NAME

       cap_get_file, cap_set_file, cap_get_fd, cap_set_fd - capability manipulation on files

SYNOPSIS

       #include <sys/capability.h>

       cap_t cap_get_file(const char *path_p);

       int cap_set_file(const char *path_p, cap_t cap_p);

       cap_t cap_get_fd(int fd);

       int cap_set_fd(int fd, cap_t caps);

       Link with -lcap.

DESCRIPTION

       cap_get_file()  and cap_get_fd() allocate a capability state in working storage and set it
       to represent the capability state of the pathname pointed to by path_p or the file open on
       descriptor  fd.   These  functions return a pointer to the newly created capability state.
       The effects of reading the capability state from any file other than  a  regular  file  is
       undefined.   The  caller  should  free any releasable memory, when the capability state in
       working storage is no longer required, by calling cap_free() with the  used  cap_t  as  an
       argument.

       cap_set_file()  and  cap_set_fd()  set  the  values  for  all  capability  flags  for  all
       capabilities for the pathname pointed to by path_p or the file open on descriptor fd, with
       the  capability  state  identified  by  cap_p.   The  new  capability state of the file is
       completely determined by the contents of cap_p.   A  NULL  value  for  cap_p  is  used  to
       indicate  that  capabilities  for  the  file  should  be  deleted.  For these functions to
       succeed, the calling process must have the effective capability, CAP_SETFCAP, enabled  and
       either  the  effective  user  ID  of  the process must match the file owner or the calling
       process must have the CAP_FOWNER flag in its effective capability  set.   The  effects  of
       writing the capability state to any file type other than a regular file are undefined.

RETURN VALUE

       cap_get_file() and cap_get_fd() return a non-NULL value on success, and NULL on failure.

       cap_set_file() and cap_set_fd() return zero on success, and -1 on failure.

       On  failure, errno is set to EACCES, EBADFD, ENAMETOOLONG, ENOENT, ENOMEM, ENOTDIR, EPERM,
       or EROFS.

CONFORMING TO

       These functions are specified by withdrawn POSIX.1e draft specification.

NOTES

       Support for file capabilities is provided on Linux since version 2.6.24.

       On Linux, the file Effective set is a single bit.  If it is enabled,  then  all  Permitted
       capabilities  are  enabled  in  the  Effective set of the calling process when the file is
       executed; otherwise, no capabilities are enabled in the process's Effective set  following
       an  execve(2).   Because  the  file  Effective  set  is a single bit, if any capability is
       enabled in the Effective set of the cap_t given to cap_set_file()  or  cap_set_fd(),  then
       all  capabilities  whose  Permitted  or  Inheritable  flag  is  enabled must also have the
       Effective flag enabled.  Conversely, if the Effective bit is enabled on a file,  then  the
       cap_t returned by cap_get_file() and cap_get_fd() will have the Effective flag enabled for
       each capability that has the Permitted or Inheritable flag enabled.

SEE ALSO

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

                                            2008-05-11                            CAP_GET_FILE(3)