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
16enum header_fields { HDR_PCR, HDR_DIGEST, HDR_TEMPLATE_NAME,
17		     HDR_TEMPLATE_DATA, HDR__LAST };
18
19static 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
28static LIST_HEAD(defined_templates);
29static DEFINE_SPINLOCK(template_list);
30static int template_setup_done;
31
32static 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
58static 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 */
67bool 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
79static 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
117static 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
138struct 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
155static const struct ima_template_field *
156lookup_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
167static 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
183int 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
234void 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
249struct 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
259int __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
275static 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);
302out:
303	return template_desc;
304}
305
306static 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. */
364int 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