Commit | Line | Data |
---|---|---|
88bd6ccd MH |
1 | /* |
2 | * linux/fs/ext4/crypto_key.c | |
3 | * | |
4 | * Copyright (C) 2015, Google, Inc. | |
5 | * | |
6 | * This contains encryption key functions for ext4 | |
7 | * | |
8 | * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015. | |
9 | */ | |
10 | ||
3f32a5be | 11 | #include <crypto/skcipher.h> |
88bd6ccd MH |
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> | |
17 | ||
18 | #include "ext4.h" | |
19 | #include "xattr.h" | |
20 | ||
21 | static void derive_crypt_complete(struct crypto_async_request *req, int rc) | |
22 | { | |
23 | struct ext4_completion_result *ecr = req->data; | |
24 | ||
25 | if (rc == -EINPROGRESS) | |
26 | return; | |
27 | ||
28 | ecr->res = rc; | |
29 | complete(&ecr->completion); | |
30 | } | |
31 | ||
32 | /** | |
33 | * ext4_derive_key_aes() - Derive a key using AES-128-ECB | |
bb9a4e7e | 34 | * @deriving_key: Encryption key used for derivation. |
88bd6ccd MH |
35 | * @source_key: Source key to which to apply derivation. |
36 | * @derived_key: Derived key. | |
37 | * | |
38 | * Return: Zero on success; non-zero otherwise. | |
39 | */ | |
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]) | |
43 | { | |
44 | int res = 0; | |
3f32a5be | 45 | struct skcipher_request *req = NULL; |
88bd6ccd MH |
46 | DECLARE_EXT4_COMPLETION_RESULT(ecr); |
47 | struct scatterlist src_sg, dst_sg; | |
3f32a5be | 48 | struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0); |
88bd6ccd MH |
49 | |
50 | if (IS_ERR(tfm)) { | |
51 | res = PTR_ERR(tfm); | |
52 | tfm = NULL; | |
53 | goto out; | |
54 | } | |
3f32a5be HX |
55 | crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY); |
56 | req = skcipher_request_alloc(tfm, GFP_NOFS); | |
88bd6ccd MH |
57 | if (!req) { |
58 | res = -ENOMEM; | |
59 | goto out; | |
60 | } | |
3f32a5be | 61 | skcipher_request_set_callback(req, |
88bd6ccd MH |
62 | CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP, |
63 | derive_crypt_complete, &ecr); | |
3f32a5be HX |
64 | res = crypto_skcipher_setkey(tfm, deriving_key, |
65 | EXT4_AES_128_ECB_KEY_SIZE); | |
88bd6ccd MH |
66 | if (res < 0) |
67 | goto out; | |
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); | |
3f32a5be HX |
70 | skcipher_request_set_crypt(req, &src_sg, &dst_sg, |
71 | EXT4_AES_256_XTS_KEY_SIZE, NULL); | |
72 | res = crypto_skcipher_encrypt(req); | |
88bd6ccd | 73 | if (res == -EINPROGRESS || res == -EBUSY) { |
88bd6ccd MH |
74 | wait_for_completion(&ecr.completion); |
75 | res = ecr.res; | |
76 | } | |
77 | ||
78 | out: | |
3f32a5be HX |
79 | skcipher_request_free(req); |
80 | crypto_free_skcipher(tfm); | |
88bd6ccd MH |
81 | return res; |
82 | } | |
83 | ||
c936e1ec | 84 | void ext4_free_crypt_info(struct ext4_crypt_info *ci) |
b7236e21 | 85 | { |
b7236e21 TT |
86 | if (!ci) |
87 | return; | |
88 | ||
89 | if (ci->ci_keyring_key) | |
90 | key_put(ci->ci_keyring_key); | |
3f32a5be | 91 | crypto_free_skcipher(ci->ci_ctfm); |
8ee03714 | 92 | kmem_cache_free(ext4_crypt_info_cachep, ci); |
c936e1ec TT |
93 | } |
94 | ||
95 | void ext4_free_encryption_info(struct inode *inode, | |
96 | struct ext4_crypt_info *ci) | |
97 | { | |
98 | struct ext4_inode_info *ei = EXT4_I(inode); | |
99 | struct ext4_crypt_info *prev; | |
100 | ||
101 | if (ci == NULL) | |
102 | ci = ACCESS_ONCE(ei->i_crypt_info); | |
103 | if (ci == NULL) | |
104 | return; | |
105 | prev = cmpxchg(&ei->i_crypt_info, ci, NULL); | |
106 | if (prev != ci) | |
107 | return; | |
108 | ||
109 | ext4_free_crypt_info(ci); | |
b7236e21 TT |
110 | } |
111 | ||
112 | int _ext4_get_encryption_info(struct inode *inode) | |
88bd6ccd MH |
113 | { |
114 | struct ext4_inode_info *ei = EXT4_I(inode); | |
b7236e21 | 115 | struct ext4_crypt_info *crypt_info; |
88bd6ccd MH |
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; | |
146aa8b1 | 121 | const struct user_key_payload *ukp; |
6ddb2447 | 122 | struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb); |
3f32a5be | 123 | struct crypto_skcipher *ctfm; |
c936e1ec TT |
124 | const char *cipher_str; |
125 | char raw_key[EXT4_MAX_KEY_SIZE]; | |
126 | char mode; | |
b7236e21 | 127 | int res; |
88bd6ccd | 128 | |
8ee03714 TT |
129 | if (!ext4_read_workqueue) { |
130 | res = ext4_init_crypto(); | |
131 | if (res) | |
132 | return res; | |
133 | } | |
134 | ||
c936e1ec TT |
135 | retry: |
136 | crypt_info = ACCESS_ONCE(ei->i_crypt_info); | |
137 | if (crypt_info) { | |
138 | if (!crypt_info->ci_keyring_key || | |
139 | key_validate(crypt_info->ci_keyring_key) == 0) | |
b7236e21 | 140 | return 0; |
c936e1ec TT |
141 | ext4_free_encryption_info(inode, crypt_info); |
142 | goto retry; | |
88bd6ccd | 143 | } |
b7236e21 TT |
144 | |
145 | res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION, | |
146 | EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, | |
147 | &ctx, sizeof(ctx)); | |
148 | if (res < 0) { | |
149 | if (!DUMMY_ENCRYPTION_ENABLED(sbi)) | |
150 | return res; | |
151 | ctx.contents_encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS; | |
152 | ctx.filenames_encryption_mode = | |
153 | EXT4_ENCRYPTION_MODE_AES_256_CTS; | |
154 | ctx.flags = 0; | |
155 | } else if (res != sizeof(ctx)) | |
156 | return -EINVAL; | |
88bd6ccd MH |
157 | res = 0; |
158 | ||
8ee03714 | 159 | crypt_info = kmem_cache_alloc(ext4_crypt_info_cachep, GFP_KERNEL); |
b7236e21 TT |
160 | if (!crypt_info) |
161 | return -ENOMEM; | |
162 | ||
b7236e21 TT |
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; | |
c936e1ec | 167 | crypt_info->ci_keyring_key = NULL; |
b7236e21 TT |
168 | memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor, |
169 | sizeof(crypt_info->ci_master_key)); | |
6ddb2447 | 170 | if (S_ISREG(inode->i_mode)) |
c936e1ec | 171 | mode = crypt_info->ci_data_mode; |
6ddb2447 | 172 | else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) |
c936e1ec | 173 | mode = crypt_info->ci_filename_mode; |
1aaa6e8b | 174 | else |
6ddb2447 | 175 | BUG(); |
c936e1ec TT |
176 | switch (mode) { |
177 | case EXT4_ENCRYPTION_MODE_AES_256_XTS: | |
178 | cipher_str = "xts(aes)"; | |
179 | break; | |
180 | case EXT4_ENCRYPTION_MODE_AES_256_CTS: | |
181 | cipher_str = "cts(cbc(aes))"; | |
182 | break; | |
183 | default: | |
184 | printk_once(KERN_WARNING | |
185 | "ext4: unsupported key mode %d (ino %u)\n", | |
186 | mode, (unsigned) inode->i_ino); | |
187 | res = -ENOKEY; | |
6ddb2447 TT |
188 | goto out; |
189 | } | |
c936e1ec TT |
190 | if (DUMMY_ENCRYPTION_ENABLED(sbi)) { |
191 | memset(raw_key, 0x42, EXT4_AES_256_XTS_KEY_SIZE); | |
192 | goto got_key; | |
193 | } | |
88bd6ccd MH |
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); | |
204 | keyring_key = NULL; | |
205 | goto out; | |
206 | } | |
c936e1ec | 207 | crypt_info->ci_keyring_key = keyring_key; |
687c3c36 TT |
208 | if (keyring_key->type != &key_type_logon) { |
209 | printk_once(KERN_WARNING | |
210 | "ext4: key type must be logon\n"); | |
211 | res = -ENOKEY; | |
212 | goto out; | |
213 | } | |
db7730e3 | 214 | down_read(&keyring_key->sem); |
146aa8b1 | 215 | ukp = user_key_payload(keyring_key); |
88bd6ccd MH |
216 | if (ukp->datalen != sizeof(struct ext4_encryption_key)) { |
217 | res = -EINVAL; | |
db7730e3 | 218 | up_read(&keyring_key->sem); |
88bd6ccd MH |
219 | goto out; |
220 | } | |
221 | master_key = (struct ext4_encryption_key *)ukp->data; | |
88bd6ccd MH |
222 | BUILD_BUG_ON(EXT4_AES_128_ECB_KEY_SIZE != |
223 | EXT4_KEY_DERIVATION_NONCE_SIZE); | |
687c3c36 TT |
224 | if (master_key->size != EXT4_AES_256_XTS_KEY_SIZE) { |
225 | printk_once(KERN_WARNING | |
226 | "ext4: key size incorrect: %d\n", | |
227 | master_key->size); | |
228 | res = -ENOKEY; | |
db7730e3 | 229 | up_read(&keyring_key->sem); |
687c3c36 TT |
230 | goto out; |
231 | } | |
e2881b1b | 232 | res = ext4_derive_key_aes(ctx.nonce, master_key->raw, |
c936e1ec | 233 | raw_key); |
db7730e3 | 234 | up_read(&keyring_key->sem); |
d76d99b2 LN |
235 | if (res) |
236 | goto out; | |
c936e1ec | 237 | got_key: |
3f32a5be | 238 | ctfm = crypto_alloc_skcipher(cipher_str, 0, 0); |
c936e1ec TT |
239 | if (!ctfm || IS_ERR(ctfm)) { |
240 | res = ctfm ? PTR_ERR(ctfm) : -ENOMEM; | |
241 | printk(KERN_DEBUG | |
242 | "%s: error %d (inode %u) allocating crypto tfm\n", | |
243 | __func__, res, (unsigned) inode->i_ino); | |
244 | goto out; | |
245 | } | |
246 | crypt_info->ci_ctfm = ctfm; | |
3f32a5be HX |
247 | crypto_skcipher_clear_flags(ctfm, ~0); |
248 | crypto_tfm_set_flags(crypto_skcipher_tfm(ctfm), | |
c936e1ec | 249 | CRYPTO_TFM_REQ_WEAK_KEY); |
3f32a5be HX |
250 | res = crypto_skcipher_setkey(ctfm, raw_key, |
251 | ext4_encryption_key_size(mode)); | |
c936e1ec TT |
252 | if (res) |
253 | goto out; | |
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); | |
257 | goto retry; | |
b7236e21 | 258 | } |
c936e1ec TT |
259 | return 0; |
260 | ||
261 | out: | |
262 | if (res == -ENOKEY) | |
263 | res = 0; | |
264 | ext4_free_crypt_info(crypt_info); | |
265 | memzero_explicit(raw_key, sizeof(raw_key)); | |
88bd6ccd MH |
266 | return res; |
267 | } | |
268 | ||
269 | int ext4_has_encryption_key(struct inode *inode) | |
270 | { | |
271 | struct ext4_inode_info *ei = EXT4_I(inode); | |
88bd6ccd | 272 | |
b7236e21 | 273 | return (ei->i_crypt_info != NULL); |
88bd6ccd | 274 | } |