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