[mirror_ubuntu-zesty-kernel.git] / kernel / capability.c

/*
 * linux/kernel/capability.c
 *
 * Copyright (C) 1997  Andrew Main <zefram@fysh.org>
 *
 * Integrated into 2.1.97+,  Andrew G. Morgan <morgan@kernel.org>
 * 30 May 2002:	Cleanup, Robert M. Love <rml@tech9.net>
 */

#include <linux/audit.h>
#include <linux/capability.h>
#include <linux/mm.h>
#include <linux/module.h>
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/pid_namespace.h>
#include <asm/uaccess.h>
#include "cred-internals.h"

/*
 * Leveraged for setting/resetting capabilities
 */

const kernel_cap_t __cap_empty_set = CAP_EMPTY_SET;
const kernel_cap_t __cap_full_set = CAP_FULL_SET;
const kernel_cap_t __cap_init_eff_set = CAP_INIT_EFF_SET;

EXPORT_SYMBOL(__cap_empty_set);
EXPORT_SYMBOL(__cap_full_set);
EXPORT_SYMBOL(__cap_init_eff_set);

int file_caps_enabled = 1;

static int __init file_caps_disable(char *str)
{
	file_caps_enabled = 0;
	return 1;
}
__setup("no_file_caps", file_caps_disable);

/*
 * More recent versions of libcap are available from:
 *
 *   http://www.kernel.org/pub/linux/libs/security/linux-privs/
 */

static void warn_legacy_capability_use(void)
{
	static int warned;
	if (!warned) {
		char name[sizeof(current->comm)];

		printk(KERN_INFO "warning: `%s' uses 32-bit capabilities"
		       " (legacy support in use)\n",
		       get_task_comm(name, current));
		warned = 1;
	}
}

/*
 * Version 2 capabilities worked fine, but the linux/capability.h file
 * that accompanied their introduction encouraged their use without
 * the necessary user-space source code changes. As such, we have
 * created a version 3 with equivalent functionality to version 2, but
 * with a header change to protect legacy source code from using
 * version 2 when it wanted to use version 1. If your system has code
 * that trips the following warning, it is using version 2 specific
 * capabilities and may be doing so insecurely.
 *
 * The remedy is to either upgrade your version of libcap (to 2.10+,
 * if the application is linked against it), or recompile your
 * application with modern kernel headers and this warning will go
 * away.
 */

static void warn_deprecated_v2(void)
{
	static int warned;

	if (!warned) {
		char name[sizeof(current->comm)];

		printk(KERN_INFO "warning: `%s' uses deprecated v2"
		       " capabilities in a way that may be insecure.\n",
		       get_task_comm(name, current));
		warned = 1;
	}
}

/*
 * Version check. Return the number of u32s in each capability flag
 * array, or a negative value on error.
 */
static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
{
	__u32 version;

	if (get_user(version, &header->version))
		return -EFAULT;

	switch (version) {
	case _LINUX_CAPABILITY_VERSION_1:
		warn_legacy_capability_use();
		*tocopy = _LINUX_CAPABILITY_U32S_1;
		break;
	case _LINUX_CAPABILITY_VERSION_2:
		warn_deprecated_v2();
		/*
		 * fall through - v3 is otherwise equivalent to v2.
		 */
	case _LINUX_CAPABILITY_VERSION_3:
		*tocopy = _LINUX_CAPABILITY_U32S_3;
		break;
	default:
		if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version))
			return -EFAULT;
		return -EINVAL;
	}

	return 0;
}

/*
 * The only thing that can change the capabilities of the current
 * process is the current process. As such, we can't be in this code
 * at the same time as we are in the process of setting capabilities
 * in this process. The net result is that we can limit our use of
 * locks to when we are reading the caps of another process.
 */
static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp,
				     kernel_cap_t *pIp, kernel_cap_t *pPp)
{
	int ret;

	if (pid && (pid != task_pid_vnr(current))) {
		struct task_struct *target;

		read_lock(&tasklist_lock);

		target = find_task_by_vpid(pid);
		if (!target)
			ret = -ESRCH;
		else
			ret = security_capget(target, pEp, pIp, pPp);

		read_unlock(&tasklist_lock);
	} else
		ret = security_capget(current, pEp, pIp, pPp);

	return ret;
}

/**
 * sys_capget - get the capabilities of a given process.
 * @header: pointer to struct that contains capability version and
 *	target pid data
 * @dataptr: pointer to struct that contains the effective, permitted,
 *	and inheritable capabilities that are returned
 *
 * Returns 0 on success and < 0 on error.
 */
SYSCALL_DEFINE2(capget, cap_user_header_t, header, cap_user_data_t, dataptr)
{
	int ret = 0;
	pid_t pid;
	unsigned tocopy;
	kernel_cap_t pE, pI, pP;

	ret = cap_validate_magic(header, &tocopy);
	if ((dataptr == NULL) || (ret != 0))
		return ((dataptr == NULL) && (ret == -EINVAL)) ? 0 : ret;

	if (get_user(pid, &header->pid))
		return -EFAULT;

	if (pid < 0)
		return -EINVAL;

	ret = cap_get_target_pid(pid, &pE, &pI, &pP);
	if (!ret) {
		struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
		unsigned i;

		for (i = 0; i < tocopy; i++) {
			kdata[i].effective = pE.cap[i];
			kdata[i].permitted = pP.cap[i];
			kdata[i].inheritable = pI.cap[i];
		}

		/*
		 * Note, in the case, tocopy < _KERNEL_CAPABILITY_U32S,
		 * we silently drop the upper capabilities here. This
		 * has the effect of making older libcap
		 * implementations implicitly drop upper capability
		 * bits when they perform a: capget/modify/capset
		 * sequence.
		 *
		 * This behavior is considered fail-safe
		 * behavior. Upgrading the application to a newer
		 * version of libcap will enable access to the newer
		 * capabilities.
		 *
		 * An alternative would be to return an error here
		 * (-ERANGE), but that causes legacy applications to
		 * unexpectidly fail; the capget/modify/capset aborts
		 * before modification is attempted and the application
		 * fails.
		 */
		if (copy_to_user(dataptr, kdata, tocopy
				 * sizeof(struct __user_cap_data_struct))) {
			return -EFAULT;
		}
	}

	return ret;
}

/**
 * sys_capset - set capabilities for a process or (*) a group of processes
 * @header: pointer to struct that contains capability version and
 *	target pid data
 * @data: pointer to struct that contains the effective, permitted,
 *	and inheritable capabilities
 *
 * Set capabilities for the current process only.  The ability to any other
 * process(es) has been deprecated and removed.
 *
 * The restrictions on setting capabilities are specified as:
 *
 * I: any raised capabilities must be a subset of the old permitted
 * P: any raised capabilities must be a subset of the old permitted
 * E: must be set to a subset of new permitted
 *
 * Returns 0 on success and < 0 on error.
 */
SYSCALL_DEFINE2(capset, cap_user_header_t, header, const cap_user_data_t, data)
{
	struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
	unsigned i, tocopy, copybytes;
	kernel_cap_t inheritable, permitted, effective;
	struct cred *new;
	int ret;
	pid_t pid;

	ret = cap_validate_magic(header, &tocopy);
	if (ret != 0)
		return ret;

	if (get_user(pid, &header->pid))
		return -EFAULT;

	/* may only affect current now */
	if (pid != 0 && pid != task_pid_vnr(current))
		return -EPERM;

	copybytes = tocopy * sizeof(struct __user_cap_data_struct);
	if (copybytes > sizeof(kdata))
		return -EFAULT;

	if (copy_from_user(&kdata, data, copybytes))
		return -EFAULT;

	for (i = 0; i < tocopy; i++) {
		effective.cap[i] = kdata[i].effective;
		permitted.cap[i] = kdata[i].permitted;
		inheritable.cap[i] = kdata[i].inheritable;
	}
	while (i < _KERNEL_CAPABILITY_U32S) {
		effective.cap[i] = 0;
		permitted.cap[i] = 0;
		inheritable.cap[i] = 0;
		i++;
	}

	new = prepare_creds();
	if (!new)
		return -ENOMEM;

	ret = security_capset(new, current_cred(),
			      &effective, &inheritable, &permitted);
	if (ret < 0)
		goto error;

	audit_log_capset(pid, new, current_cred());

	return commit_creds(new);

error:
	abort_creds(new);
	return ret;
}

/**
 * capable - Determine if the current task has a superior capability in effect
 * @cap: The capability to be tested for
 *
 * Return true if the current task has the given superior capability currently
 * available for use, false if not.
 *
 * This sets PF_SUPERPRIV on the task if the capability is available on the
 * assumption that it's about to be used.
 */
int capable(int cap)
{
	if (unlikely(!cap_valid(cap))) {
		printk(KERN_CRIT "capable() called with invalid cap=%u\n", cap);
		BUG();
	}

	if (security_capable(cap) == 0) {
		current->flags |= PF_SUPERPRIV;
		return 1;
	}
	return 0;
}
EXPORT_SYMBOL(capable);
Commit	Line	Data
1da177e4 LT	1	/*
	2	* linux/kernel/capability.c
	3	*
	4	* Copyright (C) 1997 Andrew Main <zefram@fysh.org>
	5	*
72c2d582	6	* Integrated into 2.1.97+, Andrew G. Morgan <morgan@kernel.org>
1da177e4	7	* 30 May 2002: Cleanup, Robert M. Love <rml@tech9.net>
314f70fd	8	*/
1da177e4	9
e68b75a0	10	#include <linux/audit.h>
c59ede7b	11	#include <linux/capability.h>
1da177e4 LT	12	#include <linux/mm.h>
	13	#include <linux/module.h>
	14	#include <linux/security.h>
	15	#include <linux/syscalls.h>
b460cbc5	16	#include <linux/pid_namespace.h>
1da177e4	17	#include <asm/uaccess.h>
d84f4f99	18	#include "cred-internals.h"
1da177e4	19
e338d263 AM	20	/*
	21	* Leveraged for setting/resetting capabilities
	22	*/
	23
	24	const kernel_cap_t __cap_empty_set = CAP_EMPTY_SET;
	25	const kernel_cap_t __cap_full_set = CAP_FULL_SET;
	26	const kernel_cap_t __cap_init_eff_set = CAP_INIT_EFF_SET;
	27
	28	EXPORT_SYMBOL(__cap_empty_set);
	29	EXPORT_SYMBOL(__cap_full_set);
	30	EXPORT_SYMBOL(__cap_init_eff_set);
	31
1f29fae2 SH	32	int file_caps_enabled = 1;
	33
	34	static int __init file_caps_disable(char *str)
	35	{
	36	file_caps_enabled = 0;
	37	return 1;
	38	}
	39	__setup("no_file_caps", file_caps_disable);
1f29fae2	40
e338d263 AM	41	/*
	42	* More recent versions of libcap are available from:
	43	*
	44	* http://www.kernel.org/pub/linux/libs/security/linux-privs/
	45	*/
	46
	47	static void warn_legacy_capability_use(void)
	48	{
	49	static int warned;
	50	if (!warned) {
	51	char name[sizeof(current->comm)];
	52
	53	printk(KERN_INFO "warning: `%s' uses 32-bit capabilities"
	54	" (legacy support in use)\n",
	55	get_task_comm(name, current));
	56	warned = 1;
	57	}
	58	}
	59
ca05a99a AM	60	/*
	61	* Version 2 capabilities worked fine, but the linux/capability.h file
	62	* that accompanied their introduction encouraged their use without
	63	* the necessary user-space source code changes. As such, we have
	64	* created a version 3 with equivalent functionality to version 2, but
	65	* with a header change to protect legacy source code from using
	66	* version 2 when it wanted to use version 1. If your system has code
	67	* that trips the following warning, it is using version 2 specific
	68	* capabilities and may be doing so insecurely.
	69	*
	70	* The remedy is to either upgrade your version of libcap (to 2.10+,
	71	* if the application is linked against it), or recompile your
	72	* application with modern kernel headers and this warning will go
	73	* away.
	74	*/
	75
	76	static void warn_deprecated_v2(void)
	77	{
	78	static int warned;
	79
	80	if (!warned) {
	81	char name[sizeof(current->comm)];
	82
	83	printk(KERN_INFO "warning: `%s' uses deprecated v2"
	84	" capabilities in a way that may be insecure.\n",
	85	get_task_comm(name, current));
	86	warned = 1;
	87	}
	88	}
	89
	90	/*
	91	* Version check. Return the number of u32s in each capability flag
	92	* array, or a negative value on error.
	93	*/
	94	static int cap_validate_magic(cap_user_header_t header, unsigned *tocopy)
	95	{
	96	__u32 version;
	97
	98	if (get_user(version, &header->version))
	99	return -EFAULT;
	100
	101	switch (version) {
	102	case _LINUX_CAPABILITY_VERSION_1:
	103	warn_legacy_capability_use();
	104	*tocopy = _LINUX_CAPABILITY_U32S_1;
	105	break;
	106	case _LINUX_CAPABILITY_VERSION_2:
	107	warn_deprecated_v2();
	108	/*
	109	* fall through - v3 is otherwise equivalent to v2.
	110	*/
	111	case _LINUX_CAPABILITY_VERSION_3:
	112	*tocopy = _LINUX_CAPABILITY_U32S_3;
	113	break;
	114	default:
	115	if (put_user((u32)_KERNEL_CAPABILITY_VERSION, &header->version))
	116	return -EFAULT;
	117	return -EINVAL;
	118	}
	119
	120	return 0;
	121	}
	122
ab763c71	123	/*
d84f4f99 DH	124	* The only thing that can change the capabilities of the current
	125	* process is the current process. As such, we can't be in this code
	126	* at the same time as we are in the process of setting capabilities
	127	* in this process. The net result is that we can limit our use of
	128	* locks to when we are reading the caps of another process.
ab763c71 AM	129	*/
	130	static inline int cap_get_target_pid(pid_t pid, kernel_cap_t *pEp,
	131	kernel_cap_t pIp, kernel_cap_t pPp)
	132	{
	133	int ret;
	134
	135	if (pid && (pid != task_pid_vnr(current))) {
	136	struct task_struct *target;
	137
ab763c71 AM	138	read_lock(&tasklist_lock);
	139
	140	target = find_task_by_vpid(pid);
	141	if (!target)
	142	ret = -ESRCH;
	143	else
	144	ret = security_capget(target, pEp, pIp, pPp);
	145
	146	read_unlock(&tasklist_lock);
ab763c71 AM	147	} else
	148	ret = security_capget(current, pEp, pIp, pPp);
	149
	150	return ret;
	151	}
	152
207a7ba8	153	/**
1da177e4	154	* sys_capget - get the capabilities of a given process.
207a7ba8 RD	155	* @header: pointer to struct that contains capability version and
	156	* target pid data
	157	* @dataptr: pointer to struct that contains the effective, permitted,
	158	* and inheritable capabilities that are returned
	159	*
	160	* Returns 0 on success and < 0 on error.
1da177e4	161	*/
b290ebe2	162	SYSCALL_DEFINE2(capget, cap_user_header_t, header, cap_user_data_t, dataptr)
1da177e4	163	{
314f70fd DW	164	int ret = 0;
314f70fd DW	165	pid_t pid;
e338d263 AM	166	unsigned tocopy;
e338d263 AM	167	kernel_cap_t pE, pI, pP;
314f70fd	168
ca05a99a	169	ret = cap_validate_magic(header, &tocopy);
c4a5af54 AM	170	if ((dataptr == NULL) \|\| (ret != 0))
c4a5af54 AM	171	return ((dataptr == NULL) && (ret == -EINVAL)) ? 0 : ret;
1da177e4	172
314f70fd DW	173	if (get_user(pid, &header->pid))
314f70fd DW	174	return -EFAULT;
1da177e4	175
314f70fd DW	176	if (pid < 0)
314f70fd DW	177	return -EINVAL;
1da177e4	178
ab763c71	179	ret = cap_get_target_pid(pid, &pE, &pI, &pP);
e338d263	180	if (!ret) {
ca05a99a	181	struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
e338d263 AM	182	unsigned i;
	183
	184	for (i = 0; i < tocopy; i++) {
	185	kdata[i].effective = pE.cap[i];
	186	kdata[i].permitted = pP.cap[i];
	187	kdata[i].inheritable = pI.cap[i];
	188	}
	189
	190	/*
ca05a99a	191	* Note, in the case, tocopy < _KERNEL_CAPABILITY_U32S,
e338d263 AM	192	* we silently drop the upper capabilities here. This
	193	* has the effect of making older libcap
	194	* implementations implicitly drop upper capability
	195	* bits when they perform a: capget/modify/capset
	196	* sequence.
	197	*
	198	* This behavior is considered fail-safe
	199	* behavior. Upgrading the application to a newer
	200	* version of libcap will enable access to the newer
	201	* capabilities.
	202	*
	203	* An alternative would be to return an error here
	204	* (-ERANGE), but that causes legacy applications to
	205	* unexpectidly fail; the capget/modify/capset aborts
	206	* before modification is attempted and the application
	207	* fails.
	208	*/
e338d263 AM	209	if (copy_to_user(dataptr, kdata, tocopy
	210	* sizeof(struct __user_cap_data_struct))) {
	211	return -EFAULT;
	212	}
	213	}
1da177e4	214
314f70fd	215	return ret;
1da177e4 LT	216	}
1da177e4 LT	217
207a7ba8	218	/**
ab763c71	219	* sys_capset - set capabilities for a process or (*) a group of processes
207a7ba8 RD	220	* @header: pointer to struct that contains capability version and
	221	* target pid data
	222	* @data: pointer to struct that contains the effective, permitted,
	223	* and inheritable capabilities
	224	*
1cdcbec1 DH	225	* Set capabilities for the current process only. The ability to any other
1cdcbec1 DH	226	* process(es) has been deprecated and removed.
1da177e4 LT	227	*
	228	* The restrictions on setting capabilities are specified as:
	229	*
1cdcbec1 DH	230	* I: any raised capabilities must be a subset of the old permitted
	231	* P: any raised capabilities must be a subset of the old permitted
	232	* E: must be set to a subset of new permitted
207a7ba8 RD	233	*
207a7ba8 RD	234	* Returns 0 on success and < 0 on error.
1da177e4	235	*/
b290ebe2	236	SYSCALL_DEFINE2(capset, cap_user_header_t, header, const cap_user_data_t, data)
1da177e4	237	{
ca05a99a	238	struct __user_cap_data_struct kdata[_KERNEL_CAPABILITY_U32S];
825332e4	239	unsigned i, tocopy, copybytes;
314f70fd	240	kernel_cap_t inheritable, permitted, effective;
d84f4f99	241	struct cred *new;
314f70fd DW	242	int ret;
	243	pid_t pid;
	244
ca05a99a AM	245	ret = cap_validate_magic(header, &tocopy);
	246	if (ret != 0)
	247	return ret;
314f70fd DW	248
	249	if (get_user(pid, &header->pid))
	250	return -EFAULT;
	251
1cdcbec1 DH	252	/* may only affect current now */
	253	if (pid != 0 && pid != task_pid_vnr(current))
	254	return -EPERM;
	255
825332e4 AV	256	copybytes = tocopy * sizeof(struct __user_cap_data_struct);
	257	if (copybytes > sizeof(kdata))
	258	return -EFAULT;
	259
	260	if (copy_from_user(&kdata, data, copybytes))
314f70fd	261	return -EFAULT;
e338d263 AM	262
	263	for (i = 0; i < tocopy; i++) {
	264	effective.cap[i] = kdata[i].effective;
	265	permitted.cap[i] = kdata[i].permitted;
	266	inheritable.cap[i] = kdata[i].inheritable;
	267	}
ca05a99a	268	while (i < _KERNEL_CAPABILITY_U32S) {
e338d263 AM	269	effective.cap[i] = 0;
	270	permitted.cap[i] = 0;
	271	inheritable.cap[i] = 0;
	272	i++;
	273	}
314f70fd	274
d84f4f99 DH	275	new = prepare_creds();
	276	if (!new)
	277	return -ENOMEM;
	278
	279	ret = security_capset(new, current_cred(),
	280	&effective, &inheritable, &permitted);
	281	if (ret < 0)
	282	goto error;
	283
57f71a0a	284	audit_log_capset(pid, new, current_cred());
e68b75a0	285
d84f4f99 DH	286	return commit_creds(new);
	287
	288	error:
	289	abort_creds(new);
314f70fd	290	return ret;
1da177e4	291	}
12b5989b	292
5cd9c58f DH	293	/**
	294	* capable - Determine if the current task has a superior capability in effect
	295	* @cap: The capability to be tested for
	296	*
	297	* Return true if the current task has the given superior capability currently
	298	* available for use, false if not.
	299	*
	300	* This sets PF_SUPERPRIV on the task if the capability is available on the
	301	* assumption that it's about to be used.
	302	*/
	303	int capable(int cap)
12b5989b	304	{
637d32dc EP	305	if (unlikely(!cap_valid(cap))) {
	306	printk(KERN_CRIT "capable() called with invalid cap=%u\n", cap);
	307	BUG();
	308	}
	309
3699c53c	310	if (security_capable(cap) == 0) {
5cd9c58f	311	current->flags \|= PF_SUPERPRIV;
12b5989b CW	312	return 1;
	313	}
	314	return 0;
	315	}
12b5989b	316	EXPORT_SYMBOL(capable);