From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: * X-Spam-Status: No, score=1.2 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, FSL_HELO_FAKE,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id B48CBC76186 for ; Mon, 29 Jul 2019 20:46:40 +0000 (UTC) Received: from lists.sourceforge.net (lists.sourceforge.net [216.105.38.7]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 7EE8E206A2; Mon, 29 Jul 2019 20:46:40 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=sourceforge.net header.i=@sourceforge.net header.b="iijxRG4v"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=sf.net header.i=@sf.net header.b="m+gaAHcH"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="K79oGysD" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7EE8E206A2 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=linux-f2fs-devel-bounces@lists.sourceforge.net Received: from [127.0.0.1] (helo=sfs-ml-2.v29.lw.sourceforge.com) by sfs-ml-2.v29.lw.sourceforge.com with esmtp (Exim 4.90_1) (envelope-from ) id 1hsCXX-0004zu-SH; Mon, 29 Jul 2019 20:46:39 +0000 Received: from [172.30.20.202] (helo=mx.sourceforge.net) by sfs-ml-2.v29.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) (envelope-from ) id 1hsCXV-0004zl-8f for linux-f2fs-devel@lists.sourceforge.net; Mon, 29 Jul 2019 20:46:37 +0000 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sourceforge.net; s=x; h=In-Reply-To:Content-Type:MIME-Version:References: Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To:Content-Transfer-Encoding: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help:List-Unsubscribe: List-Subscribe:List-Post:List-Owner:List-Archive; bh=pf5AMvh1xxgs/Bq5LKamHgjq2spjhAoE1QhEizd9KJc=; b=iijxRG4vBXmyp8aPN8dy3b9rpD mMd8rG4KcsN5Uan9Fov+pu4deQh/364UoPwaJxMbvjXcEAllxh828xm4SDF0YzdyX4GS1pEE0syZ7 vvROYbQQkvlK6sVr3rnJwM3toVnvS5wXaMjV5c9JYvX686Fb3WJMNmBAQmoezye86KMo=; DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=sf.net; s=x ; h=In-Reply-To:Content-Type:MIME-Version:References:Message-ID:Subject:Cc:To :From:Date:Sender:Reply-To:Content-Transfer-Encoding:Content-ID: Content-Description:Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc :Resent-Message-ID:List-Id:List-Help:List-Unsubscribe:List-Subscribe: List-Post:List-Owner:List-Archive; bh=pf5AMvh1xxgs/Bq5LKamHgjq2spjhAoE1QhEizd9KJc=; b=m+gaAHcHdgqY+Vap/LHeDeNdGl Zq9AL0PLUQq/oQtXf6kNtzWLjgJpsFMU4NqYg1ZQ8LgSwGagaQgOFcqbPBlOb6w4zjJzhYb/+R3zP UeRkrXxPNwP4oiaRS74y0U7bjZvUWCSsy426+OCC94FKfMUN68wJbXx+sp5iYIrSnvgA=; Received: from mail.kernel.org ([198.145.29.99]) by sfi-mx-4.v28.lw.sourceforge.com with esmtps (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.90_1) id 1hsCXU-003hzu-3k for linux-f2fs-devel@lists.sourceforge.net; Mon, 29 Jul 2019 20:46:37 +0000 Received: from gmail.com (unknown [104.132.1.77]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 2D6B0206A2; Mon, 29 Jul 2019 20:46:30 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1564433190; bh=DNMh2YRc0dQISTUq/gkVxZiJ3MfUwE+LBvvMLd0sx0w=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=K79oGysDbp1R9KcVqj1mKpfGB23D0dx9KzJwL1URFJI/8PotFaTXB1QXv/9jPmJ5e cd4dzd2ixOf8QsiHSDEd5r1iJBny2qYoC0vd1z0wpsTIbfCpr52p94FTMkHI78oJ2t NisulN2mchZN4cYXAX27Nu925MXHkVW50WusaYRo= Date: Mon, 29 Jul 2019 13:46:28 -0700 From: Eric Biggers To: "Theodore Y. Ts'o" Message-ID: <20190729204627.GH169027@gmail.com> Mail-Followup-To: "Theodore Y. Ts'o" , linux-fscrypt@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-mtd@lists.infradead.org, linux-api@vger.kernel.org, linux-crypto@vger.kernel.org, keyrings@vger.kernel.org, Paul Crowley , Satya Tangirala References: <20190726224141.14044-1-ebiggers@kernel.org> <20190726224141.14044-11-ebiggers@kernel.org> <20190728211730.GK6088@mit.edu> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190728211730.GK6088@mit.edu> User-Agent: Mutt/1.10.1 (2018-07-13) X-Headers-End: 1hsCXU-003hzu-3k Subject: Re: [f2fs-dev] [PATCH v7 10/16] fscrypt: v2 encryption policy support X-BeenThere: linux-f2fs-devel@lists.sourceforge.net X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Satya Tangirala , linux-api@vger.kernel.org, linux-f2fs-devel@lists.sourceforge.net, linux-fscrypt@vger.kernel.org, keyrings@vger.kernel.org, linux-mtd@lists.infradead.org, linux-crypto@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-ext4@vger.kernel.org, Paul Crowley Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: linux-f2fs-devel-bounces@lists.sourceforge.net On Sun, Jul 28, 2019 at 05:17:30PM -0400, Theodore Y. Ts'o wrote: > On Fri, Jul 26, 2019 at 03:41:35PM -0700, Eric Biggers wrote: > > @@ -319,6 +329,31 @@ int fscrypt_ioctl_add_key(struct file *filp, void __user *_uarg) > > if (!capable(CAP_SYS_ADMIN)) > > goto out_wipe_secret; > > > > + if (arg.key_spec.type != FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR) { > > This should be "== FSCRYPT_KEY_SPEC_TYPE_INDENTIFIER" instead. That's > because you use the identifier part of the union: > > > + /* Calculate the key identifier and return it to userspace. */ > > + err = fscrypt_hkdf_expand(&secret.hkdf, > > + HKDF_CONTEXT_KEY_IDENTIFIER, > > + NULL, 0, arg.key_spec.u.identifier, > > If we ever add a new key specifier type, and alternative in the union, > this is going to come back to bite us. Well, I did it this way because the next patch changes the code to: if (arg.key_spec.type == FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR) { ... } else { ... } We already validated that it's either TYPE_DESCRIPTOR or TYPE_IDENTIFIER. But I guess to be more clear I'll just make it handle the default case again. switch (arg.key_spec.type) { case FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR: ... break; case FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER: ... break; default: err = -EINVAL; break; } > > > + if (policy->version == FSCRYPT_POLICY_V1) { > > + /* > > + * The original encryption policy version provided no way of > > + * verifying that the correct master key was supplied, which was > > + * insecure in scenarios where multiple users have access to the > > + * same encrypted files (even just read-only access). > > Which scenario do you have in mind? With read-only access, Alice can > fetch the encryption policy for a directory, and introduce a key with > the same descriptor, but the "wrong" key, but that's only going to > affect Alice's use of the key. It won't affect what key is used by > Bob, since Alice doesn't have write access to Bob's keyrings. > > If what you mean is the risk when there is a single global > filesystem-specific keyring, where Alice could introduce a "wrong" key > identified with a specific descriptor, then sure, Alice could trick > Bob into encrypting his data with the wrong key (one known to Alice). > But we don't allow keys usable by V1 policies to be used in the > filesystem-specific keyring, do we? > The scenario is that Alice lists the directory with the wrong key, then Bob lists the directory too and gets the wrong filenames. This happens because the inode, fscrypt_info, dentry cache, page cache, etc. are the same for everyone. Bob's key is never looked up because the inode already has a key cached. This also applies to regular files and symlinks. - Eric _______________________________________________ Linux-f2fs-devel mailing list Linux-f2fs-devel@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel