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345
iTechSharp/srcbc/crypto/modes/CcmBlockCipher.cs
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345
iTechSharp/srcbc/crypto/modes/CcmBlockCipher.cs
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using System;
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using System.IO;
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using Org.BouncyCastle.Crypto;
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using Org.BouncyCastle.Crypto.Macs;
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using Org.BouncyCastle.Crypto.Parameters;
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using Org.BouncyCastle.Utilities;
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namespace Org.BouncyCastle.Crypto.Modes
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{
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/**
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* Implements the Counter with Cipher Block Chaining mode (CCM) detailed in
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* NIST Special Publication 800-38C.
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* <p>
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* <b>Note</b>: this mode is a packet mode - it needs all the data up front.
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* </p>
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*/
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public class CcmBlockCipher
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: IAeadBlockCipher
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{
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private static readonly int BlockSize = 16;
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private readonly IBlockCipher cipher;
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private readonly byte[] macBlock;
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private bool forEncryption;
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private byte[] nonce;
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private byte[] associatedText;
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private int macSize;
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private ICipherParameters keyParam;
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private readonly MemoryStream data = new MemoryStream();
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/**
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* Basic constructor.
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*
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* @param cipher the block cipher to be used.
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*/
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public CcmBlockCipher(
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IBlockCipher cipher)
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{
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this.cipher = cipher;
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this.macBlock = new byte[BlockSize];
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if (cipher.GetBlockSize() != BlockSize)
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throw new ArgumentException("cipher required with a block size of " + BlockSize + ".");
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}
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/**
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* return the underlying block cipher that we are wrapping.
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*
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* @return the underlying block cipher that we are wrapping.
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*/
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public virtual IBlockCipher GetUnderlyingCipher()
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{
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return cipher;
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}
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public virtual void Init(
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bool forEncryption,
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ICipherParameters parameters)
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{
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this.forEncryption = forEncryption;
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if (parameters is AeadParameters)
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{
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AeadParameters param = (AeadParameters) parameters;
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nonce = param.GetNonce();
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associatedText = param.GetAssociatedText();
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macSize = param.MacSize / 8;
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keyParam = param.Key;
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}
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else if (parameters is ParametersWithIV)
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{
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ParametersWithIV param = (ParametersWithIV) parameters;
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nonce = param.GetIV();
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associatedText = null;
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macSize = macBlock.Length / 2;
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keyParam = param.Parameters;
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}
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else
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{
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throw new ArgumentException("invalid parameters passed to CCM");
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}
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}
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public virtual string AlgorithmName
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{
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get { return cipher.AlgorithmName + "/CCM"; }
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}
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public virtual int GetBlockSize()
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{
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return cipher.GetBlockSize();
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}
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public virtual int ProcessByte(
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byte input,
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byte[] outBytes,
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int outOff)
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{
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data.WriteByte(input);
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return 0;
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}
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public virtual int ProcessBytes(
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byte[] inBytes,
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int inOff,
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int inLen,
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byte[] outBytes,
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int outOff)
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{
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data.Write(inBytes, inOff, inLen);
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return 0;
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}
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public virtual int DoFinal(
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byte[] outBytes,
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int outOff)
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{
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byte[] text = data.ToArray();
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byte[] enc = ProcessPacket(text, 0, text.Length);
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Array.Copy(enc, 0, outBytes, outOff, enc.Length);
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Reset();
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return enc.Length;
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}
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public virtual void Reset()
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{
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cipher.Reset();
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data.SetLength(0);
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}
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/**
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* Returns a byte array containing the mac calculated as part of the
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* last encrypt or decrypt operation.
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*
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* @return the last mac calculated.
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*/
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public virtual byte[] GetMac()
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{
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byte[] mac = new byte[macSize];
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Array.Copy(macBlock, 0, mac, 0, mac.Length);
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return mac;
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}
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public virtual int GetUpdateOutputSize(
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int len)
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{
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return 0;
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}
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public int GetOutputSize(
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int len)
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{
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if (forEncryption)
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{
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return (int) data.Length + len + macSize;
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}
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return (int) data.Length + len - macSize;
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}
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public byte[] ProcessPacket(
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byte[] input,
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int inOff,
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int inLen)
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{
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if (keyParam == null)
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throw new InvalidOperationException("CCM cipher unitialized.");
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IBlockCipher ctrCipher = new SicBlockCipher(cipher);
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byte[] iv = new byte[BlockSize];
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byte[] output;
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iv[0] = (byte)(((15 - nonce.Length) - 1) & 0x7);
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Array.Copy(nonce, 0, iv, 1, nonce.Length);
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ctrCipher.Init(forEncryption, new ParametersWithIV(keyParam, iv));
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if (forEncryption)
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{
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int index = inOff;
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int outOff = 0;
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output = new byte[inLen + macSize];
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calculateMac(input, inOff, inLen, macBlock);
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ctrCipher.ProcessBlock(macBlock, 0, macBlock, 0); // S0
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while (index < inLen - BlockSize) // S1...
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{
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ctrCipher.ProcessBlock(input, index, output, outOff);
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outOff += BlockSize;
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index += BlockSize;
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}
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byte[] block = new byte[BlockSize];
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Array.Copy(input, index, block, 0, inLen - index);
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ctrCipher.ProcessBlock(block, 0, block, 0);
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Array.Copy(block, 0, output, outOff, inLen - index);
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outOff += inLen - index;
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Array.Copy(macBlock, 0, output, outOff, output.Length - outOff);
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}
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else
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{
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int index = inOff;
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int outOff = 0;
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output = new byte[inLen - macSize];
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Array.Copy(input, inOff + inLen - macSize, macBlock, 0, macSize);
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ctrCipher.ProcessBlock(macBlock, 0, macBlock, 0);
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for (int i = macSize; i != macBlock.Length; i++)
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{
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macBlock[i] = 0;
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}
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while (outOff < output.Length - BlockSize)
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{
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ctrCipher.ProcessBlock(input, index, output, outOff);
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outOff += BlockSize;
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index += BlockSize;
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}
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byte[] block = new byte[BlockSize];
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Array.Copy(input, index, block, 0, output.Length - outOff);
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ctrCipher.ProcessBlock(block, 0, block, 0);
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Array.Copy(block, 0, output, outOff, output.Length - outOff);
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byte[] calculatedMacBlock = new byte[BlockSize];
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calculateMac(output, 0, output.Length, calculatedMacBlock);
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if (!Arrays.AreEqual(macBlock, calculatedMacBlock))
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throw new InvalidCipherTextException("mac check in CCM failed");
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}
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return output;
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}
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private int calculateMac(byte[] data, int dataOff, int dataLen, byte[] macBlock)
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{
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IMac cMac = new CbcBlockCipherMac(cipher, macSize * 8);
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cMac.Init(keyParam);
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//
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// build b0
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//
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byte[] b0 = new byte[16];
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if (hasAssociatedText())
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{
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b0[0] |= 0x40;
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}
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b0[0] |= (byte)((((cMac.GetMacSize() - 2) / 2) & 0x7) << 3);
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b0[0] |= (byte)(((15 - nonce.Length) - 1) & 0x7);
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Array.Copy(nonce, 0, b0, 1, nonce.Length);
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int q = dataLen;
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int count = 1;
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while (q > 0)
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{
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b0[b0.Length - count] = (byte)(q & 0xff);
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q >>= 8;
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count++;
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}
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cMac.BlockUpdate(b0, 0, b0.Length);
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//
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// process associated text
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//
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if (hasAssociatedText())
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{
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int extra;
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if (associatedText.Length < ((1 << 16) - (1 << 8)))
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{
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cMac.Update((byte)(associatedText.Length >> 8));
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cMac.Update((byte)associatedText.Length);
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extra = 2;
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}
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else // can't go any higher than 2^32
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{
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cMac.Update((byte)0xff);
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cMac.Update((byte)0xfe);
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cMac.Update((byte)(associatedText.Length >> 24));
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cMac.Update((byte)(associatedText.Length >> 16));
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cMac.Update((byte)(associatedText.Length >> 8));
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cMac.Update((byte)associatedText.Length);
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extra = 6;
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}
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cMac.BlockUpdate(associatedText, 0, associatedText.Length);
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extra = (extra + associatedText.Length) % 16;
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if (extra != 0)
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{
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for (int i = 0; i != 16 - extra; i++)
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{
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cMac.Update((byte)0x00);
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}
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}
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}
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//
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// add the text
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//
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cMac.BlockUpdate(data, dataOff, dataLen);
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return cMac.DoFinal(macBlock, 0);
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}
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private bool hasAssociatedText()
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{
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return associatedText != null && associatedText.Length != 0;
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}
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}
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}
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