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 #define TMPBUFLEN 12
  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[TMPBUFLEN];
  37         ssize_t len;
  38
  39         len = scnprintf(tmpbuf, TMPBUFLEN, "%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         u32 pcr = CONFIG_IMA_MEASURE_PCR_IDX;
 127         bool is_ima_template = false;
 128         int i;
 129
 130         /* get entry */
 131         e = qe->entry;
 132         if (e == NULL)
 133                 return -1;
 134
 135         template_name = (e->template_desc->name[0] != '\0') ?
 136             e->template_desc->name : e->template_desc->fmt;
 137
 138         /*
 139          * 1st: PCRIndex
 140          * PCR used is always the same (config option) in
 141          * little-endian format
 142          */
 143         ima_putc(m, &pcr, sizeof(pcr));
 144
 145         /* 2nd: template digest */
 146         ima_putc(m, e->digest, TPM_DIGEST_SIZE);
 147
 148         /* 3rd: template name size */
 149         namelen = strlen(template_name);
 150         ima_putc(m, &namelen, sizeof(namelen));
 151
 152         /* 4th:  template name */
 153         ima_putc(m, template_name, namelen);
 154
 155         /* 5th:  template length (except for 'ima' template) */
 156         if (strcmp(template_name, IMA_TEMPLATE_IMA_NAME) == 0)
 157                 is_ima_template = true;
 158
 159         if (!is_ima_template)
 160                 ima_putc(m, &e->template_data_len,
 161                          sizeof(e->template_data_len));
 162
 163         /* 6th:  template specific data */
 164         for (i = 0; i < e->template_desc->num_fields; i++) {
 165                 enum ima_show_type show = IMA_SHOW_BINARY;
 166                 struct ima_template_field *field = e->template_desc->fields[i];
 167
 168                 if (is_ima_template && strcmp(field->field_id, "d") == 0)
 169                         show = IMA_SHOW_BINARY_NO_FIELD_LEN;
 170                 if (is_ima_template && strcmp(field->field_id, "n") == 0)
 171                         show = IMA_SHOW_BINARY_OLD_STRING_FMT;
 172                 field->field_show(m, show, &e->template_data[i]);
 173         }
 174         return 0;
 175 }
 176
 177 static const struct seq_operations ima_measurments_seqops = {
 178         .start = ima_measurements_start,
 179         .next = ima_measurements_next,
 180         .stop = ima_measurements_stop,
 181         .show = ima_measurements_show
 182 };
 183
 184 static int ima_measurements_open(struct inode *inode, struct file *file)
 185 {
 186         return seq_open(file, &ima_measurments_seqops);
 187 }
 188
 189 static const struct file_operations ima_measurements_ops = {
 190         .open = ima_measurements_open,
 191         .read = seq_read,
 192         .llseek = seq_lseek,
 193         .release = seq_release,
 194 };
 195
 196 void ima_print_digest(struct seq_file *m, u8 *digest, u32 size)
 197 {
 198         u32 i;
 199
 200         for (i = 0; i < size; i++)
 201                 seq_printf(m, "%02x", *(digest + i));
 202 }
 203
 204 /* print in ascii */
 205 static int ima_ascii_measurements_show(struct seq_file *m, void *v)
 206 {
 207         /* the list never shrinks, so we don't need a lock here */
 208         struct ima_queue_entry *qe = v;
 209         struct ima_template_entry *e;
 210         char *template_name;
 211         int i;
 212
 213         /* get entry */
 214         e = qe->entry;
 215         if (e == NULL)
 216                 return -1;
 217
 218         template_name = (e->template_desc->name[0] != '\0') ?
 219             e->template_desc->name : e->template_desc->fmt;
 220
 221         /* 1st: PCR used (config option) */
 222         seq_printf(m, "%2d ", CONFIG_IMA_MEASURE_PCR_IDX);
 223
 224         /* 2nd: SHA1 template hash */
 225         ima_print_digest(m, e->digest, TPM_DIGEST_SIZE);
 226
 227         /* 3th:  template name */
 228         seq_printf(m, " %s", template_name);
 229
 230         /* 4th:  template specific data */
 231         for (i = 0; i < e->template_desc->num_fields; i++) {
 232                 seq_puts(m, " ");
 233                 if (e->template_data[i].len == 0)
 234                         continue;
 235
 236                 e->template_desc->fields[i]->field_show(m, IMA_SHOW_ASCII,
 237                                                         &e->template_data[i]);
 238         }
 239         seq_puts(m, "\n");
 240         return 0;
 241 }
 242
 243 static const struct seq_operations ima_ascii_measurements_seqops = {
 244         .start = ima_measurements_start,
 245         .next = ima_measurements_next,
 246         .stop = ima_measurements_stop,
 247         .show = ima_ascii_measurements_show
 248 };
 249
 250 static int ima_ascii_measurements_open(struct inode *inode, struct file *file)
 251 {
 252         return seq_open(file, &ima_ascii_measurements_seqops);
 253 }
 254
 255 static const struct file_operations ima_ascii_measurements_ops = {
 256         .open = ima_ascii_measurements_open,
 257         .read = seq_read,
 258         .llseek = seq_lseek,
 259         .release = seq_release,
 260 };
 261
 262 static ssize_t ima_read_policy(char *path)
 263 {
 264         void *data;
 265         char *datap;
 266         loff_t size;
 267         int rc, pathlen = strlen(path);
 268
 269         char *p;
 270
 271         /* remove \n */
 272         datap = path;
 273         strsep(&datap, "\n");
 274
 275         rc = kernel_read_file_from_path(path, &data, &size, 0, READING_POLICY);
 276         if (rc < 0) {
 277                 pr_err("Unable to open file: %s (%d)", path, rc);
 278                 return rc;
 279         }
 280
 281         datap = data;
 282         while (size > 0 && (p = strsep(&datap, "\n"))) {
 283                 pr_debug("rule: %s\n", p);
 284                 rc = ima_parse_add_rule(p);
 285                 if (rc < 0)
 286                         break;
 287                 size -= rc;
 288         }
 289
 290         vfree(data);
 291         if (rc < 0)
 292                 return rc;
 293         else if (size)
 294                 return -EINVAL;
 295         else
 296                 return pathlen;
 297 }
 298
 299 static ssize_t ima_write_policy(struct file *file, const char __user *buf,
 300                                 size_t datalen, loff_t *ppos)
 301 {
 302         char *data;
 303         ssize_t result;
 304
 305         if (datalen >= PAGE_SIZE)
 306                 datalen = PAGE_SIZE - 1;
 307
 308         /* No partial writes. */
 309         result = -EINVAL;
 310         if (*ppos != 0)
 311                 goto out;
 312
 313         result = -ENOMEM;
 314         data = kmalloc(datalen + 1, GFP_KERNEL);
 315         if (!data)
 316                 goto out;
 317
 318         *(data + datalen) = '\0';
 319
 320         result = -EFAULT;
 321         if (copy_from_user(data, buf, datalen))
 322                 goto out_free;
 323
 324         result = mutex_lock_interruptible(&ima_write_mutex);
 325         if (result < 0)
 326                 goto out_free;
 327
 328         if (data[0] == '/') {
 329                 result = ima_read_policy(data);
 330         } else if (ima_appraise & IMA_APPRAISE_POLICY) {
 331                 pr_err("IMA: signed policy file (specified as an absolute pathname) required\n");
 332                 integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
 333                                     "policy_update", "signed policy required",
 334                                     1, 0);
 335                 if (ima_appraise & IMA_APPRAISE_ENFORCE)
 336                         result = -EACCES;
 337         } else {
 338                 result = ima_parse_add_rule(data);
 339         }
 340         mutex_unlock(&ima_write_mutex);
 341 out_free:
 342         kfree(data);
 343 out:
 344         if (result < 0)
 345                 valid_policy = 0;
 346
 347         return result;
 348 }
 349
 350 static struct dentry *ima_dir;
 351 static struct dentry *binary_runtime_measurements;
 352 static struct dentry *ascii_runtime_measurements;
 353 static struct dentry *runtime_measurements_count;
 354 static struct dentry *violations;
 355 static struct dentry *ima_policy;
 356
 357 enum ima_fs_flags {
 358         IMA_FS_BUSY,
 359 };
 360
 361 static unsigned long ima_fs_flags;
 362
 363 #ifdef  CONFIG_IMA_READ_POLICY
 364 static const struct seq_operations ima_policy_seqops = {
 365                 .start = ima_policy_start,
 366                 .next = ima_policy_next,
 367                 .stop = ima_policy_stop,
 368                 .show = ima_policy_show,
 369 };
 370 #endif
 371
 372 /*
 373  * ima_open_policy: sequentialize access to the policy file
 374  */
 375 static int ima_open_policy(struct inode *inode, struct file *filp)
 376 {
 377         if (!(filp->f_flags & O_WRONLY)) {
 378 #ifndef CONFIG_IMA_READ_POLICY
 379                 return -EACCES;
 380 #else
 381                 if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
 382                         return -EACCES;
 383                 if (!capable(CAP_SYS_ADMIN))
 384                         return -EPERM;
 385                 return seq_open(filp, &ima_policy_seqops);
 386 #endif
 387         }
 388         if (test_and_set_bit(IMA_FS_BUSY, &ima_fs_flags))
 389                 return -EBUSY;
 390         return 0;
 391 }
 392
 393 /*
 394  * ima_release_policy - start using the new measure policy rules.
 395  *
 396  * Initially, ima_measure points to the default policy rules, now
 397  * point to the new policy rules, and remove the securityfs policy file,
 398  * assuming a valid policy.
 399  */
 400 static int ima_release_policy(struct inode *inode, struct file *file)
 401 {
 402         const char *cause = valid_policy ? "completed" : "failed";
 403
 404         if ((file->f_flags & O_ACCMODE) == O_RDONLY)
 405                 return 0;
 406
 407         if (valid_policy && ima_check_policy() < 0) {
 408                 cause = "failed";
 409                 valid_policy = 0;
 410         }
 411
 412         pr_info("IMA: policy update %s\n", cause);
 413         integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
 414                             "policy_update", cause, !valid_policy, 0);
 415
 416         if (!valid_policy) {
 417                 ima_delete_rules();
 418                 valid_policy = 1;
 419                 clear_bit(IMA_FS_BUSY, &ima_fs_flags);
 420                 return 0;
 421         }
 422
 423         ima_update_policy();
 424 #ifndef CONFIG_IMA_WRITE_POLICY
 425         securityfs_remove(ima_policy);
 426         ima_policy = NULL;
 427 #else
 428         clear_bit(IMA_FS_BUSY, &ima_fs_flags);
 429 #endif
 430         return 0;
 431 }
 432
 433 static const struct file_operations ima_measure_policy_ops = {
 434         .open = ima_open_policy,
 435         .write = ima_write_policy,
 436         .read = seq_read,
 437         .release = ima_release_policy,
 438         .llseek = generic_file_llseek,
 439 };
 440
 441 int __init ima_fs_init(void)
 442 {
 443         ima_dir = securityfs_create_dir("ima", NULL);
 444         if (IS_ERR(ima_dir))
 445                 return -1;
 446
 447         binary_runtime_measurements =
 448             securityfs_create_file("binary_runtime_measurements",
 449                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 450                                    &ima_measurements_ops);
 451         if (IS_ERR(binary_runtime_measurements))
 452                 goto out;
 453
 454         ascii_runtime_measurements =
 455             securityfs_create_file("ascii_runtime_measurements",
 456                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 457                                    &ima_ascii_measurements_ops);
 458         if (IS_ERR(ascii_runtime_measurements))
 459                 goto out;
 460
 461         runtime_measurements_count =
 462             securityfs_create_file("runtime_measurements_count",
 463                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 464                                    &ima_measurements_count_ops);
 465         if (IS_ERR(runtime_measurements_count))
 466                 goto out;
 467
 468         violations =
 469             securityfs_create_file("violations", S_IRUSR | S_IRGRP,
 470                                    ima_dir, NULL, &ima_htable_violations_ops);
 471         if (IS_ERR(violations))
 472                 goto out;
 473
 474         ima_policy = securityfs_create_file("policy", POLICY_FILE_FLAGS,
 475                                             ima_dir, NULL,
 476                                             &ima_measure_policy_ops);
 477         if (IS_ERR(ima_policy))
 478                 goto out;
 479
 480         return 0;
 481 out:
 482         securityfs_remove(violations);
 483         securityfs_remove(runtime_measurements_count);
 484         securityfs_remove(ascii_runtime_measurements);
 485         securityfs_remove(binary_runtime_measurements);
 486         securityfs_remove(ima_dir);
 487         securityfs_remove(ima_policy);
 488         return -1;
 489 }