void OnPostMsgButtonClick(object sender, RoutedEventArgs e)
{
User toUser;
bool queryResult = User.AllUsers.TryGetValue(toTextBox.Text, out toUser);
if (!queryResult)
{
ExclamationMsgBox("User does not exist", "User does not exist");
return;
}
using (X509Certificate2 toUserCert = CryptoService.FindCertificate(toUser))
{
if (toUserCert == null)
{
ExclamationMsgBox($"Can not find certificate for user: \"{toUser.FullName}\"",
"Can not find certificate");
return;
}
using (RSA toUserPublicKey = toUserCert.GetRSAPublicKey())
{
// No rsa public key or cert not valid
if (toUserPublicKey == null || !CryptoService.ValidateCertificate(toUserCert))
{
ExclamationMsgBox($"Certificate not valid for user: \"{toUser.FullName}\"",
"Certificate not valid");
return;
}
byte[] signature;
byte[] data;
try
{
using (RSA userPrivateKey = PrivateKeyDialog())
{
//Null means we cancel
if (userPrivateKey == null)
{
return;
}
string formattedMsg = Message.MakeXml(currentUser, msgTextBox.Text);
data = Encoding.UTF8.GetBytes(formattedMsg);
signature = CryptoService.SignData(data, userPrivateKey);
}
}
catch (FileFormatException)
{
ExclamationMsgBox("Invalid pem file", "Invalid pem file");
return;
}
byte[] symmKey = CryptoService.GenerateSymmetricKey();
byte[] iV = CryptoService.GenerateIV();
byte[] envelope = CryptoService.EncryptSymmetricData(symmKey, iV, toUserPublicKey);
byte[] dataAndSign = Utility.CombineByteArrays(data, signature);
byte[] encData = CryptoService.EncryptData(dataAndSign, symmKey, iV);
// Zero out the symmetric key
Array.Clear(symmKey, 0, symmKey.Length);
byte[] payload = Utility.CombineByteArrays(envelope, encData);
string imagePath = imageTextBox.Text;
try
{
Steganography.Embed(imagePath, imagePath, payload);
}
//TODO: Implement separate exception for small image
catch (FileFormatException)
{
MessageBox.Show("Image is too small for given message", "Small image",
MessageBoxButton.OK, MessageBoxImage.Exclamation);
return;
}
string hash = CryptoService.HashFile(imagePath);
UnreadList list = new UnreadList(toUser.UnreadFile);
list.Add(imagePath, hash);
list.Write(toUser.UnreadFile);
MessageBox.Show("Message post succesful", "Success", MessageBoxButton.OK);
}
}
}