1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
|
// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (C) 2021 Microsoft Corporation
*
* Author: Tushar Sugandhi <tusharsu@linux.microsoft.com>
*
* File: dm-ima.c
* Enables IMA measurements for DM targets
*/
#include "dm-core.h"
#include "dm-ima.h"
#include <linux/ima.h>
#include <crypto/hash.h>
#include <linux/crypto.h>
#include <crypto/hash_info.h>
#define DM_MSG_PREFIX "ima"
/*
* Internal function to prefix separator characters in input buffer with escape
* character, so that they don't interfere with the construction of key-value pairs,
* and clients can split the key1=val1,key2=val2,key3=val3; pairs properly.
*/
static void fix_separator_chars(char **buf)
{
int l = strlen(*buf);
int i, j, sp = 0;
for (i = 0; i < l; i++)
if ((*buf)[i] == '\\' || (*buf)[i] == ';' || (*buf)[i] == '=' || (*buf)[i] == ',')
sp++;
if (!sp)
return;
for (i = l-1, j = i+sp; i >= 0; i--) {
(*buf)[j--] = (*buf)[i];
if ((*buf)[i] == '\\' || (*buf)[i] == ';' || (*buf)[i] == '=' || (*buf)[i] == ',')
(*buf)[j--] = '\\';
}
}
/*
* Internal function to allocate memory for IMA measurements.
*/
static void *dm_ima_alloc(size_t len, gfp_t flags, bool noio)
{
unsigned int noio_flag;
void *ptr;
if (noio)
noio_flag = memalloc_noio_save();
ptr = kzalloc(len, flags);
if (noio)
memalloc_noio_restore(noio_flag);
return ptr;
}
/*
* Internal function to allocate and copy name and uuid for IMA measurements.
*/
static int dm_ima_alloc_and_copy_name_uuid(struct mapped_device *md, char **dev_name,
char **dev_uuid, bool noio)
{
int r;
*dev_name = dm_ima_alloc(DM_NAME_LEN*2, GFP_KERNEL, noio);
if (!(*dev_name)) {
r = -ENOMEM;
goto error;
}
*dev_uuid = dm_ima_alloc(DM_UUID_LEN*2, GFP_KERNEL, noio);
if (!(*dev_uuid)) {
r = -ENOMEM;
goto error;
}
r = dm_copy_name_and_uuid(md, *dev_name, *dev_uuid);
if (r)
goto error;
fix_separator_chars(dev_name);
fix_separator_chars(dev_uuid);
return 0;
error:
kfree(*dev_name);
kfree(*dev_uuid);
*dev_name = NULL;
*dev_uuid = NULL;
return r;
}
/*
* Internal function to allocate and copy device data for IMA measurements.
*/
static int dm_ima_alloc_and_copy_device_data(struct mapped_device *md, char **device_data,
unsigned int num_targets, bool noio)
{
char *dev_name = NULL, *dev_uuid = NULL;
int r;
r = dm_ima_alloc_and_copy_name_uuid(md, &dev_name, &dev_uuid, noio);
if (r)
return r;
*device_data = dm_ima_alloc(DM_IMA_DEVICE_BUF_LEN, GFP_KERNEL, noio);
if (!(*device_data)) {
r = -ENOMEM;
goto error;
}
scnprintf(*device_data, DM_IMA_DEVICE_BUF_LEN,
"name=%s,uuid=%s,major=%d,minor=%d,minor_count=%d,num_targets=%u;",
dev_name, dev_uuid, md->disk->major, md->disk->first_minor,
md->disk->minors, num_targets);
error:
kfree(dev_name);
kfree(dev_uuid);
return r;
}
/*
* Internal wrapper function to call IMA to measure DM data.
*/
static void dm_ima_measure_data(const char *event_name, const void *buf, size_t buf_len,
bool noio)
{
unsigned int noio_flag;
if (noio)
noio_flag = memalloc_noio_save();
ima_measure_critical_data(DM_NAME, event_name, buf, buf_len, false);
if (noio)
memalloc_noio_restore(noio_flag);
}
/*
* Internal function to allocate and copy current device capacity for IMA measurements.
*/
static int dm_ima_alloc_and_copy_capacity_str(struct mapped_device *md, char **capacity_str,
bool noio)
{
sector_t capacity;
capacity = get_capacity(md->disk);
*capacity_str = dm_ima_alloc(DM_IMA_DEVICE_CAPACITY_BUF_LEN, GFP_KERNEL, noio);
if (!(*capacity_str))
return -ENOMEM;
scnprintf(*capacity_str, DM_IMA_DEVICE_BUF_LEN, "current_device_capacity=%llu;",
capacity);
return 0;
}
/*
* Initialize/reset the dm ima related data structure variables.
*/
void dm_ima_reset_data(struct mapped_device *md)
{
memset(&(md->ima), 0, sizeof(md->ima));
}
/*
* Build up the IMA data for each target, and finally measure.
*/
void dm_ima_measure_on_table_load(struct dm_table *table, unsigned int status_flags)
{
size_t device_data_buf_len, target_metadata_buf_len, target_data_buf_len, l = 0;
char *target_metadata_buf = NULL, *target_data_buf = NULL, *digest_buf = NULL;
char *ima_buf = NULL, *device_data_buf = NULL;
int digest_size, last_target_measured = -1, r;
status_type_t type = STATUSTYPE_IMA;
size_t cur_total_buf_len = 0;
unsigned int num_targets, i;
SHASH_DESC_ON_STACK(shash, NULL);
struct crypto_shash *tfm = NULL;
u8 *digest = NULL;
bool noio = false;
ima_buf = dm_ima_alloc(DM_IMA_MEASUREMENT_BUF_LEN, GFP_KERNEL, noio);
if (!ima_buf)
return;
target_metadata_buf = dm_ima_alloc(DM_IMA_TARGET_METADATA_BUF_LEN, GFP_KERNEL, noio);
if (!target_metadata_buf)
goto error;
target_data_buf = dm_ima_alloc(DM_IMA_TARGET_DATA_BUF_LEN, GFP_KERNEL, noio);
if (!target_data_buf)
goto error;
num_targets = dm_table_get_num_targets(table);
if (dm_ima_alloc_and_copy_device_data(table->md, &device_data_buf, num_targets, noio))
goto error;
tfm = crypto_alloc_shash("sha256", 0, 0);
if (IS_ERR(tfm))
goto error;
shash->tfm = tfm;
digest_size = crypto_shash_digestsize(tfm);
digest = dm_ima_alloc(digest_size, GFP_KERNEL, noio);
if (!digest)
goto error;
r = crypto_shash_init(shash);
if (r)
goto error;
device_data_buf_len = strlen(device_data_buf);
memcpy(ima_buf + l, device_data_buf, device_data_buf_len);
l += device_data_buf_len;
for (i = 0; i < num_targets; i++) {
struct dm_target *ti = dm_table_get_target(table, i);
if (!ti)
goto error;
last_target_measured = 0;
/*
* First retrieve the target metadata.
*/
scnprintf(target_metadata_buf, DM_IMA_TARGET_METADATA_BUF_LEN,
"target_index=%d,target_begin=%llu,target_len=%llu,",
i, ti->begin, ti->len);
target_metadata_buf_len = strlen(target_metadata_buf);
/*
* Then retrieve the actual target data.
*/
if (ti->type->status)
ti->type->status(ti, type, status_flags, target_data_buf,
DM_IMA_TARGET_DATA_BUF_LEN);
else
target_data_buf[0] = '\0';
target_data_buf_len = strlen(target_data_buf);
/*
* Check if the total data can fit into the IMA buffer.
*/
cur_total_buf_len = l + target_metadata_buf_len + target_data_buf_len;
/*
* IMA measurements for DM targets are best-effort.
* If the total data buffered so far, including the current target,
* is too large to fit into DM_IMA_MEASUREMENT_BUF_LEN, measure what
* we have in the current buffer, and continue measuring the remaining
* targets by prefixing the device metadata again.
*/
if (unlikely(cur_total_buf_len >= DM_IMA_MEASUREMENT_BUF_LEN)) {
dm_ima_measure_data("table_load", ima_buf, l, noio);
r = crypto_shash_update(shash, (const u8 *)ima_buf, l);
if (r < 0)
goto error;
memset(ima_buf, 0, DM_IMA_MEASUREMENT_BUF_LEN);
l = 0;
/*
* Each new "table_load" entry in IMA log should have device data
* prefix, so that multiple records from the same table_load for
* a given device can be linked together.
*/
memcpy(ima_buf + l, device_data_buf, device_data_buf_len);
l += device_data_buf_len;
/*
* If this iteration of the for loop turns out to be the last target
* in the table, dm_ima_measure_data("table_load", ...) doesn't need
* to be called again, just the hash needs to be finalized.
* "last_target_measured" tracks this state.
*/
last_target_measured = 1;
}
/*
* Fill-in all the target metadata, so that multiple targets for the same
* device can be linked together.
*/
memcpy(ima_buf + l, target_metadata_buf, target_metadata_buf_len);
l += target_metadata_buf_len;
memcpy(ima_buf + l, target_data_buf, target_data_buf_len);
l += target_data_buf_len;
}
if (!last_target_measured) {
dm_ima_measure_data("table_load", ima_buf, l, noio);
r = crypto_shash_update(shash, (const u8 *)ima_buf, l);
if (r < 0)
goto error;
}
/*
* Finalize the table hash, and store it in table->md->ima.inactive_table.hash,
* so that the table data can be verified against the future device state change
* events, e.g. resume, rename, remove, table-clear etc.
*/
r = crypto_shash_final(shash, digest);
if (r < 0)
goto error;
digest_buf = dm_ima_alloc((digest_size*2)+1, GFP_KERNEL, noio);
if (!digest_buf)
goto error;
for (i = 0; i < digest_size; i++)
snprintf((digest_buf+(i*2)), 3, "%02x", digest[i]);
if (table->md->ima.active_table.hash != table->md->ima.inactive_table.hash)
kfree(table->md->ima.inactive_table.hash);
table->md->ima.inactive_table.hash = digest_buf;
table->md->ima.inactive_table.hash_len = strlen(digest_buf);
table->md->ima.inactive_table.num_targets = num_targets;
if (table->md->ima.active_table.device_metadata !=
table->md->ima.inactive_table.device_metadata)
kfree(table->md->ima.inactive_table.device_metadata);
table->md->ima.inactive_table.device_metadata = device_data_buf;
table->md->ima.inactive_table.device_metadata_len = device_data_buf_len;
goto exit;
error:
kfree(digest_buf);
kfree(device_data_buf);
exit:
kfree(digest);
if (tfm)
crypto_free_shash(tfm);
kfree(ima_buf);
kfree(target_metadata_buf);
kfree(target_data_buf);
}
/*
* Measure IMA data on device resume.
*/
void dm_ima_measure_on_device_resume(struct mapped_device *md, bool swap)
{
char *device_table_data, *dev_name = NULL, *dev_uuid = NULL, *capacity_str = NULL;
char active[] = "active_table_hash=";
unsigned int active_len = strlen(active), capacity_len = 0;
unsigned int l = 0;
bool noio = true;
int r;
device_table_data = dm_ima_alloc(DM_IMA_DEVICE_BUF_LEN, GFP_KERNEL, noio);
if (!device_table_data)
return;
r = dm_ima_alloc_and_copy_capacity_str(md, &capacity_str, noio);
if (r)
goto error;
if (swap) {
if (md->ima.active_table.hash != md->ima.inactive_table.hash)
kfree(md->ima.active_table.hash);
md->ima.active_table.hash = NULL;
md->ima.active_table.hash_len = 0;
if (md->ima.active_table.device_metadata !=
md->ima.inactive_table.device_metadata)
kfree(md->ima.active_table.device_metadata);
md->ima.active_table.device_metadata = NULL;
md->ima.active_table.device_metadata_len = 0;
md->ima.active_table.num_targets = 0;
if (md->ima.inactive_table.hash) {
md->ima.active_table.hash = md->ima.inactive_table.hash;
md->ima.active_table.hash_len = md->ima.inactive_table.hash_len;
md->ima.inactive_table.hash = NULL;
md->ima.inactive_table.hash_len = 0;
}
if (md->ima.inactive_table.device_metadata) {
md->ima.active_table.device_metadata =
md->ima.inactive_table.device_metadata;
md->ima.active_table.device_metadata_len =
md->ima.inactive_table.device_metadata_len;
md->ima.active_table.num_targets = md->ima.inactive_table.num_targets;
md->ima.inactive_table.device_metadata = NULL;
md->ima.inactive_table.device_metadata_len = 0;
md->ima.inactive_table.num_targets = 0;
}
}
if (md->ima.active_table.device_metadata) {
l = md->ima.active_table.device_metadata_len;
memcpy(device_table_data, md->ima.active_table.device_metadata, l);
}
if (md->ima.active_table.hash) {
memcpy(device_table_data + l, active, active_len);
l += active_len;
memcpy(device_table_data + l, md->ima.active_table.hash,
md->ima.active_table.hash_len);
l += md->ima.active_table.hash_len;
memcpy(device_table_data + l, ";", 1);
l++;
}
if (!l) {
r = dm_ima_alloc_and_copy_name_uuid(md, &dev_name, &dev_uuid, noio);
if (r)
goto error;
scnprintf(device_table_data, DM_IMA_DEVICE_BUF_LEN,
"name=%s,uuid=%s;device_resume=no_data;",
dev_name, dev_uuid);
l += strlen(device_table_data);
}
capacity_len = strlen(capacity_str);
memcpy(device_table_data + l, capacity_str, capacity_len);
l += capacity_len;
dm_ima_measure_data("device_resume", device_table_data, l, noio);
kfree(dev_name);
kfree(dev_uuid);
error:
kfree(capacity_str);
kfree(device_table_data);
}
|