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2411e2008b
authenticate each frame before parsing its contents. Each connection starts with a tag, followed by any number of frames, each starting with the frame number (32 bits) and payload length (16 bits), and ending with a MAC (256 bits). Tags have the following format: 32 bits reserved, 16 bits for the transport ID, 32 bits for the connection number, 32 bits (set to zero in the tag) for the frame number, and 16 bits (set to zero in the tag) for the block number. The tag is encrypted with the tag key in ECB mode. Frame numbers for each connection must start from zero and must be contiguous and strictly increasing. Each frame is encrypted with the frame key in CTR mode, using the plaintext tag with the appropriate frame number to initialise the counter. The maximum frame size is 64 KiB, including header and footer. The maximum amount of data that can be sent over a connection is 2^32 frames - roughly 2^48 bytes, or 8 terabytes, with the maximum frame size of 64 KiB. If that isn't sufficient we can add another 16 bits to the frame counter.
101 lines
3.4 KiB
Java
101 lines
3.4 KiB
Java
package net.sf.briar.transport;
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import static net.sf.briar.api.transport.TransportConstants.TAG_LENGTH;
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import java.util.Collection;
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import java.util.Collections;
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import javax.crypto.Cipher;
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import javax.crypto.SecretKey;
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import junit.framework.TestCase;
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import net.sf.briar.api.ContactId;
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import net.sf.briar.api.crypto.CryptoComponent;
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import net.sf.briar.api.db.DatabaseComponent;
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import net.sf.briar.api.transport.ConnectionWindow;
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import net.sf.briar.crypto.CryptoModule;
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import org.jmock.Expectations;
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import org.jmock.Mockery;
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import org.junit.Test;
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import com.google.inject.Guice;
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import com.google.inject.Injector;
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public class ConnectionRecogniserImplTest extends TestCase {
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private final CryptoComponent crypto;
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private final ContactId contactId;
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private final byte[] secret;
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private final int transportId;
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private final ConnectionWindow connectionWindow;
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public ConnectionRecogniserImplTest() {
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super();
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Injector i = Guice.createInjector(new CryptoModule());
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crypto = i.getInstance(CryptoComponent.class);
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contactId = new ContactId(1);
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secret = new byte[18];
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transportId = 123;
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connectionWindow = new ConnectionWindowImpl(0L, 0);
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}
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@Test
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public void testUnexpectedTag() throws Exception {
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Mockery context = new Mockery();
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final DatabaseComponent db = context.mock(DatabaseComponent.class);
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context.checking(new Expectations() {{
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oneOf(db).addListener(with(any(ConnectionRecogniserImpl.class)));
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oneOf(db).getContacts();
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will(returnValue(Collections.singleton(contactId)));
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oneOf(db).getSharedSecret(contactId);
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will(returnValue(secret));
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oneOf(db).getConnectionWindow(contactId, transportId);
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will(returnValue(connectionWindow));
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}});
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final ConnectionRecogniserImpl c =
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new ConnectionRecogniserImpl(transportId, crypto, db);
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assertNull(c.acceptConnection(new byte[TAG_LENGTH]));
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context.assertIsSatisfied();
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}
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@Test
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public void testExpectedTag() throws Exception {
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// Calculate the expected tag for connection number 3
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SecretKey tagKey = crypto.deriveIncomingTagKey(secret);
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Cipher tagCipher = crypto.getTagCipher();
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tagCipher.init(Cipher.ENCRYPT_MODE, tagKey);
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byte[] tag = TagEncoder.encodeTag(transportId, 3L);
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byte[] encryptedTag = tagCipher.doFinal(tag);
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Mockery context = new Mockery();
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final DatabaseComponent db = context.mock(DatabaseComponent.class);
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context.checking(new Expectations() {{
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oneOf(db).addListener(with(any(ConnectionRecogniserImpl.class)));
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oneOf(db).getContacts();
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will(returnValue(Collections.singleton(contactId)));
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oneOf(db).getSharedSecret(contactId);
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will(returnValue(secret));
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oneOf(db).getConnectionWindow(contactId, transportId);
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will(returnValue(connectionWindow));
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oneOf(db).setConnectionWindow(contactId, transportId,
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connectionWindow);
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}});
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final ConnectionRecogniserImpl c =
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new ConnectionRecogniserImpl(transportId, crypto, db);
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// First time - the tag should be expected
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assertEquals(contactId, c.acceptConnection(encryptedTag));
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// Second time - the tag should no longer be expected
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assertNull(c.acceptConnection(encryptedTag));
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// The window should have advanced
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assertEquals(4L, connectionWindow.getCentre());
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Collection<Long> unseen = connectionWindow.getUnseenConnectionNumbers();
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assertEquals(19, unseen.size());
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for(int i = 0; i < 19; i++) {
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if(i == 3) continue;
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assertTrue(unseen.contains(Long.valueOf(i)));
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}
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context.assertIsSatisfied();
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}
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}
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