using System;
using Org.BouncyCastle.Crypto.Digests;
using Org.BouncyCastle.Crypto.Modes;
using Org.BouncyCastle.Crypto.Parameters;
using Org.BouncyCastle.Security;
using Org.BouncyCastle.Utilities;
namespace Org.BouncyCastle.Crypto.Engines{
/**
* Wrap keys according to
* <a href="http://www.ietf.org/internet-drafts/draft-ietf-smime-key-wrap-01.txt">
* draft-ietf-smime-key-wrap-01.txt</a>.
* <p>
* Note:
* <ul>
* <li>this is based on a draft, and as such is subject to change - don't use this class for anything requiring long term storage.</li>
* <li>if you are using this to wrap triple-des keys you need to set the
* parity bits on the key and, if it's a two-key triple-des key, pad it
* yourself.</li>
* </ul>
* </p>
*/
public class DesEdeWrapEngine
: IWrapper
{
/** Field engine */
private CbcBlockCipher engine;
/** Field param */
private KeyParameter param;
/** Field paramPlusIV */
private ParametersWithIV paramPlusIV;
/** Field iv */
private byte[] iv;
/** Field forWrapping */
private bool forWrapping;
/** Field IV2 */
private static readonly byte[] IV2 = { (byte) 0x4a, (byte) 0xdd, (byte) 0xa2,
(byte) 0x2c, (byte) 0x79, (byte) 0xe8,
(byte) 0x21, (byte) 0x05 };
//
// checksum digest
//
private readonly IDigest sha1 = new Sha1Digest();
private readonly byte[] digest = new byte[20];
/**
* Method init
*
* @param forWrapping
* @param param
*/
public void Init(
bool forWrapping,
ICipherParameters parameters)
{
this.forWrapping = forWrapping;
this.engine = new CbcBlockCipher(new DesEdeEngine());
SecureRandom sr;
if (parameters is ParametersWithRandom)
{
ParametersWithRandom pr = (ParametersWithRandom) parameters;
parameters = pr.Parameters;
sr = pr.Random;
}
else
{
sr = new SecureRandom();
}
if (parameters is KeyParameter)
{
this.param = (KeyParameter) parameters;
if (this.forWrapping)
{
// Hm, we have no IV but we want to wrap ?!?
// well, then we have to create our own IV.
this.iv = new byte[8];
sr.NextBytes(iv);
this.paramPlusIV = new ParametersWithIV(this.param, this.iv);
}
}
else if (parameters is ParametersWithIV)
{
if (!forWrapping)
throw new ArgumentException("You should not supply an IV for unwrapping");
this.paramPlusIV = (ParametersWithIV) parameters;
this.iv = this.paramPlusIV.GetIV();
this.param = (KeyParameter) this.paramPlusIV.Parameters;
if (this.iv.Length != 8)
throw new ArgumentException("IV is not 8 octets", "parameters");
}
}
/**
* Method GetAlgorithmName
*
* @return
*/
public string AlgorithmName
{
get { return "DESede"; }
}
/**
* Method wrap
*
* @param in
* @param inOff
* @param inLen
* @return
*/
public byte[] Wrap(
byte[] input,
int inOff,
int length)
{
if (!forWrapping)
{
throw new InvalidOperationException("Not initialized for wrapping");
}
byte[] keyToBeWrapped = new byte[length];
Array.Copy(input, inOff, keyToBeWrapped, 0, length);
// Compute the CMS Key Checksum, (section 5.6.1), call this CKS.
byte[] CKS = CalculateCmsKeyChecksum(keyToBeWrapped);
// Let WKCKS = WK || CKS where || is concatenation.
byte[] WKCKS = new byte[keyToBeWrapped.Length + CKS.Length];
Array.Copy(keyToBeWrapped, 0, WKCKS, 0, keyToBeWrapped.Length);
Array.Copy(CKS, 0, WKCKS, keyToBeWrapped.Length, CKS.Length);
// Encrypt WKCKS in CBC mode using KEK as the key and IV as the
// initialization vector. Call the results TEMP1.
int blockSize = engine.GetBlockSize();
if (WKCKS.Length % blockSize != 0)
throw new InvalidOperationException("Not multiple of block length");
engine.Init(true, paramPlusIV);
byte [] TEMP1 = new byte[WKCKS.Length];
for (int currentBytePos = 0; currentBytePos != WKCKS.Length; currentBytePos += blockSize)
{
engine.ProcessBlock(WKCKS, currentBytePos, TEMP1, currentBytePos);
}
// Let TEMP2 = IV || TEMP1.
byte[] TEMP2 = new byte[this.iv.Length + TEMP1.Length];
Array.Copy(this.iv, 0, TEMP2, 0, this.iv.Length);
Array.Copy(TEMP1, 0, TEMP2, this.iv.Length, TEMP1.Length);
// Reverse the order of the octets in TEMP2 and call the result TEMP3.
byte[] TEMP3 = reverse(TEMP2);
// Encrypt TEMP3 in CBC mode using the KEK and an initialization vector
// of 0x 4a dd a2 2c 79 e8 21 05. The resulting cipher text is the desired
// result. It is 40 octets long if a 168 bit key is being wrapped.
ParametersWithIV param2 = new ParametersWithIV(this.param, IV2);
this.engine.Init(true, param2);
for (int currentBytePos = 0; currentBytePos != TEMP3.Length; currentBytePos += blockSize)
{
engine.ProcessBlock(TEMP3, currentBytePos, TEMP3, currentBytePos);
}
return TEMP3;
}
/**
* Method unwrap
*
* @param in
* @param inOff
* @param inLen
* @return
* @throws InvalidCipherTextException
*/
public byte[] Unwrap(
byte[] input,
int inOff,
int length)
{
if (forWrapping)
{
throw new InvalidOperationException("Not set for unwrapping");
}
if (input == null)
{
throw new InvalidCipherTextException("Null pointer as ciphertext");
}
int blockSize = engine.GetBlockSize();
if (length % blockSize != 0)
{
throw new InvalidCipherTextException("Ciphertext not multiple of " + blockSize);
}
/*
// Check if the length of the cipher text is reasonable given the key
// type. It must be 40 bytes for a 168 bit key and either 32, 40, or
// 48 bytes for a 128, 192, or 256 bit key. If the length is not supported
// or inconsistent with the algorithm for which the key is intended,
// return error.
//
// we do not accept 168 bit keys. it has to be 192 bit.
int lengthA = (estimatedKeyLengthInBit / 8) + 16;
int lengthB = estimatedKeyLengthInBit % 8;
if ((lengthA != keyToBeUnwrapped.Length) || (lengthB != 0)) {
throw new XMLSecurityException("empty");
}
*/
// Decrypt the cipher text with TRIPLedeS in CBC mode using the KEK
// and an initialization vector (IV) of 0x4adda22c79e82105. Call the output TEMP3.
ParametersWithIV param2 = new ParametersWithIV(this.param, IV2);
this.engine.Init(false, param2);
byte [] TEMP3 = new byte[length];
for (int currentBytePos = 0; currentBytePos != TEMP3.Length; currentBytePos += blockSize)
{
engine.ProcessBlock(input, inOff + currentBytePos, TEMP3, currentBytePos);
}
// Reverse the order of the octets in TEMP3 and call the result TEMP2.
byte[] TEMP2 = reverse(TEMP3);
// Decompose TEMP2 into IV, the first 8 octets, and TEMP1, the remaining octets.
this.iv = new byte[8];
byte[] TEMP1 = new byte[TEMP2.Length - 8];
Array.Copy(TEMP2, 0, this.iv, 0, 8);
Array.Copy(TEMP2, 8, TEMP1, 0, TEMP2.Length - 8);
// Decrypt TEMP1 using TRIPLedeS in CBC mode using the KEK and the IV
// found in the previous step. Call the result WKCKS.
this.paramPlusIV = new ParametersWithIV(this.param, this.iv);
this.engine.Init(false, this.paramPlusIV);
byte[] WKCKS = new byte[TEMP1.Length];
for (int currentBytePos = 0; currentBytePos != WKCKS.Length; currentBytePos += blockSize)
{
engine.ProcessBlock(TEMP1, currentBytePos, WKCKS, currentBytePos);
}
// Decompose WKCKS. CKS is the last 8 octets and WK, the wrapped key, are
// those octets before the CKS.
byte[] result = new byte[WKCKS.Length - 8];
byte[] CKStoBeVerified = new byte[8];
Array.Copy(WKCKS, 0, result, 0, WKCKS.Length - 8);
Array.Copy(WKCKS, WKCKS.Length - 8, CKStoBeVerified, 0, 8);
// Calculate a CMS Key Checksum, (section 5.6.1), over the WK and compare
// with the CKS extracted in the above step. If they are not equal, return error.
if (!CheckCmsKeyChecksum(result, CKStoBeVerified)) {
throw new InvalidCipherTextException(
"Checksum inside ciphertext is corrupted");
}
// WK is the wrapped key, now extracted for use in data decryption.
return result;
}
/**
* Some key wrap algorithms make use of the Key Checksum defined
* in CMS [CMS-Algorithms]. This is used to provide an integrity
* check value for the key being wrapped. The algorithm is
*
* - Compute the 20 octet SHA-1 hash on the key being wrapped.
* - Use the first 8 octets of this hash as the checksum value.
*
* @param key
* @return
* @throws Exception
* @see http://www.w3.org/TR/xmlenc-core/#sec-CMSKeyChecksum
*/
private byte[] CalculateCmsKeyChecksum(
byte[] key)
{
sha1.BlockUpdate(key, 0, key.Length);
sha1.DoFinal(digest, 0);
byte[] result = new byte[8];
Array.Copy(digest, 0, result, 0, 8);
return result;
}
/**
* @param key
* @param checksum
* @return
* @see http://www.w3.org/TR/xmlenc-core/#sec-CMSKeyChecksum
*/
private bool CheckCmsKeyChecksum(
byte[] key,
byte[] checksum)
{
return Arrays.ConstantTimeAreEqual(CalculateCmsKeyChecksum(key), checksum);
}
private static byte[] reverse(byte[] bs)
{
byte[] result = new byte[bs.Length];
for (int i = 0; i < bs.Length; i++)
{
result[i] = bs[bs.Length - (i + 1)];
}
return result;
}
}
}
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