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 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       to succeed, and that authority must not have been revoked.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 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
       permits that.  The key type may reject the data if it's in the wrong format 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 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

       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 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

       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)