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) 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 * @func: caller identifier 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, enum ima_hooks func) 172 { 173 int flags = IMA_MEASURE | IMA_AUDIT | IMA_APPRAISE; 174 175 flags &= ima_policy_flag; 176 177 return ima_match_policy(inode, func, 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, void *buf, loff_t size, 192 enum hash_algo algo) 193 { 194 const char *audit_cause = "failed"; 195 struct inode *inode = file_inode(file); 196 const char *filename = file->f_path.dentry->d_name.name; 197 int result = 0; 198 struct { 199 struct ima_digest_data hdr; 200 char digest[IMA_MAX_DIGEST_SIZE]; 201 } hash; 202 203 if (!(iint->flags & IMA_COLLECTED)) { 204 u64 i_version = file_inode(file)->i_version; 205 206 if (file->f_flags & O_DIRECT) { 207 audit_cause = "failed(directio)"; 208 result = -EACCES; 209 goto out; 210 } 211 212 hash.hdr.algo = algo; 213 214 result = (!buf) ? ima_calc_file_hash(file, &hash.hdr) : 215 ima_calc_buffer_hash(buf, size, &hash.hdr); 216 if (!result) { 217 int length = sizeof(hash.hdr) + hash.hdr.length; 218 void *tmpbuf = krealloc(iint->ima_hash, length, 219 GFP_NOFS); 220 if (tmpbuf) { 221 iint->ima_hash = tmpbuf; 222 memcpy(iint->ima_hash, &hash, length); 223 iint->version = i_version; 224 iint->flags |= IMA_COLLECTED; 225 } else 226 result = -ENOMEM; 227 } 228 } 229 out: 230 if (result) 231 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, 232 filename, "collect_data", audit_cause, 233 result, 0); 234 return result; 235 } 236 237 /* 238 * ima_store_measurement - store file measurement 239 * 240 * Create an "ima" template and then store the template by calling 241 * ima_store_template. 242 * 243 * We only get here if the inode has not already been measured, 244 * but the measurement could already exist: 245 * - multiple copies of the same file on either the same or 246 * different filesystems. 247 * - the inode was previously flushed as well as the iint info, 248 * containing the hashing info. 249 * 250 * Must be called with iint->mutex held. 251 */ 252 void ima_store_measurement(struct integrity_iint_cache *iint, 253 struct file *file, const unsigned char *filename, 254 struct evm_ima_xattr_data *xattr_value, 255 int xattr_len) 256 { 257 static const char op[] = "add_template_measure"; 258 static const char audit_cause[] = "ENOMEM"; 259 int result = -ENOMEM; 260 struct inode *inode = file_inode(file); 261 struct ima_template_entry *entry; 262 struct ima_event_data event_data = {iint, file, filename, xattr_value, 263 xattr_len, NULL}; 264 int violation = 0; 265 266 if (iint->flags & IMA_MEASURED) 267 return; 268 269 result = ima_alloc_init_template(&event_data, &entry); 270 if (result < 0) { 271 integrity_audit_msg(AUDIT_INTEGRITY_PCR, inode, filename, 272 op, audit_cause, result, 0); 273 return; 274 } 275 276 result = ima_store_template(entry, violation, inode, filename); 277 if (!result || result == -EEXIST) 278 iint->flags |= IMA_MEASURED; 279 if (result < 0) 280 ima_free_template_entry(entry); 281 } 282 283 void ima_audit_measurement(struct integrity_iint_cache *iint, 284 const unsigned char *filename) 285 { 286 struct audit_buffer *ab; 287 char hash[(iint->ima_hash->length * 2) + 1]; 288 const char *algo_name = hash_algo_name[iint->ima_hash->algo]; 289 char algo_hash[sizeof(hash) + strlen(algo_name) + 2]; 290 int i; 291 292 if (iint->flags & IMA_AUDITED) 293 return; 294 295 for (i = 0; i < iint->ima_hash->length; i++) 296 hex_byte_pack(hash + (i * 2), iint->ima_hash->digest[i]); 297 hash[i * 2] = '\0'; 298 299 ab = audit_log_start(current->audit_context, GFP_KERNEL, 300 AUDIT_INTEGRITY_RULE); 301 if (!ab) 302 return; 303 304 audit_log_format(ab, "file="); 305 audit_log_untrustedstring(ab, filename); 306 audit_log_format(ab, " hash="); 307 snprintf(algo_hash, sizeof(algo_hash), "%s:%s", algo_name, hash); 308 audit_log_untrustedstring(ab, algo_hash); 309 310 audit_log_task_info(ab, current); 311 audit_log_end(ab); 312 313 iint->flags |= IMA_AUDITED; 314 } 315 316 const char *ima_d_path(const struct path *path, char **pathbuf) 317 { 318 char *pathname = NULL; 319 320 *pathbuf = __getname(); 321 if (*pathbuf) { 322 pathname = d_absolute_path(path, *pathbuf, PATH_MAX); 323 if (IS_ERR(pathname)) { 324 __putname(*pathbuf); 325 *pathbuf = NULL; 326 pathname = NULL; 327 } 328 } 329 return pathname ?: (const char *)path->dentry->d_name.name; 330 } 331