1 /*
2  * copied from linux/fs/ext4/crypto_policy.c
3  *
4  * Copyright (C) 2015, Google, Inc.
5  * Copyright (C) 2015, Motorola Mobility.
6  *
7  * This contains encryption policy functions for f2fs with some modifications
8  * to support f2fs-specific xattr APIs.
9  *
10  * Written by Michael Halcrow, 2015.
11  * Modified by Jaegeuk Kim, 2015.
12  */
13 #include <linux/random.h>
14 #include <linux/string.h>
15 #include <linux/types.h>
16 #include <linux/f2fs_fs.h>
17 
18 #include "f2fs.h"
19 #include "xattr.h"
20 
f2fs_inode_has_encryption_context(struct inode * inode)21 static int f2fs_inode_has_encryption_context(struct inode *inode)
22 {
23 	int res = f2fs_getxattr(inode, F2FS_XATTR_INDEX_ENCRYPTION,
24 			F2FS_XATTR_NAME_ENCRYPTION_CONTEXT, NULL, 0, NULL);
25 	return (res > 0);
26 }
27 
28 /*
29  * check whether the policy is consistent with the encryption context
30  * for the inode
31  */
f2fs_is_encryption_context_consistent_with_policy(struct inode * inode,const struct f2fs_encryption_policy * policy)32 static int f2fs_is_encryption_context_consistent_with_policy(
33 	struct inode *inode, const struct f2fs_encryption_policy *policy)
34 {
35 	struct f2fs_encryption_context ctx;
36 	int res = f2fs_getxattr(inode, F2FS_XATTR_INDEX_ENCRYPTION,
37 				F2FS_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
38 				sizeof(ctx), NULL);
39 
40 	if (res != sizeof(ctx))
41 		return 0;
42 
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));
50 }
51 
f2fs_create_encryption_context_from_policy(struct inode * inode,const struct f2fs_encryption_policy * policy)52 static int f2fs_create_encryption_context_from_policy(
53 	struct inode *inode, const struct f2fs_encryption_policy *policy)
54 {
55 	struct f2fs_encryption_context ctx;
56 
57 	ctx.format = F2FS_ENCRYPTION_CONTEXT_FORMAT_V1;
58 	memcpy(ctx.master_key_descriptor, policy->master_key_descriptor,
59 			F2FS_KEY_DESCRIPTOR_SIZE);
60 
61 	if (!f2fs_valid_contents_enc_mode(policy->contents_encryption_mode)) {
62 		printk(KERN_WARNING
63 		       "%s: Invalid contents encryption mode %d\n", __func__,
64 			policy->contents_encryption_mode);
65 		return -EINVAL;
66 	}
67 
68 	if (!f2fs_valid_filenames_enc_mode(policy->filenames_encryption_mode)) {
69 		printk(KERN_WARNING
70 		       "%s: Invalid filenames encryption mode %d\n", __func__,
71 			policy->filenames_encryption_mode);
72 		return -EINVAL;
73 	}
74 
75 	if (policy->flags & ~F2FS_POLICY_FLAGS_VALID)
76 		return -EINVAL;
77 
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);
83 
84 	return f2fs_setxattr(inode, F2FS_XATTR_INDEX_ENCRYPTION,
85 			F2FS_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
86 			sizeof(ctx), NULL, XATTR_CREATE);
87 }
88 
f2fs_process_policy(const struct f2fs_encryption_policy * policy,struct inode * inode)89 int f2fs_process_policy(const struct f2fs_encryption_policy *policy,
90 			struct inode *inode)
91 {
92 	if (policy->version != 0)
93 		return -EINVAL;
94 
95 	if (!S_ISDIR(inode->i_mode))
96 		return -EINVAL;
97 
98 	if (!f2fs_inode_has_encryption_context(inode)) {
99 		if (!f2fs_empty_dir(inode))
100 			return -ENOTEMPTY;
101 		return f2fs_create_encryption_context_from_policy(inode,
102 								  policy);
103 	}
104 
105 	if (f2fs_is_encryption_context_consistent_with_policy(inode, policy))
106 		return 0;
107 
108 	printk(KERN_WARNING "%s: Policy inconsistent with encryption context\n",
109 	       __func__);
110 	return -EINVAL;
111 }
112 
f2fs_get_policy(struct inode * inode,struct f2fs_encryption_policy * policy)113 int f2fs_get_policy(struct inode *inode, struct f2fs_encryption_policy *policy)
114 {
115 	struct f2fs_encryption_context ctx;
116 	int res;
117 
118 	if (!f2fs_encrypted_inode(inode))
119 		return -ENODATA;
120 
121 	res = f2fs_getxattr(inode, F2FS_XATTR_INDEX_ENCRYPTION,
122 				F2FS_XATTR_NAME_ENCRYPTION_CONTEXT,
123 				&ctx, sizeof(ctx), NULL);
124 	if (res != sizeof(ctx))
125 		return -ENODATA;
126 	if (ctx.format != F2FS_ENCRYPTION_CONTEXT_FORMAT_V1)
127 		return -EINVAL;
128 
129 	policy->version = 0;
130 	policy->contents_encryption_mode = ctx.contents_encryption_mode;
131 	policy->filenames_encryption_mode = ctx.filenames_encryption_mode;
132 	policy->flags = ctx.flags;
133 	memcpy(&policy->master_key_descriptor, ctx.master_key_descriptor,
134 			F2FS_KEY_DESCRIPTOR_SIZE);
135 	return 0;
136 }
137 
f2fs_is_child_context_consistent_with_parent(struct inode * parent,struct inode * child)138 int f2fs_is_child_context_consistent_with_parent(struct inode *parent,
139 						struct inode *child)
140 {
141 	struct f2fs_crypt_info *parent_ci, *child_ci;
142 	int res;
143 
144 	if ((parent == NULL) || (child == NULL)) {
145 		pr_err("parent %p child %p\n", parent, child);
146 		BUG_ON(1);
147 	}
148 
149 	/* no restrictions if the parent directory is not encrypted */
150 	if (!f2fs_encrypted_inode(parent))
151 		return 1;
152 	/* if the child directory is not encrypted, this is always a problem */
153 	if (!f2fs_encrypted_inode(child))
154 		return 0;
155 	res = f2fs_get_encryption_info(parent);
156 	if (res)
157 		return 0;
158 	res = f2fs_get_encryption_info(child);
159 	if (res)
160 		return 0;
161 	parent_ci = F2FS_I(parent)->i_crypt_info;
162 	child_ci = F2FS_I(child)->i_crypt_info;
163 	if (!parent_ci && !child_ci)
164 		return 1;
165 	if (!parent_ci || !child_ci)
166 		return 0;
167 
168 	return (memcmp(parent_ci->ci_master_key,
169 			child_ci->ci_master_key,
170 			F2FS_KEY_DESCRIPTOR_SIZE) == 0 &&
171 		(parent_ci->ci_data_mode == child_ci->ci_data_mode) &&
172 		(parent_ci->ci_filename_mode == child_ci->ci_filename_mode) &&
173 		(parent_ci->ci_flags == child_ci->ci_flags));
174 }
175 
176 /**
177  * f2fs_inherit_context() - Sets a child context from its parent
178  * @parent: Parent inode from which the context is inherited.
179  * @child:  Child inode that inherits the context from @parent.
180  *
181  * Return: Zero on success, non-zero otherwise
182  */
f2fs_inherit_context(struct inode * parent,struct inode * child,struct page * ipage)183 int f2fs_inherit_context(struct inode *parent, struct inode *child,
184 						struct page *ipage)
185 {
186 	struct f2fs_encryption_context ctx;
187 	struct f2fs_crypt_info *ci;
188 	int res;
189 
190 	res = f2fs_get_encryption_info(parent);
191 	if (res < 0)
192 		return res;
193 
194 	ci = F2FS_I(parent)->i_crypt_info;
195 	BUG_ON(ci == NULL);
196 
197 	ctx.format = F2FS_ENCRYPTION_CONTEXT_FORMAT_V1;
198 
199 	ctx.contents_encryption_mode = ci->ci_data_mode;
200 	ctx.filenames_encryption_mode = ci->ci_filename_mode;
201 	ctx.flags = ci->ci_flags;
202 	memcpy(ctx.master_key_descriptor, ci->ci_master_key,
203 			F2FS_KEY_DESCRIPTOR_SIZE);
204 
205 	get_random_bytes(ctx.nonce, F2FS_KEY_DERIVATION_NONCE_SIZE);
206 	return f2fs_setxattr(child, F2FS_XATTR_INDEX_ENCRYPTION,
207 				F2FS_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
208 				sizeof(ctx), ipage, XATTR_CREATE);
209 }
210