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have been revoked.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.
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_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 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),
request-key(8)