BUG: emacs: fcc duplicates messages with variant bodies due to mml security
Daniel Kahn Gillmor
dkg at fifthhorseman.net
Sun Oct 22 16:28:12 PDT 2017
I'm concerned that notmuch-emacs is causing variant messages of
encrypted/signed messages to be generated.
In particular, if notmuch-fcc-dirs is not nil, two variants of the
message bodies will be created: one will be sent through "notmuch
insert" and the other will be sent to sendmail.
the mml security modes (e.g. "#secure method=pgpmime mode=sign" (in
angle brackets)) take place after this bifurcation.
The result for a signed message is:
* the message sent to "notmuch insert" has one cryptographic signature
* the message sent to sendmail has a different cryptographic
signature, in particular if it is made more than 1 second later
(some signature algorithms will produce identical signatures if made
in the same second)
You can try this out by:
0) put ignore-cache-for-signing in ~/.gnupg/gpg-agent.conf
1) run "gpgconf --kill gpg-agent" to ensure the config is re-read
2) send yourself a signed message with message-id $mid.
3) Pull it back in however you receive mail, and then:
diff -u $(notmuch search --output=files "id:$mid")
If the messages were more than 1 second apart, you'll see the signature
part differs.
The result for an encrypted message is:
* the message sent to "notmuch insert" is encrypted with one session
key
* the message sent to sendmail is encrypted with a different session key
So the entire body of the message will be different.
I'm currently working around this by setting notmuch-fcc-dirs to nil,
and setting message-send-mail-hook to (dkg-notmuch-fcc), which is defined
as:
(defun dkg-notmuch-fcc ()
(shell-command-on-region (point-min) (point-max) "notmuch insert"))
this takes advantage of message-send-mail-hook's late-send. as the
documentation for that var says:
This hook is run very late -- just before the message is sent as
mail.
But this isn't something normal users should need to do manually.
Any emacs gurus want to propose a way to improve the situation? i'm at
a bit of a loss.
--dkg
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