projects/linux·blob v4.0 · refs

167 lines · 4.5 KiB

1/* General persistent per-UID keyrings register
2 *
3 * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells ([email protected])
5 *
6 * This program is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU General Public Licence
8 * as published by the Free Software Foundation; either version
9 * 2 of the Licence, or (at your option) any later version.
10 */
11
12#include <linux/user_namespace.h>
13#include "internal.h"
14
15unsigned persistent_keyring_expiry = 3 * 24 * 3600; /* Expire after 3 days of non-use */
16
17/*
18 * Create the persistent keyring register for the current user namespace.
19 *
20 * Called with the namespace's sem locked for writing.
21 */
22static int key_create_persistent_register(struct user_namespace *ns)
23{
24 struct key *reg = keyring_alloc(".persistent_register",
25 KUIDT_INIT(0), KGIDT_INIT(0),
26 current_cred(),
27 ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
28 KEY_USR_VIEW | KEY_USR_READ),
29 KEY_ALLOC_NOT_IN_QUOTA, NULL);
30 if (IS_ERR(reg))
31 return PTR_ERR(reg);
32
33 ns->persistent_keyring_register = reg;
34 return 0;
35}
36
37/*
38 * Create the persistent keyring for the specified user.
39 *
40 * Called with the namespace's sem locked for writing.
41 */
42static key_ref_t key_create_persistent(struct user_namespace *ns, kuid_t uid,
43 struct keyring_index_key *index_key)
44{
45 struct key *persistent;
46 key_ref_t reg_ref, persistent_ref;
47
48 if (!ns->persistent_keyring_register) {
49 long err = key_create_persistent_register(ns);
50 if (err < 0)
51 return ERR_PTR(err);
52 } else {
53 reg_ref = make_key_ref(ns->persistent_keyring_register, true);
54 persistent_ref = find_key_to_update(reg_ref, index_key);
55 if (persistent_ref)
56 return persistent_ref;
57 }
58
59 persistent = keyring_alloc(index_key->description,
60 uid, INVALID_GID, current_cred(),
61 ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
62 KEY_USR_VIEW | KEY_USR_READ),
63 KEY_ALLOC_NOT_IN_QUOTA,
64 ns->persistent_keyring_register);
65 if (IS_ERR(persistent))
66 return ERR_CAST(persistent);
67
68 return make_key_ref(persistent, true);
69}
70
71/*
72 * Get the persistent keyring for a specific UID and link it to the nominated
73 * keyring.
74 */
75static long key_get_persistent(struct user_namespace *ns, kuid_t uid,
76 key_ref_t dest_ref)
77{
78 struct keyring_index_key index_key;
79 struct key *persistent;
80 key_ref_t reg_ref, persistent_ref;
81 char buf[32];
82 long ret;
83
84 /* Look in the register if it exists */
85 index_key.type = &key_type_keyring;
86 index_key.description = buf;
87 index_key.desc_len = sprintf(buf, "_persistent.%u", from_kuid(ns, uid));
88
89 if (ns->persistent_keyring_register) {
90 reg_ref = make_key_ref(ns->persistent_keyring_register, true);
91 down_read(&ns->persistent_keyring_register_sem);
92 persistent_ref = find_key_to_update(reg_ref, &index_key);
93 up_read(&ns->persistent_keyring_register_sem);
94
95 if (persistent_ref)
96 goto found;
97 }
98
99 /* It wasn't in the register, so we'll need to create it. We might
100 * also need to create the register.
101 */
102 down_write(&ns->persistent_keyring_register_sem);
103 persistent_ref = key_create_persistent(ns, uid, &index_key);
104 up_write(&ns->persistent_keyring_register_sem);
105 if (!IS_ERR(persistent_ref))
106 goto found;
107
108 return PTR_ERR(persistent_ref);
109
110found:
111 ret = key_task_permission(persistent_ref, current_cred(), KEY_NEED_LINK);
112 if (ret == 0) {
113 persistent = key_ref_to_ptr(persistent_ref);
114 ret = key_link(key_ref_to_ptr(dest_ref), persistent);
115 if (ret == 0) {
116 key_set_timeout(persistent, persistent_keyring_expiry);
117 ret = persistent->serial;
118 }
119 }
120
121 key_ref_put(persistent_ref);
122 return ret;
123}
124
125/*
126 * Get the persistent keyring for a specific UID and link it to the nominated
127 * keyring.
128 */
129long keyctl_get_persistent(uid_t _uid, key_serial_t destid)
130{
131 struct user_namespace *ns = current_user_ns();
132 key_ref_t dest_ref;
133 kuid_t uid;
134 long ret;
135
136 /* -1 indicates the current user */
137 if (_uid == (uid_t)-1) {
138 uid = current_uid();
139 } else {
140 uid = make_kuid(ns, _uid);
141 if (!uid_valid(uid))
142 return -EINVAL;
143
144 /* You can only see your own persistent cache if you're not
145 * sufficiently privileged.
146 */
147 if (!uid_eq(uid, current_uid()) &&
148 !uid_eq(uid, current_euid()) &&
149 !ns_capable(ns, CAP_SETUID))
150 return -EPERM;
151 }
152
153 /* There must be a destination keyring */
154 dest_ref = lookup_user_key(destid, KEY_LOOKUP_CREATE, KEY_NEED_WRITE);
155 if (IS_ERR(dest_ref))
156 return PTR_ERR(dest_ref);
157 if (key_ref_to_ptr(dest_ref)->type != &key_type_keyring) {
158 ret = -ENOTDIR;
159 goto out_put_dest;
160 }
161
162 ret = key_get_persistent(ns, uid, dest_ref);
163
164out_put_dest:
165 key_ref_put(dest_ref);
166 return ret;
167}