fs/f2fs/crypto_policy.c

   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
  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  */
  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
  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
  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
 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
 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  */
 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 }