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If there's space for a partial final frame, use it.

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This commit is contained in:
akwizgran
2012-08-29 18:11:30 +01:00
parent a104548f7c
commit 88e7cc786f
2 changed files with 117 additions and 8 deletions
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28
components/net/sf/briar/transport/OutgoingEncryptionLayer.java
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@@ -24,7 +24,7 @@ class OutgoingEncryptionLayer implements FrameWriter {
private final AuthenticatedCipher frameCipher;
private final ErasableKey tagKey, frameKey;
private final byte[] iv, aad, ciphertext;
private final int frameLength;
private final int frameLength, maxPayloadLength;
private long capacity, frameNumber;
private boolean writeTag;
@@ -40,6 +40,7 @@ class OutgoingEncryptionLayer implements FrameWriter {
this.tagKey = tagKey;
this.frameKey = frameKey;
this.frameLength = frameLength;
maxPayloadLength = frameLength - HEADER_LENGTH - MAC_LENGTH;
iv = new byte[IV_LENGTH];
aad = new byte[AAD_LENGTH];
ciphertext = new byte[frameLength];
@@ -56,6 +57,7 @@ class OutgoingEncryptionLayer implements FrameWriter {
this.frameCipher = frameCipher;
this.frameKey = frameKey;
this.frameLength = frameLength;
maxPayloadLength = frameLength - HEADER_LENGTH - MAC_LENGTH;
tagCipher = null;
tagKey = null;
iv = new byte[IV_LENGTH];
@@ -125,10 +127,26 @@ class OutgoingEncryptionLayer implements FrameWriter {
}
public long getRemainingCapacity() {
long capacityExcludingTag = writeTag ? capacity - TAG_LENGTH : capacity;
long frames = capacityExcludingTag / frameLength;
// How many frame numbers can we use?
long frameNumbers = MAX_32_BIT_UNSIGNED - frameNumber + 1;
int maxPayloadLength = frameLength - HEADER_LENGTH - MAC_LENGTH;
return maxPayloadLength * Math.min(frames, frameNumbers);
// How many full frames do we have space for?
long bytes = writeTag ? capacity - TAG_LENGTH : capacity;
long fullFrames = bytes / frameLength;
// Are we limited by frame numbers or space?
if(frameNumbers > fullFrames) {
// Can we send a partial frame after the full frames?
int partialFrame = (int) (bytes - fullFrames * frameLength);
if(partialFrame > HEADER_LENGTH + MAC_LENGTH) {
// Send full frames and a partial frame, limited by space
int partialPayload = partialFrame - HEADER_LENGTH - MAC_LENGTH;
return maxPayloadLength * fullFrames + partialPayload;
} else {
// Send full frames only, limited by space
return maxPayloadLength * fullFrames;
}
} else {
// Send full frames only, limited by frame numbers
return maxPayloadLength * frameNumbers;
}
}
}

97
test/net/sf/briar/transport/OutgoingEncryptionLayerTest.java
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@@ -1,12 +1,103 @@
package net.sf.briar.transport;
import static net.sf.briar.api.transport.TransportConstants.HEADER_LENGTH;
import static net.sf.briar.api.transport.TransportConstants.MAC_LENGTH;
import static net.sf.briar.api.transport.TransportConstants.TAG_LENGTH;
import java.io.ByteArrayOutputStream;
import javax.crypto.Cipher;
import net.sf.briar.BriarTestCase;
import net.sf.briar.api.crypto.AuthenticatedCipher;
import net.sf.briar.api.crypto.CryptoComponent;
import net.sf.briar.crypto.CryptoModule;
import org.junit.Test;
import net.sf.briar.BriarTestCase;
import com.google.inject.Guice;
import com.google.inject.Injector;
public class OutgoingEncryptionLayerTest extends BriarTestCase {
// FIXME: Write tests
// FIXME: Write more tests
private final CryptoComponent crypto;
private final Cipher tagCipher;
private final AuthenticatedCipher frameCipher;
public OutgoingEncryptionLayerTest() {
super();
Injector i = Guice.createInjector(new CryptoModule());
crypto = i.getInstance(CryptoComponent.class);
tagCipher = crypto.getTagCipher();
frameCipher = crypto.getFrameCipher();
}
@Test
public void testNothing() {}
public void testRemainingCapacityWithTag() throws Exception {
int frameLength = 1024;
int maxPayloadLength = frameLength - HEADER_LENGTH - MAC_LENGTH;
long capacity = 10 * frameLength;
ByteArrayOutputStream out = new ByteArrayOutputStream();
OutgoingEncryptionLayer o = new OutgoingEncryptionLayer(out, capacity,
tagCipher, frameCipher, crypto.generateTestKey(),
crypto.generateTestKey(), frameLength);
// There should be space for nine full frames and one partial frame
byte[] frame = new byte[frameLength];
assertEquals(10 * maxPayloadLength - TAG_LENGTH,
o.getRemainingCapacity());
// Write nine frames, each containing a partial payload
for(int i = 9; i > 0; i--) {
o.writeFrame(frame, 123, false);
assertEquals(i * maxPayloadLength - TAG_LENGTH,
o.getRemainingCapacity());
}
// Write the final frame, which will not be padded
o.writeFrame(frame, 123, true);
int finalFrameLength = HEADER_LENGTH + 123 + MAC_LENGTH;
assertEquals(maxPayloadLength - TAG_LENGTH - finalFrameLength,
o.getRemainingCapacity());
}
@Test
public void testRemainingCapacityWithoutTag() throws Exception {
int frameLength = 1024;
int maxPayloadLength = frameLength - HEADER_LENGTH - MAC_LENGTH;
long capacity = 10 * frameLength;
ByteArrayOutputStream out = new ByteArrayOutputStream();
OutgoingEncryptionLayer o = new OutgoingEncryptionLayer(out, capacity,
frameCipher, crypto.generateTestKey(), frameLength);
// There should be space for ten full frames
assertEquals(10 * maxPayloadLength, o.getRemainingCapacity());
// Write nine frames, each containing a partial payload
byte[] frame = new byte[frameLength];
for(int i = 9; i > 0; i--) {
o.writeFrame(frame, 123, false);
assertEquals(i * maxPayloadLength, o.getRemainingCapacity());
}
// Write the final frame, which will not be padded
o.writeFrame(frame, 123, true);
int finalFrameLength = HEADER_LENGTH + 123 + MAC_LENGTH;
assertEquals(maxPayloadLength - finalFrameLength,
o.getRemainingCapacity());
}
@Test
public void testRemainingCapacityLimitedByFrameNumbers() throws Exception {
int frameLength = 1024;
int maxPayloadLength = frameLength - HEADER_LENGTH - MAC_LENGTH;
long capacity = Long.MAX_VALUE;
ByteArrayOutputStream out = new ByteArrayOutputStream();
OutgoingEncryptionLayer o = new OutgoingEncryptionLayer(out, capacity,
frameCipher, crypto.generateTestKey(), frameLength);
// There should be enough frame numbers for 2^32 frames
assertEquals((1L << 32) * maxPayloadLength, o.getRemainingCapacity());
// Write a frame containing a partial payload
byte[] frame = new byte[frameLength];
o.writeFrame(frame, 123, false);
// There should be enough frame numbers for 2^32 - 1 frames
assertEquals(((1L << 32) - 1) * maxPayloadLength,
o.getRemainingCapacity());
}
}