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.\" keyctl_chown
.\" keyctl_setperm
.\" keyctl_set_timeout
.\" keyctl_instantiate - destination keyring
.\" keyctl_instantiate_iov - destination keyring
.\" keyctl_negate - destination keyring
.\" keyctl_reject - destination keyring
.\" keyctl_get_persistent - destination keyring
.\"
.\" will all create a keyring under some circumstances. whereas the rest,
.\" such as keyctl_get_security, keyctl_read and keyctl_revoke, won't.
.pp
if the
.br keyctl (2)
.br keyctl_set_reqkey_keyring
operation specifies
.br key_reqkey_defl_default
(or no
.br keyctl_set_reqkey_keyring
operation is performed),
then the kernel looks for a keyring
starting from the beginning of the list.
.\"
.ss requesting user-space instantiation of a key
if the kernel cannot find a key matching
.ir type
and
.ir description ,
and
.i callout
is not null, then the kernel attempts to invoke a user-space
program to instantiate a key with the given
.ir type
and
.ir description .
in this case, the following steps are performed:
.ip a) 4
the kernel creates an uninstantiated key, u, with the requested
.i type
and
.ir description .
.ip b)
the kernel creates an authorization key, v,
.\" struct request_key_auth, defined in security/keys/internal.h
that refers to the key u and records the facts that the caller of
.br request_key ()
is:
.rs
.ip (1) 4
the context in which the key u should be instantiated and secured, and
.ip (2)
the context from which associated key requests may be satisfied.
.re
.ip
the authorization key is constructed as follows:
.rs
.ip * 3
the key type is
.ir """.request_key_auth""" .
.ip *
the key's uid and gid are the same as the corresponding filesystem ids
of the requesting process.
.ip *
the key grants
.ir view ,
.ir read ,
and
.ir search
permissions to the key possessor as well as
.ir view
permission for the key user.
.ip *
the description (name) of the key is the hexadecimal
string representing the id of the key that is to be instantiated
in the requesting program.
.ip *
the payload of the key is taken from the data specified in
.ir callout_info .
.ip *
internally, the kernel also records the pid of the process that called
.br request_key ().
.re
.ip c)
the kernel creates a process that executes a user-space service such as
.br request\-key (8)
with a new session keyring that contains a link to the authorization key, v.
.\" the request\-key(8) program can be invoked in circumstances *other* than
.\" when triggered by request_key(2). for example, upcalls from places such
.\" as the dns resolver.
.ip
this program is supplied with the following command-line arguments:
.rs
.ip [0] 4
the string
.ir """/sbin/request\-key""" .
.ip [1]
the string
.i """create"""
(indicating that a key is to be created).
.ip [2]