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 | ||
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> | |
16 | ||
17 | #include "ext4.h" | |
18 | #include "xattr.h" | |
19 | ||
20 | static void derive_crypt_complete(struct crypto_async_request *req, int rc) | |
21 | { | |
22 | struct ext4_completion_result *ecr = req->data; | |
23 | ||
24 | if (rc == -EINPROGRESS) | |
25 | return; | |
26 | ||
27 | ecr->res = rc; | |
28 | complete(&ecr->completion); | |
29 | } | |
30 | ||
31 | /** | |
32 | * ext4_derive_key_aes() - Derive a key using AES-128-ECB | |
33 | * @deriving_key: Encryption key used for derivatio. | |
34 | * @source_key: Source key to which to apply derivation. | |
35 | * @derived_key: Derived key. | |
36 | * | |
37 | * Return: Zero on success; non-zero otherwise. | |
38 | */ | |
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]) | |
42 | { | |
43 | int res = 0; | |
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, | |
48 | 0); | |
49 | ||
50 | if (IS_ERR(tfm)) { | |
51 | res = PTR_ERR(tfm); | |
52 | tfm = NULL; | |
53 | goto out; | |
54 | } | |
55 | crypto_ablkcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY); | |
56 | req = ablkcipher_request_alloc(tfm, GFP_NOFS); | |
57 | if (!req) { | |
58 | res = -ENOMEM; | |
59 | goto out; | |
60 | } | |
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); | |
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); | |
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 | BUG_ON(req->base.data != &ecr); | |
75 | wait_for_completion(&ecr.completion); | |
76 | res = ecr.res; | |
77 | } | |
78 | ||
79 | out: | |
80 | if (req) | |
81 | ablkcipher_request_free(req); | |
82 | if (tfm) | |
83 | crypto_free_ablkcipher(tfm); | |
84 | return res; | |
85 | } | |
86 | ||
c936e1ec | 87 | void ext4_free_crypt_info(struct ext4_crypt_info *ci) |
b7236e21 | 88 | { |
b7236e21 TT |
89 | if (!ci) |
90 | return; | |
91 | ||
92 | if (ci->ci_keyring_key) | |
93 | key_put(ci->ci_keyring_key); | |
94 | crypto_free_ablkcipher(ci->ci_ctfm); | |
8ee03714 | 95 | kmem_cache_free(ext4_crypt_info_cachep, ci); |
c936e1ec TT |
96 | } |
97 | ||
98 | void ext4_free_encryption_info(struct inode *inode, | |
99 | struct ext4_crypt_info *ci) | |
100 | { | |
101 | struct ext4_inode_info *ei = EXT4_I(inode); | |
102 | struct ext4_crypt_info *prev; | |
103 | ||
104 | if (ci == NULL) | |
105 | ci = ACCESS_ONCE(ei->i_crypt_info); | |
106 | if (ci == NULL) | |
107 | return; | |
108 | prev = cmpxchg(&ei->i_crypt_info, ci, NULL); | |
109 | if (prev != ci) | |
110 | return; | |
111 | ||
112 | ext4_free_crypt_info(ci); | |
b7236e21 TT |
113 | } |
114 | ||
115 | int _ext4_get_encryption_info(struct inode *inode) | |
88bd6ccd MH |
116 | { |
117 | struct ext4_inode_info *ei = EXT4_I(inode); | |
b7236e21 | 118 | struct ext4_crypt_info *crypt_info; |
88bd6ccd MH |
119 | char full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE + |
120 | (EXT4_KEY_DESCRIPTOR_SIZE * 2) + 1]; | |
121 | struct key *keyring_key = NULL; | |
122 | struct ext4_encryption_key *master_key; | |
123 | struct ext4_encryption_context ctx; | |
124 | struct user_key_payload *ukp; | |
6ddb2447 | 125 | struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb); |
c936e1ec TT |
126 | struct crypto_ablkcipher *ctfm; |
127 | const char *cipher_str; | |
128 | char raw_key[EXT4_MAX_KEY_SIZE]; | |
129 | char mode; | |
b7236e21 | 130 | int res; |
88bd6ccd | 131 | |
8ee03714 TT |
132 | if (!ext4_read_workqueue) { |
133 | res = ext4_init_crypto(); | |
134 | if (res) | |
135 | return res; | |
136 | } | |
137 | ||
c936e1ec TT |
138 | retry: |
139 | crypt_info = ACCESS_ONCE(ei->i_crypt_info); | |
140 | if (crypt_info) { | |
141 | if (!crypt_info->ci_keyring_key || | |
142 | key_validate(crypt_info->ci_keyring_key) == 0) | |
b7236e21 | 143 | return 0; |
c936e1ec TT |
144 | ext4_free_encryption_info(inode, crypt_info); |
145 | goto retry; | |
88bd6ccd | 146 | } |
b7236e21 TT |
147 | |
148 | res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION, | |
149 | EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, | |
150 | &ctx, sizeof(ctx)); | |
151 | if (res < 0) { | |
152 | if (!DUMMY_ENCRYPTION_ENABLED(sbi)) | |
153 | return res; | |
154 | ctx.contents_encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS; | |
155 | ctx.filenames_encryption_mode = | |
156 | EXT4_ENCRYPTION_MODE_AES_256_CTS; | |
157 | ctx.flags = 0; | |
158 | } else if (res != sizeof(ctx)) | |
159 | return -EINVAL; | |
88bd6ccd MH |
160 | res = 0; |
161 | ||
8ee03714 | 162 | crypt_info = kmem_cache_alloc(ext4_crypt_info_cachep, GFP_KERNEL); |
b7236e21 TT |
163 | if (!crypt_info) |
164 | return -ENOMEM; | |
165 | ||
b7236e21 TT |
166 | crypt_info->ci_flags = ctx.flags; |
167 | crypt_info->ci_data_mode = ctx.contents_encryption_mode; | |
168 | crypt_info->ci_filename_mode = ctx.filenames_encryption_mode; | |
169 | crypt_info->ci_ctfm = NULL; | |
c936e1ec | 170 | crypt_info->ci_keyring_key = NULL; |
b7236e21 TT |
171 | memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor, |
172 | sizeof(crypt_info->ci_master_key)); | |
6ddb2447 | 173 | if (S_ISREG(inode->i_mode)) |
c936e1ec | 174 | mode = crypt_info->ci_data_mode; |
6ddb2447 | 175 | else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) |
c936e1ec | 176 | mode = crypt_info->ci_filename_mode; |
1aaa6e8b | 177 | else |
6ddb2447 | 178 | BUG(); |
c936e1ec TT |
179 | switch (mode) { |
180 | case EXT4_ENCRYPTION_MODE_AES_256_XTS: | |
181 | cipher_str = "xts(aes)"; | |
182 | break; | |
183 | case EXT4_ENCRYPTION_MODE_AES_256_CTS: | |
184 | cipher_str = "cts(cbc(aes))"; | |
185 | break; | |
186 | default: | |
187 | printk_once(KERN_WARNING | |
188 | "ext4: unsupported key mode %d (ino %u)\n", | |
189 | mode, (unsigned) inode->i_ino); | |
190 | res = -ENOKEY; | |
6ddb2447 TT |
191 | goto out; |
192 | } | |
c936e1ec TT |
193 | if (DUMMY_ENCRYPTION_ENABLED(sbi)) { |
194 | memset(raw_key, 0x42, EXT4_AES_256_XTS_KEY_SIZE); | |
195 | goto got_key; | |
196 | } | |
88bd6ccd MH |
197 | memcpy(full_key_descriptor, EXT4_KEY_DESC_PREFIX, |
198 | EXT4_KEY_DESC_PREFIX_SIZE); | |
199 | sprintf(full_key_descriptor + EXT4_KEY_DESC_PREFIX_SIZE, | |
200 | "%*phN", EXT4_KEY_DESCRIPTOR_SIZE, | |
201 | ctx.master_key_descriptor); | |
202 | full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE + | |
203 | (2 * EXT4_KEY_DESCRIPTOR_SIZE)] = '\0'; | |
204 | keyring_key = request_key(&key_type_logon, full_key_descriptor, NULL); | |
205 | if (IS_ERR(keyring_key)) { | |
206 | res = PTR_ERR(keyring_key); | |
207 | keyring_key = NULL; | |
208 | goto out; | |
209 | } | |
c936e1ec | 210 | crypt_info->ci_keyring_key = keyring_key; |
88bd6ccd MH |
211 | BUG_ON(keyring_key->type != &key_type_logon); |
212 | ukp = ((struct user_key_payload *)keyring_key->payload.data); | |
213 | if (ukp->datalen != sizeof(struct ext4_encryption_key)) { | |
214 | res = -EINVAL; | |
215 | goto out; | |
216 | } | |
217 | master_key = (struct ext4_encryption_key *)ukp->data; | |
88bd6ccd MH |
218 | BUILD_BUG_ON(EXT4_AES_128_ECB_KEY_SIZE != |
219 | EXT4_KEY_DERIVATION_NONCE_SIZE); | |
220 | BUG_ON(master_key->size != EXT4_AES_256_XTS_KEY_SIZE); | |
e2881b1b | 221 | res = ext4_derive_key_aes(ctx.nonce, master_key->raw, |
c936e1ec TT |
222 | raw_key); |
223 | got_key: | |
224 | ctfm = crypto_alloc_ablkcipher(cipher_str, 0, 0); | |
225 | if (!ctfm || IS_ERR(ctfm)) { | |
226 | res = ctfm ? PTR_ERR(ctfm) : -ENOMEM; | |
227 | printk(KERN_DEBUG | |
228 | "%s: error %d (inode %u) allocating crypto tfm\n", | |
229 | __func__, res, (unsigned) inode->i_ino); | |
230 | goto out; | |
231 | } | |
232 | crypt_info->ci_ctfm = ctfm; | |
233 | crypto_ablkcipher_clear_flags(ctfm, ~0); | |
234 | crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctfm), | |
235 | CRYPTO_TFM_REQ_WEAK_KEY); | |
236 | res = crypto_ablkcipher_setkey(ctfm, raw_key, | |
237 | ext4_encryption_key_size(mode)); | |
238 | if (res) | |
239 | goto out; | |
240 | memzero_explicit(raw_key, sizeof(raw_key)); | |
241 | if (cmpxchg(&ei->i_crypt_info, NULL, crypt_info) != NULL) { | |
242 | ext4_free_crypt_info(crypt_info); | |
243 | goto retry; | |
b7236e21 | 244 | } |
c936e1ec TT |
245 | return 0; |
246 | ||
247 | out: | |
248 | if (res == -ENOKEY) | |
249 | res = 0; | |
250 | ext4_free_crypt_info(crypt_info); | |
251 | memzero_explicit(raw_key, sizeof(raw_key)); | |
88bd6ccd MH |
252 | return res; |
253 | } | |
254 | ||
255 | int ext4_has_encryption_key(struct inode *inode) | |
256 | { | |
257 | struct ext4_inode_info *ei = EXT4_I(inode); | |
88bd6ccd | 258 | |
b7236e21 | 259 | return (ei->i_crypt_info != NULL); |
88bd6ccd | 260 | } |