[linux-block.git] / include / linux / fscrypt_supp.h

/* 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 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_pages(struct fscrypt_ctx *, struct 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 */
Commit	Line	Data
b2441318	1	/* SPDX-License-Identifier: GPL-2.0 */
46f47e48 EB	2	/*
	3	* fscrypt_supp.h
	4	*
734f0d24	5	* Do not include this file directly. Use fscrypt.h instead!
46f47e48	6	*/
734f0d24 DC	7	#ifndef _LINUX_FSCRYPT_H
	8	#error "Incorrect include of linux/fscrypt_supp.h!"
	9	#endif
46f47e48 EB	10
	11	#ifndef _LINUX_FSCRYPT_SUPP_H
	12	#define _LINUX_FSCRYPT_SUPP_H
	13
a575784c EB	14	#include <linux/mm.h>
	15	#include <linux/slab.h>
	16
bdd23476 EB	17	/*
	18	* fscrypt superblock flags
	19	*/
	20	#define FS_CFLG_OWN_PAGES (1U << 1)
	21
	22	/*
	23	* crypto operations for filesystems
	24	*/
	25	struct fscrypt_operations {
	26	unsigned int flags;
	27	const char *key_prefix;
	28	int (get_context)(struct inode , void *, size_t);
	29	int (set_context)(struct inode , const void , size_t, void );
	30	bool (dummy_context)(struct inode );
	31	bool (empty_dir)(struct inode );
	32	unsigned (max_namelen)(struct inode );
	33	};
	34
542060c0 EB	35	struct fscrypt_ctx {
	36	union {
	37	struct {
	38	struct page bounce_page; / Ciphertext page */
	39	struct page control_page; / Original page */
	40	} w;
	41	struct {
	42	struct bio *bio;
	43	struct work_struct work;
	44	} r;
	45	struct list_head free_list; /* Free list */
	46	};
	47	u8 flags; /* Flags */
	48	};
	49
3d463f28 EB	50	static inline bool fscrypt_has_encryption_key(const struct inode *inode)
	51	{
	52	return (inode->i_crypt_info != NULL);
	53	}
	54
1493651b EB	55	static inline bool fscrypt_dummy_context_enabled(struct inode *inode)
	56	{
	57	return inode->i_sb->s_cop->dummy_context &&
	58	inode->i_sb->s_cop->dummy_context(inode);
	59	}
	60
46f47e48	61	/* crypto.c */
46f47e48 EB	62	extern struct fscrypt_ctx fscrypt_get_ctx(const struct inode , gfp_t);
	63	extern void fscrypt_release_ctx(struct fscrypt_ctx *);
	64	extern struct page fscrypt_encrypt_page(const struct inode , struct page *,
	65	unsigned int, unsigned int,
	66	u64, gfp_t);
	67	extern int fscrypt_decrypt_page(const struct inode , struct page , unsigned int,
	68	unsigned int, u64);
4fd4b15c EB	69
	70	static inline struct page fscrypt_control_page(struct page page)
	71	{
	72	return ((struct fscrypt_ctx *)page_private(page))->w.control_page;
	73	}
	74
46f47e48 EB	75	extern void fscrypt_restore_control_page(struct page *);
	76
	77	extern const struct dentry_operations fscrypt_d_ops;
	78
	79	static inline void fscrypt_set_d_op(struct dentry *dentry)
	80	{
	81	d_set_d_op(dentry, &fscrypt_d_ops);
	82	}
	83
	84	static inline void fscrypt_set_encrypted_dentry(struct dentry *dentry)
	85	{
	86	spin_lock(&dentry->d_lock);
	87	dentry->d_flags \|= DCACHE_ENCRYPTED_WITH_KEY;
	88	spin_unlock(&dentry->d_lock);
	89	}
	90
	91	/* policy.c */
	92	extern int fscrypt_ioctl_set_policy(struct file , const void __user );
	93	extern int fscrypt_ioctl_get_policy(struct file , void __user );
	94	extern int fscrypt_has_permitted_context(struct inode , struct inode );
	95	extern int fscrypt_inherit_context(struct inode , struct inode ,
	96	void *, bool);
	97	/* keyinfo.c */
	98	extern int fscrypt_get_encryption_info(struct inode *);
3d204e24	99	extern void fscrypt_put_encryption_info(struct inode *);
46f47e48 EB	100
	101	/* fname.c */
	102	extern int fscrypt_setup_filename(struct inode , const struct qstr ,
	103	int lookup, struct fscrypt_name *);
27e47a63 EB	104
	105	static inline void fscrypt_free_filename(struct fscrypt_name *fname)
	106	{
	107	kfree(fname->crypto_buf.name);
	108	}
	109
46f47e48 EB	110	extern int fscrypt_fname_alloc_buffer(const struct inode *, u32,
	111	struct fscrypt_str *);
	112	extern void fscrypt_fname_free_buffer(struct fscrypt_str *);
	113	extern int fscrypt_fname_disk_to_usr(struct inode *, u32, u32,
	114	const struct fscrypt_str , struct fscrypt_str );
46f47e48	115
17159420 EB	116	#define FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE 32
	117
	118	/* Extracts the second-to-last ciphertext block; see explanation below */
	119	#define FSCRYPT_FNAME_DIGEST(name, len) \
	120	((name) + round_down((len) - FS_CRYPTO_BLOCK_SIZE - 1, \
	121	FS_CRYPTO_BLOCK_SIZE))
	122
	123	#define FSCRYPT_FNAME_DIGEST_SIZE FS_CRYPTO_BLOCK_SIZE
	124
	125	/**
	126	* fscrypt_digested_name - alternate identifier for an on-disk filename
	127	*
	128	* When userspace lists an encrypted directory without access to the key,
	129	* filenames whose ciphertext is longer than FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE
	130	* bytes are shown in this abbreviated form (base64-encoded) rather than as the
	131	* full ciphertext (base64-encoded). This is necessary to allow supporting
	132	* filenames up to NAME_MAX bytes, since base64 encoding expands the length.
	133	*
	134	* To make it possible for filesystems to still find the correct directory entry
	135	* despite not knowing the full on-disk name, we encode any filesystem-specific
	136	* 'hash' and/or 'minor_hash' which the filesystem may need for its lookups,
	137	* followed by the second-to-last ciphertext block of the filename. Due to the
	138	* use of the CBC-CTS encryption mode, the second-to-last ciphertext block
	139	* depends on the full plaintext. (Note that ciphertext stealing causes the
6f9d696f EB	140	* last two blocks to appear "flipped".) This makes accidental collisions very
	141	* unlikely: just a 1 in 2^128 chance for two filenames to collide even if they
	142	* share the same filesystem-specific hashes.
17159420	143	*
6f9d696f EB	144	* However, this scheme isn't immune to intentional collisions, which can be
	145	* created by anyone able to create arbitrary plaintext filenames and view them
	146	* without the key. Making the "digest" be a real cryptographic hash like
	147	* SHA-256 over the full ciphertext would prevent this, although it would be
	148	* less efficient and harder to implement, especially since the filesystem would
	149	* need to calculate it for each directory entry examined during a search.
17159420 EB	150	*/
	151	struct fscrypt_digested_name {
	152	u32 hash;
	153	u32 minor_hash;
	154	u8 digest[FSCRYPT_FNAME_DIGEST_SIZE];
	155	};
	156
	157	/**
	158	* fscrypt_match_name() - test whether the given name matches a directory entry
	159	* @fname: the name being searched for
	160	* @de_name: the name from the directory entry
	161	* @de_name_len: the length of @de_name in bytes
	162	*
	163	* Normally @fname->disk_name will be set, and in that case we simply compare
	164	* that to the name stored in the directory entry. The only exception is that
	165	* if we don't have the key for an encrypted directory and a filename in it is
	166	* very long, then we won't have the full disk_name and we'll instead need to
	167	* match against the fscrypt_digested_name.
	168	*
	169	* Return: %true if the name matches, otherwise %false.
	170	*/
	171	static inline bool fscrypt_match_name(const struct fscrypt_name *fname,
	172	const u8 *de_name, u32 de_name_len)
	173	{
	174	if (unlikely(!fname->disk_name.name)) {
	175	const struct fscrypt_digested_name *n =
	176	(const void *)fname->crypto_buf.name;
	177	if (WARN_ON_ONCE(fname->usr_fname->name[0] != '_'))
	178	return false;
	179	if (de_name_len <= FSCRYPT_FNAME_MAX_UNDIGESTED_SIZE)
	180	return false;
	181	return !memcmp(FSCRYPT_FNAME_DIGEST(de_name, de_name_len),
	182	n->digest, FSCRYPT_FNAME_DIGEST_SIZE);
	183	}
	184
	185	if (de_name_len != fname->disk_name.len)
	186	return false;
	187	return !memcmp(de_name, fname->disk_name.name, fname->disk_name.len);
	188	}
	189
46f47e48 EB	190	/* bio.c */
	191	extern void fscrypt_decrypt_bio_pages(struct fscrypt_ctx , struct bio );
	192	extern void fscrypt_pullback_bio_page(struct page **, bool);
	193	extern int fscrypt_zeroout_range(const struct inode *, pgoff_t, sector_t,
	194	unsigned int);
	195
efcc7ae2 EB	196	/* hooks.c */
efcc7ae2 EB	197	extern int fscrypt_file_open(struct inode inode, struct file filp);
0ea87a96	198	extern int __fscrypt_prepare_link(struct inode inode, struct inode dir);
94b26f36 EB	199	extern int __fscrypt_prepare_rename(struct inode *old_dir,
	200	struct dentry *old_dentry,
	201	struct inode *new_dir,
	202	struct dentry *new_dentry,
	203	unsigned int flags);
32c3cf02	204	extern int __fscrypt_prepare_lookup(struct inode dir, struct dentry dentry);
76e81d6d EB	205	extern int __fscrypt_prepare_symlink(struct inode *dir, unsigned int len,
	206	unsigned int max_len,
	207	struct fscrypt_str *disk_link);
	208	extern int __fscrypt_encrypt_symlink(struct inode inode, const char target,
	209	unsigned int len,
	210	struct fscrypt_str *disk_link);
3b0d8837 EB	211	extern const char fscrypt_get_symlink(struct inode inode, const void *caddr,
	212	unsigned int max_size,
	213	struct delayed_call *done);
efcc7ae2	214
46f47e48	215	#endif /* _LINUX_FSCRYPT_SUPP_H */