Commit 3486740a authored by Serge E. Hallyn's avatar Serge E. Hallyn Committed by Linus Torvalds

userns: security: make capabilities relative to the user namespace

- Introduce ns_capable to test for a capability in a non-default
  user namespace.
- Teach cap_capable to handle capabilities in a non-default
  user namespace.

The motivation is to get to the unprivileged creation of new
namespaces.  It looks like this gets us 90% of the way there, with
only potential uid confusion issues left.

I still need to handle getting all caps after creation but otherwise I
think I have a good starter patch that achieves all of your goals.

Changelog:
	11/05/2010: [serge] add apparmor
	12/14/2010: [serge] fix capabilities to created user namespaces
	Without this, if user serge creates a user_ns, he won't have
	capabilities to the user_ns he created.  THis is because we
	were first checking whether his effective caps had the caps
	he needed and returning -EPERM if not, and THEN checking whether
	he was the creator.  Reverse those checks.
	12/16/2010: [serge] security_real_capable needs ns argument in !security case
	01/11/2011: [serge] add task_ns_capable helper
	01/11/2011: [serge] add nsown_capable() helper per Bastian Blank suggestion
	02/16/2011: [serge] fix a logic bug: the root user is always creator of
		    init_user_ns, but should not always have capabilities to
		    it!  Fix the check in cap_capable().
	02/21/2011: Add the required user_ns parameter to security_capable,
		    fixing a compile failure.
	02/23/2011: Convert some macros to functions as per akpm comments.  Some
		    couldn't be converted because we can't easily forward-declare
		    them (they are inline if !SECURITY, extern if SECURITY).  Add
		    a current_user_ns function so we can use it in capability.h
		    without #including cred.h.  Move all forward declarations
		    together to the top of the #ifdef __KERNEL__ section, and use
		    kernel-doc format.
	02/23/2011: Per dhowells, clean up comment in cap_capable().
	02/23/2011: Per akpm, remove unreachable 'return -EPERM' in cap_capable.

(Original written and signed off by Eric;  latest, modified version
acked by him)

[akpm@linux-foundation.org: fix build]
[akpm@linux-foundation.org: export current_user_ns() for ecryptfs]
[serge.hallyn@canonical.com: remove unneeded extra argument in selinux's task_has_capability]
Signed-off-by: default avatarEric W. Biederman <ebiederm@xmission.com>
Signed-off-by: default avatarSerge E. Hallyn <serge.hallyn@canonical.com>
Acked-by: default avatar"Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: default avatarDaniel Lezcano <daniel.lezcano@free.fr>
Acked-by: default avatarDavid Howells <dhowells@redhat.com>
Cc: James Morris <jmorris@namei.org>
Signed-off-by: default avatarSerge E. Hallyn <serge.hallyn@canonical.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 59607db3
......@@ -369,7 +369,7 @@ pci_read_config(struct file *filp, struct kobject *kobj,
u8 *data = (u8*) buf;
/* Several chips lock up trying to read undefined config space */
if (security_capable(filp->f_cred, CAP_SYS_ADMIN) == 0) {
if (security_capable(&init_user_ns, filp->f_cred, CAP_SYS_ADMIN) == 0) {
size = dev->cfg_size;
} else if (dev->hdr_type == PCI_HEADER_TYPE_CARDBUS) {
size = 128;
......
......@@ -368,6 +368,17 @@ struct cpu_vfs_cap_data {
#ifdef __KERNEL__
struct dentry;
struct user_namespace;
extern struct user_namespace init_user_ns;
struct user_namespace *current_user_ns(void);
extern const kernel_cap_t __cap_empty_set;
extern const kernel_cap_t __cap_full_set;
extern const kernel_cap_t __cap_init_eff_set;
/*
* Internal kernel functions only
*/
......@@ -530,10 +541,6 @@ static inline kernel_cap_t cap_raise_nfsd_set(const kernel_cap_t a,
cap_intersect(permitted, __cap_nfsd_set));
}
extern const kernel_cap_t __cap_empty_set;
extern const kernel_cap_t __cap_full_set;
extern const kernel_cap_t __cap_init_eff_set;
/**
* has_capability - Determine if a task has a superior capability available
* @t: The task in question
......@@ -544,7 +551,7 @@ extern const kernel_cap_t __cap_init_eff_set;
*
* Note that this does not set PF_SUPERPRIV on the task.
*/
#define has_capability(t, cap) (security_real_capable((t), (cap)) == 0)
#define has_capability(t, cap) (security_real_capable((t), &init_user_ns, (cap)) == 0)
/**
* has_capability_noaudit - Determine if a task has a superior capability available (unaudited)
......@@ -558,12 +565,25 @@ extern const kernel_cap_t __cap_init_eff_set;
* Note that this does not set PF_SUPERPRIV on the task.
*/
#define has_capability_noaudit(t, cap) \
(security_real_capable_noaudit((t), (cap)) == 0)
(security_real_capable_noaudit((t), &init_user_ns, (cap)) == 0)
extern int capable(int cap);
extern bool capable(int cap);
extern bool ns_capable(struct user_namespace *ns, int cap);
extern bool task_ns_capable(struct task_struct *t, int cap);
/**
* nsown_capable - Check superior capability to one's own user_ns
* @cap: The capability in question
*
* Return true if the current task has the given superior capability
* targeted at its own user namespace.
*/
static inline bool nsown_capable(int cap)
{
return ns_capable(current_user_ns(), cap);
}
/* audit system wants to get cap info from files as well */
struct dentry;
extern int get_vfs_caps_from_disk(const struct dentry *dentry, struct cpu_vfs_cap_data *cpu_caps);
#endif /* __KERNEL__ */
......
......@@ -354,9 +354,11 @@ static inline void put_cred(const struct cred *_cred)
#define current_fsgid() (current_cred_xxx(fsgid))
#define current_cap() (current_cred_xxx(cap_effective))
#define current_user() (current_cred_xxx(user))
#define current_user_ns() (current_cred_xxx(user)->user_ns)
#define _current_user_ns() (current_cred_xxx(user)->user_ns)
#define current_security() (current_cred_xxx(security))
extern struct user_namespace *current_user_ns(void);
#define current_uid_gid(_uid, _gid) \
do { \
const struct cred *__cred; \
......
......@@ -47,13 +47,14 @@
struct ctl_table;
struct audit_krule;
struct user_namespace;
/*
* These functions are in security/capability.c and are used
* as the default capabilities functions
*/
extern int cap_capable(struct task_struct *tsk, const struct cred *cred,
int cap, int audit);
struct user_namespace *ns, int cap, int audit);
extern int cap_settime(const struct timespec *ts, const struct timezone *tz);
extern int cap_ptrace_access_check(struct task_struct *child, unsigned int mode);
extern int cap_ptrace_traceme(struct task_struct *parent);
......@@ -1262,6 +1263,7 @@ static inline void security_free_mnt_opts(struct security_mnt_opts *opts)
* credentials.
* @tsk contains the task_struct for the process.
* @cred contains the credentials to use.
* @ns contains the user namespace we want the capability in
* @cap contains the capability <include/linux/capability.h>.
* @audit: Whether to write an audit message or not
* Return 0 if the capability is granted for @tsk.
......@@ -1384,7 +1386,7 @@ struct security_operations {
const kernel_cap_t *inheritable,
const kernel_cap_t *permitted);
int (*capable) (struct task_struct *tsk, const struct cred *cred,
int cap, int audit);
struct user_namespace *ns, int cap, int audit);
int (*quotactl) (int cmds, int type, int id, struct super_block *sb);
int (*quota_on) (struct dentry *dentry);
int (*syslog) (int type);
......@@ -1665,9 +1667,12 @@ int security_capset(struct cred *new, const struct cred *old,
const kernel_cap_t *effective,
const kernel_cap_t *inheritable,
const kernel_cap_t *permitted);
int security_capable(const struct cred *cred, int cap);
int security_real_capable(struct task_struct *tsk, int cap);
int security_real_capable_noaudit(struct task_struct *tsk, int cap);
int security_capable(struct user_namespace *ns, const struct cred *cred,
int cap);
int security_real_capable(struct task_struct *tsk, struct user_namespace *ns,
int cap);
int security_real_capable_noaudit(struct task_struct *tsk,
struct user_namespace *ns, int cap);
int security_quotactl(int cmds, int type, int id, struct super_block *sb);
int security_quota_on(struct dentry *dentry);
int security_syslog(int type);
......@@ -1860,28 +1865,29 @@ static inline int security_capset(struct cred *new,
return cap_capset(new, old, effective, inheritable, permitted);
}
static inline int security_capable(const struct cred *cred, int cap)
static inline int security_capable(struct user_namespace *ns,
const struct cred *cred, int cap)
{
return cap_capable(current, cred, cap, SECURITY_CAP_AUDIT);
return cap_capable(current, cred, ns, cap, SECURITY_CAP_AUDIT);
}
static inline int security_real_capable(struct task_struct *tsk, int cap)
static inline int security_real_capable(struct task_struct *tsk, struct user_namespace *ns, int cap)
{
int ret;
rcu_read_lock();
ret = cap_capable(tsk, __task_cred(tsk), cap, SECURITY_CAP_AUDIT);
ret = cap_capable(tsk, __task_cred(tsk), ns, cap, SECURITY_CAP_AUDIT);
rcu_read_unlock();
return ret;
}
static inline
int security_real_capable_noaudit(struct task_struct *tsk, int cap)
int security_real_capable_noaudit(struct task_struct *tsk, struct user_namespace *ns, int cap)
{
int ret;
rcu_read_lock();
ret = cap_capable(tsk, __task_cred(tsk), cap,
ret = cap_capable(tsk, __task_cred(tsk), ns, cap,
SECURITY_CAP_NOAUDIT);
rcu_read_unlock();
return ret;
......
......@@ -14,6 +14,7 @@
#include <linux/security.h>
#include <linux/syscalls.h>
#include <linux/pid_namespace.h>
#include <linux/user_namespace.h>
#include <asm/uaccess.h>
/*
......@@ -299,17 +300,48 @@ SYSCALL_DEFINE2(capset, cap_user_header_t, header, const cap_user_data_t, data)
* 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)
bool capable(int cap)
{
return ns_capable(&init_user_ns, cap);
}
EXPORT_SYMBOL(capable);
/**
* ns_capable - Determine if the current task has a superior capability in effect
* @ns: The usernamespace we want the capability in
* @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.
*/
bool ns_capable(struct user_namespace *ns, int cap)
{
if (unlikely(!cap_valid(cap))) {
printk(KERN_CRIT "capable() called with invalid cap=%u\n", cap);
BUG();
}
if (security_capable(current_cred(), cap) == 0) {
if (security_capable(ns, current_cred(), cap) == 0) {
current->flags |= PF_SUPERPRIV;
return 1;
return true;
}
return 0;
return false;
}
EXPORT_SYMBOL(capable);
EXPORT_SYMBOL(ns_capable);
/**
* task_ns_capable - Determine whether current task has a superior
* capability targeted at a specific task's user namespace.
* @t: The task whose user namespace is targeted.
* @cap: The capability in question.
*
* Return true if it does, false otherwise.
*/
bool task_ns_capable(struct task_struct *t, int cap)
{
return ns_capable(task_cred_xxx(t, user)->user_ns, cap);
}
EXPORT_SYMBOL(task_ns_capable);
......@@ -741,6 +741,12 @@ int set_create_files_as(struct cred *new, struct inode *inode)
}
EXPORT_SYMBOL(set_create_files_as);
struct user_namespace *current_user_ns(void)
{
return _current_user_ns();
}
EXPORT_SYMBOL(current_user_ns);
#ifdef CONFIG_DEBUG_CREDENTIALS
bool creds_are_invalid(const struct cred *cred)
......
......@@ -22,6 +22,7 @@
#include <linux/ctype.h>
#include <linux/sysctl.h>
#include <linux/audit.h>
#include <linux/user_namespace.h>
#include <net/sock.h>
#include "include/apparmor.h"
......@@ -136,11 +137,11 @@ static int apparmor_capget(struct task_struct *target, kernel_cap_t *effective,
}
static int apparmor_capable(struct task_struct *task, const struct cred *cred,
int cap, int audit)
struct user_namespace *ns, int cap, int audit)
{
struct aa_profile *profile;
/* cap_capable returns 0 on success, else -EPERM */
int error = cap_capable(task, cred, cap, audit);
int error = cap_capable(task, cred, ns, cap, audit);
if (!error) {
profile = aa_cred_profile(cred);
if (!unconfined(profile))
......
......@@ -27,6 +27,7 @@
#include <linux/sched.h>
#include <linux/prctl.h>
#include <linux/securebits.h>
#include <linux/user_namespace.h>
/*
* If a non-root user executes a setuid-root binary in
......@@ -67,6 +68,7 @@ EXPORT_SYMBOL(cap_netlink_recv);
* cap_capable - Determine whether a task has a particular effective capability
* @tsk: The task to query
* @cred: The credentials to use
* @ns: The user namespace in which we need the capability
* @cap: The capability to check for
* @audit: Whether to write an audit message or not
*
......@@ -78,10 +80,30 @@ EXPORT_SYMBOL(cap_netlink_recv);
* cap_has_capability() returns 0 when a task has a capability, but the
* kernel's capable() and has_capability() returns 1 for this case.
*/
int cap_capable(struct task_struct *tsk, const struct cred *cred, int cap,
int audit)
int cap_capable(struct task_struct *tsk, const struct cred *cred,
struct user_namespace *targ_ns, int cap, int audit)
{
return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
for (;;) {
/* The creator of the user namespace has all caps. */
if (targ_ns != &init_user_ns && targ_ns->creator == cred->user)
return 0;
/* Do we have the necessary capabilities? */
if (targ_ns == cred->user->user_ns)
return cap_raised(cred->cap_effective, cap) ? 0 : -EPERM;
/* Have we tried all of the parent namespaces? */
if (targ_ns == &init_user_ns)
return -EPERM;
/*
*If you have a capability in a parent user ns, then you have
* it over all children user namespaces as well.
*/
targ_ns = targ_ns->creator->user_ns;
}
/* We never get here */
}
/**
......@@ -176,7 +198,8 @@ static inline int cap_inh_is_capped(void)
/* they are so limited unless the current task has the CAP_SETPCAP
* capability
*/
if (cap_capable(current, current_cred(), CAP_SETPCAP,
if (cap_capable(current, current_cred(),
current_cred()->user->user_ns, CAP_SETPCAP,
SECURITY_CAP_AUDIT) == 0)
return 0;
return 1;
......@@ -828,7 +851,8 @@ int cap_task_prctl(int option, unsigned long arg2, unsigned long arg3,
& (new->securebits ^ arg2)) /*[1]*/
|| ((new->securebits & SECURE_ALL_LOCKS & ~arg2)) /*[2]*/
|| (arg2 & ~(SECURE_ALL_LOCKS | SECURE_ALL_BITS)) /*[3]*/
|| (cap_capable(current, current_cred(), CAP_SETPCAP,
|| (cap_capable(current, current_cred(),
current_cred()->user->user_ns, CAP_SETPCAP,
SECURITY_CAP_AUDIT) != 0) /*[4]*/
/*
* [1] no changing of bits that are locked
......@@ -893,7 +917,7 @@ int cap_vm_enough_memory(struct mm_struct *mm, long pages)
{
int cap_sys_admin = 0;
if (cap_capable(current, current_cred(), CAP_SYS_ADMIN,
if (cap_capable(current, current_cred(), &init_user_ns, CAP_SYS_ADMIN,
SECURITY_CAP_NOAUDIT) == 0)
cap_sys_admin = 1;
return __vm_enough_memory(mm, pages, cap_sys_admin);
......@@ -920,7 +944,7 @@ int cap_file_mmap(struct file *file, unsigned long reqprot,
int ret = 0;
if (addr < dac_mmap_min_addr) {
ret = cap_capable(current, current_cred(), CAP_SYS_RAWIO,
ret = cap_capable(current, current_cred(), &init_user_ns, CAP_SYS_RAWIO,
SECURITY_CAP_AUDIT);
/* set PF_SUPERPRIV if it turns out we allow the low mmap */
if (ret == 0)
......
......@@ -154,29 +154,33 @@ int security_capset(struct cred *new, const struct cred *old,
effective, inheritable, permitted);
}
int security_capable(const struct cred *cred, int cap)
int security_capable(struct user_namespace *ns, const struct cred *cred,
int cap)
{
return security_ops->capable(current, cred, cap, SECURITY_CAP_AUDIT);
return security_ops->capable(current, cred, ns, cap,
SECURITY_CAP_AUDIT);
}
int security_real_capable(struct task_struct *tsk, int cap)
int security_real_capable(struct task_struct *tsk, struct user_namespace *ns,
int cap)
{
const struct cred *cred;
int ret;
cred = get_task_cred(tsk);
ret = security_ops->capable(tsk, cred, cap, SECURITY_CAP_AUDIT);
ret = security_ops->capable(tsk, cred, ns, cap, SECURITY_CAP_AUDIT);
put_cred(cred);
return ret;
}
int security_real_capable_noaudit(struct task_struct *tsk, int cap)
int security_real_capable_noaudit(struct task_struct *tsk,
struct user_namespace *ns, int cap)
{
const struct cred *cred;
int ret;
cred = get_task_cred(tsk);
ret = security_ops->capable(tsk, cred, cap, SECURITY_CAP_NOAUDIT);
ret = security_ops->capable(tsk, cred, ns, cap, SECURITY_CAP_NOAUDIT);
put_cred(cred);
return ret;
}
......
......@@ -79,6 +79,7 @@
#include <linux/mutex.h>
#include <linux/posix-timers.h>
#include <linux/syslog.h>
#include <linux/user_namespace.h>
#include "avc.h"
#include "objsec.h"
......@@ -1846,11 +1847,11 @@ static int selinux_capset(struct cred *new, const struct cred *old,
*/
static int selinux_capable(struct task_struct *tsk, const struct cred *cred,
int cap, int audit)
struct user_namespace *ns, int cap, int audit)
{
int rc;
rc = cap_capable(tsk, cred, cap, audit);
rc = cap_capable(tsk, cred, ns, cap, audit);
if (rc)
return rc;
......@@ -1931,7 +1932,8 @@ static int selinux_vm_enough_memory(struct mm_struct *mm, long pages)
{
int rc, cap_sys_admin = 0;
rc = selinux_capable(current, current_cred(), CAP_SYS_ADMIN,
rc = selinux_capable(current, current_cred(),
&init_user_ns, CAP_SYS_ADMIN,
SECURITY_CAP_NOAUDIT);
if (rc == 0)
cap_sys_admin = 1;
......@@ -2834,7 +2836,8 @@ static int selinux_inode_getsecurity(const struct inode *inode, const char *name
* and lack of permission just means that we fall back to the
* in-core context value, not a denial.
*/
error = selinux_capable(current, current_cred(), CAP_MAC_ADMIN,
error = selinux_capable(current, current_cred(),
&init_user_ns, CAP_MAC_ADMIN,
SECURITY_CAP_NOAUDIT);
if (!error)
error = security_sid_to_context_force(isec->sid, &context,
......@@ -2968,7 +2971,7 @@ static int selinux_file_ioctl(struct file *file, unsigned int cmd,
case KDSKBENT:
case KDSKBSENT:
error = task_has_capability(current, cred, CAP_SYS_TTY_CONFIG,
SECURITY_CAP_AUDIT);
SECURITY_CAP_AUDIT);
break;
/* default case assumes that the command will go
......
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