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Add methods for deriving static master and root keys.

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This commit is contained in:
akwizgran
2019-05-30 14:30:39 +01:00
parent b222107044
commit 9b4f60088f
3 changed files with 66 additions and 8 deletions
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16
bramble-api/src/main/java/org/briarproject/bramble/api/crypto/TransportCrypto.java
View File

@@ -3,12 +3,28 @@ package org.briarproject.bramble.api.crypto;
import org.briarproject.bramble.api.plugin.TransportId;
import org.briarproject.bramble.api.transport.TransportKeys;
import java.security.GeneralSecurityException;
/**
* Crypto operations for the transport security protocol - see
* https://code.briarproject.org/briar/briar-spec/blob/master/protocols/BTP.md
*/
public interface TransportCrypto {
/**
* Derives the static master key shared with a contact or pending contact.
*/
SecretKey deriveStaticMasterKey(PublicKey theirHandshakePublicKey,
KeyPair ourHandshakeKeyPair) throws GeneralSecurityException;
/**
* Derives the handshake mode root key from the static master key.
* @param pendingContact Whether the static master key is shared with a
* pending contact or a contact
*/
SecretKey deriveHandshakeRootKey(SecretKey staticMasterKey,
boolean pendingContact);
/**
* Derives initial rotation mode transport keys for the given transport in
* the given time period from the given root key.

28
bramble-api/src/main/java/org/briarproject/bramble/api/transport/TransportConstants.java
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@@ -63,14 +63,6 @@ public interface TransportConstants {
int MAX_PAYLOAD_LENGTH = MAX_FRAME_LENGTH - FRAME_HEADER_LENGTH
- MAC_LENGTH;
/**
* The minimum stream length in bytes that all transport plugins must
* support. Streams may be shorter than this length, but all transport
* plugins must support streams of at least this length.
*/
int MIN_STREAM_LENGTH = STREAM_HEADER_LENGTH + FRAME_HEADER_LENGTH
+ MAC_LENGTH;
/**
* The maximum difference in milliseconds between two peers' clocks.
*/
@@ -81,6 +73,26 @@ public interface TransportConstants {
*/
int REORDERING_WINDOW_SIZE = 32;
/**
* Label for deriving the static master key from handshake key pairs.
*/
String STATIC_MASTER_KEY_LABEL =
"org.briarproject.bramble.transport/STATIC_MASTER_KEY";
/**
* Label for deriving the handshake mode root key for a pending contact
* from the static master key.
*/
String PENDING_CONTACT_ROOT_KEY_LABEL =
"org.briarproject.bramble.transport/PENDING_CONTACT_ROOT_KEY";
/**
* Label for deriving the handshake mode root key for a contact from the
* static master key.
*/
String CONTACT_ROOT_KEY_LABEL =
"org.briarproject.bramble.transport/CONTACT_ROOT_KEY";
/**
* Label for deriving Alice's initial tag key from the root key in
* rotation mode.

30
bramble-core/src/main/java/org/briarproject/bramble/crypto/TransportCryptoImpl.java
View File

@@ -1,6 +1,8 @@
package org.briarproject.bramble.crypto;
import org.briarproject.bramble.api.crypto.CryptoComponent;
import org.briarproject.bramble.api.crypto.KeyPair;
import org.briarproject.bramble.api.crypto.PublicKey;
import org.briarproject.bramble.api.crypto.SecretKey;
import org.briarproject.bramble.api.crypto.TransportCrypto;
import org.briarproject.bramble.api.plugin.TransportId;
@@ -10,9 +12,12 @@ import org.briarproject.bramble.api.transport.TransportKeys;
import org.spongycastle.crypto.Digest;
import org.spongycastle.crypto.digests.Blake2bDigest;
import java.security.GeneralSecurityException;
import javax.inject.Inject;
import static java.lang.System.arraycopy;
import static org.briarproject.bramble.api.Bytes.compare;
import static org.briarproject.bramble.api.transport.TransportConstants.ALICE_HANDSHAKE_HEADER_LABEL;
import static org.briarproject.bramble.api.transport.TransportConstants.ALICE_HANDSHAKE_TAG_LABEL;
import static org.briarproject.bramble.api.transport.TransportConstants.ALICE_HEADER_LABEL;
@@ -21,7 +26,10 @@ import static org.briarproject.bramble.api.transport.TransportConstants.BOB_HAND
import static org.briarproject.bramble.api.transport.TransportConstants.BOB_HANDSHAKE_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.CONTACT_ROOT_KEY_LABEL;
import static org.briarproject.bramble.api.transport.TransportConstants.PENDING_CONTACT_ROOT_KEY_LABEL;
import static org.briarproject.bramble.api.transport.TransportConstants.ROTATE_LABEL;
import static org.briarproject.bramble.api.transport.TransportConstants.STATIC_MASTER_KEY_LABEL;
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_64_BYTES;
@@ -40,6 +48,28 @@ class TransportCryptoImpl implements TransportCrypto {
this.crypto = crypto;
}
@Override
public SecretKey deriveStaticMasterKey(PublicKey theirHandshakePublicKey,
KeyPair ourHandshakeKeyPair) throws GeneralSecurityException {
byte[] theirPublic = theirHandshakePublicKey.getEncoded();
byte[] ourPublic = ourHandshakeKeyPair.getPublic().getEncoded();
boolean alice = compare(ourPublic, theirPublic) < 0;
byte[][] inputs = {
alice ? ourPublic : theirPublic,
alice ? theirPublic : ourPublic
};
return crypto.deriveSharedSecret(STATIC_MASTER_KEY_LABEL,
theirHandshakePublicKey, ourHandshakeKeyPair, inputs);
}
@Override
public SecretKey deriveHandshakeRootKey(SecretKey staticMasterKey,
boolean pendingContact) {
String label = pendingContact ?
PENDING_CONTACT_ROOT_KEY_LABEL : CONTACT_ROOT_KEY_LABEL;
return crypto.deriveKey(label, staticMasterKey);
}
@Override
public TransportKeys deriveRotationKeys(TransportId t,
SecretKey rootKey, long timePeriod, boolean weAreAlice,