2 * copied from linux/fs/ext4/crypto_policy.c
4 * Copyright (C) 2015, Google, Inc.
5 * Copyright (C) 2015, Motorola Mobility.
7 * This contains encryption policy functions for f2fs with some modifications
8 * to support f2fs-specific xattr APIs.
10 * Written by Michael Halcrow, 2015.
11 * Modified by Jaegeuk Kim, 2015.
13 #include <linux/random.h>
14 #include <linux/string.h>
15 #include <linux/types.h>
16 #include <linux/f2fs_fs.h>
21 static int f2fs_inode_has_encryption_context(struct inode *inode)
23 int res = f2fs_getxattr(inode, F2FS_XATTR_INDEX_ENCRYPTION,
24 F2FS_XATTR_NAME_ENCRYPTION_CONTEXT, NULL, 0, NULL);
29 * check whether the policy is consistent with the encryption context
32 static int f2fs_is_encryption_context_consistent_with_policy(
33 struct inode *inode, const struct f2fs_encryption_policy *policy)
35 struct f2fs_encryption_context ctx;
36 int res = f2fs_getxattr(inode, F2FS_XATTR_INDEX_ENCRYPTION,
37 F2FS_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
40 if (res != sizeof(ctx))
43 return (memcmp(ctx.master_key_descriptor, policy->master_key_descriptor,
44 F2FS_KEY_DESCRIPTOR_SIZE) == 0 &&
45 (ctx.flags == policy->flags) &&
46 (ctx.contents_encryption_mode ==
47 policy->contents_encryption_mode) &&
48 (ctx.filenames_encryption_mode ==
49 policy->filenames_encryption_mode));
52 static int f2fs_create_encryption_context_from_policy(
53 struct inode *inode, const struct f2fs_encryption_policy *policy)
55 struct f2fs_encryption_context ctx;
57 ctx.format = F2FS_ENCRYPTION_CONTEXT_FORMAT_V1;
58 memcpy(ctx.master_key_descriptor, policy->master_key_descriptor,
59 F2FS_KEY_DESCRIPTOR_SIZE);
61 if (!f2fs_valid_contents_enc_mode(policy->contents_encryption_mode)) {
63 "%s: Invalid contents encryption mode %d\n", __func__,
64 policy->contents_encryption_mode);
68 if (!f2fs_valid_filenames_enc_mode(policy->filenames_encryption_mode)) {
70 "%s: Invalid filenames encryption mode %d\n", __func__,
71 policy->filenames_encryption_mode);
75 if (policy->flags & ~F2FS_POLICY_FLAGS_VALID)
78 ctx.contents_encryption_mode = policy->contents_encryption_mode;
79 ctx.filenames_encryption_mode = policy->filenames_encryption_mode;
80 ctx.flags = policy->flags;
81 BUILD_BUG_ON(sizeof(ctx.nonce) != F2FS_KEY_DERIVATION_NONCE_SIZE);
82 get_random_bytes(ctx.nonce, F2FS_KEY_DERIVATION_NONCE_SIZE);
84 return f2fs_setxattr(inode, F2FS_XATTR_INDEX_ENCRYPTION,
85 F2FS_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
86 sizeof(ctx), NULL, XATTR_CREATE);
89 int f2fs_process_policy(const struct f2fs_encryption_policy *policy,
92 if (!inode_owner_or_capable(inode))
95 if (policy->version != 0)
98 if (!S_ISDIR(inode->i_mode))
101 if (!f2fs_inode_has_encryption_context(inode)) {
102 if (IS_DEADDIR(inode))
104 if (!f2fs_empty_dir(inode))
106 return f2fs_create_encryption_context_from_policy(inode,
110 if (f2fs_is_encryption_context_consistent_with_policy(inode, policy))
113 printk(KERN_WARNING "%s: Policy inconsistent with encryption context\n",
118 int f2fs_get_policy(struct inode *inode, struct f2fs_encryption_policy *policy)
120 struct f2fs_encryption_context ctx;
123 if (!f2fs_encrypted_inode(inode))
126 res = f2fs_getxattr(inode, F2FS_XATTR_INDEX_ENCRYPTION,
127 F2FS_XATTR_NAME_ENCRYPTION_CONTEXT,
128 &ctx, sizeof(ctx), NULL);
129 if (res != sizeof(ctx))
131 if (ctx.format != F2FS_ENCRYPTION_CONTEXT_FORMAT_V1)
135 policy->contents_encryption_mode = ctx.contents_encryption_mode;
136 policy->filenames_encryption_mode = ctx.filenames_encryption_mode;
137 policy->flags = ctx.flags;
138 memcpy(&policy->master_key_descriptor, ctx.master_key_descriptor,
139 F2FS_KEY_DESCRIPTOR_SIZE);
143 int f2fs_is_child_context_consistent_with_parent(struct inode *parent,
146 const struct f2fs_crypt_info *parent_ci, *child_ci;
147 struct f2fs_encryption_context parent_ctx, child_ctx;
150 /* No restrictions on file types which are never encrypted */
151 if (!S_ISREG(child->i_mode) && !S_ISDIR(child->i_mode) &&
152 !S_ISLNK(child->i_mode))
155 /* No restrictions if the parent directory is unencrypted */
156 if (!f2fs_encrypted_inode(parent))
159 /* Encrypted directories must not contain unencrypted files */
160 if (!f2fs_encrypted_inode(child))
164 * Both parent and child are encrypted, so verify they use the same
165 * encryption policy. Compare the fscrypt_info structs if the keys are
166 * available, otherwise retrieve and compare the fscrypt_contexts.
168 * Note that the fscrypt_context retrieval will be required frequently
169 * when accessing an encrypted directory tree without the key.
170 * Performance-wise this is not a big deal because we already don't
171 * really optimize for file access without the key (to the extent that
172 * such access is even possible), given that any attempted access
173 * already causes a fscrypt_context retrieval and keyring search.
175 * In any case, if an unexpected error occurs, fall back to "forbidden".
178 res = f2fs_get_encryption_info(parent);
181 res = f2fs_get_encryption_info(child);
184 parent_ci = F2FS_I(parent)->i_crypt_info;
185 child_ci = F2FS_I(child)->i_crypt_info;
186 if (parent_ci && child_ci) {
187 return memcmp(parent_ci->ci_master_key, child_ci->ci_master_key,
188 F2FS_KEY_DESCRIPTOR_SIZE) == 0 &&
189 (parent_ci->ci_data_mode == child_ci->ci_data_mode) &&
190 (parent_ci->ci_filename_mode ==
191 child_ci->ci_filename_mode) &&
192 (parent_ci->ci_flags == child_ci->ci_flags);
195 res = f2fs_getxattr(parent, F2FS_XATTR_INDEX_ENCRYPTION,
196 F2FS_XATTR_NAME_ENCRYPTION_CONTEXT,
197 &parent_ctx, sizeof(parent_ctx), NULL);
198 if (res != sizeof(parent_ctx))
201 res = f2fs_getxattr(child, F2FS_XATTR_INDEX_ENCRYPTION,
202 F2FS_XATTR_NAME_ENCRYPTION_CONTEXT,
203 &child_ctx, sizeof(child_ctx), NULL);
204 if (res != sizeof(child_ctx))
207 return memcmp(parent_ctx.master_key_descriptor,
208 child_ctx.master_key_descriptor,
209 F2FS_KEY_DESCRIPTOR_SIZE) == 0 &&
210 (parent_ctx.contents_encryption_mode ==
211 child_ctx.contents_encryption_mode) &&
212 (parent_ctx.filenames_encryption_mode ==
213 child_ctx.filenames_encryption_mode) &&
214 (parent_ctx.flags == child_ctx.flags);
218 * f2fs_inherit_context() - Sets a child context from its parent
219 * @parent: Parent inode from which the context is inherited.
220 * @child: Child inode that inherits the context from @parent.
222 * Return: Zero on success, non-zero otherwise
224 int f2fs_inherit_context(struct inode *parent, struct inode *child,
227 struct f2fs_encryption_context ctx;
228 struct f2fs_crypt_info *ci;
231 res = f2fs_get_encryption_info(parent);
235 ci = F2FS_I(parent)->i_crypt_info;
238 ctx.format = F2FS_ENCRYPTION_CONTEXT_FORMAT_V1;
240 ctx.contents_encryption_mode = ci->ci_data_mode;
241 ctx.filenames_encryption_mode = ci->ci_filename_mode;
242 ctx.flags = ci->ci_flags;
243 memcpy(ctx.master_key_descriptor, ci->ci_master_key,
244 F2FS_KEY_DESCRIPTOR_SIZE);
246 get_random_bytes(ctx.nonce, F2FS_KEY_DERIVATION_NONCE_SIZE);
247 return f2fs_setxattr(child, F2FS_XATTR_INDEX_ENCRYPTION,
248 F2FS_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
249 sizeof(ctx), ipage, XATTR_CREATE);