Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S266116AbUIPCcR (ORCPT ); Wed, 15 Sep 2004 22:32:17 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S266555AbUIPCcR (ORCPT ); Wed, 15 Sep 2004 22:32:17 -0400 Received: from [205.233.219.253] ([205.233.219.253]:63393 "EHLO conifer.conscoop.ottawa.on.ca") by vger.kernel.org with ESMTP id S266116AbUIPCbt (ORCPT ); Wed, 15 Sep 2004 22:31:49 -0400 Date: Wed, 15 Sep 2004 22:31:18 -0400 From: Jody McIntyre To: "Jack O'Quin" Cc: James Morris , Lee Revell , linux-kernel , torbenh@gmx.de Subject: Re: [PATCH] Realtime LSM Message-ID: <20040916023118.GE2945@conscoop.ottawa.on.ca> References: <871xh7thzx.fsf@sulphur.joq.us> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <871xh7thzx.fsf@sulphur.joq.us> User-Agent: Mutt/1.5.4i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 13147 Lines: 421 On Sun, Sep 12, 2004 at 02:16:50PM -0500, Jack O'Quin wrote: > I have not implemented that yet because (1) the current approach has > proven adequate for the Linux audio user community, and (2) I haven't > wanted to spend time mastering the internal kernel interfaces for > accessing /proc from an LSM. I know it's not difficult, but I had > other things I'd rather do. :-) Here's a patch based on the one posted in <1095117752.1360.5.camel@krustophenia.net> that adds a sysctl (/proc/sys) interface. These sysctls don't seem to fit into any of the existing groups, so I added CTL_SECURITY (/proc/sys/security). Example: # modprobe realtime # echo 29 > /proc/sys/security/realtime/gid Signed-Off-By: Lee Revell Signed-off-by: Jody McIntyre Index: linux/Documentation/realtime-lsm.txt =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ linux/Documentation/realtime-lsm.txt 2004-09-15 15:47:39.000000000 -0400 @@ -0,0 +1,47 @@ + + Realtime Linux Security Module + + +This Linux Security Module (LSM) enables realtime capabilities. It +was written by Torben Hohn and Jack O'Quin, under the provisions of +the GPL (see the COPYING file). We make no warranty concerning the +safety, security or even stability of your system when using it. But, +we will fix problems if you report them. + +Once the LSM has been installed and the kernel for which it was built +is running, the root user can load it and pass parameters as follows: + + # modprobe realtime any=1 + + Any program can request realtime privileges. This allows any local + user to crash the system by hogging the CPU in a tight loop or + locking down too much memory. But, it is simple to administer. :-) + + # modprobe realtime gid=29 + + All users belonging to group 29 and programs that are setgid to that + group have realtime privileges. Use any group number you like. + + # modprobe realtime mlock=0 + + Grants realtime scheduling privileges without the ability to lock + memory using mlock() or mlockall() system calls. This option can be + used in conjunction with any of the other options. + + # modprobe realtime allcaps=1 + + Enables all capabilities, including CAP_SETPCAP. This is equivalent + to the 2.4 kernel capabilities patch. It is needed for root + programs to assign realtime capabilities to other processes. This + option can be used in conjunction with any of the other options. + + The JACK Audio Connection Kit (jackit.sourceforge.net) includes a + `jackstart' program which uses CAP_SETPCAP to run the JACK daemon + and its clients with realtime capabilities. + + There are serious security exposures with CAP_SETPCAP. If an + attacker manages to subvert some system daemon running with root + privileges, it can use this capability to deny needed privileges to + other root processes. + +Jack O'Quin, joq@joq.us Index: linux/security/Makefile =================================================================== --- linux.orig/security/Makefile 2004-09-15 15:47:11.000000000 -0400 +++ linux/security/Makefile 2004-09-15 15:47:39.000000000 -0400 @@ -15,3 +15,4 @@ obj-$(CONFIG_SECURITY) += security.o d obj-$(CONFIG_SECURITY_SELINUX) += selinux/built-in.o obj-$(CONFIG_SECURITY_CAPABILITIES) += commoncap.o capability.o obj-$(CONFIG_SECURITY_ROOTPLUG) += commoncap.o root_plug.o +obj-$(CONFIG_SECURITY_REALTIME) += commoncap.o realtime.o Index: linux/security/realtime.c =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ linux/security/realtime.c 2004-09-15 17:54:18.000000000 -0400 @@ -0,0 +1,283 @@ +/* + * Realtime Capabilities Linux Security Module + * + * Copyright (C) 2003 Torben Hohn + * Copyright (C) 2003, 2004 Jack O'Quin + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + */ + +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#ifdef CONFIG_SECURITY + +#define RT_LSM "Realtime LSM " /* syslog module name prefix */ +#define RT_ERR "Realtime: " /* syslog error message prefix */ + +#include +MODULE_INFO(vermagic,VERMAGIC_STRING); + +/* this is needed for the proc_dointvec_minmax for allowed GID */ +static int maxuid = 65535; +static int minuid = -1; + +/* module parameters */ +static int any = 0; /* if TRUE, any process is realtime */ +MODULE_PARM(any, "i"); +MODULE_PARM_DESC(any, " grant realtime privileges to any process."); + +static int gid = -1; /* realtime group id, or NO_GROUP */ +MODULE_PARM(gid, "i"); +MODULE_PARM_DESC(gid, " the group ID with access to realtime privileges."); + +static int mlock = 1; /* enable mlock() privileges */ +MODULE_PARM(mlock, "i"); +MODULE_PARM_DESC(mlock, " enable memory locking privileges."); + +static int allcaps = 0; /* enable all capabilities */ +MODULE_PARM(allcaps, "i"); +MODULE_PARM_DESC(allcaps, " enable all capabilities, including CAP_SETPCAP."); + +static kernel_cap_t cap_bset_save; /* place to save cap-bound */ + +int realtime_bprm_set_security(struct linux_binprm *bprm) +{ + /* Copied from security/commoncap.c: cap_bprm_set_security()... */ + /* Copied from fs/exec.c:prepare_binprm. */ + /* We don't have VFS support for capabilities yet */ + cap_clear(bprm->cap_inheritable); + cap_clear(bprm->cap_permitted); + cap_clear(bprm->cap_effective); + + /* If a non-zero `any' parameter was specified, we grant + * realtime privileges to every process. If the `gid' + * parameter was specified and it matches the group id of the + * executable, of the current process or any supplementary + * groups, we grant realtime capabilites. + */ + + if (any || (gid != -1)) { + + int rt_ok = 1; + + /* check group permissions */ + if ((gid != -1) && + (gid != bprm->e_gid) && + (gid != current->gid)) { + int i; + rt_ok = 0; + + get_group_info(current->group_info); + for (i = 0; i < current->group_info->ngroups; ++i) { + if (gid == GROUP_AT(current->group_info, i)) { + rt_ok = 1; + break; + } + } + put_group_info(current->group_info); + } + + if (rt_ok) { + cap_raise(bprm->cap_effective, CAP_SYS_NICE); + cap_raise(bprm->cap_permitted, CAP_SYS_NICE); + if (mlock) { + cap_raise(bprm->cap_effective, CAP_IPC_LOCK); + cap_raise(bprm->cap_permitted, CAP_IPC_LOCK); + cap_raise(bprm->cap_effective, + CAP_SYS_RESOURCE); + cap_raise(bprm->cap_permitted, + CAP_SYS_RESOURCE); + } + } + } + + /* To support inheritance of root-permissions and suid-root + * executables under compatibility mode, we raise all three + * capability sets for the file. + * + * If only the real uid is 0, we only raise the inheritable + * and permitted sets of the executable file. + */ + + if (bprm->e_uid == 0 || current->uid == 0) { + cap_set_full (bprm->cap_inheritable); + cap_set_full (bprm->cap_permitted); + } + if (bprm->e_uid == 0) + cap_set_full (bprm->cap_effective); + + return 0; +} + +static struct security_operations capability_ops = { + .ptrace = cap_ptrace, + .capget = cap_capget, + .capset_check = cap_capset_check, + .capset_set = cap_capset_set, + .capable = cap_capable, + .netlink_send = cap_netlink_send, + .netlink_recv = cap_netlink_recv, + .bprm_apply_creds = cap_bprm_apply_creds, + .bprm_set_security = realtime_bprm_set_security, + .bprm_secureexec = cap_bprm_secureexec, + .task_post_setuid = cap_task_post_setuid, + .task_reparent_to_init = cap_task_reparent_to_init, + .syslog = cap_syslog, + .vm_enough_memory = cap_vm_enough_memory, +}; + +#define MY_NAME __stringify(KBUILD_MODNAME) + +static ctl_table realtime_table[] = +{ + { .ctl_name = 1, + .procname = "any", + .data = &any, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = &proc_dointvec, + }, + { .ctl_name = 2, + .procname = "gid", + .data = &gid, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = &proc_dointvec_minmax, + .extra1 = &minuid, + .extra2 = &maxuid + }, + { .ctl_name = 3, + .procname = "mlock", + .data = &mlock, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = &proc_dointvec, + }, + { .ctl_name = 4, + .procname = "allcaps", + .data = &allcaps, + .maxlen = sizeof(int), + .mode = 0644, + .proc_handler = &proc_dointvec, + }, + { } +}; + +static ctl_table realtime_root_table[] = +{ + { .ctl_name = SECURITY_REALTIME, + .procname = "realtime", + .mode = 0555, + .child = realtime_table }, + { } +}; + +static ctl_table security_root_table[] = +{ + { .ctl_name = CTL_SECURITY, + .procname = "security", + .mode = 0555, + .child = realtime_root_table }, + { } +}; + +static struct ctl_table_header *sysctl_header; + +static void __exit exit_sysctl(void) +{ + unregister_sysctl_table(sysctl_header); +} + +/* flag to keep track of how we were registered */ +static int secondary; + +static void __exit exit_security(void) +{ + cap_bset = cap_bset_save; /* restore cap-bound */ + + /* remove ourselves from the security framework */ + if (secondary) { + if (mod_unreg_security(MY_NAME, &capability_ops)) + printk(KERN_INFO RT_ERR "Failure unregistering " + "capabilities with primary module.\n"); + + } else if (unregister_security(&capability_ops)) { + printk(KERN_INFO RT_ERR + "Failure unregistering capabilities with the kernel\n"); + } + printk(KERN_INFO "Realtime Capability LSM exiting\n"); +} + +static int __init capability_init(void) +{ + /* register ourselves with the security framework */ + if (register_security(&capability_ops)) { + + /* try registering with primary module */ + if (mod_reg_security(MY_NAME, &capability_ops)) { + printk(KERN_INFO RT_ERR "Failure registering " + "capabilities with primary security module.\n"); + printk(KERN_INFO RT_ERR "Is kernel configured " + "with CONFIG_SECURITY_CAPABILITIES=m?\n"); + return -EINVAL; + } + secondary = 1; + } + + cap_bset_save = cap_bset; /* save cap-bound */ + + sysctl_header = register_sysctl_table(security_root_table, 0); + if (!sysctl_header) { + exit_security(); + return -ENOMEM; + } + + if (allcaps) { + cap_bset = to_cap_t(~0); + printk(KERN_INFO RT_LSM "enabling all capabilities\n"); + } + + if (any) + printk(KERN_INFO RT_LSM + "initialized (all groups, mlock=%d)\n", mlock); + else if (gid == -1) + printk(KERN_INFO RT_LSM + "initialized (no groups, mlock=%d)\n", mlock); + else + printk(KERN_INFO RT_LSM + "initialized (group %d, mlock=%d)\n", gid, mlock); + + return 0; +} + +static void __exit capability_exit(void) +{ + exit_sysctl(); + exit_security(); +} + +security_initcall(capability_init); +module_exit(capability_exit); + +MODULE_DESCRIPTION("Realtime Capabilities Security Module"); +MODULE_LICENSE("GPL"); + +#endif /* CONFIG_SECURITY */ Index: linux/include/linux/sysctl.h =================================================================== --- linux.orig/include/linux/sysctl.h 2004-09-15 11:59:54.000000000 -0400 +++ linux/include/linux/sysctl.h 2004-09-15 16:56:21.000000000 -0400 @@ -61,7 +61,14 @@ enum CTL_DEV=7, /* Devices */ CTL_BUS=8, /* Busses */ CTL_ABI=9, /* Binary emulation */ - CTL_CPU=10 /* CPU stuff (speed scaling, etc) */ + CTL_CPU=10, /* CPU stuff (speed scaling, etc) */ + CTL_SECURITY=11 /* Security modules */ +}; + +/* CTL_SECURITY names: */ +enum +{ + SECURITY_REALTIME=1 /* Realtime LSM */ }; /* CTL_BUS names: */ Index: linux/security/Kconfig =================================================================== --- linux.orig/security/Kconfig 2004-09-15 15:47:11.000000000 -0400 +++ linux/security/Kconfig 2004-09-15 15:47:39.000000000 -0400 @@ -44,6 +44,20 @@ config SECURITY_ROOTPLUG If you are unsure how to answer this question, answer N. +config SECURITY_REALTIME + tristate "Realtime Capabilities" + depends on SECURITY && SECURITY_CAPABILITIES!=y + default n + help + Answer M to build realtime support as a Linux Security + Module. Answering Y to build realtime capabilities into the + kernel makes no sense. + + This module selectively grants realtime privileges + controlled by load-time parameters. + + If you are unsure how to answer this question, answer N. + source security/selinux/Kconfig endmenu - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/