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 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 length]
 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         char *template_name;
 122         int namelen;
 123         u32 pcr = CONFIG_IMA_MEASURE_PCR_IDX;
 124         bool is_ima_template = false;
 125         int i;
 126
 127         /* get entry */
 128         e = qe->entry;
 129         if (e == NULL)
 130                 return -1;
 131
 132         template_name = (e->template_desc->name[0] != '\0') ?
 133             e->template_desc->name : e->template_desc->fmt;
 134
 135         /*
 136          * 1st: PCRIndex
 137          * PCR used is always the same (config option) in
 138          * little-endian format
 139          */
 140         ima_putc(m, &pcr, sizeof(pcr));
 141
 142         /* 2nd: template digest */
 143         ima_putc(m, e->digest, TPM_DIGEST_SIZE);
 144
 145         /* 3rd: template name size */
 146         namelen = strlen(template_name);
 147         ima_putc(m, &namelen, sizeof(namelen));
 148
 149         /* 4th:  template name */
 150         ima_putc(m, template_name, namelen);
 151
 152         /* 5th:  template length (except for 'ima' template) */
 153         if (strcmp(template_name, IMA_TEMPLATE_IMA_NAME) == 0)
 154                 is_ima_template = true;
 155
 156         if (!is_ima_template)
 157                 ima_putc(m, &e->template_data_len,
 158                          sizeof(e->template_data_len));
 159
 160         /* 6th:  template specific data */
 161         for (i = 0; i < e->template_desc->num_fields; i++) {
 162                 enum ima_show_type show = IMA_SHOW_BINARY;
 163                 struct ima_template_field *field = e->template_desc->fields[i];
 164
 165                 if (is_ima_template && strcmp(field->field_id, "d") == 0)
 166                         show = IMA_SHOW_BINARY_NO_FIELD_LEN;
 167                 if (is_ima_template && strcmp(field->field_id, "n") == 0)
 168                         show = IMA_SHOW_BINARY_OLD_STRING_FMT;
 169                 field->field_show(m, show, &e->template_data[i]);
 170         }
 171         return 0;
 172 }
 173
 174 static const struct seq_operations ima_measurments_seqops = {
 175         .start = ima_measurements_start,
 176         .next = ima_measurements_next,
 177         .stop = ima_measurements_stop,
 178         .show = ima_measurements_show
 179 };
 180
 181 static int ima_measurements_open(struct inode *inode, struct file *file)
 182 {
 183         return seq_open(file, &ima_measurments_seqops);
 184 }
 185
 186 static const struct file_operations ima_measurements_ops = {
 187         .open = ima_measurements_open,
 188         .read = seq_read,
 189         .llseek = seq_lseek,
 190         .release = seq_release,
 191 };
 192
 193 void ima_print_digest(struct seq_file *m, u8 *digest, u32 size)
 194 {
 195         u32 i;
 196
 197         for (i = 0; i < size; i++)
 198                 seq_printf(m, "%02x", *(digest + i));
 199 }
 200
 201 /* print in ascii */
 202 static int ima_ascii_measurements_show(struct seq_file *m, void *v)
 203 {
 204         /* the list never shrinks, so we don't need a lock here */
 205         struct ima_queue_entry *qe = v;
 206         struct ima_template_entry *e;
 207         char *template_name;
 208         int i;
 209
 210         /* get entry */
 211         e = qe->entry;
 212         if (e == NULL)
 213                 return -1;
 214
 215         template_name = (e->template_desc->name[0] != '\0') ?
 216             e->template_desc->name : e->template_desc->fmt;
 217
 218         /* 1st: PCR used (config option) */
 219         seq_printf(m, "%2d ", CONFIG_IMA_MEASURE_PCR_IDX);
 220
 221         /* 2nd: SHA1 template hash */
 222         ima_print_digest(m, e->digest, TPM_DIGEST_SIZE);
 223
 224         /* 3th:  template name */
 225         seq_printf(m, " %s", template_name);
 226
 227         /* 4th:  template specific data */
 228         for (i = 0; i < e->template_desc->num_fields; i++) {
 229                 seq_puts(m, " ");
 230                 if (e->template_data[i].len == 0)
 231                         continue;
 232
 233                 e->template_desc->fields[i]->field_show(m, IMA_SHOW_ASCII,
 234                                                         &e->template_data[i]);
 235         }
 236         seq_puts(m, "\n");
 237         return 0;
 238 }
 239
 240 static const struct seq_operations ima_ascii_measurements_seqops = {
 241         .start = ima_measurements_start,
 242         .next = ima_measurements_next,
 243         .stop = ima_measurements_stop,
 244         .show = ima_ascii_measurements_show
 245 };
 246
 247 static int ima_ascii_measurements_open(struct inode *inode, struct file *file)
 248 {
 249         return seq_open(file, &ima_ascii_measurements_seqops);
 250 }
 251
 252 static const struct file_operations ima_ascii_measurements_ops = {
 253         .open = ima_ascii_measurements_open,
 254         .read = seq_read,
 255         .llseek = seq_lseek,
 256         .release = seq_release,
 257 };
 258
 259 static ssize_t ima_write_policy(struct file *file, const char __user *buf,
 260                                 size_t datalen, loff_t *ppos)
 261 {
 262         char *data = NULL;
 263         ssize_t result;
 264
 265         if (datalen >= PAGE_SIZE)
 266                 datalen = PAGE_SIZE - 1;
 267
 268         /* No partial writes. */
 269         result = -EINVAL;
 270         if (*ppos != 0)
 271                 goto out;
 272
 273         result = -ENOMEM;
 274         data = kmalloc(datalen + 1, GFP_KERNEL);
 275         if (!data)
 276                 goto out;
 277
 278         *(data + datalen) = '\0';
 279
 280         result = -EFAULT;
 281         if (copy_from_user(data, buf, datalen))
 282                 goto out;
 283
 284         result = ima_parse_add_rule(data);
 285 out:
 286         if (result < 0)
 287                 valid_policy = 0;
 288         kfree(data);
 289         return result;
 290 }
 291
 292 static struct dentry *ima_dir;
 293 static struct dentry *binary_runtime_measurements;
 294 static struct dentry *ascii_runtime_measurements;
 295 static struct dentry *runtime_measurements_count;
 296 static struct dentry *violations;
 297 static struct dentry *ima_policy;
 298
 299 enum ima_fs_flags {
 300         IMA_FS_BUSY,
 301 };
 302
 303 static unsigned long ima_fs_flags;
 304
 305 /*
 306  * ima_open_policy: sequentialize access to the policy file
 307  */
 308 static int ima_open_policy(struct inode *inode, struct file *filp)
 309 {
 310         /* No point in being allowed to open it if you aren't going to write */
 311         if (!(filp->f_flags & O_WRONLY))
 312                 return -EACCES;
 313         if (test_and_set_bit(IMA_FS_BUSY, &ima_fs_flags))
 314                 return -EBUSY;
 315         return 0;
 316 }
 317
 318 /*
 319  * ima_release_policy - start using the new measure policy rules.
 320  *
 321  * Initially, ima_measure points to the default policy rules, now
 322  * point to the new policy rules, and remove the securityfs policy file,
 323  * assuming a valid policy.
 324  */
 325 static int ima_release_policy(struct inode *inode, struct file *file)
 326 {
 327         const char *cause = valid_policy ? "completed" : "failed";
 328
 329         pr_info("IMA: policy update %s\n", cause);
 330         integrity_audit_msg(AUDIT_INTEGRITY_STATUS, NULL, NULL,
 331                             "policy_update", cause, !valid_policy, 0);
 332
 333         if (!valid_policy) {
 334                 ima_delete_rules();
 335                 valid_policy = 1;
 336                 clear_bit(IMA_FS_BUSY, &ima_fs_flags);
 337                 return 0;
 338         }
 339         ima_update_policy();
 340         securityfs_remove(ima_policy);
 341         ima_policy = NULL;
 342         return 0;
 343 }
 344
 345 static const struct file_operations ima_measure_policy_ops = {
 346         .open = ima_open_policy,
 347         .write = ima_write_policy,
 348         .release = ima_release_policy,
 349         .llseek = generic_file_llseek,
 350 };
 351
 352 int __init ima_fs_init(void)
 353 {
 354         ima_dir = securityfs_create_dir("ima", NULL);
 355         if (IS_ERR(ima_dir))
 356                 return -1;
 357
 358         binary_runtime_measurements =
 359             securityfs_create_file("binary_runtime_measurements",
 360                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 361                                    &ima_measurements_ops);
 362         if (IS_ERR(binary_runtime_measurements))
 363                 goto out;
 364
 365         ascii_runtime_measurements =
 366             securityfs_create_file("ascii_runtime_measurements",
 367                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 368                                    &ima_ascii_measurements_ops);
 369         if (IS_ERR(ascii_runtime_measurements))
 370                 goto out;
 371
 372         runtime_measurements_count =
 373             securityfs_create_file("runtime_measurements_count",
 374                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 375                                    &ima_measurements_count_ops);
 376         if (IS_ERR(runtime_measurements_count))
 377                 goto out;
 378
 379         violations =
 380             securityfs_create_file("violations", S_IRUSR | S_IRGRP,
 381                                    ima_dir, NULL, &ima_htable_violations_ops);
 382         if (IS_ERR(violations))
 383                 goto out;
 384
 385         ima_policy = securityfs_create_file("policy",
 386                                             S_IWUSR,
 387                                             ima_dir, NULL,
 388                                             &ima_measure_policy_ops);
 389         if (IS_ERR(ima_policy))
 390                 goto out;
 391
 392         return 0;
 393 out:
 394         securityfs_remove(violations);
 395         securityfs_remove(runtime_measurements_count);
 396         securityfs_remove(ascii_runtime_measurements);
 397         securityfs_remove(binary_runtime_measurements);
 398         securityfs_remove(ima_dir);
 399         securityfs_remove(ima_policy);
 400         return -1;
 401 }