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.\"
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.TH ADD_KEY 2 2016-07-17 Linux "Linux Key Management Calls"
.SH NAME
add_key \- add a key to the kernel's key management facility
.SH SYNOPSIS
.nf
.B #include <keyutils.h>
.sp
.BI "key_serial_t add_key(const char *" type ", const char *" description ,
.BI "                     const void *" payload ", size_t " plen ,
.BI "                     key_serial_t " keyring ");"
.fi
.SH DESCRIPTION
.BR add_key ()
creates or updates a key of the given
.I type
and
.IR description ,
instantiates it with the
.I payload
of length
.IR plen ,
attaches it to the nominated
.IR keyring ,
and return the key's serial number.
.P
The key type may reject the data if it is in the wrong format or
is in some other way invalid.
.P
If the destination
.I keyring
already contains a key that matches the specified
.IR type
and
.IR description ,
then, if the key type supports it, that key will be updated rather than a new
key being created; if not, a new key will be created and it will displace the
link to the extant key from the keyring.
.P
The destination
.I keyring
serial number may be that of a valid keyring for which the caller has
.I write
permission, or it may be one of the following special keyring IDs:
.TP
.B KEY_SPEC_THREAD_KEYRING
This specifies the caller's thread-specific keyring.
.TP
.B KEY_SPEC_PROCESS_KEYRING
This specifies the caller's process-specific keyring.
.TP
.B KEY_SPEC_SESSION_KEYRING
This specifies the caller's session-specific keyring.
.TP
.B KEY_SPEC_USER_KEYRING
This specifies the caller's UID-specific keyring.
.TP
.B KEY_SPEC_USER_SESSION_KEYRING
This specifies the caller's UID-session keyring.
.SS Key types
There are a number of key types available in the core key management code, and
these can be specified to this function:
.TP
.B \*(lquser\*(rq
Keys of the user-defined key type may contain a blob of arbitrary data, and the
.I description
may be any valid string, though it is preferred that the description be
prefixed with a string representing the service to which the key is of interest
and a colon (for instance
.RB \*(lq afs:mykey \*(rq).
.TP
.B \*(lqkeyring\*(rq
Keyrings are special key types that may contain links to sequences of other
keys of any type.
If this interface is used to create a keyring, then a NULL
.I payload
should be specified, and
.I plen
should be zero.
.SH RETURN VALUE
On success,
.BR add_key ()
returns the serial number of the key it created or updated.
On error, \-1 is returned and
.I errno
is set to indicate the cause of the error.
.SH ERRORS
.TP
.B EACCES
The keyring wasn't available for modification by the user.
.TP
.B EINVAL
The payload data was invalid.
.TP
.B EKEYEXPIRED
The keyring has expired.
.TP
.B EKEYREVOKED
The keyring has been revoked.
.TP
.B ENOKEY
The keyring doesn't exist.
.TP
.B ENOMEM
Insufficient memory to create a key.
.TP
.B EDQUOT
The key quota for this user would be exceeded by creating this key or linking
it to the keyring.
.SH VERSIONS
This system call first appeared in Linux 2.6.11.
.SH CONFORMING TO
This system call is a nonstandard Linux extension.
.SH NOTES
Although this is a Linux system call, it is not present in
.I libc
but can be found rather in
.IR libkeyutils .
When linking,
.B -lkeyutils
should be specified to the linker.
.SH SEE ALSO
.BR keyctl (1),
.BR keyctl (2),
.BR request_key (2),
.BR keyctl (3),
.BR keyrings (7)

The kernel source files
.IR Documentation/security/keys.txt
and
.IR Documentation/security/keys-request-key.txt .