2 .\" Copyright (C) 2006 Red Hat, Inc. All Rights Reserved.
3 .\" Written by David Howells (dhowells@redhat.com)
5 .\" This program is free software; you can redistribute it and/or
6 .\" modify it under the terms of the GNU General Public License
7 .\" as published by the Free Software Foundation; either version
8 .\" 2 of the License, or (at your option) any later version.
10 .TH REQUEST_KEY 2 2010-02-25 Linux "Linux Key Management Calls"
12 request_key \- Request a key from the kernel's key management facility
15 .B #include <keyutils.h>
17 .BI "key_serial_t request_key(const char *" type ", const char *" description ,
18 .BI " const char *" callout_info ,
19 .BI " key_serial_t " keyring ");"
22 asks the kernel to find a key of the given
24 that matches the specified
26 and, if successful, to attach it to the nominated
28 and to return its serial number.
31 first recursively searches all the keyrings attached to the calling process in
32 the order thread-specific keyring, process-specific keyring and then session
33 keyring for a matching key.
37 is called from a program invoked by
39 on behalf of some other process to generate a key, then the keyrings of that
40 other process will be searched next, using that other process's UID, GID,
41 groups and security context to control access.
43 The keys in each keyring searched are checked for a match before any child
44 keyrings are recursed into. Only keys that are
46 for the caller may be found, and only
48 keyrings may be searched.
50 If the key is not found then, if
52 is set, this function will attempt to look further afield. In such a case, the
54 is passed to a userspace service such as
58 If that is unsuccessful also, then an error will be returned, and a temporary
59 negative key will be installed in the nominated
61 This will expire after a few seconds, but will cause subsequent
64 to fail until it does.
68 serial number may be that of a valid keyring to which the caller has write
69 permission, or it may be a special keyring ID:
71 .B KEY_SPEC_THREAD_KEYRING
72 This specifies the caller's thread-specific keyring.
74 .B KEY_SPEC_PROCESS_KEYRING
75 This specifies the caller's process-specific keyring.
77 .B KEY_SPEC_SESSION_KEYRING
78 This specifies the caller's session-specific keyring.
80 .B KEY_SPEC_USER_KEYRING
81 This specifies the caller's UID-specific keyring.
83 .B KEY_SPEC_USER_SESSION_KEYRING
84 This specifies the caller's UID-session keyring.
86 If a key is created, no matter whether it's a valid key or a negative key, it
87 will displace any other key of the same type and description from the
93 returns the serial number of the key it found.
96 will be returned and errno will have been set to an appropriate error.
100 The keyring wasn't available for modification by the user.
103 The request was interrupted by a signal.
106 The key quota for this user would be exceeded by creating this key or linking
110 An expired key was found, but no replacement could be obtained.
113 The attempt to generate a new key was rejected.
116 A revoked key was found, but no replacement could be obtained.
119 Insufficient memory to create a key.
122 No matching key was found.
124 Although this is a Linux system call, it is not present in
126 but can be found rather in
130 should be specified to the linker.