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                 wait_for_completion(&ecr.completion);
  79                 res = ecr.res;
  80         }
  81 out:
  82         if (req)
  83                 ablkcipher_request_free(req);
  84         if (tfm)
  85                 crypto_free_ablkcipher(tfm);
  86         return res;
  87 }
  88
  89 static void f2fs_free_crypt_info(struct f2fs_crypt_info *ci)
  90 {
  91         if (!ci)
  92                 return;
  93
  94         crypto_free_ablkcipher(ci->ci_ctfm);
  95         kmem_cache_free(f2fs_crypt_info_cachep, ci);
  96 }
  97
  98 void f2fs_free_encryption_info(struct inode *inode, struct f2fs_crypt_info *ci)
  99 {
 100         struct f2fs_inode_info *fi = F2FS_I(inode);
 101         struct f2fs_crypt_info *prev;
 102
 103         if (ci == NULL)
 104                 ci = ACCESS_ONCE(fi->i_crypt_info);
 105         if (ci == NULL)
 106                 return;
 107         prev = cmpxchg(&fi->i_crypt_info, ci, NULL);
 108         if (prev != ci)
 109                 return;
 110
 111         f2fs_free_crypt_info(ci);
 112 }
 113
 114 int f2fs_get_encryption_info(struct inode *inode)
 115 {
 116         struct f2fs_inode_info *fi = F2FS_I(inode);
 117         struct f2fs_crypt_info *crypt_info;
 118         char full_key_descriptor[F2FS_KEY_DESC_PREFIX_SIZE +
 119                                 (F2FS_KEY_DESCRIPTOR_SIZE * 2) + 1];
 120         struct key *keyring_key = NULL;
 121         struct f2fs_encryption_key *master_key;
 122         struct f2fs_encryption_context ctx;
 123         const struct user_key_payload *ukp;
 124         struct crypto_ablkcipher *ctfm;
 125         const char *cipher_str;
 126         char raw_key[F2FS_MAX_KEY_SIZE];
 127         char mode;
 128         int res;
 129
 130         if (fi->i_crypt_info)
 131                 return 0;
 132
 133         res = f2fs_crypto_initialize();
 134         if (res)
 135                 return res;
 136
 137         res = f2fs_getxattr(inode, F2FS_XATTR_INDEX_ENCRYPTION,
 138                                 F2FS_XATTR_NAME_ENCRYPTION_CONTEXT,
 139                                 &ctx, sizeof(ctx), NULL);
 140         if (res < 0)
 141                 return res;
 142         else if (res != sizeof(ctx))
 143                 return -EINVAL;
 144         res = 0;
 145
 146         crypt_info = kmem_cache_alloc(f2fs_crypt_info_cachep, GFP_NOFS);
 147         if (!crypt_info)
 148                 return -ENOMEM;
 149
 150         crypt_info->ci_flags = ctx.flags;
 151         crypt_info->ci_data_mode = ctx.contents_encryption_mode;
 152         crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
 153         crypt_info->ci_ctfm = NULL;
 154         memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
 155                                 sizeof(crypt_info->ci_master_key));
 156         if (S_ISREG(inode->i_mode))
 157                 mode = crypt_info->ci_data_mode;
 158         else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
 159                 mode = crypt_info->ci_filename_mode;
 160         else
 161                 BUG();
 162
 163         switch (mode) {
 164         case F2FS_ENCRYPTION_MODE_AES_256_XTS:
 165                 cipher_str = "xts(aes)";
 166                 break;
 167         case F2FS_ENCRYPTION_MODE_AES_256_CTS:
 168                 cipher_str = "cts(cbc(aes))";
 169                 break;
 170         default:
 171                 printk_once(KERN_WARNING
 172                             "f2fs: unsupported key mode %d (ino %u)\n",
 173                             mode, (unsigned) inode->i_ino);
 174                 res = -ENOKEY;
 175                 goto out;
 176         }
 177
 178         memcpy(full_key_descriptor, F2FS_KEY_DESC_PREFIX,
 179                                         F2FS_KEY_DESC_PREFIX_SIZE);
 180         sprintf(full_key_descriptor + F2FS_KEY_DESC_PREFIX_SIZE,
 181                                         "%*phN", F2FS_KEY_DESCRIPTOR_SIZE,
 182                                         ctx.master_key_descriptor);
 183         full_key_descriptor[F2FS_KEY_DESC_PREFIX_SIZE +
 184                                         (2 * F2FS_KEY_DESCRIPTOR_SIZE)] = '\0';
 185         keyring_key = request_key(&key_type_logon, full_key_descriptor, NULL);
 186         if (IS_ERR(keyring_key)) {
 187                 res = PTR_ERR(keyring_key);
 188                 keyring_key = NULL;
 189                 goto out;
 190         }
 191         if (keyring_key->type != &key_type_logon) {
 192                 printk_once(KERN_WARNING "f2fs: key type must be logon\n");
 193                 res = -ENOKEY;
 194                 goto out;
 195         }
 196         down_read(&keyring_key->sem);
 197         ukp = user_key_payload(keyring_key);
 198         if (!ukp) {
 199                 /* key was revoked before we acquired its semaphore */
 200                 res = -EKEYREVOKED;
 201                 up_read(&keyring_key->sem);
 202                 goto out;
 203         }
 204         if (ukp->datalen != sizeof(struct f2fs_encryption_key)) {
 205                 res = -EINVAL;
 206                 up_read(&keyring_key->sem);
 207                 goto out;
 208         }
 209         master_key = (struct f2fs_encryption_key *)ukp->data;
 210         BUILD_BUG_ON(F2FS_AES_128_ECB_KEY_SIZE !=
 211                                 F2FS_KEY_DERIVATION_NONCE_SIZE);
 212         if (master_key->size != F2FS_AES_256_XTS_KEY_SIZE) {
 213                 printk_once(KERN_WARNING
 214                                 "f2fs: key size incorrect: %d\n",
 215                                 master_key->size);
 216                 res = -ENOKEY;
 217                 up_read(&keyring_key->sem);
 218                 goto out;
 219         }
 220         res = f2fs_derive_key_aes(ctx.nonce, master_key->raw,
 221                                   raw_key);
 222         up_read(&keyring_key->sem);
 223         if (res)
 224                 goto out;
 225
 226         ctfm = crypto_alloc_ablkcipher(cipher_str, 0, 0);
 227         if (!ctfm || IS_ERR(ctfm)) {
 228                 res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
 229                 printk(KERN_DEBUG
 230                        "%s: error %d (inode %u) allocating crypto tfm\n",
 231                        __func__, res, (unsigned) inode->i_ino);
 232                 goto out;
 233         }
 234         crypt_info->ci_ctfm = ctfm;
 235         crypto_ablkcipher_clear_flags(ctfm, ~0);
 236         crypto_tfm_set_flags(crypto_ablkcipher_tfm(ctfm),
 237                              CRYPTO_TFM_REQ_WEAK_KEY);
 238         res = crypto_ablkcipher_setkey(ctfm, raw_key,
 239                                         f2fs_encryption_key_size(mode));
 240         if (res)
 241                 goto out;
 242
 243         if (cmpxchg(&fi->i_crypt_info, NULL, crypt_info) == NULL)
 244                 crypt_info = NULL;
 245 out:
 246         if (res == -ENOKEY && !S_ISREG(inode->i_mode))
 247                 res = 0;
 248         key_put(keyring_key);
 249         f2fs_free_crypt_info(crypt_info);
 250         memzero_explicit(raw_key, sizeof(raw_key));
 251         return res;
 252 }
 253
 254 int f2fs_has_encryption_key(struct inode *inode)
 255 {
 256         struct f2fs_inode_info *fi = F2FS_I(inode);
 257
 258         return (fi->i_crypt_info != NULL);
 259 }