man-pages/man7/user-session-keyring.7

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.TH "USER-SESSION-KEYRING" 7 2016-11-01 Linux "Linux Programmer's Manual"
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.SH NAME
user-session-keyring \- per-user default session keyring
.SH DESCRIPTION
The
.B 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.  This keyring is associated with
the record that the kernel maintains for the UID and, once created, is retained
as long as that record persists.  It is shared amongst all processes of that
UID.
.P
The user session keyring is created on demand when a thread requests it or when
a thread asks for its \fBsession keyring\fP and that doesn't exist.  In the
latter case, a user session keyring will be created and, if the session keyring
wasn't to be created, the user session keyring will be set as the process's
actual session keyring.
.P
The user session keyring is searched by \fBrequest_key\fP() if the actual
session keyring does not exist and is ignored otherwise.
.P
A special serial number value, \fBKEY_SPEC_USER_SESSION_KEYRING\fP, is defined
that can be used in lieu of the calling process's user session keyring's actual
serial number.
.P
From the keyctl utility, '\fB@us\fP' can be used instead of a numeric key ID in
much the same way.
.P
User session keyrings are independent of clone(), fork(), vfork(), execve() and
exit() excepting that the keyring is destroyed when the UID record is destroyed
when the last process pinning it exits.
.P
If a user session keyring does not exist when it is accessed, it will be
created.
.P
It is strongly recommended that a \fBsession keyring\fP be set explicitly, for
example by \fBpam_keyinit\fP, rather than relying on the user session keyring -
particularly if a process is running as root.
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.SH SEE ALSO
.ad l
.nh
.BR keyctl (1),
.BR keyctl (3),
.BR keyrings (7),
.BR persistent\-keyring (7),
.BR process\-keyring (7),
.BR session\-keyring (7),
.BR thread\-keyring (7),
.BR user\-keyring (7)