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