1/*
2 * linux/fs/ext4/ext4_crypto.h
3 *
4 * Copyright (C) 2015, Google, Inc.
5 *
6 * This contains encryption header content for ext4
7 *
8 * Written by Michael Halcrow, 2015.
9 */
10
11#ifndef _EXT4_CRYPTO_H
12#define _EXT4_CRYPTO_H
13
14#include <linux/fs.h>
15
16#define EXT4_KEY_DESCRIPTOR_SIZE 8
17
18/* Policy provided via an ioctl on the topmost directory */
19struct ext4_encryption_policy {
20	char version;
21	char contents_encryption_mode;
22	char filenames_encryption_mode;
23	char flags;
24	char master_key_descriptor[EXT4_KEY_DESCRIPTOR_SIZE];
25} __attribute__((__packed__));
26
27#define EXT4_ENCRYPTION_CONTEXT_FORMAT_V1 1
28#define EXT4_KEY_DERIVATION_NONCE_SIZE 16
29
30#define EXT4_POLICY_FLAGS_PAD_4		0x00
31#define EXT4_POLICY_FLAGS_PAD_8		0x01
32#define EXT4_POLICY_FLAGS_PAD_16	0x02
33#define EXT4_POLICY_FLAGS_PAD_32	0x03
34#define EXT4_POLICY_FLAGS_PAD_MASK	0x03
35#define EXT4_POLICY_FLAGS_VALID		0x03
36
37/**
38 * Encryption context for inode
39 *
40 * Protector format:
41 *  1 byte: Protector format (1 = this version)
42 *  1 byte: File contents encryption mode
43 *  1 byte: File names encryption mode
44 *  1 byte: Reserved
45 *  8 bytes: Master Key descriptor
46 *  16 bytes: Encryption Key derivation nonce
47 */
48struct ext4_encryption_context {
49	char format;
50	char contents_encryption_mode;
51	char filenames_encryption_mode;
52	char flags;
53	char master_key_descriptor[EXT4_KEY_DESCRIPTOR_SIZE];
54	char nonce[EXT4_KEY_DERIVATION_NONCE_SIZE];
55} __attribute__((__packed__));
56
57/* Encryption parameters */
58#define EXT4_XTS_TWEAK_SIZE 16
59#define EXT4_AES_128_ECB_KEY_SIZE 16
60#define EXT4_AES_256_GCM_KEY_SIZE 32
61#define EXT4_AES_256_CBC_KEY_SIZE 32
62#define EXT4_AES_256_CTS_KEY_SIZE 32
63#define EXT4_AES_256_XTS_KEY_SIZE 64
64#define EXT4_MAX_KEY_SIZE 64
65
66#define EXT4_KEY_DESC_PREFIX "ext4:"
67#define EXT4_KEY_DESC_PREFIX_SIZE 5
68
69struct ext4_encryption_key {
70	uint32_t mode;
71	char raw[EXT4_MAX_KEY_SIZE];
72	uint32_t size;
73};
74
75#define EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL             0x00000001
76#define EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL     0x00000002
77
78struct ext4_crypto_ctx {
79	struct crypto_tfm *tfm;         /* Crypto API context */
80	struct page *bounce_page;       /* Ciphertext page on write path */
81	struct page *control_page;      /* Original page on write path */
82	struct bio *bio;                /* The bio for this context */
83	struct work_struct work;        /* Work queue for read complete path */
84	struct list_head free_list;     /* Free list */
85	int flags;                      /* Flags */
86	int mode;                       /* Encryption mode for tfm */
87};
88
89struct ext4_completion_result {
90	struct completion completion;
91	int res;
92};
93
94#define DECLARE_EXT4_COMPLETION_RESULT(ecr) \
95	struct ext4_completion_result ecr = { \
96		COMPLETION_INITIALIZER((ecr).completion), 0 }
97
98static inline int ext4_encryption_key_size(int mode)
99{
100	switch (mode) {
101	case EXT4_ENCRYPTION_MODE_AES_256_XTS:
102		return EXT4_AES_256_XTS_KEY_SIZE;
103	case EXT4_ENCRYPTION_MODE_AES_256_GCM:
104		return EXT4_AES_256_GCM_KEY_SIZE;
105	case EXT4_ENCRYPTION_MODE_AES_256_CBC:
106		return EXT4_AES_256_CBC_KEY_SIZE;
107	case EXT4_ENCRYPTION_MODE_AES_256_CTS:
108		return EXT4_AES_256_CTS_KEY_SIZE;
109	default:
110		BUG();
111	}
112	return 0;
113}
114
115#define EXT4_FNAME_NUM_SCATTER_ENTRIES	4
116#define EXT4_CRYPTO_BLOCK_SIZE		16
117#define EXT4_FNAME_CRYPTO_DIGEST_SIZE	32
118
119struct ext4_str {
120	unsigned char *name;
121	u32 len;
122};
123
124struct ext4_fname_crypto_ctx {
125	u32 lim;
126	char tmp_buf[EXT4_CRYPTO_BLOCK_SIZE];
127	struct crypto_ablkcipher *ctfm;
128	struct crypto_hash *htfm;
129	struct page *workpage;
130	struct ext4_encryption_key key;
131	unsigned flags : 8;
132	unsigned has_valid_key : 1;
133	unsigned ctfm_key_is_ready : 1;
134};
135
136/**
137 * For encrypted symlinks, the ciphertext length is stored at the beginning
138 * of the string in little-endian format.
139 */
140struct ext4_encrypted_symlink_data {
141	__le16 len;
142	char encrypted_path[1];
143} __attribute__((__packed__));
144
145/**
146 * This function is used to calculate the disk space required to
147 * store a filename of length l in encrypted symlink format.
148 */
149static inline u32 encrypted_symlink_data_len(u32 l)
150{
151	if (l < EXT4_CRYPTO_BLOCK_SIZE)
152		l = EXT4_CRYPTO_BLOCK_SIZE;
153	return (l + sizeof(struct ext4_encrypted_symlink_data) - 1);
154}
155
156#endif	/* _EXT4_CRYPTO_H */
157