2 * linux/fs/ext4/crypto_key.c
4 * Copyright (C) 2015, Google, Inc.
6 * This contains encryption key functions for ext4
8 * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
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>
20 static void derive_crypt_complete(struct crypto_async_request *req, int rc)
22 struct ext4_completion_result *ecr = req->data;
24 if (rc == -EINPROGRESS)
28 complete(&ecr->completion);
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.
37 * Return: Zero on success; non-zero otherwise.
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])
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,
55 crypto_ablkcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
56 req = ablkcipher_request_alloc(tfm, GFP_NOFS);
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);
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);
80 ablkcipher_request_free(req);
82 crypto_free_ablkcipher(tfm);
86 void ext4_free_crypt_info(struct ext4_crypt_info *ci)
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);
97 void ext4_free_encryption_info(struct inode *inode,
98 struct ext4_crypt_info *ci)
100 struct ext4_inode_info *ei = EXT4_I(inode);
101 struct ext4_crypt_info *prev;
104 ci = ACCESS_ONCE(ei->i_crypt_info);
107 prev = cmpxchg(&ei->i_crypt_info, ci, NULL);
111 ext4_free_crypt_info(ci);
114 int _ext4_get_encryption_info(struct inode *inode)
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 const 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];
131 if (!ext4_read_workqueue) {
132 res = ext4_init_crypto();
138 crypt_info = ACCESS_ONCE(ei->i_crypt_info);
140 if (!crypt_info->ci_keyring_key ||
141 key_validate(crypt_info->ci_keyring_key) == 0)
143 ext4_free_encryption_info(inode, crypt_info);
147 res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
148 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
151 if (!DUMMY_ENCRYPTION_ENABLED(sbi))
153 ctx.contents_encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS;
154 ctx.filenames_encryption_mode =
155 EXT4_ENCRYPTION_MODE_AES_256_CTS;
157 } else if (res != sizeof(ctx))
161 crypt_info = kmem_cache_alloc(ext4_crypt_info_cachep, GFP_KERNEL);
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;
179 case EXT4_ENCRYPTION_MODE_AES_256_XTS:
180 cipher_str = "xts(aes)";
182 case EXT4_ENCRYPTION_MODE_AES_256_CTS:
183 cipher_str = "cts(cbc(aes))";
186 printk_once(KERN_WARNING
187 "ext4: unsupported key mode %d (ino %u)\n",
188 mode, (unsigned) inode->i_ino);
192 if (DUMMY_ENCRYPTION_ENABLED(sbi)) {
193 memset(raw_key, 0x42, EXT4_AES_256_XTS_KEY_SIZE);
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);
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");
216 down_read(&keyring_key->sem);
217 ukp = user_key_payload(keyring_key);
218 if (ukp->datalen != sizeof(struct ext4_encryption_key)) {
220 up_read(&keyring_key->sem);
223 master_key = (struct ext4_encryption_key *)ukp->data;
224 BUILD_BUG_ON(EXT4_AES_128_ECB_KEY_SIZE !=
225 EXT4_KEY_DERIVATION_NONCE_SIZE);
226 if (master_key->size != EXT4_AES_256_XTS_KEY_SIZE) {
227 printk_once(KERN_WARNING
228 "ext4: key size incorrect: %d\n",
231 up_read(&keyring_key->sem);
234 res = ext4_derive_key_aes(ctx.nonce, master_key->raw,
236 up_read(&keyring_key->sem);
240 ctfm = crypto_alloc_ablkcipher(cipher_str, 0, 0);
241 if (!ctfm || IS_ERR(ctfm)) {
242 res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
244 "%s: error %d (inode %u) allocating crypto tfm\n",
245 __func__, res, (unsigned) inode->i_ino);
248 crypt_info->ci_ctfm = ctfm;
249 crypto_ablkcipher_clear_flags(ctfm, ~0);
250 crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctfm),
251 CRYPTO_TFM_REQ_WEAK_KEY);
252 res = crypto_ablkcipher_setkey(ctfm, raw_key,
253 ext4_encryption_key_size(mode));
256 memzero_explicit(raw_key, sizeof(raw_key));
257 if (cmpxchg(&ei->i_crypt_info, NULL, crypt_info) != NULL) {
258 ext4_free_crypt_info(crypt_info);
266 ext4_free_crypt_info(crypt_info);
267 memzero_explicit(raw_key, sizeof(raw_key));
271 int ext4_has_encryption_key(struct inode *inode)
273 struct ext4_inode_info *ei = EXT4_I(inode);
275 return (ei->i_crypt_info != NULL);