/// <summary>
/// Signs the given mail item using the provided signer. The mailItem object will be updated so that it includes the signature.
/// </summary>
/// <param name="domainSigner">The domain and its signer</param>
/// <param name="mailItem">The mail item to sign</param>
/// <returns></returns>
public void SignMessage(DomainElementSigner domainSigner, MailItem mailItem)
{
using (Stream stream = mailItem.GetMimeReadStream())
{
stream.Seek(0, SeekOrigin.Begin);
Logger.LogDebug("Parsing the MimeMessage");
MimeMessage message = MimeMessage.Load(stream, true);
Logger.LogDebug("Signing the message");
lock (settingsMutex)
{
message.Sign(domainSigner.Signer, eligibleHeaders, headerCanonicalization, bodyCanonicalization);
}
var value = message.Headers[HeaderId.DkimSignature];
Logger.LogDebug("Got signing header: " + value);
// we first need to create a memory stream, because if WriteTo is called with mailItem Stream directly, it throws an exception somehow.
MemoryStream memoryOutputStream = new MemoryStream();
message.WriteTo(FormatOptions.Default, memoryOutputStream);
memoryOutputStream.Seek(0, SeekOrigin.Begin);
using (Stream outputStream = mailItem.GetMimeWriteStream())
{
memoryOutputStream.WriteTo(outputStream);
outputStream.Close();
}
stream.Close();
}
}
/// <summary>
/// Signs the given mail item using the provided signer. The mailItem object will be updated so that it includes the signature.
/// </summary>
/// <param name="domainSigner">The domain and its signer</param>
/// <param name="mailItem">The mail item to sign</param>
/// <returns></returns>
public void SignMessage(DomainElementSigner domainSigner, MailItem mailItem)
{
// MailItem.GetMimeWriteStream() internally uses
// Microsoft.Exchange.Data.Mime.MimeDocument.GetLoadStream(), which may reformat the
// message using different formatting than is originally read from
// MailItem.GetMimeReadStream(). To prevent these formatting changes from invalidating
// the DKIM signature, we must read then write then re-read the message to ensure that
// any formatting changes are made before we sign the message.
using (MemoryStream memStream = new MemoryStream())
{
using (Stream inputStream = mailItem.GetMimeReadStream())
{
inputStream.Seek(0, SeekOrigin.Begin);
#if EX_2007_SP3 || EX_2010 || EX_2010_SP1 || EX_2010_SP2 || EX_2010_SP3
byte[] buffer = new byte[16 * 1024];
int size;
while ((size = inputStream.Read(buffer, 0, buffer.Length)) > 0)
{
memStream.Write(buffer, 0, size);
}
#else
inputStream.CopyTo(memStream);
#endif
}
memStream.Seek(0, SeekOrigin.Begin);
using (Stream outputStream = mailItem.GetMimeWriteStream())
{
memStream.WriteTo(outputStream);
}
}
using (Stream inputStream = mailItem.GetMimeReadStream())
{
inputStream.Seek(0, SeekOrigin.Begin);
Logger.LogDebug("Parsing the MimeMessage");
MimeMessage message = MimeMessage.Load(inputStream, true);
// 'inputStream' cannot be disposed until we are done with 'message'
Logger.LogDebug("Signing the message");
lock (settingsMutex)
{
message.Sign(domainSigner.Signer, eligibleHeaders, headerCanonicalization, bodyCanonicalization);
}
var value = message.Headers[HeaderId.DkimSignature];
Logger.LogDebug("Got signing header: " + value);
// The Stream returned by mailItem.GetMimeWriteStream() will throw an exception if
// Stream.Write() is called after Stream.Flush() has been called, but
// MimeMessage.WriteTo(FormatOptions, Stream) may call Stream.Flush() before the full
// message has been written. To avoid exceptions we must buffer the message in a
// MemoryStream.
using (MemoryStream memStream = new MemoryStream())
{
message.WriteTo(FormatOptions.Default, memStream);
memStream.Seek(0, SeekOrigin.Begin);
using (Stream outputStream = mailItem.GetMimeWriteStream())
{
memStream.WriteTo(outputStream);
}
}
}
}
