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 (!inode_owner_or_capable(inode))
  93                 return -EACCES;
  94
  95         if (policy->version != 0)
  96                 return -EINVAL;
  97
  98         if (!S_ISDIR(inode->i_mode))
  99                 return -EINVAL;
 100
 101         if (!f2fs_inode_has_encryption_context(inode)) {
 102                 if (!f2fs_empty_dir(inode))
 103                         return -ENOTEMPTY;
 104                 return f2fs_create_encryption_context_from_policy(inode,
 105                                                                   policy);
 106         }
 107
 108         if (f2fs_is_encryption_context_consistent_with_policy(inode, policy))
 109                 return 0;
 110
 111         printk(KERN_WARNING "%s: Policy inconsistent with encryption context\n",
 112                __func__);
 113         return -EINVAL;
 114 }
 115
 116 int f2fs_get_policy(struct inode *inode, struct f2fs_encryption_policy *policy)
 117 {
 118         struct f2fs_encryption_context ctx;
 119         int res;
 120
 121         if (!f2fs_encrypted_inode(inode))
 122                 return -ENODATA;
 123
 124         res = f2fs_getxattr(inode, F2FS_XATTR_INDEX_ENCRYPTION,
 125                                 F2FS_XATTR_NAME_ENCRYPTION_CONTEXT,
 126                                 &ctx, sizeof(ctx), NULL);
 127         if (res != sizeof(ctx))
 128                 return -ENODATA;
 129         if (ctx.format != F2FS_ENCRYPTION_CONTEXT_FORMAT_V1)
 130                 return -EINVAL;
 131
 132         policy->version = 0;
 133         policy->contents_encryption_mode = ctx.contents_encryption_mode;
 134         policy->filenames_encryption_mode = ctx.filenames_encryption_mode;
 135         policy->flags = ctx.flags;
 136         memcpy(&policy->master_key_descriptor, ctx.master_key_descriptor,
 137                         F2FS_KEY_DESCRIPTOR_SIZE);
 138         return 0;
 139 }
 140
 141 int f2fs_is_child_context_consistent_with_parent(struct inode *parent,
 142                                                 struct inode *child)
 143 {
 144         const struct f2fs_crypt_info *parent_ci, *child_ci;
 145         struct f2fs_encryption_context parent_ctx, child_ctx;
 146         int res;
 147
 148         /* No restrictions on file types which are never encrypted */
 149         if (!S_ISREG(child->i_mode) && !S_ISDIR(child->i_mode) &&
 150             !S_ISLNK(child->i_mode))
 151                 return 1;
 152
 153         /* No restrictions if the parent directory is unencrypted */
 154         if (!f2fs_encrypted_inode(parent))
 155                 return 1;
 156
 157         /* Encrypted directories must not contain unencrypted files */
 158         if (!f2fs_encrypted_inode(child))
 159                 return 0;
 160
 161         /*
 162          * Both parent and child are encrypted, so verify they use the same
 163          * encryption policy.  Compare the fscrypt_info structs if the keys are
 164          * available, otherwise retrieve and compare the fscrypt_contexts.
 165          *
 166          * Note that the fscrypt_context retrieval will be required frequently
 167          * when accessing an encrypted directory tree without the key.
 168          * Performance-wise this is not a big deal because we already don't
 169          * really optimize for file access without the key (to the extent that
 170          * such access is even possible), given that any attempted access
 171          * already causes a fscrypt_context retrieval and keyring search.
 172          *
 173          * In any case, if an unexpected error occurs, fall back to "forbidden".
 174          */
 175
 176         res = f2fs_get_encryption_info(parent);
 177         if (res)
 178                 return 0;
 179         res = f2fs_get_encryption_info(child);
 180         if (res)
 181                 return 0;
 182         parent_ci = F2FS_I(parent)->i_crypt_info;
 183         child_ci = F2FS_I(child)->i_crypt_info;
 184         if (parent_ci && child_ci) {
 185                 return memcmp(parent_ci->ci_master_key, child_ci->ci_master_key,
 186                               F2FS_KEY_DESCRIPTOR_SIZE) == 0 &&
 187                         (parent_ci->ci_data_mode == child_ci->ci_data_mode) &&
 188                         (parent_ci->ci_filename_mode ==
 189                          child_ci->ci_filename_mode) &&
 190                         (parent_ci->ci_flags == child_ci->ci_flags);
 191         }
 192
 193         res = f2fs_getxattr(parent, F2FS_XATTR_INDEX_ENCRYPTION,
 194                             F2FS_XATTR_NAME_ENCRYPTION_CONTEXT,
 195                             &parent_ctx, sizeof(parent_ctx), NULL);
 196         if (res != sizeof(parent_ctx))
 197                 return 0;
 198
 199         res = f2fs_getxattr(child, F2FS_XATTR_INDEX_ENCRYPTION,
 200                             F2FS_XATTR_NAME_ENCRYPTION_CONTEXT,
 201                             &child_ctx, sizeof(child_ctx), NULL);
 202         if (res != sizeof(child_ctx))
 203                 return 0;
 204
 205         return memcmp(parent_ctx.master_key_descriptor,
 206                       child_ctx.master_key_descriptor,
 207                       F2FS_KEY_DESCRIPTOR_SIZE) == 0 &&
 208                 (parent_ctx.contents_encryption_mode ==
 209                  child_ctx.contents_encryption_mode) &&
 210                 (parent_ctx.filenames_encryption_mode ==
 211                  child_ctx.filenames_encryption_mode) &&
 212                 (parent_ctx.flags == child_ctx.flags);
 213 }
 214
 215 /**
 216  * f2fs_inherit_context() - Sets a child context from its parent
 217  * @parent: Parent inode from which the context is inherited.
 218  * @child:  Child inode that inherits the context from @parent.
 219  *
 220  * Return: Zero on success, non-zero otherwise
 221  */
 222 int f2fs_inherit_context(struct inode *parent, struct inode *child,
 223                                                 struct page *ipage)
 224 {
 225         struct f2fs_encryption_context ctx;
 226         struct f2fs_crypt_info *ci;
 227         int res;
 228
 229         res = f2fs_get_encryption_info(parent);
 230         if (res < 0)
 231                 return res;
 232
 233         ci = F2FS_I(parent)->i_crypt_info;
 234         BUG_ON(ci == NULL);
 235
 236         ctx.format = F2FS_ENCRYPTION_CONTEXT_FORMAT_V1;
 237
 238         ctx.contents_encryption_mode = ci->ci_data_mode;
 239         ctx.filenames_encryption_mode = ci->ci_filename_mode;
 240         ctx.flags = ci->ci_flags;
 241         memcpy(ctx.master_key_descriptor, ci->ci_master_key,
 242                         F2FS_KEY_DESCRIPTOR_SIZE);
 243
 244         get_random_bytes(ctx.nonce, F2FS_KEY_DERIVATION_NONCE_SIZE);
 245         return f2fs_setxattr(child, F2FS_XATTR_INDEX_ENCRYPTION,
 246                                 F2FS_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
 247                                 sizeof(ctx), ipage, XATTR_CREATE);
 248 }