2 * Encryption policy functions for per-file encryption support.
4 * Copyright (C) 2015, Google, Inc.
5 * Copyright (C) 2015, Motorola Mobility.
7 * Written by Michael Halcrow, 2015.
8 * Modified by Jaegeuk Kim, 2015.
11 #include <linux/random.h>
12 #include <linux/string.h>
13 #include <linux/fscrypto.h>
14 #include <linux/mount.h>
16 static int inode_has_encryption_context(struct inode
*inode
)
18 if (!inode
->i_sb
->s_cop
->get_context
)
20 return (inode
->i_sb
->s_cop
->get_context(inode
, NULL
, 0L) > 0);
24 * check whether the policy is consistent with the encryption context
27 static int is_encryption_context_consistent_with_policy(struct inode
*inode
,
28 const struct fscrypt_policy
*policy
)
30 struct fscrypt_context ctx
;
33 if (!inode
->i_sb
->s_cop
->get_context
)
36 res
= inode
->i_sb
->s_cop
->get_context(inode
, &ctx
, sizeof(ctx
));
37 if (res
!= sizeof(ctx
))
40 return (memcmp(ctx
.master_key_descriptor
, policy
->master_key_descriptor
,
41 FS_KEY_DESCRIPTOR_SIZE
) == 0 &&
42 (ctx
.flags
== policy
->flags
) &&
43 (ctx
.contents_encryption_mode
==
44 policy
->contents_encryption_mode
) &&
45 (ctx
.filenames_encryption_mode
==
46 policy
->filenames_encryption_mode
));
49 static int create_encryption_context_from_policy(struct inode
*inode
,
50 const struct fscrypt_policy
*policy
)
52 struct fscrypt_context ctx
;
55 if (!inode
->i_sb
->s_cop
->set_context
)
58 if (inode
->i_sb
->s_cop
->prepare_context
) {
59 res
= inode
->i_sb
->s_cop
->prepare_context(inode
);
64 ctx
.format
= FS_ENCRYPTION_CONTEXT_FORMAT_V1
;
65 memcpy(ctx
.master_key_descriptor
, policy
->master_key_descriptor
,
66 FS_KEY_DESCRIPTOR_SIZE
);
68 if (!fscrypt_valid_contents_enc_mode(
69 policy
->contents_encryption_mode
)) {
71 "%s: Invalid contents encryption mode %d\n", __func__
,
72 policy
->contents_encryption_mode
);
76 if (!fscrypt_valid_filenames_enc_mode(
77 policy
->filenames_encryption_mode
)) {
79 "%s: Invalid filenames encryption mode %d\n", __func__
,
80 policy
->filenames_encryption_mode
);
84 if (policy
->flags
& ~FS_POLICY_FLAGS_VALID
)
87 ctx
.contents_encryption_mode
= policy
->contents_encryption_mode
;
88 ctx
.filenames_encryption_mode
= policy
->filenames_encryption_mode
;
89 ctx
.flags
= policy
->flags
;
90 BUILD_BUG_ON(sizeof(ctx
.nonce
) != FS_KEY_DERIVATION_NONCE_SIZE
);
91 get_random_bytes(ctx
.nonce
, FS_KEY_DERIVATION_NONCE_SIZE
);
93 return inode
->i_sb
->s_cop
->set_context(inode
, &ctx
, sizeof(ctx
), NULL
);
96 int fscrypt_process_policy(struct file
*filp
,
97 const struct fscrypt_policy
*policy
)
99 struct inode
*inode
= file_inode(filp
);
102 if (!inode_owner_or_capable(inode
))
105 if (policy
->version
!= 0)
108 ret
= mnt_want_write_file(filp
);
112 if (!inode_has_encryption_context(inode
)) {
113 if (!S_ISDIR(inode
->i_mode
))
115 else if (!inode
->i_sb
->s_cop
->empty_dir
)
117 else if (!inode
->i_sb
->s_cop
->empty_dir(inode
))
120 ret
= create_encryption_context_from_policy(inode
,
122 } else if (!is_encryption_context_consistent_with_policy(inode
,
125 "%s: Policy inconsistent with encryption context\n",
130 mnt_drop_write_file(filp
);
133 EXPORT_SYMBOL(fscrypt_process_policy
);
135 int fscrypt_get_policy(struct inode
*inode
, struct fscrypt_policy
*policy
)
137 struct fscrypt_context ctx
;
140 if (!inode
->i_sb
->s_cop
->get_context
||
141 !inode
->i_sb
->s_cop
->is_encrypted(inode
))
144 res
= inode
->i_sb
->s_cop
->get_context(inode
, &ctx
, sizeof(ctx
));
145 if (res
!= sizeof(ctx
))
147 if (ctx
.format
!= FS_ENCRYPTION_CONTEXT_FORMAT_V1
)
151 policy
->contents_encryption_mode
= ctx
.contents_encryption_mode
;
152 policy
->filenames_encryption_mode
= ctx
.filenames_encryption_mode
;
153 policy
->flags
= ctx
.flags
;
154 memcpy(&policy
->master_key_descriptor
, ctx
.master_key_descriptor
,
155 FS_KEY_DESCRIPTOR_SIZE
);
158 EXPORT_SYMBOL(fscrypt_get_policy
);
160 int fscrypt_has_permitted_context(struct inode
*parent
, struct inode
*child
)
162 struct fscrypt_info
*parent_ci
, *child_ci
;
165 if ((parent
== NULL
) || (child
== NULL
)) {
166 printk(KERN_ERR
"parent %p child %p\n", parent
, child
);
170 /* no restrictions if the parent directory is not encrypted */
171 if (!parent
->i_sb
->s_cop
->is_encrypted(parent
))
173 /* if the child directory is not encrypted, this is always a problem */
174 if (!parent
->i_sb
->s_cop
->is_encrypted(child
))
176 res
= fscrypt_get_encryption_info(parent
);
179 res
= fscrypt_get_encryption_info(child
);
182 parent_ci
= parent
->i_crypt_info
;
183 child_ci
= child
->i_crypt_info
;
184 if (!parent_ci
&& !child_ci
)
186 if (!parent_ci
|| !child_ci
)
189 return (memcmp(parent_ci
->ci_master_key
,
190 child_ci
->ci_master_key
,
191 FS_KEY_DESCRIPTOR_SIZE
) == 0 &&
192 (parent_ci
->ci_data_mode
== child_ci
->ci_data_mode
) &&
193 (parent_ci
->ci_filename_mode
== child_ci
->ci_filename_mode
) &&
194 (parent_ci
->ci_flags
== child_ci
->ci_flags
));
196 EXPORT_SYMBOL(fscrypt_has_permitted_context
);
199 * fscrypt_inherit_context() - Sets a child context from its parent
200 * @parent: Parent inode from which the context is inherited.
201 * @child: Child inode that inherits the context from @parent.
202 * @fs_data: private data given by FS.
203 * @preload: preload child i_crypt_info
205 * Return: Zero on success, non-zero otherwise
207 int fscrypt_inherit_context(struct inode
*parent
, struct inode
*child
,
208 void *fs_data
, bool preload
)
210 struct fscrypt_context ctx
;
211 struct fscrypt_info
*ci
;
214 if (!parent
->i_sb
->s_cop
->set_context
)
217 res
= fscrypt_get_encryption_info(parent
);
221 ci
= parent
->i_crypt_info
;
225 ctx
.format
= FS_ENCRYPTION_CONTEXT_FORMAT_V1
;
226 if (fscrypt_dummy_context_enabled(parent
)) {
227 ctx
.contents_encryption_mode
= FS_ENCRYPTION_MODE_AES_256_XTS
;
228 ctx
.filenames_encryption_mode
= FS_ENCRYPTION_MODE_AES_256_CTS
;
230 memset(ctx
.master_key_descriptor
, 0x42, FS_KEY_DESCRIPTOR_SIZE
);
233 ctx
.contents_encryption_mode
= ci
->ci_data_mode
;
234 ctx
.filenames_encryption_mode
= ci
->ci_filename_mode
;
235 ctx
.flags
= ci
->ci_flags
;
236 memcpy(ctx
.master_key_descriptor
, ci
->ci_master_key
,
237 FS_KEY_DESCRIPTOR_SIZE
);
239 get_random_bytes(ctx
.nonce
, FS_KEY_DERIVATION_NONCE_SIZE
);
240 res
= parent
->i_sb
->s_cop
->set_context(child
, &ctx
,
241 sizeof(ctx
), fs_data
);
244 return preload
? fscrypt_get_encryption_info(child
): 0;
246 EXPORT_SYMBOL(fscrypt_inherit_context
);