1// SPDX-License-Identifier: GPL-2.0 2/* 3 * Encryption policy functions for per-file encryption support. 4 * 5 * Copyright (C) 2015, Google, Inc. 6 * Copyright (C) 2015, Motorola Mobility. 7 * 8 * Originally written by Michael Halcrow, 2015. 9 * Modified by Jaegeuk Kim, 2015. 10 * Modified by Eric Biggers, 2019 for v2 policy support. 11 */ 12 13#include <linux/fs_context.h> 14#include <linux/random.h> 15#include <linux/seq_file.h> 16#include <linux/string.h> 17#include <linux/mount.h> 18#include "fscrypt_private.h" 19 20/** 21 * fscrypt_policies_equal() - check whether two encryption policies are the same 22 * @policy1: the first policy 23 * @policy2: the second policy 24 * 25 * Return: %true if equal, else %false 26 */ 27bool fscrypt_policies_equal(const union fscrypt_policy *policy1, 28 const union fscrypt_policy *policy2) 29{ 30 if (policy1->version != policy2->version) 31 return false; 32 33 return !memcmp(policy1, policy2, fscrypt_policy_size(policy1)); 34} 35 36int fscrypt_policy_to_key_spec(const union fscrypt_policy *policy, 37 struct fscrypt_key_specifier *key_spec) 38{ 39 switch (policy->version) { 40 case FSCRYPT_POLICY_V1: 41 key_spec->type = FSCRYPT_KEY_SPEC_TYPE_DESCRIPTOR; 42 memcpy(key_spec->u.descriptor, policy->v1.master_key_descriptor, 43 FSCRYPT_KEY_DESCRIPTOR_SIZE); 44 return 0; 45 case FSCRYPT_POLICY_V2: 46 key_spec->type = FSCRYPT_KEY_SPEC_TYPE_IDENTIFIER; 47 memcpy(key_spec->u.identifier, policy->v2.master_key_identifier, 48 FSCRYPT_KEY_IDENTIFIER_SIZE); 49 return 0; 50 default: 51 WARN_ON_ONCE(1); 52 return -EINVAL; 53 } 54} 55 56const union fscrypt_policy *fscrypt_get_dummy_policy(struct super_block *sb) 57{ 58 if (!sb->s_cop->get_dummy_policy) 59 return NULL; 60 return sb->s_cop->get_dummy_policy(sb); 61} 62 63/* 64 * Return %true if the given combination of encryption modes is supported for v1 65 * (and later) encryption policies. 66 * 67 * Do *not* add anything new here, since v1 encryption policies are deprecated. 68 * New combinations of modes should go in fscrypt_valid_enc_modes_v2() only. 69 */ 70static bool fscrypt_valid_enc_modes_v1(u32 contents_mode, u32 filenames_mode) 71{ 72 if (contents_mode == FSCRYPT_MODE_AES_256_XTS && 73 filenames_mode == FSCRYPT_MODE_AES_256_CTS) 74 return true; 75 76 if (contents_mode == FSCRYPT_MODE_AES_128_CBC && 77 filenames_mode == FSCRYPT_MODE_AES_128_CTS) 78 return true; 79 80 if (contents_mode == FSCRYPT_MODE_ADIANTUM && 81 filenames_mode == FSCRYPT_MODE_ADIANTUM) 82 return true; 83 84 return false; 85} 86 87static bool fscrypt_valid_enc_modes_v2(u32 contents_mode, u32 filenames_mode) 88{ 89 if (contents_mode == FSCRYPT_MODE_AES_256_XTS && 90 filenames_mode == FSCRYPT_MODE_AES_256_HCTR2) 91 return true; 92 93 if (contents_mode == FSCRYPT_MODE_SM4_XTS && 94 filenames_mode == FSCRYPT_MODE_SM4_CTS) 95 return true; 96 97 return fscrypt_valid_enc_modes_v1(contents_mode, filenames_mode); 98} 99 100static bool supported_direct_key_modes(const struct inode *inode, 101 u32 contents_mode, u32 filenames_mode) 102{ 103 const struct fscrypt_mode *mode; 104 105 if (contents_mode != filenames_mode) { 106 fscrypt_warn(inode, 107 "Direct key flag not allowed with different contents and filenames modes"); 108 return false; 109 } 110 mode = &fscrypt_modes[contents_mode]; 111 112 if (mode->ivsize < offsetofend(union fscrypt_iv, nonce)) { 113 fscrypt_warn(inode, "Direct key flag not allowed with %s", 114 mode->friendly_name); 115 return false; 116 } 117 return true; 118} 119 120static bool supported_iv_ino_lblk_policy(const struct fscrypt_policy_v2 *policy, 121 const struct inode *inode) 122{ 123 const char *type = (policy->flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64) 124 ? "IV_INO_LBLK_64" : "IV_INO_LBLK_32"; 125 struct super_block *sb = inode->i_sb; 126 127 /* 128 * IV_INO_LBLK_* exist only because of hardware limitations, and 129 * currently the only known use case for them involves AES-256-XTS. 130 * That's also all we test currently. For these reasons, for now only 131 * allow AES-256-XTS here. This can be relaxed later if a use case for 132 * IV_INO_LBLK_* with other encryption modes arises. 133 */ 134 if (policy->contents_encryption_mode != FSCRYPT_MODE_AES_256_XTS) { 135 fscrypt_warn(inode, 136 "Can't use %s policy with contents mode other than AES-256-XTS", 137 type); 138 return false; 139 } 140 141 /* 142 * It's unsafe to include inode numbers in the IVs if the filesystem can 143 * potentially renumber inodes, e.g. via filesystem shrinking. 144 */ 145 if (!sb->s_cop->has_stable_inodes || 146 !sb->s_cop->has_stable_inodes(sb)) { 147 fscrypt_warn(inode, 148 "Can't use %s policy on filesystem '%s' because it doesn't have stable inode numbers", 149 type, sb->s_id); 150 return false; 151 } 152 153 /* 154 * IV_INO_LBLK_64 and IV_INO_LBLK_32 both require that inode numbers fit 155 * in 32 bits. In principle, IV_INO_LBLK_32 could support longer inode 156 * numbers because it hashes the inode number; however, currently the 157 * inode number is gotten from inode::i_ino which is 'unsigned long'. 158 * So for now the implementation limit is 32 bits. 159 */ 160 if (!sb->s_cop->has_32bit_inodes) { 161 fscrypt_warn(inode, 162 "Can't use %s policy on filesystem '%s' because its inode numbers are too long", 163 type, sb->s_id); 164 return false; 165 } 166 167 /* 168 * IV_INO_LBLK_64 and IV_INO_LBLK_32 both require that file data unit 169 * indices fit in 32 bits. 170 */ 171 if (fscrypt_max_file_dun_bits(sb, 172 fscrypt_policy_v2_du_bits(policy, inode)) > 32) { 173 fscrypt_warn(inode, 174 "Can't use %s policy on filesystem '%s' because its maximum file size is too large", 175 type, sb->s_id); 176 return false; 177 } 178 return true; 179} 180 181static bool fscrypt_supported_v1_policy(const struct fscrypt_policy_v1 *policy, 182 const struct inode *inode) 183{ 184 if (!fscrypt_valid_enc_modes_v1(policy->contents_encryption_mode, 185 policy->filenames_encryption_mode)) { 186 fscrypt_warn(inode, 187 "Unsupported encryption modes (contents %d, filenames %d)", 188 policy->contents_encryption_mode, 189 policy->filenames_encryption_mode); 190 return false; 191 } 192 193 if (policy->flags & ~(FSCRYPT_POLICY_FLAGS_PAD_MASK | 194 FSCRYPT_POLICY_FLAG_DIRECT_KEY)) { 195 fscrypt_warn(inode, "Unsupported encryption flags (0x%02x)", 196 policy->flags); 197 return false; 198 } 199 200 if ((policy->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) && 201 !supported_direct_key_modes(inode, policy->contents_encryption_mode, 202 policy->filenames_encryption_mode)) 203 return false; 204 205 if (IS_CASEFOLDED(inode)) { 206 /* With v1, there's no way to derive dirhash keys. */ 207 fscrypt_warn(inode, 208 "v1 policies can't be used on casefolded directories"); 209 return false; 210 } 211 212 return true; 213} 214 215static bool fscrypt_supported_v2_policy(const struct fscrypt_policy_v2 *policy, 216 const struct inode *inode) 217{ 218 int count = 0; 219 220 if (!fscrypt_valid_enc_modes_v2(policy->contents_encryption_mode, 221 policy->filenames_encryption_mode)) { 222 fscrypt_warn(inode, 223 "Unsupported encryption modes (contents %d, filenames %d)", 224 policy->contents_encryption_mode, 225 policy->filenames_encryption_mode); 226 return false; 227 } 228 229 if (policy->flags & ~(FSCRYPT_POLICY_FLAGS_PAD_MASK | 230 FSCRYPT_POLICY_FLAG_DIRECT_KEY | 231 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64 | 232 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32)) { 233 fscrypt_warn(inode, "Unsupported encryption flags (0x%02x)", 234 policy->flags); 235 return false; 236 } 237 238 count += !!(policy->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY); 239 count += !!(policy->flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64); 240 count += !!(policy->flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32); 241 if (count > 1) { 242 fscrypt_warn(inode, "Mutually exclusive encryption flags (0x%02x)", 243 policy->flags); 244 return false; 245 } 246 247 if (policy->log2_data_unit_size) { 248 if (!inode->i_sb->s_cop->supports_subblock_data_units) { 249 fscrypt_warn(inode, 250 "Filesystem does not support configuring crypto data unit size"); 251 return false; 252 } 253 if (policy->log2_data_unit_size > inode->i_blkbits || 254 policy->log2_data_unit_size < SECTOR_SHIFT /* 9 */) { 255 fscrypt_warn(inode, 256 "Unsupported log2_data_unit_size in encryption policy: %d", 257 policy->log2_data_unit_size); 258 return false; 259 } 260 if (policy->log2_data_unit_size != inode->i_blkbits && 261 (policy->flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32)) { 262 /* 263 * Not safe to enable yet, as we need to ensure that DUN 264 * wraparound can only occur on a FS block boundary. 265 */ 266 fscrypt_warn(inode, 267 "Sub-block data units not yet supported with IV_INO_LBLK_32"); 268 return false; 269 } 270 } 271 272 if ((policy->flags & FSCRYPT_POLICY_FLAG_DIRECT_KEY) && 273 !supported_direct_key_modes(inode, policy->contents_encryption_mode, 274 policy->filenames_encryption_mode)) 275 return false; 276 277 if ((policy->flags & (FSCRYPT_POLICY_FLAG_IV_INO_LBLK_64 | 278 FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32)) && 279 !supported_iv_ino_lblk_policy(policy, inode)) 280 return false; 281 282 if (memchr_inv(policy->__reserved, 0, sizeof(policy->__reserved))) { 283 fscrypt_warn(inode, "Reserved bits set in encryption policy"); 284 return false; 285 } 286 287 return true; 288} 289 290/** 291 * fscrypt_supported_policy() - check whether an encryption policy is supported 292 * @policy_u: the encryption policy 293 * @inode: the inode on which the policy will be used 294 * 295 * Given an encryption policy, check whether all its encryption modes and other 296 * settings are supported by this kernel on the given inode. (But we don't 297 * currently don't check for crypto API support here, so attempting to use an 298 * algorithm not configured into the crypto API will still fail later.) 299 * 300 * Return: %true if supported, else %false 301 */ 302bool fscrypt_supported_policy(const union fscrypt_policy *policy_u, 303 const struct inode *inode) 304{ 305 switch (policy_u->version) { 306 case FSCRYPT_POLICY_V1: 307 return fscrypt_supported_v1_policy(&policy_u->v1, inode); 308 case FSCRYPT_POLICY_V2: 309 return fscrypt_supported_v2_policy(&policy_u->v2, inode); 310 } 311 return false; 312} 313 314/** 315 * fscrypt_new_context() - create a new fscrypt_context 316 * @ctx_u: output context 317 * @policy_u: input policy 318 * @nonce: nonce to use 319 * 320 * Create an fscrypt_context for an inode that is being assigned the given 321 * encryption policy. @nonce must be a new random nonce. 322 * 323 * Return: the size of the new context in bytes. 324 */ 325static int fscrypt_new_context(union fscrypt_context *ctx_u, 326 const union fscrypt_policy *policy_u, 327 const u8 nonce[FSCRYPT_FILE_NONCE_SIZE]) 328{ 329 memset(ctx_u, 0, sizeof(*ctx_u)); 330 331 switch (policy_u->version) { 332 case FSCRYPT_POLICY_V1: { 333 const struct fscrypt_policy_v1 *policy = &policy_u->v1; 334 struct fscrypt_context_v1 *ctx = &ctx_u->v1; 335 336 ctx->version = FSCRYPT_CONTEXT_V1; 337 ctx->contents_encryption_mode = 338 policy->contents_encryption_mode; 339 ctx->filenames_encryption_mode = 340 policy->filenames_encryption_mode; 341 ctx->flags = policy->flags; 342 memcpy(ctx->master_key_descriptor, 343 policy->master_key_descriptor, 344 sizeof(ctx->master_key_descriptor)); 345 memcpy(ctx->nonce, nonce, FSCRYPT_FILE_NONCE_SIZE); 346 return sizeof(*ctx); 347 } 348 case FSCRYPT_POLICY_V2: { 349 const struct fscrypt_policy_v2 *policy = &policy_u->v2; 350 struct fscrypt_context_v2 *ctx = &ctx_u->v2; 351 352 ctx->version = FSCRYPT_CONTEXT_V2; 353 ctx->contents_encryption_mode = 354 policy->contents_encryption_mode; 355 ctx->filenames_encryption_mode = 356 policy->filenames_encryption_mode; 357 ctx->flags = policy->flags; 358 ctx->log2_data_unit_size = policy->log2_data_unit_size; 359 memcpy(ctx->master_key_identifier, 360 policy->master_key_identifier, 361 sizeof(ctx->master_key_identifier)); 362 memcpy(ctx->nonce, nonce, FSCRYPT_FILE_NONCE_SIZE); 363 return sizeof(*ctx); 364 } 365 } 366 BUG(); 367} 368 369/** 370 * fscrypt_policy_from_context() - convert an fscrypt_context to 371 * an fscrypt_policy 372 * @policy_u: output policy 373 * @ctx_u: input context 374 * @ctx_size: size of input context in bytes 375 * 376 * Given an fscrypt_context, build the corresponding fscrypt_policy. 377 * 378 * Return: 0 on success, or -EINVAL if the fscrypt_context has an unrecognized 379 * version number or size. 380 * 381 * This does *not* validate the settings within the policy itself, e.g. the 382 * modes, flags, and reserved bits. Use fscrypt_supported_policy() for that. 383 */ 384int fscrypt_policy_from_context(union fscrypt_policy *policy_u, 385 const union fscrypt_context *ctx_u, 386 int ctx_size) 387{ 388 memset(policy_u, 0, sizeof(*policy_u)); 389 390 if (!fscrypt_context_is_valid(ctx_u, ctx_size)) 391 return -EINVAL; 392 393 switch (ctx_u->version) { 394 case FSCRYPT_CONTEXT_V1: { 395 const struct fscrypt_context_v1 *ctx = &ctx_u->v1; 396 struct fscrypt_policy_v1 *policy = &policy_u->v1; 397 398 policy->version = FSCRYPT_POLICY_V1; 399 policy->contents_encryption_mode = 400 ctx->contents_encryption_mode; 401 policy->filenames_encryption_mode = 402 ctx->filenames_encryption_mode; 403 policy->flags = ctx->flags; 404 memcpy(policy->master_key_descriptor, 405 ctx->master_key_descriptor, 406 sizeof(policy->master_key_descriptor)); 407 return 0; 408 } 409 case FSCRYPT_CONTEXT_V2: { 410 const struct fscrypt_context_v2 *ctx = &ctx_u->v2; 411 struct fscrypt_policy_v2 *policy = &policy_u->v2; 412 413 policy->version = FSCRYPT_POLICY_V2; 414 policy->contents_encryption_mode = 415 ctx->contents_encryption_mode; 416 policy->filenames_encryption_mode = 417 ctx->filenames_encryption_mode; 418 policy->flags = ctx->flags; 419 policy->log2_data_unit_size = ctx->log2_data_unit_size; 420 memcpy(policy->__reserved, ctx->__reserved, 421 sizeof(policy->__reserved)); 422 memcpy(policy->master_key_identifier, 423 ctx->master_key_identifier, 424 sizeof(policy->master_key_identifier)); 425 return 0; 426 } 427 } 428 /* unreachable */ 429 return -EINVAL; 430} 431 432/* Retrieve an inode's encryption policy */ 433static int fscrypt_get_policy(struct inode *inode, union fscrypt_policy *policy) 434{ 435 const struct fscrypt_inode_info *ci; 436 union fscrypt_context ctx; 437 int ret; 438 439 ci = fscrypt_get_inode_info(inode); 440 if (ci) { 441 /* key available, use the cached policy */ 442 *policy = ci->ci_policy; 443 return 0; 444 } 445 446 if (!IS_ENCRYPTED(inode)) 447 return -ENODATA; 448 449 ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); 450 if (ret < 0) 451 return (ret == -ERANGE) ? -EINVAL : ret; 452 453 return fscrypt_policy_from_context(policy, &ctx, ret); 454} 455 456static int set_encryption_policy(struct inode *inode, 457 const union fscrypt_policy *policy) 458{ 459 u8 nonce[FSCRYPT_FILE_NONCE_SIZE]; 460 union fscrypt_context ctx; 461 int ctxsize; 462 int err; 463 464 if (!fscrypt_supported_policy(policy, inode)) 465 return -EINVAL; 466 467 switch (policy->version) { 468 case FSCRYPT_POLICY_V1: 469 /* 470 * The original encryption policy version provided no way of 471 * verifying that the correct master key was supplied, which was 472 * insecure in scenarios where multiple users have access to the 473 * same encrypted files (even just read-only access). The new 474 * encryption policy version fixes this and also implies use of 475 * an improved key derivation function and allows non-root users 476 * to securely remove keys. So as long as compatibility with 477 * old kernels isn't required, it is recommended to use the new 478 * policy version for all new encrypted directories. 479 */ 480 pr_warn_once("%s (pid %d) is setting deprecated v1 encryption policy; recommend upgrading to v2.\n", 481 current->comm, current->pid); 482 break; 483 case FSCRYPT_POLICY_V2: 484 err = fscrypt_verify_key_added(inode->i_sb, 485 policy->v2.master_key_identifier); 486 if (err) 487 return err; 488 if (policy->v2.flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32) 489 pr_warn_once("%s (pid %d) is setting an IV_INO_LBLK_32 encryption policy. This should only be used if there are certain hardware limitations.\n", 490 current->comm, current->pid); 491 break; 492 default: 493 WARN_ON_ONCE(1); 494 return -EINVAL; 495 } 496 497 get_random_bytes(nonce, FSCRYPT_FILE_NONCE_SIZE); 498 ctxsize = fscrypt_new_context(&ctx, policy, nonce); 499 500 return inode->i_sb->s_cop->set_context(inode, &ctx, ctxsize, NULL); 501} 502 503int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg) 504{ 505 union fscrypt_policy policy; 506 union fscrypt_policy existing_policy; 507 struct inode *inode = file_inode(filp); 508 u8 version; 509 int size; 510 int ret; 511 512 if (get_user(policy.version, (const u8 __user *)arg)) 513 return -EFAULT; 514 515 size = fscrypt_policy_size(&policy); 516 if (size <= 0) 517 return -EINVAL; 518 519 /* 520 * We should just copy the remaining 'size - 1' bytes here, but a 521 * bizarre bug in gcc 7 and earlier (fixed by gcc r255731) causes gcc to 522 * think that size can be 0 here (despite the check above!) *and* that 523 * it's a compile-time constant. Thus it would think copy_from_user() 524 * is passed compile-time constant ULONG_MAX, causing the compile-time 525 * buffer overflow check to fail, breaking the build. This only occurred 526 * when building an i386 kernel with -Os and branch profiling enabled. 527 * 528 * Work around it by just copying the first byte again... 529 */ 530 version = policy.version; 531 if (copy_from_user(&policy, arg, size)) 532 return -EFAULT; 533 policy.version = version; 534 535 if (!inode_owner_or_capable(&nop_mnt_idmap, inode)) 536 return -EACCES; 537 538 ret = mnt_want_write_file(filp); 539 if (ret) 540 return ret; 541 542 inode_lock(inode); 543 544 ret = fscrypt_get_policy(inode, &existing_policy); 545 if (ret == -ENODATA) { 546 if (!S_ISDIR(inode->i_mode)) 547 ret = -ENOTDIR; 548 else if (IS_DEADDIR(inode)) 549 ret = -ENOENT; 550 else if (!inode->i_sb->s_cop->empty_dir(inode)) 551 ret = -ENOTEMPTY; 552 else 553 ret = set_encryption_policy(inode, &policy); 554 } else if (ret == -EINVAL || 555 (ret == 0 && !fscrypt_policies_equal(&policy, 556 &existing_policy))) { 557 /* The file already uses a different encryption policy. */ 558 ret = -EEXIST; 559 } 560 561 inode_unlock(inode); 562 563 mnt_drop_write_file(filp); 564 return ret; 565} 566EXPORT_SYMBOL(fscrypt_ioctl_set_policy); 567 568/* Original ioctl version; can only get the original policy version */ 569int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg) 570{ 571 union fscrypt_policy policy; 572 int err; 573 574 err = fscrypt_get_policy(file_inode(filp), &policy); 575 if (err) 576 return err; 577 578 if (policy.version != FSCRYPT_POLICY_V1) 579 return -EINVAL; 580 581 if (copy_to_user(arg, &policy, sizeof(policy.v1))) 582 return -EFAULT; 583 return 0; 584} 585EXPORT_SYMBOL(fscrypt_ioctl_get_policy); 586 587/* Extended ioctl version; can get policies of any version */ 588int fscrypt_ioctl_get_policy_ex(struct file *filp, void __user *uarg) 589{ 590 struct fscrypt_get_policy_ex_arg arg; 591 union fscrypt_policy *policy = (union fscrypt_policy *)&arg.policy; 592 size_t policy_size; 593 int err; 594 595 /* arg is policy_size, then policy */ 596 BUILD_BUG_ON(offsetof(typeof(arg), policy_size) != 0); 597 BUILD_BUG_ON(offsetofend(typeof(arg), policy_size) != 598 offsetof(typeof(arg), policy)); 599 BUILD_BUG_ON(sizeof(arg.policy) != sizeof(*policy)); 600 601 err = fscrypt_get_policy(file_inode(filp), policy); 602 if (err) 603 return err; 604 policy_size = fscrypt_policy_size(policy); 605 606 if (copy_from_user(&arg, uarg, sizeof(arg.policy_size))) 607 return -EFAULT; 608 609 if (policy_size > arg.policy_size) 610 return -EOVERFLOW; 611 arg.policy_size = policy_size; 612 613 if (copy_to_user(uarg, &arg, sizeof(arg.policy_size) + policy_size)) 614 return -EFAULT; 615 return 0; 616} 617EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_policy_ex); 618 619/* FS_IOC_GET_ENCRYPTION_NONCE: retrieve file's encryption nonce for testing */ 620int fscrypt_ioctl_get_nonce(struct file *filp, void __user *arg) 621{ 622 struct inode *inode = file_inode(filp); 623 union fscrypt_context ctx; 624 int ret; 625 626 ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx)); 627 if (ret < 0) 628 return ret; 629 if (!fscrypt_context_is_valid(&ctx, ret)) 630 return -EINVAL; 631 if (copy_to_user(arg, fscrypt_context_nonce(&ctx), 632 FSCRYPT_FILE_NONCE_SIZE)) 633 return -EFAULT; 634 return 0; 635} 636EXPORT_SYMBOL_GPL(fscrypt_ioctl_get_nonce); 637 638/** 639 * fscrypt_has_permitted_context() - is a file's encryption policy permitted 640 * within its directory? 641 * 642 * @parent: inode for parent directory 643 * @child: inode for file being looked up, opened, or linked into @parent 644 * 645 * Filesystems must call this before permitting access to an inode in a 646 * situation where the parent directory is encrypted (either before allowing 647 * ->lookup() to succeed, or for a regular file before allowing it to be opened) 648 * and before any operation that involves linking an inode into an encrypted 649 * directory, including link, rename, and cross rename. It enforces the 650 * constraint that within a given encrypted directory tree, all files use the 651 * same encryption policy. The pre-access check is needed to detect potentially 652 * malicious offline violations of this constraint, while the link and rename 653 * checks are needed to prevent online violations of this constraint. 654 * 655 * Return: 1 if permitted, 0 if forbidden. 656 */ 657int fscrypt_has_permitted_context(struct inode *parent, struct inode *child) 658{ 659 union fscrypt_policy parent_policy, child_policy; 660 int err, err1, err2; 661 662 /* No restrictions on file types which are never encrypted */ 663 if (!S_ISREG(child->i_mode) && !S_ISDIR(child->i_mode) && 664 !S_ISLNK(child->i_mode)) 665 return 1; 666 667 /* No restrictions if the parent directory is unencrypted */ 668 if (!IS_ENCRYPTED(parent)) 669 return 1; 670 671 /* Encrypted directories must not contain unencrypted files */ 672 if (!IS_ENCRYPTED(child)) 673 return 0; 674 675 /* 676 * Both parent and child are encrypted, so verify they use the same 677 * encryption policy. Compare the cached policies if the keys are 678 * available, otherwise retrieve and compare the fscrypt_contexts. 679 * 680 * Note that the fscrypt_context retrieval will be required frequently 681 * when accessing an encrypted directory tree without the key. 682 * Performance-wise this is not a big deal because we already don't 683 * really optimize for file access without the key (to the extent that 684 * such access is even possible), given that any attempted access 685 * already causes a fscrypt_context retrieval and keyring search. 686 * 687 * In any case, if an unexpected error occurs, fall back to "forbidden". 688 */ 689 690 err = fscrypt_get_encryption_info(parent, true); 691 if (err) 692 return 0; 693 err = fscrypt_get_encryption_info(child, true); 694 if (err) 695 return 0; 696 697 err1 = fscrypt_get_policy(parent, &parent_policy); 698 err2 = fscrypt_get_policy(child, &child_policy); 699 700 /* 701 * Allow the case where the parent and child both have an unrecognized 702 * encryption policy, so that files with an unrecognized encryption 703 * policy can be deleted. 704 */ 705 if (err1 == -EINVAL && err2 == -EINVAL) 706 return 1; 707 708 if (err1 || err2) 709 return 0; 710 711 return fscrypt_policies_equal(&parent_policy, &child_policy); 712} 713EXPORT_SYMBOL(fscrypt_has_permitted_context); 714 715/* 716 * Return the encryption policy that new files in the directory will inherit, or 717 * NULL if none, or an ERR_PTR() on error. If the directory is encrypted, also 718 * ensure that its key is set up, so that the new filename can be encrypted. 719 */ 720const union fscrypt_policy *fscrypt_policy_to_inherit(struct inode *dir) 721{ 722 int err; 723 724 if (IS_ENCRYPTED(dir)) { 725 err = fscrypt_require_key(dir); 726 if (err) 727 return ERR_PTR(err); 728 return &dir->i_crypt_info->ci_policy; 729 } 730 731 return fscrypt_get_dummy_policy(dir->i_sb); 732} 733 734/** 735 * fscrypt_context_for_new_inode() - create an encryption context for a new inode 736 * @ctx: where context should be written 737 * @inode: inode from which to fetch policy and nonce 738 * 739 * Given an in-core "prepared" (via fscrypt_prepare_new_inode) inode, 740 * generate a new context and write it to ctx. ctx _must_ be at least 741 * FSCRYPT_SET_CONTEXT_MAX_SIZE bytes. 742 * 743 * Return: size of the resulting context or a negative error code. 744 */ 745int fscrypt_context_for_new_inode(void *ctx, struct inode *inode) 746{ 747 struct fscrypt_inode_info *ci = inode->i_crypt_info; 748 749 BUILD_BUG_ON(sizeof(union fscrypt_context) != 750 FSCRYPT_SET_CONTEXT_MAX_SIZE); 751 752 /* fscrypt_prepare_new_inode() should have set up the key already. */ 753 if (WARN_ON_ONCE(!ci)) 754 return -ENOKEY; 755 756 return fscrypt_new_context(ctx, &ci->ci_policy, ci->ci_nonce); 757} 758EXPORT_SYMBOL_GPL(fscrypt_context_for_new_inode); 759 760/** 761 * fscrypt_set_context() - Set the fscrypt context of a new inode 762 * @inode: a new inode 763 * @fs_data: private data given by FS and passed to ->set_context() 764 * 765 * This should be called after fscrypt_prepare_new_inode(), generally during a 766 * filesystem transaction. Everything here must be %GFP_NOFS-safe. 767 * 768 * Return: 0 on success, -errno on failure 769 */ 770int fscrypt_set_context(struct inode *inode, void *fs_data) 771{ 772 struct fscrypt_inode_info *ci = inode->i_crypt_info; 773 union fscrypt_context ctx; 774 int ctxsize; 775 776 ctxsize = fscrypt_context_for_new_inode(&ctx, inode); 777 if (ctxsize < 0) 778 return ctxsize; 779 780 /* 781 * This may be the first time the inode number is available, so do any 782 * delayed key setup that requires the inode number. 783 */ 784 if (ci->ci_policy.version == FSCRYPT_POLICY_V2 && 785 (ci->ci_policy.v2.flags & FSCRYPT_POLICY_FLAG_IV_INO_LBLK_32)) 786 fscrypt_hash_inode_number(ci, ci->ci_master_key); 787 788 return inode->i_sb->s_cop->set_context(inode, &ctx, ctxsize, fs_data); 789} 790EXPORT_SYMBOL_GPL(fscrypt_set_context); 791 792/** 793 * fscrypt_parse_test_dummy_encryption() - parse the test_dummy_encryption mount option 794 * @param: the mount option 795 * @dummy_policy: (input/output) the place to write the dummy policy that will 796 * result from parsing the option. Zero-initialize this. If a policy is 797 * already set here (due to test_dummy_encryption being given multiple 798 * times), then this function will verify that the policies are the same. 799 * 800 * Return: 0 on success; -EINVAL if the argument is invalid; -EEXIST if the 801 * argument conflicts with one already specified; or -ENOMEM. 802 */ 803int fscrypt_parse_test_dummy_encryption(const struct fs_parameter *param, 804 struct fscrypt_dummy_policy *dummy_policy) 805{ 806 const char *arg = "v2"; 807 union fscrypt_policy *policy; 808 int err; 809 810 if (param->type == fs_value_is_string && *param->string) 811 arg = param->string; 812 813 policy = kzalloc(sizeof(*policy), GFP_KERNEL); 814 if (!policy) 815 return -ENOMEM; 816 817 if (!strcmp(arg, "v1")) { 818 policy->version = FSCRYPT_POLICY_V1; 819 policy->v1.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS; 820 policy->v1.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS; 821 memset(policy->v1.master_key_descriptor, 0x42, 822 FSCRYPT_KEY_DESCRIPTOR_SIZE); 823 } else if (!strcmp(arg, "v2")) { 824 policy->version = FSCRYPT_POLICY_V2; 825 policy->v2.contents_encryption_mode = FSCRYPT_MODE_AES_256_XTS; 826 policy->v2.filenames_encryption_mode = FSCRYPT_MODE_AES_256_CTS; 827 err = fscrypt_get_test_dummy_key_identifier( 828 policy->v2.master_key_identifier); 829 if (err) 830 goto out; 831 } else { 832 err = -EINVAL; 833 goto out; 834 } 835 836 if (dummy_policy->policy) { 837 if (fscrypt_policies_equal(policy, dummy_policy->policy)) 838 err = 0; 839 else 840 err = -EEXIST; 841 goto out; 842 } 843 dummy_policy->policy = policy; 844 policy = NULL; 845 err = 0; 846out: 847 kfree(policy); 848 return err; 849} 850EXPORT_SYMBOL_GPL(fscrypt_parse_test_dummy_encryption); 851 852/** 853 * fscrypt_dummy_policies_equal() - check whether two dummy policies are equal 854 * @p1: the first test dummy policy (may be unset) 855 * @p2: the second test dummy policy (may be unset) 856 * 857 * Return: %true if the dummy policies are both set and equal, or both unset. 858 */ 859bool fscrypt_dummy_policies_equal(const struct fscrypt_dummy_policy *p1, 860 const struct fscrypt_dummy_policy *p2) 861{ 862 if (!p1->policy && !p2->policy) 863 return true; 864 if (!p1->policy || !p2->policy) 865 return false; 866 return fscrypt_policies_equal(p1->policy, p2->policy); 867} 868EXPORT_SYMBOL_GPL(fscrypt_dummy_policies_equal); 869 870/** 871 * fscrypt_show_test_dummy_encryption() - show '-o test_dummy_encryption' 872 * @seq: the seq_file to print the option to 873 * @sep: the separator character to use 874 * @sb: the filesystem whose options are being shown 875 * 876 * Show the test_dummy_encryption mount option, if it was specified. 877 * This is mainly used for /proc/mounts. 878 */ 879void fscrypt_show_test_dummy_encryption(struct seq_file *seq, char sep, 880 struct super_block *sb) 881{ 882 const union fscrypt_policy *policy = fscrypt_get_dummy_policy(sb); 883 int vers; 884 885 if (!policy) 886 return; 887 888 vers = policy->version; 889 if (vers == FSCRYPT_POLICY_V1) /* Handle numbering quirk */ 890 vers = 1; 891 892 seq_printf(seq, "%ctest_dummy_encryption=v%d", sep, vers); 893} 894EXPORT_SYMBOL_GPL(fscrypt_show_test_dummy_encryption); 895