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ext4 crypto: add encryption policy and password salt support 

Signed-off-by: Michael Halcrow <mhalcrow@google.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: Ildar Muslukhov <muslukhovi@gmail.com>
This commit is contained in:
Michael Halcrow 2015-04-11 07:48:01 -04:00 committed by Theodore Ts'o
parent 887e2c4522
commit 9bd8212f98
5 changed files with 317 additions and 0 deletions
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1
fs/ext4/Makefile
View File

@ -12,3 +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

167
fs/ext4/crypto_policy.c Normal file
View File

@ -0,0 +1,167 @@
/*
* linux/fs/ext4/crypto_policy.c
*
* Copyright (C) 2015, Google, Inc.
*
* This contains encryption policy functions for ext4
*
* Written by Michael Halcrow, 2015.
*/
#include <linux/random.h>
#include <linux/string.h>
#include <linux/types.h>
#include "ext4.h"
#include "xattr.h"
static int ext4_inode_has_encryption_context(struct inode *inode)
{
int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, NULL, 0);
return (res > 0);
}
/*
* check whether the policy is consistent with the encryption context
* for the inode
*/
static int ext4_is_encryption_context_consistent_with_policy(
struct inode *inode, const struct ext4_encryption_policy *policy)
{
struct ext4_encryption_context ctx;
int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
sizeof(ctx));
if (res != sizeof(ctx))
return 0;
return (memcmp(ctx.master_key_descriptor, policy->master_key_descriptor,
EXT4_KEY_DESCRIPTOR_SIZE) == 0 &&
(ctx.contents_encryption_mode ==
policy->contents_encryption_mode) &&
(ctx.filenames_encryption_mode ==
policy->filenames_encryption_mode));
}
static int ext4_create_encryption_context_from_policy(
struct inode *inode, const struct ext4_encryption_policy *policy)
{
struct ext4_encryption_context ctx;
int res = 0;
ctx.format = EXT4_ENCRYPTION_CONTEXT_FORMAT_V1;
memcpy(ctx.master_key_descriptor, policy->master_key_descriptor,
EXT4_KEY_DESCRIPTOR_SIZE);
ctx.contents_encryption_mode = policy->contents_encryption_mode;
ctx.filenames_encryption_mode = policy->filenames_encryption_mode;
BUILD_BUG_ON(sizeof(ctx.nonce) != EXT4_KEY_DERIVATION_NONCE_SIZE);
get_random_bytes(ctx.nonce, EXT4_KEY_DERIVATION_NONCE_SIZE);
res = ext4_xattr_set(inode, EXT4_XATTR_INDEX_ENCRYPTION,
EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
sizeof(ctx), 0);
if (!res)
ext4_set_inode_flag(inode, EXT4_INODE_ENCRYPT);
return res;
}
int ext4_process_policy(const struct ext4_encryption_policy *policy,
struct inode *inode)
{
if (policy->version != 0)
return -EINVAL;
if (!ext4_inode_has_encryption_context(inode)) {
if (!ext4_empty_dir(inode))
return -ENOTEMPTY;
return ext4_create_encryption_context_from_policy(inode,
policy);
}
if (ext4_is_encryption_context_consistent_with_policy(inode, policy))
return 0;
printk(KERN_WARNING "%s: Policy inconsistent with encryption context\n",
__func__);
return -EINVAL;
}
int ext4_get_policy(struct inode *inode, struct ext4_encryption_policy *policy)
{
struct ext4_encryption_context ctx;
int res = ext4_xattr_get(inode, EXT4_XATTR_INDEX_ENCRYPTION,
EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
&ctx, sizeof(ctx));
if (res != sizeof(ctx))
return -ENOENT;
if (ctx.format != EXT4_ENCRYPTION_CONTEXT_FORMAT_V1)
return -EINVAL;
policy->version = 0;
policy->contents_encryption_mode = ctx.contents_encryption_mode;
policy->filenames_encryption_mode = ctx.filenames_encryption_mode;
memcpy(&policy->master_key_descriptor, ctx.master_key_descriptor,
EXT4_KEY_DESCRIPTOR_SIZE);
return 0;
}
int ext4_is_child_context_consistent_with_parent(struct inode *parent,
struct inode *child)
{
struct ext4_encryption_context parent_ctx, child_ctx;
int res;
if ((parent == NULL) || (child == NULL)) {
pr_err("parent %p child %p\n", parent, child);
BUG_ON(1);
}
/* no restrictions if the parent directory is not encrypted */
if (!ext4_encrypted_inode(parent))
return 1;
res = ext4_xattr_get(parent, EXT4_XATTR_INDEX_ENCRYPTION,
EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
&parent_ctx, sizeof(parent_ctx));
if (res != sizeof(parent_ctx))
return 0;
/* if the child directory is not encrypted, this is always a problem */
if (!ext4_encrypted_inode(child))
return 0;
res = ext4_xattr_get(child, EXT4_XATTR_INDEX_ENCRYPTION,
EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
&child_ctx, sizeof(child_ctx));
if (res != sizeof(child_ctx))
return 0;
return (memcmp(parent_ctx.master_key_descriptor,
child_ctx.master_key_descriptor,
EXT4_KEY_DESCRIPTOR_SIZE) == 0 &&
(parent_ctx.contents_encryption_mode ==
child_ctx.contents_encryption_mode) &&
(parent_ctx.filenames_encryption_mode ==
child_ctx.filenames_encryption_mode));
}
/**
* ext4_inherit_context() - Sets a child context from its parent
* @parent: Parent inode from which the context is inherited.
* @child: Child inode that inherits the context from @parent.
*
* Return: Zero on success, non-zero otherwise
*/
int ext4_inherit_context(struct inode *parent, struct inode *child)
{
struct ext4_encryption_context ctx;
int res = ext4_xattr_get(parent, EXT4_XATTR_INDEX_ENCRYPTION,
EXT4_XATTR_NAME_ENCRYPTION_CONTEXT,
&ctx, sizeof(ctx));
if (res != sizeof(ctx))
return -ENOENT;
get_random_bytes(ctx.nonce, EXT4_KEY_DERIVATION_NONCE_SIZE);
res = ext4_xattr_set(child, EXT4_XATTR_INDEX_ENCRYPTION,
EXT4_XATTR_NAME_ENCRYPTION_CONTEXT, &ctx,
sizeof(ctx), 0);
if (!res)
ext4_set_inode_flag(child, EXT4_INODE_ENCRYPT);
return res;
}

15
fs/ext4/ext4.h
View File

@ -589,6 +589,8 @@ enum {
#define EXT4_ENCRYPTION_MODE_AES_256_CBC 3
#define EXT4_ENCRYPTION_MODE_AES_256_CTS 4
#include "ext4_crypto.h"
/*
* ioctl commands
*/
@ -610,6 +612,9 @@ enum {
#define EXT4_IOC_RESIZE_FS _IOW('f', 16, __u64)
#define EXT4_IOC_SWAP_BOOT _IO('f', 17)
#define EXT4_IOC_PRECACHE_EXTENTS _IO('f', 18)
#define EXT4_IOC_SET_ENCRYPTION_POLICY _IOR('f', 19, struct ext4_encryption_policy)
#define EXT4_IOC_GET_ENCRYPTION_PWSALT _IOW('f', 20, __u8[16])
#define EXT4_IOC_GET_ENCRYPTION_POLICY _IOW('f', 21, struct ext4_encryption_policy)
#if defined(__KERNEL__) && defined(CONFIG_COMPAT)
/*
@ -2011,6 +2016,16 @@ extern unsigned ext4_free_clusters_after_init(struct super_block *sb,
struct ext4_group_desc *gdp);
ext4_fsblk_t ext4_inode_to_goal_block(struct inode *);
/* crypto_policy.c */
int ext4_is_child_context_consistent_with_parent(struct inode *parent,
struct inode *child);
int ext4_inherit_context(struct inode *parent, struct inode *child);
void ext4_to_hex(char *dst, char *src, size_t src_size);
int ext4_process_policy(const struct ext4_encryption_policy *policy,
struct inode *inode);
int ext4_get_policy(struct inode *inode,
struct ext4_encryption_policy *policy);
/* dir.c */
extern int __ext4_check_dir_entry(const char *, unsigned int, struct inode *,
struct file *,

49
fs/ext4/ext4_crypto.h Normal file
View File

@ -0,0 +1,49 @@
/*
* linux/fs/ext4/ext4_crypto.h
*
* Copyright (C) 2015, Google, Inc.
*
* This contains encryption header content for ext4
*
* Written by Michael Halcrow, 2015.
*/
#ifndef _EXT4_CRYPTO_H
#define _EXT4_CRYPTO_H
#include <linux/fs.h>
#define EXT4_KEY_DESCRIPTOR_SIZE 8
/* Policy provided via an ioctl on the topmost directory */
struct ext4_encryption_policy {
char version;
char contents_encryption_mode;
char filenames_encryption_mode;
char master_key_descriptor[EXT4_KEY_DESCRIPTOR_SIZE];
} __attribute__((__packed__));
#define EXT4_ENCRYPTION_CONTEXT_FORMAT_V1 1
#define EXT4_KEY_DERIVATION_NONCE_SIZE 16
/**
* Encryption context for inode
*
* Protector format:
* 1 byte: Protector format (1 = this version)
* 1 byte: File contents encryption mode
* 1 byte: File names encryption mode
* 1 byte: Reserved
* 8 bytes: Master Key descriptor
* 16 bytes: Encryption Key derivation nonce
*/
struct ext4_encryption_context {
char format;
char contents_encryption_mode;
char filenames_encryption_mode;
char reserved;
char master_key_descriptor[EXT4_KEY_DESCRIPTOR_SIZE];
char nonce[EXT4_KEY_DERIVATION_NONCE_SIZE];
} __attribute__((__packed__));
#endif /* _EXT4_CRYPTO_H */

85
fs/ext4/ioctl.c
View File

@ -13,6 +13,7 @@
#include <linux/compat.h>
#include <linux/mount.h>
#include <linux/file.h>
#include <linux/random.h>
#include <asm/uaccess.h>
#include "ext4_jbd2.h"
#include "ext4.h"
@ -195,6 +196,16 @@ journal_err_out:
return err;
}
static int uuid_is_zero(__u8 u[16])
{
int i;
for (i = 0; i < 16; i++)
if (u[i])
return 0;
return 1;
}
long ext4_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
{
struct inode *inode = file_inode(filp);
@ -614,7 +625,78 @@ resizefs_out:
}
case EXT4_IOC_PRECACHE_EXTENTS:
return ext4_ext_precache(inode);
case EXT4_IOC_SET_ENCRYPTION_POLICY: {
#ifdef CONFIG_EXT4_FS_ENCRYPTION
struct ext4_encryption_policy policy;
int err = 0;
if (copy_from_user(&policy,
(struct ext4_encryption_policy __user *)arg,
sizeof(policy))) {
err = -EFAULT;
goto encryption_policy_out;
}
err = ext4_process_policy(&policy, inode);
encryption_policy_out:
return err;
#else
return -EOPNOTSUPP;
#endif
}
case EXT4_IOC_GET_ENCRYPTION_PWSALT: {
int err, err2;
struct ext4_sb_info *sbi = EXT4_SB(sb);
handle_t *handle;
if (!ext4_sb_has_crypto(sb))
return -EOPNOTSUPP;
if (uuid_is_zero(sbi->s_es->s_encrypt_pw_salt)) {
err = mnt_want_write_file(filp);
if (err)
return err;
handle = ext4_journal_start_sb(sb, EXT4_HT_MISC, 1);
if (IS_ERR(handle)) {
err = PTR_ERR(handle);
goto pwsalt_err_exit;
}
err = ext4_journal_get_write_access(handle, sbi->s_sbh);
if (err)
goto pwsalt_err_journal;
generate_random_uuid(sbi->s_es->s_encrypt_pw_salt);
err = ext4_handle_dirty_metadata(handle, NULL,
sbi->s_sbh);
pwsalt_err_journal:
err2 = ext4_journal_stop(handle);
if (err2 && !err)
err = err2;
pwsalt_err_exit:
mnt_drop_write_file(filp);
if (err)
return err;
}
if (copy_to_user((void *) arg, sbi->s_es->s_encrypt_pw_salt,
16))
return -EFAULT;
return 0;
}
case EXT4_IOC_GET_ENCRYPTION_POLICY: {
#ifdef CONFIG_EXT4_FS_ENCRYPTION
struct ext4_encryption_policy policy;
int err = 0;
if (!ext4_encrypted_inode(inode))
return -ENOENT;
err = ext4_get_policy(inode, &policy);
if (err)
return err;
if (copy_to_user((void *)arg, &policy, sizeof(policy)))
return -EFAULT;
return 0;
#else
return -EOPNOTSUPP;
#endif
}
default:
return -ENOTTY;
}
@ -679,6 +761,9 @@ long ext4_compat_ioctl(struct file *file, unsigned int cmd, unsigned long arg)
case FITRIM:
case EXT4_IOC_RESIZE_FS:
case EXT4_IOC_PRECACHE_EXTENTS:
case EXT4_IOC_SET_ENCRYPTION_POLICY:
case EXT4_IOC_GET_ENCRYPTION_PWSALT:
case EXT4_IOC_GET_ENCRYPTION_POLICY:
break;
default:
return -ENOIOCTLCMD;