1 // SPDX-License-Identifier: GPL-2.0-only
2 /*
3 * Copyright (C) 2013 Politecnico di Torino, Italy
4 * TORSEC group -- https://security.polito.it
5 *
6 * Author: Roberto Sassu <roberto.sassu@polito.it>
7 *
8 * File: ima_template.c
9 * Helpers to manage template descriptors.
10 */
11
12 #include <linux/rculist.h>
13 #include "ima.h"
14 #include "ima_template_lib.h"
15
16 enum header_fields { HDR_PCR, HDR_DIGEST, HDR_TEMPLATE_NAME,
17 HDR_TEMPLATE_DATA, HDR__LAST };
18
19 static struct ima_template_desc builtin_templates[] = {
20 {.name = IMA_TEMPLATE_IMA_NAME, .fmt = IMA_TEMPLATE_IMA_FMT},
21 {.name = "ima-ng", .fmt = "d-ng|n-ng"},
22 {.name = "ima-sig", .fmt = "d-ng|n-ng|sig"},
23 {.name = "ima-buf", .fmt = "d-ng|n-ng|buf"},
24 {.name = "ima-modsig", .fmt = "d-ng|n-ng|sig|d-modsig|modsig"},
25 {.name = "evm-sig",
26 .fmt = "d-ng|n-ng|evmsig|xattrnames|xattrlengths|xattrvalues|iuid|igid|imode"},
27 {.name = "", .fmt = ""}, /* placeholder for a custom format */
28 };
29
30 static LIST_HEAD(defined_templates);
31 static DEFINE_SPINLOCK(template_list);
32 static int template_setup_done;
33
34 static const struct ima_template_field supported_fields[] = {
35 {.field_id = "d", .field_init = ima_eventdigest_init,
36 .field_show = ima_show_template_digest},
37 {.field_id = "n", .field_init = ima_eventname_init,
38 .field_show = ima_show_template_string},
39 {.field_id = "d-ng", .field_init = ima_eventdigest_ng_init,
40 .field_show = ima_show_template_digest_ng},
41 {.field_id = "n-ng", .field_init = ima_eventname_ng_init,
42 .field_show = ima_show_template_string},
43 {.field_id = "sig", .field_init = ima_eventsig_init,
44 .field_show = ima_show_template_sig},
45 {.field_id = "buf", .field_init = ima_eventbuf_init,
46 .field_show = ima_show_template_buf},
47 {.field_id = "d-modsig", .field_init = ima_eventdigest_modsig_init,
48 .field_show = ima_show_template_digest_ng},
49 {.field_id = "modsig", .field_init = ima_eventmodsig_init,
50 .field_show = ima_show_template_sig},
51 {.field_id = "evmsig", .field_init = ima_eventevmsig_init,
52 .field_show = ima_show_template_sig},
53 {.field_id = "iuid", .field_init = ima_eventinodeuid_init,
54 .field_show = ima_show_template_uint},
55 {.field_id = "igid", .field_init = ima_eventinodegid_init,
56 .field_show = ima_show_template_uint},
57 {.field_id = "imode", .field_init = ima_eventinodemode_init,
58 .field_show = ima_show_template_uint},
59 {.field_id = "xattrnames",
60 .field_init = ima_eventinodexattrnames_init,
61 .field_show = ima_show_template_string},
62 {.field_id = "xattrlengths",
63 .field_init = ima_eventinodexattrlengths_init,
64 .field_show = ima_show_template_sig},
65 {.field_id = "xattrvalues",
66 .field_init = ima_eventinodexattrvalues_init,
67 .field_show = ima_show_template_sig},
68 };
69
70 /*
71 * Used when restoring measurements carried over from a kexec. 'd' and 'n' don't
72 * need to be accounted for since they shouldn't be defined in the same template
73 * description as 'd-ng' and 'n-ng' respectively.
74 */
75 #define MAX_TEMPLATE_NAME_LEN \
76 sizeof("d-ng|n-ng|evmsig|xattrnames|xattrlengths|xattrvalues|iuid|igid|imode")
77
78 static struct ima_template_desc *ima_template;
79 static struct ima_template_desc *ima_buf_template;
80
81 /**
82 * ima_template_has_modsig - Check whether template has modsig-related fields.
83 * @ima_template: IMA template to check.
84 *
85 * Tells whether the given template has fields referencing a file's appended
86 * signature.
87 */
ima_template_has_modsig(const struct ima_template_desc * ima_template)88 bool ima_template_has_modsig(const struct ima_template_desc *ima_template)
89 {
90 int i;
91
92 for (i = 0; i < ima_template->num_fields; i++)
93 if (!strcmp(ima_template->fields[i]->field_id, "modsig") ||
94 !strcmp(ima_template->fields[i]->field_id, "d-modsig"))
95 return true;
96
97 return false;
98 }
99
ima_template_setup(char * str)100 static int __init ima_template_setup(char *str)
101 {
102 struct ima_template_desc *template_desc;
103 int template_len = strlen(str);
104
105 if (template_setup_done)
106 return 1;
107
108 if (!ima_template)
109 ima_init_template_list();
110
111 /*
112 * Verify that a template with the supplied name exists.
113 * If not, use CONFIG_IMA_DEFAULT_TEMPLATE.
114 */
115 template_desc = lookup_template_desc(str);
116 if (!template_desc) {
117 pr_err("template %s not found, using %s\n",
118 str, CONFIG_IMA_DEFAULT_TEMPLATE);
119 return 1;
120 }
121
122 /*
123 * Verify whether the current hash algorithm is supported
124 * by the 'ima' template.
125 */
126 if (template_len == 3 && strcmp(str, IMA_TEMPLATE_IMA_NAME) == 0 &&
127 ima_hash_algo != HASH_ALGO_SHA1 && ima_hash_algo != HASH_ALGO_MD5) {
128 pr_err("template does not support hash alg\n");
129 return 1;
130 }
131
132 ima_template = template_desc;
133 template_setup_done = 1;
134 return 1;
135 }
136 __setup("ima_template=", ima_template_setup);
137
ima_template_fmt_setup(char * str)138 static int __init ima_template_fmt_setup(char *str)
139 {
140 int num_templates = ARRAY_SIZE(builtin_templates);
141
142 if (template_setup_done)
143 return 1;
144
145 if (template_desc_init_fields(str, NULL, NULL) < 0) {
146 pr_err("format string '%s' not valid, using template %s\n",
147 str, CONFIG_IMA_DEFAULT_TEMPLATE);
148 return 1;
149 }
150
151 builtin_templates[num_templates - 1].fmt = str;
152 ima_template = builtin_templates + num_templates - 1;
153 template_setup_done = 1;
154
155 return 1;
156 }
157 __setup("ima_template_fmt=", ima_template_fmt_setup);
158
lookup_template_desc(const char * name)159 struct ima_template_desc *lookup_template_desc(const char *name)
160 {
161 struct ima_template_desc *template_desc;
162 int found = 0;
163
164 rcu_read_lock();
165 list_for_each_entry_rcu(template_desc, &defined_templates, list) {
166 if ((strcmp(template_desc->name, name) == 0) ||
167 (strcmp(template_desc->fmt, name) == 0)) {
168 found = 1;
169 break;
170 }
171 }
172 rcu_read_unlock();
173 return found ? template_desc : NULL;
174 }
175
176 static const struct ima_template_field *
lookup_template_field(const char * field_id)177 lookup_template_field(const char *field_id)
178 {
179 int i;
180
181 for (i = 0; i < ARRAY_SIZE(supported_fields); i++)
182 if (strncmp(supported_fields[i].field_id, field_id,
183 IMA_TEMPLATE_FIELD_ID_MAX_LEN) == 0)
184 return &supported_fields[i];
185 return NULL;
186 }
187
template_fmt_size(const char * template_fmt)188 static int template_fmt_size(const char *template_fmt)
189 {
190 char c;
191 int template_fmt_len = strlen(template_fmt);
192 int i = 0, j = 0;
193
194 while (i < template_fmt_len) {
195 c = template_fmt[i];
196 if (c == '|')
197 j++;
198 i++;
199 }
200
201 return j + 1;
202 }
203
template_desc_init_fields(const char * template_fmt,const struct ima_template_field *** fields,int * num_fields)204 int template_desc_init_fields(const char *template_fmt,
205 const struct ima_template_field ***fields,
206 int *num_fields)
207 {
208 const char *template_fmt_ptr;
209 const struct ima_template_field *found_fields[IMA_TEMPLATE_NUM_FIELDS_MAX];
210 int template_num_fields;
211 int i, len;
212
213 if (num_fields && *num_fields > 0) /* already initialized? */
214 return 0;
215
216 template_num_fields = template_fmt_size(template_fmt);
217
218 if (template_num_fields > IMA_TEMPLATE_NUM_FIELDS_MAX) {
219 pr_err("format string '%s' contains too many fields\n",
220 template_fmt);
221 return -EINVAL;
222 }
223
224 for (i = 0, template_fmt_ptr = template_fmt; i < template_num_fields;
225 i++, template_fmt_ptr += len + 1) {
226 char tmp_field_id[IMA_TEMPLATE_FIELD_ID_MAX_LEN + 1];
227
228 len = strchrnul(template_fmt_ptr, '|') - template_fmt_ptr;
229 if (len == 0 || len > IMA_TEMPLATE_FIELD_ID_MAX_LEN) {
230 pr_err("Invalid field with length %d\n", len);
231 return -EINVAL;
232 }
233
234 memcpy(tmp_field_id, template_fmt_ptr, len);
235 tmp_field_id[len] = '\0';
236 found_fields[i] = lookup_template_field(tmp_field_id);
237 if (!found_fields[i]) {
238 pr_err("field '%s' not found\n", tmp_field_id);
239 return -ENOENT;
240 }
241 }
242
243 if (fields && num_fields) {
244 *fields = kmalloc_array(i, sizeof(**fields), GFP_KERNEL);
245 if (*fields == NULL)
246 return -ENOMEM;
247
248 memcpy(*fields, found_fields, i * sizeof(**fields));
249 *num_fields = i;
250 }
251
252 return 0;
253 }
254
ima_init_template_list(void)255 void ima_init_template_list(void)
256 {
257 int i;
258
259 if (!list_empty(&defined_templates))
260 return;
261
262 spin_lock(&template_list);
263 for (i = 0; i < ARRAY_SIZE(builtin_templates); i++) {
264 list_add_tail_rcu(&builtin_templates[i].list,
265 &defined_templates);
266 }
267 spin_unlock(&template_list);
268 }
269
ima_template_desc_current(void)270 struct ima_template_desc *ima_template_desc_current(void)
271 {
272 if (!ima_template) {
273 ima_init_template_list();
274 ima_template =
275 lookup_template_desc(CONFIG_IMA_DEFAULT_TEMPLATE);
276 }
277 return ima_template;
278 }
279
ima_template_desc_buf(void)280 struct ima_template_desc *ima_template_desc_buf(void)
281 {
282 if (!ima_buf_template) {
283 ima_init_template_list();
284 ima_buf_template = lookup_template_desc("ima-buf");
285 }
286 return ima_buf_template;
287 }
288
ima_init_template(void)289 int __init ima_init_template(void)
290 {
291 struct ima_template_desc *template = ima_template_desc_current();
292 int result;
293
294 result = template_desc_init_fields(template->fmt,
295 &(template->fields),
296 &(template->num_fields));
297 if (result < 0) {
298 pr_err("template %s init failed, result: %d\n",
299 (strlen(template->name) ?
300 template->name : template->fmt), result);
301 return result;
302 }
303
304 template = ima_template_desc_buf();
305 if (!template) {
306 pr_err("Failed to get ima-buf template\n");
307 return -EINVAL;
308 }
309
310 result = template_desc_init_fields(template->fmt,
311 &(template->fields),
312 &(template->num_fields));
313 if (result < 0)
314 pr_err("template %s init failed, result: %d\n",
315 (strlen(template->name) ?
316 template->name : template->fmt), result);
317
318 return result;
319 }
320
restore_template_fmt(char * template_name)321 static struct ima_template_desc *restore_template_fmt(char *template_name)
322 {
323 struct ima_template_desc *template_desc = NULL;
324 int ret;
325
326 ret = template_desc_init_fields(template_name, NULL, NULL);
327 if (ret < 0) {
328 pr_err("attempting to initialize the template \"%s\" failed\n",
329 template_name);
330 goto out;
331 }
332
333 template_desc = kzalloc(sizeof(*template_desc), GFP_KERNEL);
334 if (!template_desc)
335 goto out;
336
337 template_desc->name = "";
338 template_desc->fmt = kstrdup(template_name, GFP_KERNEL);
339 if (!template_desc->fmt) {
340 kfree(template_desc);
341 template_desc = NULL;
342 goto out;
343 }
344
345 spin_lock(&template_list);
346 list_add_tail_rcu(&template_desc->list, &defined_templates);
347 spin_unlock(&template_list);
348 out:
349 return template_desc;
350 }
351
ima_restore_template_data(struct ima_template_desc * template_desc,void * template_data,int template_data_size,struct ima_template_entry ** entry)352 static int ima_restore_template_data(struct ima_template_desc *template_desc,
353 void *template_data,
354 int template_data_size,
355 struct ima_template_entry **entry)
356 {
357 struct tpm_digest *digests;
358 int ret = 0;
359 int i;
360
361 *entry = kzalloc(struct_size(*entry, template_data,
362 template_desc->num_fields), GFP_NOFS);
363 if (!*entry)
364 return -ENOMEM;
365
366 digests = kcalloc(NR_BANKS(ima_tpm_chip) + ima_extra_slots,
367 sizeof(*digests), GFP_NOFS);
368 if (!digests) {
369 kfree(*entry);
370 return -ENOMEM;
371 }
372
373 (*entry)->digests = digests;
374
375 ret = ima_parse_buf(template_data, template_data + template_data_size,
376 NULL, template_desc->num_fields,
377 (*entry)->template_data, NULL, NULL,
378 ENFORCE_FIELDS | ENFORCE_BUFEND, "template data");
379 if (ret < 0) {
380 kfree((*entry)->digests);
381 kfree(*entry);
382 return ret;
383 }
384
385 (*entry)->template_desc = template_desc;
386 for (i = 0; i < template_desc->num_fields; i++) {
387 struct ima_field_data *field_data = &(*entry)->template_data[i];
388 u8 *data = field_data->data;
389
390 (*entry)->template_data[i].data =
391 kzalloc(field_data->len + 1, GFP_KERNEL);
392 if (!(*entry)->template_data[i].data) {
393 ret = -ENOMEM;
394 break;
395 }
396 memcpy((*entry)->template_data[i].data, data, field_data->len);
397 (*entry)->template_data_len += sizeof(field_data->len);
398 (*entry)->template_data_len += field_data->len;
399 }
400
401 if (ret < 0) {
402 ima_free_template_entry(*entry);
403 *entry = NULL;
404 }
405
406 return ret;
407 }
408
409 /* Restore the serialized binary measurement list without extending PCRs. */
ima_restore_measurement_list(loff_t size,void * buf)410 int ima_restore_measurement_list(loff_t size, void *buf)
411 {
412 char template_name[MAX_TEMPLATE_NAME_LEN];
413 unsigned char zero[TPM_DIGEST_SIZE] = { 0 };
414
415 struct ima_kexec_hdr *khdr = buf;
416 struct ima_field_data hdr[HDR__LAST] = {
417 [HDR_PCR] = {.len = sizeof(u32)},
418 [HDR_DIGEST] = {.len = TPM_DIGEST_SIZE},
419 };
420
421 void *bufp = buf + sizeof(*khdr);
422 void *bufendp;
423 struct ima_template_entry *entry;
424 struct ima_template_desc *template_desc;
425 DECLARE_BITMAP(hdr_mask, HDR__LAST);
426 unsigned long count = 0;
427 int ret = 0;
428
429 if (!buf || size < sizeof(*khdr))
430 return 0;
431
432 if (ima_canonical_fmt) {
433 khdr->version = le16_to_cpu((__force __le16)khdr->version);
434 khdr->count = le64_to_cpu((__force __le64)khdr->count);
435 khdr->buffer_size = le64_to_cpu((__force __le64)khdr->buffer_size);
436 }
437
438 if (khdr->version != 1) {
439 pr_err("attempting to restore a incompatible measurement list");
440 return -EINVAL;
441 }
442
443 if (khdr->count > ULONG_MAX - 1) {
444 pr_err("attempting to restore too many measurements");
445 return -EINVAL;
446 }
447
448 bitmap_zero(hdr_mask, HDR__LAST);
449 bitmap_set(hdr_mask, HDR_PCR, 1);
450 bitmap_set(hdr_mask, HDR_DIGEST, 1);
451
452 /*
453 * ima kexec buffer prefix: version, buffer size, count
454 * v1 format: pcr, digest, template-name-len, template-name,
455 * template-data-size, template-data
456 */
457 bufendp = buf + khdr->buffer_size;
458 while ((bufp < bufendp) && (count++ < khdr->count)) {
459 int enforce_mask = ENFORCE_FIELDS;
460
461 enforce_mask |= (count == khdr->count) ? ENFORCE_BUFEND : 0;
462 ret = ima_parse_buf(bufp, bufendp, &bufp, HDR__LAST, hdr, NULL,
463 hdr_mask, enforce_mask, "entry header");
464 if (ret < 0)
465 break;
466
467 if (hdr[HDR_TEMPLATE_NAME].len >= MAX_TEMPLATE_NAME_LEN) {
468 pr_err("attempting to restore a template name that is too long\n");
469 ret = -EINVAL;
470 break;
471 }
472
473 /* template name is not null terminated */
474 memcpy(template_name, hdr[HDR_TEMPLATE_NAME].data,
475 hdr[HDR_TEMPLATE_NAME].len);
476 template_name[hdr[HDR_TEMPLATE_NAME].len] = 0;
477
478 if (strcmp(template_name, "ima") == 0) {
479 pr_err("attempting to restore an unsupported template \"%s\" failed\n",
480 template_name);
481 ret = -EINVAL;
482 break;
483 }
484
485 template_desc = lookup_template_desc(template_name);
486 if (!template_desc) {
487 template_desc = restore_template_fmt(template_name);
488 if (!template_desc)
489 break;
490 }
491
492 /*
493 * Only the running system's template format is initialized
494 * on boot. As needed, initialize the other template formats.
495 */
496 ret = template_desc_init_fields(template_desc->fmt,
497 &(template_desc->fields),
498 &(template_desc->num_fields));
499 if (ret < 0) {
500 pr_err("attempting to restore the template fmt \"%s\" failed\n",
501 template_desc->fmt);
502 ret = -EINVAL;
503 break;
504 }
505
506 ret = ima_restore_template_data(template_desc,
507 hdr[HDR_TEMPLATE_DATA].data,
508 hdr[HDR_TEMPLATE_DATA].len,
509 &entry);
510 if (ret < 0)
511 break;
512
513 if (memcmp(hdr[HDR_DIGEST].data, zero, sizeof(zero))) {
514 ret = ima_calc_field_array_hash(
515 &entry->template_data[0],
516 entry);
517 if (ret < 0) {
518 pr_err("cannot calculate template digest\n");
519 ret = -EINVAL;
520 break;
521 }
522 }
523
524 entry->pcr = !ima_canonical_fmt ? *(u32 *)(hdr[HDR_PCR].data) :
525 le32_to_cpu(*(__le32 *)(hdr[HDR_PCR].data));
526 ret = ima_restore_measurement_entry(entry);
527 if (ret < 0)
528 break;
529
530 }
531 return ret;
532 }
533