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/module.h>
  20 #include <linux/seq_file.h>
  21 #include <linux/rculist.h>
  22 #include <linux/rcupdate.h>
  23 #include <linux/parser.h>
  24
  25 #include "ima.h"
  26
  27 static int valid_policy = 1;
  28 #define TMPBUFLEN 12
  29 static ssize_t ima_show_htable_value(char __user *buf, size_t count,
  30                                      loff_t *ppos, atomic_long_t *val)
  31 {
  32         char tmpbuf[TMPBUFLEN];
  33         ssize_t len;
  34
  35         len = scnprintf(tmpbuf, TMPBUFLEN, "%li\n", atomic_long_read(val));
  36         return simple_read_from_buffer(buf, count, ppos, tmpbuf, len);
  37 }
  38
  39 static ssize_t ima_show_htable_violations(struct file *filp,
  40                                           char __user *buf,
  41                                           size_t count, loff_t *ppos)
  42 {
  43         return ima_show_htable_value(buf, count, ppos, &ima_htable.violations);
  44 }
  45
  46 static struct file_operations ima_htable_violations_ops = {
  47         .read = ima_show_htable_violations
  48 };
  49
  50 static ssize_t ima_show_measurements_count(struct file *filp,
  51                                            char __user *buf,
  52                                            size_t count, loff_t *ppos)
  53 {
  54         return ima_show_htable_value(buf, count, ppos, &ima_htable.len);
  55
  56 }
  57
  58 static struct file_operations ima_measurements_count_ops = {
  59         .read = ima_show_measurements_count
  60 };
  61
  62 /* returns pointer to hlist_node */
  63 static void *ima_measurements_start(struct seq_file *m, loff_t *pos)
  64 {
  65         loff_t l = *pos;
  66         struct ima_queue_entry *qe;
  67
  68         /* we need a lock since pos could point beyond last element */
  69         rcu_read_lock();
  70         list_for_each_entry_rcu(qe, &ima_measurements, later) {
  71                 if (!l--) {
  72                         rcu_read_unlock();
  73                         return qe;
  74                 }
  75         }
  76         rcu_read_unlock();
  77         return NULL;
  78 }
  79
  80 static void *ima_measurements_next(struct seq_file *m, void *v, loff_t *pos)
  81 {
  82         struct ima_queue_entry *qe = v;
  83
  84         /* lock protects when reading beyond last element
  85          * against concurrent list-extension
  86          */
  87         rcu_read_lock();
  88         qe = list_entry_rcu(qe->later.next,
  89                             struct ima_queue_entry, later);
  90         rcu_read_unlock();
  91         (*pos)++;
  92
  93         return (&qe->later == &ima_measurements) ? NULL : qe;
  94 }
  95
  96 static void ima_measurements_stop(struct seq_file *m, void *v)
  97 {
  98 }
  99
 100 static void ima_putc(struct seq_file *m, void *data, int datalen)
 101 {
 102         while (datalen--)
 103                 seq_putc(m, *(char *)data++);
 104 }
 105
 106 /* print format:
 107  *       32bit-le=pcr#
 108  *       char[20]=template digest
 109  *       32bit-le=template name size
 110  *       char[n]=template name
 111  *       eventdata[n]=template specific data
 112  */
 113 static int ima_measurements_show(struct seq_file *m, void *v)
 114 {
 115         /* the list never shrinks, so we don't need a lock here */
 116         struct ima_queue_entry *qe = v;
 117         struct ima_template_entry *e;
 118         int namelen;
 119         u32 pcr = CONFIG_IMA_MEASURE_PCR_IDX;
 120
 121         /* get entry */
 122         e = qe->entry;
 123         if (e == NULL)
 124                 return -1;
 125
 126         /*
 127          * 1st: PCRIndex
 128          * PCR used is always the same (config option) in
 129          * little-endian format
 130          */
 131         ima_putc(m, &pcr, sizeof pcr);
 132
 133         /* 2nd: template digest */
 134         ima_putc(m, e->digest, IMA_DIGEST_SIZE);
 135
 136         /* 3rd: template name size */
 137         namelen = strlen(e->template_name);
 138         ima_putc(m, &namelen, sizeof namelen);
 139
 140         /* 4th:  template name */
 141         ima_putc(m, (void *)e->template_name, namelen);
 142
 143         /* 5th:  template specific data */
 144         ima_template_show(m, (struct ima_template_data *)&e->template,
 145                           IMA_SHOW_BINARY);
 146         return 0;
 147 }
 148
 149 static const struct seq_operations ima_measurments_seqops = {
 150         .start = ima_measurements_start,
 151         .next = ima_measurements_next,
 152         .stop = ima_measurements_stop,
 153         .show = ima_measurements_show
 154 };
 155
 156 static int ima_measurements_open(struct inode *inode, struct file *file)
 157 {
 158         return seq_open(file, &ima_measurments_seqops);
 159 }
 160
 161 static struct file_operations ima_measurements_ops = {
 162         .open = ima_measurements_open,
 163         .read = seq_read,
 164         .llseek = seq_lseek,
 165         .release = seq_release,
 166 };
 167
 168 static void ima_print_digest(struct seq_file *m, u8 *digest)
 169 {
 170         int i;
 171
 172         for (i = 0; i < IMA_DIGEST_SIZE; i++)
 173                 seq_printf(m, "%02x", *(digest + i));
 174 }
 175
 176 void ima_template_show(struct seq_file *m, void *e, enum ima_show_type show)
 177 {
 178         struct ima_template_data *entry = e;
 179         int namelen;
 180
 181         switch (show) {
 182         case IMA_SHOW_ASCII:
 183                 ima_print_digest(m, entry->digest);
 184                 seq_printf(m, " %s\n", entry->file_name);
 185                 break;
 186         case IMA_SHOW_BINARY:
 187                 ima_putc(m, entry->digest, IMA_DIGEST_SIZE);
 188
 189                 namelen = strlen(entry->file_name);
 190                 ima_putc(m, &namelen, sizeof namelen);
 191                 ima_putc(m, entry->file_name, namelen);
 192         default:
 193                 break;
 194         }
 195 }
 196
 197 /* print in ascii */
 198 static int ima_ascii_measurements_show(struct seq_file *m, void *v)
 199 {
 200         /* the list never shrinks, so we don't need a lock here */
 201         struct ima_queue_entry *qe = v;
 202         struct ima_template_entry *e;
 203
 204         /* get entry */
 205         e = qe->entry;
 206         if (e == NULL)
 207                 return -1;
 208
 209         /* 1st: PCR used (config option) */
 210         seq_printf(m, "%2d ", CONFIG_IMA_MEASURE_PCR_IDX);
 211
 212         /* 2nd: SHA1 template hash */
 213         ima_print_digest(m, e->digest);
 214
 215         /* 3th:  template name */
 216         seq_printf(m, " %s ", e->template_name);
 217
 218         /* 4th:  template specific data */
 219         ima_template_show(m, (struct ima_template_data *)&e->template,
 220                           IMA_SHOW_ASCII);
 221         return 0;
 222 }
 223
 224 static const struct seq_operations ima_ascii_measurements_seqops = {
 225         .start = ima_measurements_start,
 226         .next = ima_measurements_next,
 227         .stop = ima_measurements_stop,
 228         .show = ima_ascii_measurements_show
 229 };
 230
 231 static int ima_ascii_measurements_open(struct inode *inode, struct file *file)
 232 {
 233         return seq_open(file, &ima_ascii_measurements_seqops);
 234 }
 235
 236 static struct file_operations ima_ascii_measurements_ops = {
 237         .open = ima_ascii_measurements_open,
 238         .read = seq_read,
 239         .llseek = seq_lseek,
 240         .release = seq_release,
 241 };
 242
 243 static ssize_t ima_write_policy(struct file *file, const char __user *buf,
 244                                 size_t datalen, loff_t *ppos)
 245 {
 246         char *data;
 247         int rc;
 248
 249         if (datalen >= PAGE_SIZE)
 250                 return -ENOMEM;
 251         if (*ppos != 0) {
 252                 /* No partial writes. */
 253                 return -EINVAL;
 254         }
 255         data = kmalloc(datalen + 1, GFP_KERNEL);
 256         if (!data)
 257                 return -ENOMEM;
 258
 259         if (copy_from_user(data, buf, datalen)) {
 260                 kfree(data);
 261                 return -EFAULT;
 262         }
 263         *(data + datalen) = '\0';
 264         rc = ima_parse_add_rule(data);
 265         if (rc < 0) {
 266                 datalen = -EINVAL;
 267                 valid_policy = 0;
 268         }
 269
 270         kfree(data);
 271         return datalen;
 272 }
 273
 274 static struct dentry *ima_dir;
 275 static struct dentry *binary_runtime_measurements;
 276 static struct dentry *ascii_runtime_measurements;
 277 static struct dentry *runtime_measurements_count;
 278 static struct dentry *violations;
 279 static struct dentry *ima_policy;
 280
 281 static atomic_t policy_opencount = ATOMIC_INIT(1);
 282 /*
 283  * ima_open_policy: sequentialize access to the policy file
 284  */
 285 int ima_open_policy(struct inode * inode, struct file * filp)
 286 {
 287         /* No point in being allowed to open it if you aren't going to write */
 288         if (!(filp->f_flags & O_WRONLY))
 289                 return -EACCES;
 290         if (atomic_dec_and_test(&policy_opencount))
 291                 return 0;
 292         return -EBUSY;
 293 }
 294
 295 /*
 296  * ima_release_policy - start using the new measure policy rules.
 297  *
 298  * Initially, ima_measure points to the default policy rules, now
 299  * point to the new policy rules, and remove the securityfs policy file,
 300  * assuming a valid policy.
 301  */
 302 static int ima_release_policy(struct inode *inode, struct file *file)
 303 {
 304         if (!valid_policy) {
 305                 ima_delete_rules();
 306                 valid_policy = 1;
 307                 atomic_set(&policy_opencount, 1);
 308                 return 0;
 309         }
 310         ima_update_policy();
 311         securityfs_remove(ima_policy);
 312         ima_policy = NULL;
 313         return 0;
 314 }
 315
 316 static struct file_operations ima_measure_policy_ops = {
 317         .open = ima_open_policy,
 318         .write = ima_write_policy,
 319         .release = ima_release_policy
 320 };
 321
 322 int __init ima_fs_init(void)
 323 {
 324         ima_dir = securityfs_create_dir("ima", NULL);
 325         if (IS_ERR(ima_dir))
 326                 return -1;
 327
 328         binary_runtime_measurements =
 329             securityfs_create_file("binary_runtime_measurements",
 330                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 331                                    &ima_measurements_ops);
 332         if (IS_ERR(binary_runtime_measurements))
 333                 goto out;
 334
 335         ascii_runtime_measurements =
 336             securityfs_create_file("ascii_runtime_measurements",
 337                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 338                                    &ima_ascii_measurements_ops);
 339         if (IS_ERR(ascii_runtime_measurements))
 340                 goto out;
 341
 342         runtime_measurements_count =
 343             securityfs_create_file("runtime_measurements_count",
 344                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 345                                    &ima_measurements_count_ops);
 346         if (IS_ERR(runtime_measurements_count))
 347                 goto out;
 348
 349         violations =
 350             securityfs_create_file("violations", S_IRUSR | S_IRGRP,
 351                                    ima_dir, NULL, &ima_htable_violations_ops);
 352         if (IS_ERR(violations))
 353                 goto out;
 354
 355         ima_policy = securityfs_create_file("policy",
 356                                             S_IWUSR,
 357                                             ima_dir, NULL,
 358                                             &ima_measure_policy_ops);
 359         if (IS_ERR(ima_policy))
 360                 goto out;
 361
 362         return 0;
 363 out:
 364         securityfs_remove(runtime_measurements_count);
 365         securityfs_remove(ascii_runtime_measurements);
 366         securityfs_remove(binary_runtime_measurements);
 367         securityfs_remove(ima_dir);
 368         securityfs_remove(ima_policy);
 369         return -1;
 370 }
 371
 372 void __exit ima_fs_cleanup(void)
 373 {
 374         securityfs_remove(violations);
 375         securityfs_remove(runtime_measurements_count);
 376         securityfs_remove(ascii_runtime_measurements);
 377         securityfs_remove(binary_runtime_measurements);
 378         securityfs_remove(ima_dir);
 379         securityfs_remove(ima_policy);
 380 }