ext4_crypto.h
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/*
* 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 flags;
char master_key_descriptor[EXT4_KEY_DESCRIPTOR_SIZE];
} __attribute__((__packed__));
#define EXT4_ENCRYPTION_CONTEXT_FORMAT_V1 1
#define EXT4_KEY_DERIVATION_NONCE_SIZE 16
#define EXT4_POLICY_FLAGS_PAD_4 0x00
#define EXT4_POLICY_FLAGS_PAD_8 0x01
#define EXT4_POLICY_FLAGS_PAD_16 0x02
#define EXT4_POLICY_FLAGS_PAD_32 0x03
#define EXT4_POLICY_FLAGS_PAD_MASK 0x03
#define EXT4_POLICY_FLAGS_VALID 0x03
/**
* 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 flags;
char master_key_descriptor[EXT4_KEY_DESCRIPTOR_SIZE];
char nonce[EXT4_KEY_DERIVATION_NONCE_SIZE];
} __attribute__((__packed__));
/* Encryption parameters */
#define EXT4_XTS_TWEAK_SIZE 16
#define EXT4_AES_128_ECB_KEY_SIZE 16
#define EXT4_AES_256_GCM_KEY_SIZE 32
#define EXT4_AES_256_CBC_KEY_SIZE 32
#define EXT4_AES_256_CTS_KEY_SIZE 32
#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];
uint32_t size;
};
#define EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL 0x00000001
#define EXT4_BOUNCE_PAGE_REQUIRES_FREE_ENCRYPT_FL 0x00000002
struct ext4_crypto_ctx {
struct crypto_tfm *tfm; /* Crypto API context */
struct page *bounce_page; /* Ciphertext page on write path */
struct page *control_page; /* Original page on write path */
struct bio *bio; /* The bio for this context */
struct work_struct work; /* Work queue for read complete path */
struct list_head free_list; /* Free list */
int flags; /* Flags */
int mode; /* Encryption mode for tfm */
};
struct ext4_completion_result {
struct completion completion;
int res;
};
#define DECLARE_EXT4_COMPLETION_RESULT(ecr) \
struct ext4_completion_result ecr = { \
COMPLETION_INITIALIZER((ecr).completion), 0 }
static inline int ext4_encryption_key_size(int mode)
{
switch (mode) {
case EXT4_ENCRYPTION_MODE_AES_256_XTS:
return EXT4_AES_256_XTS_KEY_SIZE;
case EXT4_ENCRYPTION_MODE_AES_256_GCM:
return EXT4_AES_256_GCM_KEY_SIZE;
case EXT4_ENCRYPTION_MODE_AES_256_CBC:
return EXT4_AES_256_CBC_KEY_SIZE;
case EXT4_ENCRYPTION_MODE_AES_256_CTS:
return EXT4_AES_256_CTS_KEY_SIZE;
default:
BUG();
}
return 0;
}
#define EXT4_FNAME_NUM_SCATTER_ENTRIES 4
#define EXT4_CRYPTO_BLOCK_SIZE 16
#define EXT4_FNAME_CRYPTO_DIGEST_SIZE 32
struct ext4_str {
unsigned char *name;
u32 len;
};
struct ext4_fname_crypto_ctx {
u32 lim;
char tmp_buf[EXT4_CRYPTO_BLOCK_SIZE];
struct crypto_ablkcipher *ctfm;
struct crypto_hash *htfm;
struct page *workpage;
struct ext4_encryption_key key;
unsigned flags : 8;
unsigned has_valid_key : 1;
unsigned ctfm_key_is_ready : 1;
};
/**
* For encrypted symlinks, the ciphertext length is stored at the beginning
* of the string in little-endian format.
*/
struct ext4_encrypted_symlink_data {
__le16 len;
char encrypted_path[1];
} __attribute__((__packed__));
/**
* This function is used to calculate the disk space required to
* store a filename of length l in encrypted symlink format.
*/
static inline u32 encrypted_symlink_data_len(u32 l)
{
if (l < EXT4_CRYPTO_BLOCK_SIZE)
l = EXT4_CRYPTO_BLOCK_SIZE;
return (l + sizeof(struct ext4_encrypted_symlink_data) - 1);
}
#endif /* _EXT4_CRYPTO_H */