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instantiate a key
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,
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have been revoked.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-
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
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_negate() marks a key as negatively instantiated and sets the
expiration timer on it. timeout specifies the lifetime of the key in
On success keyctl_instantiate() returns 0. On error, the value -1 will
be returned and errno will have been set to an appropriate error.
ENOKEY The key or keyring specified is invalid.
The keyring specified has expired.
The key or keyring specified had been revoked, or the authorisa-
tion has been revoked.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
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
EACCES The key exists, but is not writable by the requester.
This is a library function that can be found in libkeyutils. When
linking, -lkeyutils should be specified to the linker.
Linux 4 May 2006 KEYCTL_INSTANTIATE(3)