From patchwork Wed Sep 28 16:08:27 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Brauner X-Patchwork-Id: 12992502 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id F0C16C6FA92 for ; Wed, 28 Sep 2022 16:13:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234299AbiI1QNg (ORCPT ); Wed, 28 Sep 2022 12:13:36 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57746 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234550AbiI1QNb (ORCPT ); Wed, 28 Sep 2022 12:13:31 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7145B97528; Wed, 28 Sep 2022 09:13:27 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 198CDB820FA; Wed, 28 Sep 2022 16:13:25 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 96668C43470; Wed, 28 Sep 2022 16:13:21 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1664381603; bh=b3gB2/tZ/ar0HvnCiBSOOYD4rc846nc+lFia47BkhEo=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Makb5PoEjneSPYFcsETWp9IkEg+vtGVQ2l3yZxa3KvEWvLNMymPvmSwQhcmlPnStX /86Gx9Swas++rKJmQOL+etYFAvxfIHZI0+xoZ4rLC5Ayw14CVk5HlDvQ89bqu4qGCZ /bHB60s0J1itFOGhVpixveecw9TrVLnMY//2aGN8vMRK4T3rsPy8jziR8cXidAFlKH NWd5/8dz//BKg0xWCGDdnnaFPgUp+cDm/XypqoPB6T95Nbt/ZltIBhDTrHQnQB+nVX SDuo4GadGhmn1+UsjL2JH/SGaD3gEWfXTexo2FfSBLUuXfcEuCZwzaqWkKQPDup1+f a2J8pXOjflyWQ== From: Christian Brauner To: linux-fsdevel@vger.kernel.org Cc: Christian Brauner , Seth Forshee , Christoph Hellwig , Al Viro , Mimi Zohar , linux-integrity@vger.kernel.org, linux-security-module@vger.kernel.org, Paul Moore Subject: [PATCH v3 13/29] evm: add post set acl hook Date: Wed, 28 Sep 2022 18:08:27 +0200 Message-Id: <20220928160843.382601-14-brauner@kernel.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20220928160843.382601-1-brauner@kernel.org> References: <20220928160843.382601-1-brauner@kernel.org> MIME-Version: 1.0 X-Developer-Signature: v=1; a=openpgp-sha256; l=2983; i=brauner@kernel.org; h=from:subject; bh=b3gB2/tZ/ar0HvnCiBSOOYD4rc846nc+lFia47BkhEo=; b=owGbwMvMwCU28Zj0gdSKO4sYT6slMSSbFNas1+0w1k0xnHCIj8NU51PuVeZE1hs3bmmlTaxaJdqz m+lKRykLgxgXg6yYIotDu0m43HKeis1GmRowc1iZQIYwcHEKwERYpBkZfvxWO+biPyWZY+/OVRw8zJ O2T0xdF9TxzSr7XLCsvXYCHyPDtDyZtCXyLHOsLj06z6T2ftbpe8v+Jyc/fH6+ZJPAsvmt3AA= X-Developer-Key: i=brauner@kernel.org; a=openpgp; fpr=4880B8C9BD0E5106FC070F4F7B3C391EFEA93624 Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org The security_inode_post_setxattr() hook is used by security modules to update their own security.* xattrs. Consequently none of the security modules operate on posix acls. So we don't need an additional security hook when post setting posix acls. However, the integrity subsystem wants to be informed about posix acl changes and specifically evm to update their hashes when the xattrs change. The callchain for evm_inode_post_setxattr() is: -> evm_inode_post_setxattr() -> evm_update_evmxattr() -> evm_calc_hmac() -> evm_calc_hmac_or_hash() and evm_cacl_hmac_or_hash() walks the global list of protected xattr names evm_config_xattrnames. This global list can be modified via /sys/security/integrity/evm/evm_xattrs. The write to "evm_xattrs" is restricted to security.* xattrs and the default xattrs in evm_config_xattrnames only contains security.* xattrs as well. So the actual value for posix acls is currently completely irrelevant for evm during evm_inode_post_setxattr() and frankly it should stay that way in the future to not cause the vfs any more headaches. But if the actual posix acl values matter then evm shouldn't operate on the binary void blob and try to hack around in the uapi struct anyway. Instead it should then in the future add a dedicated hook which takes a struct posix_acl argument passing the posix acls in the proper vfs format. For now it is sufficient to make evm_inode_post_set_acl() a wrapper around evm_inode_post_setxattr() not passing any actual values down. This will still cause the hashes to be updated as before. Reviewed-by: Paul Moore Signed-off-by: Christian Brauner (Microsoft) --- Notes: /* v2 */ unchanged /* v3 */ Reviewed-by: Paul Moore include/linux/evm.h | 13 +++++++++++++ 1 file changed, 13 insertions(+) diff --git a/include/linux/evm.h b/include/linux/evm.h index 86139be48992..117ac01b2432 100644 --- a/include/linux/evm.h +++ b/include/linux/evm.h @@ -44,6 +44,12 @@ static inline int evm_inode_remove_acl(struct user_namespace *mnt_userns, { return evm_inode_set_acl(mnt_userns, dentry, acl_name, NULL); } +static inline void evm_inode_post_set_acl(struct dentry *dentry, + const char *acl_name, + struct posix_acl *kacl) +{ + return evm_inode_post_setxattr(dentry, acl_name, NULL, 0); +} extern int evm_inode_init_security(struct inode *inode, const struct xattr *xattr_array, struct xattr *evm); @@ -131,6 +137,13 @@ static inline int evm_inode_remove_acl(struct user_namespace *mnt_userns, return 0; } +static inline void evm_inode_post_set_acl(struct dentry *dentry, + const char *acl_name, + struct posix_acl *kacl) +{ + return; +} + static inline int evm_inode_init_security(struct inode *inode, const struct xattr *xattr_array, struct xattr *evm)