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 (dhowells@redhat.com)
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 * Create the persistent keyring for the specified user.
37 *
38 * Called with the namespace's sem locked for writing.
39 */
40static key_ref_t key_create_persistent(struct user_namespace *ns, kuid_t uid,
41				       struct keyring_index_key *index_key)
42{
43	struct key *persistent;
44	key_ref_t reg_ref, persistent_ref;
45
46	if (!ns->persistent_keyring_register) {
47		long err = key_create_persistent_register(ns);
48		if (err < 0)
49			return ERR_PTR(err);
50	} else {
51		reg_ref = make_key_ref(ns->persistent_keyring_register, true);
52		persistent_ref = find_key_to_update(reg_ref, index_key);
53		if (persistent_ref)
54			return persistent_ref;
55	}
56
57	persistent = keyring_alloc(index_key->description,
58				   uid, INVALID_GID, current_cred(),
59				   ((KEY_POS_ALL & ~KEY_POS_SETATTR) |
60				    KEY_USR_VIEW | KEY_USR_READ),
61				   KEY_ALLOC_NOT_IN_QUOTA, NULL,
62				   ns->persistent_keyring_register);
63	if (IS_ERR(persistent))
64		return ERR_CAST(persistent);
65
66	return make_key_ref(persistent, true);
67}
68
69/*
70 * Get the persistent keyring for a specific UID and link it to the nominated
71 * keyring.
72 */
73static long key_get_persistent(struct user_namespace *ns, kuid_t uid,
74			       key_ref_t dest_ref)
75{
76	struct keyring_index_key index_key;
77	struct key *persistent;
78	key_ref_t reg_ref, persistent_ref;
79	char buf[32];
80	long ret;
81
82	/* Look in the register if it exists */
83	memset(&index_key, 0, sizeof(index_key));
84	index_key.type = &key_type_keyring;
85	index_key.description = buf;
86	index_key.desc_len = sprintf(buf, "_persistent.%u", from_kuid(ns, uid));
87	key_set_index_key(&index_key);
88
89	if (ns->persistent_keyring_register) {
90		reg_ref = make_key_ref(ns->persistent_keyring_register, true);
91		down_read(&ns->keyring_sem);
92		persistent_ref = find_key_to_update(reg_ref, &index_key);
93		up_read(&ns->keyring_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->keyring_sem);
103	persistent_ref = key_create_persistent(ns, uid, &index_key);
104	up_write(&ns->keyring_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}
168