1 /*
2  * linux/fs/f2fs/crypto_key.c
3  *
4  * Copied from linux/fs/f2fs/crypto_key.c
5  *
6  * Copyright (C) 2015, Google, Inc.
7  *
8  * This contains encryption key functions for f2fs
9  *
10  * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
11  */
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 #include <crypto/hash.h>
18 #include <linux/f2fs_fs.h>
19 
20 #include "f2fs.h"
21 #include "xattr.h"
22 
derive_crypt_complete(struct crypto_async_request * req,int rc)23 static void derive_crypt_complete(struct crypto_async_request *req, int rc)
24 {
25 	struct f2fs_completion_result *ecr = req->data;
26 
27 	if (rc == -EINPROGRESS)
28 		return;
29 
30 	ecr->res = rc;
31 	complete(&ecr->completion);
32 }
33 
34 /**
35  * f2fs_derive_key_aes() - Derive a key using AES-128-ECB
36  * @deriving_key: Encryption key used for derivatio.
37  * @source_key:   Source key to which to apply derivation.
38  * @derived_key:  Derived key.
39  *
40  * Return: Zero on success; non-zero otherwise.
41  */
f2fs_derive_key_aes(char deriving_key[F2FS_AES_128_ECB_KEY_SIZE],char source_key[F2FS_AES_256_XTS_KEY_SIZE],char derived_key[F2FS_AES_256_XTS_KEY_SIZE])42 static int f2fs_derive_key_aes(char deriving_key[F2FS_AES_128_ECB_KEY_SIZE],
43 				char source_key[F2FS_AES_256_XTS_KEY_SIZE],
44 				char derived_key[F2FS_AES_256_XTS_KEY_SIZE])
45 {
46 	int res = 0;
47 	struct ablkcipher_request *req = NULL;
48 	DECLARE_F2FS_COMPLETION_RESULT(ecr);
49 	struct scatterlist src_sg, dst_sg;
50 	struct crypto_ablkcipher *tfm = crypto_alloc_ablkcipher("ecb(aes)", 0,
51 								0);
52 
53 	if (IS_ERR(tfm)) {
54 		res = PTR_ERR(tfm);
55 		tfm = NULL;
56 		goto out;
57 	}
58 	crypto_ablkcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
59 	req = ablkcipher_request_alloc(tfm, GFP_NOFS);
60 	if (!req) {
61 		res = -ENOMEM;
62 		goto out;
63 	}
64 	ablkcipher_request_set_callback(req,
65 			CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
66 			derive_crypt_complete, &ecr);
67 	res = crypto_ablkcipher_setkey(tfm, deriving_key,
68 				F2FS_AES_128_ECB_KEY_SIZE);
69 	if (res < 0)
70 		goto out;
71 
72 	sg_init_one(&src_sg, source_key, F2FS_AES_256_XTS_KEY_SIZE);
73 	sg_init_one(&dst_sg, derived_key, F2FS_AES_256_XTS_KEY_SIZE);
74 	ablkcipher_request_set_crypt(req, &src_sg, &dst_sg,
75 					F2FS_AES_256_XTS_KEY_SIZE, NULL);
76 	res = crypto_ablkcipher_encrypt(req);
77 	if (res == -EINPROGRESS || res == -EBUSY) {
78 		BUG_ON(req->base.data != &ecr);
79 		wait_for_completion(&ecr.completion);
80 		res = ecr.res;
81 	}
82 out:
83 	if (req)
84 		ablkcipher_request_free(req);
85 	if (tfm)
86 		crypto_free_ablkcipher(tfm);
87 	return res;
88 }
89 
f2fs_free_crypt_info(struct f2fs_crypt_info * ci)90 static void f2fs_free_crypt_info(struct f2fs_crypt_info *ci)
91 {
92 	if (!ci)
93 		return;
94 
95 	key_put(ci->ci_keyring_key);
96 	crypto_free_ablkcipher(ci->ci_ctfm);
97 	kmem_cache_free(f2fs_crypt_info_cachep, ci);
98 }
99 
f2fs_free_encryption_info(struct inode * inode,struct f2fs_crypt_info * ci)100 void f2fs_free_encryption_info(struct inode *inode, struct f2fs_crypt_info *ci)
101 {
102 	struct f2fs_inode_info *fi = F2FS_I(inode);
103 	struct f2fs_crypt_info *prev;
104 
105 	if (ci == NULL)
106 		ci = ACCESS_ONCE(fi->i_crypt_info);
107 	if (ci == NULL)
108 		return;
109 	prev = cmpxchg(&fi->i_crypt_info, ci, NULL);
110 	if (prev != ci)
111 		return;
112 
113 	f2fs_free_crypt_info(ci);
114 }
115 
_f2fs_get_encryption_info(struct inode * inode)116 int _f2fs_get_encryption_info(struct inode *inode)
117 {
118 	struct f2fs_inode_info *fi = F2FS_I(inode);
119 	struct f2fs_crypt_info *crypt_info;
120 	char full_key_descriptor[F2FS_KEY_DESC_PREFIX_SIZE +
121 				(F2FS_KEY_DESCRIPTOR_SIZE * 2) + 1];
122 	struct key *keyring_key = NULL;
123 	struct f2fs_encryption_key *master_key;
124 	struct f2fs_encryption_context ctx;
125 	const struct user_key_payload *ukp;
126 	struct crypto_ablkcipher *ctfm;
127 	const char *cipher_str;
128 	char raw_key[F2FS_MAX_KEY_SIZE];
129 	char mode;
130 	int res;
131 
132 	res = f2fs_crypto_initialize();
133 	if (res)
134 		return res;
135 retry:
136 	crypt_info = ACCESS_ONCE(fi->i_crypt_info);
137 	if (crypt_info) {
138 		if (!crypt_info->ci_keyring_key ||
139 				key_validate(crypt_info->ci_keyring_key) == 0)
140 			return 0;
141 		f2fs_free_encryption_info(inode, crypt_info);
142 		goto retry;
143 	}
144 
145 	res = f2fs_getxattr(inode, F2FS_XATTR_INDEX_ENCRYPTION,
146 				F2FS_XATTR_NAME_ENCRYPTION_CONTEXT,
147 				&ctx, sizeof(ctx), NULL);
148 	if (res < 0)
149 		return res;
150 	else if (res != sizeof(ctx))
151 		return -EINVAL;
152 	res = 0;
153 
154 	crypt_info = kmem_cache_alloc(f2fs_crypt_info_cachep, GFP_NOFS);
155 	if (!crypt_info)
156 		return -ENOMEM;
157 
158 	crypt_info->ci_flags = ctx.flags;
159 	crypt_info->ci_data_mode = ctx.contents_encryption_mode;
160 	crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
161 	crypt_info->ci_ctfm = NULL;
162 	crypt_info->ci_keyring_key = NULL;
163 	memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
164 				sizeof(crypt_info->ci_master_key));
165 	if (S_ISREG(inode->i_mode))
166 		mode = crypt_info->ci_data_mode;
167 	else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
168 		mode = crypt_info->ci_filename_mode;
169 	else
170 		BUG();
171 
172 	switch (mode) {
173 	case F2FS_ENCRYPTION_MODE_AES_256_XTS:
174 		cipher_str = "xts(aes)";
175 		break;
176 	case F2FS_ENCRYPTION_MODE_AES_256_CTS:
177 		cipher_str = "cts(cbc(aes))";
178 		break;
179 	default:
180 		printk_once(KERN_WARNING
181 			    "f2fs: unsupported key mode %d (ino %u)\n",
182 			    mode, (unsigned) inode->i_ino);
183 		res = -ENOKEY;
184 		goto out;
185 	}
186 
187 	memcpy(full_key_descriptor, F2FS_KEY_DESC_PREFIX,
188 					F2FS_KEY_DESC_PREFIX_SIZE);
189 	sprintf(full_key_descriptor + F2FS_KEY_DESC_PREFIX_SIZE,
190 					"%*phN", F2FS_KEY_DESCRIPTOR_SIZE,
191 					ctx.master_key_descriptor);
192 	full_key_descriptor[F2FS_KEY_DESC_PREFIX_SIZE +
193 					(2 * F2FS_KEY_DESCRIPTOR_SIZE)] = '\0';
194 	keyring_key = request_key(&key_type_logon, full_key_descriptor, NULL);
195 	if (IS_ERR(keyring_key)) {
196 		res = PTR_ERR(keyring_key);
197 		keyring_key = NULL;
198 		goto out;
199 	}
200 	crypt_info->ci_keyring_key = keyring_key;
201 	BUG_ON(keyring_key->type != &key_type_logon);
202 	ukp = user_key_payload(keyring_key);
203 	if (ukp->datalen != sizeof(struct f2fs_encryption_key)) {
204 		res = -EINVAL;
205 		goto out;
206 	}
207 	master_key = (struct f2fs_encryption_key *)ukp->data;
208 	BUILD_BUG_ON(F2FS_AES_128_ECB_KEY_SIZE !=
209 				F2FS_KEY_DERIVATION_NONCE_SIZE);
210 	BUG_ON(master_key->size != F2FS_AES_256_XTS_KEY_SIZE);
211 	res = f2fs_derive_key_aes(ctx.nonce, master_key->raw,
212 				  raw_key);
213 	if (res)
214 		goto out;
215 
216 	ctfm = crypto_alloc_ablkcipher(cipher_str, 0, 0);
217 	if (!ctfm || IS_ERR(ctfm)) {
218 		res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
219 		printk(KERN_DEBUG
220 		       "%s: error %d (inode %u) allocating crypto tfm\n",
221 		       __func__, res, (unsigned) inode->i_ino);
222 		goto out;
223 	}
224 	crypt_info->ci_ctfm = ctfm;
225 	crypto_ablkcipher_clear_flags(ctfm, ~0);
226 	crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctfm),
227 			     CRYPTO_TFM_REQ_WEAK_KEY);
228 	res = crypto_ablkcipher_setkey(ctfm, raw_key,
229 					f2fs_encryption_key_size(mode));
230 	if (res)
231 		goto out;
232 
233 	memzero_explicit(raw_key, sizeof(raw_key));
234 	if (cmpxchg(&fi->i_crypt_info, NULL, crypt_info) != NULL) {
235 		f2fs_free_crypt_info(crypt_info);
236 		goto retry;
237 	}
238 	return 0;
239 
240 out:
241 	if (res == -ENOKEY && !S_ISREG(inode->i_mode))
242 		res = 0;
243 
244 	f2fs_free_crypt_info(crypt_info);
245 	memzero_explicit(raw_key, sizeof(raw_key));
246 	return res;
247 }
248 
f2fs_has_encryption_key(struct inode * inode)249 int f2fs_has_encryption_key(struct inode *inode)
250 {
251 	struct f2fs_inode_info *fi = F2FS_I(inode);
252 
253 	return (fi->i_crypt_info != NULL);
254 }
255