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-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 ? *(hdr[HDR_PCR].data) :
 498                              le32_to_cpu(*(hdr[HDR_PCR].data));
 499                 ret = ima_restore_measurement_entry(entry);
 500                 if (ret < 0)
 501                         break;
 502
 503         }
 504         return ret;
 505 }