1 /* 2 * Copyright (C) 2005,2006,2007,2008 IBM Corporation 3 * 4 * Authors: 5 * Reiner Sailer <sailer@watson.ibm.com> 6 * Serge Hallyn <serue@us.ibm.com> 7 * Kylene Hall <kylene@us.ibm.com> 8 * Mimi Zohar <zohar@us.ibm.com> 9 * 10 * This program is free software; you can redistribute it and/or 11 * modify it under the terms of the GNU General Public License as 12 * published by the Free Software Foundation, version 2 of the 13 * License. 14 * 15 * File: ima_main.c 16 * implements the IMA hooks: ima_bprm_check, ima_file_mmap, 17 * and ima_file_check. 18 */ 19 #include <linux/module.h> 20 #include <linux/file.h> 21 #include <linux/binfmts.h> 22 #include <linux/mount.h> 23 #include <linux/mman.h> 24 #include <linux/slab.h> 25 #include <linux/xattr.h> 26 #include <linux/ima.h> 27 #include <crypto/hash_info.h> 28 29 #include "ima.h" 30 31 int ima_initialized; 32 33 #ifdef CONFIG_IMA_APPRAISE 34 int ima_appraise = IMA_APPRAISE_ENFORCE; 35 #else 36 int ima_appraise; 37 #endif 38 39 int ima_hash_algo = HASH_ALGO_SHA1; 40 static int hash_setup_done; 41 42 static int __init hash_setup(char *str) 43 { 44 struct ima_template_desc *template_desc = ima_template_desc_current(); 45 int i; 46 47 if (hash_setup_done) 48 return 1; 49 50 if (strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) == 0) { 51 if (strncmp(str, "sha1", 4) == 0) 52 ima_hash_algo = HASH_ALGO_SHA1; 53 else if (strncmp(str, "md5", 3) == 0) 54 ima_hash_algo = HASH_ALGO_MD5; 55 goto out; 56 } 57 58 for (i = 0; i < HASH_ALGO__LAST; i++) { 59 if (strcmp(str, hash_algo_name[i]) == 0) { 60 ima_hash_algo = i; 61 break; 62 } 63 } 64 out: 65 hash_setup_done = 1; 66 return 1; 67 } 68 __setup("ima_hash=", hash_setup); 69 70 /* 71 * ima_rdwr_violation_check 72 * 73 * Only invalidate the PCR for measured files: 74 * - Opening a file for write when already open for read, 75 * results in a time of measure, time of use (ToMToU) error. 76 * - Opening a file for read when already open for write, 77 * could result in a file measurement error. 78 * 79 */ 80 static void ima_rdwr_violation_check(struct file *file) 81 { 82 struct inode *inode = file_inode(file); 83 fmode_t mode = file->f_mode; 84 int must_measure; 85 bool send_tomtou = false, send_writers = false; 86 char *pathbuf = NULL; 87 const char *pathname; 88 89 if (!S_ISREG(inode->i_mode) || !ima_initialized) 90 return; 91 92 mutex_lock(&inode->i_mutex); /* file metadata: permissions, xattr */ 93 94 if (mode & FMODE_WRITE) { 95 if (atomic_read(&inode->i_readcount) && IS_IMA(inode)) 96 send_tomtou = true; 97 goto out; 98 } 99 100 must_measure = ima_must_measure(inode, MAY_READ, FILE_CHECK); 101 if (!must_measure) 102 goto out; 103 104 if (atomic_read(&inode->i_writecount) > 0) 105 send_writers = true; 106 out: 107 mutex_unlock(&inode->i_mutex); 108 109 if (!send_tomtou && !send_writers) 110 return; 111 112 pathname = ima_d_path(&file->f_path, &pathbuf); 113 114 if (send_tomtou) 115 ima_add_violation(file, pathname, "invalid_pcr", "ToMToU"); 116 if (send_writers) 117 ima_add_violation(file, pathname, 118 "invalid_pcr", "open_writers"); 119 kfree(pathbuf); 120 } 121 122 static void ima_check_last_writer(struct integrity_iint_cache *iint, 123 struct inode *inode, struct file *file) 124 { 125 fmode_t mode = file->f_mode; 126 127 if (!(mode & FMODE_WRITE)) 128 return; 129 130 mutex_lock(&inode->i_mutex); 131 if (atomic_read(&inode->i_writecount) == 1 && 132 iint->version != inode->i_version) { 133 iint->flags &= ~IMA_DONE_MASK; 134 if (iint->flags & IMA_APPRAISE) 135 ima_update_xattr(iint, file); 136 } 137 mutex_unlock(&inode->i_mutex); 138 } 139 140 /** 141 * ima_file_free - called on __fput() 142 * @file: pointer to file structure being freed 143 * 144 * Flag files that changed, based on i_version 145 */ 146 void ima_file_free(struct file *file) 147 { 148 struct inode *inode = file_inode(file); 149 struct integrity_iint_cache *iint; 150 151 if (!iint_initialized || !S_ISREG(inode->i_mode)) 152 return; 153 154 iint = integrity_iint_find(inode); 155 if (!iint) 156 return; 157 158 ima_check_last_writer(iint, inode, file); 159 } 160 161 static int process_measurement(struct file *file, const char *filename, 162 int mask, int function) 163 { 164 struct inode *inode = file_inode(file); 165 struct integrity_iint_cache *iint; 166 struct ima_template_desc *template_desc = ima_template_desc_current(); 167 char *pathbuf = NULL; 168 const char *pathname = NULL; 169 int rc = -ENOMEM, action, must_appraise, _func; 170 struct evm_ima_xattr_data *xattr_value = NULL, **xattr_ptr = NULL; 171 int xattr_len = 0; 172 173 if (!ima_initialized || !S_ISREG(inode->i_mode)) 174 return 0; 175 176 /* Return an IMA_MEASURE, IMA_APPRAISE, IMA_AUDIT action 177 * bitmask based on the appraise/audit/measurement policy. 178 * Included is the appraise submask. 179 */ 180 action = ima_get_action(inode, mask, function); 181 if (!action) 182 return 0; 183 184 must_appraise = action & IMA_APPRAISE; 185 186 /* Is the appraise rule hook specific? */ 187 _func = (action & IMA_FILE_APPRAISE) ? FILE_CHECK : function; 188 189 mutex_lock(&inode->i_mutex); 190 191 iint = integrity_inode_get(inode); 192 if (!iint) 193 goto out; 194 195 /* Determine if already appraised/measured based on bitmask 196 * (IMA_MEASURE, IMA_MEASURED, IMA_XXXX_APPRAISE, IMA_XXXX_APPRAISED, 197 * IMA_AUDIT, IMA_AUDITED) 198 */ 199 iint->flags |= action; 200 action &= IMA_DO_MASK; 201 action &= ~((iint->flags & IMA_DONE_MASK) >> 1); 202 203 /* Nothing to do, just return existing appraised status */ 204 if (!action) { 205 if (must_appraise) 206 rc = ima_get_cache_status(iint, _func); 207 goto out_digsig; 208 } 209 210 if (strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) == 0) { 211 if (action & IMA_APPRAISE_SUBMASK) 212 xattr_ptr = &xattr_value; 213 } else 214 xattr_ptr = &xattr_value; 215 216 rc = ima_collect_measurement(iint, file, xattr_ptr, &xattr_len); 217 if (rc != 0) 218 goto out_digsig; 219 220 pathname = filename ?: ima_d_path(&file->f_path, &pathbuf); 221 222 if (action & IMA_MEASURE) 223 ima_store_measurement(iint, file, pathname, 224 xattr_value, xattr_len); 225 if (action & IMA_APPRAISE_SUBMASK) 226 rc = ima_appraise_measurement(_func, iint, file, pathname, 227 xattr_value, xattr_len); 228 if (action & IMA_AUDIT) 229 ima_audit_measurement(iint, pathname); 230 kfree(pathbuf); 231 out_digsig: 232 if ((mask & MAY_WRITE) && (iint->flags & IMA_DIGSIG)) 233 rc = -EACCES; 234 out: 235 mutex_unlock(&inode->i_mutex); 236 kfree(xattr_value); 237 if ((rc && must_appraise) && (ima_appraise & IMA_APPRAISE_ENFORCE)) 238 return -EACCES; 239 return 0; 240 } 241 242 /** 243 * ima_file_mmap - based on policy, collect/store measurement. 244 * @file: pointer to the file to be measured (May be NULL) 245 * @prot: contains the protection that will be applied by the kernel. 246 * 247 * Measure files being mmapped executable based on the ima_must_measure() 248 * policy decision. 249 * 250 * On success return 0. On integrity appraisal error, assuming the file 251 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. 252 */ 253 int ima_file_mmap(struct file *file, unsigned long prot) 254 { 255 if (file && (prot & PROT_EXEC)) 256 return process_measurement(file, NULL, MAY_EXEC, MMAP_CHECK); 257 return 0; 258 } 259 260 /** 261 * ima_bprm_check - based on policy, collect/store measurement. 262 * @bprm: contains the linux_binprm structure 263 * 264 * The OS protects against an executable file, already open for write, 265 * from being executed in deny_write_access() and an executable file, 266 * already open for execute, from being modified in get_write_access(). 267 * So we can be certain that what we verify and measure here is actually 268 * what is being executed. 269 * 270 * On success return 0. On integrity appraisal error, assuming the file 271 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. 272 */ 273 int ima_bprm_check(struct linux_binprm *bprm) 274 { 275 return process_measurement(bprm->file, 276 (strcmp(bprm->filename, bprm->interp) == 0) ? 277 bprm->filename : bprm->interp, 278 MAY_EXEC, BPRM_CHECK); 279 } 280 281 /** 282 * ima_path_check - based on policy, collect/store measurement. 283 * @file: pointer to the file to be measured 284 * @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE 285 * 286 * Measure files based on the ima_must_measure() policy decision. 287 * 288 * On success return 0. On integrity appraisal error, assuming the file 289 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. 290 */ 291 int ima_file_check(struct file *file, int mask) 292 { 293 ima_rdwr_violation_check(file); 294 return process_measurement(file, NULL, 295 mask & (MAY_READ | MAY_WRITE | MAY_EXEC), 296 FILE_CHECK); 297 } 298 EXPORT_SYMBOL_GPL(ima_file_check); 299 300 /** 301 * ima_module_check - based on policy, collect/store/appraise measurement. 302 * @file: pointer to the file to be measured/appraised 303 * 304 * Measure/appraise kernel modules based on policy. 305 * 306 * On success return 0. On integrity appraisal error, assuming the file 307 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. 308 */ 309 int ima_module_check(struct file *file) 310 { 311 if (!file) { 312 #ifndef CONFIG_MODULE_SIG_FORCE 313 if ((ima_appraise & IMA_APPRAISE_MODULES) && 314 (ima_appraise & IMA_APPRAISE_ENFORCE)) 315 return -EACCES; /* INTEGRITY_UNKNOWN */ 316 #endif 317 return 0; /* We rely on module signature checking */ 318 } 319 return process_measurement(file, NULL, MAY_EXEC, MODULE_CHECK); 320 } 321 322 static int __init init_ima(void) 323 { 324 int error; 325 326 hash_setup(CONFIG_IMA_DEFAULT_HASH); 327 error = ima_init(); 328 if (!error) 329 ima_initialized = 1; 330 return error; 331 } 332 333 late_initcall(init_ima); /* Start IMA after the TPM is available */ 334 335 MODULE_DESCRIPTION("Integrity Measurement Architecture"); 336 MODULE_LICENSE("GPL"); 337