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
  26 #include "ima.h"
  27
  28 static DEFINE_MUTEX(ima_write_mutex);
  29
  30 static int valid_policy = 1;
  31 #define TMPBUFLEN 12
  32 static ssize_t ima_show_htable_value(char __user *buf, size_t count,
  33                                      loff_t *ppos, atomic_long_t *val)
  34 {
  35         char tmpbuf[TMPBUFLEN];
  36         ssize_t len;
  37
  38         len = scnprintf(tmpbuf, TMPBUFLEN, "%li\n", atomic_long_read(val));
  39         return simple_read_from_buffer(buf, count, ppos, tmpbuf, len);
  40 }
  41
  42 static ssize_t ima_show_htable_violations(struct file *filp,
  43                                           char __user *buf,
  44                                           size_t count, loff_t *ppos)
  45 {
  46         return ima_show_htable_value(buf, count, ppos, &ima_htable.violations);
  47 }
  48
  49 static const struct file_operations ima_htable_violations_ops = {
  50         .read = ima_show_htable_violations,
  51         .llseek = generic_file_llseek,
  52 };
  53
  54 static ssize_t ima_show_measurements_count(struct file *filp,
  55                                            char __user *buf,
  56                                            size_t count, loff_t *ppos)
  57 {
  58         return ima_show_htable_value(buf, count, ppos, &ima_htable.len);
  59
  60 }
  61
  62 static const struct file_operations ima_measurements_count_ops = {
  63         .read = ima_show_measurements_count,
  64         .llseek = generic_file_llseek,
  65 };
  66
  67 /* returns pointer to hlist_node */
  68 static void *ima_measurements_start(struct seq_file *m, loff_t *pos)
  69 {
  70         loff_t l = *pos;
  71         struct ima_queue_entry *qe;
  72
  73         /* we need a lock since pos could point beyond last element */
  74         rcu_read_lock();
  75         list_for_each_entry_rcu(qe, &ima_measurements, later) {
  76                 if (!l--) {
  77                         rcu_read_unlock();
  78                         return qe;
  79                 }
  80         }
  81         rcu_read_unlock();
  82         return NULL;
  83 }
  84
  85 static void *ima_measurements_next(struct seq_file *m, void *v, loff_t *pos)
  86 {
  87         struct ima_queue_entry *qe = v;
  88
  89         /* lock protects when reading beyond last element
  90          * against concurrent list-extension
  91          */
  92         rcu_read_lock();
  93         qe = list_entry_rcu(qe->later.next, struct ima_queue_entry, later);
  94         rcu_read_unlock();
  95         (*pos)++;
  96
  97         return (&qe->later == &ima_measurements) ? NULL : qe;
  98 }
  99
 100 static void ima_measurements_stop(struct seq_file *m, void *v)
 101 {
 102 }
 103
 104 void ima_putc(struct seq_file *m, void *data, int datalen)
 105 {
 106         while (datalen--)
 107                 seq_putc(m, *(char *)data++);
 108 }
 109
 110 /* print format:
 111  *       32bit-le=pcr#
 112  *       char[20]=template digest
 113  *       32bit-le=template name size
 114  *       char[n]=template name
 115  *       [eventdata length]
 116  *       eventdata[n]=template specific data
 117  */
 118 static int ima_measurements_show(struct seq_file *m, void *v)
 119 {
 120         /* the list never shrinks, so we don't need a lock here */
 121         struct ima_queue_entry *qe = v;
 122         struct ima_template_entry *e;
 123         char *template_name;
 124         int namelen;
 125         u32 pcr = CONFIG_IMA_MEASURE_PCR_IDX;
 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 is always the same (config option) in
 140          * little-endian format
 141          */
 142         ima_putc(m, &pcr, sizeof(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 ", CONFIG_IMA_MEASURE_PCR_IDX);
 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_write_policy(struct file *file, const char __user *buf,
 262                                 size_t datalen, loff_t *ppos)
 263 {
 264         char *data;
 265         ssize_t result;
 266
 267         if (datalen >= PAGE_SIZE)
 268                 datalen = PAGE_SIZE - 1;
 269
 270         /* No partial writes. */
 271         result = -EINVAL;
 272         if (*ppos != 0)
 273                 goto out;
 274
 275         result = -ENOMEM;
 276         data = kmalloc(datalen + 1, GFP_KERNEL);
 277         if (!data)
 278                 goto out;
 279
 280         *(data + datalen) = '\0';
 281
 282         result = -EFAULT;
 283         if (copy_from_user(data, buf, datalen))
 284                 goto out_free;
 285
 286         result = mutex_lock_interruptible(&ima_write_mutex);
 287         if (result < 0)
 288                 goto out_free;
 289         result = ima_parse_add_rule(data);
 290         mutex_unlock(&ima_write_mutex);
 291
 292 out_free:
 293         kfree(data);
 294 out:
 295         if (result < 0)
 296                 valid_policy = 0;
 297
 298         return result;
 299 }
 300
 301 static struct dentry *ima_dir;
 302 static struct dentry *binary_runtime_measurements;
 303 static struct dentry *ascii_runtime_measurements;
 304 static struct dentry *runtime_measurements_count;
 305 static struct dentry *violations;
 306 static struct dentry *ima_policy;
 307
 308 enum ima_fs_flags {
 309         IMA_FS_BUSY,
 310 };
 311
 312 static unsigned long ima_fs_flags;
 313
 314 #ifdef  CONFIG_IMA_READ_POLICY
 315 static const struct seq_operations ima_policy_seqops = {
 316                 .start = ima_policy_start,
 317                 .next = ima_policy_next,
 318                 .stop = ima_policy_stop,
 319                 .show = ima_policy_show,
 320 };
 321 #endif
 322
 323 /*
 324  * ima_open_policy: sequentialize access to the policy file
 325  */
 326 static int ima_open_policy(struct inode *inode, struct file *filp)
 327 {
 328         if (!(filp->f_flags & O_WRONLY)) {
 329 #ifndef CONFIG_IMA_READ_POLICY
 330                 return -EACCES;
 331 #else
 332                 if ((filp->f_flags & O_ACCMODE) != O_RDONLY)
 333                         return -EACCES;
 334                 if (!capable(CAP_SYS_ADMIN))
 335                         return -EPERM;
 336                 return seq_open(filp, &ima_policy_seqops);
 337 #endif
 338         }
 339         if (test_and_set_bit(IMA_FS_BUSY, &ima_fs_flags))
 340                 return -EBUSY;
 341         return 0;
 342 }
 343
 344 /*
 345  * ima_release_policy - start using the new measure policy rules.
 346  *
 347  * Initially, ima_measure points to the default policy rules, now
 348  * point to the new policy rules, and remove the securityfs policy file,
 349  * assuming a valid policy.
 350  */
 351 static int ima_release_policy(struct inode *inode, struct file *file)
 352 {
 353         const char *cause = valid_policy ? "completed" : "failed";
 354
 355         if ((file->f_flags & O_ACCMODE) == O_RDONLY)
 356                 return 0;
 357
 358         if (valid_policy && ima_check_policy() < 0) {
 359                 cause = "failed";
 360                 valid_policy = 0;
 361         }
 362
 363         pr_info("IMA: policy update %s\n", cause);
 364         integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
 365                             "policy_update", cause, !valid_policy, 0);
 366
 367         if (!valid_policy) {
 368                 ima_delete_rules();
 369                 valid_policy = 1;
 370                 clear_bit(IMA_FS_BUSY, &ima_fs_flags);
 371                 return 0;
 372         }
 373
 374         ima_update_policy();
 375 #ifndef CONFIG_IMA_WRITE_POLICY
 376         securityfs_remove(ima_policy);
 377         ima_policy = NULL;
 378 #else
 379         clear_bit(IMA_FS_BUSY, &ima_fs_flags);
 380 #endif
 381         return 0;
 382 }
 383
 384 static const struct file_operations ima_measure_policy_ops = {
 385         .open = ima_open_policy,
 386         .write = ima_write_policy,
 387         .read = seq_read,
 388         .release = ima_release_policy,
 389         .llseek = generic_file_llseek,
 390 };
 391
 392 int __init ima_fs_init(void)
 393 {
 394         ima_dir = securityfs_create_dir("ima", NULL);
 395         if (IS_ERR(ima_dir))
 396                 return -1;
 397
 398         binary_runtime_measurements =
 399             securityfs_create_file("binary_runtime_measurements",
 400                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 401                                    &ima_measurements_ops);
 402         if (IS_ERR(binary_runtime_measurements))
 403                 goto out;
 404
 405         ascii_runtime_measurements =
 406             securityfs_create_file("ascii_runtime_measurements",
 407                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 408                                    &ima_ascii_measurements_ops);
 409         if (IS_ERR(ascii_runtime_measurements))
 410                 goto out;
 411
 412         runtime_measurements_count =
 413             securityfs_create_file("runtime_measurements_count",
 414                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 415                                    &ima_measurements_count_ops);
 416         if (IS_ERR(runtime_measurements_count))
 417                 goto out;
 418
 419         violations =
 420             securityfs_create_file("violations", S_IRUSR | S_IRGRP,
 421                                    ima_dir, NULL, &ima_htable_violations_ops);
 422         if (IS_ERR(violations))
 423                 goto out;
 424
 425         ima_policy = securityfs_create_file("policy", POLICY_FILE_FLAGS,
 426                                             ima_dir, NULL,
 427                                             &ima_measure_policy_ops);
 428         if (IS_ERR(ima_policy))
 429                 goto out;
 430
 431         return 0;
 432 out:
 433         securityfs_remove(violations);
 434         securityfs_remove(runtime_measurements_count);
 435         securityfs_remove(ascii_runtime_measurements);
 436         securityfs_remove(binary_runtime_measurements);
 437         securityfs_remove(ima_dir);
 438         securityfs_remove(ima_policy);
 439         return -1;
 440 }