Commit | Line | Data |
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b4d0d230 | 1 | // SPDX-License-Identifier: GPL-2.0-or-later |
ab3c3587 DH |
2 | /* Large capacity key type |
3 | * | |
521fd61c | 4 | * Copyright (C) 2017-2020 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved. |
ab3c3587 DH |
5 | * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved. |
6 | * Written by David Howells (dhowells@redhat.com) | |
ab3c3587 DH |
7 | */ |
8 | ||
7df3e59c | 9 | #define pr_fmt(fmt) "big_key: "fmt |
ab3c3587 DH |
10 | #include <linux/init.h> |
11 | #include <linux/seq_file.h> | |
12 | #include <linux/file.h> | |
13 | #include <linux/shmem_fs.h> | |
14 | #include <linux/err.h> | |
428490e3 | 15 | #include <linux/random.h> |
ab3c3587 DH |
16 | #include <keys/user-type.h> |
17 | #include <keys/big_key-type.h> | |
521fd61c | 18 | #include <crypto/chacha20poly1305.h> |
d9f4bb1a | 19 | |
146aa8b1 DH |
20 | /* |
21 | * Layout of key payload words. | |
22 | */ | |
c1298a3a KC |
23 | struct big_key_payload { |
24 | u8 *data; | |
25 | struct path path; | |
26 | size_t length; | |
146aa8b1 | 27 | }; |
c1298a3a KC |
28 | #define to_big_key_payload(payload) \ |
29 | (struct big_key_payload *)((payload).data) | |
146aa8b1 | 30 | |
ab3c3587 DH |
31 | /* |
32 | * If the data is under this limit, there's no point creating a shm file to | |
33 | * hold it as the permanently resident metadata for the shmem fs will be at | |
34 | * least as large as the data. | |
35 | */ | |
36 | #define BIG_KEY_FILE_THRESHOLD (sizeof(struct inode) + sizeof(struct dentry)) | |
37 | ||
38 | /* | |
39 | * big_key defined keys take an arbitrary string as the description and an | |
40 | * arbitrary blob of data as the payload | |
41 | */ | |
42 | struct key_type key_type_big_key = { | |
43 | .name = "big_key", | |
002edaf7 DH |
44 | .preparse = big_key_preparse, |
45 | .free_preparse = big_key_free_preparse, | |
46 | .instantiate = generic_key_instantiate, | |
ab3c3587 DH |
47 | .revoke = big_key_revoke, |
48 | .destroy = big_key_destroy, | |
49 | .describe = big_key_describe, | |
50 | .read = big_key_read, | |
b6f61c31 | 51 | .update = big_key_update, |
ab3c3587 DH |
52 | }; |
53 | ||
54 | /* | |
002edaf7 | 55 | * Preparse a big key |
ab3c3587 | 56 | */ |
002edaf7 | 57 | int big_key_preparse(struct key_preparsed_payload *prep) |
ab3c3587 | 58 | { |
c1298a3a | 59 | struct big_key_payload *payload = to_big_key_payload(prep->payload); |
ab3c3587 | 60 | struct file *file; |
521fd61c | 61 | u8 *buf, *enckey; |
ab3c3587 | 62 | ssize_t written; |
521fd61c JD |
63 | size_t datalen = prep->datalen; |
64 | size_t enclen = datalen + CHACHA20POLY1305_AUTHTAG_SIZE; | |
ab3c3587 DH |
65 | int ret; |
66 | ||
c1298a3a KC |
67 | BUILD_BUG_ON(sizeof(*payload) != sizeof(prep->payload.data)); |
68 | ||
ab3c3587 | 69 | if (datalen <= 0 || datalen > 1024 * 1024 || !prep->data) |
d9f4bb1a | 70 | return -EINVAL; |
ab3c3587 DH |
71 | |
72 | /* Set an arbitrary quota */ | |
002edaf7 | 73 | prep->quotalen = 16; |
ab3c3587 | 74 | |
c1298a3a | 75 | payload->length = datalen; |
ab3c3587 DH |
76 | |
77 | if (datalen > BIG_KEY_FILE_THRESHOLD) { | |
78 | /* Create a shmem file to store the data in. This will permit the data | |
79 | * to be swapped out if needed. | |
80 | * | |
13100a72 | 81 | * File content is stored encrypted with randomly generated key. |
521fd61c JD |
82 | * Since the key is random for each file, we can set the nonce |
83 | * to zero, provided we never define a ->update() call. | |
ab3c3587 | 84 | */ |
e13ec939 | 85 | loff_t pos = 0; |
13100a72 | 86 | |
521fd61c | 87 | buf = kvmalloc(enclen, GFP_KERNEL); |
d9f4bb1a | 88 | if (!buf) |
13100a72 | 89 | return -ENOMEM; |
13100a72 KM |
90 | |
91 | /* generate random key */ | |
521fd61c | 92 | enckey = kmalloc(CHACHA20POLY1305_KEY_SIZE, GFP_KERNEL); |
13100a72 KM |
93 | if (!enckey) { |
94 | ret = -ENOMEM; | |
95 | goto error; | |
96 | } | |
521fd61c | 97 | ret = get_random_bytes_wait(enckey, CHACHA20POLY1305_KEY_SIZE); |
428490e3 | 98 | if (unlikely(ret)) |
13100a72 KM |
99 | goto err_enckey; |
100 | ||
521fd61c JD |
101 | /* encrypt data */ |
102 | chacha20poly1305_encrypt(buf, prep->data, datalen, NULL, 0, | |
103 | 0, enckey); | |
13100a72 KM |
104 | |
105 | /* save aligned data to file */ | |
106 | file = shmem_kernel_file_setup("", enclen, 0); | |
d2b86970 WY |
107 | if (IS_ERR(file)) { |
108 | ret = PTR_ERR(file); | |
13100a72 | 109 | goto err_enckey; |
d2b86970 | 110 | } |
ab3c3587 | 111 | |
521fd61c | 112 | written = kernel_write(file, buf, enclen, &pos); |
13100a72 | 113 | if (written != enclen) { |
97826c82 | 114 | ret = written; |
ab3c3587 | 115 | if (written >= 0) |
521fd61c | 116 | ret = -EIO; |
ab3c3587 DH |
117 | goto err_fput; |
118 | } | |
119 | ||
120 | /* Pin the mount and dentry to the key so that we can open it again | |
121 | * later | |
122 | */ | |
c1298a3a KC |
123 | payload->data = enckey; |
124 | payload->path = file->f_path; | |
125 | path_get(&payload->path); | |
ab3c3587 | 126 | fput(file); |
272a1219 | 127 | kvfree_sensitive(buf, enclen); |
ab3c3587 DH |
128 | } else { |
129 | /* Just store the data in a buffer */ | |
130 | void *data = kmalloc(datalen, GFP_KERNEL); | |
13100a72 | 131 | |
002edaf7 DH |
132 | if (!data) |
133 | return -ENOMEM; | |
ab3c3587 | 134 | |
c1298a3a | 135 | payload->data = data; |
146aa8b1 | 136 | memcpy(data, prep->data, prep->datalen); |
ab3c3587 DH |
137 | } |
138 | return 0; | |
139 | ||
140 | err_fput: | |
141 | fput(file); | |
13100a72 | 142 | err_enckey: |
453431a5 | 143 | kfree_sensitive(enckey); |
ab3c3587 | 144 | error: |
272a1219 | 145 | kvfree_sensitive(buf, enclen); |
ab3c3587 DH |
146 | return ret; |
147 | } | |
148 | ||
002edaf7 DH |
149 | /* |
150 | * Clear preparsement. | |
151 | */ | |
152 | void big_key_free_preparse(struct key_preparsed_payload *prep) | |
153 | { | |
c1298a3a | 154 | struct big_key_payload *payload = to_big_key_payload(prep->payload); |
13100a72 | 155 | |
c1298a3a KC |
156 | if (prep->datalen > BIG_KEY_FILE_THRESHOLD) |
157 | path_put(&payload->path); | |
158 | kfree_sensitive(payload->data); | |
002edaf7 DH |
159 | } |
160 | ||
ab3c3587 DH |
161 | /* |
162 | * dispose of the links from a revoked keyring | |
163 | * - called with the key sem write-locked | |
164 | */ | |
165 | void big_key_revoke(struct key *key) | |
166 | { | |
c1298a3a | 167 | struct big_key_payload *payload = to_big_key_payload(key->payload); |
ab3c3587 DH |
168 | |
169 | /* clear the quota */ | |
170 | key_payload_reserve(key, 0); | |
c1298a3a KC |
171 | if (key_is_positive(key) && payload->length > BIG_KEY_FILE_THRESHOLD) |
172 | vfs_truncate(&payload->path, 0); | |
ab3c3587 DH |
173 | } |
174 | ||
175 | /* | |
176 | * dispose of the data dangling from the corpse of a big_key key | |
177 | */ | |
178 | void big_key_destroy(struct key *key) | |
179 | { | |
c1298a3a | 180 | struct big_key_payload *payload = to_big_key_payload(key->payload); |
13100a72 | 181 | |
c1298a3a KC |
182 | if (payload->length > BIG_KEY_FILE_THRESHOLD) { |
183 | path_put(&payload->path); | |
184 | payload->path.mnt = NULL; | |
185 | payload->path.dentry = NULL; | |
ab3c3587 | 186 | } |
c1298a3a KC |
187 | kfree_sensitive(payload->data); |
188 | payload->data = NULL; | |
ab3c3587 DH |
189 | } |
190 | ||
b6f61c31 DH |
191 | /* |
192 | * Update a big key | |
193 | */ | |
194 | int big_key_update(struct key *key, struct key_preparsed_payload *prep) | |
195 | { | |
196 | int ret; | |
197 | ||
198 | ret = key_payload_reserve(key, prep->datalen); | |
199 | if (ret < 0) | |
200 | return ret; | |
201 | ||
202 | if (key_is_positive(key)) | |
203 | big_key_destroy(key); | |
204 | ||
205 | return generic_key_instantiate(key, prep); | |
206 | } | |
207 | ||
ab3c3587 DH |
208 | /* |
209 | * describe the big_key key | |
210 | */ | |
211 | void big_key_describe(const struct key *key, struct seq_file *m) | |
212 | { | |
c1298a3a | 213 | struct big_key_payload *payload = to_big_key_payload(key->payload); |
ab3c3587 DH |
214 | |
215 | seq_puts(m, key->description); | |
216 | ||
363b02da | 217 | if (key_is_positive(key)) |
146aa8b1 | 218 | seq_printf(m, ": %zu [%s]", |
c1298a3a KC |
219 | payload->length, |
220 | payload->length > BIG_KEY_FILE_THRESHOLD ? "file" : "buff"); | |
ab3c3587 DH |
221 | } |
222 | ||
223 | /* | |
224 | * read the key data | |
225 | * - the key's semaphore is read-locked | |
226 | */ | |
d3ec10aa | 227 | long big_key_read(const struct key *key, char *buffer, size_t buflen) |
ab3c3587 | 228 | { |
c1298a3a KC |
229 | struct big_key_payload *payload = to_big_key_payload(key->payload); |
230 | size_t datalen = payload->length; | |
ab3c3587 DH |
231 | long ret; |
232 | ||
233 | if (!buffer || buflen < datalen) | |
234 | return datalen; | |
235 | ||
236 | if (datalen > BIG_KEY_FILE_THRESHOLD) { | |
ab3c3587 | 237 | struct file *file; |
c1298a3a | 238 | u8 *buf, *enckey = payload->data; |
521fd61c | 239 | size_t enclen = datalen + CHACHA20POLY1305_AUTHTAG_SIZE; |
bdd1d2d3 | 240 | loff_t pos = 0; |
13100a72 | 241 | |
521fd61c | 242 | buf = kvmalloc(enclen, GFP_KERNEL); |
d9f4bb1a | 243 | if (!buf) |
13100a72 | 244 | return -ENOMEM; |
ab3c3587 | 245 | |
c1298a3a | 246 | file = dentry_open(&payload->path, O_RDONLY, current_cred()); |
13100a72 KM |
247 | if (IS_ERR(file)) { |
248 | ret = PTR_ERR(file); | |
249 | goto error; | |
250 | } | |
ab3c3587 | 251 | |
13100a72 | 252 | /* read file to kernel and decrypt */ |
521fd61c JD |
253 | ret = kernel_read(file, buf, enclen, &pos); |
254 | if (ret != enclen) { | |
255 | if (ret >= 0) | |
256 | ret = -EIO; | |
13100a72 KM |
257 | goto err_fput; |
258 | } | |
259 | ||
521fd61c JD |
260 | ret = chacha20poly1305_decrypt(buf, buf, enclen, NULL, 0, 0, |
261 | enckey) ? 0 : -EBADMSG; | |
262 | if (unlikely(ret)) | |
13100a72 KM |
263 | goto err_fput; |
264 | ||
265 | ret = datalen; | |
266 | ||
d3ec10aa | 267 | /* copy out decrypted data */ |
521fd61c | 268 | memcpy(buffer, buf, datalen); |
13100a72 KM |
269 | |
270 | err_fput: | |
271 | fput(file); | |
272 | error: | |
272a1219 | 273 | kvfree_sensitive(buf, enclen); |
ab3c3587 DH |
274 | } else { |
275 | ret = datalen; | |
c1298a3a | 276 | memcpy(buffer, payload->data, datalen); |
ab3c3587 DH |
277 | } |
278 | ||
279 | return ret; | |
280 | } | |
281 | ||
13100a72 KM |
282 | /* |
283 | * Register key type | |
284 | */ | |
ab3c3587 DH |
285 | static int __init big_key_init(void) |
286 | { | |
521fd61c | 287 | return register_key_type(&key_type_big_key); |
13100a72 KM |
288 | } |
289 | ||
7df3e59c | 290 | late_initcall(big_key_init); |