Merge remote-tracking branch 'lts/linux-4.4.y' into linux-linaro-lsk-v4.4
[firefly-linux-kernel-4.4.55.git] / fs / ext4 / crypto_policy.c
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
19 static 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  */
30 static 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
49 static 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
102 int ext4_process_policy(const struct ext4_encryption_policy *policy,
103                         struct inode *inode)
104 {
105         if (!inode_owner_or_capable(inode))
106                 return -EACCES;
107
108         if (policy->version != 0)
109                 return -EINVAL;
110
111         if (!ext4_inode_has_encryption_context(inode)) {
112                 if (!S_ISDIR(inode->i_mode))
113                         return -EINVAL;
114                 if (!ext4_empty_dir(inode))
115                         return -ENOTEMPTY;
116                 return ext4_create_encryption_context_from_policy(inode,
117                                                                   policy);
118         }
119
120         if (ext4_is_encryption_context_consistent_with_policy(inode, policy))
121                 return 0;
122
123         printk(KERN_WARNING "%s: Policy inconsistent with encryption context\n",
124                __func__);
125         return -EINVAL;
126 }
127
128 int ext4_get_policy(struct inode *inode, struct ext4_encryption_policy *policy)
129 {
130         struct ext4_encryption_context ctx;
131
132         int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
133                                  EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
134                                  &ctx, sizeof(ctx));
135         if (res != sizeof(ctx))
136                 return -ENOENT;
137         if (ctx.format != EXT4_ENCRYPTION_CONTEXT_FORMAT_V1)
138                 return -EINVAL;
139         policy->version = 0;
140         policy->contents_encryption_mode = ctx.contents_encryption_mode;
141         policy->filenames_encryption_mode = ctx.filenames_encryption_mode;
142         policy->flags = ctx.flags;
143         memcpy(&policy->master_key_descriptor, ctx.master_key_descriptor,
144                EXT4_KEY_DESCRIPTOR_SIZE);
145         return 0;
146 }
147
148 int ext4_is_child_context_consistent_with_parent(struct inode *parent,
149                                                  struct inode *child)
150 {
151         struct ext4_crypt_info *parent_ci, *child_ci;
152         int res;
153
154         if ((parent == NULL) || (child == NULL)) {
155                 pr_err("parent %p child %p\n", parent, child);
156                 WARN_ON(1);     /* Should never happen */
157                 return 0;
158         }
159         /* no restrictions if the parent directory is not encrypted */
160         if (!ext4_encrypted_inode(parent))
161                 return 1;
162         /* if the child directory is not encrypted, this is always a problem */
163         if (!ext4_encrypted_inode(child))
164                 return 0;
165         res = ext4_get_encryption_info(parent);
166         if (res)
167                 return 0;
168         res = ext4_get_encryption_info(child);
169         if (res)
170                 return 0;
171         parent_ci = EXT4_I(parent)->i_crypt_info;
172         child_ci = EXT4_I(child)->i_crypt_info;
173         if (!parent_ci && !child_ci)
174                 return 1;
175         if (!parent_ci || !child_ci)
176                 return 0;
177
178         return (memcmp(parent_ci->ci_master_key,
179                        child_ci->ci_master_key,
180                        EXT4_KEY_DESCRIPTOR_SIZE) == 0 &&
181                 (parent_ci->ci_data_mode == child_ci->ci_data_mode) &&
182                 (parent_ci->ci_filename_mode == child_ci->ci_filename_mode) &&
183                 (parent_ci->ci_flags == child_ci->ci_flags));
184 }
185
186 /**
187  * ext4_inherit_context() - Sets a child context from its parent
188  * @parent: Parent inode from which the context is inherited.
189  * @child:  Child inode that inherits the context from @parent.
190  *
191  * Return: Zero on success, non-zero otherwise
192  */
193 int ext4_inherit_context(struct inode *parent, struct inode *child)
194 {
195         struct ext4_encryption_context ctx;
196         struct ext4_crypt_info *ci;
197         int res;
198
199         res = ext4_get_encryption_info(parent);
200         if (res < 0)
201                 return res;
202         ci = EXT4_I(parent)->i_crypt_info;
203         if (ci == NULL)
204                 return -ENOKEY;
205
206         ctx.format = EXT4_ENCRYPTION_CONTEXT_FORMAT_V1;
207         if (DUMMY_ENCRYPTION_ENABLED(EXT4_SB(parent->i_sb))) {
208                 ctx.contents_encryption_mode = EXT4_ENCRYPTION_MODE_AES_256_XTS;
209                 ctx.filenames_encryption_mode =
210                         EXT4_ENCRYPTION_MODE_AES_256_CTS;
211                 ctx.flags = 0;
212                 memset(ctx.master_key_descriptor, 0x42,
213                        EXT4_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                        EXT4_KEY_DESCRIPTOR_SIZE);
221         }
222         get_random_bytes(ctx.nonce, EXT4_KEY_DERIVATION_NONCE_SIZE);
223         res = ext4_xattr_set(child, EXT4_XATTR_INDEX_ENCRYPTION,
224                              EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
225                              sizeof(ctx), 0);
226         if (!res) {
227                 ext4_set_inode_flag(child, EXT4_INODE_ENCRYPT);
228                 ext4_clear_inode_state(child, EXT4_STATE_MAY_INLINE_DATA);
229                 res = ext4_get_encryption_info(child);
230         }
231         return res;
232 }