fs/f2fs/crypto_key.c

   1 /*
   2  * linux/fs/f2fs/crypto_key.c
   3  *
   4  * Copied from linux/fs/f2fs/crypto_key.c
   5  *
   6  * Copyright (C) 2015, Google, Inc.
   7  *
   8  * This contains encryption key functions for f2fs
   9  *
  10  * Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
  11  */
  12 #include <keys/encrypted-type.h>
  13 #include <keys/user-type.h>
  14 #include <linux/random.h>
  15 #include <linux/scatterlist.h>
  16 #include <uapi/linux/keyctl.h>
  17 #include <crypto/skcipher.h>
  18 #include <linux/f2fs_fs.h>
  19
  20 #include "f2fs.h"
  21 #include "xattr.h"
  22
  23 static void derive_crypt_complete(struct crypto_async_request *req, int rc)
  24 {
  25         struct f2fs_completion_result *ecr = req->data;
  26
  27         if (rc == -EINPROGRESS)
  28                 return;
  29
  30         ecr->res = rc;
  31         complete(&ecr->completion);
  32 }
  33
  34 /**
  35  * f2fs_derive_key_aes() - Derive a key using AES-128-ECB
  36  * @deriving_key: Encryption key used for derivatio.
  37  * @source_key:   Source key to which to apply derivation.
  38  * @derived_key:  Derived key.
  39  *
  40  * Return: Zero on success; non-zero otherwise.
  41  */
  42 static int f2fs_derive_key_aes(char deriving_key[F2FS_AES_128_ECB_KEY_SIZE],
  43                                 char source_key[F2FS_AES_256_XTS_KEY_SIZE],
  44                                 char derived_key[F2FS_AES_256_XTS_KEY_SIZE])
  45 {
  46         int res = 0;
  47         struct skcipher_request *req = NULL;
  48         DECLARE_F2FS_COMPLETION_RESULT(ecr);
  49         struct scatterlist src_sg, dst_sg;
  50         struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0);
  51
  52         if (IS_ERR(tfm)) {
  53                 res = PTR_ERR(tfm);
  54                 tfm = NULL;
  55                 goto out;
  56         }
  57         crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
  58         req = skcipher_request_alloc(tfm, GFP_NOFS);
  59         if (!req) {
  60                 res = -ENOMEM;
  61                 goto out;
  62         }
  63         skcipher_request_set_callback(req,
  64                         CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
  65                         derive_crypt_complete, &ecr);
  66         res = crypto_skcipher_setkey(tfm, deriving_key,
  67                                 F2FS_AES_128_ECB_KEY_SIZE);
  68         if (res < 0)
  69                 goto out;
  70
  71         sg_init_one(&src_sg, source_key, F2FS_AES_256_XTS_KEY_SIZE);
  72         sg_init_one(&dst_sg, derived_key, F2FS_AES_256_XTS_KEY_SIZE);
  73         skcipher_request_set_crypt(req, &src_sg, &dst_sg,
  74                                         F2FS_AES_256_XTS_KEY_SIZE, NULL);
  75         res = crypto_skcipher_encrypt(req);
  76         if (res == -EINPROGRESS || res == -EBUSY) {
  77                 BUG_ON(req->base.data != &ecr);
  78                 wait_for_completion(&ecr.completion);
  79                 res = ecr.res;
  80         }
  81 out:
  82         skcipher_request_free(req);
  83         crypto_free_skcipher(tfm);
  84         return res;
  85 }
  86
  87 static void f2fs_free_crypt_info(struct f2fs_crypt_info *ci)
  88 {
  89         if (!ci)
  90                 return;
  91
  92         key_put(ci->ci_keyring_key);
  93         crypto_free_skcipher(ci->ci_ctfm);
  94         kmem_cache_free(f2fs_crypt_info_cachep, ci);
  95 }
  96
  97 void f2fs_free_encryption_info(struct inode *inode, struct f2fs_crypt_info *ci)
  98 {
  99         struct f2fs_inode_info *fi = F2FS_I(inode);
 100         struct f2fs_crypt_info *prev;
 101
 102         if (ci == NULL)
 103                 ci = ACCESS_ONCE(fi->i_crypt_info);
 104         if (ci == NULL)
 105                 return;
 106         prev = cmpxchg(&fi->i_crypt_info, ci, NULL);
 107         if (prev != ci)
 108                 return;
 109
 110         f2fs_free_crypt_info(ci);
 111 }
 112
 113 int _f2fs_get_encryption_info(struct inode *inode)
 114 {
 115         struct f2fs_inode_info *fi = F2FS_I(inode);
 116         struct f2fs_crypt_info *crypt_info;
 117         char full_key_descriptor[F2FS_KEY_DESC_PREFIX_SIZE +
 118                                 (F2FS_KEY_DESCRIPTOR_SIZE * 2) + 1];
 119         struct key *keyring_key = NULL;
 120         struct f2fs_encryption_key *master_key;
 121         struct f2fs_encryption_context ctx;
 122         const struct user_key_payload *ukp;
 123         struct crypto_skcipher *ctfm;
 124         const char *cipher_str;
 125         char raw_key[F2FS_MAX_KEY_SIZE];
 126         char mode;
 127         int res;
 128
 129         res = f2fs_crypto_initialize();
 130         if (res)
 131                 return res;
 132 retry:
 133         crypt_info = ACCESS_ONCE(fi->i_crypt_info);
 134         if (crypt_info) {
 135                 if (!crypt_info->ci_keyring_key ||
 136                                 key_validate(crypt_info->ci_keyring_key) == 0)
 137                         return 0;
 138                 f2fs_free_encryption_info(inode, crypt_info);
 139                 goto retry;
 140         }
 141
 142         res = f2fs_getxattr(inode, F2FS_XATTR_INDEX_ENCRYPTION,
 143                                 F2FS_XATTR_NAME_ENCRYPTION_CONTEXT,
 144                                 &ctx, sizeof(ctx), NULL);
 145         if (res < 0)
 146                 return res;
 147         else if (res != sizeof(ctx))
 148                 return -EINVAL;
 149         res = 0;
 150
 151         crypt_info = kmem_cache_alloc(f2fs_crypt_info_cachep, GFP_NOFS);
 152         if (!crypt_info)
 153                 return -ENOMEM;
 154
 155         crypt_info->ci_flags = ctx.flags;
 156         crypt_info->ci_data_mode = ctx.contents_encryption_mode;
 157         crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
 158         crypt_info->ci_ctfm = NULL;
 159         crypt_info->ci_keyring_key = NULL;
 160         memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
 161                                 sizeof(crypt_info->ci_master_key));
 162         if (S_ISREG(inode->i_mode))
 163                 mode = crypt_info->ci_data_mode;
 164         else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
 165                 mode = crypt_info->ci_filename_mode;
 166         else
 167                 BUG();
 168
 169         switch (mode) {
 170         case F2FS_ENCRYPTION_MODE_AES_256_XTS:
 171                 cipher_str = "xts(aes)";
 172                 break;
 173         case F2FS_ENCRYPTION_MODE_AES_256_CTS:
 174                 cipher_str = "cts(cbc(aes))";
 175                 break;
 176         default:
 177                 printk_once(KERN_WARNING
 178                             "f2fs: unsupported key mode %d (ino %u)\n",
 179                             mode, (unsigned) inode->i_ino);
 180                 res = -ENOKEY;
 181                 goto out;
 182         }
 183
 184         memcpy(full_key_descriptor, F2FS_KEY_DESC_PREFIX,
 185                                         F2FS_KEY_DESC_PREFIX_SIZE);
 186         sprintf(full_key_descriptor + F2FS_KEY_DESC_PREFIX_SIZE,
 187                                         "%*phN", F2FS_KEY_DESCRIPTOR_SIZE,
 188                                         ctx.master_key_descriptor);
 189         full_key_descriptor[F2FS_KEY_DESC_PREFIX_SIZE +
 190                                         (2 * F2FS_KEY_DESCRIPTOR_SIZE)] = '\0';
 191         keyring_key = request_key(&key_type_logon, full_key_descriptor, NULL);
 192         if (IS_ERR(keyring_key)) {
 193                 res = PTR_ERR(keyring_key);
 194                 keyring_key = NULL;
 195                 goto out;
 196         }
 197         crypt_info->ci_keyring_key = keyring_key;
 198         BUG_ON(keyring_key->type != &key_type_logon);
 199         ukp = user_key_payload(keyring_key);
 200         if (ukp->datalen != sizeof(struct f2fs_encryption_key)) {
 201                 res = -EINVAL;
 202                 goto out;
 203         }
 204         master_key = (struct f2fs_encryption_key *)ukp->data;
 205         BUILD_BUG_ON(F2FS_AES_128_ECB_KEY_SIZE !=
 206                                 F2FS_KEY_DERIVATION_NONCE_SIZE);
 207         BUG_ON(master_key->size != F2FS_AES_256_XTS_KEY_SIZE);
 208         res = f2fs_derive_key_aes(ctx.nonce, master_key->raw,
 209                                   raw_key);
 210         if (res)
 211                 goto out;
 212
 213         ctfm = crypto_alloc_skcipher(cipher_str, 0, 0);
 214         if (!ctfm || IS_ERR(ctfm)) {
 215                 res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
 216                 printk(KERN_DEBUG
 217                        "%s: error %d (inode %u) allocating crypto tfm\n",
 218                        __func__, res, (unsigned) inode->i_ino);
 219                 goto out;
 220         }
 221         crypt_info->ci_ctfm = ctfm;
 222         crypto_skcipher_clear_flags(ctfm, ~0);
 223         crypto_skcipher_set_flags(ctfm, CRYPTO_TFM_REQ_WEAK_KEY);
 224         res = crypto_skcipher_setkey(ctfm, raw_key,
 225                                      f2fs_encryption_key_size(mode));
 226         if (res)
 227                 goto out;
 228
 229         memzero_explicit(raw_key, sizeof(raw_key));
 230         if (cmpxchg(&fi->i_crypt_info, NULL, crypt_info) != NULL) {
 231                 f2fs_free_crypt_info(crypt_info);
 232                 goto retry;
 233         }
 234         return 0;
 235
 236 out:
 237         if (res == -ENOKEY && !S_ISREG(inode->i_mode))
 238                 res = 0;
 239
 240         f2fs_free_crypt_info(crypt_info);
 241         memzero_explicit(raw_key, sizeof(raw_key));
 242         return res;
 243 }
 244
 245 int f2fs_has_encryption_key(struct inode *inode)
 246 {
 247         struct f2fs_inode_info *fi = F2FS_I(inode);
 248
 249         return (fi->i_crypt_info != NULL);
 250 }