blob: 0f9961eede1e74021c43c4943b2bb419ed09a198 [file] [log] [blame]
Jaegeuk Kim0b81d072015-05-15 16:26:10 -07001/*
2 * Encryption policy functions for per-file encryption support.
3 *
4 * Copyright (C) 2015, Google, Inc.
5 * Copyright (C) 2015, Motorola Mobility.
6 *
7 * Written by Michael Halcrow, 2015.
8 * Modified by Jaegeuk Kim, 2015.
9 */
10
11#include <linux/random.h>
12#include <linux/string.h>
13#include <linux/fscrypto.h>
14
15static int inode_has_encryption_context(struct inode *inode)
16{
17 if (!inode->i_sb->s_cop->get_context)
18 return 0;
19 return (inode->i_sb->s_cop->get_context(inode, NULL, 0L) > 0);
20}
21
22/*
23 * check whether the policy is consistent with the encryption context
24 * for the inode
25 */
26static int is_encryption_context_consistent_with_policy(struct inode *inode,
27 const struct fscrypt_policy *policy)
28{
29 struct fscrypt_context ctx;
30 int res;
31
32 if (!inode->i_sb->s_cop->get_context)
33 return 0;
34
35 res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
36 if (res != sizeof(ctx))
37 return 0;
38
39 return (memcmp(ctx.master_key_descriptor, policy->master_key_descriptor,
40 FS_KEY_DESCRIPTOR_SIZE) == 0 &&
41 (ctx.flags == policy->flags) &&
42 (ctx.contents_encryption_mode ==
43 policy->contents_encryption_mode) &&
44 (ctx.filenames_encryption_mode ==
45 policy->filenames_encryption_mode));
46}
47
48static int create_encryption_context_from_policy(struct inode *inode,
49 const struct fscrypt_policy *policy)
50{
51 struct fscrypt_context ctx;
52 int res;
53
54 if (!inode->i_sb->s_cop->set_context)
55 return -EOPNOTSUPP;
56
57 if (inode->i_sb->s_cop->prepare_context) {
58 res = inode->i_sb->s_cop->prepare_context(inode);
59 if (res)
60 return res;
61 }
62
63 ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
64 memcpy(ctx.master_key_descriptor, policy->master_key_descriptor,
65 FS_KEY_DESCRIPTOR_SIZE);
66
67 if (!fscrypt_valid_contents_enc_mode(
68 policy->contents_encryption_mode)) {
69 printk(KERN_WARNING
70 "%s: Invalid contents encryption mode %d\n", __func__,
71 policy->contents_encryption_mode);
72 return -EINVAL;
73 }
74
75 if (!fscrypt_valid_filenames_enc_mode(
76 policy->filenames_encryption_mode)) {
77 printk(KERN_WARNING
78 "%s: Invalid filenames encryption mode %d\n", __func__,
79 policy->filenames_encryption_mode);
80 return -EINVAL;
81 }
82
83 if (policy->flags & ~FS_POLICY_FLAGS_VALID)
84 return -EINVAL;
85
86 ctx.contents_encryption_mode = policy->contents_encryption_mode;
87 ctx.filenames_encryption_mode = policy->filenames_encryption_mode;
88 ctx.flags = policy->flags;
89 BUILD_BUG_ON(sizeof(ctx.nonce) != FS_KEY_DERIVATION_NONCE_SIZE);
90 get_random_bytes(ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE);
91
92 return inode->i_sb->s_cop->set_context(inode, &ctx, sizeof(ctx), NULL);
93}
94
95int fscrypt_process_policy(struct inode *inode,
96 const struct fscrypt_policy *policy)
97{
98 if (policy->version != 0)
99 return -EINVAL;
100
101 if (!inode_has_encryption_context(inode)) {
102 if (!inode->i_sb->s_cop->empty_dir)
103 return -EOPNOTSUPP;
104 if (!inode->i_sb->s_cop->empty_dir(inode))
105 return -ENOTEMPTY;
106 return create_encryption_context_from_policy(inode, policy);
107 }
108
109 if (is_encryption_context_consistent_with_policy(inode, policy))
110 return 0;
111
112 printk(KERN_WARNING "%s: Policy inconsistent with encryption context\n",
113 __func__);
114 return -EINVAL;
115}
116EXPORT_SYMBOL(fscrypt_process_policy);
117
118int fscrypt_get_policy(struct inode *inode, struct fscrypt_policy *policy)
119{
120 struct fscrypt_context ctx;
121 int res;
122
123 if (!inode->i_sb->s_cop->get_context ||
124 !inode->i_sb->s_cop->is_encrypted(inode))
125 return -ENODATA;
126
127 res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
128 if (res != sizeof(ctx))
129 return -ENODATA;
130 if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1)
131 return -EINVAL;
132
133 policy->version = 0;
134 policy->contents_encryption_mode = ctx.contents_encryption_mode;
135 policy->filenames_encryption_mode = ctx.filenames_encryption_mode;
136 policy->flags = ctx.flags;
137 memcpy(&policy->master_key_descriptor, ctx.master_key_descriptor,
138 FS_KEY_DESCRIPTOR_SIZE);
139 return 0;
140}
141EXPORT_SYMBOL(fscrypt_get_policy);
142
143int fscrypt_has_permitted_context(struct inode *parent, struct inode *child)
144{
145 struct fscrypt_info *parent_ci, *child_ci;
146 int res;
147
148 if ((parent == NULL) || (child == NULL)) {
149 printk(KERN_ERR "parent %p child %p\n", parent, child);
150 BUG_ON(1);
151 }
152
153 /* no restrictions if the parent directory is not encrypted */
154 if (!parent->i_sb->s_cop->is_encrypted(parent))
155 return 1;
156 /* if the child directory is not encrypted, this is always a problem */
157 if (!parent->i_sb->s_cop->is_encrypted(child))
158 return 0;
159 res = fscrypt_get_encryption_info(parent);
160 if (res)
161 return 0;
162 res = fscrypt_get_encryption_info(child);
163 if (res)
164 return 0;
165 parent_ci = parent->i_crypt_info;
166 child_ci = child->i_crypt_info;
167 if (!parent_ci && !child_ci)
168 return 1;
169 if (!parent_ci || !child_ci)
170 return 0;
171
172 return (memcmp(parent_ci->ci_master_key,
173 child_ci->ci_master_key,
174 FS_KEY_DESCRIPTOR_SIZE) == 0 &&
175 (parent_ci->ci_data_mode == child_ci->ci_data_mode) &&
176 (parent_ci->ci_filename_mode == child_ci->ci_filename_mode) &&
177 (parent_ci->ci_flags == child_ci->ci_flags));
178}
179EXPORT_SYMBOL(fscrypt_has_permitted_context);
180
181/**
182 * fscrypt_inherit_context() - Sets a child context from its parent
183 * @parent: Parent inode from which the context is inherited.
184 * @child: Child inode that inherits the context from @parent.
185 * @fs_data: private data given by FS.
186 * @preload: preload child i_crypt_info
187 *
188 * Return: Zero on success, non-zero otherwise
189 */
190int fscrypt_inherit_context(struct inode *parent, struct inode *child,
191 void *fs_data, bool preload)
192{
193 struct fscrypt_context ctx;
194 struct fscrypt_info *ci;
195 int res;
196
197 if (!parent->i_sb->s_cop->set_context)
198 return -EOPNOTSUPP;
199
200 res = fscrypt_get_encryption_info(parent);
201 if (res < 0)
202 return res;
203
204 ci = parent->i_crypt_info;
205 if (ci == NULL)
206 return -ENOKEY;
207
208 ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
209 if (fscrypt_dummy_context_enabled(parent)) {
210 ctx.contents_encryption_mode = FS_ENCRYPTION_MODE_AES_256_XTS;
211 ctx.filenames_encryption_mode = FS_ENCRYPTION_MODE_AES_256_CTS;
212 ctx.flags = 0;
213 memset(ctx.master_key_descriptor, 0x42, FS_KEY_DESCRIPTOR_SIZE);
214 res = 0;
215 } else {
216 ctx.contents_encryption_mode = ci->ci_data_mode;
217 ctx.filenames_encryption_mode = ci->ci_filename_mode;
218 ctx.flags = ci->ci_flags;
219 memcpy(ctx.master_key_descriptor, ci->ci_master_key,
220 FS_KEY_DESCRIPTOR_SIZE);
221 }
222 get_random_bytes(ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE);
223 res = parent->i_sb->s_cop->set_context(child, &ctx,
224 sizeof(ctx), fs_data);
225 if (res)
226 return res;
227 return preload ? fscrypt_get_encryption_info(child): 0;
228}
229EXPORT_SYMBOL(fscrypt_inherit_context);