Merge branch 'waitid-fix' of git://git.kernel.org/pub/scm/linux/kernel/git/viro/vfs
[muen/linux.git] / fs / crypto / keyinfo.c
1 /*
2  * key management facility for FS encryption support.
3  *
4  * Copyright (C) 2015, Google, Inc.
5  *
6  * This contains encryption key functions.
7  *
8  * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
9  */
10
11 #include <keys/user-type.h>
12 #include <linux/scatterlist.h>
13 #include "fscrypt_private.h"
14
15 static void derive_crypt_complete(struct crypto_async_request *req, int rc)
16 {
17         struct fscrypt_completion_result *ecr = req->data;
18
19         if (rc == -EINPROGRESS)
20                 return;
21
22         ecr->res = rc;
23         complete(&ecr->completion);
24 }
25
26 /**
27  * derive_key_aes() - Derive a key using AES-128-ECB
28  * @deriving_key: Encryption key used for derivation.
29  * @source_key:   Source key to which to apply derivation.
30  * @derived_key:  Derived key.
31  *
32  * Return: Zero on success; non-zero otherwise.
33  */
34 static int derive_key_aes(u8 deriving_key[FS_AES_128_ECB_KEY_SIZE],
35                                 u8 source_key[FS_AES_256_XTS_KEY_SIZE],
36                                 u8 derived_key[FS_AES_256_XTS_KEY_SIZE])
37 {
38         int res = 0;
39         struct skcipher_request *req = NULL;
40         DECLARE_FS_COMPLETION_RESULT(ecr);
41         struct scatterlist src_sg, dst_sg;
42         struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0);
43
44         if (IS_ERR(tfm)) {
45                 res = PTR_ERR(tfm);
46                 tfm = NULL;
47                 goto out;
48         }
49         crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
50         req = skcipher_request_alloc(tfm, GFP_NOFS);
51         if (!req) {
52                 res = -ENOMEM;
53                 goto out;
54         }
55         skcipher_request_set_callback(req,
56                         CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
57                         derive_crypt_complete, &ecr);
58         res = crypto_skcipher_setkey(tfm, deriving_key,
59                                         FS_AES_128_ECB_KEY_SIZE);
60         if (res < 0)
61                 goto out;
62
63         sg_init_one(&src_sg, source_key, FS_AES_256_XTS_KEY_SIZE);
64         sg_init_one(&dst_sg, derived_key, FS_AES_256_XTS_KEY_SIZE);
65         skcipher_request_set_crypt(req, &src_sg, &dst_sg,
66                                         FS_AES_256_XTS_KEY_SIZE, NULL);
67         res = crypto_skcipher_encrypt(req);
68         if (res == -EINPROGRESS || res == -EBUSY) {
69                 wait_for_completion(&ecr.completion);
70                 res = ecr.res;
71         }
72 out:
73         skcipher_request_free(req);
74         crypto_free_skcipher(tfm);
75         return res;
76 }
77
78 static int validate_user_key(struct fscrypt_info *crypt_info,
79                         struct fscrypt_context *ctx, u8 *raw_key,
80                         const char *prefix)
81 {
82         char *description;
83         struct key *keyring_key;
84         struct fscrypt_key *master_key;
85         const struct user_key_payload *ukp;
86         int res;
87
88         description = kasprintf(GFP_NOFS, "%s%*phN", prefix,
89                                 FS_KEY_DESCRIPTOR_SIZE,
90                                 ctx->master_key_descriptor);
91         if (!description)
92                 return -ENOMEM;
93
94         keyring_key = request_key(&key_type_logon, description, NULL);
95         kfree(description);
96         if (IS_ERR(keyring_key))
97                 return PTR_ERR(keyring_key);
98         down_read(&keyring_key->sem);
99
100         if (keyring_key->type != &key_type_logon) {
101                 printk_once(KERN_WARNING
102                                 "%s: key type must be logon\n", __func__);
103                 res = -ENOKEY;
104                 goto out;
105         }
106         ukp = user_key_payload_locked(keyring_key);
107         if (ukp->datalen != sizeof(struct fscrypt_key)) {
108                 res = -EINVAL;
109                 goto out;
110         }
111         master_key = (struct fscrypt_key *)ukp->data;
112         BUILD_BUG_ON(FS_AES_128_ECB_KEY_SIZE != FS_KEY_DERIVATION_NONCE_SIZE);
113
114         if (master_key->size != FS_AES_256_XTS_KEY_SIZE) {
115                 printk_once(KERN_WARNING
116                                 "%s: key size incorrect: %d\n",
117                                 __func__, master_key->size);
118                 res = -ENOKEY;
119                 goto out;
120         }
121         res = derive_key_aes(ctx->nonce, master_key->raw, raw_key);
122 out:
123         up_read(&keyring_key->sem);
124         key_put(keyring_key);
125         return res;
126 }
127
128 static int determine_cipher_type(struct fscrypt_info *ci, struct inode *inode,
129                                  const char **cipher_str_ret, int *keysize_ret)
130 {
131         if (S_ISREG(inode->i_mode)) {
132                 if (ci->ci_data_mode == FS_ENCRYPTION_MODE_AES_256_XTS) {
133                         *cipher_str_ret = "xts(aes)";
134                         *keysize_ret = FS_AES_256_XTS_KEY_SIZE;
135                         return 0;
136                 }
137                 pr_warn_once("fscrypto: unsupported contents encryption mode "
138                              "%d for inode %lu\n",
139                              ci->ci_data_mode, inode->i_ino);
140                 return -ENOKEY;
141         }
142
143         if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode)) {
144                 if (ci->ci_filename_mode == FS_ENCRYPTION_MODE_AES_256_CTS) {
145                         *cipher_str_ret = "cts(cbc(aes))";
146                         *keysize_ret = FS_AES_256_CTS_KEY_SIZE;
147                         return 0;
148                 }
149                 pr_warn_once("fscrypto: unsupported filenames encryption mode "
150                              "%d for inode %lu\n",
151                              ci->ci_filename_mode, inode->i_ino);
152                 return -ENOKEY;
153         }
154
155         pr_warn_once("fscrypto: unsupported file type %d for inode %lu\n",
156                      (inode->i_mode & S_IFMT), inode->i_ino);
157         return -ENOKEY;
158 }
159
160 static void put_crypt_info(struct fscrypt_info *ci)
161 {
162         if (!ci)
163                 return;
164
165         crypto_free_skcipher(ci->ci_ctfm);
166         kmem_cache_free(fscrypt_info_cachep, ci);
167 }
168
169 int fscrypt_get_encryption_info(struct inode *inode)
170 {
171         struct fscrypt_info *crypt_info;
172         struct fscrypt_context ctx;
173         struct crypto_skcipher *ctfm;
174         const char *cipher_str;
175         int keysize;
176         u8 *raw_key = NULL;
177         int res;
178
179         if (inode->i_crypt_info)
180                 return 0;
181
182         res = fscrypt_initialize(inode->i_sb->s_cop->flags);
183         if (res)
184                 return res;
185
186         res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
187         if (res < 0) {
188                 if (!fscrypt_dummy_context_enabled(inode) ||
189                     inode->i_sb->s_cop->is_encrypted(inode))
190                         return res;
191                 /* Fake up a context for an unencrypted directory */
192                 memset(&ctx, 0, sizeof(ctx));
193                 ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
194                 ctx.contents_encryption_mode = FS_ENCRYPTION_MODE_AES_256_XTS;
195                 ctx.filenames_encryption_mode = FS_ENCRYPTION_MODE_AES_256_CTS;
196                 memset(ctx.master_key_descriptor, 0x42, FS_KEY_DESCRIPTOR_SIZE);
197         } else if (res != sizeof(ctx)) {
198                 return -EINVAL;
199         }
200
201         if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1)
202                 return -EINVAL;
203
204         if (ctx.flags & ~FS_POLICY_FLAGS_VALID)
205                 return -EINVAL;
206
207         crypt_info = kmem_cache_alloc(fscrypt_info_cachep, GFP_NOFS);
208         if (!crypt_info)
209                 return -ENOMEM;
210
211         crypt_info->ci_flags = ctx.flags;
212         crypt_info->ci_data_mode = ctx.contents_encryption_mode;
213         crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
214         crypt_info->ci_ctfm = NULL;
215         memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
216                                 sizeof(crypt_info->ci_master_key));
217
218         res = determine_cipher_type(crypt_info, inode, &cipher_str, &keysize);
219         if (res)
220                 goto out;
221
222         /*
223          * This cannot be a stack buffer because it is passed to the scatterlist
224          * crypto API as part of key derivation.
225          */
226         res = -ENOMEM;
227         raw_key = kmalloc(FS_MAX_KEY_SIZE, GFP_NOFS);
228         if (!raw_key)
229                 goto out;
230
231         res = validate_user_key(crypt_info, &ctx, raw_key, FS_KEY_DESC_PREFIX);
232         if (res && inode->i_sb->s_cop->key_prefix) {
233                 int res2 = validate_user_key(crypt_info, &ctx, raw_key,
234                                              inode->i_sb->s_cop->key_prefix);
235                 if (res2) {
236                         if (res2 == -ENOKEY)
237                                 res = -ENOKEY;
238                         goto out;
239                 }
240         } else if (res) {
241                 goto out;
242         }
243         ctfm = crypto_alloc_skcipher(cipher_str, 0, 0);
244         if (!ctfm || IS_ERR(ctfm)) {
245                 res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
246                 printk(KERN_DEBUG
247                        "%s: error %d (inode %u) allocating crypto tfm\n",
248                        __func__, res, (unsigned) inode->i_ino);
249                 goto out;
250         }
251         crypt_info->ci_ctfm = ctfm;
252         crypto_skcipher_clear_flags(ctfm, ~0);
253         crypto_skcipher_set_flags(ctfm, CRYPTO_TFM_REQ_WEAK_KEY);
254         res = crypto_skcipher_setkey(ctfm, raw_key, keysize);
255         if (res)
256                 goto out;
257
258         if (cmpxchg(&inode->i_crypt_info, NULL, crypt_info) == NULL)
259                 crypt_info = NULL;
260 out:
261         if (res == -ENOKEY)
262                 res = 0;
263         put_crypt_info(crypt_info);
264         kzfree(raw_key);
265         return res;
266 }
267 EXPORT_SYMBOL(fscrypt_get_encryption_info);
268
269 void fscrypt_put_encryption_info(struct inode *inode, struct fscrypt_info *ci)
270 {
271         struct fscrypt_info *prev;
272
273         if (ci == NULL)
274                 ci = ACCESS_ONCE(inode->i_crypt_info);
275         if (ci == NULL)
276                 return;
277
278         prev = cmpxchg(&inode->i_crypt_info, ci, NULL);
279         if (prev != ci)
280                 return;
281
282         put_crypt_info(ci);
283 }
284 EXPORT_SYMBOL(fscrypt_put_encryption_info);