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 static int template_setup_done;
  31
  32 static 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
  58 static 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  */
  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 (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
 117 static 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
 138 struct 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
 155 static const struct ima_template_field *
 156 lookup_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
 167 static 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
 183 int 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
 234 void 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
 249 struct 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
 259 int __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
 275 static 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                 goto out;
 295
 296         spin_lock(&template_list);
 297         list_add_tail_rcu(&template_desc->list, &defined_templates);
 298         spin_unlock(&template_list);
 299 out:
 300         return template_desc;
 301 }
 302
 303 static int ima_restore_template_data(struct ima_template_desc *template_desc,
 304                                      void *template_data,
 305                                      int template_data_size,
 306                                      struct ima_template_entry **entry)
 307 {
 308         struct tpm_digest *digests;
 309         int ret = 0;
 310         int i;
 311
 312         *entry = kzalloc(struct_size(*entry, template_data,
 313                                      template_desc->num_fields), GFP_NOFS);
 314         if (!*entry)
 315                 return -ENOMEM;
 316
 317         digests = kcalloc(NR_BANKS(ima_tpm_chip) + ima_extra_slots,
 318                           sizeof(*digests), GFP_NOFS);
 319         if (!digests) {
 320                 kfree(*entry);
 321                 return -ENOMEM;
 322         }
 323
 324         (*entry)->digests = digests;
 325
 326         ret = ima_parse_buf(template_data, template_data + template_data_size,
 327                             NULL, template_desc->num_fields,
 328                             (*entry)->template_data, NULL, NULL,
 329                             ENFORCE_FIELDS | ENFORCE_BUFEND, "template data");
 330         if (ret < 0) {
 331                 kfree((*entry)->digests);
 332                 kfree(*entry);
 333                 return ret;
 334         }
 335
 336         (*entry)->template_desc = template_desc;
 337         for (i = 0; i < template_desc->num_fields; i++) {
 338                 struct ima_field_data *field_data = &(*entry)->template_data[i];
 339                 u8 *data = field_data->data;
 340
 341                 (*entry)->template_data[i].data =
 342                         kzalloc(field_data->len + 1, GFP_KERNEL);
 343                 if (!(*entry)->template_data[i].data) {
 344                         ret = -ENOMEM;
 345                         break;
 346                 }
 347                 memcpy((*entry)->template_data[i].data, data, field_data->len);
 348                 (*entry)->template_data_len += sizeof(field_data->len);
 349                 (*entry)->template_data_len += field_data->len;
 350         }
 351
 352         if (ret < 0) {
 353                 ima_free_template_entry(*entry);
 354                 *entry = NULL;
 355         }
 356
 357         return ret;
 358 }
 359
 360 /* Restore the serialized binary measurement list without extending PCRs. */
 361 int ima_restore_measurement_list(loff_t size, void *buf)
 362 {
 363         char template_name[MAX_TEMPLATE_NAME_LEN];
 364         unsigned char zero[TPM_DIGEST_SIZE] = { 0 };
 365
 366         struct ima_kexec_hdr *khdr = buf;
 367         struct ima_field_data hdr[HDR__LAST] = {
 368                 [HDR_PCR] = {.len = sizeof(u32)},
 369                 [HDR_DIGEST] = {.len = TPM_DIGEST_SIZE},
 370         };
 371
 372         void *bufp = buf + sizeof(*khdr);
 373         void *bufendp;
 374         struct ima_template_entry *entry;
 375         struct ima_template_desc *template_desc;
 376         DECLARE_BITMAP(hdr_mask, HDR__LAST);
 377         unsigned long count = 0;
 378         int ret = 0;
 379
 380         if (!buf || size < sizeof(*khdr))
 381                 return 0;
 382
 383         if (ima_canonical_fmt) {
 384                 khdr->version = le16_to_cpu(khdr->version);
 385                 khdr->count = le64_to_cpu(khdr->count);
 386                 khdr->buffer_size = le64_to_cpu(khdr->buffer_size);
 387         }
 388
 389         if (khdr->version != 1) {
 390                 pr_err("attempting to restore a incompatible measurement list");
 391                 return -EINVAL;
 392         }
 393
 394         if (khdr->count > ULONG_MAX - 1) {
 395                 pr_err("attempting to restore too many measurements");
 396                 return -EINVAL;
 397         }
 398
 399         bitmap_zero(hdr_mask, HDR__LAST);
 400         bitmap_set(hdr_mask, HDR_PCR, 1);
 401         bitmap_set(hdr_mask, HDR_DIGEST, 1);
 402
 403         /*
 404          * ima kexec buffer prefix: version, buffer size, count
 405          * v1 format: pcr, digest, template-name-len, template-name,
 406          *            template-data-size, template-data
 407          */
 408         bufendp = buf + khdr->buffer_size;
 409         while ((bufp < bufendp) && (count++ < khdr->count)) {
 410                 int enforce_mask = ENFORCE_FIELDS;
 411
 412                 enforce_mask |= (count == khdr->count) ? ENFORCE_BUFEND : 0;
 413                 ret = ima_parse_buf(bufp, bufendp, &bufp, HDR__LAST, hdr, NULL,
 414                                     hdr_mask, enforce_mask, "entry header");
 415                 if (ret < 0)
 416                         break;
 417
 418                 if (hdr[HDR_TEMPLATE_NAME].len >= MAX_TEMPLATE_NAME_LEN) {
 419                         pr_err("attempting to restore a template name that is too long\n");
 420                         ret = -EINVAL;
 421                         break;
 422                 }
 423
 424                 /* template name is not null terminated */
 425                 memcpy(template_name, hdr[HDR_TEMPLATE_NAME].data,
 426                        hdr[HDR_TEMPLATE_NAME].len);
 427                 template_name[hdr[HDR_TEMPLATE_NAME].len] = 0;
 428
 429                 if (strcmp(template_name, "ima") == 0) {
 430                         pr_err("attempting to restore an unsupported template \"%s\" failed\n",
 431                                template_name);
 432                         ret = -EINVAL;
 433                         break;
 434                 }
 435
 436                 template_desc = lookup_template_desc(template_name);
 437                 if (!template_desc) {
 438                         template_desc = restore_template_fmt(template_name);
 439                         if (!template_desc)
 440                                 break;
 441                 }
 442
 443                 /*
 444                  * Only the running system's template format is initialized
 445                  * on boot.  As needed, initialize the other template formats.
 446                  */
 447                 ret = template_desc_init_fields(template_desc->fmt,
 448                                                 &(template_desc->fields),
 449                                                 &(template_desc->num_fields));
 450                 if (ret < 0) {
 451                         pr_err("attempting to restore the template fmt \"%s\" failed\n",
 452                                template_desc->fmt);
 453                         ret = -EINVAL;
 454                         break;
 455                 }
 456
 457                 ret = ima_restore_template_data(template_desc,
 458                                                 hdr[HDR_TEMPLATE_DATA].data,
 459                                                 hdr[HDR_TEMPLATE_DATA].len,
 460                                                 &entry);
 461                 if (ret < 0)
 462                         break;
 463
 464                 if (memcmp(hdr[HDR_DIGEST].data, zero, sizeof(zero))) {
 465                         ret = ima_calc_field_array_hash(
 466                                                 &entry->template_data[0],
 467                                                 entry);
 468                         if (ret < 0) {
 469                                 pr_err("cannot calculate template digest\n");
 470                                 ret = -EINVAL;
 471                                 break;
 472                         }
 473                 }
 474
 475                 entry->pcr = !ima_canonical_fmt ? *(u32 *)(hdr[HDR_PCR].data) :
 476                              le32_to_cpu(*(u32 *)(hdr[HDR_PCR].data));
 477                 ret = ima_restore_measurement_entry(entry);
 478                 if (ret < 0)
 479                         break;
 480
 481         }
 482         return ret;
 483 }