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 DB4B4CCA483 for ; Fri, 8 Jul 2022 14:02:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S238418AbiGHOCD (ORCPT ); Fri, 8 Jul 2022 10:02:03 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33168 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238375AbiGHOCC (ORCPT ); Fri, 8 Jul 2022 10:02:02 -0400 Received: from mail-ot1-x32b.google.com (mail-ot1-x32b.google.com [IPv6:2607:f8b0:4864:20::32b]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 368EF18395 for ; Fri, 8 Jul 2022 07:02:00 -0700 (PDT) Received: by mail-ot1-x32b.google.com with SMTP id l9-20020a056830268900b006054381dd35so16269258otu.4 for ; Fri, 08 Jul 2022 07:02:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=cloudflare.com; s=google; h=message-id:date:mime-version:user-agent:subject:content-language:to :cc:references:from:in-reply-to:content-transfer-encoding; bh=AgCA7JC4n87M0J4Cctl8zaLThkaSJBjNpAQEBOK0n1E=; b=YuCU3LC4EmqmDANYLVa2rGn4cR9g+9cw2DLgXF8oCoF6AZxLFRfSQJPVMFb5dcnxhI a05pFGlm/tVZW44jkqy1SXPlR5wDktz+7LIkeToD/5YkiElWGugxmgLSpDUf+s2OskWJ Cp37s+zDo3qupWC0gw3gLYxdm4Zdfrlycfxyk= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:message-id:date:mime-version:user-agent:subject :content-language:to:cc:references:from:in-reply-to :content-transfer-encoding; bh=AgCA7JC4n87M0J4Cctl8zaLThkaSJBjNpAQEBOK0n1E=; b=gG7WFeH5lXJKNsWyyZ5ScKmo6G29V8GhWpjtA0x6O5+q05amTw/nWzJPSTNmSWntnD aSwJKSvXzBVz96qHiTrBTLxtMB6GHewyD+2IuL4+Wu597Cu6yTpXN4iohhaAYcaN09L3 EXwbFvZ4rNWcjRDmWQZ9IQqPMaZFQn15WDoXb8TiXB0SI+c+ztbpkIXG3eUXePpdzahB uNxxpyEcsKxKLGfKBDaxlPOSlNaeNC7vpNVhsPQRhlHPUFcBSsH8T5AYUAmTIxB9cjvG FkV5hyQlXqj/Q6PCZ/Rw5AO/6AiOfEbsDdT5BIbSGpq59oDSL9pWDXasupGcuKcI7p8f FA/g== X-Gm-Message-State: AJIora/IQ2DireVvxpqQZmRDvrueg/Plek5bNUuKur/7hcrtPw6732c2 7ksNyaQeD5QblbZWTmDOJarxmQ== X-Google-Smtp-Source: AGRyM1sIQoZ2at//x/8ubeDtbsVzTdvW8iCJcL4x2IwszMFpKBYhfmP4STbUFtn8jkNHayqOr+h8zw== X-Received: by 2002:a05:6830:2331:b0:61c:2c18:555 with SMTP id q17-20020a056830233100b0061c2c180555mr1212008otg.367.1657288919372; Fri, 08 Jul 2022 07:01:59 -0700 (PDT) Received: from [192.168.0.41] ([184.4.90.121]) by smtp.gmail.com with ESMTPSA id x10-20020a9d704a000000b00616d98ad780sm12787337otj.52.2022.07.08.07.01.36 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 08 Jul 2022 07:01:43 -0700 (PDT) Message-ID: <3dbd5b30-f869-b284-1383-309ca6994557@cloudflare.com> Date: Fri, 8 Jul 2022 09:01:32 -0500 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.10.0 Subject: Re: [PATCH v2 0/4] Introduce security_create_user_ns() Content-Language: en-US To: =?UTF-8?Q?Christian_G=c3=b6ttsche?= Cc: KP Singh , revest@chromium.org, jackmanb@chromium.org, Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Song Liu , Yonghong Song , John Fastabend , James Morris , "Serge E. Hallyn" , Paul Moore , Stephen Smalley , Eric Paris , shuah@kernel.org, Christian Brauner , Casey Schaufler , "Eric W. Biederman" , bpf@vger.kernel.org, linux-security-module@vger.kernel.org, SElinux list , linux-kselftest@vger.kernel.org, Linux kernel mailing list , netdev@vger.kernel.org, kernel-team@cloudflare.com References: <20220707223228.1940249-1-fred@cloudflare.com> From: Frederick Lawler In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 7/8/22 7:10 AM, Christian Göttsche wrote: > ,On Fri, 8 Jul 2022 at 00:32, Frederick Lawler wrote: >> >> 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 create_user_ns LSM hook, then marks the hook as sleepable in BPF. > > Some thoughts: > > I. > > Why not make the hook more generic, e.g. support all other existing > and potential future namespaces? The main issue with a generic hook is that different namespaces have different calling contexts. We decided in a previous discussion to opt-out of a generic hook for this reason. [1] > Also I think the naming scheme is _. That's a good call out. I was originally hoping to keep the security_*() match with the hook name matched with the caller function to keep things all aligned. If no one objects to renaming the hook, I can rename the hook for v3. > > LSM_HOOK(int, 0, namespace_create, const struct cred *cred, > unsigned int flags) > > where flags is a bitmap of CLONE flags from include/uapi/linux/sched.h > (like CLONE_NEWUSER). > > II. > > While adding policing for namespaces maybe also add a new hook for setns(2) > > LSM_HOOK(int, 0, namespace_join, const struct cred *subj, const > struct cred *obj, unsigned int flags) > IIUC, setns() will create a new namespace for the other namespaces except for user namespace. If we add a security hook for the other create_*_ns() functions, then we can catch setns() at that point. > III. > > Maybe even attach a security context to namespaces so they can be > further governed? > SELinux example: > > type domainA_userns_t; > type_transition domainA_t domainA_t : namespace domainA_userns_t "user"; > allow domainA_t domainA_userns_t:namespace create; > > # domainB calling setns(2) with domainA as target > allow domainB_t domainA_userns_t:namespace join; > Links: 1. https://lore.kernel.org/all/CAHC9VhSTkEMT90Tk+=iTyp3npWEm+3imrkFVX2qb=XsOPp9F=A@mail.gmail.com/ >> >> 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/ >> >> 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_create_user_ns() sleepable >> selftests/bpf: Add tests verifying bpf lsm create_user_ns hook >> selinux: Implement create_user_ns 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 | 88 +++++++++++++++++++ >> .../selftests/bpf/progs/test_deny_namespace.c | 39 ++++++++ >> 10 files changed, 160 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 >> >> -- >> 2.30.2 >>