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/init.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                 const struct ima_template_field *field =
 183                         e->template_desc->fields[i];
 184
 185                 if (is_ima_template && strcmp(field->field_id, "d") == 0)
 186                         show = IMA_SHOW_BINARY_NO_FIELD_LEN;
 187                 if (is_ima_template && strcmp(field->field_id, "n") == 0)
 188                         show = IMA_SHOW_BINARY_OLD_STRING_FMT;
 189                 field->field_show(m, show, &e->template_data[i]);
 190         }
 191         return 0;
 192 }
 193
 194 static const struct seq_operations ima_measurments_seqops = {
 195         .start = ima_measurements_start,
 196         .next = ima_measurements_next,
 197         .stop = ima_measurements_stop,
 198         .show = ima_measurements_show
 199 };
 200
 201 static int ima_measurements_open(struct inode *inode, struct file *file)
 202 {
 203         return seq_open(file, &ima_measurments_seqops);
 204 }
 205
 206 static const struct file_operations ima_measurements_ops = {
 207         .open = ima_measurements_open,
 208         .read = seq_read,
 209         .llseek = seq_lseek,
 210         .release = seq_release,
 211 };
 212
 213 void ima_print_digest(struct seq_file *m, u8 *digest, u32 size)
 214 {
 215         u32 i;
 216
 217         for (i = 0; i < size; i++)
 218                 seq_printf(m, "%02x", *(digest + i));
 219 }
 220
 221 /* print in ascii */
 222 static int ima_ascii_measurements_show(struct seq_file *m, void *v)
 223 {
 224         /* the list never shrinks, so we don't need a lock here */
 225         struct ima_queue_entry *qe = v;
 226         struct ima_template_entry *e;
 227         char *template_name;
 228         int i;
 229
 230         /* get entry */
 231         e = qe->entry;
 232         if (e == NULL)
 233                 return -1;
 234
 235         template_name = (e->template_desc->name[0] != '\0') ?
 236             e->template_desc->name : e->template_desc->fmt;
 237
 238         /* 1st: PCR used (config option) */
 239         seq_printf(m, "%2d ", e->pcr);
 240
 241         /* 2nd: SHA1 template hash */
 242         ima_print_digest(m, e->digest, TPM_DIGEST_SIZE);
 243
 244         /* 3th:  template name */
 245         seq_printf(m, " %s", template_name);
 246
 247         /* 4th:  template specific data */
 248         for (i = 0; i < e->template_desc->num_fields; i++) {
 249                 seq_puts(m, " ");
 250                 if (e->template_data[i].len == 0)
 251                         continue;
 252
 253                 e->template_desc->fields[i]->field_show(m, IMA_SHOW_ASCII,
 254                                                         &e->template_data[i]);
 255         }
 256         seq_puts(m, "\n");
 257         return 0;
 258 }
 259
 260 static const struct seq_operations ima_ascii_measurements_seqops = {
 261         .start = ima_measurements_start,
 262         .next = ima_measurements_next,
 263         .stop = ima_measurements_stop,
 264         .show = ima_ascii_measurements_show
 265 };
 266
 267 static int ima_ascii_measurements_open(struct inode *inode, struct file *file)
 268 {
 269         return seq_open(file, &ima_ascii_measurements_seqops);
 270 }
 271
 272 static const struct file_operations ima_ascii_measurements_ops = {
 273         .open = ima_ascii_measurements_open,
 274         .read = seq_read,
 275         .llseek = seq_lseek,
 276         .release = seq_release,
 277 };
 278
 279 static ssize_t ima_read_policy(char *path)
 280 {
 281         void *data;
 282         char *datap;
 283         loff_t size;
 284         int rc, pathlen = strlen(path);
 285
 286         char *p;
 287
 288         /* remove \n */
 289         datap = path;
 290         strsep(&datap, "\n");
 291
 292         rc = kernel_read_file_from_path(path, &data, &size, 0, READING_POLICY);
 293         if (rc < 0) {
 294                 pr_err("Unable to open file: %s (%d)", path, rc);
 295                 return rc;
 296         }
 297
 298         datap = data;
 299         while (size > 0 && (p = strsep(&datap, "\n"))) {
 300                 pr_debug("rule: %s\n", p);
 301                 rc = ima_parse_add_rule(p);
 302                 if (rc < 0)
 303                         break;
 304                 size -= rc;
 305         }
 306
 307         vfree(data);
 308         if (rc < 0)
 309                 return rc;
 310         else if (size)
 311                 return -EINVAL;
 312         else
 313                 return pathlen;
 314 }
 315
 316 static ssize_t ima_write_policy(struct file *file, const char __user *buf,
 317                                 size_t datalen, loff_t *ppos)
 318 {
 319         char *data;
 320         ssize_t result;
 321
 322         if (datalen >= PAGE_SIZE)
 323                 datalen = PAGE_SIZE - 1;
 324
 325         /* No partial writes. */
 326         result = -EINVAL;
 327         if (*ppos != 0)
 328                 goto out;
 329
 330         data = memdup_user_nul(buf, datalen);
 331         if (IS_ERR(data)) {
 332                 result = PTR_ERR(data);
 333                 goto out;
 334         }
 335
 336         result = mutex_lock_interruptible(&ima_write_mutex);
 337         if (result < 0)
 338                 goto out_free;
 339
 340         if (data[0] == '/') {
 341                 result = ima_read_policy(data);
 342         } else if (ima_appraise & IMA_APPRAISE_POLICY) {
 343                 pr_err("signed policy file (specified as an absolute pathname) required\n");
 344                 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
 345                                     "policy_update", "signed policy required",
 346                                     1, 0);
 347                 if (ima_appraise & IMA_APPRAISE_ENFORCE)
 348                         result = -EACCES;
 349         } else {
 350                 result = ima_parse_add_rule(data);
 351         }
 352         mutex_unlock(&ima_write_mutex);
 353 out_free:
 354         kfree(data);
 355 out:
 356         if (result < 0)
 357                 valid_policy = 0;
 358
 359         return result;
 360 }
 361
 362 static struct dentry *ima_dir;
 363 static struct dentry *ima_symlink;
 364 static struct dentry *binary_runtime_measurements;
 365 static struct dentry *ascii_runtime_measurements;
 366 static struct dentry *runtime_measurements_count;
 367 static struct dentry *violations;
 368 static struct dentry *ima_policy;
 369
 370 enum ima_fs_flags {
 371         IMA_FS_BUSY,
 372 };
 373
 374 static unsigned long ima_fs_flags;
 375
 376 #ifdef  CONFIG_IMA_READ_POLICY
 377 static const struct seq_operations ima_policy_seqops = {
 378                 .start = ima_policy_start,
 379                 .next = ima_policy_next,
 380                 .stop = ima_policy_stop,
 381                 .show = ima_policy_show,
 382 };
 383 #endif
 384
 385 /*
 386  * ima_open_policy: sequentialize access to the policy file
 387  */
 388 static int ima_open_policy(struct inode *inode, struct file *filp)
 389 {
 390         if (!(filp->f_flags & O_WRONLY)) {
 391 #ifndef CONFIG_IMA_READ_POLICY
 392                 return -EACCES;
 393 #else
 394                 if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
 395                         return -EACCES;
 396                 if (!capable(CAP_SYS_ADMIN))
 397                         return -EPERM;
 398                 return seq_open(filp, &ima_policy_seqops);
 399 #endif
 400         }
 401         if (test_and_set_bit(IMA_FS_BUSY, &ima_fs_flags))
 402                 return -EBUSY;
 403         return 0;
 404 }
 405
 406 /*
 407  * ima_release_policy - start using the new measure policy rules.
 408  *
 409  * Initially, ima_measure points to the default policy rules, now
 410  * point to the new policy rules, and remove the securityfs policy file,
 411  * assuming a valid policy.
 412  */
 413 static int ima_release_policy(struct inode *inode, struct file *file)
 414 {
 415         const char *cause = valid_policy ? "completed" : "failed";
 416
 417         if ((file->f_flags & O_ACCMODE) == O_RDONLY)
 418                 return seq_release(inode, file);
 419
 420         if (valid_policy && ima_check_policy() < 0) {
 421                 cause = "failed";
 422                 valid_policy = 0;
 423         }
 424
 425         pr_info("policy update %s\n", cause);
 426         integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
 427                             "policy_update", cause, !valid_policy, 0);
 428
 429         if (!valid_policy) {
 430                 ima_delete_rules();
 431                 valid_policy = 1;
 432                 clear_bit(IMA_FS_BUSY, &ima_fs_flags);
 433                 return 0;
 434         }
 435
 436         ima_update_policy();
 437 #if !defined(CONFIG_IMA_WRITE_POLICY) && !defined(CONFIG_IMA_READ_POLICY)
 438         securityfs_remove(ima_policy);
 439         ima_policy = NULL;
 440 #elif defined(CONFIG_IMA_WRITE_POLICY)
 441         clear_bit(IMA_FS_BUSY, &ima_fs_flags);
 442 #elif defined(CONFIG_IMA_READ_POLICY)
 443         inode->i_mode &= ~S_IWUSR;
 444 #endif
 445         return 0;
 446 }
 447
 448 static const struct file_operations ima_measure_policy_ops = {
 449         .open = ima_open_policy,
 450         .write = ima_write_policy,
 451         .read = seq_read,
 452         .release = ima_release_policy,
 453         .llseek = generic_file_llseek,
 454 };
 455
 456 int __init ima_fs_init(void)
 457 {
 458         ima_dir = securityfs_create_dir("ima", integrity_dir);
 459         if (IS_ERR(ima_dir))
 460                 return -1;
 461
 462         ima_symlink = securityfs_create_symlink("ima", NULL, "integrity/ima",
 463                                                 NULL);
 464         if (IS_ERR(ima_symlink))
 465                 goto out;
 466
 467         binary_runtime_measurements =
 468             securityfs_create_file("binary_runtime_measurements",
 469                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 470                                    &ima_measurements_ops);
 471         if (IS_ERR(binary_runtime_measurements))
 472                 goto out;
 473
 474         ascii_runtime_measurements =
 475             securityfs_create_file("ascii_runtime_measurements",
 476                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 477                                    &ima_ascii_measurements_ops);
 478         if (IS_ERR(ascii_runtime_measurements))
 479                 goto out;
 480
 481         runtime_measurements_count =
 482             securityfs_create_file("runtime_measurements_count",
 483                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 484                                    &ima_measurements_count_ops);
 485         if (IS_ERR(runtime_measurements_count))
 486                 goto out;
 487
 488         violations =
 489             securityfs_create_file("violations", S_IRUSR | S_IRGRP,
 490                                    ima_dir, NULL, &ima_htable_violations_ops);
 491         if (IS_ERR(violations))
 492                 goto out;
 493
 494         ima_policy = securityfs_create_file("policy", POLICY_FILE_FLAGS,
 495                                             ima_dir, NULL,
 496                                             &ima_measure_policy_ops);
 497         if (IS_ERR(ima_policy))
 498                 goto out;
 499
 500         return 0;
 501 out:
 502         securityfs_remove(violations);
 503         securityfs_remove(runtime_measurements_count);
 504         securityfs_remove(ascii_runtime_measurements);
 505         securityfs_remove(binary_runtime_measurements);
 506         securityfs_remove(ima_symlink);
 507         securityfs_remove(ima_dir);
 508         securityfs_remove(ima_policy);
 509         return -1;
 510 }