class Net::IMAP::BodyTypeAttachment

BodyTypeAttachment is not used and will be removed in an upcoming release.

Bug Analysis

IMAP body structures are parenthesized lists and assign their fields positionally, so missing fields change the intepretation of all following fields. Additionally, different body types have a different number of required fields, followed by optional “extension” fields.

BodyTypeAttachment was previously returned when a “message/rfc822” part, which should be sent as body-type-msg with ten required fields, was actually sent as a body-type-basic with seven required fields.

basic => type, subtype, param, id, desc, enc, octets, md5=nil,  dsp=nil, lang=nil, loc=nil, *ext
msg   => type, subtype, param, id, desc, enc, octets, envelope, body,    lines,    md5=nil, ...

Normally, envelope and md5 are incompatible, but Net::IMAP leniently allowed buggy servers to send NIL for envelope. As a result, when a server sent a message/rfc822 part with NIL for md5 and a non-NIL dsp, Net::IMAP mis-interpreted the Content-Disposition as if it were a strange body type. In all reported cases, the Content-Disposition was “attachment”, so BodyTypeAttachment was created as the workaround.

Current behavior

When interpreted strictly, envelope and md5 are incompatible. So the current parsing algorithm peeks ahead after it has recieved the seventh body field. If the next token is not the start of an envelope, we assume the server has incorrectly sent us a body-type-basic and return BodyTypeBasic. As a result, what was previously BodyTypeMessage#body => BodyTypeAttachment is now BodyTypeBasic#disposition => ContentDisposition.

Public Instance Methods

dsp_type → string click to toggle source

Returns the content disposition type, as defined by [DISPOSITION].

# File net-imap-, line 1093
media_type() click to toggle source
# File net-imap-, line 1079
      def media_type
        warn(<<~WARN, uplevel: 1)
          BodyTypeAttachment#media_type is obsolete.  Use dsp_type instead.
multipart?() click to toggle source
# File net-imap-, line 1107
def multipart?
  return false
param → hash click to toggle source

Returns a hash representing parameters of the Content-Disposition field, as defined by [DISPOSITION].

# File net-imap-, line 1100
subtype() click to toggle source

*invalid for BodyTypeAttachment*

# File net-imap-, line 1087
def subtype
  warn("BodyTypeAttachment#subtype is obsolete.\n", uplevel: 1)