From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Gregory Heytings Newsgroups: gmane.emacs.devel Subject: Re: Unicode confusables and reordering characters considered harmful Date: Wed, 03 Nov 2021 00:28:54 +0000 Message-ID: <11d5fecb44af1d388b7f@heytings.org> References: <875ytag0hb.fsf@yahoo.com> <87zgqmd5np.fsf@mat.ucm.es> <83wnlqk3rn.fsf@gnu.org> <72dd5c2a-42c7-b12e-05ed-e93adbd89727@gmail.com> <83ilxajyhw.fsf@gnu.org> <83fssejxf8.fsf@gnu.org> <835ytajsv2.fsf@gnu.org> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="Hsj9KhKqEa" Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="14753"; mail-complaints-to="usenet@ciao.gmane.io" Cc: Eli Zaretskii , Stefan Kangas , cpitclaudel@gmail.com, emacs-devel@gnu.org To: Stefan Monnier Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Wed Nov 03 01:30:10 2021 Return-path: Envelope-to: ged-emacs-devel@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1mi4AL-0003gY-P5 for ged-emacs-devel@m.gmane-mx.org; Wed, 03 Nov 2021 01:30:09 +0100 Original-Received: from localhost ([::1]:56176 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mi4AK-0004OC-AZ for ged-emacs-devel@m.gmane-mx.org; Tue, 02 Nov 2021 20:30:08 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:36832) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mi49I-0003ht-K3 for emacs-devel@gnu.org; Tue, 02 Nov 2021 20:29:04 -0400 Original-Received: from heytings.org ([95.142.160.155]:50360) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mi49E-0004FZ-Gi; Tue, 02 Nov 2021 20:29:02 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=heytings.org; s=20210101; t=1635899334; bh=Hwy9WH19hh63JBQYResawiZ+RkAByAj6w0NRl4IfXvI=; h=Date:From:To:cc:Subject:In-Reply-To:Message-ID:References:From; b=W7gJFVewAkqIpcoHiPG3drzT1jAGRjkIeYizZ3iXQogySrSaMK7hAzxm7loHNPdkO EjC2xdw8uge56lyAmzfXOWjYUWSxIVUsO/gcOcC+X5ud7gzZgJdIuVnnxZHYNeFaVZ gJKo4/7RgydOkb59Cb6UrSbIMBz2xYaJ6CmSXgkJqCbKpgOT3E/UeJ7C2BvA2BGNHc 8J7IIcdAAZGJYwxYfeoXUsbnKJVOey0cip7SAP0woaDZgM1BagyXs7z7qE6r2jo9Lm VE00rHl+dAuAIXZpHeKeK2sWo69fYukuo0yIYFip0tyiI7bf4IcSs22hhr2sKIWaG/ EQLmJB7nue9UQ== In-Reply-To: Content-ID: <11d5fecb44ff232092af@heytings.org> Received-SPF: pass client-ip=95.142.160.155; envelope-from=gregory@heytings.org; helo=heytings.org X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.io gmane.emacs.devel:278549 Archived-At: --Hsj9KhKqEa Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable Content-ID: <11d5fecb44b4ec7d7e7e@heytings.org> > > But that's the core of the vulnerability: if you just look at the screen= =20 > (and just scroll through it) you will have an incorrect understanding of= =20 > what the code does. > > It's good that such bidi override chars are displayed as a thin space,=20 > but it's mostly useful to make it possible to edit them (or to `C-x =3D`= =20 > on them), but I don't think it makes a significant different in terms of= =20 > the security issues introduced by the presence of those chars in the=20 > code. > Given that the vulnerability is limited to source code, in which AFAIU=20 there's no legitimate use of such characters, would the following not be=20 enough? (defun make-bidi-reordering-characters-apparent () (setq buffer-display-table (make-display-table)) (aset buffer-display-table ?=E2=80=AA [?=E2=AD=A4]) (aset buffer-display-table ?=E2=80=AB [?=E2=AD=A4]) (aset buffer-display-table ?=E2=80=AD [?=E2=AD=A4]) (aset buffer-display-table ?=E2=80=AE [?=E2=AD=A4]) (aset buffer-display-table ?=E2=81=A6 [?=E2=AD=A4]) (aset buffer-display-table ?=E2=81=A7 [?=E2=AD=A4]) (aset buffer-display-table ?=E2=81=A8 [?=E2=AD=A4]) (aset buffer-display-table ?=E2=80=AC [?=E2=AD=A4]) (aset buffer-display-table ?=E2=81=A9 [?=E2=AD=A4]) (font-lock-add-keywords nil '(("=E2=AD=A4" . 'font-lock-warning-face)))) (add-hook 'prog-mode-hook #'make-bidi-reordering-characters-apparent) --Hsj9KhKqEa--