CAP_GET_FILE
Section: Linux Programmer's Manual (3)
Updated: 202-1-16
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NAME
cap_get_file, cap_set_file, cap_get_fd, cap_set_fd, cap_get_nsowner, cap_set_nsowner - 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);
uid_t cap_get_nsowner(cap_t caps);
int cap_set_nsowner(cap_t caps, uid_t rootuid);
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
CAP_SETFCAP
capability in its effective set
and either the effective user ID of the process must match the
file owner or the calling process must have the
CAP_FOWNER
capability in its effective capability set. The effects of writing the
capability state to any file type other than a regular file are
undefined.
A capability set held in memory can be associated with the root user ID in
use in a specific user namespace. It is possible to get and set this value
(in the memory copy) with
cap_get_nsowner()
and
cap_set_nsowner()
respectively. The root user ID is ignored by the libcap library in all cases
other than when the capability is written to a file. Only if the value
is no-zero will the library attempt to include it in the written file
capability set.
RETURN VALUE
cap_get_file()
and
cap_get_fd()
return a no-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),
user_namespaces(7)
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- CONFORMING TO
-
- NOTES
-
- SEE ALSO
-
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