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