security/integrity/ima/ima_fs.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2 /*
   3  * Copyright (C) 2005,2006,2007,2008 IBM Corporation
   4  *
   5  * Authors:
   6  * Kylene Hall <kjhall@us.ibm.com>
   7  * Reiner Sailer <sailer@us.ibm.com>
   8  * Mimi Zohar <zohar@us.ibm.com>
   9  *
  10  * File: ima_fs.c
  11  *      implemenents security file system for reporting
  12  *      current measurement list and IMA statistics
  13  */
  14
  15 #include <linux/fcntl.h>
  16 #include <linux/kernel_read_file.h>
  17 #include <linux/slab.h>
  18 #include <linux/init.h>
  19 #include <linux/seq_file.h>
  20 #include <linux/rculist.h>
  21 #include <linux/rcupdate.h>
  22 #include <linux/parser.h>
  23 #include <linux/vmalloc.h>
  24
  25 #include "ima.h"
  26
  27 static DEFINE_MUTEX(ima_write_mutex);
  28
  29 bool ima_canonical_fmt;
  30 static int __init default_canonical_fmt_setup(char *str)
  31 {
  32 #ifdef __BIG_ENDIAN
  33         ima_canonical_fmt = true;
  34 #endif
  35         return 1;
  36 }
  37 __setup("ima_canonical_fmt", default_canonical_fmt_setup);
  38
  39 static int valid_policy = 1;
  40
  41 static ssize_t ima_show_htable_value(char __user *buf, size_t count,
  42                                      loff_t *ppos, atomic_long_t *val)
  43 {
  44         char tmpbuf[32];        /* greater than largest 'long' string value */
  45         ssize_t len;
  46
  47         len = scnprintf(tmpbuf, sizeof(tmpbuf), "%li\n", atomic_long_read(val));
  48         return simple_read_from_buffer(buf, count, ppos, tmpbuf, len);
  49 }
  50
  51 static ssize_t ima_show_htable_violations(struct file *filp,
  52                                           char __user *buf,
  53                                           size_t count, loff_t *ppos)
  54 {
  55         return ima_show_htable_value(buf, count, ppos, &ima_htable.violations);
  56 }
  57
  58 static const struct file_operations ima_htable_violations_ops = {
  59         .read = ima_show_htable_violations,
  60         .llseek = generic_file_llseek,
  61 };
  62
  63 static ssize_t ima_show_measurements_count(struct file *filp,
  64                                            char __user *buf,
  65                                            size_t count, loff_t *ppos)
  66 {
  67         return ima_show_htable_value(buf, count, ppos, &ima_htable.len);
  68
  69 }
  70
  71 static const struct file_operations ima_measurements_count_ops = {
  72         .read = ima_show_measurements_count,
  73         .llseek = generic_file_llseek,
  74 };
  75
  76 /* returns pointer to hlist_node */
  77 static void *ima_measurements_start(struct seq_file *m, loff_t *pos)
  78 {
  79         loff_t l = *pos;
  80         struct ima_queue_entry *qe;
  81
  82         /* we need a lock since pos could point beyond last element */
  83         rcu_read_lock();
  84         list_for_each_entry_rcu(qe, &ima_measurements, later) {
  85                 if (!l--) {
  86                         rcu_read_unlock();
  87                         return qe;
  88                 }
  89         }
  90         rcu_read_unlock();
  91         return NULL;
  92 }
  93
  94 static void *ima_measurements_next(struct seq_file *m, void *v, loff_t *pos)
  95 {
  96         struct ima_queue_entry *qe = v;
  97
  98         /* lock protects when reading beyond last element
  99          * against concurrent list-extension
 100          */
 101         rcu_read_lock();
 102         qe = list_entry_rcu(qe->later.next, struct ima_queue_entry, later);
 103         rcu_read_unlock();
 104         (*pos)++;
 105
 106         return (&qe->later == &ima_measurements) ? NULL : qe;
 107 }
 108
 109 static void ima_measurements_stop(struct seq_file *m, void *v)
 110 {
 111 }
 112
 113 void ima_putc(struct seq_file *m, void *data, int datalen)
 114 {
 115         while (datalen--)
 116                 seq_putc(m, *(char *)data++);
 117 }
 118
 119 /* print format:
 120  *       32bit-le=pcr#
 121  *       char[20]=template digest
 122  *       32bit-le=template name size
 123  *       char[n]=template name
 124  *       [eventdata length]
 125  *       eventdata[n]=template specific data
 126  */
 127 int ima_measurements_show(struct seq_file *m, void *v)
 128 {
 129         /* the list never shrinks, so we don't need a lock here */
 130         struct ima_queue_entry *qe = v;
 131         struct ima_template_entry *e;
 132         char *template_name;
 133         u32 pcr, namelen, template_data_len; /* temporary fields */
 134         bool is_ima_template = false;
 135         int i;
 136
 137         /* get entry */
 138         e = qe->entry;
 139         if (e == NULL)
 140                 return -1;
 141
 142         template_name = (e->template_desc->name[0] != '\0') ?
 143             e->template_desc->name : e->template_desc->fmt;
 144
 145         /*
 146          * 1st: PCRIndex
 147          * PCR used defaults to the same (config option) in
 148          * little-endian format, unless set in policy
 149          */
 150         pcr = !ima_canonical_fmt ? e->pcr : cpu_to_le32(e->pcr);
 151         ima_putc(m, &pcr, sizeof(e->pcr));
 152
 153         /* 2nd: template digest */
 154         ima_putc(m, e->digests[ima_sha1_idx].digest, TPM_DIGEST_SIZE);
 155
 156         /* 3rd: template name size */
 157         namelen = !ima_canonical_fmt ? strlen(template_name) :
 158                 cpu_to_le32(strlen(template_name));
 159         ima_putc(m, &namelen, sizeof(namelen));
 160
 161         /* 4th:  template name */
 162         ima_putc(m, template_name, strlen(template_name));
 163
 164         /* 5th:  template length (except for 'ima' template) */
 165         if (strcmp(template_name, IMA_TEMPLATE_IMA_NAME) == 0)
 166                 is_ima_template = true;
 167
 168         if (!is_ima_template) {
 169                 template_data_len = !ima_canonical_fmt ? e->template_data_len :
 170                         cpu_to_le32(e->template_data_len);
 171                 ima_putc(m, &template_data_len, sizeof(e->template_data_len));
 172         }
 173
 174         /* 6th:  template specific data */
 175         for (i = 0; i < e->template_desc->num_fields; i++) {
 176                 enum ima_show_type show = IMA_SHOW_BINARY;
 177                 const struct ima_template_field *field =
 178                         e->template_desc->fields[i];
 179
 180                 if (is_ima_template && strcmp(field->field_id, "d") == 0)
 181                         show = IMA_SHOW_BINARY_NO_FIELD_LEN;
 182                 if (is_ima_template && strcmp(field->field_id, "n") == 0)
 183                         show = IMA_SHOW_BINARY_OLD_STRING_FMT;
 184                 field->field_show(m, show, &e->template_data[i]);
 185         }
 186         return 0;
 187 }
 188
 189 static const struct seq_operations ima_measurments_seqops = {
 190         .start = ima_measurements_start,
 191         .next = ima_measurements_next,
 192         .stop = ima_measurements_stop,
 193         .show = ima_measurements_show
 194 };
 195
 196 static int ima_measurements_open(struct inode *inode, struct file *file)
 197 {
 198         return seq_open(file, &ima_measurments_seqops);
 199 }
 200
 201 static const struct file_operations ima_measurements_ops = {
 202         .open = ima_measurements_open,
 203         .read = seq_read,
 204         .llseek = seq_lseek,
 205         .release = seq_release,
 206 };
 207
 208 void ima_print_digest(struct seq_file *m, u8 *digest, u32 size)
 209 {
 210         u32 i;
 211
 212         for (i = 0; i < size; i++)
 213                 seq_printf(m, "%02x", *(digest + i));
 214 }
 215
 216 /* print in ascii */
 217 static int ima_ascii_measurements_show(struct seq_file *m, void *v)
 218 {
 219         /* the list never shrinks, so we don't need a lock here */
 220         struct ima_queue_entry *qe = v;
 221         struct ima_template_entry *e;
 222         char *template_name;
 223         int i;
 224
 225         /* get entry */
 226         e = qe->entry;
 227         if (e == NULL)
 228                 return -1;
 229
 230         template_name = (e->template_desc->name[0] != '\0') ?
 231             e->template_desc->name : e->template_desc->fmt;
 232
 233         /* 1st: PCR used (config option) */
 234         seq_printf(m, "%2d ", e->pcr);
 235
 236         /* 2nd: SHA1 template hash */
 237         ima_print_digest(m, e->digests[ima_sha1_idx].digest, TPM_DIGEST_SIZE);
 238
 239         /* 3th:  template name */
 240         seq_printf(m, " %s", template_name);
 241
 242         /* 4th:  template specific data */
 243         for (i = 0; i < e->template_desc->num_fields; i++) {
 244                 seq_puts(m, " ");
 245                 if (e->template_data[i].len == 0)
 246                         continue;
 247
 248                 e->template_desc->fields[i]->field_show(m, IMA_SHOW_ASCII,
 249                                                         &e->template_data[i]);
 250         }
 251         seq_puts(m, "\n");
 252         return 0;
 253 }
 254
 255 static const struct seq_operations ima_ascii_measurements_seqops = {
 256         .start = ima_measurements_start,
 257         .next = ima_measurements_next,
 258         .stop = ima_measurements_stop,
 259         .show = ima_ascii_measurements_show
 260 };
 261
 262 static int ima_ascii_measurements_open(struct inode *inode, struct file *file)
 263 {
 264         return seq_open(file, &ima_ascii_measurements_seqops);
 265 }
 266
 267 static const struct file_operations ima_ascii_measurements_ops = {
 268         .open = ima_ascii_measurements_open,
 269         .read = seq_read,
 270         .llseek = seq_lseek,
 271         .release = seq_release,
 272 };
 273
 274 static ssize_t ima_read_policy(char *path)
 275 {
 276         void *data = NULL;
 277         char *datap;
 278         size_t size;
 279         int rc, pathlen = strlen(path);
 280
 281         char *p;
 282
 283         /* remove \n */
 284         datap = path;
 285         strsep(&datap, "\n");
 286
 287         rc = kernel_read_file_from_path(path, 0, &data, INT_MAX, NULL,
 288                                         READING_POLICY);
 289         if (rc < 0) {
 290                 pr_err("Unable to open file: %s (%d)", path, rc);
 291                 return rc;
 292         }
 293         size = rc;
 294         rc = 0;
 295
 296         datap = data;
 297         while (size > 0 && (p = strsep(&datap, "\n"))) {
 298                 pr_debug("rule: %s\n", p);
 299                 rc = ima_parse_add_rule(p);
 300                 if (rc < 0)
 301                         break;
 302                 size -= rc;
 303         }
 304
 305         vfree(data);
 306         if (rc < 0)
 307                 return rc;
 308         else if (size)
 309                 return -EINVAL;
 310         else
 311                 return pathlen;
 312 }
 313
 314 static ssize_t ima_write_policy(struct file *file, const char __user *buf,
 315                                 size_t datalen, loff_t *ppos)
 316 {
 317         char *data;
 318         ssize_t result;
 319
 320         if (datalen >= PAGE_SIZE)
 321                 datalen = PAGE_SIZE - 1;
 322
 323         /* No partial writes. */
 324         result = -EINVAL;
 325         if (*ppos != 0)
 326                 goto out;
 327
 328         data = memdup_user_nul(buf, datalen);
 329         if (IS_ERR(data)) {
 330                 result = PTR_ERR(data);
 331                 goto out;
 332         }
 333
 334         result = mutex_lock_interruptible(&ima_write_mutex);
 335         if (result < 0)
 336                 goto out_free;
 337
 338         if (data[0] == '/') {
 339                 result = ima_read_policy(data);
 340         } else if (ima_appraise & IMA_APPRAISE_POLICY) {
 341                 pr_err("signed policy file (specified as an absolute pathname) required\n");
 342                 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
 343                                     "policy_update", "signed policy required",
 344                                     1, 0);
 345                 result = -EACCES;
 346         } else {
 347                 result = ima_parse_add_rule(data);
 348         }
 349         mutex_unlock(&ima_write_mutex);
 350 out_free:
 351         kfree(data);
 352 out:
 353         if (result < 0)
 354                 valid_policy = 0;
 355
 356         return result;
 357 }
 358
 359 static struct dentry *ima_dir;
 360 static struct dentry *ima_symlink;
 361 static struct dentry *binary_runtime_measurements;
 362 static struct dentry *ascii_runtime_measurements;
 363 static struct dentry *runtime_measurements_count;
 364 static struct dentry *violations;
 365 static struct dentry *ima_policy;
 366
 367 enum ima_fs_flags {
 368         IMA_FS_BUSY,
 369 };
 370
 371 static unsigned long ima_fs_flags;
 372
 373 #ifdef  CONFIG_IMA_READ_POLICY
 374 static const struct seq_operations ima_policy_seqops = {
 375                 .start = ima_policy_start,
 376                 .next = ima_policy_next,
 377                 .stop = ima_policy_stop,
 378                 .show = ima_policy_show,
 379 };
 380 #endif
 381
 382 /*
 383  * ima_open_policy: sequentialize access to the policy file
 384  */
 385 static int ima_open_policy(struct inode *inode, struct file *filp)
 386 {
 387         if (!(filp->f_flags & O_WRONLY)) {
 388 #ifndef CONFIG_IMA_READ_POLICY
 389                 return -EACCES;
 390 #else
 391                 if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
 392                         return -EACCES;
 393                 if (!capable(CAP_SYS_ADMIN))
 394                         return -EPERM;
 395                 return seq_open(filp, &ima_policy_seqops);
 396 #endif
 397         }
 398         if (test_and_set_bit(IMA_FS_BUSY, &ima_fs_flags))
 399                 return -EBUSY;
 400         return 0;
 401 }
 402
 403 /*
 404  * ima_release_policy - start using the new measure policy rules.
 405  *
 406  * Initially, ima_measure points to the default policy rules, now
 407  * point to the new policy rules, and remove the securityfs policy file,
 408  * assuming a valid policy.
 409  */
 410 static int ima_release_policy(struct inode *inode, struct file *file)
 411 {
 412         const char *cause = valid_policy ? "completed" : "failed";
 413
 414         if ((file->f_flags & O_ACCMODE) == O_RDONLY)
 415                 return seq_release(inode, file);
 416
 417         if (valid_policy && ima_check_policy() < 0) {
 418                 cause = "failed";
 419                 valid_policy = 0;
 420         }
 421
 422         pr_info("policy update %s\n", cause);
 423         integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
 424                             "policy_update", cause, !valid_policy, 0);
 425
 426         if (!valid_policy) {
 427                 ima_delete_rules();
 428                 valid_policy = 1;
 429                 clear_bit(IMA_FS_BUSY, &ima_fs_flags);
 430                 return 0;
 431         }
 432
 433         ima_update_policy();
 434 #if !defined(CONFIG_IMA_WRITE_POLICY) && !defined(CONFIG_IMA_READ_POLICY)
 435         securityfs_remove(ima_policy);
 436         ima_policy = NULL;
 437 #elif defined(CONFIG_IMA_WRITE_POLICY)
 438         clear_bit(IMA_FS_BUSY, &ima_fs_flags);
 439 #elif defined(CONFIG_IMA_READ_POLICY)
 440         inode->i_mode &= ~S_IWUSR;
 441 #endif
 442         return 0;
 443 }
 444
 445 static const struct file_operations ima_measure_policy_ops = {
 446         .open = ima_open_policy,
 447         .write = ima_write_policy,
 448         .read = seq_read,
 449         .release = ima_release_policy,
 450         .llseek = generic_file_llseek,
 451 };
 452
 453 int __init ima_fs_init(void)
 454 {
 455         ima_dir = securityfs_create_dir("ima", integrity_dir);
 456         if (IS_ERR(ima_dir))
 457                 return -1;
 458
 459         ima_symlink = securityfs_create_symlink("ima", NULL, "integrity/ima",
 460                                                 NULL);
 461         if (IS_ERR(ima_symlink))
 462                 goto out;
 463
 464         binary_runtime_measurements =
 465             securityfs_create_file("binary_runtime_measurements",
 466                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 467                                    &ima_measurements_ops);
 468         if (IS_ERR(binary_runtime_measurements))
 469                 goto out;
 470
 471         ascii_runtime_measurements =
 472             securityfs_create_file("ascii_runtime_measurements",
 473                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 474                                    &ima_ascii_measurements_ops);
 475         if (IS_ERR(ascii_runtime_measurements))
 476                 goto out;
 477
 478         runtime_measurements_count =
 479             securityfs_create_file("runtime_measurements_count",
 480                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 481                                    &ima_measurements_count_ops);
 482         if (IS_ERR(runtime_measurements_count))
 483                 goto out;
 484
 485         violations =
 486             securityfs_create_file("violations", S_IRUSR | S_IRGRP,
 487                                    ima_dir, NULL, &ima_htable_violations_ops);
 488         if (IS_ERR(violations))
 489                 goto out;
 490
 491         ima_policy = securityfs_create_file("policy", POLICY_FILE_FLAGS,
 492                                             ima_dir, NULL,
 493                                             &ima_measure_policy_ops);
 494         if (IS_ERR(ima_policy))
 495                 goto out;
 496
 497         return 0;
 498 out:
 499         securityfs_remove(violations);
 500         securityfs_remove(runtime_measurements_count);
 501         securityfs_remove(ascii_runtime_measurements);
 502         securityfs_remove(binary_runtime_measurements);
 503         securityfs_remove(ima_symlink);
 504         securityfs_remove(ima_dir);
 505         securityfs_remove(ima_policy);
 506         return -1;
 507 }