Release 4.7 fs/ext4/ext4_crypto.h

/*
 * 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

/* This is passed in from userspace into the kernel keyring */

struct ext4_encryption_key {
        
__u32 mode;
        
char raw[EXT4_MAX_KEY_SIZE];
        
__u32 size;
} __attribute__((__packed__));


struct ext4_crypt_info {
	
char		ci_data_mode;
	
char		ci_filename_mode;
	
char		ci_flags;
	
struct crypto_skcipher *ci_ctfm;
	
struct key	*ci_keyring_key;
	
char		ci_master_key[EXT4_KEY_DESCRIPTOR_SIZE];
};


#define EXT4_CTX_REQUIRES_FREE_ENCRYPT_FL             0x00000001

#define EXT4_WRITE_PATH_FL			      0x00000002


struct ext4_crypto_ctx {
	union {
		struct {
			
struct page *bounce_page;       /* Ciphertext page */
			
struct page *control_page;      /* Original page  */
		} 
w;
		struct {
			
struct bio *bio;
			
struct work_struct work;
		} 
r;
		
struct list_head free_list;     /* Free list */
	};
	
char flags;                      /* Flags */
	
char 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;
}

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#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;
};

/**
 * 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);
}

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#endif	/* _EXT4_CRYPTO_H */
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Directory: fs/ext4

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