From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS31976 209.132.180.0/23 X-Spam-Status: No, score=-3.7 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,RCVD_IN_DNSWL_HI,RP_MATCHES_RCVD,T_DKIM_INVALID shortcircuit=no autolearn=ham autolearn_force=no version=3.4.0 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by dcvr.yhbt.net (Postfix) with ESMTP id 164EC2022D for ; Thu, 23 Feb 2017 16:52:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751320AbdBWQwo (ORCPT ); Thu, 23 Feb 2017 11:52:44 -0500 Received: from kitenet.net ([66.228.36.95]:33944 "EHLO kitenet.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751119AbdBWQwn (ORCPT ); Thu, 23 Feb 2017 11:52:43 -0500 X-Greylist: delayed 389 seconds by postgrey-1.27 at vger.kernel.org; Thu, 23 Feb 2017 11:52:43 EST X-Question: 42 DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=joeyh.name; s=mail; t=1487868372; bh=oQwLSpCbsNaFhIPDGiYNLoO0PCRl7hfFCt3GizIGtRQ=; h=Date:From:To:Subject:From; b=E0fhJWRntZw78fZ3X5xo8uZjh9aTFGu5Yq/vJF8sAVjkBIxoQz2uuR4KFfixv+PjC 6kabGRnRNzPS7n5R99WVZ9dePTm2RBD2DybZYJfHAkWtTr4dp+H0a2K/PmtY1a1vV/ F0hyLOtJfcWZ3QqnJdSEp/nZa+67yPbTQqGTkzq4= DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=joeyh.name; s=mail; t=1487868186; bh=oQwLSpCbsNaFhIPDGiYNLoO0PCRl7hfFCt3GizIGtRQ=; h=Date:From:To:Subject:From; b=eqe90P2w94P4JixsYVdqLU91BS5nCj7f+PqnwxcEV23mYh6gdoeSpe8hK8TWjNgb/ en1a7hhM4OY9eBVQYqpVHq99NNlClKkjSscMrdsIByVG1h6v6/urDOzsm4aBo7XTMI Os8JoeF20aYn+LWN30fQdyVTnDb/vEHpgl/uk76I= Date: Thu, 23 Feb 2017 12:43:06 -0400 From: Joey Hess To: git@vger.kernel.org Subject: SHA1 collisions found Message-ID: <20170223164306.spg2avxzukkggrpb@kitenet.net> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="2gtyzd63bduirdmw" Content-Disposition: inline User-Agent: NeoMutt/20161126 (1.7.1) Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org --2gtyzd63bduirdmw Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable https://shattered.io/static/shattered.pdf https://freedom-to-tinker.com/2017/02/23/rip-sha-1/ IIRC someone has been working on parameterizing git's SHA1 assumptions so a repository could eventually use a more secure hash. How far has that gotten? There are still many "40" constants in git.git HEAD. In the meantime, git commit -S, and checks that commits are signed, seems like the only way to mitigate against attacks such as the ones described in the threads at https://joeyh.name/blog/sha-1/ and https://joeyh.name/blog/entry/size_of_the_git_sha1_collision_attack_surface/ Since we now have collisions in valid PDF files, collisions in valid git commit and tree objects are probably able to be constructed. --=20 see shy jo --2gtyzd63bduirdmw Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEE6FpfY7MdJMHr8NgcyRDZIiUS48cFAlivERoACgkQyRDZIiUS 48eaoA//chGZEsK1QlW/tDMeG21rQ5Qz/RoI76UYwWLLouVqzeTxaxfYRgjj7QUG 6azLobp0zx0UmLwviJ4z+f+sYWbuM1z5Gucz2MwPSsaGWOjhs0FbxFwtS1Aldm6D bx6ZB6J5VdQAXO+Pxul2/0xu5aAoNIgjmw9bXzo7IdtAotreRLCoWE+VWuwjEoc4 RUm1/jgDf4NQAMRVMo7+EA02Lm2VXK9jJR5wjSOjneCqdUw8s8vWfDwSx5NDi0NE Hgwrx0f+dMrs43UUIHLlLXGT8suVuwvCCX2ujIwzPs2lmBHH7XPsZ+yynWVg8ZVZ YwH9esVOAR+q8JiYoHOFb/okHPgbiboMYBUXJiE4vYg4KbVRvVQVYQF1p8OLk3/r 046oWrBQFofxABRXvSdQbah9OL5M1TW3n40eIozTnS+s6Hw2cdU44EGw5PLkSHb2 oSgHiC7GQe/L0fpC2NUO/ut8QNv7nKDJKp0CzYdvQUpigszMvfJumy64qEPK8IoS Rx8AuaSt6FzBZkaNhHTbouA/iO9IiIdsz4hMuQsffE9zdbqzaSAvKQwquA9zaTFA dz1gLh1If6m/+8H8b1z4icgz+CWHcEkOX9/+eRISiBX/DqH2XoqtPpiOeXpGDAmW C99uDdQcyWpE0kZ1VHLwiv92ZYw8SkEo7Sk8cjYgGGOO1Sk+uGw= =R1UC -----END PGP SIGNATURE----- --2gtyzd63bduirdmw--