public string Decrypt(string passphrase, string encryptedText)
{
if (string.IsNullOrWhiteSpace(passphrase))
{
throw new ArgumentNullException();
}
using (var unencrypted = new MemoryStream())
using (var encrypted = new MemoryStream(Encoding.ASCII.GetBytes(encryptedText)))
{
_gpg.Passphrase = passphrase;
_gpg.OutputType = OutputTypes.AsciiArmor;
_gpg.Decrypt(encrypted, unencrypted);
using (var reader = new StreamReader(unencrypted))
{
unencrypted.Position = 0;
return(reader.ReadToEnd());
}
}
}
internal void DecryptEmail(Outlook.MailItem mailItem)
{
string mail = mailItem.Body;
Outlook.OlBodyFormat mailType = mailItem.BodyFormat;
if (mailType != Outlook.OlBodyFormat.olFormatPlain)
{
MessageBox.Show(
"OutlookGnuPG can only decrypt plain text mails.",
"Invalid Mail Format",
MessageBoxButtons.OK,
MessageBoxIcon.Error);
return;
}
if (Regex.IsMatch(mailItem.Body, _pgpEncryptedHeader) == false)
{
MessageBox.Show(
"OutlookGnuPG cannot help here.",
"Mail is not encrypted",
MessageBoxButtons.OK,
MessageBoxIcon.Exclamation);
return;
}
// Still no gpg.exe path... Annoy the user once again, maybe he'll get it ;)
if (string.IsNullOrEmpty(_settings.GnuPgPath))
Settings();
// Stubborn, give up
if (string.IsNullOrEmpty(_settings.GnuPgPath))
{
MessageBox.Show(
"OutlookGnuPG can only decrypt when you provide a valid gpg.exe path. Please open Settings and configure it.",
"Invalid GnuPG Executable",
MessageBoxButtons.OK,
MessageBoxIcon.Error);
return;
}
string passphrase = string.Empty;
string privateKey = string.Empty;
// Popup UI to select the passphrase and private key.
Passphrase passphraseDialog = new Passphrase(_settings.DefaultKey, "Decrypt");
DialogResult passphraseResult = passphraseDialog.ShowDialog();
if (passphraseResult != DialogResult.OK)
{
// The user closed the passphrase dialog, prevent sending the mail
return;
}
passphrase = passphraseDialog.EnteredPassphrase;
privateKey = passphraseDialog.SelectedKey;
passphraseDialog.Close();
if (string.IsNullOrEmpty(privateKey))
{
MessageBox.Show(
"OutlookGnuPG needs a private key for decrypting. No keys were detected.",
"Invalid Private Key",
MessageBoxButtons.OK,
MessageBoxIcon.Error);
return;
}
// Decrypt without fd-status (might already blow up, early out)
// Decrypt with fd-status and cut out the stdout of normal decrypt (prevents BAD/GOODMC messages in message confusing us)
string stdOutResult = string.Empty;
using (MemoryStream inputStream = new MemoryStream(mail.Length))
using (MemoryStream outputStream = new MemoryStream())
{
using (StreamWriter writer = new StreamWriter(inputStream))
{
writer.Write(mail);
writer.Flush();
inputStream.Position = 0;
try
{
_gnuPg.OutputStatus = false;
_gnuPg.Passphrase = passphrase;
_gnuPg.Decrypt(inputStream, outputStream, new MemoryStream());
}
catch (Exception ex)
{
string error = ex.Message;
// We deal with bad signature later
if (!error.ToLowerInvariant().Contains("bad signature"))
{
MessageBox.Show(
error,
"GnuPG Error",
MessageBoxButtons.OK,
MessageBoxIcon.Error);
return;
}
}
}
using (StreamReader reader = new StreamReader(outputStream))
{
outputStream.Position = 0;
stdOutResult = reader.ReadToEnd();
}
}
string verifyResult = string.Empty;
string errorResult = string.Empty;
using (MemoryStream inputStream = new MemoryStream(mail.Length))
using (MemoryStream outputStream = new MemoryStream())
using (MemoryStream errorStream = new MemoryStream())
{
using (StreamWriter writer = new StreamWriter(inputStream))
{
writer.Write(mail);
writer.Flush();
inputStream.Position = 0;
try
{
_gnuPg.OutputStatus = true;
_gnuPg.Passphrase = passphrase;
_gnuPg.Decrypt(inputStream, outputStream, errorStream);
}
catch (Exception ex)
{
string error = ex.Message;
// We deal with bad signature later
if (!error.ToLowerInvariant().Contains("bad signature"))
{
MessageBox.Show(
error,
"GnuPG Error",
MessageBoxButtons.OK,
MessageBoxIcon.Error);
return;
}
}
}
using (StreamReader reader = new StreamReader(outputStream))
{
outputStream.Position = 0;
verifyResult = reader.ReadToEnd();
}
using (StreamReader reader = new StreamReader(errorStream))
{
errorStream.Position = 0;
errorResult = reader.ReadToEnd();
}
}
verifyResult = verifyResult.Replace(stdOutResult, string.Empty);
// Verify: status-fd
// stdOut: the message
// error: gpg error/status
if (verifyResult.Contains("BADMDC"))
{
errorResult = RemoveInvalidAka(errorResult.Replace("gpg: ", string.Empty));
MessageBox.Show(
errorResult,
"Invalid Encryption",
MessageBoxButtons.OK,
MessageBoxIcon.Error);
}
else if (verifyResult.Contains("GOODMDC"))
{
// Decrypted OK, check for validsig
if (verifyResult.Contains("BADSIG"))
{
errorResult = RemoveInvalidAka(errorResult.Replace("gpg: ", string.Empty));
MessageBox.Show(
errorResult,
"Invalid Signature",
MessageBoxButtons.OK,
MessageBoxIcon.Error);
}
else if (verifyResult.Contains("GOODSIG"))
{
errorResult = RemoveInvalidAka(errorResult.Replace("gpg: ", string.Empty));
MessageBox.Show(
errorResult,
"Valid Signature",
MessageBoxButtons.OK,
MessageBoxIcon.Information);
// Valid signature!
mailItem.Body = stdOutResult;
}
else
{
// No signature?
mailItem.Body = stdOutResult;
}
}
else
{
errorResult = RemoveInvalidAka(errorResult.Replace("gpg: ", string.Empty));
errorResult = errorResult.Replace("WARNING", Environment.NewLine + "WARNING");
DialogResult res = MessageBox.Show(
errorResult + Environment.NewLine + "Decrypt mail anyway?",
"Unknown Encryption",
MessageBoxButtons.OKCancel,
MessageBoxIcon.Exclamation);
if (res == DialogResult.OK)
mailItem.Body = stdOutResult;
}
}
