From patchwork Mon Feb 21 21:25:19 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: 12754164 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 C2855C433EF for ; Mon, 21 Feb 2022 21:23:07 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234819AbiBUVX3 (ORCPT ); Mon, 21 Feb 2022 16:23:29 -0500 Received: from mxb-00190b01.gslb.pphosted.com ([23.128.96.19]:60426 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234695AbiBUVXT (ORCPT ); Mon, 21 Feb 2022 16:23:19 -0500 X-Greylist: delayed 457 seconds by postgrey-1.37 at lindbergh.monkeyblade.net; Mon, 21 Feb 2022 13:22:52 PST Received: from smtp-190b.mail.infomaniak.ch (smtp-190b.mail.infomaniak.ch [185.125.25.11]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B0D2026DA; Mon, 21 Feb 2022 13:22:51 -0800 (PST) Received: from smtp-3-0000.mail.infomaniak.ch (unknown [10.4.36.107]) by smtp-2-3000.mail.infomaniak.ch (Postfix) with ESMTPS id 4K2Znv6PCHzMqJwT; Mon, 21 Feb 2022 22:15:15 +0100 (CET) Received: from localhost (unknown [23.97.221.149]) by smtp-3-0000.mail.infomaniak.ch (Postfix) with ESMTPA id 4K2Znv4XcCzljTg3; Mon, 21 Feb 2022 22:15:15 +0100 (CET) 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 , Kees Cook , Konstantin Meskhidze , Paul Moore , Shuah Khan , linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-security-module@vger.kernel.org, =?utf-8?q?Micka=C3=ABl_Sala=C3=BCn?= Subject: [PATCH v1 08/11] samples/landlock: Add support for file reparenting Date: Mon, 21 Feb 2022 22:25:19 +0100 Message-Id: <20220221212522.320243-9-mic@digikod.net> X-Mailer: git-send-email 2.35.1 In-Reply-To: <20220221212522.320243-1-mic@digikod.net> References: <20220221212522.320243-1-mic@digikod.net> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org From: Mickaël Salaün 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. Signed-off-by: Mickaël Salaün Link: https://lore.kernel.org/r/20220221212522.320243-9-mic@digikod.net Reviewed-by: Paul Moore --- samples/landlock/sandboxer.c | 37 +++++++++++++++++++++++++----------- 1 file changed, 26 insertions(+), 11 deletions(-) diff --git a/samples/landlock/sandboxer.c b/samples/landlock/sandboxer.c index 7a15910d2171..8509543fcbbb 100644 --- a/samples/landlock/sandboxer.c +++ b/samples/landlock/sandboxer.c @@ -153,16 +153,21 @@ static int populate_ruleset( 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) 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) { @@ -183,11 +188,11 @@ 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, "Hint: Landlock is not supported by the current kernel. " @@ -205,12 +210,22 @@ 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)) {