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linux-next/include/linux/fscrypto.h
Jaegeuk Kim b5a7aef1ef fscrypto/f2fs: allow fs-specific key prefix for fs encryption 
This patch allows fscrypto to handle a second key prefix given by filesystem.
The main reason is to provide backward compatibility, since previously f2fs
used "f2fs:" as a crypto prefix instead of "fscrypt:".
Later, ext4 should also provide key_prefix() to give "ext4:".

One concern decribed by Ted would be kinda double check overhead of prefixes.
In x86, for example, validate_user_key consumes 8 ms after boot-up, which turns
out derive_key_aes() consumed most of the time to load specific crypto module.
After such the cold miss, it shows almost zero latencies, which treats as a
negligible overhead.
Note that request_key() detects wrong prefix in prior to derive_key_aes() even.

Cc: Ted Tso <tytso@mit.edu>
Cc: stable@vger.kernel.org # v4.6
Signed-off-by: Jaegeuk Kim <jaegeuk@kernel.org>
2016-05-07 10:32:33 -07:00

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/*
* General per-file encryption definition
*
* Copyright (C) 2015, Google, Inc.
*
* Written by Michael Halcrow, 2015.
* Modified by Jaegeuk Kim, 2015.
*/
#ifndef _LINUX_FSCRYPTO_H
#define _LINUX_FSCRYPTO_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_KEY_DERIVATION_NONCE_SIZE 16
#define FS_ENCRYPTION_CONTEXT_FORMAT_V1 1
#define FS_POLICY_FLAGS_PAD_4 0x00
#define FS_POLICY_FLAGS_PAD_8 0x01
#define FS_POLICY_FLAGS_PAD_16 0x02
#define FS_POLICY_FLAGS_PAD_32 0x03
#define FS_POLICY_FLAGS_PAD_MASK 0x03
#define FS_POLICY_FLAGS_VALID 0x03
/* Encryption algorithms */
#define FS_ENCRYPTION_MODE_INVALID 0
#define FS_ENCRYPTION_MODE_AES_256_XTS 1
#define FS_ENCRYPTION_MODE_AES_256_GCM 2
#define FS_ENCRYPTION_MODE_AES_256_CBC 3
#define FS_ENCRYPTION_MODE_AES_256_CTS 4
/**
* Encryption context for inode
*
* Protector format:
* 1 byte: Protector format (1 = this version)
* 1 byte: File contents encryption mode
* 1 byte: File names encryption mode
* 1 byte: Flags
* 8 bytes: Master Key descriptor
* 16 bytes: Encryption Key derivation nonce
*/
struct fscrypt_context {
u8 format;
u8 contents_encryption_mode;
u8 filenames_encryption_mode;
u8 flags;
u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
} __packed;
/* Encryption parameters */
#define FS_XTS_TWEAK_SIZE 16
#define FS_AES_128_ECB_KEY_SIZE 16
#define FS_AES_256_GCM_KEY_SIZE 32
#define FS_AES_256_CBC_KEY_SIZE 32
#define FS_AES_256_CTS_KEY_SIZE 32
#define FS_AES_256_XTS_KEY_SIZE 64
#define FS_MAX_KEY_SIZE 64
#define FS_KEY_DESC_PREFIX "fscrypt:"
#define FS_KEY_DESC_PREFIX_SIZE 8
/* This is passed in from userspace into the kernel keyring */
struct fscrypt_key {
u32 mode;
u8 raw[FS_MAX_KEY_SIZE];
u32 size;
} __packed;
struct fscrypt_info {
u8 ci_data_mode;
u8 ci_filename_mode;
u8 ci_flags;
struct crypto_skcipher *ci_ctfm;
struct key *ci_keyring_key;
u8 ci_master_key[FS_KEY_DESCRIPTOR_SIZE];
};
#define FS_CTX_REQUIRES_FREE_ENCRYPT_FL 0x00000001
#define FS_WRITE_PATH_FL 0x00000002
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 */
u8 mode; /* Encryption mode for tfm */
};
struct fscrypt_completion_result {
struct completion completion;
int res;
};
#define DECLARE_FS_COMPLETION_RESULT(ecr) \
struct fscrypt_completion_result ecr = { \
COMPLETION_INITIALIZER((ecr).completion), 0 }
static inline int fscrypt_key_size(int mode)
{
switch (mode) {
case FS_ENCRYPTION_MODE_AES_256_XTS:
return FS_AES_256_XTS_KEY_SIZE;
case FS_ENCRYPTION_MODE_AES_256_GCM:
return FS_AES_256_GCM_KEY_SIZE;
case FS_ENCRYPTION_MODE_AES_256_CBC:
return FS_AES_256_CBC_KEY_SIZE;
case FS_ENCRYPTION_MODE_AES_256_CTS:
return FS_AES_256_CTS_KEY_SIZE;
default:
BUG();
}
return 0;
}
#define FS_FNAME_NUM_SCATTER_ENTRIES 4
#define FS_CRYPTO_BLOCK_SIZE 16
#define FS_FNAME_CRYPTO_DIGEST_SIZE 32
/**
* 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)
/*
* crypto opertions for filesystems
*/
struct fscrypt_operations {
int (*get_context)(struct inode *, void *, size_t);
int (*key_prefix)(struct inode *, u8 **);
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 u32 fscrypt_validate_encryption_key_size(u32 mode, u32 size)
{
if (size == fscrypt_key_size(mode))
return size;
return 0;
}
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(struct inode *inode)
{
#if IS_ENABLED(CONFIG_FS_ENCRYPTION)
return (inode->i_crypt_info != NULL);
#else
return 0;
#endif
}
static inline void fscrypt_set_encrypted_dentry(struct dentry *dentry)
{
#if IS_ENABLED(CONFIG_FS_ENCRYPTION)
spin_lock(&dentry->d_lock);
dentry->d_flags |= DCACHE_ENCRYPTED_WITH_KEY;
spin_unlock(&dentry->d_lock);
#endif
}
#if IS_ENABLED(CONFIG_FS_ENCRYPTION)
extern const struct dentry_operations fscrypt_d_ops;
#endif
static inline void fscrypt_set_d_op(struct dentry *dentry)
{
#if IS_ENABLED(CONFIG_FS_ENCRYPTION)
d_set_d_op(dentry, &fscrypt_d_ops);
#endif
}
#if IS_ENABLED(CONFIG_FS_ENCRYPTION)
/* crypto.c */
extern struct kmem_cache *fscrypt_info_cachep;
int fscrypt_initialize(void);
extern struct fscrypt_ctx *fscrypt_get_ctx(struct inode *, gfp_t);
extern void fscrypt_release_ctx(struct fscrypt_ctx *);
extern struct page *fscrypt_encrypt_page(struct inode *, struct page *, gfp_t);
extern int fscrypt_decrypt_page(struct page *);
extern void fscrypt_decrypt_bio_pages(struct fscrypt_ctx *, struct bio *);
extern void fscrypt_pullback_bio_page(struct page **, bool);
extern void fscrypt_restore_control_page(struct page *);
extern int fscrypt_zeroout_range(struct inode *, pgoff_t, sector_t,
unsigned int);
/* policy.c */
extern int fscrypt_process_policy(struct inode *,
const struct fscrypt_policy *);
extern int fscrypt_get_policy(struct inode *, struct fscrypt_policy *);
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 get_crypt_info(struct inode *);
extern int fscrypt_get_encryption_info(struct inode *);
extern void fscrypt_put_encryption_info(struct inode *, struct fscrypt_info *);
/* fname.c */
extern int fscrypt_setup_filename(struct inode *, const struct qstr *,
int lookup, struct fscrypt_name *);
extern void fscrypt_free_filename(struct fscrypt_name *);
extern u32 fscrypt_fname_encrypted_size(struct inode *, u32);
extern int fscrypt_fname_alloc_buffer(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 *);
extern int fscrypt_fname_usr_to_disk(struct inode *, const struct qstr *,
struct fscrypt_str *);
#endif
/* crypto.c */
static inline struct fscrypt_ctx *fscrypt_notsupp_get_ctx(struct inode *i,
gfp_t f)
{
return ERR_PTR(-EOPNOTSUPP);
}
static inline void fscrypt_notsupp_release_ctx(struct fscrypt_ctx *c)
{
return;
}
static inline struct page *fscrypt_notsupp_encrypt_page(struct inode *i,
struct page *p, gfp_t f)
{
return ERR_PTR(-EOPNOTSUPP);
}
static inline int fscrypt_notsupp_decrypt_page(struct page *p)
{
return -EOPNOTSUPP;
}
static inline void fscrypt_notsupp_decrypt_bio_pages(struct fscrypt_ctx *c,
struct bio *b)
{
return;
}
static inline void fscrypt_notsupp_pullback_bio_page(struct page **p, bool b)
{
return;
}
static inline void fscrypt_notsupp_restore_control_page(struct page *p)
{
return;
}
static inline int fscrypt_notsupp_zeroout_range(struct inode *i, pgoff_t p,
sector_t s, unsigned int f)
{
return -EOPNOTSUPP;
}
/* policy.c */
static inline int fscrypt_notsupp_process_policy(struct inode *i,
const struct fscrypt_policy *p)
{
return -EOPNOTSUPP;
}
static inline int fscrypt_notsupp_get_policy(struct inode *i,
struct fscrypt_policy *p)
{
return -EOPNOTSUPP;
}
static inline int fscrypt_notsupp_has_permitted_context(struct inode *p,
struct inode *i)
{
return 0;
}
static inline int fscrypt_notsupp_inherit_context(struct inode *p,
struct inode *i, void *v, bool b)
{
return -EOPNOTSUPP;
}
/* keyinfo.c */
static inline int fscrypt_notsupp_get_encryption_info(struct inode *i)
{
return -EOPNOTSUPP;
}
static inline void fscrypt_notsupp_put_encryption_info(struct inode *i,
struct fscrypt_info *f)
{
return;
}
/* fname.c */
static inline int fscrypt_notsupp_setup_filename(struct inode *dir,
const struct qstr *iname,
int lookup, struct fscrypt_name *fname)
{
if (dir->i_sb->s_cop->is_encrypted(dir))
return -EOPNOTSUPP;
memset(fname, 0, sizeof(struct fscrypt_name));
fname->usr_fname = iname;
fname->disk_name.name = (unsigned char *)iname->name;
fname->disk_name.len = iname->len;
return 0;
}
static inline void fscrypt_notsupp_free_filename(struct fscrypt_name *fname)
{
return;
}
static inline u32 fscrypt_notsupp_fname_encrypted_size(struct inode *i, u32 s)
{
/* never happens */
WARN_ON(1);
return 0;
}
static inline int fscrypt_notsupp_fname_alloc_buffer(struct inode *inode,
u32 ilen, struct fscrypt_str *crypto_str)
{
return -EOPNOTSUPP;
}
static inline void fscrypt_notsupp_fname_free_buffer(struct fscrypt_str *c)
{
return;
}
static inline int fscrypt_notsupp_fname_disk_to_usr(struct inode *inode,
u32 hash, u32 minor_hash,
const struct fscrypt_str *iname,
struct fscrypt_str *oname)
{
return -EOPNOTSUPP;
}
static inline int fscrypt_notsupp_fname_usr_to_disk(struct inode *inode,
const struct qstr *iname,
struct fscrypt_str *oname)
{
return -EOPNOTSUPP;
}
#endif /* _LINUX_FSCRYPTO_H */
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