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         int namelen;
 122         u32 pcr = CONFIG_IMA_MEASURE_PCR_IDX;
 123         bool is_ima_template = false;
 124         int i;
 125
 126         /* get entry */
 127         e = qe->entry;
 128         if (e == NULL)
 129                 return -1;
 130
 131         /*
 132          * 1st: PCRIndex
 133          * PCR used is always the same (config option) in
 134          * little-endian format
 135          */
 136         ima_putc(m, &pcr, sizeof(pcr));
 137
 138         /* 2nd: template digest */
 139         ima_putc(m, e->digest, TPM_DIGEST_SIZE);
 140
 141         /* 3rd: template name size */
 142         namelen = strlen(e->template_desc->name);
 143         ima_putc(m, &namelen, sizeof(namelen));
 144
 145         /* 4th:  template name */
 146         ima_putc(m, e->template_desc->name, namelen);
 147
 148         /* 5th:  template length (except for 'ima' template) */
 149         if (strcmp(e->template_desc->name, IMA_TEMPLATE_IMA_NAME) == 0)
 150                 is_ima_template = true;
 151
 152         if (!is_ima_template)
 153                 ima_putc(m, &e->template_data_len,
 154                          sizeof(e->template_data_len));
 155
 156         /* 6th:  template specific data */
 157         for (i = 0; i < e->template_desc->num_fields; i++) {
 158                 enum ima_show_type show = IMA_SHOW_BINARY;
 159                 struct ima_template_field *field = e->template_desc->fields[i];
 160
 161                 if (is_ima_template && strcmp(field->field_id, "d") == 0)
 162                         show = IMA_SHOW_BINARY_NO_FIELD_LEN;
 163                 if (is_ima_template && strcmp(field->field_id, "n") == 0)
 164                         show = IMA_SHOW_BINARY_OLD_STRING_FMT;
 165                 field->field_show(m, show, &e->template_data[i]);
 166         }
 167         return 0;
 168 }
 169
 170 static const struct seq_operations ima_measurments_seqops = {
 171         .start = ima_measurements_start,
 172         .next = ima_measurements_next,
 173         .stop = ima_measurements_stop,
 174         .show = ima_measurements_show
 175 };
 176
 177 static int ima_measurements_open(struct inode *inode, struct file *file)
 178 {
 179         return seq_open(file, &ima_measurments_seqops);
 180 }
 181
 182 static const struct file_operations ima_measurements_ops = {
 183         .open = ima_measurements_open,
 184         .read = seq_read,
 185         .llseek = seq_lseek,
 186         .release = seq_release,
 187 };
 188
 189 void ima_print_digest(struct seq_file *m, u8 *digest, int size)
 190 {
 191         int i;
 192
 193         for (i = 0; i < size; i++)
 194                 seq_printf(m, "%02x", *(digest + i));
 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         int i;
 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, TPM_DIGEST_SIZE);
 215
 216         /* 3th:  template name */
 217         seq_printf(m, " %s", e->template_desc->name);
 218
 219         /* 4th:  template specific data */
 220         for (i = 0; i < e->template_desc->num_fields; i++) {
 221                 seq_puts(m, " ");
 222                 if (e->template_data[i].len == 0)
 223                         continue;
 224
 225                 e->template_desc->fields[i]->field_show(m, IMA_SHOW_ASCII,
 226                                                         &e->template_data[i]);
 227         }
 228         seq_puts(m, "\n");
 229         return 0;
 230 }
 231
 232 static const struct seq_operations ima_ascii_measurements_seqops = {
 233         .start = ima_measurements_start,
 234         .next = ima_measurements_next,
 235         .stop = ima_measurements_stop,
 236         .show = ima_ascii_measurements_show
 237 };
 238
 239 static int ima_ascii_measurements_open(struct inode *inode, struct file *file)
 240 {
 241         return seq_open(file, &ima_ascii_measurements_seqops);
 242 }
 243
 244 static const struct file_operations ima_ascii_measurements_ops = {
 245         .open = ima_ascii_measurements_open,
 246         .read = seq_read,
 247         .llseek = seq_lseek,
 248         .release = seq_release,
 249 };
 250
 251 static ssize_t ima_write_policy(struct file *file, const char __user *buf,
 252                                 size_t datalen, loff_t *ppos)
 253 {
 254         char *data = NULL;
 255         ssize_t result;
 256
 257         if (datalen >= PAGE_SIZE)
 258                 datalen = PAGE_SIZE - 1;
 259
 260         /* No partial writes. */
 261         result = -EINVAL;
 262         if (*ppos != 0)
 263                 goto out;
 264
 265         result = -ENOMEM;
 266         data = kmalloc(datalen + 1, GFP_KERNEL);
 267         if (!data)
 268                 goto out;
 269
 270         *(data + datalen) = '\0';
 271
 272         result = -EFAULT;
 273         if (copy_from_user(data, buf, datalen))
 274                 goto out;
 275
 276         result = ima_parse_add_rule(data);
 277 out:
 278         if (result < 0)
 279                 valid_policy = 0;
 280         kfree(data);
 281         return result;
 282 }
 283
 284 static struct dentry *ima_dir;
 285 static struct dentry *binary_runtime_measurements;
 286 static struct dentry *ascii_runtime_measurements;
 287 static struct dentry *runtime_measurements_count;
 288 static struct dentry *violations;
 289 static struct dentry *ima_policy;
 290
 291 static atomic_t policy_opencount = ATOMIC_INIT(1);
 292 /*
 293  * ima_open_policy: sequentialize access to the policy file
 294  */
 295 static int ima_open_policy(struct inode *inode, struct file *filp)
 296 {
 297         /* No point in being allowed to open it if you aren't going to write */
 298         if (!(filp->f_flags & O_WRONLY))
 299                 return -EACCES;
 300         if (atomic_dec_and_test(&policy_opencount))
 301                 return 0;
 302         return -EBUSY;
 303 }
 304
 305 /*
 306  * ima_release_policy - start using the new measure policy rules.
 307  *
 308  * Initially, ima_measure points to the default policy rules, now
 309  * point to the new policy rules, and remove the securityfs policy file,
 310  * assuming a valid policy.
 311  */
 312 static int ima_release_policy(struct inode *inode, struct file *file)
 313 {
 314         if (!valid_policy) {
 315                 ima_delete_rules();
 316                 valid_policy = 1;
 317                 atomic_set(&policy_opencount, 1);
 318                 return 0;
 319         }
 320         ima_update_policy();
 321         securityfs_remove(ima_policy);
 322         ima_policy = NULL;
 323         return 0;
 324 }
 325
 326 static const struct file_operations ima_measure_policy_ops = {
 327         .open = ima_open_policy,
 328         .write = ima_write_policy,
 329         .release = ima_release_policy,
 330         .llseek = generic_file_llseek,
 331 };
 332
 333 int __init ima_fs_init(void)
 334 {
 335         ima_dir = securityfs_create_dir("ima", NULL);
 336         if (IS_ERR(ima_dir))
 337                 return -1;
 338
 339         binary_runtime_measurements =
 340             securityfs_create_file("binary_runtime_measurements",
 341                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 342                                    &ima_measurements_ops);
 343         if (IS_ERR(binary_runtime_measurements))
 344                 goto out;
 345
 346         ascii_runtime_measurements =
 347             securityfs_create_file("ascii_runtime_measurements",
 348                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 349                                    &ima_ascii_measurements_ops);
 350         if (IS_ERR(ascii_runtime_measurements))
 351                 goto out;
 352
 353         runtime_measurements_count =
 354             securityfs_create_file("runtime_measurements_count",
 355                                    S_IRUSR | S_IRGRP, ima_dir, NULL,
 356                                    &ima_measurements_count_ops);
 357         if (IS_ERR(runtime_measurements_count))
 358                 goto out;
 359
 360         violations =
 361             securityfs_create_file("violations", S_IRUSR | S_IRGRP,
 362                                    ima_dir, NULL, &ima_htable_violations_ops);
 363         if (IS_ERR(violations))
 364                 goto out;
 365
 366         ima_policy = securityfs_create_file("policy",
 367                                             S_IWUSR,
 368                                             ima_dir, NULL,
 369                                             &ima_measure_policy_ops);
 370         if (IS_ERR(ima_policy))
 371                 goto out;
 372
 373         return 0;
 374 out:
 375         securityfs_remove(violations);
 376         securityfs_remove(runtime_measurements_count);
 377         securityfs_remove(ascii_runtime_measurements);
 378         securityfs_remove(binary_runtime_measurements);
 379         securityfs_remove(ima_dir);
 380         securityfs_remove(ima_policy);
 381         return -1;
 382 }