2 * linux/fs/ext4/crypto_key.c
4 * Copyright (C) 2015, Google, Inc.
6 * This contains encryption key functions for ext4
8 * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
11 #include <crypto/skcipher.h>
12 #include <keys/encrypted-type.h>
13 #include <keys/user-type.h>
14 #include <linux/random.h>
15 #include <linux/scatterlist.h>
16 #include <uapi/linux/keyctl.h>
21 static void derive_crypt_complete(struct crypto_async_request
*req
, int rc
)
23 struct ext4_completion_result
*ecr
= req
->data
;
25 if (rc
== -EINPROGRESS
)
29 complete(&ecr
->completion
);
33 * ext4_derive_key_aes() - Derive a key using AES-128-ECB
34 * @deriving_key: Encryption key used for derivation.
35 * @source_key: Source key to which to apply derivation.
36 * @derived_key: Derived key.
38 * Return: Zero on success; non-zero otherwise.
40 static int ext4_derive_key_aes(char deriving_key
[EXT4_AES_128_ECB_KEY_SIZE
],
41 char source_key
[EXT4_AES_256_XTS_KEY_SIZE
],
42 char derived_key
[EXT4_AES_256_XTS_KEY_SIZE
])
45 struct skcipher_request
*req
= NULL
;
46 DECLARE_EXT4_COMPLETION_RESULT(ecr
);
47 struct scatterlist src_sg
, dst_sg
;
48 struct crypto_skcipher
*tfm
= crypto_alloc_skcipher("ecb(aes)", 0, 0);
55 crypto_skcipher_set_flags(tfm
, CRYPTO_TFM_REQ_WEAK_KEY
);
56 req
= skcipher_request_alloc(tfm
, GFP_NOFS
);
61 skcipher_request_set_callback(req
,
62 CRYPTO_TFM_REQ_MAY_BACKLOG
| CRYPTO_TFM_REQ_MAY_SLEEP
,
63 derive_crypt_complete
, &ecr
);
64 res
= crypto_skcipher_setkey(tfm
, deriving_key
,
65 EXT4_AES_128_ECB_KEY_SIZE
);
68 sg_init_one(&src_sg
, source_key
, EXT4_AES_256_XTS_KEY_SIZE
);
69 sg_init_one(&dst_sg
, derived_key
, EXT4_AES_256_XTS_KEY_SIZE
);
70 skcipher_request_set_crypt(req
, &src_sg
, &dst_sg
,
71 EXT4_AES_256_XTS_KEY_SIZE
, NULL
);
72 res
= crypto_skcipher_encrypt(req
);
73 if (res
== -EINPROGRESS
|| res
== -EBUSY
) {
74 wait_for_completion(&ecr
.completion
);
79 skcipher_request_free(req
);
80 crypto_free_skcipher(tfm
);
84 void ext4_free_crypt_info(struct ext4_crypt_info
*ci
)
89 if (ci
->ci_keyring_key
)
90 key_put(ci
->ci_keyring_key
);
91 crypto_free_skcipher(ci
->ci_ctfm
);
92 kmem_cache_free(ext4_crypt_info_cachep
, ci
);
95 void ext4_free_encryption_info(struct inode
*inode
,
96 struct ext4_crypt_info
*ci
)
98 struct ext4_inode_info
*ei
= EXT4_I(inode
);
99 struct ext4_crypt_info
*prev
;
102 ci
= ACCESS_ONCE(ei
->i_crypt_info
);
105 prev
= cmpxchg(&ei
->i_crypt_info
, ci
, NULL
);
109 ext4_free_crypt_info(ci
);
112 int _ext4_get_encryption_info(struct inode
*inode
)
114 struct ext4_inode_info
*ei
= EXT4_I(inode
);
115 struct ext4_crypt_info
*crypt_info
;
116 char full_key_descriptor
[EXT4_KEY_DESC_PREFIX_SIZE
+
117 (EXT4_KEY_DESCRIPTOR_SIZE
* 2) + 1];
118 struct key
*keyring_key
= NULL
;
119 struct ext4_encryption_key
*master_key
;
120 struct ext4_encryption_context ctx
;
121 const struct user_key_payload
*ukp
;
122 struct ext4_sb_info
*sbi
= EXT4_SB(inode
->i_sb
);
123 struct crypto_skcipher
*ctfm
;
124 const char *cipher_str
;
125 char raw_key
[EXT4_MAX_KEY_SIZE
];
129 if (!ext4_read_workqueue
) {
130 res
= ext4_init_crypto();
136 crypt_info
= ACCESS_ONCE(ei
->i_crypt_info
);
138 if (!crypt_info
->ci_keyring_key
||
139 key_validate(crypt_info
->ci_keyring_key
) == 0)
141 ext4_free_encryption_info(inode
, crypt_info
);
145 res
= ext4_xattr_get(inode
, EXT4_XATTR_INDEX_ENCRYPTION
,
146 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT
,
149 if (!DUMMY_ENCRYPTION_ENABLED(sbi
))
151 ctx
.contents_encryption_mode
= EXT4_ENCRYPTION_MODE_AES_256_XTS
;
152 ctx
.filenames_encryption_mode
=
153 EXT4_ENCRYPTION_MODE_AES_256_CTS
;
155 } else if (res
!= sizeof(ctx
))
159 crypt_info
= kmem_cache_alloc(ext4_crypt_info_cachep
, GFP_KERNEL
);
163 crypt_info
->ci_flags
= ctx
.flags
;
164 crypt_info
->ci_data_mode
= ctx
.contents_encryption_mode
;
165 crypt_info
->ci_filename_mode
= ctx
.filenames_encryption_mode
;
166 crypt_info
->ci_ctfm
= NULL
;
167 crypt_info
->ci_keyring_key
= NULL
;
168 memcpy(crypt_info
->ci_master_key
, ctx
.master_key_descriptor
,
169 sizeof(crypt_info
->ci_master_key
));
170 if (S_ISREG(inode
->i_mode
))
171 mode
= crypt_info
->ci_data_mode
;
172 else if (S_ISDIR(inode
->i_mode
) || S_ISLNK(inode
->i_mode
))
173 mode
= crypt_info
->ci_filename_mode
;
177 case EXT4_ENCRYPTION_MODE_AES_256_XTS
:
178 cipher_str
= "xts(aes)";
180 case EXT4_ENCRYPTION_MODE_AES_256_CTS
:
181 cipher_str
= "cts(cbc(aes))";
184 printk_once(KERN_WARNING
185 "ext4: unsupported key mode %d (ino %u)\n",
186 mode
, (unsigned) inode
->i_ino
);
190 if (DUMMY_ENCRYPTION_ENABLED(sbi
)) {
191 memset(raw_key
, 0x42, EXT4_AES_256_XTS_KEY_SIZE
);
194 memcpy(full_key_descriptor
, EXT4_KEY_DESC_PREFIX
,
195 EXT4_KEY_DESC_PREFIX_SIZE
);
196 sprintf(full_key_descriptor
+ EXT4_KEY_DESC_PREFIX_SIZE
,
197 "%*phN", EXT4_KEY_DESCRIPTOR_SIZE
,
198 ctx
.master_key_descriptor
);
199 full_key_descriptor
[EXT4_KEY_DESC_PREFIX_SIZE
+
200 (2 * EXT4_KEY_DESCRIPTOR_SIZE
)] = '\0';
201 keyring_key
= request_key(&key_type_logon
, full_key_descriptor
, NULL
);
202 if (IS_ERR(keyring_key
)) {
203 res
= PTR_ERR(keyring_key
);
207 crypt_info
->ci_keyring_key
= keyring_key
;
208 if (keyring_key
->type
!= &key_type_logon
) {
209 printk_once(KERN_WARNING
210 "ext4: key type must be logon\n");
214 down_read(&keyring_key
->sem
);
215 ukp
= user_key_payload(keyring_key
);
216 if (ukp
->datalen
!= sizeof(struct ext4_encryption_key
)) {
218 up_read(&keyring_key
->sem
);
221 master_key
= (struct ext4_encryption_key
*)ukp
->data
;
222 BUILD_BUG_ON(EXT4_AES_128_ECB_KEY_SIZE
!=
223 EXT4_KEY_DERIVATION_NONCE_SIZE
);
224 if (master_key
->size
!= EXT4_AES_256_XTS_KEY_SIZE
) {
225 printk_once(KERN_WARNING
226 "ext4: key size incorrect: %d\n",
229 up_read(&keyring_key
->sem
);
232 res
= ext4_derive_key_aes(ctx
.nonce
, master_key
->raw
,
234 up_read(&keyring_key
->sem
);
238 ctfm
= crypto_alloc_skcipher(cipher_str
, 0, 0);
239 if (!ctfm
|| IS_ERR(ctfm
)) {
240 res
= ctfm
? PTR_ERR(ctfm
) : -ENOMEM
;
242 "%s: error %d (inode %u) allocating crypto tfm\n",
243 __func__
, res
, (unsigned) inode
->i_ino
);
246 crypt_info
->ci_ctfm
= ctfm
;
247 crypto_skcipher_clear_flags(ctfm
, ~0);
248 crypto_tfm_set_flags(crypto_skcipher_tfm(ctfm
),
249 CRYPTO_TFM_REQ_WEAK_KEY
);
250 res
= crypto_skcipher_setkey(ctfm
, raw_key
,
251 ext4_encryption_key_size(mode
));
254 memzero_explicit(raw_key
, sizeof(raw_key
));
255 if (cmpxchg(&ei
->i_crypt_info
, NULL
, crypt_info
) != NULL
) {
256 ext4_free_crypt_info(crypt_info
);
264 ext4_free_crypt_info(crypt_info
);
265 memzero_explicit(raw_key
, sizeof(raw_key
));
269 int ext4_has_encryption_key(struct inode
*inode
)
271 struct ext4_inode_info
*ei
= EXT4_I(inode
);
273 return (ei
->i_crypt_info
!= NULL
);