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