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 <crypto/hash_info.h>
  22 #include "ima.h"
  23
  24 /*
  25  * ima_free_template_entry - free an existing template entry
  26  */
  27 void ima_free_template_entry(struct ima_template_entry *entry)
  28 {
  29         int i;
  30
  31         for (i = 0; i < entry->template_desc->num_fields; i++)
  32                 kfree(entry->template_data[i].data);
  33
  34         kfree(entry);
  35 }
  36
  37 /*
  38  * ima_alloc_init_template - create and initialize a new template entry
  39  */
  40 int ima_alloc_init_template(struct ima_event_data *event_data,
  41                             struct ima_template_entry **entry)
  42 {
  43         struct ima_template_desc *template_desc = ima_template_desc_current();
  44         int i, result = 0;
  45
  46         *entry = kzalloc(sizeof(**entry) + template_desc->num_fields *
  47                          sizeof(struct ima_field_data), GFP_NOFS);
  48         if (!*entry)
  49                 return -ENOMEM;
  50
  51         (*entry)->template_desc = template_desc;
  52         for (i = 0; i < template_desc->num_fields; i++) {
  53                 struct ima_template_field *field = template_desc->fields[i];
  54                 u32 len;
  55
  56                 result = field->field_init(event_data,
  57                                            &((*entry)->template_data[i]));
  58                 if (result != 0)
  59                         goto out;
  60
  61                 len = (*entry)->template_data[i].len;
  62                 (*entry)->template_data_len += sizeof(len);
  63                 (*entry)->template_data_len += len;
  64         }
  65         return 0;
  66 out:
  67         ima_free_template_entry(*entry);
  68         *entry = NULL;
  69         return result;
  70 }
  71
  72 /*
  73  * ima_store_template - store ima template measurements
  74  *
  75  * Calculate the hash of a template entry, add the template entry
  76  * to an ordered list of measurement entries maintained inside the kernel,
  77  * and also update the aggregate integrity value (maintained inside the
  78  * configured TPM PCR) over the hashes of the current list of measurement
  79  * entries.
  80  *
  81  * Applications retrieve the current kernel-held measurement list through
  82  * the securityfs entries in /sys/kernel/security/ima. The signed aggregate
  83  * TPM PCR (called quote) can be retrieved using a TPM user space library
  84  * and is used to validate the measurement list.
  85  *
  86  * Returns 0 on success, error code otherwise
  87  */
  88 int ima_store_template(struct ima_template_entry *entry,
  89                        int violation, struct inode *inode,
  90                        const unsigned char *filename)
  91 {
  92         static const char op[] = "add_template_measure";
  93         static const char audit_cause[] = "hashing_error";
  94         char *template_name = entry->template_desc->name;
  95         int result;
  96         struct {
  97                 struct ima_digest_data hdr;
  98                 char digest[TPM_DIGEST_SIZE];
  99         } hash;
 100
 101         if (!violation) {
 102                 int num_fields = entry->template_desc->num_fields;
 103
 104                 /* this function uses default algo */
 105                 hash.hdr.algo = HASH_ALGO_SHA1;
 106                 result = ima_calc_field_array_hash(&entry->template_data[0],
 107                                                    entry->template_desc,
 108                                                    num_fields, &hash.hdr);
 109                 if (result < 0) {
 110                         integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode,
 111                                             template_name, op,
 112                                             audit_cause, result, 0);
 113                         return result;
 114                 }
 115                 memcpy(entry->digest, hash.hdr.digest, hash.hdr.length);
 116         }
 117         result = ima_add_template_entry(entry, violation, op, inode, filename);
 118         return result;
 119 }
 120
 121 /*
 122  * ima_add_violation - add violation to measurement list.
 123  *
 124  * Violations are flagged in the measurement list with zero hash values.
 125  * By extending the PCR with 0xFF's instead of with zeroes, the PCR
 126  * value is invalidated.
 127  */
 128 void ima_add_violation(struct file *file, const unsigned char *filename,
 129                        struct integrity_iint_cache *iint,
 130                        const char *op, const char *cause)
 131 {
 132         struct ima_template_entry *entry;
 133         struct inode *inode = file_inode(file);
 134         struct ima_event_data event_data = {iint, file, filename, NULL, 0,
 135                                             cause};
 136         int violation = 1;
 137         int result;
 138
 139         /* can overflow, only indicator */
 140         atomic_long_inc(&ima_htable.violations);
 141
 142         result = ima_alloc_init_template(&event_data, &entry);
 143         if (result < 0) {
 144                 result = -ENOMEM;
 145                 goto err_out;
 146         }
 147         result = ima_store_template(entry, violation, inode, filename);
 148         if (result < 0)
 149                 ima_free_template_entry(entry);
 150 err_out:
 151         integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
 152                             op, cause, result, 0);
 153 }
 154
 155 /**
 156  * ima_get_action - appraise & measure decision based on policy.
 157  * @inode: pointer to inode to measure
 158  * @mask: contains the permission mask (MAY_READ, MAY_WRITE, MAY_EXECUTE)
 159  * @function: calling function (FILE_CHECK, BPRM_CHECK, MMAP_CHECK, MODULE_CHECK)
 160  *
 161  * The policy is defined in terms of keypairs:
 162  *              subj=, obj=, type=, func=, mask=, fsmagic=
 163  *      subj,obj, and type: are LSM specific.
 164  *      func: FILE_CHECK | BPRM_CHECK | MMAP_CHECK | MODULE_CHECK
 165  *      mask: contains the permission mask
 166  *      fsmagic: hex value
 167  *
 168  * Returns IMA_MEASURE, IMA_APPRAISE mask.
 169  *
 170  */
 171 int ima_get_action(struct inode *inode, int mask, int function)
 172 {
 173         int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE;
 174
 175         flags &= ima_policy_flag;
 176
 177         return ima_match_policy(inode, function, mask, flags);
 178 }
 179
 180 /*
 181  * ima_collect_measurement - collect file measurement
 182  *
 183  * Calculate the file hash, if it doesn't already exist,
 184  * storing the measurement and i_version in the iint.
 185  *
 186  * Must be called with iint->mutex held.
 187  *
 188  * Return 0 on success, error code otherwise
 189  */
 190 int ima_collect_measurement(struct integrity_iint_cache *iint,
 191                             struct file *file,
 192                             struct evm_ima_xattr_data **xattr_value,
 193                             int *xattr_len)
 194 {
 195         const char *audit_cause = "failed";
 196         struct inode *inode = file_inode(file);
 197         const char *filename = file->f_path.dentry->d_name.name;
 198         int result = 0;
 199         struct {
 200                 struct ima_digest_data hdr;
 201                 char digest[IMA_MAX_DIGEST_SIZE];
 202         } hash;
 203
 204         if (xattr_value)
 205                 *xattr_len = ima_read_xattr(file->f_path.dentry, xattr_value);
 206
 207         if (!(iint->flags & IMA_COLLECTED)) {
 208                 u64 i_version = file_inode(file)->i_version;
 209
 210                 if (file->f_flags & O_DIRECT) {
 211                         audit_cause = "failed(directio)";
 212                         result = -EACCES;
 213                         goto out;
 214                 }
 215
 216                 /* use default hash algorithm */
 217                 hash.hdr.algo = ima_hash_algo;
 218
 219                 if (xattr_value)
 220                         ima_get_hash_algo(*xattr_value, *xattr_len, &hash.hdr);
 221
 222                 result = ima_calc_file_hash(file, &hash.hdr);
 223                 if (!result) {
 224                         int length = sizeof(hash.hdr) + hash.hdr.length;
 225                         void *tmpbuf = krealloc(iint->ima_hash, length,
 226                                                 GFP_NOFS);
 227                         if (tmpbuf) {
 228                                 iint->ima_hash = tmpbuf;
 229                                 memcpy(iint->ima_hash, &hash, length);
 230                                 iint->version = i_version;
 231                                 iint->flags |= IMA_COLLECTED;
 232                         } else
 233                                 result = -ENOMEM;
 234                 }
 235         }
 236 out:
 237         if (result)
 238                 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
 239                                     filename, "collect_data", audit_cause,
 240                                     result, 0);
 241         return result;
 242 }
 243
 244 /*
 245  * ima_store_measurement - store file measurement
 246  *
 247  * Create an "ima" template and then store the template by calling
 248  * ima_store_template.
 249  *
 250  * We only get here if the inode has not already been measured,
 251  * but the measurement could already exist:
 252  *      - multiple copies of the same file on either the same or
 253  *        different filesystems.
 254  *      - the inode was previously flushed as well as the iint info,
 255  *        containing the hashing info.
 256  *
 257  * Must be called with iint->mutex held.
 258  */
 259 void ima_store_measurement(struct integrity_iint_cache *iint,
 260                            struct file *file, const unsigned char *filename,
 261                            struct evm_ima_xattr_data *xattr_value,
 262                            int xattr_len)
 263 {
 264         static const char op[] = "add_template_measure";
 265         static const char audit_cause[] = "ENOMEM";
 266         int result = -ENOMEM;
 267         struct inode *inode = file_inode(file);
 268         struct ima_template_entry *entry;
 269         struct ima_event_data event_data = {iint, file, filename, xattr_value,
 270                                             xattr_len, NULL};
 271         int violation = 0;
 272
 273         if (iint->flags & IMA_MEASURED)
 274                 return;
 275
 276         result = ima_alloc_init_template(&event_data, &entry);
 277         if (result < 0) {
 278                 integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
 279                                     op, audit_cause, result, 0);
 280                 return;
 281         }
 282
 283         result = ima_store_template(entry, violation, inode, filename);
 284         if (!result || result == -EEXIST)
 285                 iint->flags |= IMA_MEASURED;
 286         if (result < 0)
 287                 ima_free_template_entry(entry);
 288 }
 289
 290 void ima_audit_measurement(struct integrity_iint_cache *iint,
 291                            const unsigned char *filename)
 292 {
 293         struct audit_buffer *ab;
 294         char hash[(iint->ima_hash->length * 2) + 1];
 295         const char *algo_name = hash_algo_name[iint->ima_hash->algo];
 296         char algo_hash[sizeof(hash) + strlen(algo_name) + 2];
 297         int i;
 298
 299         if (iint->flags & IMA_AUDITED)
 300                 return;
 301
 302         for (i = 0; i < iint->ima_hash->length; i++)
 303                 hex_byte_pack(hash + (i * 2), iint->ima_hash->digest[i]);
 304         hash[i * 2] = '\0';
 305
 306         ab = audit_log_start(current->audit_context, GFP_KERNEL,
 307                              AUDIT_INTEGRITY_RULE);
 308         if (!ab)
 309                 return;
 310
 311         audit_log_format(ab, "file=");
 312         audit_log_untrustedstring(ab, filename);
 313         audit_log_format(ab, " hash=");
 314         snprintf(algo_hash, sizeof(algo_hash), "%s:%s", algo_name, hash);
 315         audit_log_untrustedstring(ab, algo_hash);
 316
 317         audit_log_task_info(ab, current);
 318         audit_log_end(ab);
 319
 320         iint->flags |= IMA_AUDITED;
 321 }
 322
 323 const char *ima_d_path(struct path *path, char **pathbuf)
 324 {
 325         char *pathname = NULL;
 326
 327         *pathbuf = __getname();
 328         if (*pathbuf) {
 329                 pathname = d_absolute_path(path, *pathbuf, PATH_MAX);
 330                 if (IS_ERR(pathname)) {
 331                         __putname(*pathbuf);
 332                         *pathbuf = NULL;
 333                         pathname = NULL;
 334                 }
 335         }
 336         return pathname ?: (const char *)path->dentry->d_name.name;
 337 }