Forum: Ruby-core SMTP does not properly dot-stuff an unterminated last line

Fab2e0c720d6e979a551782631dca58e?d=identicon&s=25 unknown (Guest)
on 2014-03-13 22:08
(Received via mailing list)
Issue #9627 has been updated by Josh Goebel.

If I'm understanding this properly I think this monkey-patch is all it
takes to fix it:

module Net
  class InternetMessageIO

    def using_each_crlf_line
      @wbuf = ''
      if not @wbuf.empty?   # unterminated last line
        write0 dot_stuff(@wbuf.chomp) + "\r\n"
      elsif @written_bytes == 0   # empty src
        write0 "\r\n"
      write0 ".\r\n"
      @wbuf = nil

    def dot_stuff(s)
      s.sub(/\A\./, '..')


You simply have to dot-stuff the remaining buffer if necessary...

Bug #9627: SMTP does not properly dot-stuff an unterminated last line

* Author: Josh Goebel
* Status: Open
* Priority: Normal
* Assignee:
* Category: lib
* Target version:
* ruby -v: ruby 1.9.3p448 (2013-06-27 revision 41675) [x86_64-linux]
* Backport: 1.9.3: UNKNOWN, 2.0.0: UNKNOWN, 2.1: UNKNOWN
str = "Date: Wed, 12 Mar 2014 16:02:26 -0400\r\nFrom:\r\nTo:\r\nMessage-ID:
1.0\r\nContent-Type: text/plain;\r\n
charset=UTF-8\r\nContent-Transfer-Encoding: 7bit\r\n\r\nlook, a period
with no endline\r\n."

      smtp =
      smtp.start(...) do |smtp_obj|
        response = smtp_obj.sendmail(message,

The SMTP server is going to throw a 400 or 500 error (depending on it's
configuration) because the last period is send un-stuffed in the DATA

look, a period with no endline

When it should be:

look, a period with no end line


(ie, not dot-stuffed) and the second period the SMTP server doesn't know
what to do with.  Adding an additional new-line fixes the problem, but I
the in-line documentation for SMTP send_message does not say anything
about a new-line being requires for message sending to work.

Sorry, I can't test against the latest Ruby right now, but this is
confirmed against 1.9.3 r448.  If someone can confirm against newer that
would be great.

I did do a search for "SMTP" and did not see this reported anywhere in
the Issues database.

I had originally filed a pull request against Mail:
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