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KEYCTL_INSTANTIATE(3)     Linux Key Management Calls     KEYCTL_INSTANTIATE(3)
NAME
       keyctl_assume_authority,   keyctl_instantiate,  keyctl_instantiate_iov,
       keyctl_reject, keyctl_negate - key instantiation functions
SYNOPSIS
       #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
       keyctl_assume_authority() assumes the authority for the calling  thread
       to deal with and instantiate the specified uninstantiated key.
       The  calling thread must have the appopriate 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       have been revoked.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 con-
       text.
       If a thread has multiple instantiations to deal with, it may call  this
       function  to change the authorisation key currently in effect.  Supply-
       ing a zero key de-assumes the currently assumed authority.
       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 per-
       mits  that.  The key type may reject the data if it's in the wrong for-
       mat or in some other way invalid.
       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 call-
       er'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 desti-
       nation for a link to be made there.
RETURN VALUE
       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
       ENOKEY The key or keyring specified is invalid.
       EKEYEXPIRED
              The keyring specified has expired.
       EKEYREVOKED
              The key or keyring specified had been revoked, or the authorisa-
              tion 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
       This  is  a  library  function  that can be found in libkeyutils.  When
       linking, -lkeyutils should be specified to the linker.
SEE ALSO
       keyctl(1), add_key(2), keyctl(2), request_key(2), keyctl(3),
       keyrings(7), keyutils(7), request-key(8)
Linux                             4 May 2006             KEYCTL_INSTANTIATE(3)