From patchwork Tue Dec 5 22:31:01 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mahesh Bandewar X-Patchwork-Id: 844954 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Authentication-Results: ozlabs.org; spf=none (mailfrom) smtp.mailfrom=vger.kernel.org (client-ip=209.132.180.67; helo=vger.kernel.org; envelope-from=netdev-owner@vger.kernel.org; receiver=) Authentication-Results: ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=bandewar-net.20150623.gappssmtp.com header.i=@bandewar-net.20150623.gappssmtp.com header.b="zy+B3BPb"; dkim-atps=neutral Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 3yrxLC0y8vz9s4q for ; Wed, 6 Dec 2017 09:31:31 +1100 (AEDT) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752835AbdLEWbL (ORCPT ); Tue, 5 Dec 2017 17:31:11 -0500 Received: from mail-pf0-f196.google.com ([209.85.192.196]:36795 "EHLO mail-pf0-f196.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752428AbdLEWbF (ORCPT ); Tue, 5 Dec 2017 17:31:05 -0500 Received: by mail-pf0-f196.google.com with SMTP id p84so1247297pfd.3 for ; Tue, 05 Dec 2017 14:31:05 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bandewar-net.20150623.gappssmtp.com; s=20150623; h=from:to:cc:subject:date:message-id; bh=4pvx6F15H3tPYEUE6Gwp1Kbah5adGQ3Mla41Y0H2ZOM=; b=zy+B3BPbjjbDaIMms92CuiBOjmfc7C4avrv5QU/1S0tnPhoajyAIOdPmCDceUyXEFm dCmH/M3jXRI5n+rF7/cebjDdB0A8CAMzv4EuqIjfHm/+45ujHofVtBGFsz6UOY2GJrTH KUSegCeAJrLiAn+sGno1IDJQoRB8VWZW73MwkjC0Pj+4ANWQMmvGSYoAihZbSzcGgtxR N5N1zTW9v99P6Wt5wnjzyAf8XziX4b0nYn0Uh6CdQry2Uwgxl1dBspR+CF8/ZKpSXTqE bUnyuovcI0s5i6zzoQ1UrmRk1wVTACU944vfPRu0gMITS8NEGIjcxKRm1ZgUIZDlix1y qk2g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id; bh=4pvx6F15H3tPYEUE6Gwp1Kbah5adGQ3Mla41Y0H2ZOM=; b=LPs6jdeSulm1YkMIdBiEV1wG1+aiQANrUXPSh413GYaqk9OTr/StU6Jo61aCfUIdMe u7/E531oLStZuRmxWRHM7VK4LpH7N3aatyh0w2jGoltWOPoinucTzcK0TucEfeloZKIL qo4LSwdiUmw7HMHA/9sBN7WO9GhFwduptkEVJwTjrCcAgGmGTsjtPair06nnjq4teWUQ psn/0b+Kr9kIOaVD7CgPPmAgZ6rt3qFQp19zTccyobcE33lK6T31dnwTEbNCQr0sDph5 Ed+mE8OXS2ubXnMcTg2NyeW+GfzHfLnqOFZBKF6OCVdFIc8Z0a6WBblOYDDXOWQnTGkq uPgQ== X-Gm-Message-State: AKGB3mKKIoRKcfJHnBX8HfSpz0dqxZbaAtpUUCqWGTBVIKiXYNgIKp33 VsieFyhMMTvDngoSnZDUOHhGag== X-Google-Smtp-Source: AGs4zMaSMahBUVwqextpZX18m4P1PgyL6kh8PzJCZ8B1Pq2TlReG3o9h67xeo9vGdKD+FDF1weLSwQ== X-Received: by 10.98.220.218 with SMTP id c87mr488293pfl.229.1512513065104; Tue, 05 Dec 2017 14:31:05 -0800 (PST) Received: from localhost ([2620:15c:2c4:201:856a:7790:de10:b700]) by smtp.gmail.com with ESMTPSA id l24sm1314564pgu.38.2017.12.05.14.31.04 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Tue, 05 Dec 2017 14:31:04 -0800 (PST) From: Mahesh Bandewar To: LKML , Netdev Cc: Kernel-hardening , Linux API , Kees Cook , Serge Hallyn , "Eric W . Biederman" , Eric Dumazet , David Miller , Mahesh Bandewar , Mahesh Bandewar Subject: [PATCHv3 1/2] capability: introduce sysctl for controlled user-ns capability whitelist Date: Tue, 5 Dec 2017 14:31:01 -0800 Message-Id: <20171205223101.12765-1-mahesh@bandewar.net> X-Mailer: git-send-email 2.15.0.531.g2ccb3012c9-goog Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Mahesh Bandewar Add a sysctl variable kernel.controlled_userns_caps_whitelist. This takes input as capability mask expressed as two comma separated hex u32 words. The mask, however, is stored in kernel as kernel_cap_t type. Any capabilities that are not part of this mask will be controlled and will not be allowed to processes in controlled user-ns. Acked-by: Serge Hallyn Signed-off-by: Mahesh Bandewar --- v3: Added couple of comments as requested by Serge Hallyn v2: Rebase v1: Initial submission Documentation/sysctl/kernel.txt | 21 ++++++++++++++++++ include/linux/capability.h | 3 +++ kernel/capability.c | 47 +++++++++++++++++++++++++++++++++++++++++ kernel/sysctl.c | 5 +++++ 4 files changed, 76 insertions(+) diff --git a/Documentation/sysctl/kernel.txt b/Documentation/sysctl/kernel.txt index 694968c7523c..a1d39dbae847 100644 --- a/Documentation/sysctl/kernel.txt +++ b/Documentation/sysctl/kernel.txt @@ -25,6 +25,7 @@ show up in /proc/sys/kernel: - bootloader_version [ X86 only ] - callhome [ S390 only ] - cap_last_cap +- controlled_userns_caps_whitelist - core_pattern - core_pipe_limit - core_uses_pid @@ -187,6 +188,26 @@ CAP_LAST_CAP from the kernel. ============================================================== +controlled_userns_caps_whitelist + +Capability mask that is whitelisted for "controlled" user namespaces. +Any capability that is missing from this mask will not be allowed to +any process that is attached to a controlled-userns. e.g. if CAP_NET_RAW +is not part of this mask, then processes running inside any controlled +userns's will not be allowed to perform action that needs CAP_NET_RAW +capability. However, processes that are attached to a parent user-ns +hierarchy that is *not* controlled and has CAP_NET_RAW can continue +performing those actions. User-namespaces are marked "controlled" at +the time of their creation based on the capabilities of the creator. +A process that does not have CAP_SYS_ADMIN will create user-namespaces +that are controlled. + +The value is expressed as two comma separated hex words (u32). This +sysctl is avaialble in init-ns and users with CAP_SYS_ADMIN in init-ns +are allowed to make changes. + +============================================================== + core_pattern: core_pattern is used to specify a core dumpfile pattern name. diff --git a/include/linux/capability.h b/include/linux/capability.h index f640dcbc880c..7d79a4689625 100644 --- a/include/linux/capability.h +++ b/include/linux/capability.h @@ -14,6 +14,7 @@ #define _LINUX_CAPABILITY_H #include +#include #define _KERNEL_CAPABILITY_VERSION _LINUX_CAPABILITY_VERSION_3 @@ -248,6 +249,8 @@ extern bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns); /* audit system wants to get cap info from files as well */ extern int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps); +int proc_douserns_caps_whitelist(struct ctl_table *table, int write, + void __user *buff, size_t *lenp, loff_t *ppos); extern int cap_convert_nscap(struct dentry *dentry, void **ivalue, size_t size); diff --git a/kernel/capability.c b/kernel/capability.c index 1e1c0236f55b..4a859b7d4902 100644 --- a/kernel/capability.c +++ b/kernel/capability.c @@ -29,6 +29,8 @@ EXPORT_SYMBOL(__cap_empty_set); int file_caps_enabled = 1; +kernel_cap_t controlled_userns_caps_whitelist = CAP_FULL_SET; + static int __init file_caps_disable(char *str) { file_caps_enabled = 0; @@ -507,3 +509,48 @@ bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns) rcu_read_unlock(); return (ret == 0); } + +/* Controlled-userns capabilities routines */ +#ifdef CONFIG_SYSCTL +int proc_douserns_caps_whitelist(struct ctl_table *table, int write, + void __user *buff, size_t *lenp, loff_t *ppos) +{ + DECLARE_BITMAP(caps_bitmap, CAP_LAST_CAP); + struct ctl_table caps_table; + char tbuf[NAME_MAX]; + int ret; + + ret = bitmap_from_u32array(caps_bitmap, CAP_LAST_CAP, + controlled_userns_caps_whitelist.cap, + _KERNEL_CAPABILITY_U32S); + if (ret != CAP_LAST_CAP) + return -1; + + scnprintf(tbuf, NAME_MAX, "%*pb", CAP_LAST_CAP, caps_bitmap); + + caps_table.data = tbuf; + caps_table.maxlen = NAME_MAX; + caps_table.mode = table->mode; + ret = proc_dostring(&caps_table, write, buff, lenp, ppos); + if (ret) + return ret; + if (write) { + kernel_cap_t tmp; + + if (!capable(CAP_SYS_ADMIN)) + return -EPERM; + + ret = bitmap_parse_user(buff, *lenp, caps_bitmap, CAP_LAST_CAP); + if (ret) + return ret; + + ret = bitmap_to_u32array(tmp.cap, _KERNEL_CAPABILITY_U32S, + caps_bitmap, CAP_LAST_CAP); + if (ret != CAP_LAST_CAP) + return -1; + + controlled_userns_caps_whitelist = tmp; + } + return 0; +} +#endif /* CONFIG_SYSCTL */ diff --git a/kernel/sysctl.c b/kernel/sysctl.c index 557d46728577..759b6c286806 100644 --- a/kernel/sysctl.c +++ b/kernel/sysctl.c @@ -1217,6 +1217,11 @@ static struct ctl_table kern_table[] = { .extra2 = &one, }, #endif + { + .procname = "controlled_userns_caps_whitelist", + .mode = 0644, + .proc_handler = proc_douserns_caps_whitelist, + }, { } }; From patchwork Tue Dec 5 22:31:05 2017 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Mahesh Bandewar X-Patchwork-Id: 844953 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Authentication-Results: ozlabs.org; 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Tue, 05 Dec 2017 14:31:08 -0800 (PST) Received: from localhost ([2620:15c:2c4:201:856a:7790:de10:b700]) by smtp.gmail.com with ESMTPSA id x21sm1475580pfi.174.2017.12.05.14.31.07 (version=TLS1_2 cipher=AES128-SHA bits=128/128); Tue, 05 Dec 2017 14:31:07 -0800 (PST) From: Mahesh Bandewar To: LKML , Netdev Cc: Kernel-hardening , Linux API , Kees Cook , Serge Hallyn , "Eric W . Biederman" , Eric Dumazet , David Miller , Mahesh Bandewar , Mahesh Bandewar Subject: [PATCHv3 2/2] userns: control capabilities of some user namespaces Date: Tue, 5 Dec 2017 14:31:05 -0800 Message-Id: <20171205223105.12845-1-mahesh@bandewar.net> X-Mailer: git-send-email 2.15.0.531.g2ccb3012c9-goog Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Mahesh Bandewar With this new notion of "controlled" user-namespaces, the controlled user-namespaces are marked at the time of their creation while the capabilities of processes that belong to them are controlled using the global mask. Init-user-ns is always uncontrolled and a process that has SYS_ADMIN that belongs to uncontrolled user-ns can create another (child) user- namespace that is uncontrolled. Any other process (that either does not have SYS_ADMIN or belongs to a controlled user-ns) can only create a user-ns that is controlled. global-capability-whitelist (controlled_userns_caps_whitelist) is used at the capability check-time and keeps the semantics for the processes that belong to uncontrolled user-ns as it is. Processes that belong to controlled user-ns however are subjected to different checks- (a) if the capability in question is controlled and process belongs to controlled user-ns, then it's always denied. (b) if the capability in question is NOT controlled then fall back to the traditional check. Acked-by: Serge Hallyn Signed-off-by: Mahesh Bandewar --- v3: Rebase v2: Don't recalculate user-ns flags for every setns() call. v1: Initial submission. include/linux/capability.h | 4 ++++ include/linux/user_namespace.h | 25 +++++++++++++++++++++++++ kernel/capability.c | 5 +++++ kernel/user_namespace.c | 4 ++++ security/commoncap.c | 8 ++++++++ 5 files changed, 46 insertions(+) diff --git a/include/linux/capability.h b/include/linux/capability.h index 7d79a4689625..383f31f066f0 100644 --- a/include/linux/capability.h +++ b/include/linux/capability.h @@ -251,6 +251,10 @@ extern bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns); extern int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps); int proc_douserns_caps_whitelist(struct ctl_table *table, int write, void __user *buff, size_t *lenp, loff_t *ppos); +/* Controlled capability is capability that is missing from the capability-mask + * controlled_userns_caps_whitelist controlled via sysctl. + */ +bool is_capability_controlled(int cap); extern int cap_convert_nscap(struct dentry *dentry, void **ivalue, size_t size); diff --git a/include/linux/user_namespace.h b/include/linux/user_namespace.h index d6b74b91096b..a5c48684b317 100644 --- a/include/linux/user_namespace.h +++ b/include/linux/user_namespace.h @@ -32,6 +32,7 @@ struct uid_gid_map { /* 64 bytes -- 1 cache line */ }; #define USERNS_SETGROUPS_ALLOWED 1UL +#define USERNS_CONTROLLED 2UL #define USERNS_INIT_FLAGS USERNS_SETGROUPS_ALLOWED @@ -112,6 +113,21 @@ static inline void put_user_ns(struct user_namespace *ns) __put_user_ns(ns); } +/* Controlled user-ns is the one that is created by a process that does not + * have CAP_SYS_ADMIN (or descended from such an user-ns). + * For more details please see the sysctl description of + * controlled_userns_caps_whitelist. + */ +static inline bool is_user_ns_controlled(const struct user_namespace *ns) +{ + return ns->flags & USERNS_CONTROLLED; +} + +static inline void mark_user_ns_controlled(struct user_namespace *ns) +{ + ns->flags |= USERNS_CONTROLLED; +} + struct seq_operations; extern const struct seq_operations proc_uid_seq_operations; extern const struct seq_operations proc_gid_seq_operations; @@ -170,6 +186,15 @@ static inline struct ns_common *ns_get_owner(struct ns_common *ns) { return ERR_PTR(-EPERM); } + +static inline bool is_user_ns_controlled(const struct user_namespace *ns) +{ + return false; +} + +static inline void mark_user_ns_controlled(struct user_namespace *ns) +{ +} #endif #endif /* _LINUX_USER_H */ diff --git a/kernel/capability.c b/kernel/capability.c index 4a859b7d4902..bffe249922de 100644 --- a/kernel/capability.c +++ b/kernel/capability.c @@ -511,6 +511,11 @@ bool ptracer_capable(struct task_struct *tsk, struct user_namespace *ns) } /* Controlled-userns capabilities routines */ +bool is_capability_controlled(int cap) +{ + return !cap_raised(controlled_userns_caps_whitelist, cap); +} + #ifdef CONFIG_SYSCTL int proc_douserns_caps_whitelist(struct ctl_table *table, int write, void __user *buff, size_t *lenp, loff_t *ppos) diff --git a/kernel/user_namespace.c b/kernel/user_namespace.c index 246d4d4ce5c7..ca0556d466b6 100644 --- a/kernel/user_namespace.c +++ b/kernel/user_namespace.c @@ -141,6 +141,10 @@ int create_user_ns(struct cred *new) goto fail_keyring; set_cred_user_ns(new, ns); + if (!ns_capable(parent_ns, CAP_SYS_ADMIN) || + is_user_ns_controlled(parent_ns)) + mark_user_ns_controlled(ns); + return 0; fail_keyring: #ifdef CONFIG_PERSISTENT_KEYRINGS diff --git a/security/commoncap.c b/security/commoncap.c index 4f8e09340956..5454e9c03ee8 100644 --- a/security/commoncap.c +++ b/security/commoncap.c @@ -73,6 +73,14 @@ int cap_capable(const struct cred *cred, struct user_namespace *targ_ns, { struct user_namespace *ns = targ_ns; + /* If the capability is controlled and user-ns that process + * belongs-to is 'controlled' then return EPERM and no need + * to check the user-ns hierarchy. + */ + if (is_user_ns_controlled(cred->user_ns) && + is_capability_controlled(cap)) + return -EPERM; + /* See if cred has the capability in the target user namespace * by examining the target user namespace and all of the target * user namespace's parents.