SESSION-KEYRING(7) Linux Programmer's Manual SESSION-KEYRING(7)
NAME
session-keyring - session shared process keyring
DESCRIPTION
The session keyring is a keyring used to anchor keys on behalf of a
process. It is typically created by pam_keyinit(8) when a user logs in
and a link will be added that refers to the user-keyring(7). Option-
ally, PAM may revoke the session keyring on logout. (In typical con-
figurations, PAM does do this revocation.) The session keyring has the
name (description) _ses.
A special serial number value, KEY_SPEC_SESSION_KEYRING, is defined
that can be used in lieu of the actual serial number of the calling
process's session keyring.
From the keyctl(1) utility, '@s' can be used instead of a numeric key
ID in much the same way.
A process's session keyring is inherited across clone(2), fork(2), and
vfork(2). The session keyring is preserved across execve(2), even when
the executable is set-user-ID or set-group-ID or has capabilities. The
session keyring is destroyed when the last process that refers to it
exits.
If a process doesn't have a session keyring when it is accessed, then,
under certain circumstances, the user-session-keyring(7) will be at-
tached as the session keyring and under others a new session keyring
will be created. (See user-session-keyring(7) for further details.)
Special operations
The keyutils library provides the following special operations for ma-
nipulating session keyrings:
keyctl_join_session_keyring(3)
This operation allows the caller to change the session keyring
that it subscribes to. The caller can join an existing keyring
with a specified name (description), create a new keyring with a
given name, or ask the kernel to create a new "anonymous" ses-
sion keyring with the name "_ses". (This function is an inter-
face to the keyctl(2) KEYCTL_JOIN_SESSION_KEYRING operation.)
keyctl_session_to_parent(3)
This operation allows the caller to make the parent process's
session keyring to the same as its own. For this to succeed,
the parent process must have identical security attributes and
must be single threaded. (This function is an interface to the
keyctl(2) KEYCTL_SESSION_TO_PARENT operation.)
These operations are also exposed through the keyctl(1) utility as:
keyctl session
keyctl session - [<prog> <arg1> <arg2> ...]
keyctl session <name> [<prog> <arg1> <arg2> ...]
and:
keyctl new_session
SEE ALSO
keyctl(1), keyctl(3), keyctl_join_session_keyring(3),
keyctl_session_to_parent(3), keyrings(7), persistent-keyring(7),
process-keyring(7), thread-keyring(7), user-keyring(7),
user-session-keyring(7), pam_keyinit(8)
COLOPHON
This page is part of release 5.07 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
https://www.kernel.org/doc/man-pages/.
Linux 2017-09-15 SESSION-KEYRING(7)