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NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | VERSIONS | CONFORMING TO | NOTES | EXAMPLE | SEE ALSO | COLOPHON |
ADD_KEY(2) Linux Key Management Calls ADD_KEY(2)
add_key - add a key to the kernel's key management facility
#include <sys/types.h>
#include <keyutils.h>
key_serial_t add_key(const char *type, const char *description,
const void *payload, size_t plen,
key_serial_t keyring);
No glibc wrapper is provided for this system call; see NOTES.
add_key() creates or updates a key of the given type and description,
instantiates it with the payload of length plen, attaches it to the
nominated keyring, and returns the key's serial number.
The key may be rejected if the provided data is in the wrong format
or it is invalid in some other way.
If the destination keyring already contains a key that matches the
specified type and 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 (with a different ID) will be created and it will displace
the link to the extant key from the keyring.
The destination keyring serial number may be that of a valid keyring
for which the caller has write permission. Alternatively, it may be
one of the following special keyring IDs:
KEY_SPEC_THREAD_KEYRING
This specifies the caller's thread-specific keyring (thread-##### keyring(7)).
keyring(7)).
KEY_SPEC_PROCESS_KEYRING
This specifies the caller's process-specific keyring (process-##### keyring(7)).
keyring(7)).
KEY_SPEC_SESSION_KEYRING
This specifies the caller's session-specific keyring (session-##### keyring(7)).
keyring(7)).
KEY_SPEC_USER_KEYRING
This specifies the caller's UID-specific keyring (user-##### keyring(7)).
keyring(7)).
KEY_SPEC_USER_SESSION_KEYRING
This specifies the caller's UID-session keyring (user-session-##### keyring(7)).
keyring(7)).
Key types
The key type is a string that specifies the key's type. Internally,
the kernel defines a number of key types that are available in the
core key management code. Among the types that are available for
user-space use and can be specified as the type argument to add_key()
are the following:
"keyring"
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 payload should be NULL and plen
should be zero.
"user" This is a general purpose key type whose payload may be read
and updated by user-space applications. The key is kept
entirely within kernel memory. The payload for keys of this
type is a blob of arbitrary data of up to 32,767 bytes.
"logon" (since Linux 3.3)
This key type is essentially the same as "user", but it does
not permit the key to read. This is suitable for storing
payloads that you do not want to be readable from user space.
This key type vets the description to ensure that it is
qualified by a "service" prefix, by checking to ensure that
the description contains a ':' that is preceded by other
characters.
"big_key" (since Linux 3.13)
This key type is similar to "user", but may hold a payload of
up to 1 MiB. If the key payload is large enough, then it may
be stored encrypted in tmpfs (which can be swapped out) rather
than kernel memory.
For further details on these key types, see keyrings(7).
On success, add_key() returns the serial number of the key it created
or updated. On error, -1 is returned and errno is set to indicate
the cause of the error.
EACCES The keyring wasn't available for modification by the user.
EDQUOT The key quota for this user would be exceeded by creating this
key or linking it to the keyring.
EFAULT One or more of type, description, and payload points outside
process's accessible address space.
EINVAL The size of the string (including the terminating null byte)
specified in type or description exceeded the limit (32 bytes
and 4096 bytes respectively).
EINVAL The payload data was invalid.
EINVAL type was "logon" and the description was not qualified with a
prefix string of the form "service:".
EKEYEXPIRED
The keyring has expired.
EKEYREVOKED
The keyring has been revoked.
ENOKEY The keyring doesn't exist.
ENOMEM Insufficient memory to create a key.
EPERM The type started with a period ('.'). Key types that begin
with a period are reserved to the implementation.
EPERM type was "keyring" and the description started with a period
('.'). Keyrings with descriptions (names) that begin with a
period are reserved to the implementation.
This system call first appeared in Linux 2.6.10.
This system call is a nonstandard Linux extension.
No wrapper for this system call is provided in glibc. A wrapper is
provided in the libkeyutils package. When employing the wrapper in
that library, link with -lkeyutils.
The program below creates a key with the type, description, and
payload specified in its command-line arguments, and links that key
into the session keyring. The following shell session demonstrates
the use of the program:
$ ./a.out user mykey "Some payload"
Key ID is 64a4dca
$ grep '64a4dca' /proc/keys
064a4dca I--Q--- 1 perm 3f010000 1000 1000 user mykey: 12
Program source
#include <sys/types.h>
#include <keyutils.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int
main(int argc, char *argv[])
{
key_serial_t key;
if (argc != 4) {
fprintf(stderr, "Usage: %s type description payload\n",
argv[0]);
exit(EXIT_FAILURE);
}
key = add_key(argv[1], argv[2], argv[3], strlen(argv[3]),
KEY_SPEC_SESSION_KEYRING);
if (key == -1) {
perror("add_key");
exit(EXIT_FAILURE);
}
printf("Key ID is %lx\n", (long) key);
exit(EXIT_SUCCESS);
}
keyctl(1), keyctl(2), request_key(2), keyctl(3), keyutils(7),
keyrings(7), persistent-keyring(7), process-keyring(7),
session-keyring(7), thread-keyring(7), user-keyring(7),
user-session-keyring(7)
The kernel source files Documentation/security/keys.txt and
Documentation/security/keys-request-key.txt.
This page is part of release 4.12 of the Linux man-pages project. A
description of the project, information about reporting bugs, and the
latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
Linux 2017-03-13 ADD_KEY(2)
Pages that refer to this page: keyctl(2), request_key(2), syscalls(2), keyctl(3), keyctl_chown(3), keyctl_clear(3), keyctl_describe(3), keyctl_get_keyring_ID(3), keyctl_get_persistent(3), keyctl_get_security(3), keyctl_instantiate(3), keyctl_invalidate(3), keyctl_join_session_keyring(3), keyctl_link(3), keyctl_read(3), keyctl_revoke(3), keyctl_search(3), keyctl_session_to_parent(3), keyctl_setperm(3), keyctl_set_reqkey_keyring(3), keyctl_set_timeout(3), keyctl_update(3), proc(5), keyrings(7), keyutils(7)