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 
13 unsigned 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  */
key_create_persistent_register(struct user_namespace * ns)20 static 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  */
key_create_persistent(struct user_namespace * ns,kuid_t uid,struct keyring_index_key * index_key)40 static 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  */
key_get_persistent(struct user_namespace * ns,kuid_t uid,key_ref_t dest_ref)73 static 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 
110 found:
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  */
keyctl_get_persistent(uid_t _uid,key_serial_t destid)129 long 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 
164 out_put_dest:
165 	key_ref_put(dest_ref);
166 	return ret;
167 }
168