xref: /linux/security/integrity/ima/ima_template.c (revision 02680c23d7b3febe45ea3d4f9818c2b2dc89020a) 
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 
31 static const struct ima_template_field supported_fields[] = {
32 	{.field_id = "d", .field_init = ima_eventdigest_init,
33 	 .field_show = ima_show_template_digest},
34 	{.field_id = "n", .field_init = ima_eventname_init,
35 	 .field_show = ima_show_template_string},
36 	{.field_id = "d-ng", .field_init = ima_eventdigest_ng_init,
37 	 .field_show = ima_show_template_digest_ng},
38 	{.field_id = "n-ng", .field_init = ima_eventname_ng_init,
39 	 .field_show = ima_show_template_string},
40 	{.field_id = "sig", .field_init = ima_eventsig_init,
41 	 .field_show = ima_show_template_sig},
42 	{.field_id = "buf", .field_init = ima_eventbuf_init,
43 	 .field_show = ima_show_template_buf},
44 	{.field_id = "d-modsig", .field_init = ima_eventdigest_modsig_init,
45 	 .field_show = ima_show_template_digest_ng},
46 	{.field_id = "modsig", .field_init = ima_eventmodsig_init,
47 	 .field_show = ima_show_template_sig},
48 };
49 
50 /*
51  * Used when restoring measurements carried over from a kexec. 'd' and 'n' don't
52  * need to be accounted for since they shouldn't be defined in the same template
53  * description as 'd-ng' and 'n-ng' respectively.
54  */
55 #define MAX_TEMPLATE_NAME_LEN sizeof("d-ng|n-ng|sig|buf|d-modisg|modsig")
56 
57 static struct ima_template_desc *ima_template;
58 static struct ima_template_desc *ima_buf_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  */
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 
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 (ima_template)
85 		return 1;
86 
87 	ima_init_template_list();
88 
89 	/*
90 	 * Verify that a template with the supplied name exists.
91 	 * If not, use CONFIG_IMA_DEFAULT_TEMPLATE.
92 	 */
93 	template_desc = lookup_template_desc(str);
94 	if (!template_desc) {
95 		pr_err("template %s not found, using %s\n",
96 		       str, CONFIG_IMA_DEFAULT_TEMPLATE);
97 		return 1;
98 	}
99 
100 	/*
101 	 * Verify whether the current hash algorithm is supported
102 	 * by the 'ima' template.
103 	 */
104 	if (template_len == 3 && strcmp(str, IMA_TEMPLATE_IMA_NAME) == 0 &&
105 	    ima_hash_algo != HASH_ALGO_SHA1 && ima_hash_algo != HASH_ALGO_MD5) {
106 		pr_err("template does not support hash alg\n");
107 		return 1;
108 	}
109 
110 	ima_template = template_desc;
111 	return 1;
112 }
113 __setup("ima_template=", ima_template_setup);
114 
115 static int __init ima_template_fmt_setup(char *str)
116 {
117 	int num_templates = ARRAY_SIZE(builtin_templates);
118 
119 	if (ima_template)
120 		return 1;
121 
122 	if (template_desc_init_fields(str, NULL, NULL) < 0) {
123 		pr_err("format string '%s' not valid, using template %s\n",
124 		       str, CONFIG_IMA_DEFAULT_TEMPLATE);
125 		return 1;
126 	}
127 
128 	builtin_templates[num_templates - 1].fmt = str;
129 	ima_template = builtin_templates + num_templates - 1;
130 
131 	return 1;
132 }
133 __setup("ima_template_fmt=", ima_template_fmt_setup);
134 
135 struct ima_template_desc *lookup_template_desc(const char *name)
136 {
137 	struct ima_template_desc *template_desc;
138 	int found = 0;
139 
140 	rcu_read_lock();
141 	list_for_each_entry_rcu(template_desc, &defined_templates, list) {
142 		if ((strcmp(template_desc->name, name) == 0) ||
143 		    (strcmp(template_desc->fmt, name) == 0)) {
144 			found = 1;
145 			break;
146 		}
147 	}
148 	rcu_read_unlock();
149 	return found ? template_desc : NULL;
150 }
151 
152 static const struct ima_template_field *
153 lookup_template_field(const char *field_id)
154 {
155 	int i;
156 
157 	for (i = 0; i < ARRAY_SIZE(supported_fields); i++)
158 		if (strncmp(supported_fields[i].field_id, field_id,
159 			    IMA_TEMPLATE_FIELD_ID_MAX_LEN) == 0)
160 			return &supported_fields[i];
161 	return NULL;
162 }
163 
164 static int template_fmt_size(const char *template_fmt)
165 {
166 	char c;
167 	int template_fmt_len = strlen(template_fmt);
168 	int i = 0, j = 0;
169 
170 	while (i < template_fmt_len) {
171 		c = template_fmt[i];
172 		if (c == '|')
173 			j++;
174 		i++;
175 	}
176 
177 	return j + 1;
178 }
179 
180 int template_desc_init_fields(const char *template_fmt,
181 			      const struct ima_template_field ***fields,
182 			      int *num_fields)
183 {
184 	const char *template_fmt_ptr;
185 	const struct ima_template_field *found_fields[IMA_TEMPLATE_NUM_FIELDS_MAX];
186 	int template_num_fields;
187 	int i, len;
188 
189 	if (num_fields && *num_fields > 0) /* already initialized? */
190 		return 0;
191 
192 	template_num_fields = template_fmt_size(template_fmt);
193 
194 	if (template_num_fields > IMA_TEMPLATE_NUM_FIELDS_MAX) {
195 		pr_err("format string '%s' contains too many fields\n",
196 		       template_fmt);
197 		return -EINVAL;
198 	}
199 
200 	for (i = 0, template_fmt_ptr = template_fmt; i < template_num_fields;
201 	     i++, template_fmt_ptr += len + 1) {
202 		char tmp_field_id[IMA_TEMPLATE_FIELD_ID_MAX_LEN + 1];
203 
204 		len = strchrnul(template_fmt_ptr, '|') - template_fmt_ptr;
205 		if (len == 0 || len > IMA_TEMPLATE_FIELD_ID_MAX_LEN) {
206 			pr_err("Invalid field with length %d\n", len);
207 			return -EINVAL;
208 		}
209 
210 		memcpy(tmp_field_id, template_fmt_ptr, len);
211 		tmp_field_id[len] = '\0';
212 		found_fields[i] = lookup_template_field(tmp_field_id);
213 		if (!found_fields[i]) {
214 			pr_err("field '%s' not found\n", tmp_field_id);
215 			return -ENOENT;
216 		}
217 	}
218 
219 	if (fields && num_fields) {
220 		*fields = kmalloc_array(i, sizeof(*fields), GFP_KERNEL);
221 		if (*fields == NULL)
222 			return -ENOMEM;
223 
224 		memcpy(*fields, found_fields, i * sizeof(*fields));
225 		*num_fields = i;
226 	}
227 
228 	return 0;
229 }
230 
231 void ima_init_template_list(void)
232 {
233 	int i;
234 
235 	if (!list_empty(&defined_templates))
236 		return;
237 
238 	spin_lock(&template_list);
239 	for (i = 0; i < ARRAY_SIZE(builtin_templates); i++) {
240 		list_add_tail_rcu(&builtin_templates[i].list,
241 				  &defined_templates);
242 	}
243 	spin_unlock(&template_list);
244 }
245 
246 struct ima_template_desc *ima_template_desc_current(void)
247 {
248 	if (!ima_template) {
249 		ima_init_template_list();
250 		ima_template =
251 		    lookup_template_desc(CONFIG_IMA_DEFAULT_TEMPLATE);
252 	}
253 	return ima_template;
254 }
255 
256 struct ima_template_desc *ima_template_desc_buf(void)
257 {
258 	if (!ima_buf_template) {
259 		ima_init_template_list();
260 		ima_buf_template = lookup_template_desc("ima-buf");
261 	}
262 	return ima_buf_template;
263 }
264 
265 int __init ima_init_template(void)
266 {
267 	struct ima_template_desc *template = ima_template_desc_current();
268 	int result;
269 
270 	result = template_desc_init_fields(template->fmt,
271 					   &(template->fields),
272 					   &(template->num_fields));
273 	if (result < 0) {
274 		pr_err("template %s init failed, result: %d\n",
275 		       (strlen(template->name) ?
276 		       template->name : template->fmt), result);
277 		return result;
278 	}
279 
280 	template = ima_template_desc_buf();
281 	if (!template) {
282 		pr_err("Failed to get ima-buf template\n");
283 		return -EINVAL;
284 	}
285 
286 	result = template_desc_init_fields(template->fmt,
287 					   &(template->fields),
288 					   &(template->num_fields));
289 	if (result < 0)
290 		pr_err("template %s init failed, result: %d\n",
291 		       (strlen(template->name) ?
292 		       template->name : template->fmt), result);
293 
294 	return result;
295 }
296 
297 static struct ima_template_desc *restore_template_fmt(char *template_name)
298 {
299 	struct ima_template_desc *template_desc = NULL;
300 	int ret;
301 
302 	ret = template_desc_init_fields(template_name, NULL, NULL);
303 	if (ret < 0) {
304 		pr_err("attempting to initialize the template \"%s\" failed\n",
305 			template_name);
306 		goto out;
307 	}
308 
309 	template_desc = kzalloc(sizeof(*template_desc), GFP_KERNEL);
310 	if (!template_desc)
311 		goto out;
312 
313 	template_desc->name = "";
314 	template_desc->fmt = kstrdup(template_name, GFP_KERNEL);
315 	if (!template_desc->fmt)
316 		goto out;
317 
318 	spin_lock(&template_list);
319 	list_add_tail_rcu(&template_desc->list, &defined_templates);
320 	spin_unlock(&template_list);
321 out:
322 	return template_desc;
323 }
324 
325 static int ima_restore_template_data(struct ima_template_desc *template_desc,
326 				     void *template_data,
327 				     int template_data_size,
328 				     struct ima_template_entry **entry)
329 {
330 	struct tpm_digest *digests;
331 	int ret = 0;
332 	int i;
333 
334 	*entry = kzalloc(struct_size(*entry, template_data,
335 				     template_desc->num_fields), GFP_NOFS);
336 	if (!*entry)
337 		return -ENOMEM;
338 
339 	digests = kcalloc(NR_BANKS(ima_tpm_chip) + ima_extra_slots,
340 			  sizeof(*digests), GFP_NOFS);
341 	if (!digests) {
342 		kfree(*entry);
343 		return -ENOMEM;
344 	}
345 
346 	(*entry)->digests = digests;
347 
348 	ret = ima_parse_buf(template_data, template_data + template_data_size,
349 			    NULL, template_desc->num_fields,
350 			    (*entry)->template_data, NULL, NULL,
351 			    ENFORCE_FIELDS | ENFORCE_BUFEND, "template data");
352 	if (ret < 0) {
353 		kfree((*entry)->digests);
354 		kfree(*entry);
355 		return ret;
356 	}
357 
358 	(*entry)->template_desc = template_desc;
359 	for (i = 0; i < template_desc->num_fields; i++) {
360 		struct ima_field_data *field_data = &(*entry)->template_data[i];
361 		u8 *data = field_data->data;
362 
363 		(*entry)->template_data[i].data =
364 			kzalloc(field_data->len + 1, GFP_KERNEL);
365 		if (!(*entry)->template_data[i].data) {
366 			ret = -ENOMEM;
367 			break;
368 		}
369 		memcpy((*entry)->template_data[i].data, data, field_data->len);
370 		(*entry)->template_data_len += sizeof(field_data->len);
371 		(*entry)->template_data_len += field_data->len;
372 	}
373 
374 	if (ret < 0) {
375 		ima_free_template_entry(*entry);
376 		*entry = NULL;
377 	}
378 
379 	return ret;
380 }
381 
382 /* Restore the serialized binary measurement list without extending PCRs. */
383 int ima_restore_measurement_list(loff_t size, void *buf)
384 {
385 	char template_name[MAX_TEMPLATE_NAME_LEN];
386 	unsigned char zero[TPM_DIGEST_SIZE] = { 0 };
387 
388 	struct ima_kexec_hdr *khdr = buf;
389 	struct ima_field_data hdr[HDR__LAST] = {
390 		[HDR_PCR] = {.len = sizeof(u32)},
391 		[HDR_DIGEST] = {.len = TPM_DIGEST_SIZE},
392 	};
393 
394 	void *bufp = buf + sizeof(*khdr);
395 	void *bufendp;
396 	struct ima_template_entry *entry;
397 	struct ima_template_desc *template_desc;
398 	DECLARE_BITMAP(hdr_mask, HDR__LAST);
399 	unsigned long count = 0;
400 	int ret = 0;
401 
402 	if (!buf || size < sizeof(*khdr))
403 		return 0;
404 
405 	if (ima_canonical_fmt) {
406 		khdr->version = le16_to_cpu(khdr->version);
407 		khdr->count = le64_to_cpu(khdr->count);
408 		khdr->buffer_size = le64_to_cpu(khdr->buffer_size);
409 	}
410 
411 	if (khdr->version != 1) {
412 		pr_err("attempting to restore a incompatible measurement list");
413 		return -EINVAL;
414 	}
415 
416 	if (khdr->count > ULONG_MAX - 1) {
417 		pr_err("attempting to restore too many measurements");
418 		return -EINVAL;
419 	}
420 
421 	bitmap_zero(hdr_mask, HDR__LAST);
422 	bitmap_set(hdr_mask, HDR_PCR, 1);
423 	bitmap_set(hdr_mask, HDR_DIGEST, 1);
424 
425 	/*
426 	 * ima kexec buffer prefix: version, buffer size, count
427 	 * v1 format: pcr, digest, template-name-len, template-name,
428 	 *	      template-data-size, template-data
429 	 */
430 	bufendp = buf + khdr->buffer_size;
431 	while ((bufp < bufendp) && (count++ < khdr->count)) {
432 		int enforce_mask = ENFORCE_FIELDS;
433 
434 		enforce_mask |= (count == khdr->count) ? ENFORCE_BUFEND : 0;
435 		ret = ima_parse_buf(bufp, bufendp, &bufp, HDR__LAST, hdr, NULL,
436 				    hdr_mask, enforce_mask, "entry header");
437 		if (ret < 0)
438 			break;
439 
440 		if (hdr[HDR_TEMPLATE_NAME].len >= MAX_TEMPLATE_NAME_LEN) {
441 			pr_err("attempting to restore a template name that is too long\n");
442 			ret = -EINVAL;
443 			break;
444 		}
445 
446 		/* template name is not null terminated */
447 		memcpy(template_name, hdr[HDR_TEMPLATE_NAME].data,
448 		       hdr[HDR_TEMPLATE_NAME].len);
449 		template_name[hdr[HDR_TEMPLATE_NAME].len] = 0;
450 
451 		if (strcmp(template_name, "ima") == 0) {
452 			pr_err("attempting to restore an unsupported template \"%s\" failed\n",
453 			       template_name);
454 			ret = -EINVAL;
455 			break;
456 		}
457 
458 		template_desc = lookup_template_desc(template_name);
459 		if (!template_desc) {
460 			template_desc = restore_template_fmt(template_name);
461 			if (!template_desc)
462 				break;
463 		}
464 
465 		/*
466 		 * Only the running system's template format is initialized
467 		 * on boot.  As needed, initialize the other template formats.
468 		 */
469 		ret = template_desc_init_fields(template_desc->fmt,
470 						&(template_desc->fields),
471 						&(template_desc->num_fields));
472 		if (ret < 0) {
473 			pr_err("attempting to restore the template fmt \"%s\" failed\n",
474 			       template_desc->fmt);
475 			ret = -EINVAL;
476 			break;
477 		}
478 
479 		ret = ima_restore_template_data(template_desc,
480 						hdr[HDR_TEMPLATE_DATA].data,
481 						hdr[HDR_TEMPLATE_DATA].len,
482 						&entry);
483 		if (ret < 0)
484 			break;
485 
486 		if (memcmp(hdr[HDR_DIGEST].data, zero, sizeof(zero))) {
487 			ret = ima_calc_field_array_hash(
488 						&entry->template_data[0],
489 						entry);
490 			if (ret < 0) {
491 				pr_err("cannot calculate template digest\n");
492 				ret = -EINVAL;
493 				break;
494 			}
495 		}
496 
497 		entry->pcr = !ima_canonical_fmt ? *(u32 *)(hdr[HDR_PCR].data) :
498 			     le32_to_cpu(*(u32 *)(hdr[HDR_PCR].data));
499 		ret = ima_restore_measurement_entry(entry);
500 		if (ret < 0)
501 			break;
502 
503 	}
504 	return ret;
505 }
506