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/*
* 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/export.h>
#include
<linux/security.h>
#include
<linux/syscalls.h>
#include
<linux/pid_namespace.h>
#include
<linux/user_namespace.h>
#include
<asm/uaccess.h>
/*
* Leveraged for setting/resetting capabilities
*/
const
kernel_cap_t
__cap_empty_set
=
CAP_EMPTY_SET
;
EXPORT_SYMBOL
(
__cap_empty_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
;
rcu_read_lock
();
target
=
find_task_by_vpid
(
pid
);
if
(!
target
)
ret
=
-
ESRCH
;
else
ret
=
security_capget
(
target
,
pEp
,
pIp
,
pPp
);
rcu_read_unlock
();
}
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
;
}
/**
* has_ns_capability - Does a task have a capability in a specific user ns
* @t: The task in question
* @ns: target user namespace
* @cap: The capability to be tested for
*
* Return true if the specified task has the given superior capability
* currently in effect to the specified user namespace, false if not.
*
* Note that this does not set PF_SUPERPRIV on the task.
*/
bool
has_ns_capability
(
struct
task_struct
*
t
,
struct
user_namespace
*
ns
,
int
cap
)
{
int
ret
;
rcu_read_lock
();
ret
=
security_capable
(
__task_cred
(
t
),
ns
,
cap
);
rcu_read_unlock
();
return
(
ret
==
0
);
}
/**
* has_capability - Does a task have a capability in init_user_ns
* @t: The task in question
* @cap: The capability to be tested for
*
* Return true if the specified task has the given superior capability
* currently in effect to the initial user namespace, false if not.
*
* Note that this does not set PF_SUPERPRIV on the task.
*/
bool
has_capability
(
struct
task_struct
*
t
,
int
cap
)
{
return
has_ns_capability
(
t
,
&
init_user_ns
,
cap
);
}
/**
* has_ns_capability_noaudit - Does a task have a capability (unaudited)
* in a specific user ns.
* @t: The task in question
* @ns: target user namespace
* @cap: The capability to be tested for
*
* Return true if the specified task has the given superior capability
* currently in effect to the specified user namespace, false if not.
* Do not write an audit message for the check.
*
* Note that this does not set PF_SUPERPRIV on the task.
*/
bool
has_ns_capability_noaudit
(
struct
task_struct
*
t
,
struct
user_namespace
*
ns
,
int
cap
)
{
int
ret
;
rcu_read_lock
();
ret
=
security_capable_noaudit
(
__task_cred
(
t
),
ns
,
cap
);
rcu_read_unlock
();
return
(
ret
==
0
);
}
/**
* has_capability_noaudit - Does a task have a capability (unaudited) in the
* initial user ns
* @t: The task in question
* @cap: The capability to be tested for
*
* Return true if the specified task has the given superior capability
* currently in effect to init_user_ns, false if not. Don't write an
* audit message for the check.
*
* Note that this does not set PF_SUPERPRIV on the task.
*/
bool
has_capability_noaudit
(
struct
task_struct
*
t
,
int
cap
)
{
return
has_ns_capability_noaudit
(
t
,
&
init_user_ns
,
cap
);
}
/**
* 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
(),
ns
,
cap
)
==
0
) {
current
->
flags
|=
PF_SUPERPRIV
;
return
true;
}
return
false;
}
EXPORT_SYMBOL
(
ns_capable
);
/**
* 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.
*/
bool
capable
(
int
cap
)
{
return
ns_capable
(
&
init_user_ns
,
cap
);
}
EXPORT_SYMBOL
(
capable
);
/**
* 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.
*/
bool
nsown_capable
(
int
cap
)
{
return
ns_capable
(
current_user_ns
(),
cap
);
}
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