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.\"
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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 Licence
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.\" as published by the Free Software Foundation; either version
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.\" 2 of the Licence, or (at your option) any later version.
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.\" %%%LICENSE_END
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.\"
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2016-11-01 17:16:43 +00:00
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.TH "PERSISTENT-KEYRING" 7 2016-11-01 Linux "Linux Programmer's Manual"
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.\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
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.SH NAME
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persistent-keyring \- per-user persistent keyring
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.SH DESCRIPTION
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The persistent 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 persistent keyring that
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is shared between all threads owned by that UID.
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.P
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The persistent keyring is created on demand when a thread requests it.
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The keyring's expiration timer is reset every time it is accessed
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to the value in:
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.IP
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/proc/sys/kernel/keys/persistent_keyring_expiry
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.P
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The persistent keyring is not searched by \fBrequest_key\fP() unless it is
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referred to by a keyring that is.
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.P
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The persistent keyring may not be accessed directly, even by processes with
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the appropriate UID.
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Instead it must be linked to one of a process's keyrings
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first before that keyring can access it by virtue of its possessor permits.
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This is done with \fBkeyctl_get_persistent\fP().
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.P
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Persistent 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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They persist until their expiration timers trigger - at which point
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they are garbage collected.
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This allows them to carry keys beyond the life of
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the kernel's record of the corresponding UID (the destruction of which results
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in the destruction of the user and user session keyrings).
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.P
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If a persistent keyring does not exist when it is accessed, it will be
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created.
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.SH SPECIAL OPERATIONS
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The keyutils library provides a special operation for manipulating persistent
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keyrings:
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.IP \fBkeyctl_get_persistent\fP()
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This operation allows the caller to get the persistent keyring corresponding
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to their own UID or, if they have
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.BR CAP_SETUID ,
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the persistent keyring
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corresponding to some other UID in the same user namespace.
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.\"""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""""
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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 keyctl_get_persistent (3),
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.BR keyrings (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\-keyring (7),
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.BR user\-session\-keyring (7)
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