Commit 88bd6ccd authored by Michael Halcrow's avatar Michael Halcrow Committed by Theodore Ts'o

ext4 crypto: add encryption key management facilities

Signed-off-by: 's avatarMichael Halcrow <mhalcrow@google.com>
Signed-off-by: 's avatarIldar Muslukhov <muslukhovi@gmail.com>
Signed-off-by: Theodore Ts'o's avatarTheodore Ts'o <tytso@mit.edu>
parent b30ab0e0
......@@ -12,4 +12,4 @@ ext4-y := balloc.o bitmap.o dir.o file.o fsync.o ialloc.o inode.o page-io.o \
ext4-$(CONFIG_EXT4_FS_POSIX_ACL) += acl.o
ext4-$(CONFIG_EXT4_FS_SECURITY) += xattr_security.o
ext4-$(CONFIG_EXT4_FS_ENCRYPTION) += crypto_policy.o crypto.o
ext4-$(CONFIG_EXT4_FS_ENCRYPTION) += crypto_policy.o crypto.o crypto_key.o
/*
* linux/fs/ext4/crypto_key.c
*
* Copyright (C) 2015, Google, Inc.
*
* This contains encryption key functions for ext4
*
* 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 "ext4.h"
#include "xattr.h"
static void derive_crypt_complete(struct crypto_async_request *req, int rc)
{
struct ext4_completion_result *ecr = req->data;
if (rc == -EINPROGRESS)
return;
ecr->res = rc;
complete(&ecr->completion);
}
/**
* ext4_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 ext4_derive_key_aes(char deriving_key[EXT4_AES_128_ECB_KEY_SIZE],
char source_key[EXT4_AES_256_XTS_KEY_SIZE],
char derived_key[EXT4_AES_256_XTS_KEY_SIZE])
{
int res = 0;
struct ablkcipher_request *req = NULL;
DECLARE_EXT4_COMPLETION_RESULT(ecr);
struct scatterlist src_sg, dst_sg;
struct crypto_ablkcipher *tfm = crypto_alloc_ablkcipher("ecb(aes)", 0,
0);
if (IS_ERR(tfm)) {
res = PTR_ERR(tfm);
tfm = NULL;
goto out;
}
crypto_ablkcipher_set_flags(tfm, CRYPTO_TFM_REQ_WEAK_KEY);
req = ablkcipher_request_alloc(tfm, GFP_NOFS);
if (!req) {
res = -ENOMEM;
goto out;
}
ablkcipher_request_set_callback(req,
CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
derive_crypt_complete, &ecr);
res = crypto_ablkcipher_setkey(tfm, deriving_key,
EXT4_AES_128_ECB_KEY_SIZE);
if (res < 0)
goto out;
sg_init_one(&src_sg, source_key, EXT4_AES_256_XTS_KEY_SIZE);
sg_init_one(&dst_sg, derived_key, EXT4_AES_256_XTS_KEY_SIZE);
ablkcipher_request_set_crypt(req, &src_sg, &dst_sg,
EXT4_AES_256_XTS_KEY_SIZE, NULL);
res = crypto_ablkcipher_encrypt(req);
if (res == -EINPROGRESS || res == -EBUSY) {
BUG_ON(req->base.data != &ecr);
wait_for_completion(&ecr.completion);
res = ecr.res;
}
out:
if (req)
ablkcipher_request_free(req);
if (tfm)
crypto_free_ablkcipher(tfm);
return res;
}
/**
* ext4_generate_encryption_key() - generates an encryption key
* @inode: The inode to generate the encryption key for.
*/
int ext4_generate_encryption_key(struct inode *inode)
{
struct ext4_inode_info *ei = EXT4_I(inode);
struct ext4_encryption_key *crypt_key = &ei->i_encryption_key;
char full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE +
(EXT4_KEY_DESCRIPTOR_SIZE * 2) + 1];
struct key *keyring_key = NULL;
struct ext4_encryption_key *master_key;
struct ext4_encryption_context ctx;
struct user_key_payload *ukp;
int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
&ctx, sizeof(ctx));
if (res != sizeof(ctx)) {
if (res > 0)
res = -EINVAL;
goto out;
}
res = 0;
memcpy(full_key_descriptor, EXT4_KEY_DESC_PREFIX,
EXT4_KEY_DESC_PREFIX_SIZE);
sprintf(full_key_descriptor + EXT4_KEY_DESC_PREFIX_SIZE,
"%*phN", EXT4_KEY_DESCRIPTOR_SIZE,
ctx.master_key_descriptor);
full_key_descriptor[EXT4_KEY_DESC_PREFIX_SIZE +
(2 * EXT4_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;
}
BUG_ON(keyring_key->type != &key_type_logon);
ukp = ((struct user_key_payload *)keyring_key->payload.data);
if (ukp->datalen != sizeof(struct ext4_encryption_key)) {
res = -EINVAL;
goto out;
}
master_key = (struct ext4_encryption_key *)ukp->data;
if (S_ISREG(inode->i_mode))
crypt_key->mode = ctx.contents_encryption_mode;
else if (S_ISDIR(inode->i_mode) || S_ISLNK(inode->i_mode))
crypt_key->mode = ctx.filenames_encryption_mode;
else {
printk(KERN_ERR "ext4 crypto: Unsupported inode type.\n");
BUG();
}
crypt_key->size = ext4_encryption_key_size(crypt_key->mode);
BUG_ON(!crypt_key->size);
BUILD_BUG_ON(EXT4_AES_128_ECB_KEY_SIZE !=
EXT4_KEY_DERIVATION_NONCE_SIZE);
BUG_ON(master_key->size != EXT4_AES_256_XTS_KEY_SIZE);
BUG_ON(crypt_key->size < EXT4_AES_256_CBC_KEY_SIZE);
res = ext4_derive_key_aes(ctx.nonce, master_key->raw, crypt_key->raw);
out:
if (keyring_key)
key_put(keyring_key);
if (res < 0)
crypt_key->mode = EXT4_ENCRYPTION_MODE_INVALID;
return res;
}
int ext4_has_encryption_key(struct inode *inode)
{
struct ext4_inode_info *ei = EXT4_I(inode);
struct ext4_encryption_key *crypt_key = &ei->i_encryption_key;
return (crypt_key->mode != EXT4_ENCRYPTION_MODE_INVALID);
}
......@@ -2078,6 +2078,19 @@ static inline int ext4_sb_has_crypto(struct super_block *sb)
}
#endif
/* crypto_key.c */
int ext4_generate_encryption_key(struct inode *inode);
#ifdef CONFIG_EXT4_FS_ENCRYPTION
int ext4_has_encryption_key(struct inode *inode);
#else
static inline int ext4_has_encryption_key(struct inode *inode)
{
return 0;
}
#endif
/* dir.c */
extern int __ext4_check_dir_entry(const char *, unsigned int, struct inode *,
struct file *,
......
......@@ -55,6 +55,9 @@ struct ext4_encryption_context {
#define EXT4_AES_256_XTS_KEY_SIZE 64
#define EXT4_MAX_KEY_SIZE 64
#define EXT4_KEY_DESC_PREFIX "ext4:"
#define EXT4_KEY_DESC_PREFIX_SIZE 5
struct ext4_encryption_key {
uint32_t mode;
char raw[EXT4_MAX_KEY_SIZE];
......
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment