b.liu | e958203 | 2025-04-17 19:18:16 +0800 | [diff] [blame^] | 1 | // SPDX-License-Identifier: GPL-2.0-only |
| 2 | /* |
| 3 | * Integrity Measurement Architecture |
| 4 | * |
| 5 | * Copyright (C) 2005,2006,2007,2008 IBM Corporation |
| 6 | * |
| 7 | * Authors: |
| 8 | * Reiner Sailer <sailer@watson.ibm.com> |
| 9 | * Serge Hallyn <serue@us.ibm.com> |
| 10 | * Kylene Hall <kylene@us.ibm.com> |
| 11 | * Mimi Zohar <zohar@us.ibm.com> |
| 12 | * |
| 13 | * File: ima_main.c |
| 14 | * implements the IMA hooks: ima_bprm_check, ima_file_mmap, |
| 15 | * and ima_file_check. |
| 16 | */ |
| 17 | |
| 18 | #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt |
| 19 | |
| 20 | #include <linux/module.h> |
| 21 | #include <linux/file.h> |
| 22 | #include <linux/binfmts.h> |
| 23 | #include <linux/mount.h> |
| 24 | #include <linux/mman.h> |
| 25 | #include <linux/slab.h> |
| 26 | #include <linux/xattr.h> |
| 27 | #include <linux/ima.h> |
| 28 | #include <linux/iversion.h> |
| 29 | #include <linux/fs.h> |
| 30 | #include <linux/iversion.h> |
| 31 | |
| 32 | #include "ima.h" |
| 33 | |
| 34 | #ifdef CONFIG_IMA_APPRAISE |
| 35 | int ima_appraise = IMA_APPRAISE_ENFORCE; |
| 36 | #else |
| 37 | int ima_appraise; |
| 38 | #endif |
| 39 | |
| 40 | int ima_hash_algo = HASH_ALGO_SHA1; |
| 41 | static int hash_setup_done; |
| 42 | |
| 43 | static struct notifier_block ima_lsm_policy_notifier = { |
| 44 | .notifier_call = ima_lsm_policy_change, |
| 45 | }; |
| 46 | |
| 47 | static int __init hash_setup(char *str) |
| 48 | { |
| 49 | struct ima_template_desc *template_desc = ima_template_desc_current(); |
| 50 | int i; |
| 51 | |
| 52 | if (hash_setup_done) |
| 53 | return 1; |
| 54 | |
| 55 | if (strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) == 0) { |
| 56 | if (strncmp(str, "sha1", 4) == 0) |
| 57 | ima_hash_algo = HASH_ALGO_SHA1; |
| 58 | else if (strncmp(str, "md5", 3) == 0) |
| 59 | ima_hash_algo = HASH_ALGO_MD5; |
| 60 | else |
| 61 | return 1; |
| 62 | goto out; |
| 63 | } |
| 64 | |
| 65 | i = match_string(hash_algo_name, HASH_ALGO__LAST, str); |
| 66 | if (i < 0) |
| 67 | return 1; |
| 68 | |
| 69 | ima_hash_algo = i; |
| 70 | out: |
| 71 | hash_setup_done = 1; |
| 72 | return 1; |
| 73 | } |
| 74 | __setup("ima_hash=", hash_setup); |
| 75 | |
| 76 | /* Prevent mmap'ing a file execute that is already mmap'ed write */ |
| 77 | static int mmap_violation_check(enum ima_hooks func, struct file *file, |
| 78 | char **pathbuf, const char **pathname, |
| 79 | char *filename) |
| 80 | { |
| 81 | struct inode *inode; |
| 82 | int rc = 0; |
| 83 | |
| 84 | if ((func == MMAP_CHECK) && mapping_writably_mapped(file->f_mapping)) { |
| 85 | rc = -ETXTBSY; |
| 86 | inode = file_inode(file); |
| 87 | |
| 88 | if (!*pathbuf) /* ima_rdwr_violation possibly pre-fetched */ |
| 89 | *pathname = ima_d_path(&file->f_path, pathbuf, |
| 90 | filename); |
| 91 | integrity_audit_msg(AUDIT_INTEGRITY_DATA, inode, *pathname, |
| 92 | "mmap_file", "mmapped_writers", rc, 0); |
| 93 | } |
| 94 | return rc; |
| 95 | } |
| 96 | |
| 97 | /* |
| 98 | * ima_rdwr_violation_check |
| 99 | * |
| 100 | * Only invalidate the PCR for measured files: |
| 101 | * - Opening a file for write when already open for read, |
| 102 | * results in a time of measure, time of use (ToMToU) error. |
| 103 | * - Opening a file for read when already open for write, |
| 104 | * could result in a file measurement error. |
| 105 | * |
| 106 | */ |
| 107 | static void ima_rdwr_violation_check(struct file *file, |
| 108 | struct integrity_iint_cache *iint, |
| 109 | int must_measure, |
| 110 | char **pathbuf, |
| 111 | const char **pathname, |
| 112 | char *filename) |
| 113 | { |
| 114 | struct inode *inode = file_inode(file); |
| 115 | fmode_t mode = file->f_mode; |
| 116 | bool send_tomtou = false, send_writers = false; |
| 117 | |
| 118 | if (mode & FMODE_WRITE) { |
| 119 | if (atomic_read(&inode->i_readcount) && IS_IMA(inode)) { |
| 120 | if (!iint) |
| 121 | iint = integrity_iint_find(inode); |
| 122 | /* IMA_MEASURE is set from reader side */ |
| 123 | if (iint && test_bit(IMA_MUST_MEASURE, |
| 124 | &iint->atomic_flags)) |
| 125 | send_tomtou = true; |
| 126 | } |
| 127 | } else { |
| 128 | if (must_measure) |
| 129 | set_bit(IMA_MUST_MEASURE, &iint->atomic_flags); |
| 130 | if (inode_is_open_for_write(inode) && must_measure) |
| 131 | send_writers = true; |
| 132 | } |
| 133 | |
| 134 | if (!send_tomtou && !send_writers) |
| 135 | return; |
| 136 | |
| 137 | *pathname = ima_d_path(&file->f_path, pathbuf, filename); |
| 138 | |
| 139 | if (send_tomtou) |
| 140 | ima_add_violation(file, *pathname, iint, |
| 141 | "invalid_pcr", "ToMToU"); |
| 142 | if (send_writers) |
| 143 | ima_add_violation(file, *pathname, iint, |
| 144 | "invalid_pcr", "open_writers"); |
| 145 | } |
| 146 | |
| 147 | static void ima_check_last_writer(struct integrity_iint_cache *iint, |
| 148 | struct inode *inode, struct file *file) |
| 149 | { |
| 150 | fmode_t mode = file->f_mode; |
| 151 | bool update; |
| 152 | |
| 153 | if (!(mode & FMODE_WRITE)) |
| 154 | return; |
| 155 | |
| 156 | mutex_lock(&iint->mutex); |
| 157 | if (atomic_read(&inode->i_writecount) == 1) { |
| 158 | update = test_and_clear_bit(IMA_UPDATE_XATTR, |
| 159 | &iint->atomic_flags); |
| 160 | if (!IS_I_VERSION(inode) || |
| 161 | !inode_eq_iversion(inode, iint->version) || |
| 162 | (iint->flags & IMA_NEW_FILE)) { |
| 163 | iint->flags &= ~(IMA_DONE_MASK | IMA_NEW_FILE); |
| 164 | iint->measured_pcrs = 0; |
| 165 | if (update) |
| 166 | ima_update_xattr(iint, file); |
| 167 | } |
| 168 | } |
| 169 | mutex_unlock(&iint->mutex); |
| 170 | } |
| 171 | |
| 172 | /** |
| 173 | * ima_file_free - called on __fput() |
| 174 | * @file: pointer to file structure being freed |
| 175 | * |
| 176 | * Flag files that changed, based on i_version |
| 177 | */ |
| 178 | void ima_file_free(struct file *file) |
| 179 | { |
| 180 | struct inode *inode = file_inode(file); |
| 181 | struct integrity_iint_cache *iint; |
| 182 | |
| 183 | if (!ima_policy_flag || !S_ISREG(inode->i_mode)) |
| 184 | return; |
| 185 | |
| 186 | iint = integrity_iint_find(inode); |
| 187 | if (!iint) |
| 188 | return; |
| 189 | |
| 190 | ima_check_last_writer(iint, inode, file); |
| 191 | } |
| 192 | |
| 193 | static int process_measurement(struct file *file, const struct cred *cred, |
| 194 | u32 secid, char *buf, loff_t size, int mask, |
| 195 | enum ima_hooks func) |
| 196 | { |
| 197 | struct inode *backing_inode, *inode = file_inode(file); |
| 198 | struct integrity_iint_cache *iint = NULL; |
| 199 | struct ima_template_desc *template_desc = NULL; |
| 200 | char *pathbuf = NULL; |
| 201 | char filename[NAME_MAX]; |
| 202 | const char *pathname = NULL; |
| 203 | int rc = 0, action, must_appraise = 0; |
| 204 | int pcr = CONFIG_IMA_MEASURE_PCR_IDX; |
| 205 | struct evm_ima_xattr_data *xattr_value = NULL; |
| 206 | struct modsig *modsig = NULL; |
| 207 | int xattr_len = 0; |
| 208 | bool violation_check; |
| 209 | enum hash_algo hash_algo; |
| 210 | |
| 211 | if (!ima_policy_flag || !S_ISREG(inode->i_mode)) |
| 212 | return 0; |
| 213 | |
| 214 | /* Return an IMA_MEASURE, IMA_APPRAISE, IMA_AUDIT action |
| 215 | * bitmask based on the appraise/audit/measurement policy. |
| 216 | * Included is the appraise submask. |
| 217 | */ |
| 218 | action = ima_get_action(inode, cred, secid, mask, func, &pcr, |
| 219 | &template_desc); |
| 220 | violation_check = ((func == FILE_CHECK || func == MMAP_CHECK) && |
| 221 | (ima_policy_flag & IMA_MEASURE)); |
| 222 | if (!action && !violation_check) |
| 223 | return 0; |
| 224 | |
| 225 | must_appraise = action & IMA_APPRAISE; |
| 226 | |
| 227 | /* Is the appraise rule hook specific? */ |
| 228 | if (action & IMA_FILE_APPRAISE) |
| 229 | func = FILE_CHECK; |
| 230 | |
| 231 | inode_lock(inode); |
| 232 | |
| 233 | if (action) { |
| 234 | iint = integrity_inode_get(inode); |
| 235 | if (!iint) |
| 236 | rc = -ENOMEM; |
| 237 | } |
| 238 | |
| 239 | if (!rc && violation_check) |
| 240 | ima_rdwr_violation_check(file, iint, action & IMA_MEASURE, |
| 241 | &pathbuf, &pathname, filename); |
| 242 | |
| 243 | inode_unlock(inode); |
| 244 | |
| 245 | if (rc) |
| 246 | goto out; |
| 247 | if (!action) |
| 248 | goto out; |
| 249 | |
| 250 | mutex_lock(&iint->mutex); |
| 251 | |
| 252 | if (test_and_clear_bit(IMA_CHANGE_ATTR, &iint->atomic_flags)) |
| 253 | /* reset appraisal flags if ima_inode_post_setattr was called */ |
| 254 | iint->flags &= ~(IMA_APPRAISE | IMA_APPRAISED | |
| 255 | IMA_APPRAISE_SUBMASK | IMA_APPRAISED_SUBMASK | |
| 256 | IMA_ACTION_FLAGS); |
| 257 | |
| 258 | /* |
| 259 | * Re-evaulate the file if either the xattr has changed or the |
| 260 | * kernel has no way of detecting file change on the filesystem. |
| 261 | * (Limited to privileged mounted filesystems.) |
| 262 | */ |
| 263 | if (test_and_clear_bit(IMA_CHANGE_XATTR, &iint->atomic_flags) || |
| 264 | ((inode->i_sb->s_iflags & SB_I_IMA_UNVERIFIABLE_SIGNATURE) && |
| 265 | !(inode->i_sb->s_iflags & SB_I_UNTRUSTED_MOUNTER) && |
| 266 | !(action & IMA_FAIL_UNVERIFIABLE_SIGS))) { |
| 267 | iint->flags &= ~IMA_DONE_MASK; |
| 268 | iint->measured_pcrs = 0; |
| 269 | } |
| 270 | |
| 271 | /* Detect and re-evaluate changes made to the backing file. */ |
| 272 | backing_inode = d_real_inode(file_dentry(file)); |
| 273 | if (backing_inode != inode && |
| 274 | (action & IMA_DO_MASK) && (iint->flags & IMA_DONE_MASK)) { |
| 275 | if (!IS_I_VERSION(backing_inode) || |
| 276 | backing_inode->i_sb->s_dev != iint->real_dev || |
| 277 | backing_inode->i_ino != iint->real_ino || |
| 278 | !inode_eq_iversion(backing_inode, iint->version)) { |
| 279 | iint->flags &= ~IMA_DONE_MASK; |
| 280 | iint->measured_pcrs = 0; |
| 281 | } |
| 282 | } |
| 283 | |
| 284 | /* Determine if already appraised/measured based on bitmask |
| 285 | * (IMA_MEASURE, IMA_MEASURED, IMA_XXXX_APPRAISE, IMA_XXXX_APPRAISED, |
| 286 | * IMA_AUDIT, IMA_AUDITED) |
| 287 | */ |
| 288 | iint->flags |= action; |
| 289 | action &= IMA_DO_MASK; |
| 290 | action &= ~((iint->flags & (IMA_DONE_MASK ^ IMA_MEASURED)) >> 1); |
| 291 | |
| 292 | /* If target pcr is already measured, unset IMA_MEASURE action */ |
| 293 | if ((action & IMA_MEASURE) && (iint->measured_pcrs & (0x1 << pcr))) |
| 294 | action ^= IMA_MEASURE; |
| 295 | |
| 296 | /* HASH sets the digital signature and update flags, nothing else */ |
| 297 | if ((action & IMA_HASH) && |
| 298 | !(test_bit(IMA_DIGSIG, &iint->atomic_flags))) { |
| 299 | xattr_len = ima_read_xattr(file_dentry(file), &xattr_value); |
| 300 | if ((xattr_value && xattr_len > 2) && |
| 301 | (xattr_value->type == EVM_IMA_XATTR_DIGSIG)) |
| 302 | set_bit(IMA_DIGSIG, &iint->atomic_flags); |
| 303 | iint->flags |= IMA_HASHED; |
| 304 | action ^= IMA_HASH; |
| 305 | set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags); |
| 306 | } |
| 307 | |
| 308 | /* Nothing to do, just return existing appraised status */ |
| 309 | if (!action) { |
| 310 | if (must_appraise) { |
| 311 | rc = mmap_violation_check(func, file, &pathbuf, |
| 312 | &pathname, filename); |
| 313 | if (!rc) |
| 314 | rc = ima_get_cache_status(iint, func); |
| 315 | } |
| 316 | goto out_locked; |
| 317 | } |
| 318 | |
| 319 | if ((action & IMA_APPRAISE_SUBMASK) || |
| 320 | strcmp(template_desc->name, IMA_TEMPLATE_IMA_NAME) != 0) { |
| 321 | /* read 'security.ima' */ |
| 322 | xattr_len = ima_read_xattr(file_dentry(file), &xattr_value); |
| 323 | |
| 324 | /* |
| 325 | * Read the appended modsig if allowed by the policy, and allow |
| 326 | * an additional measurement list entry, if needed, based on the |
| 327 | * template format and whether the file was already measured. |
| 328 | */ |
| 329 | if (iint->flags & IMA_MODSIG_ALLOWED) { |
| 330 | rc = ima_read_modsig(func, buf, size, &modsig); |
| 331 | |
| 332 | if (!rc && ima_template_has_modsig(template_desc) && |
| 333 | iint->flags & IMA_MEASURED) |
| 334 | action |= IMA_MEASURE; |
| 335 | } |
| 336 | } |
| 337 | |
| 338 | hash_algo = ima_get_hash_algo(xattr_value, xattr_len); |
| 339 | |
| 340 | rc = ima_collect_measurement(iint, file, buf, size, hash_algo, modsig); |
| 341 | if (rc != 0 && rc != -EBADF && rc != -EINVAL) |
| 342 | goto out_locked; |
| 343 | |
| 344 | if (!pathbuf) /* ima_rdwr_violation possibly pre-fetched */ |
| 345 | pathname = ima_d_path(&file->f_path, &pathbuf, filename); |
| 346 | |
| 347 | if (action & IMA_MEASURE) |
| 348 | ima_store_measurement(iint, file, pathname, |
| 349 | xattr_value, xattr_len, modsig, pcr, |
| 350 | template_desc); |
| 351 | if (rc == 0 && (action & IMA_APPRAISE_SUBMASK)) { |
| 352 | inode_lock(inode); |
| 353 | rc = ima_appraise_measurement(func, iint, file, pathname, |
| 354 | xattr_value, xattr_len, modsig); |
| 355 | inode_unlock(inode); |
| 356 | if (!rc) |
| 357 | rc = mmap_violation_check(func, file, &pathbuf, |
| 358 | &pathname, filename); |
| 359 | } |
| 360 | if (action & IMA_AUDIT) |
| 361 | ima_audit_measurement(iint, pathname); |
| 362 | |
| 363 | if ((file->f_flags & O_DIRECT) && (iint->flags & IMA_PERMIT_DIRECTIO)) |
| 364 | rc = 0; |
| 365 | out_locked: |
| 366 | if ((mask & MAY_WRITE) && test_bit(IMA_DIGSIG, &iint->atomic_flags) && |
| 367 | !(iint->flags & IMA_NEW_FILE)) |
| 368 | rc = -EACCES; |
| 369 | mutex_unlock(&iint->mutex); |
| 370 | kfree(xattr_value); |
| 371 | ima_free_modsig(modsig); |
| 372 | out: |
| 373 | if (pathbuf) |
| 374 | __putname(pathbuf); |
| 375 | if (must_appraise) { |
| 376 | if (rc && (ima_appraise & IMA_APPRAISE_ENFORCE)) |
| 377 | return -EACCES; |
| 378 | if (file->f_mode & FMODE_WRITE) |
| 379 | set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags); |
| 380 | } |
| 381 | return 0; |
| 382 | } |
| 383 | |
| 384 | /** |
| 385 | * ima_file_mmap - based on policy, collect/store measurement. |
| 386 | * @file: pointer to the file to be measured (May be NULL) |
| 387 | * @reqprot: protection requested by the application |
| 388 | * @prot: protection that will be applied by the kernel |
| 389 | * @flags: operational flags |
| 390 | * |
| 391 | * Measure files being mmapped executable based on the ima_must_measure() |
| 392 | * policy decision. |
| 393 | * |
| 394 | * On success return 0. On integrity appraisal error, assuming the file |
| 395 | * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. |
| 396 | */ |
| 397 | int ima_file_mmap(struct file *file, unsigned long reqprot, |
| 398 | unsigned long prot, unsigned long flags) |
| 399 | { |
| 400 | u32 secid; |
| 401 | |
| 402 | if (file && (prot & PROT_EXEC)) { |
| 403 | security_task_getsecid(current, &secid); |
| 404 | return process_measurement(file, current_cred(), secid, NULL, |
| 405 | 0, MAY_EXEC, MMAP_CHECK); |
| 406 | } |
| 407 | |
| 408 | return 0; |
| 409 | } |
| 410 | |
| 411 | /** |
| 412 | * ima_bprm_check - based on policy, collect/store measurement. |
| 413 | * @bprm: contains the linux_binprm structure |
| 414 | * |
| 415 | * The OS protects against an executable file, already open for write, |
| 416 | * from being executed in deny_write_access() and an executable file, |
| 417 | * already open for execute, from being modified in get_write_access(). |
| 418 | * So we can be certain that what we verify and measure here is actually |
| 419 | * what is being executed. |
| 420 | * |
| 421 | * On success return 0. On integrity appraisal error, assuming the file |
| 422 | * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. |
| 423 | */ |
| 424 | int ima_bprm_check(struct linux_binprm *bprm) |
| 425 | { |
| 426 | int ret; |
| 427 | u32 secid; |
| 428 | |
| 429 | security_task_getsecid(current, &secid); |
| 430 | ret = process_measurement(bprm->file, current_cred(), secid, NULL, 0, |
| 431 | MAY_EXEC, BPRM_CHECK); |
| 432 | if (ret) |
| 433 | return ret; |
| 434 | |
| 435 | security_cred_getsecid(bprm->cred, &secid); |
| 436 | return process_measurement(bprm->file, bprm->cred, secid, NULL, 0, |
| 437 | MAY_EXEC, CREDS_CHECK); |
| 438 | } |
| 439 | |
| 440 | /** |
| 441 | * ima_path_check - based on policy, collect/store measurement. |
| 442 | * @file: pointer to the file to be measured |
| 443 | * @mask: contains MAY_READ, MAY_WRITE, MAY_EXEC or MAY_APPEND |
| 444 | * |
| 445 | * Measure files based on the ima_must_measure() policy decision. |
| 446 | * |
| 447 | * On success return 0. On integrity appraisal error, assuming the file |
| 448 | * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. |
| 449 | */ |
| 450 | int ima_file_check(struct file *file, int mask) |
| 451 | { |
| 452 | u32 secid; |
| 453 | |
| 454 | security_task_getsecid(current, &secid); |
| 455 | return process_measurement(file, current_cred(), secid, NULL, 0, |
| 456 | mask & (MAY_READ | MAY_WRITE | MAY_EXEC | |
| 457 | MAY_APPEND), FILE_CHECK); |
| 458 | } |
| 459 | EXPORT_SYMBOL_GPL(ima_file_check); |
| 460 | |
| 461 | /** |
| 462 | * ima_post_create_tmpfile - mark newly created tmpfile as new |
| 463 | * @file : newly created tmpfile |
| 464 | * |
| 465 | * No measuring, appraising or auditing of newly created tmpfiles is needed. |
| 466 | * Skip calling process_measurement(), but indicate which newly, created |
| 467 | * tmpfiles are in policy. |
| 468 | */ |
| 469 | void ima_post_create_tmpfile(struct inode *inode) |
| 470 | { |
| 471 | struct integrity_iint_cache *iint; |
| 472 | int must_appraise; |
| 473 | |
| 474 | must_appraise = ima_must_appraise(inode, MAY_ACCESS, FILE_CHECK); |
| 475 | if (!must_appraise) |
| 476 | return; |
| 477 | |
| 478 | /* Nothing to do if we can't allocate memory */ |
| 479 | iint = integrity_inode_get(inode); |
| 480 | if (!iint) |
| 481 | return; |
| 482 | |
| 483 | /* needed for writing the security xattrs */ |
| 484 | set_bit(IMA_UPDATE_XATTR, &iint->atomic_flags); |
| 485 | iint->ima_file_status = INTEGRITY_PASS; |
| 486 | } |
| 487 | |
| 488 | /** |
| 489 | * ima_post_path_mknod - mark as a new inode |
| 490 | * @dentry: newly created dentry |
| 491 | * |
| 492 | * Mark files created via the mknodat syscall as new, so that the |
| 493 | * file data can be written later. |
| 494 | */ |
| 495 | void ima_post_path_mknod(struct dentry *dentry) |
| 496 | { |
| 497 | struct integrity_iint_cache *iint; |
| 498 | struct inode *inode = dentry->d_inode; |
| 499 | int must_appraise; |
| 500 | |
| 501 | must_appraise = ima_must_appraise(inode, MAY_ACCESS, FILE_CHECK); |
| 502 | if (!must_appraise) |
| 503 | return; |
| 504 | |
| 505 | /* Nothing to do if we can't allocate memory */ |
| 506 | iint = integrity_inode_get(inode); |
| 507 | if (!iint) |
| 508 | return; |
| 509 | |
| 510 | /* needed for re-opening empty files */ |
| 511 | iint->flags |= IMA_NEW_FILE; |
| 512 | } |
| 513 | |
| 514 | /** |
| 515 | * ima_read_file - pre-measure/appraise hook decision based on policy |
| 516 | * @file: pointer to the file to be measured/appraised/audit |
| 517 | * @read_id: caller identifier |
| 518 | * |
| 519 | * Permit reading a file based on policy. The policy rules are written |
| 520 | * in terms of the policy identifier. Appraising the integrity of |
| 521 | * a file requires a file descriptor. |
| 522 | * |
| 523 | * For permission return 0, otherwise return -EACCES. |
| 524 | */ |
| 525 | int ima_read_file(struct file *file, enum kernel_read_file_id read_id) |
| 526 | { |
| 527 | /* |
| 528 | * READING_FIRMWARE_PREALLOC_BUFFER |
| 529 | * |
| 530 | * Do devices using pre-allocated memory run the risk of the |
| 531 | * firmware being accessible to the device prior to the completion |
| 532 | * of IMA's signature verification any more than when using two |
| 533 | * buffers? |
| 534 | */ |
| 535 | return 0; |
| 536 | } |
| 537 | |
| 538 | const int read_idmap[READING_MAX_ID] = { |
| 539 | [READING_FIRMWARE] = FIRMWARE_CHECK, |
| 540 | [READING_FIRMWARE_PREALLOC_BUFFER] = FIRMWARE_CHECK, |
| 541 | [READING_MODULE] = MODULE_CHECK, |
| 542 | [READING_KEXEC_IMAGE] = KEXEC_KERNEL_CHECK, |
| 543 | [READING_KEXEC_INITRAMFS] = KEXEC_INITRAMFS_CHECK, |
| 544 | [READING_POLICY] = POLICY_CHECK |
| 545 | }; |
| 546 | |
| 547 | /** |
| 548 | * ima_post_read_file - in memory collect/appraise/audit measurement |
| 549 | * @file: pointer to the file to be measured/appraised/audit |
| 550 | * @buf: pointer to in memory file contents |
| 551 | * @size: size of in memory file contents |
| 552 | * @read_id: caller identifier |
| 553 | * |
| 554 | * Measure/appraise/audit in memory file based on policy. Policy rules |
| 555 | * are written in terms of a policy identifier. |
| 556 | * |
| 557 | * On success return 0. On integrity appraisal error, assuming the file |
| 558 | * is in policy and IMA-appraisal is in enforcing mode, return -EACCES. |
| 559 | */ |
| 560 | int ima_post_read_file(struct file *file, void *buf, loff_t size, |
| 561 | enum kernel_read_file_id read_id) |
| 562 | { |
| 563 | enum ima_hooks func; |
| 564 | u32 secid; |
| 565 | |
| 566 | if (!file && read_id == READING_FIRMWARE) { |
| 567 | if ((ima_appraise & IMA_APPRAISE_FIRMWARE) && |
| 568 | (ima_appraise & IMA_APPRAISE_ENFORCE)) { |
| 569 | pr_err("Prevent firmware loading_store.\n"); |
| 570 | return -EACCES; /* INTEGRITY_UNKNOWN */ |
| 571 | } |
| 572 | return 0; |
| 573 | } |
| 574 | |
| 575 | /* permit signed certs */ |
| 576 | if (!file && read_id == READING_X509_CERTIFICATE) |
| 577 | return 0; |
| 578 | |
| 579 | if (!file || !buf || size == 0) { /* should never happen */ |
| 580 | if (ima_appraise & IMA_APPRAISE_ENFORCE) |
| 581 | return -EACCES; |
| 582 | return 0; |
| 583 | } |
| 584 | |
| 585 | func = read_idmap[read_id] ?: FILE_CHECK; |
| 586 | security_task_getsecid(current, &secid); |
| 587 | return process_measurement(file, current_cred(), secid, buf, size, |
| 588 | MAY_READ, func); |
| 589 | } |
| 590 | |
| 591 | /** |
| 592 | * ima_load_data - appraise decision based on policy |
| 593 | * @id: kernel load data caller identifier |
| 594 | * |
| 595 | * Callers of this LSM hook can not measure, appraise, or audit the |
| 596 | * data provided by userspace. Enforce policy rules requring a file |
| 597 | * signature (eg. kexec'ed kernel image). |
| 598 | * |
| 599 | * For permission return 0, otherwise return -EACCES. |
| 600 | */ |
| 601 | int ima_load_data(enum kernel_load_data_id id) |
| 602 | { |
| 603 | bool ima_enforce, sig_enforce; |
| 604 | |
| 605 | ima_enforce = |
| 606 | (ima_appraise & IMA_APPRAISE_ENFORCE) == IMA_APPRAISE_ENFORCE; |
| 607 | |
| 608 | switch (id) { |
| 609 | case LOADING_KEXEC_IMAGE: |
| 610 | if (IS_ENABLED(CONFIG_KEXEC_SIG) |
| 611 | && arch_ima_get_secureboot()) { |
| 612 | pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n"); |
| 613 | return -EACCES; |
| 614 | } |
| 615 | |
| 616 | if (ima_enforce && (ima_appraise & IMA_APPRAISE_KEXEC)) { |
| 617 | pr_err("impossible to appraise a kernel image without a file descriptor; try using kexec_file_load syscall.\n"); |
| 618 | return -EACCES; /* INTEGRITY_UNKNOWN */ |
| 619 | } |
| 620 | break; |
| 621 | case LOADING_FIRMWARE: |
| 622 | if (ima_enforce && (ima_appraise & IMA_APPRAISE_FIRMWARE)) { |
| 623 | pr_err("Prevent firmware sysfs fallback loading.\n"); |
| 624 | return -EACCES; /* INTEGRITY_UNKNOWN */ |
| 625 | } |
| 626 | break; |
| 627 | case LOADING_MODULE: |
| 628 | sig_enforce = is_module_sig_enforced(); |
| 629 | |
| 630 | if (ima_enforce && (!sig_enforce |
| 631 | && (ima_appraise & IMA_APPRAISE_MODULES))) { |
| 632 | pr_err("impossible to appraise a module without a file descriptor. sig_enforce kernel parameter might help\n"); |
| 633 | return -EACCES; /* INTEGRITY_UNKNOWN */ |
| 634 | } |
| 635 | break; |
| 636 | default: |
| 637 | break; |
| 638 | } |
| 639 | return 0; |
| 640 | } |
| 641 | |
| 642 | /* |
| 643 | * process_buffer_measurement - Measure the buffer to ima log. |
| 644 | * @buf: pointer to the buffer that needs to be added to the log. |
| 645 | * @size: size of buffer(in bytes). |
| 646 | * @eventname: event name to be used for the buffer entry. |
| 647 | * @cred: a pointer to a credentials structure for user validation. |
| 648 | * @secid: the secid of the task to be validated. |
| 649 | * |
| 650 | * Based on policy, the buffer is measured into the ima log. |
| 651 | */ |
| 652 | static void process_buffer_measurement(const void *buf, int size, |
| 653 | const char *eventname, |
| 654 | const struct cred *cred, u32 secid) |
| 655 | { |
| 656 | int ret = 0; |
| 657 | struct ima_template_entry *entry = NULL; |
| 658 | struct integrity_iint_cache iint = {}; |
| 659 | struct ima_event_data event_data = {.iint = &iint, |
| 660 | .filename = eventname, |
| 661 | .buf = buf, |
| 662 | .buf_len = size}; |
| 663 | struct ima_template_desc *template_desc = NULL; |
| 664 | struct { |
| 665 | struct ima_digest_data hdr; |
| 666 | char digest[IMA_MAX_DIGEST_SIZE]; |
| 667 | } hash = {}; |
| 668 | int violation = 0; |
| 669 | int pcr = CONFIG_IMA_MEASURE_PCR_IDX; |
| 670 | int action = 0; |
| 671 | |
| 672 | action = ima_get_action(NULL, cred, secid, 0, KEXEC_CMDLINE, &pcr, |
| 673 | &template_desc); |
| 674 | if (!(action & IMA_MEASURE)) |
| 675 | return; |
| 676 | |
| 677 | iint.ima_hash = &hash.hdr; |
| 678 | iint.ima_hash->algo = ima_hash_algo; |
| 679 | iint.ima_hash->length = hash_digest_size[ima_hash_algo]; |
| 680 | |
| 681 | ret = ima_calc_buffer_hash(buf, size, iint.ima_hash); |
| 682 | if (ret < 0) |
| 683 | goto out; |
| 684 | |
| 685 | ret = ima_alloc_init_template(&event_data, &entry, template_desc); |
| 686 | if (ret < 0) |
| 687 | goto out; |
| 688 | |
| 689 | ret = ima_store_template(entry, violation, NULL, buf, pcr); |
| 690 | |
| 691 | if (ret < 0) |
| 692 | ima_free_template_entry(entry); |
| 693 | |
| 694 | out: |
| 695 | return; |
| 696 | } |
| 697 | |
| 698 | /** |
| 699 | * ima_kexec_cmdline - measure kexec cmdline boot args |
| 700 | * @buf: pointer to buffer |
| 701 | * @size: size of buffer |
| 702 | * |
| 703 | * Buffers can only be measured, not appraised. |
| 704 | */ |
| 705 | void ima_kexec_cmdline(const void *buf, int size) |
| 706 | { |
| 707 | u32 secid; |
| 708 | |
| 709 | if (buf && size != 0) { |
| 710 | security_task_getsecid(current, &secid); |
| 711 | process_buffer_measurement(buf, size, "kexec-cmdline", |
| 712 | current_cred(), secid); |
| 713 | } |
| 714 | } |
| 715 | |
| 716 | static int __init init_ima(void) |
| 717 | { |
| 718 | int error; |
| 719 | |
| 720 | ima_init_template_list(); |
| 721 | hash_setup(CONFIG_IMA_DEFAULT_HASH); |
| 722 | error = ima_init(); |
| 723 | |
| 724 | if (error && strcmp(hash_algo_name[ima_hash_algo], |
| 725 | CONFIG_IMA_DEFAULT_HASH) != 0) { |
| 726 | pr_info("Allocating %s failed, going to use default hash algorithm %s\n", |
| 727 | hash_algo_name[ima_hash_algo], CONFIG_IMA_DEFAULT_HASH); |
| 728 | hash_setup_done = 0; |
| 729 | hash_setup(CONFIG_IMA_DEFAULT_HASH); |
| 730 | error = ima_init(); |
| 731 | } |
| 732 | |
| 733 | if (error) |
| 734 | return error; |
| 735 | |
| 736 | error = register_blocking_lsm_notifier(&ima_lsm_policy_notifier); |
| 737 | if (error) |
| 738 | pr_warn("Couldn't register LSM notifier, error %d\n", error); |
| 739 | |
| 740 | if (!error) |
| 741 | ima_update_policy_flag(); |
| 742 | |
| 743 | return error; |
| 744 | } |
| 745 | |
| 746 | late_initcall(init_ima); /* Start IMA after the TPM is available */ |