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 enum header_fields { HDR_PCR, HDR_DIGEST, HDR_TEMPLATE_NAME,
  23                      HDR_TEMPLATE_DATA, HDR__LAST };
  24
  25 static struct ima_template_desc builtin_templates[] = {
  26         {.name = IMA_TEMPLATE_IMA_NAME, .fmt = IMA_TEMPLATE_IMA_FMT},
  27         {.name = "ima-ng", .fmt = "d-ng|n-ng"},
  28         {.name = "ima-sig", .fmt = "d-ng|n-ng|sig"},
  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 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 = "n-ng", .field_init = ima_eventname_ng_init,
  44          .field_show = ima_show_template_string},
  45         {.field_id = "sig", .field_init = ima_eventsig_init,
  46          .field_show = ima_show_template_sig},
  47 };
  48 #define MAX_TEMPLATE_NAME_LEN 15
  49
  50 static struct ima_template_desc *ima_template;
  51 static struct ima_template_desc *lookup_template_desc(const char *name);
  52 static int template_desc_init_fields(const char *template_fmt,
  53                                      struct ima_template_field ***fields,
  54                                      int *num_fields);
  55
  56 static int __init ima_template_setup(char *str)
  57 {
  58         struct ima_template_desc *template_desc;
  59         int template_len = strlen(str);
  60
  61         if (template_setup_done)
  62                 return 1;
  63
  64         if (!ima_template)
  65                 ima_init_template_list();
  66
  67         /*
  68          * Verify that a template with the supplied name exists.
  69          * If not, use CONFIG_IMA_DEFAULT_TEMPLATE.
  70          */
  71         template_desc = lookup_template_desc(str);
  72         if (!template_desc) {
  73                 pr_err("template %s not found, using %s\n",
  74                        str, CONFIG_IMA_DEFAULT_TEMPLATE);
  75                 return 1;
  76         }
  77
  78         /*
  79          * Verify whether the current hash algorithm is supported
  80          * by the 'ima' template.
  81          */
  82         if (template_len == 3 && strcmp(str, IMA_TEMPLATE_IMA_NAME) == 0 &&
  83             ima_hash_algo != HASH_ALGO_SHA1 && ima_hash_algo != HASH_ALGO_MD5) {
  84                 pr_err("template does not support hash alg\n");
  85                 return 1;
  86         }
  87
  88         ima_template = template_desc;
  89         template_setup_done = 1;
  90         return 1;
  91 }
  92 __setup("ima_template=", ima_template_setup);
  93
  94 static int __init ima_template_fmt_setup(char *str)
  95 {
  96         int num_templates = ARRAY_SIZE(builtin_templates);
  97
  98         if (template_setup_done)
  99                 return 1;
 100
 101         if (template_desc_init_fields(str, NULL, NULL) < 0) {
 102                 pr_err("format string '%s' not valid, using template %s\n",
 103                        str, CONFIG_IMA_DEFAULT_TEMPLATE);
 104                 return 1;
 105         }
 106
 107         builtin_templates[num_templates - 1].fmt = str;
 108         ima_template = builtin_templates + num_templates - 1;
 109         template_setup_done = 1;
 110
 111         return 1;
 112 }
 113 __setup("ima_template_fmt=", ima_template_fmt_setup);
 114
 115 static struct ima_template_desc *lookup_template_desc(const char *name)
 116 {
 117         struct ima_template_desc *template_desc;
 118         int found = 0;
 119
 120         rcu_read_lock();
 121         list_for_each_entry_rcu(template_desc, &defined_templates, list) {
 122                 if ((strcmp(template_desc->name, name) == 0) ||
 123                     (strcmp(template_desc->fmt, name) == 0)) {
 124                         found = 1;
 125                         break;
 126                 }
 127         }
 128         rcu_read_unlock();
 129         return found ? template_desc : NULL;
 130 }
 131
 132 static struct ima_template_field *lookup_template_field(const char *field_id)
 133 {
 134         int i;
 135
 136         for (i = 0; i < ARRAY_SIZE(supported_fields); i++)
 137                 if (strncmp(supported_fields[i].field_id, field_id,
 138                             IMA_TEMPLATE_FIELD_ID_MAX_LEN) == 0)
 139                         return &supported_fields[i];
 140         return NULL;
 141 }
 142
 143 static int template_fmt_size(const char *template_fmt)
 144 {
 145         char c;
 146         int template_fmt_len = strlen(template_fmt);
 147         int i = 0, j = 0;
 148
 149         while (i < template_fmt_len) {
 150                 c = template_fmt[i];
 151                 if (c == '|')
 152                         j++;
 153                 i++;
 154         }
 155
 156         return j + 1;
 157 }
 158
 159 static int template_desc_init_fields(const char *template_fmt,
 160                                      struct ima_template_field ***fields,
 161                                      int *num_fields)
 162 {
 163         const char *template_fmt_ptr;
 164         struct ima_template_field *found_fields[IMA_TEMPLATE_NUM_FIELDS_MAX];
 165         int template_num_fields;
 166         int i, len;
 167
 168         if (num_fields && *num_fields > 0) /* already initialized? */
 169                 return 0;
 170
 171         template_num_fields = template_fmt_size(template_fmt);
 172
 173         if (template_num_fields > IMA_TEMPLATE_NUM_FIELDS_MAX) {
 174                 pr_err("format string '%s' contains too many fields\n",
 175                        template_fmt);
 176                 return -EINVAL;
 177         }
 178
 179         for (i = 0, template_fmt_ptr = template_fmt; i < template_num_fields;
 180              i++, template_fmt_ptr += len + 1) {
 181                 char tmp_field_id[IMA_TEMPLATE_FIELD_ID_MAX_LEN + 1];
 182
 183                 len = strchrnul(template_fmt_ptr, '|') - template_fmt_ptr;
 184                 if (len == 0 || len > IMA_TEMPLATE_FIELD_ID_MAX_LEN) {
 185                         pr_err("Invalid field with length %d\n", len);
 186                         return -EINVAL;
 187                 }
 188
 189                 memcpy(tmp_field_id, template_fmt_ptr, len);
 190                 tmp_field_id[len] = '\0';
 191                 found_fields[i] = lookup_template_field(tmp_field_id);
 192                 if (!found_fields[i]) {
 193                         pr_err("field '%s' not found\n", tmp_field_id);
 194                         return -ENOENT;
 195                 }
 196         }
 197
 198         if (fields && num_fields) {
 199                 *fields = kmalloc_array(i, sizeof(*fields), GFP_KERNEL);
 200                 if (*fields == NULL)
 201                         return -ENOMEM;
 202
 203                 memcpy(*fields, found_fields, i * sizeof(*fields));
 204                 *num_fields = i;
 205         }
 206
 207         return 0;
 208 }
 209
 210 void ima_init_template_list(void)
 211 {
 212         int i;
 213
 214         if (!list_empty(&defined_templates))
 215                 return;
 216
 217         spin_lock(&template_list);
 218         for (i = 0; i < ARRAY_SIZE(builtin_templates); i++) {
 219                 list_add_tail_rcu(&builtin_templates[i].list,
 220                                   &defined_templates);
 221         }
 222         spin_unlock(&template_list);
 223 }
 224
 225 struct ima_template_desc *ima_template_desc_current(void)
 226 {
 227         if (!ima_template) {
 228                 ima_init_template_list();
 229                 ima_template =
 230                     lookup_template_desc(CONFIG_IMA_DEFAULT_TEMPLATE);
 231         }
 232         return ima_template;
 233 }
 234
 235 int __init ima_init_template(void)
 236 {
 237         struct ima_template_desc *template = ima_template_desc_current();
 238         int result;
 239
 240         result = template_desc_init_fields(template->fmt,
 241                                            &(template->fields),
 242                                            &(template->num_fields));
 243         if (result < 0)
 244                 pr_err("template %s init failed, result: %d\n",
 245                        (strlen(template->name) ?
 246                        template->name : template->fmt), result);
 247
 248         return result;
 249 }
 250
 251 static struct ima_template_desc *restore_template_fmt(char *template_name)
 252 {
 253         struct ima_template_desc *template_desc = NULL;
 254         int ret;
 255
 256         ret = template_desc_init_fields(template_name, NULL, NULL);
 257         if (ret < 0) {
 258                 pr_err("attempting to initialize the template \"%s\" failed\n",
 259                         template_name);
 260                 goto out;
 261         }
 262
 263         template_desc = kzalloc(sizeof(*template_desc), GFP_KERNEL);
 264         if (!template_desc)
 265                 goto out;
 266
 267         template_desc->name = "";
 268         template_desc->fmt = kstrdup(template_name, GFP_KERNEL);
 269         if (!template_desc->fmt)
 270                 goto out;
 271
 272         spin_lock(&template_list);
 273         list_add_tail_rcu(&template_desc->list, &defined_templates);
 274         spin_unlock(&template_list);
 275 out:
 276         return template_desc;
 277 }
 278
 279 static int ima_restore_template_data(struct ima_template_desc *template_desc,
 280                                      void *template_data,
 281                                      int template_data_size,
 282                                      struct ima_template_entry **entry)
 283 {
 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         ret = ima_parse_buf(template_data, template_data + template_data_size,
 294                             NULL, template_desc->num_fields,
 295                             (*entry)->template_data, NULL, NULL,
 296                             ENFORCE_FIELDS | ENFORCE_BUFEND, "template data");
 297         if (ret < 0) {
 298                 kfree(*entry);
 299                 return ret;
 300         }
 301
 302         (*entry)->template_desc = template_desc;
 303         for (i = 0; i < template_desc->num_fields; i++) {
 304                 struct ima_field_data *field_data = &(*entry)->template_data[i];
 305                 u8 *data = field_data->data;
 306
 307                 (*entry)->template_data[i].data =
 308                         kzalloc(field_data->len + 1, GFP_KERNEL);
 309                 if (!(*entry)->template_data[i].data) {
 310                         ret = -ENOMEM;
 311                         break;
 312                 }
 313                 memcpy((*entry)->template_data[i].data, data, field_data->len);
 314                 (*entry)->template_data_len += sizeof(field_data->len);
 315                 (*entry)->template_data_len += field_data->len;
 316         }
 317
 318         if (ret < 0) {
 319                 ima_free_template_entry(*entry);
 320                 *entry = NULL;
 321         }
 322
 323         return ret;
 324 }
 325
 326 /* Restore the serialized binary measurement list without extending PCRs. */
 327 int ima_restore_measurement_list(loff_t size, void *buf)
 328 {
 329         char template_name[MAX_TEMPLATE_NAME_LEN];
 330
 331         struct ima_kexec_hdr *khdr = buf;
 332         struct ima_field_data hdr[HDR__LAST] = {
 333                 [HDR_PCR] = {.len = sizeof(u32)},
 334                 [HDR_DIGEST] = {.len = TPM_DIGEST_SIZE},
 335         };
 336
 337         void *bufp = buf + sizeof(*khdr);
 338         void *bufendp;
 339         struct ima_template_entry *entry;
 340         struct ima_template_desc *template_desc;
 341         DECLARE_BITMAP(hdr_mask, HDR__LAST);
 342         unsigned long count = 0;
 343         int ret = 0;
 344
 345         if (!buf || size < sizeof(*khdr))
 346                 return 0;
 347
 348         if (ima_canonical_fmt) {
 349                 khdr->version = le16_to_cpu(khdr->version);
 350                 khdr->count = le64_to_cpu(khdr->count);
 351                 khdr->buffer_size = le64_to_cpu(khdr->buffer_size);
 352         }
 353
 354         if (khdr->version != 1) {
 355                 pr_err("attempting to restore a incompatible measurement list");
 356                 return -EINVAL;
 357         }
 358
 359         if (khdr->count > ULONG_MAX - 1) {
 360                 pr_err("attempting to restore too many measurements");
 361                 return -EINVAL;
 362         }
 363
 364         bitmap_zero(hdr_mask, HDR__LAST);
 365         bitmap_set(hdr_mask, HDR_PCR, 1);
 366         bitmap_set(hdr_mask, HDR_DIGEST, 1);
 367
 368         /*
 369          * ima kexec buffer prefix: version, buffer size, count
 370          * v1 format: pcr, digest, template-name-len, template-name,
 371          *            template-data-size, template-data
 372          */
 373         bufendp = buf + khdr->buffer_size;
 374         while ((bufp < bufendp) && (count++ < khdr->count)) {
 375                 int enforce_mask = ENFORCE_FIELDS;
 376
 377                 enforce_mask |= (count == khdr->count) ? ENFORCE_BUFEND : 0;
 378                 ret = ima_parse_buf(bufp, bufendp, &bufp, HDR__LAST, hdr, NULL,
 379                                     hdr_mask, enforce_mask, "entry header");
 380                 if (ret < 0)
 381                         break;
 382
 383                 if (hdr[HDR_TEMPLATE_NAME].len >= MAX_TEMPLATE_NAME_LEN) {
 384                         pr_err("attempting to restore a template name \
 385                                 that is too long\n");
 386                         ret = -EINVAL;
 387                         break;
 388                 }
 389
 390                 /* template name is not null terminated */
 391                 memcpy(template_name, hdr[HDR_TEMPLATE_NAME].data,
 392                        hdr[HDR_TEMPLATE_NAME].len);
 393                 template_name[hdr[HDR_TEMPLATE_NAME].len] = 0;
 394
 395                 if (strcmp(template_name, "ima") == 0) {
 396                         pr_err("attempting to restore an unsupported \
 397                                 template \"%s\" failed\n", template_name);
 398                         ret = -EINVAL;
 399                         break;
 400                 }
 401
 402                 template_desc = lookup_template_desc(template_name);
 403                 if (!template_desc) {
 404                         template_desc = restore_template_fmt(template_name);
 405                         if (!template_desc)
 406                                 break;
 407                 }
 408
 409                 /*
 410                  * Only the running system's template format is initialized
 411                  * on boot.  As needed, initialize the other template formats.
 412                  */
 413                 ret = template_desc_init_fields(template_desc->fmt,
 414                                                 &(template_desc->fields),
 415                                                 &(template_desc->num_fields));
 416                 if (ret < 0) {
 417                         pr_err("attempting to restore the template fmt \"%s\" \
 418                                 failed\n", template_desc->fmt);
 419                         ret = -EINVAL;
 420                         break;
 421                 }
 422
 423                 ret = ima_restore_template_data(template_desc,
 424                                                 hdr[HDR_TEMPLATE_DATA].data,
 425                                                 hdr[HDR_TEMPLATE_DATA].len,
 426                                                 &entry);
 427                 if (ret < 0)
 428                         break;
 429
 430                 memcpy(entry->digest, hdr[HDR_DIGEST].data,
 431                        hdr[HDR_DIGEST].len);
 432                 entry->pcr = !ima_canonical_fmt ? *(hdr[HDR_PCR].data) :
 433                              le32_to_cpu(*(hdr[HDR_PCR].data));
 434                 ret = ima_restore_measurement_entry(entry);
 435                 if (ret < 0)
 436                         break;
 437
 438         }
 439         return ret;
 440 }