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: 10094037 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 8E3CF6056E for ; Tue, 5 Dec 2017 22:31:30 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 818502933B for ; Tue, 5 Dec 2017 22:31:30 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 7491029A11; Tue, 5 Dec 2017 22:31:30 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-4.1 required=2.0 tests=BAYES_00,DKIM_SIGNED, RCVD_IN_DNSWL_MED,T_DKIM_INVALID autolearn=ham version=3.3.1 Received: from mother.openwall.net (mother.openwall.net [195.42.179.200]) by mail.wl.linuxfoundation.org (Postfix) with SMTP id 1534129A13 for ; Tue, 5 Dec 2017 22:31:28 +0000 (UTC) Received: (qmail 7562 invoked by uid 550); 5 Dec 2017 22:31:19 -0000 Mailing-List: contact kernel-hardening-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Delivered-To: mailing list kernel-hardening@lists.openwall.com Received: (qmail 7249 invoked from network); 5 Dec 2017 22:31:17 -0000 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=Jp+XfyyNPTmGOR1gW9MF6QtjLMaDkp/WvH9Ni+qOjRIqHNpL4QfgwXlqpPo2VjCLU6 lY61WGezyPiSP3qt1ivnJGtG6a2r1ID65Z6WBGh2jgQU9d/p4CvEhW+hckR5lnv8UBcB X3RpnyZcQuLU/e9K7I0bwgwoyPG9Lfc4o4+siFC6QlJMFVefkAN8yMDvyuGbQ3+otsLm jTQGYm2LihgkU9zlJO3k8a/8kgM/JzME8zfxiXevAAtIUPRC0NEyh6f3bHQx4GgjjHkk RcUNno3JzF6Ju08JEv5hsNXZoTwfnESPKu3NwWmbZMFgUbNSGMN5BYN3FhwxQJ3CwpKD 2uGA== X-Gm-Message-State: AKGB3mKW6zfkbueAW1PuNcyxugJUzBf75hsaYrDb2b0uEAQEfoQkfj0K CXEJMpQ60fZFd1kN1D13hCY0Tw== 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) 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 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 Subject: [kernel-hardening] [PATCHv3 1/2] capability: introduce sysctl for controlled user-ns capability whitelist X-Virus-Scanned: ClamAV using ClamSMTP 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, + }, { } };