summaryrefslogtreecommitdiff
path: root/fs/ext4/ext4_crypto.h
blob: ac7d4e81379630d2f720ea8d389b8322a784f4cf (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
/*
 * linux/fs/ext4/ext4_crypto.h
 *
 * Copyright (C) 2015, Google, Inc.
 *
 * This contains encryption header content for ext4
 *
 * Written by Michael Halcrow, 2015.
 */

#ifndef _EXT4_CRYPTO_H
#define _EXT4_CRYPTO_H

#include <linux/fs.h>

#define EXT4_KEY_DESCRIPTOR_SIZE 8

/* Policy provided via an ioctl on the topmost directory */
struct ext4_encryption_policy {
	char version;
	char contents_encryption_mode;
	char filenames_encryption_mode;
	char flags;
	char master_key_descriptor[EXT4_KEY_DESCRIPTOR_SIZE];
} __attribute__((__packed__));

#define EXT4_ENCRYPTION_CONTEXT_FORMAT_V1 1
#define EXT4_KEY_DERIVATION_NONCE_SIZE 16

#define EXT4_POLICY_FLAGS_PAD_4		0x00
#define EXT4_POLICY_FLAGS_PAD_8		0x01
#define EXT4_POLICY_FLAGS_PAD_16	0x02
#define EXT4_POLICY_FLAGS_PAD_32	0x03
#define EXT4_POLICY_FLAGS_PAD_MASK	0x03
#define EXT4_POLICY_FLAGS_VALID		0x03

/**
 * 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: Reserved
 *  8 bytes: Master Key descriptor
 *  16 bytes: Encryption Key derivation nonce
 */
struct ext4_encryption_context {
	char format;
	char contents_encryption_mode;
	char filenames_encryption_mode;
	char flags;
	char master_key_descriptor[EXT4_KEY_DESCRIPTOR_SIZE];
	char nonce[EXT4_KEY_DERIVATION_NONCE_SIZE];
} __attribute__((__packed__));

/* Encryption parameters */
#define EXT4_XTS_TWEAK_SIZE 16
#define EXT4_AES_128_ECB_KEY_SIZE 16
#define EXT4_AES_256_GCM_KEY_SIZE 32
#define EXT4_AES_256_CBC_KEY_SIZE 32
#define EXT4_AES_256_CTS_KEY_SIZE 32
#define EXT4_AES_256_XTS_KEY_SIZE 64
#define EXT4_MAX_KEY_SIZE 64

#define EXT4_KEY_DESC_PREFIX "ext4:"
#define EXT4_KEY_DESC_PREFIX_SIZE 5

/* This is passed in from userspace into the kernel keyring */
struct ext4_encryption_key {
        __u32 mode;
        char raw[EXT4_MAX_KEY_SIZE];
        __u32 size;
} __attribute__((__packed__));

struct ext4_crypt_info {
	char		ci_data_mode;
	char		ci_filename_mode;
	char		ci_flags;
	struct crypto_ablkcipher *ci_ctfm;
	struct key	*ci_keyring_key;
	char		ci_master_key[EXT4_KEY_DESCRIPTOR_SIZE];
};

#define EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL             0x00000001
#define EXT4_WRITE_PATH_FL			      0x00000002

struct ext4_crypto_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 */
	};
	char flags;                      /* Flags */
	char mode;                       /* Encryption mode for tfm */
};

struct ext4_completion_result {
	struct completion completion;
	int res;
};

#define DECLARE_EXT4_COMPLETION_RESULT(ecr) \
	struct ext4_completion_result ecr = { \
		COMPLETION_INITIALIZER((ecr).completion), 0 }

static inline int ext4_encryption_key_size(int mode)
{
	switch (mode) {
	case EXT4_ENCRYPTION_MODE_AES_256_XTS:
		return EXT4_AES_256_XTS_KEY_SIZE;
	case EXT4_ENCRYPTION_MODE_AES_256_GCM:
		return EXT4_AES_256_GCM_KEY_SIZE;
	case EXT4_ENCRYPTION_MODE_AES_256_CBC:
		return EXT4_AES_256_CBC_KEY_SIZE;
	case EXT4_ENCRYPTION_MODE_AES_256_CTS:
		return EXT4_AES_256_CTS_KEY_SIZE;
	default:
		BUG();
	}
	return 0;
}

#define EXT4_FNAME_NUM_SCATTER_ENTRIES	4
#define EXT4_CRYPTO_BLOCK_SIZE		16
#define EXT4_FNAME_CRYPTO_DIGEST_SIZE	32

struct ext4_str {
	unsigned char *name;
	u32 len;
};

/**
 * For encrypted symlinks, the ciphertext length is stored at the beginning
 * of the string in little-endian format.
 */
struct ext4_encrypted_symlink_data {
	__le16 len;
	char encrypted_path[1];
} __attribute__((__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 encrypted_symlink_data_len(u32 l)
{
	if (l < EXT4_CRYPTO_BLOCK_SIZE)
		l = EXT4_CRYPTO_BLOCK_SIZE;
	return (l + sizeof(struct ext4_encrypted_symlink_data) - 1);
}

#endif	/* _EXT4_CRYPTO_H */