bug#45711: 27.1; Ambiguous account match in .authinfo still used by smtpmail

[Duncan Bayne]

Ted Zlatanov writes:

> On Thu, 07 Jan 2021 23:12:09 +1100 Duncan Bayne <duncan@bayne.id.au> wrote:
>
> DB> I think the correct behaviour here would be to have smtpmail to refuse
> DB> to send if there's an ambiguous account match in .authinfo.  I can't
> DB> off-hand think of a single case where I'd *want* it to just take the
> DB> first matching account where there are several possibilities.
>
> I think it's common to have more specific matches on top, and less
> specific matches down the list. That's why returning the first one makes
> sense, and potentially there's always an ambiguous entry. It would break
> such setups to do what you're suggesting.

To be clear here I meant smtpmail as 'it'.

I think it's the right thing for auth-source-search to return a list of
matches, but I think it's a bug for smtpmail-try-auth-methods to just
quietly use the first match in that case.

The code in question is in smtpmail.el:510 ...

(defun smtpmail-try-auth-methods (process supported-extensions host port
                                  &optional ask-for-password)
         ;; snip
         (auth-info (car
                     (auth-source-search
                      :host host
                      :port port
                      :user smtpmail-smtp-user
                      :max 1
                      :require (and ask-for-password
                                    '(:user :secret))
                      :create ask-for-password)))

What it seems to be doing with (car (... :max 1) is to simply take the
first match and use that.

What I *think* it should do is either a) error out in the case of an
ambiguous match, or b) prompt the use to ask which of the various
matches it should use.

Meta: this is my first Emacs bug report, and I'm planning to write a
patch to address it.  Not sure whether the discussion of whether it's a
bug, and if so, what the appropriate fix is, belongs here or on the
emacs-devel list.  Happy to take the conversation there if that's
protocol.

--
Duncan Bayne
+61 420 817 082 | https://duncan.bayne.id.au/

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