From patchwork Mon Aug 1 18:01:43 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Frederick Lawler X-Patchwork-Id: 12933960 X-Patchwork-Delegate: paul@paul-moore.com 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 73EC0C00144 for ; Mon, 1 Aug 2022 18:02:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233527AbiHASCW (ORCPT ); Mon, 1 Aug 2022 14:02:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42040 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233869AbiHASCU (ORCPT ); Mon, 1 Aug 2022 14:02:20 -0400 Received: from mail-oa1-x2a.google.com (mail-oa1-x2a.google.com [IPv6:2001:4860:4864:20::2a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C6FC82715F for ; Mon, 1 Aug 2022 11:02:17 -0700 (PDT) Received: by mail-oa1-x2a.google.com with SMTP id 586e51a60fabf-10e6bdbe218so14561420fac.10 for ; Mon, 01 Aug 2022 11:02:17 -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=qEASjFQgHEXoxjCsMlwe3mWZuEgE+ke0lwJ4HSwmC1o=; b=IfFAjRq+tt0+0QkOil6iDkdm5PR1dhXxMMxF03kiwCYv+F35KXZll/Aos3m0bfnTPi ovfmDfsxJ2/RIRYdW+e+N27wxkP57PDcj+IKBbsr/h0smuJR0MFpmf3MmZUA0r9ow4fk 1RWQ/JoDadNY0VcpELObOrpway7EKWAzd/7Us= 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=qEASjFQgHEXoxjCsMlwe3mWZuEgE+ke0lwJ4HSwmC1o=; b=wiu5VYXL3YPLxOQPuc792BDs5sdCqoL+/6JFpjSLe7WHyFJ3N+vVAJSTVzwy1sq7qe kU2divdu33OTPKk3waOuZSV0RaDWTBb+uUNW4HWe7Q6dv0J8cDHb7Pd0EMqCnW88qofz BlE7BDr6ifCLFfP+sPt4X9maHwC93a8cCGePzrWCawXCMzqxnJgK872CPB82mRKyazYb JZAusvKsijp00WkOzI85CNdcMn+DOqQ+v6zaBG3w8Uwd+I2h3XWQjCOBWhatmThjdzqd UguKLUZVgY56F5Qpq+LrceQyeEWZLBa0THCDuRT9GYMhzELvh1lW3U0CkzUiXQyOHY1p 4Maw== X-Gm-Message-State: AJIora/1y19JcfCCV3SujWb09Y50A+C8xRM4cBc9O+D9y1Lv/9pabN9H WWHMHAeJzVmKBbxaFv5q+l9nWQ== X-Google-Smtp-Source: AGRyM1sD4g9Y9q/qyaXFCXmpcHuPT+pZOrtXQ6KE1YfTchLBWdjWov0aG3GFbThSnBywcxw6nVYfgw== X-Received: by 2002:a05:6870:d59c:b0:101:7e59:d723 with SMTP id u28-20020a056870d59c00b001017e59d723mr8156224oao.165.1659376936978; Mon, 01 Aug 2022 11:02:16 -0700 (PDT) Received: from localhost.localdomain ([184.4.90.121]) by smtp.gmail.com with ESMTPSA id n14-20020a9d64ce000000b00618fa37308csm2881348otl.35.2022.08.01.11.02.15 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 01 Aug 2022 11:02:16 -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 1/4] security, lsm: Introduce security_create_user_ns() Date: Mon, 1 Aug 2022 13:01:43 -0500 Message-Id: <20220801180146.1157914-2-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: Preventing user namespace (privileged or otherwise) creation comes in a few of forms in order of granularity: 1. /proc/sys/user/max_user_namespaces sysctl 2. OS specific patch(es) 3. CONFIG_USER_NS To block a task based on its attributes, the LSM hook cred_prepare is a good candidate for use because it provides more granular control, and it is called before create_user_ns(): cred = prepare_creds() security_prepare_creds() call_int_hook(cred_prepare, ... if (cred) create_user_ns(cred) Since security_prepare_creds() is meant for LSMs to copy and prepare credentials, access control is an unintended use of the hook. Therefore introduce a new function security_create_user_ns() with an accompanying userns_create LSM hook. This hook takes the prepared creds for LSM authors to write policy against. On success, the new namespace is applied to credentials, otherwise an error is returned. Signed-off-by: Frederick Lawler Reviewed-by: Christian Brauner (Microsoft) Reviewed-by: KP Singh --- Changes since v3: - No changes Changes since v2: - Rename create_user_ns hook to userns_create Changes since v1: - Changed commit wording - Moved execution to be after id mapping check - Changed signature to only accept a const struct cred * --- include/linux/lsm_hook_defs.h | 1 + include/linux/lsm_hooks.h | 4 ++++ include/linux/security.h | 6 ++++++ kernel/user_namespace.c | 5 +++++ security/security.c | 5 +++++ 5 files changed, 21 insertions(+) diff --git a/include/linux/lsm_hook_defs.h b/include/linux/lsm_hook_defs.h index eafa1d2489fd..7ff93cb8ca8d 100644 --- a/include/linux/lsm_hook_defs.h +++ b/include/linux/lsm_hook_defs.h @@ -223,6 +223,7 @@ LSM_HOOK(int, -ENOSYS, task_prctl, int option, unsigned long arg2, unsigned long arg3, unsigned long arg4, unsigned long arg5) LSM_HOOK(void, LSM_RET_VOID, task_to_inode, struct task_struct *p, struct inode *inode) +LSM_HOOK(int, 0, userns_create, const struct cred *cred) LSM_HOOK(int, 0, ipc_permission, struct kern_ipc_perm *ipcp, short flag) LSM_HOOK(void, LSM_RET_VOID, ipc_getsecid, struct kern_ipc_perm *ipcp, u32 *secid) diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h index 91c8146649f5..54fe534d0e01 100644 --- a/include/linux/lsm_hooks.h +++ b/include/linux/lsm_hooks.h @@ -799,6 +799,10 @@ * security attributes, e.g. for /proc/pid inodes. * @p contains the task_struct for the task. * @inode contains the inode structure for the inode. + * @userns_create: + * Check permission prior to creating a new user namespace. + * @cred points to prepared creds. + * Return 0 if successful, otherwise < 0 error code. * * Security hooks for Netlink messaging. * diff --git a/include/linux/security.h b/include/linux/security.h index 7fc4e9f49f54..a195bf33246a 100644 --- a/include/linux/security.h +++ b/include/linux/security.h @@ -435,6 +435,7 @@ int security_task_kill(struct task_struct *p, struct kernel_siginfo *info, int security_task_prctl(int option, unsigned long arg2, unsigned long arg3, unsigned long arg4, unsigned long arg5); void security_task_to_inode(struct task_struct *p, struct inode *inode); +int security_create_user_ns(const struct cred *cred); int security_ipc_permission(struct kern_ipc_perm *ipcp, short flag); void security_ipc_getsecid(struct kern_ipc_perm *ipcp, u32 *secid); int security_msg_msg_alloc(struct msg_msg *msg); @@ -1185,6 +1186,11 @@ static inline int security_task_prctl(int option, unsigned long arg2, static inline void security_task_to_inode(struct task_struct *p, struct inode *inode) { } +static inline int security_create_user_ns(const struct cred *cred) +{ + return 0; +} + static inline int security_ipc_permission(struct kern_ipc_perm *ipcp, short flag) { diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index 5481ba44a8d6..3f464bbda0e9 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -9,6 +9,7 @@ #include #include #include +#include #include #include #include @@ -113,6 +114,10 @@ int create_user_ns(struct cred *new) !kgid_has_mapping(parent_ns, group)) goto fail_dec; + ret = security_create_user_ns(new); + if (ret < 0) + goto fail_dec; + ret = -ENOMEM; ns = kmem_cache_zalloc(user_ns_cachep, GFP_KERNEL); if (!ns) diff --git a/security/security.c b/security/security.c index 188b8f782220..ec9b4696e86c 100644 --- a/security/security.c +++ b/security/security.c @@ -1903,6 +1903,11 @@ void security_task_to_inode(struct task_struct *p, struct inode *inode) call_void_hook(task_to_inode, p, inode); } +int security_create_user_ns(const struct cred *cred) +{ + return call_int_hook(userns_create, 0, cred); +} + int security_ipc_permission(struct kern_ipc_perm *ipcp, short flag) { return call_int_hook(ipc_permission, 0, ipcp, flag); From patchwork Mon Aug 1 18:01:44 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Frederick Lawler X-Patchwork-Id: 12933961 X-Patchwork-Delegate: paul@paul-moore.com 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 EFBECC19F2D for ; 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Mon, 01 Aug 2022 11:02:18 -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 2/4] bpf-lsm: Make bpf_lsm_userns_create() sleepable Date: Mon, 1 Aug 2022 13:01:44 -0500 Message-Id: <20220801180146.1157914-3-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: Users may want to audit calls to security_create_user_ns() and access user space memory. Also create_user_ns() runs without pagefault_disabled(). Therefore, make bpf_lsm_userns_create() sleepable for mandatory access control policies. Signed-off-by: Frederick Lawler Acked-by: Christian Brauner (Microsoft) Acked-by: Alexei Starovoitov Acked-by: KP Singh --- Changes since v3: - None Changes since v2: - Rename create_user_ns hook to userns_create Changes since v1: - None --- kernel/bpf/bpf_lsm.c | 1 + 1 file changed, 1 insertion(+) diff --git a/kernel/bpf/bpf_lsm.c b/kernel/bpf/bpf_lsm.c index c1351df9f7ee..4593437809cc 100644 --- a/kernel/bpf/bpf_lsm.c +++ b/kernel/bpf/bpf_lsm.c @@ -250,6 +250,7 @@ BTF_ID(func, bpf_lsm_task_getsecid_obj) BTF_ID(func, bpf_lsm_task_prctl) BTF_ID(func, bpf_lsm_task_setscheduler) BTF_ID(func, bpf_lsm_task_to_inode) +BTF_ID(func, bpf_lsm_userns_create) BTF_SET_END(sleepable_lsm_hooks) bool bpf_lsm_is_sleepable_hook(u32 btf_id) 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: 12933962 X-Patchwork-Delegate: paul@paul-moore.com 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 08079C00144 for ; Mon, 1 Aug 2022 18:02:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234298AbiHASCx (ORCPT ); Mon, 1 Aug 2022 14:02:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42040 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233927AbiHASCc (ORCPT ); Mon, 1 Aug 2022 14:02:32 -0400 Received: from mail-oi1-x234.google.com (mail-oi1-x234.google.com [IPv6:2607:f8b0:4864:20::234]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0547D28727 for ; Mon, 1 Aug 2022 11:02:22 -0700 (PDT) Received: by mail-oi1-x234.google.com with SMTP id h188so13549438oia.13 for ; Mon, 01 Aug 2022 11:02:22 -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=iTHyDV7O/4/aj22aomoIG4JrbrPpPTPFiG+U3L1bpzZP7InrXoe/volkqjIzDCKT5J k2fdIHOn8MFXOK2a90N1rNPQ2ZxSFX4ghk4IZ/wh2pIEXQzRTw0E9aYTcjALfmP/V5N0 qTJG/09wMpbQziLn5XXpG4mNMJGxFLsySDtktf5GRaU2xcej6FfK4dtiMeQ707uEmVaZ tuWuS34s7RggD2TAUK7oEvZehWu5W6z6JLcnegqnjzNF7YuvmjkroXGCBi7aVMQrcFuE 21lAlwUdMQnMVvmkvTB/mGPrfXaoEV7rkPN4fuVt/KwaCCLyK89TvfEqqwBUI+PC7ZPX L/5w== X-Gm-Message-State: AJIora8OWlo/rtRqudfah/kA8uIdQH4gPmetsaPstHEbx2AdZ3rFfDx1 C54U0UMh3SU0AeNW9TXYQBdZnQ== 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: 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; +} From patchwork Mon Aug 1 18:01:46 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Frederick Lawler X-Patchwork-Id: 12933963 X-Patchwork-Delegate: paul@paul-moore.com 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 D7D2BC25B06 for ; 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Mon, 01 Aug 2022 11:02:22 -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 4/4] selinux: Implement userns_create hook Date: Mon, 1 Aug 2022 13:01:46 -0500 Message-Id: <20220801180146.1157914-5-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: Unprivileged user namespace creation is an intended feature to enable sandboxing, however this feature is often used to as an initial step to perform a privilege escalation attack. This patch implements a new user_namespace { create } access control permission to restrict which domains allow or deny user namespace creation. This is necessary for system administrators to quickly protect their systems while waiting for vulnerability patches to be applied. This permission can be used in the following way: allow domA_t domA_t : user_namespace { create }; Signed-off-by: Frederick Lawler --- Changes since v3: - None 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: - Introduce this patch --- security/selinux/hooks.c | 9 +++++++++ security/selinux/include/classmap.h | 2 ++ 2 files changed, 11 insertions(+) diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c index beceb89f68d9..afc9da0249e7 100644 --- a/security/selinux/hooks.c +++ b/security/selinux/hooks.c @@ -4227,6 +4227,14 @@ static void selinux_task_to_inode(struct task_struct *p, spin_unlock(&isec->lock); } +static int selinux_userns_create(const struct cred *cred) +{ + u32 sid = current_sid(); + + return avc_has_perm(&selinux_state, sid, sid, SECCLASS_USER_NAMESPACE, + USER_NAMESPACE__CREATE, NULL); +} + /* Returns error only if unable to parse addresses */ static int selinux_parse_skb_ipv4(struct sk_buff *skb, struct common_audit_data *ad, u8 *proto) @@ -7117,6 +7125,7 @@ static struct security_hook_list selinux_hooks[] __lsm_ro_after_init = { LSM_HOOK_INIT(task_movememory, selinux_task_movememory), LSM_HOOK_INIT(task_kill, selinux_task_kill), LSM_HOOK_INIT(task_to_inode, selinux_task_to_inode), + LSM_HOOK_INIT(userns_create, selinux_userns_create), LSM_HOOK_INIT(ipc_permission, selinux_ipc_permission), LSM_HOOK_INIT(ipc_getsecid, selinux_ipc_getsecid), diff --git a/security/selinux/include/classmap.h b/security/selinux/include/classmap.h index ff757ae5f253..0bff55bb9cde 100644 --- a/security/selinux/include/classmap.h +++ b/security/selinux/include/classmap.h @@ -254,6 +254,8 @@ const struct security_class_mapping secclass_map[] = { { COMMON_FILE_PERMS, NULL } }, { "io_uring", { "override_creds", "sqpoll", NULL } }, + { "user_namespace", + { "create", NULL } }, { NULL } };