KEYCTL_INSTANTIATE(3)					    Linux Key Management Calls					     KEYCTL_INSTANTIATE(3)

NAME

       keyctl_assume_authority	-  Assume  the	authority  to  instantiate a key keyctl_instantiate - Instantiate a key keyctl_negate - Negatively
       instantiate a key

SYNOPSIS

       #include <keyutils.h>

       long keyctl_assume_authority(key_serial_t key);

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

       long keyctl_negate(key_serial_t key, unsigned timeout,
       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       not have been revoked.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
       context.

       If a thread has multiple instantiations to deal with, it may call this function to change the authorisation key currently in effect.   Sup-
       plying 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_negate() marks a key as negatively instantiated and sets the expiration timer on it.  timeout specifies the lifetime of the  key	in
       seconds.

       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  spe-
       cial 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_get_keyring_ID(3),
       keyctl_join_session_keyring(3),
       keyctl_update(3),
       keyctl_revoke(3),
       keyctl_chown(3),
       keyctl_setperm(3),
       keyctl_describe(3),
       keyctl_clear(3),
       keyctl_link(3),
       keyctl_unlink(3),
       keyctl_search(3),
       keyctl_read(3),
       keyctl_set_reqkey_keyring(3),
       keyctl_set_timeout(3),
       keyctl_describe_alloc(3),
       keyctl_read_alloc(3),
       request-key(8)

Linux								    4 May 2006						     KEYCTL_INSTANTIATE(3)