2 * Encryption policy functions for per-file encryption support.
4 * Copyright (C) 2015, Google, Inc.
5 * Copyright (C) 2015, Motorola Mobility.
7 * Written by Michael Halcrow, 2015.
8 * Modified by Jaegeuk Kim, 2015.
11 #include <linux/random.h>
12 #include <linux/string.h>
13 #include <linux/mount.h>
14 #include "fscrypt_private.h"
17 * check whether an encryption policy is consistent with an encryption context
19 static bool is_encryption_context_consistent_with_policy(
20 const struct fscrypt_context *ctx,
21 const struct fscrypt_policy *policy)
23 return memcmp(ctx->master_key_descriptor, policy->master_key_descriptor,
24 FS_KEY_DESCRIPTOR_SIZE) == 0 &&
25 (ctx->flags == policy->flags) &&
26 (ctx->contents_encryption_mode ==
27 policy->contents_encryption_mode) &&
28 (ctx->filenames_encryption_mode ==
29 policy->filenames_encryption_mode);
32 static int create_encryption_context_from_policy(struct inode *inode,
33 const struct fscrypt_policy *policy)
35 struct fscrypt_context ctx;
38 if (!inode->i_sb->s_cop->set_context)
41 if (inode->i_sb->s_cop->prepare_context) {
42 res = inode->i_sb->s_cop->prepare_context(inode);
47 ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
48 memcpy(ctx.master_key_descriptor, policy->master_key_descriptor,
49 FS_KEY_DESCRIPTOR_SIZE);
51 if (!fscrypt_valid_contents_enc_mode(
52 policy->contents_encryption_mode))
55 if (!fscrypt_valid_filenames_enc_mode(
56 policy->filenames_encryption_mode))
59 if (policy->flags & ~FS_POLICY_FLAGS_VALID)
62 ctx.contents_encryption_mode = policy->contents_encryption_mode;
63 ctx.filenames_encryption_mode = policy->filenames_encryption_mode;
64 ctx.flags = policy->flags;
65 BUILD_BUG_ON(sizeof(ctx.nonce) != FS_KEY_DERIVATION_NONCE_SIZE);
66 get_random_bytes(ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE);
68 return inode->i_sb->s_cop->set_context(inode, &ctx, sizeof(ctx), NULL);
71 int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg)
73 struct fscrypt_policy policy;
74 struct inode *inode = file_inode(filp);
76 struct fscrypt_context ctx;
78 if (copy_from_user(&policy, arg, sizeof(policy)))
81 if (!inode_owner_or_capable(inode))
84 if (policy.version != 0)
87 ret = mnt_want_write_file(filp);
93 ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
94 if (ret == -ENODATA) {
95 if (!S_ISDIR(inode->i_mode))
97 else if (!inode->i_sb->s_cop->empty_dir)
99 else if (!inode->i_sb->s_cop->empty_dir(inode))
102 ret = create_encryption_context_from_policy(inode,
104 } else if (ret == sizeof(ctx) &&
105 is_encryption_context_consistent_with_policy(&ctx,
107 /* The file already uses the same encryption policy. */
109 } else if (ret >= 0 || ret == -ERANGE) {
110 /* The file already uses a different encryption policy. */
116 mnt_drop_write_file(filp);
119 EXPORT_SYMBOL(fscrypt_ioctl_set_policy);
121 int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg)
123 struct inode *inode = file_inode(filp);
124 struct fscrypt_context ctx;
125 struct fscrypt_policy policy;
128 if (!inode->i_sb->s_cop->get_context ||
129 !inode->i_sb->s_cop->is_encrypted(inode))
132 res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
133 if (res < 0 && res != -ERANGE)
135 if (res != sizeof(ctx))
137 if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1)
141 policy.contents_encryption_mode = ctx.contents_encryption_mode;
142 policy.filenames_encryption_mode = ctx.filenames_encryption_mode;
143 policy.flags = ctx.flags;
144 memcpy(policy.master_key_descriptor, ctx.master_key_descriptor,
145 FS_KEY_DESCRIPTOR_SIZE);
147 if (copy_to_user(arg, &policy, sizeof(policy)))
151 EXPORT_SYMBOL(fscrypt_ioctl_get_policy);
153 int fscrypt_has_permitted_context(struct inode *parent, struct inode *child)
155 struct fscrypt_info *parent_ci, *child_ci;
158 if ((parent == NULL) || (child == NULL)) {
159 printk(KERN_ERR "parent %p child %p\n", parent, child);
163 /* No restrictions on file types which are never encrypted */
164 if (!S_ISREG(child->i_mode) && !S_ISDIR(child->i_mode) &&
165 !S_ISLNK(child->i_mode))
168 /* no restrictions if the parent directory is not encrypted */
169 if (!parent->i_sb->s_cop->is_encrypted(parent))
171 /* if the child directory is not encrypted, this is always a problem */
172 if (!parent->i_sb->s_cop->is_encrypted(child))
174 res = fscrypt_get_encryption_info(parent);
177 res = fscrypt_get_encryption_info(child);
180 parent_ci = parent->i_crypt_info;
181 child_ci = child->i_crypt_info;
182 if (!parent_ci && !child_ci)
184 if (!parent_ci || !child_ci)
187 return (memcmp(parent_ci->ci_master_key,
188 child_ci->ci_master_key,
189 FS_KEY_DESCRIPTOR_SIZE) == 0 &&
190 (parent_ci->ci_data_mode == child_ci->ci_data_mode) &&
191 (parent_ci->ci_filename_mode == child_ci->ci_filename_mode) &&
192 (parent_ci->ci_flags == child_ci->ci_flags));
194 EXPORT_SYMBOL(fscrypt_has_permitted_context);
197 * fscrypt_inherit_context() - Sets a child context from its parent
198 * @parent: Parent inode from which the context is inherited.
199 * @child: Child inode that inherits the context from @parent.
200 * @fs_data: private data given by FS.
201 * @preload: preload child i_crypt_info if true
203 * Return: 0 on success, -errno on failure
205 int fscrypt_inherit_context(struct inode *parent, struct inode *child,
206 void *fs_data, bool preload)
208 struct fscrypt_context ctx;
209 struct fscrypt_info *ci;
212 if (!parent->i_sb->s_cop->set_context)
215 res = fscrypt_get_encryption_info(parent);
219 ci = parent->i_crypt_info;
223 ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
224 ctx.contents_encryption_mode = ci->ci_data_mode;
225 ctx.filenames_encryption_mode = ci->ci_filename_mode;
226 ctx.flags = ci->ci_flags;
227 memcpy(ctx.master_key_descriptor, ci->ci_master_key,
228 FS_KEY_DESCRIPTOR_SIZE);
229 get_random_bytes(ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE);
230 res = parent->i_sb->s_cop->set_context(child, &ctx,
231 sizeof(ctx), fs_data);
234 return preload ? fscrypt_get_encryption_info(child): 0;
236 EXPORT_SYMBOL(fscrypt_inherit_context);