NAME

       user-session-keyring - per-user default session keyring

DESCRIPTION

       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_ses.<UID> where <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'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.

       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's user session keyring.

       From the keyctl(1) utility, '@us' 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).

NOTES

       The  user  session  keyring was added to support situations where a process doesn't have a
       session keyring, perhaps because it was created via a  pathway  that  didn'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).

SEE ALSO

       keyctl(1), keyctl(3), keyrings(7), persistent-keyring(7), process-keyring(7),
       session-keyring(7), thread-keyring(7), user-keyring(7)

COLOPHON

       This page is part of release 5.13 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/.