[PATCH] Omit User-Agent: header by default

[Daniel Kahn Gillmor]

The User-Agent: header can be fun and interesting, but it also leaks
quite a bit of information about the user and their software stack.

This represents a potential security risk (attackers can target the
particular stack) and also an anonymity risk (a user trying to
preserve their anonymity by sending mail from a non-associated account
might reveal quite a lot of information if their choice of mail user
agent is exposed).

This change also avoids hiding the User-Agent header by default, so
that people who decide they want to send it will at least see it (and
can edit it if they want to) before sending.

It makes sense to have safer defaults.
---
 emacs/notmuch-mua.el | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/emacs/notmuch-mua.el b/emacs/notmuch-mua.el
index 1ca8056..f3a4e5a 100644
--- a/emacs/notmuch-mua.el
+++ b/emacs/notmuch-mua.el
@@ -62,7 +62,7 @@ disabled: this would result in an incorrect behavior."))
 		 (const :tag "Compose mail in a new window"  new-window)
 		 (const :tag "Compose mail in a new frame"   new-frame)))
 
-(defcustom notmuch-mua-user-agent-function 'notmuch-mua-user-agent-full
+(defcustom notmuch-mua-user-agent-function nil
   "Function used to generate a `User-Agent:' string. If this is
 `nil' then no `User-Agent:' will be generated."
   :type '(choice (const :tag "No user agent string" nil)
@@ -73,7 +73,7 @@ disabled: this would result in an incorrect behavior."))
 			   :value notmuch-mua-user-agent-full))
   :group 'notmuch-send)
 
-(defcustom notmuch-mua-hidden-headers '("^User-Agent:")
+(defcustom notmuch-mua-hidden-headers nil
   "Headers that are added to the `message-mode' hidden headers
 list."
   :type '(repeat string)
-- 
2.8.1