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

ext4 crypto: add encryption key management facilities 



Signed-off-by: default avatarMichael Halcrow <mhalcrow@google.com>
Signed-off-by: default avatarIldar Muslukhov <muslukhovi@gmail.com>
Signed-off-by: default avatarTheodore Ts'o <tytso@mit.edu>
parent b30ab0e0

fs/ext4/Makefile

+1 −1
Original line number Diff line number Diff line
@@ -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

fs/ext4/crypto_key.c

0 → 100644
+162 −0
Original line number Diff line number Diff line 
/*

 * 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);

}

fs/ext4/ext4.h

+13 −0
Original line number Diff line number Diff line
@@ -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 *,

fs/ext4/ext4_crypto.h

+3 −0
Original line number Diff line number Diff line
@@ -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];