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
  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, int pcr)
  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         entry->pcr = pcr;
 118         result = ima_add_template_entry(entry, violation, op, inode, filename);
 119         return result;
 120 }
 121
 122 /*
 123  * ima_add_violation - add violation to measurement list.
 124  *
 125  * Violations are flagged in the measurement list with zero hash values.
 126  * By extending the PCR with 0xFF's instead of with zeroes, the PCR
 127  * value is invalidated.
 128  */
 129 void ima_add_violation(struct file *file, const unsigned char *filename,
 130                        struct integrity_iint_cache *iint,
 131                        const char *op, const char *cause)
 132 {
 133         struct ima_template_entry *entry;
 134         struct inode *inode = file_inode(file);
 135         struct ima_event_data event_data = {iint, file, filename, NULL, 0,
 136                                             cause};
 137         int violation = 1;
 138         int result;
 139
 140         /* can overflow, only indicator */
 141         atomic_long_inc(&ima_htable.violations);
 142
 143         result = ima_alloc_init_template(&event_data, &entry);
 144         if (result < 0) {
 145                 result = -ENOMEM;
 146                 goto err_out;
 147         }
 148         result = ima_store_template(entry, violation, inode,
 149                                     filename, CONFIG_IMA_MEASURE_PCR_IDX);
 150         if (result < 0)
 151                 ima_free_template_entry(entry);
 152 err_out:
 153         integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
 154                             op, cause, result, 0);
 155 }
 156
 157 /**
 158  * ima_get_action - appraise & measure decision based on policy.
 159  * @inode: pointer to inode to measure
 160  * @mask: contains the permission mask (MAY_READ, MAY_WRITE, MAY_EXEC,
 161  *        MAY_APPEND)
 162  * @func: caller identifier
 163  * @pcr: pointer filled in if matched measure policy sets pcr=
 164  *
 165  * The policy is defined in terms of keypairs:
 166  *              subj=, obj=, type=, func=, mask=, fsmagic=
 167  *      subj,obj, and type: are LSM specific.
 168  *      func: FILE_CHECK | BPRM_CHECK | MMAP_CHECK | MODULE_CHECK
 169  *      mask: contains the permission mask
 170  *      fsmagic: hex value
 171  *
 172  * Returns IMA_MEASURE, IMA_APPRAISE mask.
 173  *
 174  */
 175 int ima_get_action(struct inode *inode, int mask, enum ima_hooks func, int *pcr)
 176 {
 177         int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE;
 178
 179         flags &= ima_policy_flag;
 180
 181         return ima_match_policy(inode, func, mask, flags, pcr);
 182 }
 183
 184 /*
 185  * ima_collect_measurement - collect file measurement
 186  *
 187  * Calculate the file hash, if it doesn't already exist,
 188  * storing the measurement and i_version in the iint.
 189  *
 190  * Must be called with iint->mutex held.
 191  *
 192  * Return 0 on success, error code otherwise
 193  */
 194 int ima_collect_measurement(struct integrity_iint_cache *iint,
 195                             struct file *file, void *buf, loff_t size,
 196                             enum hash_algo algo)
 197 {
 198         const char *audit_cause = "failed";
 199         struct inode *inode = file_inode(file);
 200         const char *filename = file->f_path.dentry->d_name.name;
 201         int result = 0;
 202         struct {
 203                 struct ima_digest_data hdr;
 204                 char digest[IMA_MAX_DIGEST_SIZE];
 205         } hash;
 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                 hash.hdr.algo = algo;
 217
 218                 result = (!buf) ?  ima_calc_file_hash(file, &hash.hdr) :
 219                         ima_calc_buffer_hash(buf, size, &hash.hdr);
 220                 if (!result) {
 221                         int length = sizeof(hash.hdr) + hash.hdr.length;
 222                         void *tmpbuf = krealloc(iint->ima_hash, length,
 223                                                 GFP_NOFS);
 224                         if (tmpbuf) {
 225                                 iint->ima_hash = tmpbuf;
 226                                 memcpy(iint->ima_hash, &hash, length);
 227                                 iint->version = i_version;
 228                                 iint->flags |= IMA_COLLECTED;
 229                         } else
 230                                 result = -ENOMEM;
 231                 }
 232         }
 233 out:
 234         if (result)
 235                 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
 236                                     filename, "collect_data", audit_cause,
 237                                     result, 0);
 238         return result;
 239 }
 240
 241 /*
 242  * ima_store_measurement - store file measurement
 243  *
 244  * Create an "ima" template and then store the template by calling
 245  * ima_store_template.
 246  *
 247  * We only get here if the inode has not already been measured,
 248  * but the measurement could already exist:
 249  *      - multiple copies of the same file on either the same or
 250  *        different filesystems.
 251  *      - the inode was previously flushed as well as the iint info,
 252  *        containing the hashing info.
 253  *
 254  * Must be called with iint->mutex held.
 255  */
 256 void ima_store_measurement(struct integrity_iint_cache *iint,
 257                            struct file *file, const unsigned char *filename,
 258                            struct evm_ima_xattr_data *xattr_value,
 259                            int xattr_len, int pcr)
 260 {
 261         static const char op[] = "add_template_measure";
 262         static const char audit_cause[] = "ENOMEM";
 263         int result = -ENOMEM;
 264         struct inode *inode = file_inode(file);
 265         struct ima_template_entry *entry;
 266         struct ima_event_data event_data = {iint, file, filename, xattr_value,
 267                                             xattr_len, NULL};
 268         int violation = 0;
 269
 270         if (iint->measured_pcrs & (0x1 << pcr))
 271                 return;
 272
 273         result = ima_alloc_init_template(&event_data, &entry);
 274         if (result < 0) {
 275                 integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
 276                                     op, audit_cause, result, 0);
 277                 return;
 278         }
 279
 280         result = ima_store_template(entry, violation, inode, filename, pcr);
 281         if (!result || result == -EEXIST) {
 282                 iint->flags |= IMA_MEASURED;
 283                 iint->measured_pcrs |= (0x1 << pcr);
 284         }
 285         if (result < 0)
 286                 ima_free_template_entry(entry);
 287 }
 288
 289 void ima_audit_measurement(struct integrity_iint_cache *iint,
 290                            const unsigned char *filename)
 291 {
 292         struct audit_buffer *ab;
 293         char hash[(iint->ima_hash->length * 2) + 1];
 294         const char *algo_name = hash_algo_name[iint->ima_hash->algo];
 295         char algo_hash[sizeof(hash) + strlen(algo_name) + 2];
 296         int i;
 297
 298         if (iint->flags & IMA_AUDITED)
 299                 return;
 300
 301         for (i = 0; i < iint->ima_hash->length; i++)
 302                 hex_byte_pack(hash + (i * 2), iint->ima_hash->digest[i]);
 303         hash[i * 2] = '\0';
 304
 305         ab = audit_log_start(current->audit_context, GFP_KERNEL,
 306                              AUDIT_INTEGRITY_RULE);
 307         if (!ab)
 308                 return;
 309
 310         audit_log_format(ab, "file=");
 311         audit_log_untrustedstring(ab, filename);
 312         audit_log_format(ab, " hash=");
 313         snprintf(algo_hash, sizeof(algo_hash), "%s:%s", algo_name, hash);
 314         audit_log_untrustedstring(ab, algo_hash);
 315
 316         audit_log_task_info(ab, current);
 317         audit_log_end(ab);
 318
 319         iint->flags |= IMA_AUDITED;
 320 }
 321
 322 /*
 323  * ima_d_path - return a pointer to the full pathname
 324  *
 325  * Attempt to return a pointer to the full pathname for use in the
 326  * IMA measurement list, IMA audit records, and auditing logs.
 327  *
 328  * On failure, return a pointer to a copy of the filename, not dname.
 329  * Returning a pointer to dname, could result in using the pointer
 330  * after the memory has been freed.
 331  */
 332 const char *ima_d_path(const struct path *path, char **pathbuf, char *namebuf)
 333 {
 334         char *pathname = NULL;
 335
 336         *pathbuf = __getname();
 337         if (*pathbuf) {
 338                 pathname = d_absolute_path(path, *pathbuf, PATH_MAX);
 339                 if (IS_ERR(pathname)) {
 340                         __putname(*pathbuf);
 341                         *pathbuf = NULL;
 342                         pathname = NULL;
 343                 }
 344         }
 345
 346         if (!pathname) {
 347                 strlcpy(namebuf, path->dentry->d_name.name, NAME_MAX);
 348                 pathname = namebuf;
 349         }
 350
 351         return pathname;
 352 }