2 * linux/fs/ext4/crypto_policy.c
4 * Copyright (C) 2015, Google, Inc.
6 * This contains encryption policy functions for ext4
8 * Written by Michael Halcrow, 2015.
11 #include <linux/random.h>
12 #include <linux/string.h>
13 #include <linux/types.h>
18 static int ext4_inode_has_encryption_context(struct inode
*inode
)
20 int res
= ext4_xattr_get(inode
, EXT4_XATTR_INDEX_ENCRYPTION
,
21 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT
, NULL
, 0);
26 * check whether the policy is consistent with the encryption context
29 static int ext4_is_encryption_context_consistent_with_policy(
30 struct inode
*inode
, const struct ext4_encryption_policy
*policy
)
32 struct ext4_encryption_context ctx
;
33 int res
= ext4_xattr_get(inode
, EXT4_XATTR_INDEX_ENCRYPTION
,
34 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT
, &ctx
,
36 if (res
!= sizeof(ctx
))
38 return (memcmp(ctx
.master_key_descriptor
, policy
->master_key_descriptor
,
39 EXT4_KEY_DESCRIPTOR_SIZE
) == 0 &&
40 (ctx
.contents_encryption_mode
==
41 policy
->contents_encryption_mode
) &&
42 (ctx
.filenames_encryption_mode
==
43 policy
->filenames_encryption_mode
));
46 static int ext4_create_encryption_context_from_policy(
47 struct inode
*inode
, const struct ext4_encryption_policy
*policy
)
49 struct ext4_encryption_context ctx
;
52 ctx
.format
= EXT4_ENCRYPTION_CONTEXT_FORMAT_V1
;
53 memcpy(ctx
.master_key_descriptor
, policy
->master_key_descriptor
,
54 EXT4_KEY_DESCRIPTOR_SIZE
);
55 if (!ext4_valid_contents_enc_mode(policy
->contents_encryption_mode
)) {
57 "%s: Invalid contents encryption mode %d\n", __func__
,
58 policy
->contents_encryption_mode
);
62 if (!ext4_valid_filenames_enc_mode(policy
->filenames_encryption_mode
)) {
64 "%s: Invalid filenames encryption mode %d\n", __func__
,
65 policy
->filenames_encryption_mode
);
69 ctx
.contents_encryption_mode
= policy
->contents_encryption_mode
;
70 ctx
.filenames_encryption_mode
= policy
->filenames_encryption_mode
;
71 BUILD_BUG_ON(sizeof(ctx
.nonce
) != EXT4_KEY_DERIVATION_NONCE_SIZE
);
72 get_random_bytes(ctx
.nonce
, EXT4_KEY_DERIVATION_NONCE_SIZE
);
74 res
= ext4_xattr_set(inode
, EXT4_XATTR_INDEX_ENCRYPTION
,
75 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT
, &ctx
,
79 ext4_set_inode_flag(inode
, EXT4_INODE_ENCRYPT
);
83 int ext4_process_policy(const struct ext4_encryption_policy
*policy
,
86 if (policy
->version
!= 0)
89 if (!ext4_inode_has_encryption_context(inode
)) {
90 if (!ext4_empty_dir(inode
))
92 return ext4_create_encryption_context_from_policy(inode
,
96 if (ext4_is_encryption_context_consistent_with_policy(inode
, policy
))
99 printk(KERN_WARNING
"%s: Policy inconsistent with encryption context\n",
104 int ext4_get_policy(struct inode
*inode
, struct ext4_encryption_policy
*policy
)
106 struct ext4_encryption_context ctx
;
108 int res
= ext4_xattr_get(inode
, EXT4_XATTR_INDEX_ENCRYPTION
,
109 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT
,
111 if (res
!= sizeof(ctx
))
113 if (ctx
.format
!= EXT4_ENCRYPTION_CONTEXT_FORMAT_V1
)
116 policy
->contents_encryption_mode
= ctx
.contents_encryption_mode
;
117 policy
->filenames_encryption_mode
= ctx
.filenames_encryption_mode
;
118 memcpy(&policy
->master_key_descriptor
, ctx
.master_key_descriptor
,
119 EXT4_KEY_DESCRIPTOR_SIZE
);
123 int ext4_is_child_context_consistent_with_parent(struct inode
*parent
,
126 struct ext4_encryption_context parent_ctx
, child_ctx
;
129 if ((parent
== NULL
) || (child
== NULL
)) {
130 pr_err("parent %p child %p\n", parent
, child
);
133 /* no restrictions if the parent directory is not encrypted */
134 if (!ext4_encrypted_inode(parent
))
136 res
= ext4_xattr_get(parent
, EXT4_XATTR_INDEX_ENCRYPTION
,
137 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT
,
138 &parent_ctx
, sizeof(parent_ctx
));
139 if (res
!= sizeof(parent_ctx
))
141 /* if the child directory is not encrypted, this is always a problem */
142 if (!ext4_encrypted_inode(child
))
144 res
= ext4_xattr_get(child
, EXT4_XATTR_INDEX_ENCRYPTION
,
145 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT
,
146 &child_ctx
, sizeof(child_ctx
));
147 if (res
!= sizeof(child_ctx
))
149 return (memcmp(parent_ctx
.master_key_descriptor
,
150 child_ctx
.master_key_descriptor
,
151 EXT4_KEY_DESCRIPTOR_SIZE
) == 0 &&
152 (parent_ctx
.contents_encryption_mode
==
153 child_ctx
.contents_encryption_mode
) &&
154 (parent_ctx
.filenames_encryption_mode
==
155 child_ctx
.filenames_encryption_mode
));
159 * ext4_inherit_context() - Sets a child context from its parent
160 * @parent: Parent inode from which the context is inherited.
161 * @child: Child inode that inherits the context from @parent.
163 * Return: Zero on success, non-zero otherwise
165 int ext4_inherit_context(struct inode
*parent
, struct inode
*child
)
167 struct ext4_encryption_context ctx
;
168 int res
= ext4_xattr_get(parent
, EXT4_XATTR_INDEX_ENCRYPTION
,
169 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT
,
172 if (res
!= sizeof(ctx
)) {
173 if (DUMMY_ENCRYPTION_ENABLED(EXT4_SB(parent
->i_sb
))) {
174 ctx
.format
= EXT4_ENCRYPTION_CONTEXT_FORMAT_V1
;
175 ctx
.contents_encryption_mode
=
176 EXT4_ENCRYPTION_MODE_AES_256_XTS
;
177 ctx
.filenames_encryption_mode
=
178 EXT4_ENCRYPTION_MODE_AES_256_CTS
;
179 memset(ctx
.master_key_descriptor
, 0x42,
180 EXT4_KEY_DESCRIPTOR_SIZE
);
186 get_random_bytes(ctx
.nonce
, EXT4_KEY_DERIVATION_NONCE_SIZE
);
187 res
= ext4_xattr_set(child
, EXT4_XATTR_INDEX_ENCRYPTION
,
188 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT
, &ctx
,
192 ext4_set_inode_flag(child
, EXT4_INODE_ENCRYPT
);