Section (7) user-session-keyring
user-session-keyring — per-user default session keyring
The user session keyring is a keyring used to anchor keys
on behalf of a user. Each UID the kernel deals with has its
own user session keyring that is shared by all processes with
that UID. The user session keyring has a name (description)
of the form
<UID> is the
user ID of the corresponding user.
The user session keyring is associated with the record that the kernel maintains for the UID. It comes into existence upon the first attempt to access either the user session keyring, the user-keyring(7), or the session-keyring(7). The keyring remains pinned in existence so long as there are processes running with that real UID or files opened by those processes remain open. (The keyring can also be pinned indefinitely by linking it into another keyring.)
The user session keyring is created on demand when a thread requests it or when a thread asks for its session-keyring(7) and that keyring doesn_zsingle_quotesz_t exist. In the latter case, a user session keyring will be created and, if the session keyring wasn_zsingle_quotesz_t to be created, the user session keyring will be set as the process_zsingle_quotesz_s actual session keyring.
The user session keyring is searched by request_key(2) if the actual session keyring does not exist and is ignored otherwise.
A special serial number value,
KEY_SPEC_USER_SESSION_KEYRING, is defined
that can be used in lieu of the actual serial number of the
calling process_zsingle_quotesz_s user session keyring.
From the keyctl(1) utility, _zsingle_quotesz_
@us_zsingle_quotesz_ can be used instead of a
numeric key ID in much the same way.
User session keyrings are independent of clone(2), fork(2), vfork(2), execve(2), and _exit(2) excepting that the keyring is destroyed when the UID record is destroyed when the last process pinning it exits.
If a user session keyring does not exist when it is accessed, it will be created.
Rather than relying on the user session keyring, it is strongly recommended—especially if the process is running as root—that a session-keyring(7) be set explicitly, for example by pam_keyinit(8).
The user session keyring was added to support situations where a process doesn_zsingle_quotesz_t have a session keyring, perhaps because it was created via a pathway that didn_zsingle_quotesz_t involve PAM (e.g., perhaps it was a daemon started by inetd(8)). In such a scenario, the user session keyring acts as a substitute for the session-keyring(7).
This page is part of release 5.04 of the Linux
man-pages project. A
description of the project, information about reporting bugs,
and the latest version of this page, can be found at
Copyright (C) 2014 Red Hat, Inc. All Rights Reserved.
Written by David Howells (dhowellsredhat.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.