From 8bdf04a28924ec76c011e979331e393235068b6e Mon Sep 17 00:00:00 2001
From: akwizgran <michael@briarproject.org>
Date: Fri, 2 Feb 2018 22:13:28 +0000
Subject: [PATCH] Clamp private keys, add test vectors.
---
.../bramble/crypto/Curve25519KeyParser.java | 11 ++++++-
.../bramble/crypto/KeyAgreementTest.java | 32 +++++++++++++++++++
2 files changed, 42 insertions(+), 1 deletion(-)
diff --git a/bramble-core/src/main/java/org/briarproject/bramble/crypto/Curve25519KeyParser.java b/bramble-core/src/main/java/org/briarproject/bramble/crypto/Curve25519KeyParser.java
index d7aeac26a2..e7b39ad8d3 100644
--- a/bramble-core/src/main/java/org/briarproject/bramble/crypto/Curve25519KeyParser.java
+++ b/bramble-core/src/main/java/org/briarproject/bramble/crypto/Curve25519KeyParser.java
@@ -21,6 +21,15 @@ class Curve25519KeyParser implements KeyParser {
public PrivateKey parsePrivateKey(byte[] encodedKey)
throws GeneralSecurityException {
if (encodedKey.length != 32) throw new GeneralSecurityException();
- return new Curve25519PrivateKey(encodedKey);
+ return new Curve25519PrivateKey(clamp(encodedKey));
+ }
+
+ static byte[] clamp(byte[] b) {
+ byte[] clamped = new byte[32];
+ System.arraycopy(b, 0, clamped, 0, 32);
+ clamped[0] &= 248;
+ clamped[31] &= 127;
+ clamped[31] |= 64;
+ return clamped;
}
}
diff --git a/bramble-core/src/test/java/org/briarproject/bramble/crypto/KeyAgreementTest.java b/bramble-core/src/test/java/org/briarproject/bramble/crypto/KeyAgreementTest.java
index a086046c36..f0505f4f13 100644
--- a/bramble-core/src/test/java/org/briarproject/bramble/crypto/KeyAgreementTest.java
+++ b/bramble-core/src/test/java/org/briarproject/bramble/crypto/KeyAgreementTest.java
@@ -7,16 +7,32 @@ import org.briarproject.bramble.api.crypto.SecretKey;
import org.briarproject.bramble.test.BrambleTestCase;
import org.briarproject.bramble.test.TestSecureRandomProvider;
import org.junit.Test;
+import org.whispersystems.curve25519.Curve25519;
import java.security.GeneralSecurityException;
import java.util.Random;
import static org.briarproject.bramble.api.keyagreement.KeyAgreementConstants.SHARED_SECRET_LABEL;
import static org.briarproject.bramble.test.TestUtils.getRandomBytes;
+import static org.briarproject.bramble.util.StringUtils.fromHexString;
import static org.junit.Assert.assertArrayEquals;
public class KeyAgreementTest extends BrambleTestCase {
+ // Test vector from RFC 7748: Alice's private and public keys, Bob's
+ // private and public keys, and the shared secret
+ // https://tools.ietf.org/html/rfc7748#section-6.1
+ private static final String ALICE_PRIVATE =
+ "77076d0a7318a57d3c16c17251b26645df4c2f87ebc0992ab177fba51db92c2a";
+ private static final String ALICE_PUBLIC =
+ "8520f0098930a754748b7ddcb43ef75a0dbf3a0d26381af4eba4a98eaa9b4e6a";
+ private static final String BOB_PRIVATE =
+ "5dab087e624a8a4b79e17f8b83800ee66f3bb1292618b6fd1c2f8b27ff88e0eb";
+ private static final String BOB_PUBLIC =
+ "de9edb7d7b7dc1b4d35b61c2ece435373f8343c85b78674dadfc7e146f882b4f";
+ private static final String SHARED_SECRET =
+ "4a5d9d5ba4ce2de1728e3bf480350f25e07e21c947d19e3376f09b3c1e161742";
+
private final CryptoComponent crypto =
new CryptoComponentImpl(new TestSecureRandomProvider(), null);
private final byte[][] inputs;
@@ -46,4 +62,20 @@ public class KeyAgreementTest extends BrambleTestCase {
crypto.deriveSharedSecret(SHARED_SECRET_LABEL, invalid, keyPair,
inputs);
}
+
+ @Test
+ public void testRfc7748TestVector() throws Exception {
+ // Private keys need to be clamped because curve25519-java does the
+ // clamping at key generation time, not multiplication time
+ byte[] aPriv = Curve25519KeyParser.clamp(fromHexString(ALICE_PRIVATE));
+ byte[] aPub = fromHexString(ALICE_PUBLIC);
+ byte[] bPriv = Curve25519KeyParser.clamp(fromHexString(BOB_PRIVATE));
+ byte[] bPub = fromHexString(BOB_PUBLIC);
+ byte[] sharedSecret = fromHexString(SHARED_SECRET);
+ Curve25519 curve25519 = Curve25519.getInstance("java");
+ assertArrayEquals(sharedSecret,
+ curve25519.calculateAgreement(aPub, bPriv));
+ assertArrayEquals(sharedSecret,
+ curve25519.calculateAgreement(bPub, aPriv));
+ }
}
--
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