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