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Add key derivation for static keys.

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This commit is contained in:
akwizgran
2019-04-10 13:22:50 +01:00
parent b568405f59
commit d4b929fc6c
5 changed files with 176 additions and 9 deletions
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18
bramble-api/src/main/java/org/briarproject/bramble/api/crypto/TransportCrypto.java
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@@ -1,6 +1,7 @@
package org.briarproject.bramble.api.crypto;
import org.briarproject.bramble.api.plugin.TransportId;
import org.briarproject.bramble.api.transport.StaticTransportKeys;
import org.briarproject.bramble.api.transport.TransportKeys;
/**
@@ -25,6 +26,23 @@ public interface TransportCrypto {
*/
TransportKeys rotateTransportKeys(TransportKeys k, long timePeriod);
/**
* Derives static transport keys for the given transport in the given time
* period from the given root key.
*
* @param alice whether the keys are for use by Alice or Bob.
*/
StaticTransportKeys deriveStaticTransportKeys(TransportId t,
SecretKey rootKey, boolean alice, long timePeriod);
/**
* Updates the given static transport keys to the given time period. If
* the keys are for the given period or any later period they are not
* updated.
*/
StaticTransportKeys updateTransportKeys(StaticTransportKeys k,
long timePeriod);
/**
* Encodes the pseudo-random tag that is used to recognise a stream.
*/

31
bramble-api/src/main/java/org/briarproject/bramble/api/transport/StaticTransportKeys.java Normal file
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@@ -0,0 +1,31 @@
package org.briarproject.bramble.api.transport;
import org.briarproject.bramble.api.crypto.SecretKey;
import org.briarproject.bramble.api.nullsafety.NotNullByDefault;
import org.briarproject.bramble.api.plugin.TransportId;
import javax.annotation.concurrent.Immutable;
@Immutable
@NotNullByDefault
public class StaticTransportKeys extends TransportKeys {
private final SecretKey rootKey;
private final boolean alice;
public StaticTransportKeys(TransportId transportId, IncomingKeys inPrev,
IncomingKeys inCurr, IncomingKeys inNext, OutgoingKeys outCurr,
SecretKey rootKey, boolean alice) {
super(transportId, inPrev, inCurr, inNext, outCurr);
this.rootKey = rootKey;
this.alice = alice;
}
public SecretKey getRootKey() {
return rootKey;
}
public boolean isAlice() {
return alice;
}
}

23
bramble-api/src/main/java/org/briarproject/bramble/api/transport/TransportConstants.java
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@@ -108,4 +108,27 @@ public interface TransportConstants {
*/
String ROTATE_LABEL = "org.briarproject.bramble.transport/ROTATE";
/**
* Label for deriving Alice's static tag key from the root key.
*/
String ALICE_STATIC_TAG_LABEL =
"org.briarproject.bramble.transport/ALICE_STATIC_TAG_KEY";
/**
* Label for deriving Bob's static tag key from the root key.
*/
String BOB_STATIC_TAG_LABEL =
"org.briarproject.bramble.transport/BOB_STATIC_TAG_KEY";
/**
* Label for deriving Alice's static header key from the root key.
*/
String ALICE_STATIC_HEADER_LABEL =
"org.briarproject.bramble.transport/ALICE_STATIC_HEADER_KEY";
/**
* Label for deriving Bob's static header key from the root key.
*/
String BOB_STATIC_HEADER_LABEL =
"org.briarproject.bramble.transport/BOB_STATIC_HEADER_KEY";
}

110
bramble-core/src/main/java/org/briarproject/bramble/crypto/TransportCryptoImpl.java
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@@ -6,17 +6,21 @@ import org.briarproject.bramble.api.crypto.TransportCrypto;
import org.briarproject.bramble.api.plugin.TransportId;
import org.briarproject.bramble.api.transport.IncomingKeys;
import org.briarproject.bramble.api.transport.OutgoingKeys;
import org.briarproject.bramble.api.transport.StaticTransportKeys;
import org.briarproject.bramble.api.transport.TransportKeys;
import org.briarproject.bramble.util.ByteUtils;
import org.briarproject.bramble.util.StringUtils;
import org.spongycastle.crypto.Digest;
import org.spongycastle.crypto.digests.Blake2bDigest;
import javax.inject.Inject;
import static java.lang.System.arraycopy;
import static org.briarproject.bramble.api.transport.TransportConstants.ALICE_HEADER_LABEL;
import static org.briarproject.bramble.api.transport.TransportConstants.ALICE_STATIC_HEADER_LABEL;
import static org.briarproject.bramble.api.transport.TransportConstants.ALICE_STATIC_TAG_LABEL;
import static org.briarproject.bramble.api.transport.TransportConstants.ALICE_TAG_LABEL;
import static org.briarproject.bramble.api.transport.TransportConstants.BOB_HEADER_LABEL;
import static org.briarproject.bramble.api.transport.TransportConstants.BOB_STATIC_HEADER_LABEL;
import static org.briarproject.bramble.api.transport.TransportConstants.BOB_STATIC_TAG_LABEL;
import static org.briarproject.bramble.api.transport.TransportConstants.BOB_TAG_LABEL;
import static org.briarproject.bramble.api.transport.TransportConstants.ROTATE_LABEL;
import static org.briarproject.bramble.api.transport.TransportConstants.TAG_LENGTH;
@@ -24,6 +28,9 @@ import static org.briarproject.bramble.util.ByteUtils.INT_16_BYTES;
import static org.briarproject.bramble.util.ByteUtils.INT_64_BYTES;
import static org.briarproject.bramble.util.ByteUtils.MAX_16_BIT_UNSIGNED;
import static org.briarproject.bramble.util.ByteUtils.MAX_32_BIT_UNSIGNED;
import static org.briarproject.bramble.util.ByteUtils.writeUint16;
import static org.briarproject.bramble.util.ByteUtils.writeUint64;
import static org.briarproject.bramble.util.StringUtils.toUtf8;
class TransportCryptoImpl implements TransportCrypto {
@@ -90,24 +97,111 @@ class TransportCryptoImpl implements TransportCrypto {
private SecretKey rotateKey(SecretKey k, long timePeriod) {
byte[] period = new byte[INT_64_BYTES];
ByteUtils.writeUint64(timePeriod, period, 0);
writeUint64(timePeriod, period, 0);
return crypto.deriveKey(ROTATE_LABEL, k, period);
}
private SecretKey deriveTagKey(SecretKey master, TransportId t,
boolean alice) {
String label = alice ? ALICE_TAG_LABEL : BOB_TAG_LABEL;
byte[] id = StringUtils.toUtf8(t.getString());
byte[] id = toUtf8(t.getString());
return crypto.deriveKey(label, master, id);
}
private SecretKey deriveHeaderKey(SecretKey master, TransportId t,
boolean alice) {
String label = alice ? ALICE_HEADER_LABEL : BOB_HEADER_LABEL;
byte[] id = StringUtils.toUtf8(t.getString());
byte[] id = toUtf8(t.getString());
return crypto.deriveKey(label, master, id);
}
@Override
public StaticTransportKeys deriveStaticTransportKeys(TransportId t,
SecretKey rootKey, boolean alice, long timePeriod) {
if (timePeriod < 1) throw new IllegalArgumentException();
IncomingKeys inPrev = deriveStaticIncomingKeys(t, rootKey, alice,
timePeriod - 1);
IncomingKeys inCurr = deriveStaticIncomingKeys(t, rootKey, alice,
timePeriod);
IncomingKeys inNext = deriveStaticIncomingKeys(t, rootKey, alice,
timePeriod + 1);
OutgoingKeys outCurr = deriveStaticOutgoingKeys(t, rootKey, alice,
timePeriod);
return new StaticTransportKeys(t, inPrev, inCurr, inNext, outCurr,
rootKey, alice);
}
private IncomingKeys deriveStaticIncomingKeys(TransportId t,
SecretKey rootKey, boolean alice, long timePeriod) {
SecretKey tag = deriveStaticTagKey(t, rootKey, !alice, timePeriod);
SecretKey header = deriveStaticHeaderKey(t, rootKey, !alice,
timePeriod);
return new IncomingKeys(tag, header, timePeriod);
}
private OutgoingKeys deriveStaticOutgoingKeys(TransportId t,
SecretKey rootKey, boolean alice, long timePeriod) {
SecretKey tag = deriveStaticTagKey(t, rootKey, alice, timePeriod);
SecretKey header = deriveStaticHeaderKey(t, rootKey, alice, timePeriod);
return new OutgoingKeys(tag, header, timePeriod, true);
}
private SecretKey deriveStaticTagKey(TransportId t, SecretKey root,
boolean alice, long timePeriod) {
String label = alice ? ALICE_STATIC_TAG_LABEL : BOB_STATIC_TAG_LABEL;
byte[] id = toUtf8(t.getString());
byte[] period = new byte[INT_64_BYTES];
writeUint64(timePeriod, period, 0);
return crypto.deriveKey(label, root, id, period);
}
private SecretKey deriveStaticHeaderKey(TransportId t, SecretKey root,
boolean alice, long timePeriod) {
String label =
alice ? ALICE_STATIC_HEADER_LABEL : BOB_STATIC_HEADER_LABEL;
byte[] id = toUtf8(t.getString());
byte[] period = new byte[INT_64_BYTES];
writeUint64(timePeriod, period, 0);
return crypto.deriveKey(label, root, id, period);
}
@Override
public StaticTransportKeys updateTransportKeys(StaticTransportKeys k,
long timePeriod) {
long elapsed = timePeriod - k.getTimePeriod();
TransportId t = k.getTransportId();
SecretKey rootKey = k.getRootKey();
boolean alice = k.isAlice();
if (elapsed <= 0) {
// The keys are for the given period or later - don't update them
return k;
} else if (elapsed == 1) {
// The keys are one period old - shift by one period
IncomingKeys inPrev = k.getCurrentIncomingKeys();
IncomingKeys inCurr = k.getNextIncomingKeys();
IncomingKeys inNext = deriveStaticIncomingKeys(t, rootKey, alice,
timePeriod + 1);
OutgoingKeys outCurr = deriveStaticOutgoingKeys(t, rootKey, alice,
timePeriod);
return new StaticTransportKeys(t, inPrev, inCurr, inNext, outCurr,
rootKey, alice);
} else if (elapsed == 2) {
// The keys are two periods old - shift by two periods
IncomingKeys inPrev = k.getNextIncomingKeys();
IncomingKeys inCurr = deriveStaticIncomingKeys(t, rootKey, alice,
timePeriod);
IncomingKeys inNext = deriveStaticIncomingKeys(t, rootKey, alice,
timePeriod + 1);
OutgoingKeys outCurr = deriveStaticOutgoingKeys(t, rootKey, alice,
timePeriod);
return new StaticTransportKeys(t, inPrev, inCurr, inNext, outCurr,
rootKey, alice);
} else {
// The keys are more than two periods old - derive fresh keys
return deriveStaticTransportKeys(t, rootKey, alice, timePeriod);
}
}
@Override
public void encodeTag(byte[] tag, SecretKey tagKey, int protocolVersion,
long streamNumber) {
@@ -124,14 +218,14 @@ class TransportCryptoImpl implements TransportCrypto {
// The input is the protocol version as a 16-bit integer, followed by
// the stream number as a 64-bit integer
byte[] protocolVersionBytes = new byte[INT_16_BYTES];
ByteUtils.writeUint16(protocolVersion, protocolVersionBytes, 0);
writeUint16(protocolVersion, protocolVersionBytes, 0);
prf.update(protocolVersionBytes, 0, protocolVersionBytes.length);
byte[] streamNumberBytes = new byte[INT_64_BYTES];
ByteUtils.writeUint64(streamNumber, streamNumberBytes, 0);
writeUint64(streamNumber, streamNumberBytes, 0);
prf.update(streamNumberBytes, 0, streamNumberBytes.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);
arraycopy(mac, 0, tag, 0, TAG_LENGTH);
}
}

3
bramble-core/src/test/java/org/briarproject/bramble/crypto/KeyDerivationTest.java
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@@ -20,6 +20,7 @@ import static org.briarproject.bramble.test.TestUtils.getSecretKey;
import static org.briarproject.bramble.test.TestUtils.getTransportId;
import static org.junit.Assert.assertArrayEquals;
import static org.junit.Assert.assertFalse;
import static org.junit.Assert.assertNotEquals;
import static org.junit.Assert.assertTrue;
public class KeyDerivationTest extends BrambleTestCase {
@@ -137,7 +138,7 @@ public class KeyDerivationTest extends BrambleTestCase {
@Test
public void testTransportIdAffectsOutput() {
TransportId transportId1 = getTransportId();
assertFalse(transportId.getString().equals(transportId1.getString()));
assertNotEquals(transportId.getString(), transportId1.getString());
TransportKeys k = transportCrypto.deriveTransportKeys(transportId,
master, 123, true, true);
TransportKeys k1 = transportCrypto.deriveTransportKeys(transportId1,