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 static const char *IMA_TEMPLATE_NAME = "ima";
  25
  26 /*
  27  * ima_store_template - store ima template measurements
  28  *
  29  * Calculate the hash of a template entry, add the template entry
  30  * to an ordered list of measurement entries maintained inside the kernel,
  31  * and also update the aggregate integrity value (maintained inside the
  32  * configured TPM PCR) over the hashes of the current list of measurement
  33  * entries.
  34  *
  35  * Applications retrieve the current kernel-held measurement list through
  36  * the securityfs entries in /sys/kernel/security/ima. The signed aggregate
  37  * TPM PCR (called quote) can be retrieved using a TPM user space library
  38  * and is used to validate the measurement list.
  39  *
  40  * Returns 0 on success, error code otherwise
  41  */
  42 int ima_store_template(struct ima_template_entry *entry,
  43                        int violation, struct inode *inode)
  44 {
  45         const char *op = "add_template_measure";
  46         const char *audit_cause = "hashing_error";
  47         int result;
  48         struct {
  49                 struct ima_digest_data hdr;
  50                 char digest[TPM_DIGEST_SIZE];
  51         } hash;
  52
  53         memset(entry->digest, 0, sizeof(entry->digest));
  54         entry->template_name = IMA_TEMPLATE_NAME;
  55         entry->template_len = sizeof(entry->template);
  56
  57         if (!violation) {
  58                 /* this function uses default algo */
  59                 hash.hdr.algo = HASH_ALGO_SHA1;
  60                 result = ima_calc_buffer_hash(&entry->template,
  61                                               entry->template_len, &hash.hdr);
  62                 if (result < 0) {
  63                         integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode,
  64                                             entry->template_name, op,
  65                                             audit_cause, result, 0);
  66                         return result;
  67                 }
  68                 memcpy(entry->digest, hash.hdr.digest, hash.hdr.length);
  69         }
  70         result = ima_add_template_entry(entry, violation, op, inode);
  71         return result;
  72 }
  73
  74 /*
  75  * ima_add_violation - add violation to measurement list.
  76  *
  77  * Violations are flagged in the measurement list with zero hash values.
  78  * By extending the PCR with 0xFF's instead of with zeroes, the PCR
  79  * value is invalidated.
  80  */
  81 void ima_add_violation(struct file *file, const unsigned char *filename,
  82                        const char *op, const char *cause)
  83 {
  84         struct ima_template_entry *entry;
  85         struct inode *inode = file->f_dentry->d_inode;
  86         int violation = 1;
  87         int result;
  88
  89         /* can overflow, only indicator */
  90         atomic_long_inc(&ima_htable.violations);
  91
  92         entry = kmalloc(sizeof(*entry), GFP_KERNEL);
  93         if (!entry) {
  94                 result = -ENOMEM;
  95                 goto err_out;
  96         }
  97         memset(&entry->template, 0, sizeof(entry->template));
  98         strncpy(entry->template.file_name, filename, IMA_EVENT_NAME_LEN_MAX);
  99         result = ima_store_template(entry, violation, inode);
 100         if (result < 0)
 101                 kfree(entry);
 102 err_out:
 103         integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
 104                             op, cause, result, 0);
 105 }
 106
 107 /**
 108  * ima_get_action - appraise & measure decision based on policy.
 109  * @inode: pointer to inode to measure
 110  * @mask: contains the permission mask (MAY_READ, MAY_WRITE, MAY_EXECUTE)
 111  * @function: calling function (FILE_CHECK, BPRM_CHECK, MMAP_CHECK, MODULE_CHECK)
 112  *
 113  * The policy is defined in terms of keypairs:
 114  *              subj=, obj=, type=, func=, mask=, fsmagic=
 115  *      subj,obj, and type: are LSM specific.
 116  *      func: FILE_CHECK | BPRM_CHECK | MMAP_CHECK | MODULE_CHECK
 117  *      mask: contains the permission mask
 118  *      fsmagic: hex value
 119  *
 120  * Returns IMA_MEASURE, IMA_APPRAISE mask.
 121  *
 122  */
 123 int ima_get_action(struct inode *inode, int mask, int function)
 124 {
 125         int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE;
 126
 127         if (!ima_appraise)
 128                 flags &= ~IMA_APPRAISE;
 129
 130         return ima_match_policy(inode, function, mask, flags);
 131 }
 132
 133 int ima_must_measure(struct inode *inode, int mask, int function)
 134 {
 135         return ima_match_policy(inode, function, mask, IMA_MEASURE);
 136 }
 137
 138 /*
 139  * ima_collect_measurement - collect file measurement
 140  *
 141  * Calculate the file hash, if it doesn't already exist,
 142  * storing the measurement and i_version in the iint.
 143  *
 144  * Must be called with iint->mutex held.
 145  *
 146  * Return 0 on success, error code otherwise
 147  */
 148 int ima_collect_measurement(struct integrity_iint_cache *iint,
 149                             struct file *file,
 150                             struct evm_ima_xattr_data **xattr_value,
 151                             int *xattr_len)
 152 {
 153         struct inode *inode = file_inode(file);
 154         const char *filename = file->f_dentry->d_name.name;
 155         int result = 0;
 156         struct {
 157                 struct ima_digest_data hdr;
 158                 char digest[IMA_MAX_DIGEST_SIZE];
 159         } hash;
 160
 161         if (xattr_value)
 162                 *xattr_len = ima_read_xattr(file->f_dentry, xattr_value);
 163
 164         if (!(iint->flags & IMA_COLLECTED)) {
 165                 u64 i_version = file_inode(file)->i_version;
 166
 167                 /* use default hash algorithm */
 168                 hash.hdr.algo = ima_hash_algo;
 169
 170                 if (xattr_value)
 171                         ima_get_hash_algo(*xattr_value, *xattr_len, &hash.hdr);
 172
 173                 result = ima_calc_file_hash(file, &hash.hdr);
 174                 if (!result) {
 175                         int length = sizeof(hash.hdr) + hash.hdr.length;
 176                         void *tmpbuf = krealloc(iint->ima_hash, length,
 177                                                 GFP_NOFS);
 178                         if (tmpbuf) {
 179                                 iint->ima_hash = tmpbuf;
 180                                 memcpy(iint->ima_hash, &hash, length);
 181                                 iint->version = i_version;
 182                                 iint->flags |= IMA_COLLECTED;
 183                         } else
 184                                 result = -ENOMEM;
 185                 }
 186         }
 187         if (result)
 188                 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
 189                                     filename, "collect_data", "failed",
 190                                     result, 0);
 191         return result;
 192 }
 193
 194 /*
 195  * ima_store_measurement - store file measurement
 196  *
 197  * Create an "ima" template and then store the template by calling
 198  * ima_store_template.
 199  *
 200  * We only get here if the inode has not already been measured,
 201  * but the measurement could already exist:
 202  *      - multiple copies of the same file on either the same or
 203  *        different filesystems.
 204  *      - the inode was previously flushed as well as the iint info,
 205  *        containing the hashing info.
 206  *
 207  * Must be called with iint->mutex held.
 208  */
 209 void ima_store_measurement(struct integrity_iint_cache *iint,
 210                            struct file *file, const unsigned char *filename)
 211 {
 212         const char *op = "add_template_measure";
 213         const char *audit_cause = "ENOMEM";
 214         int result = -ENOMEM;
 215         struct inode *inode = file_inode(file);
 216         struct ima_template_entry *entry;
 217         int violation = 0;
 218
 219         if (iint->flags & IMA_MEASURED)
 220                 return;
 221
 222         entry = kmalloc(sizeof(*entry), GFP_KERNEL);
 223         if (!entry) {
 224                 integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename,
 225                                     op, audit_cause, result, 0);
 226                 return;
 227         }
 228         memset(&entry->template, 0, sizeof(entry->template));
 229         if (iint->ima_hash->algo != ima_hash_algo) {
 230                 struct {
 231                         struct ima_digest_data hdr;
 232                         char digest[IMA_MAX_DIGEST_SIZE];
 233                 } hash;
 234
 235                 hash.hdr.algo = ima_hash_algo;
 236                 result = ima_calc_file_hash(file, &hash.hdr);
 237                 if (result)
 238                         integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode,
 239                                             filename, "collect_data", "failed",
 240                                             result, 0);
 241                 else
 242                         memcpy(entry->template.digest, hash.hdr.digest,
 243                                hash.hdr.length);
 244         } else
 245                 memcpy(entry->template.digest, iint->ima_hash->digest,
 246                        iint->ima_hash->length);
 247         strcpy(entry->template.file_name,
 248                (strlen(filename) > IMA_EVENT_NAME_LEN_MAX) ?
 249                file->f_dentry->d_name.name : filename);
 250
 251         result = ima_store_template(entry, violation, inode);
 252         if (!result || result == -EEXIST)
 253                 iint->flags |= IMA_MEASURED;
 254         if (result < 0)
 255                 kfree(entry);
 256 }
 257
 258 void ima_audit_measurement(struct integrity_iint_cache *iint,
 259                            const unsigned char *filename)
 260 {
 261         struct audit_buffer *ab;
 262         char hash[(iint->ima_hash->length * 2) + 1];
 263         int i;
 264
 265         if (iint->flags & IMA_AUDITED)
 266                 return;
 267
 268         for (i = 0; i < iint->ima_hash->length; i++)
 269                 hex_byte_pack(hash + (i * 2), iint->ima_hash->digest[i]);
 270         hash[i * 2] = '\0';
 271
 272         ab = audit_log_start(current->audit_context, GFP_KERNEL,
 273                              AUDIT_INTEGRITY_RULE);
 274         if (!ab)
 275                 return;
 276
 277         audit_log_format(ab, "file=");
 278         audit_log_untrustedstring(ab, filename);
 279         audit_log_format(ab, " hash=");
 280         audit_log_untrustedstring(ab, hash);
 281
 282         audit_log_task_info(ab, current);
 283         audit_log_end(ab);
 284
 285         iint->flags |= IMA_AUDITED;
 286 }
 287
 288 const char *ima_d_path(struct path *path, char **pathbuf)
 289 {
 290         char *pathname = NULL;
 291
 292         /* We will allow 11 spaces for ' (deleted)' to be appended */
 293         *pathbuf = kmalloc(PATH_MAX + 11, GFP_KERNEL);
 294         if (*pathbuf) {
 295                 pathname = d_path(path, *pathbuf, PATH_MAX + 11);
 296                 if (IS_ERR(pathname)) {
 297                         kfree(*pathbuf);
 298                         *pathbuf = NULL;
 299                         pathname = NULL;
 300                 }
 301         }
 302         return pathname;
 303 }