/// <summary>
/// Initializes a new instance of the SymmetricKey class.
/// </summary>
/// <param name="provider">One of the <see cref="CryptoProvider"/> values.</param>
/// <param name="algorithm">One of the <see cref="CryptoAlgorithm"/> values.</param>
/// <exception cref="SecurityException">An error occurs when generating a new key.</exception>
public SymmetricKey(CryptoProvider provider, CryptoAlgorithm algorithm) : this(provider) {
m_Handle = 0;
if (SspiProvider.CryptGenKey(m_Provider, new IntPtr((int)algorithm), SecurityConstants.CRYPT_EXPORTABLE, ref m_Handle) == 0)
{
throw new SecurityException("Cannot generate session key.");
}
}
/// <summary>
/// Dynamically creates an exponent-of-one key.
/// </summary>
/// <returns>The handle of a exponent-of-one key.</returns>
/// <exception cref="SecurityException">An error occurs while creating the key.</exception>
private int CreateDynamicExponentOfOneKey()
{
int hPrivateKey = 0;
int dwKeyBlob = 0;
IntPtr keyblob = IntPtr.Zero;
int dwBitLen;
try {
if (SspiProvider.CryptGenKey(m_Provider, new IntPtr(SecurityConstants.AT_KEYEXCHANGE), SecurityConstants.CRYPT_EXPORTABLE, ref hPrivateKey) == 0)
{
throw new SecurityException("Cannot generate key pair.");
}
// Export the private key, we'll convert it to a private
// exponent of one key
if (SspiProvider.CryptExportKey(hPrivateKey, 0, SecurityConstants.PRIVATEKEYBLOB, 0, IntPtr.Zero, ref dwKeyBlob) == 0)
{
throw new SecurityException("Cannot export generated key.");
}
keyblob = Marshal.AllocHGlobal(dwKeyBlob);
if (SspiProvider.CryptExportKey(hPrivateKey, 0, SecurityConstants.PRIVATEKEYBLOB, 0, keyblob, ref dwKeyBlob) == 0)
{
throw new SecurityException("Cannot export generated key.");
}
SspiProvider.CryptDestroyKey(hPrivateKey);
hPrivateKey = 0;
// Get the bit length of the key
dwBitLen = Marshal.ReadInt32(keyblob, 12);
/* Modify the Exponent in Key BLOB format [Key BLOB format is documented in SDK] */
// Convert pubexp in rsapubkey to 1
int offset = 16;
for (int i = 0; i < 4; i++)
{
if (i == 0)
{
Marshal.WriteByte(keyblob, offset, 1);
}
else
{
Marshal.WriteByte(keyblob, offset + i, 0);
}
}
// Skip pubexp
offset += 4;
// Skip modulus, prime1, prime2
offset += dwBitLen / 8;
offset += dwBitLen / 16;
offset += dwBitLen / 16;
// Convert exponent1 to 1
for (int i = 0; i < dwBitLen / 16; i++)
{
if (i == 0)
{
Marshal.WriteByte(keyblob, offset, 1);
}
else
{
Marshal.WriteByte(keyblob, offset + i, 0);
}
}
// Skip exponent1
offset += dwBitLen / 16;
// Convert exponent2 to 1
for (int i = 0; i < dwBitLen / 16; i++)
{
if (i == 0)
{
Marshal.WriteByte(keyblob, offset, 1);
}
else
{
Marshal.WriteByte(keyblob, offset + i, 0);
}
}
// Skip exponent2, coefficient
offset += dwBitLen / 16;
offset += dwBitLen / 16;
// Convert privateExponent to 1
for (int i = 0; i < dwBitLen / 8; i++)
{
if (i == 0)
{
Marshal.WriteByte(keyblob, offset, 1);
}
else
{
Marshal.WriteByte(keyblob, offset + i, 0);
}
}
// Import the exponent-of-one private key.
if (SspiProvider.CryptImportKey(m_Provider, keyblob, dwKeyBlob, 0, SecurityConstants.CRYPT_EXPORTABLE, ref hPrivateKey) == 0)
{
throw new SecurityException("Could not import modified key.");
}
} catch (Exception e) {
if (hPrivateKey != 0)
{
SspiProvider.CryptDestroyKey(hPrivateKey);
}
throw e;
} finally {
if (keyblob != IntPtr.Zero)
{
Marshal.FreeHGlobal(keyblob);
}
}
return(hPrivateKey);
}
/// <summary>
/// Imports a specified key.
/// </summary>
/// <param name="provider">The handle of the CSP.</param>
/// <param name="algorithm">One of the <see cref="CryptoAlgorithm"/> values.</param>
/// <param name="key">The key to import.</param>
/// <returns>The handle of the symmetric key.</returns>
/// <exception cref="SecurityException">An error occurs while importing the specified key.</exception>
private int KeyFromBytes(int provider, CryptoAlgorithm algorithm, byte[] key)
{
int dwFlags = SecurityConstants.CRYPT_FIRST, dwSize, dwProvSessionKeySize = 0, dwPublicKeySize = 0, dwSessionBlob, offset = 0, hTempKey = 0, hSessionKey = 0;
IntPtr algo = new IntPtr((int)algorithm), dwPrivKeyAlg = IntPtr.Zero, pbSessionBlob = IntPtr.Zero;
IntPtr provEnum = IntPtr.Zero;
try {
// Double check to see if this provider supports this algorithm
// and key size
bool found = false;
provEnum = Marshal.AllocHGlobal(84 + IntPtr.Size);
do
{
dwSize = 84 + IntPtr.Size;
if (SspiProvider.CryptGetProvParam(provider, SecurityConstants.PP_ENUMALGS_EX, provEnum, ref dwSize, dwFlags) == 0)
{
break;
}
dwFlags = 0;
if (Marshal.ReadIntPtr(provEnum) == algo)
{
found = true;
}
} while (!found);
if (!found)
{
throw new SecurityException("CSP does not support selected algorithm.");
}
// We have to get the key size(including padding)
// from an HCRYPTKEY handle. PP_ENUMALGS_EX contains
// the key size without the padding so we can't use it.
if (SspiProvider.CryptGenKey(provider, algo, 0, ref hTempKey) == 0)
{
throw new SecurityException("Cannot generate temporary key.");
}
dwSize = 4; // sizeof(int)
if (SspiProvider.CryptGetKeyParam(hTempKey, SecurityConstants.KP_KEYLEN, ref dwProvSessionKeySize, ref dwSize, 0) == 0)
{
throw new SecurityException("Cannot retrieve key parameters.");
}
// Our key is too big, leave
if ((key.Length * 8) > dwProvSessionKeySize)
{
throw new SecurityException("Key too big.");
}
// Get private key's algorithm
dwSize = IntPtr.Size; //sizeof(ALG_ID)
if (SspiProvider.CryptGetKeyParam(m_ExponentOfOne, SecurityConstants.KP_ALGID, ref dwPrivKeyAlg, ref dwSize, 0) == 0)
{
throw new SecurityException("Unable to get the private key's algorithm.");
}
// Get private key's length in bits
dwSize = 4; // sizeof(DWORD)
if (SspiProvider.CryptGetKeyParam(m_ExponentOfOne, SecurityConstants.KP_KEYLEN, ref dwPublicKeySize, ref dwSize, 0) == 0)
{
throw new SecurityException("Unable to get the key length.");
}
// calculate Simple blob's length
dwSessionBlob = (dwPublicKeySize / 8) + IntPtr.Size /*sizeof(ALG_ID)*/ + 4 + IntPtr.Size /*sizeof(BLOBHEADER)*/;
// allocate simple blob buffer
pbSessionBlob = Marshal.AllocHGlobal(dwSessionBlob);
// SIMPLEBLOB Format is documented in SDK
// Copy header to buffer
PUBLICKEYSTRUC pks = new PUBLICKEYSTRUC();
pks.bType = SecurityConstants.SIMPLEBLOB;
pks.bVersion = 2;
pks.reserved = 0;
pks.aiKeyAlg = algo;
Marshal.StructureToPtr(pks, pbSessionBlob, false);
Marshal.WriteIntPtr(pbSessionBlob, offset = Marshal.SizeOf(pks), dwPrivKeyAlg);
offset += IntPtr.Size; // sizeof(ALG_ID)
// Place the key material in reverse order
for (int i = 0; i < key.Length; i++)
{
Marshal.WriteByte(pbSessionBlob, offset + key.Length - i - 1, key[i]);
}
// 3 is for the first reserved byte after the key material + the 2 reserved bytes at the end.
dwSize = dwSessionBlob - (IntPtr.Size /*sizeof(ALG_ID)*/ + IntPtr.Size + 4 /*sizeof(BLOBHEADER)*/ + key.Length + 3);
offset += key.Length + 1;
// Generate random data for the rest of the buffer
// (except that last two bytes)
if (SspiProvider.CryptGenRandom(provider, dwSize, new IntPtr(pbSessionBlob.ToInt64() + offset)) == 0)
{
throw new SecurityException("Could not generate random data.");
}
for (int i = 0; i < dwSize; i++)
{
if (Marshal.ReadByte(pbSessionBlob, offset) == 0)
{
Marshal.WriteByte(pbSessionBlob, offset, 1);
}
offset++;
}
Marshal.WriteByte(pbSessionBlob, dwSessionBlob - 2, 2);
if (SspiProvider.CryptImportKey(provider, pbSessionBlob, dwSessionBlob, m_ExponentOfOne, SecurityConstants.CRYPT_EXPORTABLE, ref hSessionKey) == 0)
{
throw new SecurityException("Cannot import key [key has right size?].");
}
} finally {
if (provEnum != IntPtr.Zero)
{
Marshal.FreeHGlobal(provEnum);
}
if (hTempKey != 0)
{
SspiProvider.CryptDestroyKey(hTempKey);
}
if (pbSessionBlob != IntPtr.Zero)
{
Marshal.FreeHGlobal(pbSessionBlob);
}
}
return(hSessionKey);
}