From 2c387f80b13c0635404809bbd9af8eb4bfb5d2b3 Mon Sep 17 00:00:00 2001
From: akwizgran <akwizgran@users.sourceforge.net>
Date: Fri, 12 Aug 2011 17:14:58 +0200
Subject: [PATCH] Packet decrypter with unit tests. Decryption is complicated
by the fact that the cipher wants to operate a block at a time even though
it's in CTR mode.
---
.../sf/briar/transport/PacketDecrypter.java | 13 ++
.../briar/transport/PacketDecrypterImpl.java | 162 ++++++++++++++++++
.../briar/transport/PacketEncrypterImpl.java | 3 +
test/build.xml | 1 +
.../transport/PacketDecrypterImplTest.java | 113 ++++++++++++
.../transport/PacketEncrypterImplTest.java | 2 +-
6 files changed, 293 insertions(+), 1 deletion(-)
create mode 100644 components/net/sf/briar/transport/PacketDecrypter.java
create mode 100644 components/net/sf/briar/transport/PacketDecrypterImpl.java
create mode 100644 test/net/sf/briar/transport/PacketDecrypterImplTest.java
diff --git a/components/net/sf/briar/transport/PacketDecrypter.java b/components/net/sf/briar/transport/PacketDecrypter.java
new file mode 100644
index 0000000000..c8587d3ae0
--- /dev/null
+++ b/components/net/sf/briar/transport/PacketDecrypter.java
@@ -0,0 +1,13 @@
+package net.sf.briar.transport;
+
+import java.io.IOException;
+import java.io.InputStream;
+
+interface PacketDecrypter {
+
+ /** Returns the input stream from which packets should be read. */
+ InputStream getInputStream();
+
+ /** Reads, decrypts and returns a tag from the underlying input stream. */
+ byte[] readTag() throws IOException;
+}
diff --git a/components/net/sf/briar/transport/PacketDecrypterImpl.java b/components/net/sf/briar/transport/PacketDecrypterImpl.java
new file mode 100644
index 0000000000..c0645af462
--- /dev/null
+++ b/components/net/sf/briar/transport/PacketDecrypterImpl.java
@@ -0,0 +1,162 @@
+package net.sf.briar.transport;
+
+import java.io.EOFException;
+import java.io.FilterInputStream;
+import java.io.IOException;
+import java.io.InputStream;
+import java.security.InvalidAlgorithmParameterException;
+import java.security.InvalidKeyException;
+import java.util.Arrays;
+
+import javax.crypto.BadPaddingException;
+import javax.crypto.Cipher;
+import javax.crypto.IllegalBlockSizeException;
+import javax.crypto.SecretKey;
+import javax.crypto.ShortBufferException;
+import javax.crypto.spec.IvParameterSpec;
+
+class PacketDecrypterImpl extends FilterInputStream implements PacketDecrypter {
+
+ private final Cipher tagCipher, packetCipher;
+ private final SecretKey packetKey;
+
+ private byte[] cipherBuf, plainBuf;
+ private int bufOff = 0, bufLen = Constants.TAG_BYTES;
+ private boolean betweenPackets = true;
+
+ PacketDecrypterImpl(byte[] firstTag, InputStream in, Cipher tagCipher,
+ Cipher packetCipher, SecretKey tagKey, SecretKey packetKey) {
+ super(in);
+ if(firstTag.length != Constants.TAG_BYTES)
+ throw new IllegalArgumentException();
+ cipherBuf = Arrays.copyOf(firstTag, firstTag.length);
+ plainBuf = new byte[Constants.TAG_BYTES];
+ this.tagCipher = tagCipher;
+ this.packetCipher = packetCipher;
+ this.packetKey = packetKey;
+ try {
+ tagCipher.init(Cipher.DECRYPT_MODE, tagKey);
+ } catch(InvalidKeyException e) {
+ throw new IllegalArgumentException(e);
+ }
+ if(tagCipher.getOutputSize(Constants.TAG_BYTES) != Constants.TAG_BYTES)
+ throw new IllegalArgumentException();
+ }
+
+ public InputStream getInputStream() {
+ return this;
+ }
+
+ public byte[] readTag() throws IOException {
+ byte[] tag = new byte[Constants.TAG_BYTES];
+ System.arraycopy(cipherBuf, bufOff, tag, 0, bufLen);
+ int offset = bufLen;
+ bufOff = bufLen = 0;
+ while(offset < tag.length) {
+ int read = in.read(tag, offset, tag.length - offset);
+ if(read == -1) throw new EOFException();
+ offset += read;
+ }
+ betweenPackets = false;
+ try {
+ byte[] decryptedTag = tagCipher.doFinal(tag);
+ IvParameterSpec iv = new IvParameterSpec(decryptedTag);
+ packetCipher.init(Cipher.DECRYPT_MODE, packetKey, iv);
+ return decryptedTag;
+ } catch(BadPaddingException badCipher) {
+ throw new RuntimeException(badCipher);
+ } catch(IllegalBlockSizeException badCipher) {
+ throw new RuntimeException(badCipher);
+ } catch(InvalidAlgorithmParameterException badIv) {
+ throw new RuntimeException(badIv);
+ } catch(InvalidKeyException badKey) {
+ throw new RuntimeException(badKey);
+ }
+ }
+
+ @Override
+ public int read() throws IOException {
+ if(betweenPackets) throw new IllegalStateException();
+ if(bufLen == 0) {
+ int read = readBlock();
+ if(read == 0) return -1;
+ bufOff = 0;
+ bufLen = read;
+ }
+ int i = plainBuf[bufOff];
+ bufOff++;
+ bufLen--;
+ return i < 0 ? i + 256 : i;
+ }
+
+ // Although we're using CTR mode, which doesn't require full blocks of
+ // ciphertext, the cipher still tries to operate a block at a time. We must
+ // either call update() with a full block or doFinal() with the last
+ // (possibly partial) block.
+ private int readBlock() throws IOException {
+ // Try to read a block of ciphertext
+ int off = 0;
+ while(off < cipherBuf.length) {
+ int read = in.read(cipherBuf, off, cipherBuf.length - off);
+ if(read == -1) break;
+ off += read;
+ }
+ if(off == 0) return 0;
+ // Did we get a whole block? If not we must be at EOF
+ if(off < cipherBuf.length) {
+ // We're at EOF so we can call doFinal() to force decryption
+ try {
+ int i = packetCipher.doFinal(cipherBuf, 0, off, plainBuf);
+ if(i < off) throw new RuntimeException();
+ betweenPackets = true;
+ } catch(BadPaddingException badCipher) {
+ throw new RuntimeException(badCipher);
+ } catch(IllegalBlockSizeException badCipher) {
+ throw new RuntimeException(badCipher);
+ } catch(ShortBufferException badCipher) {
+ throw new RuntimeException(badCipher);
+ }
+ } else {
+ // We're not at EOF but we have a whole block to decrypt
+ try {
+ int i = packetCipher.update(cipherBuf, 0, off, plainBuf);
+ if(i < off) throw new RuntimeException();
+ } catch(ShortBufferException badCipher) {
+ throw new RuntimeException(badCipher);
+ }
+ }
+ return off;
+ }
+
+ @Override
+ public int read(byte[] b) throws IOException {
+ if(betweenPackets) throw new IllegalStateException();
+ if(bufLen == 0) {
+ int read = readBlock();
+ if(read == 0) return -1;
+ bufOff = 0;
+ bufLen = read;
+ }
+ int length = Math.min(b.length, bufLen);
+ System.arraycopy(plainBuf, bufOff, b, 0, length);
+ bufOff += length;
+ bufLen -= length;
+ return length;
+ }
+
+ @Override
+ public int read(byte[] b, int off, int len) throws IOException {
+ if(betweenPackets) throw new IllegalStateException();
+ if(bufLen == 0) {
+ int read = readBlock();
+ if(read == 0) return -1;
+ bufOff = 0;
+ bufLen = read;
+ }
+ int length = Math.min(len, bufLen);
+ System.arraycopy(plainBuf, bufOff, b, off, length);
+ bufOff += length;
+ bufLen -= length;
+ return length;
+ }
+}
diff --git a/components/net/sf/briar/transport/PacketEncrypterImpl.java b/components/net/sf/briar/transport/PacketEncrypterImpl.java
index 69ca0c9ca3..5629bcae44 100644
--- a/components/net/sf/briar/transport/PacketEncrypterImpl.java
+++ b/components/net/sf/briar/transport/PacketEncrypterImpl.java
@@ -67,18 +67,21 @@ implements PacketEncrypter {
@Override
public void write(int b) throws IOException {
+ // FIXME: Encrypt into same buffer
byte[] ciphertext = packetCipher.update(new byte[] {(byte) b});
if(ciphertext != null) out.write(ciphertext);
}
@Override
public void write(byte[] b) throws IOException {
+ // FIXME: Encrypt into same buffer
byte[] ciphertext = packetCipher.update(b);
if(ciphertext != null) out.write(ciphertext);
}
@Override
public void write(byte[] b, int off, int len) throws IOException {
+ // FIXME: Encrypt into same buffer
byte[] ciphertext = packetCipher.update(b, off, len);
if(ciphertext != null) out.write(ciphertext);
}
diff --git a/test/build.xml b/test/build.xml
index d008290f42..90ccb67ce2 100644
--- a/test/build.xml
+++ b/test/build.xml
@@ -34,6 +34,7 @@
<test name='net.sf.briar.setup.SetupWorkerTest'/>
<test name='net.sf.briar.transport.ConnectionRecogniserImplTest'/>
<test name='net.sf.briar.transport.ConnectionWindowImplTest'/>
+ <test name='net.sf.briar.transport.PacketDecrypterImplTest'/>
<test name='net.sf.briar.transport.PacketEncrypterImplTest'/>
<test name='net.sf.briar.transport.PacketWriterImplTest'/>
<test name='net.sf.briar.transport.TagEncoderTest'/>
diff --git a/test/net/sf/briar/transport/PacketDecrypterImplTest.java b/test/net/sf/briar/transport/PacketDecrypterImplTest.java
new file mode 100644
index 0000000000..e4ec4f2d3c
--- /dev/null
+++ b/test/net/sf/briar/transport/PacketDecrypterImplTest.java
@@ -0,0 +1,113 @@
+package net.sf.briar.transport;
+
+import java.io.ByteArrayInputStream;
+import java.util.Arrays;
+
+import javax.crypto.Cipher;
+import javax.crypto.SecretKey;
+import javax.crypto.spec.IvParameterSpec;
+
+import junit.framework.TestCase;
+import net.sf.briar.api.crypto.CryptoComponent;
+import net.sf.briar.crypto.CryptoModule;
+
+import org.junit.Test;
+
+import com.google.inject.Guice;
+import com.google.inject.Injector;
+
+public class PacketDecrypterImplTest extends TestCase {
+
+ private final Cipher tagCipher, packetCipher;
+ private final SecretKey tagKey, packetKey;
+
+ public PacketDecrypterImplTest() {
+ super();
+ Injector i = Guice.createInjector(new CryptoModule());
+ CryptoComponent crypto = i.getInstance(CryptoComponent.class);
+ tagCipher = crypto.getTagCipher();
+ packetCipher = crypto.getPacketCipher();
+ tagKey = crypto.generateSecretKey();
+ packetKey = crypto.generateSecretKey();
+ }
+
+ @Test
+ public void testSingleBytePackets() throws Exception {
+ byte[] ciphertext = new byte[(Constants.TAG_BYTES + 1) * 2];
+ ByteArrayInputStream in = new ByteArrayInputStream(ciphertext);
+ byte[] firstTag = new byte[Constants.TAG_BYTES];
+ assertEquals(Constants.TAG_BYTES, in.read(firstTag));
+ PacketDecrypter p = new PacketDecrypterImpl(firstTag, in, tagCipher,
+ packetCipher, tagKey, packetKey);
+ byte[] decryptedTag = p.readTag();
+ assertEquals(Constants.TAG_BYTES, decryptedTag.length);
+ assertTrue(p.getInputStream().read() > -1);
+ byte[] decryptedTag1 = p.readTag();
+ assertEquals(Constants.TAG_BYTES, decryptedTag1.length);
+ assertTrue(p.getInputStream().read() > -1);
+ }
+
+ @Test
+ public void testDecryption() throws Exception {
+ byte[] tag = new byte[Constants.TAG_BYTES];
+ byte[] packet = new byte[123];
+ byte[] tag1 = new byte[Constants.TAG_BYTES];
+ byte[] packet1 = new byte[234];
+ // Calculate the first expected decrypted tag
+ tagCipher.init(Cipher.DECRYPT_MODE, tagKey);
+ byte[] expectedTag = tagCipher.doFinal(tag);
+ assertEquals(tag.length, expectedTag.length);
+ // Calculate the first expected decrypted packet
+ IvParameterSpec iv = new IvParameterSpec(expectedTag);
+ packetCipher.init(Cipher.DECRYPT_MODE, packetKey, iv);
+ byte[] expectedPacket = packetCipher.doFinal(packet);
+ assertEquals(packet.length, expectedPacket.length);
+ // Calculate the second expected decrypted tag
+ tagCipher.init(Cipher.DECRYPT_MODE, tagKey);
+ byte[] expectedTag1 = tagCipher.doFinal(tag1);
+ assertEquals(tag1.length, expectedTag1.length);
+ // Calculate the second expected decrypted packet
+ IvParameterSpec iv1 = new IvParameterSpec(expectedTag1);
+ packetCipher.init(Cipher.DECRYPT_MODE, packetKey, iv1);
+ byte[] expectedPacket1 = packetCipher.doFinal(packet1);
+ assertEquals(packet1.length, expectedPacket1.length);
+ // Check that the PacketDecrypter gets the same results
+ byte[] ciphertext = new byte[tag.length + packet.length
+ + tag1.length + packet1.length];
+ System.arraycopy(tag, 0, ciphertext, 0, tag.length);
+ System.arraycopy(packet, 0, ciphertext, tag.length, packet.length);
+ System.arraycopy(tag1, 0, ciphertext, tag.length + packet.length,
+ tag1.length);
+ System.arraycopy(packet1, 0, ciphertext,
+ tag.length + packet.length + tag1.length, packet1.length);
+ ByteArrayInputStream in = new ByteArrayInputStream(ciphertext);
+ PacketDecrypter p = new PacketDecrypterImpl(tag, in, tagCipher,
+ packetCipher, tagKey, packetKey);
+ // First tag
+ assertTrue(Arrays.equals(expectedTag, p.readTag()));
+ // First packet
+ byte[] actualPacket = new byte[packet.length];
+ int offset = 0;
+ while(offset < actualPacket.length) {
+ int read = p.getInputStream().read(actualPacket, offset,
+ actualPacket.length - offset);
+ if(read == -1) break;
+ offset += read;
+ }
+ assertEquals(actualPacket.length, offset);
+ assertTrue(Arrays.equals(expectedPacket, actualPacket));
+ // Second tag
+ assertTrue(Arrays.equals(expectedTag1, p.readTag()));
+ // Second packet
+ byte[] actualPacket1 = new byte[packet1.length];
+ offset = 0;
+ while(offset < actualPacket1.length) {
+ int read = p.getInputStream().read(actualPacket1, offset,
+ actualPacket1.length - offset);
+ if(read == -1) break;
+ offset += read;
+ }
+ assertEquals(actualPacket1.length, offset);
+ assertTrue(Arrays.equals(expectedPacket1, actualPacket1));
+ }
+}
diff --git a/test/net/sf/briar/transport/PacketEncrypterImplTest.java b/test/net/sf/briar/transport/PacketEncrypterImplTest.java
index 2132223f2c..2b06dfae38 100644
--- a/test/net/sf/briar/transport/PacketEncrypterImplTest.java
+++ b/test/net/sf/briar/transport/PacketEncrypterImplTest.java
@@ -39,7 +39,7 @@ public class PacketEncrypterImplTest extends TestCase {
p.writeTag(new byte[Constants.TAG_BYTES]);
p.getOutputStream().write((byte) 0);
p.finishPacket();
- assertEquals(17, out.toByteArray().length);
+ assertEquals(Constants.TAG_BYTES + 1, out.toByteArray().length);
}
@Test
--
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