Exceptions in Disposition during folder listing

[breedbekkikker]

Hi,

The following exception occurs when listing a folder:

Exception: Illegal characters in disposition value.
Parameter name: value

The IMAP protocol logging:

C: B00000020 FETCH 1:* (UID FLAGS INTERNALDATE RFC822.SIZE ENVELOPE BODYSTRUCTURE)
S: * 1 FETCH (UID 3 FLAGS (\Seen) INTERNALDATE " 6-Apr-2017 10:50:20 +0200" RFC822.SIZE 1315 ENVELOPE ("Thu, 6 Apr 2017 10:50:20 +0200" "test" ((NIL NIL "test" "acme.com")) ((NIL NIL "test" "acme.com")) ((NIL NIL "test" "acme.com")) NIL NIL NIL NIL "<58B634343442A1@acme.com>") BODYSTRUCTURE (((("TEXT" "PLAIN" NIL NIL NIL "7bit" 3 1) "ALTERNATIVE" ("boundary" "==boundary-2"))("IMAGE" "GIF" ("name" "image1.gif") "<PHP-image-1>" NIL "base64" 6 NIL ({8}
S: "inline" NIL)) "RELATED" ("boundary" "==boundary-3")) "MIXED" ("boundary" "==boundary-1")))

The original mail contains the following MIME part headers:

--==boundary-3
Content-type: image/gif; name="image1.gif"
Content-Transfer-Encoding: base64
Content-ID: <PHP-image-1>
Content-Disposition: "inline"

Another exception occurring is:

Exception: The disposition is not allowed to be empty.
Parameter name: value

The IMAP protocol logging:

C: M00000020 FETCH 1:* (UID FLAGS INTERNALDATE RFC822.SIZE ENVELOPE BODYSTRUCTURE)
S: * 1 FETCH (UID 5 FLAGS (\Seen) INTERNALDATE " 6-Apr-2017 10:59:05 +0200" RFC822.SIZE 1300 ENVELOPE ("Thu, 6 Apr 2017 10:59:05 +0200" "test" ((NIL NIL "test" "acme.com")) ((NIL NIL "test" "acme.com")) ((NIL NIL "test" "acme.com")) NIL NIL NIL NIL "<58B634343442A2@acme.com>") BODYSTRUCTURE (((("TEXT" "PLAIN" NIL NIL NIL "7bit" 0 0) "ALTERNATIVE" ("boundary" "==boundary-2"))("APPLICATION" "PDF" ("name" "file.pdf") NIL NIL "base64" 6 NIL ("" ("filename" "file.pdf"))) "RELATED" ("boundary" "==boundary-3")) "MIXED" ("boundary" "==boundary-1")))

The original mail contains the following MIME part headers:

--==boundary-3
Content-Type: application/pdf; name="file.pdf"
Content-Transfer-Encoding: base64
Content-Disposition: ; filename="file.pdf"

Is there are a solution possible for these invalid disposition headers within MailKit/MimeKit?

Thanks!

[jstedfast]

As far as I can tell, this can't happen unless you ToString() the MessageSummary and then parse it back? From what I can tell, these exceptions must be coming from BodyPart.TryParse()?

[jstedfast]

Added 2 work-arounds for these in the ContentDisposition parser in MimeKit, but that's not where you were getting these exceptions from...

[breedbekkikker]

Here's where the exception occurs:

public async Task<IEnumerable<IMessageSummary>> GetMessageSummaryForAllMessagesAsync(IMailFolder mailFolder)
{
   try
   {
      await mailFolder.OpenAsync(FolderAccess.ReadOnly);
      IEnumerable<IMessageSummary> messageSummaries = await mailFolder.FetchAsync(0, -1, SummaryItems);

      return messageSummaries;
   }
   catch (Exception exception)
   {
      throw new Exception("Retrieving MessageSummaries failed", exception);
   }
}

MessageSummaries:

private const MessageSummaryItems SummaryItems = MessageSummaryItems.BodyStructure |
                                                       MessageSummaryItems.InternalDate |
                                                       MessageSummaryItems.Envelope |
                                                       MessageSummaryItems.Flags |
                                                       MessageSummaryItems.MessageSize |
                                                       MessageSummaryItems.UniqueId;

[jstedfast]

Can you provide a stack trace? I get that it's happening there, but I need more specifics because I don't see how it's possible to hit those particular exceptions.

The problem is, the only way to hit both of those exceptions are:

new ContentDisposition ("\"inline\"");

or

disposition.Disposition = "\"inline\"";

The problem is that neither of those occur anywhere in ImapUtils.cs where the ContentDisposition is "parsed" from the IMAP FETCH response.

Instead, what that code does is construct a string from the response and then calls ContentDisposition.TryParse() which sets the disposition member variable directly instead of via the Disposition property which is where the validation occurs.

The only place I can find in both MimeKit and MailKit that could emit these exceptions is in the BodyPart.TryParse() method which is never used within MailKit, but is there for consumers to use if they serialize the IMessageSummary.Body and then parse it back.

[jstedfast]

Wait, never mind... I found where ImapUtils.cs calls new ContentDisposition (str)

[jstedfast]

ok, fixed now :)

[jstedfast]

On the plus side, I also added similar work-arounds to MimeKit's parser... (not that it would throw exceptions before, but the MimePart.ContentDisposition would be null before due to being unable to parse those cases - now it'll work around them and try to provide at least something).

[breedbekkikker]

Perfect! Thanks a lot!

[jstedfast]

MimeKit & MailKit 1.14 have been released with this fix.