fscrypt_common.h

/*
 * fscrypt_common.h: common declarations for per-file encryption
 *
 * Copyright (C) 2015, Google, Inc.
 *
 * Written by Michael Halcrow, 2015.
 * Modified by Jaegeuk Kim, 2015.
 */

#ifndef _LINUX_FSCRYPT_COMMON_H
#define _LINUX_FSCRYPT_COMMON_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;

/**
 * This function is used to calculate the disk space required to
 * store a filename of length l in encrypted symlink format.
 */
static inline u32 fscrypt_symlink_data_len(u32 l)
{
	if (l < FS_CRYPTO_BLOCK_SIZE)
		l = FS_CRYPTO_BLOCK_SIZE;
	return (l + sizeof(struct fscrypt_symlink_data) - 1);
}

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 (*prepare_context)(struct inode *);
	int (*set_context)(struct inode *, const void *, size_t, void *);
	int (*dummy_context)(struct inode *);
	bool (*is_encrypted)(struct inode *);
	bool (*empty_dir)(struct inode *);
	unsigned (*max_namelen)(struct inode *);
};

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_contents_enc_mode(u32 mode)
{
	return (mode == FS_ENCRYPTION_MODE_AES_256_XTS);
}

static inline bool fscrypt_valid_filenames_enc_mode(u32 mode)
{
	return (mode == FS_ENCRYPTION_MODE_AES_256_CTS);
}

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;
}

static inline struct page *fscrypt_control_page(struct page *page)
{
#if IS_ENABLED(CONFIG_FS_ENCRYPTION)
	return ((struct fscrypt_ctx *)page_private(page))->w.control_page;
#else
	WARN_ON_ONCE(1);
	return ERR_PTR(-EINVAL);
#endif
}

static inline int fscrypt_has_encryption_key(const struct inode *inode)
{
#if IS_ENABLED(CONFIG_FS_ENCRYPTION)
	return (inode->i_crypt_info != NULL);
#else
	return 0;
#endif
}

#endif	/* _LINUX_FSCRYPT_COMMON_H */