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  */
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 
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 
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 
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 *
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 
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 
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 
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 
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 
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 
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 
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 		goto out;
341 
342 	spin_lock(&template_list);
343 	list_add_tail_rcu(&template_desc->list, &defined_templates);
344 	spin_unlock(&template_list);
345 out:
346 	return template_desc;
347 }
348 
349 static int ima_restore_template_data(struct ima_template_desc *template_desc,
350 				     void *template_data,
351 				     int template_data_size,
352 				     struct ima_template_entry **entry)
353 {
354 	struct tpm_digest *digests;
355 	int ret = 0;
356 	int i;
357 
358 	*entry = kzalloc(struct_size(*entry, template_data,
359 				     template_desc->num_fields), GFP_NOFS);
360 	if (!*entry)
361 		return -ENOMEM;
362 
363 	digests = kcalloc(NR_BANKS(ima_tpm_chip) + ima_extra_slots,
364 			  sizeof(*digests), GFP_NOFS);
365 	if (!digests) {
366 		kfree(*entry);
367 		return -ENOMEM;
368 	}
369 
370 	(*entry)->digests = digests;
371 
372 	ret = ima_parse_buf(template_data, template_data + template_data_size,
373 			    NULL, template_desc->num_fields,
374 			    (*entry)->template_data, NULL, NULL,
375 			    ENFORCE_FIELDS | ENFORCE_BUFEND, "template data");
376 	if (ret < 0) {
377 		kfree((*entry)->digests);
378 		kfree(*entry);
379 		return ret;
380 	}
381 
382 	(*entry)->template_desc = template_desc;
383 	for (i = 0; i < template_desc->num_fields; i++) {
384 		struct ima_field_data *field_data = &(*entry)->template_data[i];
385 		u8 *data = field_data->data;
386 
387 		(*entry)->template_data[i].data =
388 			kzalloc(field_data->len + 1, GFP_KERNEL);
389 		if (!(*entry)->template_data[i].data) {
390 			ret = -ENOMEM;
391 			break;
392 		}
393 		memcpy((*entry)->template_data[i].data, data, field_data->len);
394 		(*entry)->template_data_len += sizeof(field_data->len);
395 		(*entry)->template_data_len += field_data->len;
396 	}
397 
398 	if (ret < 0) {
399 		ima_free_template_entry(*entry);
400 		*entry = NULL;
401 	}
402 
403 	return ret;
404 }
405 
406 /* Restore the serialized binary measurement list without extending PCRs. */
407 int ima_restore_measurement_list(loff_t size, void *buf)
408 {
409 	char template_name[MAX_TEMPLATE_NAME_LEN];
410 	unsigned char zero[TPM_DIGEST_SIZE] = { 0 };
411 
412 	struct ima_kexec_hdr *khdr = buf;
413 	struct ima_field_data hdr[HDR__LAST] = {
414 		[HDR_PCR] = {.len = sizeof(u32)},
415 		[HDR_DIGEST] = {.len = TPM_DIGEST_SIZE},
416 	};
417 
418 	void *bufp = buf + sizeof(*khdr);
419 	void *bufendp;
420 	struct ima_template_entry *entry;
421 	struct ima_template_desc *template_desc;
422 	DECLARE_BITMAP(hdr_mask, HDR__LAST);
423 	unsigned long count = 0;
424 	int ret = 0;
425 
426 	if (!buf || size < sizeof(*khdr))
427 		return 0;
428 
429 	if (ima_canonical_fmt) {
430 		khdr->version = le16_to_cpu((__force __le16)khdr->version);
431 		khdr->count = le64_to_cpu((__force __le64)khdr->count);
432 		khdr->buffer_size = le64_to_cpu((__force __le64)khdr->buffer_size);
433 	}
434 
435 	if (khdr->version != 1) {
436 		pr_err("attempting to restore a incompatible measurement list");
437 		return -EINVAL;
438 	}
439 
440 	if (khdr->count > ULONG_MAX - 1) {
441 		pr_err("attempting to restore too many measurements");
442 		return -EINVAL;
443 	}
444 
445 	bitmap_zero(hdr_mask, HDR__LAST);
446 	bitmap_set(hdr_mask, HDR_PCR, 1);
447 	bitmap_set(hdr_mask, HDR_DIGEST, 1);
448 
449 	/*
450 	 * ima kexec buffer prefix: version, buffer size, count
451 	 * v1 format: pcr, digest, template-name-len, template-name,
452 	 *	      template-data-size, template-data
453 	 */
454 	bufendp = buf + khdr->buffer_size;
455 	while ((bufp < bufendp) && (count++ < khdr->count)) {
456 		int enforce_mask = ENFORCE_FIELDS;
457 
458 		enforce_mask |= (count == khdr->count) ? ENFORCE_BUFEND : 0;
459 		ret = ima_parse_buf(bufp, bufendp, &bufp, HDR__LAST, hdr, NULL,
460 				    hdr_mask, enforce_mask, "entry header");
461 		if (ret < 0)
462 			break;
463 
464 		if (hdr[HDR_TEMPLATE_NAME].len >= MAX_TEMPLATE_NAME_LEN) {
465 			pr_err("attempting to restore a template name that is too long\n");
466 			ret = -EINVAL;
467 			break;
468 		}
469 
470 		/* template name is not null terminated */
471 		memcpy(template_name, hdr[HDR_TEMPLATE_NAME].data,
472 		       hdr[HDR_TEMPLATE_NAME].len);
473 		template_name[hdr[HDR_TEMPLATE_NAME].len] = 0;
474 
475 		if (strcmp(template_name, "ima") == 0) {
476 			pr_err("attempting to restore an unsupported template \"%s\" failed\n",
477 			       template_name);
478 			ret = -EINVAL;
479 			break;
480 		}
481 
482 		template_desc = lookup_template_desc(template_name);
483 		if (!template_desc) {
484 			template_desc = restore_template_fmt(template_name);
485 			if (!template_desc)
486 				break;
487 		}
488 
489 		/*
490 		 * Only the running system's template format is initialized
491 		 * on boot.  As needed, initialize the other template formats.
492 		 */
493 		ret = template_desc_init_fields(template_desc->fmt,
494 						&(template_desc->fields),
495 						&(template_desc->num_fields));
496 		if (ret < 0) {
497 			pr_err("attempting to restore the template fmt \"%s\" failed\n",
498 			       template_desc->fmt);
499 			ret = -EINVAL;
500 			break;
501 		}
502 
503 		ret = ima_restore_template_data(template_desc,
504 						hdr[HDR_TEMPLATE_DATA].data,
505 						hdr[HDR_TEMPLATE_DATA].len,
506 						&entry);
507 		if (ret < 0)
508 			break;
509 
510 		if (memcmp(hdr[HDR_DIGEST].data, zero, sizeof(zero))) {
511 			ret = ima_calc_field_array_hash(
512 						&entry->template_data[0],
513 						entry);
514 			if (ret < 0) {
515 				pr_err("cannot calculate template digest\n");
516 				ret = -EINVAL;
517 				break;
518 			}
519 		}
520 
521 		entry->pcr = !ima_canonical_fmt ? *(u32 *)(hdr[HDR_PCR].data) :
522 			     le32_to_cpu(*(__le32 *)(hdr[HDR_PCR].data));
523 		ret = ima_restore_measurement_entry(entry);
524 		if (ret < 0)
525 			break;
526 
527 	}
528 	return ret;
529 }
530