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;
37 if (!inode->i_sb->s_cop->set_context)
40 ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
41 memcpy(ctx.master_key_descriptor, policy->master_key_descriptor,
42 FS_KEY_DESCRIPTOR_SIZE);
44 if (!fscrypt_valid_contents_enc_mode(
45 policy->contents_encryption_mode))
48 if (!fscrypt_valid_filenames_enc_mode(
49 policy->filenames_encryption_mode))
52 if (policy->flags & ~FS_POLICY_FLAGS_VALID)
55 ctx.contents_encryption_mode = policy->contents_encryption_mode;
56 ctx.filenames_encryption_mode = policy->filenames_encryption_mode;
57 ctx.flags = policy->flags;
58 BUILD_BUG_ON(sizeof(ctx.nonce) != FS_KEY_DERIVATION_NONCE_SIZE);
59 get_random_bytes(ctx.nonce, FS_KEY_DERIVATION_NONCE_SIZE);
61 return inode->i_sb->s_cop->set_context(inode, &ctx, sizeof(ctx), NULL);
64 int fscrypt_ioctl_set_policy(struct file *filp, const void __user *arg)
66 struct fscrypt_policy policy;
67 struct inode *inode = file_inode(filp);
69 struct fscrypt_context ctx;
71 if (copy_from_user(&policy, arg, sizeof(policy)))
74 if (!inode_owner_or_capable(inode))
77 if (policy.version != 0)
80 ret = mnt_want_write_file(filp);
86 ret = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
87 if (ret == -ENODATA) {
88 if (!S_ISDIR(inode->i_mode))
90 else if (!inode->i_sb->s_cop->empty_dir)
92 else if (!inode->i_sb->s_cop->empty_dir(inode))
95 ret = create_encryption_context_from_policy(inode,
97 } else if (ret == sizeof(ctx) &&
98 is_encryption_context_consistent_with_policy(&ctx,
100 /* The file already uses the same encryption policy. */
102 } else if (ret >= 0 || ret == -ERANGE) {
103 /* The file already uses a different encryption policy. */
109 mnt_drop_write_file(filp);
112 EXPORT_SYMBOL(fscrypt_ioctl_set_policy);
114 int fscrypt_ioctl_get_policy(struct file *filp, void __user *arg)
116 struct inode *inode = file_inode(filp);
117 struct fscrypt_context ctx;
118 struct fscrypt_policy policy;
121 if (!inode->i_sb->s_cop->get_context ||
122 !inode->i_sb->s_cop->is_encrypted(inode))
125 res = inode->i_sb->s_cop->get_context(inode, &ctx, sizeof(ctx));
126 if (res < 0 && res != -ERANGE)
128 if (res != sizeof(ctx))
130 if (ctx.format != FS_ENCRYPTION_CONTEXT_FORMAT_V1)
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);
140 if (copy_to_user(arg, &policy, sizeof(policy)))
144 EXPORT_SYMBOL(fscrypt_ioctl_get_policy);
146 int fscrypt_has_permitted_context(struct inode *parent, struct inode *child)
148 struct fscrypt_info *parent_ci, *child_ci;
151 if ((parent == NULL) || (child == NULL)) {
152 printk(KERN_ERR "parent %p child %p\n", parent, child);
156 /* No restrictions on file types which are never encrypted */
157 if (!S_ISREG(child->i_mode) && !S_ISDIR(child->i_mode) &&
158 !S_ISLNK(child->i_mode))
161 /* no restrictions if the parent directory is not encrypted */
162 if (!parent->i_sb->s_cop->is_encrypted(parent))
164 /* if the child directory is not encrypted, this is always a problem */
165 if (!parent->i_sb->s_cop->is_encrypted(child))
167 res = fscrypt_get_encryption_info(parent);
170 res = fscrypt_get_encryption_info(child);
173 parent_ci = parent->i_crypt_info;
174 child_ci = child->i_crypt_info;
175 if (!parent_ci && !child_ci)
177 if (!parent_ci || !child_ci)
180 return (memcmp(parent_ci->ci_master_key,
181 child_ci->ci_master_key,
182 FS_KEY_DESCRIPTOR_SIZE) == 0 &&
183 (parent_ci->ci_data_mode == child_ci->ci_data_mode) &&
184 (parent_ci->ci_filename_mode == child_ci->ci_filename_mode) &&
185 (parent_ci->ci_flags == child_ci->ci_flags));
187 EXPORT_SYMBOL(fscrypt_has_permitted_context);
190 * fscrypt_inherit_context() - Sets a child context from its parent
191 * @parent: Parent inode from which the context is inherited.
192 * @child: Child inode that inherits the context from @parent.
193 * @fs_data: private data given by FS.
194 * @preload: preload child i_crypt_info if true
196 * Return: 0 on success, -errno on failure
198 int fscrypt_inherit_context(struct inode *parent, struct inode *child,
199 void *fs_data, bool preload)
201 struct fscrypt_context ctx;
202 struct fscrypt_info *ci;
205 if (!parent->i_sb->s_cop->set_context)
208 res = fscrypt_get_encryption_info(parent);
212 ci = parent->i_crypt_info;
216 ctx.format = FS_ENCRYPTION_CONTEXT_FORMAT_V1;
217 ctx.contents_encryption_mode = ci->ci_data_mode;
218 ctx.filenames_encryption_mode = ci->ci_filename_mode;
219 ctx.flags = ci->ci_flags;
220 memcpy(ctx.master_key_descriptor, ci->ci_master_key,
221 FS_KEY_DESCRIPTOR_SIZE);
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);
227 return preload ? fscrypt_get_encryption_info(child): 0;
229 EXPORT_SYMBOL(fscrypt_inherit_context);