diff options
Diffstat (limited to 'fs/crypto/hooks.c')
| -rw-r--r-- | fs/crypto/hooks.c | 180 |
1 files changed, 127 insertions, 53 deletions
diff --git a/fs/crypto/hooks.c b/fs/crypto/hooks.c index 5ef861742921..7b8c5a1104b5 100644 --- a/fs/crypto/hooks.c +++ b/fs/crypto/hooks.c @@ -5,12 +5,10 @@ * Encryption hooks for higher-level filesystem operations. */ -#include <linux/key.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 * @@ -54,15 +52,12 @@ EXPORT_SYMBOL_GPL(fscrypt_file_open); int __fscrypt_prepare_link(struct inode *inode, struct inode *dir, struct dentry *dentry) { - int err; - - err = fscrypt_require_key(dir); - if (err) - return err; - - /* ... in case we looked up ciphertext name before key was added */ - if (dentry->d_flags & DCACHE_ENCRYPTED_NAME) + 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 -EXDEV; @@ -75,20 +70,13 @@ 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; - - /* ... in case we looked up ciphertext name(s) before key was added */ - if ((old_dentry->d_flags | new_dentry->d_flags) & - DCACHE_ENCRYPTED_NAME) + 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) && @@ -114,16 +102,29 @@ int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry, if (err && err != -ENOENT) return err; - if (fname->is_ciphertext_name) { + if (fname->is_nokey_name) { spin_lock(&dentry->d_lock); - dentry->d_flags |= DCACHE_ENCRYPTED_NAME; + dentry->d_flags |= DCACHE_NOKEY_NAME; spin_unlock(&dentry->d_lock); - d_set_d_op(dentry, &fscrypt_d_ops); } return err; } EXPORT_SYMBOL_GPL(__fscrypt_prepare_lookup); +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 @@ -154,38 +155,63 @@ int fscrypt_prepare_setflags(struct inode *inode, ci = inode->i_crypt_info; if (ci->ci_policy.version != FSCRYPT_POLICY_V2) return -EINVAL; - mk = ci->ci_master_key->payload.data[0]; - down_read(&mk->mk_secret_sem); + mk = ci->ci_master_key; + down_read(&mk->mk_sem); if (is_master_key_secret_present(&mk->mk_secret)) err = fscrypt_derive_dirhash_key(ci, mk); else err = -ENOKEY; - up_read(&mk->mk_secret_sem); + up_read(&mk->mk_sem); return err; } return 0; } -int __fscrypt_prepare_symlink(struct inode *dir, unsigned int len, - unsigned int max_len, - struct fscrypt_str *disk_link) +/** + * 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) { - int err; + 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 @@ -198,16 +224,16 @@ 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), + &disk_link->len)) return -ENAMETOOLONG; disk_link->len += sizeof(struct fscrypt_symlink_data); 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) @@ -217,9 +243,13 @@ 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 */ @@ -262,7 +292,7 @@ err_free_sd: 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 @@ -297,7 +327,7 @@ const char *fscrypt_get_symlink(struct inode *inode, const void *caddr, * 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); @@ -319,7 +349,7 @@ const char *fscrypt_get_symlink(struct inode *inode, const void *caddr, if (cstr.len + sizeof(*sd) - 1 > 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); @@ -350,3 +380,47 @@ 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); |