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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id CE7B3C00144 for ; Fri, 29 Jul 2022 10:43:56 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232387AbiG2Kn4 (ORCPT ); Fri, 29 Jul 2022 06:43:56 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39394 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231218AbiG2Knz (ORCPT ); Fri, 29 Jul 2022 06:43:55 -0400 Received: from smtp-8fac.mail.infomaniak.ch (smtp-8fac.mail.infomaniak.ch [IPv6:2001:1600:4:17::8fac]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9153783211 for ; Fri, 29 Jul 2022 03:43:50 -0700 (PDT) Received: from smtp-3-0001.mail.infomaniak.ch (unknown [10.4.36.108]) by smtp-3-3000.mail.infomaniak.ch (Postfix) with ESMTPS id 4LvPJN6QGQzMq5TW; Fri, 29 Jul 2022 12:43:48 +0200 (CEST) Received: from ns3096276.ip-94-23-54.eu (unknown [23.97.221.149]) by smtp-3-0001.mail.infomaniak.ch (Postfix) with ESMTPA id 4LvPJN1cR1zlnSCl; Fri, 29 Jul 2022 12:43:48 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=digikod.net; s=20191114; t=1659091428; bh=9gjEg7fe/cA+CMdYwmX60kCbVB9P/cNnk+OUwcWGb3o=; h=Date:From:To:Cc:References:Subject:In-Reply-To:From; b=LbVxqknxWoNxWhMuundY5ddZc4VGsKYawEHau3yRyYBPaeWTOoc8h/e93fOnNTaOA O6lTNo5XEGjrC2Fvwa2cwsF8TQkL/pPI+btqeVpjwcadG+Mwvkin04geccd2qwP2M2 ofxgUyJYMC47cjCiguSkOq8sBRrUc0Fetk2cQ2+o= Message-ID: <62c37433-b9bd-ce7d-0b45-18ecfb15b248@digikod.net> Date: Fri, 29 Jul 2022 12:43:47 +0200 MIME-Version: 1.0 User-Agent: Content-Language: en-US From: =?UTF-8?Q?Micka=c3=abl_Sala=c3=bcn?= To: =?UTF-8?Q?G=c3=bcnther_Noack?= , linux-security-module@vger.kernel.org Cc: James Morris , Paul Moore , "Serge E . Hallyn" References: <20220712211405.14705-1-gnoack3000@gmail.com> <20220712211405.14705-4-gnoack3000@gmail.com> <731b40e2-a95d-5eef-077b-375a50061a11@digikod.net> Subject: Re: [PATCH v2 3/4] samples/landlock: Extend sample tool to support LANDLOCK_ACCESS_FS_TRUNCATE In-Reply-To: <731b40e2-a95d-5eef-077b-375a50061a11@digikod.net> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: On 29/07/2022 12:38, Mickaël Salaün wrote: > > On 29/07/2022 12:31, Mickaël Salaün wrote: >> >> On 12/07/2022 23:14, Günther Noack wrote: >>> The sample tool will restrict the truncate operation if possible with >>> the current kernel. >> >> "Update the sandboxer sample to restrict truncate actions. This is >> automatically enabled by default if the running kernel supports >> LANDLOCK_ACCESS_FS_TRUNCATE, except for the paths listed in the LL_FS_RW >> environment variable." >> >> >>> >>> Signed-off-by: Günther Noack >>> Link: https://lore.kernel.org/all/20220707200612.132705-1-gnoack3000@gmail.com/ >>> --- >>> samples/landlock/sandboxer.c | 15 +++++++++++++-- >>> 1 file changed, 13 insertions(+), 2 deletions(-) >>> >>> diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c >>> index 3e404e51ec64..4c3ed0097ffd 100644 >>> --- a/samples/landlock/sandboxer.c >>> +++ b/samples/landlock/sandboxer.c >>> @@ -76,7 +76,8 @@ static int parse_path(char *env_path, const char ***const path_list) >>> #define ACCESS_FILE ( \ >>> LANDLOCK_ACCESS_FS_EXECUTE | \ >>> LANDLOCK_ACCESS_FS_WRITE_FILE | \ >>> - LANDLOCK_ACCESS_FS_READ_FILE) >>> + LANDLOCK_ACCESS_FS_READ_FILE | \ >>> + LANDLOCK_ACCESS_FS_TRUNCATE) >>> >>> /* clang-format on */ >>> >>> @@ -160,11 +161,15 @@ static int populate_ruleset(const char *const env_var, const int ruleset_fd, >>> LANDLOCK_ACCESS_FS_MAKE_FIFO | \ >>> LANDLOCK_ACCESS_FS_MAKE_BLOCK | \ >>> LANDLOCK_ACCESS_FS_MAKE_SYM | \ >>> - LANDLOCK_ACCESS_FS_REFER) >>> + LANDLOCK_ACCESS_FS_REFER | \ >>> + LANDLOCK_ACCESS_FS_TRUNCATE) >>> >>> #define ACCESS_ABI_2 ( \ >>> LANDLOCK_ACCESS_FS_REFER) >>> >>> +#define ACCESS_ABI_3 ( \ >>> + LANDLOCK_ACCESS_FS_TRUNCATE) >>> + >>> /* clang-format on */ >>> >>> int main(const int argc, char *const argv[], char *const *const envp) >>> @@ -226,6 +231,12 @@ int main(const int argc, char *const argv[], char *const *const envp) >>> return 1; >>> } >>> /* Best-effort security. */ >>> + if (abi < 3) { >>> + ruleset_attr.handled_access_fs &= ~ACCESS_ABI_3; >>> + access_fs_ro &= ~ACCESS_ABI_3; >>> + access_fs_rw &= ~ACCESS_ABI_3; >>> + } >> >> I think it is a good time to start replacing this "if" check with a >> switch one: >> >> switch (abi) { >> case 1: >> ruleset_attr.handled_access_fs &= ~ACCESS_ABI_2; >> access_fs_rw &= ~ACCESS_ABI_2; >> __attribute__((fallthrough)); >> case 2: >> ruleset_attr.handled_access_fs &= ~ACCESS_ABI_3; >> access_fs_rw &= ~ACCESS_ABI_3; >> } > > Well, we can just mask ruleset_attr.handled_access_fs in this > switch/case and after mask access_fs_ro and access_fs_rw after. In fact, we can remove ACCESS_ABI_2 and ACCESS_ABI_3 (which are only used here).