1 /* 2 * Copyright (C) 2011 IBM Corporation 3 * 4 * Author: 5 * Mimi Zohar <zohar@us.ibm.com> 6 * 7 * This program is free software; you can redistribute it and/or modify 8 * it under the terms of the GNU General Public License as published by 9 * the Free Software Foundation, version 2 of the License. 10 */ 11 #include <linux/module.h> 12 #include <linux/file.h> 13 #include <linux/fs.h> 14 #include <linux/xattr.h> 15 #include <linux/magic.h> 16 #include <linux/ima.h> 17 #include <linux/evm.h> 18 #include <crypto/hash_info.h> 19 20 #include "ima.h" 21 22 static int __init default_appraise_setup(char *str) 23 { 24 if (strncmp(str, "off", 3) == 0) 25 ima_appraise = 0; 26 else if (strncmp(str, "log", 3) == 0) 27 ima_appraise = IMA_APPRAISE_LOG; 28 else if (strncmp(str, "fix", 3) == 0) 29 ima_appraise = IMA_APPRAISE_FIX; 30 return 1; 31 } 32 33 __setup("ima_appraise=", default_appraise_setup); 34 35 /* 36 * ima_must_appraise - set appraise flag 37 * 38 * Return 1 to appraise 39 */ 40 int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func) 41 { 42 if (!ima_appraise) 43 return 0; 44 45 return ima_match_policy(inode, func, mask, IMA_APPRAISE); 46 } 47 48 static int ima_fix_xattr(struct dentry *dentry, 49 struct integrity_iint_cache *iint) 50 { 51 int rc, offset; 52 u8 algo = iint->ima_hash->algo; 53 54 if (algo <= HASH_ALGO_SHA1) { 55 offset = 1; 56 iint->ima_hash->xattr.sha1.type = IMA_XATTR_DIGEST; 57 } else { 58 offset = 0; 59 iint->ima_hash->xattr.ng.type = IMA_XATTR_DIGEST_NG; 60 iint->ima_hash->xattr.ng.algo = algo; 61 } 62 rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_IMA, 63 &iint->ima_hash->xattr.data[offset], 64 (sizeof(iint->ima_hash->xattr) - offset) + 65 iint->ima_hash->length, 0); 66 return rc; 67 } 68 69 /* Return specific func appraised cached result */ 70 enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint, 71 int func) 72 { 73 switch (func) { 74 case MMAP_CHECK: 75 return iint->ima_mmap_status; 76 case BPRM_CHECK: 77 return iint->ima_bprm_status; 78 case MODULE_CHECK: 79 return iint->ima_module_status; 80 case FIRMWARE_CHECK: 81 return iint->ima_firmware_status; 82 case FILE_CHECK: 83 default: 84 return iint->ima_file_status; 85 } 86 } 87 88 static void ima_set_cache_status(struct integrity_iint_cache *iint, 89 int func, enum integrity_status status) 90 { 91 switch (func) { 92 case MMAP_CHECK: 93 iint->ima_mmap_status = status; 94 break; 95 case BPRM_CHECK: 96 iint->ima_bprm_status = status; 97 break; 98 case MODULE_CHECK: 99 iint->ima_module_status = status; 100 break; 101 case FIRMWARE_CHECK: 102 iint->ima_firmware_status = status; 103 break; 104 case FILE_CHECK: 105 default: 106 iint->ima_file_status = status; 107 break; 108 } 109 } 110 111 static void ima_cache_flags(struct integrity_iint_cache *iint, int func) 112 { 113 switch (func) { 114 case MMAP_CHECK: 115 iint->flags |= (IMA_MMAP_APPRAISED | IMA_APPRAISED); 116 break; 117 case BPRM_CHECK: 118 iint->flags |= (IMA_BPRM_APPRAISED | IMA_APPRAISED); 119 break; 120 case MODULE_CHECK: 121 iint->flags |= (IMA_MODULE_APPRAISED | IMA_APPRAISED); 122 break; 123 case FIRMWARE_CHECK: 124 iint->flags |= (IMA_FIRMWARE_APPRAISED | IMA_APPRAISED); 125 break; 126 case FILE_CHECK: 127 default: 128 iint->flags |= (IMA_FILE_APPRAISED | IMA_APPRAISED); 129 break; 130 } 131 } 132 133 void ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value, int xattr_len, 134 struct ima_digest_data *hash) 135 { 136 struct signature_v2_hdr *sig; 137 138 if (!xattr_value || xattr_len < 2) 139 return; 140 141 switch (xattr_value->type) { 142 case EVM_IMA_XATTR_DIGSIG: 143 sig = (typeof(sig))xattr_value; 144 if (sig->version != 2 || xattr_len <= sizeof(*sig)) 145 return; 146 hash->algo = sig->hash_algo; 147 break; 148 case IMA_XATTR_DIGEST_NG: 149 hash->algo = xattr_value->digest[0]; 150 break; 151 case IMA_XATTR_DIGEST: 152 /* this is for backward compatibility */ 153 if (xattr_len == 21) { 154 unsigned int zero = 0; 155 if (!memcmp(&xattr_value->digest[16], &zero, 4)) 156 hash->algo = HASH_ALGO_MD5; 157 else 158 hash->algo = HASH_ALGO_SHA1; 159 } else if (xattr_len == 17) 160 hash->algo = HASH_ALGO_MD5; 161 break; 162 } 163 } 164 165 int ima_read_xattr(struct dentry *dentry, 166 struct evm_ima_xattr_data **xattr_value) 167 { 168 struct inode *inode = dentry->d_inode; 169 170 if (!inode->i_op->getxattr) 171 return 0; 172 173 return vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)xattr_value, 174 0, GFP_NOFS); 175 } 176 177 /* 178 * ima_appraise_measurement - appraise file measurement 179 * 180 * Call evm_verifyxattr() to verify the integrity of 'security.ima'. 181 * Assuming success, compare the xattr hash with the collected measurement. 182 * 183 * Return 0 on success, error code otherwise 184 */ 185 int ima_appraise_measurement(int func, struct integrity_iint_cache *iint, 186 struct file *file, const unsigned char *filename, 187 struct evm_ima_xattr_data *xattr_value, 188 int xattr_len, int opened) 189 { 190 static const char op[] = "appraise_data"; 191 char *cause = "unknown"; 192 struct dentry *dentry = file->f_path.dentry; 193 struct inode *inode = dentry->d_inode; 194 enum integrity_status status = INTEGRITY_UNKNOWN; 195 int rc = xattr_len, hash_start = 0; 196 197 if (!inode->i_op->getxattr) 198 return INTEGRITY_UNKNOWN; 199 200 if (rc <= 0) { 201 if (rc && rc != -ENODATA) 202 goto out; 203 204 cause = "missing-hash"; 205 status = INTEGRITY_NOLABEL; 206 if (opened & FILE_CREATED) { 207 iint->flags |= IMA_NEW_FILE; 208 status = INTEGRITY_PASS; 209 } 210 goto out; 211 } 212 213 status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint); 214 if ((status != INTEGRITY_PASS) && (status != INTEGRITY_UNKNOWN)) { 215 if ((status == INTEGRITY_NOLABEL) 216 || (status == INTEGRITY_NOXATTRS)) 217 cause = "missing-HMAC"; 218 else if (status == INTEGRITY_FAIL) 219 cause = "invalid-HMAC"; 220 goto out; 221 } 222 switch (xattr_value->type) { 223 case IMA_XATTR_DIGEST_NG: 224 /* first byte contains algorithm id */ 225 hash_start = 1; 226 case IMA_XATTR_DIGEST: 227 if (iint->flags & IMA_DIGSIG_REQUIRED) { 228 cause = "IMA-signature-required"; 229 status = INTEGRITY_FAIL; 230 break; 231 } 232 if (xattr_len - sizeof(xattr_value->type) - hash_start >= 233 iint->ima_hash->length) 234 /* xattr length may be longer. md5 hash in previous 235 version occupied 20 bytes in xattr, instead of 16 236 */ 237 rc = memcmp(&xattr_value->digest[hash_start], 238 iint->ima_hash->digest, 239 iint->ima_hash->length); 240 else 241 rc = -EINVAL; 242 if (rc) { 243 cause = "invalid-hash"; 244 status = INTEGRITY_FAIL; 245 break; 246 } 247 status = INTEGRITY_PASS; 248 break; 249 case EVM_IMA_XATTR_DIGSIG: 250 iint->flags |= IMA_DIGSIG; 251 rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA, 252 (const char *)xattr_value, rc, 253 iint->ima_hash->digest, 254 iint->ima_hash->length); 255 if (rc == -EOPNOTSUPP) { 256 status = INTEGRITY_UNKNOWN; 257 } else if (rc) { 258 cause = "invalid-signature"; 259 status = INTEGRITY_FAIL; 260 } else { 261 status = INTEGRITY_PASS; 262 } 263 break; 264 default: 265 status = INTEGRITY_UNKNOWN; 266 cause = "unknown-ima-data"; 267 break; 268 } 269 270 out: 271 if (status != INTEGRITY_PASS) { 272 if ((ima_appraise & IMA_APPRAISE_FIX) && 273 (!xattr_value || 274 xattr_value->type != EVM_IMA_XATTR_DIGSIG)) { 275 if (!ima_fix_xattr(dentry, iint)) 276 status = INTEGRITY_PASS; 277 } 278 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, 279 op, cause, rc, 0); 280 } else { 281 ima_cache_flags(iint, func); 282 } 283 ima_set_cache_status(iint, func, status); 284 return status; 285 } 286 287 /* 288 * ima_update_xattr - update 'security.ima' hash value 289 */ 290 void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file) 291 { 292 struct dentry *dentry = file->f_path.dentry; 293 int rc = 0; 294 295 /* do not collect and update hash for digital signatures */ 296 if (iint->flags & IMA_DIGSIG) 297 return; 298 299 rc = ima_collect_measurement(iint, file, NULL, NULL); 300 if (rc < 0) 301 return; 302 303 ima_fix_xattr(dentry, iint); 304 } 305 306 /** 307 * ima_inode_post_setattr - reflect file metadata changes 308 * @dentry: pointer to the affected dentry 309 * 310 * Changes to a dentry's metadata might result in needing to appraise. 311 * 312 * This function is called from notify_change(), which expects the caller 313 * to lock the inode's i_mutex. 314 */ 315 void ima_inode_post_setattr(struct dentry *dentry) 316 { 317 struct inode *inode = dentry->d_inode; 318 struct integrity_iint_cache *iint; 319 int must_appraise, rc; 320 321 if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode) 322 || !inode->i_op->removexattr) 323 return; 324 325 must_appraise = ima_must_appraise(inode, MAY_ACCESS, POST_SETATTR); 326 iint = integrity_iint_find(inode); 327 if (iint) { 328 iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED | 329 IMA_APPRAISE_SUBMASK | IMA_APPRAISED_SUBMASK | 330 IMA_ACTION_FLAGS); 331 if (must_appraise) 332 iint->flags |= IMA_APPRAISE; 333 } 334 if (!must_appraise) 335 rc = inode->i_op->removexattr(dentry, XATTR_NAME_IMA); 336 return; 337 } 338 339 /* 340 * ima_protect_xattr - protect 'security.ima' 341 * 342 * Ensure that not just anyone can modify or remove 'security.ima'. 343 */ 344 static int ima_protect_xattr(struct dentry *dentry, const char *xattr_name, 345 const void *xattr_value, size_t xattr_value_len) 346 { 347 if (strcmp(xattr_name, XATTR_NAME_IMA) == 0) { 348 if (!capable(CAP_SYS_ADMIN)) 349 return -EPERM; 350 return 1; 351 } 352 return 0; 353 } 354 355 static void ima_reset_appraise_flags(struct inode *inode, int digsig) 356 { 357 struct integrity_iint_cache *iint; 358 359 if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode)) 360 return; 361 362 iint = integrity_iint_find(inode); 363 if (!iint) 364 return; 365 366 iint->flags &= ~IMA_DONE_MASK; 367 if (digsig) 368 iint->flags |= IMA_DIGSIG; 369 return; 370 } 371 372 int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name, 373 const void *xattr_value, size_t xattr_value_len) 374 { 375 const struct evm_ima_xattr_data *xvalue = xattr_value; 376 int result; 377 378 result = ima_protect_xattr(dentry, xattr_name, xattr_value, 379 xattr_value_len); 380 if (result == 1) { 381 if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST)) 382 return -EINVAL; 383 ima_reset_appraise_flags(dentry->d_inode, 384 (xvalue->type == EVM_IMA_XATTR_DIGSIG) ? 1 : 0); 385 result = 0; 386 } 387 return result; 388 } 389 390 int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name) 391 { 392 int result; 393 394 result = ima_protect_xattr(dentry, xattr_name, NULL, 0); 395 if (result == 1) { 396 ima_reset_appraise_flags(dentry->d_inode, 0); 397 result = 0; 398 } 399 return result; 400 } 401