1 /*
2 * linux/fs/ext4/crypto_policy.c
3 *
4 * Copyright (C) 2015, Google, Inc.
5 *
6 * This contains encryption policy functions for ext4
7 *
8 * Written by Michael Halcrow, 2015.
9 */
10
11 #include <linux/random.h>
12 #include <linux/string.h>
13 #include <linux/types.h>
14
15 #include "ext4.h"
16 #include "xattr.h"
17
ext4_inode_has_encryption_context(struct inode * inode)18 static int ext4_inode_has_encryption_context(struct inode *inode)
19 {
20 int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
21 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, NULL, 0);
22 return (res > 0);
23 }
24
25 /*
26 * check whether the policy is consistent with the encryption context
27 * for the inode
28 */
ext4_is_encryption_context_consistent_with_policy(struct inode * inode,const struct ext4_encryption_policy * policy)29 static int ext4_is_encryption_context_consistent_with_policy(
30 struct inode *inode, const struct ext4_encryption_policy *policy)
31 {
32 struct ext4_encryption_context ctx;
33 int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
34 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
35 sizeof(ctx));
36 if (res != sizeof(ctx))
37 return 0;
38 return (memcmp(ctx.master_key_descriptor, policy->master_key_descriptor,
39 EXT4_KEY_DESCRIPTOR_SIZE) == 0 &&
40 (ctx.flags ==
41 policy->flags) &&
42 (ctx.contents_encryption_mode ==
43 policy->contents_encryption_mode) &&
44 (ctx.filenames_encryption_mode ==
45 policy->filenames_encryption_mode));
46 }
47
ext4_create_encryption_context_from_policy(struct inode * inode,const struct ext4_encryption_policy * policy)48 static int ext4_create_encryption_context_from_policy(
49 struct inode *inode, const struct ext4_encryption_policy *policy)
50 {
51 struct ext4_encryption_context ctx;
52 int res = 0;
53
54 res = ext4_convert_inline_data(inode);
55 if (res)
56 return res;
57
58 ctx.format = EXT4_ENCRYPTION_CONTEXT_FORMAT_V1;
59 memcpy(ctx.master_key_descriptor, policy->master_key_descriptor,
60 EXT4_KEY_DESCRIPTOR_SIZE);
61 if (!ext4_valid_contents_enc_mode(policy->contents_encryption_mode)) {
62 printk(KERN_WARNING
63 "%s: Invalid contents encryption mode %d\n", __func__,
64 policy->contents_encryption_mode);
65 return -EINVAL;
66 }
67 if (!ext4_valid_filenames_enc_mode(policy->filenames_encryption_mode)) {
68 printk(KERN_WARNING
69 "%s: Invalid filenames encryption mode %d\n", __func__,
70 policy->filenames_encryption_mode);
71 return -EINVAL;
72 }
73 if (policy->flags & ~EXT4_POLICY_FLAGS_VALID)
74 return -EINVAL;
75 ctx.contents_encryption_mode = policy->contents_encryption_mode;
76 ctx.filenames_encryption_mode = policy->filenames_encryption_mode;
77 ctx.flags = policy->flags;
78 BUILD_BUG_ON(sizeof(ctx.nonce) != EXT4_KEY_DERIVATION_NONCE_SIZE);
79 get_random_bytes(ctx.nonce, EXT4_KEY_DERIVATION_NONCE_SIZE);
80
81 res = ext4_xattr_set(inode, EXT4_XATTR_INDEX_ENCRYPTION,
82 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
83 sizeof(ctx), 0);
84 if (!res)
85 ext4_set_inode_flag(inode, EXT4_INODE_ENCRYPT);
86 return res;
87 }
88
ext4_process_policy(const struct ext4_encryption_policy * policy,struct inode * inode)89 int ext4_process_policy(const struct ext4_encryption_policy *policy,
90 struct inode *inode)
91 {
92 if (policy->version != 0)
93 return -EINVAL;
94
95 if (!ext4_inode_has_encryption_context(inode)) {
96 if (!S_ISDIR(inode->i_mode))
97 return -EINVAL;
98 if (!ext4_empty_dir(inode))
99 return -ENOTEMPTY;
100 return ext4_create_encryption_context_from_policy(inode,
101 policy);
102 }
103
104 if (ext4_is_encryption_context_consistent_with_policy(inode, policy))
105 return 0;
106
107 printk(KERN_WARNING "%s: Policy inconsistent with encryption context\n",
108 __func__);
109 return -EINVAL;
110 }
111
ext4_get_policy(struct inode * inode,struct ext4_encryption_policy * policy)112 int ext4_get_policy(struct inode *inode, struct ext4_encryption_policy *policy)
113 {
114 struct ext4_encryption_context ctx;
115
116 int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
117 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
118 &ctx, sizeof(ctx));
119 if (res != sizeof(ctx))
120 return -ENOENT;
121 if (ctx.format != EXT4_ENCRYPTION_CONTEXT_FORMAT_V1)
122 return -EINVAL;
123 policy->version = 0;
124 policy->contents_encryption_mode = ctx.contents_encryption_mode;
125 policy->filenames_encryption_mode = ctx.filenames_encryption_mode;
126 policy->flags = ctx.flags;
127 memcpy(&policy->master_key_descriptor, ctx.master_key_descriptor,
128 EXT4_KEY_DESCRIPTOR_SIZE);
129 return 0;
130 }
131
ext4_is_child_context_consistent_with_parent(struct inode * parent,struct inode * child)132 int ext4_is_child_context_consistent_with_parent(struct inode *parent,
133 struct inode *child)
134 {
135 struct ext4_crypt_info *parent_ci, *child_ci;
136 int res;
137
138 if ((parent == NULL) || (child == NULL)) {
139 pr_err("parent %p child %p\n", parent, child);
140 BUG_ON(1);
141 }
142 /* no restrictions if the parent directory is not encrypted */
143 if (!ext4_encrypted_inode(parent))
144 return 1;
145 /* if the child directory is not encrypted, this is always a problem */
146 if (!ext4_encrypted_inode(child))
147 return 0;
148 res = ext4_get_encryption_info(parent);
149 if (res)
150 return 0;
151 res = ext4_get_encryption_info(child);
152 if (res)
153 return 0;
154 parent_ci = EXT4_I(parent)->i_crypt_info;
155 child_ci = EXT4_I(child)->i_crypt_info;
156 if (!parent_ci && !child_ci)
157 return 1;
158 if (!parent_ci || !child_ci)
159 return 0;
160
161 return (memcmp(parent_ci->ci_master_key,
162 child_ci->ci_master_key,
163 EXT4_KEY_DESCRIPTOR_SIZE) == 0 &&
164 (parent_ci->ci_data_mode == child_ci->ci_data_mode) &&
165 (parent_ci->ci_filename_mode == child_ci->ci_filename_mode) &&
166 (parent_ci->ci_flags == child_ci->ci_flags));
167 }
168
169 /**
170 * ext4_inherit_context() - Sets a child context from its parent
171 * @parent: Parent inode from which the context is inherited.
172 * @child: Child inode that inherits the context from @parent.
173 *
174 * Return: Zero on success, non-zero otherwise
175 */
ext4_inherit_context(struct inode * parent,struct inode * child)176 int ext4_inherit_context(struct inode *parent, struct inode *child)
177 {
178 struct ext4_encryption_context ctx;
179 struct ext4_crypt_info *ci;
180 int res;
181
182 res = ext4_get_encryption_info(parent);
183 if (res < 0)
184 return res;
185 ci = EXT4_I(parent)->i_crypt_info;
186 if (ci == NULL)
187 return -ENOKEY;
188
189 ctx.format = EXT4_ENCRYPTION_CONTEXT_FORMAT_V1;
190 if (DUMMY_ENCRYPTION_ENABLED(EXT4_SB(parent->i_sb))) {
191 ctx.contents_encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS;
192 ctx.filenames_encryption_mode =
193 EXT4_ENCRYPTION_MODE_AES_256_CTS;
194 ctx.flags = 0;
195 memset(ctx.master_key_descriptor, 0x42,
196 EXT4_KEY_DESCRIPTOR_SIZE);
197 res = 0;
198 } else {
199 ctx.contents_encryption_mode = ci->ci_data_mode;
200 ctx.filenames_encryption_mode = ci->ci_filename_mode;
201 ctx.flags = ci->ci_flags;
202 memcpy(ctx.master_key_descriptor, ci->ci_master_key,
203 EXT4_KEY_DESCRIPTOR_SIZE);
204 }
205 get_random_bytes(ctx.nonce, EXT4_KEY_DERIVATION_NONCE_SIZE);
206 res = ext4_xattr_set(child, EXT4_XATTR_INDEX_ENCRYPTION,
207 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
208 sizeof(ctx), 0);
209 if (!res) {
210 ext4_set_inode_flag(child, EXT4_INODE_ENCRYPT);
211 ext4_clear_inode_state(child, EXT4_STATE_MAY_INLINE_DATA);
212 res = ext4_get_encryption_info(child);
213 }
214 return res;
215 }
216