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 dentry *dentry = file->f_path.dentry; 83 struct inode *inode = file_inode(file); 84 fmode_t mode = file->f_mode; 85 int must_measure; 86 bool send_tomtou = false, send_writers = false; 87 char *pathbuf = NULL; 88 const char *pathname; 89 90 if (!S_ISREG(inode->i_mode) || !ima_initialized) 91 return; 92 93 mutex_lock(&inode->i_mutex); /* file metadata: permissions, xattr */ 94 95 if (mode & FMODE_WRITE) { 96 if (atomic_read(&inode->i_readcount) && IS_IMA(inode)) 97 send_tomtou = true; 98 goto out; 99 } 100 101 must_measure = ima_must_measure(inode, MAY_READ, FILE_CHECK); 102 if (!must_measure) 103 goto out; 104 105 if (atomic_read(&inode->i_writecount) > 0) 106 send_writers = true; 107 out: 108 mutex_unlock(&inode->i_mutex); 109 110 if (!send_tomtou && !send_writers) 111 return; 112 113 pathname = ima_d_path(&file->f_path, &pathbuf); 114 if (!pathname || strlen(pathname) > IMA_EVENT_NAME_LEN_MAX) 115 pathname = dentry->d_name.name; 116 117 if (send_tomtou) 118 ima_add_violation(file, pathname, "invalid_pcr", "ToMToU"); 119 if (send_writers) 120 ima_add_violation(file, pathname, 121 "invalid_pcr", "open_writers"); 122 kfree(pathbuf); 123 } 124 125 static void ima_check_last_writer(struct integrity_iint_cache *iint, 126 struct inode *inode, struct file *file) 127 { 128 fmode_t mode = file->f_mode; 129 130 if (!(mode & FMODE_WRITE)) 131 return; 132 133 mutex_lock(&inode->i_mutex); 134 if (atomic_read(&inode->i_writecount) == 1 && 135 iint->version != inode->i_version) { 136 iint->flags &= ~IMA_DONE_MASK; 137 if (iint->flags & IMA_APPRAISE) 138 ima_update_xattr(iint, file); 139 } 140 mutex_unlock(&inode->i_mutex); 141 } 142 143 /** 144 * ima_file_free - called on __fput() 145 * @file: pointer to file structure being freed 146 * 147 * Flag files that changed, based on i_version 148 */ 149 void ima_file_free(struct file *file) 150 { 151 struct inode *inode = file_inode(file); 152 struct integrity_iint_cache *iint; 153 154 if (!iint_initialized || !S_ISREG(inode->i_mode)) 155 return; 156 157 iint = integrity_iint_find(inode); 158 if (!iint) 159 return; 160 161 ima_check_last_writer(iint, inode, file); 162 } 163 164 static int process_measurement(struct file *file, const char *filename, 165 int mask, int function) 166 { 167 struct inode *inode = file_inode(file); 168 struct integrity_iint_cache *iint; 169 struct ima_template_desc *template_desc = ima_template_desc_current(); 170 char *pathbuf = NULL; 171 const char *pathname = NULL; 172 int rc = -ENOMEM, action, must_appraise, _func; 173 struct evm_ima_xattr_data *xattr_value = NULL, **xattr_ptr = NULL; 174 int xattr_len = 0; 175 176 if (!ima_initialized || !S_ISREG(inode->i_mode)) 177 return 0; 178 179 /* Return an IMA_MEASURE, IMA_APPRAISE, IMA_AUDIT action 180 * bitmask based on the appraise/audit/measurement policy. 181 * Included is the appraise submask. 182 */ 183 action = ima_get_action(inode, mask, function); 184 if (!action) 185 return 0; 186 187 must_appraise = action & IMA_APPRAISE; 188 189 /* Is the appraise rule hook specific? */ 190 _func = (action & IMA_FILE_APPRAISE) ? FILE_CHECK : function; 191 192 mutex_lock(&inode->i_mutex); 193 194 iint = integrity_inode_get(inode); 195 if (!iint) 196 goto out; 197 198 /* Determine if already appraised/measured based on bitmask 199 * (IMA_MEASURE, IMA_MEASURED, IMA_XXXX_APPRAISE, IMA_XXXX_APPRAISED, 200 * IMA_AUDIT, IMA_AUDITED) 201 */ 202 iint->flags |= action; 203 action &= IMA_DO_MASK; 204 action &= ~((iint->flags & IMA_DONE_MASK) >> 1); 205 206 /* Nothing to do, just return existing appraised status */ 207 if (!action) { 208 if (must_appraise) 209 rc = ima_get_cache_status(iint, _func); 210 goto out_digsig; 211 } 212 213 if (strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) == 0) { 214 if (action & IMA_APPRAISE_SUBMASK) 215 xattr_ptr = &xattr_value; 216 } else 217 xattr_ptr = &xattr_value; 218 219 rc = ima_collect_measurement(iint, file, xattr_ptr, &xattr_len); 220 if (rc != 0) 221 goto out_digsig; 222 223 pathname = !filename ? ima_d_path(&file->f_path, &pathbuf) : filename; 224 if (!pathname) 225 pathname = (const char *)file->f_dentry->d_name.name; 226 227 if (action & IMA_MEASURE) 228 ima_store_measurement(iint, file, pathname, 229 xattr_value, xattr_len); 230 if (action & IMA_APPRAISE_SUBMASK) 231 rc = ima_appraise_measurement(_func, iint, file, pathname, 232 xattr_value, xattr_len); 233 if (action & IMA_AUDIT) 234 ima_audit_measurement(iint, pathname); 235 kfree(pathbuf); 236 out_digsig: 237 if ((mask & MAY_WRITE) && (iint->flags & IMA_DIGSIG)) 238 rc = -EACCES; 239 out: 240 mutex_unlock(&inode->i_mutex); 241 kfree(xattr_value); 242 if ((rc && must_appraise) && (ima_appraise & IMA_APPRAISE_ENFORCE)) 243 return -EACCES; 244 return 0; 245 } 246 247 /** 248 * ima_file_mmap - based on policy, collect/store measurement. 249 * @file: pointer to the file to be measured (May be NULL) 250 * @prot: contains the protection that will be applied by the kernel. 251 * 252 * Measure files being mmapped executable based on the ima_must_measure() 253 * policy decision. 254 * 255 * On success return 0. On integrity appraisal error, assuming the file 256 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. 257 */ 258 int ima_file_mmap(struct file *file, unsigned long prot) 259 { 260 if (file && (prot & PROT_EXEC)) 261 return process_measurement(file, NULL, MAY_EXEC, MMAP_CHECK); 262 return 0; 263 } 264 265 /** 266 * ima_bprm_check - based on policy, collect/store measurement. 267 * @bprm: contains the linux_binprm structure 268 * 269 * The OS protects against an executable file, already open for write, 270 * from being executed in deny_write_access() and an executable file, 271 * already open for execute, from being modified in get_write_access(). 272 * So we can be certain that what we verify and measure here is actually 273 * what is being executed. 274 * 275 * On success return 0. On integrity appraisal error, assuming the file 276 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. 277 */ 278 int ima_bprm_check(struct linux_binprm *bprm) 279 { 280 return process_measurement(bprm->file, 281 (strcmp(bprm->filename, bprm->interp) == 0) ? 282 bprm->filename : bprm->interp, 283 MAY_EXEC, BPRM_CHECK); 284 } 285 286 /** 287 * ima_path_check - based on policy, collect/store measurement. 288 * @file: pointer to the file to be measured 289 * @mask: contains MAY_READ, MAY_WRITE or MAY_EXECUTE 290 * 291 * Measure files based on the ima_must_measure() policy decision. 292 * 293 * On success return 0. On integrity appraisal error, assuming the file 294 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. 295 */ 296 int ima_file_check(struct file *file, int mask) 297 { 298 ima_rdwr_violation_check(file); 299 return process_measurement(file, NULL, 300 mask & (MAY_READ | MAY_WRITE | MAY_EXEC), 301 FILE_CHECK); 302 } 303 EXPORT_SYMBOL_GPL(ima_file_check); 304 305 /** 306 * ima_module_check - based on policy, collect/store/appraise measurement. 307 * @file: pointer to the file to be measured/appraised 308 * 309 * Measure/appraise kernel modules based on policy. 310 * 311 * On success return 0. On integrity appraisal error, assuming the file 312 * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. 313 */ 314 int ima_module_check(struct file *file) 315 { 316 if (!file) { 317 #ifndef CONFIG_MODULE_SIG_FORCE 318 if ((ima_appraise & IMA_APPRAISE_MODULES) && 319 (ima_appraise & IMA_APPRAISE_ENFORCE)) 320 return -EACCES; /* INTEGRITY_UNKNOWN */ 321 #endif 322 return 0; /* We rely on module signature checking */ 323 } 324 return process_measurement(file, NULL, MAY_EXEC, MODULE_CHECK); 325 } 326 327 static int __init init_ima(void) 328 { 329 int error; 330 331 hash_setup(CONFIG_IMA_DEFAULT_HASH); 332 error = ima_init(); 333 if (!error) 334 ima_initialized = 1; 335 return error; 336 } 337 338 late_initcall(init_ima); /* Start IMA after the TPM is available */ 339 340 MODULE_DESCRIPTION("Integrity Measurement Architecture"); 341 MODULE_LICENSE("GPL"); 342