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int cap_set_proc(cap_t cap_p);
int cap_get_bound(cap_value_t cap);
int cap_drop_bound(cap_value_t cap);
cap_t cap_get_pid(pid_t pid);
Link with -lcap.
cap_get_proc() allocates a capability state in working storage, sets
its state to that of the calling process, and returns a pointer to this
newly created capability state. The caller should free any releasable
memory, when the capability state in working storage is no longer
required, by calling cap_free() with the cap_t as an argument.
cap_set_proc() sets the values for all capability flags for all capa-
bilities to the capability state identified by cap_p. The new capabil-
ity state of the process will be completely determined by the contents
of cap_p upon successful return from this function. If any flag in
cap_p is set for any capability not currently permitted for the calling
process, the function will fail, and the capability state of the pro-
cess will remain unchanged.
cap_get_pid() returns cap_d, see cap_init(3), with the process capabil-
ities of the process indicated by pid. This information can also be
obtained from the /proc/<pid>/status file.
cap_get_bound() with a cap as an argument returns the current value of
this bounding set capability flag in effect for the current process.
This operation is unpriveged. Note, a macro function CAP_IS_SUP-
PORTED(cap_value_t cap) is provided that evaluates to true (1) if the
system supports the specified capability, cap. If the system does not
support the capability, this function returns 0. This macro works by
testing for an error condition with cap_get_bound().
cap_drop_bound() can be used to lower the specified bounding set capa-
bility, cap, To complete successfully, the prevailing effective capa-
bility set must have a raised CAP_SETPCAP.
POSIX.1e draft specification. cap_get_pid() is a Linux extension.
The library also supports the deprecated functions:
int capgetp(pid_t pid, cap_t cap_d);
int capsetp(pid_t pid, cap_t cap_d);
capgetp() attempts to obtain the capabilities of some other process;
storing the capabilities in a pre-allocated cap_d.See cap_init() for
information on allocating an empty capability set. This function,
capgetp(), is deprecated, you should use cap_get_pid().
capsetp() attempts to set the capabilities of some other process(es),
pid. If pid is positive it refers to a specific process; if it is
zero, it refers to the current process; -1 refers to all processes
other than the current process and process '1' (typically init(8));
other negative values refer to the -pid process group. In order to use
this function, the kernel must support it and the current process must
have CAP_SETPCAP raised in its Effective capability set. The capabili-
ties set in the target process(es) are those contained in cap_d. Ker-
nels that support filesystem capabilities redefine the semantics of
CAP_SETPCAP and on such systems this function will always fail for any
target not equal to the current process. capsetp() returns zero for
success, and -1 on failure.
Where supported by the kernel, the function capsetp() should be used
with care. It existed, primarily, to overcome an early lack of support
for capabilities in the filesystems supported by Linux. Note that, by
default, the only processes that have CAP_SETPCAP available to them are
processes started as a kernel thread. (Typically this includes
init(8), kflushd and kswapd). You will need to recompile the kernel to
modify this default.
The code segment below raises the CAP_FOWNER and CAP_SETFCAP effective
capabilities for the caller:
/* handle error */
caps = cap_get_proc();
if (caps == NULL)
/* handle error */;
cap_list = CAP_FOWNER;
cap_list = CAP_SETFCAP;
if (cap_set_flag(caps, CAP_EFFECTIVE, 2, cap_list, CAP_SET) == -1)