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 BUG_ON(req->base.data != &ecr);
75 wait_for_completion(&ecr.completion);
81 ablkcipher_request_free(req);
83 crypto_free_ablkcipher(tfm);
87 void ext4_free_crypt_info(struct ext4_crypt_info *ci)
92 if (ci->ci_keyring_key)
93 key_put(ci->ci_keyring_key);
94 crypto_free_ablkcipher(ci->ci_ctfm);
95 kmem_cache_free(ext4_crypt_info_cachep, ci);
98 void ext4_free_encryption_info(struct inode *inode,
99 struct ext4_crypt_info *ci)
101 struct ext4_inode_info *ei = EXT4_I(inode);
102 struct ext4_crypt_info *prev;
105 ci = ACCESS_ONCE(ei->i_crypt_info);
108 prev = cmpxchg(&ei->i_crypt_info, ci, NULL);
112 ext4_free_crypt_info(ci);
115 int _ext4_get_encryption_info(struct inode *inode)
117 struct ext4_inode_info *ei = EXT4_I(inode);
118 struct ext4_crypt_info *crypt_info;
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;
125 struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
126 struct crypto_ablkcipher *ctfm;
127 const char *cipher_str;
128 char raw_key[EXT4_MAX_KEY_SIZE];
132 if (!ext4_read_workqueue) {
133 res = ext4_init_crypto();
139 crypt_info = ACCESS_ONCE(ei->i_crypt_info);
141 if (!crypt_info->ci_keyring_key ||
142 key_validate(crypt_info->ci_keyring_key) == 0)
144 ext4_free_encryption_info(inode, crypt_info);
148 res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
149 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
152 if (!DUMMY_ENCRYPTION_ENABLED(sbi))
154 ctx.contents_encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS;
155 ctx.filenames_encryption_mode =
156 EXT4_ENCRYPTION_MODE_AES_256_CTS;
158 } else if (res != sizeof(ctx))
162 crypt_info = kmem_cache_alloc(ext4_crypt_info_cachep, GFP_KERNEL);
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;
170 crypt_info->ci_keyring_key = NULL;
171 memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
172 sizeof(crypt_info->ci_master_key));
173 if (S_ISREG(inode->i_mode))
174 mode = crypt_info->ci_data_mode;
175 else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
176 mode = crypt_info->ci_filename_mode;
180 case EXT4_ENCRYPTION_MODE_AES_256_XTS:
181 cipher_str = "xts(aes)";
183 case EXT4_ENCRYPTION_MODE_AES_256_CTS:
184 cipher_str = "cts(cbc(aes))";
187 printk_once(KERN_WARNING
188 "ext4: unsupported key mode %d (ino %u)\n",
189 mode, (unsigned) inode->i_ino);
193 if (DUMMY_ENCRYPTION_ENABLED(sbi)) {
194 memset(raw_key, 0x42, EXT4_AES_256_XTS_KEY_SIZE);
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);
210 crypt_info->ci_keyring_key = keyring_key;
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)) {
217 master_key = (struct ext4_encryption_key *)ukp->data;
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);
221 res = ext4_derive_key_aes(ctx.nonce, master_key->raw,
226 ctfm = crypto_alloc_ablkcipher(cipher_str, 0, 0);
227 if (!ctfm || IS_ERR(ctfm)) {
228 res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
230 "%s: error %d (inode %u) allocating crypto tfm\n",
231 __func__, res, (unsigned) inode->i_ino);
234 crypt_info->ci_ctfm = ctfm;
235 crypto_ablkcipher_clear_flags(ctfm, ~0);
236 crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctfm),
237 CRYPTO_TFM_REQ_WEAK_KEY);
238 res = crypto_ablkcipher_setkey(ctfm, raw_key,
239 ext4_encryption_key_size(mode));
242 memzero_explicit(raw_key, sizeof(raw_key));
243 if (cmpxchg(&ei->i_crypt_info, NULL, crypt_info) != NULL) {
244 ext4_free_crypt_info(crypt_info);
252 ext4_free_crypt_info(crypt_info);
253 memzero_explicit(raw_key, sizeof(raw_key));
257 int ext4_has_encryption_key(struct inode *inode)
259 struct ext4_inode_info *ei = EXT4_I(inode);
261 return (ei->i_crypt_info != NULL);