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