Re: privacy problem: text/html parts pull in network resources

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+From: Tomi Ollila <tomi.ollila@iki.fi>\r
+To: Daniel Kahn Gillmor <dkg@fifthhorseman.net>,\r
+       notmuch mailing list <notmuch@notmuchmail.org>\r
+Subject: Re: privacy problem: text/html parts pull in network resources\r
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+References: <87ppa7q25w.fsf@alice.fifthhorseman.net>\r
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+Date: Thu, 22 Jan 2015 09:25:39 +0200\r
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+\r
+On Wed, Jan 21 2015, Daniel Kahn Gillmor <dkg@fifthhorseman.net> wrote:\r
+\r
+> If i send a message with a text/html part (either it's only text/html,\r
+> or all parts are rendered, or it's multipart/alternative with only a\r
+> text/html subpart) and that HTML has <img\r
+> src="http://example.org/test.png"/> in it, then notmuch will make a\r
+> network request for that image.\r
+\r
+I noticed the same a few days ago and first test to avoid that was \r
+\r
+(defun open-network-stream (&rest) nil)\r
+\r
+(but then I tried to send email and that failed ;/)\r
+\r
+next was M-x debug-on-entry RER open-network-stream RET\r
+\r
+... but I don,t remember how to manipulate how that continues.\r
+\r
+Latest I've been thinking defadvice around open-network-stream which\r
+asks whether to proceed to it or just return nil.\r
+\r
+I'd like to have buffer-local defadvices... ;) .. but there one could\r
+probably store original open-network-stream location and then flet (or\r
+was it letf) it there...\r
+\r
+Anyway, if there is better, more robust alternative I am (also) very\r
+interested of it...\r
+\r
+Tomi\r
+\r
+\r
+>\r
+> This is a privacy disaster, because it enables an e-mail sender to use\r
+> "web bugs" to tell when a given notmuch user has opened their e-mail.\r
+>\r
+> It's also a bit of a consistency/storage/indexing disaster because it\r
+> means that what you see when you open a given message will change\r
+> depending on the network environment you're in when you open it.\r
+>\r
+> It's also potentially a security problem because it means that anyone in\r
+> control of the remote server (or the network between you and the remote\r
+> server if the image isn't sourced over https) can feed arbitrary data\r
+> into whatever emacs image rendering library is being used.  (granted,\r
+> this is not a unique problem because this can already be done by the\r
+> original message sender with a multipart/mixed message, but it's an\r
+> additional exposure of attack surface)\r
+>\r
+> I just raised this on #notmuch, and i don't have the time or the\r
+> knowledge to look into it now, but i think the defaults here need to be\r
+> to avoid network access entirely unless the user explicitly requests it.\r
+>\r
+>    --dkg\r
+> _______________________________________________\r
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