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         if (ci->ci_keyring_key)
  96                 key_put(ci->ci_keyring_key);
  97         crypto_free_ablkcipher(ci->ci_ctfm);
  98         kmem_cache_free(f2fs_crypt_info_cachep, ci);
  99 }
 100
 101 void f2fs_free_encryption_info(struct inode *inode, struct f2fs_crypt_info *ci)
 102 {
 103         struct f2fs_inode_info *fi = F2FS_I(inode);
 104         struct f2fs_crypt_info *prev;
 105
 106         if (ci == NULL)
 107                 ci = ACCESS_ONCE(fi->i_crypt_info);
 108         if (ci == NULL)
 109                 return;
 110         prev = cmpxchg(&fi->i_crypt_info, ci, NULL);
 111         if (prev != ci)
 112                 return;
 113
 114         f2fs_free_crypt_info(ci);
 115 }
 116
 117 int _f2fs_get_encryption_info(struct inode *inode)
 118 {
 119         struct f2fs_inode_info *fi = F2FS_I(inode);
 120         struct f2fs_crypt_info *crypt_info;
 121         char full_key_descriptor[F2FS_KEY_DESC_PREFIX_SIZE +
 122                                 (F2FS_KEY_DESCRIPTOR_SIZE * 2) + 1];
 123         struct key *keyring_key = NULL;
 124         struct f2fs_encryption_key *master_key;
 125         struct f2fs_encryption_context ctx;
 126         struct user_key_payload *ukp;
 127         struct crypto_ablkcipher *ctfm;
 128         const char *cipher_str;
 129         char raw_key[F2FS_MAX_KEY_SIZE];
 130         char mode;
 131         int res;
 132
 133         res = f2fs_crypto_initialize();
 134         if (res)
 135                 return res;
 136 retry:
 137         crypt_info = ACCESS_ONCE(fi->i_crypt_info);
 138         if (crypt_info) {
 139                 if (!crypt_info->ci_keyring_key ||
 140                                 key_validate(crypt_info->ci_keyring_key) == 0)
 141                         return 0;
 142                 f2fs_free_encryption_info(inode, crypt_info);
 143                 goto retry;
 144         }
 145
 146         res = f2fs_getxattr(inode, F2FS_XATTR_INDEX_ENCRYPTION,
 147                                 F2FS_XATTR_NAME_ENCRYPTION_CONTEXT,
 148                                 &ctx, sizeof(ctx), NULL);
 149         if (res < 0)
 150                 return res;
 151         else if (res != sizeof(ctx))
 152                 return -EINVAL;
 153         res = 0;
 154
 155         crypt_info = kmem_cache_alloc(f2fs_crypt_info_cachep, GFP_NOFS);
 156         if (!crypt_info)
 157                 return -ENOMEM;
 158
 159         crypt_info->ci_flags = ctx.flags;
 160         crypt_info->ci_data_mode = ctx.contents_encryption_mode;
 161         crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
 162         crypt_info->ci_ctfm = NULL;
 163         crypt_info->ci_keyring_key = NULL;
 164         memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
 165                                 sizeof(crypt_info->ci_master_key));
 166         if (S_ISREG(inode->i_mode))
 167                 mode = crypt_info->ci_data_mode;
 168         else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
 169                 mode = crypt_info->ci_filename_mode;
 170         else
 171                 BUG();
 172
 173         switch (mode) {
 174         case F2FS_ENCRYPTION_MODE_AES_256_XTS:
 175                 cipher_str = "xts(aes)";
 176                 break;
 177         case F2FS_ENCRYPTION_MODE_AES_256_CTS:
 178                 cipher_str = "cts(cbc(aes))";
 179                 break;
 180         default:
 181                 printk_once(KERN_WARNING
 182                             "f2fs: unsupported key mode %d (ino %u)\n",
 183                             mode, (unsigned) inode->i_ino);
 184                 res = -ENOKEY;
 185                 goto out;
 186         }
 187
 188         memcpy(full_key_descriptor, F2FS_KEY_DESC_PREFIX,
 189                                         F2FS_KEY_DESC_PREFIX_SIZE);
 190         sprintf(full_key_descriptor + F2FS_KEY_DESC_PREFIX_SIZE,
 191                                         "%*phN", F2FS_KEY_DESCRIPTOR_SIZE,
 192                                         ctx.master_key_descriptor);
 193         full_key_descriptor[F2FS_KEY_DESC_PREFIX_SIZE +
 194                                         (2 * F2FS_KEY_DESCRIPTOR_SIZE)] = '\0';
 195         keyring_key = request_key(&key_type_logon, full_key_descriptor, NULL);
 196         if (IS_ERR(keyring_key)) {
 197                 res = PTR_ERR(keyring_key);
 198                 keyring_key = NULL;
 199                 goto out;
 200         }
 201         crypt_info->ci_keyring_key = keyring_key;
 202         BUG_ON(keyring_key->type != &key_type_logon);
 203         ukp = ((struct user_key_payload *)keyring_key->payload.data);
 204         if (ukp->datalen != sizeof(struct f2fs_encryption_key)) {
 205                 res = -EINVAL;
 206                 goto out;
 207         }
 208         master_key = (struct f2fs_encryption_key *)ukp->data;
 209         BUILD_BUG_ON(F2FS_AES_128_ECB_KEY_SIZE !=
 210                                 F2FS_KEY_DERIVATION_NONCE_SIZE);
 211         BUG_ON(master_key->size != F2FS_AES_256_XTS_KEY_SIZE);
 212         res = f2fs_derive_key_aes(ctx.nonce, master_key->raw,
 213                                   raw_key);
 214         if (res)
 215                 goto out;
 216
 217         ctfm = crypto_alloc_ablkcipher(cipher_str, 0, 0);
 218         if (!ctfm || IS_ERR(ctfm)) {
 219                 res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
 220                 printk(KERN_DEBUG
 221                        "%s: error %d (inode %u) allocating crypto tfm\n",
 222                        __func__, res, (unsigned) inode->i_ino);
 223                 goto out;
 224         }
 225         crypt_info->ci_ctfm = ctfm;
 226         crypto_ablkcipher_clear_flags(ctfm, ~0);
 227         crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctfm),
 228                              CRYPTO_TFM_REQ_WEAK_KEY);
 229         res = crypto_ablkcipher_setkey(ctfm, raw_key,
 230                                         f2fs_encryption_key_size(mode));
 231         if (res)
 232                 goto out;
 233
 234         memzero_explicit(raw_key, sizeof(raw_key));
 235         if (cmpxchg(&fi->i_crypt_info, NULL, crypt_info) != NULL) {
 236                 f2fs_free_crypt_info(crypt_info);
 237                 goto retry;
 238         }
 239         return 0;
 240
 241 out:
 242         if (res == -ENOKEY && !S_ISREG(inode->i_mode))
 243                 res = 0;
 244
 245         f2fs_free_crypt_info(crypt_info);
 246         memzero_explicit(raw_key, sizeof(raw_key));
 247         return res;
 248 }
 249
 250 int f2fs_has_encryption_key(struct inode *inode)
 251 {
 252         struct f2fs_inode_info *fi = F2FS_I(inode);
 253
 254         return (fi->i_crypt_info != NULL);
 255 }