From patchwork Fri May 6 16:10:59 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Patchwork-Submitter: =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= X-Patchwork-Id: 12841387 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 BFBA2C4167D for ; Fri, 6 May 2022 16:11:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1391190AbiEFQPB (ORCPT ); Fri, 6 May 2022 12:15:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43440 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1443620AbiEFQNc (ORCPT ); Fri, 6 May 2022 12:13:32 -0400 Received: from smtp-1908.mail.infomaniak.ch (smtp-1908.mail.infomaniak.ch [185.125.25.8]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 4E1B66EB04 for ; Fri, 6 May 2022 09:09:46 -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 4KvwWF19pTzMqTZL; Fri, 6 May 2022 18:09:45 +0200 (CEST) Received: from localhost (unknown [23.97.221.149]) by smtp-3-0001.mail.infomaniak.ch (Postfix) with ESMTPA id 4KvwWD6HB4zlhMCN; Fri, 6 May 2022 18:09:44 +0200 (CEST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=digikod.net; s=20191114; t=1651853385; bh=ljovP71bccFdIQBtI9sMUdEAuBH4+SXJzMjB1yNMBwg=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=uz9RZ3eCGwGmMzuEoGv34Ydf4g1cdG4CK8yUwnerI+GS0q3GPFcUarBzILvsLm9I1 Zu2vERsO6qDlmohE5nz0XvkCjqtt20N029DRXvw5caW3n6/BO9V5BoHGrH1rlCu8p2 iFoFpSTTzcNF5Fxle2TCCQwzwwqu/C0wlDw9LtEA= From: =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= To: James Morris , "Serge E . Hallyn" Cc: =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= , Al Viro , Jann Horn , John Johansen , Kees Cook , Konstantin Meskhidze , Paul Moore , Shuah Khan , Tetsuo Handa , linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org Subject: [PATCH v3 09/12] samples/landlock: Add support for file reparenting Date: Fri, 6 May 2022 18:10:59 +0200 Message-Id: <20220506161102.525323-10-mic@digikod.net> In-Reply-To: <20220506161102.525323-1-mic@digikod.net> References: <20220506161102.525323-1-mic@digikod.net> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Add LANDLOCK_ACCESS_FS_REFER to the "roughly write" access rights and leverage the Landlock ABI version to only try to enforce it if it is supported by the running kernel. Reviewed-by: Paul Moore Signed-off-by: Mickaël Salaün Link: https://lore.kernel.org/r/20220506161102.525323-10-mic@digikod.net --- Changes since v2: * Format with clang-format and rebase. Changes since v1: * Add Reviewed-by: Paul Moore. --- samples/landlock/sandboxer.c | 40 ++++++++++++++++++++++++------------ 1 file changed, 27 insertions(+), 13 deletions(-) diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c index c089e9cdaf32..3e404e51ec64 100644 --- a/samples/landlock/sandboxer.c +++ b/samples/landlock/sandboxer.c @@ -159,7 +159,11 @@ static int populate_ruleset(const char *const env_var, const int ruleset_fd, LANDLOCK_ACCESS_FS_MAKE_SOCK | \ LANDLOCK_ACCESS_FS_MAKE_FIFO | \ LANDLOCK_ACCESS_FS_MAKE_BLOCK | \ - LANDLOCK_ACCESS_FS_MAKE_SYM) + LANDLOCK_ACCESS_FS_MAKE_SYM | \ + LANDLOCK_ACCESS_FS_REFER) + +#define ACCESS_ABI_2 ( \ + LANDLOCK_ACCESS_FS_REFER) /* clang-format on */ @@ -167,10 +171,11 @@ int main(const int argc, char *const argv[], char *const *const envp) { const char *cmd_path; char *const *cmd_argv; - int ruleset_fd; + int ruleset_fd, abi; + __u64 access_fs_ro = ACCESS_FS_ROUGHLY_READ, + access_fs_rw = ACCESS_FS_ROUGHLY_READ | ACCESS_FS_ROUGHLY_WRITE; struct landlock_ruleset_attr ruleset_attr = { - .handled_access_fs = ACCESS_FS_ROUGHLY_READ | - ACCESS_FS_ROUGHLY_WRITE, + .handled_access_fs = access_fs_rw, }; if (argc < 2) { @@ -196,12 +201,11 @@ int main(const int argc, char *const argv[], char *const *const envp) return 1; } - ruleset_fd = - landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0); - if (ruleset_fd < 0) { + abi = landlock_create_ruleset(NULL, 0, LANDLOCK_CREATE_RULESET_VERSION); + if (abi < 0) { const int err = errno; - perror("Failed to create a ruleset"); + perror("Failed to check Landlock compatibility"); switch (err) { case ENOSYS: fprintf(stderr, @@ -221,13 +225,23 @@ int main(const int argc, char *const argv[], char *const *const envp) } return 1; } - if (populate_ruleset(ENV_FS_RO_NAME, ruleset_fd, - ACCESS_FS_ROUGHLY_READ)) { + /* Best-effort security. */ + if (abi < 2) { + ruleset_attr.handled_access_fs &= ~ACCESS_ABI_2; + access_fs_ro &= ~ACCESS_ABI_2; + access_fs_rw &= ~ACCESS_ABI_2; + } + + ruleset_fd = + landlock_create_ruleset(&ruleset_attr, sizeof(ruleset_attr), 0); + if (ruleset_fd < 0) { + perror("Failed to create a ruleset"); + return 1; + } + if (populate_ruleset(ENV_FS_RO_NAME, ruleset_fd, access_fs_ro)) { goto err_close_ruleset; } - if (populate_ruleset(ENV_FS_RW_NAME, ruleset_fd, - ACCESS_FS_ROUGHLY_READ | - ACCESS_FS_ROUGHLY_WRITE)) { + if (populate_ruleset(ENV_FS_RW_NAME, ruleset_fd, access_fs_rw)) { goto err_close_ruleset; } if (prctl(PR_SET_NO_NEW_PRIVS, 1, 0, 0, 0)) {