[linux.git] / kernel / capability.c

/*
 * linux/kernel/capability.c
 *
 * Copyright (C) 1997  Andrew Main <[email protected]>
 *
 * Integrated into 2.1.97+,  Andrew G. Morgan <[email protected]>
 * 30 May 2002:	Cleanup, Robert M. Love <[email protected]>
 */

#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);

#ifdef CONFIG_SECURITY_FILE_CAPABILITIES
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);
#endif

/*
 * 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 (ret != 0)
		return 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;
	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;

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