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Diffstat (limited to 'include/linux/fscrypt.h')
| -rw-r--r-- | include/linux/fscrypt.h | 294 |
1 files changed, 294 insertions, 0 deletions
diff --git a/include/linux/fscrypt.h b/include/linux/fscrypt.h new file mode 100644 index 000000000000..08b4b40c5aa8 --- /dev/null +++ b/include/linux/fscrypt.h @@ -0,0 +1,294 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +/* + * fscrypt.h: declarations for per-file encryption + * + * Filesystems that implement per-file encryption include this header + * file with the __FS_HAS_ENCRYPTION set according to whether that filesystem + * is being built with encryption support or not. + * + * Copyright (C) 2015, Google, Inc. + * + * Written by Michael Halcrow, 2015. + * Modified by Jaegeuk Kim, 2015. + */ +#ifndef _LINUX_FSCRYPT_H +#define _LINUX_FSCRYPT_H + +#include <linux/key.h> +#include <linux/fs.h> +#include <linux/mm.h> +#include <linux/bio.h> +#include <linux/dcache.h> +#include <crypto/skcipher.h> +#include <uapi/linux/fs.h> + +#define FS_CRYPTO_BLOCK_SIZE 16 + +struct fscrypt_info; + +struct fscrypt_ctx { + union { + struct { + struct page *bounce_page; /* Ciphertext page */ + struct page *control_page; /* Original page */ + } w; + struct { + struct bio *bio; + struct work_struct work; + } r; + struct list_head free_list; /* Free list */ + }; + u8 flags; /* Flags */ +}; + +/** + * For encrypted symlinks, the ciphertext length is stored at the beginning + * of the string in little-endian format. + */ +struct fscrypt_symlink_data { + __le16 len; + char encrypted_path[1]; +} __packed; + +struct fscrypt_str { + unsigned char *name; + u32 len; +}; + +struct fscrypt_name { + const struct qstr *usr_fname; + struct fscrypt_str disk_name; + u32 hash; + u32 minor_hash; + struct fscrypt_str crypto_buf; +}; + +#define FSTR_INIT(n, l) { .name = n, .len = l } +#define FSTR_TO_QSTR(f) QSTR_INIT((f)->name, (f)->len) +#define fname_name(p) ((p)->disk_name.name) +#define fname_len(p) ((p)->disk_name.len) + +/* + * fscrypt superblock flags + */ +#define FS_CFLG_OWN_PAGES (1U << 1) + +/* + * crypto opertions for filesystems + */ +struct fscrypt_operations { + unsigned int flags; + const char *key_prefix; + int (*get_context)(struct inode *, void *, size_t); + int (*set_context)(struct inode *, const void *, size_t, void *); + bool (*dummy_context)(struct inode *); + bool (*empty_dir)(struct inode *); + unsigned (*max_namelen)(struct inode *); +}; + +/* Maximum value for the third parameter of fscrypt_operations.set_context(). */ +#define FSCRYPT_SET_CONTEXT_MAX_SIZE 28 + +static inline bool fscrypt_dummy_context_enabled(struct inode *inode) +{ + if (inode->i_sb->s_cop->dummy_context && + inode->i_sb->s_cop->dummy_context(inode)) + return true; + return false; +} + +static inline bool fscrypt_valid_enc_modes(u32 contents_mode, + u32 filenames_mode) +{ + if (contents_mode == FS_ENCRYPTION_MODE_AES_128_CBC && + filenames_mode == FS_ENCRYPTION_MODE_AES_128_CTS) + return true; + + if (contents_mode == FS_ENCRYPTION_MODE_AES_256_XTS && + filenames_mode == FS_ENCRYPTION_MODE_AES_256_CTS) + return true; + + return false; +} + +static inline bool fscrypt_is_dot_dotdot(const struct qstr *str) +{ + if (str->len == 1 && str->name[0] == '.') + return true; + + if (str->len == 2 && str->name[0] == '.' && str->name[1] == '.') + return true; + + return false; +} + +#if __FS_HAS_ENCRYPTION + +static inline struct page *fscrypt_control_page(struct page *page) +{ + return ((struct fscrypt_ctx *)page_private(page))->w.control_page; +} + +static inline bool fscrypt_has_encryption_key(const struct inode *inode) +{ + return (inode->i_crypt_info != NULL); +} + +#include <linux/fscrypt_supp.h> + +#else /* !__FS_HAS_ENCRYPTION */ + +static inline struct page *fscrypt_control_page(struct page *page) +{ + WARN_ON_ONCE(1); + return ERR_PTR(-EINVAL); +} + +static inline bool fscrypt_has_encryption_key(const struct inode *inode) +{ + return 0; +} + +#include <linux/fscrypt_notsupp.h> +#endif /* __FS_HAS_ENCRYPTION */ + +/** + * fscrypt_require_key - require an inode's encryption key + * @inode: the inode we need the key for + * + * If the inode is encrypted, set up its encryption key if not already done. + * Then require that the key be present and return -ENOKEY otherwise. + * + * No locks are needed, and the key will live as long as the struct inode --- so + * it won't go away from under you. + * + * Return: 0 on success, -ENOKEY if the key is missing, or another -errno code + * if a problem occurred while setting up the encryption key. + */ +static inline int fscrypt_require_key(struct inode *inode) +{ + if (IS_ENCRYPTED(inode)) { + int err = fscrypt_get_encryption_info(inode); + + if (err) + return err; + if (!fscrypt_has_encryption_key(inode)) + return -ENOKEY; + } + return 0; +} + +/** + * fscrypt_prepare_link - prepare to link an inode into a possibly-encrypted directory + * @old_dentry: an existing dentry for the inode being linked + * @dir: the target directory + * @dentry: negative dentry for the target filename + * + * A new link can only be added to an encrypted directory if the directory's + * encryption key is available --- since otherwise we'd have no way to encrypt + * the filename. Therefore, we first set up the directory's encryption key (if + * not already done) and return an error if it's unavailable. + * + * We also verify that the link will not violate the constraint that all files + * in an encrypted directory tree use the same encryption policy. + * + * Return: 0 on success, -ENOKEY if the directory's encryption key is missing, + * -EPERM if the link would result in an inconsistent encryption policy, or + * another -errno code. + */ +static inline int fscrypt_prepare_link(struct dentry *old_dentry, + struct inode *dir, + struct dentry *dentry) +{ + if (IS_ENCRYPTED(dir)) + return __fscrypt_prepare_link(d_inode(old_dentry), dir); + return 0; +} + +/** + * fscrypt_prepare_rename - prepare for a rename between possibly-encrypted directories + * @old_dir: source directory + * @old_dentry: dentry for source file + * @new_dir: target directory + * @new_dentry: dentry for target location (may be negative unless exchanging) + * @flags: rename flags (we care at least about %RENAME_EXCHANGE) + * + * Prepare for ->rename() where the source and/or target directories may be + * encrypted. A new link can only be added to an encrypted directory if the + * directory's encryption key is available --- since otherwise we'd have no way + * to encrypt the filename. A rename to an existing name, on the other hand, + * *is* cryptographically possible without the key. However, we take the more + * conservative approach and just forbid all no-key renames. + * + * We also verify that the rename will not violate the constraint that all files + * in an encrypted directory tree use the same encryption policy. + * + * Return: 0 on success, -ENOKEY if an encryption key is missing, -EPERM if the + * rename would cause inconsistent encryption policies, or another -errno code. + */ +static inline int fscrypt_prepare_rename(struct inode *old_dir, + struct dentry *old_dentry, + struct inode *new_dir, + struct dentry *new_dentry, + unsigned int flags) +{ + if (IS_ENCRYPTED(old_dir) || IS_ENCRYPTED(new_dir)) + return __fscrypt_prepare_rename(old_dir, old_dentry, + new_dir, new_dentry, flags); + return 0; +} + +/** + * fscrypt_prepare_lookup - prepare to lookup a name in a possibly-encrypted directory + * @dir: directory being searched + * @dentry: filename being looked up + * @flags: lookup flags + * + * Prepare for ->lookup() in a directory which may be encrypted. Lookups can be + * done with or without the directory's encryption key; without the key, + * filenames are presented in encrypted form. Therefore, we'll try to set up + * the directory's encryption key, but even without it the lookup can continue. + * + * To allow invalidating stale dentries if the directory's encryption key is + * added later, we also install a custom ->d_revalidate() method and use the + * DCACHE_ENCRYPTED_WITH_KEY flag to indicate whether a given dentry is a + * plaintext name (flag set) or a ciphertext name (flag cleared). + * + * Return: 0 on success, -errno if a problem occurred while setting up the + * encryption key + */ +static inline int fscrypt_prepare_lookup(struct inode *dir, + struct dentry *dentry, + unsigned int flags) +{ + if (IS_ENCRYPTED(dir)) + return __fscrypt_prepare_lookup(dir, dentry); + return 0; +} + +/** + * fscrypt_prepare_setattr - prepare to change a possibly-encrypted inode's attributes + * @dentry: dentry through which the inode is being changed + * @attr: attributes to change + * + * Prepare for ->setattr() on a possibly-encrypted inode. On an encrypted file, + * most attribute changes are allowed even without the encryption key. However, + * without the encryption key we do have to forbid truncates. This is needed + * because the size being truncated to may not be a multiple of the filesystem + * block size, and in that case we'd have to decrypt the final block, zero the + * portion past i_size, and re-encrypt it. (We *could* allow truncating to a + * filesystem block boundary, but it's simpler to just forbid all truncates --- + * and we already forbid all other contents modifications without the key.) + * + * Return: 0 on success, -ENOKEY if the key is missing, or another -errno code + * if a problem occurred while setting up the encryption key. + */ +static inline 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; +} + +#endif /* _LINUX_FSCRYPT_H */ |