Quoth Justus Winter on Jun 23 at 3:11 pm: > Hi, > > I recently had a problem replying to a mail written by Thomas Schwinge > using an oldish notmuch. Not sure if it has been fixed in more recent > versions, but I think notmuch could improve uppon its header > generation (see below). Problematic part of the mail: > > ~~~ snip ~~~ > [...] > To: someone@example.org, "line > break" <linebreak@example.org>, someoneelse@example.org > User-Agent: Notmuch/0.9-101-g81dad07 (http://notmuchmail.org) Emacs/23.4.1 (i486-pc-linux-gnu) > [...] > ~~~ snap ~~~ > > http://tools.ietf.org/html/rfc2822#section-2.2.3 says: > > Note: Though structured field bodies are defined in such a way that > folding can take place between many of the lexical tokens (and even > within some of the lexical tokens), folding SHOULD be limited to > placing the CRLF at higher-level syntactic breaks. For instance, if > a field body is defined as comma-separated values, it is recommended > that folding occur after the comma separating the structured items in > preference to other places where the field could be folded, even if > it is allowed elsewhere. > > So notmuch "rfc-SHOULD" place the newlines after the comma. > > The rfc goes on: > > The process of moving from this folded multiple-line representation > of a header field to its single line representation is called > "unfolding". Unfolding is accomplished by simply removing any CRLF > that is immediately followed by WSP. Each header field should be > treated in its unfolded form for further syntactic and semantic > evaluation. > > My interpretation is that unfolding simply removes any linebreaks > first, so the value does not contain any newlines. But pythons email > module discriminates quoted and unquoted parts of the value: > > ~~~ snip ~~~ > from __future__ import print_function > import email > from email.utils import getaddresses > > m = email.message_from_string('''To: "line > break" <linebreak@example.org>, line > break <linebreak@example.org>''') > print("m['To'] = ", m['To']) > print("getaddresses(m.get_all('To')) = ", getaddresses(m.get_all('To'))) > ~~~ snap ~~~ > > % python3 test.py > m['To'] = "line > break" <linebreak@example.org>, line > break <linebreak@example.org> > getaddresses(m.get_all('To')) = [('line\n break', 'linebreak@example.org'), ('line break', 'linebreak@example.org')] > > I believe that is what's preventing me from replying to the message > using alot without sanitizing the To header first. Not really sure who > is wrong or right here... any thoughts? There are at least two bugs here. Regardless of what we RFC-should do, that folding *is* permitted by RFC2822, since quoted strings can contain folding whitespace: http://tools.ietf.org/html/rfc2822#section-3.2.5 For completeness, the full derivation for this "To" header is: to = "To:" address-list CRLF address-list = (address *("," address)) / obs-addr-list address = mailbox / group mailbox = name-addr / addr-spec name-addr = [display-name] angle-addr display-name = phrase phrase = 1*word / obs-phrase word = atom / quoted-string quoted-string = [CFWS] DQUOTE *([FWS] qcontent) [FWS] DQUOTE [CFWS] Do you happen to know how the strangely folded "to" header was produced for this message? In notmuch-emacs, a user can put whatever they want in a message-mode buffer's headers and mm will dutifully pass it on to their MTA. We could validate it, but that's a slippery slope and I would hope that the MTA itself is validating it (and probably more thoroughly than we could). That said, the first bug here is in Python. As I mentioned above, foldable whitespace is allowed in quoted strings. In fact, though the standard is rather long-winded about whitespace, if you dig into the grammar, you'll find that *all whitespace can be folded* (except in the obsolete grammar, which allowed whitespace between the header name and the colon, which obviously can't be folded). I'm not sure what Python is doing, but I bet it's going to a lot of effort to mis-implement something very simple. There also appears to be a bug in the notmuch CLI's reply command where it omits addresses that were folded in the original message. I don't know if alot uses the CLI's reply command, so this may or may not be related to your specific issue. I haven't dug into this yet, other than to confirm that it's the CLI's fault and not notmuch-emacs's. > Justus