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 int valid_policy = 1;
  29 #define TMPBUFLEN 12
  30 static ssize_t ima_show_htable_value(char __user *buf, size_t count,
  31                                      loff_t *ppos, atomic_long_t *val)
  32 {
  33         char tmpbuf[TMPBUFLEN];
  34         ssize_t len;
  35
  36         len = scnprintf(tmpbuf, TMPBUFLEN, "%li\n", atomic_long_read(val));
  37         return simple_read_from_buffer(buf, count, ppos, tmpbuf, len);
  38 }
  39
  40 static ssize_t ima_show_htable_violations(struct file *filp,
  41                                           char __user *buf,
  42                                           size_t count, loff_t *ppos)
  43 {
  44         return ima_show_htable_value(buf, count, ppos, &ima_htable.violations);
  45 }
  46
  47 static const struct file_operations ima_htable_violations_ops = {
  48         .read = ima_show_htable_violations
  49 };
  50
  51 static ssize_t ima_show_measurements_count(struct file *filp,
  52                                            char __user *buf,
  53                                            size_t count, loff_t *ppos)
  54 {
  55         return ima_show_htable_value(buf, count, ppos, &ima_htable.len);
  56
  57 }
  58
  59 static const struct file_operations ima_measurements_count_ops = {
  60         .read = ima_show_measurements_count
  61 };
  62
  63 /* returns pointer to hlist_node */
  64 static void *ima_measurements_start(struct seq_file *m, loff_t *pos)
  65 {
  66         loff_t l = *pos;
  67         struct ima_queue_entry *qe;
  68
  69         /* we need a lock since pos could point beyond last element */
  70         rcu_read_lock();
  71         list_for_each_entry_rcu(qe, &ima_measurements, later) {
  72                 if (!l--) {
  73                         rcu_read_unlock();
  74                         return qe;
  75                 }
  76         }
  77         rcu_read_unlock();
  78         return NULL;
  79 }
  80
  81 static void *ima_measurements_next(struct seq_file *m, void *v, loff_t *pos)
  82 {
  83         struct ima_queue_entry *qe = v;
  84
  85         /* lock protects when reading beyond last element
  86          * against concurrent list-extension
  87          */
  88         rcu_read_lock();
  89         qe = list_entry_rcu(qe->later.next,
  90                             struct ima_queue_entry, later);
  91         rcu_read_unlock();
  92         (*pos)++;
  93
  94         return (&qe->later == &ima_measurements) ? NULL : qe;
  95 }
  96
  97 static void ima_measurements_stop(struct seq_file *m, void *v)
  98 {
  99 }
 100
 101 static void ima_putc(struct seq_file *m, void *data, int datalen)
 102 {
 103         while (datalen--)
 104                 seq_putc(m, *(char *)data++);
 105 }
 106
 107 /* print format:
 108  *       32bit-le=pcr#
 109  *       char[20]=template digest
 110  *       32bit-le=template name size
 111  *       char[n]=template name
 112  *       eventdata[n]=template specific data
 113  */
 114 static int ima_measurements_show(struct seq_file *m, void *v)
 115 {
 116         /* the list never shrinks, so we don't need a lock here */
 117         struct ima_queue_entry *qe = v;
 118         struct ima_template_entry *e;
 119         int namelen;
 120         u32 pcr = CONFIG_IMA_MEASURE_PCR_IDX;
 121
 122         /* get entry */
 123         e = qe->entry;
 124         if (e == NULL)
 125                 return -1;
 126
 127         /*
 128          * 1st: PCRIndex
 129          * PCR used is always the same (config option) in
 130          * little-endian format
 131          */
 132         ima_putc(m, &pcr, sizeof pcr);
 133
 134         /* 2nd: template digest */
 135         ima_putc(m, e->digest, IMA_DIGEST_SIZE);
 136
 137         /* 3rd: template name size */
 138         namelen = strlen(e->template_name);
 139         ima_putc(m, &namelen, sizeof namelen);
 140
 141         /* 4th:  template name */
 142         ima_putc(m, (void *)e->template_name, namelen);
 143
 144         /* 5th:  template specific data */
 145         ima_template_show(m, (struct ima_template_data *)&e->template,
 146                           IMA_SHOW_BINARY);
 147         return 0;
 148 }
 149
 150 static const struct seq_operations ima_measurments_seqops = {
 151         .start = ima_measurements_start,
 152         .next = ima_measurements_next,
 153         .stop = ima_measurements_stop,
 154         .show = ima_measurements_show
 155 };
 156
 157 static int ima_measurements_open(struct inode *inode, struct file *file)
 158 {
 159         return seq_open(file, &ima_measurments_seqops);
 160 }
 161
 162 static const struct file_operations ima_measurements_ops = {
 163         .open = ima_measurements_open,
 164         .read = seq_read,
 165         .llseek = seq_lseek,
 166         .release = seq_release,
 167 };
 168
 169 static void ima_print_digest(struct seq_file *m, u8 *digest)
 170 {
 171         int i;
 172
 173         for (i = 0; i < IMA_DIGEST_SIZE; i++)
 174                 seq_printf(m, "%02x", *(digest + i));
 175 }
 176
 177 void ima_template_show(struct seq_file *m, void *e, enum ima_show_type show)
 178 {
 179         struct ima_template_data *entry = e;
 180         int namelen;
 181
 182         switch (show) {
 183         case IMA_SHOW_ASCII:
 184                 ima_print_digest(m, entry->digest);
 185                 seq_printf(m, " %s\n", entry->file_name);
 186                 break;
 187         case IMA_SHOW_BINARY:
 188                 ima_putc(m, entry->digest, IMA_DIGEST_SIZE);
 189
 190                 namelen = strlen(entry->file_name);
 191                 ima_putc(m, &namelen, sizeof namelen);
 192                 ima_putc(m, entry->file_name, namelen);
 193         default:
 194                 break;
 195         }
 196 }
 197
 198 /* print in ascii */
 199 static int ima_ascii_measurements_show(struct seq_file *m, void *v)
 200 {
 201         /* the list never shrinks, so we don't need a lock here */
 202         struct ima_queue_entry *qe = v;
 203         struct ima_template_entry *e;
 204
 205         /* get entry */
 206         e = qe->entry;
 207         if (e == NULL)
 208                 return -1;
 209
 210         /* 1st: PCR used (config option) */
 211         seq_printf(m, "%2d ", CONFIG_IMA_MEASURE_PCR_IDX);
 212
 213         /* 2nd: SHA1 template hash */
 214         ima_print_digest(m, e->digest);
 215
 216         /* 3th:  template name */
 217         seq_printf(m, " %s ", e->template_name);
 218
 219         /* 4th:  template specific data */
 220         ima_template_show(m, (struct ima_template_data *)&e->template,
 221                           IMA_SHOW_ASCII);
 222         return 0;
 223 }
 224
 225 static const struct seq_operations ima_ascii_measurements_seqops = {
 226         .start = ima_measurements_start,
 227         .next = ima_measurements_next,
 228         .stop = ima_measurements_stop,
 229         .show = ima_ascii_measurements_show
 230 };
 231
 232 static int ima_ascii_measurements_open(struct inode *inode, struct file *file)
 233 {
 234         return seq_open(file, &ima_ascii_measurements_seqops);
 235 }
 236
 237 static const struct file_operations ima_ascii_measurements_ops = {
 238         .open = ima_ascii_measurements_open,
 239         .read = seq_read,
 240         .llseek = seq_lseek,
 241         .release = seq_release,
 242 };
 243
 244 static ssize_t ima_write_policy(struct file *file, const char __user *buf,
 245                                 size_t datalen, loff_t *ppos)
 246 {
 247         char *data = NULL;
 248         ssize_t result;
 249
 250         if (datalen >= PAGE_SIZE)
 251                 datalen = PAGE_SIZE - 1;
 252
 253         /* No partial writes. */
 254         result = -EINVAL;
 255         if (*ppos != 0)
 256                 goto out;
 257
 258         result = -ENOMEM;
 259         data = kmalloc(datalen + 1, GFP_KERNEL);
 260         if (!data)
 261                 goto out;
 262
 263         *(data + datalen) = '\0';
 264
 265         result = -EFAULT;
 266         if (copy_from_user(data, buf, datalen))
 267                 goto out;
 268
 269         result = ima_parse_add_rule(data);
 270 out:
 271         if (result < 0)
 272                 valid_policy = 0;
 273         kfree(data);
 274         return result;
 275 }
 276
 277 static struct dentry *ima_dir;
 278 static struct dentry *binary_runtime_measurements;
 279 static struct dentry *ascii_runtime_measurements;
 280 static struct dentry *runtime_measurements_count;
 281 static struct dentry *violations;
 282 static struct dentry *ima_policy;
 283
 284 static atomic_t policy_opencount = ATOMIC_INIT(1);
 285 /*
 286  * ima_open_policy: sequentialize access to the policy file
 287  */
 288 int ima_open_policy(struct inode * inode, struct file * filp)
 289 {
 290         /* No point in being allowed to open it if you aren't going to write */
 291         if (!(filp->f_flags & O_WRONLY))
 292                 return -EACCES;
 293         if (atomic_dec_and_test(&policy_opencount))
 294                 return 0;
 295         return -EBUSY;
 296 }
 297
 298 /*
 299  * ima_release_policy - start using the new measure policy rules.
 300  *
 301  * Initially, ima_measure points to the default policy rules, now
 302  * point to the new policy rules, and remove the securityfs policy file,
 303  * assuming a valid policy.
 304  */
 305 static int ima_release_policy(struct inode *inode, struct file *file)
 306 {
 307         if (!valid_policy) {
 308                 ima_delete_rules();
 309                 valid_policy = 1;
 310                 atomic_set(&policy_opencount, 1);
 311                 return 0;
 312         }
 313         ima_update_policy();
 314         securityfs_remove(ima_policy);
 315         ima_policy = NULL;
 316         return 0;
 317 }
 318
 319 static const struct file_operations ima_measure_policy_ops = {
 320         .open = ima_open_policy,
 321         .write = ima_write_policy,
 322         .release = ima_release_policy
 323 };
 324
 325 int __init ima_fs_init(void)
 326 {
 327         ima_dir = securityfs_create_dir("ima", NULL);
 328         if (IS_ERR(ima_dir))
 329                 return -1;
 330
 331         binary_runtime_measurements =
 332             securityfs_create_file("binary_runtime_measurements",
 333                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 334                                    &ima_measurements_ops);
 335         if (IS_ERR(binary_runtime_measurements))
 336                 goto out;
 337
 338         ascii_runtime_measurements =
 339             securityfs_create_file("ascii_runtime_measurements",
 340                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 341                                    &ima_ascii_measurements_ops);
 342         if (IS_ERR(ascii_runtime_measurements))
 343                 goto out;
 344
 345         runtime_measurements_count =
 346             securityfs_create_file("runtime_measurements_count",
 347                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 348                                    &ima_measurements_count_ops);
 349         if (IS_ERR(runtime_measurements_count))
 350                 goto out;
 351
 352         violations =
 353             securityfs_create_file("violations", S_IRUSR | S_IRGRP,
 354                                    ima_dir, NULL, &ima_htable_violations_ops);
 355         if (IS_ERR(violations))
 356                 goto out;
 357
 358         ima_policy = securityfs_create_file("policy",
 359                                             S_IWUSR,
 360                                             ima_dir, NULL,
 361                                             &ima_measure_policy_ops);
 362         if (IS_ERR(ima_policy))
 363                 goto out;
 364
 365         return 0;
 366 out:
 367         securityfs_remove(runtime_measurements_count);
 368         securityfs_remove(ascii_runtime_measurements);
 369         securityfs_remove(binary_runtime_measurements);
 370         securityfs_remove(ima_dir);
 371         securityfs_remove(ima_policy);
 372         return -1;
 373 }
 374
 375 void __exit ima_fs_cleanup(void)
 376 {
 377         securityfs_remove(violations);
 378         securityfs_remove(runtime_measurements_count);
 379         securityfs_remove(ascii_runtime_measurements);
 380         securityfs_remove(binary_runtime_measurements);
 381         securityfs_remove(ima_dir);
 382         securityfs_remove(ima_policy);
 383 }