1
2
3
4
5
6
7
8
9
10
11
12
13#define pr_fmt(fmt) "big_key: "fmt
14#include <linux/init.h>
15#include <linux/seq_file.h>
16#include <linux/file.h>
17#include <linux/shmem_fs.h>
18#include <linux/err.h>
19#include <linux/scatterlist.h>
20#include <linux/random.h>
21#include <linux/vmalloc.h>
22#include <keys/user-type.h>
23#include <keys/big_key-type.h>
24#include <crypto/aead.h>
25
26struct big_key_buf {
27 unsigned int nr_pages;
28 void *virt;
29 struct scatterlist *sg;
30 struct page *pages[];
31};
32
33
34
35
36enum {
37 big_key_data,
38 big_key_path,
39 big_key_path_2nd_part,
40 big_key_len,
41};
42
43
44
45
46enum big_key_op {
47 BIG_KEY_ENC,
48 BIG_KEY_DEC,
49};
50
51
52
53
54
55
56#define BIG_KEY_FILE_THRESHOLD (sizeof(struct inode) + sizeof(struct dentry))
57
58
59
60
61#define ENC_KEY_SIZE 32
62
63
64
65
66#define ENC_AUTHTAG_SIZE 16
67
68
69
70
71
72struct key_type key_type_big_key = {
73 .name = "big_key",
74 .preparse = big_key_preparse,
75 .free_preparse = big_key_free_preparse,
76 .instantiate = generic_key_instantiate,
77 .revoke = big_key_revoke,
78 .destroy = big_key_destroy,
79 .describe = big_key_describe,
80 .read = big_key_read,
81
82};
83
84
85
86
87static const char big_key_alg_name[] = "gcm(aes)";
88
89
90
91
92static struct crypto_aead *big_key_aead;
93
94
95
96
97static DEFINE_MUTEX(big_key_aead_lock);
98
99
100
101
102static int big_key_crypt(enum big_key_op op, struct big_key_buf *buf, size_t datalen, u8 *key)
103{
104 int ret;
105 struct aead_request *aead_req;
106
107
108
109
110
111
112 u8 zero_nonce[crypto_aead_ivsize(big_key_aead)];
113
114 aead_req = aead_request_alloc(big_key_aead, GFP_KERNEL);
115 if (!aead_req)
116 return -ENOMEM;
117
118 memset(zero_nonce, 0, sizeof(zero_nonce));
119 aead_request_set_crypt(aead_req, buf->sg, buf->sg, datalen, zero_nonce);
120 aead_request_set_callback(aead_req, CRYPTO_TFM_REQ_MAY_SLEEP, NULL, NULL);
121 aead_request_set_ad(aead_req, 0);
122
123 mutex_lock(&big_key_aead_lock);
124 if (crypto_aead_setkey(big_key_aead, key, ENC_KEY_SIZE)) {
125 ret = -EAGAIN;
126 goto error;
127 }
128 if (op == BIG_KEY_ENC)
129 ret = crypto_aead_encrypt(aead_req);
130 else
131 ret = crypto_aead_decrypt(aead_req);
132error:
133 mutex_unlock(&big_key_aead_lock);
134 aead_request_free(aead_req);
135 return ret;
136}
137
138
139
140
141static void big_key_free_buffer(struct big_key_buf *buf)
142{
143 unsigned int i;
144
145 if (buf->virt) {
146 memset(buf->virt, 0, buf->nr_pages * PAGE_SIZE);
147 vunmap(buf->virt);
148 }
149
150 for (i = 0; i < buf->nr_pages; i++)
151 if (buf->pages[i])
152 __free_page(buf->pages[i]);
153
154 kfree(buf);
155}
156
157
158
159
160
161static void *big_key_alloc_buffer(size_t len)
162{
163 struct big_key_buf *buf;
164 unsigned int npg = (len + PAGE_SIZE - 1) >> PAGE_SHIFT;
165 unsigned int i, l;
166
167 buf = kzalloc(sizeof(struct big_key_buf) +
168 sizeof(struct page) * npg +
169 sizeof(struct scatterlist) * npg,
170 GFP_KERNEL);
171 if (!buf)
172 return NULL;
173
174 buf->nr_pages = npg;
175 buf->sg = (void *)(buf->pages + npg);
176 sg_init_table(buf->sg, npg);
177
178 for (i = 0; i < buf->nr_pages; i++) {
179 buf->pages[i] = alloc_page(GFP_KERNEL);
180 if (!buf->pages[i])
181 goto nomem;
182
183 l = min_t(size_t, len, PAGE_SIZE);
184 sg_set_page(&buf->sg[i], buf->pages[i], l, 0);
185 len -= l;
186 }
187
188 buf->virt = vmap(buf->pages, buf->nr_pages, VM_MAP, PAGE_KERNEL);
189 if (!buf->virt)
190 goto nomem;
191
192 return buf;
193
194nomem:
195 big_key_free_buffer(buf);
196 return NULL;
197}
198
199
200
201
202int big_key_preparse(struct key_preparsed_payload *prep)
203{
204 struct big_key_buf *buf;
205 struct path *path = (struct path *)&prep->payload.data[big_key_path];
206 struct file *file;
207 u8 *enckey;
208 ssize_t written;
209 size_t datalen = prep->datalen, enclen = datalen + ENC_AUTHTAG_SIZE;
210 int ret;
211
212 if (datalen <= 0 || datalen > 1024 * 1024 || !prep->data)
213 return -EINVAL;
214
215
216 prep->quotalen = 16;
217
218 prep->payload.data[big_key_len] = (void *)(unsigned long)datalen;
219
220 if (datalen > BIG_KEY_FILE_THRESHOLD) {
221
222
223
224
225
226 loff_t pos = 0;
227
228 buf = big_key_alloc_buffer(enclen);
229 if (!buf)
230 return -ENOMEM;
231 memcpy(buf->virt, prep->data, datalen);
232
233
234 enckey = kmalloc(ENC_KEY_SIZE, GFP_KERNEL);
235 if (!enckey) {
236 ret = -ENOMEM;
237 goto error;
238 }
239 ret = get_random_bytes_wait(enckey, ENC_KEY_SIZE);
240 if (unlikely(ret))
241 goto err_enckey;
242
243
244 ret = big_key_crypt(BIG_KEY_ENC, buf, datalen, enckey);
245 if (ret)
246 goto err_enckey;
247
248
249 file = shmem_kernel_file_setup("", enclen, 0);
250 if (IS_ERR(file)) {
251 ret = PTR_ERR(file);
252 goto err_enckey;
253 }
254
255 written = kernel_write(file, buf->virt, enclen, &pos);
256 if (written != enclen) {
257 ret = written;
258 if (written >= 0)
259 ret = -ENOMEM;
260 goto err_fput;
261 }
262
263
264
265
266 prep->payload.data[big_key_data] = enckey;
267 *path = file->f_path;
268 path_get(path);
269 fput(file);
270 big_key_free_buffer(buf);
271 } else {
272
273 void *data = kmalloc(datalen, GFP_KERNEL);
274
275 if (!data)
276 return -ENOMEM;
277
278 prep->payload.data[big_key_data] = data;
279 memcpy(data, prep->data, prep->datalen);
280 }
281 return 0;
282
283err_fput:
284 fput(file);
285err_enckey:
286 kzfree(enckey);
287error:
288 big_key_free_buffer(buf);
289 return ret;
290}
291
292
293
294
295void big_key_free_preparse(struct key_preparsed_payload *prep)
296{
297 if (prep->datalen > BIG_KEY_FILE_THRESHOLD) {
298 struct path *path = (struct path *)&prep->payload.data[big_key_path];
299
300 path_put(path);
301 }
302 kzfree(prep->payload.data[big_key_data]);
303}
304
305
306
307
308
309void big_key_revoke(struct key *key)
310{
311 struct path *path = (struct path *)&key->payload.data[big_key_path];
312
313
314 key_payload_reserve(key, 0);
315 if (key_is_positive(key) &&
316 (size_t)key->payload.data[big_key_len] > BIG_KEY_FILE_THRESHOLD)
317 vfs_truncate(path, 0);
318}
319
320
321
322
323void big_key_destroy(struct key *key)
324{
325 size_t datalen = (size_t)key->payload.data[big_key_len];
326
327 if (datalen > BIG_KEY_FILE_THRESHOLD) {
328 struct path *path = (struct path *)&key->payload.data[big_key_path];
329
330 path_put(path);
331 path->mnt = NULL;
332 path->dentry = NULL;
333 }
334 kzfree(key->payload.data[big_key_data]);
335 key->payload.data[big_key_data] = NULL;
336}
337
338
339
340
341void big_key_describe(const struct key *key, struct seq_file *m)
342{
343 size_t datalen = (size_t)key->payload.data[big_key_len];
344
345 seq_puts(m, key->description);
346
347 if (key_is_positive(key))
348 seq_printf(m, ": %zu [%s]",
349 datalen,
350 datalen > BIG_KEY_FILE_THRESHOLD ? "file" : "buff");
351}
352
353
354
355
356
357long big_key_read(const struct key *key, char __user *buffer, size_t buflen)
358{
359 size_t datalen = (size_t)key->payload.data[big_key_len];
360 long ret;
361
362 if (!buffer || buflen < datalen)
363 return datalen;
364
365 if (datalen > BIG_KEY_FILE_THRESHOLD) {
366 struct big_key_buf *buf;
367 struct path *path = (struct path *)&key->payload.data[big_key_path];
368 struct file *file;
369 u8 *enckey = (u8 *)key->payload.data[big_key_data];
370 size_t enclen = datalen + ENC_AUTHTAG_SIZE;
371 loff_t pos = 0;
372
373 buf = big_key_alloc_buffer(enclen);
374 if (!buf)
375 return -ENOMEM;
376
377 file = dentry_open(path, O_RDONLY, current_cred());
378 if (IS_ERR(file)) {
379 ret = PTR_ERR(file);
380 goto error;
381 }
382
383
384 ret = kernel_read(file, buf->virt, enclen, &pos);
385 if (ret >= 0 && ret != enclen) {
386 ret = -EIO;
387 goto err_fput;
388 }
389
390 ret = big_key_crypt(BIG_KEY_DEC, buf, enclen, enckey);
391 if (ret)
392 goto err_fput;
393
394 ret = datalen;
395
396
397 if (copy_to_user(buffer, buf->virt, datalen) != 0)
398 ret = -EFAULT;
399
400err_fput:
401 fput(file);
402error:
403 big_key_free_buffer(buf);
404 } else {
405 ret = datalen;
406 if (copy_to_user(buffer, key->payload.data[big_key_data],
407 datalen) != 0)
408 ret = -EFAULT;
409 }
410
411 return ret;
412}
413
414
415
416
417static int __init big_key_init(void)
418{
419 int ret;
420
421
422 big_key_aead = crypto_alloc_aead(big_key_alg_name, 0, CRYPTO_ALG_ASYNC);
423 if (IS_ERR(big_key_aead)) {
424 ret = PTR_ERR(big_key_aead);
425 pr_err("Can't alloc crypto: %d\n", ret);
426 return ret;
427 }
428 ret = crypto_aead_setauthsize(big_key_aead, ENC_AUTHTAG_SIZE);
429 if (ret < 0) {
430 pr_err("Can't set crypto auth tag len: %d\n", ret);
431 goto free_aead;
432 }
433
434 ret = register_key_type(&key_type_big_key);
435 if (ret < 0) {
436 pr_err("Can't register type: %d\n", ret);
437 goto free_aead;
438 }
439
440 return 0;
441
442free_aead:
443 crypto_free_aead(big_key_aead);
444 return ret;
445}
446
447late_initcall(big_key_init);
448