| blob | 2cd5b9acb3feebd76d3f0ec31e374a8f0fb8edce |
1 ext4 crypto: add encryption key management facilities
3 From: Michael Halcrow <mhalcrow@google.com>
5 Signed-off-by: Michael Halcrow <mhalcrow@google.com>
6 Signed-off-by: Ildar Muslukhov <muslukhovi@gmail.com>
7 Signed-off-by: Theodore Ts'o <tytso@mit.edu>
8 ---
9 fs/ext4/Makefile | 2 +-
10 fs/ext4/crypto_key.c | 162 +++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
11 fs/ext4/ext4.h | 13 +++++++
12 fs/ext4/ext4_crypto.h | 3 ++
13 4 files changed, 179 insertions(+), 1 deletion(-)
15 diff --git a/fs/ext4/Makefile b/fs/ext4/Makefile
16 index 1b1c561..4e5af21 100644
17 --- a/fs/ext4/Makefile
18 +++ b/fs/ext4/Makefile
19 @@ -12,4 +12,4 @@ ext4-y := balloc.o bitmap.o dir.o file.o fsync.o ialloc.o inode.o page-io.o \
21 ext4-$(CONFIG_EXT4_FS_POSIX_ACL) += acl.o
22 ext4-$(CONFIG_EXT4_FS_SECURITY) += xattr_security.o
23 -ext4-$(CONFIG_EXT4_FS_ENCRYPTION) += crypto_policy.o crypto.o
24 +ext4-$(CONFIG_EXT4_FS_ENCRYPTION) += crypto_policy.o crypto.o crypto_key.o
25 diff --git a/fs/ext4/crypto_key.c b/fs/ext4/crypto_key.c
26 new file mode 100644
27 index 0000000..572bd97
28 --- /dev/null
29 +++ b/fs/ext4/crypto_key.c
30 @@ -0,0 +1,162 @@
31 +/*
32 + * linux/fs/ext4/crypto_key.c
33 + *
34 + * Copyright (C) 2015, Google, Inc.
35 + *
36 + * This contains encryption key functions for ext4
37 + *
38 + * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
39 + */
40 +
41 +#include <keys/encrypted-type.h>
42 +#include <keys/user-type.h>
43 +#include <linux/random.h>
44 +#include <linux/scatterlist.h>
45 +#include <uapi/linux/keyctl.h>
46 +
47 +#include "ext4.h"
48 +#include "xattr.h"
49 +
50 +static void derive_crypt_complete(struct crypto_async_request *req, int rc)
51 +{
52 + struct ext4_completion_result *ecr = req->data;
53 +
54 + if (rc == -EINPROGRESS)
55 + return;
56 +
57 + ecr->res = rc;
58 + complete(&ecr->completion);
59 +}
60 +
61 +/**
62 + * ext4_derive_key_aes() - Derive a key using AES-128-ECB
63 + * @deriving_key: Encryption key used for derivatio.
64 + * @source_key: Source key to which to apply derivation.
65 + * @derived_key: Derived key.
66 + *
67 + * Return: Zero on success; non-zero otherwise.
68 + */
69 +static int ext4_derive_key_aes(char deriving_key[EXT4_AES_128_ECB_KEY_SIZE],
70 + char source_key[EXT4_AES_256_XTS_KEY_SIZE],
71 + char derived_key[EXT4_AES_256_XTS_KEY_SIZE])
72 +{
73 + int res = 0;
74 + struct ablkcipher_request *req = NULL;
75 + DECLARE_EXT4_COMPLETION_RESULT(ecr);
76 + struct scatterlist src_sg, dst_sg;
77 + struct crypto_ablkcipher *tfm = crypto_alloc_ablkcipher("ecb(aes)", 0,
78 + 0);
79 +
80 + if (IS_ERR(tfm)) {
81 + res = PTR_ERR(tfm);
82 + tfm = NULL;
83 + goto out;
84 + }
85 + crypto_ablkcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
86 + req = ablkcipher_request_alloc(tfm, GFP_NOFS);
87 + if (!req) {
88 + res = -ENOMEM;
89 + goto out;
90 + }
91 + ablkcipher_request_set_callback(req,
92 + CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
93 + derive_crypt_complete, &ecr);
94 + res = crypto_ablkcipher_setkey(tfm, deriving_key,
95 + EXT4_AES_128_ECB_KEY_SIZE);
96 + if (res < 0)
97 + goto out;
98 + sg_init_one(&src_sg, source_key, EXT4_AES_256_XTS_KEY_SIZE);
99 + sg_init_one(&dst_sg, derived_key, EXT4_AES_256_XTS_KEY_SIZE);
100 + ablkcipher_request_set_crypt(req, &src_sg, &dst_sg,
101 + EXT4_AES_256_XTS_KEY_SIZE, NULL);
102 + res = crypto_ablkcipher_encrypt(req);
103 + if (res == -EINPROGRESS || res == -EBUSY) {
104 + BUG_ON(req->base.data != &ecr);
105 + wait_for_completion(&ecr.completion);
106 + res = ecr.res;
107 + }
108 +
109 +out:
110 + if (req)
111 + ablkcipher_request_free(req);
112 + if (tfm)
113 + crypto_free_ablkcipher(tfm);
114 + return res;
115 +}
116 +
117 +/**
118 + * ext4_generate_encryption_key() - generates an encryption key
119 + * @inode: The inode to generate the encryption key for.
120 + */
121 +int ext4_generate_encryption_key(struct inode *inode)
122 +{
123 + struct ext4_inode_info *ei = EXT4_I(inode);
124 + struct ext4_encryption_key *crypt_key = &ei->i_encryption_key;
125 + char full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE +
126 + (EXT4_KEY_DESCRIPTOR_SIZE * 2) + 1];
127 + struct key *keyring_key = NULL;
128 + struct ext4_encryption_key *master_key;
129 + struct ext4_encryption_context ctx;
130 + struct user_key_payload *ukp;
131 + int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
132 + EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
133 + &ctx, sizeof(ctx));
134 +
135 + if (res != sizeof(ctx)) {
136 + if (res > 0)
137 + res = -EINVAL;
138 + goto out;
139 + }
140 + res = 0;
141 +
142 + memcpy(full_key_descriptor, EXT4_KEY_DESC_PREFIX,
143 + EXT4_KEY_DESC_PREFIX_SIZE);
144 + sprintf(full_key_descriptor + EXT4_KEY_DESC_PREFIX_SIZE,
145 + "%*phN", EXT4_KEY_DESCRIPTOR_SIZE,
146 + ctx.master_key_descriptor);
147 + full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE +
148 + (2 * EXT4_KEY_DESCRIPTOR_SIZE)] = '\0';
149 + keyring_key = request_key(&key_type_logon, full_key_descriptor, NULL);
150 + if (IS_ERR(keyring_key)) {
151 + res = PTR_ERR(keyring_key);
152 + keyring_key = NULL;
153 + goto out;
154 + }
155 + BUG_ON(keyring_key->type != &key_type_logon);
156 + ukp = ((struct user_key_payload *)keyring_key->payload.data);
157 + if (ukp->datalen != sizeof(struct ext4_encryption_key)) {
158 + res = -EINVAL;
159 + goto out;
160 + }
161 + master_key = (struct ext4_encryption_key *)ukp->data;
162 +
163 + if (S_ISREG(inode->i_mode))
164 + crypt_key->mode = ctx.contents_encryption_mode;
165 + else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
166 + crypt_key->mode = ctx.filenames_encryption_mode;
167 + else {
168 + printk(KERN_ERR "ext4 crypto: Unsupported inode type.\n");
169 + BUG();
170 + }
171 + crypt_key->size = ext4_encryption_key_size(crypt_key->mode);
172 + BUG_ON(!crypt_key->size);
173 + BUILD_BUG_ON(EXT4_AES_128_ECB_KEY_SIZE !=
174 + EXT4_KEY_DERIVATION_NONCE_SIZE);
175 + BUG_ON(master_key->size != EXT4_AES_256_XTS_KEY_SIZE);
176 + BUG_ON(crypt_key->size < EXT4_AES_256_CBC_KEY_SIZE);
177 + res = ext4_derive_key_aes(ctx.nonce, master_key->raw, crypt_key->raw);
178 +out:
179 + if (keyring_key)
180 + key_put(keyring_key);
181 + if (res < 0)
182 + crypt_key->mode = EXT4_ENCRYPTION_MODE_INVALID;
183 + return res;
184 +}
185 +
186 +int ext4_has_encryption_key(struct inode *inode)
187 +{
188 + struct ext4_inode_info *ei = EXT4_I(inode);
189 + struct ext4_encryption_key *crypt_key = &ei->i_encryption_key;
190 +
191 + return (crypt_key->mode != EXT4_ENCRYPTION_MODE_INVALID);
192 +}
193 diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
194 index 4533e94..b5255eb 100644
195 --- a/fs/ext4/ext4.h
196 +++ b/fs/ext4/ext4.h
197 @@ -2064,6 +2064,19 @@ static inline int ext4_sb_has_crypto(struct super_block *sb)
198 }
199 #endif
201 +/* crypto_key.c */
202 +int ext4_generate_encryption_key(struct inode *inode);
203 +
204 +#ifdef CONFIG_EXT4_FS_ENCRYPTION
205 +int ext4_has_encryption_key(struct inode *inode);
206 +#else
207 +static inline int ext4_has_encryption_key(struct inode *inode)
208 +{
209 + return 0;
210 +}
211 +#endif
212 +
213 +
214 /* dir.c */
215 extern int __ext4_check_dir_entry(const char *, unsigned int, struct inode *,
216 struct file *,
217 diff --git a/fs/ext4/ext4_crypto.h b/fs/ext4/ext4_crypto.h
218 index 9d5d2e5..6a7c0c0 100644
219 --- a/fs/ext4/ext4_crypto.h
220 +++ b/fs/ext4/ext4_crypto.h
221 @@ -55,6 +55,9 @@ struct ext4_encryption_context {
222 #define EXT4_AES_256_XTS_KEY_SIZE 64
223 #define EXT4_MAX_KEY_SIZE 64
225 +#define EXT4_KEY_DESC_PREFIX "ext4:"
226 +#define EXT4_KEY_DESC_PREFIX_SIZE 5
227 +
228 struct ext4_encryption_key {
229 uint32_t mode;
230 char raw[EXT4_MAX_KEY_SIZE];