diff options
Diffstat (limited to 'fs/crypto/hooks.c')
| -rw-r--r-- | fs/crypto/hooks.c | 348 |
1 files changed, 275 insertions, 73 deletions
diff --git a/fs/crypto/hooks.c b/fs/crypto/hooks.c index 926e5df20ec3..b97de0d1430f 100644 --- a/fs/crypto/hooks.c +++ b/fs/crypto/hooks.c @@ -1,14 +1,16 @@ +// SPDX-License-Identifier: GPL-2.0-only /* * fs/crypto/hooks.c * * Encryption hooks for higher-level filesystem operations. */ -#include <linux/ratelimit.h> +#include <linux/export.h> + #include "fscrypt_private.h" /** - * fscrypt_file_open - prepare to open a possibly-encrypted regular file + * fscrypt_file_open() - prepare to open a possibly-encrypted regular file * @inode: the inode being opened * @filp: the struct file being set up * @@ -30,35 +32,57 @@ int fscrypt_file_open(struct inode *inode, struct file *filp) { int err; - struct dentry *dir; + struct dentry *dentry, *dentry_parent; + struct inode *inode_parent; err = fscrypt_require_key(inode); if (err) return err; - dir = dget_parent(file_dentry(filp)); - if (IS_ENCRYPTED(d_inode(dir)) && - !fscrypt_has_permitted_context(d_inode(dir), inode)) { - fscrypt_warn(inode->i_sb, - "inconsistent encryption contexts: %lu/%lu", - d_inode(dir)->i_ino, inode->i_ino); + dentry = file_dentry(filp); + + /* + * Getting a reference to the parent dentry is needed for the actual + * encryption policy comparison, but it's expensive on multi-core + * systems. Since this function runs on unencrypted files too, start + * with a lightweight RCU-mode check for the parent directory being + * unencrypted (in which case it's fine for the child to be either + * unencrypted, or encrypted with any policy). Only continue on to the + * full policy check if the parent directory is actually encrypted. + */ + rcu_read_lock(); + dentry_parent = READ_ONCE(dentry->d_parent); + inode_parent = d_inode_rcu(dentry_parent); + if (inode_parent != NULL && !IS_ENCRYPTED(inode_parent)) { + rcu_read_unlock(); + return 0; + } + rcu_read_unlock(); + + dentry_parent = dget_parent(dentry); + if (!fscrypt_has_permitted_context(d_inode(dentry_parent), inode)) { + fscrypt_warn(inode, + "Inconsistent encryption context (parent directory: %lu)", + d_inode(dentry_parent)->i_ino); err = -EPERM; } - dput(dir); + dput(dentry_parent); return err; } EXPORT_SYMBOL_GPL(fscrypt_file_open); -int __fscrypt_prepare_link(struct inode *inode, struct inode *dir) +int __fscrypt_prepare_link(struct inode *inode, struct inode *dir, + struct dentry *dentry) { - int err; - - err = fscrypt_require_key(dir); - if (err) - return err; + if (fscrypt_is_nokey_name(dentry)) + return -ENOKEY; + /* + * We don't need to separately check that the directory inode's key is + * available, as it's implied by the dentry not being a no-key name. + */ if (!fscrypt_has_permitted_context(dir, inode)) - return -EPERM; + return -EXDEV; return 0; } @@ -68,70 +92,173 @@ int __fscrypt_prepare_rename(struct inode *old_dir, struct dentry *old_dentry, struct inode *new_dir, struct dentry *new_dentry, unsigned int flags) { - int err; - - err = fscrypt_require_key(old_dir); - if (err) - return err; - - err = fscrypt_require_key(new_dir); - if (err) - return err; + if (fscrypt_is_nokey_name(old_dentry) || + fscrypt_is_nokey_name(new_dentry)) + return -ENOKEY; + /* + * We don't need to separately check that the directory inodes' keys are + * available, as it's implied by the dentries not being no-key names. + */ if (old_dir != new_dir) { if (IS_ENCRYPTED(new_dir) && !fscrypt_has_permitted_context(new_dir, d_inode(old_dentry))) - return -EPERM; + return -EXDEV; if ((flags & RENAME_EXCHANGE) && IS_ENCRYPTED(old_dir) && !fscrypt_has_permitted_context(old_dir, d_inode(new_dentry))) - return -EPERM; + return -EXDEV; } return 0; } EXPORT_SYMBOL_GPL(__fscrypt_prepare_rename); -int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry) +int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry, + struct fscrypt_name *fname) { - int err = fscrypt_get_encryption_info(dir); + int err = fscrypt_setup_filename(dir, &dentry->d_name, 1, fname); - if (err) + if (err && err != -ENOENT) return err; - if (fscrypt_has_encryption_key(dir)) { - spin_lock(&dentry->d_lock); - dentry->d_flags |= DCACHE_ENCRYPTED_WITH_KEY; - spin_unlock(&dentry->d_lock); - } + fscrypt_prepare_dentry(dentry, fname->is_nokey_name); - d_set_d_op(dentry, &fscrypt_d_ops); - return 0; + return err; } EXPORT_SYMBOL_GPL(__fscrypt_prepare_lookup); -int __fscrypt_prepare_symlink(struct inode *dir, unsigned int len, - unsigned int max_len, - struct fscrypt_str *disk_link) +/** + * fscrypt_prepare_lookup_partial() - prepare lookup without filename setup + * @dir: the encrypted directory being searched + * @dentry: the dentry being looked up in @dir + * + * This function should be used by the ->lookup and ->atomic_open methods of + * filesystems that handle filename encryption and no-key name encoding + * themselves and thus can't use fscrypt_prepare_lookup(). Like + * fscrypt_prepare_lookup(), this will try to set up the directory's encryption + * key and will set DCACHE_NOKEY_NAME on the dentry if the key is unavailable. + * However, this function doesn't set up a struct fscrypt_name for the filename. + * + * Return: 0 on success; -errno on error. Note that the encryption key being + * unavailable is not considered an error. It is also not an error if + * the encryption policy is unsupported by this kernel; that is treated + * like the key being unavailable, so that files can still be deleted. + */ +int fscrypt_prepare_lookup_partial(struct inode *dir, struct dentry *dentry) { + int err = fscrypt_get_encryption_info(dir, true); + bool is_nokey_name = (!err && !fscrypt_has_encryption_key(dir)); + + fscrypt_prepare_dentry(dentry, is_nokey_name); + + return err; +} +EXPORT_SYMBOL_GPL(fscrypt_prepare_lookup_partial); + +int __fscrypt_prepare_readdir(struct inode *dir) +{ + return fscrypt_get_encryption_info(dir, true); +} +EXPORT_SYMBOL_GPL(__fscrypt_prepare_readdir); + +int __fscrypt_prepare_setattr(struct dentry *dentry, struct iattr *attr) +{ + if (attr->ia_valid & ATTR_SIZE) + return fscrypt_require_key(d_inode(dentry)); + return 0; +} +EXPORT_SYMBOL_GPL(__fscrypt_prepare_setattr); + +/** + * fscrypt_prepare_setflags() - prepare to change flags with FS_IOC_SETFLAGS + * @inode: the inode on which flags are being changed + * @oldflags: the old flags + * @flags: the new flags + * + * The caller should be holding i_rwsem for write. + * + * Return: 0 on success; -errno if the flags change isn't allowed or if + * another error occurs. + */ +int fscrypt_prepare_setflags(struct inode *inode, + unsigned int oldflags, unsigned int flags) +{ + struct fscrypt_inode_info *ci; + struct fscrypt_master_key *mk; int err; /* + * When the CASEFOLD flag is set on an encrypted directory, we must + * derive the secret key needed for the dirhash. This is only possible + * if the directory uses a v2 encryption policy. + */ + if (IS_ENCRYPTED(inode) && (flags & ~oldflags & FS_CASEFOLD_FL)) { + err = fscrypt_require_key(inode); + if (err) + return err; + ci = fscrypt_get_inode_info_raw(inode); + if (ci->ci_policy.version != FSCRYPT_POLICY_V2) + return -EINVAL; + mk = ci->ci_master_key; + down_read(&mk->mk_sem); + if (mk->mk_present) + fscrypt_derive_dirhash_key(ci, mk); + else + err = -ENOKEY; + up_read(&mk->mk_sem); + return err; + } + return 0; +} + +/** + * fscrypt_prepare_symlink() - prepare to create a possibly-encrypted symlink + * @dir: directory in which the symlink is being created + * @target: plaintext symlink target + * @len: length of @target excluding null terminator + * @max_len: space the filesystem has available to store the symlink target + * @disk_link: (out) the on-disk symlink target being prepared + * + * This function computes the size the symlink target will require on-disk, + * stores it in @disk_link->len, and validates it against @max_len. An + * encrypted symlink may be longer than the original. + * + * Additionally, @disk_link->name is set to @target if the symlink will be + * unencrypted, but left NULL if the symlink will be encrypted. For encrypted + * symlinks, the filesystem must call fscrypt_encrypt_symlink() to create the + * on-disk target later. (The reason for the two-step process is that some + * filesystems need to know the size of the symlink target before creating the + * inode, e.g. to determine whether it will be a "fast" or "slow" symlink.) + * + * Return: 0 on success, -ENAMETOOLONG if the symlink target is too long, + * -ENOKEY if the encryption key is missing, or another -errno code if a problem + * occurred while setting up the encryption key. + */ +int fscrypt_prepare_symlink(struct inode *dir, const char *target, + unsigned int len, unsigned int max_len, + struct fscrypt_str *disk_link) +{ + const union fscrypt_policy *policy; + + /* * To calculate the size of the encrypted symlink target we need to know * the amount of NUL padding, which is determined by the flags set in * the encryption policy which will be inherited from the directory. - * The easiest way to get access to this is to just load the directory's - * fscrypt_info, since we'll need it to create the dir_entry anyway. - * - * Note: in test_dummy_encryption mode, @dir may be unencrypted. */ - err = fscrypt_get_encryption_info(dir); - if (err) - return err; - if (!fscrypt_has_encryption_key(dir)) - return -ENOKEY; + policy = fscrypt_policy_to_inherit(dir); + if (policy == NULL) { + /* Not encrypted */ + disk_link->name = (unsigned char *)target; + disk_link->len = len + 1; + if (disk_link->len > max_len) + return -ENAMETOOLONG; + return 0; + } + if (IS_ERR(policy)) + return PTR_ERR(policy); /* * Calculate the size of the encrypted symlink and verify it won't @@ -144,16 +271,16 @@ int __fscrypt_prepare_symlink(struct inode *dir, unsigned int len, * counting it (even though it is meaningless for ciphertext) is simpler * for now since filesystems will assume it is there and subtract it. */ - if (!fscrypt_fname_encrypted_size(dir, len, - max_len - sizeof(struct fscrypt_symlink_data), - &disk_link->len)) + if (!__fscrypt_fname_encrypted_size(policy, len, + max_len - sizeof(struct fscrypt_symlink_data) - 1, + &disk_link->len)) return -ENAMETOOLONG; - disk_link->len += sizeof(struct fscrypt_symlink_data); + disk_link->len += sizeof(struct fscrypt_symlink_data) + 1; disk_link->name = NULL; return 0; } -EXPORT_SYMBOL_GPL(__fscrypt_prepare_symlink); +EXPORT_SYMBOL_GPL(fscrypt_prepare_symlink); int __fscrypt_encrypt_symlink(struct inode *inode, const char *target, unsigned int len, struct fscrypt_str *disk_link) @@ -163,9 +290,13 @@ int __fscrypt_encrypt_symlink(struct inode *inode, const char *target, struct fscrypt_symlink_data *sd; unsigned int ciphertext_len; - err = fscrypt_require_key(inode); - if (err) - return err; + /* + * fscrypt_prepare_new_inode() should have already set up the new + * symlink inode's encryption key. We don't wait until now to do it, + * since we may be in a filesystem transaction now. + */ + if (WARN_ON_ONCE(!fscrypt_has_encryption_key(inode))) + return -ENOKEY; if (disk_link->name) { /* filesystem-provided buffer */ @@ -175,15 +306,14 @@ int __fscrypt_encrypt_symlink(struct inode *inode, const char *target, if (!sd) return -ENOMEM; } - ciphertext_len = disk_link->len - sizeof(*sd); + ciphertext_len = disk_link->len - sizeof(*sd) - 1; sd->len = cpu_to_le16(ciphertext_len); - err = fname_encrypt(inode, &iname, sd->encrypted_path, ciphertext_len); - if (err) { - if (!disk_link->name) - kfree(sd); - return err; - } + err = fscrypt_fname_encrypt(inode, &iname, sd->encrypted_path, + ciphertext_len); + if (err) + goto err_free_sd; + /* * Null-terminating the ciphertext doesn't make sense, but we still * count the null terminator in the length, so we might as well @@ -191,18 +321,29 @@ int __fscrypt_encrypt_symlink(struct inode *inode, const char *target, */ sd->encrypted_path[ciphertext_len] = '\0'; + /* Cache the plaintext symlink target for later use by get_link() */ + err = -ENOMEM; + inode->i_link = kmemdup(target, len + 1, GFP_NOFS); + if (!inode->i_link) + goto err_free_sd; + if (!disk_link->name) disk_link->name = (unsigned char *)sd; return 0; + +err_free_sd: + if (!disk_link->name) + kfree(sd); + return err; } EXPORT_SYMBOL_GPL(__fscrypt_encrypt_symlink); /** - * fscrypt_get_symlink - get the target of an encrypted symlink + * fscrypt_get_symlink() - get the target of an encrypted symlink * @inode: the symlink inode * @caddr: the on-disk contents of the symlink * @max_size: size of @caddr buffer - * @done: if successful, will be set up to free the returned target + * @done: if successful, will be set up to free the returned target if needed * * If the symlink's encryption key is available, we decrypt its target. * Otherwise, we encode its target for presentation. @@ -217,26 +358,33 @@ const char *fscrypt_get_symlink(struct inode *inode, const void *caddr, { const struct fscrypt_symlink_data *sd; struct fscrypt_str cstr, pstr; + bool has_key; int err; /* This is for encrypted symlinks only */ - if (WARN_ON(!IS_ENCRYPTED(inode))) + if (WARN_ON_ONCE(!IS_ENCRYPTED(inode))) return ERR_PTR(-EINVAL); + /* If the decrypted target is already cached, just return it. */ + pstr.name = READ_ONCE(inode->i_link); + if (pstr.name) + return pstr.name; + /* * Try to set up the symlink's encryption key, but we can continue * regardless of whether the key is available or not. */ - err = fscrypt_get_encryption_info(inode); + err = fscrypt_get_encryption_info(inode, false); if (err) return ERR_PTR(err); + has_key = fscrypt_has_encryption_key(inode); /* * For historical reasons, encrypted symlink targets are prefixed with * the ciphertext length, even though this is redundant with i_size. */ - if (max_size < sizeof(*sd)) + if (max_size < sizeof(*sd) + 1) return ERR_PTR(-EUCLEAN); sd = caddr; cstr.name = (unsigned char *)sd->encrypted_path; @@ -245,10 +393,10 @@ const char *fscrypt_get_symlink(struct inode *inode, const void *caddr, if (cstr.len == 0) return ERR_PTR(-EUCLEAN); - if (cstr.len + sizeof(*sd) - 1 > max_size) + if (cstr.len + sizeof(*sd) > max_size) return ERR_PTR(-EUCLEAN); - err = fscrypt_fname_alloc_buffer(inode, cstr.len, &pstr); + err = fscrypt_fname_alloc_buffer(cstr.len, &pstr); if (err) return ERR_PTR(err); @@ -261,7 +409,17 @@ const char *fscrypt_get_symlink(struct inode *inode, const void *caddr, goto err_kfree; pstr.name[pstr.len] = '\0'; - set_delayed_call(done, kfree_link, pstr.name); + + /* + * Cache decrypted symlink targets in i_link for later use. Don't cache + * symlink targets encoded without the key, since those become outdated + * once the key is added. This pairs with the READ_ONCE() above and in + * the VFS path lookup code. + */ + if (!has_key || + cmpxchg_release(&inode->i_link, NULL, pstr.name) != NULL) + set_delayed_call(done, kfree_link, pstr.name); + return pstr.name; err_kfree: @@ -269,3 +427,47 @@ err_kfree: return ERR_PTR(err); } EXPORT_SYMBOL_GPL(fscrypt_get_symlink); + +/** + * fscrypt_symlink_getattr() - set the correct st_size for encrypted symlinks + * @path: the path for the encrypted symlink being queried + * @stat: the struct being filled with the symlink's attributes + * + * Override st_size of encrypted symlinks to be the length of the decrypted + * symlink target (or the no-key encoded symlink target, if the key is + * unavailable) rather than the length of the encrypted symlink target. This is + * necessary for st_size to match the symlink target that userspace actually + * sees. POSIX requires this, and some userspace programs depend on it. + * + * This requires reading the symlink target from disk if needed, setting up the + * inode's encryption key if possible, and then decrypting or encoding the + * symlink target. This makes lstat() more heavyweight than is normally the + * case. However, decrypted symlink targets will be cached in ->i_link, so + * usually the symlink won't have to be read and decrypted again later if/when + * it is actually followed, readlink() is called, or lstat() is called again. + * + * Return: 0 on success, -errno on failure + */ +int fscrypt_symlink_getattr(const struct path *path, struct kstat *stat) +{ + struct dentry *dentry = path->dentry; + struct inode *inode = d_inode(dentry); + const char *link; + DEFINE_DELAYED_CALL(done); + + /* + * To get the symlink target that userspace will see (whether it's the + * decrypted target or the no-key encoded target), we can just get it in + * the same way the VFS does during path resolution and readlink(). + */ + link = READ_ONCE(inode->i_link); + if (!link) { + link = inode->i_op->get_link(dentry, inode, &done); + if (IS_ERR(link)) + return PTR_ERR(link); + } + stat->size = strlen(link); + do_delayed_call(&done); + return 0; +} +EXPORT_SYMBOL_GPL(fscrypt_symlink_getattr); |