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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_jbd2.h"
16#include "ext4.h"
17#include "xattr.h"
18
19static int ext4_inode_has_encryption_context(struct inode *inode)
20{
21 int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
22 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, NULL, 0);
23 return (res > 0);
24}
25
26/*
27 * check whether the policy is consistent with the encryption context
28 * for the inode
29 */
30static int ext4_is_encryption_context_consistent_with_policy(
31 struct inode *inode, const struct ext4_encryption_policy *policy)
32{
33 struct ext4_encryption_context ctx;
34 int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
35 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
36 sizeof(ctx));
37 if (res != sizeof(ctx))
38 return 0;
39 return (memcmp(ctx.master_key_descriptor, policy->master_key_descriptor,
40 EXT4_KEY_DESCRIPTOR_SIZE) == 0 &&
41 (ctx.flags ==
42 policy->flags) &&
43 (ctx.contents_encryption_mode ==
44 policy->contents_encryption_mode) &&
45 (ctx.filenames_encryption_mode ==
46 policy->filenames_encryption_mode));
47}
48
49static int ext4_create_encryption_context_from_policy(
50 struct inode *inode, const struct ext4_encryption_policy *policy)
51{
52 struct ext4_encryption_context ctx;
53 handle_t *handle;
54 int res, res2;
55
56 res = ext4_convert_inline_data(inode);
57 if (res)
58 return res;
59
60 ctx.format = EXT4_ENCRYPTION_CONTEXT_FORMAT_V1;
61 memcpy(ctx.master_key_descriptor, policy->master_key_descriptor,
62 EXT4_KEY_DESCRIPTOR_SIZE);
63 if (!ext4_valid_contents_enc_mode(policy->contents_encryption_mode)) {
64 printk(KERN_WARNING
65 "%s: Invalid contents encryption mode %d\n", __func__,
66 policy->contents_encryption_mode);
67 return -EINVAL;
68 }
69 if (!ext4_valid_filenames_enc_mode(policy->filenames_encryption_mode)) {
70 printk(KERN_WARNING
71 "%s: Invalid filenames encryption mode %d\n", __func__,
72 policy->filenames_encryption_mode);
73 return -EINVAL;
74 }
75 if (policy->flags & ~EXT4_POLICY_FLAGS_VALID)
76 return -EINVAL;
77 ctx.contents_encryption_mode = policy->contents_encryption_mode;
78 ctx.filenames_encryption_mode = policy->filenames_encryption_mode;
79 ctx.flags = policy->flags;
80 BUILD_BUG_ON(sizeof(ctx.nonce) != EXT4_KEY_DERIVATION_NONCE_SIZE);
81 get_random_bytes(ctx.nonce, EXT4_KEY_DERIVATION_NONCE_SIZE);
82
83 handle = ext4_journal_start(inode, EXT4_HT_MISC,
84 ext4_jbd2_credits_xattr(inode));
85 if (IS_ERR(handle))
86 return PTR_ERR(handle);
87 res = ext4_xattr_set(inode, EXT4_XATTR_INDEX_ENCRYPTION,
88 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
89 sizeof(ctx), 0);
90 if (!res) {
91 ext4_set_inode_flag(inode, EXT4_INODE_ENCRYPT);
92 res = ext4_mark_inode_dirty(handle, inode);
93 if (res)
94 EXT4_ERROR_INODE(inode, "Failed to mark inode dirty");
95 }
96 res2 = ext4_journal_stop(handle);
97 if (!res)
98 res = res2;
99 return res;
100}
101
102int ext4_process_policy(const struct ext4_encryption_policy *policy,
103 struct inode *inode)
104{
105 if (policy->version != 0)
106 return -EINVAL;
107
108 if (!ext4_inode_has_encryption_context(inode)) {
109 if (!S_ISDIR(inode->i_mode))
110 return -EINVAL;
111 if (!ext4_empty_dir(inode))
112 return -ENOTEMPTY;
113 return ext4_create_encryption_context_from_policy(inode,
114 policy);
115 }
116
117 if (ext4_is_encryption_context_consistent_with_policy(inode, policy))
118 return 0;
119
120 printk(KERN_WARNING "%s: Policy inconsistent with encryption context\n",
121 __func__);
122 return -EINVAL;
123}
124
125int ext4_get_policy(struct inode *inode, struct ext4_encryption_policy *policy)
126{
127 struct ext4_encryption_context ctx;
128
129 int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
130 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
131 &ctx, sizeof(ctx));
132 if (res != sizeof(ctx))
133 return -ENOENT;
134 if (ctx.format != EXT4_ENCRYPTION_CONTEXT_FORMAT_V1)
135 return -EINVAL;
136 policy->version = 0;
137 policy->contents_encryption_mode = ctx.contents_encryption_mode;
138 policy->filenames_encryption_mode = ctx.filenames_encryption_mode;
139 policy->flags = ctx.flags;
140 memcpy(&policy->master_key_descriptor, ctx.master_key_descriptor,
141 EXT4_KEY_DESCRIPTOR_SIZE);
142 return 0;
143}
144
145int ext4_is_child_context_consistent_with_parent(struct inode *parent,
146 struct inode *child)
147{
148 struct ext4_crypt_info *parent_ci, *child_ci;
149 int res;
150
151 if ((parent == NULL) || (child == NULL)) {
152 pr_err("parent %p child %p\n", parent, child);
153 WARN_ON(1); /* Should never happen */
154 return 0;
155 }
156 /* no restrictions if the parent directory is not encrypted */
157 if (!ext4_encrypted_inode(parent))
158 return 1;
159 /* if the child directory is not encrypted, this is always a problem */
160 if (!ext4_encrypted_inode(child))
161 return 0;
162 res = ext4_get_encryption_info(parent);
163 if (res)
164 return 0;
165 res = ext4_get_encryption_info(child);
166 if (res)
167 return 0;
168 parent_ci = EXT4_I(parent)->i_crypt_info;
169 child_ci = EXT4_I(child)->i_crypt_info;
170 if (!parent_ci && !child_ci)
171 return 1;
172 if (!parent_ci || !child_ci)
173 return 0;
174
175 return (memcmp(parent_ci->ci_master_key,
176 child_ci->ci_master_key,
177 EXT4_KEY_DESCRIPTOR_SIZE) == 0 &&
178 (parent_ci->ci_data_mode == child_ci->ci_data_mode) &&
179 (parent_ci->ci_filename_mode == child_ci->ci_filename_mode) &&
180 (parent_ci->ci_flags == child_ci->ci_flags));
181}
182
183/**
184 * ext4_inherit_context() - Sets a child context from its parent
185 * @parent: Parent inode from which the context is inherited.
186 * @child: Child inode that inherits the context from @parent.
187 *
188 * Return: Zero on success, non-zero otherwise
189 */
190int ext4_inherit_context(struct inode *parent, struct inode *child)
191{
192 struct ext4_encryption_context ctx;
193 struct ext4_crypt_info *ci;
194 int res;
195
196 res = ext4_get_encryption_info(parent);
197 if (res < 0)
198 return res;
199 ci = EXT4_I(parent)->i_crypt_info;
200 if (ci == NULL)
201 return -ENOKEY;
202
203 ctx.format = EXT4_ENCRYPTION_CONTEXT_FORMAT_V1;
204 if (DUMMY_ENCRYPTION_ENABLED(EXT4_SB(parent->i_sb))) {
205 ctx.contents_encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS;
206 ctx.filenames_encryption_mode =
207 EXT4_ENCRYPTION_MODE_AES_256_CTS;
208 ctx.flags = 0;
209 memset(ctx.master_key_descriptor, 0x42,
210 EXT4_KEY_DESCRIPTOR_SIZE);
211 res = 0;
212 } else {
213 ctx.contents_encryption_mode = ci->ci_data_mode;
214 ctx.filenames_encryption_mode = ci->ci_filename_mode;
215 ctx.flags = ci->ci_flags;
216 memcpy(ctx.master_key_descriptor, ci->ci_master_key,
217 EXT4_KEY_DESCRIPTOR_SIZE);
218 }
219 get_random_bytes(ctx.nonce, EXT4_KEY_DERIVATION_NONCE_SIZE);
220 res = ext4_xattr_set(child, EXT4_XATTR_INDEX_ENCRYPTION,
221 EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
222 sizeof(ctx), 0);
223 if (!res) {
224 ext4_set_inode_flag(child, EXT4_INODE_ENCRYPT);
225 ext4_clear_inode_state(child, EXT4_STATE_MAY_INLINE_DATA);
226 res = ext4_get_encryption_info(child);
227 }
228 return res;
229}