair class to fix keys which use S2K usage of value {@link SecretKeyPacket#USAGE_CHECKSUM}.
* The method {@link #replaceUsageChecksumWithUsageSha1(PGPSecretKeyRing, SecretKeyRingProtector)} ensures
* that such keys are encrypted using S2K usage {@link SecretKeyPacket#USAGE_SHA1} instead.
*
* @see <a href="https://github.com/pgpainless/pgpainless/issues/176">Related PGPainless Bug Report</a>
* @see <a href="https://github.com/pgpainless/pgpainless/issues/178">Related PGPainless Feature Request</a>
* @see <a href="https://github.com/bcgit/bc-java/issues/1020">Related upstream BC bug report</a>
*/
public final class S2KUsageFix {
private S2KUsageFix() {
}
/**
* Repair method for keys which use S2K usage <pre>USAGE_CHECKSUM</pre> which is deemed insecure.
* This method fixes the private keys by changing them to <pre>USAGE_SHA1</pre> instead.
*
* @param keys keys
* @param protector protector to unlock and re-lock affected private keys
* @return fixed key ring
* @throws PGPException in case of a PGP error.
*/
public static PGPSecretKeyRing replaceUsageChecksumWithUsageSha1(PGPSecretKeyRing keys, SecretKeyRingProtector protector) throws PGPException {
return replaceUsageChecksumWithUsageSha1(keys, protector, false);
}
/**
* Repair method for keys which use S2K usage <pre>USAGE_CHECKSUM</pre> which is deemed insecure.
* This method fixes the private keys by changing them to <pre>USAGE_SHA1</pre> instead.
*
* @param keys keys
* @param protector protector to unlock and re-lock affected private keys
* @param skipKeysWithMissingPassphrase if set to true, missing subkey passphrases will cause the subkey to stay unaffected.
* @return fixed key ring
* @throws PGPException in case of a PGP error.
*/
public static PGPSecretKeyRing replaceUsageChecksumWithUsageSha1(PGPSecretKeyRing keys,
SecretKeyRingProtector protector,
boolean skipKeysWithMissingPassphrase) throws PGPException {
PGPDigestCalculator digestCalculator = ImplementationFactory.getInstance().getPGPDigestCalculator(HashAlgorithm.SHA1);
for (PGPSecretKey key : keys) {
// CHECKSUM is not recommended
if (key.getS2KUsage() != SecretKeyPacket.USAGE_CHECKSUM) {
continue;
}
long keyId = key.getKeyID();
PBESecretKeyEncryptor encryptor = protector.getEncryptor(keyId);
if (encryptor == null) {
if (skipKeysWithMissingPassphrase) {
continue;
}
throw new WrongPassphraseException("Missing passphrase for key with ID " + Long.toHexString(keyId));
}
PGPPrivateKey privateKey = UnlockSecretKey.unlockSecretKey(key, protector);
// This constructor makes use of USAGE_SHA1 by default
PGPSecretKey fixedKey = new PGPSecretKey(
privateKey,
key.getPublicKey(),
digestCalculator,
key.isMasterKey(),
protector.getEncryptor(keyId)
);
// replace the original key with the fixed one
keys = PGPSecretKeyRing.insertSecretKey(keys, fixedKey);
}
return keys;
}
}

19
pgpainless-core/src/main/java/org/pgpainless/key/protection/fixes/package-info.java Normal file
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@ -0,0 +1,19 @@
/*
* Copyright 2021 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.
*/
/**
* Secret Key Protection Fixes.
*/
package org.pgpainless.key.protection.fixes;

135
pgpainless-core/src/test/java/org/pgpainless/key/protection/fixes/EnsureSecureS2KUsageTest.java Normal file
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@ -0,0 +1,135 @@
/*
* Copyright 2021 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.pgpainless.key.protection.fixes;
import static org.junit.jupiter.api.Assertions.assertArrayEquals;
import static org.junit.jupiter.api.Assertions.assertEquals;
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 org.bouncycastle.bcpg.SecretKeyPacket;
import org.bouncycastle.openpgp.PGPException;
import org.bouncycastle.openpgp.PGPSecretKey;
import org.bouncycastle.openpgp.PGPSecretKeyRing;
import org.bouncycastle.util.io.Streams;
import org.junit.jupiter.api.Test;
import org.pgpainless.PGPainless;
import org.pgpainless.decryption_verification.ConsumerOptions;
import org.pgpainless.decryption_verification.DecryptionStream;
import org.pgpainless.key.protection.SecretKeyRingProtector;
import org.pgpainless.util.Passphrase;
public class EnsureSecureS2KUsageTest {
private static final String KEY_WITH_USAGE_CHECKSUM = "-----BEGIN PGP PRIVATE KEY BLOCK-----\n" +
"Version: PGPainless\n" +
"Comment: 23BF 0F50 8FE4 2304 6AC6 6EE3 7616 09ED DAF2 A7EE\n" +
"Comment: Alice\n" +
"\n" +
"lHQEYTpM0xYJKwYBBAHaRw8BAQdA77HCCgjnEWBk9O9guvePTA7235v6yoTGUmUo\n" +
"91V2OVr/CQMC5+tUnE2l4Ypg4dv9+qzBXjlQKAU5fktbQpIvYV9+pPXY6O+Wa7qJ\n" +
"mIJsX2GsMR4uSLeAeQtFuPP0ZydL8rQFQWxpY2WIeAQTFgoAIAUCYTpM1AIbAQUW\n" +
"AgMBAAQLCQgHBRUKCQgLAh4BAhkBAAoJEHYWCe3a8qfu9uYBAJGoTlRUEPCmzDBY\n" +
"iqAXI8q1ZJDpYAF/AgdyfHgPZBLZAQDFagfWe/YyZV36EQ8P978gycUn4psQZyXE\n" +
"QoNByDZDAJx5BGE6TNQSCisGAQQBl1UBBQEBB0BM9uoewIA3wDjChe7qdpp9B/uD\n" +
"fQwxFj8AFcgR0qmDNgMBCAf/CQMC4B9NmOhlt+BgyZTk4BqqudczkJsRhoKPPC3e\n" +
"TEqvyeBavp1fPgvAUfsZdL7Z8RoVQNd0LFptsj2zN2VcmIh1BBgWCgAdBQJhOkzU\n" +
"AhsMBRYCAwEABAsJCAcFFQoJCAsCHgEACgkQdhYJ7dryp+4FxgEA29VePCidazQt\n" +
"F6DfQCyNPW/d0Y+rm64KaMfBHJGCorQA/Rdg/gGVH7RoMiIJ8+kDxWOC92tn8JBJ\n" +
"nIekiMcU45QJnHQEYTpM1BYJKwYBBAHaRw8BAQdAv2fItqEBrRsnrtWOU0Rc/S62\n" +
"tafcr2huX3W5Nu6R1On/CQMCR9EMBma4cl9gE854C43bgYY2o53XSnBS/OMzo1rt\n" +
"h+ixzZ6RZNafiAcXRUldVa55kc5KUvpc3y8lMlkDjYjVBBgWCgB9BQJhOkzUAhsC\n" +
"BRYCAwEABAsJCAcFFQoJCAsCHgFfIAQZFgoABgUCYTpM1AAKCRB7qwD3I/Rg7Iic\n" +
"AP4gOcJFEkRcNJMXVyXWWMaHGzvH7SJSn7/NDxjlbo+IhAD9HiPJoOm/88mHWxSr\n" +
"udMemY82nrspaOyxcwqgkJbT8wIACgkQdhYJ7dryp+6yUQD+IufwT/XdopWA+GPD\n" +
"IgT1CHRecJCkeYYmr7sZdPCLs3YA/jeVaFw4Z0drFnys4rh6aSoG6uf+YSba56V3\n" +
"VBL8P8MC\n" +
"=m6iF\n" +
"-----END PGP PRIVATE KEY BLOCK-----";
// message encrypted to above key
private static final String MESSAGE = "-----BEGIN PGP MESSAGE-----\n" +
"Version: PGPainless\n" +
"\n" +
"hF4DnMY7X1OYFewSAQdAxAxbWTZordzH+fN5s32ZU4PjYM/Og8z6DG7mrjOy+2Mw\n" +
"BCiqa3G9GNZrRQyXihd1sFaxlgqiHrhhmFyCCMLgj2RxjZ7DJ4E0tA7RbF0lkqx4\n" +
"0kAB1XXqAOJ50mEEQLYRN94xojDoJrlz2ZdmV1zqC2ZFd6YITEPIqSdwBuEG61rd\n" +
"BLkPg8RuGdPMKZHZzOxIALtv\n" +
"=//m8\n" +
"-----END PGP MESSAGE-----";
// same message, but unencrypted
private static final String MESSAGE_PLAIN = "Hello, World!\n";
@Test
public void verifyBouncycastleChangesUnprotectedKeysTo_USAGE_CHECKSUM() throws PGPException, InvalidAlgorithmParameterException, NoSuchAlgorithmException, IOException {
// Bouncycastle unfortunately uses USAGE_CHECKSUM as default S2K usage when setting a passphrase
// on a previously unprotected key.
// This test verifies this hypothesis by creating a fresh, protected key (which uses the recommended USAGE_SHA1),
// unprotecting the key and then again setting a passphrase on it.
PGPSecretKeyRing before = PGPainless.generateKeyRing().modernKeyRing("Alice", "before");
for (PGPSecretKey key : before) {
assertEquals(SecretKeyPacket.USAGE_SHA1, key.getS2KUsage());
}
PGPSecretKeyRing unprotected = PGPainless.modifyKeyRing(before)
.changePassphraseFromOldPassphrase(Passphrase.fromPassword("before"))
.withSecureDefaultSettings()
.toNoPassphrase()
.done();
for (PGPSecretKey key : unprotected) {
assertEquals(SecretKeyPacket.USAGE_NONE, key.getS2KUsage());
}
PGPSecretKeyRing after = PGPainless.modifyKeyRing(unprotected)
.changePassphraseFromOldPassphrase(null)
.withSecureDefaultSettings()
.toNewPassphrase(Passphrase.fromPassword("after"))
.done();
for (PGPSecretKey key : after) {
assertEquals(SecretKeyPacket.USAGE_CHECKSUM, key.getS2KUsage(), "Looks like BC fixed the default S2K usage. Yay!");
}
}
@Test
public void testFixS2KUsageFrom_USAGE_CHECKSUM_to_USAGE_SHA1() throws IOException, PGPException {
PGPSecretKeyRing keys = PGPainless.readKeyRing().secretKeyRing(KEY_WITH_USAGE_CHECKSUM);
SecretKeyRingProtector protector = SecretKeyRingProtector.unlockAllKeysWith(Passphrase.fromPassword("after"), keys);
PGPSecretKeyRing fixed = S2KUsageFix.replaceUsageChecksumWithUsageSha1(keys, protector);
for (PGPSecretKey key : fixed) {
assertEquals(SecretKeyPacket.USAGE_SHA1, key.getS2KUsage());
}
testCanStillDecrypt(keys, protector);
}
private void testCanStillDecrypt(PGPSecretKeyRing keys, SecretKeyRingProtector protector) throws PGPException, IOException {
ByteArrayInputStream in = new ByteArrayInputStream(MESSAGE.getBytes(StandardCharsets.UTF_8));
DecryptionStream decryptionStream = PGPainless.decryptAndOrVerify()
.onInputStream(in)
.withOptions(new ConsumerOptions()
.addDecryptionKey(keys, protector));
ByteArrayOutputStream out = new ByteArrayOutputStream();
Streams.pipeAll(decryptionStream, out);
decryptionStream.close();
assertArrayEquals(MESSAGE_PLAIN.getBytes(StandardCharsets.UTF_8), out.toByteArray());
}
}