| NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | LINKING | SEE ALSO | COLOPHON | The Linux Programming Interface |
REQUEST_KEY(2) Linux Key Management Calls REQUEST_KEY(2)
request_key - Request a key from the kernel's key management facility
#include <keyutils.h>
key_serial_t request_key(const char *type, const char *description,
const char *callout_info, key_serial_t keyring);
request_key() asks the kernel to find a key of the given type that matches the
specified description and, if successful, to attach it to the nominated
keyring and to return its serial number.
request_key() first recursively searches all the keyrings attached to the
calling process in the order thread-specific keyring, process-specific keyring
and then session keyring for a matching key.
If request_key() is called from a program invoked by request_key() on behalf
of some other process to generate a key, then the keyrings of that other
process will be searched next, using that other process's UID, GID, groups and
security context to control access.
The keys in each keyring searched are checked for a match before any child
keyrings are recursed into. Only keys that are searchable for the caller may
be found, and only searchable keyrings may be searched.
If the key is not found then, if callout_info is set, this function will
attempt to look further afield. In such a case, the callout_info is passed to
a userspace service such as /sbin/request-key to generate the key.
If that is unsuccessful also, then an error will be returned, and a temporary
negative key will be installed in the nominated keyring. This will expire
after a few seconds, but will cause subsequent calls to request_key() to fail
until it does.
The keyring serial number may be that of a valid keyring to which the caller
has write permission, or it may be a special keyring ID:
KEY_SPEC_THREAD_KEYRING
This specifies the caller's thread-specific keyring.
KEY_SPEC_PROCESS_KEYRING
This specifies the caller's process-specific keyring.
KEY_SPEC_SESSION_KEYRING
This specifies the caller's session-specific keyring.
KEY_SPEC_USER_KEYRING
This specifies the caller's UID-specific keyring.
KEY_SPEC_USER_SESSION_KEYRING
This specifies the caller's UID-session keyring.
If a key is created, no matter whether it's a valid key or a negative key, it
will displace any other key of the same type and description from the
destination keyring.
On success request_key() returns the serial number of the key it found. On
error, the value -1 will be returned and errno will have been set to an
appropriate error.
EACCES The keyring wasn't available for modification by the user.
EINTR The request was interrupted by a signal.
EDQUOT The key quota for this user would be exceeded by creating this key or
linking it to the keyring.
EKEYEXPIRED
An expired key was found, but no replacement could be obtained.
EKEYREJECTED
The attempt to generate a new key was rejected.
EKEYREVOKED
A revoked key was found, but no replacement could be obtained.
ENOMEM Insufficient memory to create a key.
ENOKEY No matching key was found.
Although this is a Linux system call, it is not present in libc but can be
found rather in libkeyutils. When linking, -lkeyutils should be specified to
the linker.
keyctl(1), add_key(2), keyctl(2), request-key(8)
This page is part of release 3.32 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can be found
at http://www.kernel.org/doc/man-pages/.
Linux 2010-02-25 REQUEST_KEY(2)
HTML rendering created 2010-12-03 by Michael Kerrisk, author of The Linux Programming Interface