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1/* SPDX-License-Identifier: GPL-2.0 */
2/*
3 * fscrypt_private.h
4 *
5 * Copyright (C) 2015, Google, Inc.
6 *
7 * This contains encryption key functions.
8 *
9 * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
10 */
11
12#ifndef _FSCRYPT_PRIVATE_H
13#define _FSCRYPT_PRIVATE_H
14
15#include <linux/fscrypt.h>
16#include <crypto/hash.h>
17
18/* Encryption parameters */
19#define FS_KEY_DERIVATION_NONCE_SIZE 16
20
21/**
22 * Encryption context for inode
23 *
24 * Protector format:
25 * 1 byte: Protector format (1 = this version)
26 * 1 byte: File contents encryption mode
27 * 1 byte: File names encryption mode
28 * 1 byte: Flags
29 * 8 bytes: Master Key descriptor
30 * 16 bytes: Encryption Key derivation nonce
31 */
32struct fscrypt_context {
33 u8 format;
34 u8 contents_encryption_mode;
35 u8 filenames_encryption_mode;
36 u8 flags;
37 u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
38 u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
39} __packed;
40
41#define FS_ENCRYPTION_CONTEXT_FORMAT_V1 1
42
43/**
44 * For encrypted symlinks, the ciphertext length is stored at the beginning
45 * of the string in little-endian format.
46 */
47struct fscrypt_symlink_data {
48 __le16 len;
49 char encrypted_path[1];
50} __packed;
51
52/*
53 * fscrypt_info - the "encryption key" for an inode
54 *
55 * When an encrypted file's key is made available, an instance of this struct is
56 * allocated and stored in ->i_crypt_info. Once created, it remains until the
57 * inode is evicted.
58 */
59struct fscrypt_info {
60
61 /* The actual crypto transform used for encryption and decryption */
62 struct crypto_skcipher *ci_ctfm;
63
64 /*
65 * Cipher for ESSIV IV generation. Only set for CBC contents
66 * encryption, otherwise is NULL.
67 */
68 struct crypto_cipher *ci_essiv_tfm;
69
70 /*
71 * Encryption mode used for this inode. It corresponds to either
72 * ci_data_mode or ci_filename_mode, depending on the inode type.
73 */
74 struct fscrypt_mode *ci_mode;
75
76 /*
77 * If non-NULL, then this inode uses a master key directly rather than a
78 * derived key, and ci_ctfm will equal ci_master_key->mk_ctfm.
79 * Otherwise, this inode uses a derived key.
80 */
81 struct fscrypt_master_key *ci_master_key;
82
83 /* fields from the fscrypt_context */
84 u8 ci_data_mode;
85 u8 ci_filename_mode;
86 u8 ci_flags;
87 u8 ci_master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
88 u8 ci_nonce[FS_KEY_DERIVATION_NONCE_SIZE];
89};
90
91typedef enum {
92 FS_DECRYPT = 0,
93 FS_ENCRYPT,
94} fscrypt_direction_t;
95
96#define FS_CTX_REQUIRES_FREE_ENCRYPT_FL 0x00000001
97
98static inline bool fscrypt_valid_enc_modes(u32 contents_mode,
99 u32 filenames_mode)
100{
101 if (contents_mode == FS_ENCRYPTION_MODE_AES_128_CBC &&
102 filenames_mode == FS_ENCRYPTION_MODE_AES_128_CTS)
103 return true;
104
105 if (contents_mode == FS_ENCRYPTION_MODE_AES_256_XTS &&
106 filenames_mode == FS_ENCRYPTION_MODE_AES_256_CTS)
107 return true;
108
109 if (contents_mode == FS_ENCRYPTION_MODE_ADIANTUM &&
110 filenames_mode == FS_ENCRYPTION_MODE_ADIANTUM)
111 return true;
112
113 return false;
114}
115
116/* crypto.c */
117extern struct kmem_cache *fscrypt_info_cachep;
118extern int fscrypt_initialize(unsigned int cop_flags);
119extern int fscrypt_crypt_block(const struct inode *inode,
120 fscrypt_direction_t rw, u64 lblk_num,
121 struct page *src_page, struct page *dest_page,
122 unsigned int len, unsigned int offs,
123 gfp_t gfp_flags);
124extern struct page *fscrypt_alloc_bounce_page(gfp_t gfp_flags);
125extern const struct dentry_operations fscrypt_d_ops;
126
127extern void __printf(3, 4) __cold
128fscrypt_msg(struct super_block *sb, const char *level, const char *fmt, ...);
129
130#define fscrypt_warn(sb, fmt, ...) \
131 fscrypt_msg(sb, KERN_WARNING, fmt, ##__VA_ARGS__)
132#define fscrypt_err(sb, fmt, ...) \
133 fscrypt_msg(sb, KERN_ERR, fmt, ##__VA_ARGS__)
134
135#define FSCRYPT_MAX_IV_SIZE 32
136
137union fscrypt_iv {
138 struct {
139 /* logical block number within the file */
140 __le64 lblk_num;
141
142 /* per-file nonce; only set in DIRECT_KEY mode */
143 u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
144 };
145 u8 raw[FSCRYPT_MAX_IV_SIZE];
146};
147
148void fscrypt_generate_iv(union fscrypt_iv *iv, u64 lblk_num,
149 const struct fscrypt_info *ci);
150
151/* fname.c */
152extern int fname_encrypt(struct inode *inode, const struct qstr *iname,
153 u8 *out, unsigned int olen);
154extern bool fscrypt_fname_encrypted_size(const struct inode *inode,
155 u32 orig_len, u32 max_len,
156 u32 *encrypted_len_ret);
157
158/* keyinfo.c */
159
160struct fscrypt_mode {
161 const char *friendly_name;
162 const char *cipher_str;
163 int keysize;
164 int ivsize;
165 bool logged_impl_name;
166 bool needs_essiv;
167};
168
169extern void __exit fscrypt_essiv_cleanup(void);
170
171#endif /* _FSCRYPT_PRIVATE_H */