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1// SPDX-License-Identifier: GPL-2.02/*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 same22 * @policy1: the first policy23 * @policy2: the second policy24 *25 * Return: %true if equal, else %false26 */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 v165 * (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, and129 * 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 only131 * allow AES-256-XTS here. This can be relaxed later if a use case for132 * 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 can143 * 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 fit155 * in 32 bits. In principle, IV_INO_LBLK_32 could support longer inode156 * numbers because it hashes the inode number; however, currently the157 * 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 unit169 * 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 DUN264 * 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 supported292 * @policy_u: the encryption policy293 * @inode: the inode on which the policy will be used294 *295 * Given an encryption policy, check whether all its encryption modes and other296 * settings are supported by this kernel on the given inode. (But we don't297 * currently don't check for crypto API support here, so attempting to use an298 * algorithm not configured into the crypto API will still fail later.)299 *300 * Return: %true if supported, else %false301 */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_context316 * @ctx_u: output context317 * @policy_u: input policy318 * @nonce: nonce to use319 *320 * Create an fscrypt_context for an inode that is being assigned the given321 * 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 to371 * an fscrypt_policy372 * @policy_u: output policy373 * @ctx_u: input context374 * @ctx_size: size of input context in bytes375 *376 * Given an fscrypt_context, build the corresponding fscrypt_policy.377 *378 * Return: 0 on success, or -EINVAL if the fscrypt_context has an unrecognized379 * version number or size.380 *381 * This does *not* validate the settings within the policy itself, e.g. the382 * 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 of471 * verifying that the correct master key was supplied, which was472 * insecure in scenarios where multiple users have access to the473 * same encrypted files (even just read-only access). The new474 * encryption policy version fixes this and also implies use of475 * an improved key derivation function and allows non-root users476 * to securely remove keys. So as long as compatibility with477 * old kernels isn't required, it is recommended to use the new478 * 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 a521 * bizarre bug in gcc 7 and earlier (fixed by gcc r255731) causes gcc to522 * think that size can be 0 here (despite the check above!) *and* that523 * it's a compile-time constant. Thus it would think copy_from_user()524 * is passed compile-time constant ULONG_MAX, causing the compile-time525 * buffer overflow check to fail, breaking the build. This only occurred526 * 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 else553 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 permitted640 * within its directory?641 *642 * @parent: inode for parent directory643 * @child: inode for file being looked up, opened, or linked into @parent644 *645 * Filesystems must call this before permitting access to an inode in a646 * situation where the parent directory is encrypted (either before allowing647 * ->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 encrypted649 * directory, including link, rename, and cross rename. It enforces the650 * constraint that within a given encrypted directory tree, all files use the651 * same encryption policy. The pre-access check is needed to detect potentially652 * malicious offline violations of this constraint, while the link and rename653 * 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 same677 * encryption policy. Compare the cached policies if the keys are678 * available, otherwise retrieve and compare the fscrypt_contexts.679 *680 * Note that the fscrypt_context retrieval will be required frequently681 * when accessing an encrypted directory tree without the key.682 * Performance-wise this is not a big deal because we already don't683 * really optimize for file access without the key (to the extent that684 * such access is even possible), given that any attempted access685 * 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 unrecognized702 * encryption policy, so that files with an unrecognized encryption703 * 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, or717 * NULL if none, or an ERR_PTR() on error. If the directory is encrypted, also718 * 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 inode736 * @ctx: where context should be written737 * @inode: inode from which to fetch policy and nonce738 *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 least741 * 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 inode762 * @inode: a new inode763 * @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 a766 * filesystem transaction. Everything here must be %GFP_NOFS-safe.767 *768 * Return: 0 on success, -errno on failure769 */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 any782 * 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 option794 * @param: the mount option795 * @dummy_policy: (input/output) the place to write the dummy policy that will796 * result from parsing the option. Zero-initialize this. If a policy is797 * already set here (due to test_dummy_encryption being given multiple798 * 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 the801 * 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 else840 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 equal854 * @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 to873 * @sep: the separator character to use874 * @sb: the filesystem whose options are being shown875 *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