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Use namespaced labels for transport key derivation.

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This commit is contained in:
akwizgran
2017-11-30 17:36:04 +00:00
parent d2348a4e7d
commit 0f2beee813
2 changed files with 39 additions and 13 deletions
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30
bramble-api/src/main/java/org/briarproject/bramble/api/transport/TransportConstants.java
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@@ -7,7 +7,7 @@ public interface TransportConstants {
/** /**
* The current version of the transport protocol. * The current version of the transport protocol.
*/ */
int PROTOCOL_VERSION = 3; int PROTOCOL_VERSION = 4;
/** /**
* The length of the pseudo-random tag in bytes. * The length of the pseudo-random tag in bytes.
@@ -80,4 +80,32 @@ public interface TransportConstants {
* The size of the reordering window. * The size of the reordering window.
*/ */
int REORDERING_WINDOW_SIZE = 32; int REORDERING_WINDOW_SIZE = 32;
/**
* Label for deriving Alice's initial tag key from the master secret.
*/
String ALICE_TAG_LABEL = "org.briarproject.bramble.transport/ALICE_TAG_KEY";
/**
* Label for deriving Bob's initial tag key from the master secret.
*/
String BOB_TAG_LABEL = "org.briarproject.bramble.transport/BOB_TAG_KEY";
/**
* Label for deriving Alice's initial header key from the master secret.
*/
String ALICE_HEADER_LABEL =
"org.briarproject.bramble.transport/ALICE_HEADER_KEY";
/**
* Label for deriving Bob's initial header key from the master secret.
*/
String BOB_HEADER_LABEL =
"org.briarproject.bramble.transport/BOB_HEADER_KEY";
/**
* Label for deriving the next period's key in key rotation.
*/
String ROTATE_LABEL = "org.briarproject.bramble.transport/ROTATE";
} }

22
bramble-core/src/main/java/org/briarproject/bramble/crypto/TransportCryptoImpl.java
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@@ -13,6 +13,11 @@ import org.spongycastle.crypto.Digest;
import javax.inject.Inject; import javax.inject.Inject;
import static org.briarproject.bramble.api.transport.TransportConstants.ALICE_HEADER_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_TAG_LABEL;
import static org.briarproject.bramble.api.transport.TransportConstants.ROTATE_LABEL;
import static org.briarproject.bramble.api.transport.TransportConstants.TAG_LENGTH; import static org.briarproject.bramble.api.transport.TransportConstants.TAG_LENGTH;
import static org.briarproject.bramble.util.ByteUtils.INT_16_BYTES; 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.INT_64_BYTES;
@@ -21,15 +26,6 @@ import static org.briarproject.bramble.util.ByteUtils.MAX_32_BIT_UNSIGNED;
class TransportCryptoImpl implements TransportCrypto { class TransportCryptoImpl implements TransportCrypto {
// KDF labels for tag key derivation
private static final String A_TAG = "ALICE_TAG_KEY";
private static final String B_TAG = "BOB_TAG_KEY";
// KDF labels for header key derivation
private static final String A_HEADER = "ALICE_HEADER_KEY";
private static final String B_HEADER = "BOB_HEADER_KEY";
// KDF label for key rotation
private static final String ROTATE = "ROTATE";
private final CryptoComponent crypto; private final CryptoComponent crypto;
@Inject @Inject
@@ -93,19 +89,21 @@ class TransportCryptoImpl implements TransportCrypto {
private SecretKey rotateKey(SecretKey k, long rotationPeriod) { private SecretKey rotateKey(SecretKey k, long rotationPeriod) {
byte[] period = new byte[INT_64_BYTES]; byte[] period = new byte[INT_64_BYTES];
ByteUtils.writeUint64(rotationPeriod, period, 0); ByteUtils.writeUint64(rotationPeriod, period, 0);
return crypto.deriveKey(ROTATE, k, period); return crypto.deriveKey(ROTATE_LABEL, k, period);
} }
private SecretKey deriveTagKey(SecretKey master, TransportId t, private SecretKey deriveTagKey(SecretKey master, TransportId t,
boolean alice) { boolean alice) {
String label = alice ? ALICE_TAG_LABEL : BOB_TAG_LABEL;
byte[] id = StringUtils.toUtf8(t.getString()); byte[] id = StringUtils.toUtf8(t.getString());
return crypto.deriveKey(alice ? A_TAG : B_TAG, master, id); return crypto.deriveKey(label, master, id);
} }
private SecretKey deriveHeaderKey(SecretKey master, TransportId t, private SecretKey deriveHeaderKey(SecretKey master, TransportId t,
boolean alice) { boolean alice) {
String label = alice ? ALICE_HEADER_LABEL : BOB_HEADER_LABEL;
byte[] id = StringUtils.toUtf8(t.getString()); byte[] id = StringUtils.toUtf8(t.getString());
return crypto.deriveKey(alice ? A_HEADER : B_HEADER, master, id); return crypto.deriveKey(label, master, id);
} }
@Override @Override