security/integrity/ima/ima_fs.c

   1 /*
   2  * Copyright (C) 2005,2006,2007,2008 IBM Corporation
   3  *
   4  * Authors:
   5  * Kylene Hall <kjhall@us.ibm.com>
   6  * Reiner Sailer <sailer@us.ibm.com>
   7  * Mimi Zohar <zohar@us.ibm.com>
   8  *
   9  * This program is free software; you can redistribute it and/or
  10  * modify it under the terms of the GNU General Public License as
  11  * published by the Free Software Foundation, version 2 of the
  12  * License.
  13  *
  14  * File: ima_fs.c
  15  *      implemenents security file system for reporting
  16  *      current measurement list and IMA statistics
  17  */
  18
  19 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
  20
  21 #include <linux/fcntl.h>
  22 #include <linux/slab.h>
  23 #include <linux/module.h>
  24 #include <linux/seq_file.h>
  25 #include <linux/rculist.h>
  26 #include <linux/rcupdate.h>
  27 #include <linux/parser.h>
  28 #include <linux/vmalloc.h>
  29
  30 #include "ima.h"
  31
  32 static DEFINE_MUTEX(ima_write_mutex);
  33
  34 bool ima_canonical_fmt;
  35 static int __init default_canonical_fmt_setup(char *str)
  36 {
  37 #ifdef __BIG_ENDIAN
  38         ima_canonical_fmt = true;
  39 #endif
  40         return 1;
  41 }
  42 __setup("ima_canonical_fmt", default_canonical_fmt_setup);
  43
  44 static int valid_policy = 1;
  45
  46 static ssize_t ima_show_htable_value(char __user *buf, size_t count,
  47                                      loff_t *ppos, atomic_long_t *val)
  48 {
  49         char tmpbuf[32];        /* greater than largest 'long' string value */
  50         ssize_t len;
  51
  52         len = scnprintf(tmpbuf, sizeof(tmpbuf), "%li\n", atomic_long_read(val));
  53         return simple_read_from_buffer(buf, count, ppos, tmpbuf, len);
  54 }
  55
  56 static ssize_t ima_show_htable_violations(struct file *filp,
  57                                           char __user *buf,
  58                                           size_t count, loff_t *ppos)
  59 {
  60         return ima_show_htable_value(buf, count, ppos, &ima_htable.violations);
  61 }
  62
  63 static const struct file_operations ima_htable_violations_ops = {
  64         .read = ima_show_htable_violations,
  65         .llseek = generic_file_llseek,
  66 };
  67
  68 static ssize_t ima_show_measurements_count(struct file *filp,
  69                                            char __user *buf,
  70                                            size_t count, loff_t *ppos)
  71 {
  72         return ima_show_htable_value(buf, count, ppos, &ima_htable.len);
  73
  74 }
  75
  76 static const struct file_operations ima_measurements_count_ops = {
  77         .read = ima_show_measurements_count,
  78         .llseek = generic_file_llseek,
  79 };
  80
  81 /* returns pointer to hlist_node */
  82 static void *ima_measurements_start(struct seq_file *m, loff_t *pos)
  83 {
  84         loff_t l = *pos;
  85         struct ima_queue_entry *qe;
  86
  87         /* we need a lock since pos could point beyond last element */
  88         rcu_read_lock();
  89         list_for_each_entry_rcu(qe, &ima_measurements, later) {
  90                 if (!l--) {
  91                         rcu_read_unlock();
  92                         return qe;
  93                 }
  94         }
  95         rcu_read_unlock();
  96         return NULL;
  97 }
  98
  99 static void *ima_measurements_next(struct seq_file *m, void *v, loff_t *pos)
 100 {
 101         struct ima_queue_entry *qe = v;
 102
 103         /* lock protects when reading beyond last element
 104          * against concurrent list-extension
 105          */
 106         rcu_read_lock();
 107         qe = list_entry_rcu(qe->later.next, struct ima_queue_entry, later);
 108         rcu_read_unlock();
 109         (*pos)++;
 110
 111         return (&qe->later == &ima_measurements) ? NULL : qe;
 112 }
 113
 114 static void ima_measurements_stop(struct seq_file *m, void *v)
 115 {
 116 }
 117
 118 void ima_putc(struct seq_file *m, void *data, int datalen)
 119 {
 120         while (datalen--)
 121                 seq_putc(m, *(char *)data++);
 122 }
 123
 124 /* print format:
 125  *       32bit-le=pcr#
 126  *       char[20]=template digest
 127  *       32bit-le=template name size
 128  *       char[n]=template name
 129  *       [eventdata length]
 130  *       eventdata[n]=template specific data
 131  */
 132 int ima_measurements_show(struct seq_file *m, void *v)
 133 {
 134         /* the list never shrinks, so we don't need a lock here */
 135         struct ima_queue_entry *qe = v;
 136         struct ima_template_entry *e;
 137         char *template_name;
 138         u32 pcr, namelen, template_data_len; /* temporary fields */
 139         bool is_ima_template = false;
 140         int i;
 141
 142         /* get entry */
 143         e = qe->entry;
 144         if (e == NULL)
 145                 return -1;
 146
 147         template_name = (e->template_desc->name[0] != '\0') ?
 148             e->template_desc->name : e->template_desc->fmt;
 149
 150         /*
 151          * 1st: PCRIndex
 152          * PCR used defaults to the same (config option) in
 153          * little-endian format, unless set in policy
 154          */
 155         pcr = !ima_canonical_fmt ? e->pcr : cpu_to_le32(e->pcr);
 156         ima_putc(m, &pcr, sizeof(e->pcr));
 157
 158         /* 2nd: template digest */
 159         ima_putc(m, e->digest, TPM_DIGEST_SIZE);
 160
 161         /* 3rd: template name size */
 162         namelen = !ima_canonical_fmt ? strlen(template_name) :
 163                 cpu_to_le32(strlen(template_name));
 164         ima_putc(m, &namelen, sizeof(namelen));
 165
 166         /* 4th:  template name */
 167         ima_putc(m, template_name, strlen(template_name));
 168
 169         /* 5th:  template length (except for 'ima' template) */
 170         if (strcmp(template_name, IMA_TEMPLATE_IMA_NAME) == 0)
 171                 is_ima_template = true;
 172
 173         if (!is_ima_template) {
 174                 template_data_len = !ima_canonical_fmt ? e->template_data_len :
 175                         cpu_to_le32(e->template_data_len);
 176                 ima_putc(m, &template_data_len, sizeof(e->template_data_len));
 177         }
 178
 179         /* 6th:  template specific data */
 180         for (i = 0; i < e->template_desc->num_fields; i++) {
 181                 enum ima_show_type show = IMA_SHOW_BINARY;
 182                 struct ima_template_field *field = e->template_desc->fields[i];
 183
 184                 if (is_ima_template && strcmp(field->field_id, "d") == 0)
 185                         show = IMA_SHOW_BINARY_NO_FIELD_LEN;
 186                 if (is_ima_template && strcmp(field->field_id, "n") == 0)
 187                         show = IMA_SHOW_BINARY_OLD_STRING_FMT;
 188                 field->field_show(m, show, &e->template_data[i]);
 189         }
 190         return 0;
 191 }
 192
 193 static const struct seq_operations ima_measurments_seqops = {
 194         .start = ima_measurements_start,
 195         .next = ima_measurements_next,
 196         .stop = ima_measurements_stop,
 197         .show = ima_measurements_show
 198 };
 199
 200 static int ima_measurements_open(struct inode *inode, struct file *file)
 201 {
 202         return seq_open(file, &ima_measurments_seqops);
 203 }
 204
 205 static const struct file_operations ima_measurements_ops = {
 206         .open = ima_measurements_open,
 207         .read = seq_read,
 208         .llseek = seq_lseek,
 209         .release = seq_release,
 210 };
 211
 212 void ima_print_digest(struct seq_file *m, u8 *digest, u32 size)
 213 {
 214         u32 i;
 215
 216         for (i = 0; i < size; i++)
 217                 seq_printf(m, "%02x", *(digest + i));
 218 }
 219
 220 /* print in ascii */
 221 static int ima_ascii_measurements_show(struct seq_file *m, void *v)
 222 {
 223         /* the list never shrinks, so we don't need a lock here */
 224         struct ima_queue_entry *qe = v;
 225         struct ima_template_entry *e;
 226         char *template_name;
 227         int i;
 228
 229         /* get entry */
 230         e = qe->entry;
 231         if (e == NULL)
 232                 return -1;
 233
 234         template_name = (e->template_desc->name[0] != '\0') ?
 235             e->template_desc->name : e->template_desc->fmt;
 236
 237         /* 1st: PCR used (config option) */
 238         seq_printf(m, "%2d ", e->pcr);
 239
 240         /* 2nd: SHA1 template hash */
 241         ima_print_digest(m, e->digest, TPM_DIGEST_SIZE);
 242
 243         /* 3th:  template name */
 244         seq_printf(m, " %s", template_name);
 245
 246         /* 4th:  template specific data */
 247         for (i = 0; i < e->template_desc->num_fields; i++) {
 248                 seq_puts(m, " ");
 249                 if (e->template_data[i].len == 0)
 250                         continue;
 251
 252                 e->template_desc->fields[i]->field_show(m, IMA_SHOW_ASCII,
 253                                                         &e->template_data[i]);
 254         }
 255         seq_puts(m, "\n");
 256         return 0;
 257 }
 258
 259 static const struct seq_operations ima_ascii_measurements_seqops = {
 260         .start = ima_measurements_start,
 261         .next = ima_measurements_next,
 262         .stop = ima_measurements_stop,
 263         .show = ima_ascii_measurements_show
 264 };
 265
 266 static int ima_ascii_measurements_open(struct inode *inode, struct file *file)
 267 {
 268         return seq_open(file, &ima_ascii_measurements_seqops);
 269 }
 270
 271 static const struct file_operations ima_ascii_measurements_ops = {
 272         .open = ima_ascii_measurements_open,
 273         .read = seq_read,
 274         .llseek = seq_lseek,
 275         .release = seq_release,
 276 };
 277
 278 static ssize_t ima_read_policy(char *path)
 279 {
 280         void *data;
 281         char *datap;
 282         loff_t size;
 283         int rc, pathlen = strlen(path);
 284
 285         char *p;
 286
 287         /* remove \n */
 288         datap = path;
 289         strsep(&datap, "\n");
 290
 291         rc = kernel_read_file_from_path(path, &data, &size, 0, READING_POLICY);
 292         if (rc < 0) {
 293                 pr_err("Unable to open file: %s (%d)", path, rc);
 294                 return rc;
 295         }
 296
 297         datap = data;
 298         while (size > 0 && (p = strsep(&datap, "\n"))) {
 299                 pr_debug("rule: %s\n", p);
 300                 rc = ima_parse_add_rule(p);
 301                 if (rc < 0)
 302                         break;
 303                 size -= rc;
 304         }
 305
 306         vfree(data);
 307         if (rc < 0)
 308                 return rc;
 309         else if (size)
 310                 return -EINVAL;
 311         else
 312                 return pathlen;
 313 }
 314
 315 static ssize_t ima_write_policy(struct file *file, const char __user *buf,
 316                                 size_t datalen, loff_t *ppos)
 317 {
 318         char *data;
 319         ssize_t result;
 320
 321         if (datalen >= PAGE_SIZE)
 322                 datalen = PAGE_SIZE - 1;
 323
 324         /* No partial writes. */
 325         result = -EINVAL;
 326         if (*ppos != 0)
 327                 goto out;
 328
 329         data = memdup_user_nul(buf, datalen);
 330         if (IS_ERR(data)) {
 331                 result = PTR_ERR(data);
 332                 goto out;
 333         }
 334
 335         result = mutex_lock_interruptible(&ima_write_mutex);
 336         if (result < 0)
 337                 goto out_free;
 338
 339         if (data[0] == '/') {
 340                 result = ima_read_policy(data);
 341         } else if (ima_appraise & IMA_APPRAISE_POLICY) {
 342                 pr_err("signed policy file (specified as an absolute pathname) required\n");
 343                 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
 344                                     "policy_update", "signed policy required",
 345                                     1, 0);
 346                 result = -EACCES;
 347         } else {
 348                 result = ima_parse_add_rule(data);
 349         }
 350         mutex_unlock(&ima_write_mutex);
 351 out_free:
 352         kfree(data);
 353 out:
 354         if (result < 0)
 355                 valid_policy = 0;
 356
 357         return result;
 358 }
 359
 360 static struct dentry *ima_dir;
 361 static struct dentry *ima_symlink;
 362 static struct dentry *binary_runtime_measurements;
 363 static struct dentry *ascii_runtime_measurements;
 364 static struct dentry *runtime_measurements_count;
 365 static struct dentry *violations;
 366 static struct dentry *ima_policy;
 367
 368 enum ima_fs_flags {
 369         IMA_FS_BUSY,
 370 };
 371
 372 static unsigned long ima_fs_flags;
 373
 374 #ifdef  CONFIG_IMA_READ_POLICY
 375 static const struct seq_operations ima_policy_seqops = {
 376                 .start = ima_policy_start,
 377                 .next = ima_policy_next,
 378                 .stop = ima_policy_stop,
 379                 .show = ima_policy_show,
 380 };
 381 #endif
 382
 383 /*
 384  * ima_open_policy: sequentialize access to the policy file
 385  */
 386 static int ima_open_policy(struct inode *inode, struct file *filp)
 387 {
 388         if (!(filp->f_flags & O_WRONLY)) {
 389 #ifndef CONFIG_IMA_READ_POLICY
 390                 return -EACCES;
 391 #else
 392                 if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
 393                         return -EACCES;
 394                 if (!capable(CAP_SYS_ADMIN))
 395                         return -EPERM;
 396                 return seq_open(filp, &ima_policy_seqops);
 397 #endif
 398         }
 399         if (test_and_set_bit(IMA_FS_BUSY, &ima_fs_flags))
 400                 return -EBUSY;
 401         return 0;
 402 }
 403
 404 /*
 405  * ima_release_policy - start using the new measure policy rules.
 406  *
 407  * Initially, ima_measure points to the default policy rules, now
 408  * point to the new policy rules, and remove the securityfs policy file,
 409  * assuming a valid policy.
 410  */
 411 static int ima_release_policy(struct inode *inode, struct file *file)
 412 {
 413         const char *cause = valid_policy ? "completed" : "failed";
 414
 415         if ((file->f_flags & O_ACCMODE) == O_RDONLY)
 416                 return seq_release(inode, file);
 417
 418         if (valid_policy && ima_check_policy() < 0) {
 419                 cause = "failed";
 420                 valid_policy = 0;
 421         }
 422
 423         pr_info("policy update %s\n", cause);
 424         integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
 425                             "policy_update", cause, !valid_policy, 0);
 426
 427         if (!valid_policy) {
 428                 ima_delete_rules();
 429                 valid_policy = 1;
 430                 clear_bit(IMA_FS_BUSY, &ima_fs_flags);
 431                 return 0;
 432         }
 433
 434         ima_update_policy();
 435 #if !defined(CONFIG_IMA_WRITE_POLICY) && !defined(CONFIG_IMA_READ_POLICY)
 436         securityfs_remove(ima_policy);
 437         ima_policy = NULL;
 438 #elif defined(CONFIG_IMA_WRITE_POLICY)
 439         clear_bit(IMA_FS_BUSY, &ima_fs_flags);
 440 #elif defined(CONFIG_IMA_READ_POLICY)
 441         inode->i_mode &= ~S_IWUSR;
 442 #endif
 443         return 0;
 444 }
 445
 446 static const struct file_operations ima_measure_policy_ops = {
 447         .open = ima_open_policy,
 448         .write = ima_write_policy,
 449         .read = seq_read,
 450         .release = ima_release_policy,
 451         .llseek = generic_file_llseek,
 452 };
 453
 454 int __init ima_fs_init(void)
 455 {
 456         ima_dir = securityfs_create_dir("ima", integrity_dir);
 457         if (IS_ERR(ima_dir))
 458                 return -1;
 459
 460         ima_symlink = securityfs_create_symlink("ima", NULL, "integrity/ima",
 461                                                 NULL);
 462         if (IS_ERR(ima_symlink))
 463                 goto out;
 464
 465         binary_runtime_measurements =
 466             securityfs_create_file("binary_runtime_measurements",
 467                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 468                                    &ima_measurements_ops);
 469         if (IS_ERR(binary_runtime_measurements))
 470                 goto out;
 471
 472         ascii_runtime_measurements =
 473             securityfs_create_file("ascii_runtime_measurements",
 474                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 475                                    &ima_ascii_measurements_ops);
 476         if (IS_ERR(ascii_runtime_measurements))
 477                 goto out;
 478
 479         runtime_measurements_count =
 480             securityfs_create_file("runtime_measurements_count",
 481                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 482                                    &ima_measurements_count_ops);
 483         if (IS_ERR(runtime_measurements_count))
 484                 goto out;
 485
 486         violations =
 487             securityfs_create_file("violations", S_IRUSR | S_IRGRP,
 488                                    ima_dir, NULL, &ima_htable_violations_ops);
 489         if (IS_ERR(violations))
 490                 goto out;
 491
 492         ima_policy = securityfs_create_file("policy", POLICY_FILE_FLAGS,
 493                                             ima_dir, NULL,
 494                                             &ima_measure_policy_ops);
 495         if (IS_ERR(ima_policy))
 496                 goto out;
 497
 498         return 0;
 499 out:
 500         securityfs_remove(violations);
 501         securityfs_remove(runtime_measurements_count);
 502         securityfs_remove(ascii_runtime_measurements);
 503         securityfs_remove(binary_runtime_measurements);
 504         securityfs_remove(ima_symlink);
 505         securityfs_remove(ima_dir);
 506         securityfs_remove(ima_policy);
 507         return -1;
 508 }