persistent-keyring - Per-user persistent keyring


   The  persistent keyring is a keyring used to anchor keys on behalf of a
   user.  Each UID the kernel deals with has its  own  persistent  keyring
   that is shared between all threads owned by that UID.

   The  persistent keyring is created on demand when a thread requests it.
   The keyring's expiration timer is reset every time it  is  accessed  to
   the value in:


   The  persistent  keyring  is not searched by request_key() unless it is
   referred to by a keyring that is.

   The persistent keyring may not be accessed directly, even by  processes
   with  the  appropriate  UID.   Instead  it  must  be linked to one of a
   process's keyrings first before that keyring can access it by virtue of
   its possessor permits.  This is done with keyctl_get_persistent().

   Persistent  keyrings  are  independent  of  clone(),  fork(),  vfork(),
   execve() and  exit().   They  persist  until  their  expiration  timers
   trigger  - at which point they are garbage collected.  This allows them
   to  carry  keys  beyond  the  life  of  the  kernel's  record  of   the
   corresponding  UID (the destruction of which results in the destruction
   of the user and user session keyrings).

   If a persistent keyring does not exist when it is accessed, it will  be


   The  keyutils  library  provides  a  special operation for manipulating
   persistent keyrings:

          This operation allows the caller to get the  persistent  keyring
          corresponding  to their own UID or, if they have CAP_SETUID, the
          persistent keyring corresponding to some other UID in  the  same
          user namespace.




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