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 from flat data
       keyctl_instantiate_iov - Instantiate a key from segmented data
       keyctl_reject - Negatively instantiate a key specifying search error
       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 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       have been revoked.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),
       request-key(8)



Linux				  4 May 2006		 KEYCTL_INSTANTIATE(3)