From 6a4aea77fb29f994f415256830786df11c35a93b Mon Sep 17 00:00:00 2001
From: akwizgran <akwizgran@users.sourceforge.net>
Date: Fri, 1 Jan 2016 14:53:54 +0000
Subject: [PATCH] Final crypto changes for BTPv2. #111
Use BLAKE2s to generate tags.
KDF arguments for key rotation.
Frame IV format.
---
.../api/transport/TransportConstants.java | 11 ++--
.../crypto/CryptoComponentImpl.java | 64 ++++++++++---------
.../org/briarproject/crypto/FrameEncoder.java | 21 +++---
.../crypto/StreamDecrypterImpl.java | 7 +-
.../crypto/StreamEncrypterImpl.java | 22 +++----
.../src/org/briarproject/util/ByteUtils.java | 13 ++++
.../org/briarproject/util/ByteUtilsTest.java | 35 +++++++---
7 files changed, 103 insertions(+), 70 deletions(-)
diff --git a/briar-api/src/org/briarproject/api/transport/TransportConstants.java b/briar-api/src/org/briarproject/api/transport/TransportConstants.java
index ae3a6c3daf..defd164982 100644
--- a/briar-api/src/org/briarproject/api/transport/TransportConstants.java
+++ b/briar-api/src/org/briarproject/api/transport/TransportConstants.java
@@ -8,12 +8,12 @@ public interface TransportConstants {
/** The length of the pseudo-random tag in bytes. */
int TAG_LENGTH = 16;
- /** The length of the stream header IV in bytes. */
- int STREAM_HEADER_IV_LENGTH = 24;
-
/** The length of the message authentication code (MAC) in bytes. */
int MAC_LENGTH = 16;
+ /** The length of the stream header initialisation vector (IV) in bytes. */
+ int STREAM_HEADER_IV_LENGTH = 24;
+
/** The length of the stream header in bytes. */
int STREAM_HEADER_LENGTH = STREAM_HEADER_IV_LENGTH + SecretKey.LENGTH
+ MAC_LENGTH;
@@ -21,8 +21,11 @@ public interface TransportConstants {
/** The length of the frame initalisation vector (IV) in bytes. */
int FRAME_IV_LENGTH = 24;
+ /** The length of the frame header payload in bytes. */
+ int FRAME_HEADER_PAYLOAD_LENGTH = 4;
+
/** The length of the frame header in bytes. */
- int FRAME_HEADER_LENGTH = 4 + MAC_LENGTH;
+ int FRAME_HEADER_LENGTH = FRAME_HEADER_PAYLOAD_LENGTH + MAC_LENGTH;
/** The maximum length of a frame in bytes, including the header and MAC. */
int MAX_FRAME_LENGTH = 1024;
diff --git a/briar-core/src/org/briarproject/crypto/CryptoComponentImpl.java b/briar-core/src/org/briarproject/crypto/CryptoComponentImpl.java
index 9735016993..c4cde4aea3 100644
--- a/briar-core/src/org/briarproject/crypto/CryptoComponentImpl.java
+++ b/briar-core/src/org/briarproject/crypto/CryptoComponentImpl.java
@@ -17,12 +17,10 @@ import org.briarproject.api.transport.TransportKeys;
import org.briarproject.util.ByteUtils;
import org.briarproject.util.StringUtils;
import org.spongycastle.crypto.AsymmetricCipherKeyPair;
-import org.spongycastle.crypto.BlockCipher;
import org.spongycastle.crypto.CipherParameters;
import org.spongycastle.crypto.Digest;
import org.spongycastle.crypto.agreement.ECDHCBasicAgreement;
import org.spongycastle.crypto.digests.SHA256Digest;
-import org.spongycastle.crypto.engines.AESLightEngine;
import org.spongycastle.crypto.generators.ECKeyPairGenerator;
import org.spongycastle.crypto.generators.PKCS5S2ParametersGenerator;
import org.spongycastle.crypto.params.ECKeyGenerationParameters;
@@ -30,6 +28,7 @@ import org.spongycastle.crypto.params.ECPrivateKeyParameters;
import org.spongycastle.crypto.params.ECPublicKeyParameters;
import org.spongycastle.crypto.params.KeyParameter;
+import java.nio.charset.Charset;
import java.security.GeneralSecurityException;
import java.security.SecureRandom;
import java.util.ArrayList;
@@ -57,33 +56,31 @@ class CryptoComponentImpl implements CryptoComponent {
private static final int PBKDF_TARGET_MILLIS = 500;
private static final int PBKDF_SAMPLES = 30;
+ private static byte[] ascii(String s) {
+ return s.getBytes(Charset.forName("US-ASCII"));
+ }
+
// KDF label for master key derivation
- private static final byte[] MASTER = { 'M', 'A', 'S', 'T', 'E', 'R' };
+ private static final byte[] MASTER = ascii("MASTER");
// KDF labels for confirmation code derivation
- private static final byte[] A_CONFIRM =
- { 'A', '_', 'C', 'O', 'N', 'F', 'I', 'R', 'M' };
- private static final byte[] B_CONFIRM =
- { 'B', '_', 'C', 'O', 'N', 'F', 'I', 'R', 'M' };
+ private static final byte[] A_CONFIRM = ascii("ALICE_CONFIRMATION_CODE");
+ private static final byte[] B_CONFIRM = ascii("BOB_CONFIRMATION_CODE");
// KDF labels for invitation stream header key derivation
- private static final byte[] A_INVITE =
- { 'A', '_', 'I', 'N', 'V', 'I', 'T', 'E' };
- private static final byte[] B_INVITE =
- { 'B', '_', 'I', 'N', 'V', 'I', 'T', 'E' };
+ private static final byte[] A_INVITE = ascii("ALICE_INVITATION_KEY");
+ private static final byte[] B_INVITE = ascii("BOB_INVITATION_KEY");
// KDF labels for signature nonce derivation
- private static final byte[] A_NONCE = { 'A', '_', 'N', 'O', 'N', 'C', 'E' };
- private static final byte[] B_NONCE = { 'B', '_', 'N', 'O', 'N', 'C', 'E' };
+ private static final byte[] A_NONCE = ascii("ALICE_SIGNATURE_NONCE");
+ private static final byte[] B_NONCE = ascii("BOB_SIGNATURE_NONCE");
// KDF label for group salt derivation
- private static final byte[] SALT = { 'S', 'A', 'L', 'T' };
+ private static final byte[] SALT = ascii("SALT");
// KDF labels for tag key derivation
- private static final byte[] A_TAG = { 'A', '_', 'T', 'A', 'G' };
- private static final byte[] B_TAG = { 'B', '_', 'T', 'A', 'G' };
+ private static final byte[] A_TAG = ascii("ALICE_TAG_KEY");
+ private static final byte[] B_TAG = ascii("BOB_TAG_KEY");
// KDF labels for header key derivation
- private static final byte[] A_HEADER =
- { 'A', '_', 'H', 'E', 'A', 'D', 'E', 'R' };
- private static final byte[] B_HEADER =
- { 'B', '_', 'H', 'E', 'A', 'D', 'E', 'R' };
+ private static final byte[] A_HEADER = ascii("ALICE_HEADER_KEY");
+ private static final byte[] B_HEADER = ascii("BOB_HEADER_KEY");
// KDF label for key rotation
- private static final byte[] ROTATE = { 'R', 'O', 'T', 'A', 'T', 'E' };
+ private static final byte[] ROTATE = ascii("ROTATE");
private final SecureRandom secureRandom;
private final ECKeyPairGenerator agreementKeyPairGenerator;
@@ -290,8 +287,8 @@ class CryptoComponentImpl implements CryptoComponent {
}
private SecretKey rotateKey(SecretKey k, long rotationPeriod) {
- byte[] period = new byte[4];
- ByteUtils.writeUint32(rotationPeriod, period, 0);
+ byte[] period = new byte[8];
+ ByteUtils.writeUint64(rotationPeriod, period, 0);
return new SecretKey(macKdf(k, ROTATE, period));
}
@@ -311,14 +308,19 @@ class CryptoComponentImpl implements CryptoComponent {
if (tag.length < TAG_LENGTH) throw new IllegalArgumentException();
if (streamNumber < 0 || streamNumber > MAX_32_BIT_UNSIGNED)
throw new IllegalArgumentException();
- for (int i = 0; i < TAG_LENGTH; i++) tag[i] = 0;
- ByteUtils.writeUint32(streamNumber, tag, 0);
- BlockCipher cipher = new AESLightEngine();
- if (cipher.getBlockSize() != TAG_LENGTH)
- throw new IllegalStateException();
- KeyParameter k = new KeyParameter(tagKey.getBytes());
- cipher.init(true, k);
- cipher.processBlock(tag, 0, tag, 0);
+ // Initialise the PRF
+ Digest prf = new Blake2sDigest(tagKey.getBytes());
+ // The output of the PRF must be long enough to use as a key
+ int macLength = prf.getDigestSize();
+ if (macLength < TAG_LENGTH) throw new IllegalStateException();
+ // The input is the stream number as a 64-bit integer
+ byte[] input = new byte[8];
+ ByteUtils.writeUint64(streamNumber, input, 0);
+ prf.update(input, 0, input.length);
+ byte[] mac = new byte[macLength];
+ prf.doFinal(mac, 0);
+ // The output is the first TAG_LENGTH bytes of the MAC
+ System.arraycopy(mac, 0, tag, 0, TAG_LENGTH);
}
public byte[] encryptWithPassword(byte[] input, String password) {
diff --git a/briar-core/src/org/briarproject/crypto/FrameEncoder.java b/briar-core/src/org/briarproject/crypto/FrameEncoder.java
index efd03ed49b..c2fb78f848 100644
--- a/briar-core/src/org/briarproject/crypto/FrameEncoder.java
+++ b/briar-core/src/org/briarproject/crypto/FrameEncoder.java
@@ -2,26 +2,23 @@ package org.briarproject.crypto;
import org.briarproject.util.ByteUtils;
-import static org.briarproject.api.transport.TransportConstants.FRAME_HEADER_LENGTH;
+import static org.briarproject.api.transport.TransportConstants.FRAME_HEADER_PAYLOAD_LENGTH;
import static org.briarproject.api.transport.TransportConstants.FRAME_IV_LENGTH;
import static org.briarproject.api.transport.TransportConstants.MAX_PAYLOAD_LENGTH;
-import static org.briarproject.util.ByteUtils.MAX_32_BIT_UNSIGNED;
class FrameEncoder {
static void encodeIv(byte[] iv, long frameNumber, boolean header) {
if (iv.length < FRAME_IV_LENGTH) throw new IllegalArgumentException();
- if (frameNumber < 0 || frameNumber > MAX_32_BIT_UNSIGNED)
- throw new IllegalArgumentException();
- ByteUtils.writeUint32(frameNumber, iv, 0);
- if (header) iv[4] = 1;
- else iv[4] = 0;
- for (int i = 5; i < FRAME_IV_LENGTH; i++) iv[i] = 0;
+ if (frameNumber < 0) throw new IllegalArgumentException();
+ ByteUtils.writeUint64(frameNumber, iv, 0);
+ if (header) iv[0] |= 0x80;
+ for (int i = 8; i < FRAME_IV_LENGTH; i++) iv[i] = 0;
}
static void encodeHeader(byte[] header, boolean finalFrame,
int payloadLength, int paddingLength) {
- if (header.length < FRAME_HEADER_LENGTH)
+ if (header.length < FRAME_HEADER_PAYLOAD_LENGTH)
throw new IllegalArgumentException();
if (payloadLength < 0) throw new IllegalArgumentException();
if (paddingLength < 0) throw new IllegalArgumentException();
@@ -33,19 +30,19 @@ class FrameEncoder {
}
static boolean isFinalFrame(byte[] header) {
- if (header.length < FRAME_HEADER_LENGTH)
+ if (header.length < FRAME_HEADER_PAYLOAD_LENGTH)
throw new IllegalArgumentException();
return (header[0] & 0x80) == 0x80;
}
static int getPayloadLength(byte[] header) {
- if (header.length < FRAME_HEADER_LENGTH)
+ if (header.length < FRAME_HEADER_PAYLOAD_LENGTH)
throw new IllegalArgumentException();
return ByteUtils.readUint16(header, 0) & 0x7FFF;
}
static int getPaddingLength(byte[] header) {
- if (header.length < FRAME_HEADER_LENGTH)
+ if (header.length < FRAME_HEADER_PAYLOAD_LENGTH)
throw new IllegalArgumentException();
return ByteUtils.readUint16(header, 2);
}
diff --git a/briar-core/src/org/briarproject/crypto/StreamDecrypterImpl.java b/briar-core/src/org/briarproject/crypto/StreamDecrypterImpl.java
index 89e18bee61..5c041ba4d6 100644
--- a/briar-core/src/org/briarproject/crypto/StreamDecrypterImpl.java
+++ b/briar-core/src/org/briarproject/crypto/StreamDecrypterImpl.java
@@ -10,6 +10,7 @@ import java.io.InputStream;
import java.security.GeneralSecurityException;
import static org.briarproject.api.transport.TransportConstants.FRAME_HEADER_LENGTH;
+import static org.briarproject.api.transport.TransportConstants.FRAME_HEADER_PAYLOAD_LENGTH;
import static org.briarproject.api.transport.TransportConstants.FRAME_IV_LENGTH;
import static org.briarproject.api.transport.TransportConstants.MAC_LENGTH;
import static org.briarproject.api.transport.TransportConstants.MAX_FRAME_LENGTH;
@@ -34,7 +35,7 @@ class StreamDecrypterImpl implements StreamDecrypter {
this.cipher = cipher;
this.streamHeaderKey = streamHeaderKey;
frameIv = new byte[FRAME_IV_LENGTH];
- frameHeader = new byte[FRAME_HEADER_LENGTH];
+ frameHeader = new byte[FRAME_HEADER_PAYLOAD_LENGTH];
frameCiphertext = new byte[MAX_FRAME_LENGTH];
frameKey = null;
frameNumber = 0;
@@ -46,6 +47,8 @@ class StreamDecrypterImpl implements StreamDecrypter {
if (payload.length < MAX_PAYLOAD_LENGTH)
throw new IllegalArgumentException();
if (finalFrame) return -1;
+ // Don't allow the frame counter to wrap
+ if (frameNumber < 0) throw new IOException();
// Read the stream header if required
if (frameKey == null) readStreamHeader();
// Read the frame header
@@ -62,7 +65,7 @@ class StreamDecrypterImpl implements StreamDecrypter {
cipher.init(false, frameKey, frameIv);
int decrypted = cipher.process(frameCiphertext, 0,
FRAME_HEADER_LENGTH, frameHeader, 0);
- if (decrypted != FRAME_HEADER_LENGTH - MAC_LENGTH)
+ if (decrypted != FRAME_HEADER_PAYLOAD_LENGTH)
throw new RuntimeException();
} catch (GeneralSecurityException e) {
throw new FormatException();
diff --git a/briar-core/src/org/briarproject/crypto/StreamEncrypterImpl.java b/briar-core/src/org/briarproject/crypto/StreamEncrypterImpl.java
index 988be7e029..0dbd8a1766 100644
--- a/briar-core/src/org/briarproject/crypto/StreamEncrypterImpl.java
+++ b/briar-core/src/org/briarproject/crypto/StreamEncrypterImpl.java
@@ -8,13 +8,13 @@ import java.io.OutputStream;
import java.security.GeneralSecurityException;
import static org.briarproject.api.transport.TransportConstants.FRAME_HEADER_LENGTH;
+import static org.briarproject.api.transport.TransportConstants.FRAME_HEADER_PAYLOAD_LENGTH;
import static org.briarproject.api.transport.TransportConstants.FRAME_IV_LENGTH;
import static org.briarproject.api.transport.TransportConstants.MAC_LENGTH;
import static org.briarproject.api.transport.TransportConstants.MAX_FRAME_LENGTH;
import static org.briarproject.api.transport.TransportConstants.MAX_PAYLOAD_LENGTH;
import static org.briarproject.api.transport.TransportConstants.STREAM_HEADER_IV_LENGTH;
import static org.briarproject.api.transport.TransportConstants.STREAM_HEADER_LENGTH;
-import static org.briarproject.util.ByteUtils.MAX_32_BIT_UNSIGNED;
class StreamEncrypterImpl implements StreamEncrypter {
@@ -22,7 +22,7 @@ class StreamEncrypterImpl implements StreamEncrypter {
private final AuthenticatedCipher cipher;
private final SecretKey streamHeaderKey, frameKey;
private final byte[] tag, streamHeaderIv;
- private final byte[] frameIv, framePlaintext, frameCiphertext;
+ private final byte[] frameIv, frameHeader, framePlaintext, frameCiphertext;
private long frameNumber;
private boolean writeTag, writeStreamHeader;
@@ -37,7 +37,8 @@ class StreamEncrypterImpl implements StreamEncrypter {
this.streamHeaderKey = streamHeaderKey;
this.frameKey = frameKey;
frameIv = new byte[FRAME_IV_LENGTH];
- framePlaintext = new byte[FRAME_HEADER_LENGTH + MAX_PAYLOAD_LENGTH];
+ frameHeader = new byte[FRAME_HEADER_PAYLOAD_LENGTH];
+ framePlaintext = new byte[MAX_PAYLOAD_LENGTH];
frameCiphertext = new byte[MAX_FRAME_LENGTH];
frameNumber = 0;
writeTag = (tag != null);
@@ -49,34 +50,33 @@ class StreamEncrypterImpl implements StreamEncrypter {
if (payloadLength + paddingLength > MAX_PAYLOAD_LENGTH)
throw new IllegalArgumentException();
// Don't allow the frame counter to wrap
- if (frameNumber > MAX_32_BIT_UNSIGNED) throw new IOException();
+ if (frameNumber < 0) throw new IOException();
// Write the tag if required
if (writeTag) writeTag();
// Write the stream header if required
if (writeStreamHeader) writeStreamHeader();
// Encode the frame header
- FrameEncoder.encodeHeader(framePlaintext, finalFrame, payloadLength,
+ FrameEncoder.encodeHeader(frameHeader, finalFrame, payloadLength,
paddingLength);
// Encrypt and authenticate the frame header
FrameEncoder.encodeIv(frameIv, frameNumber, true);
try {
cipher.init(true, frameKey, frameIv);
- int encrypted = cipher.process(framePlaintext, 0,
- FRAME_HEADER_LENGTH - MAC_LENGTH, frameCiphertext, 0);
+ int encrypted = cipher.process(frameHeader, 0,
+ FRAME_HEADER_PAYLOAD_LENGTH, frameCiphertext, 0);
if (encrypted != FRAME_HEADER_LENGTH) throw new RuntimeException();
} catch (GeneralSecurityException badCipher) {
throw new RuntimeException(badCipher);
}
// Combine the payload and padding
- System.arraycopy(payload, 0, framePlaintext, FRAME_HEADER_LENGTH,
- payloadLength);
+ System.arraycopy(payload, 0, framePlaintext, 0, payloadLength);
for (int i = 0; i < paddingLength; i++)
- framePlaintext[FRAME_HEADER_LENGTH + payloadLength + i] = 0;
+ framePlaintext[payloadLength + i] = 0;
// Encrypt and authenticate the payload and padding
FrameEncoder.encodeIv(frameIv, frameNumber, false);
try {
cipher.init(true, frameKey, frameIv);
- int encrypted = cipher.process(framePlaintext, FRAME_HEADER_LENGTH,
+ int encrypted = cipher.process(framePlaintext, 0,
payloadLength + paddingLength, frameCiphertext,
FRAME_HEADER_LENGTH);
if (encrypted != payloadLength + paddingLength + MAC_LENGTH)
diff --git a/briar-core/src/org/briarproject/util/ByteUtils.java b/briar-core/src/org/briarproject/util/ByteUtils.java
index 777d823189..6f47e00146 100644
--- a/briar-core/src/org/briarproject/util/ByteUtils.java
+++ b/briar-core/src/org/briarproject/util/ByteUtils.java
@@ -37,6 +37,19 @@ public class ByteUtils {
b[offset + 3] = (byte) (i & 0xFF);
}
+ public static void writeUint64(long i, byte[] b, int offset) {
+ if (i < 0) throw new IllegalArgumentException();
+ if (b.length < offset + 8) throw new IllegalArgumentException();
+ b[offset] = (byte) (i >> 56);
+ b[offset + 1] = (byte) (i >> 48 & 0xFF);
+ b[offset + 2] = (byte) (i >> 40 & 0xFF);
+ b[offset + 3] = (byte) (i >> 32 & 0xFF);
+ b[offset + 4] = (byte) (i >> 24 & 0xFF);
+ b[offset + 5] = (byte) (i >> 16 & 0xFF);
+ b[offset + 6] = (byte) (i >> 8 & 0xFF);
+ b[offset + 7] = (byte) (i & 0xFF);
+ }
+
public static int readUint16(byte[] b, int offset) {
if (b.length < offset + 2) throw new IllegalArgumentException();
return ((b[offset] & 0xFF) << 8) | (b[offset + 1] & 0xFF);
diff --git a/briar-tests/src/org/briarproject/util/ByteUtilsTest.java b/briar-tests/src/org/briarproject/util/ByteUtilsTest.java
index 0df6548bd6..67ad3fe1a7 100644
--- a/briar-tests/src/org/briarproject/util/ByteUtilsTest.java
+++ b/briar-tests/src/org/briarproject/util/ByteUtilsTest.java
@@ -30,24 +30,39 @@ public class ByteUtilsTest extends BriarTestCase {
@Test
public void testWriteUint16() {
- byte[] b = new byte[3];
+ byte[] b = new byte[4];
ByteUtils.writeUint16(0, b, 1);
- assertEquals("000000", StringUtils.toHexString(b));
+ assertEquals("00000000", StringUtils.toHexString(b));
ByteUtils.writeUint16(1, b, 1);
- assertEquals("000001", StringUtils.toHexString(b));
- ByteUtils.writeUint16(65535, b, 1);
- assertEquals("00FFFF", StringUtils.toHexString(b));
+ assertEquals("00000100", StringUtils.toHexString(b));
+ ByteUtils.writeUint16(Short.MAX_VALUE, b, 1);
+ assertEquals("007FFF00", StringUtils.toHexString(b));
+ ByteUtils.writeUint16(ByteUtils.MAX_16_BIT_UNSIGNED, b, 1);
+ assertEquals("00FFFF00", StringUtils.toHexString(b));
}
@Test
public void testWriteUint32() {
- byte[] b = new byte[5];
+ byte[] b = new byte[6];
ByteUtils.writeUint32(0, b, 1);
- assertEquals("0000000000", StringUtils.toHexString(b));
+ assertEquals("000000000000", StringUtils.toHexString(b));
ByteUtils.writeUint32(1, b, 1);
- assertEquals("0000000001", StringUtils.toHexString(b));
- ByteUtils.writeUint32(4294967295L, b, 1);
- assertEquals("00FFFFFFFF", StringUtils.toHexString(b));
+ assertEquals("000000000100", StringUtils.toHexString(b));
+ ByteUtils.writeUint32(Integer.MAX_VALUE, b, 1);
+ assertEquals("007FFFFFFF00", StringUtils.toHexString(b));
+ ByteUtils.writeUint32(ByteUtils.MAX_32_BIT_UNSIGNED, b, 1);
+ assertEquals("00FFFFFFFF00", StringUtils.toHexString(b));
+ }
+
+ @Test
+ public void testWriteUint64() {
+ byte[] b = new byte[10];
+ ByteUtils.writeUint64(0, b, 1);
+ assertEquals("00000000000000000000", StringUtils.toHexString(b));
+ ByteUtils.writeUint64(1, b, 1);
+ assertEquals("00000000000000000100", StringUtils.toHexString(b));
+ ByteUtils.writeUint64(Long.MAX_VALUE, b, 1);
+ assertEquals("007FFFFFFFFFFFFFFF00", StringUtils.toHexString(b));
}
@Test
--
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