mirror of https://github.com/mkerrisk/man-pages
88 lines
2.6 KiB
Groff
88 lines
2.6 KiB
Groff
.\"
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.\" Copyright (C) 2014 Red Hat, Inc. All Rights Reserved.
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.\" Written by David Howells (dhowells@redhat.com)
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.\"
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.\" %%%LICENSE_START(GPLv2+_SW_ONEPARA)
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.\" This program is free software; you can redistribute it and/or
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.\" modify it under the terms of the GNU General Public License
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.\" as published by the Free Software Foundation; either version
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.\" 2 of the License, or (at your option) any later version.
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.\" %%%LICENSE_END
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.\"
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.TH "USER-KEYRING" 7 2017-03-13 Linux "Linux Programmer's Manual"
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.SH NAME
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user-keyring \- per-user keyring
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.SH DESCRIPTION
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The user keyring is a keyring used to anchor keys on behalf of a user.
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Each UID the kernel deals with has its own user keyring that
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is shared by all processes with that UID.
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The user keyring has a name (description) of the form
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.I _uid.<UID>
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where
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.I <UID>
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is the user ID of the corresponding user.
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.PP
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The user keyring is associated with the record that the kernel maintains
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for the UID.
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It comes into existence upon the first attempt to access either the
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user keyring, the
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.BR user-session-keyring (7),
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or the
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.BR session-keyring (7).
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The keyring remains pinned in existence so long as there are processes
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running with that real UID or files opened by those processes remain open.
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(The keyring can also be pinned indefinitely by linking it
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into another keyring.)
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.PP
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Typically, the user keyring is created by
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.BR pam_keyinit (8)
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when a user logs in.
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.PP
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The user keyring is not searched by default by
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.BR request_key (2).
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When
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.BR pam_keyinit (8)
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creates a session keyring, it adds to it a link to the user
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keyring so that the user keyring will be searched when the session keyring is.
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.PP
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A special serial number value,
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.BR KEY_SPEC_USER_KEYRING ,
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is defined that can be used in lieu of the actual serial number of
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the calling process's user keyring.
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.PP
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From the
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.BR keyctl (1)
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utility, '\fB@u\fP' can be used instead of a numeric key ID in
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much the same way.
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.PP
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User keyrings are independent of
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.BR clone (2),
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.BR fork (2),
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.BR vfork (2),
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.BR execve (2),
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and
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.BR _exit (2)
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excepting that the keyring is destroyed when the UID record is destroyed when
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the last process pinning it exits.
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.PP
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If it is necessary for a key associated with a user to exist beyond the UID
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record being garbage collected\(emfor example, for use by a
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.BR cron (8)
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script\(emthen the
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.BR persistent-keyring (7)
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should be used instead.
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.PP
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If a user keyring does not exist when it is accessed, it will be created.
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.SH SEE ALSO
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.ad l
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.nh
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.BR keyctl (1),
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.BR keyctl (3),
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.BR keyrings (7),
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.BR persistent\-keyring (7),
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.BR process\-keyring (7),
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.BR session\-keyring (7),
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.BR thread\-keyring (7),
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.BR user\-session\-keyring (7),
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.BR pam_keyinit (8)
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