fscrypt_supp.h
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/* SPDX-License-Identifier: GPL-2.0 */
/*
* fscrypt_supp.h
*
* Do not include this file directly. Use fscrypt.h instead!
*/
#ifndef _LINUX_FSCRYPT_H
#error "Incorrect include of linux/fscrypt_supp.h!"
#endif
#ifndef _LINUX_FSCRYPT_SUPP_H
#define _LINUX_FSCRYPT_SUPP_H
#include <linux/mm.h>
#include <linux/slab.h>
/*
* fscrypt superblock flags
*/
#define FS_CFLG_OWN_PAGES (1U << 1)
/*
* crypto operations 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 *);
};
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 */
};
static inline bool fscrypt_has_encryption_key(const struct inode *inode)
{
return (inode->i_crypt_info != NULL);
}
static inline bool fscrypt_dummy_context_enabled(struct inode *inode)
{
return inode->i_sb->s_cop->dummy_context &&
inode->i_sb->s_cop->dummy_context(inode);
}
/* crypto.c */
extern void fscrypt_enqueue_decrypt_work(struct work_struct *);
extern struct fscrypt_ctx *fscrypt_get_ctx(const struct inode *, gfp_t);
extern void fscrypt_release_ctx(struct fscrypt_ctx *);
extern struct page *fscrypt_encrypt_page(const struct inode *, struct page *,
unsigned int, unsigned int,
u64, gfp_t);
extern int fscrypt_decrypt_page(const struct inode *, struct page *, unsigned int,
unsigned int, u64);
static inline struct page *fscrypt_control_page(struct page *page)
{
return ((struct fscrypt_ctx *)page_private(page))->w.control_page;
}
extern void fscrypt_restore_control_page(struct page *);
extern const struct dentry_operations fscrypt_d_ops;
static inline void fscrypt_set_d_op(struct dentry *dentry)
{
d_set_d_op(dentry, &fscrypt_d_ops);
}
static inline void fscrypt_set_encrypted_dentry(struct dentry *dentry)
{
spin_lock(&dentry->d_lock);
dentry->d_flags |= DCACHE_ENCRYPTED_WITH_KEY;
spin_unlock(&dentry->d_lock);
}
/* policy.c */
extern int fscrypt_ioctl_set_policy(struct file *, const void __user *);
extern int fscrypt_ioctl_get_policy(struct file *, void __user *);
extern int fscrypt_has_permitted_context(struct inode *, struct inode *);
extern int fscrypt_inherit_context(struct inode *, struct inode *,
void *, bool);
/* keyinfo.c */
extern int fscrypt_get_encryption_info(struct inode *);
extern void fscrypt_put_encryption_info(struct inode *);
/* fname.c */
extern int fscrypt_setup_filename(struct inode *, const struct qstr *,
int lookup, struct fscrypt_name *);
static inline void fscrypt_free_filename(struct fscrypt_name *fname)
{
kfree(fname->crypto_buf.name);
}
extern int fscrypt_fname_alloc_buffer(const struct inode *, u32,
struct fscrypt_str *);
extern void fscrypt_fname_free_buffer(struct fscrypt_str *);
extern int fscrypt_fname_disk_to_usr(struct inode *, u32, u32,
const struct fscrypt_str *, struct fscrypt_str *);
#define FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE 32
/* Extracts the second-to-last ciphertext block; see explanation below */
#define FSCRYPT_FNAME_DIGEST(name, len) \
((name) + round_down((len) - FS_CRYPTO_BLOCK_SIZE - 1, \
FS_CRYPTO_BLOCK_SIZE))
#define FSCRYPT_FNAME_DIGEST_SIZE FS_CRYPTO_BLOCK_SIZE
/**
* fscrypt_digested_name - alternate identifier for an on-disk filename
*
* When userspace lists an encrypted directory without access to the key,
* filenames whose ciphertext is longer than FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE
* bytes are shown in this abbreviated form (base64-encoded) rather than as the
* full ciphertext (base64-encoded). This is necessary to allow supporting
* filenames up to NAME_MAX bytes, since base64 encoding expands the length.
*
* To make it possible for filesystems to still find the correct directory entry
* despite not knowing the full on-disk name, we encode any filesystem-specific
* 'hash' and/or 'minor_hash' which the filesystem may need for its lookups,
* followed by the second-to-last ciphertext block of the filename. Due to the
* use of the CBC-CTS encryption mode, the second-to-last ciphertext block
* depends on the full plaintext. (Note that ciphertext stealing causes the
* last two blocks to appear "flipped".) This makes accidental collisions very
* unlikely: just a 1 in 2^128 chance for two filenames to collide even if they
* share the same filesystem-specific hashes.
*
* However, this scheme isn't immune to intentional collisions, which can be
* created by anyone able to create arbitrary plaintext filenames and view them
* without the key. Making the "digest" be a real cryptographic hash like
* SHA-256 over the full ciphertext would prevent this, although it would be
* less efficient and harder to implement, especially since the filesystem would
* need to calculate it for each directory entry examined during a search.
*/
struct fscrypt_digested_name {
u32 hash;
u32 minor_hash;
u8 digest[FSCRYPT_FNAME_DIGEST_SIZE];
};
/**
* fscrypt_match_name() - test whether the given name matches a directory entry
* @fname: the name being searched for
* @de_name: the name from the directory entry
* @de_name_len: the length of @de_name in bytes
*
* Normally @fname->disk_name will be set, and in that case we simply compare
* that to the name stored in the directory entry. The only exception is that
* if we don't have the key for an encrypted directory and a filename in it is
* very long, then we won't have the full disk_name and we'll instead need to
* match against the fscrypt_digested_name.
*
* Return: %true if the name matches, otherwise %false.
*/
static inline bool fscrypt_match_name(const struct fscrypt_name *fname,
const u8 *de_name, u32 de_name_len)
{
if (unlikely(!fname->disk_name.name)) {
const struct fscrypt_digested_name *n =
(const void *)fname->crypto_buf.name;
if (WARN_ON_ONCE(fname->usr_fname->name[0] != '_'))
return false;
if (de_name_len <= FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE)
return false;
return !memcmp(FSCRYPT_FNAME_DIGEST(de_name, de_name_len),
n->digest, FSCRYPT_FNAME_DIGEST_SIZE);
}
if (de_name_len != fname->disk_name.len)
return false;
return !memcmp(de_name, fname->disk_name.name, fname->disk_name.len);
}
/* bio.c */
extern void fscrypt_decrypt_bio(struct bio *);
extern void fscrypt_enqueue_decrypt_bio(struct fscrypt_ctx *ctx,
struct bio *bio);
extern void fscrypt_pullback_bio_page(struct page **, bool);
extern int fscrypt_zeroout_range(const struct inode *, pgoff_t, sector_t,
unsigned int);
/* hooks.c */
extern int fscrypt_file_open(struct inode *inode, struct file *filp);
extern int __fscrypt_prepare_link(struct inode *inode, struct inode *dir);
extern int __fscrypt_prepare_rename(struct inode *old_dir,
struct dentry *old_dentry,
struct inode *new_dir,
struct dentry *new_dentry,
unsigned int flags);
extern int __fscrypt_prepare_lookup(struct inode *dir, struct dentry *dentry);
extern int __fscrypt_prepare_symlink(struct inode *dir, unsigned int len,
unsigned int max_len,
struct fscrypt_str *disk_link);
extern int __fscrypt_encrypt_symlink(struct inode *inode, const char *target,
unsigned int len,
struct fscrypt_str *disk_link);
extern const char *fscrypt_get_symlink(struct inode *inode, const void *caddr,
unsigned int max_size,
struct delayed_call *done);
#endif /* _LINUX_FSCRYPT_SUPP_H */