Loading...
1// SPDX-License-Identifier: GPL-2.0-or-later
2/* Large capacity key type
3 *
4 * Copyright (C) 2017-2020 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
5 * Copyright (C) 2013 Red Hat, Inc. All Rights Reserved.
6 * Written by David Howells (dhowells@redhat.com)
7 */
8
9#define pr_fmt(fmt) "big_key: "fmt
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>
15#include <linux/random.h>
16#include <keys/user-type.h>
17#include <keys/big_key-type.h>
18#include <crypto/chacha20poly1305.h>
19
20/*
21 * Layout of key payload words.
22 */
23enum {
24 big_key_data,
25 big_key_path,
26 big_key_path_2nd_part,
27 big_key_len,
28};
29
30/*
31 * If the data is under this limit, there's no point creating a shm file to
32 * hold it as the permanently resident metadata for the shmem fs will be at
33 * least as large as the data.
34 */
35#define BIG_KEY_FILE_THRESHOLD (sizeof(struct inode) + sizeof(struct dentry))
36
37/*
38 * big_key defined keys take an arbitrary string as the description and an
39 * arbitrary blob of data as the payload
40 */
41struct key_type key_type_big_key = {
42 .name = "big_key",
43 .preparse = big_key_preparse,
44 .free_preparse = big_key_free_preparse,
45 .instantiate = generic_key_instantiate,
46 .revoke = big_key_revoke,
47 .destroy = big_key_destroy,
48 .describe = big_key_describe,
49 .read = big_key_read,
50 .update = big_key_update,
51};
52
53/*
54 * Preparse a big key
55 */
56int big_key_preparse(struct key_preparsed_payload *prep)
57{
58 struct path *path = (struct path *)&prep->payload.data[big_key_path];
59 struct file *file;
60 u8 *buf, *enckey;
61 ssize_t written;
62 size_t datalen = prep->datalen;
63 size_t enclen = datalen + CHACHA20POLY1305_AUTHTAG_SIZE;
64 int ret;
65
66 if (datalen <= 0 || datalen > 1024 * 1024 || !prep->data)
67 return -EINVAL;
68
69 /* Set an arbitrary quota */
70 prep->quotalen = 16;
71
72 prep->payload.data[big_key_len] = (void *)(unsigned long)datalen;
73
74 if (datalen > BIG_KEY_FILE_THRESHOLD) {
75 /* Create a shmem file to store the data in. This will permit the data
76 * to be swapped out if needed.
77 *
78 * File content is stored encrypted with randomly generated key.
79 * Since the key is random for each file, we can set the nonce
80 * to zero, provided we never define a ->update() call.
81 */
82 loff_t pos = 0;
83
84 buf = kvmalloc(enclen, GFP_KERNEL);
85 if (!buf)
86 return -ENOMEM;
87
88 /* generate random key */
89 enckey = kmalloc(CHACHA20POLY1305_KEY_SIZE, GFP_KERNEL);
90 if (!enckey) {
91 ret = -ENOMEM;
92 goto error;
93 }
94 ret = get_random_bytes_wait(enckey, CHACHA20POLY1305_KEY_SIZE);
95 if (unlikely(ret))
96 goto err_enckey;
97
98 /* encrypt data */
99 chacha20poly1305_encrypt(buf, prep->data, datalen, NULL, 0,
100 0, enckey);
101
102 /* save aligned data to file */
103 file = shmem_kernel_file_setup("", enclen, 0);
104 if (IS_ERR(file)) {
105 ret = PTR_ERR(file);
106 goto err_enckey;
107 }
108
109 written = kernel_write(file, buf, enclen, &pos);
110 if (written != enclen) {
111 ret = written;
112 if (written >= 0)
113 ret = -EIO;
114 goto err_fput;
115 }
116
117 /* Pin the mount and dentry to the key so that we can open it again
118 * later
119 */
120 prep->payload.data[big_key_data] = enckey;
121 *path = file->f_path;
122 path_get(path);
123 fput(file);
124 memzero_explicit(buf, enclen);
125 kvfree(buf);
126 } else {
127 /* Just store the data in a buffer */
128 void *data = kmalloc(datalen, GFP_KERNEL);
129
130 if (!data)
131 return -ENOMEM;
132
133 prep->payload.data[big_key_data] = data;
134 memcpy(data, prep->data, prep->datalen);
135 }
136 return 0;
137
138err_fput:
139 fput(file);
140err_enckey:
141 kfree_sensitive(enckey);
142error:
143 memzero_explicit(buf, enclen);
144 kvfree(buf);
145 return ret;
146}
147
148/*
149 * Clear preparsement.
150 */
151void big_key_free_preparse(struct key_preparsed_payload *prep)
152{
153 if (prep->datalen > BIG_KEY_FILE_THRESHOLD) {
154 struct path *path = (struct path *)&prep->payload.data[big_key_path];
155
156 path_put(path);
157 }
158 kfree_sensitive(prep->payload.data[big_key_data]);
159}
160
161/*
162 * dispose of the links from a revoked keyring
163 * - called with the key sem write-locked
164 */
165void big_key_revoke(struct key *key)
166{
167 struct path *path = (struct path *)&key->payload.data[big_key_path];
168
169 /* clear the quota */
170 key_payload_reserve(key, 0);
171 if (key_is_positive(key) &&
172 (size_t)key->payload.data[big_key_len] > BIG_KEY_FILE_THRESHOLD)
173 vfs_truncate(path, 0);
174}
175
176/*
177 * dispose of the data dangling from the corpse of a big_key key
178 */
179void big_key_destroy(struct key *key)
180{
181 size_t datalen = (size_t)key->payload.data[big_key_len];
182
183 if (datalen > BIG_KEY_FILE_THRESHOLD) {
184 struct path *path = (struct path *)&key->payload.data[big_key_path];
185
186 path_put(path);
187 path->mnt = NULL;
188 path->dentry = NULL;
189 }
190 kfree_sensitive(key->payload.data[big_key_data]);
191 key->payload.data[big_key_data] = NULL;
192}
193
194/*
195 * Update a big key
196 */
197int big_key_update(struct key *key, struct key_preparsed_payload *prep)
198{
199 int ret;
200
201 ret = key_payload_reserve(key, prep->datalen);
202 if (ret < 0)
203 return ret;
204
205 if (key_is_positive(key))
206 big_key_destroy(key);
207
208 return generic_key_instantiate(key, prep);
209}
210
211/*
212 * describe the big_key key
213 */
214void big_key_describe(const struct key *key, struct seq_file *m)
215{
216 size_t datalen = (size_t)key->payload.data[big_key_len];
217
218 seq_puts(m, key->description);
219
220 if (key_is_positive(key))
221 seq_printf(m, ": %zu [%s]",
222 datalen,
223 datalen > BIG_KEY_FILE_THRESHOLD ? "file" : "buff");
224}
225
226/*
227 * read the key data
228 * - the key's semaphore is read-locked
229 */
230long big_key_read(const struct key *key, char *buffer, size_t buflen)
231{
232 size_t datalen = (size_t)key->payload.data[big_key_len];
233 long ret;
234
235 if (!buffer || buflen < datalen)
236 return datalen;
237
238 if (datalen > BIG_KEY_FILE_THRESHOLD) {
239 struct path *path = (struct path *)&key->payload.data[big_key_path];
240 struct file *file;
241 u8 *buf, *enckey = (u8 *)key->payload.data[big_key_data];
242 size_t enclen = datalen + CHACHA20POLY1305_AUTHTAG_SIZE;
243 loff_t pos = 0;
244
245 buf = kvmalloc(enclen, GFP_KERNEL);
246 if (!buf)
247 return -ENOMEM;
248
249 file = dentry_open(path, O_RDONLY, current_cred());
250 if (IS_ERR(file)) {
251 ret = PTR_ERR(file);
252 goto error;
253 }
254
255 /* read file to kernel and decrypt */
256 ret = kernel_read(file, buf, enclen, &pos);
257 if (ret != enclen) {
258 if (ret >= 0)
259 ret = -EIO;
260 goto err_fput;
261 }
262
263 ret = chacha20poly1305_decrypt(buf, buf, enclen, NULL, 0, 0,
264 enckey) ? 0 : -EBADMSG;
265 if (unlikely(ret))
266 goto err_fput;
267
268 ret = datalen;
269
270 /* copy out decrypted data */
271 memcpy(buffer, buf, datalen);
272
273err_fput:
274 fput(file);
275error:
276 memzero_explicit(buf, enclen);
277 kvfree(buf);
278 } else {
279 ret = datalen;
280 memcpy(buffer, key->payload.data[big_key_data], datalen);
281 }
282
283 return ret;
284}
285
286/*
287 * Register key type
288 */
289static int __init big_key_init(void)
290{
291 return register_key_type(&key_type_big_key);
292}
293
294late_initcall(big_key_init);
1/* Large capacity key type
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#define pr_fmt(fmt) "big_key: "fmt
13#include <linux/init.h>
14#include <linux/seq_file.h>
15#include <linux/file.h>
16#include <linux/shmem_fs.h>
17#include <linux/err.h>
18#include <linux/scatterlist.h>
19#include <keys/user-type.h>
20#include <keys/big_key-type.h>
21#include <crypto/rng.h>
22#include <crypto/skcipher.h>
23
24/*
25 * Layout of key payload words.
26 */
27enum {
28 big_key_data,
29 big_key_path,
30 big_key_path_2nd_part,
31 big_key_len,
32};
33
34/*
35 * Crypto operation with big_key data
36 */
37enum big_key_op {
38 BIG_KEY_ENC,
39 BIG_KEY_DEC,
40};
41
42/*
43 * If the data is under this limit, there's no point creating a shm file to
44 * hold it as the permanently resident metadata for the shmem fs will be at
45 * least as large as the data.
46 */
47#define BIG_KEY_FILE_THRESHOLD (sizeof(struct inode) + sizeof(struct dentry))
48
49/*
50 * Key size for big_key data encryption
51 */
52#define ENC_KEY_SIZE 16
53
54/*
55 * big_key defined keys take an arbitrary string as the description and an
56 * arbitrary blob of data as the payload
57 */
58struct key_type key_type_big_key = {
59 .name = "big_key",
60 .preparse = big_key_preparse,
61 .free_preparse = big_key_free_preparse,
62 .instantiate = generic_key_instantiate,
63 .revoke = big_key_revoke,
64 .destroy = big_key_destroy,
65 .describe = big_key_describe,
66 .read = big_key_read,
67};
68
69/*
70 * Crypto names for big_key data encryption
71 */
72static const char big_key_rng_name[] = "stdrng";
73static const char big_key_alg_name[] = "ecb(aes)";
74
75/*
76 * Crypto algorithms for big_key data encryption
77 */
78static struct crypto_rng *big_key_rng;
79static struct crypto_skcipher *big_key_skcipher;
80
81/*
82 * Generate random key to encrypt big_key data
83 */
84static inline int big_key_gen_enckey(u8 *key)
85{
86 return crypto_rng_get_bytes(big_key_rng, key, ENC_KEY_SIZE);
87}
88
89/*
90 * Encrypt/decrypt big_key data
91 */
92static int big_key_crypt(enum big_key_op op, u8 *data, size_t datalen, u8 *key)
93{
94 int ret = -EINVAL;
95 struct scatterlist sgio;
96 SKCIPHER_REQUEST_ON_STACK(req, big_key_skcipher);
97
98 if (crypto_skcipher_setkey(big_key_skcipher, key, ENC_KEY_SIZE)) {
99 ret = -EAGAIN;
100 goto error;
101 }
102
103 skcipher_request_set_tfm(req, big_key_skcipher);
104 skcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_SLEEP,
105 NULL, NULL);
106
107 sg_init_one(&sgio, data, datalen);
108 skcipher_request_set_crypt(req, &sgio, &sgio, datalen, NULL);
109
110 if (op == BIG_KEY_ENC)
111 ret = crypto_skcipher_encrypt(req);
112 else
113 ret = crypto_skcipher_decrypt(req);
114
115 skcipher_request_zero(req);
116
117error:
118 return ret;
119}
120
121/*
122 * Preparse a big key
123 */
124int big_key_preparse(struct key_preparsed_payload *prep)
125{
126 struct path *path = (struct path *)&prep->payload.data[big_key_path];
127 struct file *file;
128 u8 *enckey;
129 u8 *data = NULL;
130 ssize_t written;
131 size_t datalen = prep->datalen;
132 int ret;
133
134 ret = -EINVAL;
135 if (datalen <= 0 || datalen > 1024 * 1024 || !prep->data)
136 goto error;
137
138 /* Set an arbitrary quota */
139 prep->quotalen = 16;
140
141 prep->payload.data[big_key_len] = (void *)(unsigned long)datalen;
142
143 if (datalen > BIG_KEY_FILE_THRESHOLD) {
144 /* Create a shmem file to store the data in. This will permit the data
145 * to be swapped out if needed.
146 *
147 * File content is stored encrypted with randomly generated key.
148 */
149 size_t enclen = ALIGN(datalen, crypto_skcipher_blocksize(big_key_skcipher));
150
151 /* prepare aligned data to encrypt */
152 data = kmalloc(enclen, GFP_KERNEL);
153 if (!data)
154 return -ENOMEM;
155
156 memcpy(data, prep->data, datalen);
157 memset(data + datalen, 0x00, enclen - datalen);
158
159 /* generate random key */
160 enckey = kmalloc(ENC_KEY_SIZE, GFP_KERNEL);
161 if (!enckey) {
162 ret = -ENOMEM;
163 goto error;
164 }
165
166 ret = big_key_gen_enckey(enckey);
167 if (ret)
168 goto err_enckey;
169
170 /* encrypt aligned data */
171 ret = big_key_crypt(BIG_KEY_ENC, data, enclen, enckey);
172 if (ret)
173 goto err_enckey;
174
175 /* save aligned data to file */
176 file = shmem_kernel_file_setup("", enclen, 0);
177 if (IS_ERR(file)) {
178 ret = PTR_ERR(file);
179 goto err_enckey;
180 }
181
182 written = kernel_write(file, data, enclen, 0);
183 if (written != enclen) {
184 ret = written;
185 if (written >= 0)
186 ret = -ENOMEM;
187 goto err_fput;
188 }
189
190 /* Pin the mount and dentry to the key so that we can open it again
191 * later
192 */
193 prep->payload.data[big_key_data] = enckey;
194 *path = file->f_path;
195 path_get(path);
196 fput(file);
197 kfree(data);
198 } else {
199 /* Just store the data in a buffer */
200 void *data = kmalloc(datalen, GFP_KERNEL);
201
202 if (!data)
203 return -ENOMEM;
204
205 prep->payload.data[big_key_data] = data;
206 memcpy(data, prep->data, prep->datalen);
207 }
208 return 0;
209
210err_fput:
211 fput(file);
212err_enckey:
213 kfree(enckey);
214error:
215 kfree(data);
216 return ret;
217}
218
219/*
220 * Clear preparsement.
221 */
222void big_key_free_preparse(struct key_preparsed_payload *prep)
223{
224 if (prep->datalen > BIG_KEY_FILE_THRESHOLD) {
225 struct path *path = (struct path *)&prep->payload.data[big_key_path];
226
227 path_put(path);
228 }
229 kfree(prep->payload.data[big_key_data]);
230}
231
232/*
233 * dispose of the links from a revoked keyring
234 * - called with the key sem write-locked
235 */
236void big_key_revoke(struct key *key)
237{
238 struct path *path = (struct path *)&key->payload.data[big_key_path];
239
240 /* clear the quota */
241 key_payload_reserve(key, 0);
242 if (key_is_instantiated(key) &&
243 (size_t)key->payload.data[big_key_len] > BIG_KEY_FILE_THRESHOLD)
244 vfs_truncate(path, 0);
245}
246
247/*
248 * dispose of the data dangling from the corpse of a big_key key
249 */
250void big_key_destroy(struct key *key)
251{
252 size_t datalen = (size_t)key->payload.data[big_key_len];
253
254 if (datalen > BIG_KEY_FILE_THRESHOLD) {
255 struct path *path = (struct path *)&key->payload.data[big_key_path];
256
257 path_put(path);
258 path->mnt = NULL;
259 path->dentry = NULL;
260 }
261 kfree(key->payload.data[big_key_data]);
262 key->payload.data[big_key_data] = NULL;
263}
264
265/*
266 * describe the big_key key
267 */
268void big_key_describe(const struct key *key, struct seq_file *m)
269{
270 size_t datalen = (size_t)key->payload.data[big_key_len];
271
272 seq_puts(m, key->description);
273
274 if (key_is_instantiated(key))
275 seq_printf(m, ": %zu [%s]",
276 datalen,
277 datalen > BIG_KEY_FILE_THRESHOLD ? "file" : "buff");
278}
279
280/*
281 * read the key data
282 * - the key's semaphore is read-locked
283 */
284long big_key_read(const struct key *key, char __user *buffer, size_t buflen)
285{
286 size_t datalen = (size_t)key->payload.data[big_key_len];
287 long ret;
288
289 if (!buffer || buflen < datalen)
290 return datalen;
291
292 if (datalen > BIG_KEY_FILE_THRESHOLD) {
293 struct path *path = (struct path *)&key->payload.data[big_key_path];
294 struct file *file;
295 u8 *data;
296 u8 *enckey = (u8 *)key->payload.data[big_key_data];
297 size_t enclen = ALIGN(datalen, crypto_skcipher_blocksize(big_key_skcipher));
298
299 data = kmalloc(enclen, GFP_KERNEL);
300 if (!data)
301 return -ENOMEM;
302
303 file = dentry_open(path, O_RDONLY, current_cred());
304 if (IS_ERR(file)) {
305 ret = PTR_ERR(file);
306 goto error;
307 }
308
309 /* read file to kernel and decrypt */
310 ret = kernel_read(file, 0, data, enclen);
311 if (ret >= 0 && ret != enclen) {
312 ret = -EIO;
313 goto err_fput;
314 }
315
316 ret = big_key_crypt(BIG_KEY_DEC, data, enclen, enckey);
317 if (ret)
318 goto err_fput;
319
320 ret = datalen;
321
322 /* copy decrypted data to user */
323 if (copy_to_user(buffer, data, datalen) != 0)
324 ret = -EFAULT;
325
326err_fput:
327 fput(file);
328error:
329 kfree(data);
330 } else {
331 ret = datalen;
332 if (copy_to_user(buffer, key->payload.data[big_key_data],
333 datalen) != 0)
334 ret = -EFAULT;
335 }
336
337 return ret;
338}
339
340/*
341 * Register key type
342 */
343static int __init big_key_init(void)
344{
345 struct crypto_skcipher *cipher;
346 struct crypto_rng *rng;
347 int ret;
348
349 rng = crypto_alloc_rng(big_key_rng_name, 0, 0);
350 if (IS_ERR(rng)) {
351 pr_err("Can't alloc rng: %ld\n", PTR_ERR(rng));
352 return PTR_ERR(rng);
353 }
354
355 big_key_rng = rng;
356
357 /* seed RNG */
358 ret = crypto_rng_reset(rng, NULL, crypto_rng_seedsize(rng));
359 if (ret) {
360 pr_err("Can't reset rng: %d\n", ret);
361 goto error_rng;
362 }
363
364 /* init block cipher */
365 cipher = crypto_alloc_skcipher(big_key_alg_name, 0, CRYPTO_ALG_ASYNC);
366 if (IS_ERR(cipher)) {
367 ret = PTR_ERR(cipher);
368 pr_err("Can't alloc crypto: %d\n", ret);
369 goto error_rng;
370 }
371
372 big_key_skcipher = cipher;
373
374 ret = register_key_type(&key_type_big_key);
375 if (ret < 0) {
376 pr_err("Can't register type: %d\n", ret);
377 goto error_cipher;
378 }
379
380 return 0;
381
382error_cipher:
383 crypto_free_skcipher(big_key_skcipher);
384error_rng:
385 crypto_free_rng(big_key_rng);
386 return ret;
387}
388
389late_initcall(big_key_init);