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// Copyright Yahoo. Licensed under the terms of the Apache 2.0 license. See LICENSE in the project root.
package com.yahoo.security;
import com.yahoo.security.hpke.Aead;
import com.yahoo.security.hpke.Ciphersuite;
import com.yahoo.security.hpke.Hpke;
import com.yahoo.security.hpke.Kdf;
import com.yahoo.security.hpke.Kem;
import org.junit.jupiter.api.Test;
import java.security.KeyPair;
import java.security.interfaces.XECPublicKey;
import static com.yahoo.security.ArrayUtils.hex;
import static com.yahoo.security.ArrayUtils.toUtf8Bytes;
import static com.yahoo.security.ArrayUtils.unhex;
import static org.junit.jupiter.api.Assertions.assertEquals;
import static org.junit.jupiter.api.Assertions.assertNotEquals;
import static org.junit.jupiter.api.Assertions.assertThrows;
/**
* @author vekterli
*/
public class HpkeTest {
static KeyPair ephemeralRrfc9180TestVectorKeyPair() {
var priv = KeyUtils.fromRawX25519PrivateKey(unhex("52c4a758a802cd8b936eceea314432798d5baf2d7e9235dc084ab1b9cfa2f736"));
var pub = KeyUtils.fromRawX25519PublicKey(unhex("37fda3567bdbd628e88668c3c8d7e97d1d1253b6d4ea6d44c150f741f1bf4431"));
return new KeyPair(pub, priv);
}
static KeyPair receiverRrfc9180TestVectorKeyPair() {
var priv = KeyUtils.fromRawX25519PrivateKey(unhex("4612c550263fc8ad58375df3f557aac531d26850903e55a9f23f21d8534e8ac8"));
var pub = KeyUtils.fromRawX25519PublicKey(unhex("3948cfe0ad1ddb695d780e59077195da6c56506b027329794ab02bca80815c4d"));
return new KeyPair(pub, priv);
}
/**
* https://www.rfc-editor.org/rfc/rfc9180.html test vector
*
* Appendix A.1.1
*
* DHKEM(X25519, HKDF-SHA256), HKDF-SHA256, AES-128-GCM
*
* Only tests first encryption, i.e. sequence number 0.
*/
@Test
void passes_rfc_9180_dhkem_x25519_hkdf_sha256_hkdf_sha256_aes_gcm_128_test_vector() {
byte[] info = unhex("4f6465206f6e2061204772656369616e2055726e");
byte[] pt = unhex("4265617574792069732074727574682c20747275746820626561757479");
byte[] aad = unhex("436f756e742d30");
var kpR = receiverRrfc9180TestVectorKeyPair();
var kem = Kem.dHKemX25519HkdfSha256(new Kem.UnsafeDeterminsticKeyPairOnlyUsedByTesting(ephemeralRrfc9180TestVectorKeyPair()));
var ciphersuite = Ciphersuite.of(kem, Kdf.hkdfSha256(), Aead.aesGcm128());
var hpke = Hpke.of(ciphersuite);
var s = hpke.sealBase((XECPublicKey) kpR.getPublic(), info, aad, pt);
// The "enc" output is the ephemeral public key
var expectedEnc = "37fda3567bdbd628e88668c3c8d7e97d1d1253b6d4ea6d44c150f741f1bf4431";
assertEquals(expectedEnc, hex(s.enc()));
var expectedCiphertext = "f938558b5d72f1a23810b4be2ab4f84331acc02fc97babc53a52ae8218a355a9" +
"6d8770ac83d07bea87e13c512a";
assertEquals(expectedCiphertext, hex(s.ciphertext()));
byte[] openedPt = hpke.openBase(s.enc(), kpR, info, aad, s.ciphertext());
assertEquals(hex(pt), hex(openedPt));
}
@Test
void sealing_creates_new_ephemeral_key_pair_per_invocation() {
byte[] info = toUtf8Bytes("the finest info");
byte[] pt = toUtf8Bytes("seagulls attack at dawn");
byte[] aad = toUtf8Bytes("cool AAD");
var kpR = receiverRrfc9180TestVectorKeyPair();
var hpke = Hpke.of(Ciphersuite.defaultSuite());
var s1 = hpke.sealBase((XECPublicKey) kpR.getPublic(), info, aad, pt);
byte[] openedPt = hpke.openBase(s1.enc(), kpR, info, aad, s1.ciphertext());
assertEquals(hex(pt), hex(openedPt));
var s2 = hpke.sealBase((XECPublicKey) kpR.getPublic(), info, aad, pt);
openedPt = hpke.openBase(s2.enc(), kpR, info, aad, s2.ciphertext());
assertEquals(hex(pt), hex(openedPt));
assertNotEquals(hex(s1.enc()), hex(s2.enc())); // This is the ephemeral public key
}
@Test
void opening_ciphertext_with_different_info_or_aad_fails() {
byte[] info = toUtf8Bytes("the finest info");
byte[] pt = toUtf8Bytes("seagulls attack at dawn");
byte[] aad = toUtf8Bytes("cool AAD");
var kpR = receiverRrfc9180TestVectorKeyPair();
var hpke = Hpke.of(Ciphersuite.defaultSuite());
var s = hpke.sealBase((XECPublicKey) kpR.getPublic(), info, aad, pt);
byte[] badInfo = toUtf8Bytes("lesser info");
// TODO better exception classes! Triggers AEAD auth tag mismatch behind the scenes
assertThrows(RuntimeException.class, () -> hpke.openBase(s.enc(), kpR, badInfo, aad, s.ciphertext()));
byte[] badAad = toUtf8Bytes("non-groovy AAD");
assertThrows(RuntimeException.class, () -> hpke.openBase(s.enc(), kpR, info, badAad, s.ciphertext()));
}
}
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