/// <summary>
/// Creates an S/MIME message using the supplied MimeBodyPart. The signature is generated using the private key
/// as supplied in the constructor. Our certificate, which is required to verify the signature is enclosed.
/// </summary>
/// <param name="mimeBodyPart"></param>
/// <param name="digestMethod"></param>
/// <returns></returns>
public MimeMessage CreateSignedMimeMessage(MimeMessage mimeBodyPart, SMimeDigestMethod digestMethod)
{
MimeMessage message = new MimeMessage();
using (var ctx = this.secContentFactory())
{
// Algorithm lookup
DigestAlgorithm algorithm;
if (digestMethod.Equals(SMimeDigestMethod.Sha1))
{
algorithm = DigestAlgorithm.Sha1;
}
else if (digestMethod.Equals(SMimeDigestMethod.Sha512))
{
algorithm = DigestAlgorithm.Sha512;
}
else
{
throw new NotSupportedException($"Algorithm {digestMethod.GetAlgorithm()} not supported");
}
// Signer identification
var cmsSigner = new CmsSigner(this.ourCertificate, this.privateKey)
{
DigestAlgorithm = algorithm
};
// Create and sign message
message.Body = MultipartSigned.Create(ctx, cmsSigner, mimeBodyPart.Body);
// Force signed content to be transferred in binary format
MimePart xml = (MimePart)message.BodyParts.First();
xml.ContentTransferEncoding = ContentEncoding.Binary;
}
// Remove unused headers
foreach (var header in message.Headers.Select(x => x.Id).ToList())
{
if (header != HeaderId.MessageId && header != HeaderId.MimeVersion && header != HeaderId.ContentType)
{
message.Headers.Remove(header);
}
}
return(message);
}
public MimeMessage CreateSignedMimeMessage(MimeEntity mimeBodyPart, SMimeDigestMethod digestMethod)
{
if (mimeBodyPart is MimePart)
{
((MimePart)mimeBodyPart).ContentTransferEncoding = ContentEncoding.Binary;
}
MultipartSigned multipart;
using (var ctx = this.secContentFactory())
{
// Algorithm lookup
DigestAlgorithm algorithm;
if (digestMethod.Equals(SMimeDigestMethod.Sha1))
{
algorithm = DigestAlgorithm.Sha1;
}
else if (digestMethod.Equals(SMimeDigestMethod.Sha512))
{
algorithm = DigestAlgorithm.Sha512;
}
else
{
throw new NotSupportedException($"Algorithm {digestMethod.GetAlgorithm()} not supported");
}
var micalg = ctx.GetDigestAlgorithmName(algorithm);
var signed = new MultipartSigned();
// set the protocol and micalg Content-Type parameters
signed.ContentType.Parameters["protocol"] = ctx.SignatureProtocol;
signed.ContentType.Parameters["micalg"] = micalg;
// add the modified/parsed entity as our first part
signed.Add(mimeBodyPart);
var cmsSigner = new CmsSigner(this.ourCertificate, this.privateKey)
{
DigestAlgorithm = algorithm
};
ApplicationPkcs7Signature signature;
using (var memory = new MemoryBlockStream())
{
// var prepared = Prepare(entity, memory);
mimeBodyPart.WriteTo(memory);
memory.Position = 0;
// sign the cleartext content
signature = ctx.Sign(cmsSigner, memory);
}
// add the detached signature as the second part
signed.Add(signature);
// Create and sign message
multipart = signed;
}
var message = new MimeMessage();
message.Body = multipart;
return(message);
}
