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/*
* linux/fs/f2fs/crypto_key.c
*
* Copied from linux/fs/f2fs/crypto_key.c
*
* Copyright (C) 2015, Google, Inc.
*
* This contains encryption key functions for f2fs
*
* Written by Michael Halcrow, Ildar Muslukhov, and Uday Savagaonkar, 2015.
*/
#include <keys/encrypted-type.h>
#include <keys/user-type.h>
#include <linux/random.h>
#include <linux/scatterlist.h>
#include <uapi/linux/keyctl.h>
#include <crypto/skcipher.h>
#include <linux/f2fs_fs.h>
#include "f2fs.h"
#include "xattr.h"
static void derive_crypt_complete(struct crypto_async_request *req, int rc)
{
struct f2fs_completion_result *ecr = req->data;
if (rc == -EINPROGRESS)
return;
ecr->res = rc;
complete(&ecr->completion);
}
/**
* f2fs_derive_key_aes() - Derive a key using AES-128-ECB
* @deriving_key: Encryption key used for derivatio.
* @source_key: Source key to which to apply derivation.
* @derived_key: Derived key.
*
* Return: Zero on success; non-zero otherwise.
*/
static int f2fs_derive_key_aes(char deriving_key[F2FS_AES_128_ECB_KEY_SIZE],
char source_key[F2FS_AES_256_XTS_KEY_SIZE],
char derived_key[F2FS_AES_256_XTS_KEY_SIZE])
{
int res = 0;
struct skcipher_request *req = NULL;
DECLARE_F2FS_COMPLETION_RESULT(ecr);
struct scatterlist src_sg, dst_sg;
struct crypto_skcipher *tfm = crypto_alloc_skcipher("ecb(aes)", 0, 0);
if (IS_ERR(tfm)) {
res = PTR_ERR(tfm);
tfm = NULL;
goto out;
}
crypto_skcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
req = skcipher_request_alloc(tfm, GFP_NOFS);
if (!req) {
res = -ENOMEM;
goto out;
}
skcipher_request_set_callback(req,
CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
derive_crypt_complete, &ecr);
res = crypto_skcipher_setkey(tfm, deriving_key,
F2FS_AES_128_ECB_KEY_SIZE);
if (res < 0)
goto out;
sg_init_one(&src_sg, source_key, F2FS_AES_256_XTS_KEY_SIZE);
sg_init_one(&dst_sg, derived_key, F2FS_AES_256_XTS_KEY_SIZE);
skcipher_request_set_crypt(req, &src_sg, &dst_sg,
F2FS_AES_256_XTS_KEY_SIZE, NULL);
res = crypto_skcipher_encrypt(req);
if (res == -EINPROGRESS || res == -EBUSY) {
BUG_ON(req->base.data != &ecr);
wait_for_completion(&ecr.completion);
res = ecr.res;
}
out:
skcipher_request_free(req);
crypto_free_skcipher(tfm);
return res;
}
static void f2fs_free_crypt_info(struct f2fs_crypt_info *ci)
{
if (!ci)
return;
key_put(ci->ci_keyring_key);
crypto_free_skcipher(ci->ci_ctfm);
kmem_cache_free(f2fs_crypt_info_cachep, ci);
}
void f2fs_free_encryption_info(struct inode *inode, struct f2fs_crypt_info *ci)
{
struct f2fs_inode_info *fi = F2FS_I(inode);
struct f2fs_crypt_info *prev;
if (ci == NULL)
ci = ACCESS_ONCE(fi->i_crypt_info);
if (ci == NULL)
return;
prev = cmpxchg(&fi->i_crypt_info, ci, NULL);
if (prev != ci)
return;
f2fs_free_crypt_info(ci);
}
int _f2fs_get_encryption_info(struct inode *inode)
{
struct f2fs_inode_info *fi = F2FS_I(inode);
struct f2fs_crypt_info *crypt_info;
char full_key_descriptor[F2FS_KEY_DESC_PREFIX_SIZE +
(F2FS_KEY_DESCRIPTOR_SIZE * 2) + 1];
struct key *keyring_key = NULL;
struct f2fs_encryption_key *master_key;
struct f2fs_encryption_context ctx;
const struct user_key_payload *ukp;
struct crypto_skcipher *ctfm;
const char *cipher_str;
char raw_key[F2FS_MAX_KEY_SIZE];
char mode;
int res;
res = f2fs_crypto_initialize();
if (res)
return res;
retry:
crypt_info = ACCESS_ONCE(fi->i_crypt_info);
if (crypt_info) {
if (!crypt_info->ci_keyring_key ||
key_validate(crypt_info->ci_keyring_key) == 0)
return 0;
f2fs_free_encryption_info(inode, crypt_info);
goto retry;
}
res = f2fs_getxattr(inode, F2FS_XATTR_INDEX_ENCRYPTION,
F2FS_XATTR_NAME_ENCRYPTION_CONTEXT,
&ctx, sizeof(ctx), NULL);
if (res < 0)
return res;
else if (res != sizeof(ctx))
return -EINVAL;
res = 0;
crypt_info = kmem_cache_alloc(f2fs_crypt_info_cachep, GFP_NOFS);
if (!crypt_info)
return -ENOMEM;
crypt_info->ci_flags = ctx.flags;
crypt_info->ci_data_mode = ctx.contents_encryption_mode;
crypt_info->ci_filename_mode = ctx.filenames_encryption_mode;
crypt_info->ci_ctfm = NULL;
crypt_info->ci_keyring_key = NULL;
memcpy(crypt_info->ci_master_key, ctx.master_key_descriptor,
sizeof(crypt_info->ci_master_key));
if (S_ISREG(inode->i_mode))
mode = crypt_info->ci_data_mode;
else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
mode = crypt_info->ci_filename_mode;
else
BUG();
switch (mode) {
case F2FS_ENCRYPTION_MODE_AES_256_XTS:
cipher_str = "xts(aes)";
break;
case F2FS_ENCRYPTION_MODE_AES_256_CTS:
cipher_str = "cts(cbc(aes))";
break;
default:
printk_once(KERN_WARNING
"f2fs: unsupported key mode %d (ino %u)\n",
mode, (unsigned) inode->i_ino);
res = -ENOKEY;
goto out;
}
memcpy(full_key_descriptor, F2FS_KEY_DESC_PREFIX,
F2FS_KEY_DESC_PREFIX_SIZE);
sprintf(full_key_descriptor + F2FS_KEY_DESC_PREFIX_SIZE,
"%*phN", F2FS_KEY_DESCRIPTOR_SIZE,
ctx.master_key_descriptor);
full_key_descriptor[F2FS_KEY_DESC_PREFIX_SIZE +
(2 * F2FS_KEY_DESCRIPTOR_SIZE)] = '\0';
keyring_key = request_key(&key_type_logon, full_key_descriptor, NULL);
if (IS_ERR(keyring_key)) {
res = PTR_ERR(keyring_key);
keyring_key = NULL;
goto out;
}
crypt_info->ci_keyring_key = keyring_key;
BUG_ON(keyring_key->type != &key_type_logon);
ukp = user_key_payload(keyring_key);
if (ukp->datalen != sizeof(struct f2fs_encryption_key)) {
res = -EINVAL;
goto out;
}
master_key = (struct f2fs_encryption_key *)ukp->data;
BUILD_BUG_ON(F2FS_AES_128_ECB_KEY_SIZE !=
F2FS_KEY_DERIVATION_NONCE_SIZE);
BUG_ON(master_key->size != F2FS_AES_256_XTS_KEY_SIZE);
res = f2fs_derive_key_aes(ctx.nonce, master_key->raw,
raw_key);
if (res)
goto out;
ctfm = crypto_alloc_skcipher(cipher_str, 0, 0);
if (!ctfm || IS_ERR(ctfm)) {
res = ctfm ? PTR_ERR(ctfm) : -ENOMEM;
printk(KERN_DEBUG
"%s: error %d (inode %u) allocating crypto tfm\n",
__func__, res, (unsigned) inode->i_ino);
goto out;
}
crypt_info->ci_ctfm = ctfm;
crypto_skcipher_clear_flags(ctfm, ~0);
crypto_skcipher_set_flags(ctfm, CRYPTO_TFM_REQ_WEAK_KEY);
res = crypto_skcipher_setkey(ctfm, raw_key,
f2fs_encryption_key_size(mode));
if (res)
goto out;
memzero_explicit(raw_key, sizeof(raw_key));
if (cmpxchg(&fi->i_crypt_info, NULL, crypt_info) != NULL) {
f2fs_free_crypt_info(crypt_info);
goto retry;
}
return 0;
out:
if (res == -ENOKEY && !S_ISREG(inode->i_mode))
res = 0;
f2fs_free_crypt_info(crypt_info);
memzero_explicit(raw_key, sizeof(raw_key));
return res;
}
int f2fs_has_encryption_key(struct inode *inode)
{
struct f2fs_inode_info *fi = F2FS_I(inode);
return (fi->i_crypt_info != NULL);
}
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