From patchwork Mon Aug 1 18:01:42 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Frederick Lawler X-Patchwork-Id: 12933959 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 6546BC19F2C for ; Mon, 1 Aug 2022 18:02:20 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233673AbiHASCS (ORCPT ); Mon, 1 Aug 2022 14:02:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41936 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233512AbiHASCR (ORCPT ); Mon, 1 Aug 2022 14:02:17 -0400 Received: from mail-oa1-x2f.google.com (mail-oa1-x2f.google.com [IPv6:2001:4860:4864:20::2f]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D086123BDE for ; Mon, 1 Aug 2022 11:02:15 -0700 (PDT) Received: by mail-oa1-x2f.google.com with SMTP id 586e51a60fabf-10e615a36b0so13045506fac.1 for ; Mon, 01 Aug 2022 11:02:15 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cloudflare.com; s=google; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:from:to:cc; bh=neYCRoMJHZhrkPomT+D8lBoa9lWbM2Zjq7tdhg++BD8=; b=Mhxk6WOQ1kBwvZATBE/fUmbfdcWPONvbLqPeeFwjgpXx30ZOq9K8e9XiO+heooXplM yIxZGuPYi6Y3upntqiTXP/fp9FqKCw4yfTan+k9O5EO5dpK1xku83lnqrHR4EC2zmuYi 1Wtv13AgwXk1J74t2M0Zv22JEVrbvaw3bB9ww= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:message-id:date:subject:cc :to:from:x-gm-message-state:from:to:cc; bh=neYCRoMJHZhrkPomT+D8lBoa9lWbM2Zjq7tdhg++BD8=; b=FnatPegy+xXUGNP3aDTsa2LzFMpyYQrRGgS6lbELQEMZuI36G7wmHBXZSGMi+un9O8 Vdpk1B+AzLjTzcr5QTJpGgivR54koh7TcitOwsQGY9Cko3BHUFoCpxn3/9ekZ8LCQTAA Zuvu6z7DhkIAkwlqAZLnoQvZz8XU+RBmX176P8kARoeOTtFRTj9Gwku8V7A6AWv8NDl8 ZXfqHLxY4YvGH/9iydWp6mNKtP3+DB1CObRLDQzzoIScMKJywt3co2e9itDpD/m7xdwK 7sX9nMzLWgH5pB//4B9/epmXbvT7BrJkj0TQ784hGxflAEeMn3WVGOouiirg3TGcAnFf VY2g== X-Gm-Message-State: AJIora9RdBdA6l7BuXEBiBVR5falm3F9vIik6XXSlGOAY5D7e4EC58xT M8uB3u/VAFZYX1Y5su7guDT35g== X-Google-Smtp-Source: AGRyM1s00uyA5RxFeoJiOwnWUCMdS5VnKo6fHkNTdsQVmzGj5TtMhEcfqeGl5rB5c+kZha+7htuYfg== X-Received: by 2002:a05:6870:4302:b0:10d:c587:d30e with SMTP id w2-20020a056870430200b0010dc587d30emr7992216oah.28.1659376935129; Mon, 01 Aug 2022 11:02:15 -0700 (PDT) Received: from localhost.localdomain ([184.4.90.121]) by smtp.gmail.com with ESMTPSA id n14-20020a9d64ce000000b00618fa37308csm2881348otl.35.2022.08.01.11.02.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 01 Aug 2022 11:02:14 -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 0/4] Introduce security_create_user_ns() Date: Mon, 1 Aug 2022 13:01:42 -0500 Message-Id: <20220801180146.1157914-1-fred@cloudflare.com> X-Mailer: git-send-email 2.30.2 MIME-Version: 1.0 Precedence: bulk List-ID: While creating a LSM BPF MAC policy to block user namespace creation, we used the LSM cred_prepare hook because that is the closest hook to prevent a call to create_user_ns(). The calls look something like this: cred = prepare_creds() security_prepare_creds() call_int_hook(cred_prepare, ... if (cred) create_user_ns(cred) We noticed that error codes were not propagated from this hook and introduced a patch [1] to propagate those errors. The discussion notes that security_prepare_creds() is not appropriate for MAC policies, and instead the hook is meant for LSM authors to prepare credentials for mutation. [2] Ultimately, we concluded that a better course of action is to introduce a new security hook for LSM authors. [3] This patch set first introduces a new security_create_user_ns() function and userns_create LSM hook, then marks the hook as sleepable in BPF. Links: 1. https://lore.kernel.org/all/20220608150942.776446-1-fred@cloudflare.com/ 2. https://lore.kernel.org/all/87y1xzyhub.fsf@email.froward.int.ebiederm.org/ 3. https://lore.kernel.org/all/9fe9cd9f-1ded-a179-8ded-5fde8960a586@cloudflare.com/ Past discussions: V3: https://lore.kernel.org/all/20220721172808.585539-1-fred@cloudflare.com/ V2: https://lore.kernel.org/all/20220707223228.1940249-1-fred@cloudflare.com/ V1: https://lore.kernel.org/all/20220621233939.993579-1-fred@cloudflare.com/ 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 - Use user_namespace as an object opposed to a generic namespace object - s/domB_t/domA_t in commit message Changes since v1: - Add selftests/bpf: Add tests verifying bpf lsm create_user_ns hook patch - Add selinux: Implement create_user_ns hook patch - Change function signature of security_create_user_ns() to only take struct cred - Move security_create_user_ns() call after id mapping check in create_user_ns() - Update documentation to reflect changes Frederick Lawler (4): security, lsm: Introduce security_create_user_ns() bpf-lsm: Make bpf_lsm_userns_create() sleepable selftests/bpf: Add tests verifying bpf lsm userns_create hook selinux: Implement userns_create hook include/linux/lsm_hook_defs.h | 1 + include/linux/lsm_hooks.h | 4 + include/linux/security.h | 6 ++ kernel/bpf/bpf_lsm.c | 1 + kernel/user_namespace.c | 5 + security/security.c | 5 + security/selinux/hooks.c | 9 ++ security/selinux/include/classmap.h | 2 + .../selftests/bpf/prog_tests/deny_namespace.c | 102 ++++++++++++++++++ .../selftests/bpf/progs/test_deny_namespace.c | 33 ++++++ 10 files changed, 168 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 Nacked-by: "Eric W. Biederman"