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176 lines · 4.5 KiB

1// SPDX-License-Identifier: GPL-2.0-or-later
2/* General persistent per-UID keyrings register
3 *
4 * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
5 * Written by David Howells ([email protected])
6 */
7
8#include <linux/user_namespace.h>
9#include <linux/cred.h>
10
11#include "internal.h"
12
13unsigned persistent_keyring_expiry = 3 * 24 * 3600; /* Expire after 3 days of non-use */
14
15/*
16 * Create the persistent keyring register for the current user namespace.
17 *
18 * Called with the namespace's sem locked for writing.
19 */
20static int key_create_persistent_register(struct user_namespace *ns)
21{
22 struct key *reg = keyring_alloc(".persistent_register",
23 KUIDT_INIT(0), KGIDT_INIT(0),
24 current_cred(),
25 ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
26 KEY_USR_VIEW | KEY_USR_READ),
27 KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
28 if (IS_ERR(reg))
29 return PTR_ERR(reg);
30
31 ns->persistent_keyring_register = reg;
32 return 0;
33}
34
35/*
36 * Get or create the persistent keyring for the specified user.
37 *
38 * Called with the namespace's sem locked for writing.
39 *
40 * Returns a boolean indicating whether the keyring already existed,
41 * or a negative error. On success, *persistent_ref holds a reference
42 * to the keyring.
43 */
44static int key_get_or_create_persistent(struct user_namespace *ns, kuid_t uid,
45 struct keyring_index_key *index_key,
46 key_ref_t *persistent_ref)
47{
48 struct key *persistent;
49 key_ref_t reg_ref;
50
51 if (!ns->persistent_keyring_register) {
52 int err = key_create_persistent_register(ns);
53
54 if (err < 0)
55 return err;
56 } else {
57 reg_ref = make_key_ref(ns->persistent_keyring_register, true);
58 *persistent_ref = find_key_to_update(reg_ref, index_key);
59 if (*persistent_ref)
60 return 1;
61 }
62
63 persistent = keyring_alloc(index_key->description,
64 uid, INVALID_GID, current_cred(),
65 ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
66 KEY_USR_VIEW | KEY_USR_READ),
67 KEY_ALLOC_NOT_IN_QUOTA, NULL,
68 ns->persistent_keyring_register);
69 if (IS_ERR(persistent))
70 return PTR_ERR(persistent);
71
72 *persistent_ref = make_key_ref(persistent, true);
73 return 0;
74}
75
76/*
77 * Get the persistent keyring for a specific UID and link it to the nominated
78 * keyring.
79 */
80static long key_get_persistent(struct user_namespace *ns, kuid_t uid,
81 key_ref_t dest_ref)
82{
83 struct keyring_index_key index_key;
84 struct key *persistent;
85 key_ref_t reg_ref, persistent_ref;
86 char buf[32];
87 long ret;
88 bool created = false;
89
90 /* Look in the register if it exists */
91 memset(&index_key, 0, sizeof(index_key));
92 index_key.type = &key_type_keyring;
93 index_key.description = buf;
94 index_key.desc_len = sprintf(buf, "_persistent.%u", from_kuid(ns, uid));
95 key_set_index_key(&index_key);
96
97 if (ns->persistent_keyring_register) {
98 reg_ref = make_key_ref(ns->persistent_keyring_register, true);
99 down_read(&ns->keyring_sem);
100 persistent_ref = find_key_to_update(reg_ref, &index_key);
101 up_read(&ns->keyring_sem);
102
103 if (persistent_ref)
104 goto found;
105 }
106
107 /* It wasn't in the register, so we'll need to create it. We might
108 * also need to create the register.
109 */
110 down_write(&ns->keyring_sem);
111 ret = key_get_or_create_persistent(ns, uid, &index_key,
112 &persistent_ref);
113 up_write(&ns->keyring_sem);
114 if (ret < 0)
115 return ret;
116 created = ret == 0;
117
118found:
119 persistent = key_ref_to_ptr(persistent_ref);
120 ret = key_task_permission(persistent_ref, current_cred(), KEY_NEED_LINK);
121 if (ret == 0)
122 ret = key_link(key_ref_to_ptr(dest_ref), persistent);
123
124 if (ret == 0 || created)
125 key_set_timeout(persistent, persistent_keyring_expiry);
126
127 if (ret == 0)
128 ret = persistent->serial;
129
130 key_ref_put(persistent_ref);
131 return ret;
132}
133
134/*
135 * Get the persistent keyring for a specific UID and link it to the nominated
136 * keyring.
137 */
138long keyctl_get_persistent(uid_t _uid, key_serial_t destid)
139{
140 struct user_namespace *ns = current_user_ns();
141 key_ref_t dest_ref;
142 kuid_t uid;
143 long ret;
144
145 /* -1 indicates the current user */
146 if (_uid == (uid_t)-1) {
147 uid = current_uid();
148 } else {
149 uid = make_kuid(ns, _uid);
150 if (!uid_valid(uid))
151 return -EINVAL;
152
153 /* You can only see your own persistent cache if you're not
154 * sufficiently privileged.
155 */
156 if (!uid_eq(uid, current_uid()) &&
157 !uid_eq(uid, current_euid()) &&
158 !ns_capable(ns, CAP_SETUID))
159 return -EPERM;
160 }
161
162 /* There must be a destination keyring */
163 dest_ref = lookup_user_key(destid, KEY_LOOKUP_CREATE, KEY_NEED_WRITE);
164 if (IS_ERR(dest_ref))
165 return PTR_ERR(dest_ref);
166 if (key_ref_to_ptr(dest_ref)->type != &key_type_keyring) {
167 ret = -ENOTDIR;
168 goto out_put_dest;
169 }
170
171 ret = key_get_persistent(ns, uid, dest_ref);
172
173out_put_dest:
174 key_ref_put(dest_ref);
175 return ret;
176}