[exim-dev] [Bug 2171] Crash at DATA ACL string expansion.

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Author: admin
Date:  
To: exim-dev
Subject: [exim-dev] [Bug 2171] Crash at DATA ACL string expansion.
https://bugs.exim.org/show_bug.cgi?id=2171

--- Comment #8 from Heiko Schlittermann <hs@???> ---
(In reply to Heiko Schlittermann from comment #7)
> Created attachment 1043 [details]
> quick fix
>
> Try applying the attached quick fix. With this fix, Exim should issue a
> proper failure message in your reproducer.


${addresses:$h_from:} is really asking for trouble if $h_from: starts with '>'
as in From: >,"Hans" <hans@???>, <foo@???>

This changes the output from (the expected) hans@???:foo@???
to the (correct) hans@???,foo@???

While this is correct and according to the spec and may be the wanted behaviour
as in

${addresses:$acl_foo$h_from:}

(even I do not have a use case), we should consider

  (a) accepting the output separator setting (>[sep]) only from literal
      strings, not from expansion
OR
  (b) encourage the use of an explicitly given output separator as in
      ${addresses:>:$h_from:}
      if we do not control the value of the expanded argument
OR
  (c) provide some kind of (to be specified) sanitization


But:
(a) is an incompatible change and requires much more effort than (b)

(c) isn't specified enough (and I'm not sure if there can be a general
specification about what is ${quote_exim:…} like

It seems that we should update the doc about the potential danger and we
should strongly recommend using ${addresses:>:$h_from:}

--
Heiko

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