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 <keys/encrypted-type.h>
12 #include <keys/user-type.h>
13 #include <linux/random.h>
14 #include <linux/scatterlist.h>
15 #include <uapi/linux/keyctl.h>
20 static void derive_crypt_complete(struct crypto_async_request
*req
, int rc
)
22 struct ext4_completion_result
*ecr
= req
->data
;
24 if (rc
== -EINPROGRESS
)
28 complete(&ecr
->completion
);
32 * ext4_derive_key_aes() - Derive a key using AES-128-ECB
33 * @deriving_key: Encryption key used for derivation.
34 * @source_key: Source key to which to apply derivation.
35 * @derived_key: Derived key.
37 * Return: Zero on success; non-zero otherwise.
39 static int ext4_derive_key_aes(char deriving_key
[EXT4_AES_128_ECB_KEY_SIZE
],
40 char source_key
[EXT4_AES_256_XTS_KEY_SIZE
],
41 char derived_key
[EXT4_AES_256_XTS_KEY_SIZE
])
44 struct ablkcipher_request
*req
= NULL
;
45 DECLARE_EXT4_COMPLETION_RESULT(ecr
);
46 struct scatterlist src_sg
, dst_sg
;
47 struct crypto_ablkcipher
*tfm
= crypto_alloc_ablkcipher("ecb(aes)", 0,
55 crypto_ablkcipher_set_flags(tfm
, CRYPTO_TFM_REQ_WEAK_KEY
);
56 req
= ablkcipher_request_alloc(tfm
, GFP_NOFS
);
61 ablkcipher_request_set_callback(req
,
62 CRYPTO_TFM_REQ_MAY_BACKLOG
| CRYPTO_TFM_REQ_MAY_SLEEP
,
63 derive_crypt_complete
, &ecr
);
64 res
= crypto_ablkcipher_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 ablkcipher_request_set_crypt(req
, &src_sg
, &dst_sg
,
71 EXT4_AES_256_XTS_KEY_SIZE
, NULL
);
72 res
= crypto_ablkcipher_encrypt(req
);
73 if (res
== -EINPROGRESS
|| res
== -EBUSY
) {
74 wait_for_completion(&ecr
.completion
);
80 ablkcipher_request_free(req
);
82 crypto_free_ablkcipher(tfm
);
86 void ext4_free_crypt_info(struct ext4_crypt_info
*ci
)
91 crypto_free_ablkcipher(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_ablkcipher
*ctfm
;
124 const char *cipher_str
;
125 char raw_key
[EXT4_MAX_KEY_SIZE
];
129 if (ei
->i_crypt_info
)
132 res
= ext4_init_crypto();
136 res
= ext4_xattr_get(inode
, EXT4_XATTR_INDEX_ENCRYPTION
,
137 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT
,
140 if (!DUMMY_ENCRYPTION_ENABLED(sbi
))
142 ctx
.contents_encryption_mode
= EXT4_ENCRYPTION_MODE_AES_256_XTS
;
143 ctx
.filenames_encryption_mode
=
144 EXT4_ENCRYPTION_MODE_AES_256_CTS
;
146 } else if (res
!= sizeof(ctx
))
150 crypt_info
= kmem_cache_alloc(ext4_crypt_info_cachep
, GFP_KERNEL
);
154 crypt_info
->ci_flags
= ctx
.flags
;
155 crypt_info
->ci_data_mode
= ctx
.contents_encryption_mode
;
156 crypt_info
->ci_filename_mode
= ctx
.filenames_encryption_mode
;
157 crypt_info
->ci_ctfm
= NULL
;
158 memcpy(crypt_info
->ci_master_key
, ctx
.master_key_descriptor
,
159 sizeof(crypt_info
->ci_master_key
));
160 if (S_ISREG(inode
->i_mode
))
161 mode
= crypt_info
->ci_data_mode
;
162 else if (S_ISDIR(inode
->i_mode
) || S_ISLNK(inode
->i_mode
))
163 mode
= crypt_info
->ci_filename_mode
;
167 case EXT4_ENCRYPTION_MODE_AES_256_XTS
:
168 cipher_str
= "xts(aes)";
170 case EXT4_ENCRYPTION_MODE_AES_256_CTS
:
171 cipher_str
= "cts(cbc(aes))";
174 printk_once(KERN_WARNING
175 "ext4: unsupported key mode %d (ino %u)\n",
176 mode
, (unsigned) inode
->i_ino
);
180 if (DUMMY_ENCRYPTION_ENABLED(sbi
)) {
181 memset(raw_key
, 0x42, EXT4_AES_256_XTS_KEY_SIZE
);
184 memcpy(full_key_descriptor
, EXT4_KEY_DESC_PREFIX
,
185 EXT4_KEY_DESC_PREFIX_SIZE
);
186 sprintf(full_key_descriptor
+ EXT4_KEY_DESC_PREFIX_SIZE
,
187 "%*phN", EXT4_KEY_DESCRIPTOR_SIZE
,
188 ctx
.master_key_descriptor
);
189 full_key_descriptor
[EXT4_KEY_DESC_PREFIX_SIZE
+
190 (2 * EXT4_KEY_DESCRIPTOR_SIZE
)] = '\0';
191 keyring_key
= request_key(&key_type_logon
, full_key_descriptor
, NULL
);
192 if (IS_ERR(keyring_key
)) {
193 res
= PTR_ERR(keyring_key
);
197 if (keyring_key
->type
!= &key_type_logon
) {
198 printk_once(KERN_WARNING
199 "ext4: key type must be logon\n");
203 down_read(&keyring_key
->sem
);
204 ukp
= user_key_payload(keyring_key
);
206 /* key was revoked before we acquired its semaphore */
208 up_read(&keyring_key
->sem
);
211 if (ukp
->datalen
!= sizeof(struct ext4_encryption_key
)) {
213 up_read(&keyring_key
->sem
);
216 master_key
= (struct ext4_encryption_key
*)ukp
->data
;
217 BUILD_BUG_ON(EXT4_AES_128_ECB_KEY_SIZE
!=
218 EXT4_KEY_DERIVATION_NONCE_SIZE
);
219 if (master_key
->size
!= EXT4_AES_256_XTS_KEY_SIZE
) {
220 printk_once(KERN_WARNING
221 "ext4: key size incorrect: %d\n",
224 up_read(&keyring_key
->sem
);
227 res
= ext4_derive_key_aes(ctx
.nonce
, master_key
->raw
,
229 up_read(&keyring_key
->sem
);
233 ctfm
= crypto_alloc_ablkcipher(cipher_str
, 0, 0);
234 if (!ctfm
|| IS_ERR(ctfm
)) {
235 res
= ctfm
? PTR_ERR(ctfm
) : -ENOMEM
;
237 "%s: error %d (inode %u) allocating crypto tfm\n",
238 __func__
, res
, (unsigned) inode
->i_ino
);
241 crypt_info
->ci_ctfm
= ctfm
;
242 crypto_ablkcipher_clear_flags(ctfm
, ~0);
243 crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctfm
),
244 CRYPTO_TFM_REQ_WEAK_KEY
);
245 res
= crypto_ablkcipher_setkey(ctfm
, raw_key
,
246 ext4_encryption_key_size(mode
));
250 if (cmpxchg(&ei
->i_crypt_info
, NULL
, crypt_info
) == NULL
)
255 key_put(keyring_key
);
256 ext4_free_crypt_info(crypt_info
);
257 memzero_explicit(raw_key
, sizeof(raw_key
));
261 int ext4_has_encryption_key(struct inode
*inode
)
263 struct ext4_inode_info
*ei
= EXT4_I(inode
);
265 return (ei
->i_crypt_info
!= NULL
);