security/integrity/ima/ima_template.c

   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-ngv2", .fmt = "d-ngv2|n-ng"},
  24         {.name = "ima-sigv2", .fmt = "d-ngv2|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 = "evm-sig",
  28          .fmt = "d-ng|n-ng|evmsig|xattrnames|xattrlengths|xattrvalues|iuid|igid|imode"},
  29         {.name = "", .fmt = ""},        /* placeholder for a custom format */
  30 };
  31
  32 static LIST_HEAD(defined_templates);
  33 static DEFINE_SPINLOCK(template_list);
  34 static int template_setup_done;
  35
  36 static const struct ima_template_field supported_fields[] = {
  37         {.field_id = "d", .field_init = ima_eventdigest_init,
  38          .field_show = ima_show_template_digest},
  39         {.field_id = "n", .field_init = ima_eventname_init,
  40          .field_show = ima_show_template_string},
  41         {.field_id = "d-ng", .field_init = ima_eventdigest_ng_init,
  42          .field_show = ima_show_template_digest_ng},
  43         {.field_id = "d-ngv2", .field_init = ima_eventdigest_ngv2_init,
  44          .field_show = ima_show_template_digest_ngv2},
  45         {.field_id = "n-ng", .field_init = ima_eventname_ng_init,
  46          .field_show = ima_show_template_string},
  47         {.field_id = "sig", .field_init = ima_eventsig_init,
  48          .field_show = ima_show_template_sig},
  49         {.field_id = "buf", .field_init = ima_eventbuf_init,
  50          .field_show = ima_show_template_buf},
  51         {.field_id = "d-modsig", .field_init = ima_eventdigest_modsig_init,
  52          .field_show = ima_show_template_digest_ng},
  53         {.field_id = "modsig", .field_init = ima_eventmodsig_init,
  54          .field_show = ima_show_template_sig},
  55         {.field_id = "evmsig", .field_init = ima_eventevmsig_init,
  56          .field_show = ima_show_template_sig},
  57         {.field_id = "iuid", .field_init = ima_eventinodeuid_init,
  58          .field_show = ima_show_template_uint},
  59         {.field_id = "igid", .field_init = ima_eventinodegid_init,
  60          .field_show = ima_show_template_uint},
  61         {.field_id = "imode", .field_init = ima_eventinodemode_init,
  62          .field_show = ima_show_template_uint},
  63         {.field_id = "xattrnames",
  64          .field_init = ima_eventinodexattrnames_init,
  65          .field_show = ima_show_template_string},
  66         {.field_id = "xattrlengths",
  67          .field_init = ima_eventinodexattrlengths_init,
  68          .field_show = ima_show_template_sig},
  69         {.field_id = "xattrvalues",
  70          .field_init = ima_eventinodexattrvalues_init,
  71          .field_show = ima_show_template_sig},
  72 };
  73
  74 /*
  75  * Used when restoring measurements carried over from a kexec. 'd' and 'n' don't
  76  * need to be accounted for since they shouldn't be defined in the same template
  77  * description as 'd-ng' and 'n-ng' respectively.
  78  */
  79 #define MAX_TEMPLATE_NAME_LEN \
  80         sizeof("d-ng|n-ng|evmsig|xattrnames|xattrlengths|xattrvalues|iuid|igid|imode")
  81
  82 static struct ima_template_desc *ima_template;
  83 static struct ima_template_desc *ima_buf_template;
  84
  85 /**
  86  * ima_template_has_modsig - Check whether template has modsig-related fields.
  87  * @ima_template: IMA template to check.
  88  *
  89  * Tells whether the given template has fields referencing a file's appended
  90  * signature.
  91  */
  92 bool ima_template_has_modsig(const struct ima_template_desc *ima_template)
  93 {
  94         int i;
  95
  96         for (i = 0; i < ima_template->num_fields; i++)
  97                 if (!strcmp(ima_template->fields[i]->field_id, "modsig") ||
  98                     !strcmp(ima_template->fields[i]->field_id, "d-modsig"))
  99                         return true;
 100
 101         return false;
 102 }
 103
 104 static int __init ima_template_setup(char *str)
 105 {
 106         struct ima_template_desc *template_desc;
 107         int template_len = strlen(str);
 108
 109         if (template_setup_done)
 110                 return 1;
 111
 112         if (!ima_template)
 113                 ima_init_template_list();
 114
 115         /*
 116          * Verify that a template with the supplied name exists.
 117          * If not, use CONFIG_IMA_DEFAULT_TEMPLATE.
 118          */
 119         template_desc = lookup_template_desc(str);
 120         if (!template_desc) {
 121                 pr_err("template %s not found, using %s\n",
 122                        str, CONFIG_IMA_DEFAULT_TEMPLATE);
 123                 return 1;
 124         }
 125
 126         /*
 127          * Verify whether the current hash algorithm is supported
 128          * by the 'ima' template.
 129          */
 130         if (template_len == 3 && strcmp(str, IMA_TEMPLATE_IMA_NAME) == 0 &&
 131             ima_hash_algo != HASH_ALGO_SHA1 && ima_hash_algo != HASH_ALGO_MD5) {
 132                 pr_err("template does not support hash alg\n");
 133                 return 1;
 134         }
 135
 136         ima_template = template_desc;
 137         template_setup_done = 1;
 138         return 1;
 139 }
 140 __setup("ima_template=", ima_template_setup);
 141
 142 static int __init ima_template_fmt_setup(char *str)
 143 {
 144         int num_templates = ARRAY_SIZE(builtin_templates);
 145
 146         if (template_setup_done)
 147                 return 1;
 148
 149         if (template_desc_init_fields(str, NULL, NULL) < 0) {
 150                 pr_err("format string '%s' not valid, using template %s\n",
 151                        str, CONFIG_IMA_DEFAULT_TEMPLATE);
 152                 return 1;
 153         }
 154
 155         builtin_templates[num_templates - 1].fmt = str;
 156         ima_template = builtin_templates + num_templates - 1;
 157         template_setup_done = 1;
 158
 159         return 1;
 160 }
 161 __setup("ima_template_fmt=", ima_template_fmt_setup);
 162
 163 struct ima_template_desc *lookup_template_desc(const char *name)
 164 {
 165         struct ima_template_desc *template_desc;
 166         int found = 0;
 167
 168         rcu_read_lock();
 169         list_for_each_entry_rcu(template_desc, &defined_templates, list) {
 170                 if ((strcmp(template_desc->name, name) == 0) ||
 171                     (strcmp(template_desc->fmt, name) == 0)) {
 172                         found = 1;
 173                         break;
 174                 }
 175         }
 176         rcu_read_unlock();
 177         return found ? template_desc : NULL;
 178 }
 179
 180 static const struct ima_template_field *
 181 lookup_template_field(const char *field_id)
 182 {
 183         int i;
 184
 185         for (i = 0; i < ARRAY_SIZE(supported_fields); i++)
 186                 if (strncmp(supported_fields[i].field_id, field_id,
 187                             IMA_TEMPLATE_FIELD_ID_MAX_LEN) == 0)
 188                         return &supported_fields[i];
 189         return NULL;
 190 }
 191
 192 static int template_fmt_size(const char *template_fmt)
 193 {
 194         char c;
 195         int template_fmt_len = strlen(template_fmt);
 196         int i = 0, j = 0;
 197
 198         while (i < template_fmt_len) {
 199                 c = template_fmt[i];
 200                 if (c == '|')
 201                         j++;
 202                 i++;
 203         }
 204
 205         return j + 1;
 206 }
 207
 208 int template_desc_init_fields(const char *template_fmt,
 209                               const struct ima_template_field ***fields,
 210                               int *num_fields)
 211 {
 212         const char *template_fmt_ptr;
 213         const struct ima_template_field *found_fields[IMA_TEMPLATE_NUM_FIELDS_MAX];
 214         int template_num_fields;
 215         int i, len;
 216
 217         if (num_fields && *num_fields > 0) /* already initialized? */
 218                 return 0;
 219
 220         template_num_fields = template_fmt_size(template_fmt);
 221
 222         if (template_num_fields > IMA_TEMPLATE_NUM_FIELDS_MAX) {
 223                 pr_err("format string '%s' contains too many fields\n",
 224                        template_fmt);
 225                 return -EINVAL;
 226         }
 227
 228         for (i = 0, template_fmt_ptr = template_fmt; i < template_num_fields;
 229              i++, template_fmt_ptr += len + 1) {
 230                 char tmp_field_id[IMA_TEMPLATE_FIELD_ID_MAX_LEN + 1];
 231
 232                 len = strchrnul(template_fmt_ptr, '|') - template_fmt_ptr;
 233                 if (len == 0 || len > IMA_TEMPLATE_FIELD_ID_MAX_LEN) {
 234                         pr_err("Invalid field with length %d\n", len);
 235                         return -EINVAL;
 236                 }
 237
 238                 memcpy(tmp_field_id, template_fmt_ptr, len);
 239                 tmp_field_id[len] = '\0';
 240                 found_fields[i] = lookup_template_field(tmp_field_id);
 241                 if (!found_fields[i]) {
 242                         pr_err("field '%s' not found\n", tmp_field_id);
 243                         return -ENOENT;
 244                 }
 245         }
 246
 247         if (fields && num_fields) {
 248                 *fields = kmalloc_array(i, sizeof(**fields), GFP_KERNEL);
 249                 if (*fields == NULL)
 250                         return -ENOMEM;
 251
 252                 memcpy(*fields, found_fields, i * sizeof(**fields));
 253                 *num_fields = i;
 254         }
 255
 256         return 0;
 257 }
 258
 259 void ima_init_template_list(void)
 260 {
 261         int i;
 262
 263         if (!list_empty(&defined_templates))
 264                 return;
 265
 266         spin_lock(&template_list);
 267         for (i = 0; i < ARRAY_SIZE(builtin_templates); i++) {
 268                 list_add_tail_rcu(&builtin_templates[i].list,
 269                                   &defined_templates);
 270         }
 271         spin_unlock(&template_list);
 272 }
 273
 274 struct ima_template_desc *ima_template_desc_current(void)
 275 {
 276         if (!ima_template) {
 277                 ima_init_template_list();
 278                 ima_template =
 279                     lookup_template_desc(CONFIG_IMA_DEFAULT_TEMPLATE);
 280         }
 281         return ima_template;
 282 }
 283
 284 struct ima_template_desc *ima_template_desc_buf(void)
 285 {
 286         if (!ima_buf_template) {
 287                 ima_init_template_list();
 288                 ima_buf_template = lookup_template_desc("ima-buf");
 289         }
 290         return ima_buf_template;
 291 }
 292
 293 int __init ima_init_template(void)
 294 {
 295         struct ima_template_desc *template = ima_template_desc_current();
 296         int result;
 297
 298         result = template_desc_init_fields(template->fmt,
 299                                            &(template->fields),
 300                                            &(template->num_fields));
 301         if (result < 0) {
 302                 pr_err("template %s init failed, result: %d\n",
 303                        (strlen(template->name) ?
 304                        template->name : template->fmt), result);
 305                 return result;
 306         }
 307
 308         template = ima_template_desc_buf();
 309         if (!template) {
 310                 pr_err("Failed to get ima-buf template\n");
 311                 return -EINVAL;
 312         }
 313
 314         result = template_desc_init_fields(template->fmt,
 315                                            &(template->fields),
 316                                            &(template->num_fields));
 317         if (result < 0)
 318                 pr_err("template %s init failed, result: %d\n",
 319                        (strlen(template->name) ?
 320                        template->name : template->fmt), result);
 321
 322         return result;
 323 }
 324
 325 static struct ima_template_desc *restore_template_fmt(char *template_name)
 326 {
 327         struct ima_template_desc *template_desc = NULL;
 328         int ret;
 329
 330         ret = template_desc_init_fields(template_name, NULL, NULL);
 331         if (ret < 0) {
 332                 pr_err("attempting to initialize the template \"%s\" failed\n",
 333                         template_name);
 334                 goto out;
 335         }
 336
 337         template_desc = kzalloc(sizeof(*template_desc), GFP_KERNEL);
 338         if (!template_desc)
 339                 goto out;
 340
 341         template_desc->name = "";
 342         template_desc->fmt = kstrdup(template_name, GFP_KERNEL);
 343         if (!template_desc->fmt) {
 344                 kfree(template_desc);
 345                 template_desc = NULL;
 346                 goto out;
 347         }
 348
 349         spin_lock(&template_list);
 350         list_add_tail_rcu(&template_desc->list, &defined_templates);
 351         spin_unlock(&template_list);
 352 out:
 353         return template_desc;
 354 }
 355
 356 static int ima_restore_template_data(struct ima_template_desc *template_desc,
 357                                      void *template_data,
 358                                      int template_data_size,
 359                                      struct ima_template_entry **entry)
 360 {
 361         struct tpm_digest *digests;
 362         int ret = 0;
 363         int i;
 364
 365         *entry = kzalloc(struct_size(*entry, template_data,
 366                                      template_desc->num_fields), GFP_NOFS);
 367         if (!*entry)
 368                 return -ENOMEM;
 369
 370         digests = kcalloc(NR_BANKS(ima_tpm_chip) + ima_extra_slots,
 371                           sizeof(*digests), GFP_NOFS);
 372         if (!digests) {
 373                 kfree(*entry);
 374                 return -ENOMEM;
 375         }
 376
 377         (*entry)->digests = digests;
 378
 379         ret = ima_parse_buf(template_data, template_data + template_data_size,
 380                             NULL, template_desc->num_fields,
 381                             (*entry)->template_data, NULL, NULL,
 382                             ENFORCE_FIELDS | ENFORCE_BUFEND, "template data");
 383         if (ret < 0) {
 384                 kfree((*entry)->digests);
 385                 kfree(*entry);
 386                 return ret;
 387         }
 388
 389         (*entry)->template_desc = template_desc;
 390         for (i = 0; i < template_desc->num_fields; i++) {
 391                 struct ima_field_data *field_data = &(*entry)->template_data[i];
 392                 u8 *data = field_data->data;
 393
 394                 (*entry)->template_data[i].data =
 395                         kzalloc(field_data->len + 1, GFP_KERNEL);
 396                 if (!(*entry)->template_data[i].data) {
 397                         ret = -ENOMEM;
 398                         break;
 399                 }
 400                 memcpy((*entry)->template_data[i].data, data, field_data->len);
 401                 (*entry)->template_data_len += sizeof(field_data->len);
 402                 (*entry)->template_data_len += field_data->len;
 403         }
 404
 405         if (ret < 0) {
 406                 ima_free_template_entry(*entry);
 407                 *entry = NULL;
 408         }
 409
 410         return ret;
 411 }
 412
 413 /* Restore the serialized binary measurement list without extending PCRs. */
 414 int ima_restore_measurement_list(loff_t size, void *buf)
 415 {
 416         char template_name[MAX_TEMPLATE_NAME_LEN];
 417         unsigned char zero[TPM_DIGEST_SIZE] = { 0 };
 418
 419         struct ima_kexec_hdr *khdr = buf;
 420         struct ima_field_data hdr[HDR__LAST] = {
 421                 [HDR_PCR] = {.len = sizeof(u32)},
 422                 [HDR_DIGEST] = {.len = TPM_DIGEST_SIZE},
 423         };
 424
 425         void *bufp = buf + sizeof(*khdr);
 426         void *bufendp;
 427         struct ima_template_entry *entry;
 428         struct ima_template_desc *template_desc;
 429         DECLARE_BITMAP(hdr_mask, HDR__LAST);
 430         unsigned long count = 0;
 431         int ret = 0;
 432
 433         if (!buf || size < sizeof(*khdr))
 434                 return 0;
 435
 436         if (ima_canonical_fmt) {
 437                 khdr->version = le16_to_cpu((__force __le16)khdr->version);
 438                 khdr->count = le64_to_cpu((__force __le64)khdr->count);
 439                 khdr->buffer_size = le64_to_cpu((__force __le64)khdr->buffer_size);
 440         }
 441
 442         if (khdr->version != 1) {
 443                 pr_err("attempting to restore a incompatible measurement list");
 444                 return -EINVAL;
 445         }
 446
 447         if (khdr->count > ULONG_MAX - 1) {
 448                 pr_err("attempting to restore too many measurements");
 449                 return -EINVAL;
 450         }
 451
 452         bitmap_zero(hdr_mask, HDR__LAST);
 453         bitmap_set(hdr_mask, HDR_PCR, 1);
 454         bitmap_set(hdr_mask, HDR_DIGEST, 1);
 455
 456         /*
 457          * ima kexec buffer prefix: version, buffer size, count
 458          * v1 format: pcr, digest, template-name-len, template-name,
 459          *            template-data-size, template-data
 460          */
 461         bufendp = buf + khdr->buffer_size;
 462         while ((bufp < bufendp) && (count++ < khdr->count)) {
 463                 int enforce_mask = ENFORCE_FIELDS;
 464
 465                 enforce_mask |= (count == khdr->count) ? ENFORCE_BUFEND : 0;
 466                 ret = ima_parse_buf(bufp, bufendp, &bufp, HDR__LAST, hdr, NULL,
 467                                     hdr_mask, enforce_mask, "entry header");
 468                 if (ret < 0)
 469                         break;
 470
 471                 if (hdr[HDR_TEMPLATE_NAME].len >= MAX_TEMPLATE_NAME_LEN) {
 472                         pr_err("attempting to restore a template name that is too long\n");
 473                         ret = -EINVAL;
 474                         break;
 475                 }
 476
 477                 /* template name is not null terminated */
 478                 memcpy(template_name, hdr[HDR_TEMPLATE_NAME].data,
 479                        hdr[HDR_TEMPLATE_NAME].len);
 480                 template_name[hdr[HDR_TEMPLATE_NAME].len] = 0;
 481
 482                 if (strcmp(template_name, "ima") == 0) {
 483                         pr_err("attempting to restore an unsupported template \"%s\" failed\n",
 484                                template_name);
 485                         ret = -EINVAL;
 486                         break;
 487                 }
 488
 489                 template_desc = lookup_template_desc(template_name);
 490                 if (!template_desc) {
 491                         template_desc = restore_template_fmt(template_name);
 492                         if (!template_desc)
 493                                 break;
 494                 }
 495
 496                 /*
 497                  * Only the running system's template format is initialized
 498                  * on boot.  As needed, initialize the other template formats.
 499                  */
 500                 ret = template_desc_init_fields(template_desc->fmt,
 501                                                 &(template_desc->fields),
 502                                                 &(template_desc->num_fields));
 503                 if (ret < 0) {
 504                         pr_err("attempting to restore the template fmt \"%s\" failed\n",
 505                                template_desc->fmt);
 506                         ret = -EINVAL;
 507                         break;
 508                 }
 509
 510                 ret = ima_restore_template_data(template_desc,
 511                                                 hdr[HDR_TEMPLATE_DATA].data,
 512                                                 hdr[HDR_TEMPLATE_DATA].len,
 513                                                 &entry);
 514                 if (ret < 0)
 515                         break;
 516
 517                 if (memcmp(hdr[HDR_DIGEST].data, zero, sizeof(zero))) {
 518                         ret = ima_calc_field_array_hash(
 519                                                 &entry->template_data[0],
 520                                                 entry);
 521                         if (ret < 0) {
 522                                 pr_err("cannot calculate template digest\n");
 523                                 ret = -EINVAL;
 524                                 break;
 525                         }
 526                 }
 527
 528                 entry->pcr = !ima_canonical_fmt ? *(u32 *)(hdr[HDR_PCR].data) :
 529                              le32_to_cpu(*(__le32 *)(hdr[HDR_PCR].data));
 530                 ret = ima_restore_measurement_entry(entry);
 531                 if (ret < 0)
 532                         break;
 533
 534         }
 535         return ret;
 536 }