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/hash.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 ablkcipher_request *req = NULL;
  48         DECLARE_F2FS_COMPLETION_RESULT(ecr);
  49         struct scatterlist src_sg, dst_sg;
  50         struct crypto_ablkcipher *tfm = crypto_alloc_ablkcipher("ecb(aes)", 0,
  51                                                                 0);
  52
  53         if (IS_ERR(tfm)) {
  54                 res = PTR_ERR(tfm);
  55                 tfm = NULL;
  56                 goto out;
  57         }
  58         crypto_ablkcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
  59         req = ablkcipher_request_alloc(tfm, GFP_NOFS);
  60         if (!req) {
  61                 res = -ENOMEM;
  62                 goto out;
  63         }
  64         ablkcipher_request_set_callback(req,
  65                         CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
  66                         derive_crypt_complete, &ecr);
  67         res = crypto_ablkcipher_setkey(tfm, deriving_key,
  68                                 F2FS_AES_128_ECB_KEY_SIZE);
  69         if (res < 0)
  70                 goto out;
  71
  72         sg_init_one(&src_sg, source_key, F2FS_AES_256_XTS_KEY_SIZE);
  73         sg_init_one(&dst_sg, derived_key, F2FS_AES_256_XTS_KEY_SIZE);
  74         ablkcipher_request_set_crypt(req, &src_sg, &dst_sg,
  75                                         F2FS_AES_256_XTS_KEY_SIZE, NULL);
  76         res = crypto_ablkcipher_encrypt(req);
  77         if (res == -EINPROGRESS || res == -EBUSY) {
  78                 BUG_ON(req->base.data != &ecr);
  79                 wait_for_completion(&ecr.completion);
  80                 res = ecr.res;
  81         }
  82 out:
  83         if (req)
  84                 ablkcipher_request_free(req);
  85         if (tfm)
  86                 crypto_free_ablkcipher(tfm);
  87         return res;
  88 }
  89
  90 static void f2fs_free_crypt_info(struct f2fs_crypt_info *ci)
  91 {
  92         if (!ci)
  93                 return;
  94
  95         key_put(ci->ci_keyring_key);
  96         crypto_free_ablkcipher(ci->ci_ctfm);
  97         kmem_cache_free(f2fs_crypt_info_cachep, ci);
  98 }
  99
 100 void f2fs_free_encryption_info(struct inode *inode, struct f2fs_crypt_info *ci)
 101 {
 102         struct f2fs_inode_info *fi = F2FS_I(inode);
 103         struct f2fs_crypt_info *prev;
 104
 105         if (ci == NULL)
 106                 ci = ACCESS_ONCE(fi->i_crypt_info);
 107         if (ci == NULL)
 108                 return;
 109         prev = cmpxchg(&fi->i_crypt_info, ci, NULL);
 110         if (prev != ci)
 111                 return;
 112
 113         f2fs_free_crypt_info(ci);
 114 }
 115
 116 int _f2fs_get_encryption_info(struct inode *inode)
 117 {
 118         struct f2fs_inode_info *fi = F2FS_I(inode);
 119         struct f2fs_crypt_info *crypt_info;
 120         char full_key_descriptor[F2FS_KEY_DESC_PREFIX_SIZE +
 121                                 (F2FS_KEY_DESCRIPTOR_SIZE * 2) + 1];
 122         struct key *keyring_key = NULL;
 123         struct f2fs_encryption_key *master_key;
 124         struct f2fs_encryption_context ctx;
 125         const struct user_key_payload *ukp;
 126         struct crypto_ablkcipher *ctfm;
 127         const char *cipher_str;
 128         char raw_key[F2FS_MAX_KEY_SIZE];
 129         char mode;
 130         int res;
 131
 132         res = f2fs_crypto_initialize();
 133         if (res)
 134                 return res;
 135 retry:
 136         crypt_info = ACCESS_ONCE(fi->i_crypt_info);
 137         if (crypt_info) {
 138                 if (!crypt_info->ci_keyring_key ||
 139                                 key_validate(crypt_info->ci_keyring_key) == 0)
 140                         return 0;
 141                 f2fs_free_encryption_info(inode, crypt_info);
 142                 goto retry;
 143         }
 144
 145         res = f2fs_getxattr(inode, F2FS_XATTR_INDEX_ENCRYPTION,
 146                                 F2FS_XATTR_NAME_ENCRYPTION_CONTEXT,
 147                                 &ctx, sizeof(ctx), NULL);
 148         if (res < 0)
 149                 return res;
 150         else if (res != sizeof(ctx))
 151                 return -EINVAL;
 152         res = 0;
 153
 154         crypt_info = kmem_cache_alloc(f2fs_crypt_info_cachep, GFP_NOFS);
 155         if (!crypt_info)
 156                 return -ENOMEM;
 157
 158         crypt_info->ci_flags = ctx.flags;
 159         crypt_info->ci_data_mode = ctx.contents_encryption_mode;
 160         crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
 161         crypt_info->ci_ctfm = NULL;
 162         crypt_info->ci_keyring_key = NULL;
 163         memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
 164                                 sizeof(crypt_info->ci_master_key));
 165         if (S_ISREG(inode->i_mode))
 166                 mode = crypt_info->ci_data_mode;
 167         else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
 168                 mode = crypt_info->ci_filename_mode;
 169         else
 170                 BUG();
 171
 172         switch (mode) {
 173         case F2FS_ENCRYPTION_MODE_AES_256_XTS:
 174                 cipher_str = "xts(aes)";
 175                 break;
 176         case F2FS_ENCRYPTION_MODE_AES_256_CTS:
 177                 cipher_str = "cts(cbc(aes))";
 178                 break;
 179         default:
 180                 printk_once(KERN_WARNING
 181                             "f2fs: unsupported key mode %d (ino %u)\n",
 182                             mode, (unsigned) inode->i_ino);
 183                 res = -ENOKEY;
 184                 goto out;
 185         }
 186
 187         memcpy(full_key_descriptor, F2FS_KEY_DESC_PREFIX,
 188                                         F2FS_KEY_DESC_PREFIX_SIZE);
 189         sprintf(full_key_descriptor + F2FS_KEY_DESC_PREFIX_SIZE,
 190                                         "%*phN", F2FS_KEY_DESCRIPTOR_SIZE,
 191                                         ctx.master_key_descriptor);
 192         full_key_descriptor[F2FS_KEY_DESC_PREFIX_SIZE +
 193                                         (2 * F2FS_KEY_DESCRIPTOR_SIZE)] = '\0';
 194         keyring_key = request_key(&key_type_logon, full_key_descriptor, NULL);
 195         if (IS_ERR(keyring_key)) {
 196                 res = PTR_ERR(keyring_key);
 197                 keyring_key = NULL;
 198                 goto out;
 199         }
 200         crypt_info->ci_keyring_key = keyring_key;
 201         BUG_ON(keyring_key->type != &key_type_logon);
 202         ukp = user_key_payload(keyring_key);
 203         if (ukp->datalen != sizeof(struct f2fs_encryption_key)) {
 204                 res = -EINVAL;
 205                 goto out;
 206         }
 207         master_key = (struct f2fs_encryption_key *)ukp->data;
 208         BUILD_BUG_ON(F2FS_AES_128_ECB_KEY_SIZE !=
 209                                 F2FS_KEY_DERIVATION_NONCE_SIZE);
 210         BUG_ON(master_key->size != F2FS_AES_256_XTS_KEY_SIZE);
 211         res = f2fs_derive_key_aes(ctx.nonce, master_key->raw,
 212                                   raw_key);
 213         if (res)
 214                 goto out;
 215
 216         ctfm = crypto_alloc_ablkcipher(cipher_str, 0, 0);
 217         if (!ctfm || IS_ERR(ctfm)) {
 218                 res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
 219                 printk(KERN_DEBUG
 220                        "%s: error %d (inode %u) allocating crypto tfm\n",
 221                        __func__, res, (unsigned) inode->i_ino);
 222                 goto out;
 223         }
 224         crypt_info->ci_ctfm = ctfm;
 225         crypto_ablkcipher_clear_flags(ctfm, ~0);
 226         crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctfm),
 227                              CRYPTO_TFM_REQ_WEAK_KEY);
 228         res = crypto_ablkcipher_setkey(ctfm, raw_key,
 229                                         f2fs_encryption_key_size(mode));
 230         if (res)
 231                 goto out;
 232
 233         memzero_explicit(raw_key, sizeof(raw_key));
 234         if (cmpxchg(&fi->i_crypt_info, NULL, crypt_info) != NULL) {
 235                 f2fs_free_crypt_info(crypt_info);
 236                 goto retry;
 237         }
 238         return 0;
 239
 240 out:
 241         if (res == -ENOKEY && !S_ISREG(inode->i_mode))
 242                 res = 0;
 243
 244         f2fs_free_crypt_info(crypt_info);
 245         memzero_explicit(raw_key, sizeof(raw_key));
 246         return res;
 247 }
 248
 249 int f2fs_has_encryption_key(struct inode *inode)
 250 {
 251         struct f2fs_inode_info *fi = F2FS_I(inode);
 252
 253         return (fi->i_crypt_info != NULL);
 254 }