1/* General persistent per-UID keyrings register
2 *
3 * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
4 * Written by David Howells (dhowells@redhat.com)
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}
168