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