NAME

       cap_get_proc, cap_set_proc, capgetp, cap_get_bound, cap_drop_bound - capability manipulation on processes

SYNOPSIS

       #include <sys/capability.h>

       cap_t cap_get_proc(void);

       int cap_set_proc(cap_t cap_p);

       int cap_get_bound(cap_value_t cap);

       CAP_IS_SUPPORTED(cap_value_t cap);

       int cap_drop_bound(cap_value_t cap);

       #include <sys/types.h>

       cap_t cap_get_pid(pid_t pid);

       Link with -lcap.

DESCRIPTION

       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  capabilities  to  the  capability  state
       identified  by  cap_p.   The  new  capability  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 process will remain unchanged.

       cap_get_pid() returns cap_t, see cap_init(3), with the process capabilities 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_SUPPORTED(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  capability,  cap,  To complete
       successfully, the prevailing effective capability set must have a raised CAP_SETPCAP.

RETURN VALUE

       The functions cap_get_proc() and cap_get_pid() return a non-NULL value on success, and NULL on failure.

       The function cap_get_bound() returns -1 if the requested capability  is  unknown,  otherwise  the  return
       value  reflects  the  current  state  of  that  capability  in the prevailing bounding set. Note, a macro
       function,

       The functions cap_set_proc() and cap_drop_bound() return zero for success, and -1 on failure.

       On failure, errno is set to EINVAL, EPERM, or ENOMEM.

CONFORMING TO

       cap_set_proc()  and  cap_get_proc()  are  specified  in  the  withdrawn  POSIX.1e  draft   specification.
       cap_get_pid() is a Linux extension.

NOTES

       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 capabilities set in the target process(es)
       are those contained in cap_d.  Kernels 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.

EXAMPLE

       The code segment below raises the CAP_FOWNER and CAP_SETFCAP effective capabilities for the caller:

           cap_t caps;
           cap_value_t cap_list[2];

           if (!CAP_IS_SUPPORTED(CAP_SETFCAP))
               /* handle error */

           caps = cap_get_proc();
           if (caps == NULL)
               /* handle error */;

           cap_list[0] = CAP_FOWNER;
           cap_list[1] = CAP_SETFCAP;
           if (cap_set_flag(caps, CAP_EFFECTIVE, 2, cap_list, CAP_SET) == -1)
               /* handle error */;

           if (cap_set_proc(caps) == -1)
               /* handle error */;

           if (cap_free(caps) == -1)
               /* handle error */;

SEE ALSO

       libcap(3), cap_clear(3), cap_copy_ext(3), cap_from_text(3), cap_get_file(3), cap_init(3), capabilities(7)

                                                   2008-05-11                                    CAP_GET_PROC(3)