1 files changed, 78 insertions, 0 deletions
diff --git a/sshlib/src/main/java/com/trilead/ssh2/crypto/cipher/CBCMode.java b/sshlib/src/main/java/com/trilead/ssh2/crypto/cipher/CBCMode.java
new file mode 100644
index 0000000..0ae51b3
--- /dev/null
+++ b/sshlib/src/main/java/com/trilead/ssh2/crypto/cipher/CBCMode.java
@@ -0,0 +1,78 @@
+package com.trilead.ssh2.crypto.cipher;
+
+/**
+ * CBCMode.
+ * 
+ * @author Christian Plattner, plattner@trilead.com
+ * @version $Id: CBCMode.java,v 1.1 2007/10/15 12:49:55 cplattne Exp $
+ */
+public class CBCMode implements BlockCipher
+{
+	BlockCipher tc;
+	int blockSize;
+	boolean doEncrypt;
+
+	byte[] cbc_vector;
+	byte[] tmp_vector;
+
+	public void init(boolean forEncryption, byte[] key)
+	{
+	}
+	
+	public CBCMode(BlockCipher tc, byte[] iv, boolean doEncrypt)
+			throws IllegalArgumentException
+	{
+		this.tc = tc;
+		this.blockSize = tc.getBlockSize();
+		this.doEncrypt = doEncrypt;
+
+		if (this.blockSize != iv.length)
+			throw new IllegalArgumentException("IV must be " + blockSize
+					+ " bytes long! (currently " + iv.length + ")");
+
+		this.cbc_vector = new byte[blockSize];
+		this.tmp_vector = new byte[blockSize];
+		System.arraycopy(iv, 0, cbc_vector, 0, blockSize);
+	}
+
+	public int getBlockSize()
+	{
+		return blockSize;
+	}
+
+	private void encryptBlock(byte[] src, int srcoff, byte[] dst, int dstoff)
+	{
+		for (int i = 0; i < blockSize; i++)
+			cbc_vector[i] ^= src[srcoff + i];
+
+		tc.transformBlock(cbc_vector, 0, dst, dstoff);
+
+		System.arraycopy(dst, dstoff, cbc_vector, 0, blockSize);
+	}
+
+	private void decryptBlock(byte[] src, int srcoff, byte[] dst, int dstoff)
+	{
+		/* Assume the worst, src and dst are overlapping... */
+		
+		System.arraycopy(src, srcoff, tmp_vector, 0, blockSize);
+		
+		tc.transformBlock(src, srcoff, dst, dstoff);
+		
+		for (int i = 0; i < blockSize; i++)
+			dst[dstoff + i] ^= cbc_vector[i];
+
+		/* ...that is why we need a tmp buffer. */
+		
+		byte[] swap = cbc_vector;
+		cbc_vector = tmp_vector;
+		tmp_vector = swap;
+	}
+
+	public void transformBlock(byte[] src, int srcoff, byte[] dst, int dstoff)
+	{
+		if (doEncrypt)
+			encryptBlock(src, srcoff, dst, dstoff);
+		else
+			decryptBlock(src, srcoff, dst, dstoff);
+	}
+}