keyctl_instantiate(3) — Linux manual page



NAME         top

       keyctl_assume_authority, keyctl_instantiate,
       keyctl_instantiate_iov, keyctl_reject, keyctl_negate - key
       instantiation functions

SYNOPSIS         top

       #include <keyutils.h>

       long keyctl_assume_authority(key_serial_t key);

       long keyctl_instantiate(key_serial_t key, const void *payload,
       size_t plen, key_serial_t keyring);

       long keyctl_instantiate_iov(key_serial_t key,
       const struct iovec *payload_iov, unsigned ioc,
       key_serial_t keyring);

       long keyctl_negate(key_serial_t key, unsigned timeout,
       key_serial_t keyring);

       long keyctl_reject(key_serial_t key, unsigned timeout,
       unsigned error, key_serial_t keyring);

DESCRIPTION         top

       keyctl_assume_authority() assumes the authority for the calling
       thread to deal with and instantiate the specified uninstantiated

       The calling thread must have the appropriate authorisation key
       resident in one of its keyrings for this to succeed, and that
       authority must not have been revoked.

       The authorising key is allocated by request_key() when it needs
       to invoke userspace to generate a key for the requesting process.
       This is then attached to one of the keyrings of the userspace
       process to which the task of instantiating the key is given:

              requester -> request_key() -> instantiator

       Calling this function modifies the way request_key() works when
       called thereafter by the calling (instantiator) thread; once the
       authority is assumed, the keyrings of the initial process are
       added to the search path, using the initial process's UID, GID,
       groups and security context.

       If a thread has multiple instantiations to deal with, it may call
       this function to change the authorisation key currently in
       effect.  Supplying a zero key de-assumes the currently assumed

       NOTE!  This is a per-thread setting and not a per-process setting
       so that a multithreaded process can be used to instantiate
       several keys at once.

       keyctl_instantiate() instantiates the payload of an
       uninstantiated key from the data specified.  payload and plen
       specify the data for the new payload.  payload may be NULL and
       plen may be zero if the key type permits that.  The key type may
       reject the data if it's in the wrong format or in some other way

       keyctl_instantiate_iov() is similar, but the data is passed in an
       array of iovec structs instead of in a flat buffer.  payload_iov
       points to the base of the array and ioc indicates how many
       elements there are.  payload_iov may be NULL or ioc may be zero
       to indicate that no data is being supplied.

       keyctl_reject() marks a key as negatively instantiated and sets
       the expiration timer on it.  timeout specifies the lifetime of
       the key in seconds.  error specifies the error to be returned
       when a search hits the key (this is typically EKEYREJECTED,
       EKEYREVOKED or EKEYEXPIRED).  Note that keyctl_reject() falls
       back to keyctl_negate() if the kernel does not support it.

       keyctl_negate() as keyctl_reject() with an error code of ENOKEY.

       Only a key for which authority has been assumed may be
       instantiated or negatively instantiated, and once instantiated,
       the authorisation key will be revoked and the requesting process
       will be able to resume.

       The destination keyring, if given, is assumed to belong to the
       initial requester, and not the instantiating process.  Therefore,
       the special keyring IDs refer to the requesting process's
       keyrings, not the caller's, and the requester's UID, etc. will be
       used to access them.

       The destination keyring can be zero if no extra link is desired.

       The requester, not the caller, must have write permission on the
       destination for a link to be made there.

RETURN VALUE         top

       On success keyctl_instantiate() returns 0.  On error, the value
       -1 will be returned and errno will have been set to an
       appropriate error.

ERRORS         top

       ENOKEY The key or keyring specified is invalid.

              The keyring specified has expired.

              The key or keyring specified had been revoked, or the
              authorisation has been revoked.

       EINVAL The payload data was invalid.

       ENOMEM Insufficient memory to store the new payload or to expand
              the destination keyring.

       EDQUOT The key quota for the key's user would be exceeded by
              increasing the size of the key to accommodate the new
              payload or the key quota for the keyring's user would be
              exceeded by expanding the destination keyring.

       EACCES The key exists, but is not writable by the requester.

LINKING         top

       This is a library function that can be found in libkeyutils.
       When linking, -lkeyutils should be specified to the linker.

SEE ALSO         top

       keyctl(1), add_key(2), keyctl(2), request_key(2), keyctl(3),
       keyrings(7), keyutils(7), request-key(8)

COLOPHON         top

       This page is part of the keyutils (key management utilities)
       project.  Information about the project can be found at [unknown
       -- if you know, please contact] If you have a
       bug report for this manual page, send it to  This page was obtained from the
       project's upstream Git repository
       on 2023-12-22.  (At that time, the date of the most recent commit
       that was found in the repository was 2023-03-20.)  If you
       discover any rendering problems in this HTML version of the page,
       or you believe there is a better or more up-to-date source for
       the page, or you have corrections or improvements to the
       information in this COLOPHON (which is not part of the original
       manual page), send a mail to

Linux                          4 May 2006          KEYCTL_INSTANTIATE(3)

Pages that refer to this page: keyctl(2)request_key(2)keyctl(3)keyrings(7)