security/integrity/ima/ima_api.c

   1 /*
   2  * Copyright (C) 2008 IBM Corporation
   3  *
   4  * Author: Mimi Zohar <zohar@us.ibm.com>
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License as
   8  * published by the Free Software Foundation, version 2 of the
   9  * License.
  10  *
  11  * File: ima_api.c
  12  *      Implements must_appraise_or_measure, collect_measurement,
  13  *      appraise_measurement, store_measurement and store_template.
  14  */
  15 #include <linux/module.h>
  16 #include <linux/slab.h>
  17 #include <linux/file.h>
  18 #include <linux/fs.h>
  19 #include <linux/xattr.h>
  20 #include <linux/evm.h>
  21 #include <linux/iversion.h>
  22
  23 #include "ima.h"
  24
  25 /*
  26  * ima_free_template_entry - free an existing template entry
  27  */
  28 void ima_free_template_entry(struct ima_template_entry *entry)
  29 {
  30         int i;
  31
  32         for (i = 0; i < entry->template_desc->num_fields; i++)
  33                 kfree(entry->template_data[i].data);
  34
  35         kfree(entry);
  36 }
  37
  38 /*
  39  * ima_alloc_init_template - create and initialize a new template entry
  40  */
  41 int ima_alloc_init_template(struct ima_event_data *event_data,
  42                             struct ima_template_entry **entry)
  43 {
  44         struct ima_template_desc *template_desc = ima_template_desc_current();
  45         int i, result = 0;
  46
  47         *entry = kzalloc(sizeof(**entry) + template_desc->num_fields *
  48                          sizeof(struct ima_field_data), GFP_NOFS);
  49         if (!*entry)
  50                 return -ENOMEM;
  51
  52         (*entry)->template_desc = template_desc;
  53         for (i = 0; i < template_desc->num_fields; i++) {
  54                 struct ima_template_field *field = template_desc->fields[i];
  55                 u32 len;
  56
  57                 result = field->field_init(event_data,
  58                                            &((*entry)->template_data[i]));
  59                 if (result != 0)
  60                         goto out;
  61
  62                 len = (*entry)->template_data[i].len;
  63                 (*entry)->template_data_len += sizeof(len);
  64                 (*entry)->template_data_len += len;
  65         }
  66         return 0;
  67 out:
  68         ima_free_template_entry(*entry);
  69         *entry = NULL;
  70         return result;
  71 }
  72
  73 /*
  74  * ima_store_template - store ima template measurements
  75  *
  76  * Calculate the hash of a template entry, add the template entry
  77  * to an ordered list of measurement entries maintained inside the kernel,
  78  * and also update the aggregate integrity value (maintained inside the
  79  * configured TPM PCR) over the hashes of the current list of measurement
  80  * entries.
  81  *
  82  * Applications retrieve the current kernel-held measurement list through
  83  * the securityfs entries in /sys/kernel/security/ima. The signed aggregate
  84  * TPM PCR (called quote) can be retrieved using a TPM user space library
  85  * and is used to validate the measurement list.
  86  *
  87  * Returns 0 on success, error code otherwise
  88  */
  89 int ima_store_template(struct ima_template_entry *entry,
  90                        int violation, struct inode *inode,
  91                        const unsigned char *filename, int pcr)
  92 {
  93         static const char op[] = "add_template_measure";
  94         static const char audit_cause[] = "hashing_error";
  95         char *template_name = entry->template_desc->name;
  96         int result;
  97         struct {
  98                 struct ima_digest_data hdr;
  99                 char digest[TPM_DIGEST_SIZE];
 100         } hash;
 101
 102         if (!violation) {
 103                 int num_fields = entry->template_desc->num_fields;
 104
 105                 /* this function uses default algo */
 106                 hash.hdr.algo = HASH_ALGO_SHA1;
 107                 result = ima_calc_field_array_hash(&entry->template_data[0],
 108                                                    entry->template_desc,
 109                                                    num_fields, &hash.hdr);
 110                 if (result < 0) {
 111                         integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode,
 112                                             template_name, op,
 113                                             audit_cause, result, 0);
 114                         return result;
 115                 }
 116                 memcpy(entry->digest, hash.hdr.digest, hash.hdr.length);
 117         }
 118         entry->pcr = pcr;
 119         result = ima_add_template_entry(entry, violation, op, inode, filename);
 120         return result;
 121 }
 122
 123 /*
 124  * ima_add_violation - add violation to measurement list.
 125  *
 126  * Violations are flagged in the measurement list with zero hash values.
 127  * By extending the PCR with 0xFF's instead of with zeroes, the PCR
 128  * value is invalidated.
 129  */
 130 void ima_add_violation(struct file *file, const unsigned char *filename,
 131                        struct integrity_iint_cache *iint,
 132                        const char *op, const char *cause)
 133 {
 134         struct ima_template_entry *entry;
 135         struct inode *inode = file_inode(file);
 136         struct ima_event_data event_data = {iint, file, filename, NULL, 0,
 137                                             cause};
 138         int violation = 1;
 139         int result;
 140
 141         /* can overflow, only indicator */
 142         atomic_long_inc(&ima_htable.violations);
 143
 144         result = ima_alloc_init_template(&event_data, &entry);
 145         if (result < 0) {
 146                 result = -ENOMEM;
 147                 goto err_out;
 148         }
 149         result = ima_store_template(entry, violation, inode,
 150                                     filename, CONFIG_IMA_MEASURE_PCR_IDX);
 151         if (result < 0)
 152                 ima_free_template_entry(entry);
 153 err_out:
 154         integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
 155                             op, cause, result, 0);
 156 }
 157
 158 /**
 159  * ima_get_action - appraise & measure decision based on policy.
 160  * @inode: pointer to inode to measure
 161  * @mask: contains the permission mask (MAY_READ, MAY_WRITE, MAY_EXEC,
 162  *        MAY_APPEND)
 163  * @func: caller identifier
 164  * @pcr: pointer filled in if matched measure policy sets pcr=
 165  *
 166  * The policy is defined in terms of keypairs:
 167  *              subj=, obj=, type=, func=, mask=, fsmagic=
 168  *      subj,obj, and type: are LSM specific.
 169  *      func: FILE_CHECK | BPRM_CHECK | MMAP_CHECK | MODULE_CHECK
 170  *      mask: contains the permission mask
 171  *      fsmagic: hex value
 172  *
 173  * Returns IMA_MEASURE, IMA_APPRAISE mask.
 174  *
 175  */
 176 int ima_get_action(struct inode *inode, int mask, enum ima_hooks func, int *pcr)
 177 {
 178         int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE | IMA_HASH;
 179
 180         flags &= ima_policy_flag;
 181
 182         return ima_match_policy(inode, func, mask, flags, pcr);
 183 }
 184
 185 /*
 186  * ima_collect_measurement - collect file measurement
 187  *
 188  * Calculate the file hash, if it doesn't already exist,
 189  * storing the measurement and i_version in the iint.
 190  *
 191  * Must be called with iint->mutex held.
 192  *
 193  * Return 0 on success, error code otherwise
 194  */
 195 int ima_collect_measurement(struct integrity_iint_cache *iint,
 196                             struct file *file, void *buf, loff_t size,
 197                             enum hash_algo algo)
 198 {
 199         const char *audit_cause = "failed";
 200         struct inode *inode = file_inode(file);
 201         const char *filename = file->f_path.dentry->d_name.name;
 202         int result = 0;
 203         int length;
 204         void *tmpbuf;
 205         u64 i_version;
 206         struct {
 207                 struct ima_digest_data hdr;
 208                 char digest[IMA_MAX_DIGEST_SIZE];
 209         } hash;
 210
 211         if (iint->flags & IMA_COLLECTED)
 212                 goto out;
 213
 214         /*
 215          * Dectecting file change is based on i_version. On filesystems
 216          * which do not support i_version, support is limited to an initial
 217          * measurement/appraisal/audit.
 218          */
 219         i_version = inode_query_iversion(inode);
 220         hash.hdr.algo = algo;
 221
 222         /* Initialize hash digest to 0's in case of failure */
 223         memset(&hash.digest, 0, sizeof(hash.digest));
 224
 225         if (buf)
 226                 result = ima_calc_buffer_hash(buf, size, &hash.hdr);
 227         else
 228                 result = ima_calc_file_hash(file, &hash.hdr);
 229
 230         if (result && result != -EBADF && result != -EINVAL)
 231                 goto out;
 232
 233         length = sizeof(hash.hdr) + hash.hdr.length;
 234         tmpbuf = krealloc(iint->ima_hash, length, GFP_NOFS);
 235         if (!tmpbuf) {
 236                 result = -ENOMEM;
 237                 goto out;
 238         }
 239
 240         iint->ima_hash = tmpbuf;
 241         memcpy(iint->ima_hash, &hash, length);
 242         iint->version = i_version;
 243
 244         /* Possibly temporary failure due to type of read (eg. O_DIRECT) */
 245         if (!result)
 246                 iint->flags |= IMA_COLLECTED;
 247 out:
 248         if (result) {
 249                 if (file->f_flags & O_DIRECT)
 250                         audit_cause = "failed(directio)";
 251
 252                 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
 253                                     filename, "collect_data", audit_cause,
 254                                     result, 0);
 255         }
 256         return result;
 257 }
 258
 259 /*
 260  * ima_store_measurement - store file measurement
 261  *
 262  * Create an "ima" template and then store the template by calling
 263  * ima_store_template.
 264  *
 265  * We only get here if the inode has not already been measured,
 266  * but the measurement could already exist:
 267  *      - multiple copies of the same file on either the same or
 268  *        different filesystems.
 269  *      - the inode was previously flushed as well as the iint info,
 270  *        containing the hashing info.
 271  *
 272  * Must be called with iint->mutex held.
 273  */
 274 void ima_store_measurement(struct integrity_iint_cache *iint,
 275                            struct file *file, const unsigned char *filename,
 276                            struct evm_ima_xattr_data *xattr_value,
 277                            int xattr_len, int pcr)
 278 {
 279         static const char op[] = "add_template_measure";
 280         static const char audit_cause[] = "ENOMEM";
 281         int result = -ENOMEM;
 282         struct inode *inode = file_inode(file);
 283         struct ima_template_entry *entry;
 284         struct ima_event_data event_data = {iint, file, filename, xattr_value,
 285                                             xattr_len, NULL};
 286         int violation = 0;
 287
 288         if (iint->measured_pcrs & (0x1 << pcr))
 289                 return;
 290
 291         result = ima_alloc_init_template(&event_data, &entry);
 292         if (result < 0) {
 293                 integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
 294                                     op, audit_cause, result, 0);
 295                 return;
 296         }
 297
 298         result = ima_store_template(entry, violation, inode, filename, pcr);
 299         if ((!result || result == -EEXIST) && !(file->f_flags & O_DIRECT)) {
 300                 iint->flags |= IMA_MEASURED;
 301                 iint->measured_pcrs |= (0x1 << pcr);
 302         }
 303         if (result < 0)
 304                 ima_free_template_entry(entry);
 305 }
 306
 307 void ima_audit_measurement(struct integrity_iint_cache *iint,
 308                            const unsigned char *filename)
 309 {
 310         struct audit_buffer *ab;
 311         char hash[(iint->ima_hash->length * 2) + 1];
 312         const char *algo_name = hash_algo_name[iint->ima_hash->algo];
 313         char algo_hash[sizeof(hash) + strlen(algo_name) + 2];
 314         int i;
 315
 316         if (iint->flags & IMA_AUDITED)
 317                 return;
 318
 319         for (i = 0; i < iint->ima_hash->length; i++)
 320                 hex_byte_pack(hash + (i * 2), iint->ima_hash->digest[i]);
 321         hash[i * 2] = '\0';
 322
 323         ab = audit_log_start(current->audit_context, GFP_KERNEL,
 324                              AUDIT_INTEGRITY_RULE);
 325         if (!ab)
 326                 return;
 327
 328         audit_log_format(ab, "file=");
 329         audit_log_untrustedstring(ab, filename);
 330         audit_log_format(ab, " hash=");
 331         snprintf(algo_hash, sizeof(algo_hash), "%s:%s", algo_name, hash);
 332         audit_log_untrustedstring(ab, algo_hash);
 333
 334         audit_log_task_info(ab, current);
 335         audit_log_end(ab);
 336
 337         iint->flags |= IMA_AUDITED;
 338 }
 339
 340 /*
 341  * ima_d_path - return a pointer to the full pathname
 342  *
 343  * Attempt to return a pointer to the full pathname for use in the
 344  * IMA measurement list, IMA audit records, and auditing logs.
 345  *
 346  * On failure, return a pointer to a copy of the filename, not dname.
 347  * Returning a pointer to dname, could result in using the pointer
 348  * after the memory has been freed.
 349  */
 350 const char *ima_d_path(const struct path *path, char **pathbuf, char *namebuf)
 351 {
 352         char *pathname = NULL;
 353
 354         *pathbuf = __getname();
 355         if (*pathbuf) {
 356                 pathname = d_absolute_path(path, *pathbuf, PATH_MAX);
 357                 if (IS_ERR(pathname)) {
 358                         __putname(*pathbuf);
 359                         *pathbuf = NULL;
 360                         pathname = NULL;
 361                 }
 362         }
 363
 364         if (!pathname) {
 365                 strlcpy(namebuf, path->dentry->d_name.name, NAME_MAX);
 366                 pathname = namebuf;
 367         }
 368
 369         return pathname;
 370 }