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 integrity_iint_cache *iint,
  41                             struct file *file, const unsigned char *filename,
  42                             struct evm_ima_xattr_data *xattr_value,
  43                             int xattr_len, struct ima_template_entry **entry)
  44 {
  45         struct ima_template_desc *template_desc = ima_template_desc_current();
  46         int i, result = 0;
  47
  48         *entry = kzalloc(sizeof(**entry) + template_desc->num_fields *
  49                          sizeof(struct ima_field_data), GFP_NOFS);
  50         if (!*entry)
  51                 return -ENOMEM;
  52
  53         (*entry)->template_desc = template_desc;
  54         for (i = 0; i < template_desc->num_fields; i++) {
  55                 struct ima_template_field *field = template_desc->fields[i];
  56                 u32 len;
  57
  58                 result = field->field_init(iint, file, filename,
  59                                            xattr_value, xattr_len,
  60                                            &((*entry)->template_data[i]));
  61                 if (result != 0)
  62                         goto out;
  63
  64                 len = (*entry)->template_data[i].len;
  65                 (*entry)->template_data_len += sizeof(len);
  66                 (*entry)->template_data_len += len;
  67         }
  68         return 0;
  69 out:
  70         ima_free_template_entry(*entry);
  71         *entry = NULL;
  72         return result;
  73 }
  74
  75 /*
  76  * ima_store_template - store ima template measurements
  77  *
  78  * Calculate the hash of a template entry, add the template entry
  79  * to an ordered list of measurement entries maintained inside the kernel,
  80  * and also update the aggregate integrity value (maintained inside the
  81  * configured TPM PCR) over the hashes of the current list of measurement
  82  * entries.
  83  *
  84  * Applications retrieve the current kernel-held measurement list through
  85  * the securityfs entries in /sys/kernel/security/ima. The signed aggregate
  86  * TPM PCR (called quote) can be retrieved using a TPM user space library
  87  * and is used to validate the measurement list.
  88  *
  89  * Returns 0 on success, error code otherwise
  90  */
  91 int ima_store_template(struct ima_template_entry *entry,
  92                        int violation, struct inode *inode,
  93                        const unsigned char *filename)
  94 {
  95         static const char op[] = "add_template_measure";
  96         static const char audit_cause[] = "hashing_error";
  97         char *template_name = entry->template_desc->name;
  98         int result;
  99         struct {
 100                 struct ima_digest_data hdr;
 101                 char digest[TPM_DIGEST_SIZE];
 102         } hash;
 103
 104         if (!violation) {
 105                 int num_fields = entry->template_desc->num_fields;
 106
 107                 /* this function uses default algo */
 108                 hash.hdr.algo = HASH_ALGO_SHA1;
 109                 result = ima_calc_field_array_hash(&entry->template_data[0],
 110                                                    entry->template_desc,
 111                                                    num_fields, &hash.hdr);
 112                 if (result < 0) {
 113                         integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode,
 114                                             template_name, op,
 115                                             audit_cause, result, 0);
 116                         return result;
 117                 }
 118                 memcpy(entry->digest, hash.hdr.digest, hash.hdr.length);
 119         }
 120         result = ima_add_template_entry(entry, violation, op, inode, filename);
 121         return result;
 122 }
 123
 124 /*
 125  * ima_add_violation - add violation to measurement list.
 126  *
 127  * Violations are flagged in the measurement list with zero hash values.
 128  * By extending the PCR with 0xFF's instead of with zeroes, the PCR
 129  * value is invalidated.
 130  */
 131 void ima_add_violation(struct file *file, const unsigned char *filename,
 132                        const char *op, const char *cause)
 133 {
 134         struct ima_template_entry *entry;
 135         struct inode *inode = file_inode(file);
 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(NULL, file, filename,
 143                                          NULL, 0, &entry);
 144         if (result < 0) {
 145                 result = -ENOMEM;
 146                 goto err_out;
 147         }
 148         result = ima_store_template(entry, violation, inode, filename);
 149         if (result < 0)
 150                 ima_free_template_entry(entry);
 151 err_out:
 152         integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
 153                             op, cause, result, 0);
 154 }
 155
 156 /**
 157  * ima_get_action - appraise & measure decision based on policy.
 158  * @inode: pointer to inode to measure
 159  * @mask: contains the permission mask (MAY_READ, MAY_WRITE, MAY_EXECUTE)
 160  * @function: calling function (FILE_CHECK, BPRM_CHECK, MMAP_CHECK, MODULE_CHECK)
 161  *
 162  * The policy is defined in terms of keypairs:
 163  *              subj=, obj=, type=, func=, mask=, fsmagic=
 164  *      subj,obj, and type: are LSM specific.
 165  *      func: FILE_CHECK | BPRM_CHECK | MMAP_CHECK | MODULE_CHECK
 166  *      mask: contains the permission mask
 167  *      fsmagic: hex value
 168  *
 169  * Returns IMA_MEASURE, IMA_APPRAISE mask.
 170  *
 171  */
 172 int ima_get_action(struct inode *inode, int mask, int function)
 173 {
 174         int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE;
 175
 176         if (!ima_appraise)
 177                 flags &= ~IMA_APPRAISE;
 178
 179         return ima_match_policy(inode, function, mask, flags);
 180 }
 181
 182 int ima_must_measure(struct inode *inode, int mask, int function)
 183 {
 184         return ima_match_policy(inode, function, mask, IMA_MEASURE);
 185 }
 186
 187 /*
 188  * ima_collect_measurement - collect file measurement
 189  *
 190  * Calculate the file hash, if it doesn't already exist,
 191  * storing the measurement and i_version in the iint.
 192  *
 193  * Must be called with iint->mutex held.
 194  *
 195  * Return 0 on success, error code otherwise
 196  */
 197 int ima_collect_measurement(struct integrity_iint_cache *iint,
 198                             struct file *file,
 199                             struct evm_ima_xattr_data **xattr_value,
 200                             int *xattr_len)
 201 {
 202         const char *audit_cause = "failed";
 203         struct inode *inode = file_inode(file);
 204         const char *filename = file->f_dentry->d_name.name;
 205         int result = 0;
 206         struct {
 207                 struct ima_digest_data hdr;
 208                 char digest[IMA_MAX_DIGEST_SIZE];
 209         } hash;
 210
 211         if (xattr_value)
 212                 *xattr_len = ima_read_xattr(file->f_dentry, xattr_value);
 213
 214         if (!(iint->flags & IMA_COLLECTED)) {
 215                 u64 i_version = file_inode(file)->i_version;
 216
 217                 if (file->f_flags & O_DIRECT) {
 218                         audit_cause = "failed(directio)";
 219                         result = -EACCES;
 220                         goto out;
 221                 }
 222
 223                 /* use default hash algorithm */
 224                 hash.hdr.algo = ima_hash_algo;
 225
 226                 if (xattr_value)
 227                         ima_get_hash_algo(*xattr_value, *xattr_len, &hash.hdr);
 228
 229                 result = ima_calc_file_hash(file, &hash.hdr);
 230                 if (!result) {
 231                         int length = sizeof(hash.hdr) + hash.hdr.length;
 232                         void *tmpbuf = krealloc(iint->ima_hash, length,
 233                                                 GFP_NOFS);
 234                         if (tmpbuf) {
 235                                 iint->ima_hash = tmpbuf;
 236                                 memcpy(iint->ima_hash, &hash, length);
 237                                 iint->version = i_version;
 238                                 iint->flags |= IMA_COLLECTED;
 239                         } else
 240                                 result = -ENOMEM;
 241                 }
 242         }
 243 out:
 244         if (result)
 245                 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
 246                                     filename, "collect_data", audit_cause,
 247                                     result, 0);
 248         return result;
 249 }
 250
 251 /*
 252  * ima_store_measurement - store file measurement
 253  *
 254  * Create an "ima" template and then store the template by calling
 255  * ima_store_template.
 256  *
 257  * We only get here if the inode has not already been measured,
 258  * but the measurement could already exist:
 259  *      - multiple copies of the same file on either the same or
 260  *        different filesystems.
 261  *      - the inode was previously flushed as well as the iint info,
 262  *        containing the hashing info.
 263  *
 264  * Must be called with iint->mutex held.
 265  */
 266 void ima_store_measurement(struct integrity_iint_cache *iint,
 267                            struct file *file, const unsigned char *filename,
 268                            struct evm_ima_xattr_data *xattr_value,
 269                            int xattr_len)
 270 {
 271         static const char op[] = "add_template_measure";
 272         static const char audit_cause[] = "ENOMEM";
 273         int result = -ENOMEM;
 274         struct inode *inode = file_inode(file);
 275         struct ima_template_entry *entry;
 276         int violation = 0;
 277
 278         if (iint->flags & IMA_MEASURED)
 279                 return;
 280
 281         result = ima_alloc_init_template(iint, file, filename,
 282                                          xattr_value, xattr_len, &entry);
 283         if (result < 0) {
 284                 integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
 285                                     op, audit_cause, result, 0);
 286                 return;
 287         }
 288
 289         result = ima_store_template(entry, violation, inode, filename);
 290         if (!result || result == -EEXIST)
 291                 iint->flags |= IMA_MEASURED;
 292         if (result < 0)
 293                 ima_free_template_entry(entry);
 294 }
 295
 296 void ima_audit_measurement(struct integrity_iint_cache *iint,
 297                            const unsigned char *filename)
 298 {
 299         struct audit_buffer *ab;
 300         char hash[(iint->ima_hash->length * 2) + 1];
 301         const char *algo_name = hash_algo_name[iint->ima_hash->algo];
 302         char algo_hash[sizeof(hash) + strlen(algo_name) + 2];
 303         int i;
 304
 305         if (iint->flags & IMA_AUDITED)
 306                 return;
 307
 308         for (i = 0; i < iint->ima_hash->length; i++)
 309                 hex_byte_pack(hash + (i * 2), iint->ima_hash->digest[i]);
 310         hash[i * 2] = '\0';
 311
 312         ab = audit_log_start(current->audit_context, GFP_KERNEL,
 313                              AUDIT_INTEGRITY_RULE);
 314         if (!ab)
 315                 return;
 316
 317         audit_log_format(ab, "file=");
 318         audit_log_untrustedstring(ab, filename);
 319         audit_log_format(ab, " hash=");
 320         snprintf(algo_hash, sizeof(algo_hash), "%s:%s", algo_name, hash);
 321         audit_log_untrustedstring(ab, algo_hash);
 322
 323         audit_log_task_info(ab, current);
 324         audit_log_end(ab);
 325
 326         iint->flags |= IMA_AUDITED;
 327 }
 328
 329 const char *ima_d_path(struct path *path, char **pathbuf)
 330 {
 331         char *pathname = NULL;
 332
 333         /* We will allow 11 spaces for ' (deleted)' to be appended */
 334         *pathbuf = kmalloc(PATH_MAX + 11, GFP_KERNEL);
 335         if (*pathbuf) {
 336                 pathname = d_path(path, *pathbuf, PATH_MAX + 11);
 337                 if (IS_ERR(pathname)) {
 338                         kfree(*pathbuf);
 339                         *pathbuf = NULL;
 340                         pathname = NULL;
 341                 }
 342         }
 343         return pathname ?: (const char *)path->dentry->d_name.name;
 344 }