private void oLoadItemButton_Click(object sender, RoutedEventArgs e)
{
// select all the certs associated with this user
X509Certificate2 oCert = GetUserKey(UserListSelected.Where <User>(u => u.IsOwnedByCurrentUser));
if (oCert == null)
{
return;
}
using (CryptureEntities oContent = new CryptureEntities())
{
// reconnect our instance so we can lookup the cipher
oContent.Entry(ThisItem).State = EntityState.Unchanged;
// look for the matching instance
Instance oInstance = ThisItem.Instances.Where(
i => StructuralComparisons.StructuralEqualityComparer.Equals(
i.User.Certificate, oCert.RawData)).FirstOrDefault();
try
{
// setup an aes decryptor using the iv and decrypted key
using (Aes oCng = AesCng.Create())
{
// always attempt to use next generation classes first before
// resorting to using legacy crytographic classes
try
{
using (RSA oRSA = oCert.GetRSAPrivateKey())
{
oCng.Key = oRSA.Decrypt(oInstance.CipherKey, RSAEncryptionPadding.Pkcs1);
oCng.IV = ThisItem.Cipher.CipherVector;
}
}
catch (CryptographicException eCryptoOperation)
{
// exit if user opted to cancel
if ((uint)eCryptoOperation.HResult == 0x8010006E)
{
return;
}
using (RSACryptoServiceProvider oRSA = oCert.PrivateKey as RSACryptoServiceProvider)
{
oCng.Key = oRSA.Decrypt(oInstance.CipherKey, false);
oCng.IV = ThisItem.Cipher.CipherVector;
}
}
// attempt to decode the data
using (MemoryStream oMemory = new MemoryStream())
using (CryptoStream oCrypto = new CryptoStream(
oMemory, oCng.CreateDecryptor(), CryptoStreamMode.Write))
{
oCrypto.Write(ThisItem.Cipher.CipherText, 0, ThisItem.Cipher.CipherText.Length);
oCrypto.FlushFinalBlock();
// process text item
if (ThisItem.ItemType == "text")
{
oItemData.Text = Encoding.Unicode.GetString(oMemory.ToArray());
}
// text binary item
else
{
BinaryItemData = oMemory.ToArray();
}
}
}
// change the ui to allow saving again
SetEditingControls(true);
}
catch (Exception eError)
{
MessageBox.Show(this,
"An error occurred during item decryption: " +
Environment.NewLine + Environment.NewLine + eError.Message,
"Error During Item Decryption", MessageBoxButton.OK, MessageBoxImage.Error);
}
}
}
