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1 /*
2  * fscrypt_private.h
3  *
4  * Copyright (C) 2015, Google, Inc.
5  *
6  * This contains encryption key functions.
7  *
8  * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
9  */
10 
11 #ifndef _FSCRYPT_PRIVATE_H
12 #define _FSCRYPT_PRIVATE_H
13 
14 #define __FS_HAS_ENCRYPTION 1
15 #include <linux/fscrypt.h>
16 #include <crypto/hash.h>
17 
18 /* Encryption parameters */
19 #define FS_IV_SIZE			16
20 #define FS_AES_128_ECB_KEY_SIZE		16
21 #define FS_AES_128_CBC_KEY_SIZE		16
22 #define FS_AES_128_CTS_KEY_SIZE		16
23 #define FS_AES_256_GCM_KEY_SIZE		32
24 #define FS_AES_256_CBC_KEY_SIZE		32
25 #define FS_AES_256_CTS_KEY_SIZE		32
26 #define FS_AES_256_XTS_KEY_SIZE		64
27 
28 #define FS_KEY_DERIVATION_NONCE_SIZE		16
29 
30 /**
31  * Encryption context for inode
32  *
33  * Protector format:
34  *  1 byte: Protector format (1 = this version)
35  *  1 byte: File contents encryption mode
36  *  1 byte: File names encryption mode
37  *  1 byte: Flags
38  *  8 bytes: Master Key descriptor
39  *  16 bytes: Encryption Key derivation nonce
40  */
41 struct fscrypt_context {
42 	u8 format;
43 	u8 contents_encryption_mode;
44 	u8 filenames_encryption_mode;
45 	u8 flags;
46 	u8 master_key_descriptor[FS_KEY_DESCRIPTOR_SIZE];
47 	u8 nonce[FS_KEY_DERIVATION_NONCE_SIZE];
48 } __packed;
49 
50 #define FS_ENCRYPTION_CONTEXT_FORMAT_V1		1
51 
52 /**
53  * For encrypted symlinks, the ciphertext length is stored at the beginning
54  * of the string in little-endian format.
55  */
56 struct fscrypt_symlink_data {
57 	__le16 len;
58 	char encrypted_path[1];
59 } __packed;
60 
61 /*
62  * A pointer to this structure is stored in the file system's in-core
63  * representation of an inode.
64  */
65 struct fscrypt_info {
66 	u8 ci_data_mode;
67 	u8 ci_filename_mode;
68 	u8 ci_flags;
69 	struct crypto_skcipher *ci_ctfm;
70 	struct crypto_cipher *ci_essiv_tfm;
71 	u8 ci_master_key[FS_KEY_DESCRIPTOR_SIZE];
72 };
73 
74 typedef enum {
75 	FS_DECRYPT = 0,
76 	FS_ENCRYPT,
77 } fscrypt_direction_t;
78 
79 #define FS_CTX_REQUIRES_FREE_ENCRYPT_FL		0x00000001
80 #define FS_CTX_HAS_BOUNCE_BUFFER_FL		0x00000002
81 
fscrypt_valid_enc_modes(u32 contents_mode,u32 filenames_mode)82 static inline bool fscrypt_valid_enc_modes(u32 contents_mode,
83 					   u32 filenames_mode)
84 {
85 	if (contents_mode == FS_ENCRYPTION_MODE_AES_128_CBC &&
86 	    filenames_mode == FS_ENCRYPTION_MODE_AES_128_CTS)
87 		return true;
88 
89 	if (contents_mode == FS_ENCRYPTION_MODE_AES_256_XTS &&
90 	    filenames_mode == FS_ENCRYPTION_MODE_AES_256_CTS)
91 		return true;
92 
93 	return false;
94 }
95 
96 /* crypto.c */
97 extern struct kmem_cache *fscrypt_info_cachep;
98 extern int fscrypt_initialize(unsigned int cop_flags);
99 extern int fscrypt_do_page_crypto(const struct inode *inode,
100 				  fscrypt_direction_t rw, u64 lblk_num,
101 				  struct page *src_page,
102 				  struct page *dest_page,
103 				  unsigned int len, unsigned int offs,
104 				  gfp_t gfp_flags);
105 extern struct page *fscrypt_alloc_bounce_page(struct fscrypt_ctx *ctx,
106 					      gfp_t gfp_flags);
107 
108 /* fname.c */
109 extern int fname_encrypt(struct inode *inode, const struct qstr *iname,
110 			 u8 *out, unsigned int olen);
111 extern bool fscrypt_fname_encrypted_size(const struct inode *inode,
112 					 u32 orig_len, u32 max_len,
113 					 u32 *encrypted_len_ret);
114 
115 /* keyinfo.c */
116 extern void __exit fscrypt_essiv_cleanup(void);
117 
118 #endif /* _FSCRYPT_PRIVATE_H */
119