security/integrity/ima/ima_template.c

   1 /*
   2  * Copyright (C) 2013 Politecnico di Torino, Italy
   3  *                    TORSEC group -- http://security.polito.it
   4  *
   5  * Author: Roberto Sassu <roberto.sassu@polito.it>
   6  *
   7  * This program is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU General Public License as
   9  * published by the Free Software Foundation, version 2 of the
  10  * License.
  11  *
  12  * File: ima_template.c
  13  *      Helpers to manage template descriptors.
  14  */
  15
  16 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  17
  18 #include <linux/rculist.h>
  19 #include "ima.h"
  20 #include "ima_template_lib.h"
  21
  22 static struct ima_template_desc builtin_templates[] = {
  23         {.name = IMA_TEMPLATE_IMA_NAME, .fmt = IMA_TEMPLATE_IMA_FMT},
  24         {.name = "ima-ng", .fmt = "d-ng|n-ng"},
  25         {.name = "ima-sig", .fmt = "d-ng|n-ng|sig"},
  26         {.name = "", .fmt = ""},        /* placeholder for a custom format */
  27 };
  28
  29 static LIST_HEAD(defined_templates);
  30 static DEFINE_SPINLOCK(template_list);
  31
  32 static 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 };
  44 #define MAX_TEMPLATE_NAME_LEN 15
  45
  46 static struct ima_template_desc *ima_template;
  47 static struct ima_template_desc *lookup_template_desc(const char *name);
  48 static int template_desc_init_fields(const char *template_fmt,
  49                                      struct ima_template_field ***fields,
  50                                      int *num_fields);
  51
  52 static int __init ima_template_setup(char *str)
  53 {
  54         struct ima_template_desc *template_desc;
  55         int template_len = strlen(str);
  56
  57         if (ima_template)
  58                 return 1;
  59
  60         ima_init_template_list();
  61
  62         /*
  63          * Verify that a template with the supplied name exists.
  64          * If not, use CONFIG_IMA_DEFAULT_TEMPLATE.
  65          */
  66         template_desc = lookup_template_desc(str);
  67         if (!template_desc) {
  68                 pr_err("template %s not found, using %s\n",
  69                        str, CONFIG_IMA_DEFAULT_TEMPLATE);
  70                 return 1;
  71         }
  72
  73         /*
  74          * Verify whether the current hash algorithm is supported
  75          * by the 'ima' template.
  76          */
  77         if (template_len == 3 && strcmp(str, IMA_TEMPLATE_IMA_NAME) == 0 &&
  78             ima_hash_algo != HASH_ALGO_SHA1 && ima_hash_algo != HASH_ALGO_MD5) {
  79                 pr_err("template does not support hash alg\n");
  80                 return 1;
  81         }
  82
  83         ima_template = template_desc;
  84         return 1;
  85 }
  86 __setup("ima_template=", ima_template_setup);
  87
  88 static int __init ima_template_fmt_setup(char *str)
  89 {
  90         int num_templates = ARRAY_SIZE(builtin_templates);
  91
  92         if (ima_template)
  93                 return 1;
  94
  95         if (template_desc_init_fields(str, NULL, NULL) < 0) {
  96                 pr_err("format string '%s' not valid, using template %s\n",
  97                        str, CONFIG_IMA_DEFAULT_TEMPLATE);
  98                 return 1;
  99         }
 100
 101         builtin_templates[num_templates - 1].fmt = str;
 102         ima_template = builtin_templates + num_templates - 1;
 103
 104         return 1;
 105 }
 106 __setup("ima_template_fmt=", ima_template_fmt_setup);
 107
 108 static struct ima_template_desc *lookup_template_desc(const char *name)
 109 {
 110         struct ima_template_desc *template_desc;
 111         int found = 0;
 112
 113         rcu_read_lock();
 114         list_for_each_entry_rcu(template_desc, &defined_templates, list) {
 115                 if ((strcmp(template_desc->name, name) == 0) ||
 116                     (strcmp(template_desc->fmt, name) == 0)) {
 117                         found = 1;
 118                         break;
 119                 }
 120         }
 121         rcu_read_unlock();
 122         return found ? template_desc : NULL;
 123 }
 124
 125 static struct ima_template_field *lookup_template_field(const char *field_id)
 126 {
 127         int i;
 128
 129         for (i = 0; i < ARRAY_SIZE(supported_fields); i++)
 130                 if (strncmp(supported_fields[i].field_id, field_id,
 131                             IMA_TEMPLATE_FIELD_ID_MAX_LEN) == 0)
 132                         return &supported_fields[i];
 133         return NULL;
 134 }
 135
 136 static int template_fmt_size(const char *template_fmt)
 137 {
 138         char c;
 139         int template_fmt_len = strlen(template_fmt);
 140         int i = 0, j = 0;
 141
 142         while (i < template_fmt_len) {
 143                 c = template_fmt[i];
 144                 if (c == '|')
 145                         j++;
 146                 i++;
 147         }
 148
 149         return j + 1;
 150 }
 151
 152 static int template_desc_init_fields(const char *template_fmt,
 153                                      struct ima_template_field ***fields,
 154                                      int *num_fields)
 155 {
 156         const char *template_fmt_ptr;
 157         struct ima_template_field *found_fields[IMA_TEMPLATE_NUM_FIELDS_MAX];
 158         int template_num_fields;
 159         int i, len;
 160
 161         if (num_fields && *num_fields > 0) /* already initialized? */
 162                 return 0;
 163
 164         template_num_fields = template_fmt_size(template_fmt);
 165
 166         if (template_num_fields > IMA_TEMPLATE_NUM_FIELDS_MAX) {
 167                 pr_err("format string '%s' contains too many fields\n",
 168                        template_fmt);
 169                 return -EINVAL;
 170         }
 171
 172         for (i = 0, template_fmt_ptr = template_fmt; i < template_num_fields;
 173              i++, template_fmt_ptr += len + 1) {
 174                 char tmp_field_id[IMA_TEMPLATE_FIELD_ID_MAX_LEN + 1];
 175
 176                 len = strchrnul(template_fmt_ptr, '|') - template_fmt_ptr;
 177                 if (len == 0 || len > IMA_TEMPLATE_FIELD_ID_MAX_LEN) {
 178                         pr_err("Invalid field with length %d\n", len);
 179                         return -EINVAL;
 180                 }
 181
 182                 memcpy(tmp_field_id, template_fmt_ptr, len);
 183                 tmp_field_id[len] = '\0';
 184                 found_fields[i] = lookup_template_field(tmp_field_id);
 185                 if (!found_fields[i]) {
 186                         pr_err("field '%s' not found\n", tmp_field_id);
 187                         return -ENOENT;
 188                 }
 189         }
 190
 191         if (fields && num_fields) {
 192                 *fields = kmalloc_array(i, sizeof(*fields), GFP_KERNEL);
 193                 if (*fields == NULL)
 194                         return -ENOMEM;
 195
 196                 memcpy(*fields, found_fields, i * sizeof(*fields));
 197                 *num_fields = i;
 198         }
 199
 200         return 0;
 201 }
 202
 203 void ima_init_template_list(void)
 204 {
 205         int i;
 206
 207         if (!list_empty(&defined_templates))
 208                 return;
 209
 210         spin_lock(&template_list);
 211         for (i = 0; i < ARRAY_SIZE(builtin_templates); i++) {
 212                 list_add_tail_rcu(&builtin_templates[i].list,
 213                                   &defined_templates);
 214         }
 215         spin_unlock(&template_list);
 216 }
 217
 218 struct ima_template_desc *ima_template_desc_current(void)
 219 {
 220         if (!ima_template) {
 221                 ima_init_template_list();
 222                 ima_template =
 223                     lookup_template_desc(CONFIG_IMA_DEFAULT_TEMPLATE);
 224         }
 225         return ima_template;
 226 }
 227
 228 int __init ima_init_template(void)
 229 {
 230         struct ima_template_desc *template = ima_template_desc_current();
 231         int result;
 232
 233         result = template_desc_init_fields(template->fmt,
 234                                            &(template->fields),
 235                                            &(template->num_fields));
 236         if (result < 0)
 237                 pr_err("template %s init failed, result: %d\n",
 238                        (strlen(template->name) ?
 239                        template->name : template->fmt), result);
 240
 241         return result;
 242 }
 243
 244 static struct ima_template_desc *restore_template_fmt(char *template_name)
 245 {
 246         struct ima_template_desc *template_desc = NULL;
 247         int ret;
 248
 249         ret = template_desc_init_fields(template_name, NULL, NULL);
 250         if (ret < 0) {
 251                 pr_err("attempting to initialize the template \"%s\" failed\n",
 252                         template_name);
 253                 goto out;
 254         }
 255
 256         template_desc = kzalloc(sizeof(*template_desc), GFP_KERNEL);
 257         if (!template_desc)
 258                 goto out;
 259
 260         template_desc->name = "";
 261         template_desc->fmt = kstrdup(template_name, GFP_KERNEL);
 262         if (!template_desc->fmt)
 263                 goto out;
 264
 265         spin_lock(&template_list);
 266         list_add_tail_rcu(&template_desc->list, &defined_templates);
 267         spin_unlock(&template_list);
 268 out:
 269         return template_desc;
 270 }
 271
 272 static int ima_restore_template_data(struct ima_template_desc *template_desc,
 273                                      void *template_data,
 274                                      int template_data_size,
 275                                      struct ima_template_entry **entry)
 276 {
 277         struct binary_field_data {
 278                 u32 len;
 279                 u8 data[0];
 280         } __packed;
 281
 282         struct binary_field_data *field_data;
 283         int offset = 0;
 284         int ret = 0;
 285         int i;
 286
 287         *entry = kzalloc(sizeof(**entry) +
 288                     template_desc->num_fields * sizeof(struct ima_field_data),
 289                     GFP_NOFS);
 290         if (!*entry)
 291                 return -ENOMEM;
 292
 293         (*entry)->template_desc = template_desc;
 294         for (i = 0; i < template_desc->num_fields; i++) {
 295                 field_data = template_data + offset;
 296
 297                 /* Each field of the template data is prefixed with a length. */
 298                 if (offset > (template_data_size - sizeof(*field_data))) {
 299                         pr_err("Restoring the template field failed\n");
 300                         ret = -EINVAL;
 301                         break;
 302                 }
 303                 offset += sizeof(*field_data);
 304
 305                 if (ima_canonical_fmt)
 306                         field_data->len = le32_to_cpu(field_data->len);
 307
 308                 if (offset > (template_data_size - field_data->len)) {
 309                         pr_err("Restoring the template field data failed\n");
 310                         ret = -EINVAL;
 311                         break;
 312                 }
 313                 offset += field_data->len;
 314
 315                 (*entry)->template_data[i].len = field_data->len;
 316                 (*entry)->template_data_len += sizeof(field_data->len);
 317
 318                 (*entry)->template_data[i].data =
 319                         kzalloc(field_data->len + 1, GFP_KERNEL);
 320                 if (!(*entry)->template_data[i].data) {
 321                         ret = -ENOMEM;
 322                         break;
 323                 }
 324                 memcpy((*entry)->template_data[i].data, field_data->data,
 325                         field_data->len);
 326                 (*entry)->template_data_len += field_data->len;
 327         }
 328
 329         if (ret < 0) {
 330                 ima_free_template_entry(*entry);
 331                 *entry = NULL;
 332         }
 333
 334         return ret;
 335 }
 336
 337 /* Restore the serialized binary measurement list without extending PCRs. */
 338 int ima_restore_measurement_list(loff_t size, void *buf)
 339 {
 340         struct binary_hdr_v1 {
 341                 u32 pcr;
 342                 u8 digest[TPM_DIGEST_SIZE];
 343                 u32 template_name_len;
 344                 char template_name[0];
 345         } __packed;
 346         char template_name[MAX_TEMPLATE_NAME_LEN];
 347
 348         struct binary_data_v1 {
 349                 u32 template_data_size;
 350                 char template_data[0];
 351         } __packed;
 352
 353         struct ima_kexec_hdr *khdr = buf;
 354         struct binary_hdr_v1 *hdr_v1;
 355         struct binary_data_v1 *data_v1;
 356
 357         void *bufp = buf + sizeof(*khdr);
 358         void *bufendp;
 359         struct ima_template_entry *entry;
 360         struct ima_template_desc *template_desc;
 361         unsigned long count = 0;
 362         int ret = 0;
 363
 364         if (!buf || size < sizeof(*khdr))
 365                 return 0;
 366
 367         if (ima_canonical_fmt) {
 368                 khdr->version = le16_to_cpu(khdr->version);
 369                 khdr->count = le64_to_cpu(khdr->count);
 370                 khdr->buffer_size = le64_to_cpu(khdr->buffer_size);
 371         }
 372
 373         if (khdr->version != 1) {
 374                 pr_err("attempting to restore a incompatible measurement list");
 375                 return -EINVAL;
 376         }
 377
 378         if (khdr->count > ULONG_MAX - 1) {
 379                 pr_err("attempting to restore too many measurements");
 380                 return -EINVAL;
 381         }
 382
 383         /*
 384          * ima kexec buffer prefix: version, buffer size, count
 385          * v1 format: pcr, digest, template-name-len, template-name,
 386          *            template-data-size, template-data
 387          */
 388         bufendp = buf + khdr->buffer_size;
 389         while ((bufp < bufendp) && (count++ < khdr->count)) {
 390                 hdr_v1 = bufp;
 391                 if (bufp > (bufendp - sizeof(*hdr_v1))) {
 392                         pr_err("attempting to restore partial measurement\n");
 393                         ret = -EINVAL;
 394                         break;
 395                 }
 396                 bufp += sizeof(*hdr_v1);
 397
 398                 if (ima_canonical_fmt)
 399                         hdr_v1->template_name_len =
 400                             le32_to_cpu(hdr_v1->template_name_len);
 401
 402                 if ((hdr_v1->template_name_len >= MAX_TEMPLATE_NAME_LEN) ||
 403                     (bufp > (bufendp - hdr_v1->template_name_len))) {
 404                         pr_err("attempting to restore a template name \
 405                                 that is too long\n");
 406                         ret = -EINVAL;
 407                         break;
 408                 }
 409                 data_v1 = bufp += (u_int8_t)hdr_v1->template_name_len;
 410
 411                 /* template name is not null terminated */
 412                 memcpy(template_name, hdr_v1->template_name,
 413                        hdr_v1->template_name_len);
 414                 template_name[hdr_v1->template_name_len] = 0;
 415
 416                 if (strcmp(template_name, "ima") == 0) {
 417                         pr_err("attempting to restore an unsupported \
 418                                 template \"%s\" failed\n", template_name);
 419                         ret = -EINVAL;
 420                         break;
 421                 }
 422
 423                 template_desc = lookup_template_desc(template_name);
 424                 if (!template_desc) {
 425                         template_desc = restore_template_fmt(template_name);
 426                         if (!template_desc)
 427                                 break;
 428                 }
 429
 430                 /*
 431                  * Only the running system's template format is initialized
 432                  * on boot.  As needed, initialize the other template formats.
 433                  */
 434                 ret = template_desc_init_fields(template_desc->fmt,
 435                                                 &(template_desc->fields),
 436                                                 &(template_desc->num_fields));
 437                 if (ret < 0) {
 438                         pr_err("attempting to restore the template fmt \"%s\" \
 439                                 failed\n", template_desc->fmt);
 440                         ret = -EINVAL;
 441                         break;
 442                 }
 443
 444                 if (bufp > (bufendp - sizeof(data_v1->template_data_size))) {
 445                         pr_err("restoring the template data size failed\n");
 446                         ret = -EINVAL;
 447                         break;
 448                 }
 449                 bufp += (u_int8_t) sizeof(data_v1->template_data_size);
 450
 451                 if (ima_canonical_fmt)
 452                         data_v1->template_data_size =
 453                             le32_to_cpu(data_v1->template_data_size);
 454
 455                 if (bufp > (bufendp - data_v1->template_data_size)) {
 456                         pr_err("restoring the template data failed\n");
 457                         ret = -EINVAL;
 458                         break;
 459                 }
 460                 bufp += data_v1->template_data_size;
 461
 462                 ret = ima_restore_template_data(template_desc,
 463                                                 data_v1->template_data,
 464                                                 data_v1->template_data_size,
 465                                                 &entry);
 466                 if (ret < 0)
 467                         break;
 468
 469                 memcpy(entry->digest, hdr_v1->digest, TPM_DIGEST_SIZE);
 470                 entry->pcr =
 471                     !ima_canonical_fmt ? hdr_v1->pcr : le32_to_cpu(hdr_v1->pcr);
 472                 ret = ima_restore_measurement_entry(entry);
 473                 if (ret < 0)
 474                         break;
 475
 476         }
 477         return ret;
 478 }