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Improve Curve25519 Public Key Handling #959

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merged 2 commits into from
Sep 13, 2024
+41 −17
Merged

Improve Curve25519 Public Key Handling #959

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18bc7ad
Improved Curve25519 Public Key Handling
exceptionfactory Aug 22, 2024
f441f41
Merge branch 'master' into issue-957
hierynomus Aug 23, 2024
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36 changes: 19 additions & 17 deletions src/main/java/net/schmizz/sshj/transport/kex/Curve25519DH.java
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Original file line number Diff line number Diff line change
Expand Up @@ -34,13 +34,14 @@ public class Curve25519DH extends DHBase {

private static final String ALGORITHM = "X25519";

private static final int ENCODED_ALGORITHM_ID_KEY_LENGTH = 44;
private static final int KEY_LENGTH = 32;

private static final int ALGORITHM_ID_LENGTH = 12;
private int encodedKeyLength;

private static final int KEY_LENGTH = 32;
private int algorithmIdLength;

private final byte[] algorithmId = new byte[ALGORITHM_ID_LENGTH];
// Algorithm Identifier is set on Key Agreement Initialization
private byte[] algorithmId = new byte[KEY_LENGTH];

public Curve25519DH() {
super(ALGORITHM, ALGORITHM);
Expand Down Expand Up @@ -81,23 +82,24 @@ public void init(final AlgorithmParameterSpec params, final Factory<Random> rand
private void setPublicKey(final PublicKey publicKey) {
final byte[] encoded = publicKey.getEncoded();

// Set key and algorithm identifier lengths based on initialized Public Key
encodedKeyLength = encoded.length;
algorithmIdLength = encodedKeyLength - KEY_LENGTH;
algorithmId = new byte[algorithmIdLength];

// Encoded public key consists of the algorithm identifier and public key
if (encoded.length == ENCODED_ALGORITHM_ID_KEY_LENGTH) {
final byte[] publicKeyEncoded = new byte[KEY_LENGTH];
System.arraycopy(encoded, ALGORITHM_ID_LENGTH, publicKeyEncoded, 0, KEY_LENGTH);
setE(publicKeyEncoded);

// Save Algorithm Identifier byte array
System.arraycopy(encoded, 0, algorithmId, 0, ALGORITHM_ID_LENGTH);
} else {
throw new IllegalArgumentException(String.format("X25519 unsupported public key length [%d]", encoded.length));
}
final byte[] publicKeyEncoded = new byte[KEY_LENGTH];
System.arraycopy(encoded, algorithmIdLength, publicKeyEncoded, 0, KEY_LENGTH);
setE(publicKeyEncoded);

// Save Algorithm Identifier byte array
System.arraycopy(encoded, 0, algorithmId, 0, algorithmIdLength);
}

private KeySpec getPeerPublicKeySpec(final byte[] peerPublicKey) {
final byte[] encodedKeySpec = new byte[ENCODED_ALGORITHM_ID_KEY_LENGTH];
System.arraycopy(algorithmId, 0, encodedKeySpec, 0, ALGORITHM_ID_LENGTH);
System.arraycopy(peerPublicKey, 0, encodedKeySpec, ALGORITHM_ID_LENGTH, KEY_LENGTH);
final byte[] encodedKeySpec = new byte[encodedKeyLength];
System.arraycopy(algorithmId, 0, encodedKeySpec, 0, algorithmIdLength);
System.arraycopy(peerPublicKey, 0, encodedKeySpec, algorithmIdLength, KEY_LENGTH);
return new X509EncodedKeySpec(encodedKeySpec);
}
}
22 changes: 22 additions & 0 deletions src/test/java/net/schmizz/sshj/transport/kex/Curve25519DHTest.java
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Expand Up @@ -15,17 +15,24 @@
*/
package net.schmizz.sshj.transport.kex;

import net.schmizz.sshj.common.SecurityUtils;
import net.schmizz.sshj.transport.random.JCERandom;
import org.junit.jupiter.api.BeforeEach;
import org.junit.jupiter.api.Test;

import java.math.BigInteger;
import java.security.GeneralSecurityException;
import java.security.KeyPairGenerator;
import java.security.Provider;
import java.security.Security;

import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertNotNull;

public class Curve25519DHTest {

private static final String ALGORITHM_FILTER = "KeyPairGenerator.X25519";

private static final int KEY_LENGTH = 32;

private static final byte[] PEER_PUBLIC_KEY = {
Expand All @@ -35,8 +42,16 @@ public class Curve25519DHTest {
1, 2, 3, 4, 5, 6, 7, 8
};

@BeforeEach
public void clearSecurityProvider() {
SecurityUtils.setSecurityProvider(null);
}

@Test
public void testInitPublicKeyLength() throws GeneralSecurityException {
final boolean bouncyCastleRegistrationRequired = isAlgorithmUnsupported();
SecurityUtils.setRegisterBouncyCastle(bouncyCastleRegistrationRequired);

final Curve25519DH dh = new Curve25519DH();
dh.init(null, new JCERandom.Factory());

Expand All @@ -48,6 +63,8 @@ public void testInitPublicKeyLength() throws GeneralSecurityException {

@Test
public void testInitComputeSharedSecretKey() throws GeneralSecurityException {
SecurityUtils.setRegisterBouncyCastle(true);

final Curve25519DH dh = new Curve25519DH();
dh.init(null, new JCERandom.Factory());

Expand All @@ -57,4 +74,9 @@ public void testInitComputeSharedSecretKey() throws GeneralSecurityException {
assertNotNull(sharedSecretKey);
assertEquals(BigInteger.ONE.signum(), sharedSecretKey.signum());
}

private boolean isAlgorithmUnsupported() {
final Provider[] providers = Security.getProviders(ALGORITHM_FILTER);
return providers == null || providers.length == 0;
}
}
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