[PATCH] emacs: sign/encrypt replies to signed/encrypted messages

[Jameson Graef Rollins]

On Sat, Apr 05 2014, Jani Nikula <jani at nikula.org> wrote:
> This is a simple approach to improving security when replying to
> signed or encrypted messages. If the message being replied to was
> signed, add mml tag to sign the reply. If the message being replied to
> was encrypted, add mml tag to sign and encrypt the reply.

Jani, thank you so much for this patch!  This is really great, and I
very much appreciate your work on it.

I've tested it and so far it does exactly as advertised: replys to
encrypted messages automatically get the correct mml tags to encrypt the
reply.  I sign all messages by default, and it doesn't seem to interact
adversely with that configuration afaict.

> This may need configuration; I for one might want to encrypt replies
> to encrypted messages, but not always sign replies to signed messages.
>
> This still includes a slight bug: if any mml tags are added, they are
> included in the region containing the quoted parts. Killing the region
> will kill the mml tags too.

Both of these issues seem pretty minor to me.  It certainly gets my vote
to push without these additional features (especially considering the
security benefits).

I just have one comment below:

> diff --git a/emacs/notmuch-mua.el b/emacs/notmuch-mua.el
> index ba3ef275ec5e..9fb84b57b030 100644
> --- a/emacs/notmuch-mua.el
> +++ b/emacs/notmuch-mua.el
> @@ -224,7 +233,10 @@ list."
>  	(set-mark (point))
>  	(goto-char start)
>  	;; Quote the original message according to the user's configured style.
> -	(message-cite-original))))
> +	(message-cite-original)))
> +
> +    ;; Sign and/or encrypt replies to signed and/or encrypted messages.
> +    (notmuch-mua-reply-crypto (plist-get original :body)))

Maybe we should check to see if crypto processing is activated before
adding this additional crypto handling.  I would have guessed we might
want something like this instead:

    (when notmuch-show-process-crypto
      (notmuch-mua-reply-crypto (plist-get original :body))))

However, for some reason I can't get this to work.  It looks like
notmuch-show-process-crypto keeps evaluating to false in this context,
regardless of whether crypto processing has been engaged.  I'm unclear
why.  Anyone know see how notmuch-show-process-crypto would evaluate to
false here, even when it evaluates to true earlier in the same
notmuch-mua-reply call?

jamie.
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