Merge remote-tracking branch 'regulator/for-next'
[karo-tx-linux.git] / fs / ext4 / crypto_key.c
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 derivation.
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                 wait_for_completion(&ecr.completion);
75                 res = ecr.res;
76         }
77
78 out:
79         if (req)
80                 ablkcipher_request_free(req);
81         if (tfm)
82                 crypto_free_ablkcipher(tfm);
83         return res;
84 }
85
86 void ext4_free_crypt_info(struct ext4_crypt_info *ci)
87 {
88         if (!ci)
89                 return;
90
91         if (ci->ci_keyring_key)
92                 key_put(ci->ci_keyring_key);
93         crypto_free_ablkcipher(ci->ci_ctfm);
94         kmem_cache_free(ext4_crypt_info_cachep, ci);
95 }
96
97 void ext4_free_encryption_info(struct inode *inode,
98                                struct ext4_crypt_info *ci)
99 {
100         struct ext4_inode_info *ei = EXT4_I(inode);
101         struct ext4_crypt_info *prev;
102
103         if (ci == NULL)
104                 ci = ACCESS_ONCE(ei->i_crypt_info);
105         if (ci == NULL)
106                 return;
107         prev = cmpxchg(&ei->i_crypt_info, ci, NULL);
108         if (prev != ci)
109                 return;
110
111         ext4_free_crypt_info(ci);
112 }
113
114 int _ext4_get_encryption_info(struct inode *inode)
115 {
116         struct ext4_inode_info *ei = EXT4_I(inode);
117         struct ext4_crypt_info *crypt_info;
118         char full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE +
119                                  (EXT4_KEY_DESCRIPTOR_SIZE * 2) + 1];
120         struct key *keyring_key = NULL;
121         struct ext4_encryption_key *master_key;
122         struct ext4_encryption_context ctx;
123         struct user_key_payload *ukp;
124         struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
125         struct crypto_ablkcipher *ctfm;
126         const char *cipher_str;
127         char raw_key[EXT4_MAX_KEY_SIZE];
128         char mode;
129         int res;
130
131         if (!ext4_read_workqueue) {
132                 res = ext4_init_crypto();
133                 if (res)
134                         return res;
135         }
136
137 retry:
138         crypt_info = ACCESS_ONCE(ei->i_crypt_info);
139         if (crypt_info) {
140                 if (!crypt_info->ci_keyring_key ||
141                     key_validate(crypt_info->ci_keyring_key) == 0)
142                         return 0;
143                 ext4_free_encryption_info(inode, crypt_info);
144                 goto retry;
145         }
146
147         res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
148                                  EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
149                                  &ctx, sizeof(ctx));
150         if (res < 0) {
151                 if (!DUMMY_ENCRYPTION_ENABLED(sbi))
152                         return res;
153                 ctx.contents_encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS;
154                 ctx.filenames_encryption_mode =
155                         EXT4_ENCRYPTION_MODE_AES_256_CTS;
156                 ctx.flags = 0;
157         } else if (res != sizeof(ctx))
158                 return -EINVAL;
159         res = 0;
160
161         crypt_info = kmem_cache_alloc(ext4_crypt_info_cachep, GFP_KERNEL);
162         if (!crypt_info)
163                 return -ENOMEM;
164
165         crypt_info->ci_flags = ctx.flags;
166         crypt_info->ci_data_mode = ctx.contents_encryption_mode;
167         crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
168         crypt_info->ci_ctfm = NULL;
169         crypt_info->ci_keyring_key = NULL;
170         memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
171                sizeof(crypt_info->ci_master_key));
172         if (S_ISREG(inode->i_mode))
173                 mode = crypt_info->ci_data_mode;
174         else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
175                 mode = crypt_info->ci_filename_mode;
176         else
177                 BUG();
178         switch (mode) {
179         case EXT4_ENCRYPTION_MODE_AES_256_XTS:
180                 cipher_str = "xts(aes)";
181                 break;
182         case EXT4_ENCRYPTION_MODE_AES_256_CTS:
183                 cipher_str = "cts(cbc(aes))";
184                 break;
185         default:
186                 printk_once(KERN_WARNING
187                             "ext4: unsupported key mode %d (ino %u)\n",
188                             mode, (unsigned) inode->i_ino);
189                 res = -ENOKEY;
190                 goto out;
191         }
192         if (DUMMY_ENCRYPTION_ENABLED(sbi)) {
193                 memset(raw_key, 0x42, EXT4_AES_256_XTS_KEY_SIZE);
194                 goto got_key;
195         }
196         memcpy(full_key_descriptor, EXT4_KEY_DESC_PREFIX,
197                EXT4_KEY_DESC_PREFIX_SIZE);
198         sprintf(full_key_descriptor + EXT4_KEY_DESC_PREFIX_SIZE,
199                 "%*phN", EXT4_KEY_DESCRIPTOR_SIZE,
200                 ctx.master_key_descriptor);
201         full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE +
202                             (2 * EXT4_KEY_DESCRIPTOR_SIZE)] = '\0';
203         keyring_key = request_key(&key_type_logon, full_key_descriptor, NULL);
204         if (IS_ERR(keyring_key)) {
205                 res = PTR_ERR(keyring_key);
206                 keyring_key = NULL;
207                 goto out;
208         }
209         crypt_info->ci_keyring_key = keyring_key;
210         if (keyring_key->type != &key_type_logon) {
211                 printk_once(KERN_WARNING
212                             "ext4: key type must be logon\n");
213                 res = -ENOKEY;
214                 goto out;
215         }
216         ukp = ((struct user_key_payload *)keyring_key->payload.data);
217         if (ukp->datalen != sizeof(struct ext4_encryption_key)) {
218                 res = -EINVAL;
219                 goto out;
220         }
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",
227                             master_key->size);
228                 res = -ENOKEY;
229                 goto out;
230         }
231         res = ext4_derive_key_aes(ctx.nonce, master_key->raw,
232                                   raw_key);
233         if (res)
234                 goto out;
235 got_key:
236         ctfm = crypto_alloc_ablkcipher(cipher_str, 0, 0);
237         if (!ctfm || IS_ERR(ctfm)) {
238                 res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
239                 printk(KERN_DEBUG
240                        "%s: error %d (inode %u) allocating crypto tfm\n",
241                        __func__, res, (unsigned) inode->i_ino);
242                 goto out;
243         }
244         crypt_info->ci_ctfm = ctfm;
245         crypto_ablkcipher_clear_flags(ctfm, ~0);
246         crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctfm),
247                              CRYPTO_TFM_REQ_WEAK_KEY);
248         res = crypto_ablkcipher_setkey(ctfm, raw_key,
249                                        ext4_encryption_key_size(mode));
250         if (res)
251                 goto out;
252         memzero_explicit(raw_key, sizeof(raw_key));
253         if (cmpxchg(&ei->i_crypt_info, NULL, crypt_info) != NULL) {
254                 ext4_free_crypt_info(crypt_info);
255                 goto retry;
256         }
257         return 0;
258
259 out:
260         if (res == -ENOKEY)
261                 res = 0;
262         ext4_free_crypt_info(crypt_info);
263         memzero_explicit(raw_key, sizeof(raw_key));
264         return res;
265 }
266
267 int ext4_has_encryption_key(struct inode *inode)
268 {
269         struct ext4_inode_info *ei = EXT4_I(inode);
270
271         return (ei->i_crypt_info != NULL);
272 }