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