From patchwork Mon Aug 1 18:01:45 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Frederick Lawler X-Patchwork-Id: 12933957 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 79774C19F2C for ; Mon, 1 Aug 2022 18:02:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234110AbiHASCz (ORCPT ); Mon, 1 Aug 2022 14:02:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42636 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234132AbiHASCf (ORCPT ); Mon, 1 Aug 2022 14:02:35 -0400 Received: from mail-oi1-x236.google.com (mail-oi1-x236.google.com [IPv6:2607:f8b0:4864:20::236]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 109CB29810 for ; Mon, 1 Aug 2022 11:02:23 -0700 (PDT) Received: by mail-oi1-x236.google.com with SMTP id s204so13921298oif.5 for ; Mon, 01 Aug 2022 11:02:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cloudflare.com; s=google; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc; bh=DFM28j1evovVIesF7892uqGHd1qTcmZDuJXeotitcvA=; b=tdpMqQ74ueJhZLF3PIkmfBOR4X5EIhlmdyEmHxx+mu54Z6yJXe905lrBIGf829wdcd tYpmmTMjMmz7GxFo+CRUNBPdt4bBxoSbOmputKkrcxGKaZI4C9Uy1WXSZSgUgiWoIa+d NX+fsqqialFm/ytOY0K3SyPgKSeuyk+nIGJ5A= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc; bh=DFM28j1evovVIesF7892uqGHd1qTcmZDuJXeotitcvA=; b=vonAVOmWkzJe8rgK35hnzL6psRDgcNvTGs106rfKPnHLOlICX/SHdD72YgpVoALVWv 4C6v743MrlEvAef0dxdkbmHR9y87y46zt6zREyEN4HPGPYxHEh6n8NiUQmuUguYESGdK Zq+7rwy2Bxa5WHe+dv8v0LtRA7SUY9NsSIiMoX6AogBNnQJ+EPbFIbCu7OpNRdow9KxF hPZ1t6LT1L84R4WwhKKgXnnhv5Uev4kNIWcKTaOl9VlpX4xYZEsFuQX0YJNikjsnJqPx /WEC9VBO934V43E49hAeTdc7Q1fnQFCNtmM6atT78tTDUOWuhnc6HI/GRY1daF6cFUNw plqw== X-Gm-Message-State: AJIora/b0yOnNjW/YSOYi7P/pndot19iC+COUUXczmaE/3wV2Dh1fjrV U8vGBGdbg6PbOxZX8x3HCwQGvw== X-Google-Smtp-Source: AGRyM1vjtPI/ODQpeiZyl8o+45Ndqv7M6XyWUy/E58LADXIUQntSE06XmvHEQbKpW8EldE0lx9iJCA== X-Received: by 2002:a05:6808:171c:b0:334:9342:63ef with SMTP id bc28-20020a056808171c00b00334934263efmr6997799oib.63.1659376940639; Mon, 01 Aug 2022 11:02:20 -0700 (PDT) Received: from localhost.localdomain ([184.4.90.121]) by smtp.gmail.com with ESMTPSA id n14-20020a9d64ce000000b00618fa37308csm2881348otl.35.2022.08.01.11.02.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 01 Aug 2022 11:02:20 -0700 (PDT) From: Frederick Lawler To: kpsingh@kernel.org, revest@chromium.org, jackmanb@chromium.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, kafai@fb.com, songliubraving@fb.com, yhs@fb.com, john.fastabend@gmail.com, jmorris@namei.org, serge@hallyn.com, paul@paul-moore.com, stephen.smalley.work@gmail.com, eparis@parisplace.org, shuah@kernel.org, brauner@kernel.org, casey@schaufler-ca.com, ebiederm@xmission.com, bpf@vger.kernel.org, linux-security-module@vger.kernel.org, selinux@vger.kernel.org, linux-kselftest@vger.kernel.org Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org, kernel-team@cloudflare.com, cgzones@googlemail.com, karl@bigbadwolfsecurity.com, Frederick Lawler Subject: [PATCH v4 3/4] selftests/bpf: Add tests verifying bpf lsm userns_create hook Date: Mon, 1 Aug 2022 13:01:45 -0500 Message-Id: <20220801180146.1157914-4-fred@cloudflare.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20220801180146.1157914-1-fred@cloudflare.com> References: <20220801180146.1157914-1-fred@cloudflare.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org The LSM hook userns_create was introduced to provide LSM's an opportunity to block or allow unprivileged user namespace creation. This test serves two purposes: it provides a test eBPF implementation, and tests the hook successfully blocks or allows user namespace creation. This tests 3 cases: 1. Unattached bpf program does not block unpriv user namespace creation. 2. Attached bpf program allows user namespace creation given CAP_SYS_ADMIN privileges. 3. Attached bpf program denies user namespace creation for a user without CAP_SYS_ADMIN. Signed-off-by: Frederick Lawler Acked-by: KP Singh --- The generic deny_namespace file name is used for future namespace expansion. I didn't want to limit these files to just the create_user_ns hook. Changes since v3: - Explicitly set CAP_SYS_ADMIN to test namespace is created given permission - Simplify BPF test to use sleepable hook only - Prefer unshare() over clone() for tests Changes since v2: - Rename create_user_ns hook to userns_create Changes since v1: - Introduce this patch --- .../selftests/bpf/prog_tests/deny_namespace.c | 102 ++++++++++++++++++ .../selftests/bpf/progs/test_deny_namespace.c | 33 ++++++ 2 files changed, 135 insertions(+) create mode 100644 tools/testing/selftests/bpf/prog_tests/deny_namespace.c create mode 100644 tools/testing/selftests/bpf/progs/test_deny_namespace.c diff --git a/tools/testing/selftests/bpf/prog_tests/deny_namespace.c b/tools/testing/selftests/bpf/prog_tests/deny_namespace.c new file mode 100644 index 000000000000..1bc6241b755b --- /dev/null +++ b/tools/testing/selftests/bpf/prog_tests/deny_namespace.c @@ -0,0 +1,102 @@ +// SPDX-License-Identifier: GPL-2.0 +#define _GNU_SOURCE +#include +#include "test_deny_namespace.skel.h" +#include +#include "cap_helpers.h" +#include + +static int wait_for_pid(pid_t pid) +{ + int status, ret; + +again: + ret = waitpid(pid, &status, 0); + if (ret == -1) { + if (errno == EINTR) + goto again; + + return -1; + } + + if (!WIFEXITED(status)) + return -1; + + return WEXITSTATUS(status); +} + +/* negative return value -> some internal error + * positive return value -> userns creation failed + * 0 -> userns creation succeeded + */ +static int create_user_ns(void) +{ + pid_t pid; + + pid = fork(); + if (pid < 0) + return -1; + + if (pid == 0) { + if (unshare(CLONE_NEWUSER)) + _exit(EXIT_FAILURE); + _exit(EXIT_SUCCESS); + } + + return wait_for_pid(pid); +} + +static void test_userns_create_bpf(void) +{ + __u32 cap_mask = 1ULL << CAP_SYS_ADMIN; + __u64 old_caps = 0; + + cap_enable_effective(cap_mask, &old_caps); + + ASSERT_OK(create_user_ns(), "priv new user ns"); + + cap_disable_effective(cap_mask, &old_caps); + + ASSERT_EQ(create_user_ns(), EPERM, "unpriv new user ns"); + + if (cap_mask & old_caps) + cap_enable_effective(cap_mask, NULL); +} + +static void test_unpriv_userns_create_no_bpf(void) +{ + __u32 cap_mask = 1ULL << CAP_SYS_ADMIN; + __u64 old_caps = 0; + + cap_disable_effective(cap_mask, &old_caps); + + ASSERT_OK(create_user_ns(), "no-bpf unpriv new user ns"); + + if (cap_mask & old_caps) + cap_enable_effective(cap_mask, NULL); +} + +void test_deny_namespace(void) +{ + struct test_deny_namespace *skel = NULL; + int err; + + if (test__start_subtest("unpriv_userns_create_no_bpf")) + test_unpriv_userns_create_no_bpf(); + + skel = test_deny_namespace__open_and_load(); + if (!ASSERT_OK_PTR(skel, "skel load")) + goto close_prog; + + err = test_deny_namespace__attach(skel); + if (!ASSERT_OK(err, "attach")) + goto close_prog; + + if (test__start_subtest("userns_create_bpf")) + test_userns_create_bpf(); + + test_deny_namespace__detach(skel); + +close_prog: + test_deny_namespace__destroy(skel); +} diff --git a/tools/testing/selftests/bpf/progs/test_deny_namespace.c b/tools/testing/selftests/bpf/progs/test_deny_namespace.c new file mode 100644 index 000000000000..09ad5a4ebd1f --- /dev/null +++ b/tools/testing/selftests/bpf/progs/test_deny_namespace.c @@ -0,0 +1,33 @@ +// SPDX-License-Identifier: GPL-2.0 +#include +#include +#include +#include +#include + +struct kernel_cap_struct { + __u32 cap[_LINUX_CAPABILITY_U32S_3]; +} __attribute__((preserve_access_index)); + +struct cred { + struct kernel_cap_struct cap_effective; +} __attribute__((preserve_access_index)); + +char _license[] SEC("license") = "GPL"; + +SEC("lsm.s/userns_create") +int BPF_PROG(test_userns_create, const struct cred *cred, int ret) +{ + struct kernel_cap_struct caps = cred->cap_effective; + int cap_index = CAP_TO_INDEX(CAP_SYS_ADMIN); + __u32 cap_mask = CAP_TO_MASK(CAP_SYS_ADMIN); + + if (ret) + return 0; + + ret = -EPERM; + if (caps.cap[cap_index] & cap_mask) + return 0; + + return -EPERM; +}