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/init.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 19 #include "ima.h" 20 21 static int __init default_appraise_setup(char *str) 22 { 23 #ifdef CONFIG_IMA_APPRAISE_BOOTPARAM 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 #endif 31 return 1; 32 } 33 34 __setup("ima_appraise=", default_appraise_setup); 35 36 /* 37 * is_ima_appraise_enabled - return appraise status 38 * 39 * Only return enabled, if not in ima_appraise="fix" or "log" modes. 40 */ 41 bool is_ima_appraise_enabled(void) 42 { 43 return ima_appraise & IMA_APPRAISE_ENFORCE; 44 } 45 46 /* 47 * ima_must_appraise - set appraise flag 48 * 49 * Return 1 to appraise or hash 50 */ 51 int ima_must_appraise(struct inode *inode, int mask, enum ima_hooks func) 52 { 53 u32 secid; 54 55 if (!ima_appraise) 56 return 0; 57 58 security_task_getsecid(current, &secid); 59 return ima_match_policy(inode, current_cred(), secid, func, mask, 60 IMA_APPRAISE | IMA_HASH, NULL); 61 } 62 63 static int ima_fix_xattr(struct dentry *dentry, 64 struct integrity_iint_cache *iint) 65 { 66 int rc, offset; 67 u8 algo = iint->ima_hash->algo; 68 69 if (algo <= HASH_ALGO_SHA1) { 70 offset = 1; 71 iint->ima_hash->xattr.sha1.type = IMA_XATTR_DIGEST; 72 } else { 73 offset = 0; 74 iint->ima_hash->xattr.ng.type = IMA_XATTR_DIGEST_NG; 75 iint->ima_hash->xattr.ng.algo = algo; 76 } 77 rc = __vfs_setxattr_noperm(dentry, XATTR_NAME_IMA, 78 &iint->ima_hash->xattr.data[offset], 79 (sizeof(iint->ima_hash->xattr) - offset) + 80 iint->ima_hash->length, 0); 81 return rc; 82 } 83 84 /* Return specific func appraised cached result */ 85 enum integrity_status ima_get_cache_status(struct integrity_iint_cache *iint, 86 enum ima_hooks func) 87 { 88 switch (func) { 89 case MMAP_CHECK: 90 return iint->ima_mmap_status; 91 case BPRM_CHECK: 92 return iint->ima_bprm_status; 93 case CREDS_CHECK: 94 return iint->ima_creds_status; 95 case FILE_CHECK: 96 case POST_SETATTR: 97 return iint->ima_file_status; 98 case MODULE_CHECK ... MAX_CHECK - 1: 99 default: 100 return iint->ima_read_status; 101 } 102 } 103 104 static void ima_set_cache_status(struct integrity_iint_cache *iint, 105 enum ima_hooks func, 106 enum integrity_status status) 107 { 108 switch (func) { 109 case MMAP_CHECK: 110 iint->ima_mmap_status = status; 111 break; 112 case BPRM_CHECK: 113 iint->ima_bprm_status = status; 114 break; 115 case CREDS_CHECK: 116 iint->ima_creds_status = status; 117 break; 118 case FILE_CHECK: 119 case POST_SETATTR: 120 iint->ima_file_status = status; 121 break; 122 case MODULE_CHECK ... MAX_CHECK - 1: 123 default: 124 iint->ima_read_status = status; 125 break; 126 } 127 } 128 129 static void ima_cache_flags(struct integrity_iint_cache *iint, 130 enum ima_hooks func) 131 { 132 switch (func) { 133 case MMAP_CHECK: 134 iint->flags |= (IMA_MMAP_APPRAISED | IMA_APPRAISED); 135 break; 136 case BPRM_CHECK: 137 iint->flags |= (IMA_BPRM_APPRAISED | IMA_APPRAISED); 138 break; 139 case CREDS_CHECK: 140 iint->flags |= (IMA_CREDS_APPRAISED | IMA_APPRAISED); 141 break; 142 case FILE_CHECK: 143 case POST_SETATTR: 144 iint->flags |= (IMA_FILE_APPRAISED | IMA_APPRAISED); 145 break; 146 case MODULE_CHECK ... MAX_CHECK - 1: 147 default: 148 iint->flags |= (IMA_READ_APPRAISED | IMA_APPRAISED); 149 break; 150 } 151 } 152 153 enum hash_algo ima_get_hash_algo(struct evm_ima_xattr_data *xattr_value, 154 int xattr_len) 155 { 156 struct signature_v2_hdr *sig; 157 enum hash_algo ret; 158 159 if (!xattr_value || xattr_len < 2) 160 /* return default hash algo */ 161 return ima_hash_algo; 162 163 switch (xattr_value->type) { 164 case EVM_IMA_XATTR_DIGSIG: 165 sig = (typeof(sig))xattr_value; 166 if (sig->version != 2 || xattr_len <= sizeof(*sig)) 167 return ima_hash_algo; 168 return sig->hash_algo; 169 break; 170 case IMA_XATTR_DIGEST_NG: 171 ret = xattr_value->digest[0]; 172 if (ret < HASH_ALGO__LAST) 173 return ret; 174 break; 175 case IMA_XATTR_DIGEST: 176 /* this is for backward compatibility */ 177 if (xattr_len == 21) { 178 unsigned int zero = 0; 179 if (!memcmp(&xattr_value->digest[16], &zero, 4)) 180 return HASH_ALGO_MD5; 181 else 182 return HASH_ALGO_SHA1; 183 } else if (xattr_len == 17) 184 return HASH_ALGO_MD5; 185 break; 186 } 187 188 /* return default hash algo */ 189 return ima_hash_algo; 190 } 191 192 int ima_read_xattr(struct dentry *dentry, 193 struct evm_ima_xattr_data **xattr_value) 194 { 195 ssize_t ret; 196 197 ret = vfs_getxattr_alloc(dentry, XATTR_NAME_IMA, (char **)xattr_value, 198 0, GFP_NOFS); 199 if (ret == -EOPNOTSUPP) 200 ret = 0; 201 return ret; 202 } 203 204 /* 205 * ima_appraise_measurement - appraise file measurement 206 * 207 * Call evm_verifyxattr() to verify the integrity of 'security.ima'. 208 * Assuming success, compare the xattr hash with the collected measurement. 209 * 210 * Return 0 on success, error code otherwise 211 */ 212 int ima_appraise_measurement(enum ima_hooks func, 213 struct integrity_iint_cache *iint, 214 struct file *file, const unsigned char *filename, 215 struct evm_ima_xattr_data *xattr_value, 216 int xattr_len) 217 { 218 static const char op[] = "appraise_data"; 219 const char *cause = "unknown"; 220 struct dentry *dentry = file_dentry(file); 221 struct inode *inode = d_backing_inode(dentry); 222 enum integrity_status status = INTEGRITY_UNKNOWN; 223 int rc = xattr_len, hash_start = 0; 224 225 if (!(inode->i_opflags & IOP_XATTR)) 226 return INTEGRITY_UNKNOWN; 227 228 if (rc <= 0) { 229 if (rc && rc != -ENODATA) 230 goto out; 231 232 cause = iint->flags & IMA_DIGSIG_REQUIRED ? 233 "IMA-signature-required" : "missing-hash"; 234 status = INTEGRITY_NOLABEL; 235 if (file->f_mode & FMODE_CREATED) 236 iint->flags |= IMA_NEW_FILE; 237 if ((iint->flags & IMA_NEW_FILE) && 238 (!(iint->flags & IMA_DIGSIG_REQUIRED) || 239 (inode->i_size == 0))) 240 status = INTEGRITY_PASS; 241 goto out; 242 } 243 244 status = evm_verifyxattr(dentry, XATTR_NAME_IMA, xattr_value, rc, iint); 245 switch (status) { 246 case INTEGRITY_PASS: 247 case INTEGRITY_PASS_IMMUTABLE: 248 case INTEGRITY_UNKNOWN: 249 break; 250 case INTEGRITY_NOXATTRS: /* No EVM protected xattrs. */ 251 case INTEGRITY_NOLABEL: /* No security.evm xattr. */ 252 cause = "missing-HMAC"; 253 goto out; 254 case INTEGRITY_FAIL: /* Invalid HMAC/signature. */ 255 cause = "invalid-HMAC"; 256 goto out; 257 default: 258 WARN_ONCE(true, "Unexpected integrity status %d\n", status); 259 } 260 261 switch (xattr_value->type) { 262 case IMA_XATTR_DIGEST_NG: 263 /* first byte contains algorithm id */ 264 hash_start = 1; 265 /* fall through */ 266 case IMA_XATTR_DIGEST: 267 if (iint->flags & IMA_DIGSIG_REQUIRED) { 268 cause = "IMA-signature-required"; 269 status = INTEGRITY_FAIL; 270 break; 271 } 272 clear_bit(IMA_DIGSIG, &iint->atomic_flags); 273 if (xattr_len - sizeof(xattr_value->type) - hash_start >= 274 iint->ima_hash->length) 275 /* xattr length may be longer. md5 hash in previous 276 version occupied 20 bytes in xattr, instead of 16 277 */ 278 rc = memcmp(&xattr_value->digest[hash_start], 279 iint->ima_hash->digest, 280 iint->ima_hash->length); 281 else 282 rc = -EINVAL; 283 if (rc) { 284 cause = "invalid-hash"; 285 status = INTEGRITY_FAIL; 286 break; 287 } 288 status = INTEGRITY_PASS; 289 break; 290 case EVM_IMA_XATTR_DIGSIG: 291 set_bit(IMA_DIGSIG, &iint->atomic_flags); 292 rc = integrity_digsig_verify(INTEGRITY_KEYRING_IMA, 293 (const char *)xattr_value, 294 xattr_len, 295 iint->ima_hash->digest, 296 iint->ima_hash->length); 297 if (rc == -EOPNOTSUPP) { 298 status = INTEGRITY_UNKNOWN; 299 break; 300 } 301 if (IS_ENABLED(CONFIG_INTEGRITY_PLATFORM_KEYRING) && rc && 302 func == KEXEC_KERNEL_CHECK) 303 rc = integrity_digsig_verify(INTEGRITY_KEYRING_PLATFORM, 304 (const char *)xattr_value, 305 xattr_len, 306 iint->ima_hash->digest, 307 iint->ima_hash->length); 308 if (rc) { 309 cause = "invalid-signature"; 310 status = INTEGRITY_FAIL; 311 } else { 312 status = INTEGRITY_PASS; 313 } 314 break; 315 default: 316 status = INTEGRITY_UNKNOWN; 317 cause = "unknown-ima-data"; 318 break; 319 } 320 321 out: 322 /* 323 * File signatures on some filesystems can not be properly verified. 324 * When such filesystems are mounted by an untrusted mounter or on a 325 * system not willing to accept such a risk, fail the file signature 326 * verification. 327 */ 328 if ((inode->i_sb->s_iflags & SB_I_IMA_UNVERIFIABLE_SIGNATURE) && 329 ((inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER) || 330 (iint->flags & IMA_FAIL_UNVERIFIABLE_SIGS))) { 331 status = INTEGRITY_FAIL; 332 cause = "unverifiable-signature"; 333 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, 334 op, cause, rc, 0); 335 } else if (status != INTEGRITY_PASS) { 336 /* Fix mode, but don't replace file signatures. */ 337 if ((ima_appraise & IMA_APPRAISE_FIX) && 338 (!xattr_value || 339 xattr_value->type != EVM_IMA_XATTR_DIGSIG)) { 340 if (!ima_fix_xattr(dentry, iint)) 341 status = INTEGRITY_PASS; 342 } 343 344 /* Permit new files with file signatures, but without data. */ 345 if (inode->i_size == 0 && iint->flags & IMA_NEW_FILE && 346 xattr_value && xattr_value->type == EVM_IMA_XATTR_DIGSIG) { 347 status = INTEGRITY_PASS; 348 } 349 350 integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, filename, 351 op, cause, rc, 0); 352 } else { 353 ima_cache_flags(iint, func); 354 } 355 356 ima_set_cache_status(iint, func, status); 357 return status; 358 } 359 360 /* 361 * ima_update_xattr - update 'security.ima' hash value 362 */ 363 void ima_update_xattr(struct integrity_iint_cache *iint, struct file *file) 364 { 365 struct dentry *dentry = file_dentry(file); 366 int rc = 0; 367 368 /* do not collect and update hash for digital signatures */ 369 if (test_bit(IMA_DIGSIG, &iint->atomic_flags)) 370 return; 371 372 if ((iint->ima_file_status != INTEGRITY_PASS) && 373 !(iint->flags & IMA_HASH)) 374 return; 375 376 rc = ima_collect_measurement(iint, file, NULL, 0, ima_hash_algo); 377 if (rc < 0) 378 return; 379 380 inode_lock(file_inode(file)); 381 ima_fix_xattr(dentry, iint); 382 inode_unlock(file_inode(file)); 383 } 384 385 /** 386 * ima_inode_post_setattr - reflect file metadata changes 387 * @dentry: pointer to the affected dentry 388 * 389 * Changes to a dentry's metadata might result in needing to appraise. 390 * 391 * This function is called from notify_change(), which expects the caller 392 * to lock the inode's i_mutex. 393 */ 394 void ima_inode_post_setattr(struct dentry *dentry) 395 { 396 struct inode *inode = d_backing_inode(dentry); 397 struct integrity_iint_cache *iint; 398 int action; 399 400 if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode) 401 || !(inode->i_opflags & IOP_XATTR)) 402 return; 403 404 action = ima_must_appraise(inode, MAY_ACCESS, POST_SETATTR); 405 if (!action) 406 __vfs_removexattr(dentry, XATTR_NAME_IMA); 407 iint = integrity_iint_find(inode); 408 if (iint) { 409 set_bit(IMA_CHANGE_ATTR, &iint->atomic_flags); 410 if (!action) 411 clear_bit(IMA_UPDATE_XATTR, &iint->atomic_flags); 412 } 413 } 414 415 /* 416 * ima_protect_xattr - protect 'security.ima' 417 * 418 * Ensure that not just anyone can modify or remove 'security.ima'. 419 */ 420 static int ima_protect_xattr(struct dentry *dentry, const char *xattr_name, 421 const void *xattr_value, size_t xattr_value_len) 422 { 423 if (strcmp(xattr_name, XATTR_NAME_IMA) == 0) { 424 if (!capable(CAP_SYS_ADMIN)) 425 return -EPERM; 426 return 1; 427 } 428 return 0; 429 } 430 431 static void ima_reset_appraise_flags(struct inode *inode, int digsig) 432 { 433 struct integrity_iint_cache *iint; 434 435 if (!(ima_policy_flag & IMA_APPRAISE) || !S_ISREG(inode->i_mode)) 436 return; 437 438 iint = integrity_iint_find(inode); 439 if (!iint) 440 return; 441 iint->measured_pcrs = 0; 442 set_bit(IMA_CHANGE_XATTR, &iint->atomic_flags); 443 if (digsig) 444 set_bit(IMA_DIGSIG, &iint->atomic_flags); 445 else 446 clear_bit(IMA_DIGSIG, &iint->atomic_flags); 447 } 448 449 int ima_inode_setxattr(struct dentry *dentry, const char *xattr_name, 450 const void *xattr_value, size_t xattr_value_len) 451 { 452 const struct evm_ima_xattr_data *xvalue = xattr_value; 453 int result; 454 455 result = ima_protect_xattr(dentry, xattr_name, xattr_value, 456 xattr_value_len); 457 if (result == 1) { 458 if (!xattr_value_len || (xvalue->type >= IMA_XATTR_LAST)) 459 return -EINVAL; 460 ima_reset_appraise_flags(d_backing_inode(dentry), 461 xvalue->type == EVM_IMA_XATTR_DIGSIG); 462 result = 0; 463 } 464 return result; 465 } 466 467 int ima_inode_removexattr(struct dentry *dentry, const char *xattr_name) 468 { 469 int result; 470 471 result = ima_protect_xattr(dentry, xattr_name, NULL, 0); 472 if (result == 1) { 473 ima_reset_appraise_flags(d_backing_inode(dentry), 0); 474 result = 0; 475 } 476 return result; 477 } 478