问题
I have located my smime.p7m
from my email message, I read it as stream and try to decrypt it using MimeKit, but it failed with Operation is not valid due to the current state of the object.
using (MemoryStream ms = new MemoryStream(data)) {
CryptographyContext.Register(typeof(WindowsSecureMimeContext));
ApplicationPkcs7Mime p7m = new ApplicationPkcs7Mime(SecureMimeType.EnvelopedData, ms);
var ctx = new WindowsSecureMimeContext(StoreLocation.CurrentUser);
p7m.Verify(ctx, out MimeEntity output);
}
Following the example on https://github.com/jstedfast/MimeKit doesn't help either. Anyone familiar with MimeKit could chime in?
EDIT:
After decrypting the p7m, am I supposed to use the MimeParser
to parse the content? I got the following from the decryption:
Content-Type: application/x-pkcs7-mime; name=smime.p7m; smime-type=signed-data
Content-Transfer-Encoding: base64
Content-Disposition: attachment; filename=smime.p7m
MIAGCSqGSIb3DQEHAqCAMIACAQExCzAJBgUrDgMCGgUAMIAGCSqGSIb3DQEHAaCAJIAEWUNvbnRl
bnQtVHlwZTogdGV4dC9wbGFpbjsNCgljaGFyc2V0PSJ1cy1hc2NpaSINCkNvbnRlbnQtVHJhbnNm
ZXItRW5jb2Rpbmc6IDdiaXQNCg0KdGVzdA0KAAAAAAAAoIImTTCCBaIwggOKoAMCAQICBguC3JQz
...more...
But when parsing with MimeParser
,
System.FormatException: Failed to parse message headers.
at MimeKit.MimeParser.ParseMessage(Byte* inbuf, CancellationToken cancellationToken)
at MimeKit.MimeParser.ParseMessage(CancellationToken cancellationToken)
UPDATE:
Ah, so it turns, calling Decrypt
only gives me the SignedData
, I need to then call Verify to pull the original data... this is kind of misleading, I thought Verify
would simply verify it... which is why I didn't bother calling it, since I don't really need to verify it... Perhaps it should be call Decode
instead? That's what I was trying to do originally, ((MimePart) signedData).Content.DecodeTo(...)
.
So in the end, I had to do something like this to extract the data.
CryptographyContext.Register(typeof(WindowsSecureMimeContext));
ApplicationPkcs7Mime p7m = new ApplicationPkcs7Mime(SecureMimeType.EnvelopedData, ms);
var ctx = new WindowsSecureMimeContext(StoreLocation.CurrentUser);
if (p7m != null && p7m.SecureMimeType == SecureMimeType.EnvelopedData)
{
// the top-level MIME part of the message is encrypted using S/MIME
p7m = p7m.Decrypt() as ApplicationPkcs7Mime;
}
if (p7m != null && p7m.SecureMimeType == SecureMimeType.SignedData)
{
p7m.Verify(out MimeEntity original); // THE REAL DECRYPTED DATA
using (MemoryStream dump = new MemoryStream())
{
original.WriteTo(dump);
decrypted = dump.GetBuffer();
}
}
回答1:
You are getting an InvalidOperationException because you are calling Verify() on a EncryptedData.
You need to call Decrypt().
Verify() is for SignedData.
来源:https://stackoverflow.com/questions/47894845/unable-to-decrypt-p7m-using-mimekit