crypto_key.c
4.73 KB
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
160
161
162
163
164
165
166
/*
* linux/fs/ext4/crypto_key.c
*
* Copyright (C) 2015, Google, Inc.
*
* This contains encryption key functions for ext4
*
* Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
*/
#include <keys/encrypted-type.h>
#include <keys/user-type.h>
#include <linux/random.h>
#include <linux/scatterlist.h>
#include <uapi/linux/keyctl.h>
#include "ext4.h"
#include "xattr.h"
static void derive_crypt_complete(struct crypto_async_request *req, int rc)
{
struct ext4_completion_result *ecr = req->data;
if (rc == -EINPROGRESS)
return;
ecr->res = rc;
complete(&ecr->completion);
}
/**
* ext4_derive_key_aes() - Derive a key using AES-128-ECB
* @deriving_key: Encryption key used for derivatio.
* @source_key: Source key to which to apply derivation.
* @derived_key: Derived key.
*
* Return: Zero on success; non-zero otherwise.
*/
static int ext4_derive_key_aes(char deriving_key[EXT4_AES_128_ECB_KEY_SIZE],
char source_key[EXT4_AES_256_XTS_KEY_SIZE],
char derived_key[EXT4_AES_256_XTS_KEY_SIZE])
{
int res = 0;
struct ablkcipher_request *req = NULL;
DECLARE_EXT4_COMPLETION_RESULT(ecr);
struct scatterlist src_sg, dst_sg;
struct crypto_ablkcipher *tfm = crypto_alloc_ablkcipher("ecb(aes)", 0,
0);
if (IS_ERR(tfm)) {
res = PTR_ERR(tfm);
tfm = NULL;
goto out;
}
crypto_ablkcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
req = ablkcipher_request_alloc(tfm, GFP_NOFS);
if (!req) {
res = -ENOMEM;
goto out;
}
ablkcipher_request_set_callback(req,
CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
derive_crypt_complete, &ecr);
res = crypto_ablkcipher_setkey(tfm, deriving_key,
EXT4_AES_128_ECB_KEY_SIZE);
if (res < 0)
goto out;
sg_init_one(&src_sg, source_key, EXT4_AES_256_XTS_KEY_SIZE);
sg_init_one(&dst_sg, derived_key, EXT4_AES_256_XTS_KEY_SIZE);
ablkcipher_request_set_crypt(req, &src_sg, &dst_sg,
EXT4_AES_256_XTS_KEY_SIZE, NULL);
res = crypto_ablkcipher_encrypt(req);
if (res == -EINPROGRESS || res == -EBUSY) {
BUG_ON(req->base.data != &ecr);
wait_for_completion(&ecr.completion);
res = ecr.res;
}
out:
if (req)
ablkcipher_request_free(req);
if (tfm)
crypto_free_ablkcipher(tfm);
return res;
}
/**
* ext4_generate_encryption_key() - generates an encryption key
* @inode: The inode to generate the encryption key for.
*/
int ext4_generate_encryption_key(struct inode *inode)
{
struct ext4_inode_info *ei = EXT4_I(inode);
struct ext4_encryption_key *crypt_key = &ei->i_encryption_key;
char full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE +
(EXT4_KEY_DESCRIPTOR_SIZE * 2) + 1];
struct key *keyring_key = NULL;
struct ext4_encryption_key *master_key;
struct ext4_encryption_context ctx;
struct user_key_payload *ukp;
struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
&ctx, sizeof(ctx));
if (res != sizeof(ctx)) {
if (res > 0)
res = -EINVAL;
goto out;
}
res = 0;
ei->i_crypt_policy_flags = ctx.flags;
if (S_ISREG(inode->i_mode))
crypt_key->mode = ctx.contents_encryption_mode;
else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
crypt_key->mode = ctx.filenames_encryption_mode;
else {
printk(KERN_ERR "ext4 crypto: Unsupported inode type.\n");
BUG();
}
crypt_key->size = ext4_encryption_key_size(crypt_key->mode);
BUG_ON(!crypt_key->size);
if (DUMMY_ENCRYPTION_ENABLED(sbi)) {
memset(crypt_key->raw, 0x42, EXT4_AES_256_XTS_KEY_SIZE);
goto out;
}
memcpy(full_key_descriptor, EXT4_KEY_DESC_PREFIX,
EXT4_KEY_DESC_PREFIX_SIZE);
sprintf(full_key_descriptor + EXT4_KEY_DESC_PREFIX_SIZE,
"%*phN", EXT4_KEY_DESCRIPTOR_SIZE,
ctx.master_key_descriptor);
full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE +
(2 * EXT4_KEY_DESCRIPTOR_SIZE)] = '\0';
keyring_key = request_key(&key_type_logon, full_key_descriptor, NULL);
if (IS_ERR(keyring_key)) {
res = PTR_ERR(keyring_key);
keyring_key = NULL;
goto out;
}
BUG_ON(keyring_key->type != &key_type_logon);
ukp = ((struct user_key_payload *)keyring_key->payload.data);
if (ukp->datalen != sizeof(struct ext4_encryption_key)) {
res = -EINVAL;
goto out;
}
master_key = (struct ext4_encryption_key *)ukp->data;
BUILD_BUG_ON(EXT4_AES_128_ECB_KEY_SIZE !=
EXT4_KEY_DERIVATION_NONCE_SIZE);
BUG_ON(master_key->size != EXT4_AES_256_XTS_KEY_SIZE);
res = ext4_derive_key_aes(ctx.nonce, master_key->raw, crypt_key->raw);
out:
if (keyring_key)
key_put(keyring_key);
if (res < 0)
crypt_key->mode = EXT4_ENCRYPTION_MODE_INVALID;
return res;
}
int ext4_has_encryption_key(struct inode *inode)
{
struct ext4_inode_info *ei = EXT4_I(inode);
struct ext4_encryption_key *crypt_key = &ei->i_encryption_key;
return (crypt_key->mode != EXT4_ENCRYPTION_MODE_INVALID);
}