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