Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
Written by David Howells (firstname.lastname@example.org)
and Copyright (C) 2016 Michael Kerrisk <email@example.com>
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version
2 of the License, or (at your option) any later version.
(The comments found at the beginning of the groff file "man2/request_key.2".)
request_key - request a key from the kernel's key management facility
key_serial_t request_key(const char *type, const char *description,
const char *callout_info,
asks the kernel to find a key of the given
that matches the specified
and, if successful, to attach it to the nominated
and to return its serial number.
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.
is called from a program invoked by
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
for the caller may be found, and only
keyrings may be searched.
If the key is not found, then, if
is set, this function will attempt to look further afield.
In such a case, the
is passed to a user-space service such as
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
This will expire after a few seconds, but will cause subsequent
to fail until it does.
serial number may be that of a valid keyring to which the caller has write
permission, or it may be a special keyring ID:
This specifies the caller's thread-specific keyring.
This specifies the caller's process-specific keyring.
This specifies the caller's session-specific keyring.
This specifies the caller's UID-specific 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
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.
The keyring wasn't available for modification by the user.
The request was interrupted by a signal.
The key quota for this user would be exceeded by creating this key or linking
it to the keyring.
An expired key was found, but no replacement could be obtained.
The attempt to generate a new key was rejected.
A revoked key was found, but no replacement could be obtained.
Insufficient memory to create a key.
No matching key was found.
Although this is a Linux system call, it is not present in
but can be found rather in
should be specified to the linker.
This page is part of release 4.04 of the Linux
A description of the project,
information about reporting bugs,
and the latest version of this page,
can be found at